GB2144922A - Substrate for thick-film electrical circuits - Google Patents

Substrate for thick-film electrical circuits Download PDF

Info

Publication number
GB2144922A
GB2144922A GB08321282A GB8321282A GB2144922A GB 2144922 A GB2144922 A GB 2144922A GB 08321282 A GB08321282 A GB 08321282A GB 8321282 A GB8321282 A GB 8321282A GB 2144922 A GB2144922 A GB 2144922A
Authority
GB
United Kingdom
Prior art keywords
thick
substrate
film circuit
molybdenum
coating
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.)
Granted
Application number
GB08321282A
Other versions
GB8321282D0 (en
GB2144922B (en
Inventor
Peter Martin Tunbridge
Anthony John Stanley
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.)
Plessey Co Ltd
Original Assignee
Plessey Co Ltd
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 Plessey Co Ltd filed Critical Plessey Co Ltd
Priority to GB08321282A priority Critical patent/GB2144922B/en
Publication of GB8321282D0 publication Critical patent/GB8321282D0/en
Priority to AU30734/84A priority patent/AU3073484A/en
Priority to NZ209104A priority patent/NZ209104A/en
Publication of GB2144922A publication Critical patent/GB2144922A/en
Application granted granted Critical
Publication of GB2144922B publication Critical patent/GB2144922B/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/03—Use of materials for the substrate
    • H05K1/05—Insulated conductive substrates, e.g. insulated metal substrate
    • H05K1/053—Insulated conductive substrates, e.g. insulated metal substrate the metal substrate being covered by an inorganic insulating layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/12—Mountings, e.g. non-detachable insulating substrates
    • H01L23/14—Mountings, e.g. non-detachable insulating substrates characterised by the material or its electrical properties
    • H01L23/142—Metallic substrates having insulating layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/095—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00 with a principal constituent of the material being a combination of two or more materials provided in the groups H01L2924/013 - H01L2924/0715
    • H01L2924/097—Glass-ceramics, e.g. devitrified glass
    • H01L2924/09701—Low temperature co-fired ceramic [LTCC]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/09—Use of materials for the conductive, e.g. metallic pattern
    • H05K1/092—Dispersed materials, e.g. conductive pastes or inks

Landscapes

  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Parts Printed On Printed Circuit Boards (AREA)
  • Insulated Metal Substrates For Printed Circuits (AREA)

Abstract

A thick-film circuit has a substrate which comprises molybdenum, e.g. pure polybdenum or a molybdenum based alloy. A method of fabricating the thick-film circuit includes the step of starting with a molybdenum based substrate and providing a coating thereon, which coating permits adhesion of one or more dielectric layers.

Description

SPECIFICATION Structure for thick film electrical circuits This invention relates to a thick film circuit structure and to a method of manufacturing such a structure.
The use of thick film technology to provide high density interconnections and passive circuit functions is well established in electronics. As normal practice, alumina substrates are used. Porcelain enamelled steel is also used as a substrate. The thermal conductivity of such substrates is not high so problems with heat dissipation can arise particularly in the case of high power devices.
The present invention seeks to enable the manufacture of thick film circuits having improved heat dissipation capabilities.
According to one aspect of the invention there is provided a thick film circuit in which the substrate comprises molybdenum.
The substrate may be pure molybdenum or a molybdenum based alloy.
The substrate may be provided with a coating on to which there is deposited one or more layers of dielectric material which is adhesively compatible therewith.
The invention also includes the method of fabricating a thick film circuit including the steps of starting with a molybdenum based substrate and providing thereon a coating which permits adhesion of one or more dielectric layers.
The invention enables high density electronic circuitry to be built up which has a very high power dissipation capability.
The invention may also provide a substrate whose surface is compatible with existing thick film inks developed for use on alumina with firing temperatures around 850 C. With the thick film inks, printed and fired multilayer interconnection patterns with resistors can be fabricated.
In order that the invention and its various other preferred features may be understood more easily, embodiments thereof, and their method of construction, will now be de scribed : The substrate consists of a Molybdenum or Molybdenum-based alloy, normally in the form of a flat sheet.
A barrier coating may be produced on the sheet to provide adhesion for subsequently applied dielectric layers. This barrier layer, in conjunction with the dielectric layers, serves to control the oxydation of the metal at high temperatures and provide an insulated surface on which an interconnection pattern can be printed.
A barrier coating, of for example Molybdenum-di-silicide, is applied by sintering the components in silicon powder at 700 C in a hydrogen atmosphere, or by electrolysis using a silicon anode and a molten alkali fluoride electrolyte at 700"C. A dielectric layer, comprising for example a ceramic loaded or devitrified glass, is applied to the initial barrier layer by screen printing. The dielectric may also be applied by electro-phoresis or powdered glass from an acqueous or organic medium, or the layer may be applied by flame spraying of such a powder.
Where the layer has been applied by thick film printing or electro-phoresis, high temperature process at a temperature in the region of 600-1000 C is required to provide for the glass to fuse together to provide a dense film with adhesion to the barrier layer.
Subsequent to the deposition of the dielectric layer, a thick film interconnection layer is built up. This is achieved by printing such combinations of thick film conductor, dielectric and resistor pastes as are necessary to achieve the desired interconnection pattern, together with any printed resistors. The process uses proprietary pastes designed for firing in the temperature range 600-1 000 C.
If nitrogen fireable thick film conductors and dielectric are used then a barrier layer is not required. The base dielectric layer may be air fired at around 500'C to burn out the organic vehicle before firing in nitrogen at the higher temperatures.
Following the production of the interconnection pattern, semiconductor and passive chip components may be soldered in place using standard techniques. Bare form components may then be wire bonded to provide electrical contact. Where bare components are used, they may be given hermetic protection by either glassing a wall on to the thick film structure, and then soldering or welding a flat lid in place, or by applying a shaped lid using solder or epoxy.
The electronic circuit thus produced may then be incorporated in an equipment in a manner similar to a printed circuits board.
Molybdenum coated with a proprietary barrier layer has been coated with a proprietary thick film dielectric layer and fired at 900 C.
The technology is being developed to provide a means of manufacturing high power dissipation hybrid thick film circuits where alumina and coated steel substrates are inadequate. A Molybdenum-based substrate meets this criteria in that it has a thermal conductivity six times that of alumina.
The substrate may be any shape or size and carry holes enabling it to be bolted firmly to a heatsink. The heatsink may be the wall of an equipment or a heat pipe. Semiconductor and passive chip components may be soldered to the thick film interconnection pattern. Bare components can be protected by the addition of a soldered or glassed on wall/lid structure.

Claims (7)

1. A thick-film circuit including a substrate comprising molybdenum.
2. A thick-film circuit as claimed in claim 1, in which the substrate is composed of pure molybdenum or a molybdenum based alloy.
3. A thick-film circuit as claimed in claim 1 or claim 2, in which the substrate is provided with a coating on to which there is deposited one or more layers of dielectric material which is adhesively compatible therewith.
4. A method of fabricating a thick-film circuit, the method including providing a coating on a molybdenum based substrate, which coating permits adhesion of one or more dielectric layers.
5. A thick-film circuit substantially as herein before described.
6. A method of fabricating a thick-film circuit substantially as herein before described.
7. Electrical equipment embodying a thick-film circuit as claimed in any one of claims 1 to 3, and 5, in which the substrate forms at least part of the equipment housing or other mechanical structure.
GB08321282A 1983-08-06 1983-08-06 Substrate for thick-film electrical circuits Expired GB2144922B (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB08321282A GB2144922B (en) 1983-08-06 1983-08-06 Substrate for thick-film electrical circuits
AU30734/84A AU3073484A (en) 1983-08-06 1984-07-16 Structure for thick film electrical circuits
NZ209104A NZ209104A (en) 1983-08-06 1984-08-03 Thick-film circuit with a substrate containing molybdenum

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08321282A GB2144922B (en) 1983-08-06 1983-08-06 Substrate for thick-film electrical circuits

Publications (3)

Publication Number Publication Date
GB8321282D0 GB8321282D0 (en) 1983-09-28
GB2144922A true GB2144922A (en) 1985-03-13
GB2144922B GB2144922B (en) 1986-06-18

Family

ID=10546965

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08321282A Expired GB2144922B (en) 1983-08-06 1983-08-06 Substrate for thick-film electrical circuits

Country Status (3)

Country Link
AU (1) AU3073484A (en)
GB (1) GB2144922B (en)
NZ (1) NZ209104A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2162694A (en) * 1984-08-04 1986-02-05 British Aerospace Printed circuits
GB2176063A (en) * 1985-05-22 1986-12-10 Michael Frederick Horgan A probe card
GB2230387A (en) * 1989-04-13 1990-10-17 L S T Lab Ltd Improvements in or relating to automotive electrical systems

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2162694A (en) * 1984-08-04 1986-02-05 British Aerospace Printed circuits
GB2176063A (en) * 1985-05-22 1986-12-10 Michael Frederick Horgan A probe card
GB2230387A (en) * 1989-04-13 1990-10-17 L S T Lab Ltd Improvements in or relating to automotive electrical systems
US5198696A (en) * 1989-04-13 1993-03-30 I.S.T. Laboratories Ltd. Automotive electrical systems
GB2230387B (en) * 1989-04-13 1993-10-06 Ist Lab Ltd Improvements in or relating to automotive electrical systems

Also Published As

Publication number Publication date
AU3073484A (en) 1985-02-07
GB8321282D0 (en) 1983-09-28
NZ209104A (en) 1987-09-30
GB2144922B (en) 1986-06-18

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Legal Events

Date Code Title Description
732 Registration of transactions, instruments or events in the register (sect. 32/1977)
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19930806