GB2085339A - Solderable paint - Google Patents
Solderable paint Download PDFInfo
- Publication number
- GB2085339A GB2085339A GB8033083A GB8033083A GB2085339A GB 2085339 A GB2085339 A GB 2085339A GB 8033083 A GB8033083 A GB 8033083A GB 8033083 A GB8033083 A GB 8033083A GB 2085339 A GB2085339 A GB 2085339A
- Authority
- GB
- United Kingdom
- Prior art keywords
- paint
- particles
- connection
- copper
- component
- 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- Withdrawn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
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
- C09D5/24—Electrically-conducting paints
-
- 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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/226—Non-corrosive coatings; Primers applied before welding
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Materials Engineering (AREA)
- Wood Science & Technology (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Conductive Materials (AREA)
- Paints Or Removers (AREA)
Abstract
An electrically conductive paint which dries or cures below 200 DEG C has a metallic content which consists solely of copper particles, the particles being dispersed in a polymeric binder together with a solvent and wetting agent. The polymeric binder may be an epoxide, methyl or ethyl cellulose, polyvinyl acetate, polyvinyl alcohol, a fluorinated rubber or acrylic copolymers including acrylamides and carboxylated acrylics. The solvent may be n- butyl acetate and the wetting agent can be triethanolamine.
Description
SPECIFICATION
Solderable paint
This invention relates to electrically conductive paint for application to electrical components to form a coating to which connnection may subsequently be made by soldering. Such paints are suitable for application particularly, though not exclusively, to solid electrolytic capacitors such as tantalum capacitors.
Tantalum capacitors have conventionally been manufactured with the cathode connection made by soldering a lead to a coating of electrically conductive silver paint applied to a portion of the outer surface of the capacitor body. It has however been found that the power factor of such capacitors degrades with time and this degradation has been attributed to the diffusion of silver from the paint into the solder.
Whilst it is possible to lessen this "leaching" of silver from the paint by including a quantity of silver in the solder formulation, this approach adds to the cost of making the capacitor and is of limited success in overcoming the problem.
Our Patent Specification No. 1,562,503 (R.D.
Weeks-W.H. Bliss 1-1 ) describes an alternative approach to the problem. This involves the use of an alternative paint formulation which includes silvercoated copper particles as well as pure silver particles. This was found to limit the power factor degradation significantly, and also had the advantage of being cheaper than a pure silver paint.
The specification of our Patent Application No.
7923112 (R. D. Weeks D. J. Croney 2-1) describes a development of this idea and involves using silver particles together with uncoated copper particles.
Such paints using uncoated copper particles have been found to afford the same improvement in the performance of tantalum capacitors, by limiting power factor degradation, as has been achieved using comparable formulations using the silver coated copper.
It has now been found that the use of the silver particles can satisfactorily be dispensed with entirely.
According to the present invention there is provided an electrically conductive metal-loaded paint which dries or cures below 200 C, the metallic content of which consists exclusively of particles of copper, which particles are dispersed in a polymeric binder together with a compatible solvent and wetting agent. The invention also resides in electrical components coated with such paints, such components to which electrical connection with the paint has been made by soldering, and in the making of such electrical connections.
There follows a description of the manufacture of a tantalum capacitor having a soldered cathode lead connection to a coating of paint embodying the invention in a preferred form. The description refers to the accompanying drawings in which:
Figure 1 shows diagrammatically the process and steps involved in making the capacitor, and
Figure 2 shows diagrammatically the modification of the steps of Figure 1 used to provide the capacitor with an alternative layout of lead connections.
A specific formulation of electrically conductive paint for use in the making of cathode connections to tantalum capacitors consists of 51.0% by weight of copper powder, 6.9% polymeric binder 42.0% by weight of a solvent compatible with the binder, and 0.1% by weight of a wetting agent. The copper powder is preferably a mixture of lamellar form copper, that is to say flake copper, and a powdered cooper which has a non-lamellarform. The proportions of the two types of powder is not critical though generally it is preferred to use a mixture with a preponderance of the non-lamellar particles. A typical mixture consists of 9 parts by weight of the non-lamellar particles to 1 part of the lamellar form ones.A suitable grade of flake copper is that marketed byWolstenholme Bronze Powders Ltd under the designation copper super ink lining grade
Y9518, while that of the other copper powder is that marketed by J.J. Makin Ltd under the designation irregular copper grade 300LD. The binder can be an acrylic copolymer sold under the trade name Surcol 530 by Allied Colloids Ltd. The solvent for this binder can be n-butyl acetate and the wetting agent can be triethanolamine.
The constituents are thoroughly mixed in a high speed rotary mixer in order to disperse the particles completely throughout the liquid.
Successful paint compositions may employ powders and solvents etc. other than those specified above. In particular the polymeric binder may be an epoxide, methyl or ethyl cellulose, polyvinyl acetate, polyvinyl alcohol, a fluorinated rubber or acrylic copolymers including acrylamides and carboxylated acrylics. Some of these binders are water reducible, and it would be advantageous from a Health and
Safety point of view to use a water-based system.
The solvent must be compatible with the binder and have a suitable volatility to provide convenient drying characteristics, n-butyl acetate has been found to provide faster drying times than the 2-ethoxyethanol used in the specific formulations disclosed in Patent Specification No. 1,562,503.
The proportions of the various constituents can be varied and still produce a successful paint. Typically the metal content constitutes between 30 and 70 weight percent of the whole, the binder between 2 and 20 percent, the solvent between 30 and 60 percent, and the wetting agent between 0.01 and 1.0 percent.
Referring now to the drawings a tantalum capacitor body anode 1 is formed by compacting and sintering tantalum powder with a lead wire 2 forming the anode lead of the capacitor. A dielectric layer of tantalum pentoxide is formed i.e. grown electrolytically, on the surface of the tantalum parti cites. The interstices of the body are filled with manganese dioxide acting as a solid dielectric material. This stage is preferably carried out several times to ensure that the interstices of the sintered body are fully impregnated. The body is then dipped in a reservoir 3 of a semi-colloidal suspension of graphite in water 4 and oven-dried at around 100"C for a 2 hour. The dipping is shown diagrammatically in Figure 1 B.
In Figure 1Cthere is shown diagrammatically a reservoir 5 of conductive paint 6 made in accordance with the specific example given earlier. Care is taken to ensure that the conductive paint covers only a part la of the body 1 and does not encroach upon the anode lead wire 2 (see also Figure 1 D). The paint can be dried at room temperature but preferably is dried in an oven, at around 1 OO"C, containing nitrogen to avoid oxidation of the copper particles.
In Figure 1 D is shown a hairpin-shaped lead wire 7 which is connected to the anode lead wire 2 by a weld at 8 and the other end 9 of the hairpin wire embraces one coated portion 1 a of the body 1.
Then the capacitor body is fluxed (not shown) and dipped in a bath 10 of solder alloy containing tin, so that the end 9 of the hairpin wire becomes soldered to the coated portion la of the body 1 (Figure 1E).
Other methods of coating are possible including spraying, brushing, screen-printing, off-set printing.
Finally, as shown in Figure 2 F, the capacitor body 1 and portions of the lead wires are encapsulated in a resin or plastics coating 11 and the end of the hairpin wire is cut off to leave residual connection leads 12 and 13.
Referring now to Figure 2 there is shown a tantalum capacitor body 14 which has been processed to the same stage as is shown in Figure 1 C above and has a coated portion 15. In this embodiment a can 15 is connected to a cathode lead wire 17 is provided with a slug 18 of solder in the bottom of the can. Onto the anode lead wire 19 is assembled a seal 20 comprising an outer metal ring 21, an intermediate insulating glass ring 22, and a metal tubulation 23. The inside of the tubulation 23 and the outside of the ring 21 are tinned so that when the whole assembly is heated the solder slug 18 melts soldering the coated portion 15 to the interior of the can.
The ring 21 is soldered to the rim of the can and the tubulation is soldered to the lead wire 19.
Thus the capacitor body becomes sealed in the can and the lead 17 is electrically connected with the coated portion 15 of the body. In this embodiment as can be seen the leads extend axially.
In both embodiments the copper particles will maintain good electrical connection between the solder and the graphite coating of the anode. Under
normal manufacturing conditions negligible oxidation of the copper particles has been found to occur.
This paintformulatedfortantalum capacitors has
been found also suitable for making silver paint: solder connections in other types of electrical com
ponents. A particular example is for edge bonding the mica stacks of mica capacitors.
Claims (1)
1. An electricaliv conductive metal-loaded paint which dries or cures below 200 C, the metallic
content of which consists exclusively of particles of
copper, which particles are dispersed in a polymeric
binder together with a compatible solvent and wetting agent.
2. A paint as claimed in claim 1 wherein the
particles of copper consist of a mixture of lamellar and non-lamellar particles.
3. A paint as claimed in claim 2 wherein the majority, by weight, of the copper particles are non-lamellar.
4. A paint as claimed in claim 3 wherein up to 95%, by weight, of the particles are non-lamellar particles.
5. A paint as claimed in any preceding claim in which the metal content constitutes between 30 and 70 weight pei cent of the whole.
6. A paint as claimed in any preceding claim wherein the polymeric binder content constitutes between 2 and 20 weight percent of the whole.
7. A paint as claimed in any preceding claim wherein the solvent content constitutes between 30 and 60 weight percent of the whole.
8. A paint as claimed in any preceding claim wherein the wetting agent content constitutes between 0.01 and 1.0 weight percent of the whole.
9. A paint as claimed in any preceding claim wherein the polymeric binder is an acrylic copolymer.
10. A paint as claimed in claim 9 wherein the solvent is n-butyl acetate.
11. A paint as claimed in claim 9 or 10 wherein the wetting agent is triethanolamine.
12. A paint as claimed in claim 1 and substantially as hereinbefore described.
13. An electrical component, a portion of which has been coated with a paint as claimed in any preceding claim.
14. An electrical component as claimed in claim 13 wherein a soldered connection has been made to the paint-coated portion by soldering with a tincontaining solder.
15. An electrical component as claimed in claim 14 which component is an electrolytic capacitor and wherein the soldered connection is the cathode lead connection of the capacitor.
16. An electrical component as claimed in claim
14 which component is a mica capacitor.
17. A mica capacitor as claimed in claim 16 wherein the paint forms an edge bonding for the mica stack of the capacitor.
18. An electrolytic capacitor provided with a soldered cathode lead connection to a coating of paint which connection is substantially as hereinbefore described with reference to the accompanying drawings.
19. A method of making electrical connection with an electrical component which method includes the steps of applying to a portion of the component a coating of a paint as claimed in any claim of claims 1 to 12 to a portion of said component, of curing the applied paint and of soldering with a tin-containing solder an electrical lead to the cured paint.
20. A method as claimed in claim 19 wherein the coating of paint is applied by dip-coating.
New claims or amendments to claims filed on 2615181 Superseded claim 1
New or amended claim:- 1
1. An electrically conductive metal-loaded paint which dries or cures below 2000C to form a material to which connection may be made by soldering, the metallic content of which paint consists exclusively of particles of copper, which particles are dispersed
in a polymeric bindertogether with a compatible
solvent and wetting agent.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8033083A GB2085339A (en) | 1980-10-14 | 1980-10-14 | Solderable paint |
GB8125130A GB2085340B (en) | 1980-10-14 | 1981-08-18 | Solderable paint |
DE19813140346 DE3140346A1 (en) | 1980-10-14 | 1981-10-10 | SOLIDABLE GUIDANCE |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8033083A GB2085339A (en) | 1980-10-14 | 1980-10-14 | Solderable paint |
Publications (1)
Publication Number | Publication Date |
---|---|
GB2085339A true GB2085339A (en) | 1982-04-28 |
Family
ID=10516653
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8033083A Withdrawn GB2085339A (en) | 1980-10-14 | 1980-10-14 | Solderable paint |
Country Status (2)
Country | Link |
---|---|
DE (1) | DE3140346A1 (en) |
GB (1) | GB2085339A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20130258555A1 (en) * | 2012-04-02 | 2013-10-03 | Apaq Technology Co., Ltd. | Capacitor unit and stacked solid electrolytic capacitor having the same |
US10032945B2 (en) | 2013-01-10 | 2018-07-24 | E I Du Pont De Nemours And Company | Electrically conductive adhesives comprising blend elastomers |
US10030176B2 (en) | 2013-01-10 | 2018-07-24 | E I Du Pont De Nemours And Company | Electrically conductive adhesives comprising fluoroelastomers |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3229952C2 (en) * | 1981-08-18 | 1985-05-15 | International Standard Electric Corp., New York, N.Y. | Electric capacitor |
US4687597A (en) * | 1986-01-29 | 1987-08-18 | E. I. Du Pont De Nemours And Company | Copper conductor compositions |
-
1980
- 1980-10-14 GB GB8033083A patent/GB2085339A/en not_active Withdrawn
-
1981
- 1981-10-10 DE DE19813140346 patent/DE3140346A1/en not_active Withdrawn
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20130258555A1 (en) * | 2012-04-02 | 2013-10-03 | Apaq Technology Co., Ltd. | Capacitor unit and stacked solid electrolytic capacitor having the same |
US10032945B2 (en) | 2013-01-10 | 2018-07-24 | E I Du Pont De Nemours And Company | Electrically conductive adhesives comprising blend elastomers |
US10030176B2 (en) | 2013-01-10 | 2018-07-24 | E I Du Pont De Nemours And Company | Electrically conductive adhesives comprising fluoroelastomers |
Also Published As
Publication number | Publication date |
---|---|
DE3140346A1 (en) | 1982-08-19 |
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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) |