Compatibility of Conformal Coatings with No Clean Flux ResidueAuthors: Mitch Holtzer, Karen Telefsen, Westin Bent (presented by William Yu)
Company: Alpha, an Alent plc Company
Date Published: 4/22/2014 Conference: SMTA China
Conformal coating is often used in high reliability automotive applications where electronic circuits may be exposed to moisture or fluids used in cars or light trucks. Because of to the highly competitive nature of the automotive electronics industry, the cost of using a cleaning step prior to conformal coating is prohibitive. To remain competitive, no clean solder paste residue must be compatible with the conformal coating used, eliminating the need to clean the flux residue. Automotive electronics parts require validation prior to being placed into service. One of the key validation tests is known as the damp thermal cycle test (IEC 60068-2-30), see Figure 1. Variants of this test method are used by Toyota, G.M., Volkswagon, Audi, Mercedes and others.
This paper shows the surface insulation resistance of 4 no-clean lead free solder pastes targeted for the automotive market when used in conjunction with the 4 popular automotive conformal coatings identified by a leading manufacturer and the top 5 automotive conformal coatings produced by another manufacturer.
In addition, an application that can be used on a touch screen device has been developed to allow the sales and CTS to show the results of the 36 combinations of solder paste and conformal coatings used in this study.
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