Solderability of Additively Manufactured Copper Surfaces

Abstract

As additive manufacturing technology for copper rapidly evolves, the likelihood for downstream joining like soldering and brazing exists. A solderability study was performed to assess process fundamentals over a variety of AM approaches. The solderability of 7 different copper (Cu) surface types were evaluated using the wetting balance technique: 4 Cu coatings (CP-007 and CP-008 conductive copper pastes, IMC-4118 conductive laser sinter paste, IMC-2501 copper ink), 2 laser processed Cu surfaces, and 1 bulk additively manufactured (AM) Cu coupon type. Laser processed surfaces were subjected to either circular or linear laser raster patterns. AM coupons were fabricated via a powder-bed laser process. In-situ force measurements were recorded while coupons were dipped into and removed from a 63Sn-37Pb (SnPb) or 96.4Sn-3.0Ag-0.6Cu (SAC305) solder bath, allowing contact angles and surface energies to be calculated. Meniscus height values were also measured. Surfaces were characterized before and after dipping via optical and electron microscopy. Results conclusively indicated that although all samples were intended to represent pure Cu, wettability was found to be strongly dependent on surface type with several samples exhibiting no wetting. Although the CP-007 paste performed the best of any non-traditional surface, all nontraditional surfaces saw signifi cant wettability improvements with aggressive cleaning via HCl etching.