Failure Analysis on Blind Vias of PCB for Novel Mobile Phones

Abstract

Failure of blind via is one of the main causes of an open circuit in printed circuit boards (PCBs). By using macroscopic and microscopic testing methods and characterization techniques, the failure analysis of the vias on PCB for novel mobile phones has been systematically carried out. Metallographic inspection shows obvious cracking along the interface of different copper layers. Micrograph observation and chemical analysis on the grain boundary have definitely identified that inappropriate location of the vias concerned with circuit design and residue sulfur related to incomplete desmear process predominantly account for cracking of blind vias, and the occurrence of the cracking is caused by the formation of a brittle Cu x S layer. Moreover, the influence of warpage on the reliability of the via was noted. Based on these defaults, improvement countermeasures and suggestions are addressed in the paper and are of significant value for reference to the safe reliability and structural integrity of PCB products during manufacturing and services.