Structure and process for applying aluminum substrate to BMS (battery management system)

Abstract

The invention relates to the technical field of battery management systems, in particular to a structure and process for applying an aluminum substrate to a BMS. An aluminum substrate is used as a base material of a BMS high-power circuit, the aluminum substrate comprises a circuit layer, an insulating layer and a metal base layer which are arranged in the vertical direction, and the metal base layer is an aluminum plate. Compared with the prior art, the problems that in the production process of the aluminum substrate, the plate is bent, the bubble proportion is large, and the requirements of over-reflow soldering for solder paste, tin thickness and furnace temperature are high are solved, so that the aluminum substrate can be better applied to a battery management system.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management systems, and more specifically to a structure and process of applying an aluminum substrate in a BMS. Background Art

[0002] A battery management system (BMS) is mainly used in fields such as electric vehicles and energy storage systems, and is responsible for monitoring the state of batteries, such as voltage, current, temperature, etc., and controlling the charging and discharging of batteries to ensure the safe and efficient operation of the batteries and extend the battery life. Among them, BMS boards can be divided into printed circuit boards (PCBs), aluminum substrates, steel substrates, and polymer composite boards.

[0003] For a printed circuit board (PCB), its advantages are low cost, suitable for mass production, high wiring density, capable of realizing complex circuit designs, mature processing technology, short production cycle, good electrical performance, excellent insulation performance and signal transmission performance; its disadvantages are poor heat conduction performance, prone to heat dissipation problems in high-power applications, relatively low mechanical strength, easily damaged by external forces, and relatively weak electromagnetic shielding performance.

[0004] For an aluminum substrate, its advantages are good heat conduction, capable of quickly dissipating heat, effectively reducing the working temperature of electronic components, and improving the stability and reliability of the system; high mechanical strength, capable of withstanding large external forces and vibrations; good electromagnetic shielding performance, which can reduce electromagnetic interference. Its disadvantages are relatively high cost; difficult processing, with high process requirements; relatively low wiring density, not suitable for complex circuit designs.

[0005] Since there are large-current application scenarios in BMS, the present invention designs a structure and process of applying an aluminum substrate in a BMS, using an aluminum substrate as the substrate and adding a welded copper bar as a connector to improve the over-current capacity of the BMS. Summary of the Invention

[0006] The present invention aims to overcome the deficiencies of the prior art and provides a structure and process of applying an aluminum substrate in a BMS.

[0007] To achieve the above object, a structure of applying an aluminum substrate in a BMS is designed. An aluminum substrate is selected as the base material for the high-power circuit of the BMS. The aluminum substrate includes a circuit layer, an insulating layer, and a metal base layer arranged in the up-down direction, and the metal base layer is made of an aluminum plate.

[0008] The models of the aluminum plates include but are not limited to 6061 aluminum plates, 5052 aluminum plates, 1060 aluminum plates, and 3003 aluminum plates.

[0009] The thickness of the aluminum substrate is one of 1.6 mm, 2.0 mm, and 3.0 mm.

[0010] A copper row is provided on one side of the aluminum substrate, and a groove is provided in the middle of the copper row.

[0011] A copper row is provided on one side of the aluminum substrate, and the length of the copper row is 1 / 10 - 1 of the length of the aluminum substrate.

[0012] The flatness of the copper row < 0.1 mm.

[0013] A copper row is provided on one side of the aluminum substrate, several air holes are provided on the surface of the copper row, and a solder mask area is provided in the copper row pad.

[0014] To achieve the above object, a process for applying an aluminum substrate in a BMS is designed, including the following steps: S1, Provide a metal base layer, wrap an insulating layer on the surface of the metal base layer, and then form a circuit layer to obtain an aluminum substrate; S2, Provide a copper row, add a solder mask area inside the copper row pad, and set several air holes on the surface of the copper row; S3, Weld the copper row on the surface of the aluminum substrate through a reflow soldering process; In step S2, it is also necessary to open a groove in the middle of the copper row and / or cut the copper row to a specified length.

[0015] In the said step S3, a low-temperature solder paste is selected, the solder thickness is adjusted, and the temperature of the reflow soldering furnace is adjusted to fully melt the solder. When adjusting the temperature of the reflow soldering furnace, it is also necessary to confirm whether each component conforms to the furnace temperature curve.

[0016] In the said step S3, it is also necessary to control the bubble ratio under the MOS and the copper row pad. The bubble ratio at the MOS is controlled below 5%, and the copper row pad is controlled below 30%.

[0017] Compared with the prior art, the present invention solves the problems of board bending, large bubble ratio, and high requirements for solder paste, solder thickness, and furnace temperature in the production process of aluminum substrates, enabling aluminum substrates to be better applied in battery management systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic structural diagram of the copper row groove in the first embodiment of the present invention.

[0019] Figure 2 It is a schematic packaging diagram of the copper row in the first embodiment of the present invention.

[0020] Figure 3 It is a schematic structural diagram of the copper row air hole in the first embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the furnace temperature curve in the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be further described below with reference to the accompanying drawings.

[0023] The present invention selects an aluminum substrate as the base material for the high-power circuit of the BMS, and the monitoring and control circuit still selects a printed circuit board (PCB) as the base material. The aluminum substrate of the present invention includes a circuit layer, an insulating layer, and a metal base layer arranged in the up-down direction, and the metal base layer is made of an aluminum plate.

[0024] The circuit layer uses an electrolytic copper foil, and a printed circuit is formed through etching for device assembly and connection. Compared with the traditional printed circuit PCB, an aluminum substrate with the same thickness and line width can carry a higher current. The insulating layer functions as bonding, insulation, and heat conduction, and its heat conduction performance directly affects the diffusion of heat during device operation. The metal base layer is made of an aluminum plate, such as one of 6061, 5052, 1060, and 3003, which has good heat conductivity, electrical insulation performance, and mechanical properties.

[0025] Among them, the metal base layer can be selected from 1-series aluminum such as 1060 according to the alloy composition. It is relatively soft, a silicon-copper alloy, with a low price and wide application. 3-series aluminum plates such as 3003 belong to manganese alloys and have rust prevention characteristics. 5-series aluminum plates such as 5052 are magnesium alloys, with high hardness and corrosion resistance.

[0026] The thickness of the aluminum substrate is 1.6 mm, 2.0 mm, or 3.0 mm. The thicker the aluminum substrate, the higher the furnace temperature required during reflow soldering. Among them, 1060 aluminum plates can be made into aluminum substrates with thicknesses of 1.6 mm and 2.0 mm, and 3003 aluminum plates and 5052 aluminum plates can be made into aluminum substrates with thicknesses of 2.0 mm and 3.0 mm.

[0027] During specific use, the process of applying the aluminum substrate in the BMS includes the following steps: S1, providing a metal base layer, wrapping an insulating layer on the surface of the metal base layer, and then forming a circuit layer to obtain an aluminum substrate; S2, providing a copper busbar 1, adding a solder mask area 4 inside the copper busbar pad, and arranging a plurality of air holes 3 on the surface of the copper busbar 1; S3, welding the copper busbar 1 on the surface of the aluminum substrate through a reflow soldering process.

[0028] In step S2, it is also necessary to open a groove 2 in the middle of the copper busbar 1 and / or cut the copper busbar 1 to 1 / 10 - 1 of the length of the aluminum substrate.

[0029] When there are components such as copper bars on the aluminum substrate, the aluminum substrate will bend during the cooling process after reflow soldering. The warpage of the board is generally controlled within seven-thousandths of the diagonal. The reason for this problem is due to the inconsistent specific heat capacities of aluminum and copper. Therefore, in the present invention, a concave groove 2 is opened in the middle of the copper bar or the length of the copper bar is reduced to reduce the contact area or length between copper and aluminum, so that the force on the aluminum during cooling is reduced, thereby controlling the deformation amount. And a reflow soldering fixture is made to press the copper bar on the aluminum substrate, and the flatness of the copper bar is required to be within 0.1 mm.

[0030] Since the aluminum substrate dissipates heat quickly, there is also a problem that the solder paste is not completely melted during the reflow soldering and chip mounting process in step S3. Therefore, in step S3 of this embodiment, low-temperature solder paste is used, the solder thickness is adjusted to 0.1 - 0.175 mm, and the reflow soldering furnace temperature is adjusted to fully melt the solder. When adjusting the reflow soldering furnace temperature, it is also necessary to confirm whether each component conforms to the furnace temperature curve, and it cannot be adjusted too high to cause component damage. The low melting point characteristic of the low-temperature solder paste ensures that the processing of the device is not damaged due to high temperature.

[0031] Moreover, attention should also be paid to the bubble ratio under the MOS and copper bar pads on the aluminum substrate. The bubble ratio of the MOS should be controlled below 5%, and that of the copper bar should be controlled below 30%. To ensure that the bubble ratio meets the requirements, it is also necessary to ensure that the stencil thickness meets the requirements and ensure whether the solder is fully melted. Additionally, the copper bar also needs to be designed for exhaust, such as Figure 2 、 Figure 3 as shown, a solder mask area 4 is added inside the copper bar pad and not soldered, and air holes 3 are opened on the copper bar, so that the air generated during the soldering process of the solder paste can be discharged through the solder mask area 4 and the air holes 3, thereby reducing the bubble ratio.

[0032] During specific use, the distance between the via hole and the copper clad on the aluminum substrate needs to meet the electrical regulation of 100V / 1mm. Example 1

[0033] This example uses an aluminum substrate made of 1 series aluminum, 1.6 mm thick, with single-layer wiring. The process of applying the aluminum substrate in the BMS includes the following steps: pasting barcodes → solder paste printing → solder thickness inspection → NXT component placement → placing the carrier → pre-placement by hand in front of the furnace → putting into the reflow furnace for reflow soldering → taking the carrier after the furnace → 3D AOI → X-RAY → ICT → dispensing → coating → coating inspection → backtesting → packaging. Figure 4 This is the reflow soldering temperature curve of the aluminum substrate in this example. It includes the temperatures corresponding to different times in the reflow soldering furnace. The temperature in the upper heating zone is 150 - 280 °C, the temperature in the lower heating zone is 0 - 280 °C, the board passing speed through the furnace is 90 cm / min, and the highest temperature of the components at different positions on the board is 254.1 °C.

[0034] The present invention uses an aluminum substrate as the substrate and soldered copper bars as the connectors to improve the overcurrent capacity of the BMS. During the application process, problems such as board bending, large proportion of bubbles, and high requirements for solder paste, solder thickness, and furnace temperature during reflow soldering are found. Therefore, the present invention solves the foregoing problems through the design of the copper bars and reflow soldering parameters, enabling the aluminum substrate to be better applied in the battery management system.

Claims

1. A structure in which an aluminum substrate is applied in a BMS, characterized in that: An aluminum substrate is selected as the substrate of the BMS high-power circuit. The aluminum substrate includes a circuit layer, an insulating layer, and a metal base layer arranged in an up-and-down direction, and the metal base layer is an aluminum plate.

2. The structure of an aluminum substrate used in a BMS according to claim 1, characterized in that: The types of aluminum plates include but are not limited to 6061 aluminum plates, 5052 aluminum plates, 1060 aluminum plates, and 3003 aluminum plates.

3. The structure of an aluminum substrate used in a BMS according to claim 1, characterized in that: The thickness of the aluminum substrate is one of 1.6 mm, 2.0 mm and 3.0 mm.

4. The structure of an aluminum substrate used in a BMS according to claim 1, characterized in that: A copper busbar (1) is provided on one side of the aluminum substrate, and a groove (2) is provided in the middle of the copper busbar (1).

5. The structure of an aluminum substrate used in a BMS according to claim 1, characterized in that: A copper bar (1) is provided on one side of the aluminum substrate, and the length of the copper bar (1) is 1 / 10-1 of the length of the aluminum substrate.

6. The structure of an aluminum substrate used in a BMS according to claim 1, characterized in that: The flatness of the copper busbar (1) is less than 0.1 mm.

7. The structure of an aluminum substrate used in a BMS according to claim 1, characterized in that: A copper busbar (1) is provided on one side of the aluminum substrate, a plurality of air holes (3) are provided on the surface of the copper busbar (1), and a solder resist area (4) is provided inside the copper busbar pad.

8. A process for applying the aluminum substrate according to claim 1 or 7 in a BMS, characterized in that: The steps include: S1, providing a metal base layer, wrapping an insulating layer on the surface of the metal base layer, and then forming a circuit layer to obtain an aluminum substrate; S2, providing a copper busbar (1), adding a solder resist area (4) inside a pad of the copper busbar, and providing a plurality of air holes (3) on a surface of the copper busbar (1); S3, soldering the copper busbar (1) to the surface of the aluminum substrate through a reflow soldering process; In step S2, it is also necessary to open a groove (2) in the middle of the copper busbar (1) and / or cut the copper busbar (1) to a specified length.

9. The process of using an aluminum substrate in a BMS according to claim 8, characterized in that: In the step S3, low-temperature solder paste is selected, the solder thickness is adjusted, and the reflow soldering furnace temperature is adjusted to fully melt the solder. When adjusting the reflow soldering furnace temperature, it is also necessary to confirm whether each component meets the furnace temperature curve.

10. The process of using an aluminum substrate in a BMS according to claim 8, characterized in that: In the step S3, the bubble proportion under the MOS and the copper busbar pad needs to be controlled. The bubble proportion at the MOS is controlled to be less than 5%, and the bubble proportion at the copper busbar pad is controlled to be less than 30%.

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