MCM prototyping using overlay interconnect process

The construction of complex multichip modules requires a means of evaluating the prototype for correct operation and characterization. A flexible prototype method is described, using the overlay interconnect approach, for probing and verification. The overlay process builds the interconnect over the top of a bare die. An overview of the process is given. The overlay interconnect method has several major areas of flexibility that can be used to facilitate the prototyping of MCMs. The ability to access pads, either on the first layer for die verification or on the top layer for control and observation, brings back part of the access for test that was lost in the size reduction. The ability to use the pads to test a partitioned design and then add the final interconnect layer allows current designs to make the transition more easily to the MCM format. Many of the advantages of using the overlay process for prototyping are outlined