Lesson-3-PCB-etching
Page 1: PCB Etching and Its Process
Page 2: What is PCB Etching?
Process of chemically removing copper from a PCB.
Leaves desired copper traces for conductive paths.
Essential for efficient and economic PCB manufacturing.
Page 3: PCB Etching Process
Chemical etchant solution dissolves unwanted copper.
A resist material protects desired copper traces.
Only the desired copper circuit pattern remains after etching.
Page 4: PCB Etching Process Steps A-B
A. PCB Design
Circuit board layout is designed; copper traces defined.
Typically done using CAD software or manually for simple circuits.
B. Print Etch Resist
Resist material is printed or coated onto copper clad PCB blank.
Common resists: dry film, liquid photoimageable soldermask, toner ink.
Page 5: PCB Etching Process Steps C-E
C. Expose and Develop Resist
PCB is exposed to UV light through a mask.
Cures and hardens resist in exposed areas.
D. Etch Copper
Strips away remaining resist material.
Reveals finished copper circuitry pattern.
E. Drill Holes and Finish PCB
Holes drilled according to circuit design.
Finish boards by cleaning and tinning.
Page 6: Types of Etchants Used
Ferric Chloride: Traditional, effective but toxic; requires safe disposal.
Ammonium Persulfate: Less toxic alternative; requires proper disposal.
Page 7: More Types of Etchants Used
Cupric Chloride: Regenerative, reuses etchant, less waste.
Hydrogen Peroxide/Acid: Powerful but requires safety precautions.
Sodium Persulfate: Safer, slower etching, produces less waste.
Page 8: Etching Methods
Tank Immersion: Common method; high volume etching.
Brush Etching: Manual, lower volume processing.
Spray Etching: Direct, fast, and efficient method.
Vertical Etching: Uses less solution and speeds up etching.
Page 9: Key Process Parameters
Etchant Concentration: Ensures proper etch rates; must be monitored.
Temperature: Higher temperatures increase etch speed but deplete etchant.
Agitation: Fresh etchant must reach copper surfaces consistently.
Page 10: More Key Process Parameters
Etch Rate: Impacts undercutting and pad areas; control is critical.
Resist Quality: Deficits can lead to unwanted etching.
Etch Consistency: Uniform etching is crucial for quality PCB traces.
Page 11: Etching Defects
Undercutting: Thinning of traces due to etchant operating under resist.
Overhanging Copper: Remnants post-etching; requires fresh etchant.
Pitting: Small imperfections from impurities; mitigate with filtration.
Page 12: More Etching Defects
Resist Damage: Imperfect resist leads to unwanted etching.
Over-Etching: Excess time removes desired copper traces.
Missing Copper: Erroneous etching of desired traces can ruin PCBs.
Page 13: Etching Safety
Use etchant-resistant containers and handle with care.
Wear protective gear including gloves and goggles.
Work in a ventilated area to avoid fume buildup.
Dispose of used etchants per regulations; do not pour down drains.
Follow safety datasheets and label all solutions clearly.