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Review
. 2023 Aug 16;14(8):1612.
doi: 10.3390/mi14081612.

Copper Wire Bonding: A Review

Hongliang Zhou  1 , Andong Chang  1 , Junling Fan  2 , Jun Cao  1 , Bin An  1 , Jie Xia  1 , Jingguang Yao  1 , Xiaobin Cui  1 , Yingchong Zhang  3
Affiliations
Review

Copper Wire Bonding: A Review

Hongliang Zhou et al. Micromachines (Basel). .

Abstract

This paper provides a comprehensive review on copper (Cu) wire bonding. Firstly, it introduces the common types of Cu wire available in the market, including bare Cu wire, coated Cu wire, insulated Cu wire, and alloyed Cu wire. For each type, their characteristics and application areas are discussed. Additionally, we provide detailed insights into the impact of Free Air Ball (FAB) morphology on bonding reliability, including its effect on bond strength and formation mechanisms. Next, the reliability of Cu wire bonding is analyzed, with a focus on the impact of intermetallic compounds and corrosion on bonding reliability. Specifically, the formation, growth, and stability of intermetallic compounds at bonding interfaces are discussed, and their effects on bonding strength and reliability are evaluated. The detrimental mechanisms of corrosion on Cu wire bonding and corrosion inhibition methods are also analyzed. Subsequently, the applications of simulation in Cu wire bonding are presented, including finite element analysis and molecular dynamics simulations, which provide important tools for a deeper understanding of the bonding process and failure mechanisms. Finally, the current development status of Cu wire bonding is summarized, and future research directions are discussed.

Keywords: Cu wire bonding; FAB morphology; applications of simulations; bonding reliability; intermetallic compounds.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
HAADF STEM images of (a) the Pd–Cu bond containing Pd showing nano-voids in the Cu (dark spots) and (b) the Pd–Cu bond with no Pd [23].
Figure 2
Figure 2
Comparison of bare Cu and insulated Cu wire bonded samples. (a) Ball bond, (b) stitch bond, and (c) IMC coverage and pattern [36].
Figure 3
Figure 3
FAB Cross section for PCC and bare Cu wire [45].
Figure 4
Figure 4
HAADF image of the bonding interface under the PCC wire [53].
Figure 5
Figure 5
(a) BF TEM image of the fully consumed Al interface between the Cu-bonding wire and the Al pad after aging at 175 °C for 2000 h. HRTEM images of (b) CuAl2 and (c) CuAl grains, and FFT images of the area marked a white square in (b,c) [60].
Figure 6
Figure 6
Cross-sectional analysis of Cu ball on Al pad revealing corrosion initiation beneath the Cu ball [70].
Figure 7
Figure 7
Cross-section of Cu/Al IMCs (a) before immersion in NaCl solution and (b) after immersion in NaCl solution [73].
Figure 8
Figure 8
SEM/EDX mapping image of broken stitch Cu wire with chloride distribution. (a) Side view and (b) front view [74].
Figure 9
Figure 9
Overall stress distributions on the entire model (MPa) for EFO Cu wire. [82].
Figure 10
Figure 10
Geometries of the Cu–Cu wire bonding models [86].
See this image and copyright information in PMC

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