GB2201111A - Bonding metal foil to ceramic - Google Patents
Bonding metal foil to ceramic Download PDFInfo
- Publication number
- GB2201111A GB2201111A GB08703904A GB8703904A GB2201111A GB 2201111 A GB2201111 A GB 2201111A GB 08703904 A GB08703904 A GB 08703904A GB 8703904 A GB8703904 A GB 8703904A GB 2201111 A GB2201111 A GB 2201111A
- Authority
- GB
- United Kingdom
- Prior art keywords
- foil
- ceramic
- bonding
- copper
- holes
- 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- Withdrawn
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B37/00—Joining burned ceramic articles with other burned ceramic articles or other articles by heating
- C04B37/02—Joining burned ceramic articles with other burned ceramic articles or other articles by heating with metallic articles
- C04B37/021—Joining burned ceramic articles with other burned ceramic articles or other articles by heating with metallic articles in a direct manner, e.g. direct copper bonding [DCB]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K33/00—Specially-profiled edge portions of workpieces for making soldering or welding connections; Filling the seams formed thereby
-
- 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
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/38—Improvement of the adhesion between the insulating substrate and the metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/36—Electric or electronic devices
- B23K2101/38—Conductors
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
- C04B2237/30—Composition of layers of ceramic laminates or of ceramic or metallic articles to be joined by heating, e.g. Si substrates
- C04B2237/32—Ceramic
- C04B2237/34—Oxidic
- C04B2237/343—Alumina or aluminates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
- C04B2237/30—Composition of layers of ceramic laminates or of ceramic or metallic articles to be joined by heating, e.g. Si substrates
- C04B2237/40—Metallic
- C04B2237/407—Copper
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
- C04B2237/50—Processing aspects relating to ceramic laminates or to the joining of ceramic articles with other articles by heating
- C04B2237/62—Forming laminates or joined articles comprising holes, channels or other types of openings
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
- C04B2237/50—Processing aspects relating to ceramic laminates or to the joining of ceramic articles with other articles by heating
- C04B2237/70—Forming laminates or joined articles comprising layers of a specific, unusual thickness
- C04B2237/704—Forming laminates or joined articles comprising layers of a specific, unusual thickness of one or more of the ceramic layers or articles
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2237/00—Aspects relating to ceramic laminates or to joining of ceramic articles with other articles by heating
- C04B2237/50—Processing aspects relating to ceramic laminates or to the joining of ceramic articles with other articles by heating
- C04B2237/70—Forming laminates or joined articles comprising layers of a specific, unusual thickness
- C04B2237/706—Forming laminates or joined articles comprising layers of a specific, unusual thickness of one or more of the metallic layers or articles
-
- 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
- H05K1/0306—Inorganic insulating substrates, e.g. ceramic, glass
-
- 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
- H05K2201/03—Conductive materials
- H05K2201/0332—Structure of the conductor
- H05K2201/0335—Layered conductors or foils
- H05K2201/0355—Metal foils
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Manufacturing Of Printed Wiring (AREA)
Abstract
Electrical conductor arrangement consists of a ceramic substrate to which a copper foil (4, 5) is bonded; the foil is provided with an array of fine holes (3) prior to bonding, so that when bonding takes place at a high temperature, any gases generated can escape rather than cause bubbles under the surface of the foil. The bonding is achieved by forming a eutectic bond at a temperature of about 1070 DEG C. The holes (3) may be formed by chemical etching and the foil may be patterned to the desired electrical circuit shape either prior to or after bonding. The ceramic may be alumina. After bonding a solderable nickel plating may be provided on the copper. <IMAGE>
Description
ELECTRICAL CONDUCTOR ARRANGEMENT
This invention relates to an electrical conductor arrangement, and is particularly applicable to such arrangements in which a thin conductive metal field is carried by an insulating substrate to which it is bonded.
In order- to make an electrical conductor arrangement which forms part of an electrical circuit and/or interconnection, it has been proposed to bond a foil of copper to a thin lamina of ceramic. If the foil has an extensive area, it often happens that gas is trapped between the foil and the substrate during the bonding process, causing poor adhesion and bubbles to form. The present invention seeks to provide an improved such arrangement
According to a first aspect of this invention an electrical conductor arrangement includes an electrical insulating ceramic substrate carrying a foil of copper which is bonded to a surface of the substrate, the foil having an array of fine holes formed prior to bonding.
According to a second aspect of this invention a method of making an electrical conductor arrangement includes the steps of forming an array of fine holes through the thickness of a copper foil; and bonding the foil to a surface of an electrically insulating ceramic substrate, gas generated during bonding being vented via said holes.
The invention is further described by way of example, with reference to the accompanying drawings, in which:
Figure 1 illustrates a sectional view through part of an electrical conductor arrangement, and
Figure 2 is a plan view of a similar arrangement in accordance with the invention.
It is increasingly common to fabricate electrical circuits as a patterned electrical conductive foil which is mounted upon an electrically insulating lamina. The way in which the foil is formed and shaped depends very largely on the nature of the foil material and that of the substrate. In the case of substrates formed of a ceramic material such as alumina, it is possible to attach a foil of copper by means of direct bonding to one surface of the ceramic. This is a relatively simple and economical process and is particularly suited for very miniaturised electrical circuits. However, it has been found difficult to reliably bond copper foils to ceramic in those instances in which the copper foil has an appreciable area.The bonding of the copper to the ceramic is often not very good over localised regions at which small bubbles form and it is believed that these bubbles are entrapped during the fabrication process during which the copper is laid down upon the ceramic. Whilst precautions can be taken to minimise the extent to which gas is trapped by, for example, carefully attaching the copper foil at one end of the substrate, and then bringing it down in a smooth action which in theory drives out gases ahead of the copper/ceramic contact, this is still not sufficiently satisfactory. It has been proposed previously to minimise the problem by providing fine' grooves across the surface of the copper but this makes it relatively difficult to lay down a complex pattern, can cause electrical discontinuities in the final circuit and moreover can result in severe distortion of the circuit which results.
In accordance with this invention a relatively thin substrate of ceramic 1 in this case alumina having a thickness of about 1 mm is carefully cleaned and prepared to receive a copper foil 2. Prior to the application of the copper foil 2 to the ceramic, a regular array of fine circular holes 3 are formed through the thickness of the foil, preferably by means of a chemical etching process utilising a photo-resist mask. These holes are typically about .5 mm in diameter and are spaced apart by about 5 mm. The dimensions and spacing of the holes will depend to a certain extent on the overall size of the copper foil and the ceramic substrate, but these dimensions are suitable for a ceramic substrate 1 having dimensions of about 10 cm x 10 cm.The diameter of the holes in relation to the thickness of the foil is likely to be of importance, and the specified ratio of 1:2 gives very satisfactory results.
The copper foil can then be patterned to provide the required electrical circuit configuration. A typical circuit configuration is shown more clearly in Figure 2 in which the copper foil is represented by the hatching lines. The fine holes 3 are represented diagramatically.
The two areas 4 and 5 of copper foil can be attached separately to the ceramic after their shapes have been fabricated as an initial step. Preferably however, the patterns are etched in the copper foil after it has been bonded to the ceramic. Once the perforated foil has been correctly sh#aped it is directly bonded to the ceramic using a known direct bonding technique. In this technique heat is applied to the copper whilst it is in contact with the ceramic to form a eutectic bond at a temperature of 1070 0C which is just below the melt temperature of copper of 1084 0C. During the bonding process a liquid phase is generated at the interface between the copper and the alumina which results in a strong mechanical bond with the ceramic. This process can give rise to the generation of gases and the periodic spacing of the fine holes 3 allows these gases to escape. By carefully choosing the dimensions and spacing of the holes they provide a sufficiently improved bond, whilst not impairing the electrical performance of the circuit of which they form a part. Furthermore, since the holes are relatively small, they do not constitute weaknesses which give rise to a distortion of the copper foil or of the ceramic substrate to which the copper is bonded. After attachment the foil is etched to form the required conductive pattern by means of a suitable chemical etchant and an appropriately shaped etch resistant mask. Finally, the copper surface is conveniently plated with a nickel compound which is receptive to solder.
Claims (10)
1. An electrical conductor arrangement including an electrical insulating ceramic substrate carrying a foil of copper which is bonded to a surface of the substrate, the foil having an array of fine holes formed prior to bonding.
2. An arrangement as claimed in claim 1 and wherein the ceramic is alumina.
3. An arrangewment as claimed in claim 1 or 2 and wherein the size of the holes are about half the thickness of the foil.
4. An arrangement as claimed in any of the preceding claims and wherein the copper foil forms a eutectic bond with the ceramic.
5. An arrangement as claimed in any of the preceding claims and wherein the foil is shaped to constitute a circuit pattern.
6. A method of making an electrical conductor arrangement including the steps of forming an array of fine holes through the thickness of a copper foil; and bonding the foil to a surface of an electrically insulating ceramic substrate, gas generated during bonding being vented via said holes.
7. A method as claim in claim 6 and wherein the foil is bonded to the ceramic at a high temperature at which a eutectic phase is produced.
8. A method as claimed in claim 7 and wherein aEter the eutectic bond has been formed, the foil is selectively removed to leave a pattern of foil on the ceramic which constitutes at least part of an electrical circuit.
9. An electrical conductor arrangement substantially as illustrated in and described with reference to the accompanying drawings.
10. A method of making an electrical conductor arrangement substantially as illustrated in and described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08703904A GB2201111A (en) | 1987-02-19 | 1987-02-19 | Bonding metal foil to ceramic |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08703904A GB2201111A (en) | 1987-02-19 | 1987-02-19 | Bonding metal foil to ceramic |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8703904D0 GB8703904D0 (en) | 1987-03-25 |
| GB2201111A true GB2201111A (en) | 1988-08-24 |
Family
ID=10612593
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08703904A Withdrawn GB2201111A (en) | 1987-02-19 | 1987-02-19 | Bonding metal foil to ceramic |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2201111A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1164638A (en) * | 1965-12-20 | 1969-09-17 | Varian Associates | Thermal Connector for Cooling Devices such as Electron Tubes |
| GB2099742A (en) * | 1981-06-05 | 1982-12-15 | Philips Electronic Associated | Bonding metals to non-metals |
-
1987
- 1987-02-19 GB GB08703904A patent/GB2201111A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1164638A (en) * | 1965-12-20 | 1969-09-17 | Varian Associates | Thermal Connector for Cooling Devices such as Electron Tubes |
| GB2099742A (en) * | 1981-06-05 | 1982-12-15 | Philips Electronic Associated | Bonding metals to non-metals |
Non-Patent Citations (1)
| Title |
|---|
| WO A1 81/00226 * |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8703904D0 (en) | 1987-03-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |