Patent Grant
9263814
The present invention relates to a metallic material for an electrical electronic component suitable for a sliding portion of a fitting-type multipole connector and the like.
A plating material provided with a plating layer of tin (Sn), a tin alloy and others on a conductive base such as copper (Cu) and a copper alloy (referred to as a base hereinafter) is known to be a high-performance conductor having excellent conductivity and strength of the base and excellent electrical connectivity, corrosion resistance and soldering quality of the plating layer. The plating material is widely used for various terminals and connectors used in electric/electronic devices. The plating material is normally undercoated with nickel (Ni), cobalt (Co), iron (Fe) and others having a barrier function on the base to prevent an alloy component (referred to as a base component hereinafter) such as zinc (Zn) from diffusing in the plating layer.
When the plating material is used as a terminal in a high-temperature environment such as an inside of an engine room of a vehicle, for example, although an oxide coating film is formed on a surface of the Sn plating layer because the Sn plating layer on a surface of the terminal is oxidizable, the oxide coating film is brittle and breaks down when the terminal is connected and a non-oxidized Sn plating layer is exposed, thereby obtaining favorable electrical connectivity.
Because a fitting-type connector is multipolarized lately with advancement of electronic control, a considerable force is necessary for plugging a male terminal group into/out of a female terminal group. In particular, plugging such a connector is difficult in a narrow space such as the engine room of the vehicle, and it has been strongly demanded to be able to reduce the force for plugging in/out such a connector. Still more, as workability in connecting the connector is improved by reducing the force for plugging in/out the connector, it has been demanded to reduce the force for plugging in/out the connector also from this point of view.
In order to reduce the plugging-in/out force, the Sn plating layer on the surface of the connector terminal may be thinned to weaken contact pressure between the terminals. However, because the Sn plating layer is soft, a fretting phenomenon may occur between contact faces of the terminals, thereby causing inferior conduction between the terminals.
In the fretting phenomenon, the soft Sn plating layer on the surface of the terminal wears and is oxidized, becoming abrasion powder having large specific resistance, due to fine vibration between the contact faces of the terminals caused by vibration and changes in temperature. The lower the contact pressure between the terminals, the more the fretting phenomenon is prone to occur.
In order to assure a low plugging force, Japanese Patent Application Laid-Open No. 2000-226645 Gazette, for example, has proposed a method of forming a hard Cu—Sn intermetallic compound layer that hardly causes the fretting phenomenon on the outermost surface by plating Sn on Cu or a Cu alloy, implementing a reflow process and then treating by heat in an atmosphere at an oxygen concentration of 5% or less. However, the method has had a problem that workability of the plating process is inferior. Japanese Patent Application Laid-Open No. 2000-226645 Gazette has no description about a concentration of Cu—Sn in the Cu—Sn intermetallic compound layer and has had a problem that it is difficult to perform the reflow heat-process in producing in line to adequately form an oxide coating layer with a controlled thickness on the surface of the Cu—Sn intermetallic compound layer.
Further, in order to assure the low plugging force and others, Japanese Patent Application Laid-Open No. 2004-68026 Gazette describes a conductive material for a connecting component that hardly causes the fretting phenomenon, in which a surface plating layer composed of a Ni layer and a Cu—Sn alloy layer is formed on a surface of a base composed of Cu or a Cu alloy in this order. However, the material is also inferior in terms of workability of plating process. Still more, it is difficult to perform the reflow heat-process in producing in line because of the Cu—Sn alloy layer controlled by an average value of the concentration of Cu—Sn.
Japanese Patent Application Laid-Open No. 2004-339555 Gazette describes forming a metal plate layer by plating metal on a surface of a metallic base and forming a plated material mixed with soft regions spreading like a net and a hard region surround by the net of the soft region by a reflow process. However, the plated material has a problem that the Cu component in the base diffuses to the plate uppermost surface and is oxidized, further increasing a contact resistance value.
Japanese Patent Application Laid-Open No. 2006-77307 Gazette describes a conductive material for a connecting component in which a Cu—Sn alloy coating layer composed of particles of several μm in diameter is formed along irregularities of a surface of a base. Further, a Sn coating layer is melt and smoothed, and a part of the Cu—Sn alloy coating layer is exposed on the surface of the material.
When there is no Cu layer in a substrate and a Ni substrate exists, there would be no problem. However, when the Cu layer exists or no Ni substrate exists, even if there would be no problem in an initial state, under an environment in which a connecting component is mounted in an actual car and sliding and thermal loads are applied at the same time, the pure Sn portion is scraped due to sliding and Cu diffuses up to a surface and oxidized, thereby increasing resistance.
According to the invention, the following aspects are provided:
The abovementioned and other features and advantages of the invention will be more apparent from the following description understood by appropriately making reference to the appended drawings.
According to the present invention, a metallic material for an electrical electronic component is provided with a Cu—Sn alloy layer on a conductive base or on an undercoat formed on the conductive base and Cu concentration in the Cu—Sn alloy layer gradually decreases from the side of the base toward the side of a surface of the metal material. The metallic material for electrical electronic component is formed by forming the Cu—Sn alloy layer by plating Sn on a plating layer formed on the conductive base and by implementing a heat treatment and by decreasing the Cu concentration gradually from the base side to the surface side.
The phrase “the Cu concentration of the Cu—Sn alloy layer gradually decreases from the base side to the surface” means that the Cu concentration measured at least three places whose depth from the surface of the layer is different in section of the Cu—Sn alloy layer is low in order closer to the surface.
While the Cu concentration of the Cu—Sn alloy layer of the invention gradually decreases from the base side to the surface, the Cu concentration in a half of the base side of the thickness is preferable to be 50 to 100 mol % and is more preferable to be 65 to 100 mol % and the Sn concentration is preferable to be 0 to 50 mol % of the remaining part and more preferable to be 0 to 35 mol % (this is concentration in which inevitable impurities other than Cu and Sn are neglected. The same applies hereinafter).
In a case when Sn or the Sn alloy is not distributed partially, the Cu concentration on a half on the surface side is preferable to be 40 to 95 mol % and more preferable to be 65 to 85 mol %. The Sn concentration is preferable to be 5 to 60 mol % and more preferable to be 15 to 35 mol %.
In a case when Sn or the Sn alloy is dispersed partially, the Cu concentration in the half of the surface side is preferable to be 0 to 95 mol % and more preferable to be 65 to 85 mol %. The Sn concentration is preferable to be 5 to 100 mol % and more preferable to be 15 to 35 mol %.
If the Cu concentration in the half of the base side is too low (the Sn concentration is too high), a pure Sn layer tends to be formed on the outermost surface and fretting resistance deteriorates.
If the Sn concentration in the half of the surface side is too low, the heat resistance decreases, leading to the quick increase of resistance when used under a high-temperature environment.
The metallic material for electrical electronic component of the invention has a room for permitting Cu to diffuse with Sn even if a Cu layer exists in a substrate or no Ni substrate exists because the Cu—Sn alloy layer is what is formed so that the Cu concentration within the Cu—Sn alloy layer on the upper side in gradation, i.e., the Sn concentration is low in the Cu—Sn alloy layer on the surface side. As a result, it becomes possible to retard Cu from being exposed on the outermost surface and being oxidized even if the metallic material for electrical electronic component receives thermal load.
A thickness of the Cu—Sn alloy layer is preferably in a range from 0.1 to 3.0 μm and more preferable to be 0.3 to 1.5 μm. If this thickness is too thick, Kirkendall voids tend to be generated in a diffusion process, possibly causing delamination of plating. Still more, it is presumed that costs for plating increase due to the increase of heat-treatment temperature and time. If the thickness is too thick, the contact resistance may increase, the heat resistance may be deteriorated and the fretting resistance may be deteriorated.
In the present invention, copper and copper alloys such as phosphor bronze, brass, alpaca, beryllium copper and Corson alloy, iron and iron alloys such as stainless steel, compound materials such as copper-coated steel material and nickel-coated steel material, various nickel alloy and aluminum alloys having conductivity, mechanical strength and heat resistance required for terminals may be used for the conductive base.
Among the metals and alloys (material) described above, the copper materials such as copper and the copper alloys are suitable in particular because they excel in the balance of the conductivity and mechanical strength. If the conductive base is made of materials other than the copper material, it is preferable to coat copper or the copper alloy on the surface of the conductive base.
While the Sn plating may be formed by nonelectrolytic plating, it is desirable to form by electroplating. A thickness of the Sn layer formed by the Sn plating is preferable to be in a range from 0.01 to 5.0 μm. Sn electroplating of the uppermost layer may be carried out under conditions of 30° C. or less of plating temperature and 5 A/cm2 of current density by employing tin sulfate bath for example. However, these conditions are not limited to these and may be appropriately set.
According to the invention, the laminate material whose uppermost layer is Sn-plated is treated by heat. Conditions for this heat treatment are selected so as to form the Cu—Sn alloy layer in which the Cu concentration gradually decreases from the base side to the surface side. When the heat treatment is implemented by a reflow process (continuous process), it is preferable to heat in an in-furnace temperature range of 300° C. or more to under 900° C. for three to 20 seconds (or preferably from 5 to 10 seconds or more preferably from 6 to 8 seconds).
These temperature and time are adopted to obtain the Cu—Sn alloy layer whose Cu concentration gradually decreases from the base side to the surface side.
It is noted that it is preferable to hold the material described above for 0.1 to 200 hours within a furnace whose temperature is 60 to 200° C. when the heat treatment is carried out in a way of batch process.
Still more, it is preferable to pass the laminate material treated by heat by the reflow process into liquid within a cooling tank by taking 1 to 100 seconds (or more preferably 3 to 10 seconds) to quench the material. Temperature of the liquid is preferable to be in a range from 20 to 80° C. (or more preferably 30 to 50° C.). It is also preferable to pass the laminate material treated by heat into gas of a cold-air unit within the in-furnace atmosphere of 20 to 60° C. by taking 1 to 300 seconds to gradually cool the material.
It becomes possible to obtain the plating structure in which the Cu concentration within the Cu—Sn alloy layer is gradational and to disperse pure Sn within the Cu—Sn alloy layer by forcibly ending the diffusion of Cu and Sn in mid-stream or by rapidly reducing their diffusion speed by such cooling process.
The dispersion state is preferable if at least part of the metallic Sn and the Sn alloy (Sn concentration is more than 80 mol %) is exposed on the surface of the uppermost layer and Sn or the Sn alloy is dispersed like an island or a dot when seen planarly. Still more, an oxide film from 0 to 100 nm may be formed on the outermost layer.
A still other embodiment of the invention is the metallic material for electrical electronic component in which the conductive base 1 coated with any one type of metal among Ni, Co and Fe or with an alloy containing those metals as a main component (more than 50 mass %) by plating and is then treated by heat to provide the Cu—Sn alloy layer 2 whose Cu concentration is gradually reduced from the base side 1 toward the surface 3.
A still different embodiment of the invention is the metallic material for electrical electronic component in which the conductive base 1 coated with any one type of metal among Ni, Co and Fe or with an alloy containing those metals as a main component (more than 50 mass %) by plating or the like, is coated with Cu and Sn in this order and is then treated by heat to provide the Cu—Sn alloy layer 2 whose Cu concentration is gradually reduced from the base side 1 toward the surface 3 and Sn or the Sn alloy is partially dispersed within the Cu—Sn alloy layer 2.
A still different embodiment of the invention is a metallic material for electrical electronic component in which the conductive base 1 coated with any one type of metal among Ni, Co and Fe or with an alloy containing those metals as a main component (more than 50 mass %) by two layers by plating or the like, is coated with Cu and Sn in this order and is then treated by heat to provide the Cu—Sn alloy layer 2 whose Cu concentration is gradually reduced from the base side 1 toward the surface 3. A combination of two types of plating implemented on the conductive base 1 is not specifically limited.
A still other embodiment of the invention is a metallic material for electrical electronic component in which the conductive base 1 coated with any one type of metal among Ni, Co and Fe or with an alloy containing those metals as a main component (more than 50 mass %) by two layers by plating or the like, is coated with Cu and Sn in this order by plating or the like and is then treated by heat to provide the Cu—Sn alloy layer 2 whose Cu concentration is gradually reduced from the base side 1 toward the surface 3 and Sn or the Sn alloy is partially dispersed within the Cu—Sn alloy layer 2. A combination of two types of plating implemented on the conductive base 1 is not specifically limited.
The Cu—Sn alloy layer in the outermost layer contains a Cu—Sn intermetallic compound layer in the present invention. The Cu—Sn intermetallic compound in the invention includes Cu6Sn5, Cu3Sn and others. The invention includes those in which those intermetallic compounds are mixed.
In the present invention, preferably the conductive base 1 is provided with the undercoat such as the Ni layer 6 as described in the modes shown in
While a fusion point of the metal (alloy) such as Ni used for the undercoat described above is as high as 1000° C., temperature of use environment of the connector is lower than 200° C., so that the undercoat itself hardly causes thermal diffusion and its barrier function is effectively exhibited. The undercoat also has a function of enhancing adhesion between the conductive base and an intermediate layer described later depending on a material of the conductive base. The barrier function of the undercoat is not fully exhibited if its thickness is under 0.01 μm and plating distortion thereof becomes large and the undercoat is prone to fall away if the thickness exceeds 3 μm. Accordingly, the thickness of the undercoat is preferable to be in a range from 0.01 to 3 μm. Considering a terminal workability, an upper limit of the thickness of the undercoat is preferable to be 1.5 μm or more preferable to be 0.5 μm.
The metallic material for electrical electronic component of the present invention is what the conductive base 1 is provided with the intermediate layer composed of the Cu layer 5 on the undercoat made of Ni or the like as described in the mode shown in
The metallic material for electrical electronic component of the invention may be formed into any shape such as a strip, round wire and rectangular wire. The metallic material for electrical electronic component of the invention may be worked into an electric/electronic part such as a fitting-type multipole connector for use in automobiles by a normal method. For instance, a connector created by using the metallic material for electrical electronic component of the invention may be what weakens a contact pressure between terminals, causes no fretting phenomenon between contact faces of terminals and suppresses an occurrence of inferior conductivity between the terminals.
The metallic material for electrical electronic component of the invention may be manufactured readily by a reflow thermal treatment and may improve heat resistance of a plating material. It is because the abundant Cu on the base side reacts with the abundant Sn on the surface side within the Cu—Sn alloy layer even under a high-temperature environment when this material is used as an electric/electronic material. Still more, the electric/electronic material manufactured by using the metallic material for electrical electronic component of the invention can remarkably suppress a sharp rise of resistance (fretting) at an electrical contact during sliding.
Still more, the metallic material for electrical electronic component in which the conductive base is provided with the undercoat made of Ni or the like can prevent the components of the base from diffusing into the outermost layer. Still more, the material in which the intermediate layer made of Cu or the like is provided on the undercoat can prevent the component such as Ni of the base from diffusing into the outermost layer. Accordingly, it becomes possible to stably obtain favorable electrical connectivity.
Further, the material in which Sn or the Sn alloy is partially dispersed within the Cu—Sn alloy layer has the effect that no CuO and the like is formed by exposed Cu and the contact resistance is stabilized because there is such a room that a Cu—Sn alloy is formed as Cu existing under the Cu—Sn alloy layer reacts with Sn or the Sn alloy dispersed within the Cu—Sn alloy layer.
Embodiments
While exemplary embodiments of the invention will be explained below in detail, the invention is not limited to them.
First Exemplary Embodiment
A plated laminate was fabricated by degreasing and pickling a copper strip of 0.25 mm thick in this order and by electroplating the copper alloy strip by laminating Ni, Cu and Sn in this order. Plating of each metal was implemented under the following conditions:
(a) Ni Plating
Plating Bath Composition
(b) Cu Plating
Plating Bath Composition
(c) Sn Plating
Plating Bath Composition
It is noted that the thickness described above may be appropriately modified by plating time.
Next, this plated laminate was treated by a reflow process within a reflow furnace at 740° C. for 7 seconds to obtain the metallic material.
As shown in Table 1 and
Second Exemplary Embodiment
A plated laminate was fabricated by degreasing and pickling a copper strip of 0.25 mm thick in this order and by electroplating the copper alloy strip by laminating Ni, Cu and Sn in this order. Plating of each metal was implemented under the following conditions:
(a) Ni Plating
Plating Bath Composition
(b) Cu Plating
Plating Bath Composition
(c) Sn Plating
Plating Bath Composition
It is noted that the thickness described above may be appropriately modified by plating time.
Next, this plated laminate was heat-treated by a reflow process within a reflow furnace at 740° C. for 7 seconds to obtain the metallic material.
As shown in Table 2 and
First Exemplary Test
The following fine sliding test was carried out on the respective metallic materials for electrical electronic component obtained in the first and second exemplary embodiments by sliding and reciprocating the material up to 1,000 times to measure changes of values of contact resistance continuously.
The fine sliding test was carried out by preparing two each pieces of testing metallic materials 31 and 32, by providing a semi-spherical bulge section (convex outer surface is the outermost layer surface) 31a having a radius of curvature of 1.8 mm in the testing metallic material piece 31, by contacting an outermost layer surface 32a of the testing metallic material piece 32 after degreasing and washing, respectively, to the semi-spherical bulge section 31a with contact pressure 3 N, by reciprocating and sliding the both in this state with 30 μm of a sliding distance under an environment of 20° C. of temperature and 65% of humidity, by flowing 5 mA of constant current while loading 20 mV of open voltage between the both testing metallic material pieces 31 and 32 and by finding the changes of electric resistance per one second by measuring a voltage drop during sliding by a four-terminal method. It is noted that frequency of the reciprocal movement was about 3.3 Hz. The value of contact resistance before the fine sliding test was 0.1 mΩ when the testing metallic material pieces 31 and 32 are used as the materials of the first embodiment and was 0.5 mΩ when used as the materials of the second embodiment. Further, the maximum contact resistance value during the fine sliding test was 4.0 mΩ when the testing metallic material pieces 31 and 32 are used as the materials of the first embodiment and was 4.1 mΩ when used as the materials of the second embodiment. Thus, no fretting occurred in the materials of the present embodiment.
Third Exemplary Embodiment
A plated laminate was fabricated by plating a copper alloy strip by laminating Ni, Cu and Sn in the same manner with the firs embodiment and the same heat treatment was implemented to obtain each metallic material. However, thicknesses of plating of Cu and Sn are those in the Cu—Sn layer in the following Table 3 and no Ni plating is implemented in the case when there is no undercoat Ni layer.
Each metallic material thus obtained was tested as a specimen piece and Table 3 shows their plating modes and evaluation results:
The followings are contents of items in Tables 3 and 4.
When the outermost surface the specimen is only pure Sn as indicated in the test No. 19 in Table 1, its fretting resistance and heat resistance after sliding are inferior. Meanwhile, it can be seen that if the Cu concentration on the surface side is lower than that on the base side like the test Nos. 1 through 16, the fretting resistance is better than that of the test No. 19.
It is noted that it was confirmed that the Cu concentration gradually decreases from the base side to the surface side in the Cu—Sn alloy layer in the test Nos. 1 through 15.
It can be also seen that in the test No. 6 through 8 whose Cu concentration in the half of the base side is 50 to 100 mol % and whose Cu concentration in the half of the surface side is not in a range of 40 to 95 mol %, their fretting resistance and heat resistance after sliding are inferior as compared to the test No. 1 through 5 that are within the range. In the same manner, when pure Sn is partially dispersed within the Cu—Sn alloy layer, it can be seen that even the test No. 16 whose Cu concentration in the half of the substrate side is 50 to 100 mol % and whose Cu concentration in the half of the surface side is low has inferior fretting resistance and heat resistance after sliding as compared to the test Nos. 11 through 15 that are within the range.
The test Nos. 9, 10, 17 and 18 whose Cu—Sn alloy layer is out of the range of 0.1 to 3.0 μm have inferior fretting resistance and heat resistance after sliding as compared to the test Nos. 1 through 5 and 11 through 15 that are within the range. Further, when the thickness of the Cu—Sn layer is thicker than 3.0 μm, they are inferior than the test Nos. 1 through 15 and 11 through 15 in the test of after-thermal load of 160° C.×120 hrs as indicated by the test Nos. 9 and 17. When the thickness of the Cu—Sn layer is thinner than 0.1 μm, they are inferior not only in the test after-thermal load of 160° C.×120 hrs but also in the test after spraying salt water and after corroding by gas as indicated by the test Nos. 10 and 18.
The test Nos. 1 through 5 and 11 through 15 that fall all within the ranges described above obtained good results in all evaluation items.
Fourth Exemplary Embodiment
A plated laminate was fabricated by plating Ni, Cu and Sn on the strip of copper alloy in the same manner with the first embodiment and a heat treatment was implemented to obtain each metallic material for electrical electronic component shown in the following Table 4. However, the thicknesses of plating of Cu and Sn are thickness indicated by thicknesses of Cu and Sn in Table 4 and no Ni plating is implemented in the case when there is no undercoat Ni layer in Table 4.
Each metallic material thus obtained was tested as specimen and Table 4 shows their plating mode and evaluation results.
While it can be seen that the Cu concentration gradually decreases from the base side to the surface side in all of the tested items, the degree of decrease of the test No, 35 whose heating temperature is as high as 900° C. is small. The fretting resistance of the test Nos. 31 through 35 having the pure Sn layer on the outermost surface is inferior. Still more, the test Nos. 32 and 34 whose heating and cooling times are short have inferior heat resistance after sliding.
The metallic material for electrical electronic component of the invention may be readily manufactured and may be suitably used for a connecting or sliding portion of a connector terminal.
While the invention has been described with its modes, the inventors have no intention of limiting any detail of the explanation of the invention unless specifically specified and consider that the invention should be construed widely without going against the spirit and scope of the invention indicated by the scope of the appended Claims.
This application claims priority from Japanese patent application Nos. 2007-142469 filed on May 29, 2007 and 2008-140186 filed on May 28, 2008. The entire contents of which are incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-142469 | May 2007 | JP | national |
| 2008-140186 | May 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/059928 | 5/29/2008 | WO | 00 | 7/15/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/146885 | 12/4/2008 | WO | A |
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|---|---|---|---|
| 20030091855 | Tanaka et al. | May 2003 | A1 |
| 20040229077 | Mori et al. | Nov 2004 | A1 |
| 20050211461 | Horikoshi et al. | Sep 2005 | A1 |
| 20070218312 | Sakuyama et al. | Sep 2007 | A1 |
| 20090061253 | Yoshida et al. | Mar 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 2157668 | Feb 2010 | EP |
| 3-202490 | Sep 1991 | JP |
| 11-140569 | May 1999 | JP |
| 2000-226645 | Aug 2000 | JP |
| 2003-213486 | Jul 2003 | JP |
| 2003-293187 | Oct 2003 | JP |
| 2004-068026 | Mar 2004 | JP |
| 2004-339555 | Dec 2004 | JP |
| 2006-077307 | Mar 2006 | JP |
| 2006-183068 | Jul 2006 | JP |
| 2007-051370 | Mar 2007 | JP |
| WO 2007097338 | Aug 2007 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20100304177 A1 | Dec 2010 | US |
