P8.4 - Optimized Electrical Feed Through for a Piezoresistive Silicon High-Pressure Sensing Element up to 500 MPa

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
P8 - Mechanical
P. Heinickel, R. Werthschützky - Technische Universität Darmstadt (Germany), W. Hummel - IL Metronic Sensortechnik GmbH, Ilmenau (Germany)
858 - 858


Applications involving high-pressure are becoming increasingly common in engineering today; these also include mass production applications. In addition to automotive systems (up to 300 MPa in research), there are applications like water jet cutting and hydroforming of up to 600 MPa.
The recently developed, optimized and presented high-pressure sensing element for a measuring range up to 500 MPa (is equivalent to 5 000 bar and about 72 500 psi) consists of a solid silicon chip connected to a solid counter body. The novel presented operation mode of mechanical restraint of the highpressure sensing element is a result of the hydrostatic pressure load. Thus, for the overload protected and cost-effective sensor, which is used within the highpressure, there is a need for an electrical feed through for high-pressure application up to 500 MPa.
State-of-the-art electrical feed through are hermetic glass-to-metal seals. Their mechanical stability is limited to a bursting pressure of about 100 MPa mostly. To increase the mechanical stability, some innovations in technology of hermetic seal lead to special material combination. Based on necessary mechanical strain between the outer and the inner material, the resulting difference in mechanical strain is advantageous for the ceramic metal compound as a high-pressure feed through.
Actually this ceramic metal compound was developed as high temperature feed through. Additionally theoretical and practical investigations showed a mechanical stability of about 300 MPa at room temperature. To meet the requirements of the presented highpressure composite element, there have been done optimizations based on structural analyses with FEM simulation tools and analytical descriptions. This results in a ceramic metal compound based on a special alloy with an outer diameter of 20 mm and 4 electrical connector pins insulated by glass. Due to the optimizations the mechanical stability is increased to 500 MPa at minimum at room temperature. Additionally, the mechanical stability arises out of pressure tests to 140 MPa at 400°C for example. Due to limited pressure of the available measuring set-up at the Institute, there is no experimental test with higher pressure than 500 MPa to investigate the bursting pressure in an experimental way. This will be done in future with external partners. With this presented optimized ceramic metal feed through it is possible to characterize metrologically the novel composite element in the extended pressure range up to 500 MPa.