The present invention relates to a communication medium capable of carrying out data read/write operations in a contactless manner and a method of producing the same.
In recent years, a communication medium of a contactless system utilizing an electromagnetic wave in information exchange with various apparatuses is developed and used in various fields, for example, as an IC card or an IC tag. The communication medium of the type comprises a module for processing and recording data, and an antenna wire for transmission/reception of the data. The module and the antenna wire are embedded in a card base member made of plastic.
There is also known a combination-type communication medium which can be used both in a contact system and a contactless system. The combination type may be called a hybrid type or a composite type.
Japanese Patent Application Publication (JP-A) No. 2003-36433 discloses an example of the combination-type communication medium in which a metal plate is used so as to increase the reliability in connection between an antenna wire and an antenna connection terminal of a module. Specifically, in a state where the antenna wire is attached to the card base member, the antenna wire is connected to the metal plate. To the metal plate, the antenna connection terminal is bonded through a conductive paste. In this manner, a bonding area between the metal plate and the antenna connection terminal can be increased so that the reliability in bonding of the antenna wire is improved.
However, since the metal plate is high in heat capacity, it is problematic to use heating and pressing treatment upon production of the communication medium of the type. Specifically, during the heating and pressing treatment, heat accumulating points are concentrated to the metal plate and an area adjacent thereto. As a consequence, deviation or nonuniformity may possibly occur in thermal expansion and thermal shrinkage of the card base member to induce deformation of the card base member.