Application of AOI light source modes in multi-chip modules inspection

Automated optical inspection (AOI) is a way of checking the assembly quality of printed circuit boards using machine vision techniques and becomes an indispensable part of the PCBA assembly process in recent years. Due to its consistent and repeatable nature, AOI is an effective process control tool. However, when AOI was applied on substrate, die or bond wire inspection in multi-chip modules, pseudo-defect or false call occurred commonly. In this paper, the influences of light source modes on probability of detection were studied and several using advices were proposed. The results showed that when using proper light source, best contrast of the detected image could be got and thus the missing defect rate of MCM could be reduced.