Failure Mechanisms of Pressurized Microchannels, Model, and Experiments

Abstract—Microchannels were created by fusion bonding of a Pyrex cover to a thermally oxidized silicon wafer, which contained anisotropically etched grooves. Such channels are frequently used in microfluidic handling systems, for example, in chemical anal-ysis. Since in some of these labs-on-a-chip, in particular those used in liquid chromatography, the channels are subjected to high pres-sures of up to a few hundred bar, it is important to have informa-tion about the mechanical stability of the channel chip, in partic-ular of the wafer bond involved in it. The latter is the subject of this paper. The maximum pressure that can be applied to several different channel chips was investigated experimentally. In order to find the relation among this maximum pressure, channel geom-etry, materials elasticity, and bond energy, an energy model was developed that is generally applicable to all types of wafer bonds. It was shown that the model is substantiated by the experimental pressure data, from which it could be calculated that the effective bond energy increased from 0.018 to 0.19 J/m2 for an annealing temperature ranging from 310 to 470 C. [517] Index Terms—Bond energy, fusion bonding, microchannels. I