Maskmaterial för djupets avborosilikatglas
The objective of this thesis was to establish a good way of wet etching a borosilicate glass named Borofloat 33 for bonding microfluidic devices. This was accomplished by wet etching with different materials as masking layers and evaluating them in different concentrations of the main etchant, which is the hydrofluoric acid (HF). The best results were obtained with a mask consisting of evaporated chromium and gold, where gold was sequentially deposited to minimize the occurrence of pinholes generated in the glass substrate. The Cr/Au mask was successfully able to protect the glass, while etching to the predefined depth of 90 micrometer, and at the same time keeping the amount of pinholes at an acceptable level. Deep and precise etching in Borofloat was possible due to an increasing knowledge about how different masking materials behave in different etching solutions as well as how the etch rate in Borofloat depends on the HF concentration. Static simulations were carried out in order to determine a beneficial design of processed micro channels for resisting internal pressure as well as optical inspection of the fluids inside the channels.
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