Apparatus for measuring a mechanical quantity

• US 8,056,421 B2
• Filed: 03/09/2010
• Issued: 11/15/2011
• Est. Priority Date: 06/17/2004
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sumigawa, Takashi, Ohta, Hiroyuki
• Primary Examiner(s): Caputo; Lisa
• Assistant Examiner(s): ROY, PUNAM P
• Application Number:
  US12/719,977
• Publication Number:
  US 20100154555A1
• Time in Patent Office: 616 Days
• Field of Search: 737/27, 737/77, 438/48, 338/5, 338/6
• US Class Current: 73/777
• CPC Class Codes: G01B 7/16 for measuring the deformation in a solid, e.g. by resistance strain gauge
• CPC Class Codes: G01B 7/18 using change in resistance
• CPC Class Codes: G01B 7/20 formed by printed-circuit technique
• CPC Class Codes: G01L 1/2206 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
• CPC Class Codes: G01L 1/2262 involving simple electrical bridges
• CPC Class Codes: G01L 5/0047 measuring forces due to residual stresses

Abstract

An apparatus structure and measurement method are provided to retain high precision and high reliability of a semiconductor mechanical quantity measuring apparatus which senses a mechanical quantity and transmits measured information wirelessly. As to a silicon substrate of the semiconductor mechanical quantity measuring apparatus, for example, a ratio of a substrate thickness to a substrate length along a measurement direction is set small, and a ratio of a substrate thickness to a substrate length along a direction perpendicular to the measurement direction is set small. The apparatus upper surface is covered with a protective member. It is possible to measure a strain along a particular direction and realize mechanical quantity measurement with less error and high precision. An impact resistance and environment resistance of the apparatus itself can be improved.

Claims

1. A mechanical quantity measuring apparatus having a strain detector formed on a principal surface of a single crystal semiconductor substrate for detecting a strain and bonded to or buried in an object to be measured to measure a strain, comprising:

an amplifier circuit disposed on the principal surface of the single crystal semiconductor substrate for amplifying a signal of the strain detector, and

a communication control unit for transmitting a signal amplified by the amplifier circuit, the communication control unit disposed on the principal surface of the single crystal semiconductor substrate toward a periphery of the mechanical quantity measuring apparatus,

wherein the strain detector includes a Wheatstone bridge circuit disposed on the principal surface, the Wheatstone bridge circuit comprising a pair of sensor resistor layers and a pair of dummy resistors, wherein a resistance value of each sensor resistor layer being equal to a resistance value of each dummy resistor, a surface of the single crystal semiconductor substrate opposite to the principal surface on which the strain detector has been formed being flat and adhered to a surface of the object,

wherein the strain detector is located closer to a central part of the principal surface of the single crystal semiconductor substrate than both the amplifying circuit and the communication control unit,

wherein a longitudinal direction of the pair of sensor resistor layers is parallel to a strain measurement direction, and a longitudinal direction of the pair of dummy resistors is substantially at 90°

or 45°

to the strain direction.

2. The mechanical quantity measuring apparatus according to claim 1, wherein both the amplifier circuit and the communication control unit are located at a side edge part of the principal surface.

3. The mechanical quantity measuring apparatus according to claim 1, wherein a ratio “

t/L₁”

is 0.3 or smaller, where

“

t”

is a thickness of the semiconductor substrate and

“

L₁”

is a length of the semiconductor substrate along a strain detection direction of the strain detector.