Enhancing Cu-Cu Stitch Bonding Reliability on Cu Leadframe Through Ultrathin Cu-Selective Passivation.

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Bibliographic Details
Title:	Enhancing Cu-Cu Stitch Bonding Reliability on Cu Leadframe Through Ultrathin Cu-Selective Passivation.
Authors:	Nair, Shyam Muralidharan¹, Perera, Duwage Anushka Sandaruwan¹, Farmer, Gavin², Abraham, James², Tran, Khanh Tuyet Anh¹, Philipose, Usha², Chyan, Oliver¹
Source:	Journal of Microelectronic & Electronic Packaging. 2026, Vol. 23 Issue 1, p9-17. 9p.
Subjects:	Wire bonding (Electronic packaging), Microelectronic packaging, Packaging industry, Corrosion prevention
Abstract:	Despite advances in 2.5D and 3D packaging, ultrasonic wedge (stitch) bonding remains the industry standard due to its cost-effectiveness. However, the transition to copper (Cu) and palladium-coated copper (PCC) wire introduces reliability challenges, traditionally mitigated by expensive and environmentally concerning silver (Ag) plating on leadframes (LF). To address this, we developed a low-cost, ultrathin Cu-selective passivation coating that suppresses oxidation, enabling direct Cu-Cu bonding without Ag. This process-compatible coating was evaluated on Cu-LFs using 25 µm Al-1 wt% Si and PCC wires under varying thermal conditions (125 ℃-200 ℃). Optimization of bonding force, time, and ultrasonic power yielded substantial improvements in pull strength. Notably, while bare-Cu bonds failed at the oxidized interface, passivated samples failed at the wire neck, confirming superior bond integrity. This work highlights a promising, environmentally sustainable alternative to Ag plating, enabling reliable Cu-Cu stitch bonding for next-generation, low-cost IC packaging solutions. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
Abstract:	Despite advances in 2.5D and 3D packaging, ultrasonic wedge (stitch) bonding remains the industry standard due to its cost-effectiveness. However, the transition to copper (Cu) and palladium-coated copper (PCC) wire introduces reliability challenges, traditionally mitigated by expensive and environmentally concerning silver (Ag) plating on leadframes (LF). To address this, we developed a low-cost, ultrathin Cu-selective passivation coating that suppresses oxidation, enabling direct Cu-Cu bonding without Ag. This process-compatible coating was evaluated on Cu-LFs using 25 µm Al-1 wt% Si and PCC wires under varying thermal conditions (125 ℃-200 ℃). Optimization of bonding force, time, and ultrasonic power yielded substantial improvements in pull strength. Notably, while bare-Cu bonds failed at the oxidized interface, passivated samples failed at the wire neck, confirming superior bond integrity. This work highlights a promising, environmentally sustainable alternative to Ag plating, enabling reliable Cu-Cu stitch bonding for next-generation, low-cost IC packaging solutions. [ABSTRACT FROM AUTHOR]
ISSN:	15514897
DOI:	10.4071/001c.156190