JP5229785B2 - Plating layer and method for forming the same - Google Patents
Plating layer and method for forming the same Download PDFInfo
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- JP5229785B2 JP5229785B2 JP2007339241A JP2007339241A JP5229785B2 JP 5229785 B2 JP5229785 B2 JP 5229785B2 JP 2007339241 A JP2007339241 A JP 2007339241A JP 2007339241 A JP2007339241 A JP 2007339241A JP 5229785 B2 JP5229785 B2 JP 5229785B2
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- 238000007747 plating Methods 0.000 title claims description 188
- 238000000034 method Methods 0.000 title claims description 41
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 28
- 229910001128 Sn alloy Inorganic materials 0.000 claims description 11
- 238000012545 processing Methods 0.000 claims description 8
- 230000035882 stress Effects 0.000 description 30
- 238000010438 heat treatment Methods 0.000 description 24
- 230000008569 process Effects 0.000 description 23
- 229910000679 solder Inorganic materials 0.000 description 23
- 230000006355 external stress Effects 0.000 description 19
- 238000007654 immersion Methods 0.000 description 19
- 238000002844 melting Methods 0.000 description 18
- 230000008018 melting Effects 0.000 description 18
- 239000000463 material Substances 0.000 description 15
- 230000012010 growth Effects 0.000 description 14
- 238000004140 cleaning Methods 0.000 description 8
- 239000013078 crystal Substances 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 6
- 238000001035 drying Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000002184 metal Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 230000001629 suppression Effects 0.000 description 5
- 210000001015 abdomen Anatomy 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000010230 functional analysis Methods 0.000 description 3
- 230000004927 fusion Effects 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 239000000155 melt Substances 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910020816 Sn Pb Inorganic materials 0.000 description 1
- 229910020922 Sn-Pb Inorganic materials 0.000 description 1
- 229910008783 Sn—Pb Inorganic materials 0.000 description 1
- QCEUXSAXTBNJGO-UHFFFAOYSA-N [Ag].[Sn] Chemical compound [Ag].[Sn] QCEUXSAXTBNJGO-UHFFFAOYSA-N 0.000 description 1
- 230000003187 abdominal effect Effects 0.000 description 1
- -1 alloys) Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- JWVAUCBYEDDGAD-UHFFFAOYSA-N bismuth tin Chemical compound [Sn].[Bi] JWVAUCBYEDDGAD-UHFFFAOYSA-N 0.000 description 1
- 230000028446 budding cell bud growth Effects 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- LQBJWKCYZGMFEV-UHFFFAOYSA-N lead tin Chemical compound [Sn].[Pb] LQBJWKCYZGMFEV-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000010297 mechanical methods and process Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 235000014593 oils and fats Nutrition 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
- 229910002058 ternary alloy Inorganic materials 0.000 description 1
- 229910001174 tin-lead alloy Inorganic materials 0.000 description 1
Landscapes
- Electroplating Methods And Accessories (AREA)
Description
本発明は、錫又は錫合金でめっきされた接続端子のウイスカの発生を抑制するめっき層及びその形成方法に関し、とりわけＦＰＣ（Ｆｌｅｘｉｂｌｅ Ｐｒｉｎｔ Ｃｉｒｃｕｉｔ）用コネクタの接続端子のめっき層及びその形成方法に関する。又このめっき層を具えたコンタクトピン、更にはこのコンタクトピンを装着したコネクタに関する。 The present invention relates to a plating layer that suppresses whisker generation of a connection terminal plated with tin or a tin alloy and a method for forming the same, and more particularly, to a plating layer for a connection terminal of a connector for FPC (Flexible Print Circuit) and a method for forming the same. The present invention also relates to a contact pin provided with this plating layer, and further to a connector equipped with this contact pin.
〈鉛フリー化〉
電子部品やコネクタの回路基板への実装は、はんだ（錫と鉛を主成分とした合金：Ｓｎ−Ｐｂ合金）が多く使われている。はんだは、融点が低く、濡れ性が良く、また価格も低廉で電子機器の接合材料として優れた特性を具えている。
<Lead-free>
For mounting electronic components and connectors on a circuit board, solder (an alloy mainly composed of tin and lead: Sn—Pb alloy) is often used. Solder has a low melting point, good wettability, low cost, and excellent properties as a bonding material for electronic equipment.
しかし、地球規模の環境保全の問題に絡んで環境負荷物質を含む構成部材の見直しが進む中で、電子部品の接合材料として鉛を含有する、はんだの使用に制限が加えられるようになってきた。現在、はんだに替わる接合材料として次のような金属（合金を含む）、Ｓｎ(錫)、Ｓｎ（錫）−Ｃｕ（銅）、Ｓｎ（錫）−Ａｇ（銀）、Ｓｎ（錫）−Ｂｉ（ビスマス）があげられるが、いずれもがウイスカの問題を含み、錫−鉛合金に置き換わる有望なはんだ材料は、まだ存在しないのが現状である。 However, with the ongoing review of components that contain environmentally hazardous substances due to global environmental conservation issues, the use of solder containing lead as a bonding material for electronic components has come to be restricted. . Currently, the following metals (including alloys), Sn (tin), Sn (tin) -Cu (copper), Sn (tin) -Ag (silver), Sn (tin) -Bi are used as bonding materials instead of solder. (Bismuth), all of which have the problem of whiskers, and there are no promising solder materials that can replace tin-lead alloys.
〈ウイスカ〉
ウイスカは、錫の単結晶が成長した針状のもので、直径１μ長さ１ｍｍに成長するものも報告されている。この針状結晶は導電性で、隣接する接続端子と短絡したり、折損物が飛散したりして、電子機器の動作に支障をきたす問題がおきている。錫−鉛はんだを使用していたときには、含有する鉛の作用によってウイスカの発生及び成長は抑制されていた。鉛フリー化による錫単体、或いは錫と鉛以外の他の金属との合金の使用によって、にわかにウイスカの問題が顕在化してきた。
<Whisker>
Whisker is a needle-like shape in which a single crystal of tin is grown, and a whisker having a diameter of 1 μ and a length of 1 mm is also reported. This needle-like crystal is conductive, and there is a problem that the operation of the electronic device is hindered by short-circuiting with an adjacent connection terminal or scattering of broken objects. When tin-lead solder was used, whisker generation and growth were suppressed by the action of the contained lead. The problem of whiskers has become apparent due to the use of tin alone or an alloy of tin and another metal other than lead.
ウイスカ現象は、「錫の再結晶中に取りこまれた異物や転位等の欠陥がウイスカ発生の芽となり、結晶内部の残留圧縮応力や、外部からの圧縮応力の集中が駆動力としてはたらいて、その芽が成長する現象である」と説明されている。しかしその詳細な発生、成長の原理及び機構については、現在解明途上である。 The whisker phenomenon is that “defects such as foreign matter and dislocations incorporated during recrystallization of tin become buds of whisker generation, and the residual compressive stress inside the crystal and the concentration of compressive stress from outside acts as the driving force, It is a phenomenon that the bud grows. " However, the detailed generation and growth principles and mechanisms are currently being elucidated.
〈ウイスカの抑制〉
ウイスカの抑制技術は、その開発の基礎となる発生のメカニズムが現在解明途上であることから、未だ方向性は定まっていない。鉛を含有する、はんだめっきに代替する材料の組成の候補にしても数多くがあがっていて、上述した種類の合金のほかにも別種金属との合金や更に３元合金についての組成も報告されている。
<Inhibition of whiskers>
The direction of whisker suppression technology has not yet been determined since the mechanism of development that is the basis for its development is currently being elucidated. There are many candidate compositions for lead-containing materials that can replace solder plating. In addition to the types of alloys mentioned above, alloys with other metals and ternary alloys have also been reported. Yes.
このような背景の下、ウイスカに関する技術については、多岐に亘って報告されており、合金組成についても多様である。また、その抑制方法は幾つもの技術が報告されているが、それぞれが問題を含んでいる。主な技術と問題点は次のようなものである。
（１）めっき後に熱処理をすることによって金属間化合物の形成等によって生じた内部応力を緩和するもの。内部応力によって発生及び成長するウイスカの抑制に有効であるが、コネクタの嵌合部に作用するような外部応力を起因とするウイスカの抑制には効果が望めない。
（２）下地にＮｉ、ＣｏもしくはＦｅのいずれか一種のめっきを施して銅と錫とからなる金属間化合物の形成バリアとするもの（特許文献１）。Ｎｉめっき等を施せない場合もあり全ての場合に有効とは言えない。また、外部応力に起因するウイスカの抑制には効果が望めない。
（３）めっき後にリフロー処理をすることによって錫合金めっき層の完全溶融を図って応力の緩和を図るもの（非特許文献１）。めっき層の外形に変化が生じ、表面実装型では実装時の不具合の発生が懸念される。また、外部応力を起因とするウイスカの抑制には効果が望めない。
Against this background, whisker-related technologies have been reported in a wide variety of fields, and alloy compositions are also diverse. In addition, several techniques have been reported for the suppression method, but each has problems. The main technologies and problems are as follows.
(1) Relieving internal stress caused by the formation of intermetallic compounds by heat treatment after plating. Although effective in suppressing whiskers generated and grown by internal stress, no effect can be expected in suppressing whiskers due to external stress acting on the fitting portion of the connector.
(2) The base is plated with any one of Ni, Co, and Fe to form a barrier for forming an intermetallic compound composed of copper and tin (Patent Document 1). In some cases, Ni plating or the like cannot be performed, and it is not effective in all cases. Moreover, an effect cannot be expected in suppression of the whisker resulting from external stress.
(3) Reflow treatment is performed after plating to achieve complete melting of the tin alloy plating layer and to relieve stress (Non-Patent Document 1). A change occurs in the outer shape of the plating layer, and there is a concern that the surface mounting type may cause defects during mounting. Moreover, an effect cannot be expected for suppression of whisker caused by external stress.
現在報告されている技術を分析すると、内部応力を起因とするウイスカの発生を抑制する技術が大半を占め、外部応力を起因とするウイスカの発生を抑制する技術についての報告は極めて少ない。また、物理的な方法によってウイスカの伸長を抑制する技術もあるが（特許文献２）、ウイスカ伸長防止壁等の構造体の製作に技術的困難性が予測される。 Analysis of currently reported techniques occupies most of the techniques for suppressing the generation of whiskers due to internal stress, and there are very few reports on the techniques for suppressing the generation of whiskers due to external stress. Moreover, although there exists a technique which suppresses expansion | extension of a whisker by a physical method (patent document 2), technical difficulty is estimated in manufacture of structures, such as a whisker expansion | extension prevention wall.
本発明は、上記事情に鑑みてなされたものであり、内部応力に起因するウイスカの発生及び成長を抑制するとともに、外部応力を起因とするウイスカの発生及び成長をも抑制するめっき層及びその形成方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and suppresses the generation and growth of whiskers due to internal stress, and also forms a plating layer that suppresses the generation and growth of whiskers due to external stress. It aims to provide a method.
本発明者は、上記課題を解決するために工場のめっき工程や、めっきされた製品の外観やその断面をつぶさに観察した。またコンタクトピンの接続機構をその構成要素に分解して、個々の要素についての機能的分析を併せておこなった。その結果、めっき層に要求されるはんだ性及び接触信頼性を損なうことなく、ウイスカの発生及び成長を効果的かつ合理的に抑制するめっき技術の開発に成功した。ここで、はんだ性とは、はんだによる固着性を言う。また、接触信頼性とは、接触による電気的機械的接続の信頼性を言う。 In order to solve the above-mentioned problems, the present inventor has closely observed the plating process in the factory, the appearance of the plated product, and its cross section. In addition, the contact pin connection mechanism was disassembled into its components, and functional analysis of each component was also performed. As a result, the inventors succeeded in developing a plating technique that effectively and rationally suppresses the generation and growth of whiskers without impairing the solderability and contact reliability required for the plating layer. Here, the solderability refers to the adhesion with solder. Moreover, contact reliability means the reliability of the electromechanical connection by contact.
〈コンタクトピンの機能分析〉
コンタクトピンは回路基板に接続するリード部と、相対するコネクタに嵌合する接点部とを含む。リード部は、はんだで回路基板に固着されるので、被覆するめっきには、接触信頼性とともに、はんだ性が要求される。一方接点部は機械的な嵌め合いで相対するコネクタに連結するところなので、接触信頼性を満たす必要はあるが、はんだ性を満たすほどのめっき厚みは要求されない。また、接点部では嵌め合い箇所で圧縮応力の集中が生じるが、リード部では実装後に外部応力の集中は想定し難い。そのためにリード部では、外部応力に起因するウイスカ現象のおそれは少ないが、接点部では、外部応力を起因とするウイスカの発生を想定した対策を講じておく必要がある。
<Functional analysis of contact pins>
The contact pin includes a lead portion connected to the circuit board and a contact portion fitted to the opposite connector. Since the lead portion is fixed to the circuit board with solder, the plating for coating requires solderability as well as contact reliability. On the other hand, since the contact portion is connected to the opposite connector by mechanical fitting, it is necessary to satisfy the contact reliability, but the plating thickness is not required to satisfy the solderability. In addition, although the compressive stress concentration occurs at the fitting portion in the contact portion, it is difficult to assume the external stress concentration after mounting in the lead portion. Therefore, although there is little risk of whisker phenomenon due to external stress in the lead part, it is necessary to take measures in the contact part assuming the occurrence of whisker due to external stress.
〈ウイスカ現象〉
背景技術で説明したように、ウイスカ現象は、錫の再結晶時に生じた欠陥と、その欠陥に作用する圧縮応力の存在が不可欠であると考えられている。そして圧縮応力には大別して、めっき層形成時に残留した内部応力に起因するものと、コネクタ等の嵌め合い部に生じる外部応力に起因するものとの２タイプが確認されている。また内部応力を除去するためには、熱処理又はリフロー処理が有効であること、更に錫原子の供給を断つことでウイスカの抑制が図れることは多くの文献報告や経験から認められるものである。
<Whisker phenomenon>
As described in the background art, it is considered that the whisker phenomenon is indispensable to the existence of defects generated during recrystallization of tin and compressive stress acting on the defects. And it divides roughly into compressive stress, and two types, what originates in the internal stress which remained at the time of plating layer formation, and what originates in the external stress produced in fitting parts, such as a connector, are confirmed. Moreover, in order to remove internal stress, it is recognized from many literature reports and experiences that the heat treatment or the reflow treatment is effective, and that the whisker can be suppressed by cutting off the supply of tin atoms.
〈熱処理及びリフロー処理〉
ここで熱処理及びリフロー処理のめっき層改質処理について考察する。言葉を明確にしておくために、ここでは、熱処理とは、めっき材料の溶け出す温度（溶融温度）未満の温度を最高温度とする高温処理を意味し、リフロー処理とは、めっき材料の溶融温度以上の温度を最高温度とする高温処理を意味する。熱処理は、めっき層を融解させないので、めっき層の形状に変化を生じさせることなく改質（内部応力の緩和）をおこなえるところに特徴がある。リフロー処理は、熱処理以上の改質（内部応力の緩和）が望める一方、めっき層の融解を伴うので、リフロー処理後のめっき層は、その表面が平坦性を失っている。
<Heat treatment and reflow treatment>
Here, the plating layer modification treatment of heat treatment and reflow treatment will be considered. For the sake of clarity, here, heat treatment means high-temperature treatment where the maximum temperature is less than the temperature at which the plating material melts (melting temperature), and reflow treatment means the melting temperature of the plating material. It means high temperature treatment with the above temperature as the maximum temperature. Since the heat treatment does not melt the plating layer, the heat treatment is characterized in that the modification (relaxation of internal stress) can be performed without causing a change in the shape of the plating layer. While the reflow treatment can be expected to be modified more than the heat treatment (relaxation of internal stress), the plating layer is melted, so that the surface of the plating layer after the reflow treatment has lost flatness.
〈考察１〉
コンタクトピンの機能分析と、ウイスカ現象の基礎的知見とから次のことが考察される。（１）リード部には、はんだ実装後に外部応力の集中がないので、ウイスカの抑制は、熱処理或いはリフロー処理を施すことで十分達成され得る。（２）接点部には、嵌合時に外部応力の集中があるので、熱処理或いはリフロー処理による内部応力の緩和だけでは、外部応力を起因とするウイスカの発生を抑制しきれない。（３）接点部には、リード部ほどのめっき厚みは必要としない。すなわち、（４）リード部は、接触信頼性と、はんだ性とが要求されるので、めっき層は、はんだ性を満たすための厚みが必要であるとともに、広範囲で接続するために、表面は平坦であることが望まれる。これに対して、（５）接点部は、接触信頼性が確保される程度のめっき厚みで足り、はんだ性を満たすためのめっき厚みを必要としない。また、基本的な事項であるが、（６）ウイスカは錫の単結晶であるから、錫原子の供給量の多寡によってウイスカの芽の発生、或いは成長スピードの抑制が可能である。
<Discussion 1>
The following is considered from the functional analysis of contact pins and basic knowledge of whisker phenomena. (1) Since there is no concentration of external stress in the lead portion after solder mounting, whisker suppression can be sufficiently achieved by performing heat treatment or reflow treatment. (2) Since there is a concentration of external stress at the time of fitting in the contact portion, it is not possible to suppress whisker generation due to external stress only by relaxing internal stress by heat treatment or reflow treatment. (3) The contact portion does not need to be as thick as the lead portion. That is, (4) Since the lead portion is required to have contact reliability and solderability, the plating layer needs to have a thickness to satisfy the solderability, and the surface is flat in order to connect in a wide range. It is desirable that On the other hand, (5) the contact portion need only have a plating thickness that ensures contact reliability, and does not require a plating thickness to satisfy solderability. Moreover, although it is a basic matter, (6) Since whisker is a single crystal of tin, the generation of whisker buds or the growth speed can be suppressed depending on the supply amount of tin atoms.
〈考察２〉
本発明者は、上述した考察と幾つかの確認実験を通してウイスカの発生及び成長を抑制するための効果的且つ合理的なめっき層及びその形成方法の発明を想到するに至った。本発明は、第１ステップ：めっき厚みが必要なリード部には、めっきを厚めに皮膜し、めっき厚みがリード部ほど必要でなく、むしろ外部応力に起因するウイスカの抑制効果を重視する必要のある接点部のめっきは薄く皮膜する。このとき、リード部と接点部とのめっきの厚み差は、接点部のめっき厚さの１５０〜３７０％である。好ましくは１５０〜２３０％である。めっき厚み差が小さすぎる場合には高温処理条件の制御が困難になり、めっき厚み差が大きすぎると接点部、リード部それぞれの機能が十分に発揮できないおそれがある。第２ステップ：めっき層形成後に高温処理をおこなうが、このとき、めっき層が到達する最高温度は、リード部では、はんだ性を確保するのを第一義にし、ウイスカ対策は内部応力の緩和が達成できることを目的とした溶融状態未満の熱処理をおこなう。接点部では、溶融しためっき材料の表面張力による形状変化はむしろ利点として作用するので、一旦めっき層を溶融させて内部応力の除去を完璧にできるリフロー処理をおこなう。
<Discussion 2>
The present inventor has come up with an invention of an effective and rational plating layer and a method for forming the same for suppressing the generation and growth of whiskers through the above-described consideration and several confirmation experiments. The present invention is the first step: the lead portion requiring plating thickness is coated with a thicker plating, and the plating thickness is not required as much as the lead portion, but rather the effect of suppressing whisker caused by external stress needs to be emphasized. Some contacts are plated thinly. At this time, the plating thickness difference between the lead portion and the contact portion is 150 to 370% of the plating thickness of the contact portion. Preferably it is 150 to 230%. If the plating thickness difference is too small, it is difficult to control the high-temperature treatment conditions. If the plating thickness difference is too large, the functions of the contact portion and the lead portion may not be sufficiently exhibited. Second step: High-temperature treatment is performed after the plating layer is formed. At this time, the highest temperature reached by the plating layer is primarily to ensure solderability at the lead part. Perform heat treatment below the molten state for the purpose of being able to be achieved. In the contact portion, the shape change due to the surface tension of the molten plating material acts rather as an advantage. Therefore, the reflow process is performed to completely remove the internal stress by once melting the plating layer.
〈接点部〉
接点部のめっき層は、リフロー処理によって内部応力が十分に除去されており、一度融解を経験したことで、コンタクトピンの四隅及び先端のテーパ部のめっき層は、表面張力によって腹部に引き込まれる。その結果、四隅及びテーパ部では薄く、腹部ではそれに比して厚くめっきが皮膜されている。接点部では、相対するコンタクトピンと嵌合したときに、外部応力を起因とするウイスカの発生及び成長を抑制することが重要である。この点について、（１）もともとのめっき層が薄いので、ウイスカを構成する錫原子の供給量が絶対的に少ない。（２）リフロー処理がなされているので内部応力が十分に除去されている。外部応力に起因するウイスカの発生を抑制するためにも、内部応力の除去は完全におこなわれていることが望ましいものと考えられる。（３）外部応力が集中してウイスカの発生しやすいコーナー部のめっき層が特に薄くなっている。これらの作用が相互に関連することで、接点部では、外部応力に起因するウイスカの発生は、最大限抑制されているものである。
<Contact part>
The internal stress of the plating layer at the contact portion is sufficiently removed by the reflow process, and the plating layer at the four corners and the tapered portion of the tip of the contact pin is drawn into the abdomen by the surface tension by experiencing melting once. As a result, the plating is thin at the four corners and the tapered portion, and thicker at the abdominal portion. In the contact portion, it is important to suppress the generation and growth of whiskers due to external stress when mated with opposing contact pins. (1) Since the original plating layer is thin, the supply amount of tin atoms constituting the whisker is absolutely small. (2) Since the reflow process is performed, the internal stress is sufficiently removed. In order to suppress the generation of whiskers due to external stress, it is considered desirable to completely remove internal stress. (3) The plating layer in the corner portion where external stress concentrates and whisker is likely to occur is particularly thin. Since these actions are related to each other, the generation of whiskers due to external stress is suppressed to the maximum at the contact portion.
〈リード部〉
一方リード部のめっき層は、熱処理によって内部応力の除去がなされている。このとき、リフロー処理によるほど内部応力の除去はなされていない。しかし回路基板に実装されたときから、リード部には外部応力の集中は生じないので、接点部ほどの内部応力の除去は必要でない。むしろこの部分は、回路基板との接続が確実になされることに機能上最も重点を置くべきところである。したがって、めっき層が形成された当初の表面の平坦性が損なわれないことを重視すべきである。
<Lead part>
On the other hand, the internal stress is removed from the plating layer of the lead portion by heat treatment. At this time, the internal stress has not been removed as much as the reflow process. However, since the external stress is not concentrated on the lead portion after being mounted on the circuit board, it is not necessary to remove the internal stress as much as the contact portion. Rather, this part should place the greatest emphasis on functionality to ensure connection with the circuit board. Therefore, it should be emphasized that the flatness of the original surface on which the plating layer is formed is not impaired.
〈温度プロファイル〉
上述したように本発明は、要求される機能が相違するリード部と、接点部とにそれぞれの機能を奏するのに適しためっき仕様を創り出すところに特徴がある。それぞれのめっき仕様を創出するための高温処理条件は、次の如くである。すなわち接点部と、リード部とのめっき厚みの差を利用する。この厚み差から生じる、めっきの必要融解熱量の差を利用するのである。両者は母材を共通にして、接点部のめっき層は薄くリード部のめっき層は厚いことから、接点部はリード部に比べて必要融解熱量が小さいことがわかる。このような状態で、めっき層を昇温して温度と、処理時間とを制御することによって、接点部のめっき層は融解するが、リード部のめっき層は融解しない状態を創り出すことができる。この状態を創り出すことによってそれぞれの部分の機能に適しためっき仕様を具えたコンタクトピンを得ることが本発明の特徴部分である。
<Temperature profile>
As described above, the present invention is characterized in that plating specifications suitable for performing the respective functions for the lead portion and the contact portion having different required functions are created. The high temperature processing conditions for creating each plating specification are as follows. That is, the difference in plating thickness between the contact portion and the lead portion is used. The difference in the amount of heat of fusion required for plating, which arises from this thickness difference, is used. Since both have a common base material and the plating layer of the contact portion is thin and the plating layer of the lead portion is thick, it can be seen that the contact portion requires less heat of fusion than the lead portion. In such a state, by heating the plating layer and controlling the temperature and processing time, it is possible to create a state in which the plating layer in the contact portion melts but the plating layer in the lead portion does not melt. It is a characteristic part of the present invention to obtain a contact pin having a plating specification suitable for the function of each part by creating this state.
本発明は、上述したようにめっき行程及び高温処理工程を経ることで、以下のウイスカの発生及び成長を抑制するめっき層及びその形成方法を提供するものである。
（１）基板実装用コネクタの接続端子に形成された錫又は錫合金のめっき層であって、前記接続端子は実装側及び嵌合側を備え、前記実装側のめっき層は前記嵌合側のめっき層と同じ錫又は錫合金からなり、前記実装側のめっき層は前記嵌合側のめっき層の１５０〜３７０％の厚みを備え、前記実装側のめっき層は前記嵌合側のめっき層と同時に高温処理を受け、前記嵌合側のめっき層は前記高温処理で溶融し、前記実装側のめっき層は前記高温処理で溶融しないところに特徴を有するめっき層。
（２）請求項１記載のめっき層を備えたコネクタ。
（３）基板実装用コネクタの接続端子に錫又は錫合金のめっき層を形成する方法であって、前記接続端子は実装側及び嵌合側を備え、前記嵌合側のめっき層を形成するステップ１Ａと、前記実装側のめっき層を形成するステップ１Ｂと、前記嵌合側及び前記実装側のめっき層を同時に高温処理するステップ２とを備え、前記実装側のめっき層は前記嵌合側のめっき層の１５０〜３７０％の厚みを備え、前記嵌合側のめっき層は前記高温処理で溶融し、前記実装側のめっき層は前記高温処理で溶融しないところに特徴を有するめっき層の形成方法。
The present invention provides a plating layer that suppresses generation and growth of the following whiskers and a method for forming the same by going through a plating step and a high-temperature treatment step as described above.
(1) A tin or tin alloy plating layer formed on a connection terminal of a board mounting connector, wherein the connection terminal includes a mounting side and a fitting side, and the mounting side plating layer is provided on the fitting side. It is made of the same tin or tin alloy as the plating layer, the mounting-side plating layer has a thickness of 150 to 370% of the fitting-side plating layer, and the mounting-side plating layer includes the fitting-side plating layer. The plating layer is characterized in that it is subjected to high-temperature treatment at the same time, the fitting-side plating layer is melted by the high-temperature treatment, and the mounting-side plating layer is not melted by the high-temperature treatment .
(2) A connector comprising the plating layer according to claim 1.
(3) A method of forming a tin or tin alloy plating layer on a connection terminal of a board mounting connector, wherein the connection terminal includes a mounting side and a fitting side, and the step of forming the fitting side plating layer 1A, Step 1B for forming the mounting-side plating layer, and Step 2 for simultaneously treating the fitting-side and the mounting-side plating layers at a high temperature, and the mounting-side plating layer on the fitting-side A method for forming a plating layer having a thickness of 150 to 370% of the plating layer, wherein the fitting-side plating layer is melted by the high-temperature treatment, and the mounting-side plating layer is not melted by the high-temperature treatment .
コンタクトピンのリード部と、接点部とのめっき状態に差を設けることによって、基板実装時に必要なはんだ性を損なうことなく、錫又は錫合金からなるめっき層のウイスカの発生及び成長を抑制することができる。 Suppressing the occurrence and growth of whiskers in the plating layer made of tin or tin alloy without impairing the solderability required when mounting on the board by providing a difference in the plating state between the lead portion of the contact pin and the contact portion Can do.
本発明を実施するための最良の形態について説明をおこなう。本発明はコンタクトピンの実装側の端部と、嵌合側の端部とのめっき層の状態をそれぞれの機能を奏するのに適しためっき仕様とすることで、上述した目的を達成するものである。具体的には実装側及び嵌合側のめっき厚みと、高温処理によるめっき層の改質の内容とを変えることで、それぞれの機能に適しためっき仕様を得ることである。なお特許請求の範囲で用いる「接続端子」は明細書で用いる「コンタクトピン」を含み、「嵌合側」は「接点部」を含み、「実装側」は「リード部」を含む。また、「無鉛はんだ」は「鉛を含まないはんだ」を意味する。 The best mode for carrying out the present invention will be described. The present invention achieves the above-described object by setting the plating layer state of the contact pin mounting end and the fitting end to a plating specification suitable for each function. is there. Specifically, the plating specifications suitable for the respective functions are obtained by changing the plating thickness on the mounting side and the fitting side and the content of the modification of the plating layer by high-temperature treatment. The “connection terminal” used in the claims includes a “ contact pin” used in the specification, the “fitting side” includes a “contact portion” , and the “mounting side” includes a “lead portion” . “Lead-free solder” means “solder that does not contain lead”.
〈コンタクトピン〉
図１の（Ａ）はＦＰＣ（Ｆｌｅｘｉｂｌｅ Ｐｒｉｎｔ Ｃｉｒｃｕｉｔ）コネクタの外観斜視図である。また図１の（Ｂ）はＦＰＣ用コネクタのコンタクトピンの外観斜視図である。ＦＰＣ用コネクタ１００は絶縁性のハウジング１０と、ハウジング１０の側面に係止する複数個のコンタクトピン２０とからなる。コンタクトピン２０はハウジング１０内に収まって、ＦＰＣ３０の端部に具わる接続部３１を挟持する接点部２０Ｓと、回路基板４０の接続部４１に、はんだによって固着されるリード部２０Ｌと、からなる。
<Contact pin>
FIG. 1A is an external perspective view of an FPC (Flexible Print Circuit) connector. FIG. 1B is an external perspective view of contact pins of the FPC connector. The FPC connector 100 includes an insulating housing 10 and a plurality of contact pins 20 that are engaged with the side surfaces of the housing 10. The contact pin 20 is housed in the housing 10 and includes a contact portion 20S that sandwiches the connection portion 31 provided at the end of the FPC 30, and a lead portion 20L that is fixed to the connection portion 41 of the circuit board 40 by solder. .
コンタクトピン２０は導電性と、バネ性とを兼ね具えており、比較的廉価な銅合金を所定形状に加工したものである。表面には、これから詳しく説明するようにめっきが皮膜されている。 The contact pin 20 has both conductivity and spring property, and is formed by processing a relatively inexpensive copper alloy into a predetermined shape. The surface is coated with plating as will be described in detail.
〈コネクタ〉
図２の（Ａ）は回路基板に実装されたＦＰＣ用コネクタの外観斜視図である。図２の（Ｂ）はＦＰＣの接続部を挟持している接点部の拡大斜視図である。図２の（Ｃ）は回路基板の接続部と、はんだで固着しているリード部との拡大斜視図である。表面実装用ＦＰＣコネクタ１００はハウジング１０の下面を回路基板４０に固定して、上面に位置する開口部でＦＰＣ３０を受け入れる。
<connector>
FIG. 2A is an external perspective view of an FPC connector mounted on a circuit board. FIG. 2B is an enlarged perspective view of the contact portion holding the connection portion of the FPC. FIG. 2C is an enlarged perspective view of the connection portion of the circuit board and the lead portion fixed with solder. The surface mount FPC connector 100 fixes the lower surface of the housing 10 to the circuit board 40 and receives the FPC 30 through an opening located on the upper surface.
〈接点部〉
接点部２０Ｓは、ＦＰＣ３０の先端の差込部３２に形成された露出状態の接続部３１を挟持することで電気的機械的接続をとるところである。接点部２０Ｓは、挟ピッチで並置されていて嵌合による圧縮応力の集中が生じるために、ウイスカが極めて発生しやすい。また接続は機械的方法をとるので、めっきはリード部２０Ｌほどの厚みはいらない。また、リード部２０Ｌほどの表面の平坦性は要求されない。
<Contact part>
The contact portion 20 </ b> S is an electromechanical connection by sandwiching the exposed connection portion 31 formed in the insertion portion 32 at the tip of the FPC 30. Since the contact portions 20S are juxtaposed at a narrow pitch and the concentration of compressive stress due to fitting occurs, whiskers are very likely to occur. Further, since the connection is a mechanical method, the plating does not need to be as thick as the lead portion 20L. Further, the flatness of the surface as much as the lead portion 20L is not required.
〈リード部〉
リード部２０Ｌは回路基板４０の端部に形成された接続部４１と、はんだ固着によって電気的機械的接続をとるところである。リード部２０Ｌは挟ピッチで並列するが、はんだ固着後に外部から圧縮応力が加わることはなく、内部応力が除去されていればウイスカの発生するおそれは極めて小さい。また、はんだ固着方法をとるので、濡れ性を確保して良好な接続形状をとるために平坦で十分なめっき層の厚みが望ましい所である。
<Lead part>
The lead portion 20L is where an electromechanical connection is established with a connection portion 41 formed at the end of the circuit board 40 by soldering. The lead portions 20L are arranged in parallel at a narrow pitch, but no compressive stress is applied from the outside after the solder is fixed, and if the internal stress is removed, the possibility of whisker generation is very small. Further, since the solder fixing method is employed, a flat and sufficient plating layer thickness is desirable in order to ensure wettability and obtain a good connection shape.
〈めっき工程〉
ここで図３にしたがって、めっき工程の説明をおこなう。図３の（Ａ）は、めっき工程のフローチャートである。図３の（Ｂ）は、めっき液浸漬条件である。めっき液浸漬条件に２段階あるが、これは接点部２０Ｓと、リード部２０Ｌとのめっき液浸漬条件が異なるからである。なお本発明の実施の形態では、めっき材料として錫１００％を使用した。融点は２３２℃で融解熱は７．０７ＫＪ（キロジュール）／ｍｏｌである。
<Plating process>
Here, the plating process will be described with reference to FIG. FIG. 3A is a flowchart of the plating process. FIG. 3B shows the plating solution immersion conditions. There are two stages in the plating solution immersion conditions because the plating solution immersion conditions for the contact portion 20S and the lead portion 20L are different. In the embodiment of the present invention, 100% tin is used as the plating material. The melting point is 232 ° C. and the heat of fusion is 7.07 KJ (kilojoules) / mol.
〈めっき工程 洗浄〉
めっき工程のフローチャートは、（１）洗浄→（２）１槽目浸漬→（３）２層目浸漬→（４）洗浄→（５）乾燥である。最初の洗浄は被めっき部の異物や油脂分を取り除くために行なう。洗浄液はユケン社製のパクナを所定の濃度に薄めたアルカリ脱脂溶液を用いる。この溶液を加熱して、４０〜６０℃で使用する。洗浄時間は０．１〜０．２分である。
<Plating process cleaning>
The flowchart of the plating process is (1) cleaning → (2) first bath immersion → (3) second layer immersion → (4) cleaning → (5) drying. The first cleaning is performed to remove foreign matters and oils and fats from the plated part. As the cleaning solution, an alkaline degreasing solution obtained by diluting Yuken Pakuna to a predetermined concentration is used. The solution is heated and used at 40-60 ° C. The washing time is 0.1 to 0.2 minutes.
〈めっき工程 めっき液浸漬〉
めっき層の形成は２段階でおこなう。接点部２０Ｓのめっきは薄く、リード部２０Ｌのめっきは厚く被膜するためである。めっき層の厚みは、接点部２０Ｓでは、１．０〜２．０μ、好ましくは、１．３〜２．０μ、より好ましくは、１・５〜２．０μである。リード部２０Ｌでは、３．０〜５．０μ、好ましくは、３．０〜４．０μ、より好ましくは、３．０〜３．５μである。どちらのめっきを先におこなってもよいが、厚めのめっき層の形成（リード部２０Ｌ）から先におこなうのが合理的である（図３の（Ｂ）の１槽目）。このときリード部２０Ｌ側を下向きにして所定の位置までめっき液に浸漬する（１槽目）。リード部２０Ｌに所定厚みのめっきが皮膜されたならば、１槽目のめっき液浸漬は終了である。次にコンタクトピン２０全体をめっき液に浸漬して（図３の（Ｂ）の２層目）、コンタクトピン２０全体のめっき処理をおこなう（２層目）。接点部２０Ｓ及びリード部２０Ｌに所定厚みのめっきを形成して２層目のめっき液浸漬を終了する。
<Plating process plating solution immersion>
The plating layer is formed in two stages. This is because the contact portion 20S is thin and the lead portion 20L is thick. The thickness of the plating layer is 1.0 to 2.0 μ, preferably 1.3 to 2.0 μ, and more preferably 1.5 to 2.0 μ in the contact portion 20S. In the lead part 20L, it is 3.0-5.0micro, Preferably, it is 3.0-4.0micro, More preferably, it is 3.0-3.5micro. Either plating may be performed first, but it is reasonable to perform the plating first from the formation of the thick plating layer (lead portion 20L) (first tank in FIG. 3B). At this time, the lead portion 20L side is directed downward and immersed in the plating solution up to a predetermined position (first tank). If the lead portion 20L is plated with a predetermined thickness, the plating bath immersion in the first tank is completed. Next, the entire contact pin 20 is immersed in a plating solution (second layer in FIG. 3B), and the entire contact pin 20 is plated (second layer). A predetermined thickness of plating is formed on the contact portion 20S and the lead portion 20L, and the second layer of plating solution immersion is completed.
〈めっき工程 陰極電流密度〉
１層目浸漬の陰極電流密度は、下地金属との組織的整合性をとるために急激な電圧の印加は避けなければならず、所定陰極電流密度まで徐々にあげていくのが望ましい。ここで所定陰極電流密度は、１０〜２５Ａ／ｄｍ２である。好ましくは、１０〜２０Ａ／ｄｍ２で、より好ましくは、１５〜２０Ａ／ｄｍ２である。印加時間は、電流密度が１０〜２０Ａ／ｄｍ２のときは、０．１５〜０．２５分であり、１５〜２０Ａ／ｄｍ２のときは、０．１〜０．２分である。
<Plating process cathode current density>
The cathode current density of the first layer immersion should avoid sudden application of voltage in order to achieve systematic consistency with the underlying metal, and is preferably gradually increased to a predetermined cathode current density. Here, the predetermined cathode current density is 10 to 25 A / dm2. Preferably, it is 10-20A / dm2, More preferably, it is 15-20A / dm2. The application time is 0.15 to 0.25 minutes when the current density is 10 to 20 A / dm2, and 0.1 to 0.2 minutes when the current density is 15 to 20 A / dm2.
〈めっき工程 洗浄〉
１槽目浸漬及び２層目浸漬のめっき液浸漬工程によって、接点部２０Ｓ及びリード部２０Ｌに予定のめっき層を形成したならば次に、めっき層表面の洗浄をおこなう。洗浄は伝導度５〜２０μｓの純水浴中でおこなう。水温は５５〜６５℃で０．１〜０．２分間おこなうのが望ましい。
<Plating process cleaning>
If the predetermined plating layer is formed on the contact part 20S and the lead part 20L by the plating solution immersion process of the first tank immersion and the second layer immersion, the plating layer surface is then cleaned. Washing is performed in a pure water bath having a conductivity of 5 to 20 μs. The water temperature is preferably 55 to 65 ° C. for 0.1 to 0.2 minutes.
〈めっき工程 洗浄〉
１槽目浸漬及び２層目浸漬のめっき液浸漬工程によって、接点部２０Ｓ及びリード部２０Ｌに予定のめっき層を形成したならば次に、めっき層表面の洗浄をおこなう。洗浄は伝道度５〜２０μｓの純水浴中でおこなう。水温は５５〜６５℃で０．１〜０．２分間おこなうのが望ましい。
<Plating process cleaning>
If the predetermined plating layer is formed on the contact part 20S and the lead part 20L by the plating solution immersion process of the first tank immersion and the second layer immersion, the plating layer surface is then cleaned. Washing is performed in a pure water bath having a mission of 5 to 20 μs. The water temperature is preferably 55 to 65 ° C. for 0.1 to 0.2 minutes.
〈めっき工程 乾燥〉
めっき層表面の洗浄を終えたならば、次に表面に付着している水滴の除去をおこなう。水滴の除去は乾燥炉でおこなう。乾燥炉の方式は熱風循環型で、乾燥の条件は炉内温度７０〜１００℃で０．１〜０．２分であるのが望ましい。
<Drying process drying>
After cleaning the plating layer surface, the water droplets adhering to the surface are then removed. Remove water droplets in a drying oven. The drying furnace is of a hot air circulation type, and the drying conditions are desirably 0.1 to 0.2 minutes at a furnace temperature of 70 to 100 ° C.
〈めっき層の状態〉
次に図４にしたがって、めっき層の状態について詳細に説明をおこなう。図４はめっき液浸漬処理後のコンタクトピンのめっき層の状態を示す図である。上段は接点部の断面拡大図である。下段はリード部の断面拡大図である。
<State of plating layer>
Next, according to FIG. 4, the state of the plating layer will be described in detail. FIG. 4 is a diagram showing the state of the plating layer of the contact pin after the plating solution immersion treatment. The upper part is an enlarged cross-sectional view of the contact part. The lower part is an enlarged cross-sectional view of the lead part.
コンタクトピン２０は全体が錫めっきされている。接点部２０Ｓは２層目浸漬だけなのでめっき層はリード部２０Ｌに比べて薄く（図４の上段）、リード部２０Ｌは１槽目浸漬及び２層目浸漬をおこなっているので接点部２０Ｓに比べてめっきは厚めに形成されている（図４の下段）。 The contact pin 20 is entirely tin-plated. Since the contact portion 20S is only immersed in the second layer, the plating layer is thinner than the lead portion 20L (upper stage in FIG. 4), and the lead portion 20L is immersed in the first tank and the second layer, so it is compared with the contact portion 20S. The plating is formed thicker (lower part of FIG. 4).
この段階でリード部２０Ｌのめっきが厚すぎる場合には、隣接リード部２０Ｌとの短絡のおそれが生じる。めっき層が薄すぎる場合には、はんだによる回路基板４０への実装の際、適切な接続がなされないおそれがあるので留意を要する。 At this stage, if the plating of the lead portion 20L is too thick, there is a risk of short circuit with the adjacent lead portion 20L. When the plating layer is too thin, it is necessary to pay attention because proper connection may not be made when mounting on the circuit board 40 with solder.
この段階でリード部２０Ｌのめっきが厚すぎる場合には、隣接リード部２０Ｌとの短絡のおそれが生じる。めっき層が薄すぎる場合には、はんだによる回路基板への実装の際、適切な接続がなされないおそれがあるので留意を要する。 At this stage, if the plating of the lead portion 20L is too thick, there is a risk of short circuit with the adjacent lead portion 20L. When the plating layer is too thin, attention must be paid because proper connection may not be made when mounting on the circuit board with solder.
〈高温処理〉
次に図５にしたがって高温処理条件について詳細に説明をおこなう。図５は温度プロファイルを示す図である。図５の（Ａ）は熱処理条件の温度プロファイルである。図５の（Ｂ）はリフロー条件の温度プロファイルである。なおここで温度プロファイルは課題部位の温度プロファイルである。
<High temperature treatment>
Next, the high temperature processing conditions will be described in detail with reference to FIG. FIG. 5 is a diagram showing a temperature profile. FIG. 5A shows a temperature profile of the heat treatment conditions. FIG. 5B shows a temperature profile under reflow conditions. Here, the temperature profile is a temperature profile of the subject part.
本実施の形態の場合では、接点部２０Ｓのめっき層の全重量Ｗｓと、リード部２０Ｌのめっき層の全重量Ｗｌとの間に生じている重量差ｄＷ（ｄＷ＝Ｗｌ−Ｗｓ＞０）を利用することによって、同じ高温条件でも接点部２０Ｓでは熱処理条件となり、リード部２０Ｌではリフロー条件となるような相違した条件を創り出すところに本発明の特徴部分がある。なお、この節で用いる重量及び熱量は、単位面積当たりのものである。 In the case of the present embodiment, the weight difference dW (dW = Wl−Ws> 0) generated between the total weight Ws of the plating layer of the contact portion 20S and the total weight Wl of the plating layer of the lead portion 20L. By using this, a characteristic feature of the present invention is that a different condition is created such that the contact portion 20S becomes a heat treatment condition and the lead portion 20L becomes a reflow condition even under the same high temperature condition. The weight and heat used in this section are per unit area.
接点部２０Ｓに形成されためっき層の全重量Ｗｓを溶融するために必要な熱量をＱｓとし、リード部２０Ｌに形成されためっき層の全重量Ｗｌを溶融するために必要な熱量をＱｌとすれば、
Ｑｓ＝Ｗｓ×ｄＱａ
Ｑｌ＝Ｗｌ×ｄＱｂと表わされる。
ここでｄＱａ及びｄＱｂは比熱容量であって両者は同一金属であるから同じ値をとる。
すなわち、ｄＱａ＝ｄＱｂである。
また、Ｗｌ−Ｗｓ＞０であるから、
Ｑｌ−Ｑｓ＞０であることがわかる。
Let Qs be the amount of heat necessary to melt the total weight Ws of the plating layer formed on the contact portion 20S, and Ql be the amount of heat necessary to melt the total weight Wl of the plating layer formed on the lead portion 20L. If
Qs = Ws × dQa
Ql = Wl × dQb.
Here, dQa and dQb are specific heat capacities, and both have the same value because they are the same metal.
That is, dQa = dQb.
Also, since W1−Ws> 0,
It can be seen that Ql−Qs> 0.
すなわち、リード部２０Ｌのめっきを完全に溶融させるために必要な熱量Ｑｌは、接点部２０Ｓのめっきを完全に溶融させるために必要な熱量Ｑｓに比べて、その値は重量差に相当した分大きく、ＤＱ＝Ｑｌ−Ｑｓ＞０の関係がある。この両者に熱量の差ＤＱが生じていることを利用して接点部２０Ｓのめっき層は溶融するが、リード部２０Ｌのめっき層は溶融しない状態を創り出すところが本発明の特徴部分である。 That is, the amount of heat Ql required to completely melt the plating of the lead portion 20L is larger than the amount of heat Qs necessary to completely melt the plating of the contact portion 20S by an amount corresponding to the weight difference. , DQ = Q1-Qs> 0. The feature of the present invention is that the plating layer of the contact portion 20S is melted by utilizing the difference in heat quantity DQ between the two, but the plating layer of the lead portion 20L is not melted.
ここで、本実施の形態では、両者の熱量の差ＤＱは、５〜２５ｃａｌである。好ましくは、１０〜２０ｃａｌである。さらに好ましくは、１４〜１７ｃａｌである。熱量の差ＤＱはある程度大きい値であることが目的に応じた高温処理を的確におこなう上で好ましい。小さすぎる場合には、高温処理時の制御が大変精度を要することとなる。 Here, in this Embodiment, the difference DQ of both calorie | heat amount is 5-25cal. Preferably, it is 10-20 cal. More preferably, it is 14-17 cal. It is preferable that the difference in heat quantity DQ is a certain large value in order to accurately perform the high-temperature treatment according to the purpose. If it is too small, control at the time of high-temperature processing requires very high accuracy.
〈熱処理 リード部〉
熱処理では、リード部２０Ｌのめっき層はその溶融温度に達しないので融解することなく熱処理前の形状を保っている。その温度プロファイルは図５の（Ａ）に示すように両端になだらかな裾野をもった山形である。山形の頂点であるリード部２０Ｌが到達する最高温度は、めっき材料である錫の溶融温度である２３２℃よりも低い温度の２００℃付近である。熱処理時間は０．２分で、その内最高温度付近にさらされる時間は０・１分である。
<Heat treatment lead part>
In the heat treatment, since the plating layer of the lead portion 20L does not reach the melting temperature, the shape before the heat treatment is maintained without melting. The temperature profile is a mountain shape with gentle skirts at both ends as shown in FIG. The maximum temperature reached by the lead portion 20L, which is the apex of the chevron, is around 200 ° C., which is lower than 232 ° C., which is the melting temperature of tin, which is the plating material. The heat treatment time is 0.2 minutes, and the time of exposure to the vicinity of the maximum temperature is 0.1 minute.
リード部２０Ｌのめっき層は、このように自身を形成するめっき材料の重量Ｗｌを融解させるために必要な熱量Ｑｌに対して、高温処理で受け取る熱量Ｑａが自身を融解させるために必要な熱量Ｑｌには足らないために、めっき層は溶融しない。その結果めっき層は、めっき層形成時の平坦な表面を保ちつつ、一方で溶融温度付近まで昇温されているので、めっき層形成時に生じた内部応力の除去は十分になされている。 The plating layer of the lead portion 20L has a heat quantity Ql necessary for melting the heat quantity Qa received by the high-temperature treatment with respect to the heat quantity Ql necessary for melting the weight Wl of the plating material forming itself. Therefore, the plating layer does not melt. As a result, the plating layer is heated to the vicinity of the melting temperature while maintaining a flat surface during the formation of the plating layer, so that internal stress generated during the formation of the plating layer is sufficiently removed.
〈リフロー処理 接点部〉
リフロー条件では、接点部２０Ｓのめっき層はその溶融温度以上に達して融解し、リフロー前後の形状は変化する。その温度プロファイルは図５の（Ｂ）に示すように両端に裾野をもった山形であるところは前記の熱処理の場合と同じであるが、被処理物の最高到達温度が熱処理の場合に比べて高いところに特徴がある。接点部２０Ｓが到達する最高温度は、めっき材料である錫の溶融温度である２３２℃よりも高く２４０〜３５０℃である。リフロー処理時間は、０．１〜０．２分で、その内最高温度付近にさらされる時間は、０．０５〜０．１分である。
<Reflow treatment contact part>
Under the reflow conditions, the plating layer of the contact portion 20S reaches the melting temperature or higher and melts, and the shape before and after the reflow changes. As shown in FIG. 5B, the temperature profile is the same as that in the case of the heat treatment described above, but the peak temperature of the workpiece is higher than that in the case of the heat treatment. It is characterized by high places. The maximum temperature reached by the contact portion 20S is 240 to 350 ° C., which is higher than 232 ° C. which is the melting temperature of tin as a plating material. The reflow treatment time is 0.1 to 0.2 minutes, and the time of exposure to the vicinity of the maximum temperature is 0.05 to 0.1 minutes.
接点部２０Ｓのめっき層は薄くその重量Ｗｓは，上述したリード部２０Ｌのそれに比べて小さい。リフロー処理によって受け取る熱量Ｑａは自身を融解させるために必要な熱量Ｑｓを越えており、処理中に接点部２０Ｓのめっき層は一度溶融することとなる。その結果めっき層の形成によって内部に蓄積された残留応力は除去されて、ほぼ完璧な改質がなされている。一方その表面は一度溶融したものが再度固化したものなので、リフロー処理前の一様平坦な形状とは相違している。 The plating layer of the contact portion 20S is thin, and its weight Ws is smaller than that of the lead portion 20L described above. The amount of heat Qa received by the reflow process exceeds the amount of heat Qs necessary for melting itself, and the plating layer of the contact portion 20S is once melted during the process. As a result, the residual stress accumulated inside by the formation of the plating layer is removed, and almost perfect modification is made. On the other hand, since the surface once melted is solidified again, it is different from the uniform flat shape before the reflow treatment.
〈めっき層の状態〉
次に図６にしたがって、熱処理若しくはリフロー処理によって形成されためっき層の状態について詳細に説明をおこなう。図６はめっき処理及び高温処理をおこなったコンタクトピンのめっき層の状態を示す写真である。上段はリフロー処理をおこなった接点部２０Ｓの断面拡大写真である。下段は熱処理をおこなったリード部２０Ｌの断面拡大写真である。
<State of plating layer>
Next, according to FIG. 6, the state of the plating layer formed by heat treatment or reflow treatment will be described in detail. FIG. 6 is a photograph showing the state of the plating layer of the contact pin that has been subjected to the plating treatment and the high temperature treatment. The upper row is an enlarged cross-sectional photograph of the contact portion 20S that has undergone reflow processing. The lower row is an enlarged cross-sectional photograph of the lead portion 20L that has been heat-treated.
〈接点部〉
接点部２０Ｓのめっき層は、全体的に薄めであるが、四隅で特に薄く腹部でやや盛り上がっているのが特徴である。これはリフロー処理で一度溶融しためっきが再度固化する際に表面張力によって隅部のめっき材料が腹部に引っ張られた結果である。前述したようにウイスカは錫の単結晶から成るもので、結晶の芽の発生や芽の成長のスピードを制御する条件として錫原子の供給量の多寡が当然影響するものであるから、めっきの絶対量が少ない上に、外部応力が集中してその芽が発生しやすい隅部のめっきの厚みが極めて薄い状態の接点部２０Ｓは、ウイスカの発生及び成長の根本的要因を取り除けている。また融点以上のリフロー処理を経ているので、ウイスカの成長の駆動力である内部応力が十分に除去されている。すなわち接点部２０Ｓは接触信頼性を損なうことなくウイスカの発生及び成長に対して十分にその抑制対策がとられている。
<Contact part>
The plating layer of the contact portion 20S is thin overall, but is characterized by being particularly thin at the four corners and slightly rising at the abdomen. This is a result of the plating material at the corners being pulled to the abdomen by the surface tension when the plating once melted by the reflow process is solidified again. As mentioned above, whiskers are composed of a single crystal of tin, and since the amount of tin atoms supplied naturally affects the rate of crystal bud generation and bud growth speed, the absolute value of plating In addition to the small amount, the contact portion 20S in which the thickness of the plating at the corner portion where external stress is concentrated and the bud is likely to be generated is extremely thin, eliminates the fundamental factor of whisker generation and growth. In addition, since the reflow treatment is performed at a temperature equal to or higher than the melting point, internal stress that is a driving force for whisker growth is sufficiently removed. In other words, the contact portion 20S has a sufficient countermeasure against the occurrence and growth of whiskers without impairing the contact reliability.
図２の（Ｂ）に示したように、接点部２０ＳはＦＰＣ３０の接続部３１を挟持して電気的機械的に接続するところである。このとき接点部２０Ｓには、外部からの圧縮応力が継続して加わり、ウイスカが発生しやすく、挟ピッチで並列していることもあってウイスカによる問題が生じやすいところである。本発明の実施の形態に係る接点部２０Ｓは、ウイスカの発生原因のひとつひとつに対策を講じたものであって、ウイスカの発生及び成長を効果的に抑制しうるものであることが解る。 As shown in FIG. 2B, the contact portion 20 </ b> S is where the connection portion 31 of the FPC 30 is sandwiched and is electrically and mechanically connected. At this time, compressive stress from the outside is continuously applied to the contact portion 20S, so that whiskers are likely to be generated. It can be understood that the contact portion 20S according to the embodiment of the present invention is a countermeasure for each cause of whisker generation, and can effectively suppress the generation and growth of whiskers.
〈リード部〉
リード部２０Ｌのめっき層は、コンタクトピン２０の外周面に沿って一様にほぼ均一な厚みを具えている。四面の腹部のみならず四隅にも十分な量のめっき層が皮膜されている。また、結晶内部に蓄積されていた内部応力も熱処理によって除去されている。
<Lead part>
The plating layer of the lead portion 20 </ b> L has a substantially uniform thickness uniformly along the outer peripheral surface of the contact pin 20. A sufficient amount of plating layer is coated not only on the four abdomen but also on the four corners. Further, the internal stress accumulated in the crystal is also removed by the heat treatment.
図２の（Ｃ）に示すようにリード部２０Ｌは回路基板４０の接続部４１に、はんだで固着されるところである。接続部４１も表面は、めっきされており、両者の固着は、はんだの溶融を介しておこり、その濡れ性によって信頼性を担保している。はんだの濡れ性を確保するために、リード部２０Ｌの表面はめっきが厚めに皮膜されていることが望ましく、はんだ固着を一様に安定的におこなうためには、両者は広い範囲で接触することが望ましい。本実施の形態では、これらの条件を充足していて十分に望ましい状態が実現されていることが解る。 As shown in FIG. 2C, the lead portion 20L is fixed to the connection portion 41 of the circuit board 40 with solder. The surface of the connection part 41 is also plated, and the fixation of both occurs through melting of the solder, and the reliability is ensured by the wettability. In order to ensure the wettability of the solder, it is desirable that the surface of the lead portion 20L is coated with a thick coating, and in order to uniformly and stably fix the solder, both of them should contact in a wide range. Is desirable. In the present embodiment, it can be seen that a sufficiently desirable state is realized by satisfying these conditions.
なお、本発明は上記実施形態に限定されるものではなく、その他この発明の要旨を逸脱しない範囲で種々の態様で実施可能である。上記実施形態では、めっき材料に錫を用いたが錫−銅、錫−銀、錫−ビスマス等の錫合金を用いてもよい。 In addition, this invention is not limited to the said embodiment, In addition, it can implement with a various aspect in the range which does not deviate from the summary of this invention. In the said embodiment, although tin was used for the plating material, you may use tin alloys, such as tin-copper, tin-silver, and tin-bismuth.
１０ ハウジング
２０ コンタクトピン
２０Ｓ 接点部
２０Ｌ リード部
３０ ＦＰＣ
３１ 接続部
３２ 差込部
４０ 回路基板
４１ 接続部
１００ コネクタ
10 Housing 20 Contact Pin 20S Contact Part 20L Lead Part 30 FPC
31 Connection 32 Insertion 40 Circuit Board 41 Connection 100 Connector
Claims (3)
前記接続端子は実装側及び嵌合側を備え、
前記実装側のめっき層は前記嵌合側のめっき層と同じ錫又は錫合金からなり、
前記実装側のめっき層は前記嵌合側のめっき層の１５０〜３７０％の厚みを備え、
前記実装側のめっき層は前記嵌合側のめっき層と同時に高温処理を受け、
前記嵌合側のめっき層は前記高温処理で溶融し、前記実装側のめっき層は前記高温処理で溶融しないところに特徴を有するめっき層。 A tin or tin alloy plating layer formed on a connection terminal of a board mounting connector,
The connection terminal includes a mounting side and a fitting side,
The mounting-side plating layer is made of the same tin or tin alloy as the fitting-side plating layer,
The mounting-side plating layer has a thickness of 150 to 370% of the fitting-side plating layer,
The mounting-side plating layer is subjected to a high-temperature treatment simultaneously with the fitting-side plating layer,
The plating layer is characterized in that the fitting-side plating layer is melted by the high-temperature treatment, and the mounting-side plating layer is not melted by the high-temperature treatment .
前記接続端子は実装側及び嵌合側を備え、
前記嵌合側のめっき層を形成するステップ１Ａと、
前記実装側のめっき層を形成するステップ１Ｂと、
前記嵌合側及び前記実装側のめっき層を同時に高温処理するステップ２とを備え、
前記実装側のめっき層は前記嵌合側のめっき層の１５０〜３７０％の厚みを備え、
前記嵌合側のめっき層は前記高温処理で溶融し、前記実装側のめっき層は前記高温処理で溶融しないところに特徴を有するめっき層の形成方法。 A method of forming a tin or tin alloy plating layer on a connection terminal of a board mounting connector,
The connection terminal includes a mounting side and a fitting side,
Step 1A for forming the fitting-side plating layer;
Step 1B for forming the mounting-side plating layer;
And step 2 of simultaneously processing the fitting side and the mounting side plating layer at a high temperature ,
The mounting-side plating layer has a thickness of 150 to 370% of the fitting-side plating layer,
The plating layer forming method characterized in that the fitting-side plating layer is melted by the high-temperature treatment, and the mounting-side plating layer is not melted by the high-temperature treatment.
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| JP4292122B2 (en) * | 2004-07-30 | 2009-07-08 | タイコエレクトロニクスアンプ株式会社 | Electrical connector |
| JP4320623B2 (en) * | 2004-08-04 | 2009-08-26 | オムロン株式会社 | Connector terminal |
| JP2006196323A (en) * | 2005-01-14 | 2006-07-27 | Takamatsu Mekki:Kk | Connection terminal and its manufacturing method |
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