The rapid advancement of microelectronic packaging has created a critical need for lead-free solder joints with enhanced mechanical and thermal reliability. This study introduces a novel approach to improve Sn-3.0Ag-0.5Cu (SAC 305) solder joints by incorporating Sn-decorated multiwalled carbon nanotubes (MWCNTs). To address the poor wettability and agglomeration of carbon nanotubes in molten solder, MWCNTs were functionalized and uniformly coated with ~70 nm Sn nanoparticles via electroless plating. Soldering was conducted using intense pulsed light (IPL), a rapid, energy-efficient heat source, and was compared with conventional reflow soldering. The study systematically investigated the influence of MWCNT content (0, 0.05, 0.1, and 0.2 wt.%) and IPL soldering conditions with pulse numbers: 27–36 for shear tests, and 30–42 for drop impact tests. IPL processing produced thinner Cu₆Sn₅ IMC layers than reflow soldering due to its shorter duration. The composite solder with 0.1 wt.% Sn-decorated MWCNTs achieved the highest density, superior thermal dissipation in LED packages, and maximum shear strength and drop impact resistance. These results demonstrate that optimizing Sn-MWCNT content, especially at 0.1 wt.%, and precisely controlling IPL energy can yield highly reliable, mechanically robust, and thermally efficient lead-free solder joints for advanced electronic packaging.

The adhesive bonding of aluminum with other materials is widely used in the aerospace, marine, automotive and railroad industries that require lightweight materials. Adhesive bonding has the advantages of reduced corrosion, stress concentration, and cost effectiveness. To improve bonding strength and performance, we examined the use of ascorbic acid (vitamin C), which is a water-soluble compound and a natural reducing agent. Owing to its reducing power and acidity, ascorbic acid allows the Al etching process to proceed efficiently to increase the surface roughness and prevent Al oxidation. In addition, this study used an eco-friendly technique of simply immersing aluminum substrates in an ascorbic acid solution with sodium chloride. The surface free energy was evaluated using the sessile drop method and calculated using the Owens–Wendt–Rabel and Kaelble method. Confocal microscope was used to investigate the roughness of the surface, and the functional groups of Al surface were analyzed by X-ray photoelectron spectroscopy. The bonding strength was measured using the single-lap joint shear test. Compared to aluminum without treatment, the bonding strength of a treated AA 6061 was enhanced by 58.6%.