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2.7 Epoxy Mixing and Handling More Guides
Outline
This procedure covers epoxy mixing and handling. The epoxy covered by this procedure has multiple uses including solder mask repair, base board repair, circuitry over-coating and delamination repair.

Note
For high strength or high temperature applications two part epoxies will generally have the best properties.

Minimum Skill Level - Intermediate
Recommended for technicians with skills in basic soldering and component rework, but may be inexperienced in general repair/rework procedures.

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.

Procedure References
1.0 Foreword
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.5 Baking And Preheating
IPC7721 2.7 Epoxy Mixing and Handling
Tools and Materials
CircuitMedic Part
Alcohol Swab
Self-saturating Isopropyl alcohol swab. Squeeze handle to release alcohol.
CircuitMedic Part
Cleaning Brushes
Disposable brushes for use with solvents for cleaning and application of coatings.
CircuitMedic Part
Circuit Bond Packs
Clear, superior strength epoxy in two-compartment plastic packages
CircuitMedic Part
Foam Swab
Ideal for absorbing cleaning solvents, and applying color agents and epoxies.
Images and Figures
2.7 Epoxy Mixing and Handling
Figure 1: For prepackaged epoxy, remove divider clip and mix resin and hardener inside package.
2.7 Epoxy Mixing and Handling
Figure 2: Apply epoxy as needed. Foam swabs may be used to add texture for soldermask repair.
Epoxy Specifications
The Epoxy referenced in this procedure has the following properties.

Packaging   -   2 gram prepackaged containers
Color   -   Clear, transparent
Pot life   -   30 minutes
Cure cycle   -   24 hours at room temperature or 1 hour @ 165F (74C)
Viscosity (after mixing)   -   1900 cps @ 77F (25C)
Operating temperature range   -   76F to 284F (-60C to 140C)
Hardness   -   88 Shore D
Dielectric strength   -   410 volts/mil

Preparation
The area where the epoxy is to be applied should be prepared prior to mixing the epoxy. This preparation may include preheating the affected area to improve absorption of the applied epoxy. The entire circuit board may also be heated in an oven or with a heat lamp.

Caution
Some components may be sensitive to high temperatures.

Procedure - Prepackaged Two Part Epoxy

  1. Remove the clip separating the resin and hardener. Mix by squeezing both halves together with your fingers. Mix for at least one minute to ensure a complete mix of the resin and activator. (See Figure 1)

  2. Cut open one end of the epoxy tube and squeeze the contents into a mixing cup. Mix again with a mixing stick to ensure a thorough mixture of the resin and hardener.

    Note
    For bubble free epoxy, remove the clip separating the resin and hardener. Cut open one end of the Epoxy tube and squeeze the contents into a mixing cup. Slowly stir the mixture with the mixing stick. Be sure to stir the mixture for at least 2 minutes to ensure that all the resin and hardener have completely mixed.

  3. If needed, add color agent to the mixed epoxy. Stir slowly to prevent bubbles.

  4. Apply or use as needed. (See Figure 2)

  5. Cure the epoxy for 24 hours at room temperature or 1 hour @ 165F (74C)
Evaluation
  1. Visual examination of epoxy for texture and color match.

  2. Testing of epoxy surface for complete cure.

  3. Electrical tests as applicable.
Procedure for reference only.
Customer Comments
"I just wanted to let you know, the 10 circuit boards that you touched up in the BGA area, all worked well. Thank you for your help. This is one happy customer."
G.C. Lowell, MA USA
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