Aluminum bond pad corrosion of wirebond packages

Mathew, Varughese; Chopin, Sheila; Chyan, Oliver; Ross, Nick; Lambert, Alexander; Asokan, Muthappan

doi:10.4071/isom-2016-wa53

Cited by 3 publications

(2 citation statements)

References 7 publications

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“…Accelerated corrosion testing was performed on the BGA wire-bonded packages by placing uncoated and polyimide-coated samples into the salt-spray chamber (Section ). Corrosive failure of the package is often associated with detachment of the bond wire from its pad . Therefore, to measure the corrosion failure, the samples were periodically removed from the chamber and viewed under an optical microscope to detect signs of bond detachment and liftoff.…”

Section: Results and Discussionmentioning

confidence: 99%

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Polyimide Films Manufactured Using Partially Wet Electrospray Deposition

Kingsley

Chiarot

2023

ACS Appl. Polym. Mater.

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In electrospray deposition (ESD), solute material is dispersed in a carrier solvent and atomized into a cloud of microdroplets under the influence of a strong electric potential. The volatility, ESD parameters, and environmental conditions determine the rate of solvent evaporation. Complete in-flight solvent evaporation produces dry particles of material that are deposited on the target. In contrast, when the evaporation is incomplete, some residual solvent is delivered with the material. We define these regimes as dry (complete evaporation) and partially wet (incomplete evaporation) ESD. Here, we compare the microstructure and functional characteristics of films deposited in both regimes. We selected polyimide as our solute material given its importance in electronic, health, and environmental applications. An electrospray printhead that provides a tunable solvent evaporation rate via co-flowing air is used to deploy the polyimide. The dry and partially wet regimes can be selected by altering the solution flow rate and the air co-flow rate. Particulate films are formed when the polyimide is delivered to the target dry (solventfree). When solvent is delivered with the polyimide, a dense (partially wet) film is formed on the target. A numerical model of droplet evaporation was developed, which shows the dominant effects of solution flow rate and freestream vapor concentration on the ESD regime. The dry and partially wet films were compared for various functional characteristics including dielectric strength, optical characteristics, and corrosion resistance. For most metrics, the partially wet ESD films outperformed the dry ESD films. Compared to the dry ESD films, the partially wet films had far greater dielectric strength (up to 340 V/μm) and higher optical transparency. Both ESD regimes provided comparable corrosion resistance, which enhanced the reliability of metallic bond joints in an electronics package.

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Section: Results and Discussionmentioning

confidence: 99%

“…Corrosive failure of the package is often associated with detachment of the bond wire from its pad. 48 Therefore, to measure the corrosion failure, the samples were periodically removed from the chamber and viewed under an optical microscope to detect signs of bond detachment and liftoff.…”

Section: Conformal Coatings For Corrosionmentioning

confidence: 99%

Polyimide Films Manufactured Using Partially Wet Electrospray Deposition

Kingsley

Chiarot

2023

ACS Appl. Polym. Mater.

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Investigation of Cu-Al Bonding Interface: Eliminating Bimetallic Corrosion Failures, and Enabling Next-Gen Cu-Cu Wire-Bonding by Nanometer Interfacial Chemistry Control

Alptekin

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The first part of this dissertation explores the chemistry of an inhibitor complexation with Cu. First, the Cu oxidation state of the complex was +1. Second, identified by differential RAIRS, one source of Cu(I) for the Cu(I)-inhibitor complex could be Cu(I) oxide. The characteristic Cu(I) oxide peak at 650 cm⁻¹ was observed to decrease after CVD coating process was applied. This led to a major hypothesis that in order for the reaction between Cu(I) oxide and the inhibitor to proceed, protons from the inhibitor and oxygen from Cu₂O are stabilized by reacting to form water. The applicability of the passivation nature of Cu(I)-inhibitor films was explored for Cu-Al wire-bonded devices in its ability to protect from Cu-Al peripheral galvanic corrosion and the galvanic corrosion of the Cu-Al intermetallic compounds in their roles for corrosion-induced liftoff. The second part of this work studied the effect of replacing Al bond pad with Cu on the corrosion induced liftoff of wire-bonds when exposed to low ppm levels of chloride contamination. Applying protective coating to the Cu pad surface before wire-bonding was found to suppress the thermally induced oxidation of Cu in air, helping to enable successful Cu-Cu direct wire-bonding. Compared to Cu-Al devices with passivation coating, which has a few wires liftoff with 6 hours, the Cu-Cu bonded devices survived much longer, over 40 days, with almost no liftoff observed. This demonstrates that removing the galvanic contact, the root cause of the corrosion induced failure, is a more robust and permanent solution to the corrosion experienced by these devices.

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Explore High Bonding Reliability of Cu Wire Bonded Devices under Extreme Halide Contaminated Environments

Asokan

Caperton

Salunke

et al. 2018

International Symposium on Microelectronics

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Copper has rapidly replaced gold as the preferred wire bonding material in microelectronic packaging due to its lower cost and many performance advantages. However, halides induced corrosion-related failures need to be carefully controlled to ensure maximum bonding reliability. Literature reported corrosion studies mostly focus on intermetallic compounds as the corrosion vulnerability. Utilizing a novel corrosion screening approach, we established that the bimetallic contact between Cu balls and Al bond pad is the real driver for the observed heavy Al pad corrosion induced by chloride ions [1]. We identified, for the first time, H2 evolution was the coupling cathodic half reaction to the Al bond pad corrosion. With these improved mechanistic insights, we developed an effective corrosion inhibition strategy that utilizes chemical vapor deposition to selectively bond corrosion inhibitors to these critical Cu ball/Al pad interfaces. A new corrosion-screening platform was developed to evaluate the effectiveness of this inhibitor protection treatment. After intentionally loaded chloride contaminants on the die surface, the molded Cu wire bonded devices with selected inhibitor treatment were subjected to PCT stress tests. The subsequent failure analyses, showed selected inhibitor treatment is highly effective of preventing Al bond pad corrosion even under the massive attack of heavy Cl− ion contamination and extensive delamination.

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Aluminum bond pad corrosion of wirebond packages

Cited by 3 publications

References 7 publications

Polyimide Films Manufactured Using Partially Wet Electrospray Deposition

Polyimide Films Manufactured Using Partially Wet Electrospray Deposition

Investigation of Cu-Al Bonding Interface: Eliminating Bimetallic Corrosion Failures, and Enabling Next-Gen Cu-Cu Wire-Bonding by Nanometer Interfacial Chemistry Control

Explore High Bonding Reliability of Cu Wire Bonded Devices under Extreme Halide Contaminated Environments

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