Thick film, LTCC or silicon microhotplate for gas sensor and other applications

This paper presents the development of Pt heater using thick film, LTCC and silicon technologies. Miniaturized alumina hotplate can be used for sintering of metallized semiconductor devices and multiple gas sensor applications. For sensor application, thick film Pt heater was fabricated on back of the alumina substrate of size 5.0 mm x 5.0 mm x 0.6 mm by precise screen printing, drying and firing processes. The Au sensor electrodes were also printed, dried and fired in a similar way. Wire connections were made to the pads of Pt heater and sensor electrodes using parallel gap welder. Pt heater was operated up to about 600 degree celsius by applying electrical power. Wire connections of Ag alloy wire were found to be stable up to 700 degree celsius. For sensing LPG, smoke, this size of heater requires a power of about 2.5 W. Miniaturized alumina hot plate of size 12.5 mm x 12.5 mm x 0.6 mm has also been developed. Considering the low power requirement for modern sensors of the order of 0.5W or less, LTCC or Si based microhotplates are to be used. Silicon microhotplate has been developed at CEERI. Development work on microhotplate using LTCC has been started.