Still Good Bang ForThe Buck

摘要

I often hear the questions: When will copper reach its limits? When will it be necessary to switch to optical interconnects? Actually, we should be asking when FR-4 will reach its limits, and what will we do about it? The answer is, pretty soon. Fortunately a new generation of materials with an attractive price/performance ratio is ready to give FR-4 a "mid-life kick." The limitations of FR-4 are most noticeable in high-speed serial links with data rates in excess of 2.5 Gbps and in backplane traces longer than 12 inches. As a signal propagates down a transmission line built with FR-4 laminate, the higher-frequency components will be attenuated more than the lower-frequency components, due to the dielectric loss of the material.