PCB Plate Processing Techniques and Functions: An In-depth Overview

1. Introduction: PCB plate making encompasses three primary methods—direct plate making, direct-indirect plate making, and indirect plate making—utilizing materials such as photosensitive paste, photosensitive film, and indirect film.
2. Direct Plate Making Method:
   • Method: Coat diazonium salt photosensitive paste onto a stretched screen, dry it, attach a plate-making negative, expose it in a printing machine, and then develop and rinse to obtain a screen printing screen.
   • Technological Process: Preparation of photosensitive paste, stretched net – degreasing – drying – coating film – drying – exposure – developing – drying – revision – final exposure – sealing net
3. Functions and Methods at Each Stage:a. Degreasing:
   • Use a degreasing agent to remove grease, ensuring proper adhesion between photosensitive paste and screen.
   b. Drying:
   • Dry moisture to prevent mesh tension change. Maintain temperature control at 40-45°C.
   c. Preparation of Photosensitive Paste:
   • Mix photosensitizer with pure water, add to photosensitive paste, stir evenly, and let it stand for 8 hours before use.
   d. Coating:
   • Evenly coat photosensitive paste using a scraper. Different coating methods, including automatic and manual coating, can be employed. Coating film thickness can be adjusted based on practical considerations.
   • Considerations: A. Correct thickness ensures durability. B. Thin coating results in poor durability. C. Thick coating on the blade surface leads to uneven light sensitivity, impacting screen life. D. Thin coating on the blade surface results in poor durability.
   e. Drying (Post-Coating):
   • Ensure even drying to prevent unevenness. Maintain a temperature of 40-45°C for approximately 10 minutes, adjusting drying time based on film thickness.
   f. Exposure:
   • Appropriate exposure facilitates photosensitive paste photopolymerization, producing a clear image through the negative plate.
   • Factors Affecting Quality: A. Correct exposure energy. B. Exposure and vacuum level. C. Cleaning of exposure machine glass.
   • Exposure Energy Adjustment: Determine correct exposure time using graded exposure methods based on screen mesh and film thickness.

This structured overview provides insights into the intricate stages and considerations involved in the PCB plate making process.