A combined protection and potting process method for a power module

Abstract

The present invention specifically relates to a combined protection and potting process method for a power module, which solves the problems that the existing PCB board cannot meet the requirements of waterproofing and corrosion resistance in harsh environments, the power module has no solder joint protection measures, and the existing cavity potting is not solid, and there are bubbles or gaps. The present invention includes the following steps: Step 1, thick layer coating of the PCB board in the power module; Step 2, combined protection of the power module; Step 2.1, applying a layer of epoxy resin adhesive to the bottom of the inductor of the power module so that the inductor and the PCB board are bonded together; Step 2.2, welding the inductor and the capacitor to the PCB board, cleaning the solder joints, and applying solder joint protection glue to the solder joints after cleaning; Step 2.3, using silicone sealant to fill the center hole of the inductor, the gap between the bottom of the inductor and the PCB board, and the gap between the bottom of the capacitor and the PCB board; Step 3, potting the power module with good combined protection.

Description

Technical Field

[0001] The invention relates to a power module protection process, and in particular to a combined protection and encapsulation process method for a power module. Background Art

[0002] The power module of a product uses a potting process to fix the components in the internal structure and transfers the heat generated by the components during operation (the maximum operating temperature is 110°C) to the shell for heat dissipation through thermally conductive potting glue. After potting with potting glue according to the conventional potting process, after 11 types of tests such as low-temperature storage, low-temperature operation, high-temperature storage, high-temperature operation, temperature shock, damp heat test, functional vibration, endurance vibration, impact test, acceleration test, and cannon vibration test, product test failures often occur. After disassembly, it is found that the solder joints at the pins of the components are cracked, causing welding failure, making the product unqualified.

[0003] The printed circuit board (PCB) in the power module has various electronic devices such as non-sealed connectors, push button switches, transformers, high-power resistors, power modules, etc. The traditional coating process technology is to directly coat a layer of three-proof paint with a thickness of about 40μm to 200μm on the surface of the printed circuit board, so that the main electronic components and pins on the printed circuit board assembly are protected by the three-proof paint, thereby delaying corrosion and extending the service life. However, during traditional selective coating, the main body of the component needs to be avoided, and the pins at the bottom of the device cannot be protected accordingly. This causes serious problems such as short circuits and discharges between electrodes when the electronic equipment on the PCB board is used in harsh environments, causing the electronic equipment to fail.

[0004] The existing potting process of power modules uses direct potting after the thermal conductive potting glue is evenly mixed. The solder joints of components and the gaps between components and single boards are not protected, and the expansion coefficient of the potting material is 5 to 10 times that of the potted parts. The failure form of unqualified products is solder joint cracking, and the local mismatch of thermal expansion coefficients between component pins and SnPb solder, PCB board and SnPb solder, SnPb solder and pad, and SnPb solder and thermal conductive potting glue brings tensile and compressive stresses and shear stresses. These stresses are a major source of solder joint failure.

[0005] The power module cavity is deep and the potting glue has high viscosity and poor fluidity. When potting is performed according to the existing potting process technology, the cavity is not densely potted and there are bubbles, gaps or cavities, and the potting quality cannot be guaranteed.

[0006] like Figure 1As shown, there is no combined protection measure at present, the solder joints are in direct contact with the potting compound, and the gaps between the components and the PCB board are also filled with the original thermal conductive potting compound 01. When the product is working, high temperature is generated, which induces local mismatch of the expansion coefficients of various components, resulting in tensile and compressive stresses and shear stresses, thus causing solder joint failure. Summary of the invention

[0007] The present invention provides a combined protection and potting process method for a power module, which is used to solve the problems that the existing PCB board cannot meet the waterproof and corrosion resistance requirements in harsh environments, the power module has no solder joint protection measures, and the existing cavity potting is not solid and there are bubbles or gaps.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] A combined protection and potting process method for a power module, which is special in that it includes the following steps:

[0010] Step 1, thick coating is performed on the PCB board in the power module;

[0011] Step 2, perform combined protection on the power module;

[0012] Step 2.1: When installing the inductor on the power module, apply a layer of epoxy resin adhesive on the bottom of the inductor to bond the inductor to the PCB board.

[0013] Step 2.2, solder the inductor and capacitor to the PCB board, then clean the solder joints, and apply solder joint protection glue to the solder joints after cleaning, so that the solder joint protection glue covers the solder joints;

[0014] Step 2.3, fill the center hole of the inductor, the gap between the bottom of the inductor and the PCB board, and the gap between the bottom of the capacitor and the PCB board with silicone sealant;

[0015] Step 3: potting the combined and protected power module.

[0016] Furthermore, the step 1 is specifically as follows:

[0017] Step 1.1, PCB board cleaning;

[0018] Step 1.2, place the PCB board horizontally;

[0019] Step 1.3, apply a thick layer of coating to one side of the PCB board, squeeze the coating material onto the coating position of the PCB board, the coating thickness is 1 to 3 mm, and the coating is uniform;

[0020] Step 1.4, after the surface of the coating material is dry, turn the PCB board over and apply a thick layer of coating on the other side according to the method of step 1.3;

[0021] Step 1.5, curing the coated PCB board;

[0022] Step 1.6, repair and inspect the cured PCB board.

[0023] Furthermore, it is characterized in that the step 3 is specifically as follows:

[0024] Step 3.1, potting preparation

[0025] Prepare the potting tools and potting materials needed in the potting process;

[0026] Step 3.2, pre-mixing

[0027] Stir the A component and the B component of the potting material separately. After stirring, the glue has no precipitation, coagulation, or stratification, so that the purpose of stirring is achieved;

[0028] Step 3.3, preparation

[0029] According to the ratio parameters of thermal conductive potting glue, accurately weigh 1:1 potting materials of component A and component B;

[0030] Step 3.4, stirring

[0031] Mix the potting materials of component A and component B weighed in step 3.3 and stir them in the same direction for 3 to 5 minutes to obtain a thermally conductive potting glue;

[0032] Step 3.5, Potting

[0033] Slowly pour the thermally conductive potting glue stirred evenly in step 3.4 into the power module cavity;

[0034] Step 3.6, vacuum degassing

[0035] Set the parameters of the vacuum equipment according to the process requirements, and put the power module after primary potting into the vacuum equipment for degassing;

[0036] Step 3.7, Vibration

[0037] Place the degassed power module on a vibration table for vibration, so that the thermal conductive potting glue can fill the power module.

[0038] Step 3.8: Repeat steps 3.5 to 3.7 until the weight of the encapsulated power module meets the technical requirements, and then proceed to the next step;

[0039] Step 3.9, curing

[0040] Place the potted power module horizontally on the workbench and wait for it to solidify;

[0041] Step 3.10, Renovation Inspection

[0042] Use a cleaning tool to clean the edge glue drops and other excess materials on the cured power module, and check whether the potting result meets the requirements of technical and process-related parameters:

[0043] If not, return to step 3.2 and continue potting;

[0044] If it meets the requirements, the potting is completed.

[0045] Furthermore, in step 2.1, the epoxy resin adhesive specifically uses a two-component epoxy resin adhesive with an operating temperature range of -60°C to +150°C and a hardness of 85 Shore D.

[0046] Furthermore, in step 2.2, the solder joint protection glue specifically uses UV curing glue, which has a solid content of 100%, and the shear strength of the UV curing glue after curing is high.

[0047] Furthermore, in step 1.5, the conditions for curing the coated PCB board are as follows:

[0048] Place the coated PCB board in a clean, dry, well-ventilated environment with a temperature of 25℃±5℃ and a humidity of less than 75% for natural drying and curing for 24 hours.

[0049] Furthermore, in step 3.9, the curing conditions of the power module that has passed the potting are as follows:

[0050] The curing time is 24 hours when the room temperature is 20℃~35℃ and the humidity is greater than 40%.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] (1) The present invention uses coating technology, combined protection and potting technology to enable the PCB board in the power module to adapt to harsh environments, so that the power module can overcome the tensile and compressive stresses and shear stresses caused by the local mismatch of the expansion coefficients of various components induced by the high temperature generated during operation, thereby causing the solder joint failure problem

[0053] (2) The present invention provides a combined protection process technology for power modules. By using various adhesives to protect solder joints, inductors, capacitors and fill gaps, the present invention solves the problems of lack of protection measures for solder joints of power modules, incomplete sealing of module cavities, and the presence of bubbles or gaps, thereby greatly reducing the influence of stress generated by temperature during operation on solder joints.

[0054] (3) The thick layer coating on the PCB board in the present invention can effectively solve the waterproof problem of electronic components that is difficult to achieve with conventional three-proof paint and potting glue, and at the same time can play a good protective effect against harsh environments (such as salt spray, mold, damp heat, acidic atmosphere, etc.), so that the coated part is isolated from the external environment, so as to achieve the purpose of meeting the environmental adaptability of the product and extending the service life of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic diagram of the effect of the existing potting method;

[0056] The specific reference numerals are as follows:

[0057] 01-Original thermal conductive potting glue.

[0058] Figure 2 This is a schematic diagram of the protective effect of the combination of various adhesives of the present invention;

[0059] Figure 3 for Figure 2 A partial enlarged view of middle I;

[0060] Figure 4 This is a coating process flow chart of the present invention;

[0061] Figure 5 It is a flow chart of the encapsulation process in the present invention.

[0062] The specific reference numerals are as follows:

[0063] 1-Silicone sealant, 2-Thermal conductive potting glue, 3-Inductor, 4-Epoxy resin adhesive, 5-Solder point protection glue, 6-Solder point, 7-PCB board. DETAILED DESCRIPTION

[0064] To make the objects, advantages and features of the present invention more clear, specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited to the specific embodiments.

[0065] The present invention provides a combined protection and potting process method for a power module, such as Figure 2 and Figure 3 As shown, the details are as follows:

[0066] Step 1: Coat and protect the PCB board 7 in the power module. Figure 4 shown.

[0067] Step 1.1, PCB board 7 cleaning

[0068] The PCB board 7 is cleaned before the protective coating, and is cleaned manually or with a cleaning device to remove excess materials such as dust, oil, and flux residues to ensure surface cleanliness.

[0069] Step 1.2, PCB board 7 placement

[0070] Place the PCB board 7 horizontally without any undesirable phenomena such as bumping, overlapping and tilting.

[0071] Step 1.3, thick layer coating

[0072] The coating material is squeezed and coated to the coating position of the PCB board 7 by hand or by equipment, and the coating material is naturally leveled, with a coating thickness of 1 to 3 mm and uniform coating. When the surface of the coating material is dry, that is, when the surface of the coating material is not sticky when touched by hand, it is turned over and a thick layer of coating is applied to the other side.

[0073] Step 1.4, curing

[0074] Place the coated PCB board 7 in a clean, dry, well-ventilated room with a temperature of 25°C ± 5°C and a humidity of less than 75% for natural drying and curing for 24 hours or cure according to the time and temperature specified by the selected coating material.

[0075] Step 1.5, Repair and Inspection

[0076] Step 2, such as Figure 5 As shown, a variety of adhesives are used to combine and protect the power module.

[0077] Step 2.1, when installing the inductor 3 in the power module, apply a layer of epoxy resin adhesive 4 on the bottom of the inductor 3 to adhere the inductor 3 to the PCB board 7. The epoxy resin adhesive 4 specifically uses a two-component epoxy resin adhesive with an operating temperature range of -60°C to +150°C and a hardness of 85 Shore D.

[0078] Step 2.2, solder the inductor 3 and the capacitor to the PCB board 7, then clean the solder joints 6, and apply the solder joint protection glue 5 to the solder joints 6 after cleaning, so that the solder joints 6 are completely covered with the solder joint protection glue 5. The solder joint protection glue 5 specifically uses UV curing glue, which has a solid content of 100%, and the UV curing glue has high shear strength after curing.

[0079] Step 2.3: Fill the center hole of the inductor 3, the gap between the bottom of the inductor 3 and the PCB board 7, and the gap between the bottom of the capacitor and the PCB board 7 with a flame-retardant, non-corrosive silicone sealant 1.

[0080] Step 3: Potting the combined and protected power module

[0081] Step 3.1, potting preparation

[0082] Prepare the vacuum machine, mixer, potting machine, potting tooling and potting materials needed in the potting process.

[0083] Step 3.2, pre-mixing

[0084] The A / B components of the thermal conductive potting glue 2 are stirred separately with a stirrer or a stirring rod. After stirring, the glue liquid has no precipitation, coagulation, stratification, etc., and is stirred evenly.

[0085] Step 3.3, preparation

[0086] According to the ratio parameters of thermal conductive potting glue 2, accurately weigh 1:1 A / B component potting glue.

[0087] Step 3.4, stirring

[0088] After mixing the potting materials of component A and component B weighed in step 3.3, stir them in the same direction with a stirrer or a stirring rod for 3 to 5 minutes until the color is visually observed to be the same color after mixing and there is no color difference.

[0089] Step 3.5, primary potting

[0090] Use a glue potting device to slowly pour the thermal conductive potting glue 2 stirred evenly in step 3.4 into the power module cavity.

[0091] Step 3.6, vacuum degassing

[0092] Set the parameters of the vacuum equipment according to the requirements of the process documents, and then put the power module after primary potting into the vacuum equipment for degassing.

[0093] Step 3.7, Vibration

[0094] Place the degassed power module on a vibration table for vibration to make the potting glue full.

[0095] Step 3.8, secondary potting / secondary vacuum degassing / vibration

[0096] Repeat steps 3.5 to 3.7 until the weight of the encapsulated power module meets the product technical requirements, then proceed to the next step.

[0097] Step 3.9, curing

[0098] Place the potted qualified power module horizontally on a clean workbench and wait for it to cure. It should not be moved, tilted or vibrated during the curing process. The curing time is 24 hours at room temperature of 20℃~35℃ and humidity greater than 40%, or high temperature curing according to the technical requirements of thermal conductive potting glue 2.

[0099] Step 3.10, Renovation Inspection

[0100] Use tools to clean the edge glue drops and other excess materials on the cured power module, and check whether the potting results meet the requirements of the relevant parameters of the technical documents and process documents;

[0101] If not, return to step 3.2 and continue potting;

[0102] If it meets the requirements, the potting is completed.

[0103] After potting, the power module still meets the technical and process requirements after the following 11 tests.

[0104]

[0105]

[0106]

Claims

1. A combined protection and potting process method for a power module, characterized in that: The following steps are involved: Step 1, performing thick layer coating on the PCB board (7) in the power module; Performing a thick layer coating on one side of the PCB board (7), extruding the coating material onto the coating position of the PCB board (7), with a coating thickness of 1 to 3 mm and coating evenly; after the surface of the coating material is dry, turning the PCB board (7) over and performing a thick layer coating on the other side according to the above method; and curing the coated PCB board (7); Place the coated PCB board (7) in a clean, dry, well-ventilated environment with a temperature of 25°C ± 5°C and a humidity of less than 75% for natural drying and curing for 24 hours; Step 2, perform combined protection on the power module; Step 2.1, when installing the inductor (3) in the power module, apply a layer of epoxy resin adhesive (4) on the bottom of the inductor (3) so that the inductor (3) and the PCB board (7) are adhered together; Step 2.2, soldering the inductor (3) and the capacitor to the PCB board (7), then cleaning the solder joint (6), and applying solder joint protective glue (5) to the solder joint (6) after cleaning, so that the solder joint protective glue (5) covers the solder joint (6); Step 2.3, fill the center hole of the inductor (3), the gap between the bottom of the inductor (3) and the PCB board (7), and the gap between the bottom of the capacitor and the PCB board (7) with silicone sealant (1); Step 3: potting the combined and protected power module.

2. The combined protection and potting process method for a power module according to claim 1, characterized in that: The step 1 is specifically as follows: Step 1.1, cleaning of the PCB board (7); Step 1.2, place the PCB board (7) horizontally; Step 1.3, performing thick coating on one side of the PCB board (7), extruding the coating material onto the coating position of the PCB board (7), with a coating thickness of 1 to 3 mm and coating evenly; Step 1.4, after the surface of the coating material is dry, the PCB board (7) is turned over and a thick layer of coating is applied to the other side according to the method of step 1.3; Step 1.5, curing the coated PCB board (7); Step 1.6, repair and inspect the cured PCB board (7).

3. A combined protection and potting process method for a power module according to claim 1 or 2, characterized in that: The step 3 is as follows: Step 3.1, potting preparation Prepare the potting tools and potting materials needed in the potting process; Step 3.2, pre-mixing Stir the A component and the B component of the potting material separately. After stirring, the glue has no precipitation, coagulation, or stratification, so that the purpose of stirring is achieved; Step 3.3, preparation According to the mixing parameters of the thermal conductive potting glue (2), accurately weigh the potting materials of component A and component B in a ratio of 1:1; Step 3.4, stirring Mix the potting materials of component A and component B weighed in step 3.3 and stir them in the same direction for 3 to 5 minutes to obtain a thermally conductive potting glue (2); Step 3.5, Potting Slowly pour the thermally conductive potting glue (2) stirred evenly in step 3.4 into the power module cavity; Step 3.6, vacuum degassing Set the parameters of the vacuum equipment according to the process requirements, and put the power module after primary potting into the vacuum equipment for degassing; Step 3.7, Vibration The degassed power module is placed on a vibration table for vibration, so that the thermal conductive potting glue (2) fills the power module; Step 3.8: Repeat steps 3.5 to 3.7 until the weight of the encapsulated power module meets the technical requirements, and then proceed to the next step; Step 3.9, curing Place the potted power module horizontally on the workbench and wait for it to solidify; Step 3.10, Renovation Inspection Use a cleaning tool to clean the edge glue drops on the cured power module and check whether the potting result meets the requirements of technical and process-related parameters: If not, return to step 3.2 and continue potting; If it meets the requirements, the filling is completed.

4. The combined protection and potting process method for a power module according to claim 3, characterized in that: In step 2.1, the epoxy resin adhesive (4) is a two-component epoxy resin adhesive having an operating temperature range of -60°C to +150°C and a hardness of 85 Shore D.

5. The combined protection and potting process method for a power module according to claim 4, characterized in that: In step 2.2, the solder joint protection glue (5) specifically uses UV curing glue, which has a solid content of 100%, and the shear strength of the UV curing glue after curing is high.

6. The combined protection and potting process method for a power module according to claim 5, characterized in that: In step 3.9, the curing conditions of the power module that has passed the potting are as follows: The curing time is 24 hours when the room temperature is 20℃~35℃ and the humidity is greater than 40%.

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