Abstract
This study establishes the polymer-stacking and metal-electroplating processes on Si-substrate to implement a flexible and transparent substrate with alignment mesa, double-side electrical routing, and distributed 3D through-hole-vias. This process is especially useful for 3D integration of micro optical components on flexible substrate. The integrated chips can be further protected and sealed by an additional parylene coating. More micro-optical components can also be vertically integrated by additional polymer molding. To demonstrate the feasibility of this approach, LED chips are bonded and sealed in flexible substrate, and the polymer microlens is further integrated with the lighting chips using molding process. The lighting of packaged LED chips is demonstrated in both air and water. In application, the study implemented the flexible-transparent substrate with 3D electrical-routings, and the assembly and integration of vertical/lateral LED chips and micro-lens was also demonstrated. The bonding strength was tested among LED-chip (Au)/Sn-paste/Ni-vias by using commercial bond-tester. The bonding strength of LED-chip and flexible substrate was 158 mg. The bulge test results show the adhesion force of Ni-vias and flexible-substrate is significantly improved by shape/area designs. Moreover, LED light-emission tests successfully demonstrate the feasibility of electrical-routings and through-hole vias of flexible substrate after bending. LED light-emission test in water further demonstrates the successfully sealing of devices. Finally, the study successful integrated packaged LED chips with PDMS-lens for light-emission testing.