Process for manufacture of thick film hydrogen sensors

DETAILED DESCRIPTION Accordingly, is an object of the present invention to provide a new and improved system for thick film production of palladium hydrogen sensing elements with enhanced accuracy and repeatability.
It is a further object of this invention that the sensors produced by the present invention process are suitable to detect hydrogen concentrations of about 1% hydrogen in air.
It is a further object of this invention that the yield, accuracy, and repeatability of the process are enhanced so that the resulting dependability of the sensors involved is maxi maximized.
The present invention process to form sensors of the present invention is a thick film process comprising printing a sensor conductor paste comprised of palladium in a suitable binder and carrier onto an essentially inert, electrically nonconductive substrate in a pattern to form at least two electrical networks, firing the substrate and sensor conductor paste at a first peak temperature and for a first duration, which temperature and duration are sufficient to firmly adhere said electrical network to said substrate, printing a passivating material which is essentially inert, electrically insulating, and hydrogen impermeable onto at least one, but less than all of the electrical networks, and firing the substrate and passivating material at a second peak temperature and for a second duration, which second temperature and second duration are sufficient to firmly adhere the passivating material to said electrical networks, without forming bubbles, voids or cracks, the second temperature being less than or equal to said first temperature.