Adhesion of Epoxy Filleting Adhesive and Parylene Conformal Coating to Plasma Treated, Solder Mask Coated Substrates

Abstract

Peel adhesion of an epoxy filleting compound and Parylene C conformal coating to plasma treated, solder mask coated substrates and the apparent contact angle of water on the treated surfaces were evaluated. No significant improvement was achieved in the case of the epoxy filleting adhesive for most solder mask coatings studied. On the other hand, Parylene C peel adhesion significantly increased after substrates were treated with air plasma and reached the level of Silane coupling agent primed substrates. This was in contrast to the decrease in Parylene adhesion to argon plasma treated substrates in comparison with the non‐treated substrates. This was related to the oxygen functionalities created on the surfaces by the air plasma versus the ablative nature of the argon plasma. No clear correlation was found between peel strength and the water contact angle in the case of the epoxy adhesive, while for the Parylene conformal coating peel strength achieved its maximum value at the middle of the contact angle range which resulted from the pretreatments applied in this study. It is concluded that air plasma is a very efficient solder mask pretreatment for Parylene conformal coating that can replace Silane primer. Also, if a calibration curve is established for each solder mask‐adhesive and solder mask‐coating system, the apparent water contact angle can serve as a convenient quality control tool for printed circuit finishing processes.

Citation

Calahorra, A., Sali, S., Hamish, Z. and Dodiuk, H. (1989), "Adhesion of Epoxy Filleting Adhesive and Parylene Conformal Coating to Plasma Treated, Solder Mask Coated Substrates", Circuit World, Vol. 15 No. 3, pp. 18-21. https://doi.org/10.1108/eb043984