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

Caution: Microblasting 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, Materials and Supplies

Flex-Rack PCB Holder
Sturdy rack for PCBs used for rework and positioning.

Cleaning Brushes
Disposable brushes for solvent cleaning and application of coatings.

Cleaner
General purpose cleaner for removing contamination.

Microblasting System
Benchtop microblasting system for removal of coatings.

Tape, Plating and Masking
Ideal for masking during plating, coating removal and microblasting.

Precision Tool Set
Nine precision-crafted tools for detailed circuit board work.

Wipes
Nonabrasive, low-linting wipes for cleanup.

Procedure

Clean the area.
Select the appropriate abrasive blasting powder and nozzle size. Set the air pressure at the desired setting per the equipment manufacturer's instructions.
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.
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.
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)
Blow off the blasting dust and clean the area.

Evaluation

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

Images and Figures

Coating Removal, Micro Blasting Method

Figure 1. The area requiring coating removal is identified.

Figure 2. Apply high-temperature tape to outline the area for coating removal.

Figure 3. Remove the coating using a micro-blasting system.

Figure 4. Continue until the required coating material has been removed.

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Product Type
Assemblies Bare PCBs Other

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2.3.6 Coating Removal, Micro Blasting Method

Procedure covers the methods for removal of coatings on circuit boards assemblies using a micro abrasive blasting system. Minimum Skill Level: Expert Conformance Level: High

Procedure covers the methods for removal of coatings on circuit boards assemblies using a micro abrasive blasting system.

Minimum Skill Level: Expert
Conformance Level: High