Sn-58Bi solder has been widely used for microelectronics packaging due to its low melting point temperature, good wetting performance, good mechanical properties, and low cost. Compared with Sn-Bi solder alloy and Sn-Pb solder alloy, the strength and plasticity of Sn-Bi solder are not enough, due to the higher brittleness of bismuth, which thus limits the application of Sn-Bi solder. In order to improve the properties of Sn-Bi solder, a novel solder paste strengthened with resin was developed by mixing epoxy resin (ER) with Sn-58Bi solder, which enhanced the joint strength at a low cost. Aimed at the electronic industry, in this study, the spreadability of the novel solder paste was investigated, and the mechanical properties and microstructure of solder joints after reflow soldering were tested and analyzed. The results showed that when the content of epoxy resin was in the optimum range, the shear strength was significantly higher, reaching nearly twice that of Sn-58Bi solder alone.

With the rapid iteration of microsystem integrated technology, the miniaturization of electronic devices requires packaging materials with higher reliability. In this work, the microstructure evolution and mechanical properties of novel epoxy composite SAC305 solder joints were studied after isothermal aging to evaluate the enhanced effect of epoxy addition. The thickness variation and morphological evolution of the interfacial layer were analyzed. The results showed that, as the aging time was prolonged, the Cu₆Sn₅ interfacial layer remarkably coarsened and Cu₃Sn compounds formed between the Cu₆Sn₅ layer and Cu pad due to the continuous atomic diffusion. Compared with the monolithic joint, the epoxy composite SAC305 joints had a lower overall IMC growth rate during aging, closely related to the initial morphologies of the interfacial layers. The shear test results showed an apparent decrease in the shear forces of all the solder joints as the aging time increased. Nevertheless, because of the extra mechanical support provided by the epoxy layer, the epoxy composite joints demonstrated notably enhanced mechanical properties. After 1000 h aging treatment, the shear force of SAC305 joints containing 8 wt.% epoxy was 26.28 N, showing a 24.08% increase over the monolithic joint. Cu-Sn IMCs were detected on the shear fracture of the monolithic joint after 1000 h aging, indicating the fracture occurred near the interface and displayed a ductile/brittle mixed fracture. Concerning the epoxy composite joints, cracks were still initiated and extended within the solder bulk, demonstrating a noticeable enhancement in ductility due to the addition of epoxy.

In this work, epoxy was added into commercial Sn-3.0Ag-0.5Cu (SAC305) solder paste to enhance the thermal cycling reliability of the joint. The microstructure and fracture surface were observed using a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a shear test was performed on the thermally cycled joint samples. The results indicated that during the thermal cycling test, the epoxy protective layer on the surface of the epoxy-enhanced SAC305 solder joint could significantly alleviate the thermal stress caused by coefficients of thermal expansion (CTE) mismatch, resulting in fewer structural defects. The interfacial compound of the original SAC305 solder joints gradually coarsened due to the accelerated atomic diffusion, but epoxy-enhanced SAC305 solder joints demonstrated a thinner interfacial layer and a smaller IMC grain size. Due to the reduced stress concentration and the additional mechanical support provided by the cured epoxy layer, epoxy-enhanced SAC305 solder joints displayed superior shear performance compared to the original joint during the thermal cycling test. After 1000 thermal cycles, Cu-Sn IMC regions were observed on the fracture surfaces of the original SAC305 solder joint, exhibiting brittle fracture characteristics. However, the fracture of the SAC305 solder joint with 8 wt.% epoxy remained within the solder bulk and exhibited a ductile fracture mode. This work indicates that epoxy-enhanced SAC305 solder pastes display high thermal cycling reliability and could meet the design needs of advanced packaging technology for high-performance electronic packaging materials.

Woven fabric composites made from commingled fibreglass and polypropylene fibres have the potential to make lightweight structural parts to replace metal structures in automobiles when competitively produced using thermostamping techniques. To expedite the acceptance of such composites, a credible design tool needs to be available to study the associated manufacturing process. For such a numerical method, a material model is required. Because the tows of the fabric are essentially inextensible, shear is the major deformation mode for assuming the stamped shape. The shear mechanical behaviour of fabric is obtained from a shear-frame test. A finite element model using a combination of truss and 2D solid elements is proposed. The truss elements represent the tows and use a nonlinear material model for capturing the increasing stiffness of the tows with increasing tensile strain. The 2D Solid elements capture the interaction between tows and the viscosity of the resin. The bias-extension test is a valuable test for investigating the shear performance of woven fabric composites. Using the finite element method, the bias-extension test is modelled, analysed and compared experimentally to verify the credibility of the woven-fabric material model.

As the size and pitch of flip chip solder joint reducing, and the thickness of the package reduce simultaneously, the solder thermal reliability become more and more critical. In this study, thermal cycling test (TCT) was performed for 3 groups of FC-CSP samples to get the crack initiation and propagation life. FE simulation had been used to get the increment of the solder strain energy density. Base on the experiment and simulation data, new empirical constants of Darveaux model were got for the FC-CSP system. With the modified Darveaux model, the influence of design parameters including packaging geometry size and material properties were compared for FC-CSP solder reliability. For the packaging geometry, substrate thickness should to be considered firstly to increasing the solder fatigue life, then is die thickness. The solder joint standoff showed little influence on the solder fatigue life. For the material properties, the Tg of MUF material should to be higher than high temperature of TCT, which is 150 °C in this study. CTE of MUF material showed the high influential on solder fatigue life. The followed influence rank are CTE of substrate and flexural modulus of MUF material, which have little difference in the influence on solder fatigue life.