Abstract
This study investigated the suppression of the growth of the intermetallic compound (IMC) layer that forms between epoxy solder joints and the substrate in electronic packaging by adding graphene nano-sheets (GNSs) to 96.5Sn–3.0Ag–0.5Cu (wt %, SAC305) solder whose bonding characteristics had been strengthened with a polymer. IMC growth was induced in isothermal aging tests at 150 °C, 125 °C and 85 °C for 504 h (21 days). Activation energies were calculated based on the IMC layer thickness, temperature, and time. The activation energy required for the formation of IMCs was 45.5 KJ/mol for the plain epoxy solder, 52.8 KJ/mol for the 0.01%-GNS solder, 62.5 KJ/mol for the 0.05%-GNS solder, and 68.7 KJ/mol for the 0.1%-GNS solder. Thus, the preventive effects were higher for increasing concentrations of GNS in the epoxy solder. In addition, shear tests were employed on the solder joints to analyze the relationship between the addition of GNSs and the bonding characteristics of the solder joints. It was found that the addition of GNSs to epoxy solder weakened the bonding characteristics of the solder, but not critically so because the shear force was higher than for normal solder (i.e., without the addition of epoxy). Thus, the addition of a small amount of GNSs to epoxy solder can suppress the formation of an IMC layer during isothermal aging without significantly weakening the bonding characteristics of the epoxy solder paste.
Highlights
The use of lead (Pb) in the electronic packaging industry has been greatly reduced because it poses a threat to the environment and to public health
intermetallic compound (IMC) layers form at the interface between the solder and a substrate, i.e., between the solder and the Generally, IMC layers form at the interface between the solder and a substrate, i.e., between the chip electrode and/or between the solder and the Cu substrate
The IMC layer formed at solder and the chip electrode and/or between the solder and the Cu substrate
Summary
The use of lead (Pb) in the electronic packaging industry has been greatly reduced because it poses a threat to the environment and to public health. Sn–Ag–Cu solder joints are prone to cracking due to the difference in the coefficients of thermal expansion (CTEs) between the copper (Cu) substrate and the solder. Another serious drawback is the formation of an intermetallic compound (IMCs) layer within the solder joint. Materials 2019, 12, 936 drawback is the formation of an intermetallic compound (IMCs) layer within the solder joint. Containing epoxy have been developed to suppress crack arraysolder (BGA)joints. In Generally, epoxyGenerally, solder joints enhance thejoints bonding strength solder suppress crack propagation solder joints. IMCs layer consisting of Cu and Cu can form of within joints between temperatures a problem
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