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Pb-free solders have been developed to replace the standard Sn–Pb eutectic solder since the prohibition on Pb used in solders. The Sn–Ag–Cu series of lead-free solders is the most extensively used in the electronics industry. The Ag₃Sn, which forms during isothermal ageing, can significantly degrade solder joint reliability. Sn–Ag–Cu solder’s high price further hindered its use in the electronics industry. This paper aims to investigate different copper percentages into Sn–xCu solder alloy to improve its microstructure and strength performance.

The solder alloys used in this work were Sn–xCu, where x = 0.0, 0.3, 0.5, 0.7, 1.0 Wt.%, which was soldered onto electroless nickel immersion gold (ENIG) substrate using carbon dioxide (CO₂) gas laser. Then these samples were subjected to isothermal aging for 0, 200, 500, 1,000 and 2,000 h. The Sn–xCu solder alloy was fabricated through a powder metallurgy process.

Microstructure characterization showed that Cu addition resulted in fine and rounded shape of Cu–Sn–Ni particles. Shear strength of Sn–xCu solder joints was increased with increasing Cu content, but at aging duration of 1,000 h, it dropped slightly. It is believed that the strength improved due to the increment of diffusion rate during isothermal aging.

In a Cu–Sn solder, the recommended amount is 1.0 Wt.% of Cu. In extensive aging procedures, it was discovered that Sn1.0Cu solder improved the reliability of solder joints. The findings indicated that the innovative solder alloys might satisfy the needs of high-reliability applications.

The study shows that the right amount of Cu enhances the solidification of Sn–Cu solder, increasing the shear force of the Cu–Sn solder joint. The Sn1.0Cu exhibits a ductile fracture on the top microstructure, improving the joint’s average shear strength.

This study aims to review the effect of copper percentage in Sn-based solder alloys (Sn-xCu, x = 0–5 Wt.%) on intermetallic compound (IMC) formation and growth after laser soldering.

This study reviews the interfacial reactions at the solder joint interface, solder joint morphology and the theory on characterizing the formation and growth of IMCs. In addition, the effects of alloying and strengthening mechanism, including wettability, melting and mechanical properties are discussed.

This paper presents a comprehensive overview of the composition of tin-copper (Sn-Cu) solders with a potential to enhance their microstructure, mechanical characteristics and wettability by varying the Cu percentage. The study found that the best Cu content in the Sn-xCu solder alloy was 0.6–0.7 Wt.%; this composition provided high shear strength, vibration fracture life value and ideal IMC thickness. A method of solder alloy preparation was also found through powder metallurgy and laser soldering to improve the solder joint reliability.

This study focuses on interfacial reactions at the solder joint interface, solder joint morphology, modelling simulation of joint strength and the theory on characterising the formation and growth of IMC.

The paper comprehensively summarises the useful findings of the Sn-Cu series. This information will be important for future trends in laser soldering on solder joint formation.

This paper aims to study the effect of aging and cooling rate on the reliability of the solder joint using electroless nickel boron (EN-Boron) as a surface finish in the electronic packaging area.

EN-Boron was plated on a Cu substrate through electroless plating method. This process was followed by reflow soldering of Sn–3.0Ag–0.5Cu solder alloy on metallized Cu substrate to form a joining. Then, the specimens were cooled using different cooling mediums such as air (slow cooling) with 15.7 °C/min and water (fast cooling) with 110.5 °C/min. After that, the specimens were subjected to isothermal aging at 150°C for 0, 250 and 1,000 h. Finally, they went through a lap shear test following ASTM D1002. Optical microscope and scanning electron microscopy were used for intermetallic compound (IMC) characterization. The type of IMC formed was confirmed by field emission scanning electron microscope-energy-dispersive X-ray spectroscopy (FESEM-EDX).

The results showed that the IMC type changed from the combination of Ni₃Sn4 and (Ni, Cu)₃Sn4 after reflow soldering into fully (Ni, Cu)₃Sn4 when aged for 1,000 h. The formation of (Ni, Cu)₃Sn4 and Cu₃Sn underneath the IMC layer played a role in reducing the shear strength of joining. Overall, water cooling was reported to provide higher shear strength of solder joint compared to air cooling medium.

The shear strength when using EN-Boron as the surface finish is comparable to the surface finish conventionally used.