To meet the increasing demand for lower cost, reliable circuits, a new barrier transition conductor was developed for interconnecting internal (buried) silver conductors to surface gold conductors in multilayer hybrids and ceramic multichip modules (MCM-Cs). The new material allows fabrication of microcircuits with internal silver conductors for low cost and high conductivity, and top layer gold conductors for wire bonding or TAB attachment. The transition material overcomes the reliability and refire problems associated with directly connecting internal silver to top gold conductors. Without the transition barrier material, metal interdiffusion, with a greater diffusion rate for silver into gold, generates Kirkendall voids which can cause opens. A novel conductor which is an effective barrier to silver diffusion is described in this paper. Materials used as a transition via fill or as an internal transition capture pad have been demonstrated for thick film multilayer and LTCC tape applications. The system of inner silver, transition material, and top gold provides extremely good yields and reliability. Thick film circuits with the transition via fill are reliable after 10 refires and 1000 thermal cycles from -50 °C to +150 °C. LTCC circuits with the transition capture pad are reliable after 15 refires and 1000 hours aging at 85 °C/85% relative humidity. Wire bond pads over vias maintain good adhesion and bondability.
|Number of pages||6|
|Journal||International Journal of Microcircuits and Electronic Packaging|
|State||Published - 1 Sep 1995|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Safety, Risk, Reliability and Quality
- Electrical and Electronic Engineering