Electrochemical Migration Behavior of Copper-Clad Laminate and Electroless Nickel/Immersion Gold Printed Circuit Boards under Thin Electrolyte Layers.

Kangkang Ding,Xiaogang Li,Pan Yi,Kui Xiao,Chaofang Dong

doi:10.3390/ma10020137

Abstract

The electrochemical migration (ECM) behavior of copper-clad laminate (PCB-Cu) and electroless nickel/immersion gold printed circuit boards (PCB-ENIG) under thin electrolyte layers of different thicknesses containing 0.1 M Na2SO4 was studied. Results showed that, under the bias voltage of 12 V, the reverse migration of ions occurred. For PCB-Cu, both copper dendrites and sulfate precipitates were found on the surface of FR-4 (board material) between two plates. Moreover, the Cu dendrite was produced between the two plates and migrated toward cathode. Compared to PCB-Cu, PCB-ENIG exhibited a higher tendency of ECM failure and suffered from seriously short circuit failure under high relative humidity (RH) environment. SKP results demonstrated that surface potentials of the anode plates were greater than those of the cathode plates, and those potentials of the two plates exhibited a descending trend as the RH increased. At the end of the paper, an electrochemical migration corrosion failure model of PCB was proposed.

Highlights

As the swift development of electronic technology, electronic devices or products are moving towards further integration and miniaturization
As relative humidity (RH) increased, the color of the cathode plate continuously deepened, and the amount of salt enrichment accumulated on some localized areas of the printed circuit boards (PCBs)-Cu increased
The electrochemical migration (ECM) behavior and mechanism of PCB-Cu and PCB-electroless nickel–gold (ENIG) under absorbed thin electrolyte films with different thicknesses were investigated in this work

Summary

Introduction

As the swift development of electronic technology, electronic devices or products are moving towards further integration and miniaturization. The corrosion failure problems of printed circuit boards (PCBs) have been occurring more frequently, and even a small amount of corrosion products can severely affect the reliability of PCBs [1]. A thin electrolyte layer that may contain corrosive particles, whose thickness dynamically varies in the service environment, can cover the surface of PCBs, leading to electrochemical corrosion failure in a dynamic thin electrolyte layer. PCB-Cu is inclined to suffer from surface oxidation or electrochemical corrosion. Under the polluted atmospheric environment, the dense Cu2 O film [4] on the surface of PCB-Cu will gradually corrode and transform into Cu4 (OH) SO4 , Cu2 (OH) Cl, Cu2 (OH) NO3 , Cu2 (OH) CO3 , and other corrosion products [5,6,7], losing its protective

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Results

Conclusion