1. Field of the Invention
The present invention relates to this external storage devices that are releasably or exchangeably used for storage equipment and external storage medium devices.
2. Description of the Related Art
Two types of storage devices, or memory elements, that are capable of recording and saving various data have been utilized. One is incorporated and fixed within storage equipment or devices, and the other is releasably or exchangeably incorporated in storage equipment or devices. In the latter type, the external storage device, for example, floppy disk, can freely be attached or detached by a one touch operation. The floppy disks, being storage mediums, can separately be used depending on purpose and object. This therefore produces easier data reduction with optional classification, recording, and saving. However, a problem arises in the floppy disks described. First, the data occasionally disappear when recording or saving the data to produce the disadvantage of less reliability. Second the floppy disk has a slow access time. Also, when employing smaller sized floppy disks in response to a miniaturization goal, the storage area of the storage medium is correspondingly smaller thereby reducing storage capacity. This thus gives an adverse effect in realizing both the compact size and high capacity. On the other hand, in semiconductor memory devices used as an external storage device, such as IC memory cards, the problems of the floppy disks, such as low reliability on recording and saving data and slow access time can largely be overcome. In general, IC memory cards comprise a functional circuit in which circuit components containing semiconductor memory devices or elements are mounted on a substrate. A resin case incorporates the functional circuit as an inside attachment. A cover covers and seals an opening surface of the resin case, and external connection terminals, such as two piece connectors, are attached on one edge of the resin case and electrically connect the functional circuit and the storage equipment.
However, IC memory cards are assembled with a large number of components and parts. Thus a relatively complicated structure is required impacting the thickness of the IC memory card, resulting in difficulty in realizing a compact size. Further, disadvantages arise in practical use because of lower cost performance and production yields in mass producing, in addition to the decreased releasability or fluctuated releasability to the storage equipment and device.