Printing a Self‐Reducing Copper Precursor on 2D and 3D Objects to Yield Copper Patterns with 50% Copper's Bulk Conductivity
Printing a Self‐Reducing Copper Precursor on 2D and 3D Objects to Yield Copper Patterns with 50% Copper's Bulk Conductivity
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DOI：
10.1002/admi.201400448
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发表时间：
2015-02
影响因子：
5.4
通讯作者：
Yitzchak S Rosen;M. Grouchko;S. Magdassi
中科院分区：
文献类型：
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作者：
Yitzchak S Rosen;M. Grouchko;S. Magdassi
DOI：10.1002/adm.201400448烧结;以及4）油墨制备非常简单，并且基于涂料工业中使用的常用技术。用于印刷铜的基本RTP设置如图1所示。首先，使用由铜前体组成的油墨将图案（“供体图案”）印刷在基底（“供体基底”）上（图1A）。根据所需的分辨率，可以通过多种方法进行打印，例如丝网、喷墨或自来水笔打印。然后，第二个基板（“受体基板”），它可以由各种材料制成，如玻璃或塑料，是平行于施主图案（图1 B）。最后，在N2气氛下在烘箱中加热两个基板。供体图案的分解导致图案从供体衬底转移到受体衬底（图1C），产生铜图案（“获得的图案”），其是供体图案的镜像（图1D）。铜前体应能够在低温下将含铜材料转移到受体衬底。因此，我们选择了甲酸铜，其分解温度低于200 °C，并且具有挥发性分解产物。Keller [ 22 ]和Badalyan [ 23 ]已将含铜挥发性产物艾德鉴定为甲酸铜（I），其在第二基板上进一步分解，沉积纯铜。为了在供体基底上存款甲酸铜，我们首先评估了使用甲酸铜水溶液作为墨水;然而，由于甲酸铜在水中的溶解度有限（12.5wt%），墨水的金属负载量限制为5.2wt%Cu。这样的低金属负载导致非常薄的不连续的铜层的转移，该铜层是不导电的。为了克服这一缺点，我们制备了一种新的油墨，其中含有甲酸铜的纳米和亚微米颗粒的分散体。通过甲酸铜盐在其几乎不溶的溶剂中的简单湿磨来制备油墨（如实验部分中所述）。该NP油墨含有51重量%甲酸铜（21重量%铜），这使其适用于RTP工艺，如将描述的。为了通过RTP工艺获得铜图案，将甲酸铜的图案用该油墨印刷（通过丝网印刷）在玻璃供体基板上。将第二玻璃基板“受体基板”放置在距印刷图案不同距离处;使用适当的玻璃间隔物来保持差距距离。然后，将两个基板在氮气气氛下在170至250 °C的温度下加热30分钟，之后可以在受体基板上看到“供体图案”的铜镜图案。图2A显示了用于将导电材料的图案-特别是金属、碳纳米管（CNT）、石墨烯和导电聚合物的图案-印刷到各种表面上的几种已知技术。[1，2]这些包括减成法，如光刻法[3，4]和添加法[5，6]，包括直接化学制造，如金属[ 7 ]和石墨烯的无电沉积。[ 8 ]添加剂方法还包括成熟的印刷工艺，如转移，[ 9-15 ]凹版印刷，[ 16 ]
DOI: 10.1002/admi.201400448 sintering; and 4) the ink preparation is very simple and is based on common technologies utilized in the paint industry. The basic RTP set-up for the printing of copper is presented in Figure 1 . First, a pattern (“donor pattern”) is printed on a substrate (“donor substrate”) using an ink composed of a copper precursor (Figure 1 A). Printing can be performed by a variety of methods, such as screen, inkjet or fountain-pen printing, depending on the required resolution. Then a second substrate (“acceptor substrate”), which can be made of various materials—such as glass or plastics—is placed in parallel to the donor pattern (Figure 1 B). Finally, both substrates are heated in an oven under a N 2 atmosphere. The decomposition of the donor pattern results in the transfer of the pattern from the donor substrate to the acceptor substrate (Figure 1 C), producing a copper pattern (“obtained pattern”) that is the mirror image of the donor pattern (Figure 1 D). The copper precursor should enable the transfer of the copper-containing material to the acceptor substrate at a low temperature. Therefore we selected copper formate, which has a decomposition temperature below 200 °C and has volatile decomposition products. The copper-containing volatile product has been identifi ed by Keller [ 22 ] and Badalyan [ 23 ] as copper(I) formate that further decomposes on the second substrate, depositing pure copper. In order to deposit the copper formate on the donor substrate, we fi rst evaluated the use of an aqueous copper formate solution as the ink; however, due to the limited solubility of copper formate in water (12.5 wt%), the metal loading of the ink is limited to 5.2 wt% Cu. Such a low metal loading leads to the transfer of a very thin, non-continuous copper layer, which is not conductive. To overcome this drawback, we prepared a new ink, which contained a dispersion of nanometer and submicrometer particles of copper formate. The ink was prepared by a simple wet-milling of the copper formate salt in a solvent where it is practically insoluble (as described in the Experimental Section). This NP ink contains 51 wt% copper formate (21 wt% copper), which makes it suitable for the RTP process, as will be described. To obtain the copper pattern by the RTP process, a pattern of copper formate was printed with this ink (by screen printing) on a glass donor substrate. A second glass substrate, “the acceptor substrate”, was placed at various distances from the printed pattern; proper glass spacers were used to maintain the gap distances. Then, the two substrates were heated under a nitrogen atmosphere at temperatures ranging from 170 to 250 °C for 30 min, after which a copper mirror pattern of the “donor pattern” could be seen on the acceptor substrate. Figure 2 A presents There are several known techniques for printing patterns of conductive materials—particularly that of metals, carbon nanotubes (CNTs), graphene, and conductive polymers—onto various surfaces. [ 1,2 ] These include subtractive processes, such as photolithography, [ 3,4 ] and additive processes [ 5,6 ] that include directed chemical fabrication, such as electroless deposition of metals [ 7 ] and graphene. [ 8 ] Additive methods also include wellestablished printing processes, such as transfer, [ 9–15 ] gravure, [ 16 ]