SIR Measurements During Modified Automotive Damp Heat Cycling: Solder Paste and Conformal Coating CompatibilityAuthors: Karen Tellefsen and Mitch Holtzer, Prof. Dr.-Ing. Marcus Reichenberger
Company: Alpha and Technische Hochschule Nürnberg Georg Simon Ohm
Date Published: 5/13/2014 Conference: ICSR (Soldering and Reliability)
In this study, Surface Insulation Resistance (SIR) coupons were reflowed with four lead-free solder pastes, and then coated with one of five conformal coatings from one manufacturer and four coatings from a second. These coatings included silicone, acrylic and urethane chemistries. These coupons were exposed to a modification of Automotive Damp Heat Cycling Test  with an applied bias of 50V and frequent SIR measurements at bias. After exposure, the coupons were examined for evidence of electrochemical migration, such as metallic dendrite formation. A water-based urethane coating was found to protect poorly in combination with all four solder pastes, while an acrylic coating from the same manufacturer provided good protection in combination with these same solder pastes. Other coatings worked well with some solder pastes, usually less activated ones, but not others.
Solder Paste, flux residue, conformal coating, SIR
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