Attachment of MEM piezoresistive silicon pressure sensor dies using different adhesives

Abstract

This paper gives comparison and discussion of adhesives used for attachment of silicon piezoresistive pressure sensor dies. Special attention is paid to low pressure sensor dies because of their extreme sensitivity on stresses, which can arise from packaging procedure and applied materials. Commercially available adhesives 'Scotch Weld 2214 Hi-Temp' from '3M Co.' and 'DM2700P/H848' from 'DIEMAT', USA, were compared. The first is an aluminum filled epoxy adhesive and the second is a low melting temperature (LMT) glass paste. Comparing test results for low pressure sensor chips we found that LMT glass (glass frit) is a better adhesive for this application. Applying LMT glass paste minimizes internal stresses caused by disagreement of coefficients of thermal expansions between the sensor die and the housing material. Also, it minimizes stresses introduced during applying external loads in the process of pressure measuring. Regarding the measurements, for the sensors installed with filled epoxy paste, the resistor for compensation of temperature offset change had negative values in all cases, which means that linear temperature compensation of sensors installed this way would be impossible. In the sensors installed with LMT glass paste, all results, without exception, were in their common limits (values), which gives the possibility of passive temperature compensation. Furthermore, LMT glass attachment can broaden temperature operating range of MEM silicon pressure sensors towards higher values, up to 120°C.

U ovom radu se porede i diskutuju adhezivi koji su korišćeni za montažu čipova silicijumskih piezorezistivnih senzora pritiska. Posebna pažnja je poklonjena montaži čipova senzora za niske pritiske ( LT 1 bar) zbog toga što su oni posebno osetljivi na naprezanja koja nastaju kao posledica samog procesa montaže i karakteristika primenjenih materijala. Za montažu čipa na kućište su korišćeni komercijalno dostupni adhezivi 'Scotch Weld 2214 Hi-Temp' proizvođača '3M Co.' i 'DM2700P/H848' proizvođača 'DIEMAT', SAD. Prvi adheziv je epoksidna pasta sa česticama aluminijuma kao puniocem, a drugi je pasta stakla sa niskom temperaturom topljenja. Poredeći karakteristike montiranih čipova piezorezistivnih MEM senzora niskog pritiska, pokazano je da je za ovu primenu montaže pogodnije koristiti pastu stakla sa niskom temperaturom topljenja, jer senzori montirani primenom ovog adheziva mogu da se pasivno temperaturno kompenzuju i ta kompenzacija je vrlo stabilna. Montaža senzora ovim adhezivom pruža mogućnost rada senzora i na povišenim temperaturama do 120°C.