A compact package for integrated silicon thermal gas flow meters

Abstract

An original packaging method suitable for\ud integrated thermal mass flow sensors is presented. The\ud method is based on a polymethyl-methacrylate (PMMA)\ud adapter, used to convey the fluid flow to the chip areas\ud where the sensing structures are located. Sealing of the\ud adapter was obtained by heating the chip itself to the PMMA\ud glass transition temperature, in order to soften the adapter\ud front surface and improve adhesion. The proposed approach\ud was applied to the packaging of thermal flow meters\ud obtained by post-processing standard integrated circuits.\ud The resulting compact devices have been characterized by\ud measuring the response to a nitrogen flow. Fabrication and\ud testing of a very compact flow sensor is described

Micromachined Thermal Flow Sensors—A Review

“…Two thermally isolated heaters instead of one were used in between two thermopiles and thermal feedback maintained equal temperature between the two heaters under varying flow conditions [84][85][86].…”

Design Issues for Low Power Integrated Thermal Flow Sensors with Ultra-Wide Dynamic Range and Low Insertion Loss

“…After post-processing, the chips were glued to ceramic DIP28 cases by means of epoxy resin and wedge bonding was used to connect selected chip pads to the case pins. A recently proposed packaging technique [30] has been used to connect the integrated flow sensor to the gas lines. This technique is based on a purposely built poly-methyl-methacrylate (PMMA) conveyor which is aligned to the chip by means of a guide and is capable to convey multiple flows to different areas of the chip [31].…”

A single chip, double channel thermal flow meter

“…Using a single chip for performing multiple tasks allows considerable size reduction, reduces costs and improves reliability. The device is based on the same chip as in the previous work (Bruschi et al 2008), designed earlier than the development of the packaging method, so that the placement of the sensing structures was not optimized to include them into separate flow channels. As a result, the channel geometry had to be designed in such a way that the two sensing structures fall into channel bends.…”

“…Recently, we have proposed a packaging method based on a PMMA adapter thermally bonded to the silicon chip (Bruschi et al 2008). The advantage of this approach is the possibility of conveying the gas flow to selected areas of a completely standard chip, with no need of particular bonding pad configurations, chip size or surface flatness.…”