Power module manufacturing method and compression plastic package mold

Abstract

The invention belongs to the technical field of semiconductors, and particularly relates to a power module manufacturing method and a compression plastic package mold, the compression plastic package mold comprises a compression plastic package upper mold and a compression plastic package lower mold, the compression plastic package upper mold is provided with a compression plastic package upper mold substrate cavity, the compression plastic package upper mold substrate cavity is used for being attached and fixed to a substrate, and the compression plastic package lower mold is provided with a compression plastic package lower mold. The compression plastic package lower mold is provided with a compression plastic package lower mold cavity, a plurality of U-shaped cavities and a plurality of material ejection blocks are arranged in the compression plastic package lower mold cavity, the U-shaped cavities are used for accommodating signal ends of the power module connecting terminals during plastic package, and the calibers of the U-shaped cavities are not greater than the outer diameters of welding ends of the connecting terminals; and the material jacking block is used for upwards jacking a molten plastic packaging material in the cavity of the compression plastic packaging lower mold to the substrate. The structure is simple, the cost is low, the filling effect is good, and it can be guaranteed that the power module is prevented from being invaded by external water vapor, sulfuration gas, other corrosive substances and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a method for manufacturing a power module and a compression plastic packaging mold. Background Art

[0002] With the advancement of technology and the evolution of market demand, power module products (the heart of power electronic systems) are facing unprecedented challenges and opportunities. The design and performance of these power module products will directly affect the efficiency, cost and reliability of photovoltaic and energy storage systems. Therefore, it is very important to improve the reliability of power modules and reduce the cost of power modules.

[0003] The package with the connection terminal drawn from the top has the advantages of short electrical path and small parasitic parameters and is widely used in photovoltaic and energy storage power modules. At present, this packaging structure adopts the method of filling with silicone gel, but the filling module has the following disadvantages: (1) The expansion coefficient of silicone gel used in the filling module is large, which is not conducive to the PC reliability of the module; (2) The filling silicone gel package has obvious deficiencies in moisture and corrosion resistance. The penetration of moisture, sulfide gas and other corrosive substances may cause damage to circuit boards and electronic components; (3) The filling package uses a lot of materials and the production process is complicated.

[0004] In order to solve the above-mentioned silicone module problems, plastic-encapsulated modules have gradually been proposed and applied. Due to their excellent moisture-proof, corrosion-resistant properties and high reliability, plastic-encapsulated modules are becoming the main solution to replace potting modules. In view of this, how to realize the plastic-encapsulated packaging structure with connecting terminals drawn out from the top has become a key issue that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of poor moisture resistance, salt spray resistance and corrosion resistance, numerous materials and complex processes in the prior art of glue-filled power modules, and to provide a power module manufacturing method based on compression molding technology and a compression plastic encapsulation mold.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a power module compression plastic packaging mold, specifically comprising:

[0007] A compression molding upper mold and a compression molding lower mold;

[0008] The compression plastic sealing upper mold is provided with a compression plastic sealing upper mold substrate cavity, and the compression plastic sealing upper mold substrate cavity is used for fitting and fixing with the substrate;

[0009] The compression molding lower mold is provided with a compression molding lower mold cavity, and a plurality of U-shaped cavities and a plurality of ejector blocks are provided in the compression molding lower mold cavity, wherein the U-shaped cavity is used to accommodate the signal end of the power module connection terminal during molding, and the caliber of the U-shaped cavity is not larger than the outer diameter of the welding end of the connection terminal, and the U-shaped cavity port and the welding end are closely fitted to ensure the sealing of the welding end to the U-shaped cavity, so as to ensure that the molding material will not enter the U-shaped cavity to form a coating on the exposed end of the external connection component;

[0010] The lifting block is used to lift the melted plastic packaging material in the compression plastic packaging lower mold cavity upward to the base plate, and the shape of the lifting block is round, square, diamond or polygonal.

[0011] Preferably, a hydraulic channel is provided below the lifting block, and the hydraulic channel is used to control the lifting and lowering of the lifting block, and the shape of the hydraulic channel is circular, square or polygonal.

[0012] Preferably, the compression molding lower mold is also provided with a bolt hole top column that can be lifted and lowered, and the shape of the bolt hole top column is circular, square, diamond or polygonal. The bolt hole top column is arranged corresponding to the connecting hole on the substrate, and the size of the bolt hole top column is larger than the size of the connecting hole, which is used to block the connecting hole to prevent the molten molding material from invading the connecting hole of the substrate.

[0013] Preferably, a top column spring for realizing the upward or downward movement of the bolt hole top column is arranged below the bolt hole top column, and the top column spring is selected from a spring or a spring leaf.

[0014] A method for manufacturing a power module, using the above-mentioned plastic encapsulation mold, comprises the following steps:

[0015] S1. Soldering a circuit board on a substrate. Specifically, laying a solder 1 on a first soldering surface of the substrate. The solder 1 is selected from solder paste, solder sheet or silver paste, and then soldering the second soldering surface of the circuit board to the first soldering surface through a reflow soldering process;

[0016] S2. Soldering the chip on the circuit board. Specifically, a second solder is laid on the circuit surface of the circuit board away from the substrate. The second solder is selected from solder paste, solder sheet or silver paste, and then the chip is soldered to the circuit surface through a reflow process or a sintering process;

[0017] S3, setting a binding member between the chip and another chip or between the chip and the circuit board, wherein the binding member is made of aluminum wire, copper wire or copper clip;

[0018] S4, welding connecting terminals on the circuit board to obtain a power module frame, wherein the connecting terminals are selected from straight PIN pins, S-bend PIN pins, square PIN pins, round PIN pins, fisheye PIN pins or special-shaped PIN pins, and the welding process is selected from reflow welding process, ultrasonic welding process or laser welding process;

[0019] S5, placing the power module frame in a plastic encapsulation mold, and using a plastic encapsulation material to perform plastic encapsulation between the heat dissipation surface of the substrate away from the circuit board and the bottom surface of the compression plastic encapsulation mold cavity to form a plastic encapsulation member covering the substrate, circuit board, chip and part of the connecting terminals, thereby obtaining a power module;

[0020] The plastic encapsulation material is selected from epoxy potting glue or epoxy molding resin.

[0021] Preferably, in step S4, the prepared power module frame includes a substrate, at least one circuit board, at least one chip, a plurality of binding parts and a plurality of connection terminals;

[0022] The substrate has a first welding surface and a heat dissipation surface that are arranged oppositely, and the circuit board has a second welding surface and a circuit surface that are arranged oppositely, the first welding surface includes a welding area and a connection area arranged outside the welding area, the welding area is used for welding with the second welding surface, the connection area is provided with a plurality of plastic sealing holes and a plurality of connection holes, the connection holes are used for connecting with the heat sink, the heat dissipation surface is provided with a convex arc surface structure, and the edge of the heat dissipation surface is also provided with a plastic sealing groove;

[0023] The chip is welded on the circuit surface, one end of the binding piece is electrically connected to the chip, and the other end is electrically connected to the circuit surface or another chip, the connecting terminal has a welding end and a signal end, the welding end is welded on the circuit surface, the signal end extends in a direction away from the circuit surface, and the signal end is designed as a pointed end with a guiding bevel.

[0024] Preferably, in step S5, the heat dissipation surface of the substrate away from the circuit board is fixedly attached to the substrate cavity of the compression molding upper mold, that is, the power module frame is inverted above the compression molding lower mold cavity, and the compression molding lower mold cavity is filled with molten molding material.

[0025] Preferably, in step S5, when the compression molding upper mold and the compression molding lower mold are closed, the signal end of the connecting terminal is inserted into the U-shaped cavity, and the substrate overcomes the elastic force of the ejector spring to squeeze the bolt hole ejector downward until the opening end of the U-shaped cavity is tightly fitted with the welding end of the connecting terminal. At this time, the ejector block moves upward under the action of the hydraulic channel and squeezes the molding material until the molding material fills the molding cavity of the compression molding lower mold, and the power module frame is immersed in the molten molding material, thereby completing the compression molding.

[0026] Preferably, in step S5, when the clamping pressure of the compression molding upper mold and the compression molding lower mold is released, the top column of the bolt hole pushes the base plate and drives the compression molding upper mold to move upward under the action of the spring rebound force of the top column, thereby achieving demolding.

[0027] Preferably, in step S5, the bolt hole top column can abut against the connection hole during mold closing, thereby supporting the power module frame and preventing the melted plastic packaging material from invading the connection hole.

[0028] After adopting the above technical solution, the power module manufacturing method and compression plastic packaging mold provided by the present invention have the following beneficial effects:

[0029] 1) The present invention adopts compression molding to mold the packaging structure with top pins. Compared with transfer molding, compression molding has the following advantages: a. No waste of runner material; b. Less impact on bonding wires; c. Better filling effect under small size;

[0030] 2) The present invention has no special requirements for the structural design of the connection terminals, which facilitates the layout of the connection terminals and does not limit the welding process of the connection terminals;

[0031] 3) Compared with the glue-filling module, the plastic-sealing module designed in the present invention uses less materials, is convenient for material management, and has a simpler production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the compression molding mold of the present invention;

[0033] Figure 2 It is a schematic diagram of the assembly of the compression molding mold and the power module frame after the mold is closed;

[0034] Figure 3 A flowchart of a manufacturing method according to an embodiment of the present invention;

[0035] Figure 4 It is a structural schematic diagram of a power module manufactured by adopting the present invention;

[0036] Figure 5 A cross-sectional schematic diagram of a power module made using the present invention connects the terminals;

[0037] Figure 6 It is a schematic structural diagram of the substrate in the present invention.

[0038] Among them: 1-substrate, 11-first welding surface, 111-welding area, 112-connecting area, 113-plastic sealing hole, 114-connecting hole, 12-heat dissipation surface, 13-plastic sealing groove, 2-circuit board, 3-chip, 4-connecting terminal, signal terminal 6-plastic sealing part, 9-binding part, 10-compression plastic sealing mold, 101-compression plastic sealing upper mold, 102-compression plastic sealing lower mold, 103-U cavity, 104-top block, 105-bolt hole top column, 106-top column spring, 107-hydraulic channel, 108-compression plastic sealing upper mold substrate cavity, 109-compression plastic sealing lower mold cavity. DETAILED DESCRIPTION

[0039] The present invention is further described clearly and completely below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] like Figure 1 As shown, this embodiment provides a compression molding mold for manufacturing a power module. The mold material surface is treated by vacuum ion plating to prevent adhesion with the molding material. The mold specifically includes:

[0041] A compression molding upper mold 101 and a compression molding lower mold 102;

[0042] The compression molding upper mold 101 is provided with a compression molding upper mold substrate cavity 108, and the compression molding upper mold substrate cavity 108 is used to fit and fix with the substrate 1;

[0043] The compression molding lower mold 102 is provided with a compression molding lower mold cavity 109 for placing melted molding materials, and the compression molding lower mold cavity 109 is provided with a plurality of U-shaped cavities 103 and a plurality of ejector blocks 104;

[0044] The U-shaped cavity 103 is used to accommodate the signal end of the power module connection terminal 4 during plastic packaging, so as to avoid the plastic packaging material climbing over the signal end, causing the power module to be unusable. It should be noted that when the U-shaped cavity 103 is set, in order to prevent the plastic packaging material from flowing into the U-shaped cavity 103, preferably, the diameter of the U-shaped cavity 103 is slightly smaller than the outer diameter of the welding end of the connection terminal 4, so as to ensure the sealing of the welding end to the U-shaped cavity 103, so as to ensure that the plastic packaging material does not enter the U-shaped cavity 103 to form a coating on the exposed end of the connection terminal 4;

[0045] The lifting block 104 is used to lift the molten plastic sealing material in the compression plastic sealing lower mold cavity 109 upward to the substrate 1, and a hydraulic channel 107 for controlling the lifting and lowering of the lifting block 104 is arranged below the lifting block 104, and the shapes of the lifting block 104 and the hydraulic channel 107 are both circular;

[0046] The compression molding lower mold 102 is also provided with a bolt hole top column 105 that can be lifted and lowered. The bolt hole top column 105 is arranged corresponding to the connecting hole 114 on the substrate 1, and the size of the bolt hole top column 105 is larger than the size of the connecting hole 114. Furthermore, the bolt hole top column 105 is circular in shape, which is used to block the connecting hole 114 to prevent the molten molding material from invading the connecting hole 114 of the substrate 1. A top column spring 106 is provided below the bolt hole top column 105 to realize its rising or falling movement.

[0047] like Figure 2-3 The present embodiment provides a method for manufacturing a power module, using the above-mentioned compression molding mold, including the following steps:

[0048] S1, laying solder 1 on the first soldering surface 11 of the substrate 1, and then reflow soldering the second soldering surface of the circuit board 2 and the first soldering surface 11 through a reflow soldering process, so that the circuit board 2 and the substrate 1 are fixedly attached;

[0049] S2, laying solder 2 on the circuit surface of the circuit board 2 away from the substrate 1, and then continue to solder the chip 3 to the circuit surface through a reflow soldering process, so that the chip 3 is fixedly soldered to the circuit surface of the circuit board 2;

[0050] S3, providing a plurality of binding members 9, wherein the binding members 9 are aluminum wires, and one end of all the aluminum wires is electrically connected to the chip 3, the other end of a portion of the aluminum wires is electrically connected to the circuit surface 22, and the other end of the remaining portion of the aluminum wires is electrically connected to another chip 3;

[0051] S4, using an ultrasonic welding head to suck the signal end of the connection terminal 4 into its cavity, and then welding the welding end to the circuit surface through an ultrasonic welding process, thereby obtaining a power module frame;

[0052] Specifically, the power module frame includes a substrate 1, at least one circuit board 2, at least one chip 3, a plurality of binding members 9 and a plurality of connection terminals 4;

[0053] The substrate 1 has a first welding surface 11 and a heat dissipation surface 12 disposed oppositely on the upper and lower sides, and the circuit board 2 has a second welding surface and a circuit surface disposed oppositely on the upper and lower sides. Figure 6As shown, the first welding surface 11 includes a welding area 111 and a connection area 112 arranged on the periphery of the welding area 111, the welding area 111 is used for welding with the second welding surface, the connection area 112 is provided with a plurality of plastic sealing holes 113 and a plurality of connection holes 114, the plastic sealing holes 113 are used for compression when the upper and lower molds of the plastic sealing are closed, the plastic sealing material extends from the first welding surface 11 side through the plastic sealing holes 113 to the heat dissipation surface 12 side, so that the bonding force between the plastic sealing part 6 and the substrate 1 can be increased after molding, that is, the structural strength of the power module is increased, the connection holes 114 are used for connecting with the heat sink, the heat dissipation surface 12 is set to a convex arc structure, which can be deformed during connection to form a better heat dissipation fit, and the edge of the heat dissipation surface 12 is further provided with a plastic sealing groove 13, which is used for compression when the upper and lower molds of the plastic sealing are closed, the plastic sealing material is wrapped around the substrate 1 and filled upward into the plastic sealing groove 13, so that the bonding force between the plastic sealing part 6 and the substrate 1 can be further increased after molding, and the structural strength of the power module is improved;

[0054] The chip 3 is welded on the circuit surface, one end of the binding member 9 is electrically connected to the chip 3, and the other end is electrically connected to the circuit surface or another chip 3, the connection terminal 4 has a welding end and a signal end, the welding end is welded on the circuit surface, the signal end extends in a direction away from the circuit surface, and the signal end is a pointed end with a guiding slope;

[0055] S5, placing the power module frame in the plastic encapsulation mold 10, specifically, the heat dissipation surface 12 of the substrate 1 away from the circuit board 2 is fixedly attached to the substrate cavity 108 of the compression plastic encapsulation upper mold, that is, the power module frame is inverted above the compression plastic encapsulation lower mold cavity 109, and the compression plastic encapsulation lower mold cavity 109 contains melted plastic encapsulation material;

[0056] When the compression molding upper mold 101 and the compression molding lower mold 102 are molded together, the signal end of the connecting terminal 4 is inserted into the U-shaped cavity 103. Since the signal end is designed as a tip with a guiding bevel, the alignment time can be reduced and the plug-in efficiency can be improved. The substrate 1 overcomes the elastic force of the top column spring 106 and squeezes the bolt hole top column 105 downward until the open end of the U-shaped cavity 103 is tightly fitted with the welding end of the connecting terminal 4. At this time, the ejector block 104 moves upward under the action of the hydraulic channel 107 and squeezes the molding material until the molding material fills the compression molding lower mold cavity 109, and the power module frame is immersed in the molten molding material, and the compression molding can be completed. The U-shaped cavity 103 open end and the welding end are tightly fitted, which can prevent the molding material from flowing into the U-shaped cavity 103, and avoid the problem that the signal end is wrapped by the molding material and cannot be used. The design of the bolt hole top column 105 can resist the connecting hole 114 when the mold is closed, and support the power module frame while preventing the molten molding material from invading the connecting hole 114;

[0057] When the clamping pressure of the compression molding upper mold 101 and the compression molding lower mold 102 is removed, the bolt hole top column 105 pushes the base plate 1 to drive the compression molding upper mold 101 to move upward under the action of the rebound force of the top column spring 106, thereby realizing demoulding;

[0058] Finally, a plastic package 6 is formed to cover the substrate 1, the circuit board 2, the chip 3 and part of the connecting terminals 4, thereby obtaining a power module. Figure 4-5 As shown, specifically, except for the signal end and the heat dissipation surface 12 exposed to the outside of the plastic package 6, the rest are completely covered by the plastic package 6 to form a sealed structure to prevent external moisture and sulfide gas from invading the interior of the power module, thereby ensuring the reliability of the power module.

[0059] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A power module compression mold, It is characterized in that include: A compression molding upper mold (101) and a compression molding lower mold (102); The compression molding upper mold (101) is provided with a compression molding upper mold substrate cavity (108), and the compression molding upper mold substrate cavity (108) is used to fit and fix with the substrate (1) of the power module; The compression molding lower mold (102) is provided with a compression molding lower mold cavity (109), and a plurality of U-shaped cavities (103) and a plurality of ejector blocks (104) are provided in the compression molding lower mold cavity (109). The U-shaped cavity (103) is used to accommodate the signal end of the power module connection terminal (4) during molding, and the diameter of the U-shaped cavity (103) is not larger than the outer diameter of the welding end of the connection terminal (4). The ejector block (104) is used to lift the molten molding material in the compression molding lower mold cavity (109) upward to the substrate (1).

2. A power module compression molding mold according to claim 1, Features: A hydraulic channel (107) is provided below the lifting block (104), and the hydraulic channel (107) is used to control the lifting and lowering of the lifting block (104).

3. The power module compression molding die according to claim 1, Features: The compression molding lower mold (102) is also provided with a bolt hole top column (105) capable of being lifted and lowered, the bolt hole top column (105) being arranged corresponding to the connection hole (114) on the base plate (1), and the size of the bolt hole top column (105) is larger than the size of the connection hole (114).

4. The power module compression molding mold according to claim 3, Features: A top column spring (106) is arranged below the bolt hole top column (105) to enable the top column to move upward or downward.

5. A method for manufacturing a power module, It is characterized in that The compression molding die according to any one of claims 1 to 4 is used, comprising the following steps: S1. welding a circuit board (2) on a substrate (1); S2, soldering a chip (3) on a circuit board (2); S3, providing a binding member (9) between the chip (3) and another chip (3) or between the chip (3) and the circuit board (2); S4, welding the connection terminals (4) on the circuit board (2), thereby obtaining a power module frame; S5. The power module frame is placed in a plastic encapsulation mold (10), and a plastic encapsulation material is used to perform plastic encapsulation between the side of the substrate (1) away from the circuit board (2) and the bottom surface of the compression molding lower mold cavity (109), so as to form a plastic encapsulation part (6) covering the substrate (1), the circuit board (2), the chip (3) and part of the connecting terminals (4), thereby obtaining a power module.

6. A method for manufacturing a power module according to claim 5, Features: In step S5, the heat dissipation surface (12) of the substrate (1) away from the circuit board (2) is fixedly attached to the substrate cavity (108) of the compression molding upper mold, and the power module frame is inverted above the compression molding lower mold cavity (109), and the compression molding lower mold cavity (109) is filled with molten molding material.

7. A method for manufacturing a power module according to claim 5, Features: In step S5, when the compression molding upper mold (101) and the compression molding lower mold (102) are closed, the signal end of the connecting terminal (4) is inserted into the U-shaped cavity (103), and the substrate (1) overcomes the elastic force of the ejector spring (106) to squeeze the bolt hole ejector (105) downward until the opening end of the U-shaped cavity (103) is tightly fitted with the welding end of the connecting terminal (4). At this time, the ejector block (104) moves upward under the action of the hydraulic channel (107) and squeezes the molding material until the molding material fills the compression molding lower mold cavity (109), and the power module frame is immersed in the molten molding material, thereby completing the compression molding.

8. A method for manufacturing a power module according to claim 5, Features: In step S5, when the clamping pressure of the compression molding upper mold (101) and the compression molding lower mold (102) is released, the bolt hole top column (105) pushes the base plate (1) and drives the compression molding upper mold (101) to move upward under the action of the rebound force of the top column spring (106), thereby achieving demoulding.

9. A method for manufacturing a power module according to claim 5, Features: In step S5, the bolt hole support column (105) can abut against the connection hole (114) when the mold is closed. The power module frame is supported while preventing melted plastic packaging material from invading the connection hole (114).

Images