The difference between spin coating and dip coating techniques in surface coating

Spin coating and dip coating are two common techniques for applying thin films or coatings to substrates. The purpose is to apply the function of surface coating to optimize and upgrade the properties of the film. The main process differences between these two techniques are The differences in molecular level interactions and resulting film morphology are compared below.

1. Process differences

The spin coating process is to distribute the liquid solution or dispersion of the coating to the center of the substrate, and then the substrate rotates rapidly, generating centrifugal force to evenly distribute the coating material on the surface. During the spin coating process, the liquid material due to various Intermolecular forces (such as van der Waals forces, hydrogen bonds or electrostatic interactions, etc.) spread and adhere to the surface of the substrate. The excess liquid is discharged from the edge. The high-speed rotation also helps to evaporate the solvent, leaving a thin and A uniform solid film of solute; while in dip coating, the substrate is immersed vertically in the coating bath and then removed at a controlled rate. When the substrate is pulled out, it depends on the coating due to capillary action and wetting forces. Due to the molecular interaction between the material and the surface of the substrate, the coating material adheres to the substrate to form a liquid film, which solidifies to form a solid film.

2. Thickness control

Spin coating can control the thickness of the film by adjusting the solution viscosity, spinning speed, and spinning time, and the thickness is uniform and the surface is smooth. This is due to the rotating action in the process that helps remove surface bubbles and makes the coating material on the base. Spread evenly on the material, the implementation of this process must use a flat substrate; dip coating can control the thickness of the film by adjusting the speed of taking out the substrate, the viscosity of the solution, and the concentration of the solute in the solution. Compared with spin coating, dip coating Coating can produce a thicker film. However, due to the gravity effect, meniscus formation and the discharge of excess coating material during the extraction process, it is easy to cause the film surface to be rough and uneven, but the shape and size requirements for the substrate are relatively wide.

3. Limitations of the two processes

The spin coating process can only be used on relatively small, flat substrates and wastes coating material because much of the coating material falls off the edges of the substrate during the spinning process; while the dip coating process is generally shorter than spin coating It is slow and difficult to control the take-out speed, so it is difficult to obtain standard thickness and very thin film materials.

The above are the process differences between the two technologies. Each has its own advantages. In addition, the interaction between material molecules, van der Waals forces and wetting characteristics in the process all play a vital role in determining the adhesion of the substrate surface. Echoing film formation, the production and research and development of polymer basic materials is a long process. Excellent technology comes from uninterrupted production and practice, come on.