JP4017088B2 - Solder paste - Google Patents
Solder paste Download PDFInfo
- Publication number
- JP4017088B2 JP4017088B2 JP22709597A JP22709597A JP4017088B2 JP 4017088 B2 JP4017088 B2 JP 4017088B2 JP 22709597 A JP22709597 A JP 22709597A JP 22709597 A JP22709597 A JP 22709597A JP 4017088 B2 JP4017088 B2 JP 4017088B2
- Authority
- JP
- Japan
- Prior art keywords
- zinc
- solder
- solder paste
- weight
- tin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/3457—Solder materials or compositions; Methods of application thereof
- H05K3/3485—Applying solder paste, slurry or powder
Landscapes
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は半田合金の粉末とフラックスとを混合してペースト状としたソルダペーストに関するものであって、特に亜鉛を含む半田合金を使用したソルダペーストの改良に関するものである。
【０００２】
【従来の技術】
従来一般に使用されているソルダペーストは、半田合金として錫−鉛系合金を使用したものが広く使用されている。しかしながら半田合金に含まれる鉛が毒性を有するため、鉛を含まない無鉛半田が検討されている。
【０００３】
特に錫−亜鉛系共晶合金は、従来の錫−鉛合金と融点が同等であり、また機械的強度やクリープ特性においても優れているため、無鉛半田を構成する合金として有望視されている。
【０００４】
【発明が解決しようとする課題】
しかしながら錫−亜鉛系半田合金においては、亜鉛のイオン化傾向が大きく反応性に富んでいるため、半田付けした状態において高温下に放置すると、半田中の亜鉛が基板の銅の表面に拡散して、銅−亜鉛金属間化合物（Ｃｕ5Ｚｎ8）を生成し、銅の表面に当該化合物の生成が進行する。
【０００５】
そのため時間の経過と共に前記半田中の亜鉛が減少してその箇所における半田組織が破壊され、亀裂が生じて強度が低下すると共に、当該半田と前記金属間化合物との間の強度差が大きくなり、接合強度が低下するのである。
【０００６】
従って錫−亜鉛系半田においては、半田付けの後に高温下に放置すると、半田と銅基板との間における前記金属間化合物層の形成が進行し、半田と銅との間の接合強度が経時的に低下するという問題が生じていたのである。
【０００７】
本発明はかかる事情に鑑みなされたものであって、錫−亜鉛系半田合金のソルダペーストにおいて、前記金属間化合物層の進行を抑制し、経時的な接合強度の低下を防止することを目的とするものである。
【０００８】
【課題を解決するための手段】
而して本発明は、錫８８〜９５重量％と亜鉛５〜１２重量％とを主体とする無鉛半田合金の粉末とフラックスとよりなるソルダペーストにおいて、ビスマス、インジウム又は銀の塩を添加したことを特徴とするものである。
【０００９】
本発明における前記半田合金は、錫−亜鉛共晶合金であることが好ましい。またソルダペーストに対する前記金属塩の量は、０．５重量％以上であり且つ、ソルダペースト中の亜鉛と同イオン当量以下とするのが好ましい。
【００１０】
本発明における半田合金としては、前述した錫−亜鉛共晶合金すなわち、錫９１．２％と亜鉛８．８％との合金が好ましい。さらに錫８８〜９５重量％と亜鉛５〜１２重量％とを主体として、これに２重量％以下のビスマス、インジウム、銅、銀、アンチモンなどを添加したものも適当である。またこれらの半田合金の粉末としては、粒径２０〜４０μｍ程度のものが適当である。
【００１２】
本発明におけるフラックスとしては、金属塩を添加することを除いて、通常のソルダペーストにおけるフラックスをそのまま使用することができる。例えばロジンに適量のワックス及び活性剤を添加し、溶剤に分散したものを使用することができる。
【００１３】
そして本発明においては、そのフラックスに金属塩を添加する。その金属塩を構成する金属は、ビスマス、インジウム、金、銀、銅、錫、アンチモン、ニッケル、コバルト又は白金が適当である。
【００１４】
これらの金属の有機酸塩及び無機酸塩を使用することができ、具体的には、塩化ビスマス、塩化インジウム、ロジン酸ビスマス、ロジン酸インジウム、ロジン酸銅、ロジン酸銀、ステアリン酸銅、クエン酸ビスマス、酢酸銀、２エチルヘキサン酸インジウムなどを挙げることができる。
【００１５】
これらの金属塩をフラックスに添加し、そのフラックスと半田合金の粉末とを混合してソルダペーストとする。半田合金とフラックスとの混合比率は、通常のソルダペーストと同程度であり、半田合金９２〜８０重量％に対し、フラックス８〜２０重量％程度が適当である。
【００１６】
本発明のソルダペーストにおける前記金属塩の添加量は、少なくとも０．５重量％以上添加するのが好ましい。０．５重量％未満では前記金属間化合物層の進行を抑制する効果が生じない。
【００１７】
また金属塩の最大量としては、当該金属塩中の金属が半田合金中の亜鉛と置換可能の量とするのがよい。すなわち、ソルダペースト中の亜鉛と同イオン当量以下とするのが好ましい。金属塩の量がこれを超えると、金属塩中の金属と亜鉛との置換反応が過度に生じ、半田合金中の亜鉛の量が不足して、適切に半田付けができなくなる可能性がある。
【００１８】
【作用】
本発明においては、銅と亜鉛との金属間化合物層の進行が抑制され、経時的に接合強度が低下することがない。本発明により前記金属間化合物層の進行が抑制されるメカニズムは必ずしも明確ではないが、半田付け時の熱により金属塩中の金属と金属間化合物中の亜鉛との置換反応が生じて金属間化合物を減少させると共に、当該置換反応により遊離した金属が銅と亜鉛との反応を抑制するのではないかと考えられる。
【００１９】
【発明の効果】
本発明によれば、半田付けした後に加熱雰囲気下に放置した状態においても、銅−亜鉛の金属間化合物層が進行することがなく、半田と銅との接合状態が維持され、接合強度が低下することがない。
【００２０】
【実施例】
［フラックスの調製］
次の組成の各成分を加熱溶解して混合し、冷却してフラックスを調製した。比較例においては金属塩を添加せず、ガムロジンの量を７２％とした。なお各成分の％は、いずれも重量％である。
【００２１】
金属塩は、次の通りのものを使用した。
実施例１ ロジン酸ビスマス
実施例２ ロジン酸インジウム
実施例３ ロジン酸銀
比較例 添加せず
【００２３】
［ソルダペーストの調製］
上記フラックスを１２重量％と、錫−亜鉛共晶合金（錫９１．２重量％−亜鉛８．８重量％）の粒径２０〜４０μｍの粉末とを混合し、混練機で撹拌してソルダペーストを調製した。
【００２４】
［試験方法］
上記のソルダペーストを使用して、基板上にセラミックコンデンサーを半田付けして接合した。その基板を１００℃の条件下に５００時間放置し、その初期と５００時間経過後における基板と接合部品との接合強度及び、金属間化合物層の厚みを測定した。
【００２５】
［試験結果］
試験結果を表１に示す。
【００２６】
【表１】
以上の結果からも明らかなように、比較例においては５００時間経過後に金属間化合物層の厚みが大幅に増加しており、接合強度が著しく低下しているのに対し、金属塩を添加した実施例においては、化合物層の進行は僅かであり、また接合強度も殆ど低下していない。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solder paste in which a solder alloy powder and a flux are mixed to form a paste, and more particularly to an improvement of a solder paste using a solder alloy containing zinc.
[0002]
[Prior art]
Conventionally used solder pastes that use a tin-lead alloy as a solder alloy are widely used. However, since lead contained in the solder alloy is toxic, lead-free solder containing no lead has been studied.
[0003]
In particular, tin-zinc-based eutectic alloys have the same melting point as conventional tin-lead alloys, and are excellent in mechanical strength and creep characteristics, and thus are promising as alloys constituting lead-free solder.
[0004]
[Problems to be solved by the invention]
However, in a tin-zinc based solder alloy, since the ionization tendency of zinc is large and rich in reactivity, when left under high temperature in the soldered state, zinc in the solder diffuses to the copper surface of the substrate, A copper-zinc intermetallic compound (Cu 5 Zn 8 ) is produced, and the production of the compound proceeds on the surface of copper.
[0005]
Therefore, with the passage of time, the zinc in the solder is reduced and the solder structure at that location is destroyed, cracks are generated and the strength is reduced, and the strength difference between the solder and the intermetallic compound is increased, Bonding strength is reduced.
[0006]
Accordingly, in the case of tin-zinc based solder, if left at a high temperature after soldering, the formation of the intermetallic compound layer proceeds between the solder and the copper substrate, and the bonding strength between the solder and copper increases over time. There was a problem that it decreased.
[0007]
The present invention has been made in view of such circumstances, and it is an object of the present invention to suppress the progress of the intermetallic compound layer in a solder paste of a tin-zinc based solder alloy and prevent a decrease in bonding strength over time. To do.
[0008]
[Means for Solving the Problems]
Thus, in the present invention, a bismuth, indium or silver salt is added to a solder paste composed of a lead-free solder alloy powder mainly composed of 88 to 95% by weight of tin and 5 to 12% by weight of zinc. It is characterized by.
[0009]
The solder alloy in the present invention is preferably a tin-zinc eutectic alloy. The amount of the metal salt with respect to the solder paste is preferably 0.5% by weight or more and the same ion equivalent or less as that of zinc in the solder paste.
[0010]
As the solder alloy in the present invention, the above-described tin-zinc eutectic alloy, that is, an alloy of 91.2% tin and 8.8% zinc is preferable. Further, it is also suitable that tin is mainly composed of 88 to 95% by weight and zinc 5 to 12% by weight, and 2% by weight or less of bismuth, indium, copper, silver, antimony and the like are added thereto. As the solder alloy powder, those having a particle size of about 20 to 40 μm are suitable.
[0012]
As the flux in the present invention, the flux in a normal solder paste can be used as it is except that a metal salt is added. For example, it is possible to use rosin added with appropriate amounts of wax and activator and dispersed in a solvent.
[0013]
In the present invention, a metal salt is added to the flux. The metal constituting the metal salt is suitably bismuth, indium, gold, silver, copper, tin, antimony, nickel, cobalt, or platinum.
[0014]
Organic salts and inorganic acid salts of these metals can be used, specifically, bismuth chloride, indium chloride, bismuth rosinate, indium rosinate, copper rosinate, silver rosinate, copper stearate, citric acid. Examples thereof include bismuth acid acid, silver acetate, and indium ethyl 2-ethylhexanoate.
[0015]
These metal salts are added to the flux, and the flux and solder alloy powder are mixed to form a solder paste. The mixing ratio of the solder alloy and the flux is about the same as that of a normal solder paste, and a flux of about 8 to 20% by weight is appropriate for the solder alloy of 92 to 80% by weight.
[0016]
The amount of the metal salt added to the solder paste of the present invention is preferably at least 0.5% by weight or more. If it is less than 0.5% by weight, the effect of suppressing the progress of the intermetallic compound layer does not occur.
[0017]
The maximum amount of the metal salt is preferably set so that the metal in the metal salt can be replaced with zinc in the solder alloy. That is, it is preferable that the ion equivalent is equal to or less than that of zinc in the solder paste. If the amount of the metal salt exceeds this amount, the substitution reaction between the metal in the metal salt and zinc occurs excessively, and the amount of zinc in the solder alloy is insufficient, and there is a possibility that proper soldering cannot be performed.
[0018]
[Action]
In the present invention, the progress of the intermetallic compound layer of copper and zinc is suppressed, and the bonding strength does not decrease with time. Although the mechanism by which the progress of the intermetallic compound layer is suppressed according to the present invention is not necessarily clear, the substitution reaction between the metal in the metal salt and the zinc in the intermetallic compound occurs due to the heat during soldering. It is considered that the metal liberated by the substitution reaction suppresses the reaction between copper and zinc.
[0019]
【The invention's effect】
According to the present invention, the copper-zinc intermetallic compound layer does not proceed even after being soldered and left in a heated atmosphere, the bonding state between the solder and copper is maintained, and the bonding strength is reduced. There is nothing to do.
[0020]
【Example】
[Preparation of flux]
Each component of the following composition was heated and dissolved, mixed, and cooled to prepare a flux. In the comparative example, no metal salt was added and the amount of gum rosin was 72%. In addition, all% of each component is weight%.
[0021]
The following metal salts were used.
Example 1 Bismuth rosinate Example 2 Indium rosinate Example 3 Silver rosinate comparative example No addition
[Preparation of solder paste]
12% by weight of the above flux and a tin-zinc eutectic alloy (91.2% by weight of tin—8.8% by weight of zinc) having a particle size of 20 to 40 μm are mixed and stirred with a kneader to obtain a solder paste. Was prepared.
[0024]
[Test method]
Using the above solder paste, a ceramic capacitor was soldered and bonded onto the substrate. The substrate was allowed to stand at 100 ° C. for 500 hours, and the bonding strength between the substrate and the bonded component and the thickness of the intermetallic compound layer were measured at the initial stage and after 500 hours.
[0025]
[Test results]
The test results are shown in Table 1.
[0026]
[Table 1]
As is clear from the above results, in the comparative example, the thickness of the intermetallic compound layer was greatly increased after the elapse of 500 hours, and the bonding strength was significantly reduced, whereas the metal salt was added. In the example, the progress of the compound layer is slight, and the bonding strength is hardly lowered.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22709597A JP4017088B2 (en) | 1997-08-07 | 1997-08-07 | Solder paste |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP22709597A JP4017088B2 (en) | 1997-08-07 | 1997-08-07 | Solder paste |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1158065A JPH1158065A (en) | 1999-03-02 |
| JP4017088B2 true JP4017088B2 (en) | 2007-12-05 |
Family
ID=16855421
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP22709597A Expired - Lifetime JP4017088B2 (en) | 1997-08-07 | 1997-08-07 | Solder paste |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4017088B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4061905B2 (en) | 1999-10-18 | 2008-03-19 | セイコーエプソン株式会社 | Display device |
| JP2001232496A (en) * | 2000-02-23 | 2001-08-28 | Taiho Kogyo Co Ltd | Flux for soldering and solder paste |
| JP4142312B2 (en) | 2002-02-28 | 2008-09-03 | ハリマ化成株式会社 | Precipitation solder composition and solder deposition method |
| CN100455400C (en) * | 2007-01-16 | 2009-01-28 | 大连理工大学 | Soldering flux in use for SnZn series solder with no lead, and preparation method |
| CN102066045B (en) * | 2008-06-23 | 2013-07-10 | 万腾荣高新材料技术和服务公司 | Gold-tin-indium solder for processing compatibility with lead-free tin-based solder |
| US11123823B2 (en) * | 2017-11-08 | 2021-09-21 | Alpha Assembly Solutions Inc. | Cost-effective lead-free solder alloy for electronic applications |
| CN114434040B (en) * | 2021-01-15 | 2024-07-30 | 重庆理工大学 | Dissimilar material interconnection zinc alloy mixed solder powder and connecting method |
-
1997
- 1997-08-07 JP JP22709597A patent/JP4017088B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1158065A (en) | 1999-03-02 |
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