GB2238267A - Brazing process - Google Patents

Brazing process Download PDF

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Publication number
GB2238267A
GB2238267A GB8924578A GB8924578A GB2238267A GB 2238267 A GB2238267 A GB 2238267A GB 8924578 A GB8924578 A GB 8924578A GB 8924578 A GB8924578 A GB 8924578A GB 2238267 A GB2238267 A GB 2238267A
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GB
United Kingdom
Prior art keywords
metal
silicon
layer
oxide film
brazable
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB8924578A
Other versions
GB8924578D0 (en
Inventor
Aubrey Michael Crick
William Alexander Reeves
Norman John Cann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STC PLC
Original Assignee
STC PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by STC PLC filed Critical STC PLC
Priority to GB8924578A priority Critical patent/GB2238267A/en
Publication of GB8924578D0 publication Critical patent/GB8924578D0/en
Publication of GB2238267A publication Critical patent/GB2238267A/en
Withdrawn legal-status Critical Current

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K1/00Soldering, e.g. brazing, or unsoldering
    • B23K1/19Soldering, e.g. brazing, or unsoldering taking account of the properties of the materials to be soldered
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/001Interlayers, transition pieces for metallurgical bonding of workpieces
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/001Interlayers, transition pieces for metallurgical bonding of workpieces
    • B23K2035/008Interlayers, transition pieces for metallurgical bonding of workpieces at least one of the workpieces being of silicium

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

In a process for brazing a silicon body (11) to a metal body (13), the silicon body is provided with an adherent oxide surface film (41). The oxide film is coated with a metal layer structure which provides a brazable surface. Attack of the silicon surface by braze alloy is prevented by the oxide film. The metal layer structure comprises titanium (42), molybdenum (43) and nickel (44). The braze (45) is a silver/copper alloy. The process may be used in the construction of e.g. a pressure sensor assembly. <IMAGE>

Description

BRAZING PROCESS This invention relates to brazing processes and in particular to a process for providing a brazed silicon to metal seal. The invention also relates to transducer structures fabricated via the brazing process.
Transducers formed from single crystal silicon are finding increasing use in remote sensing applications. Such transducers generally consist of an integral or multipart structure formed by relative etching from single crystal silicon and having one or more flexible piezo-sensitive elements whose displacement provides a measure of the physical parameter, e.g. temperature or pressure, to be determined. Transducers of this type are described for example in our co-pending application No. 88 23234.3 and No. 88 03355.
A particular application for single crystal silicon transducers is in the oil and gas exploration industry where there is a requirement for down-well monitoring of temperature and pressure. The use of silicon transducers in such applications has however been restricted by the necessity to mount the transducer on a metal support or leader to provide a structure that will withstand the very high pressures and temperatures pertaining in an oil or gas well. Specifically, difficulties have been experienced in providing a gas tight seal between the silicon structure and the metal support. Typically the support comprises molybdenum or a nickel ion cobalt alloy, these materials being thermally matched to silicon.Attempts to provide a gas tight seal by brazing the silicon transducer to the housing have not been successful as it has been found that the braze alloys normally employed to effect gas tight seals react vigorously with silicon to form low melting point intermetallic materials. This results in failure of the joint.
The object of the invention is to minimise or to overcome this disadvantage.
According to the invention there is provided a method of brazing a silicon body to a metal body, the method including providing a surface insulating refractory film on the silicon body whereby to prevent contact of the silicon surface with the braze material.
According to the invention there is further provided a method of forming a gas-tight brazed seal between a silicon body and a metal body, the method including oxidising the surface of the silicon body to form an adherent oxide film, applying to said oxide film a film of a brazable metal, providing a braze alloy on the brazable metal film, contacting the brazable metal with said metal body, and heating the assembly to fuse the braze alloy and effect the brazed seal, the oxide film providing a barrier between the braze alloy and the silicon surface.
According to the invention there is further provided a method of forming a gas-tight brazed seal between a silicon transducer element and a metal support, the method including providing an oxide film on a surface of the silicon element, applying a metal bonding layer to the oxide film, applying a layer of a brazable metal to the bonding layer, contacting the brazable metal layer with said metal support, heating the assembly, and providing a braze alloy at the interface of the support and the brazable layer whereby to provide a brazed joint therebetween, the oxide film providing a barrier between-the braze alloy and the silicon surface.
The oxide layer and the bonding layer provide a physical barrier between the silicon surface and the brazing alloy. This prevents the formation of low melting point intermetallic compounds and thus provides a gas-tight seal that retains its integrity even at elevated temperatures and pressures. The oxide layer further provides a firm bond between the metal layer and the silicon surface.
An embodiment of the invention will now be described with reference to the accompanying drawings in which: Figs. 1 to 3 illustrate successive stages in the provision of a brazed silicon to metal seal.
Referring to Figs. 1 to 3, these Figures illustrate the brazing process. An insulating refractory, e.g. oxide, film 41 is formed on the surface of a silicon body 1 to provide a firmly adherent barrier layer whereby a subsequently applied braze alloy is separated from the silicon surface. The oxide film 41 may be formed by heating the silicon in air and is typically about 1 micron in thickness. Next an adherent bonding layer 42 (Fig. 5) is applied to the oxide film 41 to provide a base for further metal/alloy layers. Typically this bonding layer 42 comprises a 0.3 micron thick layer of titanium applied by sputtering.
The bonding layer 42 is coated with a layer 43 of a brazable metal such as molybdenum. This layer 43 may be about 2 microns in thickness and may be applied by sputtering.
Advantageously a nickel layer 44 is applied to the surface of the brazable layer 43 to improve the brazing qualities of the structure. Typically the nickel layer is applied by sputtering and is 1 micron in thickness.
A layer 45 (Fig. 3) of braze alloy is applied to the structure which is then mounted in abutment with a metal body 13 to which the silicon body 11 is to be brazed. Typically this metal body 13 is formed from a material having a thermal expansion coefficient similar to that of silica. We have employed molybdenum and nickel/iron/cobalt alloys such as KOVAR (Registered Trade Mark) for this purpose.
The assembly is next heated to fuse the braze alloy and to effect sealing of the joint between the tube 11 and the header 13. Advantageously the braze alloy comprises a silver/copper eutectic mixture.
During the brazing process the oxide layer 41 and the bonding layer 42 provide a physical barrier between the alloy and the silicon surface thus preventing attack of the silicon. We have found that the oxide and metal layer structure is strongly adherent to the silicon surface thus assuming that a reliable brazed seal is provided by the process described above.
It will be appreciated that the relative thicknesses of the various layers depicted in Figs. 1 to 3 are not to scale.
The brazing process described above is particularly appropriate for mounting a silicon transducer in a metallic housing to form e.g. a pressure sensor. It will however be appreciated that the process is not limited to this particular application but is of general use in the provision of a brazed joint between a silicon body and a metal body.

Claims (9)

1. A method of brazing a silicon body to a metal body, the method including providing a surface insulating refractory film on the silicon body whereby to prevent direct contact of the silicon surface with the braze material.
2. A method of forming a gas-tight brazed seal between a silicon body and a metal body, the method including oxidising the surface of the silicon body to form an adherent oxide film, applying to said oxide film a film of a brazable metal, providing a braze alloy on the brazable metal film, contacting the brazable metal with said metal body, and heating the assembly to fuse the braze alloy and effect the brazed seal, the oxide film providing a barrier between the braze alloy and the silicon surface.
3. A method of forming a gas-tight brazed seal between a silicon transducer element and a metal support, the method including providing an oxide film on a surface of the silicon element, applying a metal bonding layer to the oxide film, applying a layer of a brazable metal to the bonding layer, contacting the brazable metal layer with said metal support, heating the assembly, and providing a braze alloy at the interface of the support and the brazable layer whereby to provide a brazed joint therebetween, the oxide film providing a barrier between the braze alloy and the silicon surface.
4. A method as claimed in claim 2 or 3, wherein said brazable metal comprises molybdenum.
5. A method as claimed in claim 4, wherein a layer of titanium is disposed between the oxide film and the molybdenum layer.
6. A method as claimed in claim 4 or 5, wherein a layer of nickel is applied to the surface of the molybdenum layer.
7. A method as claimed in any one of the preceding claims wherein the braze alloy comprises a silver/copper eutectic mixtures.
8. A method of brazing a silicon body to a metal body substantially as detailed herein with reference to Figs. 1 to 3 of the accompanying drawings.
9. A transducer assembly fabricated by a method as claimed in any one of claims 1 to 8.
GB8924578A 1989-11-01 1989-11-01 Brazing process Withdrawn GB2238267A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8924578A GB2238267A (en) 1989-11-01 1989-11-01 Brazing process

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8924578A GB2238267A (en) 1989-11-01 1989-11-01 Brazing process

Publications (2)

Publication Number Publication Date
GB8924578D0 GB8924578D0 (en) 1989-12-20
GB2238267A true GB2238267A (en) 1991-05-29

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB8924578A Withdrawn GB2238267A (en) 1989-11-01 1989-11-01 Brazing process

Country Status (1)

Country Link
GB (1) GB2238267A (en)

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2254278A (en) * 1991-03-09 1992-10-07 Bosch Gmbh Robert Method of mounting silicon chips on metallic mounting surfaces
GB2264662A (en) * 1992-03-05 1993-09-08 Westinghouse Brake & Signal Soldering silicon
GB2273582A (en) * 1992-12-18 1994-06-22 Hr Textron Inc Fluidic deflector jet servovalve
US6505811B1 (en) 2000-06-27 2003-01-14 Kelsey-Hayes Company High-pressure fluid control valve assembly having a microvalve device attached to fluid distributing substrate
US6523560B1 (en) 1998-09-03 2003-02-25 General Electric Corporation Microvalve with pressure equalization
US6761420B2 (en) 1998-09-03 2004-07-13 Ge Novasensor Proportional micromechanical device
US7011378B2 (en) 1998-09-03 2006-03-14 Ge Novasensor, Inc. Proportional micromechanical valve
US7803281B2 (en) 2004-03-05 2010-09-28 Microstaq, Inc. Selective bonding for forming a microvalve
US8011388B2 (en) 2003-11-24 2011-09-06 Microstaq, INC Thermally actuated microvalve with multiple fluid ports
US8113482B2 (en) 2008-08-12 2012-02-14 DunAn Microstaq Microvalve device with improved fluid routing
US8156962B2 (en) 2006-12-15 2012-04-17 Dunan Microstaq, Inc. Microvalve device
US8387659B2 (en) 2007-03-31 2013-03-05 Dunan Microstaq, Inc. Pilot operated spool valve
US8393344B2 (en) 2007-03-30 2013-03-12 Dunan Microstaq, Inc. Microvalve device with pilot operated spool valve and pilot microvalve
US8540207B2 (en) 2008-12-06 2013-09-24 Dunan Microstaq, Inc. Fluid flow control assembly
US8593811B2 (en) 2009-04-05 2013-11-26 Dunan Microstaq, Inc. Method and structure for optimizing heat exchanger performance
US8662468B2 (en) 2008-08-09 2014-03-04 Dunan Microstaq, Inc. Microvalve device
US8925793B2 (en) 2012-01-05 2015-01-06 Dunan Microstaq, Inc. Method for making a solder joint
US8956884B2 (en) 2010-01-28 2015-02-17 Dunan Microstaq, Inc. Process for reconditioning semiconductor surface to facilitate bonding
US8996141B1 (en) 2010-08-26 2015-03-31 Dunan Microstaq, Inc. Adaptive predictive functional controller
US9006844B2 (en) 2010-01-28 2015-04-14 Dunan Microstaq, Inc. Process and structure for high temperature selective fusion bonding
US9140613B2 (en) 2012-03-16 2015-09-22 Zhejiang Dunan Hetian Metal Co., Ltd. Superheat sensor
US9188375B2 (en) 2013-12-04 2015-11-17 Zhejiang Dunan Hetian Metal Co., Ltd. Control element and check valve assembly
US9702481B2 (en) 2009-08-17 2017-07-11 Dunan Microstaq, Inc. Pilot-operated spool valve

Cited By (31)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5215244A (en) * 1991-03-09 1993-06-01 Robert Bosch Gmbh Method of mounting silicon wafers on metallic mounting surfaces
GB2254278A (en) * 1991-03-09 1992-10-07 Bosch Gmbh Robert Method of mounting silicon chips on metallic mounting surfaces
GB2254278B (en) * 1991-03-09 1994-08-03 Bosch Gmbh Robert A method of manufacturing a valve, and a valve manufactured by the method
DE4306871C2 (en) * 1992-03-05 2003-03-20 Westcode Semiconductors Ltd Soldered connection and process for its manufacture
GB2264662A (en) * 1992-03-05 1993-09-08 Westinghouse Brake & Signal Soldering silicon
US5380598A (en) * 1992-03-05 1995-01-10 Westinghouse Brake & Signal Holdings Ltd. Solder joint
GB2264662B (en) * 1992-03-05 1995-07-12 Westinghouse Brake & Signal A solder joint
GB2273582A (en) * 1992-12-18 1994-06-22 Hr Textron Inc Fluidic deflector jet servovalve
GB2273582B (en) * 1992-12-18 1996-01-24 Hr Textron Inc A deflector jet servovalve
US6523560B1 (en) 1998-09-03 2003-02-25 General Electric Corporation Microvalve with pressure equalization
US6761420B2 (en) 1998-09-03 2004-07-13 Ge Novasensor Proportional micromechanical device
US7011378B2 (en) 1998-09-03 2006-03-14 Ge Novasensor, Inc. Proportional micromechanical valve
US6505811B1 (en) 2000-06-27 2003-01-14 Kelsey-Hayes Company High-pressure fluid control valve assembly having a microvalve device attached to fluid distributing substrate
US8011388B2 (en) 2003-11-24 2011-09-06 Microstaq, INC Thermally actuated microvalve with multiple fluid ports
US7803281B2 (en) 2004-03-05 2010-09-28 Microstaq, Inc. Selective bonding for forming a microvalve
US8156962B2 (en) 2006-12-15 2012-04-17 Dunan Microstaq, Inc. Microvalve device
US8393344B2 (en) 2007-03-30 2013-03-12 Dunan Microstaq, Inc. Microvalve device with pilot operated spool valve and pilot microvalve
US8387659B2 (en) 2007-03-31 2013-03-05 Dunan Microstaq, Inc. Pilot operated spool valve
US8662468B2 (en) 2008-08-09 2014-03-04 Dunan Microstaq, Inc. Microvalve device
US8113482B2 (en) 2008-08-12 2012-02-14 DunAn Microstaq Microvalve device with improved fluid routing
US8540207B2 (en) 2008-12-06 2013-09-24 Dunan Microstaq, Inc. Fluid flow control assembly
US8593811B2 (en) 2009-04-05 2013-11-26 Dunan Microstaq, Inc. Method and structure for optimizing heat exchanger performance
US9702481B2 (en) 2009-08-17 2017-07-11 Dunan Microstaq, Inc. Pilot-operated spool valve
US8956884B2 (en) 2010-01-28 2015-02-17 Dunan Microstaq, Inc. Process for reconditioning semiconductor surface to facilitate bonding
US9006844B2 (en) 2010-01-28 2015-04-14 Dunan Microstaq, Inc. Process and structure for high temperature selective fusion bonding
US8996141B1 (en) 2010-08-26 2015-03-31 Dunan Microstaq, Inc. Adaptive predictive functional controller
US8925793B2 (en) 2012-01-05 2015-01-06 Dunan Microstaq, Inc. Method for making a solder joint
US9404815B2 (en) 2012-03-16 2016-08-02 Zhejiang Dunan Hetian Metal Co., Ltd. Superheat sensor having external temperature sensor
US9140613B2 (en) 2012-03-16 2015-09-22 Zhejiang Dunan Hetian Metal Co., Ltd. Superheat sensor
US9772235B2 (en) 2012-03-16 2017-09-26 Zhejiang Dunan Hetian Metal Co., Ltd. Method of sensing superheat
US9188375B2 (en) 2013-12-04 2015-11-17 Zhejiang Dunan Hetian Metal Co., Ltd. Control element and check valve assembly

Also Published As

Publication number Publication date
GB8924578D0 (en) 1989-12-20

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