Laser programmable multichip module using vertical make-link

This paper presents a new design of laser-programmable substrate for multichip module (LPMCM) using a novel vertical make-link structure. The vertical make-link results from the cracked dielectric formed by the thermal expansion of metal from a laser energy and the molten metal filing on the crack when a laser pulse with appropriate parameters is directed to the link region. These connections are utilized for the patterning of wiring connections between pads on a LPMCM substrate. In order to improve the resistance and reliability of the link, Blech effect in lower metal line and multiple link structures have been considered and designed into the link region. After the laser linking process, integrated circuit chips are mounted, circuit side up, on the substrate, and the chip pads are wire-bonded to the substrate pads by thermal compression. Due to the elimination of an entire level of packaging in chip-to chip connection and the fast programmability by laser linking process, this LPMCM substrate will decrease the time and cost for fabrication of MCM which will meet user's needs with sufficient reliability.