GB2133934A - Improvements relating to thick film circuits - Google Patents

Improvements relating to thick film circuits Download PDF

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Publication number
GB2133934A
GB2133934A GB8401153A GB8401153A GB2133934A GB 2133934 A GB2133934 A GB 2133934A GB 8401153 A GB8401153 A GB 8401153A GB 8401153 A GB8401153 A GB 8401153A GB 2133934 A GB2133934 A GB 2133934A
Authority
GB
United Kingdom
Prior art keywords
thick
substrate
dielectric material
film circuit
film
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
GB8401153A
Other versions
GB2133934B (en
GB8401153D0 (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 GB8401153A priority Critical patent/GB2133934B/en
Publication of GB8401153D0 publication Critical patent/GB8401153D0/en
Publication of GB2133934A publication Critical patent/GB2133934A/en
Application granted granted Critical
Publication of GB2133934B publication Critical patent/GB2133934B/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
    • H05K1/056—Insulated conductive substrates, e.g. insulated metal substrate the metal substrate being covered by an organic 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
    • H01L23/13—Mountings, e.g. non-detachable insulating substrates characterised by the shape
    • 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
    • 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
    • H05K1/0277—Bendability or stretchability details
    • H05K1/0278—Rigid circuit boards or rigid supports of circuit boards locally made bendable, e.g. by removal or replacement of material
    • 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
    • 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
    • H05K1/0284—Details of three-dimensional rigid printed circuit boards
    • 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
    • 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
    • H05K1/095—Dispersed materials, e.g. conductive pastes or inks for polymer thick films, i.e. having a permanent organic polymeric binder
    • 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
    • H05K1/18—Printed circuits structurally associated with non-printed electric components
    • H05K1/189—Printed circuits structurally associated with non-printed electric components characterised by the use of a flexible or folded printed circuit
    • 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
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/01—Dielectrics
    • H05K2201/0183—Dielectric layers
    • H05K2201/0187—Dielectric layers with regions of different dielectrics in the same layer, e.g. in a printed capacitor for locally changing the dielectric properties
    • 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
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/30—Details of processes not otherwise provided for in H05K2203/01 - H05K2203/17
    • H05K2203/302—Bending a rigid substrate; Breaking rigid substrates by bending

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)

Abstract

A thick-film circuit is provided with a substrate 1 comprising titanium, e.g. commercially pure titanium or titanium based alloy. After printing of the thick- film components and interconnections on the usual substrate base dielectric layer 2, 3, the substrate may be bent to conform to the shape of the equipment housing of which the thick-film circuit substrate may form part. <IMAGE>

Description

SPECIFICATION Improvements relating to thick-film circuits This invention relates to thick-film circuits and the manufacture thereof.
It is well known to use thick-film technology for producing circuits containing passive components (e.g. resistors and capacitors) and appropriate conductive interconnections. In the manufacture of such thick-film circuits one or more layers of dielectric material comprising a suitable glaze or cement may be deposited on to a substrate commonly of ceramic material (e.g. alumina) and the desired circuit pattern of passive components and interconnections produced on the dielectric material using silk screen printing or some other thick-film forming technique. Porcelain enamelled steel may alternatively be used as the substrate for the thick-film circuit.
Difficulties arise with these thick-film circuit structures due to the fact that ceramic substrates are mechanically fragile and cannot easily be made in large sizes whereas the use of porcelain enamelled steel, or possibly porcelain enamelled copper clad Invar, as the substrate is limited by the characteristics of the enamel which may not in general allow for processing of the substrate at the high firing temperatures (e.g. 8000 C upwards) which are necessary to achieve good results with conventional thick film inks used in the silk screen printing technique. Moreover, the glassy nature of the enamel provides a surface which readily cracks.
The present invention is directed to the provision of thick-film circuits having substrates which can, if necessary, readily be manufactured in large sizes and which due to their thermal/mechanical properties facilitate a relatively high packing density of power circuit components and the production of strong relatively lightweight thick-film circuit assemblies of widely varying sizes and configurations according to requirements.
The present invention also seeks to provide thick-film circuits with substrates which are not subject to the above referred to problems experienced with porcelain enamelled substrates and which are compatible with existing thick film inks developed for use on alumina substrates in processes using firing temperatures in excess of 6000 C.
According to the present invention a thick-film circuit is provided with a substrate comprising titanium.
The substrate of the circuit may be composed of commercially pure titanium or it may be composed of a titanium-based alloy.
The substrate of the thick-film circuit which may be flat or bent may have dielectric material applied to one or more selected parts thereof where the thick-film circuitry is located. This dielectric material may comprise one or more layers and is preferably applied by a silk screen printing technique which enables the selective positioning of these areas on the substrate to be more easily achieved than with alternative deposition techniques.
It may here be mentioned that tor good adhesion of the dielectric material to the substrate a thin barrier layer is required and this layer may be constituted by a naturally occurring layer of oxide on the titanium or titanium-based alloy substrate or, alternatively, such layer may be produced by controlled oxidation of the substrate surface.
After deposition of the dielectric material, any exposed areas of the substrate may be suitably coated (e.g. glassy material) in order to prevent excessive oxidation of the substrate at the high firing temperatures which obtain during screen printing of passive components and appropriate interconnections on the dielectric material.
After printing of the circuit components and interconnections, the substrate may, if necessary, readily be bent along lines running between or offset from the areas of dielectric material applied to the substrate so that the overall shape of the thick-film circuit assembly conforms to the contour and other requirements (e.g. heat dissipation) of a larger piece of equipment of which the thick-film circuit assembly is to form part.
Before bending of the substrate, polymer conductors sandwiched between layers of polymer dielectric material are applied to the substrate in order to provide interconnections between separate parts of the thick-film circuitry across those regions where bending of the substrate is to take place.
After the passive components and interconnections of the thick-film circuit are produced active, components and other components may be added to the circuit assembly. Where bending of the substrate is required, the components just referred to may be added before or after bending of the substrate according to the size and required location of the components in question.
The substrate may be bolted or otherwise secured in good heat exchange relationship with a preferably finned heat sink to promote dissipation of heat generated by the power components of the circuit assembly.
By way of example the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective diagrammatic view of a thick-film circuit assembly constructed in accordance with the invention; and, Figure 2 is a diagram which illustrates the manner of providing bridging circuit interconnections at the bends in the thick-film circuit assembly shown in Figure 1.
Referring to the drawings, a thick-film circuit according to the present invention comprises a substrate 1 of commercially pure titanium or a titanium-based alloy. The substrate may initially be cut from a flat sheet of such metal and the relatively lightweight nature and high mechanical strength of the metal compared to ceramic and porcelainised steel used previously facilitates the use of relatively large substrates the size and final shape of which will be predetermined in accordance with specific requirements.
The substrate 1 will usually include a naturallyoccurring thin surface layer of oxide which ensures good adhesion between the substrate 1 and base dielectric material which is next applied to the substrate to form an insulative and low capacitative base for the thick-film circuitry to be formed thereon.
In the present example the base dielectric material is selectively applied to rectangular areas of the substrate, two such areas being shown at 2 and 3 in Figures 1 and 2. The base dielectric material may comprise a ceramic loaded or devitrified glass which is preferably applied to the substrate 1 in the form of a thick-film ink by a screen printing process. Engelhard zero-flow glasses have been found particularly suitable for use as the dielectric material.
The base dielectric material could alternatively be applied to the substrate 1 by electro-phoresis of powdered glass from an aqueous or organic medium or by plasma flame spraying of glass on to the substrate.
During the screen printing process or electrophoresis to lay down one or more layers of base dielectric material a temperature in the region of 60O#10000 C will be needed in order to ensure proper fusion of the glass so that it defines a coherent dense film or layer adhering strongly to the substrate 1. If the temperature is to exceed about 8000 C the substrate 1 should be suitably supported, as for example on a ceramic tile, in order to prevent sagging of the substrate.
Following the deposition of the base dielectric layer or layers the thick-film circuit passive components and interconnections will be built up in the usual way but it may be desirable prior to the step of printing the circuitry to coat all areas of the substrate, such as the areas 4 and 5, which are not already covered with base dielectric material with a material which prevents excessive oxidation of these areas of substrate during the firing process to form the circuit components and interconnections.
The process of building up the requisite pattern of passive components (e.g. resistors, capacitors) and conductive interconnections on the dielectric material areas involves the printing of such combinations of thick-film conductor, dielectric and resistor pastes as are necessary to achieve the desired pattern of circuitry, together with any printed resistors. Proprietary thick-film inks are used in this screen printing process and the printed components and interconnections will be subjected to firing temperatures in the range 6000 C~1000 C. Again the substrate 1 may be supported on a ceramic tile during the firing process.
The thick-film circuitry embodies a multiplicity of passive components comprising capacitors and resistors (e.g. printed resistor 6) and a pattern of interconnections (not shown). In order to interconnect the thick-film circuitry formed on the respective areas of the base dielectric material (e.g. areas 2 and 3) an insulating layer of polymer dielectric material 7 extending between the areas 2 and 3 may be applied to the substrate as shown in Figure 2. To this insulating layer 7 is applied a plurality of strip polymer conductors 8 electrically connected at their respective ends to components or interconnections forming part of the thick-film circuitry and a further insulating layer of polymer dielectric 9 is applied over the strip conductors 8.
The substrate 1 may then easily be bent along parallel lines running between the areas of base dielectric material (e.g. areas 2 and 3) in order to define a channel-shaped thick-film circuit assembly as shown in Figure 1 of the drawing. It will of course be appreciated that in other embodiments of the invention different and/or more complex shapes of substrate may be provided in order to meet the specific contour and mechanical/thermal requirements of the equipment concerned.
After bending, many active components such as integrated circuits (e.g. 10 and 1 1), transistors (e.g. 12), diodes (e.g. 13) are then mounted on the surface of the thick-film circuit together with other electronic components (e.g. variable resistors and capacitors such as those shown at 14 and 1 5, inductors, relays and connectors two of which are shown at 16 and 17. Semiconductor components may comprise bare chips or pre-packaged components. For the attachment of these components to the thick-film circuit conductive and/or non-conductive epoxies may be used or they may be suitably soldered to the thick-film interconnection pattern. Where bare semiconductor dual-in-line components are used wire bonds may be used to provide interconnection from the top surface of the components to the substrate.
To promote the dissipation of heat produced by power components of the circuit assembly a finned heat sink 18 (e.g. aluminium may be attached as by bolts to the substrate 1. These power components may be bolted through the substrate to the heat sink.
Thick film circuit assemblies (flat or shaped) produced according to the invention may be incorporated in a larger equipment in a manner similar to a printed circuit board or they may form an integral part of the mechanical structure of such equipment.
As will be appreciated from the foregoing, lightweight and mechanically strong thick-film circuits constructed in accordance with the present invention are particularly suitable for use in portable equipment (e.g. radios) and/or where the substrate may constitute part of the equipment casing which would in turn serve to promote cooling of the assembly.

Claims (12)

1. A thick-film circuit including a substrate comprising titanium.
2. A thick-film circuit as claimed in claim 1, in 'which the substrate is composed of commercially pure titanium or titanium-based alloy.
3. A thick-film circuit as claimed in claim 1 or claim 2, in which the substrate has base dielectric material applied to one or more selected parts thereof where the thick-film circuitry is located.
4. A thick-film circuit as claimed in claim 3, in which the base dielectric material is applied to the substrate by a silk screen printing process.
5. A thick-film circuit as claimed in claim 3 or claim 4, in which the base dielectric material is applied directly to the surface of the substrate which has a thin layer of naturally occurring oxide thereon which promotes good adhesion of the dielectric material to the substrate.
6. A thick-film circuit as claimed in any of claims 3 to 5, in which the dielectric material is applied to selected spaced-apart areas of the substrate which is bent along a line or lines running between or offset from said areas in accordance with the mechanical requirements of equipment of which the circuit is to form part.
7. A thick-film circuit as claimed in claim 6, in which thick-film circuitry (e.g. capacitors resistors and interconnections) built up on spaced apart areas of base dielectric material, as by screen printing, is interconnected by suitably insulated strip conductors applied to the substrate and extending between the said areas where the substrate is bent.
8. A thick-film circuit as claimed in any of claims 3 to 7, in which those areas of the substrate which are not covered with dielectric material are coated with a material which prevents excessive oxidation of the substrate during the firing step of printing passive components and interconnections on said base dielectric material.
9. A thick-film circuit as claimed in any preceding claim, in which active and/or other electrical components are mechanically and electrically connected to the thick-film circuitry.
10. A thick-film circuit as claimed in any preceding claim, in which the substrate is bolted or otherwise secured in good heat exchange relationship with a preferably finned heat sink.
1 1. A thick-film circuit substantially as herein before described with reference to the accompanying drawings.
12. Electrical equipment embodying a thickfilm circuit as claimed in any preceding claim, in which the substrate forms at least part of the equipment housing or other mechanical structure.
GB8401153A 1983-01-17 1984-01-17 Improvements relating to thick film circuits Expired GB2133934B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8401153A GB2133934B (en) 1983-01-17 1984-01-17 Improvements relating to thick film circuits

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8301153 1983-01-17
GB8401153A GB2133934B (en) 1983-01-17 1984-01-17 Improvements relating to thick film circuits

Publications (3)

Publication Number Publication Date
GB8401153D0 GB8401153D0 (en) 1984-02-22
GB2133934A true GB2133934A (en) 1984-08-01
GB2133934B GB2133934B (en) 1987-07-29

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Cited By (6)

* 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
GB2172437A (en) * 1985-03-16 1986-09-17 Marconi Electronic Devices 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
GB2255676A (en) * 1991-05-08 1992-11-11 Fuji Electric Co Ltd Metallic printed circuit board
WO2010043540A1 (en) * 2008-10-14 2010-04-22 Robert Bosch Gmbh Method for producing a ductile substrate provided with electrical elements

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1276527A (en) * 1968-11-01 1972-06-01 Int Electronic Res Corp Thermal dissipating metal core printed circuit board
GB1419193A (en) * 1972-06-30 1975-12-24 Ibm Hybrid circuit panel
GB1591895A (en) * 1977-12-12 1981-07-01 Smolko G G Electronic devices

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1276527A (en) * 1968-11-01 1972-06-01 Int Electronic Res Corp Thermal dissipating metal core printed circuit board
GB1419193A (en) * 1972-06-30 1975-12-24 Ibm Hybrid circuit panel
GB1591895A (en) * 1977-12-12 1981-07-01 Smolko G G Electronic devices

Cited By (13)

* 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
GB2172437A (en) * 1985-03-16 1986-09-17 Marconi Electronic Devices Printed circuits
EP0203680A2 (en) * 1985-03-16 1986-12-03 Marconi Electronic Devices Limited Electrical device including a printed circuit
EP0203680A3 (en) * 1985-03-16 1987-09-02 Marconi Electronic Devices Limited Electrical device including a printed circuit
GB2176063A (en) * 1985-05-22 1986-12-10 Michael Frederick Horgan A probe card
GB2230387B (en) * 1989-04-13 1993-10-06 Ist 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
GB2230387A (en) * 1989-04-13 1990-10-17 L S T Lab Ltd Improvements in or relating to automotive electrical systems
GB2255676A (en) * 1991-05-08 1992-11-11 Fuji Electric Co Ltd Metallic printed circuit board
DE4215084A1 (en) * 1991-05-08 1992-11-12 Fuji Electric Co Ltd METALLIC PRINTPLATE
US5316831A (en) * 1991-05-08 1994-05-31 Fuji Electric Co., Ltd. Metallic printed board
GB2255676B (en) * 1991-05-08 1995-09-27 Fuji Electric Co Ltd Metallic printed board
WO2010043540A1 (en) * 2008-10-14 2010-04-22 Robert Bosch Gmbh Method for producing a ductile substrate provided with electrical elements

Also Published As

Publication number Publication date
GB2133934B (en) 1987-07-29
GB8401153D0 (en) 1984-02-22

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