Reliability investigations and improvements of interconnection technologies for the wireless brain-machine interface — ‘BrainCon’

We developed an implantable wireless, hermetically sealed brain-computer interface which is intended to stay functional within the body for decades. Such an ambitious task demands interconnection technologies of high reliability and reproducibility. Investigating soft-soldering, poor wetting behavior of SnAg solder and destructive influences of additional fluxing materials excluded the lead-free compound from our list of suitable sealing and interconnection materials. We developed a robust and reliable welded interconnection method, which allows us to join a multichannel electrode array, even if materials such as MP35N are involved, which are inherently difficult to solder. For solder-sealing of the implant package with leakage rates in the desired range of <;10^-9mbar l s^-1 we found SnPbCu solder to be the best choice.