Leadless direct attach interconnect structure and smart power module

Abstract

The application discloses a leadless direct-attached interconnection structure, comprising: a substrate; an IGBT power chip, the inside of the IGBT power chip comprising a first copper column, the first copper column penetrating the IGBT power chip and leading a collector electrode to the other side, the IGBT power chip being fixed on the substrate; a diode power chip, the inside of the diode power chip comprising a second copper column, the second copper column penetrating the diode power chip and leading an anode electrode to the other side, the diode power chip being fixed on the substrate; and a driving chip, the inside of the driving chip comprising a third copper column, the third copper column penetrating the driving chip and leading a substrate to the other side, the driving chip being fixed on the substrate. The leadless direct-attached interconnection structure does not comprise a lead. The electrodes of the chips are led to the same side of the chips through the copper columns penetrating the chips, and the side is directly fixed on the substrate, so that high-frequency switching loss and electromagnetic interference are reduced, and long-term reliability, power density and heat dissipation efficiency of the module are improved.

Description

Technical Field

[0001] This invention relates to the field of power semiconductors, and more particularly to a leadless direct-mount interconnect structure and a smart power module. Background Technology

[0002] An IPM (Intelligent Power Module) is an electronic component that integrates power switching devices and drive protection circuits into a single unit, widely used in variable frequency home appliances, industrial servos, and new energy inverters. In traditional IPM packaging structures, IGBT power chips typically use a back-side collector mounted on the substrate, while the gate and emitter are located on the front side of the chip. Fast recovery diode power chips also use a back-side cathode mounted on the substrate, with the anode located on the front side. The electrodes on the front side of the chip need to be electrically connected to the pins on the IC (Integrated Circuit) chip via metal bonding leads. The IGBT collector, diode cathode, and IC substrate are connected to the substrate wiring. This packaging method, with bonding leads as the core interconnection method, has formed a relatively mature process system through long-term industrial application.

[0003] However, as power electronic devices evolve towards higher frequencies and higher power densities, the traditional packaging structures mentioned above are increasingly unable to meet application requirements. The bonding wires themselves are long and thin, arching across the chip and substrate, introducing significant parasitic inductance and capacitance into the circuit. Under high-frequency switching conditions, voltage and current overshoot are pronounced, leading to increased switching losses and significant electromagnetic interference. The bonding wires are connected to the chip electrodes and substrate pads via bonding points, continuously subjected to thermal stress from temperature and power cycling during long-term module operation. Once fatigue occurs at the bonding interface, detachment or even breakage can easily occur, limiting the long-term reliability and lifespan of the module. The power chip and driver IC are separated by leads, resulting in long interconnect paths. This makes it difficult to achieve compact chip arrangement on the substrate, leading to a larger overall module size and hindering the improvement of power density. The heat dissipation path from the chip front through the bonding wires is circuitous and difficult to conduct to the external heat sink in a timely manner, further limiting the module's output capability under high-power conditions. Traditional wire-bonded IPM packages have difficulty balancing parasitic parameters, long-term reliability, integration density, and heat dissipation efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention discloses a leadless direct-attach interconnect structure for use in smart power modules, comprising: substrate; IGBT power chip, the IGBT power chip includes a first copper pillar inside, one end of the first copper pillar is connected to the collector electrode on the first surface of the IGBT power chip, and the other end of the first copper pillar is led out from the second surface of the IGBT power chip, the second surface of the IGBT power chip is fixed on the substrate; A diode power chip, wherein the diode power chip includes a second copper pillar inside, one end of the second copper pillar is connected to the anode on the first surface of the diode power chip, and the other end of the second copper pillar is led out from the second surface of the diode power chip, and the second surface of the diode power chip is fixed on the substrate; A driver chip, the driver chip having a third copper pillar inside, one end of the third copper pillar being connected to a substrate on a first surface of the driver chip, and the other end of the third copper pillar being led out from a second surface of the driver chip, the second surface of the driver chip being fixed on the substrate; The leadless direct-attach interconnect structure does not include leads.

[0005] Preferably, the substrate includes a copper wiring layer; The second side of the IGBT power chip includes a gate copper pillar bump corresponding to the gate, an emitter copper pillar bump corresponding to the emitter, and a collector copper pillar bump corresponding to the first copper pillar. The second side of the diode power chip includes a cathode copper pillar bump corresponding to the cathode and an anode copper pillar bump corresponding to the second copper pillar. The second side of the driver chip includes pin copper pillar bumps corresponding to each pin and substrate copper pillar bumps corresponding to the third copper pillar. The gate copper pillar bump, the emitter copper pillar bump, the collector copper pillar bump, the cathode copper pillar bump, the anode copper pillar bump, the lead copper pillar bump, and the substrate copper pillar bump are all connected to the copper wiring layer by soldering.

[0006] Preferably, the upper layer of the substrate is the copper wiring layer, the middle layer of the substrate is a ceramic layer, and the bottom layer of the substrate is copper foil.

[0007] Preferably, the bottom layer of the substrate is connected to an external heat sink.

[0008] Preferably, the IGBT power chip, the diode power chip, and the driver chip are encapsulated in a molding compound.

[0009] Preferably, the molding compound is made of epoxy resin.

[0010] Preferably, the thickness of the IGBT power chip is 100~200μm.

[0011] Preferably, the thickness of the diode power chip is 100~200μm.

[0012] Preferably, the thickness of the driver chip is 200~300μm.

[0013] This invention discloses an intelligent power module, comprising a substrate, an IGBT power chip, a diode power chip, and a driver chip in the leadless direct-mount interconnect structure.

[0014] The following beneficial effects can be obtained by using the present invention: By using copper pillars that penetrate the chip to bring the electrodes of each chip to the same surface of the chip and directly fix that surface to the substrate, the problems of large parasitic inductance and capacitance, easy fatigue fracture of the bonding interface, long interconnect path and low integration, and detour of heat dissipation path in traditional wire bonding IPM packaging are solved. This reduces high-frequency switching losses and electromagnetic interference, and improves the long-term reliability, power density and heat dissipation efficiency of the module. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the leadless direct-attach interconnect structure in this invention; Figure 2 This is a schematic diagram of the IGBT power chip in this invention; Figure 3 This is a schematic diagram of the diode power chip in this invention; Figure 4 This is a schematic diagram of the driver chip in this invention.

[0016] In the attached image: 1. Substrate; 2. IGBT power chip; 3. First copper pillar; 4. Collector; 5. Diode power chip; 6. Second copper pillar; 7. Anode; 8. Driver chip; 9. Third copper pillar; 10. Substrate; 11. Gate; 12. Gate copper pillar bump; 13. Emitter; 14. Emitter copper pillar bump; 15. Collector copper pillar bump; 16. Cathode; 17. Cathode copper pillar bump; 18. Anode copper pillar bump; 19. Lead; 20. Lead copper pillar bump; 21. Substrate copper pillar bump; 22. Molding compound. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0020] This invention discloses a leadless direct-mount interconnect structure for use in smart power modules, such as... Figures 1 to 4 As shown, it includes: substrate; The IGBT power chip includes a first copper pillar inside. One end of the first copper pillar is connected to the collector on the first surface of the IGBT power chip, and the other end of the first copper pillar is led out from the second surface of the IGBT power chip. The second surface of the IGBT power chip is fixed on the substrate. A diode power chip includes a second copper pillar inside. One end of the second copper pillar is connected to the anode on the first surface of the diode power chip, and the other end of the second copper pillar is led out from the second surface of the diode power chip. The second surface of the diode power chip is fixed on the substrate. The driver chip includes a third copper pillar inside. One end of the third copper pillar is connected to the substrate on the first surface of the driver chip, and the other end of the third copper pillar is led out from the second surface of the driver chip. The second surface of the driver chip is fixed on the substrate. Leadless direct-mount interconnect structures do not include leads.

[0021] Specifically, the IGBT power chip has a vertical conductive structure with a first side and a second side facing away from each other. The first side is the back of the chip, and a collector is located on the first side. The second side is the front of the chip, and a gate and an emitter are located on the second side. Inside the IGBT power chip, there is a first copper pillar that penetrates the silicon substrate along the chip's thickness direction. One end of the first copper pillar is connected to the collector located on the first side, and the other end is led out from the second side. The first copper pillar is a TSV (Through-Silicon Via) copper pillar formed by etching through-holes in the silicon substrate and filling them with conductive copper. It is used to vertically guide the collector, originally located on the back of the chip, to the front of the chip, so that all three electrodes of the IGBT power chip are located on the same side facing the substrate. The IGBT power chip is fixed to the substrate with its second side facing the substrate, so that the gate, emitter, and collector terminal led out from the first copper pillar are all located on one side of the second side.

[0022] The diode power chip is a fast recovery diode, also with a vertical conductivity structure, having a first side and a second side facing away from each other. The first side is the front of the chip, and it contains the anode. The second side is the back of the chip, and it contains the cathode. Inside the diode power chip, there is a second copper pillar that penetrates the silicon substrate along the chip's thickness direction. One end of the second copper pillar is connected to the anode located on the first side, and the other end extends from the second side. The second copper pillar is a TSV copper pillar, used to vertically guide the anode from the front side to the back side of the chip, so that the anode and cathode are both located on the same side facing the substrate. The diode power chip is fixed to the substrate with its second side facing the substrate.

[0023] The driver chip is a bare die of an integrated circuit for gate driving and protection inside the intelligent power module, having a first side and a second side facing away from each other. The first side is the back side of the chip, on which a substrate is located, and the substrate is grounded in the circuit. The second side is the front side of the chip, on which multiple functional pins are located. The driver chip contains a third copper pillar that penetrates the silicon substrate along the chip's thickness direction, with one end connected to the substrate on the first side and the other end leading out from the second side. The third copper pillar is a TSV copper pillar, used to guide the back substrate to the front side of the chip, so that the substrate and all functional pins are located on the same side facing the substrate. The driver chip is fixed on the substrate with its second side facing the substrate.

[0024] Furthermore, the second side of each of the three chips is fixed to the substrate, and each electrode is directly connected to the conductive wiring on the substrate through a vertical interconnect structure between the chip and the substrate. Signal and power transmission between the chips is accomplished through the substrate wiring. The interconnect structure does not include any leads, thereby eliminating the parasitic parameters and reliability issues caused by bonding leads.

[0025] In a preferred embodiment of the present invention, such as Figure 1 As shown, the substrate includes a copper wiring layer; The second side of the IGBT power chip includes a gate copper pillar bump corresponding to the gate, an emitter copper pillar bump corresponding to the emitter, and a collector copper pillar bump corresponding to the first copper pillar. The second side of the diode power chip includes a cathode copper pillar bump corresponding to the cathode and an anode copper pillar bump corresponding to the second copper pillar; The second side of the driver chip includes pin copper pillar bumps corresponding to each pin and substrate copper pillar bumps corresponding to the third copper pillar. The gate copper pillar bump, emitter copper pillar bump, collector copper pillar bump, cathode copper pillar bump, anode copper pillar bump, lead copper pillar bump, and substrate copper pillar bump are all connected to the copper wiring layer by soldering.

[0026] Specifically, the second side of the IGBT power chip has three copper pillar bumps: a gate copper pillar bump corresponding to the gate, an emitter copper pillar bump corresponding to the emitter, and a collector copper pillar bump corresponding to the first copper pillar lead-out terminal. The second side of the diode power chip has two copper pillar bumps: a cathode copper pillar bump corresponding to the cathode and an anode copper pillar bump corresponding to the second copper pillar lead-out terminal. The second side of the driver chip has multiple pin copper pillar bumps corresponding to each pin and a substrate copper pillar bump corresponding to the third copper pillar lead-out terminal. The pins include functional pins such as gate drive pins, power supply pins, and fault detection pins.

[0027] The gate copper pillar bumps, emitter copper pillar bumps, collector copper pillar bumps, cathode copper pillar bumps, anode copper pillar bumps, lead copper pillar bumps, and substrate copper pillar bumps are all connected to the copper wiring layer by soldering, achieving both electrical connection and mechanical fixation.

[0028] In one embodiment, each copper pillar bump is formed on the electrode pads on the second side of the chip via electroplating, with a height of 50 to 150 micrometers. A solder layer is formed between the copper pillar bumps and the copper wiring layer using high-temperature solder sintering. High-temperature solder sintering offers advantages such as low contact resistance, good heat dissipation, high connection strength, and strong high-temperature resistance, making it suitable for the high-current and high-temperature operating environments of power modules. The pin surface can be formed with copper pillar bumps and then connected via solder, or it can be directly connected to the copper wiring layer via solder.

[0029] In a preferred embodiment of the present invention, the upper layer of the substrate is a copper wiring layer, the middle layer of the substrate is a ceramic layer, and the bottom layer of the substrate is a copper foil.

[0030] Specifically, the copper wiring layer is used to realize the electrical connection of IGBT power chips, diode power chips and driver chips.

[0031] The ceramic layer is made of ceramic materials such as alumina or aluminum nitride and is used for electrical insulation and thermal conductivity.

[0032] Copper foil covers the lower surface of the ceramic layer.

[0033] The copper wiring layer and the underlying copper foil are directly bonded to both sides of the ceramic layer using a high-temperature bonding process, forming a three-layer composite structure. This structure combines the high electrical and thermal conductivity of copper with the high-voltage insulation properties of ceramic.

[0034] In a preferred embodiment of the present invention, the bottom layer of the substrate is connected to an external heat sink.

[0035] Specifically, the bottom copper foil is bonded to the heat sink surface via a thermally conductive interface material, allowing the heat generated by the chip to be conducted vertically through the copper pillar bumps, copper wiring layer, ceramic layer, and bottom copper foil to the heat sink for dissipation. This vertical heat dissipation path is short and has low thermal resistance, which helps to reduce the chip junction temperature and improve the module's power output capability.

[0036] In a preferred embodiment of the present invention, the IGBT power chip, the diode power chip, and the driver chip are encapsulated in a molding compound.

[0037] Specifically, the molding compound is an encapsulating insulating colloid, formed through a molding process, and filled on top of the substrate, completely covering the three chips, their copper pillar bumps, and solder layer. The first side of the IGBT power chip facing away from the substrate, the first side of the diode power chip facing away from the substrate, and the first side of the driver chip facing away from the substrate are all in a suspended state without contact with the substrate. These suspended surfaces and the sides of the chips are all filled and sealed with the molding compound.

[0038] Molding compound serves two purposes: firstly, it provides electrical insulation and environmental protection, preventing chips from being affected by moisture, pollutants, and mechanical damage; secondly, it provides mechanical support for the chips, improving the overall structural stability of the module.

[0039] In a preferred embodiment of the present invention, the molding compound is made of epoxy resin.

[0040] Specifically, epoxy resin has excellent electrical insulation properties, resistance to damp heat and mechanical strength, and good adhesion to silicon chips, copper materials and substrates, making it suitable for mass packaging through transfer molding processes.

[0041] In one embodiment, the epoxy resin molding compound is a solid epoxy molding compound, which is heated and melted and then injected into the mold cavity. After curing, it forms a dense package that completely seals the three chips and the area above the substrate.

[0042] In a preferred embodiment of the present invention, the thickness of the IGBT power chip is 100~200μm.

[0043] Specifically, a thickness range of 100~200μm meets the aspect ratio requirements of TSV via etching and copper filling processes, facilitating the reliable formation of the first copper pillar.

[0044] The thinner chip shortens the length of the first copper pillar, reduces the vertical resistance and thermal resistance, and also reduces the chip size, which is beneficial for module compactness.

[0045] Within a thickness range of 100~200μm, IGBT power chips can maintain sufficient mechanical strength to withstand the stress during flip-chip mounting and molding processes, while also achieving superior electrical and thermal performance.

[0046] In a preferred embodiment of the present invention, the thickness of the diode power chip is 100~200μm.

[0047] Specifically, a thickness range of 100~200μm facilitates the processing of the second copper pillar through the silicon substrate and minimizes the vertical conductive path from the anode to the second surface, reducing forward conduction loss and thermal resistance, while also supporting the overall thin design of the module.

[0048] The thinned fast recovery diode also has the advantages of short reverse recovery time and fast switching speed, making it suitable for high-frequency applications.

[0049] In a preferred embodiment of the present invention, the thickness of the driver chip is 200~300μm.

[0050] Specifically, the driver chip integrates gate drive circuits, logic control circuits, and protection circuits, making its structure relatively complex. The thickness of the driver chip is greater than that of IGBT power chips and diode power chips, which helps to ensure the mechanical strength and circuit yield of the driver chip.

[0051] Furthermore, the third copper pillar can reliably penetrate the silicon substrate within this thickness range, guiding the substrate to the second surface. This thickness range also ensures that the height difference between the driver chip and the IGBT power chip and diode power chip is kept within a reasonable range during flip-chip mounting, facilitating molding compound filling and copper pillar bump soldering.

[0052] This invention discloses an intelligent power module, comprising a substrate, an IGBT power chip, a diode power chip, and a driver chip in the aforementioned leadless direct-mount interconnect structure.

[0053] Here is an example of an intelligent power module: The power module includes a DBC (Direct Bonded Copper) substrate, an IGBT power chip, an FRD (Fast Recovery Diode) power chip, and a driver chip.

[0054] The entire intelligent power module has no internal leads.

[0055] The DBC substrate consists of an upper copper wiring layer, a middle ceramic layer, and a bottom copper foil. In actual use, the bottom copper foil contacts the external heat sink, forming a vertical and efficient heat dissipation path. The three chips, copper pillar bumps, and solder layer are all encapsulated in epoxy resin.

[0056] The IGBT power chip is 100 to 200 micrometers thick. Internally, TSV vias are etched and filled with pure copper to form the first copper pillar, connecting the back collector to the front pads. Copper pillar bumps, with a height of 50 to 150 micrometers, are electroplated onto the gate, emitter, and collector pads on the front side of the IGBT. The IGBT is flip-chip mounted face down, and the copper pillar bumps are sintered onto the copper wiring layer of the DBC substrate using high-temperature solder, achieving electrical and mechanical connections. The back collector of the IGBT is completely suspended, not in contact with any substrate, and is sealed and encapsulated with epoxy resin.

[0057] The FRD power chip is 100 to 200 micrometers thick. Internally, TSV vias are etched and filled with pure copper to form a second copper pillar, connecting the front anode to the back pads. Copper pillar bumps, ranging from 50 to 150 micrometers in height, are electroplated onto both the cathode and anode pads on the back of the FRD. The FRD is flip-chip mounted with the back side facing down, and each copper pillar bump is sintered onto the copper wiring layer of the DBC substrate using high-temperature solder. The front anode of the FRD is completely suspended, not in contact with any substrate, and is sealed and encapsulated with epoxy resin.

[0058] The driver chip has a thickness of 200 to 300 micrometers. TSV vias are etched inside and filled with pure copper to form a third copper pillar, connecting the back substrate to the front. The driver chip is flip-chip mounted face down. Its substrate copper pillar bumps, the pin copper pillar bumps corresponding to each functional pin, and high-temperature solder are connected to the DBC substrate. It achieves leadless interconnection with IGBTs and FRDs through substrate copper wiring.

[0059] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A leadless direct-mount interconnect structure, applied to a smart power module, characterized in that, include: substrate; IGBT power chip, the IGBT power chip includes a first copper pillar inside, one end of the first copper pillar is connected to the collector electrode on the first surface of the IGBT power chip, and the other end of the first copper pillar is led out from the second surface of the IGBT power chip, the second surface of the IGBT power chip is fixed on the substrate; A diode power chip, wherein the diode power chip includes a second copper pillar inside, one end of the second copper pillar is connected to the anode on the first surface of the diode power chip, and the other end of the second copper pillar is led out from the second surface of the diode power chip, and the second surface of the diode power chip is fixed on the substrate; A driver chip, the driver chip having a third copper pillar inside, one end of the third copper pillar being connected to a substrate on a first surface of the driver chip, and the other end of the third copper pillar being led out from a second surface of the driver chip, the second surface of the driver chip being fixed on the substrate; The leadless direct-attach interconnect structure does not include leads.

2. The leadless direct-attach interconnect structure according to claim 1, characterized in that, The substrate includes a copper wiring layer; The second side of the IGBT power chip includes a gate copper pillar bump corresponding to the gate, an emitter copper pillar bump corresponding to the emitter, and a collector copper pillar bump corresponding to the first copper pillar. The second side of the diode power chip includes a cathode copper pillar bump corresponding to the cathode and an anode copper pillar bump corresponding to the second copper pillar. The second side of the driver chip includes pin copper pillar bumps corresponding to each pin and substrate copper pillar bumps corresponding to the third copper pillar. The gate copper pillar bump, the emitter copper pillar bump, the collector copper pillar bump, the cathode copper pillar bump, the anode copper pillar bump, the lead copper pillar bump, and the substrate copper pillar bump are all connected to the copper wiring layer by soldering.

3. The leadless direct-attach interconnect structure according to claim 2, characterized in that, The upper layer of the substrate is the copper wiring layer, the middle layer of the substrate is the ceramic layer, and the bottom layer of the substrate is copper foil.

4. The leadless direct-attach interconnect structure according to claim 3, characterized in that, The bottom layer of the substrate is connected to an external heat sink.

5. The leadless direct-attach interconnect structure according to claim 1, characterized in that, The IGBT power chip, the diode power chip, and the driver chip are encapsulated in plastic.

6. The leadless direct-attach interconnect structure according to claim 5, characterized in that, The molding compound is made of epoxy resin.

7. The leadless direct-attach interconnect structure according to claim 1, characterized in that, The thickness of the IGBT power chip is 100~200μm.

8. The leadless direct-attach interconnect structure according to claim 1, characterized in that, The thickness of the diode power chip is 100~200μm.

9. The leadless direct-attach interconnect structure according to claim 1, characterized in that, The thickness of the driver chip is 200~300μm.

10. A smart power module, characterized in that, It includes the substrate, IGBT power chip, diode power chip and driver chip in the leadless direct-mount interconnect structure as described in any one of claims 1-9.

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