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. 2021 Jan 11;14(2):335.
doi: 10.3390/ma14020335.

Interfacial Reactions and Mechanical Properties of Sn-58Bi Solder Joints with Ag Nanoparticles Prepared Using Ultra-Fast Laser Bonding

Gyuwon Jeong  1   2 , Dong-Yurl Yu  1   3 , Seongju Baek  1   4 , Junghwan Bang  1 , Tae-Ik Lee  1 , Seung-Boo Jung  2 , JungSoo Kim  1 , Yong-Ho Ko  1   5
Affiliations

Interfacial Reactions and Mechanical Properties of Sn-58Bi Solder Joints with Ag Nanoparticles Prepared Using Ultra-Fast Laser Bonding

Gyuwon Jeong et al. Materials (Basel). .

Abstract

The effects of Ag nanoparticle (Ag NP) addition on interfacial reaction and mechanical properties of Sn-58Bi solder joints using ultra-fast laser soldering were investigated. Laser-assisted low-temperature bonding was used to solder Sn-58Bi based pastes, with different Ag NP contents, onto organic surface preservative-finished Cu pads of printed circuit boards. The solder joints after laser bonding were examined to determine the effects of Ag NPs on interfacial reactions and intermetallic compounds (IMCs) and high-temperature storage tests performed to investigate its effects on the long-term reliabilities of solder joints. Their mechanical properties were also assessed using shear tests. Although the bonding time of the laser process was shorter than that of a conventional reflow process, Cu-Sn IMCs, such as Cu6Sn5 and Cu3Sn, were well formed at the interface of the solder joint. The addition of Ag NPs also improved the mechanical properties of the solder joints by reducing brittle fracture and suppressing IMC growth. However, excessive addition of Ag NPs degraded the mechanical properties due to coarsened Ag3Sn IMCs. Thus, this research predicts that the laser bonding process can be applied to low-temperature bonding to reduce thermal damage and improve the mechanical properties of Sn-58Bi solders, whose microstructure and related mechanical properties can be improved by adding optimal amounts of Ag NPs.

Keywords: Ag nanoparticle (Ag NP); interfacial reaction; intermetallic compounds (IMCs); laser process; low-temperature bonding; mechanical property.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Schematic of the fabrication process for test samples and (b) profiles for bonding conditions by the laser process.
Figure 2
Figure 2
Cross-sectional scanning electron microscopy (SEM) micrographs of the Sn–58Bi Ag NP composite solder joints after high-temperature storage (HTS) tests at 85 °C.
Figure 3
Figure 3
Cross-sectional scanning electron microscopy (SEM) micrographs of the Sn–58Bi Ag NP composite solder joints after high-temperature storage (HTS) tests at 100 °C.
Figure 4
Figure 4
Cross-sectional scanning electron microscopy (SEM) micrographs of the Sn–58Bi Ag NP composite solder joints after high-temperature storage (HTS) tests at 115 °C.
Figure 5
Figure 5
Total intermetallic compounds (IMCs) thickness as a function of test time at temperatures: (a) 85 °C (b) 100 °C, and (c) 115 °C.
Figure 6
Figure 6
Arrhenius plots of intermetallic compound (IMC) growth rate as a function of Ag NP content of Sn–58Bi solder.
Figure 7
Figure 7
Shear strengths of Sn–58Bi composite solder joints with the test times and Ag NP contents after a high-temperature storage (HTS) tests at (a) 85 °C, (b) 100 °C, and (c) 115 °C.
Figure 7
Figure 7
Shear strengths of Sn–58Bi composite solder joints with the test times and Ag NP contents after a high-temperature storage (HTS) tests at (a) 85 °C, (b) 100 °C, and (c) 115 °C.
Figure 8
Figure 8
Top-view scanning electron microscopy (SEM) micrographs of fracture surfaces after a high-temperature storage (HTS) test at 85 °C: (a) 0.1 m/s and (b) 1.0 m/s.
Figure 9
Figure 9
Top-view scanning electron microscopy (SEM) micrographs of fracture surfaces after a high-temperature storage (HTS) test at 100 °C: (a) 0.1 m/s and (b) 1.0 m/s.
Figure 10
Figure 10
Top-view scanning electron microscopy (SEM) micrographs of fracture surfaces after a high-temperature storage (HTS) test at 115 °C: (a) 0.1 m/s and (b) 1.0 m/s.
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