As semiconductor devices evolve, so do the packages that house them an
d the printed circuit boards (PCBs) that support and interconnect them
to form systems. The higher numbers of connections per device are squ
eezed into smaller pitches, both on the package and in the PCB, to fit
into the available space and to improve electrical performance. Ultim
ately, individual packages are not required for each device. This pape
r describes substrates available from GEC-Marconi Research Centre suit
able for carrying and interconnecting packaged or unpackaged devices,
or a combination of them, manufactured using techniques and materials
familiar to the PCB industry. Multi-chip modules using lamination tech
niques to make the substrates (MCM-Ls) are a natural extension of prin
ted circuit technology to meet the ever increasing demands of system i
ntegration and density. As with other forms of multi-chip module (MCM)
, the interconnection density is so high that most circuits need very
few signal layers - often only two. The substrate can also incorporate
layers to control thermal expansion and extract heat. MCM-L substrate
s are extraordinarily versatile; they can accommodate packaged ICs (fo
r example, fine-pitch surface mount technology), unpackaged ICs, other
MCMs, and odd-form components. These ultra-fine feature substrates ca
n provide solutions for a wide range of sizes, complexities, performan
ce and market sectors at competitive prices.