Release Date: June 14, 2026 Source: Coating Industry Column "Coating Junior" On June 14, a technical popular science article was released by the coating industry column, systematically analyzing four major causes of pinhole defects in film coating and offering complete troubleshooting guides for lithium battery separator and optical film production lines. Pinholes refer to micron-sized voids formed before or during coating drying, categorized into bubble-induced, contamination-induced, poor wetting and improper drying types. Bubbles stem from air entrainment during stirring or pipeline leakage; contamination comes from substrate dust and workshop fiber lint; insufficient wetting creates ring-shaped craters; rapid oven heating leads to volcanic pinholes. Combined with actual lithium coating cases, the article notes pinholes usually result from multiple overlapping issues. Operators can identify faults via dyne pens, transparent pipeline observation and segmented coating tests. Practical solutions including lowering stirring speed, gradient temperature drying, regular equipment cleaning and substrate corona treatment are provided to effectively reduce coating reject rates.