Investigation on PCB pad strength

Abstract

In this paper, a pin pull test is introduced as an effective way to assess the PCB pad strength. The pad strength is evaluated by different level of strain, pad type, PCB life phase and accumulation effect of various stations. Finite element analysis (FEA) is employed to analyze whether the PCB material affects the pad strength. It is found that PCB pad strength is sensitive to the rework process, product station and thermal cycling. Meanwhile, it is confirmed that the pad strength will degrade with the increasing strain loaded on PCB. A suitable and safe strain limit related to PCB pad strength should be established for each PCBA manufacturing process. The pad cracking issue may be also improved by selecting pad type or changing a suitable material of PCB. Optimal design should be considered to minimize the risk of pad crack in PCB production. To contain the PCB cratering issue, the pin pull test described in this work is shown effective and low cost and could be used in the production line for either process monitoring or incoming quality control.