Characterization and Electrochemical Mechanism for Bromide-Containing Conductive Anodic Filament (CAF) Failure

We have studied porous anodic alumina template through the second anodic oxidation of preparation. Observing the morphology of nanoscale AAO template using scanning electron microscope (SEM), the results indicate that the pores are orderly paralleled arranged with uniform pore diameter, perpendicular to the template surface. A detailed study of the influence of different oxidation conditions, such as different type of electrolyte, concentration, voltage and temperature on the template of alumina and its electrochemical mechanism were performed. By changing the oxidation voltage, electrolyte type, concentration, pore diameter and template thickness can be altered in a wide range such that we can obtain the desired aspect ratio. <br>

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Failure Localization of Intermittent Short Failures Caused by Vertical Conductive Anodic Filament Formation

ISTFA 2014: Conference Proceedings from the 40th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2014p0218 ◽

2014 ◽

Author(s):

Daniel Nuez ◽

Phoumra Tan

Keyword(s):

Glass Fibers ◽

Vertical Plane ◽

Axis Formation ◽

Metal Trace ◽

Conductive Anodic Filament ◽

Plated Through Hole ◽

Voltage Gradients ◽

Ic Package ◽

Through Hole ◽

Failure Localization

Abstract Conductive anodic filament (CAF) formation is a mechanism caused by an electrochemical migration of metals from a metal trace in ICs or in PCBs. This is commonly caused by the moisture build-up in the affected metal terminals in an IC package or PC board caused by critical temperature, high humidity and high voltage gradients conditions. This phenomenon is known to have caused catastrophic field failures on various OEMs electronic components in the past [1,7]. Most published articles on CAF described the formation of the filament in a lateral formation through the glass fiber interfaces between two adjacent metal planes [1-6, 8-12]. One common example is the CAF formation seen between PTH (Plated through Hole) in the laminated substrate with two different potentials causing shorts [1-6, 8-12]. In this paper, the Cu filament grows in a vertical fashion (z-axis formation) creating a vertical plane shorts between the upper and lower metal terminals in a laminated IC package substrate. The copper growth migration does not follow the fiber strands laterally or vertically through them. Instead, it grows through the stress created gaps between the impregnated carbon epoxy fillers from the upper metal trace to the lower metal trace with two different potentials, between the glass fibers. This vertical CAF mechanism creates a low resistive short that was sometimes found to be intermittent in nature. This paper presents some successful failure analysis approaches used to isolate and detect the failure locations for this type of failing devices. This paper also exposes the unique physical appearance of the vertical CAF formation.

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