(PWB) technology to form copper conductors on a plastic laminated-base dielectric [7]. The advantages of MCM-L include low cost and small size compared to conventional printed wiring board. However, the disadvantages include low routing density, large vias, poor thermal conductivity through the substrate and a large thermal expansion coefficient compared to silicon. Some of the basic parameters for an MCM-L are listed in Table 
.
Over the past years, review articles on MCM technology have painted MCM-L as the ideal low-cost MCM technology for many applications. This perception has been widely accepted and shared within the industry. However, some have portrayed MCM-D as the technology with the most promise, greatest ability to handle high clock frequencies, and long term choice for high performance applications. Even though MCM-D does not provide as many interconnection layers as other MCM technologies, it could still supersede the level of interconnection density provided by the other MCM technologies. This can be explained by understanding the term interconnection density, which is the ratio of the number of layers in a technology to the average wire pitch in that technology. Therefore, the small number of layers in MCM-D is compensated for by the very small wire pitch in that technology.
For cost effectiveness reasons, some of the above technologies may be combined. For example an MCM substrate can be a deposited dielectric substrate on a cofired ceramic substrate - this is referred to as MCM-D/C. This combination provides a single substrate that functions as the signal interconnect, substrate base, package body and module level I/O connections.