WO2021116192A1 - Power semiconductor module with terminal block - Google Patents

Power semiconductor module with terminal block Download PDF

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Publication number
WO2021116192A1
WO2021116192A1 PCT/EP2020/085325 EP2020085325W WO2021116192A1 WO 2021116192 A1 WO2021116192 A1 WO 2021116192A1 EP 2020085325 W EP2020085325 W EP 2020085325W WO 2021116192 A1 WO2021116192 A1 WO 2021116192A1
Authority
WO
WIPO (PCT)
Prior art keywords
terminal
power semiconductor
semiconductor module
terminals
terminal block
Prior art date
Application number
PCT/EP2020/085325
Other languages
French (fr)
Inventor
Harald Beyer
David GUILLON
Roman EHRBAR
Original Assignee
Abb Power Grids Switzerland Ag
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 Abb Power Grids Switzerland Ag filed Critical Abb Power Grids Switzerland Ag
Priority to CN202090001000.2U priority Critical patent/CN219716867U/en
Priority to DE212020000777.2U priority patent/DE212020000777U1/en
Priority to JP2022600087U priority patent/JP3239985U/en
Publication of WO2021116192A1 publication Critical patent/WO2021116192A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes
    • H01L25/04—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers
    • H01L25/07—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L29/00
    • H01L25/072—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. assemblies of rectifier diodes the devices not having separate containers the devices being of a type provided for in group H01L29/00 the devices being arranged next to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/02—Containers; Seals
    • H01L23/04—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls
    • H01L23/053—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls the container being a hollow construction and having an insulating or insulated base as a mounting for the semiconductor body
    • 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
    • H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
    • H01L23/49811—Additional leads joined to the metallisation on the insulating substrate, e.g. pins, bumps, wires, flat leads
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/36—Selection of materials, or shaping, to facilitate cooling or heating, e.g. heatsinks
    • H01L23/373—Cooling facilitated by selection of materials for the device or materials for thermal expansion adaptation, e.g. carbon
    • H01L23/3735—Laminates or multilayers, e.g. direct bond copper ceramic substrates

Definitions

  • the invention relates to the field of power electronics.
  • the invention relates to a power semiconductor module as well as to a method of manufacturing such a power semiconductor module.
  • a terminal block may be used.
  • Such terminal blocks may be preprocessed parts comprising several terminals embedded into a common resin body to form a building block.
  • the handling of such a terminal block may be significantly easier than the handling of several single terminals.
  • Terminal blocks are typically molded from thermoplastic resin in an injection molding process.
  • the thermoplastic resin may be filled with glass fibers to improve the mechanical strength of the resin material.
  • an injection molding process may be comparably easy to perform, the use of thermoplastic material may have some disadvantages with respect to thermal and thermomechanical behavior. Even with a filler content of 30 percent, there may be a strong mismatch between a thermal expansion of the thermoplastic material and a thermal expansion of a material of the terminals, e. g. copper or copper alloy.
  • thermoplastic materials may become unstable in humid environment, especially at high temperatures. Since thermoplastic materials typically have a comparably low glass transition temperature, a CTE (coefficient of thermal expansion) mismatch between the thermoplastic resin and the terminals may become quite important. Also, thermal decomposition of the thermoplastic resin may occur at high temperatures.
  • EP 0 791 961 A2 shows a power semiconductor module with a resin case in which terminals are integrated by integral molding.
  • JP 2011-060800 A shows a terminal block structure consisting of two terminals which are separated by one or two electrically isolating layers. The complete structure is embedded in resin. DESCRIPTION OF THE INVENTION
  • thermomechanical properties of the terminal block may be improved.
  • a mismatch between a CTE of the resin material and a CTE of the material of the terminals may be significantly reduced, which may reduce thermomechanical stress and, consequently, increase lifetime of the power semiconductor module.
  • the CTE of the resin material may be adjusted by adding an appropriate amount of an appropriate filler material.
  • a standard mold compound for transfer molding may have a filler content of up to 90 percent.
  • the glass transition temperature of thermosetting resin is higher than the glass transition temperature of thermoplastic resin.
  • thermosetting resin may be more stable in humid environment and less prone to thermal decomposition.
  • transfer molding using thermosetting resin offers the possibility of manufacturing comparably thin structures.
  • thermosetting resin as a mold compound for molding the terminal block
  • the CTE as well as the thermal conductivity of the matrix material may be easily adjusted by adjusting the filler material and content accordingly.
  • the filler material may also comprise fibers to mechanically reinforce the thermosetting resin.
  • the stability of the terminal block against heat, humidity and hazardous gases may be improved. Due to a lower thermal mismatch between the different materials of the terminal block, the terminal block may have a distinctly longer lifetime.
  • a first aspect of the invention relates to a power semiconductor module.
  • the power semiconductor module comprises a substrate with a terminal area, at least one power semiconductor chip, which may be bonded to the substrate, and which is electrically connected to the terminal area, and at least two terminals embedded in a thermosetting polymer, which thermosetting polymer forms a terminal block.
  • the terminal block exposes an end of each of the terminals for electrically connecting the end.
  • the end of each terminal is connected, for example bonded, to the terminal area.
  • the end may be directly bonded to the substrate.
  • the end may be connected to the substrate and/or the power semiconductor chip by wire bonding.
  • the terminal block may expose a first end and a second end of each of the terminals, wherein the first ends may be attached to the terminal area and the second ends may extend along an outer surface of the terminal block.
  • the second ends may also extend vertically from the housing.
  • At least one of the terminals may have a foot protruding from the terminal block, wherein the foot may be connected, for example bonded, to the terminal area.
  • the foot may be the end of the terminal connected to the terminal area.
  • a foot may be seen as a protruding portion of the terminal.
  • the foot and the terminal may be made in one piece of the same material.
  • the terminal area may be composed of several parts, which are electrically connected to different parts of the one or more semiconductor chips.
  • a semiconductor module may be any device composed of one or more semiconductor chips, their electrical and mechanical interconnections and a housing for these components.
  • the power semiconductor module may be used in various power electronics applications to switch or rectify electric currents.
  • the term “power” as in “power semiconductor module” and similar instances mentioned above and below may refer to modules and/or semiconductor chips adapted for processing current of more than 100 V and/or more than 10 A.
  • the power semiconductor chip may be based on silicon (Si) and/or silicon carbide (SiC) and/or may provide one or more semiconductor elements, such as diodes and/or solid-state semiconductor switches.
  • a switch may be a transistor, a thyristor, an IGBT (insulated- gate bipolar transistor) or a MOSFET (metal-oxide-semiconductor field-effect transistor).
  • the power semiconductor module comprises a semiconductor chip with a switch, and a semiconductor chip with a diode connected anti-parallel to the switch via conductors of a metallization layer.
  • the power semiconductor module may comprise one or more half-bridges composed of such combinations of switch and diode.
  • the one or more power semiconductor chips and the respective ends of the terminals may be connected, for example bonded, to the substrate. Bonding may refer to soldering, sintering, and welding, e. g. ultrasonic welding.
  • the power semiconductor module may have multiple electrical terminals for connecting DC and AC load currents to an external busbar.
  • the power semiconductor module may also have auxiliary terminals, such as for controlling the gates of the semiconductor chips in the module, which may be connected to an external gate driver circuit board.
  • An auxiliary terminal may also be an auxiliary emitter, an auxiliary collector, or a signal terminal for an intelligent power module.
  • the terminals may be made of copper or a copper alloy.
  • the terminals may at least partially be coated with a metallization layer, e. g. a nickel layer.
  • the substrate may carry the power semiconductor chip and may provide electrical and thermal contact as well as electrical insulation.
  • the substrate may be a plate of an electrically insulating material, such as plastics or ceramics, which is covered with a metallization layer on one or both sides.
  • the metallization layer may be structured to provide electrical conductors to which the power semiconductor chip may be connected.
  • the terminal area may be made of one or more electrically conductive portions of the substrate.
  • the terminal area may comprise a portion of said metallization layer and may be electrically connected to the power semiconductor chip via the metallization layer. Additionally or alternatively, the terminal area may be electrically connected to the power semiconductor chip with clips or by wire bonding.
  • thermosetting polymer also called thermosetting resin or thermoset
  • thermosetting resin may be a polymer that is irreversibly hardened by curing from a soft solid or viscous liquid prepolymer or resin.
  • the curing may be induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst.
  • the result of such curing may be an infusible and insoluble polymer network consisting of chemically crosslinked polymer chains.
  • the thermosetting polymer may be an epoxy resin.
  • thermosetting polymer may further comprise one or more filling materials.
  • thermosetting polymer may also be understood as a mixture of a thermosetting polymer and one or more filling materials.
  • the filling material may be provided as particles, such as beads and/or fibers.
  • the terminal block may be generated by transfer molding.
  • the thermosetting polymer may enclose at least a central part of the terminals. One or both ends of each terminal may not be enclosed with the thermosetting polymer so that they are accessible from outside the terminal block.
  • the terminal block may define one or more cavities when combined with the substrate and/or with a base plate of the power semiconductor module. For example, the cavities may be filled with a gel.
  • the terminal block may also be configured as a fixture for soldering or welding of terminal feet and/or ends to the substrate, which may allow for a more accurate positioning of the terminals.
  • the power semiconductor module may further comprise a housing and a base plate.
  • the substrate and the housing may be attached to the base plate.
  • the housing may at least partially cover the substrate.
  • the housing may be molded by transfer or injection molding.
  • the housing may completely cover the power semiconductor chip, the terminal area and/or conductors electrically interconnecting the power semiconductor chip and the terminal area.
  • the housing may completely cover the substrate.
  • the housing may comprise a border part in the form of a frame, which may extend along a border of the substrate and/or a border of the base plate. It is also possible that the housing is made with a least one opening to access parts within the housing. The one or more openings may be covered with a suitable cover.
  • the cover may be made from a different material than the rest of the housing.
  • the base plate may be a metal plate or be made from a compound material like AlSiC or MgSiC, for example.
  • the base plate may be attached to the substrate opposite to the power semiconductor chip.
  • the base plate may serve as a cooling plate.
  • the power semiconductor module may further comprise a housing.
  • the housing may be attached to the substrate and may at least partially cover the substrate.
  • the terminal block and the housing may be made in one piece of the same material, i. e. the thermosetting polymer.
  • the terminal block and the housing may be made from two or more pieces, wherein the terminal block may include one or more parts of the housing.
  • the terminal block and the housing may both be molded from the same thermosetting polymer by transfer molding.
  • the terminals may at least partially run through a border part of the molded piece. This may simplify the manufacturing of the power semiconductor module.
  • the terminal block and the housing are made of different materials.
  • the terminal block and the housing may be realized as separate parts of different materials.
  • the housing may be molded from a thermoplastic polymer by injection molding.
  • the terminal block may be attached to the housing and/or the base plate. This has the advantage that the terminal block may be provided independently from the housing.
  • the housing may comprise one or more mounting areas to mount the terminal block during assembly of the power semiconductor module, exemplarily for fixing the terminals during bonding of the terminals to the terminal area.
  • terminal block and/or the housing may have connecting elements, such as stop positions or notches, which may simplify assembly of the terminal block and the housing.
  • the thermosetting polymer has a filler content of at least 50 percent.
  • at least 50 percent of a mold compound used for molding the terminal block may be particles added to a thermosetting polymer matrix.
  • the thermosetting polymer may typically have a filler content of at least 60 to 90 percent.
  • a filler material used to fill the thermosetting polymer may be a mineral or glass based material in the form of particulates and/or fibers. With this embodiment, the CTE of the thermosetting polymer may be significantly reduced.
  • the thermosetting polymer has a filler content adapted with regard to a coefficient of thermal expansion of a material of the terminals.
  • the filler content may be adapted so that a discrepancy between a CTE of a mold compound comprising a thermosetting polymer matrix and a CTE of the terminals is 25 percent or less.
  • the thermosetting polymer may comprise at least one of the following materials: glass fibers, carbon fibers, fused silica, epoxysilane, aminosilane, silicon dioxide, metal oxide, antimony oxide, phosphate ester, brominated epoxy, bismuth, pigments.
  • epoxysilanes and/or aminosilanes may be used as adhesion promoter.
  • a dielectric strength of the terminal block may be increased by adding silicon dioxide as a filler.
  • a CTI (comparative tracking index) of the terminal block may be adapted by adding metal oxides such as iron oxide, magnesium oxide or aluminum oxide.
  • phosphate ester, antimony oxide and/or brominated epoxy may be added as a flame retardant to prevent or slow the development of an ignition.
  • Bismuth may be added as an ion trapping agent.
  • Pigments may be added for coloring the terminal block.
  • at least one of the two terminals may be at least partially coated with a metallization layer, e. g. nickel.
  • the terminal block may comprise at least one thread insert and expose a first end and a second end of at least one of the terminals.
  • the first end may be connected, for example bonded, to the terminal area.
  • the second end may extend along an outer surface of the terminal block and have an opening opposite to the thread insert.
  • the thread insert may be embedded into the thermosetting polymer when the terminal block is being formed by transfer molding.
  • the thread insert may be seen as an embedded nut.
  • an electrical contact element such as an external busbar, may be easily and securely connected to the power semiconductor module.
  • the terminal block may comprise a rib structure to increase a creepage length between the terminals. Dirt, pollution, salt, and exemplarily water on the surface of the terminal block may create a conductive path across it, causing leakage currents and flashovers.
  • the rib structure may be seen as a structure shaped to maximize a creepage distance along the surface of the terminal block and to minimize these leakage currents.
  • the rib structure may comprise one or more ribs and valleys arranged next to each other.
  • the rib structure may be seen as a corrugation or a series of corrugations.
  • the at least two terminals comprise at least one of a power terminal and an auxiliary terminal.
  • a power terminal may be a terminal adapted for conducting a load current through the power semiconductor module.
  • An auxiliary terminal may be adapted for conducting sensing and/or control signals. It is also possible that the terminal block comprise only power terminals or only auxiliary terminals.
  • the terminal area comprises at least one of a power terminal area and an auxiliary terminal area.
  • the terminal area may be a power terminal area, which may be electrically connected to a load electrode or a power electrode of the power semiconductor chip, such as a collector or an emitter.
  • An auxiliary terminal area also may be electrically connected to a gate of the semiconductor chip.
  • An area of the auxiliary terminal area may be smaller than an area of the power terminal area.
  • an area of the auxiliary terminal may be connected to an area of a metallization layer on the substrate.
  • the power semiconductor module may further comprise a circuit board with an auxiliary terminal area, and at least one auxiliary terminal embedded in the thermosetting polymer of the terminal block.
  • the terminal block may expose a further end of the auxiliary terminal.
  • the further end of the auxiliary terminal may be connected to the substrate, e. g., to an auxiliary terminal area of the substrate, and/or the power semiconductor chip.
  • the further end may be connected by wire bonding or directly bonded to the substrate and/or the power semiconductor chip.
  • a further aspect of the invention relates to a method of manufacturing a power semiconductor module.
  • the method comprises the following steps: providing a substrate with a terminal area and with at least one power semiconductor chip, which may be bonded to the substrate, and which may be electrically connected to the terminal area, forming a terminal block by embedding at least two terminals in a thermosetting polymer, wherein the terminal block exposes an end of each of the terminals, and connecting, such as bonding, the end of each of the terminals to the terminal area.
  • the forming may be done in a transfer molding process. Transfer molding and post curing under inert atmosphere, such as nitrogen, may be beneficial to avoid oxidation of the terminal area. Depending on the process for connecting a terminal to the terminal area, a selective or complete plating of the terminal and/or the terminal area may be performed prior to or after the forming.
  • Fig. 1 schematically shows a power semiconductor module according to an embodiment of the invention.
  • Fig. 2 schematically shows a power semiconductor module according to a further embodiment of the invention.
  • Fig. 1 shows a cross section of a power semiconductor module 100.
  • the power semiconductor module 100 comprises a substrate 102 which carries a power semiconductor chip 104. It is possible that two or more power semiconductor chips 104 are bonded to the substrate 102, as described above. However, only one power semiconductor chip 104 is shown in Fig. 1.
  • the substrate 102 is bonded to a base plate 110, for example a metal plate.
  • the base plate 110 may also serve as a cooling body. It is also possible that the substrate 102 is a printed circuit board or a lead frame.
  • the metallization layer 106 and the power semiconductor chip 104 are bonded to an upper side of the substrate 102, opposite to the base plate 110.
  • the substrate 102 is at least partially covered by a housing 112 which is mounted to the base plate 110.
  • the housing 112 may be screwed or glued onto the base plate 110. It is also possible that the housing 112 is mounted to the substrate 102. In this case, the substrate 102 may serve as a base plate.
  • the power semiconductor module 100 further comprises a terminal block 114, in which a DC+ terminal 116 and a DC- terminal 118 are embedded.
  • the terminal block 114 and the housing 112 are manufactured as separate parts.
  • the terminal block 114 is molded from a thermosetting polymer such as epoxy resin by transfer molding.
  • the housing 112 may be molded from a thermoplastic polymer by injection molding.
  • the terminal block 114 may be attached to the housing 112 and/or the base plate 110 after the housing 112 has been attached to the base plate 110.
  • part of the housing 112 e. g., a border part extending along a border of the base plate 110, may be formed as the terminal block 114.
  • the terminal block 114 and the rest of the housing 112 may be made of the same material, i. e. the thermosetting polymer.
  • the housing 112 and the terminal block 114 may be made in one piece in the same transfer molding process.
  • the terminals 116, 118 may be made of copper or a copper alloy.
  • the terminals 116, 118 may be bent plates or sheets.
  • Each of the terminals 116, 118 has a first end 120 and a second end 122.
  • the first ends 120 are each formed as a foot protruding from the terminal block 114 and bonded to the terminal area 106, for example by means of ultrasonic welding. More precisely, the feet are each bent to an L shape with a horizontal portion which is bonded to the terminal area 108.
  • the second ends 122 each extend along an upper surface of the terminal block 114, opposite to the base plate 110. However, the second ends 122 may also extend vertically from the housing.
  • a central part of the terminals 116, 118 between the first ends 120 and the second ends 122 is completely enclosed with the thermosetting polymer which electrically isolates the terminals 116, 118 from each other.
  • an outer surface of the housing 110 has a rib structure comprising a plurality of alternating ribs 124 and valleys 126.
  • the rib structure increases a creepage length between the two terminals 116, 118.
  • the rib structure also extends vertically along a border part of the housing 112 in order to increase a creepage length between the terminals 116, 118 and the base plate 110.
  • two thread inserts 128 are embedded in the terminal block 114.
  • Each of the second ends 122 has a screw opening 130 opposite to one of the threads in the thread inserts 128, so that a screw can be inserted through the second ends 122 and screwed into the thread inserts 128.
  • the thread inserts 128 may be used to screw an external busbar onto the terminals 116, 118.
  • the terminal block 114 may enclose one or more cavities 136 with the base plate 110 and/or the substrate 102.
  • the cavities 136 may be filled with a gel.
  • the terminal block 114 may be designed as a fixture for prepositioning the first ends 120 above the terminal area 108 prior to a bonding process.
  • thermosetting polymer for molding the terminal block 114 may result in several advantages compared to the use of a thermoplastic material, such as the adjustment of the thermal expansion coefficient of the terminal block 114 by adapting a filler content of the thermosetting polymer.
  • a suitable filler may consist of particles and/or fibers.
  • the thermosetting polymer used for the terminal block 114 may also be mechanically reinforced by fibers.
  • Another advantage is the improved stability of the terminal block 114 against heat, humidity, and hazardous gases.
  • shape stability of the terminal block 114 after processing, due to a reduced thermal mismatch between a material of the terminals 116, 118, e. g. copper, and the thermosetting polymer of the terminal block 114, may be improved.
  • the molding process is performed at a process temperature of 170 °C to 180 °C for transfer molding. Due to a melting point of 290 °C, the process temperature of the thermoplastic material is about 140 °C higher than the process temperature of the transfer molding compound.
  • the embedding of the terminals 116, 118 which, if made of copper, may have a thermal expansion coefficient of 16.4 ppm/K at room temperature, is performed at the process temperature.
  • the process temperature 170 °C to 180 °C
  • the system is in a stress-free situation, whereas the melting temperature of the thermoplastic material is at least 110 °C higher.
  • strong thermomechanical stress may occur between the terminals and the thermoplastic material, which may not only cause cracks, but also deteriorate shape stability.
  • the clearly lower CTE and the higher glass transition temperature of the transfer mold compound, resulting in a larger temperature range staying in the CTE1 regime may contribute to an additional stress reduction compared with the thermoplastic material and also improve reproducibility of the shape.
  • thermosetting polymer matrix By embedding two or more power and/or auxiliary terminals into a thermosetting polymer matrix to realize one common building block, such as the terminal block 114 described above and below, the thermal mismatch between the terminals 116, 118 and the polymer matrix may be minimized. This may also significantly reduce stress in the terminal block 114 during thermal cycling.
  • the transfer mold compound may be filled with fibers, e. g. glass or carbon fibers, and/or with particles, e. g. fused silica, to achieve a high filler content of up to 90 percent, exemplarily with respect to an adjustment of the CTE.
  • fibers e. g. glass or carbon fibers
  • particles e. g. fused silica
  • Fig. 1 also shows a circuit board 138, which is a gate driver board for controlling the gates of the one or more power semiconductor chip 104.
  • the circuit board 138 may be covered by the cover 134.
  • Fig. 2 shows a cross section of a power semiconductor module 100 according to a further embodiment. Unless otherwise described, the components of the module 100 of Fig. 2 may be the same and/or may have the same properties as the one of Fig. 1. In contrast to Fig. 1, where the terminal block 114 encloses the one or more cavities 136, the terminal block 114 of Fig. 2 is formed as a compact building block.
  • the circuit board 138 may have an auxiliary terminal area 202.
  • the auxiliary terminal area 202 may be electrically interconnected with the gate electrode of the power semiconductor chip 104.
  • Two auxiliary terminals 204 are bonded with an end onto the auxiliary terminal area 202.
  • the two auxiliary terminals 204 each run through the cover 134 and end on an upper surface of the cover 134 to provide planar contact surfaces for electrically contacting the auxiliary terminals 204 from outside the housing 112.
  • the terminal block 114 and the cover 134 are made of the same thermosetting polymer.
  • the cover 134 is part of the terminal block 114 so that the auxiliary terminals 204 are embedded in the terminal block 114 in the same manner as the power terminals 116, 118. It is possible that the terminal block 114 and the cover 134 are made in one piece.
  • the cover 134 may also be a separate transfer molded part with integrated auxiliary terminals.
  • the circuit board 138 may be mounted on a protruding portion 206 inside the power semiconductor module 100.
  • the protruding portion 206 may, for example, protrude from an inner surface of the terminal block 114.
  • Fig. 3 shows a flow diagram for a method 300 of manufacturing the power semiconductor module of Fig. 1 or Fig. 2.
  • the substrate 102 with the terminal area 108 and with the power semiconductor chip 104 bonded to the substrate 102 and electrically connected to the terminal area 108 is provided.
  • the substrate 102 may be mounted to the base plate 110.
  • the housing 112 may be mounted to the base plate 110.
  • the housing 112 may also be solely mounted to the substrate 104.
  • the terminal block 114 is formed by embedding the terminals 116, 118 in the thermosetting polymer.
  • the forming is performed in a transfer molding process in such a way that the two ends 120, 122 of each of the terminals 116, 118 are not enclosed with the thermosetting polymer.
  • the terminal block 114 may then be mounted to the housing 112 by mechanical connection.
  • a third step 330 the first ends 120 are bonded to the terminal area 108.
  • the housing 112 and terminal block 114 may be separate parts made from different materials by different kinds of molding processes.
  • the terminal block 114 may be made by transfer molding from a thermosetting polymer.
  • the terminal block 114 and/or the housing 112 may be provided with notches and/or stop positions for easy assembly.
  • the auxiliary terminals 204 may each have a first end mounted to the substrate 102 and/or connected to the circuit board 138 and a second end adapted for receiving a screw and/or an external pin.
  • the auxiliary terminals 204 and the power terminals 116, 118 may be embedded into the same terminal block 114.
  • the auxiliary terminals 204 may be embedded into a separate part, e. g. the cover 134.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Structures Or Materials For Encapsulating Or Coating Semiconductor Devices Or Solid State Devices (AREA)
  • Wire Bonding (AREA)

Abstract

The invention relates to a power semiconductor module (100). The power semiconductor module (100) comprises a substrate (102) with a terminal area (108), at least one power semiconductor chip (104) electrically connected to the terminal area (108), and at least two terminals (116, 118) embedded in a thermosetting polymer to form a terminal block (114). The terminal block (114) exposes an end (120, 122) of each of the terminals (116, 118) and the end (120) of each terminal (116, 118) is connected to the terminal area (108).

Description

DESCRIPTION
POWER SEMICONDUCTOR MODULE WITH TERMINAL BLOCK
FIELD OF THE INVENTION
The invention relates to the field of power electronics. In particular, the invention relates to a power semiconductor module as well as to a method of manufacturing such a power semiconductor module.
BACKGROUND OF THE INVENTION
To simplify the assembly process of a power semiconductor module, a terminal block may be used. Such terminal blocks may be preprocessed parts comprising several terminals embedded into a common resin body to form a building block. The handling of such a terminal block may be significantly easier than the handling of several single terminals.
Terminal blocks are typically molded from thermoplastic resin in an injection molding process. The thermoplastic resin may be filled with glass fibers to improve the mechanical strength of the resin material. Although an injection molding process may be comparably easy to perform, the use of thermoplastic material may have some disadvantages with respect to thermal and thermomechanical behavior. Even with a filler content of 30 percent, there may be a strong mismatch between a thermal expansion of the thermoplastic material and a thermal expansion of a material of the terminals, e. g. copper or copper alloy. Furthermore, thermoplastic materials may become unstable in humid environment, especially at high temperatures. Since thermoplastic materials typically have a comparably low glass transition temperature, a CTE (coefficient of thermal expansion) mismatch between the thermoplastic resin and the terminals may become quite important. Also, thermal decomposition of the thermoplastic resin may occur at high temperatures.
EP 0 791 961 A2 shows a power semiconductor module with a resin case in which terminals are integrated by integral molding.
JP 2011-060800 A shows a terminal block structure consisting of two terminals which are separated by one or two electrically isolating layers. The complete structure is embedded in resin. DESCRIPTION OF THE INVENTION
It is an objective of the invention to provide a power semiconductor module with a terminal block which combines both the advantages of simple manufacturing and thermal stability.
This objective is achieved by the subject-matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.
By molding the terminal block from thermosetting resin instead of thermoplastic resin, the thermomechanical properties of the terminal block may be improved. Exemplarily, a mismatch between a CTE of the resin material and a CTE of the material of the terminals may be significantly reduced, which may reduce thermomechanical stress and, consequently, increase lifetime of the power semiconductor module. For example, the CTE of the resin material may be adjusted by adding an appropriate amount of an appropriate filler material. For example, a standard mold compound for transfer molding may have a filler content of up to 90 percent. Furthermore, the glass transition temperature of thermosetting resin is higher than the glass transition temperature of thermoplastic resin. Thus, even at high temperatures, the CTE of thermosetting resin may remain on a moderate level. Additionally, thermosetting resin may be more stable in humid environment and less prone to thermal decomposition. Finally, transfer molding using thermosetting resin offers the possibility of manufacturing comparably thin structures.
Briefly summarized, by using thermosetting resin as a mold compound for molding the terminal block, the CTE as well as the thermal conductivity of the matrix material may be easily adjusted by adjusting the filler material and content accordingly. The filler material may also comprise fibers to mechanically reinforce the thermosetting resin. Furthermore, the stability of the terminal block against heat, humidity and hazardous gases may be improved. Due to a lower thermal mismatch between the different materials of the terminal block, the terminal block may have a distinctly longer lifetime.
A first aspect of the invention relates to a power semiconductor module. The power semiconductor module comprises a substrate with a terminal area, at least one power semiconductor chip, which may be bonded to the substrate, and which is electrically connected to the terminal area, and at least two terminals embedded in a thermosetting polymer, which thermosetting polymer forms a terminal block. The terminal block exposes an end of each of the terminals for electrically connecting the end. The end of each terminal is connected, for example bonded, to the terminal area. For example, the end may be directly bonded to the substrate. Alternatively, the end may be connected to the substrate and/or the power semiconductor chip by wire bonding.
For example, the terminal block may expose a first end and a second end of each of the terminals, wherein the first ends may be attached to the terminal area and the second ends may extend along an outer surface of the terminal block. The second ends may also extend vertically from the housing.
Further, at least one of the terminals may have a foot protruding from the terminal block, wherein the foot may be connected, for example bonded, to the terminal area. The foot may be the end of the terminal connected to the terminal area. In general, a foot may be seen as a protruding portion of the terminal. In other words, the foot and the terminal may be made in one piece of the same material.
It has to be noted that the terminal area may be composed of several parts, which are electrically connected to different parts of the one or more semiconductor chips.
In general, a semiconductor module may be any device composed of one or more semiconductor chips, their electrical and mechanical interconnections and a housing for these components. The power semiconductor module may be used in various power electronics applications to switch or rectify electric currents. The term “power” as in “power semiconductor module” and similar instances mentioned above and below may refer to modules and/or semiconductor chips adapted for processing current of more than 100 V and/or more than 10 A.
The power semiconductor chip may be based on silicon (Si) and/or silicon carbide (SiC) and/or may provide one or more semiconductor elements, such as diodes and/or solid-state semiconductor switches. Such a switch may be a transistor, a thyristor, an IGBT (insulated- gate bipolar transistor) or a MOSFET (metal-oxide-semiconductor field-effect transistor).
It may be that the power semiconductor module comprises a semiconductor chip with a switch, and a semiconductor chip with a diode connected anti-parallel to the switch via conductors of a metallization layer. Furthermore, the power semiconductor module may comprise one or more half-bridges composed of such combinations of switch and diode.
The one or more power semiconductor chips and the respective ends of the terminals may be connected, for example bonded, to the substrate. Bonding may refer to soldering, sintering, and welding, e. g. ultrasonic welding. The power semiconductor module may have multiple electrical terminals for connecting DC and AC load currents to an external busbar. In addition to such power terminals, the power semiconductor module may also have auxiliary terminals, such as for controlling the gates of the semiconductor chips in the module, which may be connected to an external gate driver circuit board. An auxiliary terminal may also be an auxiliary emitter, an auxiliary collector, or a signal terminal for an intelligent power module. The terminals may be made of copper or a copper alloy. Optionally, the terminals may at least partially be coated with a metallization layer, e. g. a nickel layer.
The substrate may carry the power semiconductor chip and may provide electrical and thermal contact as well as electrical insulation. The substrate may be a plate of an electrically insulating material, such as plastics or ceramics, which is covered with a metallization layer on one or both sides. The metallization layer may be structured to provide electrical conductors to which the power semiconductor chip may be connected.
The terminal area may be made of one or more electrically conductive portions of the substrate. For example, the terminal area may comprise a portion of said metallization layer and may be electrically connected to the power semiconductor chip via the metallization layer. Additionally or alternatively, the terminal area may be electrically connected to the power semiconductor chip with clips or by wire bonding.
A thermosetting polymer, also called thermosetting resin or thermoset, may be a polymer that is irreversibly hardened by curing from a soft solid or viscous liquid prepolymer or resin. The curing may be induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst. The result of such curing may be an infusible and insoluble polymer network consisting of chemically crosslinked polymer chains. For example, the thermosetting polymer may be an epoxy resin.
The thermosetting polymer may further comprise one or more filling materials. Thus, the term “thermosetting polymer” may also be understood as a mixture of a thermosetting polymer and one or more filling materials. In general, the filling material may be provided as particles, such as beads and/or fibers.
The terminal block may be generated by transfer molding. The thermosetting polymer may enclose at least a central part of the terminals. One or both ends of each terminal may not be enclosed with the thermosetting polymer so that they are accessible from outside the terminal block. Further, the terminal block may define one or more cavities when combined with the substrate and/or with a base plate of the power semiconductor module. For example, the cavities may be filled with a gel. The terminal block may also be configured as a fixture for soldering or welding of terminal feet and/or ends to the substrate, which may allow for a more accurate positioning of the terminals.
According to an embodiment of the invention, the power semiconductor module may further comprise a housing and a base plate. The substrate and the housing may be attached to the base plate. The housing may at least partially cover the substrate.
For example, the housing may be molded by transfer or injection molding. The housing may completely cover the power semiconductor chip, the terminal area and/or conductors electrically interconnecting the power semiconductor chip and the terminal area. Further, the housing may completely cover the substrate. The housing may comprise a border part in the form of a frame, which may extend along a border of the substrate and/or a border of the base plate. It is also possible that the housing is made with a least one opening to access parts within the housing. The one or more openings may be covered with a suitable cover. For example, the cover may be made from a different material than the rest of the housing.
The base plate may be a metal plate or be made from a compound material like AlSiC or MgSiC, for example. The base plate may be attached to the substrate opposite to the power semiconductor chip. For example, the base plate may serve as a cooling plate.
According to an embodiment, the power semiconductor module may further comprise a housing. The housing may be attached to the substrate and may at least partially cover the substrate.
According to an embodiment of the invention, the terminal block and the housing may be made in one piece of the same material, i. e. the thermosetting polymer. Alternatively, the terminal block and the housing may be made from two or more pieces, wherein the terminal block may include one or more parts of the housing. In other words, the terminal block and the housing may both be molded from the same thermosetting polymer by transfer molding. The terminals may at least partially run through a border part of the molded piece. This may simplify the manufacturing of the power semiconductor module.
According to an embodiment of the invention, the terminal block and the housing are made of different materials. Also, the terminal block and the housing may be realized as separate parts of different materials. For example, the housing may be molded from a thermoplastic polymer by injection molding. The terminal block may be attached to the housing and/or the base plate. This has the advantage that the terminal block may be provided independently from the housing. For example, the housing may comprise one or more mounting areas to mount the terminal block during assembly of the power semiconductor module, exemplarily for fixing the terminals during bonding of the terminals to the terminal area.
Additionally, the terminal block and/or the housing, regardless of the materials they are made of, may have connecting elements, such as stop positions or notches, which may simplify assembly of the terminal block and the housing.
According to an embodiment of the invention, a part of the housing may be formed of a thermoplastic polymer. For example, the housing may comprise a removable cover for covering an opening of the housing. The cover may be made of a thermoplastic polymer. Optionally, a further part of the housing may be formed as the terminal block from the thermosetting polymer. With this embodiment, manufacturing costs may be reduced.
According to an embodiment of the invention, the thermosetting polymer has a filler content of at least 50 percent. In other words, at least 50 percent of a mold compound used for molding the terminal block may be particles added to a thermosetting polymer matrix. Exemplarily, the thermosetting polymer may typically have a filler content of at least 60 to 90 percent. In general, a filler material used to fill the thermosetting polymer may be a mineral or glass based material in the form of particulates and/or fibers. With this embodiment, the CTE of the thermosetting polymer may be significantly reduced.
According to an embodiment of the invention, the thermosetting polymer has a filler content adapted with regard to a coefficient of thermal expansion of a material of the terminals. For example, the filler content may be adapted so that a discrepancy between a CTE of a mold compound comprising a thermosetting polymer matrix and a CTE of the terminals is 25 percent or less.
According to an embodiment of the invention, the thermosetting polymer may comprise at least one of the following materials: glass fibers, carbon fibers, fused silica, epoxysilane, aminosilane, silicon dioxide, metal oxide, antimony oxide, phosphate ester, brominated epoxy, bismuth, pigments. For example, epoxysilanes and/or aminosilanes may be used as adhesion promoter. A dielectric strength of the terminal block may be increased by adding silicon dioxide as a filler. A CTI (comparative tracking index) of the terminal block may be adapted by adding metal oxides such as iron oxide, magnesium oxide or aluminum oxide. Further, phosphate ester, antimony oxide and/or brominated epoxy may be added as a flame retardant to prevent or slow the development of an ignition. Bismuth may be added as an ion trapping agent. Pigments may be added for coloring the terminal block. Additionally or alternatively, at least one of the two terminals may be at least partially coated with a metallization layer, e. g. nickel.
According to an embodiment of the invention, the terminal block may comprise at least one thread insert and expose a first end and a second end of at least one of the terminals. The first end may be connected, for example bonded, to the terminal area. The second end may extend along an outer surface of the terminal block and have an opening opposite to the thread insert. For example, the thread insert may be embedded into the thermosetting polymer when the terminal block is being formed by transfer molding. The thread insert may be seen as an embedded nut. With this embodiment, an electrical contact element, such as an external busbar, may be easily and securely connected to the power semiconductor module.
According to an embodiment of the invention, the terminal block may comprise a rib structure to increase a creepage length between the terminals. Dirt, pollution, salt, and exemplarily water on the surface of the terminal block may create a conductive path across it, causing leakage currents and flashovers. In general, the rib structure may be seen as a structure shaped to maximize a creepage distance along the surface of the terminal block and to minimize these leakage currents. To accomplish this, the rib structure may comprise one or more ribs and valleys arranged next to each other. In general, the rib structure may be seen as a corrugation or a series of corrugations.
According to an embodiment of the invention, the at least two terminals comprise at least one of a power terminal and an auxiliary terminal. A power terminal may be a terminal adapted for conducting a load current through the power semiconductor module. An auxiliary terminal may be adapted for conducting sensing and/or control signals. It is also possible that the terminal block comprise only power terminals or only auxiliary terminals.
According to an embodiment of the invention, the terminal area comprises at least one of a power terminal area and an auxiliary terminal area. The terminal area may be a power terminal area, which may be electrically connected to a load electrode or a power electrode of the power semiconductor chip, such as a collector or an emitter. An auxiliary terminal area also may be electrically connected to a gate of the semiconductor chip. An area of the auxiliary terminal area may be smaller than an area of the power terminal area. Additionally, an area of the auxiliary terminal may be connected to an area of a metallization layer on the substrate. According to an embodiment of the invention, the power semiconductor module may further comprise a circuit board with an auxiliary terminal area, and at least one auxiliary terminal embedded in the thermosetting polymer of the terminal block. The terminal block may expose an end of the auxiliary terminal. The end of the auxiliary terminal may be connected, for example bonded, to the auxiliary terminal area on the circuit board. The end of the auxiliary terminal may be directly bonded to a gate driver board, for example. A structure of the end of the auxiliary terminal may be similar to a structure of the second ends of the power terminals. For example, the circuit board may be a gate driver board or serve for interconnection purposes only. Accordingly, the auxiliary terminal area may be electrically connected to a gate electrode of the power semiconductor chip. The auxiliary terminals may be adapted for transmitting auxiliary signals, such as for controlling gate drivers. However, it is also possible that the auxiliary terminal area and/or a further auxiliary terminal area is located on the substrate. For example, auxiliary terminals embedded in the terminal block may be directly bonded to a corresponding metallization pattern on the substrate itself and/or to the circuit board. The circuit board may be located inside or outside a housing of the power semiconductor module.
According to an embodiment of the invention, the terminal block may expose a further end of the auxiliary terminal. The further end of the auxiliary terminal may be connected to the substrate, e. g., to an auxiliary terminal area of the substrate, and/or the power semiconductor chip. For example, the further end may be connected by wire bonding or directly bonded to the substrate and/or the power semiconductor chip.
A further aspect of the invention relates to a method of manufacturing a power semiconductor module. The method comprises the following steps: providing a substrate with a terminal area and with at least one power semiconductor chip, which may be bonded to the substrate, and which may be electrically connected to the terminal area, forming a terminal block by embedding at least two terminals in a thermosetting polymer, wherein the terminal block exposes an end of each of the terminals, and connecting, such as bonding, the end of each of the terminals to the terminal area.
The forming may be done in a transfer molding process. Transfer molding and post curing under inert atmosphere, such as nitrogen, may be beneficial to avoid oxidation of the terminal area. Depending on the process for connecting a terminal to the terminal area, a selective or complete plating of the terminal and/or the terminal area may be performed prior to or after the forming.
It has to be understood that features of the power semiconductor module as described above and below may be features of the method as described above and below.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings.
Fig. 1 schematically shows a power semiconductor module according to an embodiment of the invention.
Fig. 2 schematically shows a power semiconductor module according to a further embodiment of the invention.
Fig. 3 shows a flow diagram for a method of manufacturing a power semiconductor module according to an embodiment of the invention.
The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Fig. 1 shows a cross section of a power semiconductor module 100. The power semiconductor module 100 comprises a substrate 102 which carries a power semiconductor chip 104. It is possible that two or more power semiconductor chips 104 are bonded to the substrate 102, as described above. However, only one power semiconductor chip 104 is shown in Fig. 1.
The substrate 102 may be a ceramics substrate with a metallization layer 106 which is structured to provide a terminal area 108 and several conductors which electrically connect the terminal area 108 with the power semiconductor chip 104. The metallization layer 106 and the power semiconductor chip 104 are bonded on the same side of the substrate 102. The power semiconductor chip 104 has, for example, two planar power electrodes and a planar gate electrode which are bonded on the conductors. Only the backside of the power semiconductor chip 104 may be bonded to the substrate 102. The top side contacts may be interconnected by wire bonding, for example. Also, a direct interconnection of the chip surface by terminals or clips is possible. The terminal area 108 is a power terminal area which is connected to the power electrodes of the power semiconductor chip 104.
The substrate 102 is bonded to a base plate 110, for example a metal plate. The base plate 110 may also serve as a cooling body. It is also possible that the substrate 102 is a printed circuit board or a lead frame. The metallization layer 106 and the power semiconductor chip 104 are bonded to an upper side of the substrate 102, opposite to the base plate 110.
The substrate 102 is at least partially covered by a housing 112 which is mounted to the base plate 110. The housing 112 may be screwed or glued onto the base plate 110. It is also possible that the housing 112 is mounted to the substrate 102. In this case, the substrate 102 may serve as a base plate.
The power semiconductor module 100 further comprises a terminal block 114, in which a DC+ terminal 116 and a DC- terminal 118 are embedded. The terminal block 114 and the housing 112 are manufactured as separate parts. The terminal block 114 is molded from a thermosetting polymer such as epoxy resin by transfer molding. The housing 112 may be molded from a thermoplastic polymer by injection molding. The terminal block 114 may be attached to the housing 112 and/or the base plate 110 after the housing 112 has been attached to the base plate 110.
Alternatively, part of the housing 112, e. g., a border part extending along a border of the base plate 110, may be formed as the terminal block 114. In this case, the terminal block 114 and the rest of the housing 112 may be made of the same material, i. e. the thermosetting polymer. In other words, the housing 112 and the terminal block 114 may be made in one piece in the same transfer molding process.
The terminals 116, 118 may be made of copper or a copper alloy. For example, the terminals 116, 118 may be bent plates or sheets.
Each of the terminals 116, 118 has a first end 120 and a second end 122. The first ends 120 are each formed as a foot protruding from the terminal block 114 and bonded to the terminal area 106, for example by means of ultrasonic welding. More precisely, the feet are each bent to an L shape with a horizontal portion which is bonded to the terminal area 108. The second ends 122 each extend along an upper surface of the terminal block 114, opposite to the base plate 110. However, the second ends 122 may also extend vertically from the housing. A central part of the terminals 116, 118 between the first ends 120 and the second ends 122 is completely enclosed with the thermosetting polymer which electrically isolates the terminals 116, 118 from each other.
Furthermore, an outer surface of the housing 110 has a rib structure comprising a plurality of alternating ribs 124 and valleys 126. The rib structure increases a creepage length between the two terminals 116, 118. The rib structure also extends vertically along a border part of the housing 112 in order to increase a creepage length between the terminals 116, 118 and the base plate 110.
In this example, two thread inserts 128 are embedded in the terminal block 114. Each of the second ends 122 has a screw opening 130 opposite to one of the threads in the thread inserts 128, so that a screw can be inserted through the second ends 122 and screwed into the thread inserts 128. The thread inserts 128 may be used to screw an external busbar onto the terminals 116, 118.
The housing 112 has a housing opening 132 for accessing inner parts of the power semiconductor module 100. The housing opening 132, which may be, for example, a central opening in the power semiconductor module 100, is covered by a cover 134. The cover 134 may be made of a different material than that of the housing 112. For example, the cover 134 may be molded from a thermoplastic polymer by injection molding. It is possible that also other parts of the power semiconductor module 100 are made of a thermoplastic polymer. Alternatively, the housing 112 including the cover 134 may be completely made of the thermosetting polymer.
As shown in Fig. 1, the terminal block 114 may enclose one or more cavities 136 with the base plate 110 and/or the substrate 102. Optionally, the cavities 136 may be filled with a gel.
The terminal block 114 may be designed as a fixture for prepositioning the first ends 120 above the terminal area 108 prior to a bonding process.
Briefly summarized, the use of a thermosetting polymer for molding the terminal block 114 may result in several advantages compared to the use of a thermoplastic material, such as the adjustment of the thermal expansion coefficient of the terminal block 114 by adapting a filler content of the thermosetting polymer. A suitable filler may consist of particles and/or fibers. In contrast to standard mold compounds used in electronic packaging, the thermosetting polymer used for the terminal block 114 may also be mechanically reinforced by fibers. Another advantage is the improved stability of the terminal block 114 against heat, humidity, and hazardous gases. Furthermore, the shape stability of the terminal block 114 after processing, due to a reduced thermal mismatch between a material of the terminals 116, 118, e. g. copper, and the thermosetting polymer of the terminal block 114, may be improved.
The following table exemplarily shows material parameters of a typical transfer mold compound (thermosetting resin) compared to a typical fiber-reinforced thermoplastic material (PA66 with 30 percent glass fibers) which may be conventionally used for molding a terminal block.
Material Property Transfer Mold Compound PA66/GF30 Filler Content (wt%) 60-90 30 Filler Shape / Size (pm) 25-100 fibers E-Modulus at RT (GPa) 10-30 11 Flexural Strength (MPa) 100-200 210-240 Water Absorption (wt%) 0.1-0.4 4.3-5.3 CTE 1 (ppm/K) 6-30 25 (longit.) / 50-60 (transv.) at 23-55°C
CTE 2 (ppm/K) 25-60
Glass Transition Temp. (°C) 125-260
Thermal Conductivity 0.7-5 0.25
Dielectric Const (at 1 kHz, RT) 3.2 3.9-4.1
Vol. Resistivity at RT (Dm) Iel2-lel4 Iel5-lel4 Melting Temperature (°C) 290 Process Temperature (°C) 170-180 310-330
Not only the comparison of the thermal expansion coefficients, but also the strongly differing melting and process temperatures show the superiority of the transfer molding compound above the thermoplastic material. It has to be taken into account that the molding process is performed at a process temperature of 170 °C to 180 °C for transfer molding. Due to a melting point of 290 °C, the process temperature of the thermoplastic material is about 140 °C higher than the process temperature of the transfer molding compound.
The embedding of the terminals 116, 118, which, if made of copper, may have a thermal expansion coefficient of 16.4 ppm/K at room temperature, is performed at the process temperature. At a process temperature of 170 °C to 180 °C, the system is in a stress-free situation, whereas the melting temperature of the thermoplastic material is at least 110 °C higher. In the latter, when the thermoplastic material is cooling down, strong thermomechanical stress may occur between the terminals and the thermoplastic material, which may not only cause cracks, but also deteriorate shape stability. Additionally, the clearly lower CTE and the higher glass transition temperature of the transfer mold compound, resulting in a larger temperature range staying in the CTE1 regime, may contribute to an additional stress reduction compared with the thermoplastic material and also improve reproducibility of the shape.
By embedding two or more power and/or auxiliary terminals into a thermosetting polymer matrix to realize one common building block, such as the terminal block 114 described above and below, the thermal mismatch between the terminals 116, 118 and the polymer matrix may be minimized. This may also significantly reduce stress in the terminal block 114 during thermal cycling.
The transfer mold compound may be filled with fibers, e. g. glass or carbon fibers, and/or with particles, e. g. fused silica, to achieve a high filler content of up to 90 percent, exemplarily with respect to an adjustment of the CTE.
Other ingredients may be added to adjust mechanical, electrical, and/or electromagnetic properties, as already described above.
Fig. 1 also shows a circuit board 138, which is a gate driver board for controlling the gates of the one or more power semiconductor chip 104. The circuit board 138 may be covered by the cover 134.
Fig. 2 shows a cross section of a power semiconductor module 100 according to a further embodiment. Unless otherwise described, the components of the module 100 of Fig. 2 may be the same and/or may have the same properties as the one of Fig. 1. In contrast to Fig. 1, where the terminal block 114 encloses the one or more cavities 136, the terminal block 114 of Fig. 2 is formed as a compact building block.
Additionally, the circuit board 138 may have an auxiliary terminal area 202. The auxiliary terminal area 202 may be electrically interconnected with the gate electrode of the power semiconductor chip 104. Two auxiliary terminals 204 are bonded with an end onto the auxiliary terminal area 202. The two auxiliary terminals 204 each run through the cover 134 and end on an upper surface of the cover 134 to provide planar contact surfaces for electrically contacting the auxiliary terminals 204 from outside the housing 112.
In this example, the terminal block 114 and the cover 134 are made of the same thermosetting polymer. In other words, the cover 134 is part of the terminal block 114 so that the auxiliary terminals 204 are embedded in the terminal block 114 in the same manner as the power terminals 116, 118. It is possible that the terminal block 114 and the cover 134 are made in one piece. The cover 134 may also be a separate transfer molded part with integrated auxiliary terminals.
The circuit board 138 may be mounted on a protruding portion 206 inside the power semiconductor module 100. The protruding portion 206 may, for example, protrude from an inner surface of the terminal block 114.
Fig. 3 shows a flow diagram for a method 300 of manufacturing the power semiconductor module of Fig. 1 or Fig. 2.
In a first step 310, the substrate 102 with the terminal area 108 and with the power semiconductor chip 104 bonded to the substrate 102 and electrically connected to the terminal area 108 is provided. Optionally, the substrate 102 may be mounted to the base plate 110. Then, the housing 112 may be mounted to the base plate 110. The housing 112 may also be solely mounted to the substrate 104.
In a second step 320, the terminal block 114 is formed by embedding the terminals 116, 118 in the thermosetting polymer. The forming is performed in a transfer molding process in such a way that the two ends 120, 122 of each of the terminals 116, 118 are not enclosed with the thermosetting polymer. The terminal block 114 may then be mounted to the housing 112 by mechanical connection.
In a third step 330, the first ends 120 are bonded to the terminal area 108.
As already described above, the housing 112 and terminal block 114 may be separate parts made from different materials by different kinds of molding processes. Exemplarily, the terminal block 114 may be made by transfer molding from a thermosetting polymer. The terminal block 114 and/or the housing 112 may be provided with notches and/or stop positions for easy assembly.
Similar to the power terminals 116, 118, the auxiliary terminals 204 may each have a first end mounted to the substrate 102 and/or connected to the circuit board 138 and a second end adapted for receiving a screw and/or an external pin. The auxiliary terminals 204 and the power terminals 116, 118 may be embedded into the same terminal block 114. Alternatively, the auxiliary terminals 204 may be embedded into a separate part, e. g. the cover 134.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or controller or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
LIST OF REFERENCE SYMBOLS 100 power semiconductor module
102 substrate
104 power semiconductor chip 106 metallization layer
108 terminal area
110 base plate
112 housing
114 terminal block 116 terminal
118 terminal
120 first end
122 second end
124 rib 126 valley
128 thread insert
130 screw opening
132 housing opening
134 cover 136 cavity
138 circuit board
202 auxiliary terminal area
204 auxiliary terminal
206 protruding portion 300 method of manufacturing
310 step of providing
320 step of forming
330 step of bonding

Claims

1. A power semiconductor module (100), comprising: a substrate (102) with a terminal area (108); at least one power semiconductor chip (104) electrically connected to the terminal area (108); at least two terminals (116, 118) embedded in a thermosetting polymer, which thermosetting polymer forms a terminal block (114); wherein the terminal block (114) exposes an end (120) of each of the terminals (116,
118); wherein the end (120) of each of the terminals (116, 118) is connected to the terminal area (108).
2. The power semiconductor module (100) of claim 1, further comprising: a housing (112); wherein the housing (112) is attached to the substrate (102); wherein the housing (112) at least partially covers the substrate (102).
3. The power semiconductor module (100) of claim 1, further comprising: a housing (112); a base plate (110); wherein the substrate (102) and the housing (112) are attached to the base plate (110); wherein the housing (112) at least partially covers the substrate (102).
4. The power semiconductor module (100) of claim 2 or 3, wherein the terminal block (114) and the housing (112) are made in one piece of the thermosetting polymer.
5. The power semiconductor module (100) of claim 2 or 3, further comprising at least one of: the terminal block (114) and the housing (112) being made of different materials; and the terminal block (114) and the housing (112) being made as separate parts, at least one of the parts having a connecting element for interconnecting the separate parts.
6. The power semiconductor module (100) of one of claims 2 to 5, wherein a part (134) of the housing (112) is formed of a thermoplastic polymer.
7. The power semiconductor module (100) of one of the previous claims, wherein the thermosetting polymer has a filler content of at least 50 percent.
8. The power semiconductor module (100) of one of the previous claims, wherein the thermosetting polymer has a filler content adapted with regard to a coefficient of thermal expansion of a material of the terminals (116, 118).
9. The power semiconductor module (100) of one of the previous claims, wherein the thermosetting polymer comprises at least one of the following materials: glass fibers, carbon fibers, fused silica, epoxysilane, aminosilane, silicon dioxide, metal oxide, antimony oxide, phosphate ester, brominated epoxy, bismuth, pigments; wherein at least one of the terminals (116, 118) is at least partially coated with a metallization layer.
10. The power semiconductor module (100) of one of the previous claims, wherein the terminal block (114) comprises at least one thread insert (128) and exposes the end (120), being a first end (120), and a second end (122) of at least one of the terminals (116, 118); wherein the first end (120) is connected to the terminal area (108); wherein the second end (122) extends along an outer surface of the terminal block (114) and has an opening (130) opposite to the thread insert (128).
11. The power semiconductor module (100) of one of the previous claims, wherein the terminal block (114) comprises a rib structure (124, 126) to increase a creepage length between the terminals (116, 118).
12. The power semiconductor module (100) of one of the previous claims, wherein the at least two terminals (116, 118) comprise at least one of a power terminal and an auxiliary terminal (304); wherein the terminal area (108) comprises at least one of a power terminal area and an auxiliary terminal area (202).
13. The power semiconductor module (100) of one of the previous claims, further comprising: a circuit board (138) with an auxiliary terminal area (202); at least one auxiliary terminal (204) embedded in the thermosetting polymer of the terminal block (114); wherein the terminal block (114) exposes an end of the auxiliary terminal (204); wherein the end of the auxiliary terminal (204) is connected to the auxiliary terminal area (202).
14. The power semiconductor module (100) of claim 13, wherein the terminal block (114) exposes a further end of the auxiliary terminal (204); wherein the further end of the auxiliary terminal (204) is connected to at least one of the substrate (102) and he power semiconductor chip (104).
15. A method (300) of manufacturing a power semiconductor module (100), the method (300) comprising: providing (310) a substrate (102) with a terminal area (108) and with at least one power semiconductor chip (104) electrically connected to the terminal area (108); forming (320) aterminal block (114) by embedding at least two terminals (116, 118) in a thermosetting polymer, wherein the terminal block (114) exposes an end (120, 122) of each of the terminals (116, 118); connecting (330) the end (120) of each terminal (116, 118) to the terminal area (108).
PCT/EP2020/085325 2019-12-10 2020-12-09 Power semiconductor module with terminal block WO2021116192A1 (en)

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CN202090001000.2U CN219716867U (en) 2019-12-10 2020-12-09 Power semiconductor module
DE212020000777.2U DE212020000777U1 (en) 2019-12-10 2020-12-09 power semiconductor module
JP2022600087U JP3239985U (en) 2019-12-10 2020-12-09 Power semiconductor module with terminal block

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EP0828341A2 (en) * 1996-09-06 1998-03-11 Hitachi, Ltd. Modular type power semiconductor apparatus
US20110012251A1 (en) * 2009-07-14 2011-01-20 Kabushiki Kaisha Toshiba Semiconductor device and method for manufacturing same
JP2011060800A (en) 2009-09-07 2011-03-24 Shin Kobe Electric Mach Co Ltd Resin molded compact
US20160240452A1 (en) * 2015-02-18 2016-08-18 Semiconductor Components Industries, Llc Semiconductor packages with sub-terminals and related methods

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EP0791961A2 (en) 1996-02-22 1997-08-27 Hitachi, Ltd. Power semiconductor module
EP0828341A2 (en) * 1996-09-06 1998-03-11 Hitachi, Ltd. Modular type power semiconductor apparatus
US20110012251A1 (en) * 2009-07-14 2011-01-20 Kabushiki Kaisha Toshiba Semiconductor device and method for manufacturing same
JP2011060800A (en) 2009-09-07 2011-03-24 Shin Kobe Electric Mach Co Ltd Resin molded compact
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022268447A1 (en) * 2021-06-25 2022-12-29 Robert Bosch Gmbh Electrical arrangement with a positioning aid, and production method

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JP3239985U (en) 2022-11-29

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