JP2005105307A - REFLOW-Sn-PLATED MEMBER, METHOD FOR MANUFACTURING THE MEMBER, AND COMPONENT FOR ELECTRICAL AND ELECTRONIC EQUIPMENT USING THE MEMBER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflow-Sn-plated member which does not cause thickness deviation even when a stamped electroconductive substrate to be reflow-Sn-plated is finely worked, and has superior solder wettability and heat resistance; a method for manufacturing the member; and an electrical and electronic component using the member. <P>SOLUTION: The reflow-Sn-plated member has a reflow-Sn-plated layer of Sn or an Sn alloy on the surface of the stamped electroconductive substrate. The reflow-Sn-plated layer has a plated structure consisting of a melt and solidified structure in an outer part and a not-yet-melt structure in an inner part. The method for manufacturing the reflow-Sn-plated member comprises forming a matte Sn layer on the surface of the stamped electroconductive substrate by electroplating, a bright Sn layer thereon by electroplating, and subsequently subjecting the electroconductive substrate to reflow treatment by traveling it in a heating oven at a predetermined temperature. The traveling speed of the electroconductive substrate in the heating oven is controlled to 80-96% of the slowest traveling speed among such speeds as not to melt the above Sn layers. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reflow Sn-plated member having no unevenness in Sn plating layer and having excellent solderability, a method for producing the member, and a component for electrical and electronic equipment using the member.

  A plated member obtained by coating the surface of a conductive base material made of Cu or Cu alloy with Sn or Sn alloy has good conductivity and mechanical strength provided by Cu or Cu alloy, etc., and good Sn or Sn alloy coating layer It is a high-performance conductor that is well combined with excellent corrosion resistance and solderability, and is widely used in electrical and electronic equipment parts such as terminals, connectors, and lead wires, and electric cables.

  In the manufacturing method of electrical and electronic equipment parts such as terminals, connectors, leads, etc., a “pre-plating method” in which Sn or Sn alloy is plated on the base material and then stamped, and Sn or Sn alloy is plated after punching. There is a “post-plating method”, and the post-plating method is used when a plated layer is also required on the punched-out surface.

Sn-Pb alloys have been used for plating materials for reasons such as low cost, excellent solderability (low melting point), and the absence of whiskers. As a result, a reflow Sn plating material that is considered to be free of whiskers is promising.
As the plating material, Sn, Sn—Cu alloy, Sn—Ag alloy, Sn—Bi alloy, Sn—Zn alloy, Sn—In alloy and the like have been studied.

However, the pre-plating method has a long history of reflow treatment and can be easily performed, but the post-plating method has a problem that uneven thickness occurs. That is, if the fluidity of the molten plating layer increases during the reflow treatment, or the molten state of the plating layer continues for a long period of time, or if the substrate vibrates vigorously during the reflow treatment, the plated layer after the reflow treatment The thickness of the material is uneven, producing thick and thin parts.
In particular, when the substrate is a square wire, the molten plating layer flows from the corner portion of the square wire to the plane portion due to the surface tension, and therefore the thickness of the plating layer after the reflow treatment is uneven. It becomes meaty and the corners become extremely thin.
And when this reflow plating member is actually used for a long time at a high temperature, the Cu component of the base material, the SnCu intermetallic compound, etc. diffuses to the surface of the plating layer and changes color in the thin part. Things happen. Such a reflow plating member is inferior in heat resistance.

  In order to deal with the uneven thickness problem, there has been proposed a reflow treatment method in which the crystal grain size of the inner layer portion of the Sn plating layer is made smaller than that of the surface layer portion (for example, Patent Document 1). This method aims to improve the solder wettability, workability, heat resistance, wear resistance, etc. of the reflow Sn plating layer.

Japanese Patent Laid-Open No. 9-228094

In recent years, with the miniaturization of terminals, connectors, and lead wires, it has been required to perform fine punching. The punching width of the base material is less than 1 mm and is becoming narrower. As a result of the research conducted by the inventor, it has been found that when the width of the punched portion is narrow, the method of Patent Document 1 tends to cause uneven thickness in the plating layer.
An object of the present invention is to provide a reflow Sn-plated member that is excellent in heat resistance and solder wettability, even when the reflow Sn plating is performed on a punched conductive substrate, even if the processing is fine. An object of the present invention is to provide a method for manufacturing the member, and a component for an electric and electronic device using the member.

  According to the first aspect of the present invention, a matte Sn plating made of Sn or Sn alloy as the first layer and a bright Sn plating made of Sn or Sn alloy as the second layer are sequentially formed on the surface of the punched conductive substrate. In the reflow-treated Sn plated member, the first layer is made of a plated structure having a crystal grain size of less than 2 μm, and the second layer is made of a melt-solidified structure having a crystal grain size of 2 μm or more. It is a Sn plating member.

  According to the second aspect of the present invention, the surface of the punched conductive substrate is matte Sn plating made of Sn or Sn alloy as the first layer, and Sn plating made of Sn alloy having a melting point lower than Sn as the second layer. In the Sn-plated member that is sequentially formed and reflowed, the first layer is made of a plated structure having a crystal grain size of less than 2 μm, and the second layer is made of a melt-solidified structure having a crystal grain size of 2 μm or more. This is a reflow Sn plating member.

  According to a third aspect of the present invention, the surface of the punched conductive substrate is electroplated with a matte Sn plating layer, and the gloss Sn plating layer is electroplated thereon, and then the conductive substrate is heated at a predetermined temperature. In the method of manufacturing a reflow Sn-plated member that travels in a heating furnace and performs reflow treatment, the traveling speed of the conductive substrate in the heating furnace is set to 80, which is the slowest traveling speed within a range where the Sn plating layer does not melt. It is a manufacturing method of the reflow Sn plating member characterized by setting it as speed of -96%.

  According to a fourth aspect of the present invention, the surface of the punched conductive base material is electroplated with a matte Sn plating layer, an Sn alloy plating layer having a melting point lower than Sn is electroplated thereon, and then the Sn plating layer In the manufacturing method of the reflow Sn plating member for running the conductive base material formed in a heating furnace at a predetermined temperature and performing the reflow treatment, the running speed of the conductive base material in the heating furnace is determined by the Sn plating layer. It is a manufacturing method of the reflow Sn plating member characterized by setting it as 80 to 96% of the slowest running speed of the range which does not melt.

  According to a fifth aspect of the present invention, there is provided an electrical / electronic equipment component in which the reflow Sn plated member according to the first or second aspect is used.

  The invention according to claim 6 is the component for electrical and electronic equipment according to claim 5, wherein the part for electrical and electronic equipment is a lead, a terminal or a connector.

  As described above, in the reflow Sn plated member of the present invention, the surface of the punched substrate is coated with the reflow Sn plated layer made of Sn or Sn alloy, and the surface layer of the reflow Sn plated layer has a molten solidified structure. Since the inner layer portion is made of an unmelted plating structure, sufficient gloss is obtained, and even in a narrow punched portion having a width of less than 1 mm, the uneven thickness of the plating layer is small or excellent in soldering. The reflow Sn-plated member can be easily manufactured by appropriately defining the traveling speed in the heating furnace during the reflow process. By electroplating a matte Sn plating layer on the punched substrate surface and a gloss plating layer or Sn alloy plating layer having a low melting point thereon, the thickness of the melt-solidified layer can be easily controlled. Therefore, the surface of the punched substrate can be coated with the reflow Sn plating layer without causing uneven thickness, and can be suitably applied to lead materials for electronic devices, terminals, connectors, and the like. Therefore, there is an industrially significant effect.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best mode for carrying out the invention will be described with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of a reflow Sn plated member of the present invention.
In this reflow Sn-plated member 1, the surface of a punched conductive base material (hereinafter abbreviated as a punched base material as appropriate) is coated with Sn plating composed of two layers of Sn or Sn alloy, and reflowed. It has been processed.

  In the present invention, copper alloy such as brass, phosphor bronze, beryllium copper, corson alloy, or white is used for the punched substrate in addition to pure copper. Moreover, the composite material which coat | covered pure copper or copper alloy on steel materials, aluminum materials, etc. can also be used.

  For the second plating layer, a Sn—Cu alloy, a Sn—Ag alloy, a Sn—In alloy, a Sn—Bi alloy, a Sn—Zn alloy, or the like is used. Preferably, the Sn alloy includes Cu exceeding 0 and not more than 2.0% by weight and the balance of Sn, or the Sn alloy including Ag exceeding 0 and not more than 5.0% by weight and the balance of Sn, or In of 10%. Sn alloy with Sn balance of less than 0.0% by weight or Sn, or Sn alloy with Bi exceeding 0 and less than 15.0% by weight and the balance of Sn, or Zn exceeding 0 and less than 15.0% by weight The balance is Sn alloy composed of Sn.

  The reflow Sn-plated member of the present invention is obtained by electroplating a matte Sn plating layer on the surface of a stamped substrate, electroplating a bright Sn plating layer or a Sn alloy layer having a melting point lower than Sn, and then The punched substrate is run in a heating furnace at a predetermined temperature and reflowed. At this time, the running speed V of the punched base material in the heating furnace was set to 80 to 96% of the slowest running speed V0 within a range where the Sn plating layer does not melt.

According to the present invention, it is glossy because it consists of a melt-solidified structure by melting the second plating layer, and further, uneven thickness is suppressed because the first plating layer consists of a fine plating structure in an unmelted state. And soldering is done well.

When the running speed V is less than 80% of the V0, the Sn plating layer is mostly melted by the reflow process, and the uneven thickness of the reflow Sn plating layer increases. Due to the uneven thickness, discoloration occurs in a thin portion of the plating layer, and heat resistance is also deteriorated. Furthermore, the fine plating structure of the inner layer portion is reduced, solder wettability is lowered, and solderability is deteriorated.
On the other hand, when the running speed V exceeds 96% of V0, the plating first layer becomes a plating structure that is mostly in an unmelted state, and sufficient gloss cannot be obtained. In addition, the plating layer has a reduced wear resistance and is pulverized and easily peels off from the punched substrate surface.

For this reason, in the present invention, the running speed V in the heating furnace of the punched base material during the reflow treatment is set to 0.8 V0 ≤ V ≤ 0.96 V0 (where V0 is the most in the range where the Sn plating layer does not melt). Slow travel speed).
Note that additives such as a smoothing agent in the electrolytic solution occluded in the crystal grain boundary are thermally decomposed and removed during the reflow treatment.

  In the present invention, plating made of Sn or an Sn alloy is performed, and the crystal grain size of the plating is 2 μm or more. Further, when reflow treatment is performed after plating, the second plating layer is melted and the crystal grain size becomes less than 2 μm. Therefore, the melt-solidified structure in the present application means that the crystal grain size is less than 2 μm. Further, the plated structure means that the crystal grain size is 2 μm or more.

  In the method for producing a reflow Sn-plated member of the present invention, a matte Sn plating layer (first layer) is electroplated on the surface of the punched substrate, and a bright Sn plating layer or an Sn alloy having a lower melting point than Sn is formed thereon. When the layer (second layer) is electroplated, the bright Sn plating layer or the Sn alloy layer has a melting point lower than that of the matte Sn plating layer, so that the reflow treatment of only the plating surface layer portion can be easily performed.

  The thickness of the Sn plating layer is preferably such that the total of the first plating layer and the second plating layer is not less than 0.5 μm and not more than 20 μm. When the thickness is 0.5 μm or less, Sn in the plating layer and Cu in the base material easily form a Cu—Sn compound due to diffusion, and solder wettability slightly decreases. Conversely, if the plating is too thick, the cost increases, so the thickness is set to 20 μm or less.

The thickness of the first plating layer is preferably 50% or more and 90% or less of the entire plating layer. This is because if the thickness of the first layer is less than 50% of the entire plating layer, the second layer becomes thicker than the first layer, so that the second layer is melted and becomes unevenly thick during the reflow process. Conversely, if it exceeds 90%, solderability deteriorates. More preferably, the thickness of the first layer is 65% or more and 80% or less of the entire plating layer.
Hereinafter, the present invention will be described in detail with reference to examples.

The brass strip (thickness 0.3 mm, width 30 mm) after the punching process having the shape shown in FIG. 1 is subjected to a pretreatment step of electrolytic degreasing → water washing → acid washing → water washing, and then Cu base plating (1.0 μm thickness) ) → Washing → Glossy Sn plating as the first layer → Glossy Sn plating (or low melting point Sn alloy plating) as the second layer, followed by water washing → Drying → Reflow treatment → Water quench (water temperature 40 ° C.) → A reflow treatment step of hot air drying was performed to obtain a reflow Sn plated member, which was wound around a coil.
The Sn plating process was performed within the scope of the present invention for Examples 1 to 7, and was performed outside the scope of the present invention for Comparative Examples 1 to 4.

For the matte Sn plating, an organic acid electrolytic solution to which a smoothing agent manufactured by Ishihara Pharmaceutical Co., Ltd. was added was used. An organic acid electrolytic solution to which a smoothing agent and a brightening agent manufactured by Ishihara Pharmaceutical Co., Ltd. were added was used for the bright Sn plating.
The thickness of the Sn plating layer was measured by a constant current anodic dissolution method.

About the narrow punching part 2 (width 0.8mm) of the obtained reflow Sn plating member 1, (1) The crystal grain diameter of a plating layer, (2) Uneven thickness, (3) Solderability by the following method Examined.
(1) Crystal grain size of the plating layer: The reflow Sn plating strip is immersed in a hydrochloric acid electrolyte, and the reflow Sn plating layer is anodically dissolved under the condition of a current density of 2 A / dm ² , from the surface of the reflow Sn plating layer. A crystal structure at a depth of 0.1 μm, 0.5 μm, and 1.0 μm was revealed, and each grain size of a crystal grain at a field of view 1000 times was measured using a scanning electron microscope, and an average value thereof was calculated. .
(2) Unevenness: Thickness (t1) at the center of the side of the reflow plating layer of the narrow punched part (width 0.5 mm) using a fluorescent X-ray micro part thickness meter (collimator diameter 0.1 mmφ) Further, the average thickness (t2) of the reflow plating layer was measured by a constant current anodic dissolution method, and the thickness deviation indicated by [t1 / t2] was determined.
(3) Solderability: Evaluation was made by measuring the zero crossing time (seconds) by the meniscograph method.
Solder bath: 230 ° C. eutectic solder, flux: 25% rosin / methanol, immersion speed: 2 mm / sec, immersion depth: 2 mm, immersion time: 10 sec. It was immersed in a bath, and the time (seconds) required until the buoyancy became zero was measured and evaluated. The shorter this time, the better the solderability. This solderability was measured immediately after the reflow treatment and after the atmospheric heating test (155 ° C. × 24 hours).

  The survey results are shown in Table 1. Table 1 also shows the configuration (thickness and composition) of the Sn plating layer and the reflow processing conditions (heating furnace temperature, travel speed of the punched substrate).

As is clear from Table 1, the reflow Sn plated member of the present invention example (sample Nos. 1 to 10) has the plating second layer melted and solidified, resulting in coarse crystal grains, sufficient gloss, and plating. The thickness of the layer was small. Moreover, since the plating first layer is a fine plating structure of crystal grains, the solderability is also excellent.
On the other hand, No. of a comparative example (sample No. 11-14). Nos. 11, 13, and 14 have a single plating layer. Since the running speed of No. 12 was outside the scope of the present invention, the uneven thickness of the plating layer was large and the solderability was inferior.

It is a top view which shows one Embodiment of the reflow Sn plating member of this invention.

Explanation of symbols

1 Reflow Sn plating member 2 Narrow punching part

Claims (6)

  On the surface of the punched conductive substrate, matte Sn plating made of Sn or Sn alloy as the first layer and glossy Sn plating made of Sn or Sn alloy as the second layer are sequentially formed and reflow-treated. An Sn plated member, wherein the first layer is made of a plated structure having a crystal grain size of less than 2 μm, and the second layer is made of a molten solidified structure having a crystal grain size of 2 μm or more.   On the surface of the punched conductive substrate, matte Sn plating made of Sn or Sn alloy as the first layer and Sn plating made of Sn alloy having a melting point lower than Sn as the second layer are sequentially formed and reflow processed. The reflow Sn-plated member according to claim 1, wherein the first layer is made of a plated structure having a crystal grain size of less than 2 μm, and the second layer is made of a melt-solidified structure having a crystal grain size of 2 μm or more.   The surface of the punched conductive base material is electroplated with a matte Sn plating layer, the bright Sn plating layer is electroplated thereon, and then the conductive base material is run in a heating furnace at a predetermined temperature. In the manufacturing method of the reflow Sn plating member to be reflowed, the traveling speed of the conductive base material in the heating furnace is 80 to 96% of the slowest traveling speed in a range where the Sn plating layer does not melt. The manufacturing method of the reflow Sn plating member characterized by the above-mentioned.   A conductive base material in which a matte Sn plating layer is electroplated on the surface of the punched conductive base material, an Sn alloy plating layer having a melting point lower than Sn is electroplated thereon, and then the Sn plating layer is formed. In the method of manufacturing a reflow Sn-plated member that travels in a heating furnace at a predetermined temperature and performs reflow treatment, the traveling speed of the conductive base material in the heating furnace is the slowest travel in a range where the Sn plating layer does not melt. The manufacturing method of the reflow Sn plating member characterized by setting it as the speed of 80 to 96% of speed.   A component for electrical and electronic equipment, wherein the reflow Sn-plated member according to claim 1 or 2 is used.   6. The electrical and electronic equipment component according to claim 5, wherein the electrical and electronic equipment component is a lead, a terminal, or a connector.

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