Novel Silver Solid-State Bonding Designs Between Two Copper Structures

Yi-Ling Chen,Chin C Lee

doi:10.1109/tcpmt.2016.2628908

Yi-Ling Chen, Chin C Lee

Open Access

https://doi.org/10.1109/tcpmt.2016.2628908

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Abstract

Both copper (Cu) and silver (Ag) have been studied extensively for electrical conductor applications. To expand the applications, two bonding designs were implemented in this paper. For the first design, a 50- $\mu \text{m}$ Ag layer was annealed at 400 °C to increase Ag grain size, thereby making it more ductile. For the second design, a 5- $\mu \text{m}$ Ag layer with cavities was created to release the thermal induced stress and allow easier plastic deformation for the bonding medium. For both designs, the resulting Cu substrates were bonded to Cu chips by the solid-state bonding process. The cross sections of bonded samples show no visible voids or gaps on Cu/Ag and Ag/Cu interfaces. The breaking forces of ten samples tested far exceed the requirement specified in the military standards MIL-STD-883J Method 2019.9. The successful demonstrations of solid-state bonding between Ag and Cu should open the possibility of bringing alternatives for bonding methods in the field of electronic packaging.

Highlights

I N ELECTRONIC devices and packages, bonding of two objects is often needed on various interfaces of the packages
Solid-state bonding processes were successfully developed between Cu chips and Cu substrates using two different types of bonding designs
Two bonding designs were presented to meet the requirements for different applications

Summary

Introduction

I N ELECTRONIC devices and packages, bonding of two objects is often needed on various interfaces of the packages. The most popular example is the soldering process [1], [2]. An example of solid-state bonding is the wire bonding process for interconnection using thermal and ultrasonic energy [3]. Various bonding media are available in the market for different applications. Traditional bonding media include conductive adhesives, lead-free tin-based solders, and gold–tin (Au–Sn) eutectic solders [4]–[6]. The conductive adhesives and lead-free solders cannot sustain temperatures higher than 150 °C [7]. The maximum operating temperature of eutectic Au–Sn solders is 200 °C [8]. For high-temperature electronic modules incorporating silicon carbide and gallium-nitride-based devices, a new bonding

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