Conductive anodic filaments formation

Ready, W. I, and Turbini, L. I, The Effect of Flux Chemistry, Applied Voltage, Conductor Spacing, and Temperature on Conductive Anodic Filament Formation, Journal of Electronic Materiab, Vol. 31, No. 11,2002, pp. 1208-1224. 

W.J. Ready, L.J. Turbini, R. Nickel, and J. Fischer, A Novel Test Circuit for Detecting Conductive Anodic Filament Formation, J. Electron. Mater, Nov 1999, p 1158-1163... 

The ability of a material to resist water absorption, either from the air or when immersed in water, is important for printed circuit rehabUity. Besides the obvious concerns of moisture causing defects when a material is subjected to thermal excursions, absorbed moisture also affects the ability of a material to resist conductive anodic filament (CAF) formation when a... 

Conductive anodic filament (CAF) formation is a term used to describe an electrochemical reaction in which conductive paths are formed within a dielectric material due to transport of metal or metal salts through the dielectric. These paths may form between two circuit traces, between two vias, or between a trace and a via, as illustrated in Fig. 9.12. CAF formation between a hole and a plane inside the PCB is also possible, and is similar in concept to hole-to-trace CAF formation. By definition, as circuit density increases, the space between these features decreases. With shorter paths between features, CAF growth becomes a more critical reliability consideration. 

Conductive anodic filament (CAF) As the base material system degrades, the resistance to CAF formation decreases. 

D. J. Lando et al. first used the term conductive anodic filament (CAF) to describe this faUtrre in 1979. They defined the mechanism of CAF formation as a two-step process degradation of the epoxy/glass interface, followed by the electrochemical reaction (see Eq. 56.2). 

Lando,D.X, Mitchell, IP., andWelsher,T. L., Conductive Anodic Filaments in Reinforced Polymeric Dielectrics Formation and Prevention, IEEE Reliability Physics Symposium Proceedings, Vol. 17, 1979, p. 51-63. 

Ready, W. 1.,Factors Which Enhance Conductive Anodic Filament (CAF) Formation, Master Thesis in Materials Science and Engineering, Georgia Institute of Technology, 1997. 

D. J. Lando, J. P. Mitchell, and T. L. Welsher, Conductive Anodic Filaments in Reinforced Polymeric Dieletrics Formation and Prevention, 17th Annual Proceedings of IEEE Reliability Physics Symposium, San Irandsco, April 24—26,1979, pp. 51-63. 

In electrochemical migration, failure can occur due to dendrite growth, open circuit short, or conductive anodic filament (CAP) formation. Dendrites can form on the surface due to con-taminahon left by the solder flux (paste) or other residues. Under a bias voltage, the metal at the anode goes into solution, migrates toward, and plates-out at the cathode. The nature of the dendrite will depend upon the surface metallization. The following oxidation reactions can occur at the anode ... 

S. R. Stock, Analysis of Catastrophic Failures Due to Conductive Anodic Filament (CAF) Formation, Electronic Packaging Materials Science X, Vol 515, D.J. Belton, M. Gaynes, E.G. Jacobs, R. Pearson, and... 

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