Abstract
This work evaluates an in-mold spraying process for the production of injection molded plastic parts with integrated Cu pathways. Prior to injection, Cu is cold sprayed on mold insert surfaces, forming a metal layer that is subsequently transferred to the plastic part. The success of the process hinges on the bond strength of the Cu to the mold, which depends on surface conditions, mold material, and spray parameters. In this study, Cu powder is cold sprayed on carbon tool steel coupons prepared by grit blasting using different grit sizes. The coupons were sprayed at longer stand-off distances using lower gas flow rates than usual to reduce particle impact velocity and thus bonding strength. Coating cross-sections were examined and surface roughness, bond strength, and residual stress were measured. The results show that bond strength varies almost linearly with root-mean-square surface roughness, R∆q, and that reducing line distance or scanning step size can improve the transferability of the Cu layer.
