【発明の詳細な説明】[Detailed description of the invention]
本発明は印刷配線板、就中、導電性を有する組
成物により所要配線図形を印刷して回路を形成し
て成る印刷配線板の製造方法に関するものであ
る。
印刷配線板は配線レイアウトの小型軽量化、単
純化、或いは回路特性や信頼性の向上が可能であ
ることから、最近各種の電子機器や電気機器に広
く使用されるようになつて来た。
印刷配線板の導電性回路を形成する方法として
は、従来より銅と絶縁基板とからなる銅複合基板
の銅層を部分的にエツチング処理して所要回路を
形成することが広く行なわれて来た。しかし、こ
の方法は銅箔と絶縁基板とを貼り合わせる工程、
所要配線図形を覆うようにエツチングレジストを
設ける工程、エツチングする工程、エツチングレ
ジストを除去する工程と数多くの工程を経るの
で、生産工程が複雑、煩瑣な上、エツチング廃液
の処理に特別の工程を要するなど種々の問題があ
つた。
最近、回路形成工程の簡略化、形成費用の低減
等を目的として、銅複合基板をエツチング処理す
る方法を用いず、絶縁基板の表面にメツキや蒸着
等のの手段により金属層をつけて所要回路を直接
形成する方法や、また導電性を有する組成物を絶
縁基板の表面に直接印刷して回路を形成する方法
等が試みられている。これらの直接回路形成方法
の中でも、導電性組成物を印刷する方法は、単に
所要回路を印刷し、固化せしめるだけで導電回路
を形成できるので、工程がより簡単で、容易に所
要配線を作成することができる。しかし、この方
法に於いても、以下にあげる如き問題点があつ
た。即ち、この方法では、基板となる樹脂に銀粉
の如き導電性粒子を添加したものを導電性組成物
として用い、これを所要配線図形に印刷し、常温
又は加熱下で乾燥或は硬化せしめる。しかし、十
分な導電性を有する組成物を得るためには基材と
なる樹脂100重量部に対して、銀粉を400〜500重
量部程度も添加する必要があつたために、導電性
組成物の価格が比較的高価になり、また回路の印
刷作業性が低下して、回路の出来上がり状況がや
や悪くなる傾向にあつた。
また、特に可撓性印刷配線板の場合に於いて
は、銀粉の配合量が増えると可撓性が極端に悪く
なり、銀粉が400〜500重量部にもなると、配線板
の可撓性が損なわれて、配線板を折り曲げると回
路部分が折れて切れてしまうようになり、目的と
する可撓性印刷配線板を作ることができなかつ
た。
本発明は、導電性組成物を絶縁基板の表面に直
接印刷して回路を形成する印刷配線板の製造方法
に於ける如上の問題点について検討を進めた結
果、達成されたものであつて、導電性組成物を直
接印刷する方法の長所である、工程の簡便さを損
なうことなく、如上の種々の問題点を解決した新
規な製造方法を提供したものである。
即ち、本発明は導電性組成物を絶縁基板の表面
に直接印刷して回路を形成する印刷配線板の製造
方法に於いて、基材となる電子線硬化型樹脂100
重量部に銀粉を80〜300重量部添加して成る組成
物により、絶縁基板の表面に回路を印刷し、該印
刷回路を電子線を照射して硬化せしめた後、加熱
処理することを特徴とする印刷配線板の製造方法
に関するものである。
特に、本発明に於いては基材となる電子線硬化
型樹脂100重量部に対し、銀粉を80〜300重量部よ
り好まくしは100〜250重量部だけ添加して成る組
成物を用いる。先に述べた如く、従来開示されて
いる技術に於いては、十分な導電性を有する組成
物を得るためには、銀粉を400〜500重量部程度も
添加する必要があつた。ところが、本発明者らは
理由は明らかではないが、電子線硬化型樹脂100
重量部に銀粉を80〜300重量部添加して成る組成
物を用いて、絶縁基板の表面に回路を印刷し、該
印刷回路を電子線を照射して硬化せしめた後、加
熱処理を行なうことによつて、不思議なことに、
銀粉の添加量が80〜300重量部と少ないのにもか
かわらず、実用上十分な導電性を有する導電回路
を形成しうることを見出し、本発明を完成するに
至つた。
本発明に用いる銀粉は、金属銀を主体とし、フ
レーク状或いは塊状の形状を有する平均粒度が
0.1〜10μｍ程度の微細粒子である。銀粉の形状や
粒度は特に限定されないが、導電性や印刷作業性
或は経済性などを考えると、形状がフレーク状
で、比表面積の大きい粒子を利用した方が良く、
またスクリーン印刷を行なうためには粒度が小さ
いものを選定することが望ましい。
本発明に於いては、基材となる電子線硬化型樹
脂100重量部に対して、銀粉を80〜300重量部添加
する。添加量が80重量部に満たないと、十分な導
電性を有する印刷回路を得ることができず、ま
た、添加量が300重量部を越えると、導電性につ
いては比較的良好となるが、先に述べた如く、導
電性組成物の価格が高くなり、印刷作業性が低下
して回路の出来上がり状況がやや悪くなる傾向に
あり、また特に可撓性印刷配線板に於いては、可
撓性が損なわれて配線板を折り曲げると折れてし
まうといつた問題が生じる。特に好ましくは、添
加量が100〜250重量部の場合であり、上に述べた
ような問題を生じることなく、十分な導電性を有
する印刷回路を形成することができる。
本発明に用いる基材となる電子線硬化型樹脂と
は、電子線を照射することによつて硬化反応を起
こす官能性を有する樹脂のことをいい、例えばエ
ポキシ樹脂、ポリウレタン樹脂、シリコン樹脂等
のポリマーを官能基で変性して官能性をもたせた
もの、或は不飽和ポリエステル樹脂、ポリブタジ
エン樹脂、スピロアセタール樹脂等の如く分子内
に官能性を有するポリマー等の官能性樹脂を用い
る。これらの官能性樹脂は単独或は必要に応じて
混合して用いる他、官能性を有するモノマーやオ
リゴマー等も添加することもできる。特に所要量
の銀粉を添加して適正な印刷作業性を現出するた
めには、比較的粘度の低い官能性モノマーやオリ
ゴマーを併用することが効果的である。この他、
塗料形態を整えるために粘度調節材料や着色料な
どを添加することも可能である。これらの官能性
を有する基材となる樹脂に銀粉を添加して組成物
を作るには、通常塗料を調整する方法により、例
えば、ロール混合により均一に十分混練すること
によつて得ることができる。
絶縁基板の表面に回路を印刷する方法は特に限
定されるものではないが、通常用いられるスクリ
ーン印刷法が望ましい。特に、本発明に於いては
従来開示されている技術に於ける場合と比べ、銀
粉の添加量が少ないので、印刷作業性が良好であ
り、スクリーン印刷法の利用に適している。
絶縁基板の表面に形成された印刷回路は電子線
を照射して硬化せしめる。
電子線照射条件は使用する樹脂に応じて適宜決
めるが、通常５〜30Mrad程度の線量が好まし
い。
本発明に於いては、印刷回路を電子線照射によ
り硬化せしめた後、加熱処理を行なう。本発明に
於いては基材となる電子線硬化型樹脂100重量部
に対して銀粉を80〜300重量部添加して成る組成
物により回路を印刷するので、電子線照射によつ
て印刷回路が硬化した時点では回路の導電性は十
分ではない。しかし、電子線照射による硬化後印
刷回路を加熱処理することによつて、印刷回路は
実用上十分な導電性を有するようになる。加熱処
理の条件は80〜200℃の範囲である。加熱処理温
度が80℃以下では十分な導電性を現出することが
できず、また200℃を越すと熱の影響などで配線
板がひずむといつた問題が生じる。望ましくは
100〜150℃の範囲が良好である。又、加熱時間は
５分〜60分程度が良い。
以下、本発明にもとづく印刷配線板の製造方法
を実施例によつて具体的に説明する。
実施例 １
アロニツクスオリゴマー（東亜合成化学工業(株)
オリゴエステルアクリレート商品名）80重量部及
びリポキシ樹脂（昭和高分子(株)エポキシアクリレ
ート樹脂商品名）20重量部から成る官能性を有す
る樹脂ベースに、表１(a)〜(f)に示した如く、金属
銀を80〜300重量部を添加して塗料を作り、ガラ
スクロス−エポキシ樹脂積層板基板に30μｍ厚さ
でスクリーン印刷し、これに電子線を15Mrad照
射して硬化せしめた。電子線照射硬化後、塗料の
導電性を測定した結果を表１に示したが、銀粉の
添加量が少ない(a)〜(c)では導電性は認められず、
また銀粉の添加量がやや多い(d)〜(f)では導電性に
バラツキが認められた。さらに、これらの材料を
150℃で15分間加熱し、導電性を測定した結果も
表１に合わせて示した。表１で認められる如く加
熱処理を行なつたものは(a)は103Ω以下、(b)〜(f)
はずれも10Ω以下の抵抗値を示すことがわかつ
た。
比較例 １
実施例１と同じ樹脂ベースに、表１(g)〜(j)に示
した如く、金属銀を50〜70重量部及び400〜500重
量部添加して塗料を作り、実施例１の場合
The present invention relates to a printed wiring board, and more particularly, to a method for manufacturing a printed wiring board in which a circuit is formed by printing a desired wiring pattern using a conductive composition. Printed wiring boards have recently come to be widely used in various electronic and electrical devices because they can reduce the size, weight, and simplicity of wiring layouts, and improve circuit characteristics and reliability. As a method for forming conductive circuits on printed wiring boards, it has been widely used to form the required circuits by partially etching the copper layer of a copper composite board consisting of copper and an insulating substrate. . However, this method involves the process of bonding the copper foil and the insulating substrate.
The production process is complicated and cumbersome, as it involves a number of steps, including the process of applying etching resist to cover the required wiring pattern, the process of etching, and the process of removing the etching resist.In addition, a special process is required to treat the etching waste liquid. Various problems arose. Recently, with the aim of simplifying the circuit formation process and reducing the formation cost, a metal layer has been applied to the surface of an insulating substrate by plating, vapor deposition, etc., instead of using the method of etching the copper composite substrate. Attempts have been made to directly form a circuit, and to form a circuit by directly printing a conductive composition on the surface of an insulating substrate. Among these direct circuit forming methods, the method of printing a conductive composition is a simpler process because a conductive circuit can be formed by simply printing the required circuit and solidifying it, making it easier to create the required wiring. be able to. However, this method also has the following problems. That is, in this method, a conductive composition prepared by adding conductive particles such as silver powder to a resin serving as a substrate is used, which is printed in a desired wiring pattern and dried or cured at room temperature or under heat. However, in order to obtain a composition with sufficient conductivity, it was necessary to add about 400 to 500 parts by weight of silver powder to 100 parts by weight of the base resin. However, the circuits tended to be relatively expensive, and the printing workability of the circuits decreased, resulting in a somewhat poor quality of circuits. In addition, especially in the case of flexible printed wiring boards, as the amount of silver powder added increases, the flexibility becomes extremely poor, and when the amount of silver powder reaches 400 to 500 parts by weight, the flexibility of the wiring board decreases. This damage caused the circuit parts to break and break when the wiring board was bent, making it impossible to create the desired flexible printed wiring board. The present invention was achieved as a result of studying the above-mentioned problems in a method for manufacturing a printed wiring board in which a circuit is formed by directly printing a conductive composition on the surface of an insulating substrate. The present invention provides a new manufacturing method that solves the various problems described above without sacrificing the simplicity of the process, which is an advantage of the method of directly printing a conductive composition. That is, the present invention provides a method for manufacturing a printed wiring board in which a circuit is formed by directly printing a conductive composition on the surface of an insulating substrate.
A circuit is printed on the surface of an insulating substrate using a composition containing 80 to 300 parts by weight of silver powder, the printed circuit is cured by irradiation with an electron beam, and then heat-treated. The present invention relates to a method of manufacturing a printed wiring board. In particular, in the present invention, a composition is used in which 80 to 300 parts by weight, preferably 100 to 250 parts by weight of silver powder is added to 100 parts by weight of the electron beam curable resin serving as the base material. As mentioned above, in the conventionally disclosed technology, in order to obtain a composition having sufficient conductivity, it was necessary to add about 400 to 500 parts by weight of silver powder. However, although the reason is not clear, the inventors have developed an electron beam curable resin 100
Printing a circuit on the surface of an insulating substrate using a composition containing 80 to 300 parts by weight of silver powder, curing the printed circuit by irradiating it with an electron beam, and then performing heat treatment. Strangely enough,
It was discovered that a conductive circuit having practically sufficient conductivity could be formed even though the amount of silver powder added was as small as 80 to 300 parts by weight, and the present invention was completed. The silver powder used in the present invention is mainly composed of metallic silver, has a flake-like or lump-like shape, and has an average particle size of
They are fine particles of about 0.1 to 10 μm. The shape and particle size of the silver powder are not particularly limited, but considering conductivity, printing workability, economic efficiency, etc., it is better to use particles that are flaky in shape and have a large specific surface area.
Furthermore, in order to perform screen printing, it is desirable to select a material with a small particle size. In the present invention, 80 to 300 parts by weight of silver powder is added to 100 parts by weight of the electron beam curable resin serving as the base material. If the amount added is less than 80 parts by weight, it will not be possible to obtain a printed circuit with sufficient conductivity, and if the amount added exceeds 300 parts by weight, the conductivity will be relatively good, but the As mentioned above, the price of conductive compositions is increasing, printing workability is decreasing, and circuit completion tends to be somewhat poor.In particular, in flexible printed wiring boards, flexible A problem arises when the wiring board is damaged and breaks when the wiring board is bent. Particularly preferably, the amount added is 100 to 250 parts by weight, and a printed circuit with sufficient conductivity can be formed without causing the above-mentioned problems. The electron beam curable resin used as the base material used in the present invention refers to a resin having functionality that causes a curing reaction when irradiated with an electron beam, such as epoxy resin, polyurethane resin, silicone resin, etc. A functional resin such as a polymer modified with a functional group to have functionality, or a polymer having functionality in the molecule such as unsaturated polyester resin, polybutadiene resin, spiroacetal resin, etc. is used. These functional resins may be used alone or in combination if necessary, and functional monomers, oligomers, etc. may also be added. In particular, in order to achieve appropriate printing workability by adding the required amount of silver powder, it is effective to use a functional monomer or oligomer with relatively low viscosity. In addition,
It is also possible to add viscosity adjusting materials, colorants, etc. to adjust the paint form. In order to make a composition by adding silver powder to a resin that is a base material having these functionalities, it can be obtained by a method for preparing a paint, for example, by uniformly and thoroughly kneading it by roll mixing. . The method of printing a circuit on the surface of the insulating substrate is not particularly limited, but a commonly used screen printing method is preferable. In particular, in the present invention, since the amount of silver powder added is smaller than in the conventionally disclosed technology, printing workability is good and it is suitable for use in screen printing. The printed circuit formed on the surface of the insulating substrate is cured by irradiating it with electron beams. The electron beam irradiation conditions are appropriately determined depending on the resin used, but a dose of about 5 to 30 Mrad is usually preferred. In the present invention, after the printed circuit is cured by electron beam irradiation, heat treatment is performed. In the present invention, since the circuit is printed using a composition made by adding 80 to 300 parts by weight of silver powder to 100 parts by weight of the electron beam curable resin that serves as the base material, the printed circuit can be formed by electron beam irradiation. Once cured, the circuit is not sufficiently conductive. However, by heat-treating the printed circuit after curing by electron beam irradiation, the printed circuit becomes sufficiently conductive for practical use. The heat treatment conditions range from 80 to 200°C. If the heat treatment temperature is below 80°C, sufficient conductivity will not be achieved, and if it exceeds 200°C, problems such as distortion of the wiring board due to the effects of heat will occur. Preferably
A range of 100 to 150°C is good. Also, the heating time is preferably about 5 to 60 minutes. Hereinafter, the method for manufacturing a printed wiring board based on the present invention will be specifically explained with reference to Examples. Example 1 Aronix oligomer (Toagosei Chemical Industry Co., Ltd.)
A functional resin base consisting of 80 parts by weight of oligoester acrylate (trade name) and 20 parts by weight of lipoxy resin (epoxy acrylate resin trade name, manufactured by Showa Kobunshi Co., Ltd.), As described above, a paint was prepared by adding 80 to 300 parts by weight of metallic silver, and the paint was screen-printed to a thickness of 30 μm on a glass cloth-epoxy resin laminate substrate, and was cured by irradiating it with an electron beam of 15 Mrad. The results of measuring the conductivity of the paint after curing with electron beam irradiation are shown in Table 1. No conductivity was observed in (a) to (c) where the amount of silver powder added was small;
Furthermore, in cases (d) to (f) in which the amount of silver powder added was slightly larger, variations in conductivity were observed. Furthermore, these materials
The results of measuring conductivity after heating at 150° C. for 15 minutes are also shown in Table 1. As shown in Table 1, for those heat treated, (a) is 10 3 Ω or less, (b) to (f)
It was found that the resistance value was less than 10Ω. Comparative Example 1 Paints were prepared by adding 50 to 70 parts by weight and 400 to 500 parts by weight of metallic silver to the same resin base as in Example 1, as shown in Tables 1(g) to (j). in the case of
【表】
と同じ条件で印刷し、電子線照射硬化並びに加熱
処理を行ない、回路の導電性を調べた。その結果
を表１に示した。銀の添加量が少ない(g)、(h)では
電子線照射硬化時及び加熱処理後とも導電性は認
められず、また、添加量が多い(i)、(j)では電子線
照射硬化時に実用上十分な導電性が得られ、更に
これらを加熱しても特性に顕著な変化は認められ
なかつた。但し、(i)、(j)は印刷性が悪く、回路の
仕上がり状況が悪くなつた。
実施例 ２
実施例１のｃ即ち、銀添加量が150重量部の塗
料を50μｍのポリイミドフイルムの表面に20μｍ
厚さでスクリーン印刷し、実施例１と同じ条件で
電子線照射硬化並びに加熱処理を行なつた。回路
の導電性を調べると10Ω以下の値を得た。また、
この印刷配線板を折り曲げたところ回路が折れる
等の異常は生じず、良好な可撓性印刷配線板を作
ることができた。
比較例 ２
比較例１の(i)、即ち、銀添加量が400重量部の
塗料を用いて実施例２と同じ条件で回路印刷、電
子線照射硬化を行なつた。回路の導電性は良好で
あつたが、印刷配線板を析り曲げたところ回路が
折れて切断し、良好な可撓性印刷配線板を作るこ
とができなかつた。更に、この配線板を加熱処理
しても特性は変わらなかつた。
上述の如く、本発明にもとづく印刷配線板の製
造方法に於いては、銀粉を基材となる樹脂100重
量部に80〜300重量部添加するだけで実用上十分
な導電性を現出せしめるので、導電性組成物の価
格が比較的安価であり、印刷作業性が良好で回路
の出来上がり状況が良好であり、また特に可撓性
印刷配線板に於いては良好な可撓性を得ることが
できる。また、導電性組成物をスクリーン印刷法
などの通常行なう方法により印刷し、これを電子
線照射による硬化並びに加熱処理を行なうことに
よつて所望の印刷配線板を得るので生産工程が簡
便であり、工業的な価値は高い。The conductivity of the circuit was examined by printing under the same conditions as in [Table], performing electron beam irradiation curing and heat treatment. The results are shown in Table 1. In cases (g) and (h) with a small amount of silver added, no conductivity was observed during electron beam irradiation curing and after heat treatment, and in cases (i) and (j) with a large amount of silver added, no conductivity was observed during electron beam irradiation curing. Practically sufficient conductivity was obtained, and no significant change in properties was observed even when these were heated. However, (i) and (j) had poor printability, resulting in poor circuit finish. Example 2 c of Example 1, that is, a paint containing 150 parts by weight of silver was applied to the surface of a 50 μm polyimide film to a thickness of 20 μm.
The film was screen printed to a certain thickness, and subjected to electron beam irradiation curing and heat treatment under the same conditions as in Example 1. When we investigated the conductivity of the circuit, we found a value of less than 10Ω. Also,
When this printed wiring board was bent, no abnormalities such as circuit bending occurred, and a good flexible printed wiring board could be produced. Comparative Example 2 Circuit printing and electron beam irradiation curing were carried out under the same conditions as in Example 2 using (i) of Comparative Example 1, that is, a coating material containing 400 parts by weight of silver. Although the conductivity of the circuit was good, when the printed wiring board was bent and bent, the circuit was bent and cut, making it impossible to produce a good flexible printed wiring board. Furthermore, even when this wiring board was heat-treated, the characteristics did not change. As mentioned above, in the method for manufacturing a printed wiring board based on the present invention, sufficient conductivity for practical use can be achieved by simply adding 80 to 300 parts by weight of silver powder to 100 parts by weight of the base resin. The price of the conductive composition is relatively low, the printing workability is good, the circuit is finished well, and especially in flexible printed wiring boards, it is possible to obtain good flexibility. can. In addition, the production process is simple because the conductive composition is printed by a commonly used method such as screen printing, and the desired printed wiring board is obtained by curing it by electron beam irradiation and heat treatment. It has high industrial value.