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2.3.6 Coating Removal, Micro Blasting Method
Outline
This coating removal method uses a micro abrasive blasting system and a very fine soft abrasive powder. The powder is propelled through a small nozzle toward the area where the coating needs to be removed.

To determine the appropriate coating removal procedure the coating must first be identified. Refer to procedure number 2.3.1.

Caution
Micro blasting will generate substantial static charges. The work area should be flooded with ionized air and the circuit board assembly should be grounded whenever possible.


Minimum Skill Level - Expert
Recommended for technicians with advanced soldering and component rework skills and extensive experience in most repair/rework procedures.

Conformance Level - High
This procedure most closely duplicates the physical characteristics of the original, and most probably complies with all the functional, environmental and serviceability factors.

Acceptability References
IPC-A-600 2.0 Externally Observable Characteristics
IPC-A-610 10.0 Laminate Conditions
Procedure References
1.0 Foreword
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.3.1 Coating Removal, Identification Of Coatings
2.4.1 Coating Replacement, Solder Mask
2.4.2 Coating Replacement, Conformal Coatings/Encapsulants
IPC7721 2.3.6 Coating Removal, Micro Blasting Method
Tools and Materials
CircuitMedic Part
Alcohol Swab
Self-saturating Isopropyl alcohol swab. Squeeze handle to release alcohol.
Cleaner
Cleaner
General purpose cleaner for removing contamination.
CircuitMedic Part
Cleaning Brushes
Disposable brushes for use with solvents for cleaning and application of coatings.
Microblasting System
Microblasting System
Benchtop microblasting system for removal of coatings.
CircuitMedic Part
Plating and Masking Tape
Ideal for masking during plating, coating removal and microblasting.
Wipes
Wipes
Nonabrasive, low-linting wipes for cleanup.
Images and Figures
2.3.6 Coating Removal, Micro Blasting Method
Coating Removal Required At Outlined Area
2.3.6 Coating Removal, Micro Blasting Method
Figure 1: Apply high temperature tape to outline the area for coating removal.
2.3.6 Coating Removal, Micro Blasting Method
Figure 2: Remove the coating using a micro-blasting system.
2.3.6 Coating Removal, Micro Blasting Method
Figure 3: Removal complete.

Procedure

  1. Clean the area.

  2. Select the appropriate abrasive blasting powder and nozzle size. Set the air pressure at the desired setting per equipment manufacturer's instructions.

  3. Apply masking tape or other masking material to protect the circuit board surface as needed. (See Figure 1) Masking materials can consist of tapes, curable liquid masks or reusable stencils.

  4. If the circuit board has static sensitive components, insert the entire circuit board into a shielded bag. Only the area needing rework should be exposed. Ground the circuit board to dissipate static charges

  5. Insert the circuit board into the blasting chamber and blast away the damaged or unwanted coating\solder mask. Slowly move the nozzle along the area where the coating is to be removed. (See Figure 2)

  6. Blow off the blasting dust and clean the area.

 Evaluation

  1. Visual examination or UV light may be used to verify complete removal of coating.

Procedure for reference only.