Solderability of additively manufactured pure copper and the effect of surface modification.

Additive manufacturing of copper enables enhanced design freedom which allows for improved performance of components in thermal management and electrical applications. Joining via soldering provides ideal electrical and thermal connections, but the solderability of complex additively manufactured surfaces is poorly understood. In the present work, the solderability of nominally pure copper coupons manufactured by three additive manufacturing techniques (laser powder bed fusion, laser engineered net shaping, and bound powder extrusion) was experimentally assessed using the wetting balance technique and pin pull testing. Coupons produced by each method were tested as built and after surface modification by dry electropolishing. Contact angles and wetting times were calculated from wettability testing. Peak tensile loads required to remove pins soldered to coupons were also recorded for each surface condition. The dipped coupons and solder joint fracture surfaces were examined with optical and scanning electron microscopes. It was found that nonuniform wetting and excessive wicking of solder can result in weak joints, and surface modification positively affected overall solderability in all cases. All surfaces were shown to be wettable, but bound powder extrusion was found to produce the most solderable copper surfaces among the additive manufacturing methods tested. [ABSTRACT FROM AUTHOR]