SMTA International Conference Proceedings

Latest Developments in Surface Finishing of PCBs Using Plasma Deposition

Authors: Tim von Werne, Ph.D., Andy Brooks, and Siobhan Woollard
Company: Semblant Ltd.
Date Published: 10/24/2010   Conference: SMTA International

Abstract: The use of plasma deposition represents a new approach to final surface finishing for the PCB industry, offering significant benefits as a replacement to plated metal finishes. The plasma finish consists of an ultra-thin fluoropolymer coating which is applied using a dry plasma deposition process in a low power plasma chamber. This coating provides unique chemical protection and substantial corrosion resistance to the board both before and after the soldering operation, while greatly simplifying the manufacturing process and reducing hazardous waste.

A substantial test programme has been undertaken investigating a wide range of performance characteristics of this plasma finish. The high frequency RF performance of this surface finish will be presented and contrasted to existing metal finishes. The unique fluoropolymer coating has been specifically developed to enable consistent and reliable Pb-free soldering. The results of solderability testing will be presented with cross sectional analysis and intermetallic layer composition of the resulting solder joints highlighted. Joint strength and reliability data for assembled boards will be discussed and compared to alternative surface finishes.

Key Words: 

surface finish, PCB coating, fluoropolymer, corrosion protection

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