PCB埋嵌铜表面凹痕缺陷问题研究

Research on problems of embedded copper surface dent defects in PCB

埋嵌铜块印制电路板(PCB)制作过程中常有表面凹痕缺陷,给后续芯片焊盘的可焊性及贴片工艺带来隐患。针对这一问题,从埋铜槽孔预留尺寸、除流胶方式、板材选择、非曝光干膜尺寸4个维度开展研究。研究发现,埋铜槽孔直径预留0.075 mm能有效降低埋嵌铜表面凹痕缺陷;除流胶方式采用“不织布除胶2次+化学除胶1次”,能实现铜块位与板面无残留流胶;板材S1000-H较IT180A具有更好的流动性,缺陷率可降低一半以上;槽孔处非曝光干膜设计为比槽孔大0.076 mm能有效降低内层短路。选择合适的埋铜槽孔预留率、除流胶方式、板材、非曝光干膜尺寸,可有效降低PCB埋嵌铜表面凹痕缺陷。

Surface dent defects often occur during the manufacturing process of embedded copper block printed circuit boards(PCBs),which bring hidden dangers to the solderability of subsequent chip pads and the patch processes.To address this issue,we conduct research from four dimensions:pre-large size of buried copper slots,glue removal method,plate selection,and non-exposed dry film size.Preliminarily increasing the diameter of the embedded copper slot hole by 0.075 mm can effectively reduce the dent defects on the surface of the embedded copper.The glue removal method is set as"non-woven glue removal twice+chemical glue removal once",which can achieve no residual glue flow between the copper block and the board surface.Sheet S1000-H has better fluidity than IT180A,and the defect rate can be reduced by more than a half.The non-exposed dry film area at the slot is designed to be 0.076 mm larger than the slot,which can effectively reduce internal short circuits.Choosing the appropriate in-reserve size rate of buried copper slots,glue removal method,plate material,and non-exposed dry film size can effectively reduce dent defects on the surface of PCB embedded copper.