2023 年 62 巻 1 号 p. 216-220
Copper foil, along with polyimide, has been used as a flexible printed circuits (FPCs) material, contributing greatly to the development of the information society. In particular, since rolled copper foil has excellent flexibility, its use in wearable devices and in–vehicle sensors, as well as smartphones, has begun to increase in recent years. In addition, as the functionality of these devices improves, FPCs with more complex wiring patterns, such as double–sided FPCs and multilayer FPCs, are increasingly being used. In many cases, FPCs with two or more layers of copper foil often require conductive processing, which involves copper plating on the copper foil, and there is concern that the copper plating layer may reduce the flexibility of the FPC.
In this study, we investigated the influence of the plating layer on flexibility by evaluating the flexibility of samples made from three types of copper foils with different crystalline structures (high flexibility rolled copper foil, standard rolled copper foil, and electro–deposited copper foil) that were given a plating layer. At the same time, the effect of the copper foil crystalline structure on the crystal growth of copper plating was also investigated.
As a result, we report that when a high flexibility rolled copper foil was used, the plating structure that grew epitaxially under the influence of the copper foil structure showed high (100) accumulation as well as the copper foil, thereby maintaining high Flexibility.
