Awards for Excellence

Citation

(2006), "Awards for Excellence", Soldering & Surface Mount Technology, Vol. 18 No. 4. https://doi.org/10.1108/ssmt.2006.21918daa.001

Awards for Excellence

Awards for Excellence

Outstanding Paper Award Soldering & Surface Mount Technology

“Microstructural investigation of lead-free BGAs soldered with tin-lead solder”

Günter Grossmann, Joy Tharian, Pascal Jud and Urs SennhauserSwiss Federal Laboratories for Material Testing and Research (EMPA), Dübendorf, Switzerland

Purpose – The goal of this work is to evaluate the feasibility of soldering tin-silver-copper balled BGAs using tin-lead-based solder and to investigate the influence of different production parameters on the microstructure of the solder joint.Design/methodology/approach – The soldering of the BGAs was done with various temperature profiles and two conveyor speeds under a nitrogen atmosphere in a full convection oven. One specimen from each temperature/time combination was cross-sectioned. The cross sections were analysed with optical microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS) at 30kV and focused ion beam microscopy (FIB).Findings – The cross sections show a metallurgical bond between the solder and the tin-silver-copper balls of the BGA, even at a peak reflow temperature of 210ºC. However, the balls alloy only partially with the solder, as the liquidus of tin-silver-copper balls is 217ºC. As soon as the peak temperature exceeds the liquidus of the ball, the solder is totally dissolved in the material of the ball. A reflow profile with a peak temperature of about 230ºC on the BGA gives a homogenous reaction of the solder with the ball with a minimum formation of voids.Research limitations/implications – The dependence of varying reflow parameters on reliability requires detailed study. Especially the effect of a partially melted ball on the degradation of the solder joint needs to be investigated.Originality/value – From the findings, it can be said that soldering lead-free balls with tin-lead solder is possible. This is useful during the transitional period that the industry is in at the moment. More and more component manufacturers are changing their components to lead-free, often without notice to the customer. If a production line is still running a tin-lead process it is essential to know how to process these components with tin-lead solder.

Keywords: Lead, Metals, Solder, Soldering

www.emeraldinsight.com/10.1108/09540910510597465

This article originally appeared in Volume 17 Number 2, 2005, pp. 10-21, of Soldering & Surface Mount Technology, Editor: David C. Whalley

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