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|Reliability of Au-Ti for High Temperature Termination on Ferrite LTCC Inductors.|
|Keywords: Termination Reliability, Ferrite LTCC Magnetics, Au-Ti|
|While ferrite LTCC inductors and transformers have undergone thermal shock and high temperature aging that focused on stability of electrical characteristics (resistance and inductance), little attention has been paid to termination reliability at high temperatures. Testing has been done on AgPt and AgPd terminations with Ag5Cd95 solder for 2000 hrs and with Pb88Sn10Ag2 solder for 25 hrs; however Ag5Cd95 is unusable in commercial applications due to ROHS restrictions and the high lead content makes Pb88Sn10Ag2 undesirable. Sn96 solder and wire bonding are common attachment methods that have not been vetted. Initial investigations show that high Sn solders may interfere with the bond between the AgPt and AgPd termination materials and the ferrite bulk of the part. An alternative terminal structure for using Sn96 solder is created by electroplating Au and Ni; however, electroplating to ferrite is challenging due to the masking involved. Also, the preferred material for wire bonding is either thick or thin film Au. To this end an alternative sputter deposited Au over Ti termination structure is being investigated. This structure was chosen for its potential to be a lower cost alternative to thickfilm Au and for its potential for simpler manufacturing than electroplating. Tests involved measuring bond strength and resistance after thermal aging and thermal shock. Baseline solder joint pull tests show strength comparable to other termination methods. Some issues with solder wetting has been noted.|
|James Galipeau, Design Engineer