Excimer Laser Structuring of Epoxy Resin Layers for MCM‐L Applications

Multichip module packaging enables a significant increase of interconnect densities and performance of electronic systems. Multichip module technology based on laminate materials (MCM‐L) is attractive due to low cost and use of the standard equipment used by PCB manufacturers. The most limiting factor for higher wiring densities in PCB technology is the mechanical drilling of plated‐through holes. Using 0.3 mm drill diameters, 0.5 mm land diameters are required, which limit the area for routing of tracks. Therefore, alternative dielectric materials, which can be structured photolithograpically, by plasma etching or laser drilling, are very attractive for MCM‐L technology. In this paper an epoxy resin layer, commercially available as a solder mask, is investigated as an interdielectric layer. Via hole drilling is investigated using an excimer laser. To show process feasibility, a two‐layer wiring system is fabricated using the excimer laser structured epoxy resin as an interdielectric layer on conventional epoxy board (FR‐4).