Highly compliant bonding material and structure for micro- and opto-electronic applications

Based on the developed analytical stress model, we demonstrate that the employment of highly compliant materials and structures as bonding layers in bi-material assemblies (joints) can lead to a significant stress relief. The model indicates that the interfacial shearing stress in an adhesively bonded or a soldered assembly is inversely proportional to the square root of the interfacial compliance, and that in "conventional" bi-material assemblies (characterized by moderately compliant bonding layers), the interfacial compliance is due to both the bonding layer and the bonded components. However, in assemblies with highly compliant bonds, it is the bonding material only that provides the high and favorable interfacial compliance. We suggest that an appropriate nano-wire array (NWA) fabricated on one or both bonded components be used as a suitable compliant bond. Based on the developed predictive model, we demonstrate that the application of the NWA as a compliant attachment can lead to a significant, about two orders of magnitude, increase in the interfacial compliance. This leads to a reduction in the interfacial shearing stress of about an order of magnitude (compared to the bonded joints using "conventional" adhesives or solders). We suggest that one of the modifications of the newly developed nano-particle material (NPM) be used in addition to, or instead of a NWA, to increase the compliance of the bonding layer. A suitable combination of both the NWA and NPM could be employed to provide a highly compliant and a highly reliable bonding material and structure. In this case the NPM is used as an embedding material for the NWA. Since the NPM has extraordinary mechanical and environmental properties, and, in combination with the appropriate NWA, can make an extremely highly compliant and a highly reliable bond, we expect that the NPM and NWA, used independently or in combination, find a wide application in various bi- and multi-material assemblies employed in micro- and optoelectronics, and well beyond the "high-tech" area