odule or M
odule) A chip package that contains several bare die mounted close together on a substrate (base). The short tracks between the chips increase performance and eliminate much of the noise that external tracks between individual chip packages can pick up. MCM allows CMOS and bipolar technologies to be used in the same package.
An MCM is also an option for fabricating large chips with several ancillary processing elements. Larger die tend to fail more in the semiconductor fab than small chips and wind up costing more. By mixing and matching a number of bare die on the same substrate, a greater variety of comprehensive systems can be manufactured at less cost.
MCMs are classified by substrate: an MCM-C uses a ceramic substrate with wire bonding between the chips. MCM-D uses a dielectric layer over a ceramic, glass or metal substrate, and thin film interconnects are created on the dielectric layer. MCM-S uses a silicon substrate with tracks created in the silicon like regular ICs. Transistors can also be formed in the substrate. MCM-L uses a laminated circuit board with up to 25 tracking layers. MCM-L evolved into the multichip module (see MCP
MCMs followed "hybrid microcircuits," which used a ceramic base, but MCMs typically have higher component and tracking densities. See system in package
, chip package