SMTA International Conference Proceedings


DOES PCB PAD FINISH AFFECT VOIDING LEVELS IN LEAD-FREE ASSEMBLIES?

Authors: David Bernard and Keith Bryant
Company: Dage Precision Industries
Date Published: 9/26/2004   Conference: SMTA International


Abstract: With European environmental legislation and market forces driving the change to lead-free solders for printed circuit board assembly, there will be significant changes in the soldering process. Voiding is one of the known major consequences of these process changes exaggerated by the use of new soldering materials. Excessive voiding can lead to poor quality joints, BGA "popcorning", open circuit failures during burn-in or thermal cycling, even field failures can be the result. Therefore voiding needs to be minimised to retain process quality and to reduce rejects and returns in the change to lead-free production.

This paper will evaluate reasons for the increase in voiding, explore the different PCB pad finishes in use for lead-free and the amount of voiding produced by a controlled soldering process using these surface finishes. With the use of advanced technology including automated digital x-ray measurements, the total amount of voiding, void size and location will be measured and compared.

The summary will contrast the findings of these tests and measurements; conclusions could then be drawn on the preferred PCB pad finishes for lead-free assembly. Those seeking to improve printed circuit assembly process control and reduce failures can use the methodology in this paper to keep voiding within acceptable levels.

Key words: Lead-free, voiding, pad finish, x-ray inspection



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