Soldered article

Details Soldered article Soldered article

1999-09-14

2001-01-30

Zimmerman, John J. (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

C174S263000, C257S772000, C420S557000, C420S561000, C420S562000, C428S647000

Reexamination Certificate

active

06180264

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to soldered articles, and more particularly, the invention relates to a soldered article including a component having a Cu conductor joined with a solder.
2. Description of the Related Art
Solders have been widely used as jointing materials for achieving electrical and mechanical connections in electronic equipment and electronic components.
On the other hand, as a material for constituting electrodes in electronic equipment and electronic components, Cu has been widely used in view of its corrosion resistance, costs, etc.
Soldered articles in which the electrodes composed of Cu are joined to objects (for example, lands on mounting substrates) have been widely used for various applications.
Although solders having Sn and Pb as major constituents have generally been used, in consideration of environmental protection, solders having Sn as a major constituent, and excluding hazardous Pb, (hereinafter referred to as “lead-free solders”) have come into use.
However, in a soldered article in which electrodes composed of Cu are joined to a mount object using a lead-free solder having Sn as a major constituent, leaching easily occurs at the electrical junction during soldering.
In comparison with the case when conventional Sn—Pb based solders are used, lead-free solders having Sn as a major constituent are inferior in solderability and joining strength at soldered sections, and are less reliable.
In order to overcome the problems described above, Sn—Cu—Bi-based solders containing Ag have been disclosed (for example, Japanese Unexamined Patent Publication Nos. 2-70033, 5-228685, and 8-132277). However, the solders in the above patent publications contain Ag, resulting in an increased cost.
SUMMARY OF THE INVENTION
To overcome the difficulties noted above, preferred embodiments of the present invention provide a soldered article using a solder which does not easily cause leaching, which has excellent solderability and joining strength, and which does not contain expensive Ag, thus being very economical.
One preferred embodiment of the present invention provides a soldered article comprising a component having a Cu conductor joined with a solder, wherein the solder comprises about 0.1 to 2.0% by weight of Cu, about 1.0 to 7.5% by weight of Bi, and the balance being Sn.
When a Cu conductor is joined to an object such as an electrode using the solder containing about 0.1 to 2.0% by weight of Cu, about 1.0 to 7.5% by weight of Bi, and the balance being Sn as described above, the occurrence of leaching is suppressed during soldering, and the solderability and joining strength can be improved. Since the solder does not contain Ag, material cost can be reduced, thus enabling reductions in the cost of the entire soldered article.
Since the lead-free solder used in the soldered article in the present invention does not contain Ag, rigid intermetallic compounds such as Ag
3
Sn are not produced, and the processing into wire solders or the like can be easily performed in comparison with lead-free solders containing Ag. The thermal shock resistance of the soldered article can also be improved.
In the present invention, the Cu conductors include sheet or linear Cu conductors in addition to metal Cu thin films such as plated films, deposited films, and sputtered films in which leaching due to solders easily occurs, and also include Cu conductors in which glass frit and various additives are added, as required.
The soldered articles in the present invention include, for example, the followings.
1) A soldered article in which a conductor provided in a component is electrically and mechanically connected to an electrode on a printed board with a solder.
2) A soldered article in which a conductor provided in an electronic component is electrically and mechanically connected to an external terminal with a solder.
3) A soldered article in which electrodes (Cu conductors) of an electronic component are electrically and mechanically connected to each other with a solder.
As is clear from the above, the concept of the soldered articles in the present invention is broad, including various articles in which conductors provided in components are joined to object conductors with solders.


REFERENCES:
patent: 4879096 (1989-11-01), Naton
patent: 5393489 (1995-02-01), Gonya et al.
patent: 5411703 (1995-05-01), Gonya et al.
patent: 5527628 (1996-06-01), Anderson et al.
patent: 5837191 (1998-11-01), Gickler
patent: 5863493 (1999-01-01), Achari et al.
patent: 0336575 (1989-10-01), None
patent: 0629464A1 (1994-12-01), None

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