Improved chip & component encapsulation by dedicated diffusion barriers to reduce corrosion sensitivity in biological and humid environments

In order to develop an advanced polymer based package technology to obtain small and flexible medical implants, diffusion barriers are essential to protect electronic chips and components for corrosion caused by leaching of body fluids. These barriers need also to stop diffusion of harmful products such as Cu from the device into the body. Furthermore, the barrier layers need to be biocompatible, biostable, compatible with all process steps of the package fabrication and sterilization. Parylene is under investigation as candidate barrier material. WVTR tests are performed to characterize diffusion of water through the Parylene layer. Adhesion tests of Parylene-C on various substrates are performed and if needed adhesion promotion treatments are optimized, since good adhesion is crucial for corrosion prevention. Dedicated corrosion tests have shown that 5um Parylene-C is protecting Cu lines for corrosion at 70°C for at least 170 hours, more testing needs to be performed. Cell culture test have shown that Cu diffusion is not sufficiently stopped by 5um Parylene-C or -N, a thicker Parylene layer or a combination with other barriers might be essential. Also dedicated cell culture protocols with non-adherent cell types will have to be developed to perform reliable tests on these hydrophobic and cytophobic barrier layers.