Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2001-04-12
2003-09-02
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S648000, C428S929000, C428S675000, C205S226000, C439S886000
Reexamination Certificate
active
06613451
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a metallic material provided with a intermediate layer in which Ni alloy or Cu alloy is plated on a base metal consisting of Cu or Cu alloy, and a surface layer in which Sn or Sn alloy is plated on this intermediate layer. More particularly, the present invention relates to a metallic material, for electronic components, having superior heat resistance, soldering properties, resistance to degradation of the appearance thereof, and insertion and withdrawal properties when the material is employed as a contact member.
BACKGROUND ART
In metallic materials for electronic components, many metallic materials of plated Sn or Sn alloy, such as for contacts, are employed primarily for connector contacts for civilian use and wire harnesses for automobile electrical systems. However, in Sn or Sn alloy plated material, interdiffusion progresses between base metals such as Cu, Ni, etc., and the plating layer at the surface, whereby many properties such as contact resistance, resistance against thermal peeling, and soldering properties, degrade over time. That is to say, the properties degrade by aging. In particular, the degradation is remarkable in the vicinity of the automobile engine, or the like, since the higher the temperature, the more this phenomenon is promoted.
In such a situation, the demand for heat resistance in the connector material has become more severe by USCAR, which sets the standards for car components, established by the three largest automobile manufacturers in the United States. In the severest use condition, heat resistance to normal use at 155° C. and a maximum allowable 175° C. are required. In particular, in automobile connector materials, demands for heat resistance has become more severe in Japan, and heat resistance to about 150° C. is required.
Moreover, in the case in which the production base for the connector manufacturer is moved to other countries, the material is sometimes stored for long periods, until it is used, after plating. Therefore, plated material in which each property thereof does not degrade even if the material is stored over long periods, that is, plated material in which aging degradation resistance is high, is required. Nevertheless, degradation in properties of the plated material is accelerated at high temperatures. Therefore, material in which the degradation in properties at high temperatures is small will not experience degradation of each of the properties even if it is stored over long periods. Therefore, a plated material having high heat resistance is required even in this field.
The above property degradation is eased to a certain extent in the case in which Cu or Ni is plated as an intermediate layer. However, resistance against thermal peeling remarkably degrades when the intermediate layer consists of Cu. When the intermediate layer consists of Ni, so that Ni may suppress diffusion of Cu, properties are also improved over the case in which Cu was used; however, it is not satisfactory from the point of view of soldering properties. Furthermore, although sealing may be tried as an after-treatment following plating, each of the properties is not sufficiently improved.
As a means for suppressing the diffusion of Cu, a means for intervening Cu—Ni alloy between the base material and the plating layer at the surface has been proposed (PCT/US96/19768). However, although increase of contact resistance is suppressed in this technique, aging degradation resistance of soldering properties is not improved.
In addition, as a problem characteristic of Sn plated material, the Sn plated material is soft, so that a gas-tight structure is produced when a male pin is adhered to a female pin employed at a point of contact in a connector. Therefore, the Sn plated material has a disadvantage in that the insertion force of the connector is higher than that for a connector consisting of Au plating, etc.
In such a situation, the demand for forming multiple cores in a connector has recently become much more severe with the increasing miniaturization, weight reduction, and multifunctionalization, not only in automobile components, but also in general connectors. However, if the present Sn plated material is used to form multiple cores, the insertion force for the connector increases. In the assembly process for automobiles in which Sn plated connectors are mainly used, the connectors are manually connected, so that increase in the insertion force directly lowers the workability thereof.
As a means of dealing with this problem, the following technique (Japanese Unexamined Patent Application Publication No. 320668/97) has been proposed. In this technique, Cu or Ni is plated as an intermediate layer, whereby wear resistance of Sn plating or Sn alloy plating at the surface is reduced, so that insertion and withdrawal properties are improved. According to this technique, problems with respect to insertion of the connector can be avoided; however, the above-mentioned heat resistance, particularly the aging degradation resistance of soldering properties, cannot be prevented.
DISCLOSURE OF INVENTION
It is therefore an object of the present invention to provide a metallic material in which aging degradation can be prevented in high temperature environments in the vicinity of automobile engines, etc., insertion and withdrawal resistance can be improved, and further more, properties such as soldering properties, etc., are not degraded even if the material is stored over long periods.
A metallic material according to the present invention is characterized in that an intermediate layer made of an alloy plating consisting of Ni alloy or Cu alloy contains at least one of P in an amount of 0.05 to 20% by weight and B in an amount of 0.05 to 20% by weight, and is provided on a base metal consisting of Cu or Cu alloy and a surface layer consisting of Sn or Sn alloy plating is further provided on the intermediate layer. Effects and preferable embodiments of the present invention will be explained. In the following explanation, “percent” refers to “percent by weight”.
According to a preferred embodiment of the present invention, an intermediate layer is made of an alloy consisting of P in an amount of 0.05 to 20%, and the balance consisting of Ni and unavoidable impurities, or an alloy consisting of B in an amount of 0.05 to 20%, and the balance consisting of Ni and unavoidable impurities. Furthermore, according to another preferred embodiment of the present invention, an intermediate layer is made of an alloy containing P in an amount of 0.05 to 20%, B in an amount of 0.05 to 20%, and the balance consisting of Ni and unavoidable impurities.
Of the primary metals constituting the intermediate layer, Ni is an element which can maintain P, B, Cu, Sn, and Zn in the intermediate layer, and can be alloy-plated with any of the above elements. As another function of Ni, suppressive effects diffusion of Cu, which is a degrading factor in heat resistance, may be mentioned. However, in the case in which the intermediate layer consists of only Ni, degradation of soldering properties after exposure to high temperature cannot be prevented. It seems that this is due to the inside of the plating layer being oxidized by the heating. That is to say, since wettability of Ni oxide for solder is generally unsatisfactory, it is assumed that soldering properties are lowered by the existence of the Ni oxide when the inside thereof is oxidized.
In contrast, in the case in which an intermediate layer consists of Ni alloy containing P and/or B, it is assumed that P and B are diffused toward the surface by heating, whereby oxidation in the inside and the surface of the surface layer is prevented, so that degradation of soldering properties is suppressed.
Furthermore, it is assumed that P oxide and B oxide films are formed on the surface by diffusion of P or B and that the insertion and withdrawal resistance, in the case in which this film is used for a connector, is lowered. Moreover, an alloy to which P or B is added to Ni is much harder than base
Asahara Hajime
Fukamachi Kazuhiko
Nippon Mining & Metals Co., Ltd.
Scully Scott Murphy & Presser
Zimmerman John J.
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