High frequency/high density build-up boards with benzocyclobutene [BCB] polymer coated Cu foil

Benzocyclobutene resin has been modified to allow fabrication of polymer coated Cu foil. New formulations show improved flexibility, flaking resistance, low tackiness, and better resin flow control during hot pressing, while keeping BCB's inherent advantages such as low moisture pick-up, high heat stability and excellent dielectric properties. BCB coated Cu foil has been laminated on FR-4 board by conventional hot press processing. Relevant build-up board processes such as laser via formation, electroless plating and drill through holes were accomplished. Test boards with a BCB build-up layer per side were evaluated and excellent reliabilities and excellent electrical performance was confirmed.