GB2211668A

GB2211668A - Repairing electrical circuits

Info

Publication number: GB2211668A
Application number: GB8828967A
Authority: GB
Inventors: Simon Charles Phillips; Robert Paul Noades
Original assignee: Flowlyne UK Ltd
Current assignee: Flowlyne UK Ltd
Priority date: 1987-12-18
Filing date: 1988-12-12
Publication date: 1989-07-05
Anticipated expiration: 2008-12-12
Also published as: GB8828967D0; WO1989006087A1; AU2902889A; GB2211668B

Abstract

A laminated structure 1 of flexible card-like form, for repairing and/or manufacturing an electrical circuit, comprises a layer 2 of solder, superimposed on a layer 3 electrically conductive material, (copper), which is in turn superimposed on a layer 4 of adhesive material. An intermediate layer 5 of brass effectively increases the surface area of the conductive layer 3. The adhesive layer 4 is covered by a removable backing layer 6 of paper. The laminated structure 1 is delineated by cuts 10 so as to form a plurality of individual conductive components which can subsequently be stripped from the structure 1 in a convenient manner. To carry out a repair to an electrical circuit, a conductive component is applied, with overlaps, to the damaged area of the circuit. The self-adhesive layer 4 of the component keeps it firmly in place whilst solder is caused to flow over the joint areas to form a strong metallurgical joint between the undamaged section of the circuit and the solder layer 2 of the component. <IMAGE>

Description

"ImDrovements in or relating to the Repair of Electrical Circuits" BACKGROIlr.D TO TFb IS^f9tTIONT This invention relates to the repair of electrical circuits, in particular printed circuits.

As used herein, "repair of electrical circuits" also includes the manufacture of electrical circuits. For example, prototype circuits.

Electrical circuits often suffer from accidental or operational damage. At the present time repairs to electrical circuits are not only time consuming, but are awkward to effect and are usually unsightly.

The manufacture of prototype circuits, comprising custom made conductive tracks, necessitates etching and tinning of copper clad fibre board. These operations are time consuming. Furthermore, the finished circuit does not provide flexibility.

SI7n9RIES OF THE INVENTION According to one aspect of the invention, a conductive component for repairing an electrical circuit comprises a layer of solder, superimposed on a layer of electrically conductive material, which is in turn superimposed on a layer of adhesive material.

An intermediate layer of material may be disposed between the layers of conductive and adhesive material, said intermediate layer serving to effectively increase the surface area of the conductive material.

The adhesive material is preferably a transfer adhesive, covered by a removable layer of protective material.

The adhesive is heat resistant to the extent that it does not melt or lose its ability to bond to any significant degree when heat sufficient to melt the solder layer is applied to the component.

According to another aspect of the invention, a laminated structure for repairing an electrical circuit comprises a plurality of conductive components as aforesaid, distributed over the structure in juxtaposed relationship, and formed so as to be stritpable from the structure.

According to a further aspect of the invention, a method of manufacturing a laminated structure for repairing an electrical circuit comprises the steps of superimposing a layer of solder on a layer of electrically conductive material, superimposing a layer of adhesive material on the said layer of conductive material, and then delineating the structure so as to form a plurality of individual conductive components thereon, each as aforesaid, which components can subsequently be stripped from the structure.

According to yet another aspect of the invention, a method of repairing and/or manufacturing an electrical circuit comprises the steps of applying to a base of insulating material at least one conductive component as aforesaid.

The invention further comprises an electrical circuit repaired and/or manufactured by the said method.

As used herein, the term "solder" means any suitable metallic material, (not necessarily an alloy), capable of being united with the electrically conductive layer, when in a melted state.

BRIEP DESCRIPTION OF THE DR T & The various aspects of the invention will now be described by way of example only, with reference to the accompanying drawings, wherein Figure 1 is a view in perspective of a laminated structure according to one aspect of the invention, Figure 2 is a plan view thereof, in rather more detail, Figure 3 illustrates various components stripped from the laminated structure of Figures 1 and 2, Figure 4 is a fragmentary view, in section, and to an enlarged scale, of the laminated structure, taken on the lines TV-TV of Figure 2, Figure 5 is a plan view of a damaged circuit board, Figure 6 is a plan view of the board of Figure 5, and illustrates how repairs are made, Figure 7 is a plan view of a prototype circuit board, Figure 8 is a view similar to that provided by Figure 4, and illustrates a modified laminated structure.

Figure 9 is a flow sheet which illustrates a method of manufacturing the laminated structure of Fire 2, (or Figure 8), and Figures 10 and 11 illustrate alternative methods of delineating the laminated structures.

In the figures, like reference numerals refer to like features and/or components.

DETAILED DESCRIPTION OF TIIE PREFERRED Sm30DIIs US with reference to Figures 1 to 4, a laminated structure 1 of card-like form for repairing an electrical circuit comprises, (in Figure 4), a layer 2 of solder, superimposed on a layer 3 of electrically conductive material, which is in turn superimposed on a layer 4 of adhesive material. An intermediate layer 5 effectively increases the surface area of the conductive material layer 3. The layer 4 of adhesive material is covered by a removable backing layer 6 of protective material. The structure 1 is a flexible structure.

In this particular example, the materials are as follows :layer 2 - lead/tin alloy of 5.0 microns thickness.

layer 3 - copper of 75.0 microns thickness.

layer 4 - an acrylic transfer adhesive tape of 50.0 microns t ickness.

(Marketed by the tT.S. based multi-national company 3M as Type 9462).

layer 5 - brassate - a flash coating of brass, on the copper layer 3, 2.0 microns in thickness. This coating has a relatively rough surface compared with that of the copper layer 3, which is relatively smooth. The brassate layer 5 thus effectively increases the surface area of the copper layer 3 so as to ensure a high-strength (indirect) bond between the copper and the adhesive layers 3, 4 respectively, layer 6 - silicone coated paper of 100.0 microns thickness.

The laminated structure 1 is delineated by cuts 10 (Figure 4) so as to form a plurality of individual conductive components differing in outline. The components comprise straight tracks 11, 12, 13 of varying width, tracks and pads 14, circular pads 15, 16, 17 of varying diameter, and integrated circuit (I.C.) pads 18.

(Figure 2).

The cuts 10 extend down through the structure 1, in directions normal to the upper surface 20 thereof, so as to penetrate the paper layer 6. This allows the individual conductive components 11, 12, 13 to 18 subsequently to be stripped from the structure 1 in a convenient manner.

It will be appreciated from the foregoing that each conductive component 11 etc. comprises the superimposed layers 2, 3, 4, 5, 6.

Figure 5 illustrates an electrical circuit board 25 comprising a base 26 of insulating material upon which are mounted circuit sections 27, 28, 29. Section 27 is undamaged; sections 28, 29 are damaged.

The damaged areas are cleaned, using a suitable solvent. For example, an isopropyl alcohol, or trichloroethene. A straight track component 11 of relatively large width, (compared with components 12, 13), is stripped out of the laminated structure 1, cut to the desired length, and any of the backing layer 6 attached to the component removed.

With additional reference to Figure 6, the trimmed-off component 11 is now applied to the damaged area of circuit section 29, with overlaps 35, 36 on to the undamaged parts of the section. The self-adhesive backing layer 4 of the component 11 keeps it firmly in place whilst solder is caused to flow over the joint areas to form a strong metallurgical joint between the circuit section 29 and the solder layer 2 of the component 11. Naturally, the joint solder is chosen so as to be compatible with the materials it unites.

The adhesive 4 is heat resistant to the extent that it does not melt or lose its ability to bond to any significant extent, when heat sufficient to melt the solder 2 is applied to the component 11.

A component 14 is used to repair circuit section 28 in the same way, employing an overlap 37. Tlle repaired joint areas are best encapsulated by one or more coatings of insulating lacquer to insulate and protect the repairs.

With reference now to Figure 7, a prototype electrical circuit board 40 can be constructed by joining up several of the components 11 and 14 removed from the laminated structure 1, applying them on an insulating base board 41 to form a predetermined circuit pattern.

The circuit illustrated by Figure 4 also uses curved components 42, not present on the example of laminated structure 1 illustrated by Figure 2, but provided by a similar structure. (rot illustrated).

Figure 8 illustrates a laminated structure la wherein two modifications are illustrated, namely : (a) two layers (51 and 52) of adhesive are provided, as well as (b) a layer 50 of silk.

Adhesive layers 51, 52 are each of 50.0 microns thickness. The thickness of the silk layer 50 is 30.0 microns.

Adhesive layer 51 comprises a permanently setting but flexible resin-based adhesive. A range of suitable adhesives is available from CItA-GEIGY S.A., the Swiss-based multi-national company. The layer 51 is used to permanently bond the silk layer 50 to the copper layer 3, (by way of the brassate layer 5).

The silk layer 50 serves as a thermal barrier, which gives added head-resisting protection to the adhesive layer 52. The adhesive layer 52 may be of the same material, (e.g. 31;I Type 9462) as layer 4 of Figure 4. however, the modification allows use of adhesive which is of a lower grade, i.e. less heat-resisting than the said layer 4.

Alternatives to silk as a thermal barrier material comprise silicon carbide, alumino silicate, and paper.

Slodifications (a) and (b) need not be incorporated in a single laminated structure.

Figure 9 is a flow sheet which illustrates a method of manufacturing the laminated structure 1, (or, with suitable adaptation, the structure la), using process steps 60 to 67.

Step 60. Raw copper strip, pre-coated with brassate, and comprising layers 3 and 5, is cleaned. For example, by use of a solvent of the type mentioned above.

Sup 61. SIasking tape is applied to layer 5 of the composite layers 3, 5.

Step 62. The solder layer 2 is plated on the non-masked surface of the copper layer 3.

Step 63. The masking strip is removed.

Step 64. The adhesive layer 4 is applied to the brassate layer 5.

Step 65. The adhesive layer 4 is covered with the protective layer 6.

Step 66. The slots 10 are formed, thus producing components 11 etc.

Step 67. The multi-laminate strip is cut into sections, each section forming a laminated structure 1 or la of flexible form.

Figures 10 and 11 illustrate two alternative methods of forming the slots 10 at Step 66.

In Figure 10, the laminated strip is passed through the nip 70 of a pair of rollers 71, 72. Roller 71 is an engraved embossing roller. Cooperating roller 72 is plain surfaced. The process employing the rollers 71, 72 is known as "kiss-cutting".

In a non-illustrated modification of this method, the structure 1 is placed in a suitable support and an impression plate is brought down into "kiss-cutting" contact with the structure.

In Figure 11, a movable laser unit 75 subjects the stationary structure 1 to a cutting laser beam 76. Alternatively, the laser unit 75 may be made stationary and the structure 1 movable.

Alternatives to the lead/tin solder 2 comprise such solders as gold, silver and platinum.

The solder(s) need not be disposed by a plating process.

Alternatives include chemical deposition.

Claims

C L A I IJ S

1. A conductive component for repairing electrical components, comprising a layer of wolder, superimposed on a layer of electrically conductive material, which is in turn superimposed on a layer of adhesive material.

2. A component as claimed in Claim 1, wherein the adhesive material is a transfer adhesive, covered by a layer of protective material.

3. A component as claimed in Claim 1 or 2, wherein an intermediate layer of material is disposed between the layers of conductive and adhesive material, the intermediate layer servin to effectively increase the surface area of the layer of conductive material.

4. A component as claimed in any one of Claims 1 to 3, wherein a thermal barrier layer is disposed between the layer of conductive material and the layer of adhesive material.

5. A laminated structure for repairing an electrical circuit, coiiiprising a plurality of conductive components each as claimed in any one of Claims 1 to 4, distributed over the structure in juxtaposed relationship and formed so as to be striptable from the structure.

6. A laminated structure as claimed in Claim 5, wherein the conductive components differ in outline.

7. A method of manufacturing a laminated structure, comprising the steps of superimposing a layer of solder on a layer of electrically conducting material, superimposing a layer of adhesive material on the said layer of conductive material, and then delineating the structure so as to form a plurality of individual conductive components, which components can subsequently be stripped from the structure.

8. The method of Claim 7, wherein the components are delineated by use of an embossing roller or plate.

9. The method of Claim 7, wherein the components are delineated by use of a cutting laser beam.

10. A method of repairing and/or manufacturing an electrical circuit, comprising the step of applying to a base of insulating material at least one conductive component as claimed in any one of Claims 1 to 4.

11. An electrical circuit repaireAand/or manufactured by the method of Claim 10.

Amendments to the claims have been filed as follows 8. The method of Claim 7, wherein the components are delineated by use of an embossing roller or plate.

9. The method of Claim 7, wherein the components are delineated by use of a cutting leser beam, 10. A method of repairing arld/or manufactulino an electrical circuit, comprising the step of applying to a base of insulating material at least one conductive component as claimed in any one of Claims 1 to 4.

11. An electrical circuit repaired and/or manufactured by the method of Claim 10.

12. A conductive component substantiallr as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

13. A conductive component substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings, modified substantially as hereinbefore described with reference to Figure 8 of said drawings.

14. A laminated structure substantially as hereinbefore described with reference to Figures 1 to 4 of the accom#anyi nt- drawings.

15. A laminated structure substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanaring drawings, modified substantially as hereinbefore described with reference to Fibre 8 of said drawings.

16. A method of manufacturing a laminated structure, substantially as hereinbefore described with reference to Figures 1, 2, 3, 4, 9 and 10 of the accompanyin dins.

17. h method of manufacturins a laminated structure, substantially as hereinbefore described with reference to Figures 1, 2, 3, 4, 9 and 11 of the accompanying drawings.

1E. A method of manufacturine a laminated structure, substantially as hereinbefore described with reference to Figures 1, 2, 8, 9 and 10 of the accompanying drawings.

19. A method of manufacturing a laminated structure, substantially as hereinbefore described with reference to Fiurs 1, 2, 8, 9 and 11 of the accompanying drawings.

20. A method of repairing an electrical circuit, substantially as hereinbefore described with reference to Figure 6 of the accompany drawings.

21 A method of manufacturing an electrical circuit, substantially as hereinbefore described with reference to figure 6 of the accompanying drawings.