Ultrapure Water Preparation Process for Display Panel Glass Substrate Cleaning

Flat panel display glass substrates require multiple precision cleaning steps before and after processes such as coating, exposure, and etching. Micro-contamination of the water can directly cause bright or dark point defects. Therefore, the requirements for ultrapure water used in cleaning are even more stringent than those in the typical semiconductor industry.
The preparation process begins with raw water pretreatment. Tap water passes through a raw water tank, a multi-media filter, and an activated carbon filter to remove suspended solids and residual chlorine. After softening treatment or antiscalant dosing, the water flows through a security filter and enters a first-stage RO unit to remove the majority of ions and organic matter. The RO permeate then enters a degassing membrane unit. This unit removes dissolved oxygen and carbon dioxide from the water through forced draft or vacuum extraction, preventing oxidation that could affect electrodes and the glass substrate. Subsequently, the system employs two-stage EDI for deep electrodeionization, raising the product water resistivity to over 15 MΩ·cm and effectively removing weakly ionized substances such as silica and boron.
The critical polishing stage comprises polishing mixed bed resin, UV oxidation, and terminal ultrafiltration. UV lamps emit light at 185 nm and 254 nm to oxidize TOC into carbon dioxide. The resulting carbon dioxide is then removed by degassing or adsorbed by the downstream polishing resin, thereby reducing TOC to below 1 ppb; the polishing mixed bed further stabilizes the product water resistivity at 18.2 MΩ·cm. The absolute pore size of the terminal ultrafiltration membrane is typically below 0.03 microns, which ensures that particles larger than 0.03 microns in the treated water are virtually zero. The piping is constructed from ultra-high-purity PVDF or electropolished stainless steel. The storage tank is sealed with clean, dry nitrogen gas. We can provide fully customized turnkey solutions, from UF pretreatment to terminal polishing mixed beds, meeting the ultrapure water demands of G6 to G10.5 generation panel production lines.