Transistor Power Module Packaging Structure and Its Packaging Method

Abstract

The present invention provides a transistor power module packaging structure and a packaging method thereof. The transistor power module packaging structure includes a lead frame, a copper-based resin heat sink, a plurality of chips, and an epoxy resin encapsulant; each of the chips is disposed on the lead frame, the copper-based resin heat sink is attached to the lead frame, and the epoxy resin encapsulant covers the outside of the lead frame, each of the chips, and the copper-based resin heat sink. By using a lead frame and a copper-based resin heat sink to replace the traditional DBC substrate, the situation of mismatched coefficient of thermal expansion can be effectively avoided, thereby avoiding the warping of the transistor, and avoiding large-area bubbles generated by welding. And by using epoxy resin for injection molding and encapsulation, the airtightness and reliability of the transistor can be effectively improved, and the reduction of heat dissipation and airtightness caused by the generation of internal bubbles due to the hardening of the transistor in a high-temperature environment can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of transistor power module packaging, and particularly relates to a transistor power module packaging structure and a packaging method thereof. Background Art

[0002] The packaging structure of the existing traditional IGBT (Insulated Gate Bipolar Transistor) power module adopts a plastic shell potting structure. This packaging structure results in a relatively large volume of the transistor.

[0003] The traditional IGBT power module packaging structure uses potting glue. The potting method of the potting glue leads to a relatively large volume of the IGBT power module. Moreover, the potting glue is prone to hardening at high temperatures, which further causes bubbles to be generated inside the product. The bubbles lead to poor contact between the chip and the potting glue, resulting in an increase in contact thermal resistance, and further reducing the heat dissipation of the product. In addition, since the inside of the bubble is air, the thermal conductivity of the air is lower than that in the potting glue, resulting in poor heat dissipation of the product, and further causing the transistor to fail.

[0004] In addition, the traditional IGBT power module packaging structure using a DBC (Direct Bonded Copper) substrate brings problems of CTE (coefficient of thermal expansion) mismatch, resulting in transistor warping problems and a large bubble rate in large-area DBC welding. Summary of the Invention

[0005] Based on this, it is necessary to provide a transistor power module packaging structure and a packaging method thereof for the above technical problems.

[0006] A transistor power module packaging structure includes: a lead frame, a copper-based resin heat sink, a plurality of chips, and an epoxy resin encapsulant;

[0007] Each of the chips is disposed on the lead frame, the copper-based resin heat sink is attached to the lead frame, and the epoxy resin encapsulant covers the outside of the lead frame, each of the chips, and the copper-based resin heat sink.

[0008] In one embodiment, the copper-based resin heat sink includes a copper base layer, a first resin layer, and a second resin layer that are sequentially laminated and connected, and the second resin layer is connected to the lead frame.

[0009] In one embodiment, the curing rates of the first resin layer and the second resin layer are set differently.

[0010] In one embodiment, the thicknesses of the first resin layer and the second resin layer are equal.

[0011] In one embodiment, the thickness of the copper base layer is from 0.3 mm to 0.5 mm.

[0012] In one embodiment, the thickness of the first resin layer is from 75 μm to 95 μm.

[0013] In one embodiment, the thickness of the second resin layer is from 75 μm to 95 μm.

[0014] In one embodiment, each of the chips is disposed on one side of the lead frame, and the copper-based resin heat sink is attached to the other side of the lead frame.

[0015] In one embodiment, the copper-based resin heat sink is thermocompression bonded to the lead frame.

[0016] In one embodiment, a U-shaped groove is provided at a position of the lead frame close to the edge.

[0017] A method for packaging a transistor power module includes:

[0018] Fixing each chip of the transistor on the lead frame;

[0019] Attaching a copper-based resin heat sink to the lead frame;

[0020] Injecting epoxy resin outside the lead frame, each of the chips, and the copper-based resin heat sink;

[0021] Curing the epoxy resin to form an epoxy resin encapsulation body, and the epoxy resin encapsulation body covers the outside of the lead frame, each of the chips, and the copper-based resin heat sink.

[0022] In one embodiment, the step of attaching the copper-based resin heat sink to the lead frame includes:

[0023] Adhering the copper-based resin heat sink to the lead frame by a thermocompression bonding method.

[0024] In one embodiment, the copper-based resin heat sink includes a copper base layer, a first resin layer, and a second resin layer that are sequentially laminated and connected, and the curing rates of the first resin layer and the second resin layer are set differently;

[0025] The step of attaching the copper-based resin heat sink to the lead frame includes:

[0026] Attaching the second resin layer to the lead frame.

[0027] The above-mentioned transistor power module packaging structure and its packaging method use a lead frame and a copper-based resin heat sink to replace the traditional DBC substrate, which can effectively avoid the situation of mismatched thermal expansion coefficients, thus avoiding the warping of the transistor, and also avoiding the large-area bubbles generated by welding. The use of epoxy resin for injection molding can effectively improve the airtightness and reliability of the transistor, and avoid the reduction of heat dissipation and airtightness caused by the generation of internal bubbles due to the hardening of the transistor in a high-temperature environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. 6 is a schematic structural diagram of one direction of the transistor power module packaging structure in an embodiment;

[0029] Figure 2 FIG. 10 is a schematic structural diagram of the transistor power module packaging structure in another direction before encapsulation in an embodiment;

[0030] Figure 3 FIG. 14 is a schematic structural diagram of one direction of the copper-based resin heat sink in an embodiment;

[0031] Figure 4 FIG. 18 is a schematic structural diagram of the lead frame in an embodiment;

[0032] Figure 5 FIG. 22 is a schematic flow chart of the transistor power module packaging method in an embodiment;

[0033] Figure 6 FIG. 26 is a schematic structural diagram of the injection molding process in the transistor power module packaging method in an embodiment;

[0034] Figure 7 FIG. 30 is a schematic flow chart of the manufacturing process of the transistor power module in an embodiment;

[0035] Figure 8 FIG. 34 is a schematic diagram of the internal circuit logic of the transistor power module in an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0037] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation.

[0038] Embodiment 1

[0039] In this embodiment, as Figure 1 and Figure 2 shown, a transistor power module packaging structure 10 is provided, including: a lead frame 100, a copper-based resin heat sink 200, several chips 300, and an epoxy resin encapsulant 400; each of the chips is disposed on the lead frame 100, the copper-based resin heat sink 200 is attached to the lead frame 100, and the epoxy resin encapsulant 400 covers the outside of the lead frame 100, each of the chips 300, and the copper-based resin heat sink 200.

[0040] Specifically, the lead frame 100 is used to support each chip 300. The chips 300 on the lead frame 100 include an IGBT chip 310, an FRD (freewheeling diode) chip 320, and an NTC (Negative Temperature Coefficient) chip 330. Among them, the IGBT chip can also be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) chip. Each chip is welded and fixed on the lead frame 100, and each chip is connected by a wire 110 and is also connected to the lead frame 100 by a wire. For example, the wire 110 is an aluminum wire. For example, each chip is soldered to the lead frame 100 by solder. For example, each chip is fixed to the lead frame 100 by silver paste. For example, the wire is an aluminum wire, and each chip is connected by an aluminum wire. In this embodiment, first, the IGBT, FRD, and NTC thermistor chips are fixed on the lead frame 100 through a die bonding process such as solder paste printing or silver paste printing, and then the wire bonding is performed to achieve the point electrical connection between the chips and between the chips and the lead frame 100.

[0041] In this embodiment, the copper-based resin heat sink 200 is also referred to as a thermally conductive and insulating copper-based resin heat sink 200. The copper-based resin heat sink 200 is attached to the surface of the lead frame 100 by means of thermocompression bonding. Since the copper-based resin heat sink 200 contains metallic copper, and metallic copper has a relatively good thermal conductivity and good heat conduction performance, it can quickly conduct the heat of the lead frame 100 and the chip and dissipate it to the outside, thereby enabling the overall transistor to have better heat dissipation performance. In addition, the copper-based resin heat sink 200 contains resin, which can play an insulating role, thereby providing insulation protection between the metallic copper in the copper-based resin heat sink 200 and the lead frame 100 and the chip.

[0042] In this embodiment, the material of the epoxy resin encapsulant 400 is epoxy resin. The epoxy resin is injected by a transfer mold on the outside of the lead frame 100, the copper-based resin heat sink 200 and each chip. After the epoxy resin is cured, the epoxy resin encapsulant 400 is formed. The epoxy resin encapsulant 400 covers the outside of the copper-based resin heat sink 200 and each chip, and covers the outside of at least part of the lead frame 100. Figure 1 In order to avoid the epoxy resin encapsulant 400 from obscuring the components encapsulated therein and facilitate viewing of the components inside the epoxy resin encapsulant 400, the epoxy resin encapsulant 400 is represented by a dotted line.

[0043] In traditional power modules, DBC substrates are used, which are prone to warping of the transistor due to mismatched thermal expansion coefficients and are also prone to large-area bubbles. In this application, the lead frame 100 and the copper-based resin heat sink 200 are used to replace the traditional DBC substrate, which can effectively avoid the situation of mismatched thermal expansion coefficients, thereby avoiding warping of the transistor and avoiding large-area bubbles generated by welding. Using epoxy resin for transfer encapsulation can effectively improve the airtightness and reliability of the transistor compared with traditional potting glue encapsulation, and avoid the reduction of heat dissipation and airtightness caused by the generation of internal bubbles due to hardening of the transistor in a high-temperature environment.

[0044] In addition, this application uses an NTC thermistor chip to replace the traditional NTC thermistor. The NTC thermistor chip has the characteristics of small volume, high precision, high stability, high reliability and fast response, which can further make the volume of the transistor power module smaller.

[0045] In one embodiment, as Figure 1As shown, each of the chips is disposed on one side of the lead frame 100, and the copper-based resin heat sink 200 is attached to the other side of the lead frame 100. Specifically, each of the chips and the copper-based resin heat sink 200 are respectively disposed on two opposite surfaces of the lead frame 100. On the one hand, it avoids the influence of the copper-based resin heat sink 200 on the layout of the chips on the lead frame 100. On the other hand, the copper-based resin heat sink 200 can well support the lead frame 100 and can quickly guide and dissipate the heat of the lead frame 100 and the chips.

[0046] In one embodiment, the copper-based resin heat sink 200 is thermally compression bonded to the lead frame 100. In this embodiment, the copper-based resin heat sink 200 is connected to the lead frame 100 by means of thermal compression bonding. In this way, the copper-based resin heat sink 200 can be firmly attached to the lead frame 100.

[0047] In one embodiment, as Figure 3 shown, the copper-based resin heat sink 200 includes a copper base layer 230, a first resin layer 210, and a second resin layer 220 that are sequentially laminated and connected, and the second resin layer 220 is connected to the lead frame 100. In this embodiment, the copper base layer 230, the first resin layer 210, and the second resin layer 220 are sequentially laminated, that is, one side of the copper base layer 230 is connected to one side of the first resin layer 210, the other side of the first resin layer 210 is connected to one side of the second resin layer 220, and the side of the second resin layer 220 facing away from the first resin layer 210 is attached to the lead frame 100. Specifically, the second resin layer 220 is attached to the lead frame 100 by means of thermal pressing, and the materials of the first resin layer 210 and the second resin layer 220 are epoxy resins.

[0048] In this embodiment, the copper-based resin heat sink 200 is attached to the lead frame 100 through the second resin layer 220. Specifically, the second resin layer 220 is attached to the side of the lead frame 100 facing away from the chips, and the copper base layer 230 is located on the outside. In this way, the copper base layer 230 can quickly and effectively absorb, guide, and dissipate the heat of the lead frame 100 to the outside, effectively improving the heat dissipation efficiency of the lead frame 100 and each chip.

[0049] In one embodiment, the curing rates of the first resin layer 210 and the second resin layer 220 are set differently. In this embodiment, the curing rates of the epoxy resins of the first resin layer 210 and the second resin layer 220 are different. In this way, the first resin layer 210 and the second resin layer 220 can have different adhesiveness and thermal conductivities. For example, if the curing rate of the first resin layer 210 is greater than that of the second resin layer 220, then the first resin layer 210 can be more firmly attached to the lead frame 100, and the first resin layer 210 has a higher thermal conductivity, which can quickly and efficiently adsorb the heat on the lead frame 100 and transfer it to the copper base layer 230 through the second resin layer 220.

[0050] In one embodiment, the thicknesses of the first resin layer 210 and the second resin layer 220 are equal. By setting the thicknesses of the first resin layer 210 and the second resin layer 220 to be equal, the two have similar strengths, which is beneficial to improving the structural stability of the copper-based resin heat sink 200.

[0051] In other embodiments, the thicknesses of the first resin layer 210 and the second resin layer 220 can also be set to be unequal.

[0052] In one embodiment, the thickness of the copper base layer 230 is 0.3 mm to 0.5 mm.

[0053] In one embodiment, the thickness of the first resin layer 210 is 75 μm to 95 μm.

[0054] In one embodiment, the thickness of the second resin layer 220 is 75 μm to 95 μm.

[0055] In the above embodiments, the thickness of the copper base layer 230 is set to 0.3 mm to 0.5 mm. On the one hand, it can make the overall thickness of the product smaller. In addition, at this thickness, the copper base layer 230 can have a higher strength and can well support the first resin layer 210 and the second resin layer 220, making the structure of the copper-based resin heat sink 200 relatively stable. On the other hand, it enables the copper-based resin heat sink 200 to have better heat dissipation performance. And the thickness of the first resin layer 210 is set to 75 μm to 95 μm, and the thickness of the second resin layer 220 is set to 75 μm to 95 μm. On the one hand, it can better adhere to the lead frame 100 and provide insulation between the lead frame 100 and the copper base layer 230. On the other hand, it makes the copper-based resin heat sink 200 have a higher strength.

[0056] In one embodiment, the first resin layer 210 is an epoxy resin layer with a thickness of 85 μm and a curing rate of 70%-90%, the second resin layer 220 is an epoxy resin layer with a thickness of 85 μm and a curing rate of 30%-60%, and the thickness of the copper base layer 230 is 0.4 mm. In this embodiment, the thickness of the first resin layer 210 is 85 μm and the curing rate is 70%-90%, and the thickness of the second resin layer 210 is 85 μm and the curing rate is 30%-60%. In this embodiment, the strength and heat dissipation efficiency of the copper-based resin heat sink 200 can be further improved, and the copper-based resin heat sink 200 can be more firmly attached to the lead frame 100.

[0057] In one embodiment, as Figure 4 shown, a U-shaped groove 106 is provided at a position near the edge of the lead frame 100. By providing the U-shaped groove 106 at the edge of the lead frame 100, moisture is prevented from entering the interior of the epoxy resin encapsulant 400. Figure 4 In, on the lead frame 100, there are provided die bonding positions 120 for IGBT chips, die bonding positions 130 for FRD chips, die bonding positions 140 for NTC thermistor chips, and a U-groove 107 for preventing solder overflow is provided.

[0058] Embodiment Two,

[0059] In this embodiment, as Figure 5 shown, a method for packaging a transistor power module is provided, including:

[0060] Step 510, fixing each chip of the transistor on the lead frame.

[0061] Specifically, each chip includes an IGBT chip, an FRD chip, and an NTC thermistor chip. In this step, it is fixed on the lead frame through a die bonding process of solder paste printing or silver paste printing, and then wire bonding is performed to achieve point electrical connection between chips and between the chips and the lead frame.

[0062] Step 520, attaching the copper-based resin heat sink to the lead frame.

[0063] In this step, the copper-based resin heat sink is attached and fixed to the side of the lead frame facing away from the chips.

[0064] Step 530, injecting epoxy resin outside the lead frame, each of the chips, and the copper-based resin heat sink.

[0065] In this step, liquid epoxy resin is injected outside the lead frame, each of the chips, and the copper-based resin heat sink, so that the epoxy resin covers the outside of each of the chips and the copper-based resin heat sink, and covers at least part of the lead frame.

[0066] Step 540 causes the epoxy resin to cure to form an epoxy resin encapsulation body, and the epoxy resin encapsulation body covers the outside of the lead frame, each of the chips, and the copper-based resin heat sink.

[0067] Specifically, after curing, the epoxy resin forms an epoxy resin encapsulation body, and the cured epoxy resin encapsulation body encapsulates each of the chips, the copper-based resin heat sink, and at least part of the lead frame, thereby realizing the encapsulation of the transistor power module.

[0068] In the above embodiments, the use of a lead frame and a copper-based resin heat sink to replace the traditional DBC substrate can effectively avoid the situation of mismatched coefficient of thermal expansion, thereby avoiding the warping of the transistor, and avoiding large-area bubbles generated by welding. And the use of epoxy resin for injection molding encapsulation can effectively improve the airtightness and reliability of the transistor, and avoid the reduction of heat dissipation and airtightness caused by the generation of bubbles inside the transistor due to hardening at high temperatures.

[0069] In one embodiment, the step of injecting epoxy resin on the outside of the lead frame, each of the chips, and the copper-based resin heat sink includes: injecting the epoxy resin on the outside of the lead frame, each of the chips, and the copper-based resin heat sink.

[0070] In this embodiment, the epoxy resin is injected on the outside of the lead frame, each of the chips, and the copper-based resin heat sink by means of injection molding. For example, the epoxy resin is injected on the outside of the lead frame, each of the chips, and the copper-based resin heat sink through an injection mold. In this embodiment, the encapsulation by injecting the epoxy resin through the injection mold can avoid bubbles generated due to hardening at high temperatures, improve the airtightness of the encapsulation, and make the connection between the copper-based resin heat sink and the lead frame closer and more stable, resulting in a better encapsulation effect.

[0071] As Figure 6 shown, it is a schematic diagram of the injection molding process of the injection mold. Before curing, the epoxy resin encapsulation body 400 covers the outside of the lead frame 100, each of the chips 300, and the copper-based resin heat sink 200. The epoxy resin injection mold sealing runner 630 injects the fluid epoxy resin into the injection mold through the first trapezoidal injection gate 610 and the second trapezoidal injection gate 630 respectively, so that the epoxy resin covers the outside of the lead frame 100, each of the chips 300, and the copper-based resin heat sink 200.

[0072] In one embodiment, the step of attaching the copper-based resin heat sink to the lead frame includes: attaching the copper-based resin heat sink to the lead frame by means of thermal pressing.

[0073] In this embodiment, the side of the copper-based resin heat sink with resin is attached to the lead frame by means of thermocompression bonding, so that the copper-based resin heat sink can be stably attached to the lead frame.

[0074] In one embodiment, the copper-based resin heat sink includes a copper base layer, a first resin layer, and a second resin layer that are sequentially laminated and connected, and the curing rates of the first resin layer and the second resin layer are set differently; the step of attaching the copper-based resin heat sink to the lead frame includes: attaching the second resin layer to the lead frame.

[0075] In this embodiment, the second resin layer is attached to the lead frame by means of thermocompression bonding. In this embodiment, the materials of the first resin layer and the second resin layer are both epoxy resins. By means of thermocompression, the first resin layer can be stably attached to the side of the lead frame facing away from the chip.

[0076] Embodiment Three

[0077] Please refer to Figure 7 , which is the product manufacturing process of a transistor power module, including IGBT DB, FRD DB, NTC DB, Al DB, internal inspection, heat sink attachment, resin encapsulation, resin curing, electroplating and lead cutting, testing, forming and printing, and appearance inspection.

[0078] Among them, DB refers to fixing the chip on the lead frame by means of brushing solder paste or silver paste.

[0079] IGBT refers to an IGBT or MOSFET chip;.

[0080] FRD refers to a freewheeling diode chip.

[0081] NTC refers to a thermistor chip;

[0082] Al WB refers to aluminum wire bonding;

[0083] Internal inspection refers to inspecting the internal structure of the product

[0084] Heat sink attachment refers to attaching a highly thermally conductive and insulating copper-based resin heat sink to the lead frame by means of thermocompression bonding;

[0085] Resin encapsulation refers to encapsulating the product by means of a transfer mold using epoxy resin;

[0086] Post-curing refers to completely curing the potted product;

[0087] Electroplating and lead cutting refers to attaching solder to the product leads by electroplating process and separating the product leads;

[0088] Testing refers to the electrical performance testing of products;

[0089] Forming and printing means forming the product pins and marking information such as product model and batch number;

[0090] Appearance inspection refers to the appearance inspection of the qualified products after testing.

[0091] In this embodiment, the encapsulation of the transistor power module is one of the product manufacturing processes of the transistor power module.

[0092] The product manufacturing process of the transistor power module is specifically as follows: First, the IGBT, FRD, and NTC thermistor chips are fixed on the lead frame through the die bonding process of solder paste printing or silver paste printing, and then the Al wire bonding is used to achieve the electrical connection between the chips and between the chips and the lead frame. Then, the high thermal conductivity epoxy resin heat sink is attached, and then the encapsulation is carried out through the epoxy resin transfer molding. This solves the problem that the traditional power module encapsulation uses potting glue to harden at high temperatures, resulting in bubbles inside the product, reducing the heat dissipation and airtightness of the product, and reducing the warpage and bubble rate of the product, as well as reducing the volume of the product.

[0093] Product electrical structure design: This structure consists of 6 IGBTs or MOSFETs, 6 freewheeling diodes FRDs, and 1 NTC thermistor chip. Every 3 IGBTs or MOSFETs are connected in parallel with 3 freewheeling diodes FRDs to form the upper and lower bridges, and a half-bridge output U / V / W phase circuit is formed. The chips are welded to the PAD part of the lead frame by using spot welding solder wire or brushing solder paste or dotting silver paste. The lead frame serves as part of the electrical conductor, structural support, and heat dissipation carrier, and the Al wire bonding method is used to achieve the electrical connection between the chip electrodes and between the chip and the lead frame.

[0094] Frame design: The lead frame adopts a sunken structure for the die bonding PAD position, and a U-groove design is carried out at specific positions of the PAD position and the pins to prevent solder overflow and water vapor from entering the product through the joint between the pins and the resin, resulting in product failure.

[0095] Realization of the manufacturing process: As Figure 6 and 7 shown, first, the die bonding processes of IGBT die bonding, FRD die bonding, and NTC thermistor chip die bonding are carried out by using the solder paste printing process, then the Al wire bonding is carried out, and then the internal inspection is carried out. Then, the realization of the new transfer molding encapsulated power module structure is carried out. First, the high thermal conductivity epoxy resin heat sink is attached to the lead frame through the hot pressing process, and then the product with the attached heat sink is placed in the mold cavity for epoxy resin transfer molding. The gate is designed in two parts, both of which are trapezoidal structures. Finally, the post-packaging testing is carried out.

[0096] The internal circuit diagram of the transistor power module manufactured by the above process is as Figure 8 shown, where each component in the figure is as follows:

[0097] 1 is the collector 1 (C1), 2 is the collector 2 (C2), and 3 is the high-side FRD chip;

[0098] 4 is the high-side IGBT chip, and 5 is the gate (G1) of the high-side IGBT chip;

[0099] 6 is the emitter (E1) of the high-side IGBT chip, and 7 is the half-bridge output U / V / W phase;

[0100] 8 is the low-side IGBT chip, and 9 is the gate (G2) of the low-side IGBT chip;

[0101] 10 is the low-side FRD chip, and 11 is the emitter (E2) of the low-side IGBT chip;

[0102] 12 is the emitter (E3) of the low-side IGBT chip, and 13 is the P pole of the NTC thermistor chip;

[0103] 14 is the NTC thermistor chip, and 15 is the N pole of the NTC thermistor chip.

[0104] The purpose of this application is to apply the injection molding encapsulation technology to the encapsulation of high-power IGBT modules, form a new type of injection molding encapsulation power module structure, and implement it with a new encapsulation process to improve the airtightness and reliability of the product, solve the problem that the traditional power module encapsulation uses potting glue to harden at high temperatures, resulting in bubbles inside the product, reducing the heat dissipation and airtightness of the product, and reducing the warping and bubble rate of the product, as well as reducing the volume of the product.

[0105] In actual use of this system, the following effects can be achieved:

[0106] 1. The use of a new type of injection molding encapsulation structure solves the problem of large volume of the traditional IGBT module encapsulation structure;

[0107] 2. The use of a new type of injection molding encapsulation structure solves the problem that the traditional IGBT module encapsulation structure uses potting glue to harden at high temperatures, resulting in bubbles inside the product, reducing the heat dissipation and airtightness of the product;

[0108] 3. The use of a new type of injection molding encapsulation structure solves the problems of warping of the product caused by CTE mismatch brought by the traditional IGBT module encapsulation structure using DBC substrates and large bubble rates generated by large-area DBC welding;

[0109] 4. The NTC thermistor chip replaces the traditional NTC thermistor, achieving small volume, high precision, high stability, high reliability, and fast response.

[0110] 5. A feasible structural design method and production process are given;

[0111] 6. The structure of the new injection mold encapsulated power module adopts an epoxy resin injection mold process. First, the IGBT, FRD, and NTC thermistor chips are fixed on the lead frame through the die bonding process of solder paste printing or silver paste printing. Then, the Al wire bonding is used to achieve the point electrical connection between the chips and between the chips and the lead frame. Then, the high thermal conductivity epoxy resin heat sink is attached. Then, the epoxy resin injection mold is used for encapsulation, which solves the problems that the traditional power module encapsulation uses potting glue to harden at high temperature, resulting in bubbles inside the product, reducing the heat dissipation and airtightness of the product, and reducing the warpage and bubble rate of the product, as well as reducing the volume of the product.

[0112] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0113] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A transistor power module packaging structure, characterized in that, Comprising: A lead frame, a copper-based resin heat sink, a plurality of chips, and an epoxy resin encapsulant; Each of the chips is disposed on the lead frame, the copper-based resin heat sink is attached to the lead frame, and the epoxy resin encapsulant covers the outside of the lead frame, each of the chips, and the copper-based resin heat sink; The lead frame is provided with die bonding positions for the chips, and U-grooves for preventing solder overflow are provided at the die bonding positions; U-shaped grooves are provided at positions of the lead frame close to the edge; The copper-based resin heat sink includes a copper base layer, a first resin layer, and a second resin layer that are sequentially laminated and connected; the thickness of the first resin layer is equal to the thickness of the second resin layer, and the first resin layer is an epoxy resin layer with a curing rate of 70%-90%, and the second resin layer is an epoxy resin layer with a curing rate of 30%-60%.

2. The transistor power module packaging structure according to claim 1, wherein The second resin layer is connected to the lead frame.

3. The transistor power module packaging structure according to claim 2, characterized in that, The curing rates of the first resin layer and the second resin layer are set differently.

4. The transistor power module packaging structure according to claim 2, characterized in that, The thickness of the copper base layer is 0.3 mm to 0.5 mm.

5. The transistor power module packaging structure according to claim 2, wherein, The thickness of the first resin layer is 75 μm to 95 μm.

6. The transistor power module packaging structure according to claim 2, characterized in that, The thickness of the second resin layer is 75 μm to 95 μm.

7. The transistor power module packaging structure according to any one of claims 1-6, characterized in that, Each of the chips is disposed on one side of the lead frame, and the copper-based resin heat sink is attached to the other side of the lead frame.

8. The transistor power module packaging structure according to any one of claims 1-6, characterized in that, The copper-based resin heat sink is thermally compression bonded to the lead frame.

9. A method for packaging a transistor power module, characterized by comprising: Fixing each chip of the transistor on the lead frame; the lead frame is provided with die bonding positions for the chips, and U-grooves for preventing solder overflow are provided at the die bonding positions; U-shaped grooves are provided at positions of the lead frame close to the edge; Attaching a copper-based resin heat sink to the lead frame; Injecting epoxy resin outside the lead frame, each of the chips, and the copper-based resin heat sink; Curing the epoxy resin to form an epoxy resin encapsulant, and the epoxy resin encapsulant covers the outside of the lead frame, each of the chips, and the copper-based resin heat sink; The step of injecting epoxy resin outside the lead frame, each of the chips, and the copper-based resin heat sink includes: injecting epoxy resin by pressure outside the lead frame, each of the chips, and the copper-based resin heat sink; The copper-based resin heat sink includes a copper base layer, a first resin layer, and a second resin layer that are sequentially laminated and connected; the thickness of the first resin layer is equal to the thickness of the second resin layer, and the first resin layer is an epoxy resin layer with a curing rate of 70%-90%, and the second resin layer is an epoxy resin layer with a curing rate of 30%-60%.

10. The method according to claim 9, wherein The step of attaching the copper-based resin heat sink to the lead frame includes: Adhering the copper-based resin heat sink to the lead frame by a thermal pressing method.

11. The transistor power module packaging structure according to claim 9, characterized in that, The curing rates of the first resin layer and the second resin layer are set differently; The step of attaching the copper-based resin heat sink to the lead frame includes: Attaching the second resin layer to the lead frame.

Images