Method to make a multilayer circuit board with intermetallic compound and related circuit boards

A method of making a multilayer circuit board from a plurality of circuit board layers, each comprising a thermoplastic dielectric layer and conductive traces thereon comprising copper material, the method comprising:

• forming a through-via in a first circuit board layer;
• plating the through-via with the copper material;
• coating a tin material onto the copper material of the first circuit board layer, the plated through-via, and the copper material of a second circuit board layer;
• aligning the first and second circuit board layers together so that the plated through-via of the first circuit board layer is adjacent a feature on the second circuit board layer;
• and
• heating and pressing the aligned first and second circuit board layers so as to laminate the thermoplastic dielectric layers together and form an intermetallic copper-tin compound bonding adjacent metal portions together and defining electrical connection paths of the multilayer circuit board.

A multilayer circuit board comprising:

• a plurality of circuit board layers, each comprising a dielectric layer and conductive traces thereon comprising a first metal;
• a first circuit board layer of said plurality thereof having a through-via therein;
• a plating in said through-via comprising the first metal;
• said first circuit board layer and a second circuit board layer of said plurality thereof being relatively aligned so that said through-via of said first circuit board layer is adjacent a feature on said second circuit board layer, and laminated together;
• and
• adjacent portions of said conductive traces being joined together by an intermetallic compound formed between the first metal and a second metal.