Manufacturing process of inverter module heat dissipation substrate

Abstract

The application discloses a structure and manufacturing process of a heat dissipation substrate of an inverter module, and the structure comprises an upper end cover, a lower end cover and a water channel layer between the two, the lower end cover is provided with holes at both ends as a water inlet and a water outlet respectively, and double-layer graphene is formed on the upper surface of the lower end cover; the water channel layer is provided with a plurality of water channels arranged side by side along the long side of the heat dissipation substrate, one end of the water channel is located above the water inlet and communicates with the water inlet, and the other end of the water channel is located above the water outlet and communicates with the water outlet; double-layer graphene is formed on the lower surface of the upper end cover, and one or more welding areas are arranged on the upper surface of the upper end cover and used for mounting the inverter module. The heat dissipation substrate manufacturing process is based on the instantaneous liquid phase diffusion welding process, and copper foils covered with graphene are placed as intermediate layers between the lower end cover and the water channel layer and between the water channel layer and the upper end cover, so that the reliability and heat conduction characteristics of the heat dissipation substrate structure are further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat dissipation substrate manufacturing, and particularly relates to a manufacturing process of a heat dissipation substrate of an inverter module. BACKGROUND

[0002] With the rapid development and wide application of new energy technology, the market demand for inverter modules is increasing, especially the development of high-power inverter modules, which puts forward higher requirements for the thermal management structure. The mainstream thermal management structure is direct cooling, which directly connects the inverter module with the heat dissipation substrate, and the heat dissipation substrate is flat plate type, pin fin type, etc. The water cooling box is installed to take away the high heat generated by the inverter module during operation in the form of fluid heat transfer and dissipate to the surrounding environment.

[0003] At present, the processing technology of the heat dissipation substrate is mainly cold forging. Although the product of this process has good surface quality and high dimensional accuracy, with the change of the packaging structure of the inverter module, the cold forging process steps of the new product development and modification process of the heat dissipation substrate are relatively long, and the mold cost is relatively high. For the case of many product specifications, small batch production and urgent needs, it is urgent to find a production efficient and economical product process for selection. SUMMARY

[0004] The purpose of the present application is to provide a manufacturing process of a heat dissipation substrate of an inverter module to solve or partially solve the problems raised in the background.

[0005] To achieve the above-mentioned purpose, the present application provides a manufacturing process of a heat dissipation substrate of an inverter module, and the steps include:

[0006] Step 1: adopt a numerical control lathe to process a copper material standby of a lower end cover, a water channel layer and an upper end cover according to the size of the drawing, wherein long holes are processed at both ends of the lower end cover, and a plurality of hollow water channels along the long side direction of the heat dissipation substrate are processed in the water channel layer; in addition, a copper foil with the same shape as the upper end cover is processed, which is called a non-groove copper foil, and a copper foil with the same shape as the lower end cover and with a hole corresponding to the position of the long hole at both ends is processed, which is called a groove copper foil;

[0007] Step 2: grow double-layer graphene on one side of the non-groove copper foil and the groove copper foil respectively by chemical vapor deposition method to obtain non-groove graphene copper foil and groove graphene copper foil;

[0008] Step 3: stack the lower end cover, the groove graphene copper foil, the water channel layer, the non-groove graphene copper foil and the upper end cover in sequence, wherein the graphene of the groove graphene copper foil faces upward, and the graphene of the non-groove graphene copper foil faces downward; one end of the water channel corresponds to the position of the long hole at one end of the lower end cover, and the other end of the water channel corresponds to the position of the long hole at the other end of the lower end cover;

[0009] Step 4: Fix the above stack structure to the diffusion welding machine using a clamp, generate heat through current conduction, and diffuse the reaction between the layers under temperature and pressure to form a tight connection;

[0010] Step 5: After cooling, remove the heat dissipation base plate of the stack structure, process mounting holes according to the size of the inverter module, and make the welding area on the upper end cover surface.

[0011] The application also provides an inverter module heat dissipation base plate structure, which is rectangular in shape and includes an upper end cover, a lower end cover, and a water channel layer between the two. The lower end cover has holes at both ends serving as the water inlet and outlet, respectively. The upper surface of the lower end cover is provided with double-layer graphene. The water channel layer has multiple water channels arranged side by side along the long side of the heat dissipation base plate. One end of the water channel is located above the water inlet and communicates with the water inlet, and the other end is located above the water outlet and communicates with the water outlet. The lower surface of the upper end cover is provided with double-layer graphene, and the upper surface of the upper end cover is provided with one or more welding areas for mounting the inverter module.

[0012] Specifically, the water channel can be made in a corrugated shape.

[0013] Specifically, the base materials of the upper end cover, the lower end cover, and the water channel layer are all copper.

[0014] Specifically, the upper end cover and the lower end cover have the same thickness of 1±0.1 mm, and the water channel layer has a thickness of 3±0.1 mm. The width of the water channel is 2.4±0.05 mm, and the distance between adjacent water channels is 3±0.05 mm.

[0015] The upper surface of the upper end cover is provided with different numbers of welding areas according to the topological structure of the inverter module. One welding area corresponds to a half-bridge inverter module, two welding areas correspond to a full-bridge inverter module, and three welding areas correspond to a three-phase bridge inverter module.

[0016] Compared with the prior art, the application has the following advantages:

[0017] 1. The application uses numerical control technology to process the single-layer structure of the heat dissipation base plate, i.e., the lower end cover, the water channel layer, and the upper end cover, and then uses diffusion welding technology to form a tight connection between the multiple layers under appropriate temperature and pressure. This can realize the complex structure design and processing of the water channel layer, reduce the cost of the mold, and improve the production efficiency.

[0018] 2. The application uses double-layer graphene-coated copper foil as the intermediate layer for diffusion welding, which can prevent the lower surface of the upper end cover and the upper surface of the lower end cover from being corroded during the flow of the cooling liquid, thereby affecting the heat dissipation performance. On the other hand, the high lateral thermal conductivity of graphene can achieve uniform heating of the entire heat dissipation base plate. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A top view of the heat dissipation substrate of the inverter module according to the present application.

[0020] Figure 2 A bottom view of the lower end cover of the heat dissipation substrate according to the present application.

[0021] Figure 3 A schematic diagram of the water channel layer structure of the heat dissipation substrate according to the present application.

[0022] Figure 4 A schematic diagram of the external structure of the heat dissipation substrate of the three-phase bridge inverter module according to the embodiment of the present application.

[0023] Figure 5 A schematic diagram of the structure of the slotless graphene copper foil made in step 2 of the embodiment of the present application.

[0024] Figure 6 A schematic diagram of the structure of the slotted graphene copper foil made in step 2 of the embodiment of the present application. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and embodiments of the present application.

[0026] In the embodiment of the present application, the structure of the heat dissipation substrate of the inverter module is as shown in Figure 1 , which includes three main parts from bottom to top: a lower end cover 10, a water channel layer 11, and an upper end cover 12. The three main parts are all rectangular and have the same planar size, and are sequentially stacked with the same longitudinal axis as the center.

[0027] Among them, the lower end cover 10 has holes at both ends as the water inlet 21 and the water outlet 22, as shown in Figure 2 . The upper surface of the lower end cover 10 is made of double-layer graphene, and the lower surface of the upper end cover 12 is made of double-layer graphene.

[0028] The water channel layer 11 has a plurality of hollow water channels 31, which are arranged side by side along the long edge direction of the heat dissipation substrate. The water channels 31 in the embodiment are of a corrugated type, as shown in Figure 3 . The starting position of the water channel 31 corresponds to the position above the water inlet 21 of the lower end cover, and the ending position corresponds to the position above the water outlet 22 of the lower end cover. The water channel width is 2.4±0.05 mm, and the distance between adjacent water channels is 3±0.05 mm.

[0029] The upper surface of the upper end cover 12 is provided with a welding area along the long edge direction. According to the topological structure of the inverter module, different numbers of welding areas are arranged. For a half-bridge inverter module, one welding area is provided, Figure 4 and for a full-bridge inverter module, two welding areas are provided. For a three-phase bridge inverter module, for example, three welding areas are provided, corresponding to the U, V, and W phases of the inverter module.

[0030] The application also provides a manufacturing process of the heat dissipation substrate of the inverter module based on the above structure, which comprises the following steps:

[0031] Step 1: A CNC lathe is used to process copper materials for the lower end cover 10, the water channel layer 11 and the upper end cover 12 according to the size of the drawing.

[0032] Among them, long holes are processed at both ends of the lower end cover 10 as the water inlet 21 and the water outlet 22; and the corrugated water channel 31 along the long side direction is processed on the water channel layer 11. The above processing can be automatically completed by using a numerical control punch according to the preset program, only a simple mold combination is needed, and compared with the traditional stamping, a large amount of mold cost is saved, the cost is low, and the period is short.

[0033] In addition, a laser cutting machine is used to process copper foils with the same shape as the upper and lower end covers, among which the copper foil with the same shape as the upper end cover is called a grooveless copper foil, and the copper foil with the same shape as the lower end cover has a hole corresponding to the position of the long hole at both ends of the lower end cover, which is called a grooved copper foil.

[0034] The thickness of the lower end cover and the upper end cover is the same, about 1 mm, and the tolerance is ±0.1 mm; the thickness of the water channel layer is about 3 mm, and the tolerance is ±0.1 mm; the thickness of the copper foil as the intermediate layer is about 25 µm.

[0035] Step 2: Under high temperature and high pressure, the copper foil can catalyze the decomposition of carbon source gas such as methane and deposit on the surface of the copper foil to form a graphene layer. By using the grooveless copper foil 50 and the grooved copper foil 51 as substrates respectively through a chemical vapor deposition method, and by optimizing the growth conditions, controlling the methane gas flow and the growth time, a double-layer graphene 52 is made on the surface of the copper foil to obtain grooveless graphene copper foil and grooved graphene copper foil for standby, as shown in Figure 5 and Figure 6 .

[0036] Step 3: The lower end cover 10, the grooved copper foil 51, the water channel layer 11, the grooveless copper foil 50 and the upper end cover 12 which have been cleaned are stacked in sequence, among which the graphene of the grooved copper foil 51 faces upward, and the graphene of the grooveless copper foil 50 faces downward, so that the double-layer graphene is exposed on both sides of the water channel and directly contacts with the cooling liquid in the water channel when used in the future.

[0037] In the subsequent use of the heat dissipation substrate, the pH value of the cooling liquid will change with the slow evaporation and chemical reaction of the cooling liquid, which will cause the corrosion of the copper substrate and affect the heat dissipation effect. The double-layer graphene 52 has a doping mechanism different on each side. The outer layer of graphene is almost not doped and close to electrical neutrality, effectively inhibiting the occurrence of surface electrochemical reactions. The inner layer of graphene has more charge transfer and stronger interaction with copper, making it more difficult for corrosive molecules to diffuse at the interface, thereby protecting the lower surface of the upper end cover 12 and the upper surface of the lower end cover 10 from corrosion. On the other hand, due to the very high lateral heat conduction capacity of the double-layer graphene 52, the heat of the heat dissipation substrate can be more evenly distributed in the plane, reducing the temperature difference between the phases of the inverter module and improving the working reliability of the module.

[0038] Step 4: Use a clamp to fix the above stack structure to a diffusion welding machine. Heat the copper parts by conducting current to ensure uniform heating. During the heating process, the temperature of the copper stack structure heat dissipation substrate rises. The copper foil has a lower melting point than the copper upper end cover, lower end cover, and water channel layer, and is the first to melt, forming an instantaneous liquid film on the bonding surface. During the subsequent heat preservation process, diffusion reactions occur between the layers under temperature and pressure, and they penetrate each other to form a secure connection.

[0039] Step 5: After the connection area cools down, remove the clamps and other fixing devices, and take out the multi-layer stack structure heat dissipation substrate. According to the size of the inverter module, process a corresponding number of mounting holes, and on the surface of the upper end cover 12, make a corresponding number of welding areas 41 corresponding to the topology structure of the inverter module.

[0040] It will be obvious to a person skilled in the art that the application is not limited to the details of the above-described exemplary embodiments, but that the application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being defined by the appended claims rather than by the above description, and it is therefore intended that all changes and modifications that fall within the meaning and range of equivalency of the elements of the claims are encompassed by the application. No reference signs in the claims should be considered as limiting the claims involved.

Claims

1. A manufacturing process for an inverter module heat dissipation substrate, characterized in that: The following steps are involved: Step 1: Use a CNC lathe to process the copper materials of the lower end cover, water channel layer and upper end cover according to the dimensions of the drawing. Long holes are processed at both ends of the lower end cover, and multiple hollow water channels are processed in the water channel layer along the long side of the heat dissipation substrate. In addition, a copper foil with the same shape as the upper end cover is called a non-grooved copper foil, and a copper foil with the same shape as the lower end cover and holes corresponding to the long holes at both ends is called a grooved copper foil. Step 2: growing double-layer graphene on one side of the copper foil without grooves and one side of the copper foil with grooves by chemical vapor deposition to obtain a copper foil without grooves and a copper foil with grooves; Step 3: Stack the lower end cover with a cleaned surface, the grooved graphene copper foil, the water channel layer, the non-grooved graphene copper foil, and the upper end cover in sequence, with the graphene of the grooved graphene copper foil facing upward and the graphene of the non-grooved graphene copper foil facing downward; one end of the water channel corresponds to the position of the long hole at one end of the lower end cover, and the other end of the water channel corresponds to the position of the long hole at the other end of the lower end cover; Step 4: Use a fixture to fix the stacked structure to a diffusion welding machine. The current conducts heat, and a diffusion reaction occurs between the layers under temperature and pressure, forming a tight connection. A heat dissipation substrate having the following structure is obtained: the heat dissipation substrate comprises an upper end cover (12), a lower end cover (10) and a water channel layer (11) therebetween; holes are opened at both ends of the lower end cover (10) as a water inlet (21) and a water outlet (22), respectively; a double-layer graphene is fabricated on the upper surface of the lower end cover (10); the water channel layer (11) comprises a plurality of water channels (31) arranged side by side along the long side of the heat dissipation substrate; one end of the water channel (31) is located above the water inlet (21) and communicates with the water inlet (21); the other end of the water channel (31) is located above the water outlet (22) and communicates with the water outlet (22); a double-layer graphene is fabricated on the lower surface of the upper end cover (12); Step 5: After cooling, remove the heat dissipation substrate of the stacked structure, process the mounting holes according to the size of the inverter module, and make the welding area on the surface of the upper end cover.

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