How to Remove PCB Solder Resist

Skill and experience come in handy when altering the complex maze of circuit boards.

Printed circuit boards (PCB) are coated with solder resist or solder mask to prevent environmental disturbances and wear from deteriorating circuitry. If you need to alter the circuitry, you will have to remove the solder resist. There are various techniques for removing the resist, which require different machines and skill levels to accomplish successfully. Resist can be removed through scraping, machining, chemical stripping or microblasting.

Things You'll Need

• Knife, pick or scraper
• Mechanical pencil with eraser
• Milling machine
• Clamps
• Masking tape
• Cotton swab
• Chemical stripper
• Clean rags
• Thin cardboard
• Microblasting machine

Instructions

Scraping

1. Scrape the surface of the circuit board with a knife, pick or scraper in the areas where you want the solder resist removed.

2. Scrape until all the resist film is removed from one area, then move to another section.

3. Remove the resist with a mechanical pencil eraser if you are worried about damaging the surface of the circuit board with a rigid instrument.

Machining

1. Place the circuit board in the milling machine. Lock the board in place with clamps.

2. Set the precision depth so that the machine will not remove too much and damage the board.

3. Guide the machine to remove resist only in the desired spots. Previous skill and experience with using the milling machine are necessary to remove resist successfully with this method.

Chemical Stripping

1. Cover the parts of the circuit board you want to keep intact with masking tape.

2. Dab a cotton swab into a chemical stripper, such as thinner cleaner solvent.

3. Apply the stripper to the untaped areas to remove solder resist. Wipe off the solder resist as it comes off of the board, using a clean rag. Refer to the chemical stripper label for safety information and additional instructions.

Microblasting

1. Mask the areas you want to keep intact with masking tape and thin cardboard. Place the circuit board on the bench top microblasting machine.

2. Point the hand-piece at the areas where you want to remove the resist.

3. Blast the resist away with the abrasive material projecting from the hand-piece. Previous experience and skill using a microblaster are required for a positive outcome.

Tips & Warnings

• Follow all safety precautions and warnings associated with each piece of equipment or chemical to reduce risk to yourself or your circuit board.

References

• MG Chemicals: Etching Your Board
• Circuit Medic: Four Techniques for Removing Solder Mask

Resources

• MG Chemicals: MSDS Thinner Cleaner