Reliability of LTCC using Electroless Nickel Immersion Gold (ENIG) Plating Technology

Abstract

In an effort to address the impact of rising gold costs on the fabrication expense for high frequency circuits, and maintain circuit quality and reliability, the DuPont™ GreenTape™ 9K7 low temperature co-fired ceramic materials (LTCC) with top silver conductors have been evaluated using electroless nickel immersion gold (ENIG) plating. Results comparable to the quality of efficiency and reliability of traditional gold conductor systems were achieved at reduced costs. LTCC coupons produced using the ENIG process were tested and compared to standard specifications for coupons with gold printed conductors. The test methods used include wire bond and adhesion pull tests on eight layer coupons, and MIL-STD-883 [1] temperature cycle testing on a layered high frequency test pattern. The reliability of the high frequency characteristics including insertion loss and return loss measurements were evaluated periodically throughout 1090 temperature cycles. Adequate results for most applications were obtained using the ENIG plated system compared to gold printed coupons. In an attempt to better understand the boundaries of the ENIG process on 9K7 LTCC and its use as an alternative for gold conductor systems; future testing will explore the effects of additional environmental testing. The added tests will include thermal shock, and temperature and humidity cycling on 9K7 LTCC test coupons. The testing will be conducted in accordance with MIL-STD-883 as a benchmark, and also evaluate wire bond and adhesion properties. This paper will report the reliability test results on plated GreenTape™ 9K7 LTCC systems after exposure to the stated environmental conditions.