PCB Pattern Transfer Process: Liquid Photoresist Technology
In PCB manufacturing, the transfer of graphics onto copper plating foil substrates is a crucial process. Liquid photoresist pattern transfer has emerged as a popular method due to its thin film, high resolution, and cost-effective nature. Let’s delve into the details of liquid photoresist and its production process:
Liquid Photosensitive Ink Application Process Flow:
- Substrate surface treatment
- Coating (screen printing)
- Pre-baking
- Exposure
- Development
- Drying
- Inspection
- Etching
- Film removal
- Inspection (Inner and Outer layer boards)
Advantages of Liquid Photoresist:
- Eliminates the need for silk screen stencils
- Superior film adhesion, etch resistance, and electroplating resistance
- Flexible coating methods
- Good adhesion, high-definition resolution
- Rectifies issues like warping and irregular lines
- Suitable for flexible PCB production
- Reduces material cost and waste
- Easy to store with a long shelf life
- Versatile for various applications
However, challenges with thickness uniformity and drying control exist, requiring careful operational oversight. Environmental and health risks from volatile additives must be managed with proper ventilation in the workplace.
Liquid Photoresist Process Flow:
The process involves pre-treatment, coating, baking, exposure, development, drying, inspection, etching or electroplating, and film removal.
Pre-Treatment:
Ensures cleanliness and roughness of the copper surface for optimal bonding with the photosensitive adhesive. Mechanical grinding and chemical pretreatment methods are commonly used, with a focus on cleanliness for wet film requirements.
Regardless of the method used, immediate drying post-treatment is essential, with inspection through a water film test to verify cleanliness. Clean handling and prompt application of photosensitive adhesive prevent copper surface reoxidation.
