# Comparison of Tensile and Fatigue Properties of Copper Thin Film Depending on Process Method
## 2 Experimental Setup  
### The Shape of the Copper Thin Film Specim  
To compare the tensile and fatigue properties of the copper thin film, the specimens are fabricated according to the rolled and electrodeposited process methods. In addition, the shape of specimens is designed differently depending on the tensile and/or fatigue.  
First, as shown in Figure 1, the specimen used for the tensile test is designed in dog-bone type. The total length is 17,500 \(\upmu\)m and the reduced section is designed to be 5000 \(\upmu\)m in length and 700 \(\upmu\)m in width. There are holes with a diameter of 850 \(\upmu\)m in the specimen fixed part and the distance between the holes is 13,500 \(\upmu\)m. The role of the hole is to fix the specimen by inserting a pin when fixing the specimen. Second, as shown in Figure 1, the specimen used for fatigue testing is designed in hour-glass type. The total length is 17,500 \(\upmu\)m, the reduced section has an arc of radius 22,470 \(\upmu\)m, and the width of reduced section is 700 \(\upmu\)m. The specimen of tensile and fatigue have all 12 \(\upmu\)m thicknesses.  
Because the material properties of thin film specimens are affected by the microstructural differences, we performed surface microstructure analysis and material component analysis by using SEM (Scanning Electron Microscope) as shown in Figures 2 and 3, respectively.  
Figure 1: The shape and dimension of the specimens (\(\upmu\)m). (**a**) Tensile specimen (**b**) Fatigue specimen.  
Figure 2 shows the images of the front-side and back-side of the rolled and electrodeposited copper thin films included loading direction (LD), respectively. SEM images of the back-side of the specimen clearly show the difference between the rolled and electrodeposited copper. Rolled copper has an anisotropic characteristic due to the rolling process and forming a grain in a specific direction. The mechanical properties of the copper thin film in the rolling process depend on the rolling direction which is shown in SEM image as RD. In this study, the loading direction is transverse to the rolling direction. Generally, it is reported that the yield strength when the loading and rolling direction are in the transverse direction. However, the fracture strain is smaller than when the loading and rolling are in the same direction [13]. However, [PERSON] et al. reported that there is a little difference in elastic modulus between the rolling directions but the yield strength and ultimate tensile strength of the traverse direction are slightly smaller than the case of same direction from tests of copper thin film [2]. On the other hand, electrodeposited copper has an isotropic characteristic because it is and electro-plating method. For this reason, in particular, rolled copper require an analysis of the surface of the specimen before performing tensile and fatigue tests in order to obtain accurate material properties.  
Figure 3: EDS analysis of copper thin film surface. (**a**) Rolled copper thin film (**b**) Electrodeposited copper thin film.  
Figure 2: Copper thin film surface image by process method from SEM (Scanning Electron Microscope). (**a**) the surface image of rolled copper (**b**) the surface image of electrodeposited copper.