THIN FILM SEMICONDUCTOR STRAIN GAUGES AND METHOD FOR MAKING SAME

• US 3,626,256 A
• Filed: 10/16/1970
• Issued: 12/07/1971
• Est. Priority Date: 10/16/1970
• Status: Expired due to Term

• Current Assignee: Verne R. Brown
• Original Assignee: Verne R. Brown
• Inventors: Brown, Verne R.
• Primary Examiner(s): Kallam, James D.
• Application Number:
  US05/081,409
• Time in Patent Office: 417 Days
• Field of Search: 317/234,235
• US Class Current: 257/417
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01L 1/2293 of the semi-conductor type semi-conductor devices controllable by variations of applied mechanical force H01L29/84
• CPC Class Codes: Y10S 438/967 Semiconductor on specified insulator
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

The strain gauge of this invention comprises a film of a high temperature resistant electrically insulative organic resin, specifically polyimide resin, having deposited thereon a piezoresistive semiconductor thin film with electrical leads bonded to the semiconductor film, and a coating of high heat resistant electrically insulative resin over the semiconductor film. Further in accordance with the preferred embodiment of the invention, such a strain gauge is manufactured by depositing the film of heat resistant organic onto a plate of ceramic, preferably aluminum oxide ceramic, sequentially depositing first the semiconductor film and then the electrical leads onto the organic resin and thereafter applying the coating of heat resistant organic resin over the deposited film of semiconductor. As the last step in manufacture suitable electrically insulated metal wires are soldered or otherwise bonded to exposed portions of the deposited electrical leads. Prior to use the strain gauge, i.e. the film of organic resin having the resin coated semiconductor film and electrical leads with associated wires thereon, can be easily peeled from the ceramic plate and suitably bonded to the structural member which is to be measured for strain.

Claims

2. A strain gauge as set forth in claim 1 wherein each of the electrical leads comprises a metal film of predetermined pattern.

3. A strain gauge as set forth in claim 1 where the film of organic resin is polyimide resin.

4. A strain gauge as set forth in claim 1 wherein both the film of organic resin and the coating of organic resin are polyimide resin.

5. A strain gauge as set forth in claim 1 wherein the film of organic resin has a thickness of about 0.2 to 0.5 mils and wherein the thin film of semiconductor material has a thickness not exceeding about 5,000 angstroms.

6. A strain gauge as set forth in claim 1 wherein the film of organic resin is deposited on a rigid plate from which the resin film can be easily peeled.

7. A strain gauge as set forth in claim 6 wherein said plate is alumina ceramic.

8. A strain gauge assembly as set forth in claim 6 wherein the plate has a surface finish of from about 40 to 60 micro inches (arithmetic average).

9. A strain gauge assembly comprising an alumina ceramic plate having deposited thereon a film of polyimide resin, said film of polyimide resin having deposited thereon a piezoresistive semiconductor thin film which is of predetermined pattern and which has bonded thereto a plurality of metal film electrical leads, and a coating of polyimide resin over said semiconductor film.

10. A method for manufacturing a strain gauge comprising depositing onto a rigid plate a film of organic resin which can subsequently be easily peeled off of said plate, depositing onto said organic resin film a piezoresistive semiconductor thin film of predetermined pattern, depositing onto said semiconductor thin film a plurality of metal film electrical leads, and thereafter coating the semiconductor thin film with a layer of organic resin.

11. A method as set forth in claim 10 wherein said plate is alumina ceramic and said resin film is polyimide resin.

12. A method as set forth in claim 10 wherein said resin film and said resin coating are polyimide resin and wherein said resin film has a thickness of from 0.2 to 0.5 mils.

13. A method as set forth in claim 10 wherein said plate is alumina ceramic and has a surface finish of from about 30 to 60 micro inches (arithmetic average).

14. A method for simultaneously manufacturing a plurality of strain gauges comprising depositing a film of organic resin onto a plate from which the organic resin film can subsequently be easily peeled, depositing onto each of a plurality of selected surface portions of said organic resin film a piezoresistive semiconductor thin film of predetermined pattern, depositing onto each of said semiconductor films a plurality of metal film electrical leads, and coating each of said semiconductor films with a layer of organic resin.

15. A method as set forth in claim 14 wherein said plate is scored for subsequent breakage into a plurality of small plates of predetermined size and shape, each of the portions of the organic resin film deposited onto each of said small plates constituting one of said selected portions of said organic resin film.

16. A method as set forth in claim 15 wherein said resin film is polyimide resin.

17. A method as set forth in claim 15 wherein said plate is alumina ceramic.