Development of a standard test method for evaluating conductive anodic filament (CAF) growth failure in PCBs

Increasing board densities, decreasing spacing between holes and features and the growing requirement for printed circuit boards to perform in high temperature/high humidity environments have led to renewed concerns about possible reliability problems caused by the growth of Conductive Anodic Filaments (CAF). To date, there has been a lack of information on standardized test procedures and failure analysis methods for various types of prepregs and laminates.This paper introduces a standard test vehicle design and discusses suitable testing, failure analysis and board manufacturing methods. It also includes the requirements for CAF resistance and there is a discussion of material benchmarking tests with some preliminary results from this testing. These methods should be applicable to boards used in all market segments, including high density interconnect, and automotive applications.