Method for making multichip module substrates by encapsulating electrical conductors and filling gaps

A method for generating a substrate for a multi-chip module, said method comprising the steps of:

• tensioning a dielectric sheet defining a surface, to provide a measure of rigidity to said surface;
• applying to said surface of said dielectric sheet, in a predetermined pattern, one or more electrical conductors having a predetermined thickness;
• applying encapsulating material to said surface of said dielectric sheet in a thickness sufficient to encapsulate said electrical conductors to thereby generate a rigid substrate element;
• fabricating through apertures in said rigid substrate element at predetermined locations at which chips are to be placed on said multi-chip module, with each of said through apertures having dimensions larger than those of the chip which will occupy the aperture;
• placing chips on a second dielectric substrate at locations registered with said through apertures, with electrical interconnects of said chips facing in a particular direction;
• affixing said rigid substrate element to said second dielectric sheet with said chips extending into said through apertures, whereby a gap lies between said semiconductor chips and their associated apertures;
• filling said gaps with a hardenable dielectric material;
• and
• applying a flexible multilayer dielectric interconnection sheet over at least said electrical interconnects of said chips, and making connections between at least some of the interconnects of said interconnection layer and some of said electrical interconnects of said chips.