DETERMINATION OF OPTIMUM SUBSTRATE THICKNESS TO CONTROL THE DISSOLUTION AND INTERFACIAL REACTION BETWEEN SOLDER/SUBSTRATE INTERFACIAL REGIONS FOR ELECTRONIC APPLICATIONS

MECHANICAL ENGINEERING

Soldering materials are back bone of various micro-electronic devices and circuits that provide good electrical continuity, and thermal and mechanical strength to the electrical joints, they join the various integrated circuits. Copper is the most common substrate material to be in direct contact with solders. Therefore, the reaction between Sn and Cu is of great practical interest. Reaction between solid Cu and liquid tin (Sn) was evaluated. All the substrate specimens were immersed (dipped) in molten Sn for duration of 3mins at a speed of 2.5mm/s by using a motor and drawn out from the liquid tin at a speed of 2.5 mm/s. The temperature of liquid Sn maintained was 3500C. An interfacial reaction between solid metals in liquid tin and vice versa was investigated. An increase in intermetallic layer with increasing immersion time was observed. The evolution of microstructure and formation of intermetallic compounds at the interface was assessed using metallurgical microscope.The reliability of solder joints is greatly influenced by the interfacial reaction between the solder and substrate because, during reflow when liquid solder react with the substrate, the intermetallic compounds (IMCs) grow at the interface . These IMCs provide a strong bond to the solder joints.

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