JP3723998B2 - Manufacturing method of thick film Cu circuit board - Google Patents
Manufacturing method of thick film Cu circuit board Download PDFInfo
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- JP3723998B2 JP3723998B2 JP30381994A JP30381994A JP3723998B2 JP 3723998 B2 JP3723998 B2 JP 3723998B2 JP 30381994 A JP30381994 A JP 30381994A JP 30381994 A JP30381994 A JP 30381994A JP 3723998 B2 JP3723998 B2 JP 3723998B2
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- boric acid
- circuit board
- thick film
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Description
【０００１】
【産業上の利用分野】
本発明は、電子機器などに用いられる厚膜Ｃｕ回路基板の製造方法に関する。
【０００２】
【従来の技術】
電子機器などに用いられる厚膜回路基板の導体としては、従来のＡｇ／Ｐｄに代わって、Ｃｕが主として用いられるようになってきた。これは、ＣｕはＡｇ／Ｐｄと比較してコストが安く、また、導体としたときの配線抵抗が低く、耐マイグレーション性に優れるためである。
【０００３】
そして、このようなＣｕを導体とした厚膜回路基板は、アルミナなどのセラミック基板上にＣｕ粉末、ガラスフリットおよび有機ビヒクルからなるＣｕペーストをスクリーン印刷法などで塗布し乾燥させた後、Ｎ2 雰囲気中で焼成することにより得られている。
【０００４】
【発明が解決しようとする課題】
ところで、高温においてＣｕはＯ2 によって容易に酸化される。このため、従来の厚膜Ｃｕ回路基板の製造において、Ｃｕペーストを塗布、乾燥させた後、Ｎ2 中で焼成するとき、焼成雰囲気中にｐｐｍオーダーで微量に存在するＯ2 によりＣｕが酸化されやすかった。
【０００５】
したがって、得られたＣｕ導体膜のはんだ濡れ性が悪くなり、その後の部品搭載工程においてはんだ付け不良が発生し、はんだ付け手直し率の増加や製品歩留まり率を減少させるという問題点を有していた。
【０００６】
そこで、本発明の目的は、はんだ付け性に優れたＣｕ導体膜を有する厚膜Ｃｕ回路基板の製造方法を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成するため、本発明の厚膜Ｃｕ回路部品の製造方法は、セラミック基板にＣｕペーストを塗布し、乾燥させて塗膜を形成した後、該塗膜上に溶媒中に硼酸を溶解してなる硼酸溶液を塗布し、その後Ｎ2 雰囲気中で焼成することを特徴とする。
【０００８】
そして、硼酸溶液中の硼酸濃度は、０．１〜０．３モル／リットルであることが好ましい。
【０００９】
【作用】
Ｃｕペースト乾燥膜に硼酸溶液を塗布することにより、Ｃｕペースト乾燥膜表面が硼酸によって薄く均一に覆われる。この硼酸によって、焼成過程におけるＣｕの酸化が防止される。
【００１０】
【実施例】
以下、本発明の厚膜Ｃｕ回路部品の製造方法について、その実施例を説明する。
まず、Ｃｕペーストを準備した。即ち、粒径１〜３μｍのＣｕ粉末が７５ｗｔ％、硼珪酸鉛系ガラスフリットが７ｗｔ％、エチルセルロース樹脂をテレピネオールに溶解した有機ビヒクルが１８ｗｔ％となるようにそれぞれを混合した後、３本ロールで分散させてＣｕペーストを調整した。さらに、イソプロピルアルコールに硼酸を溶解させて、０．０５モル／リットルから０．４モル／リットルまで５種類の濃度の硼酸溶液を作製した。
【００１１】
次に、セラミック基板としてのアルミナ基板に先に準備したＣｕペーストをスクリーン印刷し、１５０℃で１０分間乾燥させて塗膜からなる回路パターンを形成した。その後、この乾燥塗膜に同じく先に準備した硼酸溶液を刷毛塗りして乾燥させた。その後、この塗膜をＮ2 雰囲気の連続焼成炉で６００℃、１０分で焼成してＣｕ導体膜を形成し、表１に示す５種類の硼酸濃度条件下で厚膜Ｃｕ回路基板を作製した。
【００１２】
なお比較例として、Ｃｕペーストの塗膜に硼酸溶液を塗布せず、その他は上記実施例と同様の方法で厚膜Ｃｕ回路基板を作製した。
【００１３】
以上得られた厚膜回路基板のＣｕ導体膜について、はんだ付け性および下地セラミック基板への接着強度の評価を行なった。
【００１４】
この場合、はんだ付け性は、はんだ濡れ拡がり率で確認した。即ち、図１に示すように、アルミナ基板１に形成されたＣｕ導体膜２の上に直径２．５ｍｍのはんだボール（はんだ組成：Ａｇ／Ｓｎ／Ｐｂ＝２／６０／３８重量比）を乗せ、このアルミナ基板１を１２０℃で６０秒間予熱した後、２３５±５℃のホットプレート上に３０秒間放置した。その後、図１に示すはんだボール３の拡がりＬａおよびＬｂを測定し、以下の式によりはんだ濡れ拡がり率（Ｓ）を求めた。
【００１５】
Ｓ（％）＝｛（Ｌａ＋Ｌｂ）／（２．５×２）−１｝×１００
また、接着強度は、Ｃｕ導体膜の２ｍｍ角の部分を２３５±５℃に保持した溶融Ｓｎ・Ｐｂ共晶はんだ中に浸漬してはんだをコートした後、線径０．８ｍｍφの錫めっき軟銅線をはんだ付けした。そして、引張り試験機により、この軟銅線をＣｕ導体膜と垂直方向に２０ｍｍ／分の速度で引張り、その破壊強度を求めた。なお、この接着強度については回路基板作製直後の初期と、１５０℃の恒温槽に４８時間保持する熱エージングを行なった後との２条件で測定した。以上の、評価結果を表１に示す。
【００１６】
【表１】
表１に示す通り、本発明の方法により、はんだ濡れ拡がり率の大きい、即ちはんだ付け性の優れたＣｕ導体膜を有する厚膜Ｃｕ回路基板を得ることができる。ただし、硼酸濃度が０．１モル／リットル未満の場合は、試料番号１に示すように、比較例と比較してはんだ濡れ拡がり率の向上がみられず、また、硼酸濃度が０．３モル／リットルを超える場合は、試料番号５に示すように、熱エージング後の接着強度がやや低下する傾向を示す。したがって、硼酸溶液中の硼酸濃度としては０．１〜０．３モル／リットルの範囲が最も好ましい。
【００１８】
なお、上記はんだ濡れ拡がり率の測定においては、はんだボールの組成がＡｇ／Ｓｎ／Ｐｂ＝２／６０／３８重量比の場合について説明したが、その他Ｓｎ−Ｐｂ共晶はんだ、Ｓｎ−Ａｇ系はんだ、Ｓｎ−Ｐｂ系の高温はんだにおいても、同様の結果が得られている。
【００１９】
また、上記実施例においては、Ｃｕ導体膜を形成するセラミック基板として、アルミナ基板を用いているが、本発明はこれのみに限定されるものではない。即ち、セラミック基板としては、アルミナなどの絶縁体セラミック基板、非還元性誘電体セラミック基板、ＢａＯ−Ａｌ2 Ｏ3 −ＳｉＯ2 などの多層セラミック用基板等、種々のセラミック基板を用いることができる。
【００２０】
また、硼酸溶液の溶媒としては、イソプロピルアルコール以外に、硼酸を溶解するアルコール系、ケトン系、炭化水素系もしくは芳香族系の有機溶剤または水を適宜用いることができる。そして、作業性の面より、沸点が比較的低温で揮発性に富んだものが好ましい。
【００２１】
さらに、乾燥塗膜への硼酸溶液の塗付方法としては、刷毛塗り以外に、スプレー法、浸漬法などを採用することができる。
【００２２】
【発明の効果】
以上の説明で明らかなように、本発明の厚膜Ｃｕ回路基板の製造方法によれば、Ｃｕペースト乾燥膜に硼酸溶液を塗布することによって、Ｃｕペースト乾燥膜表面が硼酸によって薄く均一に覆われる。そして、この硼酸によって、焼成過程におけるＣｕの酸化が防止される。
【００２３】
したがって、はんだ付け性に優れたＣｕ導体膜を有する厚膜Ｃｕ回路基板を製造することができる。
【図面の簡単な説明】
【図１】はんだ濡れ拡がり率の測定方法を示す斜視図である。[0001]
[Industrial application fields]
The present invention relates to a method for manufacturing a thick film Cu circuit board used in electronic equipment and the like.
[0002]
[Prior art]
Cu has been mainly used as a conductor for thick film circuit boards used in electronic devices and the like, instead of conventional Ag / Pd. This is because Cu is cheaper than Ag / Pd, has low wiring resistance when used as a conductor, and is excellent in migration resistance.
[0003]
Then, such a thick film circuit board with conductor of Cu is, Cu powder ceramic substrate such as alumina, after a Cu paste comprising glass frit and an organic vehicle was applied by screen printing drying, N 2 It is obtained by firing in an atmosphere.
[0004]
[Problems to be solved by the invention]
By the way, Cu is easily oxidized by O 2 at a high temperature. For this reason, in the manufacture of conventional thick film Cu circuit boards, when Cu paste is applied and dried and then fired in N 2 , Cu is oxidized by O 2 present in a trace amount in the order of ppm in the firing atmosphere. It was easy.
[0005]
Therefore, solder wettability of the obtained Cu conductor film is deteriorated, and soldering failure occurs in the subsequent component mounting process, and there is a problem that the soldering rework rate increases and the product yield rate decreases. .
[0006]
Accordingly, an object of the present invention is to provide a method of manufacturing a thick film Cu circuit board having a Cu conductor film excellent in solderability.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the method of manufacturing a thick film Cu circuit component of the present invention, a Cu paste is applied to a ceramic substrate and dried to form a coating film, and then boric acid is dissolved in the solvent on the coating film. A boric acid solution is applied, and then fired in an N 2 atmosphere.
[0008]
The boric acid concentration in the boric acid solution is preferably 0.1 to 0.3 mol / liter.
[0009]
[Action]
By applying a boric acid solution to the Cu paste dry film, the surface of the Cu paste dry film is thinly and uniformly covered with boric acid. This boric acid prevents the oxidation of Cu during the firing process.
[0010]
【Example】
Examples of the method for manufacturing a thick film Cu circuit component according to the present invention will be described below.
First, a Cu paste was prepared. That is, after mixing them so that Cu powder having a particle diameter of 1 to 3 μm is 75 wt%, lead borosilicate glass frit is 7 wt%, and an organic vehicle in which ethyl cellulose resin is dissolved in terpineol is 18 wt%, Cu paste was prepared by dispersing. Further, boric acid was dissolved in isopropyl alcohol to prepare boric acid solutions having five concentrations from 0.05 mol / liter to 0.4 mol / liter.
[0011]
Next, the Cu paste prepared previously was screen-printed on an alumina substrate as a ceramic substrate and dried at 150 ° C. for 10 minutes to form a circuit pattern made of a coating film. Thereafter, the previously prepared boric acid solution was brushed on the dried coating film and dried. Thereafter, this coating film was baked at 600 ° C. for 10 minutes in a continuous baking furnace in an N 2 atmosphere to form a Cu conductor film, and a thick film Cu circuit board was produced under the five types of boric acid concentration conditions shown in Table 1. .
[0012]
As a comparative example, a boric acid solution was not applied to the coating film of the Cu paste, and a thick film Cu circuit board was produced in the same manner as in the above example.
[0013]
The Cu conductor film of the thick film circuit board obtained as described above was evaluated for solderability and adhesion strength to the underlying ceramic substrate.
[0014]
In this case, the solderability was confirmed by the solder wetting spread rate. That is, as shown in FIG. 1, a 2.5 mm diameter solder ball (solder composition: Ag / Sn / Pb = 2/60/38 weight ratio) is placed on the Cu conductor film 2 formed on the alumina substrate 1. The alumina substrate 1 was preheated at 120 ° C. for 60 seconds and then left on a 235 ± 5 ° C. hot plate for 30 seconds. Thereafter, the spread La and Lb of the
[0015]
S (%) = {(La + Lb) / (2.5 × 2) −1} × 100
Also, the adhesive strength was determined by immersing the 2 mm square part of the Cu conductor film in molten Sn / Pb eutectic solder held at 235 ± 5 ° C. Soldered. Then, the annealed copper wire was pulled at a rate of 20 mm / min in the direction perpendicular to the Cu conductor film by a tensile tester, and the breaking strength was obtained. The adhesive strength was measured under two conditions: the initial stage immediately after the circuit board was produced and the thermal aging that was held in a thermostatic bath at 150 ° C. for 48 hours. The above evaluation results are shown in Table 1.
[0016]
[Table 1]
As shown in Table 1, according to the method of the present invention, a thick film Cu circuit substrate having a Cu conductor film having a high solder wetting spread rate, that is, excellent solderability can be obtained. However, when the boric acid concentration is less than 0.1 mol / liter, as shown in Sample No. 1, the improvement of the solder wetting spread rate is not observed as compared with the comparative example, and the boric acid concentration is 0.3 mol. When exceeding / liter, as shown in Sample No. 5, the adhesive strength after thermal aging tends to be slightly reduced. Therefore, the boric acid concentration in the boric acid solution is most preferably in the range of 0.1 to 0.3 mol / liter.
[0018]
In the measurement of the solder wetting spread rate, the case where the composition of the solder balls is Ag / Sn / Pb = 2/60/38 weight ratio has been described. However, other Sn—Pb eutectic solders and Sn—Ag solder Similar results were obtained with Sn-Pb high-temperature solder.
[0019]
Moreover, in the said Example, although the alumina substrate is used as a ceramic substrate which forms Cu conductor film, this invention is not limited only to this. That is, as the ceramic substrate, various ceramic substrates such as an insulating ceramic substrate such as alumina, a non-reducing dielectric ceramic substrate, and a multilayer ceramic substrate such as BaO—Al 2 O 3 —SiO 2 can be used.
[0020]
As a solvent for the boric acid solution, in addition to isopropyl alcohol, an alcohol-based, ketone-based, hydrocarbon-based or aromatic-based organic solvent that dissolves boric acid or water can be used as appropriate. From the viewpoint of workability, those having a relatively low boiling point and high volatility are preferred.
[0021]
Furthermore, as a method for applying the boric acid solution to the dried coating film, a spray method, a dipping method, or the like can be employed in addition to brush coating.
[0022]
【The invention's effect】
As apparent from the above description, according to the method for manufacturing a thick film Cu circuit board of the present invention, the surface of the Cu paste dry film is thinly and uniformly covered with boric acid by applying a boric acid solution to the Cu paste dry film. . The boric acid prevents Cu oxidation during the firing process.
[0023]
Therefore, a thick film Cu circuit board having a Cu conductor film excellent in solderability can be manufactured.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a method for measuring a solder wetting spread rate.
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30381994A JP3723998B2 (en) | 1994-12-07 | 1994-12-07 | Manufacturing method of thick film Cu circuit board |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30381994A JP3723998B2 (en) | 1994-12-07 | 1994-12-07 | Manufacturing method of thick film Cu circuit board |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08162738A JPH08162738A (en) | 1996-06-21 |
| JP3723998B2 true JP3723998B2 (en) | 2005-12-07 |
Family
ID=17925693
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30381994A Expired - Fee Related JP3723998B2 (en) | 1994-12-07 | 1994-12-07 | Manufacturing method of thick film Cu circuit board |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3723998B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100369118B1 (en) * | 2000-05-13 | 2003-01-24 | 한국과학기술연구원 | High density ceramic thick film fabrication method by screen printing |
-
1994
- 1994-12-07 JP JP30381994A patent/JP3723998B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH08162738A (en) | 1996-06-21 |
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