JP3587276B2 - Solder coating method for printed circuit boards - Google Patents
Solder coating method for printed circuit boards Download PDFInfo
- Publication number
- JP3587276B2 JP3587276B2 JP15636796A JP15636796A JP3587276B2 JP 3587276 B2 JP3587276 B2 JP 3587276B2 JP 15636796 A JP15636796 A JP 15636796A JP 15636796 A JP15636796 A JP 15636796A JP 3587276 B2 JP3587276 B2 JP 3587276B2
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- Prior art keywords
- solder
- pattern
- printed circuit
- circuit board
- paste
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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
- H05K3/3468—Applying molten solder
-
- 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、プリント基板、特にＱＦＰやＳＯＰのような面実装部品を搭載するプリント基板のパターンにはんだをコートする方法に関する。
【０００２】
【従来の技術】
電子機器に使用する電子部品には、長いリードを有するディスクリート部品と、本体の端部がリードとなっていたり本体から多数の短いリードが突出したりした面実装部品とがある。ディスクリート部品をはんだ付けするプリント基板のはんだ付け部をランドといい、面実装部品をはんだ付けする部分をパターンという。
【０００３】
ディスクリート部品とプリント基板のはんだ付けは、長いリードをランドに穿設された穴に挿入した後、プリント基板の下面にフラックス塗布、予備加熱を行ってから、はんだ槽の溶融はんだに接触させるという浸漬法によって行う。この浸漬法では、ランド間が狭いとランド間にはんだが跨がって付着するというブリッジを形成することがあった。
【０００４】
面実装部品とプリント基板のはんだ付けは、はんだ粉とフラックスから成るソルダペーストが用いられていた。ソルダペーストによる面実装部品とプリント基板のはんだ付けは、先ずプリント基板のパターンにソルダペーストを印刷塗布する。この印刷は、プリント基板のはんだ付け部であるパターンと同一箇所に穴が穿設されたメタルマスクを該メタルマスクの穴とパターンが一致するようにしてプリント基板上に重ね合わせる。そしてメタルマスクの上にソルダペーストを置き、メタルマスク上のソルダペーストをスキージで掻いてメタルマスクの穴にソルダペーストを充填する。その後メタルマスクを上方に持ち上げると、ソルダペーストがプリント基板のパターンに付着する。このようにしてソルダペーストが印刷塗布されたプリント基板のパターン上に面実装部品を搭載し、ソルダペーストの粘着力で面実装部品を仮固定してから該プリント基板をリフロー炉のような加熱装置で加熱し、ソルダペーストを溶融させてはんだ付けするものである。
【０００５】
ところで近時の電子機器が軽薄短小となってきていることから、面実装部品も小型となってきており、リード間隔が非常に狭くなっている。たとえばＱＦＰではリード間隔が０．３ｍｍ以下という所謂ファインピッチというものも出現してきている。
【０００６】
このようなファインピッチの面実装部品をソルダペーストではんだ付けすると、はんだが隣接したリード間にブリッジを形成してしまうことがあった。電子部品のはんだ付け部にブリッジが形成されると、電子機器の機能が全く損なわれて商品価値がなくなってしまう。
【０００７】
ブリッジは、ファインピッチの電子部品のはんだ付けにもかかわらず、ソルダペーストの塗布量が多いことに起因している。つまりソルダペーストの塗布量を多くするのは、面実装部品のリードとプリント基板のパターンとの接合部に充分にはんだを供給することにより、信頼性を向上させるためである。接合部へのはんだの充分な供給は、特に熱サイクルによる金属疲労防止に効果がある。熱サイクルによる金属疲労とは、電子機器使用時にコンデンサーやトランスから発熱して電子機器のケース内の温度が上がり、使用を中止したときに温度が下がるが、この昇温と降温の繰り返しではんだ付け部が熱膨張・収縮してはんだが金属疲労を起こしてしまうものである。
【０００８】
確かにはんだ付け部に多量のはんだが付着していれば金属疲労が少なくなり、はんだの割れや剥離等という事故は起こりにくくなる。しかしながらファインピッチのパターンにソルダペーストを多量に塗布すると前述のように、はんだ付け時にブリッジを形成してしまうという問題があった。
【０００９】
そこで従来よりファインピッチの電子部品のはんだ付けでは、パターンに予めはんだを付着させたはんだコートではんだ付けすることが行われていた。はんだコートされたプリント基板は、ソルダペーストを使わず、はんだコートの上に直接面実装部品のリードを置き、局部的にボンディング・ツールのようなもので加熱すれば、はんだコートが溶融してリードとパターンをはんだ付けできる。従って、プリント基板のはんだコートは、リードとパターンを完全にはんだ付けができ、しかも金属疲労を起こさない充分なはんだ量が必要である。このはんだ量は、リードピッチが０．２５ｍｍであれば約２５μｍ、０．３ｍｍであれば約３０μｍの厚さが適当な量であるといわれている。
【００１０】
プリント基板のはんだコート方法としては、電解法、浸漬法、リフロー法等がある。電解法とは、はんだの電解液の中でプリント基板に陰極、電極のはんだに陽極を接続して直流電気を通すことによりプリント基板のパターンにはんだを電気メッキする方法であり、浸漬法とは、プリント基板を立てた状態ではんだ槽の溶融はんだに浸漬してパターンにはんだを付着させる方法であり、そしてリフロー法とは、電子部品のリフローはんだ付けと同様にプリント基板のパターンと同一箇所に穴のあいたメタルマスクでパターンにソルダペーストを印刷塗布し、それをリフロー炉で加熱してパターンにはんだを付着させる方法である。
【００１１】
【発明が解決しようとする課題】
電解法では、パターンにはんだを厚く付着させることができない。電解法でのはんだコートの厚さは精々数μｍ程度であり、到底このはんだ量では面実装部品をはんだ付けできないものである。しかも電解法で得られたはんだコートは、はんだとパターンの銅箔とが金属的な接合となっていないため、はんだ付け時にはんだが完全に濡れないというディウエットとなってしまうことがあった。
【００１２】
浸漬法では、電解法よりもパターンにはんだを厚く付着させることができるが、プリント基板をはんだ槽に浸漬後もやはりプリント基板を立てた状態で引き上げるためパターンに付着したはんだが垂れ落ちて必要なの厚さにすることができないばかりでなく、引き上げ時にパターンの下方に偏って付着してしまうという問題があった。
【００１３】
リフロー法は、メタルマスクの板厚を厚くして穴に充填するソルダペーストの量を多くすれば、パターンへの塗布量は多くなるが、ソルダペーストの溶融時にソルダペーストがだれて隣接したパターンのソルダペーストと融合し、ブリッジを形成してしまうものであった。
【００１４】
本発明は、はんだを所望の厚さだけ付着させることができるにもかかわらず、決してブリッジを発生させないというプリント基板のはんだコート方法を提供することにある。
【００１５】
【課題を解決するための手段】
本発明者は、浸漬法での長所とリフロー法での長所、即ち浸漬法ではパターン全てに完全にはんだメッキが行え、リフロー法では偏りのないはんだの付着が行えることを採用してはんだコートを行えば、はんだ付けに必要な充分な厚さのはんだコートが得られ、しかもブリッジも発生しないことに着目して本発明を完成させた。
【００１６】
本発明は、多数のパターンが並列して設置されたプリント基板にはんだをコートする方法において、プリント基板をはんだ槽の溶融はんだに浸漬してパターンにはんだメッキを行い、次いで該プリント基板のパターンにソルダペーストを塗布した後、該ソルダペーストを加熱溶融することを特徴とするプリント基板のはんだコート方法である。
【００１７】
【発明の実施の形態】
本発明に使用するはんだ槽は、プリント基板のパターンにはんだを完全に金属的に付着できるものであれば如何なるはんだ槽でもよく、たとえば超音波はんだ槽や噴流はんだ槽、静止はんだ槽等が使用可能である。
【００１８】
またはんだ槽でのはんだメッキ後にパターンに塗布するソルダペーストの粉末はんだは、はんだ槽に投入されたはんだと同一組成のものでもよいが、溶融時にパターン間で切れてブリッジを形成しにくいはんだ、たとえばＰｂ−Ｓｎ−Ｂｉ系のはんだを用いるとブリッジの発生がなくなる。本発明の使用に適したＰｂ−Ｓｎ−Ｂｉ系としてはＰｂ−４６Ｓｎ−８Ｂｉ系である。
【００１９】
本発明では、浸漬法ではんだメッキしたパターンにソルダペーストを塗布する方法は、パターンと同一箇所に穴が穿設されたメタルマスクで各パターン毎に印刷したり、長穴が穿設されたメタルマスクで一文字印刷したりする。一文字印刷とは並列した複数のパターンの一端から他端まで連続して塗布することである。
ソルダペーストの一文字は、横方に一列または二列にして塗布してもよい。ソルダペーストを一文字に塗布するには、パターンの長辺よりも短い幅で、並列したパターンの一端から他端迄の長さに穿設されたメタルマスクを用いて印刷する他にディスペンサーで連続的に吐出塗布することもできる。
【００２０】
【実施例】
実施例１
○プリント基板：０．３ｍｍピッチ、一列に１６パターンが並列したＱＦＰ搭載用、パターンの大きさは０．１５×１．５（ｍｍ）
○はんだ槽：静止はんだ槽、大気中
○はんだ槽のはんだの組成：Ｐｂ−６３Ｓｎ
○メッキ用フラックス：松脂、活性剤をアルコールで溶解
○ソルダペースト：フラックス量は１０．５重量％、粉末はんだの組成はＰｂ−６３Ｓｎ
○メタルマスク：厚さ０．１ｍｍ、パターンと一致した穴が穿設されたマスク
プリント基板にフラックスを塗布してからはんだ槽に浸漬し、はんだ槽からの引き上げ時に圧縮空気を吹き付けて余剰のはんだを除去してパターンにはんだメッキ行った。このときのはんだの付着状態を拡大鏡で観察したところブリッジの発生は皆無であり、またはんだの付着厚さを非接触深度測定機（ユニオン光学社製）で測定したところ１０μｍであった。該はんだメッキされた各パターン上にメタルマスクでソルダペーストを印刷塗布した後、リフロー炉で加熱してソルダペーストを溶融する。冷却後プリント基板を拡大鏡で観察し、付着厚さを非接触深度測定機で測定したところ、ブリッジの発生は皆無であり、はんだの付着厚さは３４μｍであった。
【００２１】
実施例２
○プリント基板：０．３ｍｍピッチ、一列に１６パターンが並列したＱＦＰ搭載用、パターンの大きさは０．１５×１．５（ｍｍ）
○はんだ槽：超音波ホーンを設置した噴流はんだ槽で酸素濃度が５０ｐｐｍの窒 素雰囲気
○はんだ槽の組成：Ｐｂ−６３Ｓｎ
○ソルダペースト：フラックス量は１０．５重量％、粉末はんだの組成はＰｂ−４６Ｓｎ−８Ｂｉ
○メタルマスク：厚さ０．１ｍｍ、並列したパターン全域と同一長の長穴が穿設された一文字印刷用マスク
プリント基板をはんだ槽に浸漬し、パターンにはんだメッキ行った。このときのはんだの付着状態を実体顕微鏡で観察したところブリッジの発生は皆無であり、また付着厚さを非接触深度測定機で測定したところ１４μｍであった。該はんだメッキされたパターン上にメタルマスクでソルダペーストを横方に連続して一列の一文字印刷塗布した後、リフロー炉で加熱してソルダペーストを溶融する。冷却後プリント基板を拡大鏡で観察し、付着厚さを非接触深度測定機で測定したところ、ブリッジの発生は皆無であり、はんだの付着厚さは３２μｍであった。
【００２２】
○比較例１
実施例１と同一のプリント基板、はんだ槽、メッキ用フラックスを用いて浸漬法でプリント基板のパターンにはんだコートを行った。該はんだコートの厚さを非接触深度測定機で測定したところ、引き上げ方向に対して下部となる部分の厚さは２０μｍ、上部となる部分の厚さは１０μｍであり、はんだ量が不足しているばかりでなく、不均一なはんだコートとなっていた。
【００２３】
○比較例２
実施例１と同一のプリント基板、ソルダペーストを用い、パターンと同一箇所に穴が穿設されたメタルマスク（厚さ０．２ｍｍ）で各パターン毎に印刷塗布を行ってから、リフロー炉でソルダペーストを溶融させてはんだコートを行った。冷却後、はんだコート部分を拡大鏡で観察したところ、多数のブリッジが発生していた。またはんだコートの厚さは２２μｍであった。
【００２４】
【発明の効果】
本発明によれば、所定量のはんだを偏りがなくプリント基板のパターンにコートすることができるため、ＱＦＰやＳＯＰのような面実装部品をはんだ付けするときに未はんだのない確実な接合ができるものである。また本発明で得られたはんだコートは、はんだ量が充分に多くなっていることから、はんだ付け部に熱サイクルを受けてもはんだ付け部が金属疲労を起こしにくく、長期間にわたって剥離やひび割れなどが生じないという信頼性の面で優れたはんだ付け部を形成することができるものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of coating solder on a pattern of a printed circuit board, particularly a printed circuit board on which a surface mount component such as QFP or SOP is mounted.
[0002]
[Prior art]
Electronic components used in electronic devices include discrete components having long leads, and surface mount components in which the ends of the main body serve as leads or a number of short leads protrude from the main body. The soldered part of the printed circuit board to which discrete components are soldered is called a land, and the part to which surface mounted components are soldered is called a pattern.
[0003]
Soldering discrete components and printed circuit boards involves inserting long leads into holes drilled in the lands, applying flux to the lower surface of the printed circuit board, preheating, and then contacting the molten solder in the solder bath. Perform by law. In this immersion method, when the land is narrow, a bridge may be formed in which the solder straddles and adheres between the lands.
[0004]
For soldering the surface mount components and the printed circuit board, a solder paste composed of solder powder and flux has been used. In soldering a surface mount component and a printed board with solder paste, first, solder paste is printed and applied to a pattern of the printed board. In this printing, a metal mask having a hole formed in the same place as the pattern which is the soldering portion of the printed circuit board is superimposed on the printed circuit board so that the hole of the metal mask and the pattern match. Then, the solder paste is placed on the metal mask, and the solder paste on the metal mask is scratched with a squeegee to fill the holes of the metal mask with the solder paste. Then, when the metal mask is lifted upward, the solder paste adheres to the pattern on the printed circuit board. In this way, the surface mount component is mounted on the pattern of the printed board on which the solder paste is printed and applied, and the surface mount component is temporarily fixed by the adhesive force of the solder paste, and then the printed board is heated by a heating device such as a reflow furnace. And soldering by melting the solder paste.
[0005]
By the way, recently, electronic devices have become lighter, thinner and smaller, so that surface mount components have become smaller, and lead intervals have become extremely narrow. For example, a so-called fine pitch having a lead interval of 0.3 mm or less has appeared in QFP.
[0006]
When such fine-pitch surface mount components are soldered with solder paste, the solder may form a bridge between adjacent leads. When a bridge is formed in a soldered portion of an electronic component, the function of the electronic device is completely lost, and the commercial value is lost.
[0007]
The bridge is caused by a large amount of solder paste applied despite the soldering of fine pitch electronic components. That is, the reason why the application amount of the solder paste is increased is to improve the reliability by sufficiently supplying the solder to the joint between the lead of the surface mount component and the pattern of the printed circuit board. Sufficient supply of solder to the joint is particularly effective in preventing metal fatigue due to thermal cycling. Metal fatigue caused by thermal cycling means that the temperature inside the case of an electronic device rises due to the heat generated by a capacitor or transformer when using the electronic device, and the temperature drops when the use is stopped. The solder expands and contracts to cause metal fatigue.
[0008]
Certainly, if a large amount of solder adheres to the soldered portion, metal fatigue is reduced, and accidents such as cracking and peeling of the solder are less likely to occur. However, when a large amount of solder paste is applied to a fine pitch pattern, there is a problem that a bridge is formed at the time of soldering as described above.
[0009]
Therefore, conventionally, in the soldering of electronic components having a fine pitch, soldering has been performed using a solder coat in which solder is previously attached to a pattern. Solder-coated printed circuit boards do not use solder paste; instead, place the leads of surface-mounted components directly on the solder coat and locally heat them with something like a bonding tool. And pattern can be soldered. Therefore, the solder coat on the printed circuit board needs to have a sufficient amount of solder that can completely solder the lead and the pattern and does not cause metal fatigue. It is said that an appropriate amount of the solder is about 25 μm when the lead pitch is 0.25 mm and about 30 μm when the lead pitch is 0.3 mm.
[0010]
As a solder coating method for a printed board, there are an electrolytic method, an immersion method, a reflow method, and the like. The electrolytic method is a method of electroplating solder on a pattern of a printed circuit board by connecting a cathode to a printed circuit board in a solder electrolyte and connecting an anode to the solder of the electrode and passing DC electricity, and the immersion method. This is a method in which the printed circuit board is immersed in molten solder in a solder tank with the printed circuit board standing, and the solder is attached to the pattern. In this method, solder paste is printed and applied to the pattern using a metal mask with holes, and the solder paste is heated in a reflow furnace to attach solder to the pattern.
[0011]
[Problems to be solved by the invention]
In the electrolytic method, the solder cannot be thickly attached to the pattern. The thickness of the solder coat by the electrolytic method is at most about several μm, and the surface mount component cannot be soldered with this amount of solder. In addition, in the solder coat obtained by the electrolytic method, since the solder and the copper foil of the pattern do not have a metallic joint, the solder may not be completely wet during soldering, and may be dewet.
[0012]
In the immersion method, the solder can be attached to the pattern thicker than in the electrolytic method.However, even after the printed circuit board is immersed in the solder bath, the solder attached to the pattern drips down because the printed circuit board is pulled up in a standing state. In addition to the problem that the thickness cannot be reduced, there is a problem that the film adheres to the lower portion of the pattern when the film is lifted.
[0013]
In the reflow method, if the thickness of the metal mask is increased and the amount of solder paste filling the holes is increased, the amount of application to the pattern increases, but when the solder paste is melted, the solder paste drops and the adjacent pattern It merged with the solder paste to form a bridge.
[0014]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of coating a printed circuit board with a solder that never causes a bridge even though the solder can be applied to a desired thickness.
[0015]
[Means for Solving the Problems]
The inventor of the present invention adopts the advantage of the immersion method and the advantage of the reflow method, that is, that the immersion method can completely perform solder plating on all the patterns, and that the reflow method allows for unbiased adhesion of the solder, so that the solder coating can be performed. The present invention has been completed by paying attention to the fact that a solder coat having a sufficient thickness necessary for soldering can be obtained and no bridging occurs.
[0016]
The present invention provides a method of coating a printed circuit board on which a large number of patterns are installed in parallel, by immersing the printed circuit board in molten solder in a solder bath to perform solder plating on the pattern, and then applying the pattern to the printed circuit board pattern. A solder coating method for a printed circuit board, which comprises applying a solder paste and then heating and melting the solder paste.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The solder bath used in the present invention may be any solder bath as long as the solder can be completely metallically attached to the pattern of the printed circuit board. For example, an ultrasonic solder bath, a jet solder bath, a static solder bath, or the like can be used. It is.
[0018]
The solder paste powder solder applied to the pattern after the solder plating in the solder bath may have the same composition as the solder put into the solder bath, but it is difficult for the solder to break between the patterns at the time of melting to form a bridge, for example, When a Pb-Sn-Bi-based solder is used, no bridge is generated. A Pb-Sn-Bi system suitable for use in the present invention is the Pb-46Sn-8Bi system.
[0019]
In the present invention, a method of applying a solder paste to a solder-plated pattern by an immersion method is performed by printing each pattern with a metal mask having a hole formed in the same place as the pattern, or a metal having a long hole formed therein. Print one character with a mask. One-character printing refers to continuous application from one end to the other end of a plurality of parallel patterns.
One character of the solder paste may be applied horizontally in one or two rows. In order to apply solder paste to one character, in addition to printing using a metal mask perforated with a width shorter than the long side of the pattern and from one end to the other end of the parallel pattern, continuous with a dispenser Can also be applied.
[0020]
【Example】
Example 1
○ Printed circuit board: 0.3mm pitch, for mounting QFP with 16 patterns arranged in a row, pattern size is 0.15 × 1.5 (mm)
○ Solder tank: Stationary solder tank, in the air ○ Solder composition of solder tank: Pb-63Sn
○ Plating flux: dissolve rosin and activator in alcohol ○ Solder paste: flux amount is 10.5% by weight, powder solder composition is Pb-63Sn
○ Metal mask: 0.1mm thick, flux is applied to a mask printed circuit board with holes that match the pattern, then immersed in a solder bath, and blown with compressed air when pulled out of the solder bath, resulting in excess solder And solder plating was performed on the pattern. Observation of the solder adhesion state at this time with a magnifying glass revealed no occurrence of a bridge, or measurement of the solder adhesion thickness with a non-contact depth measuring instrument (manufactured by Union Optical Co., Ltd.) revealed that the thickness was 10 μm. After printing and applying a solder paste on each of the solder-plated patterns using a metal mask, the solder paste is heated in a reflow furnace to melt the solder paste. After cooling, the printed circuit board was observed with a magnifying glass, and the adhesion thickness was measured by a non-contact depth measuring instrument. As a result, no bridge was generated, and the solder adhesion thickness was 34 μm.
[0021]
Example 2
○ Printed circuit board: 0.3mm pitch, for mounting QFP with 16 patterns arranged in a row, pattern size is 0.15 × 1.5 (mm)
○ Solder bath: Nitrogen atmosphere with an oxygen concentration of 50 ppm in a jet solder bath equipped with an ultrasonic horn ○ Solder bath composition: Pb-63Sn
-Solder paste: The flux amount is 10.5% by weight, and the composition of the powder solder is Pb-46Sn-8Bi.
Metal mask: A mask printed board for printing a single character, having a thickness of 0.1 mm and a long hole of the same length as the entire area of the parallel pattern, was immersed in a solder bath, and the pattern was subjected to solder plating. Observation of the attached state of the solder at this time by a stereoscopic microscope revealed no occurrence of a bridge, and the thickness of the attached layer measured by a non-contact depth measuring instrument was 14 μm. A solder paste is applied in a row in a row on the solder-plated pattern using a metal mask and then heated in a reflow furnace to melt the solder paste. After cooling, the printed circuit board was observed with a magnifying glass, and the adhesion thickness was measured with a non-contact depth measuring instrument. As a result, no bridge was generated and the thickness of the solder adhesion was 32 μm.
[0022]
○ Comparative Example 1
Using the same printed circuit board, solder bath, and plating flux as in Example 1, solder coating was performed on the pattern of the printed circuit board by an immersion method. When the thickness of the solder coat was measured with a non-contact depth measuring instrument, the thickness of the lower portion was 20 μm and the thickness of the upper portion was 10 μm with respect to the pulling direction. In addition, the solder coat was uneven.
[0023]
○ Comparative Example 2
Using the same printed circuit board and solder paste as in Example 1, using a metal mask (thickness 0.2 mm) having holes drilled in the same locations as the patterns, printing and applying each pattern, and then soldering in a reflow furnace The paste was melted and solder coated. After cooling, the solder coat was observed with a magnifying glass, and found that many bridges had occurred. The thickness of the solder coat was 22 μm.
[0024]
【The invention's effect】
According to the present invention, a predetermined amount of solder can be coated on a pattern of a printed circuit board without bias, so that when soldering a surface mount component such as QFP or SOP, reliable bonding without unsoldering can be performed. Things. Also, since the solder coat obtained in the present invention has a sufficiently large amount of solder, the soldered portion hardly causes metal fatigue even when subjected to a heat cycle to the soldered portion, and peeling and cracking over a long period of time. Thus, it is possible to form a soldered portion excellent in reliability in that no soldering occurs.
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15636796A JP3587276B2 (en) | 1996-05-29 | 1996-05-29 | Solder coating method for printed circuit boards |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15636796A JP3587276B2 (en) | 1996-05-29 | 1996-05-29 | Solder coating method for printed circuit boards |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09321420A JPH09321420A (en) | 1997-12-12 |
| JP3587276B2 true JP3587276B2 (en) | 2004-11-10 |
Family
ID=15626209
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15636796A Expired - Lifetime JP3587276B2 (en) | 1996-05-29 | 1996-05-29 | Solder coating method for printed circuit boards |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3587276B2 (en) |
-
1996
- 1996-05-29 JP JP15636796A patent/JP3587276B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09321420A (en) | 1997-12-12 |
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