PCB Dry Film Exposure: Principles and Process Parameters

What Is Dry Film Exposure?

Dry film exposure uses ultraviolet light to transfer the circuit pattern from artwork onto the dry film. The exposed portion undergoes cross-linking.

PCB dry film exposure infographic showing UV exposure, alignment, vacuum, pattern transfer, and process parameters

Exposure Process

Important operations include alignment, vacuum, UV exposure, and pattern transfer.

Exposure Energy

Reference exposure energy in the training material: 25–60 mJ/cm².

Exposure scale: approximately 6–9 levels using an ETERTEC 21-step exposure scale.

Alignment

Alignment ensures that the artwork pattern matches required PCB positions, including hole locations.

Vacuum

Vacuum removes air between the Mylar film, artwork, PCB, and exposure-machine glass, helping reduce light refraction. The training material specifies a vacuum level of at least 80% in its process-control section.

Common Exposure Problems

Check vacuum, vacuum delay, exposure scale, machine cleanliness, and artwork cleanliness. Reference vacuum delay: 5–15 seconds.

Conclusion

Stable vacuum, correct exposure energy, accurate alignment, clean equipment, and controlled exposure-scale settings contribute to consistent pattern transfer.