Effect of micro-nanostructured Cu coating on the growth and mechanical behavior of Cu-Sn intermetallic compound joints

Micro-nanostructured Cu coatings were created on Cu substrates by direct current electrodeposition, and Cu-Sn micro solder joints were made using the transient liquid phase bonding technique. The surface characteristics of the coatings and the fracture morphology of the solder joints were analyzed employing scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, a contact angle measurement instrument, and a white light interferometer. The results indicated that the wetting angle of liquid Sn on the Cu substrate with micro-nanostructured Cu coating was reduced by 54 %, which enhanced the contact area between Sn and Cu, thereby promoting the growth of the intermetallic compound layer. Shear strength tests revealed that the highest shear strength of joints with micro-nanostructured Cu coatings was achieved after heating at 250 degrees C under 0.07 MPa for 7 minutes, reaching up to 41.17 MPa. Furthermore, the influence of surface micro-nanostructured Cu coatings on the growth behavior of interfacial intermetallic compounds was investigated. It was observed that incorporating micro-nanostructured Cu coatings decreased the growth time exponent of IMC from 0.478 to 0.279, resulting in a shift in growth mechanism from volume diffusion-controlled to grain boundary diffusion- controlled. This change significantly accelerated the formation of all-IMC joints.