Lead-Free Process and Component Damage Assessment with Acoustic Micro Imaging (AMI)

摘要

With the environmental push towards lead-free solders there is the disadvantage of using higher temperatures for mounting the components to the boards. The smaller components, such as CSPs and TSOPs, are subjected to the largest temperature variations during the reflow process. The potential for these components to see a temperature as high as 255°C is real. Therefore it becomes necessary to evaluate the components for excessive physical damage on a pre and post reflow process basis. Through NEMI, a consortium of companies pulled together their resources to evaluate the lead-free solders, the reflow process requirements, solder joint reliability and component damage. One of the ways to assess the component damage is via a non-destructive technique called Acoustic M cro Imaging (AMI). AMI can be used to characterize any physical defects that may pre-exist in the components, such as a CSP, etc., due to manufacturing and allows you to compare the same sample after reflow. Example data v ill be provided from the analysis done of the parts for the NEMI program and of the types of defects to be concerned about during manufacturing, as well as the reflow process. Emphasis will be placed on the "critical" defects for CSP and TSOP packages as related to J-STD-020.