3.3.1 Hole Repair, Epoxy Method
| Printed Board Type: R/W | Skill Level: Advanced | Conformance Level: High | Rev.: D | Rev. Date: Jul 7, 2000 |
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Outline
This method is used to repair cosmetic defects or minor
damage to an unsupported tooling or mounting hole. The
hole may have component leads, wires, fasteners, pins,
terminals or other hardware run through it. This repair
method uses high strength epoxy to restore the damaged
surface surrounding the hole. This method can be used
on single sided, double sided or multilayer circuit
boards and assemblies.
Caution
Damaged inner-layer connections may require surface
wire adds.
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Acceptability References |
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IPC-A-610 |
2.0 |
Externally Observable
Characteristics |
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IPC-A-600 |
10.0 |
Laminate Conditions |
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Damaged Hole
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Procedure
Figure 1: Mill away damaged material with the Micro-Drill
and ball mill.
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| 1. |
Clean the area.
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| 2. |
Mill away the damaged board base material using
the Micro-Drill and ball mill. All damaged base
board material and solder mask must be removed.
No fibers of laminate material should be exposed
at the surface perimeter of the hole. (See Figure
1).
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Note
To clearly see that all damaged
material has been removed, flood the area with
alcohol or solvent. Damaged internal fibers
of the base material will show up clearly.
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| 3. |
Remove all loose material and clean the area.
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| 4. |
Where needed, apply Kapton tape to protect exposed
parts of the circuit board. Tape may be required
inside the hole. If epoxy reduces the inside
diameter, the hole may have to be redrilled
after the epoxy has cured.
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Note
The circuit board may be preheated
prior to filling the area with epoxy. A preheated
PC Board will allow the epoxy to easily flow
and level out. Epoxy applied to an unheated
circuit board may settle below the circuit board
surface as the epoxy cures.
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Caution
Some components may be sensitive
to high temperatures. |
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Figure 2: Apply epoxy with a mixing
stick sharpened at one end.
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| 5. |
Mix the epoxy. If desired, add color agent to
the mixed epoxy to match the PC board color.
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| 6. |
Coat the area with epoxy up to and flush with
the circuit board surface. A mixing stick may
be used to apply and spread the epoxy. (See
Figure 2).
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Note
A slight overfill of epoxy may be desired to allow
for shrinkage when epoxy cures. |
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| 7. |
Cure the epoxy per Procedure 2.7
Epoxy Mixing and Handling. |
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| 8. |
After the epoxy has cured, remove the tape.
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| 9. |
If needed, use a knife or scraper and scrape
off any excess epoxy. Scrape until the new epoxy
surface is level with the surrounding circuit
board surface.
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Note
Apply surface coating to match prior coating as
required. |
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| 10. |
Remove all loose material. Clean
the area. |
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Figure 3: Micro-Drill System.
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Evaluation |
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| 1. |
Visual examination for texture
and color match. |
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| 2. |
Hole size measurement to specification. |
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| 3. |
Electrical tests to conductors
around the repaired area as applicable. |
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