Circuit Technology Center

3.5.1 Base Material Repair, Epoxy Method

This procedure is used to repair minor damage to circuit base board material. Scrapes and scratches in the base board material may be caused by accidents during handling. Burns in the base material may be caused by improper use of soldering and desoldering tools.

Caution: This method may be used when the damage extends deep into the base material but not completely through. If the baseboard material is damaged completely through, see Procedure No. 3.5.2 or 3.5.3.

Caution: Surface circuits may need to be replaced in the damaged area. Be sure that the appropriate circuit diagrams or photographs reflecting the original circuits are available so that they may be replaced after repairing the base board material. Damage to internal circuits or planes may have to be restored using surface wires.

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
Procedure References
1.0 Foreword
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.5 Baking And Preheating
2.7 Epoxy Mixing and Handling
IPC7721 3.5.1 Base Material Repair, Epoxy Method
Kits and Systems
Professional Repair Kit
Kit to repair circuit board damage including pads, lands, conductors, base material and plated holes.
Master Repair Kit
Kit to repair circuit board damage including pads, lands, conductors and base material.
Base Board Repair Kit
Kit to repair base board and laminate damage on circuit boards.
Circuit Bond Kit
Includes packages of clear, low viscosity, superior strength epoxy for circuit board damage repair.
Micro Drill System
Versatile power tool for milling, drilling, grinding, cutting and sanding circuit boards.
Repair Skills Practice Kit
Training kit to practice circuit board repair skills prior to testing for certification.
Precision Tool Set
Nine precision-crafted tools for detailed circuit board work.
Tools and Materials
Ball Mills, Abrasives, Cutting Tools
Ball mills, abrasives and cutting tools for working on circuit boards.
Cleaning Brushes
Disposable brushes for solvent cleaning and application of coatings.
Color Agents
Use to tint the color of epoxy used for solder mask repair or circuit base board repair.
Circuit Bond Epoxy
Clear, superior strength epoxy in two-compartment plastic packages.
Foam Swab, Small
Swabs for use with solvents and application of color agents and epoxies.
High Temp Tape Discs
High temperature polyimide tape discs, .50" diameter.
Knife with #16 Blades
A must-have tool for precise cutting, scraping and trimming.
Scraper, Curved Tip
Hardened stainless steel tip for scraping solder mask and removing defects.
Additional Items and Supplies
General purpose cleaner for removing contamination.
Precision microscope with stand and lighting for work and inspection.
General purpose oven for drying, baking and curing epoxies.
Nonabrasive, low-linting wipes for cleanup.
Circuit Bond Epoxy
Circuit Bond is a clear, low viscosity, superior strength epoxy precisely measured out into two-compartment plastic packages, so it's easy to use, and there's no measuring. For over a decade, this high-strength epoxy has been qualified and used by thousands of high-rel electronics manufacturers across the globe.
1. Circuit Bond has a working pot life of 30 minutes. It should not be mixed until ready to use.
2. To use Circuit Bond, remove the plastic clip separating the resin and hardener. Squeeze back and forth from one half of the package to the other to mix the contents.
3. Cut a corner off the package and squeeze all the contents into a Plastic Cup. Stir the contents to ensure it is thoroughly mixed.
4. Circuit Bond may contain bubbles from the mixing process. If needed, use a vacuum system to remove bubbles.
5. Color Agent can be mixed in with Circuit Bond to match surface colors if desired.
6. Apply using a Foam Swab, Micro Probe, or Mixing Stick as required.
7. Cure Circuit Bond for 24 hours at room temperature or 4 hours at 65°C (150°F).
Packaging2 gram pre-measured packages
Mix ratio4 parts resin to 1 part hardener
Mix Ratio by Weight (R/H)100/25
ColorClear, transparent
Pot life30 minutes
Cure cycle24 hours at room temp (25 °C) or 4 hours @ 65°C
Thixotropic Index1
Specific Gravity1.20
Percent Solids100%
Viscosity (after mixing)2000 cps
Operating temperature range-55°C to 135°C
Hardness88 Shore D
Lap Shear, Alum to Alum1100 psi
Glass Transition Temperature, Ultimate92°C
Coefficient of Expansion, cm/cm/°C6 E-05
Dielectric strength400 volts/mil
Dielectric Constant, 1KHz@25°C4
Shelf Life6 months minimum
Color Agents
Color Agent is a one-part, air-drying, semi-paste ink commonly used to print hard surfaces, including circuit board base materials. Color Agent can be used to tint the color of epoxy used for solder mask repair or circuit baseboard repair. To use, mix a small amount of color agent with 2 part epoxy as the epoxy is initially mixed. Add more color agents to increase the color intensity if needed.
Part No. Description
115-9102 115-9102 Color Agent, Yellow
115-9185 115-9185 Color Agent, Red
115-9293 115-9293 Color Agent, Blue
115-9348 115-9348 Color Agent, Green
115-9358 115-9358 Color Agent, Light Green
115-9376 115-9376 Color Agent, Medium Green
115-9424 115-9424 Color Agent, Dark Gray
115-9457 115-9457 Color Agent, Light Brown
115-9560 115-9560 Color Agent, Dark Green
115-9561 115-9561 Color Agent, Green
115-9995 115-9995 Color Agent, Black
115-9996 115-9996 Color Agent - White
Images and Figures
3.5.1 Base Material Repair, Epoxy Method
Damaged Base Material
3.5.1 Base Material Repair, Epoxy Method
Figure 1: Scrape away damaged base board material with a knife.
3.5.1 Base Material Repair, Epoxy Method
Figure 2: Micro-Drill System.

3.5.1 Base Material Repair, Epoxy Method
Figure 3: An undercut, to enhance mechanical strength, may be desired for class 3 product.
3.5.1 Base Material Repair, Epoxy Method
Figure 4: Apply the epoxy with a mixing stick sharpened at the end.
3.5.1 Base Material Repair, Epoxy Method
Figure 5: For large areas, apply the epoxy with a foam swab to create a texture.

3.5.1 Base Material Repair, Epoxy Method
Figure 6. Completed repair.
  1. Clean the damaged area.
  2. Scrape away the damaged base board material using a knife. All damaged base board material and solder mask must be removed at the surface. (See Figure 1) or mill away the damaged base board material using the Micro-Drill System and ball mill. All damaged base board material and solder mask must be removed. (See Figure 2)
    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.
    Note: An undercut to enhance mechanical strength may be desired for a class 3 product. (See figure 3)
  3. Remove all loose material and clean the area.
  4. Where needed, apply High-Temperature tape to protect exposed parts of the circuit board.
    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.
  5. Mix the epoxy. If desired, add a color agent to the mixed epoxy to match the PC board color.
  6. Fill the area with epoxy up to and flush with the circuit board surface. No fibers of laminate material should be exposed. A mixing stick sharpened at the end may be used to apply and spread the epoxy. For large areas, apply the epoxy with a foam swab to create a texture in the surface. (See Figures 4 and 5)
    Note: A slight overfill of epoxy may be desired to allow for shrinkage when epoxy cures.
    Note: Epoxy may be applied using a foam swab to restore the surface appearance.
  7. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
    Caution: Some components may be sensitive to high temperatures.
  8. After the epoxy has cured, remove the tape.
  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.
  10. Remove all loose material. Clean the area. (See Figure 6)
    Note: If needed, apply an additional thin coating to seal any scraped areas.
  1. Visual examination for texture and color match.
  2. Electrical tests to conductors around the repaired area as applicable.
  3. No excess epoxy covering circuits or sensitive areas.
  4. Epoxy fully bonded. No evidence of chipping.
Procedure for reference only.