Signal Integrity Considerations in High Reliability Design
Over the past several years OEMs, contract manufacturers, PCB fabricators, and material suppliers have been tackling the issues that arose once the European Union passed the RoHS and WEEE legislation. One aspect of the legislation was the restriction of lead from electronics, which subsequently led to changes in assembly processing of PCBs. For a majority of lead-free assembly applications, traditional dicy-cured FR-4 materials have been shown to perform poorly during lead-free assembly or have significantly deteriorated thermal reliability after lead-free assembly. The laminate industry has responded with numerous types of lead-free compatible FR-4 materials based on a phenolic-cured chemistry. These materials have generally been robust during lead-free assembly and demonstrated improved long-term reliability. Although the needs of thermal performance appear to have been met, the impact these new materials have on signal integrity needs further consideration.
05 March 2007