Mechanism for different laser textured bumps formation

Laser texturing on NIP substrate is a promising method for high-density hard disk manufacturing. The tribology property at the head-disk interface depends on the morphology of laser textured bumps. A model has been made to find the relationship of bump morphology on the hard disk, the parameters employed in laser texturing and the properties of the substrate material. We can find type of bumps through numerical calculation of the model. The model involves two steps. The temperature distribution is calculated first by solving heat conduction equation. The surface structure formation is studied at the second step. The surface structure is formed by thermocapillary force. The model treats the melting substrate as a kind of viscous liquid. The final shape of the substrate surface depends on the movement of the liquid. The viscosity of the liquid plays an important role because it increases sharply when the liquid cools down. This will stop the further movement of the melted surface. Our model can not only help to understand the mechanism of pulse laser microprocessing, but also has applications in laser texturing, which can increase the storage density of the hard disk. By comparison of the calculation results and experimental results, appropriate parameters can be chosen for manufacturing purpose.