The size and design of a slider phone, which is one of the most important IT applications, are strongly affected by the deformation of the spring unit and the interface for PCB-to-PCB connection located in the same drive space. This implies that the components contribute to the enhancement of the degree of freedom in the design. Past technical developments have focused on thickness and cost reduction, but no fundamental research has been performed on the design. We propose a spring unit in which the interface is integrated with the spring unit in order to share the drive space. Finally, the degree of freedom of the H/W PCB artwork can be enhanced on the basis of the disposition of parts that have major functions. Therefore, a simplified spring that is capable of unifying the interface with the spring unit is proposed, and the type of interface appropriate for this study is identified. Finally, five spring unit samples are evaluated by testing the mechanical performance on the basis of the sliding force; further, reliability tests are performed to examine the life cycle, and environmental tests such as thermal shock and salt-spray tests are performed after assembling the spring unit of the mock-up phone.