First-Aid Kits for Circuit Boards
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3.4.1 Key and Slot Repair, Epoxy
Outline
This method is used to repair minor damage to a key slot, or other cutout in a printed board or assembly. The area is repaired using high strength epoxy.
Caution
Care should be taken to limit the application of epoxy to the specific areas desired and to avoid damage to the conductive patterns, contacts and components.
Minimum Skill Level - Advanced
Recommended for technicians with soldering and component rework skills and exposure to most repair/rework procedures, but lacking extensive experience.
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 |
| Tools and Materials |
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Cleaner
General purpose cleaner for removing contamination. |
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Epoxy Kit
High temperature epoxy for masking and structural repairs to circuit boards. |
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Oven
General purpose oven for drying, baking and curing epoxies. |
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Syringes
Polypropylene syringe barrels with stainless steel dispensing tips. |
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Wipes
Nonabrasive, low-linting wipes for cleanup. |
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| Images and Figures |
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| Damaged Key Slot |
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| Figure 1: Mill away the damaged board base material using a Micro-Drill System and ball mill. |
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| Figure 2: Apply epoxy to the edges of the key slot using a mixing stick sharpened at the end. |
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| Figure 3: Completed key slot repair. |
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| Figure 4: Micro-Drill System. |
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Procedure
- Clean the area to be filled, including the edges.
- Mill away the damaged board base material using a Micro-Drill System and ball mill. All damaged base board material must be removed. No fibers of laminate material should be exposed at the surface of the keyslot. (See Figure 1).
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.
Caution
Abrasion operations can generate electrostatic charges.
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Remove all loose material and clean the area.
- Apply Kapton tape to the surface of the circuit board adjacent to the slot. The Kapton tape should protect any adjacent contacts or components.
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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Mix the epoxy. If desired, add color agent to the mixed epoxy to match the PC board color.
- Apply a small amount of epoxy to the edges of the slot. A mixing stick sharpened at the end may be used. (See Figure. 2).
Note
A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures.
Note
The circuit board may be turned on its side to keep the epoxy in place while it cures.
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Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
Caution
Some components may be sensitive to high temperature.
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After the epoxy has cured remove the Kapton tape.
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If needed use a knife or scraper and scrape off any excess epoxy.
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If precision is required, machine the edges of the slot using a milling machine or Precision Drill System and appropriate milling cutter. Use great care to correctly relocate the slot.
Note
If needed, apply additional thin coating to seal any scraped areas.
- Clean the area.
Evaluation
- Visual examination and measurement of key slot location and dimension.
This procedure is for reference only. Refer to the Procedure References listed above, or contact Circuit Technology Center for appropriate industry approved references.
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CircuitMedic
22 Parkridge Road, Haverhill, MA 01835 USA
Phone: 978-373-1600 - Fax: 978-372-5700
Division of Circuit Technology Center, Inc.
Copyright © 2012 All rights reserved.
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ISO9000:2008 Certified
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Member Since 1986
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