SMTA International Conference Proceedings


EFFECT OF THE REFLOW PROFILE ON BGA VOIDING IN A LEAD-FREE PROCESS

Authors: Felix Bruno and Frank Grano et al.
Company: Sanmina-SCI Tech. Dvpmt. Ctr.
Date Published: 9/26/2004   Conference: SMTA International


Seika Machinery, Inc.

Abstract: The impact of voiding on BGA (Ball Grid Array) solder joint reliability has been a debatable topic for some time. It is believed that certain categories of voiding do not significantly affect the reliability of the solder joints and that voiding is preferred and acceptable to a certain extent. The reason for this is that voids are believed to change the direction of, or halt the propagation of cracks and thereby improve the reliability of the solder joint. However, excess voiding is considered to aggravate the solder joint failure.

The formation of voids can be attributed to different process parameters - surface contamination and moisture absorption in BGAs and Printed Circuit Boards (PCBs), solder paste & operating conditions and reflow profiles - to mention a few. Among these, the reflow profile is one of the very critical parameters in electronics manufacturing.

Several experiments have been conducted in the past to study the impact of reflow profile. In addition, the electronics manufacturing industry is gradually moving towards a lead-free environment. This has resulted in higher peak temperatures for the reflow profiles. However, with higher peak temperatures, the other reflow parameters also have to be varied. An optimum range for all the reflow parameters would reduce (or even eliminate) the formation of solder voids.

This paper investigates the impact of the reflow profile on the quality of the lead-free surface mount solder joint. In particular, the impact of the reflow profile on solder joint voiding for lead-free assemblies is analyzed. The critical reflow profile parameters that are responsible for voiding such as preheat temperature, ramp-up rate, and peak temperature were varied within the allowable process limits to verify if the voiding could be minimized. Ball Grid Arrays (BGAs) were assembled using varying reflow profiles. The analysis involved x-ray examination to observe the formation of solder voids.



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