# Post Wire-Bonding Corrosion Prevention Strategies to Mitigate Chloride- and Bromide-Induced Corrosion Failures in Cu- and PCC-Based Wire-Bonded Packages

## TL;DR

This paper explores ways to prevent corrosion in copper and palladium-coated copper wire-bonded packages used in automotive ICs, which can fail due to chloride and bromide exposure.

## Contribution

The study introduces a novel Cu-selective passivation and phosphonic-acid-based inhibitor to significantly reduce corrosion failures in wire-bonded packages.

## Key findings

- Control PCC-Al devices with a Pd overlayer showed 21 ± 1.6% lift-off failures in mixed-ion solution.
- Applying Cu-selective passivation reduced lift-off failures to 3.3 ± 0.6%.
- Phosphonic-acid-based inhibitors eliminated lift-off failures in mixed-ion solution.

## Abstract

To ensure the highest safety standards in modern automobiles, the industry is constantly adopting zero-defect frameworks, such as AEC-Q100, which aims for defective-parts-per-billion (DPPB) or grade-0 level reliability standards in automotive integrated-circuit (IC) packages. Most contemporary wire-bonded packages use either pure copper (Cu) or palladium (Pd)-coated copper (PCC) wires bonded to aluminum (Al) bond pads as interconnections. This choice is made due to their lower cost and superior electrical and mechanical performance, compared to traditional gold wire-based devices. However, these Cu–Al wire-bonded interconnections are prone to ion-induced lift-off/open-circuit corrosion failures when exposed to even trace amounts (<20 ppm) of extrinsic and/or intrinsic halide (Cl− and Br−) contaminants, decreasing device longevity. This study investigates corrosion failure mechanisms in Cu and PCC wire-based devices by subjecting non-encapsulated devices to a highly accelerated aqueous-immersion screening test containing 100 ppm chloride (Cl−), 100 ppm bromide (Br−), and a mixed-ion solution (MX: Cl− + Br−). The screening results indicate that even control PCC-Al devices with a Pd overlayer can be susceptible to Cl− and Br− induced corrosion, with 21 ± 1.6% lift-off failures in MX-solution. In contrast, applying a novel Cu-selective passivation reduced lift-off to 3.3 ± 0.6% and introducing phosphonic-acid-based inhibitor into the MX solution eliminated lift-off failures, demonstrating markedly improved reliability.