Method of making an acceleration sensor

• US 5,546,644 A
• Filed: 04/25/1995
• Issued: 08/20/1996
• Est. Priority Date: 12/17/1991
• Status: Expired due to Fees

• Current Assignee: Atsugi Unisia Corporation
• Original Assignee: Atsugi Unisia Corporation
• Inventors: Kakizaki, Shinobu, Kasajima, Kimihisa
• Primary Examiner(s): Hall, Carl E.
• Application Number:
  US08/428,680
• Time in Patent Office: 483 Days
• Field of Search: 29/25.35, 29/25.42, 29/854-856, 73/493, 73/516 R, 73/517 R, 73/517 A, 73/517 AV, 73/517 B
• US Class Current: 29/25.35
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/435 Solid dielectric type

Abstract

A semiconductor type acceleration sensor comprises a flexible printed circuit board on which a semiconductor type detector chip section is mounted. The detector chip is formed with openings therethrough overlapping an opening formed in a rear-side base plate of the flexible printed circuit board such that the detector chip section is supported only by a bridge portion. In case of excess input in an acceleration direction, elastic deformation of the bridge portion and a bending portion of the flexible printed circuit board provide absorption of the excess input for protecting the detector chip section.

Claims

1. A method of assembling an acceleration sensor, comprising:

a) forming an elongate flexible substrate;

b) mounting an acceleration detection means on said flexible substrate so as to be active to detect acceleration applied to said sensor;

c) mounting signal processing means on said flexible substrate in connection with said acceration detection means so as to receive an output thereof;

d) mounting connecting terminals to said flexible substrate in connection with said signal processing means;

e) adhering opposing portions of said flexible substrate to respective plates, one of said plates having an opening defined therethrough, a portion of said flexible substrate mounting said acceleration detection means being positioned over said opening;

f) folding said flexible substrate along a central folding portion;

g) inserting said plates and said folded flexible substrate into a casing having an open portion such that one plate is inserted topmost and said acceleration detecting means mounted on flexible substrate is facing in an acceleration direction, the shape of the plates conforming to the circumferential shape of the casing and the other plate being inset at the bottom of the open portion of the casing;

h) installing connecting means connecting said acceleration detecting means with an output external to said casing; and

i) sealing said casing via a sealing agent.

2. A method as set forth in claim 1, further including the step of forming an opening in said flexible substrate in the vicinity of said acceleration detection means such that, after said adhering step is carried out, a portion of said opening will overlap said opening of said one plate.

3. A method as set forth in claim 1, further including the step of forming a plurality of openings in said flexible substrate in the vicinity of said acceleration detection means such that a portion of said openings will overlap said opening of said one plate after said adhering step.

4. An method as set forth in claim 3, wherein said opening in said one plate is circular and said plurality of said openings in said flexible substrate are circular and smaller than said opening in said plate, said plurality of smaller openings being arranged symmetrically around said acceleration detection means.

5. A method as set forth in claim 1, wherein said acceleration detection means comprises a semiconductor acceleration sensor formed on a silicon substrate, said semiconductor acceleration sensor including a mass formed on a cantilever and having a weight and positioning determined such that said mass is displacable in at least said acceleration direction, and a strain gauge positioned so as to be responsive to movement of said mass, said strain gauge comprising a piezo resistance element, said acceleration detection means being assembled on said substrate.

6. A method as set forth in claim 1, wherein said signal processing means includes at least an amplifier circuit and a filter circuit.

7. A method as set forth in claim 1, wherein said acceleration detection means is a capacitance acceleration sensor detecting variation of capacitance of a capacitor due to displacement of a mass arranged at one side of the capacitor.

8. A method as set forth in claim 1, wherein said acceleration detection means is mounted on said flexible substrate at a location remote from said connection means such that, after said folding step, said acceleration detection means is adhered over said one, topmost place and said connection means is adhered to said other plate positioned below said topmost plate.

9. A method as set forth in claim 1, wherein a size of at least said one plate is selected so as to allow said folded portion of said flexible substrate to resiliently support said one plate relative to said other plate.