When designing flexible circuit boards, have you encountered troubles in choosing solder masks and overlays? The solder mask and the cover layer have the same basic insulation function. Do you know the difference between the solder mask and the cover layer? Can the solder mask and the cover layer be overlapped for insulation? Do you think that the flexible solder mask is the same as the rigid printed circuit solder mask?
Design: In fact, coverlay is widely used in flexible circuit boards. Because most FPCs need to add PI/FR4 reinforcement and EMI shielding layer. However, if there are BGA pads and a dense solder mask opening area, it will limit the minimum size of the opening and the smallest material net, which can then be kept between adjacent openings. I want to share with you the cover layer and solder mask that the FPCB covers together. Cover the cover layer first, and then slightly overlap the solder mask to cover the cover layer to prevent any gaps in the combined layer. This design has higher requirements for our production to ensure your function and reliable design.
Thickness: Why choose to use green solder resist instead of covering layer? The normal cover layer thickness is 27.5/50um. The thickness of the solder mask is 8/12um. Because customers need ultra-thin flexible PCB. Then, we recommend that customers use solder mask instead of overlay.
Color: The most popular cover film color is yellow, we usually prepare yellow, white and black cover films in stock. Solder masks are available in green, black, white, yellow and other colors. Please note that FPC solder mask is completely different from PCB. The cost of FPC solder mask is much higher than that of PCB, because the bending resistance and high temperature resistance of flexible circuit board solder mask are better than PCB.