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Abstract

The introduction of lead-free soldering is inevitable for the electronics industry and its use poses a number of challenges. Manufacturing processes need to be re-evaluated and any reliability issue needs to be addressed. In this study the effect of lead free solder on a reflow soldering process is investigated. Experimental design techniques were used to examine a reflow soldering process using the process parameters as experimental factors. The factors included the conveyor belt speed of the reflow oven and the preheat, soak and reflow temperatures of the temperature profile. Micro Ball Grid Array (EGA) packages were used as the test components. No standard method exists to assess the quality of EGA solder joints. Solder joint quality is normally assessed using lengthy reliability tests that measure joint strength. It is highly advantageous if a qualitative assessment method was available that could determine the joint quality. This study presents a scoring method that can be used to evaluate this solder joint quality quickly and inexpensively. EGA solder joint quality was assessed using x-ray and micro section inspection techniques. This qualitative data was scored and weighted. The weighted solder joint quality scores were statistically analysed to check for effect significance. It was found that conveyor belt speed had a statistically significant effect on the weighted score. The statistical approach was verified using residual analysis. The results of the experiment demonstrate that the scoring method is a practical way of assessing EGA solder joint quality. This paper presents a unique scoring method for assessing the joint quality of EGA packages.

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