SMTA International Conference Proceedings


INSPECTION OF LEAD-FREE SOLDER JOINTS ON PRINTED CIRCUIT ASSEMBLIES USING AUTOMATED INSPECTION TECHNIQUES

Authors: Andrew Pollock
Company: Celestica
Date Published: 9/26/2004   Conference: SMTA International


Abstract: As the WEEE/RoHS legislation deadline of July 1st, 2006 quickly approaches, it is becoming apparent that final lead-free solder joints are visually different from conventional tin-lead solder joints. Research and development observations over the past four years include problems such as: increased joint surface roughness; joint shrinkage and increased voiding on ball grid array (BGA) devices; reduced ball to ball clearances; exposed pad after reflow; pin through-hole (PTH) barrel hole fill; fillet lifting; and dull "grainy" looking solder joints. These challenges need to be addressed in newly drafted revisions of industry standards. To date, the industry has been using specifications such as IPC A-610 to help inspectors ensure quality solder joint formation after assembly.

This paper is intended to aid in the transition from tin-lead to lead-free solder with reference to automated inspection methods. Specifically, the paper discusses many of the general solder joint differences observed within lead-free assemblies and discusses how this will affect Automated Optical Inspection (AOI) and Automated X-ray Inspection (AXI) in terms of the capability to perform lead-free component and solder joint inspection. The paper further discusses the utilisation of a Lead-Free Qualification Matrix to gather data to ensure that lead free assemblies can be effectively and reliably inspected using current automated inspection techniques.

Key words: Lead free, test, automated inspection, AOI, AXI.



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