Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1998-07-16
2001-02-13
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S670000, C428S671000, C428S672000, C428S674000, C428S429000, C439S886000, C439S887000, C205S170000, C205S176000
Reexamination Certificate
active
06187454
ABSTRACT:
The present invention relates to a method of coating a metal part that is to be soldered, to a coating used for this purpose, and to a metal part coated in this way.
BACKGROUND OF THE INVENTION
It has been known for a long time to galvanize metals in order to protect them against corrosion.
This applies in particular to electrically conductive parts that have for a long time been covered in a fine layer of nickel.
Since nickel is a magnetic material, it is unsuitable for coating parts of electrical connectors, particularly those that are to convey high frequency signals.
Nickel has therefore been replaced by bronze, preferably white bronze of silvery appearance that is close to that of nickel, which material has sufficient electrical conductivity for the intended purpose, and has hardness that also protects coated parts effectively against the friction to which they can be subjected.
The drawback of untreated white bronze is its poor suitability for soldering.
To overcome that difficulty, it has been the practice to use activated soldering fluxes, thereby making it possible to solder appropriately, but requiring cleaning operations based on chlorofluorocarbons (CFCs).
Since the use of such substances has now been banned, solder joints on metal parts coated in white bronze are of poorer quality than before, and that can give rise to problems of reliability with connectors.
OBJECT AND SUMMARY OF THE INVENTION
The present invention seeks to solve this problem by providing a novel method of coating a metal part without degrading its suitability for soldering.
The present invention provides a method of coating a metal part that is to be soldered, in particular an electrical component, in which a layer of white bronze is applied to said part, wherein the layer of white bronze is covered firstly in a fine layer of palladium and then in a fine layer of gold.
In the invention, the term “fine layer” is used to mean a layer of thickness that lies preferably in the range 0.1 &mgr;m to 0.2 &mgr;m; the layer of gold can even be as fine as 0.05 &mgr;m.
The method of the invention thus provides metal parts suitable for soldering without subsequent CFC treatment, which parts are protected against corrosion, have sufficient surface hardness to withstand possible friction, are sufficiently conductive via their surfaces, and are non-magnetic.
In addition, these parts are durably protected in the sense that the coating they have degrades very slowly or not at all over time.
The invention also provides an anti-corrosion coating that is hard, non-toxic, non-magnetic, and solderable for metal parts, in particular electrical components, wherein the coating is constituted by:
a layer of white bronze;
covered in a fine layer of palladium; and
covered in a fine layer of gold.
The term “non-toxic” is used to mean that the coating does not contain any metal that is known to be dangerous and that implementing the method is not harmful to the environment.
Because the coating is easily soldered, coated parts can be flow soldered with high efficiency and high reliability.
The invention also provides a metal part, in particular an electrical component, coated in the above-described coating.
The component is preferably a part of an electrical connector, in particular a high frequency electrical connector.
REFERENCES:
patent: 4034149 (1977-07-01), Zaleckas
patent: 5180482 (1993-01-01), Abys et al.
Miranda Lymarie
Radiall
Schweitzer Cornman Gross & Bondell LLP
Turner Archene
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