source:Industry News release time:2022-06-21 Article author:yu Popular:pcb
The warpage of the PCB long board/strip board has a great influence on the production of the printed circuit board, and warpage is also one of the important problems in the production process of the PCB long board/strip board. The long board is bent after welding, and the component feet are difficult to align. The PCB long board/strip board cannot be installed on the chassis or the socket in the machine, so the warpage of the circuit board will affect the normal operation of the entire subsequent process. At this stage, the printed circuit board has entered the era of surface mounting and chip mounting, and the requirements for the warpage of the circuit board are getting higher and higher. So we have to find the reason for the warping of the halfway gang.
1. Engineering design: Matters needing attention in the design of PCB long board/strip board: A. The arrangement of the prepreg between layers should be symmetrical, such as a six-layer circuit board, the thickness between 1-2 and 5-6 layers and the number of sheets of prepreg It should be consistent, otherwise it will warp easily after lamination. B. Multilayer circuit board core board and prepreg should use the same supplier's products. C. The area of the circuit pattern on the A side and the B side of the outer layer should be as close as possible. If the A side is a large copper surface, and the B side only has a few lines, this kind of printed circuit board is easy to warp after etching. If the line area on the two sides is too different, you can add some independent grids on the thin side for balance.
2. Baking the board before cutting: The purpose of baking the board before cutting the copper clad laminate (150 degrees Celsius, time 8±2 hours) is to remove the moisture in the board, and at the same time, the resin in the board is completely cured, and the remaining stress in the board is further eliminated. This is helpful in preventing board warping. At present, many double-sided and multi-layer boards still insist on the step of baking the board before or after cutting. However, there are some exceptions for board factories. At present, the time requirements for PCB long board/strip board baking are also inconsistent, ranging from 4 to 10 hours. Decide. Baking after cutting into a jigsaw or drying the whole piece of aniseed before unloading, both methods are feasible, it is recommended to bake the board after cutting. The inner board should also be baked.
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