Motorola Corporation

Gregory D Stamm

Marc Kenneth Chason

Shiuh-Hui Steven Chen

Donald O Myers

Joseph P Tomase

A hermetically sealed interface is constructed with a substrate (101) having a first surface (103) with a first orifice (201). The substrate (101) also has an opposing second surface (105) with a second orifice (205). The first and second orifices (201, 205) are connected via a passageway (107). The passageway (107) has an inner surface (209) with a first metal coating (111). The first metal coating (111) and the substrate (101) provide a first predetermined thermal coefficient of expansion for the passageway (107). A plug (221) with an outer surface (223) has a second metal coating (225). The second metal coating (225) and the plug (221) provide a second predetermined thermal coefficient of expansion substantially similar to the first predetermined thermal coefficient of expansion of the passageway (107). The plug (221) is disposed in the passageway (107) of the substrate (101). The first metal coating (111), of the inner surface ( 209) of the passageway (107), and the second metal coating (225), of the outer surface (223) of the plug (221), are bonded together and provide, with the plug, (221) a hermetic barrier between the first and second orifices (201, 205) of the substrate (101). Preferably, this hermetically sealed interface is used in a capacitive pressure sensor.

Hermetically sealed interface

The undesired temperature variation of a capacitive pressure sensing element (10) having a positive temperature coefficient of capacitance (TCC) is compensated by a series resistor R and compensating capacitor (C.sub.c) connected in parallel to the pressure sensing capacitor (C.sub.x). The compensating capacitor and presssure sensing element have opposite polarity temperature coefficients of capacitance, and the magnitude of the resistor is selected such that its resistive impedance is nonnegligible and is comparable to the magnitude of the capacitive reactance of the pressure sensing capacitor or compensating capacitor at a predetermined operative frequency of an electrical signal applied to and/or determined by the pressure sensing and compensating capacitors.

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LaGrange, IL, United States of America

Gregory D Stamm