High-Density Embedded Electronics in Textiles with 3D Flex Package Transfer

Hybrid device-flex-textile interconnect and integration technologies were developed to realize smart wireless sensing systems. Test vehicles were fabricated to emulate high-density 3D flex packages in textiles. Representative test chips were assembled onto patterned copper traces on Liquid Crystal Polymer (LCP) flex substrates. These flex circuits were embedded into textiles with deformable silver adhesive interconnects. Fluoroelastomers were utilized as encapsulants to suppress moisture permeation and interaction with the embedded electronics. Contact resistances of the flex-to-textile and device-to-flex interconnects were investigated after fabrication, flexing, thermal and humidity treatments. DC resistances were extracted through Kelvin Probe structures and their stability during thermal and humidity exposure conditions were investigated. In addition to DC resistance, RF loss performance was also improved when we use silver adhesive interconnects to replace bulky and inflexible solder interconnects.