A novel microscale selective laser sintering (μ-SLS) process for the fabrication of microelectronic parts

Abstract

One of the biggest challenges in microscale additive manufacturing is the production of three-dimensional, microscale metal parts with a high enough throughput to be relevant for commercial applications. This paper presents a new microscale additive manufacturing process called microscale selective laser sintering (μ-SLS) that can produce true 3D metal parts with sub-5\u2009μm resolution and a throughput of greater than 60\u2009mm3/hour. In μ-SLS, a layer of metal nanoparticle ink is first coated onto a substrate using a slot die coating system. The ink is then dried to produce a uniform nanoparticle layer. Next, the substrate is precisely positioned under an optical subsystem using a set of coarse and fine nanopositioning stages. In the optical subsystem, laser light that has been patterned using a digital micromirror array is used to heat and sinter the nanoparticles into the desired patterns. This set of steps is then repeated to build up each layer of the 3D part in the μ-SLS system. Overall, this new technology offers the potential to overcome many of the current limitations in microscale additive manufacturing of metals and become an important process in microelectronics packaging applications. A new 3D fabrication process could greatly accelerate the manufacture of finely-detailed microelectronic devices for a plethora of applications. Additive manufacturing strategies such as 3D printing are becoming commonplace in many industries, but these are generally ill-suited for producing the tiny metallic structures required for microelectronic devices. Researchers led by Michael Cullinan at the University of Texas at Austin have now developed a powerful process for 3D printing metal nanoparticles to generate precision structures with resolution below 5 microns. The authors demonstrate their microscale selective laser sintering (μ-SLS) technique in the context of producing lightweight lattice structures and metallic pillars that can serve as next-generation interconnects for microelectronics. Future iterations of μ-SLS could tackle even more aspects of the device fabrication process, or facilitate the production of specialized materials for plasmonics, microfluidics or other applications.