Impact of fiber weaves on 56 Gbps SerDes interface in glass epoxy packages

Some package substrates are composed of glass fiber bundles and epoxy resin which have different electrical properties. These differences result in variations in characteristic impedance and propagation speeds, which may be detrimental at high data rates. The insertion loss (IL), within pair skew and differential to common mode conversion ratio of transmission lines may drastically increase due to the fiber weave effect. Consequently, the link budget of high speed communication channels may be significantly hindered. This paper addresses the problems due to the fiber weave effect and provides mitigation techniques at the package level, particularly for 56 Gbps Serializer/Deserializer (SerDes) interface.