Abstract: A new crosshatching technology on polyimide flexible substrate is described using chemical etching method. The etching solution is composed of Potassium hydroxide, Sodium hydroxide, and additives. The window of demanding is crosshatched in certain conditions on polyimide flexible substrate. The technology process and mechanism of etching are also discussed in detail with examples of hollowing board process. The demerits of the pre-investment and maintenance costs too high or precision too low to traditional crosshatching process are conquered. The new crosshatching technology on polyimide flexible substrate can be applied in the small and high-density FPCB products that have high added value.