JP2006283149A - Surface treatment method for copper or copper alloy, surface-treated material, and electronic component using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment method for suppressing whiskers easily and relatively inexpensively practicable for copper or a copper alloy usable particularly as an electronic component such as a terminal, a switch, a lead frame or the like. <P>SOLUTION: The surface treatment method for copper or a copper alloy comprises: a plating stage where tinning is applied to a part or the whole of the surface in copper or a copper alloy; a reflow stage where the tinning is heated and melted; a cooling stage where the obtained reflown tinned material is cooled; and a coating stage where the surface of the reflown tinned surface in the cooled reflown tinned material is coated with one or more silane coupling agents, and one or more nitrogen-containing compounds selected from a benzotriazole based compound expressed by general formula (A) and a benzotiazole based compound expressed by general formula (B) in optional order (including a simultaneous case); wherein, R<SB>1</SB>denotes a hydrogen atom, an alkyl group or a substituted alkyl group; R<SB>2</SB>denotes an alkali metal, a hydrogen atom, an alkyl group or a substituted alkyl group; and R<SB>3</SB>denotes an alkali metal or a hydrogen atom. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface treatment method of copper or copper alloy and a surface treatment material obtained by the method, and more particularly to a surface treatment method of copper or copper alloy that can be used for electronic parts such as connectors, terminals, switches and lead frames, and the like. The present invention relates to a surface treatment material obtained by the above method, and further to an electronic component using the surface treatment material.

  In general, copper or copper alloy is used as a base material for electronic parts such as connectors and terminals used in various electronic devices such as automobiles, home appliances, OA devices, and the like, such as rust prevention, improved corrosion resistance, and improved electrical characteristics. Plating treatment is performed for the purpose of functional improvement. There are various types of plating such as gold, silver, copper, tin, nickel, solder, and palladium. In particular, tin or tin alloy plating is used in terms of cost, contact reliability, solderability, etc. It is often used for outer lead parts of lead frames. Conventionally, solder (Sn—Pb) plating has been often used as tin or tin alloy plating, but since the use of Pb (lead) is scheduled to be regulated, Sn, Sn—Cu as an alternative to solder plating In recent years, research on lead-free plating based on Sn, such as Sn-Bi and Sn-Ag plating, has been actively carried out.

  However, since the lead-free plating does not contain Pb that suppresses the generation of whiskers, there is a problem that whiskers are likely to occur, and among them, Sn plating tends to generate whiskers.

Whisker is a growth of needle-like crystals of tin, but in some cases, it grows in a bowl shape with a length of several tens of μm and may cause an electrical short circuit. This whisker phenomenon is caused by recrystallization of Sn, and compressive stress acting on the plating film (internal stress of plating, Cu ₆ Sn ₅ diffusion, Sn oxidation, expansion and contraction of base material, stress generated when processing into parts, etc.) In the case where lead-free plating is applied to terminals, connectors (particularly FPC connectors), etc., where stress tends to concentrate on the contacts. The whisker problem becomes more serious.

In order to control the occurrence of the whisker phenomenon as described above, techniques such as a method by improving the plating bath and a heat treatment method have been proposed so far.
For example, in Japanese Examined Patent Publication No. 59-15993, whisker is difficult to generate Sn plating. Baths with added phosphate esters have been proposed.
Also, Toshihisa Hara and Motohiko Suzuki, “Copper Alloy Sheet with Tin Plating”, Kobe Steel Technical Report, April 2004, Vol. 54, no. 1 and p11-12, it is reported that reflow tin plating relieves internal stress and suppresses the generation of whiskers.

On the other hand, although not related to whisker suppression technology, it is also known that tin plating is subjected to surface treatment for the purpose of improving solder characteristics and electrical characteristics.
For example, Japanese Patent Laid-Open No. 2003-328153 discloses a tin-plated copper or copper alloy material having a low dynamic friction coefficient and excellent solder wettability and electrical reliability (contact resistance). In the present invention, a surface of a base material made of copper or a copper alloy is subjected to tin or tin alloy plating of 0.4 μm or more, and a silane coupling agent is bonded to the surface to thereby form a coating of the silane compound or the silane compound and its organic function. It is characterized by forming a film made of an organic substance bonded to a group.
Japanese Patent Application Laid-Open No. 7-173675 discloses a surface treatment solution for a plating material that suppresses deterioration over time of solderability of a tin or tin-alloy plating material and is excellent in corrosion resistance. The surface treatment liquid according to the present invention is characterized by containing one or more selected from the group consisting of benzotriazole compounds, mercaptobenzothiazole compounds, and triazine compounds.

Japanese Patent Publication No.59-15993 JP 2003-328153 A Japanese Patent Laid-Open No. 7-173675 Toshihisa Hara and Motohiko Suzuki, “Copper alloy strip with tin plating”, Kobe Steel Technical Report, April 2004, Vol. 54, no. 1, p11-12

Elucidation of the generation mechanism that is the basis for the development of whisker suppression technology is still in progress. The Japan Electronics Industry Association (JEITA), the American Electronics Manufacturers Association (NEMI) Tin Technology's Soldering Technology Center (SOLDERTEC) has just agreed in 2003 to elucidate the mechanism of whisker growth and establish standardization of whisker test methods.
As described above, the background of the whisker problem exemplified above shows only one aspect of the whisker suppression problem, and there are many difficult aspects to solve the whisker problem. For example, the Sn, Sn-Cu, Sn-Bi, and Sn-Ag platings exemplified above have their merits and demerits, so it is most effective as an alternative to solder plating, including whisker measures. The current situation is that there is no fixed direction.
In addition to the above-mentioned technologies for suppressing whiskers, in addition to the above-mentioned technologies, technologies such as formation of diffusion barriers based on Ni or Ag, flash plating of Au, Pd or Ag, organic coating processing using heat-resistant preflux, etc. are also included. Because of the wide variety of possibilities, it is quite difficult to focus on the development of whisker suppression technology.

  In spite of the current situation as described above, the advanced functionality and downsizing of information equipment associated with the rapid development of IT has inevitably urged further improvement of whisker suppression technology. Development is required. If whisker suppression technology that can be implemented by a simple method with little new capital investment is provided, it will contribute to the development of the industry.

Therefore, one of the main problems of the present invention is to suppress whiskers that can be carried out easily and relatively inexpensively, particularly for copper or copper alloys that can be used as electronic components such as connectors, terminals, switches, and lead frames. It is to provide a surface treatment method.
Another main problem of the present invention is to provide a surface-treated material obtained by this surface treatment method that is less likely to produce whiskers and has a short whisker length, and an electronic component using the same. It is to be.

In order to develop a technique for suppressing whiskers whose generation mechanism has not been sufficiently elucidated as described above, the present inventor has conducted extensive research and first found out the direction of development for Sn plating.
That is, Sn plating is generally inferior in whisker resistance compared to Sn—Cu, Sn—Bi, and Sn—Ag plating. However, Sn plating has an advantage that it has excellent appearance and ductility, and is easier to maintain and manage the plating solution and has less influence on the environment than binary plating. Further, since Sn-Ag plating has a problem of cost and Sn-Bi plating has a brittleness problem, it is considered that Sn plating may become a mainstream of lead-free plating if the problem of whisker resistance is solved.

  The present inventor has continued diligent research to solve the above-described problems. As a result, there has been a combination of a silane coupling agent and a benzotriazole-based compound and / or a benzothiazole-based compound that has not been reported so far in relation to whisker suppression. Surprisingly, it was found that it contributes to whisker suppression.

（式中、Ｒ₁は水素原子、アルキル基又は置換アルキル基を表し、Ｒ₂はアルカリ金属、水素原子、アルキル基又は置換アルキル基を表す。Ｒ₃はアルカリ金属又は水素原子を表す。）
また本発明は別の一側面において、前記被覆工程が前記１種又は２種以上のシランカップリング剤を含有する表面処理液及び前記１種又は２種以上の含窒素化合物を含有する表面処理液に任意の順に、或いは前記１種又は２種以上のシランカップリング剤及び前記１種又は２種以上の含窒素化合物の両者を含有する表面処理液に前記リフロー錫めっき材を浸漬することを含む表面処理方法である。
また本発明は別の一側面において、前記リフロー工程により得られた前記リフロー錫めっき材を前記１種又は２種以上のシランカップリング剤と前記１種又は２種以上の含窒素化合物とを含有する３０℃〜８０℃の表面処理液に接触させることによって被覆工程が冷却工程を兼ねる表面処理方法である。
また本発明は別の一側面において、前記表面処理を受ける前記銅又は銅合金が条又は条をプレス加工した端子の形態にあることを特徴とする表面処理方法である。
また本発明は別の一側面において前記表面処理方法によって得られた表面処理材である。
また本発明は別の一側面において、前記リフロー錫めっき表面をＸＰＳで分析した際に検出されるＳｉ及びＮの濃度が、下記の条件式（Ａ）及び（Ｂ）を同時に満たすことを特徴とする表面処理材である。
（Ａ） ０．００５≦ 〔Ｓｉ〕／（〔Ｃ〕＋〔Ｓｉ〕＋〔Ｎ〕） ≦０．２
（Ｂ） ０．００２≦ 〔Ｎ〕／（〔Ｃ〕＋〔Ｓｉ〕＋〔Ｎ〕） ≦０．３
（上記式において、〔Ｓｉ〕、〔Ｎ〕、〔Ｃ〕はそれぞれ、錫めっき表面からＸＰＳで検出されるＳｉ、Ｎ及びＣの濃度（原子百分率（ａｔ％））を表す。）
また本発明は別の一側面において、ＸＰＳで表面分析した際に検出されるＳｉ及びＮの濃度が、下記の条件式（Ａ）及び（Ｂ）を同時に満たすように表面が被覆されたリフロー錫めっき材である。
（Ａ） ０．００５≦ 〔Ｓｉ〕／（〔Ｃ〕＋〔Ｓｉ〕＋〔Ｎ〕） ≦０．２
（Ｂ） ０．００２≦ 〔Ｎ〕／（〔Ｃ〕＋〔Ｓｉ〕＋〔Ｎ〕） ≦０．３
（上記式において、〔Ｓｉ〕、〔Ｎ〕、〔Ｃ〕はそれぞれ、錫めっき表面からＸＰＳで検出されるＳｉ、Ｎ及びＣの濃度（原子百分率（ａｔ％））を表す。）
また本発明は別の一側面において、前記表面処理材又は前記リフロー錫めっき材を用いた電子部品である。 This invention is completed based on the said knowledge, and is specified by the following.
In one aspect, the present invention cools a reflow tin plating material obtained by performing a plating step of performing tin plating on a part of or the entire surface of copper or a copper alloy, a reflow step of heating and melting the tin plating, and a reflow tin plating material obtained thereby. The cooling process and the reflow tin plating surface of the cooled reflow tin plating material are represented by one or more silane coupling agents, a benzotriazole compound represented by the following general formula (A), and the following general formula (I) A surface treatment method for copper or a copper alloy including a coating step of coating in any order (including simultaneous) with one or two or more nitrogen-containing compounds selected from the shown benzothiazole compounds.

(In the formula, R ₁ represents a hydrogen atom, an alkyl group or a substituted alkyl group, R ₂ represents an alkali metal, a hydrogen atom, an alkyl group or a substituted alkyl group. R ₃ represents an alkali metal or a hydrogen atom.)
In another aspect of the present invention, the coating step includes a surface treatment liquid containing the one or more silane coupling agents and a surface treatment liquid containing the one or more nitrogen-containing compounds. Or immersing the reflow tin plating material in a surface treatment solution containing both of the one or more silane coupling agents and the one or more nitrogen-containing compounds in any order. This is a surface treatment method.
In another aspect of the present invention, the reflow tin-plated material obtained by the reflow step contains the one or more silane coupling agents and the one or more nitrogen-containing compounds. This is a surface treatment method in which the coating step also serves as a cooling step by bringing it into contact with a surface treatment solution at 30 ° C to 80 ° C.
According to another aspect of the present invention, there is provided a surface treatment method in which the copper or copper alloy subjected to the surface treatment is in the form of a strip or a terminal obtained by pressing a strip.
Moreover, this invention is a surface treatment material obtained by the said surface treatment method in another one side.
In another aspect of the present invention, the Si and N concentrations detected when the reflow tin plating surface is analyzed by XPS satisfy the following conditional expressions (A) and (B) simultaneously: Surface treatment material.
(A) 0.005 ≦ [Si] / ([C] + [Si] + [N]) ≦ 0.2
(B) 0.002 ≦ [N] / ([C] + [Si] + [N]) ≦ 0.3
(In the above formula, [Si], [N], and [C] represent the concentrations (atomic percentage (at%)) of Si, N, and C, respectively, detected by XPS from the tin plating surface.)
Further, in another aspect of the present invention, the reflow tin whose surface is coated so that the concentrations of Si and N detected upon surface analysis by XPS satisfy the following conditional expressions (A) and (B) simultaneously: It is a plating material.
(A) 0.005 ≦ [Si] / ([C] + [Si] + [N]) ≦ 0.2
(B) 0.002 ≦ [N] / ([C] + [Si] + [N]) ≦ 0.3
(In the above formula, [Si], [N], and [C] represent the concentrations (atomic percentage (at%)) of Si, N, and C, respectively, detected by XPS from the tin plating surface.)
According to another aspect of the present invention, there is provided an electronic component using the surface treatment material or the reflow tin plating material.

  According to the present invention, whiskers are hardly generated and the length of the generated whiskers is short. The present invention is a whisker suppression technique that can be carried out easily and at a relatively low cost because it does not require any change in the tin plating solution and does not require any significant remodeling of existing tin plating equipment.

Plating Step In the surface treatment method according to the present invention, a plating treatment is performed in which a part or the whole of the surface of copper or copper alloy is subjected to tin plating. The area to be plated may be determined as desired. For example, the entire surface of copper or copper alloy in various forms (including the form of terminals) may be plated, or only one side or a partial plating may be applied. Also good.

Tin (Sn) plating can be performed by a method known per se. For example, an organic acid bath (for example, a phenolsulfonic acid bath, an alkanesulfonic acid bath and an alkanolsulfonic acid bath), a borofluoric acid bath, a halogen bath, sulfuric acid Electroplating can be performed using an acidic bath such as a bath, a pyrophosphate bath, or an alkaline bath such as a potassium bath or a sodium bath. Further, as described in Japanese Patent Publication No. 59-15993, a phosphate ester of hydroxyethane is added to a bath in which stannous chloride and stannous sulfate are the main components and the bath pH is neutral with caustic soda or phosphoric acid. An added neutral bath can also be used. Among these baths, an organic acid bath is preferable from the viewpoint of whisker suppression and plating appearance. The composition and working conditions of the tin plating bath are appropriately set by methods known to those skilled in the art, but the tin ion concentration is 10 to 50 g / L, the acid concentration is 0.5 to 1.5 N, and the cathode current density is 3 to 30 A / dm ^2. Is preferable.
The thickness of the tin plating is usually 0.5 to 5.0 μm, preferably 0.7 to 2.0 μm, for reasons of whisker suppression effect, appearance, and plating cost.
In addition, various pretreatments known to those skilled in the art may be performed on copper or a copper alloy before performing the surface treatment according to the present invention. For example, Ni for the purpose of suppressing the growth of the Cu—Sn compound or Cu underplating for the purpose of improving the appearance may be applied, or a multilayer underplating of Ni or Cu may be applied. However, in terms of the whisker suppressing effect, whiskering cannot be suppressed even if Ni undercoating is performed, if external stress is applied to the tin plating.

Reflow process In the surface treatment method according to the present invention, a reflow process is performed in which tin plating applied to a part or the whole of the surface of copper or copper alloy is heated to a melting point of tin or higher by the plating process defined above. . Without reflow treatment, whisker cannot be effectively suppressed even if coating treatment is performed with the silane coupling agent and the nitrogen-containing compound. In the reflow treatment, the temperature is 250 to 600 ° C., preferably 300 to 500 ° C., more preferably 350 to 450 ° C. in order to relax the internal stress of tin plating, and the time is 3 to 40 to improve the plating appearance. Second, preferably 5 to 30 seconds, more preferably 5 to 20 seconds of heat treatment is applied to melt the tin for a moment. As a result, the residual stress inside the plating (which causes whisker generation and growth) is released, making it difficult for the whiskers to grow.
In addition, the heating is preferably performed in a reducing atmosphere or an inert atmosphere condition.

Cooling Step In the surface treatment method according to the present invention, the reflow tin plating material obtained by the reflow treatment defined above is cooled. Cooling can be performed by any known means, for example, air cooling, water cooling, etc. In the case of water cooling, spraying to the plating material that came out of the reflow furnace, immersion of the plating material in a water tank, etc. It is done. In order to improve the plating appearance, it is preferably cooled to about 20 ° C. to 90 ° C. by immersion in a water bath.

In the surface treatment method according to the present invention, the reflow tin-plated surface of the cooled reflow tin plating material is selected from one or more silane coupling agents, benzotriazole compounds, and benzothiazole compounds. It coat | covers with 1 type, or 2 or more types of nitrogen-containing compounds.
There is no particular limitation on the order of coating the surface that has been subjected to reflow tin plating with the one or more silane coupling agents and the one or more nitrogen-containing compounds. For example, it may be coated first with one or more silane coupling agents and then coated with one or more nitrogen-containing compounds, or one or more nitrogen-containing compounds. After coating first, one or two or more silane coupling agents may be applied thereon. Moreover, it is also possible to coat | cover simultaneously with 1 type, 2 or more types of silane coupling agents, and 1 type or 2 types or more of nitrogen-containing compounds by mixing both. The above operations may be combined.
In the coating process, the surface of the plating material may be dried or wet with the cooling water in the cooling step.
By the coating process, the silane coupling agent and the nitrogen-containing compound are adsorbed on the surface of the plating material to form a film. It is considered that the film obtained by the above mechanism becomes a barrier and the starting point of whisker generation is reduced, and the growth is suppressed. Further, the surface of the plating material is less likely to generate minute scratches due to the silane coating, and the fretting corrosion can be reduced because oxidation is suppressed.
More preferably, in the case of sequentially coating with one or more silane coupling agents and one or more nitrogen-containing compounds, the coating is first performed with one or more nitrogen-containing compounds. And it is preferable from a viewpoint of the whisker suppression effect to coat | cover with 1 type (s) or 2 or more types of silane coupling agents later, or to coat | cover with these simultaneously.

  In order to coat the surface of the plating material with a silane coupling agent and a nitrogen-containing compound, the silane coupling agent and the nitrogen-containing compound itself are individually or mixed as a surface treatment solution and directly applied to the surface of the plating material. Also good. However, in order to adjust the coating amount, water or an alcohol such as ethanol, a ketone such as acetone, an ester such as ethyl acetate or toluene, n-decane, and a silane coupling agent and a nitrogen-containing compound are individually or mixed. It may be coated with a surface treatment liquid that is added to an organic solvent such as N-methyl-2-pyrrolidone or propylene carbonate and dispersed or dissolved by stirring sufficiently to be uniform. As the solvent, n-decane or the like is preferably used for safety reasons.

The temperature of the surface treatment liquid is 20 to 100 ° C., preferably 30 to 80 ° C., more preferably 50 to 70 ° C. from the viewpoint of the whisker suppressing effect.
The concentration of the silane coupling agent in the surface treatment liquid is not particularly limited, but is 0.05 to 10% by weight, preferably 0, based on the weight of the whole surface treatment liquid from the viewpoint of whisker suppression and cost. A concentration of 1 to 5.0% by weight. Further, the concentration of the nitrogen-containing compound in the surface treatment liquid is not particularly limited, but is 0.01 to 10% by weight, preferably 0. The concentration is 1 to 5.0% by weight.

  Examples of the method of coating the surface of the plating material with the surface treatment liquid include spray coating, flow coating, spin coating, dip coating, roll coating, and the like, and dip coating or spray coating is preferable from the viewpoint of productivity.

  Here, when the surface of the plating material is coated with the surface treatment liquid, the plating material is cooled by bringing the reflow tin plating material coming out of the reflow furnace into contact with the surface treatment liquid at about 30 ° C. to 80 ° C. In addition, it is preferable that the coating process also serves as a cooling process. Since the surface of the plating material at a high temperature (usually 300 to 400 ° C.) immediately after coming out of the reflow furnace is rich in activity, by bringing the high-temperature material after heating and melting (reflow) into contact with the surface treatment liquid, This is because not only the cooling effect but also the effect that the silane coupling agent and the nitrogen-containing compound are more strongly adsorbed on the surface of the tin plating is obtained, and the production efficiency is further increased. In addition, when the oxide film is thick on the surface of tin, the reaction with the processing solution becomes somewhat dull, so that the plating material from the reflow furnace is brought into contact with the processing solution as quickly as possible without touching it with air or other gases as much as possible. However, in practice, a sufficient effect can be obtained if it is carried out continuously in a plating line such as a reel-to-reel.

  When the coating process also serves as a cooling process, the contact of the surface treatment solution with the reflow tin plating material is mainly to cool the high temperature reflow tin plating material and to coat the surface of the plating material with the surface treatment solution. Do as purpose. Therefore, as a method of bringing the surface treatment solution into contact with the plating material, a method of spraying the surface treatment solution onto the plating material or a method of immersing the plating material in the surface treatment solution is preferable. In the case where the coating process also serves as a cooling process, the temperature of the surface treatment liquid to be used is usually 20 to 100 ° C., preferably 30 to 80 ° C., for reasons of increasing the reactivity between the liquid component and tin plating. Preferably it is 50-70 degreeC. The time for bringing the plating material into contact with the cooling liquid is usually 0.5 to 60 seconds, preferably 1 to 40 seconds, and more preferably 5 to 30 seconds, so that the silane coupling agent and the nitrogen-containing compound are sufficient. Adsorption is obtained.

Since coating is often performed using an aqueous solution or the like, drying is usually performed after the coating step. That is, after the surface of the plating material is coated with the surface treatment liquid, drying is performed. Examples of the drying method include air drying and heat drying, and heat drying is preferable from the viewpoint of productivity. This is because the solvent is removed and the dehydration condensation of the silane coupling agent is promoted to fix the plating material surface. When the coating process also serves as a cooling process, it is preferable to cool the plating material to 20 to 90 ° C., preferably 50 to 80 ° C. by contact with the surface treatment liquid, and then dry it for the reason of shortening the drying time.
When the surface of the plating material is coated with one or more silane coupling agents and one or more nitrogen-containing compounds in a plurality of times, each coating step may be carried out continuously. However, it is preferable to provide a drying step between the respective coating steps, and to coat the one that has been previously coated, after drying by the above-described method. This is because if the first coating is performed before drying, the first coating may be detached from the surface of the plating material during the subsequent coating.

  The surface treatment described so far is not particularly limited in time except for the points particularly pointed out above, but it is preferable to carry out in a series of steps from an industrial viewpoint.

Copper or copper alloy Although there is no particular limitation on the type of copper or copper alloy to be surface-treated according to the present invention, the main purpose is that these copper or copper alloy is used as a material for electronic components such as connectors and terminals. Therefore, it is desirable to have strength, springiness, workability, conductivity, etc. suitable for these applications. Accordingly, examples of the copper or copper alloy include phosphor bronze, brass, beryllium copper, titanium copper, and Corson alloy.

  There is no restriction | limiting in particular in the form of the copper or copper alloy which receives the surface treatment which concerns on this invention. Therefore, the surface treatment according to the present invention may be performed at the stage of the material before pressing, or may be performed during or after pressing. However, it is preferable that the surface treatment according to the present invention is performed when it is in the form of a strip before press working, or after pressing it into a form of a terminal or a lead frame from the viewpoint of industrial properties and applications.

Silane coupling agent The type of the silane coupling agent according to the present invention is not particularly limited and can be used. In this specification, the silane coupling agent refers to an organosilicon compound having at least one hydrolyzable group and at least one organic functional group in one molecule. Examples of the hydrolyzable group include a halogen group such as a chloro group, an alkoxy group, an acetoxy group, an isopropenoxy group, and an amino group, and an alkoxy group is preferable from the viewpoint of stability and ease of handling. Examples of the alkoxy group include linear, branched or cyclic alkoxy groups having 1 to 20, preferably 1 to 10, more preferably 1 to 6 carbon atoms, and more specifically, For example, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, secondary butoxy group, tertiary butoxy group, pentyloxy group, hexyloxy group, cyclopropyloxy group, cyclopentyloxy group, Examples include a cyclohexyloxy group. The alkoxy group may have a substituent.
Examples of the organic functional group include a vinyl group, an epoxy group, a styryl group, an acryloxy group, a methacryloxy group, an amino group, an N-phenylaminopropyl group, a ureido group, a chloropropyl group, a mercapto group, an isocyanate group, and a sulfide group. An amino group is preferable from the viewpoint of whisker suppression.
Two or more silane coupling agents can be used in combination.

（式中、Ｒ₁は水素原子、アルキル基又は置換アルキル基を表わし、Ｒ₂はアルカリ金属、水素原子、アルキル基又は置換アルキル基を表わす。Ｒ₃はアルカリ金属又は水素原子を表す。）で表わされる。Ｒ₁及びＲ₂のアルキル基は各々独立に、直鎖状、分枝状又は環状であってよく、炭素数も特に制約されないが、通常１〜２２、好ましくは１〜１２、より好ましくは１〜８である。アルキル基の例としてはメチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｔ−ブチル基、ｎ−ペンチル基、シクロペンチル基、シクロヘキシル基が挙げられ、置換アルキル基の例としては少なくとも一個のハロゲン原子によって置換されたこれらのアルキル基が挙げられる。Ｒ₃は溶媒が水の場合にはアルカリ金属であることが好ましく、アルカリ金属としてはナトリウム又はカリウムが好ましい。
一般式（ア）で表わされる化合物のうち好ましいものを挙げると、例えば、ベンゾトリアゾール（Ｒ₁、Ｒ₂ともに水素）、１−メチルベンゾトリアゾール（Ｒ₁が水素、Ｒ₂がメチル）、トリルトリアゾール（Ｒ₁がメチル、Ｒ₂が水素）、１−（Ｎ，Ｎ−ジオクチルアミノメチル）ベンゾトリアゾール（Ｒ₁が水素、Ｒ₂がＮ，Ｎ−ジオクチルアミノメチル）などである。
一般式（イ）で表わされる化合物のうち好ましいものを挙げると、例えば、メルカプトベンゾチアゾール、メルカプトベンゾチアゾールのナトリウム塩、メルカプトベンゾチアゾールのカリウム塩などがある。
含窒素化合物は２種以上を組み合わせて用いることもできる。 Nitrogen-containing compound In the present invention, one or more nitrogen-containing compounds selected from the group consisting of a benzotriazole-based compound represented by the following general formula (A) and a benzothiazole-based compound represented by the following general formula (I) Use compounds.
It is considered that the compounds (a) and (b) contribute to preventing soldering deterioration and improving corrosion resistance, and have a whisker suppressing effect synergistically by combining with the silane coupling agent.

(Wherein R ₁ represents a hydrogen atom, an alkyl group or a substituted alkyl group, R ₂ represents an alkali metal, a hydrogen atom, an alkyl group or a substituted alkyl group. R ₃ represents an alkali metal or a hydrogen atom). Represented. The alkyl groups for R ₁ and R ₂ may be each independently linear, branched or cyclic, and the carbon number is not particularly limited, but is usually 1 to 22, preferably 1 to 12, more preferably 1 ~ 8. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, n-pentyl, cyclopentyl, and cyclohexyl groups. Examples of substituted alkyl groups These alkyl groups substituted by at least one halogen atom are mentioned. R ₃ is preferably an alkali metal when the solvent is water, and the alkali metal is preferably sodium or potassium.
Preferred examples of the compound represented by the general formula (a) include, for example, benzotriazole (both R ₁ and R ₂ are hydrogen), 1-methylbenzotriazole (R ₁ is hydrogen, R ₂ is methyl), tolyltriazole (R ₁ is methyl, R ₂ is hydrogen), 1- (N, N-dioctylaminomethyl) benzotriazole (R ₁ is hydrogen, R ₂ is N, N-dioctylaminomethyl), and the like.
Preferred examples of the compound represented by the general formula (I) include mercaptobenzothiazole, mercaptobenzothiazole sodium salt, mercaptobenzothiazole potassium salt, and the like.
Two or more nitrogen-containing compounds can be used in combination.

The XPS analysis silane coupling agent has Si (silicon atom) as a component, and nitrogen-containing compounds (benzotriazole compounds and benzothiazole compounds) have N (nitrogen atom) as a component. The concentration of these components in the tin plating can be confirmed by surface analysis by XPS (X-ray photoelectron spectroscopy). The present inventors have measured the strength (concentration) of Si, N, and C adsorbed on the tin plating surface by XPS and obtained the following knowledge.
The whisker suppression effect by the surface treatment method according to the present invention depends on the concentration of each component adsorbed on the reflow tin plating surface, and the whisker suppression effect is not sufficient unless the surface concentration exceeds a certain specified level. Further, if the Si or N concentration adsorbed on the tin plating surface is too high, whisker suppression effect can be obtained, but contact resistance increases.
Also, if the ratio of Si or N to the total concentration of C, Si and N detected is too high, the contact resistance will increase, and conversely if the ratio of Si or N is too low, the whisker suppression effect will be insufficient. I understood.

As a result of intensive studies, the present inventor has found that when the following conditional expressions (a) and (b) are simultaneously satisfied, a good balance between the whisker suppressing effect and the contact resistance is exhibited. This is considered to be because whisker suppression and contact resistance depend on the concentrations of Si and N adsorbed on the tin plating surface.
(A) 0.005 ≦ [Si] / ([C] + [Si] + [N]) ≦ 0.2
(B) 0.002 ≦ [N] / ([C] + [Si] + [N]) ≦ 0.3
Here, [Si], [N], and [C] represent the concentrations (atomic percentage (at%)) of Si, N, and C, respectively, detected by XPS from the surface of the tin plating material.
[Si] / ([C] + [Si] + [N]) is preferably 0.007 or more, more preferably 0.01 or more, preferably 0.18 or less, more preferably 0.15 or less. is there. [N] / ([C] + [Si] + [N]) is preferably 0.003 or more, more preferably 0.005 or more, preferably 0.27 or less, more preferably 0.25 or less. is there.

  [Si] / ([C] + [Si] + [N]) and [N] / ([C] + [Si] + [N]) are the types of silane coupling agents, benzotriazoles, and thiazole compounds. It can be adjusted based on the type, the concentration in the cooling liquid, and the liquid temperature. To increase these numerical values, for example, the component concentration may be increased, and to decrease it, the component concentration may be decreased. Accordingly, if the concentrations of the silane coupling agent and the benzotriazole compound are each 0.1 to 1.0%, [Si] / ([C] + [Si] + [N]) and [N] within the above ranges. / ([C] + [Si] + [N]) can be obtained. However, since the value of the above formula also depends on the molecular weight and molecular structure of each organic component, the C (carbon) concentration is also added to the formula.

  The surface treatment material obtained by the various embodiments of the surface treatment method according to the present invention described above corresponds to another embodiment of the present invention, and the surface treatment material includes connectors, terminals, switches, and leads. It can be used as a part or the whole of an electronic component such as a frame.

  In order that the invention and its advantages may be fully understood, examples of the invention are set forth below, which are not intended to limit the invention.

(1) Preparation of reflow tin-plated sample On a brass plate having a width of 50 mm, a length of 100 mm, and a thickness of 0.64 mm, a base plating of 0.6 μm thick Cu plating (using a sulfuric acid bath) was performed, and a thickness of 1.2 μm was formed thereon. Was subjected to tin plating (using a methanesulfonic acid bath).
The sample after tin plating was heated and melted (reflowed) at 300 to 400 ° C. for 15 seconds in a nitrogen atmosphere to melt the tin plating film, and then the material was placed in 3 L of cooling water maintained at about 60 ° C. for 10 seconds. It was immersed and cooled. Next, various surface treatment liquids of 60 ° C. according to the present invention were applied to the plating surface by an immersion method. Thereafter, the sample was dried with warm air.
Samples were produced by changing the presence / absence of reflow and the composition, concentration and treatment method of the treatment liquid applied to the plating.
Table 1 shows the samples used in each example.

(2) Analysis method by X-ray photoelectron spectroscopy (XPS) Using an X-ray photoelectron spectrometer (model: 5600MC, manufactured by ULVAC-PHI), the concentration of each element (at. %).

(3) Whisker evaluation method The whisker is evaluated by contacting a tin plate surface with an indenter (a stainless steel ball having a diameter of 1.4 mm), applying a load of 1.5 N, and allowing it to stand in an air atmosphere at room temperature for 168 hours. Was taken out and the surface was observed with SEM.
The average whisker length was obtained by taking one piece near the center of the sample surface with a magnification of 1000 to 2000 times by SEM, selecting the three longest whiskers in the photograph, and taking the average value.

(4) Contact resistance measurement method As a contact resistance measuring device, a contact simulator (manufactured by Yamazaki Seiki Co., Ltd.) was used, and contact resistance was measured under conditions of a contact load of 0.49 N and a current of 10 mA.

(5) Solderability evaluation method after heating The test conditions were as follows, and the case where the solder wetting time was less than 3 seconds was evaluated as ◯, and the case where the solder wetting time was 3 seconds or more was evaluated as x.
・ Heating condition: 155 ° C., 16 hours heating in air atmosphere ・ Solder: Sn 60% -Pb 40% solder (235 ° C.)
・ Flux: Rosin-isopropyl alcohol solution ・ Measurement device: SA-5000 manufactured by Reska Co., Ltd.

(6) Evaluation Results of Each Sample (Example, Comparative Example) In Invention Examples 1 to 6, the average length of whiskers is as short as about 6 μm, and the contact resistance is a low value of 10 mΩ or less, making it difficult for the whiskers to grow. It was confirmed. Moreover, the solderability after heating was also good.
Invention Example 7 is a case where the values of [Si] / ([C] + [Si] + [N]) and [N] / ([C] + [Si] + [N]) are low. Although the growth is suppressed, the whisker is longer than in Examples 1-6.
Invention Example 8 is a case where the values of [Si] / ([C] + [Si] + [N]) and [N] / ([C] + [Si] + [N]) are high. Growth is suppressed, but contact resistance is high.
In Comparative Example 1, the treatment liquid was not applied to the plating surface, and in this case, whiskers grew longer. Also, the solderability after heating was poor.
The comparative example 2 is an example when the tin plating is not reflowed, and the whisker grows longer in this case as well.
In Comparative Example 3, the surface treatment was performed with the epoxy-based silane coupling agent alone, and the whisker suppressing effect was not high. Also, the solderability after heating was poor.
Comparative Example 4 is a surface treatment with an amino-based silane coupling agent alone and has a whisker suppressing effect than an epoxy-based silane coupling agent, but is inferior to Invention Example 3 in which benzotriazole is added thereto. Also, the solderability after heating was poor.
Comparative Example 5 was surface-treated with benzotriazole alone, and the whisker suppressing effect was not high.

Claims (9)

A plating step for performing tin plating on a part or all of the surface of copper or copper alloy, a reflow step for heating and melting the tin plating, a cooling step for cooling the tin-plated material obtained thereby, and a cooled reflow The reflow tin plating surface of the tin plating material is selected from one or more silane coupling agents, a benzotriazole compound represented by the following general formula (A), and a benzothiazole compound represented by the following general formula (I) A surface treatment method for copper or a copper alloy, including a coating step of coating in any order (including simultaneous) with one or two or more nitrogen-containing compounds.

(In the formula, R ₁ represents a hydrogen atom, an alkyl group or a substituted alkyl group, R ₂ represents an alkali metal, a hydrogen atom, an alkyl group or a substituted alkyl group. R ₃ represents an alkali metal or a hydrogen atom.)   The coating step is performed in any order in the surface treatment liquid containing the one or more silane coupling agents and the surface treatment liquid containing the one or more nitrogen-containing compounds, or the one or The surface treatment method of Claim 1 including immersing the said reflow tin plating material in the surface treatment liquid containing both 2 or more types of silane coupling agents and the said 1 type or 2 or more types of nitrogen-containing compound.   The reflow tin plating material obtained by the reflow step is a surface treatment solution at 30 ° C. to 80 ° C. containing the one or more silane coupling agents and the one or more nitrogen-containing compounds. The surface treatment method according to claim 1, wherein the coating step also serves as a cooling step by contacting the substrate.   The surface treatment method according to any one of claims 1 to 3, wherein the copper or copper alloy subjected to the surface treatment is in the form of a strip or a terminal obtained by pressing the strip.   The surface treatment material obtained by the surface treatment method as described in any one of Claims 1-4. The surface treatment material according to claim 5, wherein the concentration of Si and N detected when the reflow tin plating surface is analyzed by XPS satisfies the following conditional expressions (A) and (B) simultaneously: .
(A) 0.005 ≦ [Si] / ([C] + [Si] + [N]) ≦ 0.2
(B) 0.002 ≦ [N] / ([C] + [Si] + [N]) ≦ 0.3
(In the above formula, [Si], [N], and [C] represent the concentrations (atomic percentage (at%)) of Si, N, and C, respectively, detected by XPS from the tin plating surface.) A reflow tin-plated material whose surface is coated so that the concentrations of Si and N detected upon surface analysis by XPS simultaneously satisfy the following conditional expressions (A) and (B).
(A) 0.005 ≦ [Si] / ([C] + [Si] + [N]) ≦ 0.2
(B) 0.002 ≦ [N] / ([C] + [Si] + [N]) ≦ 0.3
(In the above formula, [Si], [N], and [C] represent the concentrations (atomic percentage (at%)) of Si, N, and C, respectively, detected by XPS from the tin plating surface.)   The electronic component using the surface treatment material as described in any one of Claim 5 or 6.   The electronic component using the reflow tin plating material of Claim 7.