Measurement of Fracture Strength of Ultra-thin Silicon Chip and Adhesive Fracture Energy

Abstract

The integrated ultra-thin silicon-based chip (<50 μm-thick) is increasingly demanded in flexible electronics due to the excellent electronic and mechanical performance. The successful chip peeling-off by needle ejecting requires that the maximum tensile stress of the chip layer should be smaller than the fracture strength, and the energy release rate (ERR) of interfacial peeling should exceed the adhesive fracture energy. The estimation of the fracture strength and the adhesive fracture energy is essential for establishing the chip peelability. However, classical linear theory on the three-point bending test is not enough to accommodate the geometric nonlinearity of ultra-thin silicon chip, and a detailed experimental determination of the adhesive fracture energy considering different peel parameters is still lacked. This chapter is organized as two parts. The fracture strength of ultra-thin silicon chip was first estimated using the three-point bending test based on the geometric large deformation and nonlinear theory. Experimental results showed that the nonlinear evaluation allowed a more comprehensive understanding of the effect of the silicon sample thickness. The peeling behavior of the adhesive tape from the adherend was also investigated. Taking into account the extensibility of the adhesive tape, the adhesive fracture energy was estimated using a novel angle/speed controlled peeling platform. Test results showed that the detachment behavior between the adhesive tape and adherend relied mostly on the peel angle and the peel speed, and more energy was required under a higher peel speed to achieve a successful chip peeling-off.