Circuit Board Repair Guide > Basic Circuit Board Repair Procedures > 2.3.6 Coating Removal Using Micro Blasting Method

Coating Removal Using Micro Blasting Method

Repair Circuit Boards | Repair SMT Pads | Repair BGA Pads | Repair Lands | Repair Edge Contacts
Repair a Conductor | Plated Hole Repair | Base Board Repair | Replace Solder Mask or Coatings

This method of coating removal 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. Coating Removal, Identification of Coatings.

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.

IPC Acceptability References
IPC-A-600 2.0 Externally Observable Characteristics
IPC-A-610 10.0 Laminate Conditions
 
Related Procedure References
CTC 1.0 Foreword - Circuit Board Repair Guide
CTC 2.1 Handling Electronic Assemblies
CTC 2.2.1 How to Clean a Circuit Board
CTC 2.2.2 Cleaning Circuit Boards, Aqueous Batch Process
CTC 2.4.1 Replace Solder Mask or Coatings on Printed Circuit Boards
CTC 2.4.2 Replace Conformal Coatings and Encapsulants on Circuit Boards
IPC 7721 2.3.6 Coating Removal, Micro Blasting Method
 
Coating removal required at outlined area
Coating Removal Required
At Outlined Area

Tools and Materials
Abrasive Powder
Micro Blasting System
Masking Tape  

2.3.6 Coating Removal, Micro Blasting Method

Printed Board Type: R/F/W/C  |  Skill Level: Expert  |  Conformance Level: High  |  Rev.: D  |  Rev. Date: Jan 5, 1998

Apply Kapton tape for coating removal

Fig. 1: Apply Kapton tape to outline area for coating removal.


Remove coating using micro blasting system

Fig. 2: Remove coating using
micro blasting system.


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
 
Verify complete removal of coating

Fig. 3: Coating removal complete.
Evaluation
   
1.  Visual examination or UV light may be used to verify complete removal of coating.
 




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