Manufacturing method of power module and power module

Abstract

The invention discloses a manufacturing method of a power module and the power module, and the method comprises the steps: enabling a plurality of power chips and a plurality of soldering lugs with corresponding sizes to be welded in a plurality of chip welding regions of a lead frame in a one-to-one correspondence manner, and obtaining a welded lead frame; carrying out welding cavity inspection and welding size inspection on the welded lead frame to obtain a qualified lead frame; bonding the qualified lead frame through a bonding device to obtain a bonded lead frame; performing colloid potting on the bonded lead frame through a colloid potting device to obtain a colloid-potting lead frame; placing the lead frame encapsulated by the colloid in a vacuum high-temperature oven for curing to obtain a cured lead frame; and cutting the cured lead frame to obtain a plurality of power modules. The lead frame is a gate electrode, an emitter electrode and a collector electrode of a power chip, the design of pins with ultra-fine spacing of the power module is realized, the welded lead frame is detected, and the stability of the module is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power modules, and in particular to a method for manufacturing a power module and a power module. Background Art

[0002] The power module is a modular intelligent power system (MIPM, Module Intelligent Power), which is a power drive product that combines power electronics and integrated circuit technology. It not only integrates power switching devices and drive circuits, but also has built-in fault detection circuits such as overvoltage, overcurrent and overheating, and can send detection signals to the CPU or DSP for terminal processing. The power module generally uses IGBT (insulated gate bipolar transistor) as the power switching element, and has built-in integrated structures such as current sensor, FDR (fast recovery diode) and drive circuit. It generally uses high-voltage driver IC (chip) to drive IGBT.

[0003] Existing power modules are usually packaged using QFN (Quad Flat No-leads) packaging technology. QFN devices are widely used in various electronic devices due to their miniaturization, light weight and excellent electrical performance. QFN devices are usually packaged in a micro lead frame copper substrate, with a large area heat dissipation pad in the center of the bottom, and signal pads arranged around the heat dissipation pad matrix. However, as electronic devices develop towards higher performance and smaller size, the process requirements for QFN packaging are becoming increasingly higher. For example, in the design of ultra-fine pitch pins, the control accuracy of solder paste printing is extremely high to avoid welding defects such as signal pad bridging. In addition, traditional QFN packaging is prone to various defects during the assembly process, such as signal pad bridging, heat dissipation pad voids, insufficient side solder joint creep height, etc., which affect the heat dissipation efficiency, signal transmission performance and reliability of the device.

[0004] In the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art:

[0005] The packaging quality of existing power modules is poor, which easily affects the terminal application performance and service life of the device. Summary of the invention

[0006] The purpose of the present invention is to provide a method for manufacturing a power module and a power module to solve the technical problem that the packaging quality of the existing power module in the prior art is poor, which easily affects the terminal application performance and service life of the device. The preferred technical solutions among the many technical solutions provided by the present invention can produce many technical effects as described below.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for manufacturing a power module, comprising:

[0009] Welding a plurality of power chips and a plurality of welding pieces of corresponding sizes in a plurality of chip welding areas of a lead frame in a one-to-one correspondence to obtain a welded lead frame;

[0010] Performing welding void inspection and welding size inspection on the welded lead frame to obtain a qualified lead frame;

[0011] Bonding the qualified lead frame by a bonding device to obtain a bonded lead frame;

[0012] Performing colloid encapsulation on the bonded lead frame by means of a glue encapsulation device to obtain a lead frame encapsulated with colloid;

[0013] Placing the colloid-encapsulated lead frame in a vacuum high-temperature oven for curing to obtain a cured lead frame;

[0014] The cured lead frame is cut to obtain a plurality of power modules.

[0015] Optionally, the step of welding a plurality of power chips and a plurality of welding pieces of corresponding sizes in a plurality of chip welding regions of a lead frame in a one-to-one correspondence to obtain a welded lead frame comprises:

[0016] Using an automatic chip mounter, the plurality of soldering pads are mounted one by one in the plurality of chip welding areas of the lead frame, and then the plurality of power chips are mounted one by one on the plurality of soldering pads to obtain a mounted lead frame;

[0017] Preheating the mounted lead frame by a vacuum welding device to obtain a preheated lead frame;

[0018] The vacuum welding device adjusts the temperature to a first preset temperature, performs vacuum welding on the preheated lead frame for a first preset time, and welds the power chip on the lead frame to obtain a vacuum welded lead frame;

[0019] The vacuum welding device adjusts the temperature to a second preset temperature, and performs a cooling process for the vacuum welded lead frame for a second preset time to obtain the welded lead frame.

[0020] Optionally, the step of performing welding void inspection and welding size inspection on the welded lead frame to obtain a qualified lead frame includes:

[0021] Placing the welded lead frame in an inspection area of ​​an X-Ray device and an optical inspection device, calling an automatic scanning plug-in to scan the welded lead frame to determine the void rate and size of the welding area;

[0022] Determining whether a void ratio of the welding area exceeds a preset void ratio, and determining whether a size of the welding area exceeds a preset size;

[0023] If not, it is determined that the welded lead frame is a qualified lead frame.

[0024] Optionally, the step of bonding the qualified lead frame by a bonding device to obtain a bonded lead frame includes:

[0025] placing the qualified lead frame on a wire bonding jig;

[0026] Placing the wire bonding jig on the workbench of the bonding device, adjusting the position of the workbench by the bonding device so that the bonding head of the bonding device is aligned with the qualified lead frame, and controlling the wire bonding jig to adsorb and fix the qualified lead frame;

[0027] The bonding device bonds the power chip on the qualified lead frame to obtain the bonded lead frame.

[0028] Optionally, the bonding device bonds the power chip on the qualified lead frame to obtain the bonded lead frame, comprising:

[0029] Introducing a bonding wire into the bonding device, and delivering the bonding wire to the bonding head;

[0030] Adjusting the bonding head to the first bonding position of the qualified lead frame, applying bonding pressure and starting ultrasonic vibration to form a metallurgical bond between the first end of the bonding wire and the first bonding position;

[0031] Adjusting the bonding head to the second bonding position of the qualified lead frame, applying bonding pressure and starting ultrasonic vibration to form a metallurgical bond between the second end of the bonding wire and the second bonding position, so that the bonding wire forms a ring structure between the first end and the second end of the bonding wire;

[0032] After the bonding between the first bonding position and the second bonding position is completed, the redundant bonding wires are cut off to complete a bonding cycle, and then the next bonding cycle is performed until all bonding cycles are performed to obtain the bonded lead frame.

[0033] Optionally, after completing one bonding cycle, the method further includes:

[0034] detecting whether the bonding between the first bonding position and the second bonding position is qualified;

[0035] If not, re-bond.

[0036] Optionally, the step of performing colloid encapsulation on the bonded lead frame by using a glue encapsulating device to obtain a colloid encapsulated lead frame comprises:

[0037] Placing the bonded lead frame in a packaging mold, wherein the packaging mold comprises a base plate, a guide plate and a limit plate, the bonded lead frame is placed in a limit groove of the base plate, the guide plate and the limit plate are fixed on the base plate and the bonded lead frame in sequence, and the bonded lead frame is packaged in the packaging mold;

[0038] The packaging mold is placed in the glue potting equipment for colloid potting to obtain the lead frame after colloid potting, wherein, during the colloid potting, the sealing colloid used by the glue potting equipment is a two-component silicone gel, the glue potting pressure of the glue potting equipment ranges from 0.6Mpa to 0.8Mpa, and the glue discharge speeds of the AB glue outlet pipes of the glue potting equipment are consistent.

[0039] Optionally, the step of placing the colloid-encapsulated lead frame in a vacuum high-temperature oven for curing to obtain a cured lead frame comprises:

[0040] The lead frame after colloid encapsulation is placed in the vacuum high-temperature oven to perform the first stage of degassing and curing and the second stage of degassing and curing, wherein the curing parameters of the first stage of degassing and curing are a temperature range of 80°C-120°C, a vacuum range of 290Pa-320Pa and a process duration range of 10min-15min, and the curing parameters of the second stage of degassing and curing are a temperature range of 100°C-150°C, a vacuum range of 300Pa-350Pa and a process duration range of 20min-35min.

[0041] Optionally, before welding the plurality of power chips and the plurality of welding pieces of corresponding sizes in a one-to-one correspondence in the plurality of chip welding areas of the lead frame to obtain the welded lead frame, the method further comprises:

[0042] The lead frame is provided, wherein the lead frame is formed by arranging a plurality of sub-frames in an array, each of the sub-frames has a chip welding area, and the material of the lead frame is copper.

[0043] A power module is manufactured by the power module manufacturing method described above, the power module comprising: a copper substrate, a welding sheet, a power chip, a bonding wire and a sealing body, the power chip is fixedly connected to the copper substrate through the welding sheet; the bonding wire connects the power chip and the copper substrate; the sealing body is used to encapsulate the copper substrate, the welding sheet, the power chip and the bonding wire.

[0044] Implementing one of the above technical solutions of the present invention has the following advantages or beneficial effects:

[0045] The present invention uses a lead frame as a base island for carrying a power chip, as well as the connection ports for the gate level, emitter and collector input and output of the power chip, to achieve ultra-fine pitch pin design of the power module. At the same time, a preheating stage, a heat activation stage and a cooling stage are sequentially performed through a vacuum welding device to complete the welding of the power chip, and the welding is quality inspected to improve the yield rate of the produced power module and ensure the stable performance of the power module. In addition, the process of the present invention is suitable for the manufacture of small-volume power modules, and the process is simple and suitable for industrial production. The products manufactured by the process of the present invention have reliable performance, and through two-stage temperature control, the product is guaranteed to be completely cured, the electrical performance and reliability of the power module are improved, and it has the advantages of high compatibility, high production yield rate, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. It is obvious that the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0047] Figure 1 is a flow chart of an embodiment of a method for manufacturing a power module of the present invention;

[0048] Figure 2 A lead frame used in an embodiment of a method for manufacturing a power module of the present invention;

[0049] Figure 3 A wire bonding jig used in an embodiment of a method for manufacturing a power module of the present invention;

[0050] Figure 4 It is a packaging mold used in an embodiment of a method for manufacturing a power module of the present invention;

[0051] Figure 5 It is a schematic diagram of the rib positions of the lead frame after cutting and curing in an embodiment of the method for manufacturing a power module of the present invention;

[0052] Figure 6It is a schematic structural diagram of a power module embodiment of the present invention.

[0053] In the figure: 1. copper substrate; 2. solder sheet; 3. power chip; 4. bonding wire; 5. encapsulation body; 6. packaging mold; 61. bottom plate; 611. limiting groove; 62. guide plate; 621. guide groove; 63. limiting plate. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present invention clearer, the various exemplary embodiments to be described below will refer to the corresponding drawings, which constitute a part of the exemplary embodiments, wherein various exemplary embodiments that may be used to implement the present invention are described. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation methods described in the following exemplary embodiments do not represent all implementation methods consistent with the present disclosure. It should be understood that they are only examples of processes, methods, devices, etc. that are consistent with some aspects of the present disclosure as detailed in the attached claims, and other embodiments may also be used, or the embodiments listed herein may be modified in structure and function without departing from the scope and essence of the present invention.

[0055] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", etc. indicate the orientation or positional relationship based on the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the elements referred to must have a specific orientation, be constructed and operated in a specific orientation. The terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "multiple" means two or more. The terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a communication connection, a direct connection, an indirect connection through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0056] In order to illustrate the technical solution of the present invention, a specific embodiment is used below for description, and only the parts related to the embodiment of the present invention are shown.

[0057] Embodiment 1:

[0058] like Figure 1 As shown, the present invention provides a method for manufacturing a power module, comprising:

[0059] S10, welding a plurality of power chips and a plurality of welding pieces of corresponding sizes in a plurality of chip welding areas of a lead frame in a one-to-one correspondence to obtain a welded lead frame;

[0060] S20, performing welding void inspection and welding size inspection on the welded lead frame to obtain a qualified lead frame;

[0061] S30, bonding the qualified lead frame by a bonding device to obtain a bonded lead frame;

[0062] S40, performing colloid encapsulation on the bonded lead frame by using a glue encapsulation device to obtain a colloid encapsulated lead frame;

[0063] S50, placing the colloid-encapsulated lead frame in a vacuum high-temperature oven for curing to obtain a cured lead frame;

[0064] S60, cutting the cured lead frame to obtain a plurality of power modules. Specifically, the method for manufacturing the power module is to sequentially perform a patch process, a welding process, a quality control, a bonding process, a glue filling process, a vacuum curing process and a rib cutting process. The patch process comprises the following steps: firstly, by means of an automatic patch machine, a plurality of soldering pads are respectively mounted on a plurality of chip welding areas of a lead frame, and then a plurality of power chips are respectively mounted on a plurality of soldering pads to obtain a mounted lead frame. By using an automatic placement machine to mount a plurality of power chips on a lead frame, high efficiency, high precision, high reliability of large-volume electronic component assembly, good thermal management and electromagnetic compatibility can be achieved.

[0065] Specifically, the welding process steps of this embodiment are as follows: placing the mounted lead frame in a vacuum welding device, and sequentially going through a preheating stage, a heat activation stage, and a cooling stage to complete the welding of the power chip.

[0066] The quality control step is to place the welded lead frame in X-Ray equipment and optical inspection equipment in turn, and through X-Ray inspection and optical inspection, detect whether there are welding voids, pad bridging and insufficient solder height of side solder joints in the power chip during the welding process, so as to obtain qualified lead frames and improve the yield rate of power module manufacturing.

[0067] The steps of the bonding process are as follows: first, place a qualified lead frame into a lead bonding jig, then place the lead bonding jig into a bonding device, the bonding device moves the bonding lead to a bonding point, applies bonding pressure and starts ultrasonic vibration, thereby bonding the first end of the bonding lead to the bonding point, and pulls the bonding lead to another bonding point as required for bonding, repeats the above steps, bonds the second end of the bonding lead to the bonding point, completes a bonding cycle, and cuts off excess bonding leads, and multiple bonding points on the qualified lead frame are bonded according to the above two-point bonding method.

[0068] The steps of the glue filling process are as follows: firstly, the bonded lead frame is placed in the packaging mold, and then the packaging mold is placed in the glue filling equipment, and the glue filling equipment fills the glue filling area formed on the packaging mold with glue.

[0069] The vacuum curing process is to place the lead frame after colloid encapsulation in a vacuum high-temperature oven, and solidify the colloid by high temperature to complete the packaging of the power chip. The rib cutting process is to cut the ribs between each two adjacent sub-frames on the cured lead frame by cutting equipment, so as to obtain multiple power modules (such as Figure 5 shown).

[0070] The present invention uses a lead frame as a base island for carrying a power chip and a connection port for gate-level, emitter and collector input and output of the power chip to realize ultra-fine pitch pin design of the power module. At the same time, a preheating stage, a thermal activation stage and a cooling stage are sequentially performed through a vacuum welding device to complete the welding of the power chip and perform quality inspection on the welding, thereby improving the yield rate of the produced power modules and ensuring stable performance of the power modules.

[0071] As an optional implementation, a plurality of power chips and a plurality of welding pieces of corresponding sizes are welded one by one in a plurality of chip welding areas of a lead frame to obtain a welded lead frame, comprising:

[0072] Using an automatic chip mounter, a plurality of soldering pads are mounted one by one on a plurality of chip welding areas of a lead frame, and a plurality of power chips are mounted one by one on the plurality of soldering pads to obtain a mounted lead frame;

[0073] The mounted lead frame is preheated and heated by a vacuum welding device to obtain a preheated lead frame;

[0074] The vacuum welding device adjusts the temperature to a first preset temperature, performs vacuum welding on the preheated lead frame for a first preset time, and welds the power chip on the lead frame to obtain a vacuum welded lead frame;

[0075] The vacuum welding device adjusts the temperature to a second preset temperature, and performs a cooling treatment for a second preset time on the lead frame after vacuum welding to obtain the welded lead frame. Specifically, the lead frame is placed in an automatic chip mounter, and a plurality of soldering pads are first mounted one by one in a plurality of chip welding areas of the lead frame, and then a plurality of power chips are mounted one by one on a plurality of soldering pads to complete the mounting of soldering pads and power chips. The mounted lead frame is placed in a vacuum welding device, and is first preheated and heated in a nitrogen environment, and then reduced with formic acid to remove the oxide layer of the pins on the side of the mounted lead frame to improve its weldability, and nitrogen protection is used to avoid incomplete melting of the solder due to individual differences between the power chip and the solder, and the presence of welding voids between the power chip and the lead frame, thereby ensuring the reliability of the device and improving the production yield of the product. Then, the vacuum welding device adjusts the temperature to a first preset temperature, and performs welding for a first preset time at a high temperature of the first preset temperature, so that the power chip is welded on the lead frame to obtain a vacuum welded lead frame.

[0076] More specifically, this embodiment takes the production of a power module with a volume specification of 30mm*26mm*5mm as an example. The range of the aforementioned first preset temperature is 300℃-350℃, the first preset temperature is preferably 320℃, the range of the first preset time is 6min-10min, and the first preset time is preferably 8min. Further, after obtaining the lead frame after vacuum welding, the vacuum welding device adjusts the temperature to the second preset temperature, and places the lead frame after vacuum welding in a nitrogen environment at the second preset temperature for cooling treatment. The cooling time is the second preset time, and the welding process is completed to obtain the welded lead frame. The range of the second preset temperature is 45℃-55℃, the second preset temperature is preferably 50℃, the range of the second preset time is 5min-10min, and the second preset time is preferably 6min. In addition, the first preset temperature, the first preset time, the second preset temperature and the second preset time can all be adaptively set according to the actual volume specification requirements of the power module. The model of the automatic placement machine can be selected as CPM-FS10 / CCSTP23001, and the model of the vacuum welding device can be selected as TFV-300 / CCSZJ23001.

[0077] As an optional implementation, performing welding void inspection and welding size inspection on the welded lead frame to obtain a qualified lead frame includes:

[0078] After placing the welded lead frame in the inspection area of ​​the X-Ray device and the optical inspection device, the automatic scanning plug-in is called to scan the welded lead frame to determine the size of the void rate in the welding area;

[0079] Determine whether the void ratio of the welding area exceeds a preset void ratio, and determine whether the size of the welding area exceeds a preset size;

[0080] If not, it is determined that the welded lead frame is a qualified lead frame.

[0081] Specifically, after the power chip is welded, the welded lead frame is taken out of the vacuum welding device and placed in the X-Ray device and the optical inspection device in turn to inspect the welding quality. The steps of the X-Ray device inspection are as follows: the welded lead frame is placed in the inspection area of ​​the X-Ray device, the hatch of the X-Ray device is closed, the voltage of the X-Ray device is adjusted to the preset voltage, the current is adjusted to the preset current, the X-Ray device is started, and the void rate of the welding area is automatically identified by the automatic scanning plug-in. After the automatic scanning plug-in scans, the acquired data information is analyzed to determine whether the void rate of the welding area exceeds the preset void rate. If so, the welded lead frame is determined to be a defective product. Further, the range of the preset voltage can be selected as 100V-145V, preferably 120V, the range of the preset current can be selected as 95A-120A, preferably 100A, and the preset void rate can be selected as 1% or lower to ensure the product welding qualification rate and provide stability for the electrical performance of the power module.

[0082] Specifically, the inspection steps of the optical inspection equipment are as follows: placing the welded lead frame in the inspection area of ​​the optical inspection equipment, closing the hatch of the optical inspection equipment, starting the optical inspection equipment, scanning the welding area, identifying the size of the welding area, and after completing the scan, analyzing the acquired data information to determine whether the size of the welding area exceeds the preset size. If so, the welded lead frame is determined to be a defective product; if not, and the void rate of the welding area does not exceed the preset void rate, the welded lead frame is determined to be a qualified lead frame.

[0083] The qualified lead frame is subjected to bonding process, glue filling process, vacuum curing process and rib cutting process in sequence, so that the power module is of high quality, with good heat dissipation effect, signal transmission performance and reliability. The model of X-Ray equipment can be LCM-10, and the model of optical inspection equipment can be MVP300CNC-H / CCYYX22001.

[0084] As an optional implementation, bonding qualified lead frames by bonding equipment to obtain bonded lead frames includes:

[0085] Place qualified lead frames on a wire bonding jig;

[0086] The wire bonding jig is placed on a workbench of the bonding equipment. The bonding equipment adjusts the position of the workbench so that the bonding head of the bonding equipment is aligned with a qualified lead frame. The bonding equipment controls the wire bonding jig to adsorb and fix the lead frame.

[0087] The bonding equipment bonds the power chip on the qualified lead frame to obtain a bonded lead frame.

[0088] Specifically, Figure 3 As shown, after the qualified lead frame is taken out from the X-Ray equipment and the optical inspection equipment, it is placed on the wire bonding jig, and then the wire bonding jig is placed in the bonding equipment. The jig in the bonding equipment cooperates with the multiple small holes opened on the wire bonding jig to provide negative pressure in the small holes. The qualified lead frame is adsorbed and fixed on the wire bonding jig through the negative pressure, ensuring that the qualified lead frame is stably fixed on the wire bonding jig to prevent poor power chip capacity cratering during the bonding process. The model of the wire bonding jig can be selected as QPIM-YCJH-1. The wire bonding jig is provided with a pick-up handle to facilitate placing the wire bonding jig into the bonding setting and removing the wire bonding jig from the bonding equipment. The wire bonding jig has a simple structure and can be adaptively set according to the product to improve production efficiency and reduce production costs. The wire bonding jig matches the lead frame, and small holes are provided at the corresponding positions of the wire bonding jig and each subframe of the lead frame to improve the stability of the qualified lead frame fixed on the wire bonding jig, so that the power chip in each subframe will not move during bonding. The bonding equipment model can be ASTERION / CCSJH22001.

[0089] The bonding equipment can set different bonding parameters according to the different wire diameters, different splitters and different lead frames used in the actual power module, and perform the bonding process according to the corresponding bonding parameters. The bonding parameters include starting pressure, bonding pressure, starting power, bonding power, bonding frequency, bonding rise time and bonding hold time. For example, Table 1 shows some reference bonding parameters corresponding to the bonding equipment using a 153-type splitter for bonding power modules with a volume specification of 30mm*26mm*5mm, and Table 2 shows some reference bonding parameters corresponding to the bonding equipment using a 175-type splitter for bonding power modules with a volume specification of 30mm*26mm*5mm:

[0090] Table 1

[0091]

[0092] Table 2

[0093]

[0094] As an optional implementation manner, a bonding device bonds a power chip on a qualified lead frame to obtain a bonded lead frame, including:

[0095] Introducing the bonding wire into the bonding equipment and delivering the bonding wire to the bonding head;

[0096] adjusting the bonding head to a first bonding position of a qualified lead frame, applying bonding pressure and starting ultrasonic vibration to form a metallurgical bond between the first end of the bonding lead and the first bonding position;

[0097] adjusting the bonding head to a second bonding position of the qualified lead frame, applying bonding pressure and starting ultrasonic vibration to form a metallurgical bond between the second end of the bonding wire and the second bonding position, so that the bonding wire forms a ring structure between the first end and the second end of the bonding wire;

[0098] After completing the bonding between the first bonding position and the second bonding position, cut off the redundant bonding wires, complete a bonding cycle, and then execute the next bonding cycle until all bonding cycles are executed to obtain the bonded lead frame. Specifically, the bonding wire is introduced into the bonding head of the bonding device, and the bonding head can control the movement and positioning of the bonding wire, thereby driving the bonding wire to be routed according to the wire diameter. The bonding head is adjusted to the first bonding position, and the bonding pressure is applied according to the bonding parameters. At the same time, ultrasonic vibration is started to flatten the first end of the bonding wire and form a wedge shape, and a metallurgical bond is initially formed between the first bonding position. Then, the bonding head is adjusted to the top of the second bonding position, and the bonding pressure is applied according to the bonding parameters. At the same time, ultrasonic vibration is started, and the second end of the bonding wire is flattened and formed into a wedge shape, and a metallurgical bond is formed between the second bonding position. In the process of bonding the second end of the bonding wire to the second bonding position, the bonding wire forms a ring structure between the first end and the second end of the bonding wire to avoid short circuit of the power module. The height and shape of the ring structure can be controlled by adjusting the bonding parameters. After completing the bonding between the two bonding positions, the bond head will move to the top of the bonding wire, and the shear mechanism of the bonding equipment will cut off the excess bonding wire to complete a bonding cycle. For other bonding positions that need to be bonded on the qualified lead frame, the bond head will repeat the bonding steps of the above bonding cycle until all bonding cycles are completed to obtain the bonded lead frame. The bonding wire is an aluminum wire. The bonding wire can make the internal connection of the power module complete and achieve the electrical performance of the power module.

[0099] When the bonding equipment starts ultrasonic vibration, it can use ultrasonic vibration to soften the bonding wire. The energy generated by ultrasonic vibration makes the molecular structure of the bonding wire active, making it easier to bond with the base material. The bonding equipment applies a preset bonding pressure while starting ultrasonic vibration, which can make the bonding wire contact with the base material and make the molecules between the bonding wire and the base material penetrate each other to form a metallurgical bond.

[0100] As an optional implementation, after completing a bonding cycle, it also includes: detecting whether the bonding between the first bonding position and the second bonding position is qualified, and if not, re-bonding. Specifically, after completing a bonding cycle, the bonding equipment usually performs visual inspection through a detection mechanism or uses other optical detection means to ensure the bonding quality. In addition, push-pull force tests of the bonding wires will also be performed to ensure that the bonding strength meets the corresponding strength requirements. When unqualified bonding is detected, it is necessary to adjust the bonding parameters to re-bond the unqualified bonding position to ensure the bonding quality of the power chip, improve the packaging quality of the power module, and improve the terminal application performance and service life of the device.

[0101] As an optional implementation, the bonded lead frame is colloid-encapsulated by a glue-encapsulating device to obtain a colloid-encapsulated lead frame, including: placing the bonded lead frame in a packaging mold, wherein the packaging mold includes a bottom plate, a guide plate and a limit plate (such as Figure 4 The bonded lead frame is placed in the limit groove of the base plate, the guide plate and the limit plate are fixed on the base plate and the bonded lead frame in turn, and the bonded lead frame is packaged in the packaging mold. The packaging mold is placed in a glue potting device for colloid potting to obtain a lead frame after colloid potting, wherein during the colloid potting, the sealing colloid used by the glue potting device is a two-component silicone gel, the glue potting pressure of the glue potting device ranges from 0.6Mpa to 0.8Mpa, and the glue discharge speeds of the AB glue outlet pipes of the glue potting device are consistent.

[0102] Specifically, the bonded lead frame is placed in the limiting groove of the bottom plate of the packaging mold, and then a plurality of guide plates are respectively arranged on each sub-frame of the bonded lead frame and fixedly connected to the bottom plate. Finally, the plurality of limiting plates are fixed one by one on the plurality of guide plates, thereby encapsulating the bonded lead frame in the packaging mold. The limiting groove of the bottom plate can increase the creepage clearance of the bonded lead frame and increase the pressure resistance of the voltage-resistant product. There are convex strips in the limiting groove, so that an auxiliary groove is provided between the power chip and the pin connection area of ​​the packaged power module, which can enhance the transient creepage clearance of the power module. A guide groove is provided on the guide plate, and the guide groove is used to pass part of the overflowed silica gel during the glue filling process, so that the surface of the product is flat and uniform after the glue filling. The packaging mold has a simple structure and can be adaptively set according to the product to improve production efficiency and reduce production costs. After the bonded lead frame is encapsulated in the encapsulation mold, the encapsulation mold is placed in the glue potting equipment. The glue potting equipment pours the sealing glue into the glue potting area formed in the middle of the guide plate and the limit plate, so as to perform glue potting on the power chip, solder pad and bonding wire on the bonded lead frame to complete the encapsulation of the power module. During the glue potting process, the glue discharge speed of the AB glue discharge hose of the glue potting equipment can be selected to be 1g / s-3g / s, and the glue mass is 5g-8g. The model of the encapsulation mold is QPIM-GJ-1, and the model of the glue potting equipment is JT-011.

[0103] As an optional implementation, the lead frame after colloid encapsulation is placed in a vacuum high-temperature oven for curing to obtain a cured lead frame, including: placing the lead frame after colloid encapsulation in a vacuum high-temperature oven, performing a first stage of degassing and curing and a second stage of degassing and curing, wherein the curing parameters of the first stage of degassing and curing are a temperature range of 80°C-120°C, a vacuum range of 290Pa-320Pa and a process duration range of 10min-15min, and the curing parameters of the second stage of degassing and curing are a temperature range of 100°C-150°C, a vacuum range of 300Pa-350Pa and a process duration range of 20min-35min.

[0104] Specifically, the bonded lead frame is colloid-encapsulated to obtain a colloid-encapsulated lead frame, which is taken out from the glue-encapsulating equipment and placed in a vacuum high-temperature oven for two-stage degassing and curing to complete the encapsulation of the power module, and then the cured lead frame is taken out from the vacuum high-temperature oven, and the encapsulation mold on the cured lead frame is removed. During the two-stage degassing and curing process, the curing parameters can be adjusted according to the curing conditions of the encapsulating colloid. The curing parameters of the first stage of degassing and curing are preferably 85°C, 300Pa, and 10min, and the curing parameters of the second stage of degassing and curing are preferably 125°C, 300Pa, and 25min. The two-stage degassing and curing can ensure that the product is fully cured and improve the electrical performance and reliability of the power module. The model of the vacuum high-temperature oven is CH-250VAC / CCSAZ22001.

[0105] As an optional embodiment, before welding a plurality of power chips and a plurality of welding pieces of corresponding sizes in a plurality of chip welding areas of a lead frame in a one-to-one correspondence to obtain a welded lead frame, the method further includes: providing a lead frame, wherein the lead frame is formed by an array of a plurality of sub-frames, each of which has a chip welding area (such as Figure 2 As shown), and the material of the lead frame is copper. Specifically, a plurality of sub-frames are arranged in an array to form a lead frame, and each sub-frame is provided with a chip welding area to ensure that a power chip can be packaged on each sub-frame. The size of the chip welding area matches the size of the power chip and the size of the welding piece. The material of the lead frame is copper, and the number of sub-frames on the lead frame is adaptively set according to actual needs. The process of this embodiment can not only carry out mass production of power modules, but also significantly improve production efficiency and product qualification rate through improvements in the glue filling process and the curing process, thereby providing good quality assurance for the terminal application of power modules.

[0106] Embodiment 2:

[0107] like Figure 6As shown, a power module is a power module made by the manufacturing method of the power module of Example 1, and the power module includes: a copper substrate, a welding piece, a power chip, a bonding lead and a sealing body. The power chip is fixedly connected to the copper substrate by the welding piece, and the bonding lead connects the power chip and the copper substrate. The sealing body is used to encapsulate the copper substrate, the welding piece, the power chip and the bonding lead. Specifically, the copper substrate is each sub-frame cut from the lead frame, and the middle part of each sub-frame is provided with a chip welding area, which is used as a base island for carrying the power chip. The peripheral side of the chip welding area on each sub-frame is used to replace the frame pin as the lead connecting the lower pin, so that when the power chip is packaged, there is no need to use a plastic package shell and a frame pin. At the same time, the copper substrate also serves as a connection port for the gate level, emitter and collector input and output of the IGBT device. The power chip is an IGBT chip, which is fixed to the chip welding area of ​​the copper substrate by welding with welding pieces. The bonding wire is in an arc-shaped structure, one end of the bonding wire is welded to the power chip, and the other end of the bonding wire is welded to the copper substrate. The bonding wire also bonds to two bonding positions on the power chip to achieve bonding of the power chip. The material of the encapsulant can be silicone gel, which can cover the copper substrate and the welding pieces fixed on the copper substrate, the power chip and the bonding wire, complete the packaging of the power chip, and form a power module.

[0108] The above description is only the preferred embodiment of the present invention. It is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the protection scope of the present invention.

Claims

1. A method for manufacturing a power module, characterized in that: include: Welding a plurality of power chips and a plurality of welding pieces of corresponding sizes in a plurality of chip welding areas of a lead frame in a one-to-one correspondence to obtain a welded lead frame; Performing welding void inspection and welding size inspection on the welded lead frame to obtain a qualified lead frame; Bonding the qualified lead frame by a bonding device to obtain a bonded lead frame; Performing colloid encapsulation on the bonded lead frame by means of a glue encapsulation device to obtain a lead frame encapsulated with colloid; Placing the colloid-encapsulated lead frame in a vacuum high-temperature oven for curing to obtain a cured lead frame; The cured lead frame is cut to obtain a plurality of power modules.

2. The method for manufacturing a power module according to claim 1, characterized in that: The method of welding a plurality of power chips and a plurality of welding pieces of corresponding sizes in a plurality of chip welding areas of a lead frame in a one-to-one correspondence manner to obtain a welded lead frame comprises: Using an automatic chip mounter, the plurality of soldering pads are mounted one by one in the plurality of chip welding areas of the lead frame, and then the plurality of power chips are mounted one by one on the plurality of soldering pads to obtain a mounted lead frame; Preheating the mounted lead frame by a vacuum welding device to obtain a preheated lead frame; The vacuum welding device adjusts the temperature to a first preset temperature, performs vacuum welding on the preheated lead frame for a first preset time, and welds the power chip on the lead frame to obtain a vacuum welded lead frame; The vacuum welding device adjusts the temperature to a second preset temperature, and performs a cooling process for the vacuum welded lead frame for a second preset time to obtain the welded lead frame.

3. The method for manufacturing a power module according to claim 1, characterized in that: The step of performing welding void inspection and welding size inspection on the welded lead frame to obtain a qualified lead frame comprises: Placing the welded lead frame in an inspection area of ​​an X-Ray device and an optical inspection device, calling an automatic scanning plug-in to scan the welded lead frame to determine the void rate and size of the welding area; Determining whether a void ratio of the welding area exceeds a preset void ratio, and determining whether a size of the welding area exceeds a preset size; If not, it is determined that the welded lead frame is a qualified lead frame.

4. The method for manufacturing a power module according to claim 1, characterized in that: The step of bonding the qualified lead frame by a bonding device to obtain a bonded lead frame comprises: placing the qualified lead frame on a wire bonding jig; Placing the wire bonding jig on the workbench of the bonding device, adjusting the position of the workbench by the bonding device so that the bonding head of the bonding device is aligned with the qualified lead frame, and controlling the wire bonding jig to adsorb and fix the qualified lead frame; The bonding device bonds the power chip on the qualified lead frame to obtain the bonded lead frame.

5. The method for manufacturing a power module according to claim 4, characterized in that: The bonding device bonds the power chip on the qualified lead frame to obtain the bonded lead frame, including: Introducing a bonding wire into the bonding device, and delivering the bonding wire to the bonding head; Adjusting the bonding head to the first bonding position of the qualified lead frame, applying bonding pressure and starting ultrasonic vibration to form a metallurgical bond between the first end of the bonding wire and the first bonding position; Adjusting the bonding head to the second bonding position of the qualified lead frame, applying bonding pressure and starting ultrasonic vibration to form a metallurgical bond between the second end of the bonding wire and the second bonding position, so that the bonding wire forms a ring structure between the first end and the second end of the bonding wire; After the bonding between the first bonding position and the second bonding position is completed, the redundant bonding wires are cut off to complete a bonding cycle, and then the next bonding cycle is performed until all bonding cycles are performed to obtain the bonded lead frame.

6. The method for manufacturing a power module according to claim 5, characterized in that: After completing a bonding cycle, the method further includes: detecting whether the bonding between the first bonding position and the second bonding position is qualified; If not, re-bond.

7. The method for manufacturing a power module according to claim 1, characterized in that: The method of performing colloid encapsulation on the bonded lead frame by using a glue encapsulation device to obtain the colloid encapsulated lead frame comprises: Placing the bonded lead frame in a packaging mold, wherein the packaging mold comprises a base plate, a guide plate and a limit plate, the bonded lead frame is placed in a limit groove of the base plate, the guide plate and the limit plate are fixed on the base plate and the bonded lead frame in sequence, and the bonded lead frame is packaged in the packaging mold; The packaging mold is placed in the glue potting equipment for colloid potting to obtain the lead frame after colloid potting, wherein, during the colloid potting, the sealing colloid used by the glue potting equipment is a two-component silicone gel, the glue potting pressure of the glue potting equipment ranges from 0.6Mpa to 0.8Mpa, and the glue discharge speeds of the AB glue outlet pipes of the glue potting equipment are consistent.

8. The method for manufacturing a power module according to claim 1, characterized in that: Placing the colloid-encapsulated lead frame in a vacuum high-temperature oven for curing to obtain a cured lead frame comprises: The lead frame after colloid encapsulation is placed in the vacuum high-temperature oven to perform the first stage of degassing and curing and the second stage of degassing and curing, wherein the curing parameters of the first stage of degassing and curing are a temperature range of 80°C-120°C, a vacuum range of 290Pa-320Pa and a process duration range of 10min-15min, and the curing parameters of the second stage of degassing and curing are a temperature range of 100°C-150°C, a vacuum range of 300Pa-350Pa and a process duration range of 20min-35min.

9. The method for manufacturing a power module according to claim 1, characterized in that: Before the multiple power chips and the multiple welding pieces of corresponding sizes are welded one by one in the multiple chip welding areas of the lead frame to obtain the welded lead frame, the method further includes: The lead frame is provided, wherein the lead frame is formed by arranging a plurality of sub-frames in an array, each of the sub-frames has a chip welding area, and the material of the lead frame is copper.

10. A power module, characterized in that: A power module manufactured by the power module manufacturing method described in any one of claims 1 to 9, the power module comprising: a copper substrate, a welding sheet, a power chip, a bonding wire and a sealing body, the power chip being fixedly connected to the copper substrate via the welding sheet; the bonding wire connecting the power chip and the copper substrate; the sealing body being used to encapsulate the copper substrate, the welding sheet, the power chip and the bonding wire.

Images