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. 2022 Dec 4;14(23):5303.
doi: 10.3390/polym14235303.

Microstructure and Shear Behaviour of Sn-3.0Ag-0.5Cu Composite Solder Pastes Enhanced by Epoxy Resin

Peng Zhang  1 , Songbai Xue  1 , Lu Liu  1 , Jie Wu  1 , Qingcheng Luo  1 , Jianhao Wang  2
Affiliations

Microstructure and Shear Behaviour of Sn-3.0Ag-0.5Cu Composite Solder Pastes Enhanced by Epoxy Resin

Peng Zhang et al. Polymers (Basel). .

Abstract

With the rapid development of microelectronics packaging technology, the demand for high-performance packaging materials has further increased. This paper developed novel epoxy-containing Sn-3.0Ag-0.5Cu (SAC305-ER) composite solder pastes, and the effects of epoxy resin on their spreading performance, microstructure, and shear behaviour were analysed. The research results showed that with the addition of epoxy resin, SAC305 solder pastes exhibited exceptional spreadability on Cu substrates, which could be attributed to the reduction in the viscosity and the surface tension of the composite solder pastes. With the addition of epoxy resin, the solder matrix microstructure and interfacial morphology of SAC305-ER composite solder joints remained unchanged. However, continuous resin protective layers were observed on the surface of SAC305-ER composite solder joints after the reflow process. The shear properties of the composite solder joints were enhanced by the extra mechanical bonding effect provided by resin layers. When the epoxy resin content was 8 wt%, the shear forces of SAC305-ER composite solder joints reached the maximum value. Fracture analysis indicated that cracked epoxy resin was observed on the surface of SAC305-ER composite solder joints, indicating that the epoxy resin also underwent obvious deformation in the shear test.

Keywords: Sn-3.0Ag-0.5Cu composite solder paste; epoxy resin; fracture morphology; microstructure analysis; shear behaviour; spreading performance.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic diagrams of (a) dimensions of the 0603 chip resistor and Cu pad (unit: mm) and (b) solder joints’ preparation.
Figure 2
Figure 2
Schematic diagram of (a) wetting process of the molten solder on the substrate and (b) spreading process of SAC305-ER solder pastes on Cu plate.
Figure 3
Figure 3
Spreading samples of plain SAC305 and SAC305-xER solder pastes on Cu plates: (a) plain SAC305, (b) x = 2 wt%, (c) x = 4 wt%, (d) x = 6 wt%, (e) x = 8 wt%, (f) x = 10 wt%, (g) x = 12 wt%.
Figure 4
Figure 4
Wetting angles of plain SAC305 and SAC305-xER solder pastes spread on Cu plates: (a) plain SAC305, (b) x = 2 wt%, (c) x = 4 wt%, (d) x = 6 wt%, (e) x = 8 wt%, (f) x = 10 wt%, (g) x = 12 wt%.
Figure 5
Figure 5
Spreading area and wetting angle of plain SAC305 and SAC305-ER solder pastes on Cu plates.
Figure 6
Figure 6
Cross-section SEM images of plain SAC305 and SAC305-ER solder joints: (a,b) plain SAC305, (c,d) x = 4 wt%, (e,f) x = 8 wt%, (g,h) x = 12 wt%.
Figure 7
Figure 7
Microstructure analysis of region O and region P in Figure 6: (a) SEM image of region O, (b) SEM image of region P, (c) EDS result of point A, (d) EDS result of point B, (e-g) EDS elemental mapping results of region O.
Figure 8
Figure 8
Interfacial morphologies of plain SAC305 and SAC305-ER solder joints: (a) plain SAC305, (b) x = 4 wt%, (c) x = 8 wt%, (d) x = 12 wt%.
Figure 9
Figure 9
Shear forces of plain SAC305 and SAC305-ER solder joints.
Figure 10
Figure 10
Fracture surfaces of plain SAC305 and SAC305-ER solder joints: (a) plain SAC305, (b) x = 4 wt%, (c) x = 8 wt%, (d) x = 12 wt%, (e) enlarged image of region Q, (f) enlarged image of region R, (g) the elemental mapping of (a), (h) the elemental mapping of (c).
See this image and copyright information in PMC

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