Abstract
By the trends of electronic package to be smaller, thinner and more integrative, organic printed circuit board is required to be finer Cu trace pitch. This paper reports on a study of failure mechanism for PCB with fine Cu trace pitch using biased HAST. In weibull analysis of the biased HAST lifetime, it is found that the acceleration factor (AF) of between 135 o C/90%RH/3.3V and 130 o C/85%RH/3.3V is 2.079. A focused ion beam (FIB) was used to polish the cross sections to reveal details of the microstructure of the failure mode. It is found that CuxO/Cu(OH)2 colloids and Cu dendrites were formed at anode (+) and at cathode (�), respectively. Thus, this gives the evidence that Cu dendrites formed at cathode by Cu 2+ ion migration lead to a short failure between a pair of Cu nets.
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