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EP 0 318 831 B1 |
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EUROPEAN PATENT SPECIFICATION |
(45) |
Mention of the grant of the patent: |
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09.09.1992 Bulletin 1992/37 |
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Date of filing: 24.11.1988 |
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International Patent Classification (IPC)5: H01R 13/03 |
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Electric power connectors
Elektrische Leistungsverbinder
Connecteurs électriques de puissance
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Designated Contracting States: |
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AT BE CH DE ES FR GB GR IT LI LU NL SE |
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Priority: |
02.12.1987 CA 553333
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Date of publication of application: |
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07.06.1989 Bulletin 1989/23 |
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Proprietor: INCO LIMITED |
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Toronto
Ontario, M5K 1N4 (CA) |
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Inventors: |
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- Bell, James Alexander Evert
Ontario L6L 5Y9 (CA)
- Hope, Douglas Albert
Ontario L5K 1Z3 (CA)
- Conard, Bruce Randolph
Ontario L6L 3X4 (CA)
- Babjak, Juraj
Ontario L5B 2V4 (CA)
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Representative: Greenstreet, Cyril Henry et al |
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Haseltine Lake Partners
Motorama Haus 502
Rosenheimer Strasse 30 D-81669 München D-81669 München (DE) |
(56) |
References cited: :
EP-A- 0 092 754
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GB-A- 2 203 450
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- METALL , 41 Jahrgang, Heft 1, January 1987, Metall-Verlag GmbH, Berlin,DE; G. WEIK
et al.: "Diffundierte Goldschichten für schaltende Kontakte"
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] The present invention is concerned with electrical connectors or contacts and, more
particularly, with electrical connectors useful in carrying substantial currents at
voltages in excess of, perhaps, 10 volts, according to the first part of the claims
1 or 9 and as known from the document GB-A-2 203 450.
[0002] It is known in electronic, particularly computer technology, to use electronic contacts
of pure gold in order to reduce to the irreducible minimum value the contact resistance
of faying, usually spring-loaded contact surfaces. Such contact surfaces having contact
resistances of less than one milliohm when tested against a lightly weighted, polished
gold probe are generally not designed for frequent make and break service. Thus, thin,
pure gold contact surfaces on circuit boards and their mating components are the standard
means for providing electrical circuits in electronic and computer devices which often
operate at voltages up to only 100 mV and with extremely low amperages. Such contacts
are very resistant to corroding media and oxidation. However, if gold is used on certain
metal bases, e.g. copper or silver, without an intermediate layer of nickel, the electronic
contacts tend to degrade if exposed to temperatures elevated above 25°C even as low
as 100°C. Gradually atoms of copper and silver migrate to the gold surface. Migrated
copper makes the contact surface subject to sulfidation and oxidation while migrated
silver is particularly detrimental when the contact surface is used in sulfidizing
atmospheres as mild as ordinary room air. Accordingly, it is generally standard practice
to employ a layer of nickel (or perhaps cobalt or a nickel- or cobalt-rich alloy)
between a base of copper or silver or copper- or silver-base alloy and the gold in
order to prevent copper or silver migration and also to provide an exposed layer of
relatively tarnish-resistant metal anywhere there may be breaks in the overlying layer
of gold. A good description of electronic-type contact materials is contained in the
article "Properties of Inlay Clad Wrought Gold Alloys", Robert J. Russell, Solid State
Technology, 10 pages (8/76).
[0003] There is a need for electrical contact materials which have a low contact resistance,
but not necessarily the extremely low contact resistances required by the electronics
industry, and which have sufficient abrasion resistance in order to survive multiple
makes and breaks.
[0004] It is an object of the present invention to provide such electrical contacts adapted
to carry reasonably high amperages at voltages in excess of perhaps 10 volts.
[0005] It is a further object of the invention to provide an electrical contact material
which can be employed in the electrical contacts of the present invention.
[0006] The present invention contemplates an electric power connector adapted to provide
an interruptible conductive path for electrical current (for example, current of at
least about 0.1 ampere) comprising at least two components adapted to be placed in
surface contact one with another. At least one of the components has a fayable surface
of contact made of an alloy of gold and nickel. At the fayable contact surface the
alloy contains about 1 to about 10% by weight of nickel. The amount of nickel in the
gold generally increases with distance from the fayable contact surface to an underlying
metallurgically bonded layer preferably of essentially pure nickel. However, the alloy
which is made by diffusing nickel from an underlayer into a gold overlayer usually
exhibits a particular structure when examined by sputtering and Auger analysis. The
immediate surface, perhaps 150 Angstrom units thick, exhibits a relatively high nickel
content. Immediately below this surface layer, the nickel content falls somewhat and
remains relatively constant for perhaps up to two-thirds of the thickness of the gold
layer which ranges from 0.3 to 2 micrometers. Over the remaining thickness of the
gold-containing layer, the nickel content rises rapidly to the nickel content of the
underlying metal. Those skilled in the art will appreciate that this type of Auger
analysis sometimes produces results at the surface of an object being examined which
may be surface artifacts and may not represent or be significant with respect to properties
of the bulk material. Accordingly, it appears safe to say that in the gold layer of
the contact structure of the present invention, the nickel content near the outer
surface is at a relatively low level. It remains at that low level until, at some
point remote from the surface the nickel content of the gold rapidly increases.
[0007] The electrical power connector can be in any conventional contact form such as male
and female plug components, pins, threaded structures or the like. Advantageously,
the connectors are of such configuration that they can be made from composite, electrical
contact material in strip form. Such contact material which is also within the contemplation
of the present invention comprises a strip-form structural base of electrically conductive
material, e.g. metal having at least one major surface comprised of nickel or nickel-rich
alloy underlying a layer of gold about 0.1 to 2 micrometers thick metallurgically
bonded to the nickel or nickel-rich alloy. This diffusion is such as to provide about
1 to about 10% by weight of nickel at the outer major surface. In this connection,
"nickel-rich alloy" means an alloy containing at least about 90% nickel advantageously
at least 95% or 99% nickel and includes commercially pure nickel and nickel-cobalt
alloys.
[0008] Specific examples of contact materials of the present invention include copper, copper-base
alloys such as brass, cupro-nickel, beryllium copper, copper-nickel-tin alloy and
copper-nickel-aluminium alloy, nickel, cobalt or nickel-cobalt alloy particularly
in strip form. In the cases of copper, copper-base alloys and cobalt the basic metal
has an electrodeposited layer of nickel about 3 to 10 micrometers thick on at least
one major surface. The outer portion of that at least one major surface comprises
a layer of electroplated gold or a gold alloy containing up to about 1% total nickel
and/or cobalt about 0.1 to about 2 micrometers thick which layer of electroplated
gold or gold alloy is heat bonded to the nickel so as to provide diffusion of nickel
to the gold surface in an amount at or near the surface of about 1% to about 10% total
nickel. The strip can be faced on all surfaces with gold or, on the two major surfaces,
i.e. the top and bottom or on one major surface.
[0009] Nickel and nickel-rich alloy strip can be made by conventional metallurgical melt
technology wherein a charge of metal is melted, then cast and then hot- and/or cold-worked
to strip form. A particularly advantageous method of making nickel, cobalt or nickel-rich
alloy strip is to roll compact metal powder, sinter bond and interdiffuse the roll-compacted
metal powder and thereafter or simultaneously roll the bonded powder product to strip
form and thickness.
[0010] Strip of metal other than nickel or nickel-rich alloy which can form the principal
structural element of the connectors of the present invention is generally made in
a conventional manner and is commercially available from many sources. The present
invention contemplates use of commercially available strip of copper, brass, aluminium
bronze, cupro-nickel, beryllium copper, copper-nickel-tin alloy and any other metal
or other electrically conductive material useful in the electrical contact art. This
strip is thoroughly cleaned by conventional means such as alkaline cleaning baths,
solvent and vapor degreasing, etc. and then electroplated to provide a layer of nickel
about 5 to about 10 micrometers thick. One of the electroplating baths set forth in
Electroplating Engineering Handbook, 3rd Ed., A. Kenneth Graham, Van Nostrand Reinhold
Company, Copyright, 1971 at page 247 can be used to electroplate nickel.
[0011] Gold is electrodeposited over either the nickel strip or plated nickel from a cyanide-type,
citrate-type or other type of bath adapted to produce a pure soft gold electro-deposit.
The strip is then heat treated at about 350°C to 600°C for times ranging from 2 hours
to 10 seconds so as to diffuse nickel into the gold to reach a level of from 1 to
10% nickel at the gold outer surface.
[0012] The electrical connector materials and electrical contacts made therefrom as contemplated
in the present invention are advantageous with respect to contacts made of base metals
in that they are and remain through their useful lives essentially free of corrosion
products and thus give reliable, stable contact service. Compared to pure gold contact
surfaces, when high currents (e.g. greater than 0.1 ampere) are passed through an
electrical circuit, the contacts and contact materials of the present invention are
advantageous when the contact must be broken periodically. In these situations, a
pure gold surface becomes galled or roughened, gold-on-gold contacting surfaces tend
to sinter or fuse together and the contact cannot readily be separated. Conversely,
the present invention is based upon the discovery that when gold contacting surfaces
contain 1 to 10% nickel such modified gold-on-modified gold contacts do not exhibit
the fusing or sintering character of pure gold and thus the contacts can always be
easily broken, provided of course, that the circuit including the contact has not
been overloaded beyond design capacity.
[0013] In making the contact materials of the present invention, those of normal skill in
the metallurgical art will appreciate that heat treatment time will normally vary
with temperatures such that longer times will be used at lower temperatures and vice
versa with a given thickness of gold. Lower temperatures and shorter times at a given
temperature will be employed with thinner gold layers than with thicker gold layers.
As disclosed in GB-A-2 203 450 diffusion of nickel into gold can be carried out simultaneously
with age-hardening of an age-hardenable substrate. Normally, this age-hardening of,
for example, copper-base-alloys such as beryllium copper or a copper-nickel-tin alloy
or a copper-nickel aluminium alloy will be carried out after the contact material
is in final form as an electrical contact. For example, strip form of beryllium copper
is blanked and shaped to contact configuration. The thus shaped contacts are then
electroplated sequentially with nickel and gold and then heat treated at a temperature
and time combination selected in consideration of the thickness of electroplated gold
so as to achieve both age-hardening of the substrate and proper gold-nickel interdiffusion
at the same time. Alternatively, contacts may be blanked out of composite gold-nickel-copper
beryllium strip, formed and then heat treated.
[0014] The annealing heat treatment which produces diffusion of nickel and gold can be carried
out simultaneously with hot rerolling of plated strip material. For example, nickel
strip made by roll compacting and then sintering and rolling nickel powder can be
electroplated with gold and then rerolled at a temperature in the range of 350°C to
500°C to enhance the metallurgical bond between the nickel and gold and effectuate
the diffusion of the nickel. Alternatively, the metallurgical bond and diffusion can
be accomplished by the annealing heat treatment as described hereinbefore and the
composite can be cold rolled either before or after annealing so as to enhance mechanical
characteristics.
[0015] In order to give those skilled in the art a greater appreciation of the advantages
of the invention the following example is given:
A nickel strip made from roll compacted and sintered nickel powder about 0.5 mm
thick, about 30 mm wide and about 70 meters long is thoroughly cleaned, mildly etched
and electroplated with gold from a citrate-base electroplating bath to provide a uniform,
pure gold deposit about 0.5 micrometer thick. The plated strip is thoroughly rinsed
to remove any trace of electrolyte, dried and then heat treated by being passed through
a furnace. The furnace is held at 480°C and contains an atmosphere of 10 volume percent
hydrogen, balance nitrogen. Cool strip is fed to the furnace and passes through with
a residence time of six minutes. As the strip exits the furnace it is cooled under
the same reducing conditions and then coiled.
[0016] The composite nickel-gold contact material made in this way gives excellent results
in electric contact service composite material to composite material. The contacts
exhibit essentially no detrimental behavior over time when exposed to normal service.
The contacts do not corrode, gall or pit in service and can be disconnected hundreds
of times without difficulty even when exposed in use to temperatures up to about 200°C.
[0017] While specific embodiments of the invention are illustrated and described herein,
those skilled in the art will understand that changes may be made in the form of the
invention covered by the claims and that certain features of the invention may sometimes
be used to advantage without a corresponding use of the other features.
1. An electric power connector adapted to provide an interruptible conductive path for
electric current comprising at least two components adapted to be placed in surface
contact, one with another, at least one of said components having a fayable surface
of contact made of an alloy of gold and nickel, said alloy containing about 1 to about
10% by weight of nickel near said fayable surface of contact, characterised by said
amount of said nickel remaining essentially constant through some distance from the
surface and then starting at a point interior of said fayable surface to increase
with distance from said fayable surface of contact toward the interface of gold-containing
metal with an underlying, metallurgically bonded layer of metal from the group of
nickel and alloys rich in nickel.
2. An electric power connector as claimed in claim 1 wherein said underlying metallurgically
bonded layer is a layer of essentially pure nickel.
3. An electric power connector as claimed in claim 2 wherein said layer of essentially
pure nickel is the principal structural element of said connector.
4. An electric power connector as claimed in claim 1 wherein said underlying metallurgically
bonded layer is an electrodeposit of nickel about 3 to about 10 micrometers thick
on an electroconductive substrate.
5. An electric power connector as claimed in claim 4 wherein said electroconductive substrate
is selected from the group of copper, brass, aluminium bronze, copper-nickel-aluminium
alloy, cupro-nickel, beryllium copper and copper-nickel-tin alloy.
6. An electric power connector as claimed in claim 5 wherein said electroconductive substrate
is selected from the group of age-hardened copper-base alloys.
7. An electric power connector as claimed in any preceding claim wherein two or more
components of said connector have fayable surfaces of said alloy of gold and nickel.
8. An electric power connector as claimed in any preceding claim having mateable male
and female components.
9. An electric power connector material comprising an electroconductive base having at
least one surface made of a metal from the group of nickel and nickel-rich alloys
and having overlying and metallurgically bonded thereto a layer of gold about 0.1
to about 2 micrometers thick, characterised by said layer of gold containing near
its outer surface about 1 to 10% by weight of nickel, the content of nickel remaining
essentially constant over some distance interior of said outer surface and starting
to increase at a point remote from said outer surface and continuing to increase as
the distance from said outer surface increases.
10. An electric power connector material as claimed in claim 9 wherein the underlying
metal is nickel.
11. An electric power connector material as claimed in claim 10 wherein said nickel is
an electrodeposit on an electroconductive base.
12. An electric power connector material as claimed in any of claims 9 to 11 wherein said
electroconductive base is a metal from the group of copper, brass, aluminium bronze,
copper-nickel-aluminium, cupro-nickel, beryllium copper and copper-nickel-tin alloy.
13. An electric power connector material as claimed in claim 12 wherein said electroconductive
substrate is an age-hardened and copper-base alloy.
14. An electric power connector material as claimed in any of claims 9 to 13 in strip
form.
1. Elektrischer Leitungsverbinder zur Herstellung eines unterbrechbaren Leitungsweges
für elektrischen Strom, umfassend mindestens zwei miteinander in Oberflächenkontakt
bringbare Bestandteile, wobei mindestens einer der genannten Bestandteile eine passende
Kontaktoberfläche aus einer Legierung von Gold und Nickel aufweist, und die genannte
Legierung ungefähr 1 bis ungefähr 10 Gew.% Nickel nahe der genannten passenden Kontaktoberfläche
enthält, dadurch gekennzeichnet, daß der genannte Nickelgehalt über eine Tiefe von
der Oberfläche im wesentlichen konstant bleibt und dann ab einem Punkt unterhalb der
genannten passenden Kontaktoberfläche mit der Tiefe von der genannten passenden Kontaktoberfläche
zur Grenzfläche aus goldhältigem Metall mit einer darunterliegenden, metallurgisch
gebundenen Schicht aus Metall aus der Gruppe umfassend Nickel und nickelreiche Legierungen
zunimmt.
2. Elektrischer Leitungsverbinder nach Anspruch 1, dadurch gekennzeichnet, daß die genannte
darunterliegende, metallurgisch gebundene Schicht eine Schicht aus im wesentlichen
reinem Nickel ist.
3. Elektrischer Leitungsverbinder nach Anspruch 2, dadurch gekennzeichnet, daß die genannte
Schicht aus im wesentlichen reinem Nickel das Hauptbauelement des genannten Verbinders
ist.
4. Elektrischer Leitungsverbinder nach Anspruch 1, dadurch gekennzeichnet, daß die genannte
darunterliegende, metallurgisch gebundene Schicht ein galvanischer Niederschlag mit
einer Dicke von ungefähr 3 bis ungefähr 10 Mikrometern auf einem elektrisch leitenden
Substrat ist.
5. Elektrischer Leitungsverbinder nach Anspruch 4, dadurch gekennzeichnet, daß das genannte
elektrisch leitende Substrat ausgewählt wird aus der Gruppe umfassend Kupfer, Messing,
Aluminiumbronze, Kupfer-Nickel-Aluminiumlegierung, Kupfernickel, Berylliumkupfer und
Kupfer-Nickel-Zinnlegierung.
6. Elektrischer Leitungsverbinder nach Anspruch 5, dadurch gekennzeichnet, daß das genannte
elektrisch leitende Substrat ausgewählt wird aus der Gruppe von ausscheidungsgehärteten
Legierungen auf Kupferbasis.
7. Elektrischer Leitungsverbinder nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet,
daß zwei oder mehrere Bestandteile des genannten Verbinders passende Oberflächen aus
der genannten Legierung aus Gold und Nickel aufweisen.
8. Elektrischer Leitungsverbinder nach einem der vorhergehenden Ansprüche mit zusammenpassenden
Steck- und Aufnahmeteilen.
9. Material für einen elektrischen Leitungsverbinder umfassend eine elektrisch leitende
Basis mit mindestens einer Oberfläche aus einem Metall aus der Gruppe umfassend Nickel
und nickelreiche Legierungen, und eine darüberliegende und metallurgisch daran gebundene
Schicht aus Gold mit einer Dicke von ungefähr 0,1 bis ungefähr 2 Mikrometern, dadurch
gekennzeichnet, daß die genannte Goldschicht nahe ihrer Außenfläche ungefähr 1 bis
10 Gew.% Nickel enthält, wobei der Nickelgehalt über eine Tiefe unterhalb der genannten
Außenfläche im wesentlichen konstant bleibt und ab einem Punkt, der von der genannten
Außenfläche entfernt liegt, zunimmt und mit zunehmender Tiefe von der genannten Außenfläche
weiter steigt.
10. Material für einen elektrischen Leitungsverbinder nach Anspruch 9, dadurch gekennzeichnet,
daß das darunterliegende Metall Nickel ist.
11. Material für einen elektrischen Leitungsverbinder nach Anspruch 10, dadurch gekennzeichnet,
daß das genannte Nickel ein galvanischer Niederschlag auf einer elektrisch leitenden
Basis ist.
12. Material für einen elektrischen Leitungsverbinder nach einem der Ansprüche 9 bis 11,
dadurch gekennzeichnet, daß die genannte elektrisch leitende Basis ein Metall aus
der Gruppe umfassend Kupfer, Messing, Aluminiumbronze, Kupfer-Nickel-Aluminium, Kupfernickel,
Berylliumkupfer und Kupfer-Nickel-Zinnlegierung ist.
13. Material für einen elektrischen Leitungsverbinder nach Anspruch 12, dadurch gekennzeichnet,
daß das genannte elektrisch leitende Substrat eine ausscheidungsgehärtete Legierung
auf Kupferbasis ist.
14. Material für einen elektrischen Leitungsverbinder nach einem der Ansprüche 9 bis 13
in Streifenform.
1. Connecteur électrique de puissance destiné à réaliser un trajet conducteur, pouvant
être coupé, pour un courant électrique, comprenant au moins deux composants destinés
à être mis en contact de surface l'un avec l'autre, au moins l'un desdits composants
ayant une surface affleurante de contact réalisée en un alliage d'or et de nickel,
ledit alliage contenant environ 1 à environ 10 % en poids de nickel à proximité de
ladite surface affleurante de contact, caractérisé en ce que ladite quantité dudit
nickel demeure sensiblement constante sur une certaine distance à partir de la surface
et ensuite, en un point situé à l'intérieur de ladite surface affleurante, commence
d'augmenter avec la distance à ladite surface affleurante de contact vers l'interface
du métal contenant de l'or et d'une couche sous-jacente, liée par voie métallurgique,
d'un métal du groupe du nickel et d'alliages riches en nickel.
2. Connecteur électrique de puissance selon la revendication 1, dans lequel ladite couche
sous-jacente, liée par voie métallurgique, est une couche de nickel sensiblement pur.
3. Connecteur électrique de puissance selon la revendication 2, dans lequel ladite couche
de nickel sensiblement pur est l'élément principal de la structure dudit connecteur.
4. Connecteur électrique de puissance selon la revendication 1, dans lequel ladite couche
sous-jacente, liée par voie métallurgique, est réalisée par électro-dépôt de nickel
sur une épaisseur d'environ 3 à environ 10 micromètres sur un substrat électro-conducteur.
5. Connecteur électrique de puissance selon la revendication 4, dans lequel ledit substrat
électro-conducteur est choisi dans le groupe du nickel, laiton, bronze d'aluminium,
alliage cuivre-nickel-aluminium, cupro-nickel, cuivre au béryllium et alliage cuivre-nickel-étain.
6. Connecteur électrique de puissance selon la revendication 5, dans lequel ledit substrat
électro-conducteur est choisi dans le groupe des alliages à base de cuivre ayant subi
un durcissement de vieillissement.
7. Connecteur électrique de puissance selon l'une quelconque des revendications précédentes,
dans lequel deux composants ou davantage dudit connecteur ont des surfaces affleurantes
dudit alliage d'or et de nickel.
8. Connecteur électrique de puissance selon l'une quelconque des revendications précédentes,
comprenant des composants complémentaires mâle et femelle.
9. Matériau de connecteur électrique de puissance comprenant une base électro-conductrice
ayant au moins une surface réalisée en un métal du groupe du nickel et d'alliages
riches en nickel et comportant une couche d'or d'environ 0,1 à 2 micromètres d'épaisseur
qui recouvre cette base et qui lui est liée par voie métallurgique, caractérisé en
ce que ladite couche d'or contient à proximité de sa surface extérieure environ 1
à 10 % en poids de nickel, la teneur en nickel demeurant sensiblement constante sur
une certaine distance vers l'intérieur de ladite surface extérieure et commençant
de croître en un point distant de ladite surface extérieure, puis continuant à croître
avec l'augmentation, de la distance à ladite surface extérieure.
10. Matériau de connecteur électrique de puissance selon la revendication 9, dans lequel
le métal sous-jacent est du nickel.
11. Matériau de connecteur électrique de puissance selon la revendication 10, dans lequel
ledit nickel est un électro-dépôt sur une base électro-conductrice.
12. Matériau de connecteur électrique de puissance selon l'une quelconque des revendications
9 à 11, dans lequel ladite base électro-conductrice est un métal du groupe du cuivre,
laiton, bronze d'aluminium, cuivre-nickel-aluminium, cupro-nickel, cuivre au béryllium
et alliage cuivre-nickel-étain.
13. Matériau de connecteur électrique de puissance selon la revendication 12, dans lequel
ledit substrat électro-conducteur est un alliage ayant subit un durcissement de vieillissement
et à base de cuivre.
14. Matériau de connecteur électrique de puissance selon l'une quelconque des revendications
9 à 13, sous forme de ruban.