JP3552241B2 - Pre-flux - Google Patents
Pre-flux Download PDFInfo
- Publication number
- JP3552241B2 JP3552241B2 JP10367693A JP10367693A JP3552241B2 JP 3552241 B2 JP3552241 B2 JP 3552241B2 JP 10367693 A JP10367693 A JP 10367693A JP 10367693 A JP10367693 A JP 10367693A JP 3552241 B2 JP3552241 B2 JP 3552241B2
- Authority
- JP
- Japan
- Prior art keywords
- flux
- tetrafluoroethylene
- circuit board
- printed circuit
- soldering
- 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
Landscapes
- Non-Metallic Protective Coatings For Printed Circuits (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Description
【0001】
【産業上の利用分野】
本発明は、プリント基板の表面を保護するプリフラックスに関する。
【0002】
【従来の技術】
プリント基板は、紙・フェノールやガラス・エポキシ等の樹脂の板の上に銅箔が回路となるようにランドが印刷法で形成されている。プリント基板に電子部品を実装するには、ランド上にソルダーペーストを塗付し、その上に表面実装部品のリード部を載置してからリフロー炉のような加熱装置で加熱してソルダーペーストを溶融することによりはんだ付けを行ったり、或はランドの孔にディスクリート部品のリードを挿入して該リードとランドとを溶融はんだではんだ付けすることが行われている。
【0003】
プリント基板のランドは、銅箔を印刷した時点では表面が非常にきれいであるが、そのまま放置しておくと空気中の酸素や湿気で表面に酸化膜を形成したり、手垢のような汚れが付着してしまう。このような酸化物や汚れが付着すると、溶融はんだとランドとの金属的な接合を邪魔してしまい、電子部品の実装時にはんだが充分に付着しないはんだ付け不良となってしまうことになる。
【0004】
このようにランドが酸素や湿気、或は人手に触れるのを防ぐために、プリント基板製造後にプリント基板の表面に被膜を被覆することがなされていた。この被膜を形成する材料がプリフラックスである。
【0005】
従来のプリフラックスは松脂やテルペンフェノールのような樹脂を溶剤で溶解し、必要に応じて少量の酸化防止剤や難燃剤等を添加したものであった。プリフラックスをプリント基板に塗付後、溶剤を乾燥させるとプリント基板の表面にこれらの樹脂の薄い被膜が形成され、この被膜が空気中の酸素や湿気を遮断してランドが酸化したり汚れたりするのを防止するものである。
【0006】
松脂やテルペンフェノール樹脂は、100℃前後で軟化し、はんだ付け時には完全に溶融状態となってランド表面を覆い、溶融したはんだがランドに近づいてくると、溶融はんだが樹脂を退かしてランドと金属的に接合するようになる。つまりプリフラックスは、平時にランドを覆っていてもはんだ付け時には全くはんだ付けを阻害しないようになっている。従って、プリフラックスを被覆したプリント基板をソルダーペーストや溶融はんだではんだ付けする時には、普通のフラックスでも充分きれいなはんだ付けが行えるものである。
【0007】
ところで、コンピューターや通信機器のように信頼性を非常に重視する電子機器では、ここに使用するプリント基板を普通のフラックスではんだ付けした時に、フラックスが不必要な箇所、たとえばプリント基板の表面やランド間に付着してしまうと、このフラックスが吸湿したりゴミやホコリを吸着させて絶縁抵抗を低げ、電子機器の機能を劣化させてしまうことがある。
【0008】
そのため、はんだ付け後のプリント基板は、不必要な箇所に付着したフラックスを除去する洗浄が行われていた。はんだ付け後のフラックスを洗浄する洗浄液としては、フロンやトリクレンのようなものが洗浄力に優れているが、これらの洗浄液は地球を取り巻くオゾン層を破壊して有害な太陽の紫外線を多量に地球に到達させ、人類に皮膚癌を発生させる原因となるため、その使用が規制されてきている。そのため、近時、これらの洗浄液に代わる洗浄液も開発されてはきているが、いずれも高価であり、しかも洗浄効果がフロンやトリクレンに劣るというものであった。
【0009】
従って、現在では、はんだ付け後にフラックスを洗浄しなくても済むという所謂「無洗浄フラックス」や「無洗浄ソルダーペースト」等という無洗浄化製品が使用されるようになってきた。これら無洗浄化製品は、松脂や活性剤等の固形成分を極めて少なくしたものである。従って、無洗浄化製品は、フラックスがプリント基板の不必要な箇所に付着しても、ここに残る固形成分が少ないためフラックスの悪影響が出てこないという特長がある。
【0010】
しかしながら、無洗浄化製品は、はんだ付け性に大いに影響のある固形成分が少ないため、はんだ付け性が非常に悪く、酸素の存在する大気下ではんだ付けを行うと未はんだやブリッジ等のはんだ付け不良を発生させてしまう。そのため無洗浄化製品は、酸素量を極めて少なくした窒素雰囲気や真空中ではんだ付けを行わなければならなかったが、これらの装置は非常に高価であるばかりでなく、生産性も悪いという欠点があった。
【0011】
本発明は、プリフラックスとしての役割を充分に果たすと同時に、大気下ではんだ付け性が良好な程度に固形成分を含有した普通のフラックスやソルダーペーストではんだ付けしても、不必要な箇所にフラックスを付着させないというプリフラックスを提供することにある。
【0012】
【課題を解決するための手段】
本発明者等は、フッ素化合物やシリコン化合物には揆水性や揆油性があって、液体が濡れ広がるのを抑える性質の或ることに着目して本発明を完成させた。
【0013】
本発明は、天然樹脂や合成樹脂を溶剤で溶解したプリフラックスにおいて、該プリフラックス中に表面張力が22dyn/cm以下の揆水性および揆油性物質を0.01〜5重量%添加したことを特徴とするプリフラックスである。
【0014】
本発明に使用する揆水性および揆油性のある物質は、表面張力が22dyn/cmを越えると、プリフラックスに添加してプリント基板に塗付した後、はんだ付けを行うと、はんだ付け時にフラックスが不必要な箇所に付着してしまうようになる。
【0015】
本発明に使用して特に効果のある揆水性および揆油性のある物質としては、分子量が20万〜400万の4フッ化エチレン重合体、6フッ化プロピレン重合体、4フッ化エチレン・6フッ化プロピレン共重合体、4フッ化エチレン・エチレン共重合体、6フッ化プロピレン・エチレン共重合体、4フッ化エチレン・6フッ化プロピレン・エチレン共重合体、4フッ化エチレン・パーフロロアルキルビニールエーテル共重合体のフッ素樹脂である。
【0016】
上記フッ素樹脂は分子量が20万未満では、樹脂自体の製造が困難であり、しかも流動性が出過ぎて流れやすくなってしまう。一方、その分子量が400万を越えると粘度が高くなり過ぎて取り扱いにくくなってしまう。
【0017】
本発明では、揆水性、揆油性のある物質としては上記フッ素樹脂ばかりでなくシリコン樹脂も使用できる。
【0018】
本発明において、揆水性、揆油性物質の添加量は0.01〜5重量%が適当である。この添加量が0.01重量%よりも少ないと、はんだ付け時にフラックスがにじみ広がるのを抑える効果が出ず、しかるに5重量%を越えて添加するとはんだ付け時にはんだがランドに付着するのを妨げるようになってしまう。
【0019】
本発明に使用する天然樹脂としてはロジン、ロジンの誘導体等であり、合成樹脂としてはテルペンフェノール樹脂のようなものが適している。またこれらの樹脂を溶解する溶剤としてはトルエンやイソプロピルアルコール(IPA)のような低沸点のものが適している。
【0020】
【実施例】
【0021】
【0022】
【0023】
【0024】
【0025】
上記実施例および比較例のプリフラックスをガラス・エポキシ樹脂のプリント基板全面に塗付した後、溶剤を完全に乾燥させる。このようにして得たプリント基板のランドにRAタイプのソルダーペーストをスクリーンで印刷塗付し、その上に表面実装部品のQFPを搭載してから、リフロー炉により150℃で60秒間の予備加熱と200℃で20秒間の本加熱を行ってプリント基板と表面実装部品をはんだ付けした。はんだ付け後のプリント基板を観察したところ、実施例のプリフラックスを塗付した基板は、ランド周囲へのフラックスの広がりはほとんどなかったが、比較例のプリフラックスを塗付した基板ではランドの周囲に大きくフラックスの広がっているのが見られた。
【0026】
【発明の効果】
以上説明した如く、本発明のプリフラックスは、はんだ付け時にフラックスを広がらせることがないため、不必要な箇所にもフラックスが付着せず、従ってはんだ付け後にフラックスを洗浄除去する必要もなくなることから、高価な洗浄液を使用したり、絶縁抵抗の低下による電子機器の性能劣化等がなくなるという従来にない優れた効果を有している。[0001]
[Industrial applications]
The present invention relates to a pre-flux for protecting the surface of a printed circuit board.
[0002]
[Prior art]
The printed board has a land formed by a printing method on a resin plate of paper, phenol, glass, epoxy, or the like so that a copper foil forms a circuit. To mount an electronic component on a printed circuit board, apply solder paste on the land, place the lead of the surface mount component on top of it, and heat it with a heating device such as a reflow furnace to remove the solder paste. Soldering is performed by melting, or a lead of a discrete component is inserted into a hole of a land, and the lead and the land are soldered with molten solder.
[0003]
The surface of the printed circuit board land is very clean when the copper foil is printed, but if left untouched, an oxide film will be formed on the surface by oxygen or moisture in the air, Will stick. If such an oxide or dirt adheres, it hinders the metallic bonding between the molten solder and the land, resulting in poor soldering in which the solder does not sufficiently adhere when mounting the electronic component.
[0004]
As described above, in order to prevent the land from touching oxygen, moisture, or human hands, a coating is formed on the surface of the printed board after the printed board is manufactured. The material that forms this coating is preflux.
[0005]
Conventional preflux is obtained by dissolving a resin such as rosin or terpene phenol with a solvent, and adding a small amount of an antioxidant or a flame retardant as necessary. After applying the pre-flux to the printed circuit board and drying the solvent, a thin film of these resins is formed on the surface of the printed circuit board, and this film blocks oxygen and moisture in the air and oxidizes and stains the land. It is to prevent that.
[0006]
The rosin and terpene phenolic resin soften at around 100 ° C and become completely molten during soldering and cover the land surface. It comes to be joined metallically. In other words, the pre-flux does not hinder the soldering at all even when covering the lands during normal times. Therefore, when a printed circuit board coated with a pre-flux is soldered with a solder paste or a molten solder, a sufficiently clean soldering can be performed even with an ordinary flux.
[0007]
By the way, in electronic equipment such as computers and communication equipment, where reliability is very important, when the printed circuit board used here is soldered with ordinary flux, places where flux is unnecessary, for example, the surface of the printed circuit board or land. If the flux adheres to the space, the flux may absorb moisture, adsorb dirt and dust, lower the insulation resistance, and deteriorate the function of the electronic device.
[0008]
For this reason, the printed circuit board after soldering has been washed to remove the flux attached to unnecessary portions. As cleaning fluid for cleaning the flux after soldering, such as Freon and Triclean are excellent in detergency, but these cleaning fluids destroy the ozone layer surrounding the earth and emit a large amount of harmful solar ultraviolet rays. And its use has been regulated because it causes skin cancer to occur in humans. For this reason, recently, cleaning liquids have been developed in place of these cleaning liquids, but all of them are expensive and have a cleaning effect inferior to that of chlorofluorocarbon or trichlene.
[0009]
Accordingly, at present, non-cleaning products such as so-called "no-cleaning flux" and "no-cleaning solder paste" that do not require cleaning of the flux after soldering have come to be used. These non-cleaning products have extremely low solid components such as rosin and activators. Therefore, the non-cleaning product has a feature that even if the flux adheres to an unnecessary portion of the printed circuit board, the solid component remaining there is small, so that the adverse effect of the flux does not appear.
[0010]
However, non-cleaning products have very low solid components that greatly affect solderability, and therefore have very poor solderability.If soldering is performed in an atmosphere containing oxygen, soldering such as unsoldering or bridges may occur. It causes defects. Therefore, non-cleaning products had to be soldered in a nitrogen atmosphere or vacuum with extremely low oxygen content, but these devices are not only very expensive, but also have the disadvantage that productivity is poor. there were.
[0011]
The present invention plays a sufficient role as a pre-flux, and at the same time, can be soldered with an ordinary flux or solder paste containing a solid component to the extent that the solderability is good in the atmosphere. An object of the present invention is to provide a pre-flux in which no flux is attached.
[0012]
[Means for Solving the Problems]
The present inventors have completed the present invention by focusing on the fact that fluorine compounds and silicon compounds have water repellency and oil repellency and have a property of suppressing the spread of liquid.
[0013]
The present invention is characterized in that in a preflux prepared by dissolving a natural resin or a synthetic resin with a solvent, 0.01 to 5% by weight of a water repellent or oil repellent substance having a surface tension of 22 dyn / cm or less is added to the preflux. Is the pre-flux.
[0014]
When the surface tension exceeds 22 dyn / cm, the material having a water repellent and oil repellent used in the present invention is added to a pre-flux, applied to a printed circuit board, and then soldered. It will adhere to unnecessary places.
[0015]
Particularly effective hydrophobizing and oleaginous substances used in the present invention include a tetrafluoroethylene polymer, a hexafluoropropylene polymer and a tetrafluoroethylene / 6-fluoropolymer having a molecular weight of 200,000 to 4,000,000. Propylene copolymer, tetrafluoroethylene / ethylene copolymer, hexafluoropropylene / ethylene copolymer, tetrafluoroethylene / hexafluoropropylene / ethylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl It is a fluororesin of an ether copolymer.
[0016]
If the molecular weight of the fluororesin is less than 200,000, it is difficult to produce the resin itself, and the fluidity is too high to flow easily. On the other hand, if the molecular weight exceeds 4,000,000, the viscosity becomes too high and handling becomes difficult.
[0017]
In the present invention, as the substance having water repellency and oil repellency, not only the above-mentioned fluororesin but also a silicone resin can be used.
[0018]
In the present invention, the addition amount of the water-repellent or oil-repellent substance is suitably from 0.01 to 5% by weight. If the addition amount is less than 0.01% by weight, the effect of suppressing the spread of the flux at the time of soldering will not be obtained. If the addition amount exceeds 5% by weight, the solder will not adhere to the land at the time of soldering. It becomes like this.
[0019]
As the natural resin used in the present invention, rosin, rosin derivative and the like are used, and as the synthetic resin, terpene phenol resin and the like are suitable. As a solvent for dissolving these resins, a solvent having a low boiling point such as toluene or isopropyl alcohol (IPA) is suitable.
[0020]
【Example】
[0021]
[0022]
[0023]
[0024]
[0025]
After applying the pre-flux of the above-mentioned Examples and Comparative Examples to the entire surface of the glass / epoxy resin printed board, the solvent is completely dried. The land of the printed circuit board thus obtained is printed and coated with an RA type solder paste on a screen, and the QFP of the surface mount component is mounted thereon, and then preheated at 150 ° C. for 60 seconds by a reflow furnace. Main heating was performed at 200 ° C. for 20 seconds to solder the printed circuit board and the surface mount components. Observation of the printed circuit board after soldering showed that the pre-flux coated board of the example showed little spread of the flux around the land, but the comparative pre-flux coated board did not The spread of the flux was large.
[0026]
【The invention's effect】
As described above, the pre-flux of the present invention does not spread the flux at the time of soldering, so that the flux does not adhere to unnecessary portions, and therefore it is not necessary to wash and remove the flux after soldering. In addition, there is an unprecedented superior effect that the use of an expensive cleaning liquid and the deterioration of the performance of electronic devices due to a decrease in insulation resistance are eliminated.
Claims (1)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10367693A JP3552241B2 (en) | 1993-04-07 | 1993-04-07 | Pre-flux |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10367693A JP3552241B2 (en) | 1993-04-07 | 1993-04-07 | Pre-flux |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH06296072A JPH06296072A (en) | 1994-10-21 |
JP3552241B2 true JP3552241B2 (en) | 2004-08-11 |
Family
ID=14360399
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP10367693A Expired - Lifetime JP3552241B2 (en) | 1993-04-07 | 1993-04-07 | Pre-flux |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP3552241B2 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN1325223C (en) * | 2003-04-25 | 2007-07-11 | 李�荣 | Soldering flux in use for iron weldment |
CA2677102C (en) * | 2007-01-04 | 2017-12-12 | Fry's Metals, Inc. | Flux formulations |
GB0703172D0 (en) * | 2007-02-19 | 2007-03-28 | Pa Knowledge Ltd | Printed circuit boards |
CN103862199A (en) * | 2014-03-24 | 2014-06-18 | 吉安谊盛电子材料有限公司 | Scaling powder special for photovoltaic solder strip |
CN103862200A (en) * | 2014-03-24 | 2014-06-18 | 吉安谊盛电子材料有限公司 | Scaling powder special for welding of solar assemblies |
JP6945136B2 (en) * | 2017-01-17 | 2021-10-06 | 株式会社弘輝 | Flux and solder composition |
-
1993
- 1993-04-07 JP JP10367693A patent/JP3552241B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPH06296072A (en) | 1994-10-21 |
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