Multichip module substrate and method of manufacture thereof

In accordance with the present invention, an MCM substrate product is manufactured in an additive process using multiple layers of a fluoropolymer composite material and copper. The copper layers are plated, and the fluoropolymer composite layers are laminated. A seeding process promotes reliable bonding between the fluoropolymer composite material and the plated copper. The use of the filled fluoropolymeric composite eliminates the need for a barrier metal layer between the insulation and the conductors. The MCM substrate device of the present invention may have multiple metal layer and multiple dielectric layers; four or five, or more, of each in a single structure would be easily achieved and is typical. The structure would include lead lines in separate mutually orthogonal planes (sometimes referred to as "x" and "y" lead lines) (84, 67) sandwiched between ground and power voltage planes of copper. The MCM substrate device of the present invention also has solid copper vias (20, 22), which may be used either as electrical interconnection between layers of the MCM substrate and/or to the I/C's to be packaged in the module, or as thermal vias (67, 67a) for heat conduction for thermal management. The manufacturing process of the present invention makes it possible to start or stop any via in any layer of the device. Further in accordance with the present invention, the uppermost layer of the MCM substrate structure (on which the I/C's would be mounted) may be rigidized to improve wire bonding and handling capabilities and characteristics of the MCM substrate structure. The rigidized upper layer is in place of a fluoropolymer layer; and preferably the rigidized upper layer is a cyanate ester/silica layer.