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. 2023 Aug 16;8(34):31021-31029.
doi: 10.1021/acsomega.3c02854. eCollection 2023 Aug 29.

Novel Cu@Ag Micro/Nanoparticle Hybrid Paste and Its Rapid Sintering Technique via Electromagnetic Induction for High-Power Electronics

Zhuohuan Wu  1 , Wei Liu  1 , Jiayun Feng  1 , Zhicheng Wen  1 , Xinyue Zhang  1 , Xinming Wang  1 , Chunqing Wang  1 , Yanhong Tian  1
Affiliations

Novel Cu@Ag Micro/Nanoparticle Hybrid Paste and Its Rapid Sintering Technique via Electromagnetic Induction for High-Power Electronics

Zhuohuan Wu et al. ACS Omega. .

Abstract

Due to the harsh working environments up to 600 °C, the exploration of high-temperature interconnection materials is significantly important for high-power devices. In this study, a hybrid paste including Cu@Ag core-shell microparticles (MPs) and Ag nanoparticles (NPs) was designed to achieve Cu-Cu bonding. The Cu@Ag MPs exhibited excellent oxidation stability in an air atmosphere with the Ag layer coating on the Cu core. Ag NPs fill the pores among the Cu@Ag MPs and reduce the sintering temperature of the hybrid paste. The Cu-hybrid paste-Cu joints were formed via electromagnetic induction heating within approximately 15 s. When sintered at 26 kW, the shear strength of the joint reached 48 MPa, the porosity decreased to 0.73%, and the resistivity was down to 13.25 μΩ·cm. Furthermore, a possible interconnection mechanism at the contact interface between the Cu substrate and the sintered hybrid paste was proposed, which is related to the melting point of metal particles and the effect of magnetic eddy currents. This fast bonding technology inspires a new approach to interconnection for high-power devices under high operation temperatures.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Schematic illustration of (a) synthesis process of Cu@Ag MPs and (b) Cu@Ag core–shell formation by a replacement reaction.
Figure 2
Figure 2
Schematic diagram of the device and heating parameters sintered by electromagnetic induction: (a) sintering setup and the sandwich structure; (b) hybrid paste cross section; and (c) magnetic induction line of the energized coil. (d) Change of temperature at different sintering times at a power of 26 kW. (e) Pulse curve of power.
Figure 3
Figure 3
XRD patterns of Cu@Ag MPs.
Figure 4
Figure 4
(a) XPS survey spectra of the Cu@Ag MPs. (b) XPS spectra showing the Cu 2p region. (c) Ag 3d region XPS spectra. (d) O 1s region XPS spectra. (e) XPS spectra of the C 1s region.
Figure 5
Figure 5
Morphological and structural analysis of the pristine micron-sized Cu and Cu@Ag MP: (a) SEM image of the Cu microparticle and (b–d) SEM image and EDS spectrum mapping: Cu and Ag elemental distribution of Cu@Ag MP.
Figure 6
Figure 6
TG-DTA curves of Ag NPs in a static air atmosphere.
Figure 7
Figure 7
(a) Shear strength and (b) porosity of the joints sintered at 22 and 26 kW for different sintering times.
Figure 8
Figure 8
Cross-sectional SEM images of joint sintered at 26 kW for (a) 9 s, (b) 12 s, (c) 15 s, and (d) 18 s.
Figure 9
Figure 9
Element mapping at the cross section of a joint sintered via the Cu@Ag MPs/Ag NPs hybrid paste at 26 kW. (a) Cross-sectional morphology. Element distribution: (b) Cu and (c) Ag.
Figure 10
Figure 10
Schematic of interconnection mechanism for the cross section of the direct Cu joint utilizing the Cu@Ag MPs/Ag NPs hybrid paste: (a) before sintering and (b) during the sintering process.
Figure 11
Figure 11
Resistivity of the hybrid paste sintered for different sintering times at 26 kW.
Figure 12
Figure 12
SEM images of joint fracture surfaces sintered at 26 kW for (a) 9 s, (b) 12 s, (c) 15 s, and (d) 18 s.
See this image and copyright information in PMC

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