PROCESS CAPABILITY, WETTING BEHAVIOR AND TEMPERATURE DEPENDENT SHEAR STRENGTH OF ALTERNATIVE LEAD FREE SOLDER JOINTSAuthors: Th. Herzog , S. Rudolph, and K.-J. Wolter
Company: Dresden University of Tech.
Date Published: 9/22/2002 Conference: SMTA International
The solutions therefore are the use of special reaction (composite) solder with two or more alloys in the paste. They have a compatible melting point but a higher creep strength and creep resistance after soldering . And as third there are investigations to find alternatives for lowcost applications like toys or consumer electronic, which will use alloys with a melting point below 150°C like Sn42Bi58.
At this background our work is dealing with different lead free solder pastes to evaluate their process capability and wetting behavior on different pad metallizations. The influence on the printing results of solder pastes at different force and speed parameters was observed. As an objective evaluation criterion we‘ve investigated the shear strength of lead free solder joints at different temperatures. Therefore passive components (R0805, R0603) were assembled on FR-4 PCBs with optimized reflow profiles assessed by wetting behavior. The measurement of wetting angle and monitored micro voids by x-ray can be used for the evaluation.
To compare the different solder alloys and the heating effects we’ve used the same homologue temperature during the shear tests for each solder. Fracture surface analysis and micro structural observations examine the fracture behavior of solder joints. The influence of different intermetallics for the fracture toughness by using different metal combinations was discussed.
Key words: lead free solder, wetting behavior, shear strength, composite solder.
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