The Limitations of High Speed, High Density PWB Substrates

This paper looks at the implications of increases in system speed and density for the interconnection system, noting particularly the increased requirements placed on the substrate and tracking system. It reviews the properties required of substrates and the limitations derived from the materials used and the processes needed to put tracks on them. Those areas where these requirements are in conflict are highlighted, including such low technology problems as the limited size availability of substrate prepregs which may limit the tracking density achievable on the newer, more advanced low dielectric materials. Some limitations and trade‐offs are identified.