KR101904884B1 - Solder ball and Package of semiconductor using the same - Google Patents
Solder ball and Package of semiconductor using the same Download PDFInfo
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- KR101904884B1 KR101904884B1 KR1020160141283A KR20160141283A KR101904884B1 KR 101904884 B1 KR101904884 B1 KR 101904884B1 KR 1020160141283 A KR1020160141283 A KR 1020160141283A KR 20160141283 A KR20160141283 A KR 20160141283A KR 101904884 B1 KR101904884 B1 KR 101904884B1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
- H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L24/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
- H01L24/28—Structure, shape, material or disposition of the layer connectors prior to the connecting process
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/492—Bases or plates or solder therefor
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
- H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L24/10—Bump connectors ; Manufacturing methods related thereto
- H01L24/12—Structure, shape, material or disposition of the bump connectors prior to the connecting process
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
- H01L2224/18—High density interconnect [HDI] connectors; Manufacturing methods related thereto
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- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
The present invention provides a solder ball comprising tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni) and palladium (Pd) , The thickness of the oxide layer is 2.0 to 3.5 nm, and the bismuth used has a specific mass number. The solder ball may be used as a solder ball for WLP.
Description
The present invention relates to a solder ball and a semiconductor package using the solder ball.
In recent years, packaging has become more and more smaller due to the increasingly sophisticated functions such as cell phones and electronic parts. In order to achieve cost reduction and high efficiency, a wafer level package (WLP) technology has been developed.
WLP technology is being applied to the current high end package technology. WLP is a technology to package process and test at one time in wafer state, then cut chip to make finished product. , It is possible to reduce the cost of package production by 20% compared to the previous model.
However, when using WLP, two problems are encountered.
First, the thermal properties due to the different thermal expansion coefficients of the constituent elements due to the absence of the substrate are particularly weak. In other words, unlike other semiconductor packages, materials with different thermal expansion coefficients are connected without a substrate in WLP, and there is stress in the solder ball portion due to lack of support by the substrate when thermal shock is applied, and exhibits weak TC (Thermal Cycling) characteristics. Therefore, it is necessary to improve TC characteristics while changing to WLP.
In this case, the thermal cycle failure refers to a phenomenon in which thermal stress occurs due to a difference in thermal expansion coefficient between a periodic high temperature and a low temperature, This is a phenomenon that occurs frequently in Japan. For this reason, good reliability of thermal cycle failure is an essential characteristic in semiconductors.
Second, it is vulnerable to alpha particles. Alpha ray is generally known as radiation that occurs when uranium decays to lead.
In the case of WLP, the solder balls are directly bonded (crystal) to the silicon chip without the substrate, so they are easily exposed to the alpha ray. Alpha ray penetrates into the silicon chip and changes the signal transmission system, causing a soft error of the device.
Therefore, in order to stably commercialize the WLP technology, it is necessary to develop a solder ball that prevents cracks and prevents the occurrence of a machining ball, while reducing the above-described problem of solder balls used as an external bonding material of a semiconductor package.
SUMMARY OF THE INVENTION The present invention provides a solder ball and a semiconductor package including the solder ball, which can improve the thermal cycle characteristics in the WLP while reducing the malfunction of the device due to the alpha line while maintaining the characteristics of the solder ball.
According to an aspect of the present invention,
As a solder ball in which an oxide layer is formed on a surface,
(Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni) and palladium (Pd)
Wherein the silver (Ag) is 0.5 to 5.0 wt%, the copper (Cu) is 0.2 to 1.0 wt%, the bismuth (Bi) is 0.8 to 2 wt%, the nickel (Ni) is 0.02 to 0.08 wt% (Pd) is contained in an amount of 0.01 to 0.05% by weight,
The remainder is composed of tin and inevitable impurities of 10 ppm or less each,
The content of oxygen atoms gradually decreases according to the depth of the oxide layer formed on the surface, and the thickness of the oxide layer is 2.0 to 3.5 nm.
At this time, it is preferable that the solder ball has a lead (Pb) content of 5 ppm or less and an alpha particle count of 0.002 cph / cm 2 or less.
The solder balls preferably have an average diameter of 100 to 250 占 퐉.
According to another aspect of the present invention, there is provided a method of manufacturing a solder ball,
A melting step of charging a solder alloy containing tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni) and palladium (Pd) into a molten metal and melting the molten metal at 230 to 250 占 폚;
An injection step of supplying the master alloy to the molten alloy and maintaining the temperature at 250 to 280 DEG C;
A heating step of induction heating the alloy into which the master alloy is introduced; And
And a ball forming step of passing the induction-heated alloy through a graphite nozzle hole to form a solder ball,
At this time,
Wherein the silver (Ag) is 0.5 to 5.0 wt%, the copper (Cu) is 0.2 to 1.0 wt%, the bismuth (Bi) is 0.8 to 2 wt%, the nickel (Ni) is 0.02 to 0.08 wt% (Pd) is contained in an amount of 0.01 to 0.05% by weight, the balance being composed of tin and inevitable impurities each having 10 ppm or less,
The content of oxygen atoms in the oxide layer formed on the surface of the solder ball gradually decreases according to the depth, and the thickness of the oxide layer is preferably 2.0 to 3.5 nm.
According to another aspect of the present invention,
A semiconductor chip;
A mold substrate surrounding the first surface and the side surface of the semiconductor chip;
At least one insulating film having a first surface attached to a second surface of the mold substrate and the semiconductor chip and longer than a length of the semiconductor chip;
At least one rewiring line formed in the insulating film and connected to the element pads of the semiconductor chip; And
At least one solder ball attached to the second surface of the insulating film and connected to the rewiring line, the semiconductor package not including the substrate on which the semiconductor chip is fixed,
The solder balls include tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni), and palladium (Pd)
Wherein the silver (Ag) is 0.5 to 5.0 wt%, the copper (Cu) is 0.2 to 1.0 wt%, the bismuth (Bi) is 0.8 to 2 wt%, the nickel (Ni) is 0.02 to 0.08 wt% (Pd) is contained in an amount of 0.01 to 0.05% by weight, the balance being composed of tin and inevitable impurities each having 10 ppm or less,
The oxide layer formed on the surface of the solder ball gradually decreases the content of oxygen atoms according to the depth, and the thickness of the oxide layer is 2.0 to 3.5 nm.
At this time, the thickness of the insulating film is preferably 10 占 퐉 or less.
Further, the semiconductor rewiring (RDL) is made of copper (Cu), and the insulating film is made of polyimide (PI) or polybenzoxazole (PBO).
The solder ball preferably has a lead (Pb) content of 5 ppm or less and an alpha particle value of 0.002 cph / cm 2 or less.
The intermetallic compound (IMC) and the grain size (Pb) of the SAC solder alloy including the filtered Sn are increased by adding Ni, Pd, and Bi to the solder balls and controlling the Pb concentration. The thermal cycle characteristics are improved, the device malfunction due to the alpha rays can be prevented, and the wettability can be improved.
SAC solder alloy as well as SAC302, SAC105, SAC1205Ni, SAC305, and SAC405, Ni, Pd and Bi are added to all SAC solder alloys.
The present invention is to provide a solder ball in which Ni, Pd, and Bi are added to the SAC (Sn, Ag, Cu) solder alloy composition and the Pb content is controlled.
The use of this solder ball also ensures the stability of the semiconductor package device using WLP technology.
1 is a perspective view of a filter device used for filtering tin according to an embodiment of the present invention.
2 is a perspective view of a filter used in the filter device of FIG. 1 according to an embodiment of the present invention.
Figure 3 is a top view of the filter of Figure 2 in accordance with an embodiment of the present invention.
4 is a perspective view of a section taken along the longitudinal direction of FIG. 2 according to an embodiment of the present invention.
5 is a cross-sectional view of a semiconductor package including a solder ball according to an embodiment of the present invention.
Figure 6 is a plot of test conditions used to evaluate the TC strength of solder ball specimens on a substrate in accordance with one embodiment of the present invention.
7 is a photograph of the analysis equipment and the specimen used in the calculation of the alpha particle value of the embodiments of the present invention.
8 is an image of a microstructure of a solder ball according to embodiments of the present invention.
FIG. 9 is an explanatory view illustrating Bulky IMC and grain shape and crack movement path according to the addition of Pd. FIG.
10 is a graph showing a result of measurement of an AES (Auger Electron Spectroscopy) method of a solder ball according to an embodiment of the present invention.
Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.
Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.
On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.
Solder ball
(Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni), and palladium (Pd) as an example of the solder ball according to one embodiment of the present invention.
One embodiment of a solder alloy according to one aspect of the present invention includes Sn, Ag, Cu, Bi, Ni, and Pd. do.
(Ag), 0.2 to 1.0% by weight of copper (Cu), 0.8 to 2% by weight of bismuth (Bi), 0.02 to 0.08% by weight of nickel (Ni) ) May include 0.01 to 0.05% by weight.
Preferably, 1.0 to 4.0 wt% of silver (Ag), 0.2 to 0.5 wt% of copper (Cu), 0.9 to 1.5 wt% of bismuth (Bi), 0.03 to 0.07 wt% of nickel (Ni) (Ag), 0.2% by weight of copper (Cu), 1% by weight of bismuth (Bi), and nickel (Ni) of 0.02 to 0.05% by weight based on the total weight of the solder alloy. 0.05% by weight, and 0.03% by weight of palladium (Pd).
The composition of Sn, Ag, and Cu can be a conventional SAC alloy composition. For example, SAC105, SAC1205Ni, SAC305, SAC302, SAC405, and the like.
Bismuth (Bi) inhibits the growth of Bulky IMCs such as Cu 6 Sn 5 and Ag 3 Sn during heat treatment, and is effective in thermal cycles (TC) by interfering with the crystal growth of Sn during the heat treatment by being dissolved in Sn.
It is preferable that Bi having a mass number of 209 be used for bismuth. This is because Bi has a half-life of 209, which is more than 1.9 × 10 19 years, so it is treated as a stable isotope and is unlikely to release alpha rays.
When the bismuth (Bi) content is less than 0.8 wt%, the expected effect on the TC characteristic is insufficient. When the bismuth content is more than 1.2 wt%, the tendency of brittle waves There is a problem that reliability is adversely affected due to a drop impact.
Nickel (Ni) can improve the fluidity at the time of melting, the heat cycle performance and drop impact. If the content of nickel (Ni) is less than 0.01% by weight, the above effect can not be obtained. If the content of nickel exceeds 0.1% by weight, the strength of the solder increases due to precipitation hardening and cracks due to warpage, Can not be prevented. In addition, the melting point increases, the flowability upon melting decreases, and the wetting is lowered.
Palladium (Pd) interferes with the formation and growth of graphite-structured Cu 3 Sn compounds which are easily structured by crack propagation due to thermal fatigue. In addition, palladium (Pd) is combined with the α-Sn phase, which is a low-temperature phase produced under experimental conditions in the temperature range of -40 ° C to 125 ° C, and the generated β-Sn phase to generate PdSn 4 compound. Since PdSn 4 has a rod-shaped structure and is located on the upper interface (especially the Ag 3 Sn interface) for phase equilibrium, the crack generated by thermal fatigue makes it difficult to propagate through the upper interface to achieve excellent thermal shock performance.
If palladium (Pd) is contained in an amount of less than 0.01% by weight, the above-mentioned effect can not be obtained. If it exceeds 0.1% by weight, Ostwald ripening occurs between palladium (Pd) And a crystal grain size exceeding 30 μm 2 is formed, and PdSn 4 is excessively generated and destroyed, and the cost also increases.
On the other hand, tin (Sn) contains filtered tin having a content of impurities such as lead (Pb), iron (Fe), aluminum (Al), bismuth (Bi) and zinc (Zn) of 10 ppm or less, Is preferably 5 ppm or less.
By controlling the content of Pb to 5 ppm or less, it is possible to minimize the soft error due to the alpha ray.
Further, the filtered tin reduces the content of impurities (Pb, Fe, Zn, Al, etc.) that can cause oxidation in the solder ball, thereby reducing the thickness of the oxide layer formed on the surface of the solder ball.
On the other hand, the content of tin (Sn) is the remainder excluding the content of the constituent components as well known to those skilled in the art, and the solder ball according to the embodiment of the present invention may further contain impurities that are unavoidable in addition to the above- .
The shape of the solder ball is not limited, but may be in the form of a spherical, cylindrical, or polygonal column, and preferably has a spherical shape.
The solder balls of this embodiment preferably have an average diameter of 100 to 250 mu m. In this case, the diameter was measured by non-contact type measurement, and the average value obtained by measuring at least six points using a three-dimensional automatic measurement or a projector.
On the surface of the solder ball, an oxide layer of SnO 2 with a constant thickness is formed, and the oxide layer has an amorphous structure, and the oxygen content gradually decreases according to the depth. The oxide layer interferes with the movement of the alpha ray, which escapes from the solder ball. When the TC is evaluated, cracks from the outside penetrate into the weakest crystals of the solder. The oxide layer, which is an amorphous layer, This prevents the penetration of cracks.
The thickness of the oxide layer of the solder ball can be measured with an AES (Auger Electron Spectroscope), and it is preferable that the oxide layer is made to have a thickness of 2.0 to 3.5 nm. When the thickness is less than 2.0 nm, as described above, the oxide layer does not prevent alpha ray movement and cracking, and also causes a problem of aggregation of balls and sphericity of the balls, A problem of missing ball occurs.
Annotation (Sn) filtering method
One embodiment of a method for filtering tin (Sn) contained in a solder ball according to an aspect of the present invention is as follows.
Tin (Sn) having a purity of 99.9% to 99.99% is melted at 250 to 350 DEG C and then passed through a filter device having a filter of 2 to 7 mu m pore under a pressure of 3 to 4 bar.
Since the melting point of tin (Sn) is 232 deg. C, the melting operation is not smooth at 250 deg. C or lower and the filtering effect is insufficient because the oxidation of tin (Sn) due to high temperature is high at 350 deg. And preferably tin (Sn) is melted at 290 to 310 占 폚.
1 is a perspective view of a filter device used to filter tin in accordance with an embodiment of the present invention. According to this, the filter device is composed of an
The
The material of the filter is ferritic stainless steel or austenitic stainless steel. The stainless steel may further include at least one of molybdenum (Mo), nickel (Ni), and chromium (Cr). For example, when molybdenum (Mo) is contained in an amount of 6% or less, it has an effect of being able to withstand cracks and stress, and when it contains 13% or more of chromium (Cr) When it contains less than 10% of nickel (Ni), it has an effect of maintaining the austenite structure from the melting point to the low temperature.
The size of the filter hole is 2 to 7 μm, and when it is less than 2 μm, the workability is deteriorated. Also, if the pressure is less than 3 bar and greater than 4 bar, there is no filtering effect.
Impurities such as lead (Pb), bismuth (Bi), iron (Fe), aluminum (Al) and zinc (Zn) are removed after tin (Sn) filtering so that the concentration of each of the impurities becomes 10 ppm or less.
The filtered tin has a lower concentration of oxygen than unfiltered tin and has a relatively high concentration of Sn, Ag, and Cu, which can minimize the Mushy region. When the liquid phase changes to a solid phase, the liquid phase and the solid phase are simultaneously present. When the liquid phase changes into a solid phase, impurities such as Pb and Fe are present, and the respective elements exist as one phase. By creating sites and increasing the time to solidify, the machine area will increase. In the case of a large machice area, the reaction time is long and the bonding reaction is slowed down.
Solder alloy manufacturing method
An embodiment of a solder alloy manufacturing method which is another aspect of the present invention is as follows.
According to one aspect of the present invention, an alloy can be manufactured in a high frequency vacuum electric induction furnace using tin (Sn) filtered according to a tin filtering method.
More particularly, the present invention relates to a method of manufacturing a high-frequency induction furnace, which comprises charging filtered tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni), and palladium (Pd) And a heating step of raising the temperature of the high-frequency vacuum induction furnace to 700 DEG C for 10 minutes, holding the same for 10 minutes, elevating the temperature to 1100 DEG C for 10 minutes, and then maintaining the temperature for 60 minutes.
At this time, the purity of each metal is preferably 4N (99.99%) or more.
The content of tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni) and palladium (Pd) charged in the charging step is, for example, 0.5 to 5.0% by weight of copper (Ag), 0.2 to 1.0% by weight of copper, 0.8 to 2% by weight of bismuth, 0.02 to 0.08% by weight of nickel and 0.01 to 0.05% by weight of palladium .
Preferably 1.0 to 4.0 wt% of silver (Ag), 0.2 to 0.5 wt% of copper (Cu), 0.9 to 1.5 wt% of bismuth (Bi), 0.03 to 0.07 wt% of nickel (Ni) 0.02 to 0.05% by weight of palladium (Pd). More preferably, 3.0 wt% of silver (Ag), 0.2 wt% of copper (Cu), 1 wt% of bismuth (Bi), 0.05 wt% of nickel (Ni), 0.03 wt% of palladium (Pd) . ≪ / RTI >
In the charging stage, the degree of vacuum of the high frequency vacuum induction furnace is 3.0 ㅧ 10 -2 torr to 6.0 ㅧ 10 -2 torr. When the degree of vacuum drops to 10 -1 torr, oxygen (O) reacts with tin (Sn) to form a large amount of tin oxide (SnO 2 ). In the case of producing an alloy in a high-frequency vacuum induction furnace, unnecessary reaction that tin (Sn) reacts with oxygen (O) to form tin oxide (SnO 2 ) is suppressed, .
Further, the agitating force due to the electrical vortex in the high-frequency vacuum induction furnace is superior to the mechanical agitating force of the conventional method using the electric furnace, and work is performed in an inert atmosphere instead of working in the atmosphere.
And a purging step of purging the high-frequency vacuum induction furnace with an inert gas between the charging step and the heating step, and then maintaining the furnace for 10 minutes. Purging refers to neutralization of an internal alloy with an inert gas that does not cause a chemical or physical reaction in a high frequency vacuum induction furnace, and a purging pressure of 750 to 760 torr is preferable.
The reason why the holding time is 60 minutes after raising the temperature to 1100 ° C for 10 minutes in the temperature rising step is that the elements having different specific weights such as silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni), palladium So as to homogenize alloys.
Solder ball manufacturing method
An embodiment of a solder ball manufacturing method using the solder alloy which is another aspect of the present invention is as follows.
Charging a solder alloy according to one aspect of the present invention into a molten metal and then melting the molten alloy at a temperature of 230 ° C to 250 ° C; injecting Sn-Ge master alloy into the molten alloy; and maintaining the temperature of the molten metal at 250 ° C to 280 ° C A heating step of inducing heating of an alloy into which a Sn-Ge master alloy is introduced, and a ball forming step of passing a heated alloy through a graphite nozzle hole using a vibrator to form a ball .
In the adding step, an alloy (Sn-Ge master alloy) containing a large amount of additive element (Sn) is made separately as a melting agent and added to a melt of a metal (filtered tin) So as to uniformly add the alloying element to be added in a predetermined amount.
In addition, since the melting point (938 ° C) of Ge alone is high, a master alloy is prepared to lower the melting point. The master alloy comprises tin (Sn) and germanium (Ge), preferably but not limited to, 0.1 to 5 wt% of germanium relative to the total weight of the master alloy.
The induction heating in the heating step is a method of converting electric energy into heat energy by electromagnetic induction and using it as a method of heating Joule's heat generated when a secondary current induced by electromagnetic induction flows into the material to be heated. In this case, the material to be heated is an alloy manufactured through the above-mentioned charging step.
The size of the solder balls formed in the ball forming step can be controlled by the frequency and the pressure. The diameter of the graphite nozzle (orifice) hole is 70 to 120 mu m, the frequency is 7 to 15 KHz, and the pressure is preferably 1000 to 2000 mbar. At this time, the formed solder balls have an average diameter of 100 to 250 mu m. The graphite nozzle has a cylindrical shape, and it is possible to realize a stable size by using graphite material.
The thickness of the oxide film formed on the surface of the solder ball is preferably 2.0 to 3.5 nm. When it is manufactured at less than 2.0 nm, the alpha ray movement and cracks can not be prevented. Also, the problem of aggregation of balls and the sphericity of balls are reduced, and when manufactured at more than 3.5 nm, the wettability is deteriorated, ). ≪ / RTI >
Semiconductor package
The solder ball according to the technical idea of the present invention is used in a semiconductor package. The solder ball according to the embodiment of the present invention is not limited to the use of the semiconductor package and can be used for various purposes. Particularly, the semiconductor package according to various embodiments of the present invention is preferably applied to a wafer level package that performs a packaging process and a test at a time in a wafer state, and then cuts a chip to produce a finished product simply.
FIG. 5 shows an embodiment of a WLP package to which the solder ball according to the present invention is applied. The semiconductor package includes a
The semiconductor chip includes a semiconductor substrate, a device protection film, and an element pad, and the upper surface and the side surface of the semiconductor chip are surrounded by the mold substrate. Here, the upper part refers to the direction opposite to the direction in which the solder balls are located. Please tell us about the structure and materials of the element pads of semiconductor chips used in WLP.
At least one insulating film is formed on the bottom surface of the mold substrate and the semiconductor chip, and an insulating film longer than the length of the semiconductor chip is provided. The insulating film is a film for insulating the rewiring line. The rewiring line is formed in the insulating film and connected to the solder ball electrically attached to the lower surface of the insulating film. In the case of the redistribution line (RDL), the material is usually Cu, and the material of the insulating film is polyimide (PI) or PBO.
According to this, the semiconductor chip is bonded to the solder ball with the insulating film therebetween without the substrate. In this case, the substrate can not expect to reduce the thermal cycle destruction as in the conventional semiconductor package, so that a solder ball is particularly needed as a branch exhibiting particularly strong resistance to thermal cycle destruction.
In addition, since the solder ball and the semiconductor chip are placed without insulating the substrate with an insulating film having a thickness of 10um or less, solder balls are required to minimize the occurrence of alpha rays in order to prevent the signal transmission due to the alpha rays.
Examples and Comparative Examples
(1) Production of solder alloy
The filtered tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni) and palladium (Pd) are weighed in weight ratio to the tin The pressure of 3.0 ㅧ 10 -2 torr was maintained for 10 minutes. The mixture was purged with an inert gas at a pressure of 760 torr and maintained for 10 minutes. The temperature was raised to 700 ° C. for 10 minutes, maintained for 10 minutes, elevated to 1100 ° C. for 10 minutes, and maintained for 60 minutes to prepare a solder alloy. A solder alloy as shown in Table 1 having the compositions of Examples 1 to 3 and the compositions of Comparative Examples 1 to 6 was prepared.
(2) Manufacture of solder balls
The solder alloy prepared according to the present invention was charged into a molten metal and melted at 240 DEG C, a Sn-Ge master alloy was charged, and the temperature of the molten metal was maintained at 260 DEG C. [ Each of the solder balls was manufactured by induction heating for 5 minutes and passing through an orifice using a vibrator. The diameter of the orifice hole used was 100 mu m, the frequency was 10 KHz, the pressure was 1500 mbar, and the average diameter of the solder balls was 200 mu m. A solder alloy as shown in Table 1 having the compositions of Examples 4 to 6 and the compositions of Comparative Examples 7 to 12 was prepared.
Table 1 shows the compositions of the examples and comparative examples of the solder alloy and solder balls prepared by the present invention.
Experimental Example
Hereinafter, characteristics of the solder ball according to the present invention will be discussed based on experimental data. In order to investigate the reliability of the solder ball, thermal cycle reliability and alpha ray reliability were performed.
Solder balls were mounted on OSP treated PCBs using Attach equipment and reflow was performed to bond the solder balls. The flux was ws type and the peak temperature peak temperature of 240 ± 5 ℃, dwell time of 40 ± 10s (over 220 ℃) and the atmosphere of O2 contents of 3000 ppm. The solder balls were then bonded to the OSP-treated board.
(1) TC reliability: In order to measure the TC strength of the specimen (JEDS22-A104-B), the evaluation was carried out at -40 ° C to 125 ° C. The measurement of one cycle was carried out as follows. The resistance of the specimen fail was measured every 50 cycles, and the short circuit was measured as the specimen out. The wafer used in the evaluation, the spec of the Board, and the test conditions are as shown in Fig.
According to Table 1, when the Bi content exceeds 2% (Comparative Example 4, Comparative Example 5), the tendency of brittle fracture increases due to the increase of the hardness of the material due to the Bi crystallization in the solder bulk, It is estimated to be insane. If Bi is less than 0.8, the expected effect on TC characteristics is insufficient and the required level is less than 600cycles. There is a problem, and the reliability is evaluated as low. At this time, it can be confirmed that when Bi is added in the range of 0.8% to 2%, there is almost no influence on the TC reliability.
In particular, it can be seen that 0.05 wt% Ni, 0.03 wt% Pd, and 1 wt% Bi act as a dopant for improving TC reliability regardless of the solder composition.
(2) Alpha Line Reliability
An alpha particle is an alpha ray particle in radiation emitted from a radioisotope, and a solder for emitting an alpha ray particle by a radioisotope in a solder is referred to as Alpha particle. solder, and a solder having an alpha ray particle emission of 0.02 cph / cm 2 or less is referred to as a low alpha solder.
Therefore, the emission levels of Low Alpha Alpha particle, Ultra low alpha, sharing a Super ultra low alpha, each figure is as follows, Low alpha <0.02cph / cm 2 , Ultra low alpha <0.002cph /
A problem caused by an alpha ray causes a soft error, and a soft error is a discrepancy between recorded information and information read from a memory cell. It is a phenomenon caused by loss. Alpha particle measurements were measured using a 1950-SE model manufactured by Alpha Science.
Alpha particle measurement was performed by applying solder to be measured on a Cu plate of 10 cm x 14 cm to make 6 sheets of sheets and measuring the Alpha particle value by measuring 107 hours in a P-10 gas flowing equipment chamber. The analytical equipment and specimens used are shown in FIG.
According to Table 1, Alpha particles were measured by Pb content. When the Pb content is less than 0.0005 wt%, the alpha particle value is measured to be less than 0.002 cph / cm 2 , which is a value that satisfies Ultra low alpha.
When the Pb content is controlled to be less than 0.0005 wt%, it is found that Ultra low alpha (0.002 cph / cm < 2 >) is used for the compositions SAC1205Ni, SAC305 and SAC405, which are commonly used, Or less).
This indicates that Ultra low alpha can be satisfied regardless of the solder composition when the Pb content is controlled to 0.0005 wt% or less.
(3) Solder microstructure according to addition of Bi
Fig. 8 is a photograph of the microstructure of the solder. According to this, the microstructure of solder with and without Bi added was observed. In the EOL (End of Lot) state, the sizes of Bulky IMC and Grain tissues are similar, but it shows that there is a difference in tissue after heat treatment. In the case of Bi added solder, the growth of Bulky IMC and Grain was suppressed by heat treatment, which is considered to be the effect of Bi. In the case of Bi added solder, the growth of Bulky IMC and Grain was suppressed by heat treatment, which is considered to be the effect of Bi. In the case of Bi, it is dissolved in Sn, which interferes with the crystal growth of Tin during heat treatment and also prevents the coarsening of Bulky IMC. This effect is considered to have an effect on TC.
(4) Bulky IMC and Grain shape with addition of Pd
FIG. 9 is an explanatory view illustrating Bulky IMC and grain shape and crack movement path according to the addition of Pd. FIG. When Pd is added to the solder, Pd is dispersed in the bulk to control (reduce) the size of the grain size and lengthen the path of the crack. At this time, palladium (Pd) can form fine crystals having a crystal grain size of 15 μm 2 to 30 μm 2 .
In addition, Ag does not form a compound because it is a solid solution solid, while it binds with Sn to form a Bulky IMC called PdSn 4 and exists in a grain boundary for phase equilibrium.
PdSn 4 existing at the interface of the interface prevents the crack generated by the thermal fatigue from moving on the upper interface and propagates, thereby improving the thermal shock performance.
(5) Thickness of oxide film of solder ball
10 is a graph showing the relationship between the thickness of the solder ball and the thickness of the solder ball measured by AES (Auger Electron Spectroscopy) method using a device MICROLAB 350 at a sputter rate (Ta 2 O 5 ) of 1.0 Å / sec This is a result.
The method of calculating the thickness of the oxide film from the results is well known to those skilled in the art, and the thickness of the oxide film is measured to be 3.1 nm based on the measurement results (FIG. 10A). On the other hand, the thickness of the oxide film of the solder ball when using a common tin (FIG. 10B) was 5.2 nm.
The features, structures, effects, and the like illustrated in the above-described embodiments can be combined and modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.
10: Filter
21: injection part 22:
30: spring
Claims (8)
(Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni) and palladium (Pd)
Wherein the silver (Ag) is 0.5 to 5.0 wt%, the copper (Cu) is 0.2 to 1.0 wt%, the bismuth (Bi) is 0.8 to 2 wt%, the nickel (Ni) is 0.02 to 0.08 wt% (Pd) is contained in an amount of 0.01 to 0.05% by weight,
The remainder is composed of filtered tin (Sn) and inevitable impurities of 10 ppm or less each,
Wherein the oxide layer formed on the surface gradually decreases the content of oxygen atoms according to the depth, the thickness of the oxide layer is 2.0 to 3.5 nm,
A solder ball having a lead (Pb) content of 5 ppm or less and an alpha particle count (count) of 0.002 cph / cm 2 or less.
Wherein the solder balls have an average diameter of 100 to 250 占 퐉.
An injection step of supplying the master alloy to the molten alloy and maintaining the temperature at 250 to 280 DEG C;
A heating step of induction heating the alloy into which the master alloy is introduced; And
And a ball forming step of passing the induction-heated alloy through a graphite nozzle hole to form a solder ball,
At this time,
Wherein the silver (Ag) is 0.5 to 5.0 wt%, the copper (Cu) is 0.2 to 1.0 wt%, the bismuth (Bi) is 0.8 to 2 wt%, the nickel (Ni) is 0.02 to 0.08 wt% (Pd) is contained in an amount of 0.01 to 0.05% by weight, and the remainder is composed of filtered tin (Sn) and inevitable impurities each having 10 ppm or less,
The oxide layer formed on the surface of the solder ball gradually decreases the content of oxygen atoms according to the depth, the thickness of the oxide layer is 2.0 to 3.5 nm,
Wherein a content of lead (Pb) is 5 ppm or less and an alpha particle count (count) is 0.002 cph / cm 2 or less.
A mold substrate surrounding the first surface and the side surface of the semiconductor chip;
At least one insulating film having a first surface attached to a second surface of the mold substrate and the semiconductor chip and longer than a length of the semiconductor chip;
At least one rewiring line formed in the insulating film and connected to the element pads of the semiconductor chip; And
At least one solder ball attached to the second surface of the insulating film and connected to the rewiring line, the semiconductor package not including the substrate on which the semiconductor chip is fixed,
The solder balls include tin (Sn), silver (Ag), copper (Cu), bismuth (Bi), nickel (Ni), and palladium (Pd)
Wherein the silver (Ag) is 0.5 to 5.0 wt%, the copper (Cu) is 0.2 to 1.0 wt%, the bismuth (Bi) is 0.8 to 2 wt%, the nickel (Ni) is 0.02 to 0.08 wt% (Pd) is contained in an amount of 0.01 to 0.05% by weight, and the balance consists of filtered tin (Sn) and inevitable impurities of 10 ppm or less,
The oxide layer formed on the surface of the solder ball gradually decreases the content of oxygen atoms according to the depth, the thickness of the oxide layer is 2.0 to 3.5 nm,
Wherein the solder ball is a solder ball having a lead (Pb) content of 5 ppm or less and an alpha particle count (count) of 0.002 cph / cm 2 or less.
Wherein a thickness of the insulating film is 10 占 퐉 or less.
Wherein the material of the redistribution line (RDL) is copper (Cu), and the material of the insulating film is made of polyimide (PI) or polybenzoxazole (PBO).
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| US20080203585A1 (en) | 2004-03-31 | 2008-08-28 | Fogel Keith E | Interconnections for flip-chip using lead-free solders and having reaction barrier layers |
| KR101539056B1 (en) * | 2014-08-01 | 2015-07-24 | 덕산하이메탈(주) | solder alloy and solder ball |
| JP5850199B1 (en) * | 2015-06-29 | 2016-02-03 | 千住金属工業株式会社 | Solder material, solder joint and solder material inspection method |
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| KR20100009896A (en) * | 2008-07-21 | 2010-01-29 | 삼성전자주식회사 | Semiconductor device package and method of fabricating the same |
| KR20110114913A (en) * | 2010-04-14 | 2011-10-20 | 앰코 테크놀로지 코리아 주식회사 | Semiconductor device and fabricating method thereof |
| KR101355694B1 (en) * | 2010-08-18 | 2014-01-28 | 닛데쓰스미킹 마이크로 메탈 가부시키가이샤 | Solder ball for semiconductor mounting and electronic member |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080203585A1 (en) | 2004-03-31 | 2008-08-28 | Fogel Keith E | Interconnections for flip-chip using lead-free solders and having reaction barrier layers |
| KR101539056B1 (en) * | 2014-08-01 | 2015-07-24 | 덕산하이메탈(주) | solder alloy and solder ball |
| JP5850199B1 (en) * | 2015-06-29 | 2016-02-03 | 千住金属工業株式会社 | Solder material, solder joint and solder material inspection method |
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