JP5748019B1 - Pin terminals and terminal materials - Google Patents

Abstract

A pin terminal having low cost and excellent corrosion resistance and a terminal material for producing the pin terminal are provided. A pin terminal includes a core material made of a Cu-Fe alloy containing 10 to 70% by mass of Fe and the balance having a chemical component composed of Cu and inevitable impurities. The pin terminal 1 includes a Ni plating film 3 present on the core material 2, a Cu plating film 4 present on the Ni plating film 3, a CuSn alloy layer 5 present on the Cu plating film 4, and a CuSn alloy. And an Sn plating film 6 existing on the layer 5. [Selection] Figure 2

Description

  The present invention relates to a pin terminal and a terminal material.

  For a board connector such as a printed circuit board (PCB) connector for automobiles, a pin terminal having a core made of a copper alloy in which a metal of about several mass% is added to copper, such as brass, is used.

  In recent years, in order to reduce the weight, size, and cost of the entire connector, a pin terminal that has higher rigidity and can reduce the material cost is desired. Thus, as a copper alloy having a high material strength and a low material cost, it has been studied to use a Cu—Fe-based alloy obtained by adding Fe (iron) to Cu (copper) as a core material of a pin terminal.

  For example, Patent Document 1 discloses an example of a spring member made of an alloy of 10 to 70% by mass of Fe in which 0.05 to 5% by mass of carbon is solid-dissolved, and the balance being Cu and inevitable impurities. A Cu—Fe-based alloy having such a chemical component tends to have a higher strength than conventional copper alloys. In addition, since the Cu—Fe-based alloy contains Fe, which is cheaper than metal, than Cu, the material cost can be easily reduced by increasing the Fe content.

  As described above, the Cu—Fe-based alloy is a material having a possibility of satisfying both a sufficient strength as a core material of the pin terminal and a material cost.

  On the other hand, the Cu-Fe-based alloy containing 10 to 70% by mass of Fe has a metal structure in which a Cu-rich phase mainly composed of Cu and a Fe-rich phase mainly composed of Fe are mixed, Both the Cu rich phase and the Fe rich phase exist on the surface of the core material. Since the Fe-rich phase is more easily corroded than copper alloys such as brass, the core material made of such a Cu-Fe alloy has a problem that the corrosion resistance is low.

  In order to enhance the corrosion resistance of the pin terminal, it is effective to cover the surface of the core material with a metal layer having high corrosion resistance to suppress the exposure of the Fe-rich phase that is easily corroded. Therefore, after providing a Sn plating film on the surface of the core material made of a Cu-Fe-based alloy, the Sn plating film is heated to perform a reflow treatment, and a CuSn alloy layer having high corrosion resistance between the core material and the Sn plating film. The method of forming is being studied.

JP-A-5-125468

  However, in the above method, the CuSn alloy layer is formed by reflow treatment in the portion where the Cu rich phase and the Sn plating film are in contact, but the portion where the Fe rich phase and the Sn plating film are in contact is formed. CuSn alloy layer is not formed. Therefore, when the Sn plating film disappears for some reason, it is difficult to suppress the exposure of the Fe-rich phase, and there is a limit to improving the corrosion resistance.

  On the other hand, in a pin terminal made of a conventional copper alloy, a CuSn alloy is formed between the Cu plating film and the Sn plating film by performing a reflow process in a state where the Cu plating film and the Sn plating film are laminated on the core material. Techniques for forming layers are known. However, in order to directly apply the above technique to a core material made of a Cu—Fe-based alloy, there are the following problems. That is, when a core material made of a Cu—Fe alloy is immersed in a Cu plating bath, a substitution reaction occurs between Fe exposed on the surface and Cu ions in the plating solution, and Cu is precipitated. Since Cu deposited by this substitution reaction has lower adhesion to the core material than Cu formed by electroplating, the Sn plating film formed on the surface of the pin terminal is easily peeled off together with Cu. Moreover, since the surface of the core material is exposed when the Sn plating film is peeled off, it is difficult to sufficiently obtain the effect of improving the corrosion resistance by the CuSn alloy layer.

  The present invention has been made in view of such a background, and intends to provide a pin terminal having low cost and excellent corrosion resistance and a terminal material for producing the pin terminal.

One aspect of the present invention contains 10 to 70 wt% of Fe, have a chemical composition that the balance of Cu and unavoidable impurities, Fe-rich phase mainly composed of Fe as a main component a Cu Cu A core material comprising a Cu-Fe-based alloy having a metal structure distributed in a rich phase and having both the Fe-rich phase and the Cu-rich phase on the surface;
A Ni plating film present on the core material;
A Cu plating film present on the Ni plating film;
A CuSn alloy layer present on the Cu plating film;
An Sn plating film present on the CuSn alloy layer ,
The Ni plating film has a thickness of 0.01 to 0.3 μm in the pin terminal.

Another aspect of the present invention is a terminal material for producing the pin terminal of the above aspect,
Containing 10 to 70 wt% of Fe, have a chemical composition that the balance of Cu and unavoidable impurities, Fe-rich phase composed mainly of Fe is distributed in the Cu-rich phase mainly composed of Cu A core material made of a Cu-Fe-based alloy having a metallic structure and having both the Fe-rich phase and the Cu-rich phase on the surface;
A Ni plating film present on the core material;
A Cu plating film present on the Ni plating film;
And Sn plating film present on the Cu plating film ,
The thickness of the Ni plating film is 0.01 to 0.3 μm in the terminal material.

  The pin terminal is manufactured using a core material having the specific chemical component. Therefore, the pin terminal can easily achieve both a sufficiently high strength and a low material cost. Moreover, since the said pin terminal contains Cu rich phase with high electrical conductivity in the said core material, the electrical conductivity equivalent to the conventional copper alloy or more can be ensured easily.

  The pin terminal includes the Ni plating film between the core material and the Cu plating film. Thus, by forming the Ni plating film on the core material, it is possible to prevent the Cu plating bath from directly contacting the core material in the subsequent step of forming the Cu plating film. As a result, Cu precipitation due to substitution reaction can be suppressed, and adhesion between the Cu plating film and the Sn plating film and the core material can be improved.

  The pin terminal has the CuSn alloy layer between the Cu plating film and the Sn plating film. Since the pin terminal can suppress exposure of the core material due to the presence of the CuSn alloy layer, the pin terminal has excellent corrosion resistance.

  As described above, the pin terminal has low cost and excellent corrosion resistance.

  Further, the terminal material has a plating film laminated on the core material in the specific order. Therefore, by heating the terminal material and performing a reflow treatment, Cu and Sn can be alloyed, and the dense CuSn alloy layer can be formed between the Cu plating film and the Sn plating film. . As described above, the terminal material can be easily manufactured by performing a simple process called a reflow process.

The perspective view of the pin terminal in an Example. The partial sectional view near the surface of a pin terminal in an example. The front view of the board | substrate connector incorporating the pin terminal in an Example. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. The SEM image of the pin terminal surface in the state which removed the Sn plating film in an Example. The partial sectional view of the pin terminal which performed reflow processing after forming Sn plating film on the core material in a comparative example. The SEM image of the pin terminal surface after spraying the sodium chloride solution in a comparative example.

In the pin terminal, the CuSn alloy layer can be formed by performing a reflow process on the terminal material as described above. In this case, it is preferable that a Cu ₆ Sn ₅ intermetallic compound is contained in the CuSn alloy layer. Since the intermetallic compound has excellent corrosion resistance, the corrosion resistance of the entire pin terminal can be further improved. Further, since the intermetallic compound is relatively hard and has high conductivity, the connection reliability when connecting the pin terminal to the counterpart terminal can be improved, and the contact resistance and the terminal insertion force are low. The state can be maintained for a long time.

The CuSn alloy layer can also be formed by performing, for example, a CuSn alloy plating process. That is, the pin terminal can be produced by sequentially laminating, for example, a Ni plating film, a Cu plating film, a CuSn plating film, and a Sn plating film on the core material. In this case, it is preferable to form a CuSn plating film made of a speculum alloy on the Cu plating film. Since the speculum alloy has a relatively high Cu content of 30 to 50% by mass, it contains a large amount of Cu ₆ Sn ₅ intermetallic compound with high corrosion resistance. Therefore, similarly to the above, the corrosion resistance and contact reliability of the pin terminal can be further improved.

  The thickness of the CuSn alloy layer is preferably 0.2 μm or more. In this case, exposure of the core material can be more effectively suppressed due to the presence of the CuSn alloy layer. As a result, the corrosion resistance of the pin terminal can be further improved. When the thickness of the CuSn alloy layer is less than 0.2 μm, the effect of improving the corrosion resistance by the CuSn alloy layer may be insufficient.

  The pin terminal has a higher corrosion resistance as the CuSn alloy layer is thicker. However, when the thickness of the CuSn alloy layer exceeds 1 μm, the effect of improving the corrosion resistance is reduced while the productivity is lowered, and the thickness is increased. It is difficult to obtain an effect commensurate with Therefore, from the viewpoint of achieving both excellent corrosion resistance and high productivity, the thickness of the CuSn alloy layer is more preferably 0.2 to 1 μm.

The thickness of the Ni plating film is 0.01 to 0.3 [mu] m. As described above, the Ni plating film suppresses the direct contact of the Cu plating bath with the core material in the process of forming the Cu plating film, and improves the adhesion between the Cu plating film and the Sn plating film and the core material. Has the effect of improving. By making the thickness of the Ni plating film 0.01 μm or more, the above effects can be sufficiently obtained.

  When the thickness of the Ni plating film is less than 0.01 μm, defects such as pinholes and pits are excessively generated in the Ni plating film, so that the Cu plating bath and the core material are likely to come into contact with each other. As a result, Cu is liable to precipitate due to the substitution reaction, and the adhesion between the Sn plating film and the Cu plating film and the core material may be reduced.

  From the viewpoint of reducing defects and improving the adhesion between the Sn plating film and Cu plating film and the core material, the Ni plating film is preferably made thick. However, it is difficult for the Ni plating film to make the current density in the electroplating process higher than that of the Cu plating, and there is a limit to increasing the film forming speed on the core material. Therefore, when it is attempted to increase the thickness of the Ni plating film, there is a problem that the time required for the plating process becomes longer and the manufacturing cost is increased. In order to obtain excellent adhesion and corrosion resistance with an Sn plating film or the like while suppressing an increase in manufacturing cost, the thickness of the Ni plating film is preferably 0.01 to 0.5 μm, It is more preferable to set it to -0.3 micrometer.

  The thickness of the Cu plating film is preferably 0.5 to 1.5 μm. In this case, the adhesion of the Sn plating film can be further improved. When the thickness of the Cu plating film is less than 0.5 μm, the adhesion of the Sn plating film becomes insufficient, and there is a possibility that the Cu plating film is easily peeled off from the core material. Moreover, when forming the said CuSn alloy layer by a reflow process, there exists a possibility that the amount of Cu spent on alloying reaction with Sn may be insufficient, and the thickness of a CuSn alloy layer may become inadequate. Therefore, in order to sufficiently obtain the above effect, the thickness of the Cu plating film is preferably 0.5 μm or more.

  In addition, although there is no upper limit in particular of the thickness of the said Cu plating film, it is preferable to set it as 1.5 micrometers or less from a viewpoint of productivity and material cost reduction, and it is more preferable to set it as 1.0 micrometer or less.

  The thickness of the Sn plating film is preferably 0.6 to 5 μm. Since the Sn plating film is relatively soft, the contact resistance with the counterpart terminal can be sufficiently lowered by setting the thickness within the above specific range, and excellent connection reliability can be obtained.

  When the thickness of the Sn plating film is less than 0.6 μm, the effect of improving the connection reliability by the Sn plating film is insufficient, and there is a risk of increasing the contact resistance. On the other hand, when the thickness of the Sn plating film exceeds 5 μm, the Sn plating film is dug up in the mating terminal at the time of fitting with the mating terminal, or is adhered to the Sn plating film existing on the surface of the mating terminal. This may cause problems such as the occurrence of a problem, and may increase the terminal insertion force. Therefore, from the viewpoint of achieving both excellent connection reliability and low terminal insertion force, the thickness of the Sn plating film is preferably 0.6 to 5 μm. From the same viewpoint, the thickness of the Sn plating film is more preferably 0.6 to 3 μm, and still more preferably 0.6 to 2 μm.

The Cu—Fe-based alloy constituting the core material contains 10 to 70% by mass or more of Fe, and the balance has chemical components composed of Cu and inevitable impurities. Cu-Fe-based alloy having such chemical composition has a metal structure Fe rich phase composed mainly of Fe are distributed in the Cu-rich phase mainly composed of Cu. Here, the above-mentioned “main component” means an element having the highest content. That is, the Cu-rich phase may contain a trace amount of Fe or impurities in addition to the main component Cu. The Fe-rich phase may contain a trace amount of Cu or impurities in addition to the main component Fe.

  The Cu—Fe-based alloy tends to increase in strength as the Fe content increases. Therefore, the said core material can fully satisfy the intensity | strength requested | required of a pin terminal by content of Fe being 10 mass% or more. Moreover, material cost can be reduced rather than the conventional copper alloy by content of Fe of the said core material being 10 mass% or more. Therefore, from the viewpoint of increasing the strength and further reducing the material cost, the Fe content is set to 10% by mass or more. From the same viewpoint, the Fe content is preferably 20% by mass or more, and more preferably 50% by mass or more.

  On the other hand, if the content of Fe in the Cu—Fe-based alloy is excessively increased, the workability at the time of bending is deteriorated, so that cracks and the like are likely to occur when the pin terminal is bent. Moreover, since the Fe-rich phase contained in the core material has a lower electrical conductivity than the Cu-rich phase, when the Fe content is excessively large, the electrical conductivity of the core material tends to be low. Therefore, if the Fe content is excessively large, it may be difficult to satisfy the electrical conductivity required for the pin terminal. These problems can be avoided by regulating the Fe content to 70% by mass or less. From the same viewpoint, the Fe content is preferably regulated to 60% by mass or less.

  As described above, the core material can satisfy various properties such as strength, workability, and conductivity required for the pin terminal by setting the Fe content to 10 to 70% by mass, and conventionally. Can also reduce material costs.

  The terminal material can be produced, for example, by performing a plating process on a Cu-Fe-based alloy wire having the chemical component in the specific range. That is, the terminal material can be produced by sequentially performing Ni plating, Cu plating and Sn plating on a wire having a desired cross-sectional shape. The terminal material may be produced by sequentially performing the above-described plating treatment on a punched material obtained by punching a Cu-Fe-based alloy plate. The terminal material obtained as described above is subjected to reflow treatment to form a CuSn alloy layer, and then becomes a pin terminal through molding by pressing and separation of the terminal. Note that the above-described wire and plate can be produced by appropriately combining known processes such as hot working, cold working, and heat treatment with an ingot of a Cu—Fe alloy.

(Example)
Examples of the pin terminals will be described with reference to the drawings. As shown in FIGS. 1 and 2, the pin terminal 1 includes a core material 2 made of a Cu—Fe based alloy containing 10 to 70% by mass of Fe and the balance having chemical components composed of Cu and inevitable impurities. Have. The pin terminal 1 includes a Ni plating film 3 present on the core material 2, a Cu plating film 4 present on the Ni plating film 3, a CuSn alloy layer 5 present on the Cu plating film 4, and a CuSn alloy. And an Sn plating film 6 existing on the layer 5.

  Hereinafter, a more detailed configuration of the pin terminal 1 will be described together with an example of a manufacturing method. In this example, first, a square wire made of a Cu—Fe alloy having a square cross section with a side of 0.64 mm and containing 50 mass% Fe was prepared. The Cu—Fe based alloy having such a composition has a metal structure (see FIG. 2) in which the Fe rich phase 21 is distributed in the Cu rich phase 20 because the Fe content exceeds the solid solubility limit. .

  Next, by sequentially performing electroplating treatment on the surface of the rectangular wire, the Ni plating film 3, the Cu plating film 4, and the Sn plating film 6 were laminated to produce a terminal material. The conditions for the electroplating treatment can be appropriately selected from conventionally known conditions. In this example, the electroplating process was performed so that the thickness of the Ni plating film 3 was 0.3 μm, the thickness of the Cu plating film 4 was 1.0 μm, and the thickness of the Sn plating film 6 was 1.0 μm. .

Next, the terminal material on which the Ni plating film 3, the Cu plating film 4 and the Sn plating film 6 are formed is heated to perform a reflow process, and a CuSn alloy layer 5 is formed between the Cu plating film 4 and the Sn plating film 6. did. The heating temperature in the reflow treatment is preferably in the range of T _{m to} T _m + 50 ° C. when the melting point of Sn is T _m . By setting the heating temperature for the reflow treatment within the specific temperature range, Sn and Cu can be alloyed, and the CuSn alloy layer 5 can be reliably formed. Moreover, when performing the said reflow process in the said specific temperature range, it is preferable to control heating time in the range of 10 to 120 second. By setting the heating temperature and the heating time within the above ranges, the dense CuSn alloy layer 5 can be easily formed.

In this example, the heating temperature in the reflow process was 280 ° C., and the heating time was 20 seconds. As a result, a CuSn alloy layer 5 having a thickness of 0.3 μm and containing a Cu ₆ Sn ₅ intermetallic compound could be formed. Although not shown in the figure, in this example, Ni of the Ni plating film 3 and Cu of the core material 2 and Cu of the Cu plating film 4 are alloyed by performing the above reflow treatment, and the core material 2 and the Ni plating are formed. CuNi alloy layers were formed between the film 3 and between the Ni plating film 3 and the Cu plating film 4.

  After the reflow treatment, the terminal material was subjected to press working, and the terminal portion 100 that was cut off at the same time as the desired length was formed into a tapered shape. Thus, the pin terminal 1 shown in FIG. 1 was obtained. In addition, in the pin terminal 1 of this example, the core material 2 is inevitably exposed to the separated terminal portion 100 when being separated by press working. However, the terminal portion 100 is not in direct contact with the counterpart terminal and does not form a current-carrying path, and the terminal portion 100 has a very small area ratio compared to the side peripheral surface 101 covered with the CuSn alloy layer 5. The exposure of the core material 2 in the portion 100 does not cause a decrease in the corrosion resistance of the entire pin terminal 1.

  The pin terminal 1 of this example can be used by being incorporated in a board connector such as the PCB connector 10 shown in FIGS. The connector 10 includes a housing 7 having a recess 71 and a plurality of pin terminals 1 disposed through the housing 7.

  The housing 7 has a substantially rectangular parallelepiped shape as shown in FIGS. 3 and 4, and includes a bottom wall portion 72 through which the pin terminal 1 penetrates, and a side wall portion 73 erected from the outer peripheral edge portion of the bottom wall portion 72. have. A space surrounded by the bottom wall portion 72 and the side wall portion 73 constitutes the recess 71.

  As shown in FIG. 4, the pin terminal 1 is disposed through the bottom wall portion 72, and has a terminal connection portion 102 that directly contacts the counterpart terminal in the recess 71. Further, the pin terminal 1 has a soldering portion 103 at the end opposite to the terminal connection portion 102. The soldering portion 103 is soldered in a state of being inserted into a through hole (not shown) of the PCB board P in the operation of mounting the connector 10 on the PCB board P. In addition, the pin terminal 1 of this example is bent so that the terminal connection portion 102 and the soldering portion 103 are perpendicular to each other in a state where the pin terminal 1 is disposed in the connector 10.

  Next, the function and effect of this example will be described. FIG. 5 shows an SEM (scanning electron microscope) image of the surface of the pin terminal 1 in a state where the Sn plating film 6 is removed by etching and the CuSn alloy layer 5 is exposed. From FIG. 5, it can be understood that the pin terminal 1 manufactured by the above method has the CuSn alloy layer 5 in which the pits and pinholes are few and the CuSn alloy crystal 50 is densely and uniformly formed. Since the pin terminal 1 of this example has such a CuSn alloy layer 5, it is considered that the core material 2 can be prevented from being exposed and has excellent corrosion resistance.

(Comparative example)
This example is an example of the pin terminal 8 (see FIG. 6) in which the Sn plating film 6 is directly formed on the surface of the core material 2 made of a Cu—Fe-based alloy and reflow treatment is performed. The pin terminal 8 of this example was manufactured by forming a Sn plating film 6 having a thickness of 1.5 μm on the surface of the core material 2 by electroplating and then performing a reflow process at a temperature of 280 ° C. for 20 seconds. . Of the reference numerals used in FIGS. 6 and 7, the same reference numerals as those used in the embodiments denote the same components as those in the embodiments unless otherwise specified.

  In this example, a neutral sodium chloride solution was continuously sprayed on the pin terminal 8 to evaluate the corrosion resistance. In addition, evaluation of corrosion resistance was performed on the conditions according to the neutral salt spray test method prescribed | regulated to JISH8502: 1999.

  FIG. 7 shows an SEM image of the surface of the pin terminal 8 after spraying the sodium chloride solution for 96 hours. As shown in FIG. 7, the Sn plating film 6 has disappeared from the surface of the pin terminal 8 after the test due to corrosion, and a region A where granular fine crystals are gathered and a relatively flat region B are present. It was mixed. Further, when an element mapping image was obtained for the same field of view as in FIG. 7, the granular fine crystals present in the region A were CuSn alloy crystals 50, and the region B was the Fe-rich phase 21 exposed on the surface. Was confirmed.

  From the above results, when reflow treatment is performed after the Sn plating film 6 is directly formed on the surface of the core material 2 as in this example, the Fe rich phase 21 and the Sn plating film 6 are in contact with each other as shown in FIG. It can be understood that the CuSn alloy layer 5 is not formed in the portion that is formed. In the pin terminal 8 of this example, after the Sn plating film 6 disappears due to corrosion or the like, corrosion may progress from the Fe-rich phase 21 exposed on the surface toward the deep part of the core material 2. From the above, it can be understood that the pin terminal 8 of this example has lower corrosion resistance than the pin terminal 1 of the example.

1 Pin terminal 2 Core material 3 Ni plating film 4 Cu plating film 5 CnSn alloy layer 6 Sn plating film

Claims (6)

Containing 10 to 70 wt% of Fe, have a chemical composition that the balance of Cu and unavoidable impurities, Fe-rich phase composed mainly of Fe is distributed in the Cu-rich phase mainly composed of Cu A core material made of a Cu-Fe-based alloy having a metallic structure and having both the Fe-rich phase and the Cu-rich phase on the surface;
A Ni plating film present on the core material;
A Cu plating film present on the Ni plating film;
A CuSn alloy layer present on the Cu plating film;
An Sn plating film present on the CuSn alloy layer ,
A pin terminal, wherein the Ni plating film has a thickness of 0.01 to 0.3 μm .   The pin terminal according to claim 1, wherein the thickness of the CuSn alloy layer is 0.2 μm or more. The pin terminal according to claim 1, wherein the CuSn alloy layer contains a Cu ₆ Sn ₅ intermetallic compound. The pin terminal according to any one of claims 1 to 3, wherein the Cu plating film has a thickness of 0.5 to 1.5 µm. The pin terminal according to any one of claims 1 to 4, wherein the Sn plating film has a thickness of 0.6 to 5 µm. A terminal material for producing the pin terminal according to any one of claims 1 to 5,
  Fe containing 10 to 70% by mass of Fe, with the balance being a chemical component consisting of Cu and inevitable impurities, Fe-rich phase containing Fe as the main component is distributed in the Cu-rich phase containing Cu as the main component A core material made of a Cu-Fe-based alloy having a metallic structure and having both the Fe-rich phase and the Cu-rich phase on the surface;
  A Ni plating film present on the core material;
  A Cu plating film present on the Ni plating film;
  And Sn plating film present on the Cu plating film,
  A terminal material, wherein the Ni plating film has a thickness of 0.01 to 0.3 μm.