Electroless Nickel and Au Plated Silver LTCC Solution for Advanced Hermetic Packages

Abstract

Low Temperature Cofired Ceramics (LTCC) for military and medical applications requires high reliability interconnects that have been traditionally met using cermet Au metallization But due to the rising cost of Au, it has become cost prohibitive in some applications to tier 1 defense contractors. The utilization of Silver cermet metallization reduces the costs of LTCC up to 50%, however requires proper coverage using either a Mixed Metal, or a Nickel (Ni) and Au (Au) Plated surface. Efforts to date on mixed metal solutions with resistive PdAg or PtAg transitions without Kirkendahl voiding have been unreliable for systems requiring post fire metallizations due to voiding at the silver to Au transition. Anaren Ceramics has developed an all Silver LTCC solution that utilizes Electroless Ni and Au (ENiG) plating, lowering the cost of entry for LTCC users up to 50%. Anaren Ceramics has developed a proprietary plating process for the DuPont 951 LTCC [1] tape material and silver metallization which meet the needs of high reliability, high cavity count LTCC packages that are fully solderable using PbSn, or AuSn materials for hermetic applications. The Anaren Ceramics solution meets Mil Std 883 test requirements and this paper will discuss the test results for plated LTCC substrates and AuSn brazed LTCC assemblies that include 350°C Bake Test, Tape Peel, X Ray Inspection, Open Header Leak Rate, Moisture under Bias, Salt Atmosphere, Die Shear, and Wire Bond.