JP4911254B2 - Wiring conductor and terminal connection - Google Patents

Abstract

A Pb-free Sn-based material part of a wiring conductor is provided at least at a part of its surface, and the Sn-based material part includes a base metal doped with an oxidation control element. The oxidation control element is at least one element selected from a group consisted of P, Ge, K, Zn, Cr, Mn, Na, V, Si, Ti, Al, Li, Mg and Ca. The wiring conductor is reflow processed, such that at least one of the Sn and the oxidation control element is diffused to form an alloy.

Description

The present invention relates to a wiring conductor and the terminal connecting portion, in particular relates to a wiring conductor and the terminal connecting portion are used in electronic devices.

  Conventionally, the surface of a wiring material, particularly copper or copper alloy, is plated with tin, silver, gold or nickel in order to prevent the wiring material from being oxidized. For example, as shown in FIG. 7, in the terminal connection part of the connector 11 and the flexible flat cable (hereinafter referred to as FFC) 13, the connector pins (metal terminals) 12 of the connector (connector member) 11 and the conductors 14 of the FFC 13 The surface is plated. In particular, Sn is inexpensive and soft, so it is easily deformed by the fitting (contact) pressure to increase the contact area and keep the contact resistance low, so the surface of the wiring material was Sn plated. Things are widely used in general.

  Conventionally, Sn-Pb alloys with good whisker resistance have been used as this Sn plating alloy, but in recent years, Pb-free materials (lead-free materials) and non-halogen materials have been used from the viewpoint of environmental compatibility. Pb-free and non-halogenated are also required for various materials used for wiring materials.

  In the field of soldering, Sn-Pb alloys have been used in the past, but Sn-Ag-Cu-based Pb-free solder has been put into practical use.

Japanese Patent Laid-Open No. 11-189894 JP 11-345737 A Japanese Patent Laid-Open No. 2001-9587 JP 2001-230151 A Japanese Patent Laid-Open No. 2002-53981

  However, with the Pb-free Sn plating, particularly in Sn or Sn-based alloy plating, whisker that is a needle crystal of Sn is generated from the plating, and as shown in FIG. There is a risk of short circuit between the conductors 14).

  In order to relieve stress during Sn plating, which is considered as one of the causes of whisker generation, it is said that reflow treatment of electroplated Sn can reduce the generation of whiskers.

  However, the exact mechanism of whisker suppression is unknown. In addition, when a new external stress such as fitting with a connector is applied, the occurrence of whiskers cannot be suppressed even if reflow processing is performed. Further, whisker can be suppressed by electrolytic plating an alloy of Sn and Bi, Ag, or the like. However, reflow treatment may cause more whisker than in the case of pure Sn plating. It has been reported. In the case of electronic components, since reflow processing is essential for component mounting, these alloy platings also have problems. As a currently effective measure, a method of applying a thin Sn plating of 1 μm or less is also disclosed, but there is a problem that the contact resistance is increased as compared with the prior art especially when left at high temperatures (for example, JEITA lead-free completion) Urgent proposal report meeting material (2005.2.17), JEITA lead-free solder practical application review 2005 report (2005.6), Japanese Patent Laid-Open No. 2005-206869, Japanese Patent Laid-Open No. 2006-45665).

  In addition, there is a concern about the occurrence of whiskers with the Pb-free solder in the Sn-based alloy.

  The object of the present invention, which was created in view of the above circumstances, is that whiskers are formed from the Sn plating film surface and the solder surface around the conductor even in an environment where a large external stress is applied such as a fitting part and a connection part with the connector. An object of the present invention is to provide a Pb-free wiring conductor and a terminal connection portion and a Pb-free solder alloy that are less likely to occur or hardly occur and that do not increase contact resistance even in a high temperature standing environment.

In order to achieve the above-mentioned object, the invention of claim 1 is used in a wiring conductor having a Pb-free Sn-based material portion at least partially on the surface , and used in a connector member. However, this is a wiring conductor characterized in that Zn is added to the Sn-based material part base material, and the addition amount is 0.002 or more and 0.5 wt% or less, and this is subjected to reflow treatment.

The invention of claim 2 is fitted to the connector member is used, the wiring conductor having a Sn-based material of Pb-free at least part of the surface, the outer layer of the Sn-based material part, containing Zn A wiring conductor provided with a layer and subjected to reflow treatment, wherein the proportion of Zn after the reflow treatment is 0.002 or more and 0.5 wt% or less.

The invention of claim 3 is fitted into the connector member is used, the wiring conductor having a Sn-based material of Pb-free at least part of the surface, the inner layer side of the Sn-based material part, containing Zn A wiring conductor provided with a layer and subjected to reflow treatment, wherein the proportion of Zn after the reflow treatment is 0.002 or more and 0.5 wt% or less.

  The invention according to claim 4 is the wiring conductor according to any one of claims 1 to 3, which is a wiring member in which a coating layer of the Sn-based material portion is provided around a core material made of a metal material.

  A fifth aspect of the present invention is the wiring conductor according to any one of the first to fourth aspects, which is a solder material or a brazing material composed entirely of the Sn-based material portion.

According to a sixth aspect of the present invention, the Sn-based material part base material is pure Sn based Sn or inevitable impurities, Sn-Ag based, Sn-Ag-Cu based, Sn-Bi based, Sn-Bi-Ag based. The conductor for wiring according to any one of claims 1 to 5, which is a Pb-free solder material such as Sn-Cu or solder material.

The invention of claim 7, when connecting the terminal ends of the metal conductors, a terminal connection unit, characterized in that is constituted by the wiring conductor according to any one of the at least one terminal of claims 1-6.

  According to the present invention, the stress generated in the Sn-based material portion of the wiring conductor having the Pb-free Sn-based material portion on at least a part of the surface can be reduced. As a result, it is possible to suppress the generation of whiskers, which are Sn needle-like crystals generated by the stress of the Sn-based material portion, and to solve problems such as a short circuit between adjacent wires in a wiring material for electronic devices. it can. In addition, there is no risk of impairing contact reliability even in a high temperature leaving environment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  The generation of whiskers is said to be due to the fact that the wiring conductor expands (wiring conductor diameter increases) due to the formation of an oxide film on the Sn surface and compressive stress is generated. As a result of intensive studies by the present inventors, it was found that whisker generation can be suppressed by preventing oxidation of Sn by adding an oxidation inhibiting element to Sn.

  The wiring conductor according to the present embodiment is composed of a conductive material (core material) 1 shown in FIG. 1 and an Sn-based material portion (covering layer) 2 plated around the conductive material (core material) 1. The Sn-based material part base material is characterized by adding an oxidation-inhibiting element for preventing oxidation, and at least the Sn-based material part 2 is subjected to reflow treatment. The term “oxidation inhibiting element” as used herein refers to an element that prevents oxidation of the Sn-based material part base material.

  Examples of the Sn-based material part base material include pure Sn and Pb-free solder (for example, Sn—Ag—Cu alloy).

  At least one selected from P, Ge, K, Zn, Cr, Mn, Na, V, Si, Ti, Al, Li, Mg, Ca, and Zr as an oxidation inhibiting element added to the Sn-based material part base material More than species. When the Sn-based material part base material is pure Sn, P, Cr, V, Ti, Ge, Al, Mg, and Zn, which are excellent in whisker resistance (the effect of suppressing whisker generation), are preferable as the oxidation suppressing element. On the other hand, when the Sn-based material part base material is Pb-free solder, P, Cr, Al, and Zn are preferable as the oxidation inhibiting element.

  The total addition amount of the oxidation inhibiting elements added to the Sn-based material part base material is 10 wt% or less. Here, if the addition ratio of the oxidation-inhibiting element in the Sn-based material part 2 exceeds 10 wt%, defects such as cracks and lowering of solderability occur, so the addition ratio is set to 10 wt% or less. The A preferable addition ratio is 1.0 wt% or less, and a more preferable addition ratio is 0.1 wt% or less.

  In the present embodiment, the case where the Sn-based material part 2 is configured by adding an oxidation-suppressing element to the Sn-based material part base material has been described. However, the present invention is not particularly limited. For example, as shown in FIG. 2, an oxidation-suppressing element layer 3 may be provided on the outer layer side of the Sn-based material part 2 composed only of the Sn-based material part base material. In addition, as shown in FIG. 3, an oxidation-suppressing element layer 3 may be provided on the inner layer side of the Sn-based material portion 2 composed only of the Sn-based material portion base material. By performing the reflow process on the wire rods of FIGS. 2 and 3, the wiring conductor according to the present embodiment having the Sn-based material portion containing the oxidation inhibiting element at least on a part of the surface can be obtained. By reflowing, at least one of Sn in the Sn-based material part 2 and the oxidation-inhibiting element constituting the oxidation-inhibiting element layer 3 diffuses, and the coating layer is made of an alloy of the Sn-based material part 2 and the oxidation-inhibiting element layer 3 Is formed.

  The annealing temperature / time for reflow is set to a temperature / time sufficient for diffusion of at least one of Sn in the Sn-based material portion 2 and the oxidation inhibiting element constituting the layer 3 of the oxidation inhibiting element. Since the annealing temperature and time vary depending on the oxidation inhibiting element used, the annealing temperature and time are appropriately adjusted according to the oxidation inhibiting element used.

  Further, by applying the configuration of the wiring conductor according to the present embodiment to at least one of the metal conductor terminals to be connected, the terminal connection portion according to a preferred embodiment of the present invention. Is obtained.

  Next, the operation of the present embodiment will be described.

  In the present embodiment, the oxidation inhibiting element added to the Sn-based material part base material is characterized by being easier to oxidize than Sn. In particular, when Sn is in a molten state (at the time of reflow treatment), these oxidation-suppressing elements are oxidized prior to Sn and volatilize from the surface or form a very thin oxide film on the surface. It is possible to prevent the internal Sn from being oxidized. This state is maintained even in a solidified state, prevents Sn from being oxidized in an environment in normal use, and suppresses whisker generation.

  When these oxidation-inhibiting elements are present on the surface of the Sn plating (see the layer 3 in FIG. 2), the inside of the Sn plating (see the Sn-based material part 2 in FIG. 1) and the underlying layer (the layer in FIG. 3) 3), these elements are easier to oxidize than Sn, so by reflowing once, these elements move to the surface of Sn plating and form a very thin oxide film on the surface of Sn plating. The effects described above can be exhibited.

  The terminal connection portion in which the configuration of the wiring conductor according to the present embodiment is applied to at least one of the metal conductor terminals to be connected can suppress whisker generation. For example, by using the wiring conductor according to the present embodiment for an electronic device wiring material, it is possible to reduce the stress generated during Sn plating of the electronic device wiring material whose surface is Sn plated. . As a result, it is possible to suppress the generation of whiskers which are Sn needle crystals generated by the stress of Sn plating, and it is possible to solve problems such as a short circuit between adjacent wirings.

  Next, another embodiment of the present invention will be described.

  In the wiring conductor of FIG. 1 described above, only the coating layer provided around the core material 1 is composed of the Sn-based material portion 2.

  On the other hand, the wiring conductor according to another preferred embodiment of the present invention is characterized in that the entire wiring conductor is composed of the Sn-based material portion 2 as shown in FIG.

  The wiring conductor becomes a Pb-free solder material or brazing material depending on the selection of the Sn-based material portion base material. For example, in a Sn—Ag—Cu solder alloy containing 0.1 to 3.5 wt% of Ag and 0.1 to 3.5 wt% of Cu, this solder alloy base material (Sn-based material part base material) Add at least one of P, Ge, K, Zn, Cr, Mn, Na, V, Si, Ti, Al, Li, Mg, Ca, and Zr as an oxidation inhibiting element at a ratio of 10 wt% or less. Thus, the wiring conductor (Pb-free solder material) according to the present embodiment, that is, a Pb-free solder alloy is obtained.

  The terminal connection portion is solder-connected by using the Pb-free solder alloy according to the present embodiment, for example, for the solder connection portion of the terminal of the metal conductor and performing a reflow process. The obtained terminal connection part can reduce the stress generated in the solder material. As a result, it is possible to suppress the generation of whiskers which are Sn needle-like crystals generated by the stress of the solder material, and it is possible to solve problems such as a short circuit between adjacent solder connection portions.

  A wiring conductor according to another preferred embodiment of the present invention will be described with reference to FIG.

  As a result of intensive studies by the present inventors, it has been found that by adding P, Zn, Al, Ti, and V into appropriate amounts of Sn, oxide film formation on the Sn surface can be suppressed and whiskers can be suppressed.

  In particular, P is preferable because it is oxidized before Sn and volatilizes from the surface when Sn is melted, and the oxide film hardly remains. Even if Zn, Al, Ti, V is added, the oxidation of Sn can be suppressed. However, if the added amount is too large, an oxide film of these added elements is formed thickly and conversely, whiskers are easily generated. It was found that by adding the amount, the oxide film of Sn and additive elements can be suppressed thinly and whiskers can be suppressed. It has also been found that the addition of these elements can suppress the oxidation of Sn, which causes an increase in contact resistance, particularly in a high temperature environment.

  As a method other than the addition of these elements, a method is disclosed in the following document, in which an organic compound is adsorbed on the Sn surface to form a barrier layer, thereby preventing oxidation of the Sn surface and suppressing whiskers (Japanese Patent Application Laid-Open Publication 2004). No. 137574 and JP 2004-156094).

  However, in these methods, the organic compound adsorbed on the surface is partially peeled off due to mechanical contact, and there is a possibility that the effect of suppressing oxidation may not be sufficiently exerted particularly on the fitting and contact portions with the connector. . In the present embodiment, since the elements that prevent the oxidation of Sn plating are added and distributed inside the Sn plating, even if scratches due to mechanical contact occur, fitting with connectors, contact portions, etc., it is stable. An effect of inhibiting oxidation can be exhibited.

  The wiring conductor according to the present embodiment is composed of a conductive material (core material) 1 and an Sn-based material portion (covering layer) 2 plated around the conductive material (core material) 1, and the Sn-based material portion 2 is composed of an Sn-based material. It is characterized in that at least one of P, Zn, Al, Ti, and V that prevents oxidation is added to the base material.

  As the Sn-based material part base material, pure Sn based Sn and inevitable impurities, or Pb such as Sn-Ag based, Sn-Ag-Cu based, Sn-Bi based, Sn-Bi-Ag based, Sn-Cu, etc. A free solder material or a brazing material may be used.

  The amount of P added to the Sn-based material part base material is preferably 0.002 wt% or more because an effect of suppressing oxidation cannot be obtained if it is less than 0.002 wt%. Further, if the amount of P exceeds 0.5 wt%, problems such as cracks occur, and therefore 0.5 wt% or less is preferable. Preferably 0.005-0.05 wt% is good.

  Further, if the addition amount of Zn is less than 0.002 wt%, the effect of suppressing oxidation cannot be obtained, so 0.002 wt% or more is preferable. Further, if the added amount of Zn exceeds 0.5 wt%, defects such as cracks occur, so 0.5 wt% or less is preferable. Preferably 0.01 to 0.10 wt% is good.

  Further, if the addition amount of Al is less than 0.002 wt%, the effect of suppressing oxidation cannot be obtained, so 0.002 wt% or more is preferable. Further, if the amount of Al added exceeds 0.008 wt%, defects such as cracks occur, so 0.008 wt% or less is preferable. Preferably 0.003-0.007 wt% is good.

  Moreover, since the oxidation inhibitory effect is not acquired if the addition amount of Ti is less than 0.002 wt%, 0.002 wt% or more is preferable. Further, if the amount of Ti exceeds 0.05 wt%, defects such as cracks occur, and therefore 0.05 wt% or less is preferable. Preferably 0.005-0.010 wt% is good.

  Further, if the amount of V added is less than 0.002 wt%, the effect of suppressing oxidation cannot be obtained, so 0.002 wt% or more is preferable. Further, if the amount of addition of V exceeds 0.1 wt%, problems such as the occurrence of cracks occur, so 0.1 wt% or less is preferable. Preferably 0.005-0.010 wt% is good.

  As the metal material constituting the core material 1, a conductive material having an electrical conductivity of 10% IACS or more, oxygen-free copper, tough pitch copper, silver, nickel, a copper-based alloy material, a Ni-based alloy base material, an aluminum-based alloy material, or iron Based alloy materials. Moreover, as a shape and form of the core material 1, a round wire, a square wire, a board | plate material, a strip material, a foil material etc. are mentioned, It does not specifically limit.

In Sn hot dipping, addition of P, Zn, Al, Ti, and V is easy. Zn can also be added by an electroplating method. P can also be added by electroplating, and by adding phosphorous acid (H ₂ PO ₂ ) to the Sn plating bath at a rate of 1 to 20 g / l, P is added to the Sn plating that is precipitated. be able to.

  When fitting and connecting the terminals of the metal conductor, for example, when fitting and connecting the conductor of the wiring member and the connector pin of the connector member or the conductors of the wiring material, at least one of the terminals is used in this embodiment. A terminal connection part is obtained by comprising with the wiring conductor which concerns.

  Sixteen kinds of wiring materials (wiring conductors) were produced. Here, P, Cr, V, Si, Ti, Mn, Zr, Ca, and Ge are added to pure Sn at a ratio of 0.01 wt%, and K, Na, Al, Li, Mg, and Zn are added at a ratio of 0.1 wt%, respectively. The wiring material which carried out the hot Sn plating using the Sn alloy which was made was made into Example 1 and Reference Examples 1-14. On the other hand, a wiring material subjected to hot dipping with pure Sn was used as Comparative Example 1.

  Each of these wiring materials is fitted with a connector, and a normal room temperature test (20 ° C. × 1000 hr), a thermal shock test (−55 ° C. to 125 ° C. × 1000 cycles), and a moisture resistance test (55 ° C., 85%) RH × 1000 hr). Thereafter, each wiring member was removed from the connector, and the occurrence of whiskers at the connector fitting portion (connection portion) on the surface of the plating film was observed with an electron microscope. Table 1 shows the evaluation results of whisker resistance of the wiring materials after each test. In Table 1, ◎ indicates that whisker is not generated, ○ indicates that a whisker having a length of less than 50 μm is generated, and × indicates that a whisker having a length of 50 μm or more is generated.

  As shown in Table 1, when compared with the wiring material of Comparative Example 1 using pure Sn without adding any oxidation inhibiting element, Example 1 and Reference Examples 1 to 14 in which an oxidation inhibiting element was added to pure Sn In each of the wiring materials, a whisker suppressing effect was obtained in all.

  Each wiring material of Example 1 and Reference Examples 1 to 14 can be applied to FFC or the like.

  Sixteen kinds of wiring materials (wiring conductors) were produced. Pb-free solder Sn-3Ag-0.5Cu alloy with 0.01 wt% of P, Cr, V, Si, Ti, Mn, Zr, Ca, Ge, K, Na, Al, Li, Mg, Zn 0 Examples 21 to 35 are wiring materials obtained by performing hot solder plating using alloys added at a ratio of 0.1 wt%. On the other hand, the wiring material which carried out the hot-dip solder plating with the Sn-3Ag-0.5Cu alloy was made into the comparative example 2.

  Each of these wiring materials is fitted with a connector, and a normal room temperature test (20 ° C. × 1000 hr), a thermal shock test (−55 ° C. to 125 ° C. × 1000 cycles), and a moisture resistance test (55 ° C., 85%) RH × 1000 hr). Thereafter, each wiring member was removed from the connector, and the occurrence of whiskers at the connector fitting portion (connection portion) on the surface of the plating film was observed with an electron microscope. The evaluation results of whisker resistance of the wiring material after each test are shown in Table 2. In Table 2, ◎ indicates that whisker is not generated, ○ indicates that a whisker having a length of less than 50 μm is generated, and × indicates that a whisker having a length of 50 μm or more is generated.

  As shown in Table 2, an example in which an oxidation inhibiting element was added to Pb-free solder when compared with the wiring material of Comparative Example 2 using an Sn-3Ag-0.5Cu alloy without adding any oxidation inhibiting element. In each of the wiring materials 2 and Reference Examples 21 to 34, the whisker suppressing effect was obtained.

  Since each wiring material of Example 2 and Reference Examples 21 to 34 has a lower melting point than the wiring materials of Example 1 and Reference Examples 1 to 14, it can be applied to a solder material or the like.

  A pure Sn hot dip plating bath in which nothing was added to Sn and a Sn alloy hot dip bath in which an arbitrary amount of P, Zn, Al, Ti, or V was added to Sn were prepared and maintained at 300 ° C.

  Next, using these hot dipping baths, a 5 mm wide and 0.3 mm thick Cu plate is subjected to hot plating of 8 to 10 μm thick and cut to 2.5 cm length to form a plating strip (sample). Form. This plating strip (sample) is fitted and brought into contact with a 0.5 mm pitch, 50 pin connector (made of phosphor bronze), and a slider is inserted under the plating strip (sample) to apply compressive stress.

  In this state, a normal room temperature standing test (20 ° C., 60% RH) 1000 hr, a temperature change test (−55 ° C. to + 125 ° C.) 1000 cycles, and a high temperature and high humidity test (55 ° C., 85% RH) 2000 hr were performed. .

  Thereafter, each plating strip (sample) was removed from the connector, and the occurrence of whiskers at the connector fitting portion (connecting portion) on the plating film surface of the plating strip (sample) was observed with an electron microscope. In the connection part (50 places), the amount of whisker having a predetermined length and the measured data of the distribution were obtained. Table 3 shows the evaluation results of whisker resistance after each test. In Table 3, ◎ indicates the maximum length of the generated whisker is less than 10 μm, ○ indicates the maximum length of the generated whisker is 10 μm or more and less than 50 μm, Δ indicates the maximum length of the generated whisker is 50 μm or more and less than 100 μm, × Indicates that the maximum length of the generated whisker is 100 μm or more.

  As shown in Table 3, whisker could not be suppressed when no additive element was added.

  Further, even when the additive element concentration was less than 0.002 wt%, a sufficient whisker suppressing effect could not be exhibited. On the other hand, although the upper limit of the concentration of the additive element varies depending on the element to be added, as a reference example, 0.50 wt% for P, 0.008 wt% for Al, 0.050 wt% for Ti, In this case, it was 0.10 wt%, and in the case of Zn as an example, it was 0.50 wt%. When added at a concentration exceeding that, whisker resistance was worsened.

  Example of analyzing maximum whisker length for each pin of Sn-0.01wt% Zn, Sn-0.1wt% Zn, Sn-1wt% Zn and pure Sn 300pin (50pin connector x 6) by extreme value statistics As shown in FIG.

  As shown in FIG. 5, the cumulative distribution of the maximum whisker length for each pin is expected to follow the Gumbel distribution of the extreme value theory shown in the following equation 1, and in fact, 2 for the cumulative distribution F (x) [%]. Taking the logarithm times, I got on a straight line. Thus, it turns out that whisker resistance worsens when the concentration of the additive element is too large.

  Pb-free solder, Sn-3 wt% Ag-0.5 wt% Cu alloy, Sn-5 wt% Bi alloy, Sn-0.7 wt% Cu alloy, hot-dipped plating bath, and P, Zn, Al, Hot dip plating baths to which an arbitrary amount of Ti or V was added were prepared and maintained at 300 ° C.

  Next, using these hot dipping baths, a 5 mm wide and 0.3 mm thick Cu plate is subjected to hot plating of 8 to 10 μm thick and cut to 2.5 cm length to form a plating strip (sample). Form. This plating strip (sample) is fitted and brought into contact with a 0.5 mm pitch, 50 pin connector (made of phosphor bronze), and a slider is inserted under the plating strip (sample) to apply compressive stress.

  In this state, a normal room temperature standing test (20 ° C., 60% RH) 1000 hr, a temperature change test (−55 ° C. to + 125 ° C.) 1000 cycles, and a high temperature and high humidity test (55 ° C., 85% RH) 2000 hr were performed. . Thereafter, each plating strip (sample) was removed from the connector, and the occurrence of whiskers at the connector fitting portion (connecting portion) on the plating film surface of the plating strip (sample) was observed with an electron microscope. In the connection part (50 places), the amount of whisker having a predetermined length and the measured data of the distribution were obtained. Table 4 shows the evaluation results of whisker resistance after each test. In Table 4, “◎” indicates that the maximum length of the generated whisker is less than 10 μm, “◯” indicates that the maximum length of the generated whisker is 10 μm or more and less than 50 μm, and “x” indicates that the maximum length of the generated whisker is 100 μm or more.

  As shown in Table 4, even in Sn-Ag-Cu, Sn-Bi, Sn-Cu Pb-free solder materials, when no additive element is added, the whisker is 100 μm due to fitting and contact with the connector. Although it grew for a long time, it has been confirmed that whisker generation can be suppressed by adding P, Al, Ti, and V as reference examples and Zn as an example at an appropriate concentration.

  A pure Sn hot dip plating bath in which nothing was added to Sn and a Sn alloy hot dip bath in which an arbitrary amount of P, Zn, Al, Ti, or V was added to Sn were prepared and maintained at 300 ° C.

  Next, using these hot dipping baths, a 5 mm wide and 0.3 mm thick Cu plate is subjected to hot plating of 8 to 10 μm thick and cut to 2.5 cm length to form a plating strip (sample). Form. This plating strip (sample) was fitted and contacted with a 0.5 mm pitch, 50 pin connector (made of phosphor bronze) and left in an 85 ° C. environment. Thereafter, contact resistance was measured at initial (0 hours), 100 hours, 200 hours, 500 hours, 1000 hours, 1500 hours, 2000 hours, and 3000 hours, and the difference from the initial value was compared. FIG. 6 shows the maximum value of the contact resistance change obtained for each standing time.

  As shown in FIG. 6, P, Al, Ti, or V as a reference example and Zn as an example are almost optimal as compared with the case where no additive element is added (Sn only, line 61). When the amount was added (lines 62 to 66), the increase in contact resistance could be significantly suppressed. The increase in contact resistance is due to the growth of a Sn oxide film having a large resistance value on the Sn surface. However, P, Al, Ti, or V as a reference example is added to an optimum amount of Zn as an example. Thus, it is considered that the growth of the Sn oxide film can be suppressed, and as a result, the increase in contact resistance can be suppressed.

It is a cross-sectional view of a wiring conductor according to a preferred embodiment of the present invention. It is one modification of FIG. It is another modification of FIG. It is a cross-sectional view of a conductor for wiring according to another preferred embodiment of the present invention. It is a figure which shows the relationship between the maximum whisker length for every pin of Example 3, and cumulative distribution. It is a figure which shows the relationship between the leaving time in the leaving test in 85 degreeC environment of Example 5, and the maximum value of a contact resistance change. It is a figure which shows the example of a fitting of a connector and FFC. It is an enlarged view of the fitting part in FIG. 7, and is a figure which shows the state which the whisker generate | occur | produced and between adjacent wiring materials is short-circuited.

1 Core material 2 Sn material part

Claims (7)

In a wiring conductor that is used by being fitted to a connector member and has a Pb-free Sn-based material part on at least a part of the surface, the Sn-based material part is obtained by adding Zn to the Sn-based material part base material. The wiring conductor is characterized in that the amount added is 0.002 wt% or more and 0.5 wt% or less, and this is subjected to reflow treatment. In a wiring conductor that is used by being fitted to a connector member and has a Pb-free Sn-based material portion on at least a part of the surface, a layer containing Zn is provided on the outer layer side of the Sn-based material portion, and reflow treatment is performed. A conductor for wiring, wherein the proportion of Zn after the reflow treatment is 0.002 wt% or more and 0.5 wt% or less. In a wiring conductor that is used by being fitted to a connector member and has a Pb-free Sn-based material part on at least a part of the surface, a layer containing Zn is provided on the inner layer side of the Sn-based material part and subjected to a reflow treatment. A conductor for wiring, wherein the proportion of Zn after the reflow treatment is 0.002 wt% or more and 0.5 wt% or less.   The wiring conductor according to any one of claims 1 to 3, wherein the wiring material is a wiring material in which a coating layer of the Sn-based material portion is provided around a core material made of a metal material.   The wiring conductor according to any one of claims 1 to 4, wherein the wiring conductor is a solder material or a brazing material that is entirely composed of the Sn-based material portion. The Sn-based material part base material is pure Sn based on Sn and inevitable impurities, or Sn-Ag based, Sn-Ag-Cu based, Sn-Bi based, Sn-Bi-Ag based, Sn-Cu based, etc. wiring conductor according to claims 1 to 5 or a solder material or braze Pb-free.
When connecting the terminal ends of the metal conductors, terminal connection unit, characterized in that it is constituted by the wiring conductor according to any one of the at least one terminal of claims 1-6.

Images