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Texture analysis of thin copper foils using X-ray pole figure measurement


Very thin Cu foils are widely used as part of the circuit board in the increasingly complex microelectronics systems, such as smartphones and laptop computers. One of the challenges engineers are facing today is the optimization of its performance in various circumstances. Understanding the texture structure of the thin foils formed during laminate process is an essential step because the thermal and electronic properties of the crystalline foils are usually anisotropic. X-ray diffraction is one of the widely used techniques for nondestructive texture analysis.


In Figure 1, the (002) pole figure of a 50 micron thick Cu foil measured on Rigaku's SmartLab X-ray diffractometer is shown. The strong (002) peak at the center of the pole figure indicates that the foil is preferably (001)-oriented along the surface normal.The four peaks seen at the rim are Cu (200), (200), (020), and (020), respectively, due to the cubic structure of the copper lattices.

X-ray pole figure of a thin Cu foil used in microelectronics
Figure 1: The X-ray pole figure of a thin Cu foil used in microelectronics


The other 12 peaks are also reflections of the [002] lattice plane group. However, their locations indicate that some grains in the foil have their (001) axis oriented along some distinct, non-random, directions other than the foil's surface normal. The observed texture should be a result of manufacturing processes of the measured foil and the pole figures can be used to analyze the relation between the texture and manufacturing processes.