Method for electrically and mechanically connecting at least two conductive layers

A method for electrically and mechanically connecting at least two conductive layers, each conductive layer having a conductive pattern and a plurality of contact pads defined thereon, and at least one contact pad being designated an interconnecting pad, each interconnecting pad on a conductive layer having a corresponding interconnecting pad on another conductive layer, each conductive layer affixed to an insulating substrate, at least one insulating substrate having a second conductive layer affixed to another surface thereof, the conductive layers affixed to the at least one insulating substrate being interconnected by means of plated through holes, the method comprising the steps of:

• layering an electrically interconnecting adhesive over a portion of one of the at least two conductive layers to form an interconnecting layer, the interconnecting adhesive comprising a non-conductive thermosetting adhesive having a plurality of deformable conductive metallic particles dispersed substantially uniformly throughout the non-conductive adhesive such that each particle is electrically insulated from substantially every other particle, the particles and the insulating substrate having substantially similar coefficients of thermal expansion, the particles having a maximum diameter that is about 90-110% of a distance between the conductive layers;
• aligning the other of the at least two conductive layers to form an uncured assembly, such that the interconnecting layer is interposed between the at least two conductive layers with the interconnecting pads on each conductive layer aligned with their corresponding pads on the other conductive layer;
• and
• subjecting the uncured assembly to an elevated temperature and a clamping pressure to form an interconnected assembly, such that the interconnecting layer becomes conductive across a thickness thereof and non-conductive throughout a coplanar direction thereof, and such that the two conductive layers are mechanically connected in a superposed relationship with a connected distance therebetween and corresponding interconnecting pads on the two conductive layers are electrically connected.