A mixed solder grid array and peripheral leaded MCM package

A low-cost multichip module (MCM) package has been developed to house a 40 MHz digital signal processor static RAM chipset. A design and prototype effort was undertaken to design, procure, assemble, and test these modules. The design constraint was to merge a state-of-the-art high-density interconnect substrate with conventional chip assembly techniques while meeting a prespecified cost goal. The package concept is that of an MCM-L substrate with more than one chip, where the chips are connected to the substrate by means of conventional gold wire bonding and the part is overmolded. A mix of solder balls and peripheral leads is used to interface to the package. The mix of package connectorization approaches is used to increase the routing resources, decouple the signal and power/ground distribution, and provide good thermal coupling between the package and the next level board. Issues such as board layout, component design and fabrication, board assembly, and first-order cost models are discussed