Test data requirements for assessment of alternative Pbfree solder alloys
Posted by Helen Holder, Gregory Henshall, Aileen Maloney et al on 10 December 2008 at 16:13
Since the implementation of EU RoHS in 2006, the electronics industry has seen a proliferation of Pb-free alloys for wave soldering, mini-pot rework, BGA and CSP solder balls and, more recently, solder pastes for mass reflow. New alloys may help reduce cost by lowering Ag content, enhance mechanical reliability and increase barrel fill, among other possible improvements. However, the risk of reduced thermal fatigue life, improper soldering with high melting point alloys, laminate damage due to high solder pot temperatures and other potential negative effects of using alternate solder alloys present challenges and possible field reliability risks for OEMs.
In order to take advantage of the opportunities afforded by these new alloys while mitigating risks, the authors have defined a set of tests that can be used for assessing new SnAgCu, SnAg and SnCu alloys for general use in electronics. The core assessment is based on reliability tests, manufacturability tests and material properties of the alloys. Detailed test definitions and reporting requirements have been established in order to enable data comparisons between different alloy assessments and to improve reproducibility.
The goal of this protocol is to standardize the test methods, test parameters, test vehicles and control samples so that the performance of each new alloy can be properly and fairly assessed relative to previously studied materials. These tests represent the minimum data required, and additional tests may be needed for special applications.
Package on package assembly features paste-only assembly or a combination of solder paste at board level and dip flux on the top row of ball terminations.