How to Avoid PCB Bending?
PCB bending is a big headache in the PCB manufacturing process. Suppose the board on auto assembly line is warp, it may cause inaccurate positioning or components fail to plug into the holes and mount onto the pad. To make matters worse, auto machine can be damaged by bending board. So to avoid PCB bending is very critical, EPCB outlines some points for your reference in this article.
a. Pay attention to the prepreg which should be balanced in the layers. For example, in an 8-layer board, the thickness and numbers of prepreg should be the same in 1~2L and 7~8L. Otherwise, the board bending is easily caused, and difficult to correct.
b. The core lamination and prepreg of multilayer boards you used are from the same supplier.
c. The PP latitude and longitude shrinkage is different after lamination, so it must keep the same direction of lamination. Otherwise, the board bending is easily caused, and difficult to correct.
d. Circuits pattern area should be close on top side and bottom side. If there’s a little different between top side and bottom side, it may cause warp after etching. If there’s big difference circuits area, add some independent grid to balance them is a good idea.
e. Baking laminate for about 8 hours at 150℃ to remove the excess water and solidify the resin is really helpful to avoid PCB bending. We suggest baking laminate after cutting not before production, and inner layer laminate also should be baked.
f. Use special pinch roll to straighten 0.4 or 0.6mm thin multilayer boards while doing electrical plating. That can effectively avoid the board bending.
g. The temperature of HAL is about 250℃. If the board isn’t cool down naturally before cleaning, or is cool down in a very short time, the board may cause warp, delamination, and blister.
Hope it is useful for you.