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28 SMT007 MAGAZINE I AUGUST 2018 Feature by Jason Fullerton ALPHA ASSEMBLY SOLUTIONS Abstract This study is an investigation and compari- son of the performance of no-clean liquid wave soldering fluxes using a commercially avail- able localized extraction and cleanliness test- ing system and surface insulation resistance (SIR) testing. The flux test coupons for both tests were prepared in accordance with IPC TM-650 The IPC B-24 coupons used were manufactured using a lead-free wave solder process. Coupons were then tested for SIR per J-STD-004B using IPC TM-650 and tested with localized cleanliness testing. The results for 15 no-clean fluxes are presented: three VOC-free rosin-free fluxes, two alcohol-based rosin-free fluxes, and 10 alcohol- based fluxes with rosin. The results with six of these fluxes were demonstrated in Part 1 of this study. [1] A divergence in test results is observed between the J-STD-004B SIR pass/fail require- ment of 100 MΩ minimum and the clean/dirty results provided by the cleanliness test system. The SIR resistance/time graphs and cleanli- ness tester current/time graphs are compared. The Corrosivity Index (CI) calculated based on the result of localized cleanliness testing is compared with final SIR values for the fluxes. Introduction Surface Insulation Resistance Tests There are various test methods available for assessing SIR properties of no-clean flux residues, including those published by IPC, Bellcore, and Japanese Industrial Standards organizations. All SIR tests are accelerated electrochemical reliability prediction tests for no-clean fluxes that incorporate manufac - turing conditions and service environment factors in the test methods. Although specific conditions can vary across the test methods, each test incorporates the following charac - teristics: 1. Test coupons utilizing comb patterns with defined comb width and spacing 2. Sufficient flux loading applied to each comb pattern

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