(3) Acid Degreasing
Purpose and Function:

• Remove oxides on the copper surface of the circuit, residual glue, and ink residue film.
• Ensure bonding force between primary copper and patterned copper or nickel electroplating.
  Why Acid Degreaser is Used:
• Alkaline degreaser damages graphic circuits as the graphic ink is not alkali-resistant.
• Only acid degreaser can be used before graphic plating.
  Production Control:
• Degreaser concentration: around 10%.
• Time: 6 minutes.
• Supplementary addition: 0.5-0.8L per 100 square meters.
  (4) Micro-Etching:
  Purpose and Function:
• Clean and roughen the copper surface for bonding between patterned copper electroplating and primary copper.
  Key Details:
• Sodium persulfate is often used.
• Concentration: around 60 g/L.
• Time: about 20 seconds.
• Control copper content below 20 g/L.
  (5) Pickling
  Function and Purpose:
• Remove oxide and activate board surface.
• Use C.P grade sulfuric acid.
  Maintenance:
• Acid leaching time should not be too long to prevent surface oxidation.
• Replace acid solution if turbid or if copper content is too high.