Ceramic packages and substrates prepared by electroless Ni-Au process

An electroless nickel-gold plating process for thin and thick film high-density ceramic packages and substrates was investigated. A highly selective electroless nickel process using immersion gold activation was developed. Activation for the electroless nickel plating using an immersion gold solution improved the deposition selectivity on conductor patterns whose width is narrower than 100 μm. The thickness of the electroless nickel must be over 4.5 μm to prevent heat discoloration of the gold surface. The dipping time of immersion gold plating on nickel must be shorter than 4 min to obtain good adhesion. An electroless gold plating solution and process were developed. The gold solution was basically composed of KAu(CN)₂ DMAB, and Sorensen buffer solution. Stabilizer masks nickel contamination and prevents the solution from decomposition. This solution has improved the following properties: poor adhesion to electroless nickel, low deposition rate, poor selectivity, short working lives, and bath instability. This electroless process makes it possible to match the characteristic impedance of signal lines on packages and substrates with the designed value