A new strategy for spatter mitigation in L-PBF with application in direct manufacturing on multimaterial substrates

Spatter ejections in Laser Powder Bed Fusion (L-PBF) are recognized among the main drivers of process instability and defect formation. Their occurrence and dynamics are strongly affected by local melting conditions, as insufficient heat dissipation and variations in the thermal regime can trigger intense and localized spattering phenomena. Such conditions can be exacerbated in multi-material L-PBF, where variations in the composition of surrounding and underneath material may alter the heat dissipation, as well as in emerging applications involving direct manufacturing on pre-existing substrates with diminished heat transfer compared to conventional baseplates. Despite extensive studies on spatter formation in L-PBF, their behavior under such challenging conditions remains poorly explored, and effective mitigation strategies are still lacking. This paper addresses this gap by presenting a new strategy based on local pre-sintering to reduce spatter ejections in L-PBF with minimal increase in production time. The effectiveness of the method is assessed under a particularly challenging and novel scenario, in which L-PBF is used to directly manufacture cooling structures on electronic substrates composed of thin layers of copper and ceramic. The limited heat dissipation associated with this configuration exacerbates intense spattering and localized heat accumulation. The study demonstrates that the proposed approach effectively stabilizes both phenomena, enabling the industrial development of L-PBF on electronic substrates. The generality of the method, however, allows it to be extended to applications where material transitions and complex thermal interactions govern spatter formation.