模拟回流焊后PCB板产生F型裂纹机理浅析

Mechanism analysis of F crack in PCB after 10X reflow

回流后,高厚径比的PCB板易在孔口拐角处产生F型裂纹而失效。分析F型裂纹产生的主因:回流时PCB整板的应力超过孔口电镀铜的抗拉强度。文章将从减小整板应力、提高电镀铜的抗拉强度出发,通过对压合、钻孔、电镀等工艺方面进行分析,改善孔壁质量、提高镀层强度和减小材料Z-CTE三个方面,梳理出改善F型裂纹的方法。

After reflow,the PCB with high ratio of thickness to diameter is easy to fail,which produces F crack at the corner of the hole.Summary of the main cause of F crack is:the stress of PCB during reflow exceeded the tensile strength of electroplated copper at the hole.Starting from reducing the stress of the whole plate and improving the tensile strength of electroplated copper,this paper will test out the methods through analyzing the process of pressing,drilling,and electroplating to improve the F crack from three aspects,such as improving the quality of hole wall,enhancing the strength of the coating and decreasing the material of Z-CTE.