Method for manufacturing vehicle-mounted circuit board

Abstract

The present invention discloses a method for manufacturing a vehicle-mounted circuit board, which comprises the following steps: a front process: manufacturing a core board; browning: roughening the copper surface of the core board; baking: placing the core board in a baking oven for baking; riveting / fusing: stacking the core board and the semi-cured sheet in a designed order, and preliminarily fixing them to form a circuit board blank; pre-arrangement: stacking a steel plate, kraft paper, a circuit board blank, kraft paper, and a steel plate in order to form a pressing unit; stacking: stacking a plurality of pressing units in a laminator; pressing: uniformly heating and pressurizing the stacked pressing units through the laminator to complete pressing; separating: separating the pressed circuit board blank from the pressing unit; forming: forming the circuit board blank; passing through an infrared reflow oven: sending the circuit board blank into an infrared reflow oven for heating; a back process: silk-screening characters and surface treatment on the circuit board blank, and then cutting out a plurality of circuit board product units.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a vehicle-mounted circuit board. Background Art

[0002] With the rapid development of the automotive industry, the demand for in-vehicle electronic products is also increasing, and with it comes higher requirements for electronic products. Since the working environment of in-vehicle electronic products is more complex and changeable than that of general electronic products, the quality standards of the circuit boards used in in-vehicle electronic products are also more stringent. For example, in-vehicle circuit boards require that the dense hole areas on the circuit board are not allowed to crack or delaminate even after five lead-free reflow soldering cycles.

[0003] The conventional PCB manufacturing process generally includes pre-processing, browning, riveting / fusion, pre-arrangement, lamination, pressing, depaneling, molding, and post-processing. Under the existing process, by adjusting and optimizing the process parameters, the occurrence of cracks and delamination in the PCB after five lead-free reflow soldering can be reduced to a certain extent. However, the conventional process has the following problems: 1. It is unable to effectively remove moisture from the core board of the PCB, which poses a risk of board explosion during the subsequent pressing process; 2. It is unable to effectively eliminate the stress inside the core board of the PCB before lamination, and the core board is prone to shrinkage during the lamination process, resulting in layer deviation; 3. When the PCB produced by the conventional process reaches the customer and is subjected to SMT mounting, the PCB will shrink as a whole due to heat, causing size changes and resulting in mounting defects. Therefore, since the conventional PCB manufacturing process cannot effectively solve these defects, the PCB produced using this process cannot well meet the quality requirements of automotive PCBs.

[0004] Therefore, how to overcome the above-mentioned defects has become an important issue to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The present invention overcomes the deficiencies of the above-mentioned technologies and provides a method for manufacturing a vehicle-mounted circuit board.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for manufacturing a vehicle-mounted circuit board comprises the following steps:

[0008] Pre-process: Prepare the core board 1 with circuit patterns;

[0009] Browning: Roughening the copper surface of the core board 1 to increase the bonding strength between the copper surface and the prepreg 2;

[0010] Baking the board: placing the browned core board 1 into an oven for baking;

[0011] Riveting / fusion: Several browned core boards 1 and prepregs 2 are alternately stacked together according to the circuit board design sequence, and then the core boards 1 and prepregs 2 are preliminarily fixed together by rivets to form a circuit board blank 3, or the core boards 1 and prepregs 2 are preliminarily fixed together by fusing them together under high temperature and pressure to form a circuit board blank 3;

[0012] Pre-layout: stack the PCB blank 3, steel plate 4, and kraft paper 5 in the order of steel plate 4, kraft paper 5, PCB blank 3, kraft paper 5, and steel plate 4 to form a pressing unit;

[0013] Lamination: stacking several lamination units in a laminator;

[0014] Lamination: The laminating machine heats and presses the stacked lamination units uniformly to complete the lamination;

[0015] Separating the boards: taking out the pressing unit from the laminator and separating the circuit board blank 3, the steel plate 4, and the kraft paper 5, thereby obtaining the pressed circuit board blank 3;

[0016] Molding: Molding the pressed circuit board blank 3;

[0017] Passing through an infrared reflow oven: sending the formed circuit board blank 3 into an infrared reflow oven for heating, so that the circuit board blank 3 shrinks due to the heat;

[0018] Post-process: Screen printing characters and surface treatment are performed on the circuit board blank 3 that has passed the infrared reflow oven, and then multiple circuit board product units are cut out.

[0019] Preferably, the prepreg 2 used in the riveting / fusing step is a prepreg 2 having the same resin composition as that used in the previous process of making the core board 1 .

[0020] Preferably, in the board baking step, the core board is baked in an oven at a temperature of A+10° C. for 130 minutes, where A is the glass transition temperature of the prepreg 2 .

[0021] Preferably, a 0.3 mm thick aluminum sheet 6 is placed between the kraft paper 5 and the circuit board blank 3 during pre-layout, and the aluminum sheet 6 also needs to be separated from the circuit board blank 3 during depaneling.

[0022] Preferably, the pressing step needs to be performed at a pressure of 420 psi and a temperature of 215°C.

[0023] Preferably, during the forming step, the aperture is compensated for in size, wherein the aperture of the hole designed to be 0.25 mm remains unchanged, the aperture of the hole designed to be 0.3 mm is changed to 0.275 mm, and the aperture of the hole designed to be 0.35 mm is changed to 0.3 mm.

[0024] Preferably, the jump drilling method is used during the drilling in the forming step, and the front and rear holes of the jump drilling are respectively located in two pcs and the distance between the two holes is greater than 5000 mil.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The automotive circuit board manufacturing method in this case adds a baking step between browning and riveting / fusion to the conventional circuit board manufacturing process. Baking the core board can remove moisture from the core board to prevent the board from bursting during the pressing process. It can also eliminate stress within the core board to prevent the core board from shrinking during the pressing process, which increases the risk of layer deviation. In addition, this case's manufacturing method also adds an infrared reflow oven step between the forming and post-processing process. By sending the formed circuit board product into the infrared reflow oven for heating, the environment of the customer's SMT patch is simulated, causing the entire circuit board product to heat and shrink in advance, avoiding the circuit board product heating and shrinking when the customer performs SMT patching, resulting in dimensional changes and patch defects. In this way, by adding the two steps of baking and passing through the infrared reflow oven to the conventional manufacturing process, this case's manufacturing method can greatly reduce the defects of cracks or delamination in the circuit board after five lead-free reflows. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the pressing unit in this case. DETAILED DESCRIPTION

[0028] The following examples further illustrate the features of the present invention and other related features to facilitate understanding by those skilled in the art:

[0029] A method for manufacturing a vehicle-mounted circuit board comprises the following steps:

[0030] Pre-process: Prepare the core board 1 with circuit patterns;

[0031] Browning: Roughening the copper surface of the core board 1 to increase the bonding strength between the copper surface and the prepreg 2;

[0032] Baking the board: placing the browned core board 1 into an oven for baking;

[0033] Riveting / fusion: Several browned core boards 1 and prepregs 2 are alternately stacked together according to the circuit board design sequence, and then the core boards 1 and prepregs 2 are preliminarily fixed together by rivets to form a circuit board blank 3, or the core boards 1 and prepregs 2 are preliminarily fixed together by fusing them together under high temperature and pressure to form a circuit board blank 3;

[0034] Pre-layout: stack the PCB blank 3, steel plate 4, and kraft paper 5 in the order of steel plate 4, kraft paper 5, PCB blank 3, kraft paper 5, and steel plate 4 to form a pressing unit;

[0035] Lamination: stacking several lamination units in a laminator;

[0036] Lamination: The laminating machine heats and presses the stacked lamination units uniformly to complete the lamination;

[0037] Separating the boards: taking out the pressing unit from the laminator and separating the circuit board blank 3, the steel plate 4, and the kraft paper 5, thereby obtaining the pressed circuit board blank 3;

[0038] Molding: Molding the pressed circuit board blank 3;

[0039] Passing through an infrared reflow oven: sending the formed circuit board blank 3 into an infrared reflow oven for heating, so that the circuit board blank 3 shrinks due to the heat;

[0040] Post-process: Screen printing characters and surface treatment are performed on the circuit board blank 3 that has passed the infrared reflow oven, and then multiple circuit board product units are cut out.

[0041] As mentioned above, the manufacturing method of the automotive circuit board in this case adds a baking step between browning and riveting / fusion on the basis of the conventional circuit board manufacturing process. By baking the core board 1, the moisture in the core board 1 can be removed to avoid the board from bursting during the pressing process. At the same time, the stress inside the core board 1 can be eliminated to avoid the core board 1 shrinking during the pressing process, which increases the risk of layer deviation. In addition, the manufacturing method in this case also adds a step of passing through an infrared reflow oven between the forming and post-processing. By sending the formed circuit board product into the infrared reflow oven for heating, the environment of the customer's SMT patch is simulated, so that the entire circuit board product is heated and shrunk in advance, avoiding the circuit board product being heated and shrunk when the customer performs SMT patch, resulting in dimensional changes and patch defects. In this way, by adding the two steps of baking and passing through an infrared reflow oven to the conventional manufacturing process, the defects of cracks or delamination of the circuit board after five lead-free reflows can be greatly reduced.

[0042] Preferably, the prepreg 2 used in the riveting / fusion step is a prepreg 2 having the same resin composition as that used in the previous process of making the core board 1, so that the fusion degree between the board and the prepreg 2 can be improved during the pressing process.

[0043] Preferably, in the baking step, the core board is baked in an oven at a temperature of A+10°C for 130 minutes, where A is the glass transition temperature of the semi-cured sheet 2. In this way, it can be ensured that the water vapor and stress kinetic energy in the core board 1 are fully eliminated.

[0044] like Figure 1 As shown, preferably, a 0.3 mm thick aluminum sheet 6 is placed between the kraft paper 5 and the circuit board blank 3 during pre-arrangement, and the aluminum sheet 6 needs to be separated from the circuit board blank 3 during separation. In this way, the thermal conductivity between the steel plate 4 and the circuit board blank 3 can be improved, and the heat distribution can be more even, thereby improving the heating rate so that the semi-cured sheet 2 has sufficient curing time.

[0045] Preferably, the pressing step needs to be performed at a pressure of 420 psi and a temperature of 215° C., so as to ensure that the layers of the circuit board blank 3 can be fully fixed together.

[0046] Preferably, during the forming step, the aperture is compensated for in size, wherein the aperture of the hole designed to be 0.25 mm remains unchanged, the aperture of the hole designed to be 0.3 mm is changed to 0.275 mm, and the aperture of the hole designed to be 0.35 mm is changed to 0.3 mm.

[0047] As mentioned above, in the conventional forming step, the hole diameter is increased to compensate for reducing the roughness of the hole wall during drilling. However, increasing the hole diameter will reduce the distance between holes, thereby increasing the risk of cracks. The manufacturing method in this case is to reduce the hole diameter while optimizing the feed speed, thereby reducing the roughness of the hole wall while increasing the distance between holes, thereby further reducing the probability of cracks.

[0048] Preferably, the jump drilling method is used during the drilling in the forming step, and the front and rear holes of the jump drilling are respectively located in two pcs and the distance between the two holes is greater than 5000 mil.

[0049] As mentioned above, compared with the conventional molding step in which the distance between the front and rear holes is only controlled at 200 mils during drilling, the production method in this case adopts the form of jumping drilling within two pcs, and at the same time controls the distance between the front and rear drilling positions to be greater than 5000 mils. In this way, it can avoid the drill needle frequently hitting the same area on the circuit board product in a short period of time, thereby reducing the probability of cracks and delamination defects on the circuit board product.

[0050] As mentioned above, this case protects a method for manufacturing an automotive circuit board, and all technical solutions that are identical or similar to this case should be deemed to fall within the scope of protection of this case.

Claims

1. A method for manufacturing a vehicle-mounted circuit board, characterized in that The following steps are involved: Pre-process: making a core board with circuit patterns (1); Browning: roughening the copper surface of the core board (1) to increase the bonding strength between the copper surface and the prepreg (2); Baking the board: placing the browned core board (1) into an oven for baking; Riveting / fusing: a plurality of core boards (1) and prepregs (2) that have been subjected to browning treatment are alternately stacked together according to the design sequence of the circuit board, and then the core boards (1) and the prepregs (2) are preliminarily fixed together by rivets to form a circuit board blank (3), or the core boards (1) and the prepregs (2) are preliminarily fixed together by fusing them together under high temperature and pressure to form a circuit board blank (3); Pre-layout: stacking the circuit board blank (3), the steel plate (4), and the kraft paper (5) in the order of steel plate (4), kraft paper (5), circuit board blank (3), kraft paper (5), and steel plate (4) to form a pressing unit; Lamination: stacking several lamination units in a laminator; Lamination: The laminating machine heats and presses the stacked lamination units uniformly to complete the lamination; Separating the boards: taking out the pressing unit in the laminator and separating the circuit board blank (3), the steel plate (4), and the kraft paper (5), thereby obtaining a pressed circuit board blank (3); Forming: forming the pressed circuit board blank (3); Passing through an infrared reflow oven: sending the formed circuit board blank (3) into the infrared reflow oven for heating, so that the circuit board blank (3) shrinks due to the heat; Post-process: silk screen printing characters and surface treatment are performed on the circuit board blank (3) that has passed the infrared reflow oven, and then a plurality of circuit board product units are cut out.

2. The method for manufacturing a vehicle-mounted circuit board according to claim 1, characterized in that The prepreg (2) used in the riveting / fusion step is a prepreg (2) having the same resin formula as that used in the previous process of making the core board (1).

3. The method for manufacturing a vehicle-mounted circuit board according to claim 1, characterized in that In the board baking step, the core board (1) is baked in an oven at a temperature of A+10° C. for 30 minutes, wherein A is the glass transition temperature of the prepreg (2).

4. The method for manufacturing a vehicle-mounted circuit board according to claim 1, characterized in that During pre-layout, a 0.3 mm thick aluminum sheet (6) is placed between the kraft paper (5) and the circuit board blank (3), and the aluminum sheet (6) also needs to be separated from the circuit board blank (3) during panel separation.

5. The method for manufacturing a vehicle-mounted circuit board according to claim 1, characterized in that The pressing step requires pressing at a pressure of 420 psi and a temperature of 215°C.

6. The method for manufacturing a vehicle-mounted circuit board according to claim 1, characterized in that During the forming step, the aperture is compensated for in size, wherein the aperture of the hole designed to be 0.25 mm remains unchanged, the aperture of the hole designed to be 0.3 mm is changed to 0.275 mm, and the aperture of the hole designed to be 0.35 mm is changed to 0.3 mm.

7. The method for manufacturing a vehicle-mounted circuit board according to claim 1, wherein the molding The jump drilling method is used for drilling. The front and rear holes of the jump drilling are located in two pcs respectively and the distance between the two holes is greater than 5000mil.

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