Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
1998-06-16
2001-02-06
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C148S023000, C148S026000, C148S283000, C204S192100, C228S206000, C228S214000, C228S223000, C427S123000, C427S190000, C427S430100, C428S615000, C428S926000
Reexamination Certificate
active
06183883
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to brazing and/or soldering materials for making connections by brazing or soldering, and a method for manufacturing such materials.
2. Description of the Related Art
Soldering is a method of connecting two base materials (or base metals) by thermally melting an alloy or metal with a melting point lower than that of the base materials so that the molten alloy or metal fills gaps between the base materials. The base materials themselves are not melted. Soldering is widely used in electronics because of its ability to connect complex, precision parts as well as metals of different types while having little effect on the base materials. Hard solder (also known as high melting solder) has a relatively high melting point and includes soldering materials such as silver, gold, as well as other types of hard solder. In contrast, soft solder (also known as low melting solder) has a relatively low melting point.
Soft solder, which is commonly referred to simply as solder, usually comprises tin and/or lead, and is widely used for lead frame connections in electronic products where a conductive connection is required. Conductivity is usually more important to solder than mechanical strength, and high wettability of the base materials is required. The presence of an oxidation coating on the joining surfaces of the base metals is known to greatly affect the wettability of solder and hard solder (brazing alloy below) used in brazing and soldering.
Flux has conventionally been used during normal soldering and brazing to remove any oxidation coating from the surfaces of the base metals. A problem common to soldering and brazing techniques that use flux for connecting leads in electronic products, even when a non-corrosive flux is used, is contamination of peripheral components and materials when the flux is applied. In addition, while there are cases in which flux containing a halogen is used for soldering, cleaning to remove any residual flux is generally required after soldering. Furthermore, while there are also cases in which residual flux is not cleaned after soldering, these methods either use a flux with a low halogen content, and thus sacrifice wettability, or use a flux with a high halogen content to assure solder wettability and thus risk the danger of migration resulting from the halogen component in the residual flux.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to overcome the aforementioned problems.
Another object of the present invention is to provide a soldering or brazing material for effectively improving the wettability of the soldered or brazed material without using flux, and to provide a manufacturing method for such material.
SUMMARY OF THE INVENTION
To achieve the above objects, a brazing or soldering material according to the present invention comprises a halide layer on a surface of a metallic base. By covering the surface of the metallic base, the halide layer prevents oxidation of the metallic base. During brazing or soldering, the halogen disperses into the metallic base or evaporates, thereby facilitating bonding between the metallic base and the metal used in the brazing alloy or solder, improving the wettability of the brazing alloy or solder without using flux, and thereby enabling easy fluxless brazing or soldering.
The halide layer is preferably a compound of a metal and a halogen. Particularly preferable are halides containing fluorine, such as silver fluoride (AgF), copper fluoride (CuF), and stannous fluoride (SnF
2
), and halides containing chlorine, such as silver chloride (AgCl), copper chloride (CuCl), and stannous chloride (SnCl
2
). The halide layer need only be formed to a thickness sufficient for the oxygen atoms in the oxidation layer on the surface of the metallic base to be replaced by the halogen, and to prevent oxidation of the metallic base surface. A thickness of 0.5 to 3 &mgr;m is thus sufficient. If the thickness of the halide layer is less than 0.5 &mgr;m, it may not be possible to prevent oxidation of the metallic base. In addition, if the halide layer thickness is greater than 3 &mgr;m, there may be an increase in ions contributing to corrosion, or a drop in wettability with pure metals.
A further brazing or soldering material according to the present invention comprises a halogen-impregnated metal. In a material thus comprised, the halogen present in the surface area of the metal prevents oxidation of the metal, and can therefore improve the wettability of the brazing or soldering material without using flux. The halogen in this case can be bromine (Br) or iodine (I), but fluorine (F) and chlorine (Cl) are preferable because of superior activity. The halogen concentration in the impregnated metal is 50 ppm to 5% by volume. When the halogen content exceeds 5%, there is a risk of an increase in ions contributing to corrosion, or a drop in wettability with pure metals as described above.
A manufacturing method for a brazing or soldering material according to the present invention comprises a step for forming a halide layer film on a surface of a metallic base by means of sputtering or vapor deposition. Film formation can also be accomplished by immersing the metallic base in a solution containing a halide, or coating a halide solution on a surface of the metallic base, and then drying naturally or by heating. Alternatively, the film can be formed by placing and then dissolving a halide on a surface of the metallic base, and then drying naturally or by heating.
A further manufacturing method for a brazing or soldering material according to the present invention comprises a step for adding and then melting a halide in a molten metal, and then solidifying the molten metal. The halide can comprise a halogen and a metal that is the same as the molten metal. For example, if the molten metal is copper, a copper halide is added, and if the molten metal is aluminum, an aluminum halide is added.
In each manufacturing method according to the present invention, the halide is preferably a halide of fluorine or chlorine.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4699806 (1987-10-01), Fait et al.
patent: 4921157 (1990-05-01), Dishon et al.
patent: 5052612 (1991-10-01), Tecle
patent: 5407121 (1995-04-01), Koopman et al.
patent: 5-304235 (1993-11-01), None
patent: 7-164136 (1995-06-01), None
patent: 2527278 (1996-06-01), None
Karasawa Yasushi
Miyakawa Takuya
Mori Yoshiaki
Takahashi Katsuhiro
Jones Deborah
Koehler Robert R.
Seiko Epson Corporation
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