EP2082423A1 - Board on chip package and process for making same - Google Patents

Board on chip package and process for making same

Info

Publication number
EP2082423A1
EP2082423A1 EP06837754A EP06837754A EP2082423A1 EP 2082423 A1 EP2082423 A1 EP 2082423A1 EP 06837754 A EP06837754 A EP 06837754A EP 06837754 A EP06837754 A EP 06837754A EP 2082423 A1 EP2082423 A1 EP 2082423A1
Authority
EP
European Patent Office
Prior art keywords
substrate
die
adhesive
opening
encapsulant
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06837754A
Other languages
German (de)
French (fr)
Inventor
Kenji Kuriyama
Paul Wojtuszewski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Henkel AG and Co KGaA
Original Assignee
Henkel AG and Co KGaA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Henkel AG and Co KGaA filed Critical Henkel AG and Co KGaA
Publication of EP2082423A1 publication Critical patent/EP2082423A1/en
Withdrawn legal-status Critical Current

Links

Classifications

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    • H01L23/31—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape
    • H01L23/3107—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape the device being completely enclosed
    • H01L23/3114—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection characterised by the arrangement or shape the device being completely enclosed the device being a chip scale package, e.g. CSP
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    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
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Definitions

  • This invention relates to a semiconductor package and a process for its manufacture.
  • BOC board-on-chip
  • These packages are also called window-type semiconductor packages and comprise a substrate formed with an opening penetrating through the same, a semiconductor chip or die mounted over the opening on an upper surface of the substrate by means of an adhesive in a face-down manner such that the active surface of the chip faces toward the substrate and is partially exposed to the opening.
  • a plurality of bonding wires electrically connect the active surface of the die, through the opening, to the lower surface of the substrate.
  • a first encapsulant is formed on the lower surface of the substrate for filling the opening and encapsulating the bonding wires and a second encapsulant is formed on the upper surface of the substrate for encapsulating the back and/or sides of the chip.
  • a plurality of solder balls are attached to the lower surface of the substrate and positioned outside the first encapsulant.
  • BOC packages can be manufactured using at least two different methods.
  • a printable adhesive paste is applied to a substrate and B- staged to a non-tacky state prior to die attach.
  • several dies are mounted on a single substrate so that multiple packages can be manufactured from a single board.
  • Figure 1 shows a top view
  • Figure 2 shows a cross-section view of a package in a typical embodiment of this method wherein the adhesive 12 is printed on the top surface 101 of the substrate 10 in a pattern which allows for the die 11 to be mounted over the openings 100 in the substrate 10.
  • wire bonds 13 are formed through the opening 100, from the wire bond pads 112 on the active side 111 of the die 11 to the bottom side 102 of the substrate 10.
  • encapsulant 15 is applied over the wire bonds 13, the inactive side 110 of the die 11, and the sides 113 of the die 11 in a molding process.
  • solder balls 14 are applied to the bottom side 102 of the substrate 10 and the packages are separated from one another in a sawing operation.
  • Figure 3 shows a cross-section of a package representing another typical embodiment of this method wherein the inactive side 110 of the die 11 is not encapsulated, but the sides 113 of the die 11 are encapsulated.
  • Figure 4A shows a typical configuration that allows for multiple packages to be produced from a single substrate 10.
  • the adhesive 12 is printed in areas around the openings 100 in the substrate 10, so that dies may later be mounted onto the adhesive 12 in position to cover the openings 100.
  • stress release is provided by incorporating substrate area that is not molded between blocks of packages that are molded, including a slit 104 in the substrate 10 in an area between blocks of molded packages.
  • Figure 4B is an enlarged view of this configuration, showing that the stress release area provided by the slits 104 necessitate the use of significantly more substrate area than is required for the memory packages themselves.
  • the substrate 10 is one of the more expensive materials used in the memory package, this waste is highly undesirable.
  • the temperature and pressure inherent in the molding process places thermal stress on the semiconductor die, which can lead to low device yield.
  • Figure 5 shows a top view
  • Figure 6 shows a cross-sectional view of a BOC package manufactured using a second method. In this method a tape adhesive 17, having an aperture corresponding in position to the opening 100 of the substrate, is applied over the tape attach area 105 of the top surface 101 of the substrate 10, with the aperture of the adhesive tape aligned with the opening of the substrate.
  • the adhesive tape 17 is thus interposed between the active surface 111 of the die 11 and the upper surface 101 of the substrate without any formation of gaps between the die 11 and the substrate 10.
  • wire bonds 13 are formed through the opening 100, from the wire bond pads 112 on the active side 111 of the die 11 to the bottom side 102 of the substrate 10.
  • encapsulant 15 is applied over the wire bonds 13 in one step and a second encapsulant 16 is applied over the sides 113 of the die 11 in a molding process.
  • solder balls 14 are applied to the bottom side 102 of the substrate 10 and the packages are separated from one another in a sawing operation.
  • encapsulant is applied to the inactive side of the die as well as the sides of the die.
  • this method eliminates the problem of the gaps between the active surface of the die and the upper surface of the substrate due to areas uncovered by the adhesive and adjacent to the opening of the substrate, it does have significant drawbacks.
  • tape adhesives are much more expensive to use than flow-able adhesives such as printable pastes.
  • the die may not be placed in perfect alignment over the tape, which can lead to the presence of some gap under the die.
  • this method requires encapsulation of the sides and/or back side of the die in a molding process. Therefore, as in the method described above, there is significant substrate waste, and thermal stress on the die.
  • This invention is a semiconductor package comprising: (a) a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; (b) a semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side, the semiconductor die mounted onto the substrate with the active side disposed over and completely covering the opening penetrating through the upper and lower surfaces of the substrate; (c) an adhesive disposed between and joining the upper surface of the substrate and the active side of the die such that the active side of the die, exclusive of the conductive areas, is completely covered by the adhesive; (d) a plurality of electrically conducting bonding wires connecting the conductive areas on the active side of the die, through the opening in the substrate, to the wire bond pads on the lower surface of the substrate; (e) an encapsulant applied onto the lower surface of the substrate, encapsulating the bonding wires and filling the opening of the substrate; and (f) a semiconductor package compris
  • this invention is a process for the manufacture of a semiconductor package comprising: (a) providing a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; (b) providing at least one semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side; (c) applying a flow-able adhesive in an adhesive pattern onto the upper surface of the substrate such that after the die is attached to the substrate the adhesive surrounds the opening and, inclusive of the opening, is at least as large as the footprint of the die, (d) optionally hardening the flow-able adhesive to a non-tacky state; (e) mounting the die onto the substrate with the active side disposed over and completely covering the opening through the upper and lower surfaces of the substrate, such that the conductive area on the active surface of the die is exposed to the opening of the substrate, and the active surface of the die, exclusive of the conductive area, is completely covered by the adhesive; (a) providing a substrate
  • this invention is a process for the manufacture of a semiconductor package comprising: (a) providing a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; (b) providing at least one semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side; (c) applying a flow-able adhesive in an adhesive pattern onto the active side of the die such that after the die is attached to the substrate the adhesive surrounds the opening and, inclusive of the opening, is at least as large as the footprint of the die; (d) optionally hardening the flow-able adhesive to a non-tacky state, (e) mounting the die onto the substrate with the active side disposed over and completely covering the opening through the upper and lower surfaces of the substrate, such that the conductive area on the active surface of the die is exposed to the opening of the substrate, and the active surface of the die, exclusive of the conductive area, is completely covered by the adhesive
  • this invention is a substrate for the manufacture of board-on-chip semiconductor packages which comprises a top surface, a bottom surface opposed to the top surface, and openings penetrating through the top surface and the bottom surface; which is characterized by the absence of a mold stress relief area.
  • FIGURE 1 (Prior Art), is a top view of a traditional semiconductor package
  • FIGURE 2 (Prior Art), is a cross-sectional view of a traditional semiconductor package
  • FIGURE 3 is a cross-sectional view another embodiment of a traditional semiconductor package
  • FIGURE 4A (Prior Art) is a top view of a traditional printing pattern for
  • FIGURE 4B is a an expanded top view of a traditional printing pattern for BOC-type packages on a substrate
  • FIGURE 5 is a top view of another embodiment of a traditional semiconductor package
  • FIGURE 6 is a cross-sectional view of another embodiment of a traditional semiconductor package
  • FIGURE 7 is a top view of the inventive semiconductor package
  • FIGURE 8A is a cross-sectional view of one embodiment of the inventive semiconductor package
  • FIGURE 8B is a cross-sectional view of another embodiment of the inventive semiconductor package
  • FIGURES 9A through 9E are top views of a substrate assembled according to the inventive process
  • FIGURES 10A and 10B illustrate a printing pattern on a wafer for another embodiment of the invention
  • FIGURE 11 is a top view of a substrate for BOC packaging characterized by the absence of a mold stress release area
  • FIGURES 12A and 12B are top views of substrates with adhesive printing patterns representing two additional embodiments of the invention
  • FIGURE 13 is a top view of a substrate with an adhesive printing pattern representing another embodiment of the invention
  • alkyl refers to a branched or un-branched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl (“Me”), ethyl
  • alkyl groups herein contain from 1 to 12 carbon atoms.
  • effective amount of a compound, product, or composition as provided herein is meant a sufficient amount of the compound, product or composition to provide the desired results. As will be pointed out below, the exact amount required will vary from package to package, depending on the particular compound, product or composition used, its mode of administration, and the like. Thus, it is not always possible to specify an exact amount; however, an effective amount may be determined by one of ordinary skill in the art using only routine experimentation.
  • the term "suitable” is used to refer to a moiety that is compatible with the compounds, products, or compositions as provided herein for the stated purpose. Suitability for the stated purpose may be determined by one of ordinary skill in the art using only routine experimentation.
  • substituted is used to refer, generally, to a carbon or suitable heteroatom having a hydrogen or other atom removed and replaced with a further moiety. Moreover, it is intended that “substituted” refer to substitutions that do not change the basic and novel utility of the underlying compounds, products or compositions utilized in the present invention.
  • B-staging (and its variants) is used to refer to the processing of a material by heat or irradiation so that if the material is solubilized or dispersed in a solvent, the solvent is evaporated off with or without partial curing of the material, or if the material is neat with no solvent, the material is partially cured to a tacky or more hardened state. If the material is a flow-able adhesive, B-staging will provide extremely low flow without fully curing, such that additional curing may be performed after the adhesive is used to join one article to another. The reduction in flow may be accomplished by evaporation of a solvent, partial advancement or curing of a resin or polymer, or both.
  • the term "printable paste” is any liquid adhesive that can be printed onto a surface such as a substrate, a die, or a wafer.
  • Figure 7 represents a top view and Figure 8A represents a cross-section view illustrating one embodiment of the semiconductor package according to the present invention.
  • the substrate 20 has an upper surface 201 and a lower surface 202 opposed to the .upper surface, with at least one opening 200 formed to penetrate through the upper 201 and lower 202 surfaces of the substrate 20.
  • the substrate contemplated for this invention is rigid or semi-rigid (not a flexible tape) primarily made of a conventional resin material including but not limited to BT resin, epoxy resin, and FR-4.
  • the substrate may be any dimensions but will typically be between 20 mm x 100 mm and 100 mm x 250 mm, and between 0.1 and 0.6 mm thick.
  • an adhesive application area 206 is defined on the upper surface 201 of the substrate 20 peripherally around the opening, such that the area 206, inclusive of the opening, is at least as large as the footprint of the die.
  • the substrate is designed such that it does not have stress release areas for molding.
  • Figure 11 illustrates a top view of one example of how the substrate can be configured, where the substrate 20 has a top surface 201 and a bottom surface opposed to the top surface and includes openings 200 penetrating through the top surface 201 and the bottom surface 202 through which wire bonds may be formed..
  • This substrate design is characterized by the absence of a mold stress relief area.
  • One skilled in the art could contemplate many variations and similar arrangements that would have the same advantage of conserving substrate area, enabled by the fact that molding of the package to encapsulate the back and/or sides of the die is not necessary with the package and processes described in the present invention.
  • the semiconductor die 21, or chip is mounted onto the substrate 20 such that the active side 211 of the die 21 is mounted over the flow-able adhesive 22, such that the adhesive 22 is interposed between the active surface 211 of the die 21 and the upper surface 201 of the substrate.
  • the active surface 211 is larger than and completely covers the opening 200, allowing the conductive area(s) on the active surface 211 of the die 21 to be exposed to the opening 200 of the substrate 20.
  • the active surface 211 of the die 21, exclusive of the conductive area(s), is completely covered by the flow-able adhesive 22 to be free of forming gaps between the die and the substrate.
  • the semiconductor chip, or die 21 can be any size and thickness and is, for instance, a silicon integrated circuit component such as a DRAM, having a thickness ranging from 0.05 to 0.4 mm.
  • the die 21 may be a silicon digital signal processor, or be made of gallium arsenide, indium phosphide or any other semiconductor material.
  • the semiconductor die 21 is prepared with an active surface 211 (also known as top or front surface) where electronic elements and circuits are formed, and an inactive surface 210 (also known as a bottom or back surface) opposed to the active surface 211.
  • the active surface 211 has a plurality of wire bond pads 212 formed on at least one conductive area, which are used for wire bonding the active surface 211 of the chip to wire bond pads 203 on the lower surface 202 of the substrate 20 to form electrical connections between the two.
  • the semiconductor die has bonding pads in multiple locations, for instance, in both the center and edge of the die.
  • the substrate includes multiple openings, to correspond to each of these bonding pad locations.
  • the adhesive 22 joins the upper surface 201 of the substrate 20 to the active side 211 of the die 21.
  • the die 21 is positioned on the substrate 20 such that the conductive area on the die 21, which contains the wire bond pads 212, is over and completely covers the opening 200 in the substrate 20. In this way the die 21 is attached to the substrate 20 without any adhesive coverage gaps between the die 21 and the substrate 20, yet the conductive area is exposed so that wire bonds 23 may be formed on the bond pads 212 contained thereon.
  • the adhesive 22 is applied to the upper surface 201 of the substrate 20. In another embodiment the adhesive 22 is applied to the active side 211 of the die 21, before singulation from the wafer. In another embodiment the adhesive 22 is applied to the active side 211 of the die 21 after it has been singulated from the wafer.
  • the adhesive 22 may be applied to either the die 21 or the substrate 20 using any method which utilizes a flow-able adhesive, including but not limited to, stencil printing, screen printing, ink jet printing, or other similar printing, spreading, dispensing, or spraying methods.
  • the adhesive 22 is applied in a pattern such that after the die 21 is attached to the substrate 20 the adhesive 22 completely covers the active surface 211 of the die 21, except for the conductive area.
  • the conductive area is left free of adhesive 22 to enable alignment with the opening 200 in the substrate 20 and wire bonding to the bond pads 212 contained on the conductive area.
  • the amount of adhesive and specific printing pattern required to achieve coverage of the die is dependent on the adhesive flow, bonding pressure, and other similar parameters and may be determined by one skilled in the art without undue experimentation.
  • the thickness of the adhesive will typically be between 10 and 250 microns when wet.
  • Figure 12A illustrates a printing pattern on a substrate 20 for one embodiment of the invention in which the adhesive 22 is applied to the upper surface 201 of the substrate 20 such that the adhesive 22 completely surrounds the openings
  • Figure 12B illustrates a printing pattern on a substrate 20 for one embodiment of the invention in which the adhesive 22 is applied to the upper surface
  • Figure 10 illustrates a printing pattern for another embodiment of the invention in which the adhesive 22 is applied to the active surface 211 of a wafer 26 in a pattern that covers the wafer (and therefore all of the dies after the wafer is singulated) except for conductive areas vacant of adhesive V leaving the conductive areas on the die exposed for aligning over the openings in the substrate.
  • the adhesive used to attach the die must be flow-able upon application to the substrate or wafer, so that it can be applied via stencil printing, screen printing, ink jet printing, or other similar printing, spreading, dispensing, or spraying methods.
  • the adhesive is not a pre-fabricated film or tape as might be applied as a pre-form, laminated, or punched onto the substrate.
  • the adhesive After application to either the wafer or the die the adhesive may be solidified, or B-staged, or cured such that it no longer has adequate flow for the application methods listed above.
  • the adhesive is a printable paste.
  • Selection of a suitable adhesive is dependent upon the die type and size, the substrate type, package geometry, and such downstream manufacturing variables as reflow temperatures and reliability required.
  • the adhesive typically will contain some type of polymer or curable resin, which could include a thermoplastic, a thermoset, an elastomer, a thermoset rubber, or a combination of these.
  • the adhesive may or may not contain solvent.
  • the polymer or curable resin will generally be a major component, excluding any fillers present.
  • a curing agent is any material or combination of materials that initiate, propagate, or accelerate cure of the adhesive and includes accelerators, catalysts, initiators, and hardeners.
  • the adhesive composition may also contain filler, in which case the filler will be present in an amount up to 95% of the total composition.
  • Resins and polymers used in the adhesive may be solid, liquid, or a combination of the two.
  • Suitable resins include epoxies, acrylates or methacrylates, maleimides, vinyl ethers, polyesters, poly(butadienes), polyimides, benzocyclobutene, siliconized olefins, silicone resins, styrene resins, cyanate ester resins, or polyolefins, or siloxanes.
  • solid aromatic bismaleimide (BMI) resin powders are included in the adhesive.
  • Suitable solid BMI resins are those having the structure O O
  • exemplary aromatic groups include:
  • n 1 - 3
  • Bismaleimide resins having these X bridging groups are commercially available, and can be obtained, for example, from Sartomer (USA) or HOS-Technic GmbH (Austria). [0069] In another embodiment, maleimide resins for use in the adhesive
  • compositions include those having the generic structure n in which n is to 3 and X 1 is an aliphatic or aromatic group.
  • exemplary X 1 entities include, poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether.
  • these types of resins are commercially available and can be obtained, for example, from National Starch and Chemical Company and Dainippon Ink and Chemical, Inc.
  • the maleimide resins are selected from the group consisting of
  • C 36 represents a linear or branched chain (with or without cyclic moieties) of 36 carbon atoms
  • Suitable acrylate resins include those having the generic structure [0076] n is 1 to 6, R 1 is -H or -CH 3 . and X 2 is an aromatic or aliphatic group. Exemplary X 2 entities include poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether.
  • the acrylate resins are selected from the group consisting of isobornyl acrylate, isobornyl methacrylate, lauryl acrylate, lauryl methacrylate, poly(butadiene) with acrylate functionality and poly(butadiene) with methacrylate functionality.
  • Suitable vinyl ether resins include those having the generic structure
  • n 1 to 6 and X 3 is an aromatic or aliphatic group.
  • Exemplary X 3 entities include poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether.
  • resins include cyclohenanedimethanol divinylether, dodecylvinylether, cyclohexyl vinylether, 2-ethylhexyl vinylether, dipropyleneglycol divinylether, hexanediol divinylether, octadecylvinylether, and butandiol divinylether available from International Speciality Products (ISP); Vectomer 4010, 4020, 4030, 4040, 4051 , 4210, 4220, 4230, 4060, 5015 available from Sigma-Aldrich, Inc.
  • ISP International Speciality Products
  • Suitable poly(butadiene) resins include poly(butadienes), epoxidized poly(butadienes), maleic poly(butadienes), acrylated poly(butadienes), butadiene- styrene copolymers, and butadiene-acrylonitrile copolymers.
  • Suitable epoxy resins include bisphenol, naphthalene, and aliphatic type epoxies.
  • Suitable epoxy resins include cycloaliphatic epoxy resins, bisphenol-A type epoxy resins, bisphenol-F type epoxy resins, epoxy novolac resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene-phenol type epoxy resins, reactive epoxy diluents, and mixtures thereof.
  • Suitable siliconized olefin resins are obtained by the selective hydrosilation reaction of silicone and divinyl materials, having the generic structure,
  • n ! is 2 or more
  • n 2 is 1 or more
  • n 1 >n 2 are commercially available and can be obtained, for example, from National Starch and Chemical Company.
  • Suitable silicone resins include reactive silicone resins having the generic structure [0083] in which n is 0 or any integer, X 4 and X 5 are hydrogen, methyl, amine, epoxy, carboxyl, hydroxy, acrylate, methacrylate, mercapto, phenol, or vinyl functional groups, R 2 and R 3 can be -H, - CH 3 , vinyl, phenyl, or any hydrocarbon structure with more than two carbons.
  • Suitable styrene resins include those resins having the generic structure
  • n 1 or greater
  • R 4 is -H or -CH 3
  • X 6 is an aliphatic group.
  • Exemplary X 3 entities include poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether. These resins are commercially available and can be obtained, for example, from National Starch and Chemical Company or Sigma-Aldrich Co. [0086] Suitable cyanate ester resins include those having the generic structure
  • I N C-O-+- X 7 ⁇ /n iin which n is 1 or larger, and X 7 is a hydrocarbon group.
  • exemplary X 7 entities include bisphenol, phenol or cresol novolac, dicyclopentadiene, polybutadiene, polycarbonate, polyurethane, polyether, or polyester.
  • Suitable polymers for the adhesive composition further include polyamide, phenoxy, polybenzoxazine, acrylate, cyanate ester, bismaleimide, polyether sulfone, polyimide, benzoxazine, vinyl ether, siliconized olefin, polyolefin, polybenzoxyzole, polyester, polystyrene, polycarbonate, polypropylene, polyvinyl chloride), polyisobutylene, polyacrylonitrile, poly(methyl methacrylate), polyvinyl acetate), poly(2-vinylpridine), cis-1 ,4-polyisoprene, 3,4-polychloroprene, vinyl copolymer, poly(ethylene oxide), poly(ethylene glycol), polyformaldehyde, polyacetaldehyde, poly(b-propiolacetone), poly(10-decanoate), poly(ethylene terephthalate), polycaprolactam, poly(11-undecanoamide), poly
  • suitable materials for inclusion in adhesive compositions include rubber polymers such as block copolymers of monovinyl aromatic hydrocarbons and conjugated diene, e.g., styrene-butadiene, styrene-butadiene-styrene (SBS), styrene- isoprene-styrene (SIS), styrene-ethylene-butylene-styrene (SEBS), and styrene- ethyiene-propylene-styrene (SEPS).
  • rubber polymers such as block copolymers of monovinyl aromatic hydrocarbons and conjugated diene, e.g., styrene-butadiene, styrene-butadiene-styrene (SBS), styrene- isoprene-styrene (SIS), styrene-ethylene-butylene-styrene (SEBS),
  • Suitable materials for inclusion in adhesive compositions include ethylene-vinyl acetate polymers, other ethylene esters and copolymers, e.g., ethylene methacrylate, ethylene n-butyl acrylate and ethylene acrylic acid; polyolefins such as polyethylene and polypropylene; polyvinyl acetate and random copolymers thereof; polyacrylates; polyamides; polyesters; and polyvinyl alcohols and copolymers thereof.
  • Thermoplastic rubbers suitable for inclusion in the adhesive composition include carboxy terminated butadiene-nitrile (CTBN)/epoxy adduct, acrylate rubber, vinyl-terminated butadiene rubber, and nitriie butadiene rubber (NBR).
  • CTBN epoxy adduct consists of about 20-80 wt% CTBN and about 20-80 wt% diglycidyl ether bisphenol A: bisphenol A epoxy (DGEBA).
  • a variety of CTBN materials are available from Noveon Inc., and a variety of bisphenol A epoxy materials are available from Dainippon Ink and Chemicals, Inc., and Shell Chemicals.
  • NBR rubbers are commercially available from Zeon Corporation.
  • Siloxanes suitable for inclusion in the adhesive formulation include elastomeric polymers comprising a backbone and pendant from the backbone at least one siloxane moiety that imparts permeability, and at least one reactive moiety capable of reacting to form a new covalent bond,.
  • siloxanes examples include elastomeric polymers prepared from: 3-(tris(trimethylsilyloxy)silyl)-propyl methacrylate, n-butyl acrylate, glycidyl methacrylate, acrylonitrile, and cyanoethyl acrylate; 3-(tris(trimethylsilyloxy)siiy!)-propyl methacrylate, n-butyl acrylate, glycidyl methacrylate, and acrylonitrile; and 3-(tris(trimethylsilyloxy)silyl)-propyl methacrylate, n-butyl acrylate, glycidyl methacrylate, and cyanoethyl acrylate.
  • curing agent is required for the adhesive composition, its selection is dependent on the polymer chemistry used and the processing conditions employed.
  • the compositions may use aromatic amines, alycyclic amines, aliphatic amines, tertiary phosphines, triazines, metal salts, aromatic hydroxyl compounds, or a combination of these.
  • Such catalysts include imidazoles, such as 2-methylimidazole, 2-undecylimidazole, 2-heptadecyl imidazole, 2-phenylimidazole, 2-ethyl 4-methylimidazole, 1-benzyl-2-methylimidazole, 1-propyl- 2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4- methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-guanaminoethyl-2-methylimidazole and addition product of an imidazole and trimellitic acid; tertiary amines, such as N,N-dimethyl benzylamine, N, N- dimethylaniline, N,N-dimethyltoluidine, N,N-dimethyl-p-anisidine, p
  • a curing accelerator may be selected from the group consisting of triphenylphosphine, alkyl-substituted imidazoles, imidazolium salts, onium salts, quartenary phosphonium compounds, onium borates, metal chelates, 1,8-diazacycIo[5.4.0]undex-7-ene or a mixture thereof.
  • the curing agent can be either a free radical initiator or cationic initiator, depending on whether a radical or ionic curing resin is chosen. If a free radical initiator is used, it will be present in an effective amount. An effective amount typically is 0.1 to 10 percent by weight of the organic compounds
  • Free-radical initiators include peroxides, such as butyl peroctoates and dicumyl peroxide, and azo compounds, such as 2,2'-azobis(2- methyl-propanenitrile) and 2,2'-azobis(2-methyl-butanenitrile).
  • a cationic initiator is used, it will be present in an effective amount.
  • An effective amount typically is 0.1 to 10 percent by weight of the organic compounds
  • Suitable cationic curing agents include dicyandiamide, phenol novolak, adipic dihydrazide, diallyl melamine, diamino malconitrile, BF3-amine complexes, amine salts and modified imidazole compounds.
  • Metal compounds also can be employed as cure accelerators for cyanate ester systems and include, but are not limited to, metal napthenates, metal acetylacetonates (chelates), metal octoates, metal acetates, metal halides, metal imidazole complexes, and metal amine complexes.
  • cure accelerators that may be included in the adhesive formulation include triphenylphosphine, alkyl-substituted imidazoles, imidazolium salts, and onium borates.
  • both cationic and free radical initiation may be desirable, in which case both free radical cure and ionic cure resins can be used in the composition.
  • These compositions would contain effective amounts of initiators for each type of resin. Such a composition would permit, for example, the curing process to be started by cationic initiation using UV irradiation, and in a later processing step, to be completed by free radical initiation upon the application of heat.
  • One or more fillers may be included in the adhesive composition and usually are added for improved Theological properties and stress reduction. Since the adhesive comes in contact with the active side of the die the filler will be electrically nonconductive.
  • nonconductive fillers examples include alumina, aluminum hydroxide, silica, vermiculite, mica, wollastonite, calcium carbonate, titania, sand, glass, barium sulfate, zirconium, carbon black, organic fillers, and halogenated ethylene polymers, such as, tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, vinylidene chloride, and vinyl chloride.
  • the filler particles may be of any appropriate size ranging from nano size to several mm. The choice of such size for any particular package configuration is within the expertise of one skilled in the art. Filler may be present in an amount from 0 to 95% by weight of the total composition.
  • the adhesive formulation includes spacers, which are particles added for the purpose of controlling the bondline to a predetermined thickness. Selection of appropriate spacers will depend on the package configuration and adhesive formulation and may be made by one skilled in the art without undue experimentation. Suitable spacers include but are not limited to silica, Teflon, polymeric or elastomeric materials. They may range in size from 25 to 150 microns and will be used in an effective amount.
  • a coupling agent may be added to the adhesive composition.
  • coupling agents are silanes, for example, epoxy-type silane coupling agent, amine-type silane coupling agent, or mercapto-type silane coupling agent.
  • Coupling agents if used, will be used in an effective amount.
  • a typical effective amount is an amount up to 5% by weight.
  • a surfactant may be added to the adhesive composition.
  • Suitable surfactants include silicones, polyethylene glycol, polyoxyethylene/polyoxypropylene block copolymers, ethylene diamine based polyoxyethylene/polyoxypropylene block copolymers, polyol-based polyoxyalkylenes, fatty alcohol-based polyoxyalkylenes, and fatty alcohol polyoxyalkylene alkyl ethers.
  • Surfactants, if used, will be used in an effective amount: a typical effective amount is an amount up to 5% by weight.
  • a wetting agent may be included in the adhesive composition.
  • Wetting agent selection will depend on the application requirements and the resin chemistry utilized. Wetting agents, if used, will be used in an effective amount: a typical effective amount is up to 5% by weight.
  • suitable wetting agents include Fluorad FC-4430 Fluorosurfactant available from 3M, Clariant Fluowet OTN, BYK W-990, Surfynol 104 Surfactant, Crompton Silwet L-7280, Triton X100 available from Rhom and Haas, Propylene glycol with a preferable Mw greater than 240, Gama-Butyrolactone, castor oil, glycerin or other fatty acids, and silanes.
  • a flow control agent may be included in the adhesive composition.
  • Flow control agent selection will depend on the application requirements and resin chemistry employed.
  • Flow control agents, if used, will be present in an effective amount: an effective amount is an amount up to 5% by weight.
  • suitable flow control agents include Cab-O-Sil TS720 available from Cabot, Aerosil R202 or R972 available from Degussa, fumed silicas, fumed aluminas, or fumed metal oxides.
  • an adhesion promoter may be included in the adhesive composition.
  • Adhesion promoter selection will depend on the application requirements and resin chemistry employed. Adhesion promoters, if used, will be used in an effective amount: an effective amount is an amount up to 5% by weight.
  • adhesion promoters examples include: silane coupling agents such as Z6040 epoxy silane or Z6020 amine silane available from Dow Corning; A186 Silane, A187 Silane, A174 Silane, or A1289 available from OSI Silquest; Organosilane SI264 available from Degussa; Johoku Chemical CBT-1 Carbobenzotriazole available from Johoku Chemical; functional benzotriazoles; thiazoles; titanates; and zirconates.
  • an air release agent may be added to the adhesive composition. Air release agent selection will depend on the application requirements and resin chemistry employed.
  • Air release agents if used, will be used in an effective amount: an effective amount will be an amount up to 5% by weight.
  • suitable air release agents include Antifoam 1400 available from Dow Corning, DuPont Modoflow, and BYK A-510.
  • compositions are formulated with tackifying resins in order to improve adhesion and introduce tack;
  • tackifying resins include naturally-occurring resins and modified naturally-occurring resins; polyterpene resins; phenolic modified terpene resins; coumarons-indene resins; aliphatic and aromatic petroleum hydrocarbon resins; phthalate esters; hydrogenated hydrocarbons, hydrogenated rosins and hydrogenated rosin esters.
  • diluents such as liquid polybutene or polypropylene
  • petroleum waxes such as paraffin and microcrystalline waxes, polyethylene greases, hydrogenated animal, fish and vegetable fats, mineral oil and synthetic waxes, naphthenic or paraffinic mineral oils.
  • additives such as stabilizers, antioxidants, impact modifiers, and colorants, in types and amounts known in the art, may also be added to the adhesive composition.
  • Common solvents with a proper boiling point ranging from 25 0 C to 230 0 C may be used in the adhesive composition.
  • solvents that may be utilized include ketones, esters, alcohols, ethers, and other common solvents that are stable and dissolve the resins in the composition.
  • Suitable solvents include ⁇ -butyrolactone, propylene glycol methyl ethyl acetate (PGMEA), and 4-methyl-2-pentanone.
  • the adhesive After the adhesive is applied to the substrate or die it may be dried and/or B- staged in an optional process step.
  • the adhesive is hardened to a non-tacky state so that the substrate, wafer, or die may be stored and/or sent to a separate location before the semiconductor die is attached.
  • the adhesive is hardened sufficiently to enable the adhesive-coated substrates, dies, or wafers, to be stacked on top of one another and stored without the use of interleafs.
  • the hardening of the adhesive may be accomplished in numerous ways, depending on the adhesive formulation employed.
  • the adhesive is a thermoplastic that is applied at a temperature above its melting point such that it is in a flow-able state.
  • the adhesive is hardened by cooling the adhesive below the melting point and/or softening point of the adhesive.
  • the adhesive contains at least a liquid thermoset resin and a solvent.
  • the adhesive is hardened to a non-tacky, or very low flow, state, by heating the adhesive and substrate sufficiently to evaporate the solvent and partially cure the thermoset resin or resins.
  • the adhesive contains a solid thermoset resin dissolved in a solvent. After application to the substrate the adhesive will be hardened to a non-tacky, or very low flow, state by heating the adhesive and substrate sufficiently to evaporate the solvent, leaving a non-tacky thermoset resin coating on the substrate.
  • the adhesive contains at least one liquid thermoset resin. After application to the substrate the adhesive will be hardened to a non-tacky, or very low flow, state by heating the adhesive and substrate sufficiently to partially advance the thermoset resin to a non-tacky, or very low flow, state.
  • the adhesive might also contain a combination of resins that could be dried, B-staged, and cured with a combination of mechanisms. For instance, the formulation might be B-staged through the use of ultraviolet radiation and, in a downstream manufacturing step after die attach, cured through the use of heat.
  • the formulation might also contain a combination of resins that have two separate cure temperatures such that the adhesive could be hardened by heating the substrate at the first (and lower) temperature, causing the first resin to cure and the overall adhesive formulation to harden to a non-tacky state.
  • the second resin which has a second (and higher) curing temperature, would be cured in a subsequent processing step after the die is attached.
  • the adhesive may or may not require curing. If the adhesive does require curing the cure may be accomplished either as an individual process step, or in conjunction with another processing operation such as solder reflow or wire bonding.
  • the B-staging temperature will generally be within a range of 8O 0 C to 200 0 C, and B-staging will be effected within a time period ranging from one minute to two hours, depending on the particular adhesive formulation chosen.
  • the time and temperature B-staging profile for each adhesive composition will vary, and different compositions can be designed to provide the B- staging profile that will be suited to the particular industrial manufacturing process.
  • the adhesive is not hardened prior to die attach. In this case the die is mounted onto the substrate while the adhesive is still in a flow- able state. This would enable the formation of a fillet around the die when the die is pressed into the adhesive.
  • Figure 13 illustrates an exemplary printing pattern for another embodiment of the invention in which the adhesive 22 is applied on the top surface 201 a substrate 20 in such a fashion that there is a small vacant flow area F which is not coated with adhesive 22, peripherally around the substrate opening 200.
  • the adhesive flow enables formation of the fillet around the outside of the die.
  • the adhesive flow also causes the adhesive 22 to flow inward into the vacant flow area F around the opening 200, such that the adhesive 22 completely covers the active surface of the die, exclusive of the conductive (wire bond pad) area, i.e., it would not flow into the opening 200 in the substrate 20.
  • a curing step is utilized for the die attach adhesive, it may be done prior to wire bonding, during wire bonding, or it may be done after wire bonding and encapsulation.
  • Die attach adhesive cure may be a separate process step, or it may be done at the same time as the curing process for the encapsulant [0122]
  • the cure temperature will generally be within a range of 80°-250°C, and curing will be effected within a time period ranging from few seconds or up to 120 minutes, depending on the particular resin chemistry and curing agents chosen.
  • the time and temperature curing profile for each adhesive composition will vary, and different compositions can be designed to provide the curing profile that will be suited to the particular industrial manufacturing process.
  • the adhesive may be cured by thermal exposure, ultraviolet (UV) irradiation, or a combination of these.
  • the curing conditions for each adhesive composition will vary, and different compositions can be designed to provide the curing profile that will be suited to the particular industrial manufacturing process.
  • the adhesive has a work life of at least two months after it has been B-staged. This long work life may be achieved by any means typically used to prolong the work life of dried or partially advanced adhesive including, but not limited to, the use of one ore more of the following in the adhesive formulation: (i) at least one latent curing agent, (ii) a high concentration of thermoplastic resin, and (iii) a high molecular weight resin.
  • a plurality of wire bonds 23 are formed through the opening 200 of the substrate 20 in a wire-bonding process.
  • the bonding wires 23 are bonded to the exposed wire bond pads 212 on the conductive area of the die 21, through the corresponding opening 200 of the substrate 20, to the wire bond pads 203 on the lower surface 202 of the substrate 20.
  • the active surface 211 of the die 21 can be electrically connected to the lower surface 202 of the substrate.
  • the bonding wires 23 are composed of any metal that will conduct electrical signals, such as gold.
  • the encapsulant 25 is formed over the wire bonds 23 on the lower surface 202 of the substrate 20 such that it surrounds, or encapsulates, the bonding wires 23 and fills the opening 200 in the substrate 20.
  • the encapsulant 25 may be applied through dispensing, potting, printing, molding, or other similar methods.
  • the encapsulant 25 may be any material that will protect the bonding wires 23 during subsequent manufacturing process steps and package use including, but not limited to, epoxies and silicones.
  • the encapsulant 25 is cured at conditions tailored to the encapsulant composition selected. The time and temperature curing profile for each encapsulant composition will vary, and different compositions can be designed to provide the curing profile that will be suited to the particular industrial manufacturing process.
  • the solder balls 24 are implanted on the lower surface 202 of the substrate 20 at an area outside the encapsulant 25.
  • the solder balls 24 may be composed of any conductive metal typically used for forming electrical connections between the package and, for instance, a circuit board.
  • This package is specifically characterized by the absence of an encapsulant on the back and/or sides of the die. Therefore, molding of the package is not required.
  • Figures 9A through 9E are presented to further illustrate this invention and show top views of a substrate in various stages, prepared according to the process of one embodiment this invention.
  • Figure 9A shows the top surface 201 of the bare substrate 20.
  • Figure 9B shows the top surface 201 of the substrate 20, after adhesive 22 deposition.
  • Figure 9C shows the top surface 201 of the substrate 20, which has adhesive 22 on it, after the dies 21 have been attached.
  • Figure 9D shows the bottom surface 202 of the substrate 20 after wire bonds 23 have been formed through the openings 200.
  • Figure 9E shows the bottom surface 202 of the substrate

Abstract

A board-on-chip (BOC) type semiconductor package comprises a substrate with an opening and a semiconductor die with a conductive area on its active surface. The die is mounted onto the substrate with the active surface facing the upper surface of the substrate and completely covering the opening in the substrate, The conductive area of the active surface of the die is exposed to the opening in the substrate. The die is joined to the substrate using an adhesive and is electrically connected to the substrate with wire bonds through the opening of the substrate. The wire bonds are protected with an encapsulant, which fills the opening in the substrate. Solder balls are implanted on the lower surface of the substrate at an area outside of the encapsulant. The package is characterized by the absence of encapsulant for the inactive side of the die and the absence of an encapsulant for the sides of the die.

Description

BOARD ON CHIP PACKAGE AND PROCESS FOR MAKING SAME
FIELD OF THE INVENTION
[0001] This invention relates to a semiconductor package and a process for its manufacture.
BACKGROUND OF THE INVENTION
[0002] A recent development in semiconductor packaging technology for DRAM
(dynamic random access memory) memory devices is the board-on-chip, or BOC package. These packages are also called window-type semiconductor packages and comprise a substrate formed with an opening penetrating through the same, a semiconductor chip or die mounted over the opening on an upper surface of the substrate by means of an adhesive in a face-down manner such that the active surface of the chip faces toward the substrate and is partially exposed to the opening.
A plurality of bonding wires electrically connect the active surface of the die, through the opening, to the lower surface of the substrate. A first encapsulant is formed on the lower surface of the substrate for filling the opening and encapsulating the bonding wires and a second encapsulant is formed on the upper surface of the substrate for encapsulating the back and/or sides of the chip. A plurality of solder balls are attached to the lower surface of the substrate and positioned outside the first encapsulant.
[0003] In practice, BOC packages can be manufactured using at least two different methods. In one method a printable adhesive paste is applied to a substrate and B- staged to a non-tacky state prior to die attach. Typically, several dies are mounted on a single substrate so that multiple packages can be manufactured from a single board. After molding and solder ball attach the packages are separated from one another to yield a single package. Figure 1 shows a top view and Figure 2 shows a cross-section view of a package in a typical embodiment of this method wherein the adhesive 12 is printed on the top surface 101 of the substrate 10 in a pattern which allows for the die 11 to be mounted over the openings 100 in the substrate 10. After the die 11 is attached over the adhesive 12, wire bonds 13 are formed through the opening 100, from the wire bond pads 112 on the active side 111 of the die 11 to the bottom side 102 of the substrate 10.
[0004] Then encapsulant 15 is applied over the wire bonds 13, the inactive side 110 of the die 11, and the sides 113 of the die 11 in a molding process. After molding, solder balls 14 are applied to the bottom side 102 of the substrate 10 and the packages are separated from one another in a sawing operation. Figure 3 shows a cross-section of a package representing another typical embodiment of this method wherein the inactive side 110 of the die 11 is not encapsulated, but the sides 113 of the die 11 are encapsulated.
[0005] This conventional approach has several drawbacks. As shown in Figures 1 and 2, the adhesive 12 is not printed along the entire perimeter of the opening 100, leaving gaps G between the active surface 111 of the die 11 and the upper surface 101 of the substrate 10. These gaps G in adhesive 12 necessitate the use of an encapsulant 15 on the inactive side and/or sides of the die, since, during the encapsualation of the wire bonds 13, the encapsulant 15 will flow between the substrate 10 and die 11 and come out along the sides 113 and/or inactive side 110 of the die 11. Furthermore, the inactive side110 and/or sides 113 of the die 11 are encapsulated in a molding compound, and large areas of molding can result in substrate warpage due to thermal stresses inherent in the molding process. This necessitates that the dies be arranged in a configuration that allows for stress release of the substrate during the molding process. [0006] Figure 4A shows a typical configuration that allows for multiple packages to be produced from a single substrate 10. In this configuration, the adhesive 12 is printed in areas around the openings 100 in the substrate 10, so that dies may later be mounted onto the adhesive 12 in position to cover the openings 100. In this configuration stress release is provided by incorporating substrate area that is not molded between blocks of packages that are molded, including a slit 104 in the substrate 10 in an area between blocks of molded packages. Figure 4B is an enlarged view of this configuration, showing that the stress release area provided by the slits 104 necessitate the use of significantly more substrate area than is required for the memory packages themselves. As the substrate 10 is one of the more expensive materials used in the memory package, this waste is highly undesirable. Finally, the temperature and pressure inherent in the molding process places thermal stress on the semiconductor die, which can lead to low device yield. [0007] Figure 5 shows a top view and Figure 6 shows a cross-sectional view of a BOC package manufactured using a second method. In this method a tape adhesive 17, having an aperture corresponding in position to the opening 100 of the substrate, is applied over the tape attach area 105 of the top surface 101 of the substrate 10, with the aperture of the adhesive tape aligned with the opening of the substrate. The adhesive tape 17 is thus interposed between the active surface 111 of the die 11 and the upper surface 101 of the substrate without any formation of gaps between the die 11 and the substrate 10. After the die 11 is attached over the tape adhesive 17, wire bonds 13 are formed through the opening 100, from the wire bond pads 112 on the active side 111 of the die 11 to the bottom side 102 of the substrate 10. Then encapsulant 15 is applied over the wire bonds 13 in one step and a second encapsulant 16 is applied over the sides 113 of the die 11 in a molding process. After molding, solder balls 14 are applied to the bottom side 102 of the substrate 10 and the packages are separated from one another in a sawing operation. [0008] In another embodiment encapsulant is applied to the inactive side of the die as well as the sides of the die. Although this method eliminates the problem of the gaps between the active surface of the die and the upper surface of the substrate due to areas uncovered by the adhesive and adjacent to the opening of the substrate, it does have significant drawbacks. First, tape adhesives are much more expensive to use than flow-able adhesives such as printable pastes. Second, the die may not be placed in perfect alignment over the tape, which can lead to the presence of some gap under the die. Finally, this method requires encapsulation of the sides and/or back side of the die in a molding process. Therefore, as in the method described above, there is significant substrate waste, and thermal stress on the die. [0009] It would be highly advantageous to have a semiconductor package and a process for the manufacture of that package that would overcome the drawbacks of both of these methods by enabling the use of flow-able pastes for die attach, eliminating gaps between the active surface of the die and the upper surface of the substrate, reducing substrate waste, and eliminating the thermal stress placed on the die during the molding process used to encapsulate the back and/or sides of the die. SUMMARY OF THE INVENTION
[0010] This invention is a semiconductor package comprising: (a) a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; (b) a semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side, the semiconductor die mounted onto the substrate with the active side disposed over and completely covering the opening penetrating through the upper and lower surfaces of the substrate; (c) an adhesive disposed between and joining the upper surface of the substrate and the active side of the die such that the active side of the die, exclusive of the conductive areas, is completely covered by the adhesive; (d) a plurality of electrically conducting bonding wires connecting the conductive areas on the active side of the die, through the opening in the substrate, to the wire bond pads on the lower surface of the substrate; (e) an encapsulant applied onto the lower surface of the substrate, encapsulating the bonding wires and filling the opening of the substrate; and (f) a plurality of solder balls implanted on the lower surface of the substrate at an area outside the encapsulant; wherein the package is characterized by the absence of an encapsulant on the inactive side of the die and the absence of an encapsulant on the sides of the die.
[0011] In another embodiment this invention is a process for the manufacture of a semiconductor package comprising: (a) providing a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; (b) providing at least one semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side; (c) applying a flow-able adhesive in an adhesive pattern onto the upper surface of the substrate such that after the die is attached to the substrate the adhesive surrounds the opening and, inclusive of the opening, is at least as large as the footprint of the die, (d) optionally hardening the flow-able adhesive to a non-tacky state; (e) mounting the die onto the substrate with the active side disposed over and completely covering the opening through the upper and lower surfaces of the substrate, such that the conductive area on the active surface of the die is exposed to the opening of the substrate, and the active surface of the die, exclusive of the conductive area, is completely covered by the adhesive; (f) optionally curing the adhesive; (g) attaching a plurality of electrically conducting bonding wires connecting the conductive areas on the active side of the die, through the opening in the substrate, to the wire bond pads on the lower surface of the substrate; (h) applying an encapsulant onto the lower surface of the substrate, encapsulating the bonding wires and filling the opening of the substrate; (i) curing the encapsulant; and (j) implanting a plurality of solder balls on the lower surface of the substrate at an area outside the encapsulant; wherein the process is characterized by the absence of an encapsulation step for the inactive side of the die and the absence of an encapsulation step for the sides of the die. [0012] In a third embodiment this invention is a process for the manufacture of a semiconductor package comprising: (a) providing a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; (b) providing at least one semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side; (c) applying a flow-able adhesive in an adhesive pattern onto the active side of the die such that after the die is attached to the substrate the adhesive surrounds the opening and, inclusive of the opening, is at least as large as the footprint of the die; (d) optionally hardening the flow-able adhesive to a non-tacky state, (e) mounting the die onto the substrate with the active side disposed over and completely covering the opening through the upper and lower surfaces of the substrate, such that the conductive area on the active surface of the die is exposed to the opening of the substrate, and the active surface of the die, exclusive of the conductive area, is completely covered by the adhesive; (f) optionally curing the adhesive, (g) attaching a plurality of electrically conducting bonding wires connecting the conductive areas on the active side of the die, through the opening in the substrate, to the wire bond pads on the lower surface of the substrate; (h) applying an encapsulant onto the lower surface of the substrate, encapsulating the bonding wires and filling the opening of the substrate; (i) curing the encapsulant; and (j) implanting a plurality of solder balls on the lower surface of the substrate at an area outside the encapsulant;wherein the process is characterized by the absence of an encapsulation step for the inactive side of the die and the absence of an encapsulation step for the sides of the die. [0013] In a fourth embodiment this invention is a substrate for the manufacture of board-on-chip semiconductor packages which comprises a top surface, a bottom surface opposed to the top surface, and openings penetrating through the top surface and the bottom surface; which is characterized by the absence of a mold stress relief area.
[0014] BRIEF DESCRIPTION OF THE FIGURES
[0015] The present invention can be more fully understood by reading the following detailed description, with reference made to the accompanying drawings, wherein:
[0016] FIGURE 1 (Prior Art), is a top view of a traditional semiconductor package
[0017] FIGURE 2 (Prior Art), is a cross-sectional view of a traditional semiconductor package
[0018] FIGURE 3 (Prior Art), is a cross-sectional view another embodiment of a traditional semiconductor package
[0019] FIGURE 4A (Prior Art) is a top view of a traditional printing pattern for
BOC-type packages on a substrate
[0020] FIGURE 4B (Prior Art) is a an expanded top view of a traditional printing pattern for BOC-type packages on a substrate
[0021] FIGURE 5 (Prior Art) is a top view of another embodiment of a traditional semiconductor package
[0022] FIGURE 6 (Prior Art) is a cross-sectional view of another embodiment of a traditional semiconductor package
[0023] FIGURE 7 is a top view of the inventive semiconductor package
[0024] FIGURE 8A is a cross-sectional view of one embodiment of the inventive semiconductor package [0025] FIGURE 8B is a cross-sectional view of another embodiment of the inventive semiconductor package
[0026] FIGURES 9A through 9E are top views of a substrate assembled according to the inventive process
[0027] FIGURES 10A and 10B illustrate a printing pattern on a wafer for another embodiment of the invention
[0028] FIGURE 11 is a top view of a substrate for BOC packaging characterized by the absence of a mold stress release area
[0029] FIGURES 12A and 12B are top views of substrates with adhesive printing patterns representing two additional embodiments of the invention
[0030] FIGURE 13 is a top view of a substrate with an adhesive printing pattern representing another embodiment of the invention
[0031] DEFINITIONS
[0032] The term "alkyl" as used herein refers to a branched or un-branched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl ("Me"), ethyl
("Et"), n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl, and the like. Preferred alkyl groups herein contain from 1 to 12 carbon atoms. [0033] By the term "effective amount" of a compound, product, or composition as provided herein is meant a sufficient amount of the compound, product or composition to provide the desired results. As will be pointed out below, the exact amount required will vary from package to package, depending on the particular compound, product or composition used, its mode of administration, and the like. Thus, it is not always possible to specify an exact amount; however, an effective amount may be determined by one of ordinary skill in the art using only routine experimentation.
[0034] As used herein, the term "suitable" is used to refer to a moiety that is compatible with the compounds, products, or compositions as provided herein for the stated purpose. Suitability for the stated purpose may be determined by one of ordinary skill in the art using only routine experimentation. [0035] As used herein, "substituted" is used to refer, generally, to a carbon or suitable heteroatom having a hydrogen or other atom removed and replaced with a further moiety. Moreover, it is intended that "substituted" refer to substitutions that do not change the basic and novel utility of the underlying compounds, products or compositions utilized in the present invention.
[0036] As used herein, "B-staging" (and its variants) is used to refer to the processing of a material by heat or irradiation so that if the material is solubilized or dispersed in a solvent, the solvent is evaporated off with or without partial curing of the material, or if the material is neat with no solvent, the material is partially cured to a tacky or more hardened state. If the material is a flow-able adhesive, B-staging will provide extremely low flow without fully curing, such that additional curing may be performed after the adhesive is used to join one article to another. The reduction in flow may be accomplished by evaporation of a solvent, partial advancement or curing of a resin or polymer, or both.
[0037] As used herein the term "printable paste" is any liquid adhesive that can be printed onto a surface such as a substrate, a die, or a wafer. [0038] DETAILED DESCRIPTION OF THE INVENTION
[0039] Figure 7 represents a top view and Figure 8A represents a cross-section view illustrating one embodiment of the semiconductor package according to the present invention. The substrate 20 has an upper surface 201 and a lower surface 202 opposed to the .upper surface, with at least one opening 200 formed to penetrate through the upper 201 and lower 202 surfaces of the substrate 20. The substrate contemplated for this invention is rigid or semi-rigid (not a flexible tape) primarily made of a conventional resin material including but not limited to BT resin, epoxy resin, and FR-4. The substrate may be any dimensions but will typically be between 20 mm x 100 mm and 100 mm x 250 mm, and between 0.1 and 0.6 mm thick. [0040] In one embodiment an adhesive application area 206 is defined on the upper surface 201 of the substrate 20 peripherally around the opening, such that the area 206, inclusive of the opening, is at least as large as the footprint of the die. [0041] In one embodiment the substrate is designed such that it does not have stress release areas for molding. Figure 11 illustrates a top view of one example of how the substrate can be configured, where the substrate 20 has a top surface 201 and a bottom surface opposed to the top surface and includes openings 200 penetrating through the top surface 201 and the bottom surface 202 through which wire bonds may be formed.. This substrate design is characterized by the absence of a mold stress relief area. One skilled in the art could contemplate many variations and similar arrangements that would have the same advantage of conserving substrate area, enabled by the fact that molding of the package to encapsulate the back and/or sides of the die is not necessary with the package and processes described in the present invention.
[0042] The semiconductor die 21, or chip, is mounted onto the substrate 20 such that the active side 211 of the die 21 is mounted over the flow-able adhesive 22, such that the adhesive 22 is interposed between the active surface 211 of the die 21 and the upper surface 201 of the substrate. The active surface 211 is larger than and completely covers the opening 200, allowing the conductive area(s) on the active surface 211 of the die 21 to be exposed to the opening 200 of the substrate 20. The active surface 211 of the die 21, exclusive of the conductive area(s), is completely covered by the flow-able adhesive 22 to be free of forming gaps between the die and the substrate.
[0043] The semiconductor chip, or die 21, can be any size and thickness and is, for instance, a silicon integrated circuit component such as a DRAM, having a thickness ranging from 0.05 to 0.4 mm. In other embodiments, the die 21 may be a silicon digital signal processor, or be made of gallium arsenide, indium phosphide or any other semiconductor material. The semiconductor die 21 is prepared with an active surface 211 (also known as top or front surface) where electronic elements and circuits are formed, and an inactive surface 210 (also known as a bottom or back surface) opposed to the active surface 211. The active surface 211 has a plurality of wire bond pads 212 formed on at least one conductive area, which are used for wire bonding the active surface 211 of the chip to wire bond pads 203 on the lower surface 202 of the substrate 20 to form electrical connections between the two. [0044] In one embodiment the semiconductor die has bonding pads in multiple locations, for instance, in both the center and edge of the die. In this embodiment the substrate includes multiple openings, to correspond to each of these bonding pad locations.
[0045] The adhesive 22 joins the upper surface 201 of the substrate 20 to the active side 211 of the die 21. The die 21 is positioned on the substrate 20 such that the conductive area on the die 21, which contains the wire bond pads 212, is over and completely covers the opening 200 in the substrate 20. In this way the die 21 is attached to the substrate 20 without any adhesive coverage gaps between the die 21 and the substrate 20, yet the conductive area is exposed so that wire bonds 23 may be formed on the bond pads 212 contained thereon.
[0046] In one embodiment the adhesive 22 is applied to the upper surface 201 of the substrate 20. In another embodiment the adhesive 22 is applied to the active side 211 of the die 21, before singulation from the wafer. In another embodiment the adhesive 22 is applied to the active side 211 of the die 21 after it has been singulated from the wafer.
[0047] The adhesive 22 may be applied to either the die 21 or the substrate 20 using any method which utilizes a flow-able adhesive, including but not limited to, stencil printing, screen printing, ink jet printing, or other similar printing, spreading, dispensing, or spraying methods. The adhesive 22 is applied in a pattern such that after the die 21 is attached to the substrate 20 the adhesive 22 completely covers the active surface 211 of the die 21, except for the conductive area. The conductive area is left free of adhesive 22 to enable alignment with the opening 200 in the substrate 20 and wire bonding to the bond pads 212 contained on the conductive area. The amount of adhesive and specific printing pattern required to achieve coverage of the die is dependent on the adhesive flow, bonding pressure, and other similar parameters and may be determined by one skilled in the art without undue experimentation. The thickness of the adhesive will typically be between 10 and 250 microns when wet.
[0048] Figure 12A illustrates a printing pattern on a substrate 20 for one embodiment of the invention in which the adhesive 22 is applied to the upper surface 201 of the substrate 20 such that the adhesive 22 completely surrounds the openings
200 in the substrate 20 and is at least as large as the footprint of the die, but which does not completely cover the upper surface 201 of the substrate 20. This embodiment might be employed to minimize adhesive usage. This type of printing pattern would result in a package as shown in the cross section Figure 8A, in which the adhesive 22 extends to the outside edge of the die 21, or very slightly beyond the edge.
[0049] Figure 12B illustrates a printing pattern on a substrate 20 for one embodiment of the invention in which the adhesive 22 is applied to the upper surface
201 of the entire substrate 20 except the openings 200. This embodiment might be employed to simplify the printing process, as fewer discrete printing elements would be required than for the pattern depicted in Figure 12A. The printing pattern illustrated in Figure 12B would result in a package as shown in the cross section Figure 8B, in which the adhesive 22 extends well beyond the outside edge of the die 21.
[0050] Figure 10 illustrates a printing pattern for another embodiment of the invention in which the adhesive 22 is applied to the active surface 211 of a wafer 26 in a pattern that covers the wafer (and therefore all of the dies after the wafer is singulated) except for conductive areas vacant of adhesive V leaving the conductive areas on the die exposed for aligning over the openings in the substrate. [0051] The adhesive used to attach the die must be flow-able upon application to the substrate or wafer, so that it can be applied via stencil printing, screen printing, ink jet printing, or other similar printing, spreading, dispensing, or spraying methods. The adhesive is not a pre-fabricated film or tape as might be applied as a pre-form, laminated, or punched onto the substrate. After application to either the wafer or the die the adhesive may be solidified, or B-staged, or cured such that it no longer has adequate flow for the application methods listed above. [0052] In one embodiment the adhesive is a printable paste. [0053] Selection of a suitable adhesive is dependent upon the die type and size, the substrate type, package geometry, and such downstream manufacturing variables as reflow temperatures and reliability required. The adhesive typically will contain some type of polymer or curable resin, which could include a thermoplastic, a thermoset, an elastomer, a thermoset rubber, or a combination of these. The adhesive may or may not contain solvent. The polymer or curable resin will generally be a major component, excluding any fillers present. Other components, typically used in adhesive compositions, may be added at the option of the practitioner; such other components include, but are not limited to, curing agents, fluxing agents, wetting agents, flow control agents, adhesion promoters, and air release agents. A curing agent is any material or combination of materials that initiate, propagate, or accelerate cure of the adhesive and includes accelerators, catalysts, initiators, and hardeners. The adhesive composition may also contain filler, in which case the filler will be present in an amount up to 95% of the total composition. [0054] Resins and polymers used in the adhesive may be solid, liquid, or a combination of the two. Suitable resins include epoxies, acrylates or methacrylates, maleimides, vinyl ethers, polyesters, poly(butadienes), polyimides, benzocyclobutene, siliconized olefins, silicone resins, styrene resins, cyanate ester resins, or polyolefins, or siloxanes.
[0055] In one embodiment, solid aromatic bismaleimide (BMI) resin powders are included in the adhesive. Suitable solid BMI resins are those having the structure O O
[0056] O O in which X is an aromatic group; exemplary aromatic groups include:
[0062]
[0065] in which n is 1 - 3,
[0068] Bismaleimide resins having these X bridging groups are commercially available, and can be obtained, for example, from Sartomer (USA) or HOS-Technic GmbH (Austria). [0069] In another embodiment, maleimide resins for use in the adhesive
composition include those having the generic structure n in which n is to 3 and X1 is an aliphatic or aromatic group. Exemplary X1 entities include, poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether. These types of resins are commercially available and can be obtained, for example, from National Starch and Chemical Company and Dainippon Ink and Chemical, Inc. [0070] In a further embodiment, the maleimide resins are selected from the group consisting of
[0071] in which C36 represents a linear or branched chain (with or without cyclic moieties) of 36 carbon atoms;
[0075] Suitable acrylate resins include those having the generic structure [0076] n is 1 to 6, R1 is -H or -CH3. and X2 is an aromatic or aliphatic group. Exemplary X2 entities include poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether. Commercially available materials include butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethyl hexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, alkyl (meth)acrylate, tridecyl (meth)acrylate, n-stearyl (meth)acrylate, cyclohexyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, 2-phenoxy ethyl(meth)acrylate, isobornyl(meth)acrylate, 1 ,4-butanediol di(meth)acrylate, 1.6 hexanediol di(meth)acrylate, 1 ,9-nonandiol di(meth)acrylate, perfluorooctylethyl (meth)acrylate, 1 ,10 decandiol di(meth)acrylate, nonylphenol polypropoxylate (meth)acrylate, and polypentoxylate tetrahydrofurfuryl acrylate, available from Kyoeisha Chemical Co., LTD; polybutadiene urethane dimethacrylate (CN302, NTX6513) and polybutadiene dimethacrylate (CN301, NTX6039, PRO6270) available from Sartomer Company, Inc; polycarbonate urethane diacrylate (ArtResin UN9200A) available from Negami Chemical Industries Co., LTD; acrylated aliphatic urethane oligomers (Ebecryl 230, 264, 265, 270,284, 4830, 4833, 4834, 4835, 4866, 4881 , 4883, 8402, 8800-20R, 8803, 8804) available from Radcure Specialities, Inc; polyester acrylate oligomers (Ebecryl 657, 770, 810, 830, 1657, 1810, 1830) available from Radcure Specialities, Inc.; and epoxy acrylate resins (CN104, 111, 112, 115, 116, 117, 118, 119, 120, 124, 136) available from Sartomer Company, Inc. In one embodiment the acrylate resins are selected from the group consisting of isobornyl acrylate, isobornyl methacrylate, lauryl acrylate, lauryl methacrylate, poly(butadiene) with acrylate functionality and poly(butadiene) with methacrylate functionality. [0077] Suitable vinyl ether resins include those having the generic structure
in which n is 1 to 6 and X3 is an aromatic or aliphatic group.
Exemplary X3 entities include poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether. Commercially available resins include cyclohenanedimethanol divinylether, dodecylvinylether, cyclohexyl vinylether, 2-ethylhexyl vinylether, dipropyleneglycol divinylether, hexanediol divinylether, octadecylvinylether, and butandiol divinylether available from International Speciality Products (ISP); Vectomer 4010, 4020, 4030, 4040, 4051 , 4210, 4220, 4230, 4060, 5015 available from Sigma-Aldrich, Inc. [0078] Suitable poly(butadiene) resins include poly(butadienes), epoxidized poly(butadienes), maleic poly(butadienes), acrylated poly(butadienes), butadiene- styrene copolymers, and butadiene-acrylonitrile copolymers. Commercially available materials include homopolymer butadiene (Ricon130, 131 , 134, 142, 150, 152, 153, 154, 156, 157, P30D) available from Sartomer Company, Inc; random copolymer of butadiene and styrene (Ricon 100, 181 , 184) available from Sartomer Company Inc.; maleinized poly(butadiene) (Ricon 130MA8, 130MA13, 130MA20, 131 MA5, 131 MA10, 131 MA17, 131 MA20, 156MA17) available from Sartomer Company, Inc.; acrylated poly(butadienes) (CN302, NTX6513, CN301 , NTX6039, PRO6270, Ricacryl 3100, Ricacryl 3500) available from Sartomer Inc.; epoxydized poly(butadienes) (Polybd 600, 605) available from Sartomer Company. Inc. and Epolead PB3600 available from Daicel Chemical Industries, Ltd; and acrylonitrile and butadiene copolymers (Hycar CTBN series, ATBN series, VTBN series and ETBN series) available from Hanse Chemical. [0079] Suitable epoxy resins include bisphenol, naphthalene, and aliphatic type epoxies. Commercially available materials include bisphenol type epoxy resins (Epiclon 830LVP, 830CRP, 835LV, 850CRP) available from Dainippon Ink & Chemicals, Inc.; naphthalene type epoxy (Epiclon HP4032) available from Dainippon Ink & Chemicals, Inc.; aliphatic epoxy resins (Araldite CY179, 184, 192, 175, 179) available from Ciba Specialty Chemicals; (Epoxy 1234, 249, 206) available from Union Carbide Corporation, and (EHPE-3150) available from Daicel Chemical Industries, Ltd. Other suitable epoxy resins include cycloaliphatic epoxy resins, bisphenol-A type epoxy resins, bisphenol-F type epoxy resins, epoxy novolac resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene-phenol type epoxy resins, reactive epoxy diluents, and mixtures thereof. [0080] Suitable siliconized olefin resins are obtained by the selective hydrosilation reaction of silicone and divinyl materials, having the generic structure,
[0081] in which n! is 2 or more, n2 is 1 or more and n1>n2. These materials are commercially available and can be obtained, for example, from National Starch and Chemical Company.
[0082] Suitable silicone resins include reactive silicone resins having the generic structure [0083] in which n is 0 or any integer, X4 and X5 are hydrogen, methyl, amine, epoxy, carboxyl, hydroxy, acrylate, methacrylate, mercapto, phenol, or vinyl functional groups, R2 and R3 can be -H, - CH3, vinyl, phenyl, or any hydrocarbon structure with more than two carbons. Commercially available materials include KF8012, KF8002, KF8003, KF-1001 , X-22- 3710, KF6001 , X-22-164C, KF2001 , X-22-170DX, X-22-173DX, X-22-174DX X-22- 176DX, KF-857, KF862, KF8001 , X-22-3367, and X-22-3939A available from Shin- Etsu Silicone International Trading (Shanghai) Co., Ltd. [0084] Suitable styrene resins include those resins having the generic structure
[0085] in which n is 1 or greater, R4 is -H or -CH3, and X6 is an aliphatic group. Exemplary X3 entities include poly(butadienes), poly(carbonates), poly(urethanes), poly(ethers), poly(esters), simple hydrocarbons, and simple hydrocarbons containing functionalities such as carbonyl, carboxyl, amide, carbamate, urea, or ether. These resins are commercially available and can be obtained, for example, from National Starch and Chemical Company or Sigma-Aldrich Co. [0086] Suitable cyanate ester resins include those having the generic structure
I N=C-O-+- X7 \ /n iin which n is 1 or larger, and X7 is a hydrocarbon group. Exemplary X7 entities include bisphenol, phenol or cresol novolac, dicyclopentadiene, polybutadiene, polycarbonate, polyurethane, polyether, or polyester. Commercially available materials include; AroCy L-10, AroCy XU366, AroCy XU371 , AroCy XU378, XU71787.02L, and XU 71787.07L, available from Huntsman LLC; Primaset PT30, Primaset PT30 S75, Primaset PT60, Primaset PT60S, Primaset BADCY, Primaset DA230S, Primaset MethylCy, and Primaset LECY, available from Lonza Group Limited; 2-allyphenol cyanate ester, 4-methoxyphenol cyanate ester, 2,2-bis(4- cyanatophenol)-1 ,1 ,1 ,3,3,3-hexafluoropropane, bisphenol A cyanate ester, diallylbisphenol A cyanate ester, 4-phenylphenol cyanate ester, 1 ,1 ,1-tris(4- cyanatophenyl)ethane, 4-cumylphenol cyanate ester, 1 ,1-bis(4- cyanateopheny!)ethane, 2,2,3,4,4,5,5,6,6,7,7-dodecafluorooctanedioI dicyanate ester, and 4,4'-bisphenol cyanate ester, available from Oakwood Products, Inc. [0087] Suitable polymers for the adhesive composition further include polyamide, phenoxy, polybenzoxazine, acrylate, cyanate ester, bismaleimide, polyether sulfone, polyimide, benzoxazine, vinyl ether, siliconized olefin, polyolefin, polybenzoxyzole, polyester, polystyrene, polycarbonate, polypropylene, polyvinyl chloride), polyisobutylene, polyacrylonitrile, poly(methyl methacrylate), polyvinyl acetate), poly(2-vinylpridine), cis-1 ,4-polyisoprene, 3,4-polychloroprene, vinyl copolymer, poly(ethylene oxide), poly(ethylene glycol), polyformaldehyde, polyacetaldehyde, poly(b-propiolacetone), poly(10-decanoate), poly(ethylene terephthalate), polycaprolactam, poly(11-undecanoamide), poly(m-phenylene- terephthalamide), poly(tetramethlyene-m-benzenesulfonamide), polyester polyarylate, poly(phenylene oxide), poly(phenylene sulfide), polysulfone, polyimide, polyetheretherketone, polyetherimide, fluorinated polyimide, polyimide siloxane, poly- iosindolo-quinazolinedione, polythioetherimide poly-phenyl-quinoxaline, polyquuinixalone, imide-aryl ether phenylquinoxaline copolymer, polyquinoxaline, polybenzimidazole, polybenzoxazole, polynorbornene, poly(arylene ethers), polysilane, parylene, benzocyclobutenes, hydroxy(benzoxazole) copolymer, poly(silarylene siloxanes), and polybenzimidazole. [0088] Other suitable materials for inclusion in adhesive compositions include rubber polymers such as block copolymers of monovinyl aromatic hydrocarbons and conjugated diene, e.g., styrene-butadiene, styrene-butadiene-styrene (SBS), styrene- isoprene-styrene (SIS), styrene-ethylene-butylene-styrene (SEBS), and styrene- ethyiene-propylene-styrene (SEPS).
[0089] Other suitable materials for inclusion in adhesive compositions include ethylene-vinyl acetate polymers, other ethylene esters and copolymers, e.g., ethylene methacrylate, ethylene n-butyl acrylate and ethylene acrylic acid; polyolefins such as polyethylene and polypropylene; polyvinyl acetate and random copolymers thereof; polyacrylates; polyamides; polyesters; and polyvinyl alcohols and copolymers thereof. [0090] Thermoplastic rubbers suitable for inclusion in the adhesive composition include carboxy terminated butadiene-nitrile (CTBN)/epoxy adduct, acrylate rubber, vinyl-terminated butadiene rubber, and nitriie butadiene rubber (NBR). In one embodiment the CTBN epoxy adduct consists of about 20-80 wt% CTBN and about 20-80 wt% diglycidyl ether bisphenol A: bisphenol A epoxy (DGEBA). A variety of CTBN materials are available from Noveon Inc., and a variety of bisphenol A epoxy materials are available from Dainippon Ink and Chemicals, Inc., and Shell Chemicals. NBR rubbers are commercially available from Zeon Corporation. [0091] Siloxanes suitable for inclusion in the adhesive formulation include elastomeric polymers comprising a backbone and pendant from the backbone at least one siloxane moiety that imparts permeability, and at least one reactive moiety capable of reacting to form a new covalent bond,. Examples of suitable siloxanes include elastomeric polymers prepared from: 3-(tris(trimethylsilyloxy)silyl)-propyl methacrylate, n-butyl acrylate, glycidyl methacrylate, acrylonitrile, and cyanoethyl acrylate; 3-(tris(trimethylsilyloxy)siiy!)-propyl methacrylate, n-butyl acrylate, glycidyl methacrylate, and acrylonitrile; and 3-(tris(trimethylsilyloxy)silyl)-propyl methacrylate, n-butyl acrylate, glycidyl methacrylate, and cyanoethyl acrylate. [0092] . If curing agent is required for the adhesive composition, its selection is dependent on the polymer chemistry used and the processing conditions employed. As curing agents, the compositions may use aromatic amines, alycyclic amines, aliphatic amines, tertiary phosphines, triazines, metal salts, aromatic hydroxyl compounds, or a combination of these. Examples of such catalysts include imidazoles, such as 2-methylimidazole, 2-undecylimidazole, 2-heptadecyl imidazole, 2-phenylimidazole, 2-ethyl 4-methylimidazole, 1-benzyl-2-methylimidazole, 1-propyl- 2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4- methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-guanaminoethyl-2-methylimidazole and addition product of an imidazole and trimellitic acid; tertiary amines, such as N,N-dimethyl benzylamine, N, N- dimethylaniline, N,N-dimethyltoluidine, N,N-dimethyl-p-anisidine, p-halogeno-N,N- dimethylaniline, 2-N-ethylanilino ethanol, tri-n-butylamine, pyridine, quinoline, N- methylmorpholine, triethanolamine, triethylenediamine, N, N, N', N'- tetramethylbutanediamine, N-methylpiperidine; phenols, such as phenol, cresol, xylenol, resorcine, and phloroglucin; organic metal salts, such as lead naphthenate, lead stearate, zinc naphthenate, zinc octolate, tin oleate, dibutyl tin maleate, manganese naphthenate, cobalt naphthenate, and acetyl aceton iron; and inorganic metal salts, such as stannic chloride, zinc chloride and aluminum chloride; peroxides, such as benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, acetyl peroxide, para- chlorobenzoyl peroxide and di-t-butyl diperphthalate; acid anhydrides, such as carboxylic acid anhydride, maleic anhydride, phthalic anhydride, lauric anhydride, pyromellitic anhydride, trimellitic anhydride, hexahydrophthalic anhydride; hexahydropyromellitic anhydride and hexahydrotrimellitic anhydride, azo compounds, such as azoisobutylonitrile, 2,2'-azobispropane, m.m'-azoxystyrene, hydrozones, and mixtures thereof. [0093] In another embodiment, a curing accelerator may be selected from the group consisting of triphenylphosphine, alkyl-substituted imidazoles, imidazolium salts, onium salts, quartenary phosphonium compounds, onium borates, metal chelates, 1,8-diazacycIo[5.4.0]undex-7-ene or a mixture thereof.
[0094] In another embodiment the curing agent can be either a free radical initiator or cationic initiator, depending on whether a radical or ionic curing resin is chosen. If a free radical initiator is used, it will be present in an effective amount. An effective amount typically is 0.1 to 10 percent by weight of the organic compounds
(excluding any filler). Free-radical initiators include peroxides, such as butyl peroctoates and dicumyl peroxide, and azo compounds, such as 2,2'-azobis(2- methyl-propanenitrile) and 2,2'-azobis(2-methyl-butanenitrile).
[0095] If a cationic initiator is used, it will be present in an effective amount. An effective amount typically is 0.1 to 10 percent by weight of the organic compounds
(excluding any filler). Suitable cationic curing agents include dicyandiamide, phenol novolak, adipic dihydrazide, diallyl melamine, diamino malconitrile, BF3-amine complexes, amine salts and modified imidazole compounds.
[0096] Metal compounds also can be employed as cure accelerators for cyanate ester systems and include, but are not limited to, metal napthenates, metal acetylacetonates (chelates), metal octoates, metal acetates, metal halides, metal imidazole complexes, and metal amine complexes.
[0097] Other cure accelerators that may be included in the adhesive formulation include triphenylphosphine, alkyl-substituted imidazoles, imidazolium salts, and onium borates.
[0098] In some cases, it may be desirable to use more than one type of cure for the adhesive composition. For example, both cationic and free radical initiation may be desirable, in which case both free radical cure and ionic cure resins can be used in the composition. These compositions would contain effective amounts of initiators for each type of resin. Such a composition would permit, for example, the curing process to be started by cationic initiation using UV irradiation, and in a later processing step, to be completed by free radical initiation upon the application of heat. [0099] One or more fillers may be included in the adhesive composition and usually are added for improved Theological properties and stress reduction. Since the adhesive comes in contact with the active side of the die the filler will be electrically nonconductive. Examples of suitable nonconductive fillers include alumina, aluminum hydroxide, silica, vermiculite, mica, wollastonite, calcium carbonate, titania, sand, glass, barium sulfate, zirconium, carbon black, organic fillers, and halogenated ethylene polymers, such as, tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, vinylidene chloride, and vinyl chloride. The filler particles may be of any appropriate size ranging from nano size to several mm. The choice of such size for any particular package configuration is within the expertise of one skilled in the art. Filler may be present in an amount from 0 to 95% by weight of the total composition. [0100] In one embodiment the adhesive formulation includes spacers, which are particles added for the purpose of controlling the bondline to a predetermined thickness. Selection of appropriate spacers will depend on the package configuration and adhesive formulation and may be made by one skilled in the art without undue experimentation. Suitable spacers include but are not limited to silica, Teflon, polymeric or elastomeric materials. They may range in size from 25 to 150 microns and will be used in an effective amount.
[0101] In another embodiment, a coupling agent may be added to the adhesive composition. Typically, coupling agents are silanes, for example, epoxy-type silane coupling agent, amine-type silane coupling agent, or mercapto-type silane coupling agent. Coupling agents, if used, will be used in an effective amount. A typical effective amount is an amount up to 5% by weight. [0102] In a further embodiment, a surfactant may be added to the adhesive composition. Suitable surfactants include silicones, polyethylene glycol, polyoxyethylene/polyoxypropylene block copolymers, ethylene diamine based polyoxyethylene/polyoxypropylene block copolymers, polyol-based polyoxyalkylenes, fatty alcohol-based polyoxyalkylenes, and fatty alcohol polyoxyalkylene alkyl ethers. Surfactants, if used, will be used in an effective amount: a typical effective amount is an amount up to 5% by weight.
[0103] In another embodiment a wetting agent may be included in the adhesive composition. Wetting agent selection will depend on the application requirements and the resin chemistry utilized. Wetting agents, if used, will be used in an effective amount: a typical effective amount is up to 5% by weight. Examples of suitable wetting agents include Fluorad FC-4430 Fluorosurfactant available from 3M, Clariant Fluowet OTN, BYK W-990, Surfynol 104 Surfactant, Crompton Silwet L-7280, Triton X100 available from Rhom and Haas, Propylene glycol with a preferable Mw greater than 240, Gama-Butyrolactone, castor oil, glycerin or other fatty acids, and silanes. [0104] In a further embodiment, a flow control agent may be included in the adhesive composition. Flow control agent selection will depend on the application requirements and resin chemistry employed. Flow control agents, if used, will be present in an effective amount: an effective amount is an amount up to 5% by weight. Examples of suitable flow control agents include Cab-O-Sil TS720 available from Cabot, Aerosil R202 or R972 available from Degussa, fumed silicas, fumed aluminas, or fumed metal oxides.
[0105] In another embodiment, an adhesion promoter may be included in the adhesive composition. Adhesion promoter selection will depend on the application requirements and resin chemistry employed. Adhesion promoters, if used, will be used in an effective amount: an effective amount is an amount up to 5% by weight. Examples of suitable adhesion promoters include: silane coupling agents such as Z6040 epoxy silane or Z6020 amine silane available from Dow Corning; A186 Silane, A187 Silane, A174 Silane, or A1289 available from OSI Silquest; Organosilane SI264 available from Degussa; Johoku Chemical CBT-1 Carbobenzotriazole available from Johoku Chemical; functional benzotriazoles; thiazoles; titanates; and zirconates. [0106] In a further embodiment, an air release agent (defoamer) may be added to the adhesive composition. Air release agent selection will depend on the application requirements and resin chemistry employed. Air release agents, if used, will be used in an effective amount: an effective amount will be an amount up to 5% by weight. Examples of suitable air release agents include Antifoam 1400 available from Dow Corning, DuPont Modoflow, and BYK A-510.
[0107] In some embodiments these compositions are formulated with tackifying resins in order to improve adhesion and introduce tack; examples of tackifying resins include naturally-occurring resins and modified naturally-occurring resins; polyterpene resins; phenolic modified terpene resins; coumarons-indene resins; aliphatic and aromatic petroleum hydrocarbon resins; phthalate esters; hydrogenated hydrocarbons, hydrogenated rosins and hydrogenated rosin esters. [0108] In some embodiments other components may be included in the adhesive composition, for example, diluents such as liquid polybutene or polypropylene; petroleum waxes such as paraffin and microcrystalline waxes, polyethylene greases, hydrogenated animal, fish and vegetable fats, mineral oil and synthetic waxes, naphthenic or paraffinic mineral oils.
[0109] Other additives, such as stabilizers, antioxidants, impact modifiers, and colorants, in types and amounts known in the art, may also be added to the adhesive composition.
[0110] Common solvents with a proper boiling point ranging from 25 0C to 230 0C may be used in the adhesive composition. Examples of solvents that may be utilized include ketones, esters, alcohols, ethers, and other common solvents that are stable and dissolve the resins in the composition. Suitable solvents include γ-butyrolactone, propylene glycol methyl ethyl acetate (PGMEA), and 4-methyl-2-pentanone.
[0111] After the adhesive is applied to the substrate or die it may be dried and/or B- staged in an optional process step. In one embodiment of the invention the adhesive is hardened to a non-tacky state so that the substrate, wafer, or die may be stored and/or sent to a separate location before the semiconductor die is attached.
Typically, the adhesive is hardened sufficiently to enable the adhesive-coated substrates, dies, or wafers, to be stacked on top of one another and stored without the use of interleafs. The hardening of the adhesive may be accomplished in numerous ways, depending on the adhesive formulation employed.
[0112] In one embodiment the adhesive is a thermoplastic that is applied at a temperature above its melting point such that it is in a flow-able state. In this case the adhesive is hardened by cooling the adhesive below the melting point and/or softening point of the adhesive.
[0113] In another embodiment the adhesive contains at least a liquid thermoset resin and a solvent. In this embodiment the adhesive is hardened to a non-tacky, or very low flow, state, by heating the adhesive and substrate sufficiently to evaporate the solvent and partially cure the thermoset resin or resins.
[0114] In another embodiment the adhesive contains a solid thermoset resin dissolved in a solvent. After application to the substrate the adhesive will be hardened to a non-tacky, or very low flow, state by heating the adhesive and substrate sufficiently to evaporate the solvent, leaving a non-tacky thermoset resin coating on the substrate.
[0115] In another embodiment the adhesive contains at least one liquid thermoset resin. After application to the substrate the adhesive will be hardened to a non-tacky, or very low flow, state by heating the adhesive and substrate sufficiently to partially advance the thermoset resin to a non-tacky, or very low flow, state. [0116] One skilled in the art would appreciate that the adhesive might also contain a combination of resins that could be dried, B-staged, and cured with a combination of mechanisms. For instance, the formulation might be B-staged through the use of ultraviolet radiation and, in a downstream manufacturing step after die attach, cured through the use of heat. The formulation might also contain a combination of resins that have two separate cure temperatures such that the adhesive could be hardened by heating the substrate at the first (and lower) temperature, causing the first resin to cure and the overall adhesive formulation to harden to a non-tacky state. In this case the second resin, which has a second (and higher) curing temperature, would be cured in a subsequent processing step after the die is attached. [0117] The adhesive may or may not require curing. If the adhesive does require curing the cure may be accomplished either as an individual process step, or in conjunction with another processing operation such as solder reflow or wire bonding. [0118] If a B-staging step is utilized, the B-staging temperature will generally be within a range of 8O0C to 2000C, and B-staging will be effected within a time period ranging from one minute to two hours, depending on the particular adhesive formulation chosen. The time and temperature B-staging profile for each adhesive composition will vary, and different compositions can be designed to provide the B- staging profile that will be suited to the particular industrial manufacturing process. [0119] In an alternative embodiment the adhesive is not hardened prior to die attach. In this case the die is mounted onto the substrate while the adhesive is still in a flow- able state. This would enable the formation of a fillet around the die when the die is pressed into the adhesive. The flow of the adhesive and the pressure used to mount the die may be tailored to give the desired amount of fillet for each specific package design. In this embodiment care must be taken to avoid flow of the adhesive into the opening in the substrate, as this would interfere with wire bonding. [0120] Figure 13 illustrates an exemplary printing pattern for another embodiment of the invention in which the adhesive 22 is applied on the top surface 201 a substrate 20 in such a fashion that there is a small vacant flow area F which is not coated with adhesive 22, peripherally around the substrate opening 200. When the die is attached the adhesive flow enables formation of the fillet around the outside of the die. The adhesive flow also causes the adhesive 22 to flow inward into the vacant flow area F around the opening 200, such that the adhesive 22 completely covers the active surface of the die, exclusive of the conductive (wire bond pad) area, i.e., it would not flow into the opening 200 in the substrate 20.
[0121] If a curing step is utilized for the die attach adhesive, it may be done prior to wire bonding, during wire bonding, or it may be done after wire bonding and encapsulation. Die attach adhesive cure may be a separate process step, or it may be done at the same time as the curing process for the encapsulant [0122] For the die attach adhesive the cure temperature will generally be within a range of 80°-250°C, and curing will be effected within a time period ranging from few seconds or up to 120 minutes, depending on the particular resin chemistry and curing agents chosen. The time and temperature curing profile for each adhesive composition will vary, and different compositions can be designed to provide the curing profile that will be suited to the particular industrial manufacturing process. [0123] If the adhesive is curable it may be cured by thermal exposure, ultraviolet (UV) irradiation, or a combination of these. The curing conditions for each adhesive composition will vary, and different compositions can be designed to provide the curing profile that will be suited to the particular industrial manufacturing process. [0124] In one embodiment the adhesive has a work life of at least two months after it has been B-staged. This long work life may be achieved by any means typically used to prolong the work life of dried or partially advanced adhesive including, but not limited to, the use of one ore more of the following in the adhesive formulation: (i) at least one latent curing agent, (ii) a high concentration of thermoplastic resin, and (iii) a high molecular weight resin. Work life is tested by checking the flow of the adhesive at normal die attach conditions, after it has been stored at ambient conditions. If the adhesive is able to wet the die surface at normal die attach conditions, it is still within its worklife. If, however, the adhesive has inadequate. flow to effect wetting of the die it is not useful for attaching the die and is considered outside of its worklife.
[0125] A plurality of wire bonds 23 are formed through the opening 200 of the substrate 20 in a wire-bonding process. The bonding wires 23 are bonded to the exposed wire bond pads 212 on the conductive area of the die 21, through the corresponding opening 200 of the substrate 20, to the wire bond pads 203 on the lower surface 202 of the substrate 20. In this manner the active surface 211 of the die 21 can be electrically connected to the lower surface 202 of the substrate. The bonding wires 23 are composed of any metal that will conduct electrical signals, such as gold.
[0126] The encapsulant 25 is formed over the wire bonds 23 on the lower surface 202 of the substrate 20 such that it surrounds, or encapsulates, the bonding wires 23 and fills the opening 200 in the substrate 20. The encapsulant 25 may be applied through dispensing, potting, printing, molding, or other similar methods. The encapsulant 25 may be any material that will protect the bonding wires 23 during subsequent manufacturing process steps and package use including, but not limited to, epoxies and silicones. The encapsulant 25 is cured at conditions tailored to the encapsulant composition selected. The time and temperature curing profile for each encapsulant composition will vary, and different compositions can be designed to provide the curing profile that will be suited to the particular industrial manufacturing process.
[0127] The solder balls 24 are implanted on the lower surface 202 of the substrate 20 at an area outside the encapsulant 25. The solder balls 24 may be composed of any conductive metal typically used for forming electrical connections between the package and, for instance, a circuit board.
[0128] This package is specifically characterized by the absence of an encapsulant on the back and/or sides of the die. Therefore, molding of the package is not required.
[0129] Figures 9A through 9E are presented to further illustrate this invention and show top views of a substrate in various stages, prepared according to the process of one embodiment this invention. Figure 9A shows the top surface 201 of the bare substrate 20. Figure 9B shows the top surface 201 of the substrate 20, after adhesive 22 deposition. Figure 9C shows the top surface 201 of the substrate 20, which has adhesive 22 on it, after the dies 21 have been attached. Figure 9D shows the bottom surface 202 of the substrate 20 after wire bonds 23 have been formed through the openings 200. Figure 9E shows the bottom surface 202 of the substrate
20, after the encapsulant 25 has been applied over the wire bonds 23.
[0130] Many modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

WHAT IS CLAIMED:
1. A semiconductor package comprising: a) a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; b) a semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side, the semiconductor die mounted onto the substrate with the active side disposed over and completely covering the opening penetrating through the upper and lower surfaces of the substrate; c) an adhesive disposed between and joining the upper surface of the substrate and the active side of the die such that the active side of the die, exclusive of the conductive areas, is completely covered by the adhesive; d) a plurality of electrically conducting bonding wires connecting the conductive areas on the active side of the die, through the opening in the substrate, to the wire bond pads on the lower surface of the substrate; e) an encapsulant applied onto the lower surface of the substrate, encapsulating the bonding wires and filling the opening of the substrate; and f) a plurality of solder balls implanted on the lower surface of the substrate at an area outside the encapsulant; wherein the package is characterized by the absence of an encapsulant on the inactive side of the die and the absence of an encapsulant on the sides of the die.
2. The package of Claim 1 wherein the substrate is selected from the group consisting of BT and FR-4.
3. The package of Claim 1 wherein the adhesive is selected from the group consisting of epoxy, bismaleimide, acrylate, siloxane, or a combination of these.
4. A process for the manufacture of a semiconductor package comprising: a) providing a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; b) providing at least one semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side; c) applying a flow-able adhesive in an adhesive pattern onto the upper surface of the substrate such that after the die is attached to the substrate the adhesive surrounds the opening and, inclusive of the opening, is at least as large as the footprint of the die, d) optionally hardening the flow-able adhesive to a non-tacky state, e) mounting the die onto the substrate with the active side disposed over and completely covering the opening through the upper and lower surfaces of the substrate, such that the conductive area on the active surface of the die is exposed to the opening of the substrate, and the active surface of the die, exclusive of the conductive area, is completely covered by the adhesive, f) optionally curing the adhesive, g) attaching a plurality of electrically conducting bonding wires connecting the conductive areas on the active side of the die, through the opening in the substrate, to the wire bond pads on the lower surface of the substrate; h) applying an encapsulant onto the lower surface of the substrate, encapsulating the bonding wires and filling the opening of the substrate; i) curing the encapsulant; and j) implanting a plurality of solder balls on the lower surface of the substrate at an area outside the encapsulant; wherein the process is characterized by the absence of an encapsulation step for the inactive side of the die and the absence of an encapsulation step for the sides of the die.
5. The process according to Claim 4 wherein the adhesive is a printable paste.
6. The process according to Claim 4 wherein the substrate is characterized by the absence of a mold stress release area.
7. The process according to Claim 4 wherein the adhesive pattern includes a small vacant area peripherally around the conductive area containing the wire bond pads, which is not coated with adhesive prior to die attach, into which adhesive flows during die attach such that it is free of forming gaps between the die and the substrate.
8. The process according to Claim 4 wherein the adhesive is B-staged prior to mounting the die onto the substrate.
9. A process for the manufacture of a semiconductor package comprising: a) providing a substrate having an upper surface, a lower surface opposed to the upper surface, an opening penetrating through the upper and lower surfaces, and wire bond pads on the lower surface; b) providing at least one semiconductor die having an active side with one or more conductive areas, and an inactive side opposed to the active side; c) applying a flow-able adhesive in an adhesive pattern onto the active side of the die such that after the die is attached to the substrate the adhesive surrounds the opening and, inclusive of the opening, is at least as large as the footprint of the die, d) optionally hardening the flow-able adhesive to a non-tacky state, e) mounting the die onto the substrate with the active side disposed over and completely covering the opening through the upper and lower surfaces of the substrate, such that the conductive area on the active surface of the die is exposed to the opening of the substrate, and the active surface of the die, exclusive of the conductive area, is completely covered by the adhesive, f) optionally curing the adhesive, g) attaching a plurality of electrically conducting bonding wires connecting the conductive areas on the active side of the die, through the opening in the substrate, to the wire bond pads on the lower surface of the substrate; h) applying an encapsulant onto the lower surface of the substrate, encapsulating the bonding wires and filling the opening of the substrate; i) curing the encapsulant; and j) implanting a plurality of solder balls on the lower surface of the substrate at an area outside the encapsulant; wherein the process is characterized by the absence of an encapsulation step for the inactive side of the die and the absence of an encapsulation step for the sides of the die.
10. The process according to Claim 9 wherein the adhesive is a printable paste.
11. The process according to Claim 9 wherein the substrate is characterized by the absence of a mold stress release area.
12. The process according to Claim 9 wherein the adhesive pattern includes a small vacant area peripherally around the conductive area containing the wire bond pads, which is not coated with adhesive prior to die attach, into which adhesive flows during die attach such that it is free of forming gaps between the die and the substrate.
13. The process according to Claim 9 wherein the adhesive is B-staged prior to mounting the die onto the substrate.
14. The process according to Claim 9 wherein the adhesive is applied to the die prior to singulation from the wafer.
15. The process according to Claim 9 wherein the adhesive is applied to the die after singulation from the wafer.
16. A substrate for the manufacture of board-on-chip semiconductor packages which comprises a top surface, a bottom surface opposed to the top surface, and openings penetrating through the top surface and the bottom surface; which is characterized by the absence of a mold stress relief area.
EP06837754A 2006-11-16 2006-11-16 Board on chip package and process for making same Withdrawn EP2082423A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2006/044465 WO2008060280A1 (en) 2006-11-16 2006-11-16 Board on chip package and process for making same

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EP2082423A1 true EP2082423A1 (en) 2009-07-29

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KR101395322B1 (en) * 2012-07-18 2014-05-16 도레이첨단소재 주식회사 Adhesive composition having improved reliability at high voltage condition and adhesive tape for semiconductor packaging using the same
US9269647B2 (en) 2014-05-29 2016-02-23 Samsung Electronics Co., Ltd. Semiconductor package having heat dissipating member

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TW411537B (en) * 1998-07-31 2000-11-11 Siliconware Precision Industries Co Ltd Semiconductor package with CSP-BGA structure
TW409377B (en) * 1999-05-21 2000-10-21 Siliconware Precision Industries Co Ltd Small scale ball grid array package
US6385049B1 (en) * 2001-07-05 2002-05-07 Walsin Advanced Electronics Ltd Multi-board BGA package
US20050062152A1 (en) * 2003-09-24 2005-03-24 Chung-Che Tsai Window ball grid array semiconductor package with substrate having opening and mehtod for fabricating the same

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