Microvia Non-Destructive Inspection Method

In this paper, the effectiveness of two non-destructive inspection techniques were investigated for quality assessment of microvias in high-density PWBs. Manufactured PWBs can fail during the reflow process due to microvia quality issues such as thin metallization in the barrel or shoulder of microvia or poor adhesion between the microvias and the metal layer underneath. The two investigated non-destructive inspection techniques are Transient Infra-red Thermography (IRT) and Time Domain Reflectometry (TDR). This study develops experimental methods to obtain thermal signatures of microvias using IRT technique and RF impedance signatures of microvias using TDR technique. Numerical analysis methods are also developed in this study to quantify and interpret the obtained microvia signatures to validate the functionality of selected non-destructive microvia inspection techniques.