How PCB Dry Film Plays a Key Role in Enhancing PCB Reliability

What is PCB Dry Film？

Dry film is a photosensitive material used in the production of PCBs to create the circuit pattern. It is applied to the surface of the copper-clad laminate and then exposed to UV light through a film mask containing the circuit pattern. The UV light cures the exposed areas of the dry film, hardening it and creating a protective layer over the copper traces. After exposure, the unexposed areas of the dry film are washed away, leaving behind the circuit pattern on the copper surface. Dry film is commonly used in PCB manufacturing due to its high resolution, good adhesion to copper, and ease of processing.Let us understand the PCB pattern production process together：

Masking Holes in Dry Film

When masking holes in the dry film process, several factors must be considered to ensure a successful outcome:

• Reduce the film temperature and pressure to avoid damage.
• Improve hole wall roughness and tip for better adhesion.
• Increase the energy of exposure to enhance film adherence.
• Reduce the developing pressure for a smoother process.
• Avoid long periods between film application and exposure to prevent film diffusion.
• Ensure the dry film is applied without excessive tightness to prevent deformation.

Penetration in Dry Film Electroplating

Penetration occurs when the electroplating solution infiltrates between the dry film and copper foil, indicating poor adhesion. This issue can be caused by:

• Incorrect film temperature, either too high or too low, affecting film adhesion.
• Improper film pressure, leading to uneven surfaces or gaps that compromise adhesion.
• Inadequate exposure energy, resulting in incomplete polymerization and weak adhesion.
• Proper control during these processes is crucial to prevent defects and ensure high-quality PCB assembly.

Surface Blistering in PCB Production

Surface blistering is a common defect in PCB production, caused by various factors:

• Substrate processing issues, such as poor adhesion between copper foil and chemical copper.
• Contamination from machining processes or other liquids, leading to oil stains.
• Excessive pressure during copper brush plating, causing deformation and subsequent blistering.
• Water washing problems, including cross-contamination and poor treatment of the board surface.
• Micro etching issues in pretreatment, leading to base material leakage and blistering.
• Strong activity of copper precipitation solution, resulting in poor coating adhesion.
• Oxidation of the board surface during production.
• Poor reworking of copper, causing blistering due to incorrect methods or insufficient control.
• Insufficient water washing after development or dust contamination in the workshop.
• Failure to replace pickling tanks, leading to cleanliness and surface roughness issues.
• Organic pollution, especially oil contamination, in electroplating tanks.
• Charging PCB boards entering tanks, especially those with air agitation, must be carefully managed to prevent defects.

By understanding these challenges and implementing proper controls, PCB manufacturers can enhance the quality and reliability of their products, meeting the demanding requirements of modern electronics.

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