SMTA International Conference Proceedings

Investigation Of The Root-Cause Of Solder Bubbles In A Via

Authors: Wang Yang and Luo Daojun
Company: Reliability Research and Analysis Center, China CEPREI Laboratory
Date Published: 10/13/2013   Conference: SMTA International

Seika Machinery, Inc.

Abstract: A failed printed circuit board assembly (PCBA) sample with solder bubble problem and a bare printed circuit board (PCB) sample were analyzed with the aid of a stereomicroscope. Cross-sectioned samples were also examined at higher magnification using a scanning electron microscope (SEM). Further, thermal stress test and solderability test were performed on the two samples. The root-cause of solder bubbles in vias in the failed PCBA sample was correlated to residual moisture or flux permeating inside the defects in barrel plating and dielectric material surrounding the viahole, venting and blasting out during high-temperature soldering. The defects around the vias could be induced by improper via drilling process. Thus to achieve acceptable via drilling quality and avoid the solder bubbles problem, drilling materials, drill thrust, quality of surface of vias and proper drilling equipment should be well selected and controlled.

Key Words: 

Solder bubbles, via, failure, cross section, SEM, PCBA.

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