Multi-Chip-Module Interconnections by Laser Direct Writing

ABSTRACTA very flexible maskless technique for thin film hybrid formation has been developed. Lay outs are transferred directly from work stations to laser controls. Openings in ceramic substrates are achieved through laser cutting, and chips are embedded to give a common chip-to-substrate surface, flat to within 2 μm. Dielectric layers of polyimide are formed by spin on techniques and are then laser structured for via hole formation.Interconnections of the embedded chips are generated by laser direct writing of thin copper lines from copper formate, followed by chemical copper deposition. Chemical pretreatments of the aluminum contact pads allow for reasonable chip contacting with these methods. Electrical measurements on the dc line conductivity and the high frequency behaviour of these interconnections have also been performed.