No. 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.
TOOLS & MATERIALS
Abrasive Powder
Micro Blasting System
Masking Tape
PROCEDURE
- Clean the area.
- Select the appropriate abrasive blasting powder and nozzle size. Set the air
pressure at the desired setting per 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 antistatic bags. 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 Fig 2).
- Blow off the blasting dust and clean the area
EVALUATION
- Visual examination or UV light may be used to verify complete removal of
coating.
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Solutions Across the Board
TM
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Product Class: R/F/W/C
Skill Level: Expert
Conformance Level: High
Revision: D
Revision Date: Jan 5, 1998
Repair Service Charge
Coating Removal Required At Outlined Area
Figure 1: Apply Kapton tape to outline area for coating removal
Figure 2: Remove coating using micro blasting system.
Figure 3: Removal complete.
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Tricks of the Trade
This is a terrific method for removing coatings. Experience is
key. If the circuit board is loaded with static sensitive devices be sure to use
a properly designed Microblasting System.
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Real Problems, Real Solutions
Circuit Technology Center was faced with the task of removing
soldermask from (4) .75" x 1.25" areas on 618 fully loaded backplanes.
Chemical removal of the soldermask was not an option. Removing the coating by
the time consuming method of scrapping it off, would have taken too long. The
solution as described above was microblasting. The system used was a Comco Microblasting System. fitted with a .046" diameter
nozzle. The media was 50 micron Sodium Bicarbonate. The project was completed in
4 days with a charge of $46.00 per backplane. These backplanes were valued at
$810.00 each.
Total Value $500,580
Total Charge $28,428 =
Total Savings $472,152
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