Development of a curable conductive copper paste in air
Development of a curable conductive copper paste in air
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空气中固化导电铜浆的研制
DOI：
10.1109/icep-iaac.2015.7111031
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Toshiyuki Sato
中科院分区：
文献类型：
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作者：
M. Kajita;Tomoyuki Takahashi;Toshiyuki Sato
银是目前应用于电子元件的导电粘合剂的最广泛使用的材料。但银在高温高湿条件下存在价格波动、电迁移等问题。近年来，铜作为银的替代物受到极大关注，因为铜的制造成本比银低得多，并且更耐电迁移。然而，铜的缺点之一是它在空气中容易氧化。因此，大多数铜膏在氮气气氛下固化。在本研究中，我们将报告在空气中固化的导电铜浆的发展。以铜粉（电解质铜粉）、树脂（甲阶酚醛型树脂）和添加剂为原料，采用简单易行的方法制备铜浆。添加剂在发展中起着重要作用。我们检查了三乙醇胺（TEA）和液体脂肪酸（例如，油酸、亚油酸和亚麻酸）。将制备的铜浆料丝网印刷在氧化铝基底上，然后在空气中在210°C下固化10分钟以获得固化的铜产物。加入添加剂后的固化物电阻率小于6.0 × 10-5 Ω·cm。未加添加剂时，电阻率为7.1 × 10-4 Ω·cm，高于加添加剂时的电阻率。当在每个样品中单独使用添加剂时，添加油酸的样品的电阻率为2.9 × 10-4 Ω·cm，添加TEA的样品的电阻率为4.7 × 10-4 Ω·cm。结果表明，TEA与液态脂肪酸在铜浆中相互作用，导致铜固化物的电阻率降低。我们发现，这两种添加剂的组合导致低电阻率，没有铜表面氧化。此外，使用液体脂肪酸和TEA的铜膏具有比其它铜膏更长的“适用期”。这一发现为我们的发展提供了宝贵的见解。
Silver is currently the most widely-used material for conductive adhesives applied to electronic components. However, silver has some problems such as price volatility and electromigration under high temperature and humidity. In recent years, copper has great attention as an alternative to silver because copper is much lower in manufacturing cost and more resistant to electromigration than silver. However, one of the drawbacks of copper is that it is easily oxidized in air. Thus, most of the copper pastes are cured under nitrogen atmosphere. In this study, we are going to report on development of conductive copper paste curable in air. The copper paste was prepared by a simple and facile method using copper powder (electrolyte copper powder) with resin (resol-type phenolic resin) and additives. Additives play an important role on the development. We examined tri-ethanolamine (TEA) and liquid fatty acid (e.g., oleic acid, linoleic acid and linolenic acid). The prepared copper paste was screen-printed on an alumina substrate, then cured at 210°C for 10 min in air to obtain cured copper product. The resistivity of the cured copper product with additives was less than 6.0 × 10-5 Ω·cm. Without the additives, the resistivity was 7.1 × 10-4 Ω·cm, it was higher than the case of with additives. When the additives were used individually in each sample, the one with oleic acid showed a resistivity of 2.9 × 10-4 Ω·cm and the one with TEA showed 4.7 × 10-4 Ω·cm, respectively. These results indicate that TEA and liquid fatty acid interact with each other in the copper paste, and then the resistivity of the cured copper product is decreased. We found the combination of these two additives leads to low resistivity without copper surface oxidation. Furthermore, the copper pastes using a liquid fatty acid and TEA had longer “pot life” than that of the other copper pastes. This finding offered a valuable insight to our development.