Adhesion Strength of PDMS to Polyimide Bonding with Thin-film Silicon Dioxide

Polyimide and PDMS are the most common materials used in the packaging of flexible electronics. Silicon dioxide being photolithographically patternable, can be used to selectively bond polyimide (PI) to PDMS to realize flexible microsystems integrating fluidic and electronic components. In this work, we characterize the plasma bond strength of polyimide (Kapton) to PDMS with thin-film SiO2 as an intermediate bonding layer. Peel strengths of samples prepared with different types of deposition methods - sputtering, plasma-enhanced chemical vapor deposition (PECVD), and atomic layer deposition (ALD) were evaluated. The measured forces (normalized to the width of the bonded area), required to separate the PDMS and Kapton films, either due to adhesive or cohesive failures, were 174-860 N/m, 79-179 N/m, and 7-12 N/m for samples bonded with sputtered, PECVD and ALD oxide, respectively. The strength of the sputtered oxide bond is comparable to the strength of the best chemical adhesive method available.