Only the 2.5 inch hard drive is a component used by CBB and its design guide does not address the integration of 1.8 inch hard drives.[1]
A notebook should support 2.5 inch SATA or PATA HDDs that are designed based on the SFF Committee Specifications, The target CBB thickness for 2.5 inch HDDs in 2006 was 9.5mm with a tolerance of +/-0.2mm, as that was the form factor most used.[1]
The HDD could be mounted with side or bottom mounting, a hard drive should comply with both, but the system could choose whichever was best suited for the application.[1]
The electrical interface for SATA HDDs should follow the electrical interface standards set by the Serial ATA International Organization (SATA-IO). For PATA HDDs they should support the specifications defined by the T13 Committee.[1]