Mechanical qualification and microstructural analysis of alumina produced by material extrusion

Ceramics with their advantageous properties such as high thermal conductivity and electrical insulation are attractive to circuit carrier materials in electronics production. Using material extrusion (MEX-AM) for reasons of flexible manufacturing, this work produces green bodies with low surface roughness, which is necessary for subsequent metalizing to create 3D circuit carriers. Systematic variation of post-treatment profiles (debinding, sintering) leads to different microstructures and thus influences mechanical properties. A comprehensive mechanical qualification of ceramic samples produced with MEX-AM and post-treated differently has been carried out, in which tensile, compressive and flexural strength are analyzed. Using the Anderson Darling Test, it is shown that statistical methods standardized for conventional ceramics are applicable to additively manufactured specimens. A mean bending fracture strength comparable to conventional ceramics could be achieved combining a low heating rate profile for debinding with a two-step sintering (TSS) approach, which resulted in reduction of grain size, as SEM analysis confirmed.