The application of tile over either plywood or a particleboard material is commonly performed, especially in more economical installations as well as speculation housing. However, the better base for any tile application is either a cement waterproof board, or even better, a mud job. A mud job will be explained as another subject within this webpage.
The application of tile over either particleboard or plywood, although, commonly performed, is an invitation for future problematic issues. The inability for the particleboard or plywood to withstand moisture and water penetration will require a perfect tile installation, without any cracking or compromise of the tile or the joints, allowing water under the tile application. Particleboard or plywood will tend to absorb any moisture that reaches its surface; this absorption will encourage mold and deterioration under your tile installation. This is all bad!
The use of a manufactured cement board, with the proper preparation of the joints and fasteners to ensure a watertight surface, is recommended, and will produce the most professional and permanent tile installation possible, other than the mud job that I will now explain.