**Acknowledgements**

*Lead Free Solders*

as the following formulae:

formula (6) expresses the dissolution of Zn in Cu.

*Schematic illustrations of reaction at ZnO/SiO2 interface at 573–673 K.*

*Schematic illustrations of reaction at Cu/Zn-doped SiO2 interface at room temperature.*

Next, interfacial reaction of the formation of the intermixing layer is dis-

Zn2SiO4 <sup>+</sup> SiO2(2Zn)⟶Pt SiO2 · SiO <sup>+</sup> 3O <sup>+</sup> 4Zn (5)

Cu + Zn → Cu(Zn) (6)

The formula (5) is a Pt-catalyzed reaction. The catalytic reaction generates free oxygen and free Zn. As shown in **Figure 11(b)**, Zn was detected in Cu film. Therefore, the repelled Zn dissolves into the depositing Cu (**Figure 15**), because Zn is well miscible in Cu according to the Cu/Zn binary phase diagram [24]. The

Cu/Zn-surface-doped SiO2 interface at room temperature. From the observation and analysis results, an extremely thin intermixing layer was formed at the interface at room temperature, and the composition of the layer was Cu42Pt18Zn0.8Si15O22 (**Figure 11**). The composition ratio of Zn, Si, and O is Zn:Si:O = 2.1:39.7:58.2. This composition has a Si/O ratio close to 2:3. Therefore, we can safely say that this phase is an oxygen-deficient silicon oxide, presumably Si2O3 (SiO2·SiO) that contains impurity Zn. The reactions can be expressed

cussed. **Figure 15** shows schematic illustrations of the reaction at the

**58**

**Figure 15.**

**Figure 14.**

We acknowledge Professor Yoichi Nabetani and Professor Tsutomu Muranaka of the University of Yamanashi for providing ZnO films. A part of this work was financially supported by a Grant-in-Aid for Young Scientists (B) (25820122) from the Japan Society for Promotion of Science (JSPS) and Grant-in-Aid for Adaptable and Seamless Technology Transfer Program through target-driven R&D (AS262Z00926M) from the Japan Science and Technology Agency.

### **Author details**

Mitsuhiro Watanabe1 \* and Eiichi Kondoh<sup>2</sup>

1 Department of Precision Machinery Engineering, College of Science and Technology, Nihon University, Funabashi, Japan

2 Interdisciplinary Graduate School, University of Yamanashi, Kofu, Japan

\*Address all correspondence to: watanabe.mitsuhiro@nihon-u.ac.jp

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
