1, engineering design: printed board design should be noted:

　　A. The arrangement of interlayer semi-cured sheets should be symmetrical, such as six-layer plates, and the thickness between 1 ~ 2 and 5 ~ 6 layers and the number of semi-cured sheets should be consistent, otherwise it is easy to warp after lamination.

　　B. Multi-layer core board and semi-cured sheet should be made of the same supplier.

　　C. The line graphic area of the outer A side and B side should be as close as possible. If the A side is a large copper side, and the B side is only a few lines, the printed board is easy to warp after etching. If the line area difference between the two sides is too large, some independent grids can be added on the thin side to balance.

　　2. Drying plate before cutting:

　　The purpose of drying the copper clad plate before cutting the material (150 degrees Celsius, time 8±2 hours) is to remove the moisture in the plate, while the resin in the plate is completely cured, further eliminating the remaining stress in the plate, which is helpful to prevent the plate warping. At present, many double-sided, multi-layer boards still adhere to the step of drying the board before or after loading. However, there are some board factory exceptions, the current PCB factory drying board time provisions are also inconsistent, from 4-10 hours, it is recommended to decide according to the production of printed board grade and customer requirements for warpage degree. Cut into pieces after drying or whole aniseed after drying, the two methods are feasible, it is recommended to cut the material after drying board. The inner board should also be baked.

　　3. Warp and weft direction of semi-cured film:

　　The warp and weft shrinkage of the semi-cured sheet after laminating are different, and the warp and weft must be distinguished when cutting and laminating. Otherwise, it is easy to cause warping of the finished plate after lamination, and it is difficult to correct even if the pressure is added to the drying plate. Many of the reasons for the warping of multilayer plates are caused by the confusion of the warp and weft of the semi-cured sheet during lamination.