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3.1 Delamination/Blister Repair, Injection Method

 
Outline
This method is used to repair mechanical or thermal blisters or delaminations in circuit board laminated base materials. The blister is sealed by injecting a low viscosity epoxy into the blister/delamination void.

Caution: This method can only be used when the laminate base material has separated sufficiently to allow the epoxy to flow throughout the void area.

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 3.1 Delamination/Blister Repair, Injection Method
Kits and Systems
201-3110
Base Board Repair Kit
Kit to repair base board and laminate damage on circuit boards.
115-1322
Circuit Bond Kit
Includes clear, low viscosity, superior strength epoxy for circuit board damage repair.
110-6380
Flex-Rack PCB Holder
Sturdy holder supports PCBs for rework, drilling, pad repair, and positioning.
Tools and Materials
cutting
Ball Mills, Abrasives, Cutting Tools
Ball mills, abrasives and cutting tools for working on circuit boards.
115-3302
Circuit Bond Epoxy
Clear, superior strength epoxy in two-compartment plastic packages.
115-3902
Syringes
Polypropylene syringe barrels with stainless steel dispensing tips.
Additional Items and Supplies
Microscope
Microscope
Precision microscope with stand and lighting for work and inspection.
Oven
Oven
General purpose oven for drying, baking and curing epoxies.
Wipes
Wipes
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).
Specifications
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
Images and Figures
3.1 Delamination/Blister Repair, Injection Method
Figure 1: This method is used to repair mechanical or thermal blisters or delaminations in circuit board laminated base materials.
3.1 Delamination/Blister Repair, Injection Method
Figure 1: Drill into the delamination blister using a ball mill and a Micro-Drill.
3.1 Delamination/Blister Repair, Injection Method
Figure 2: Inject epoxy into the delamination blister.

3.1 Delamination/Blister Repair, Injection Method
Figure 3: Completed repair.
3.1 Delamination/Blister Repair, Injection Method
Figure 4: Micro-Drill System.
Procedure
  1. Clean the area.
  2. Drill into delamination blister with the Micro-Drill and ball mill. Drill in an area clear of circuitry or components. Drill at least two holes opposite each other around the perimeter of the delamination. (See Figure 1) Brush away all loose material.
    Caution: Be careful not to drill too deep, exposing internal circuits or planes.
    Caution: Abrasion operations can generate electrostatic charges.
  3. Bake the circuit board to remove any entrapped moisture. Do not allow the circuit board to cool prior to injecting the epoxy.
    Caution: Some components may be sensitive to high temperatures.
  4. Mix the epoxy. See manufacturer's instructions on how to mix epoxy without bubbles.
    Caution: Exercise care to prevent bubbles in the epoxy mixture.
  5. Pour the epoxy into the epoxy cartridge.
  6. Inject the epoxy into one of the holes in the delamination. (See Figure 2) The heat retained in the circuit board will improve the flow characteristics of the epoxy and will draw the epoxy into the void area, filling it completely.
  7. If the void does not fill completely, the following procedures may be used:
    - Apply light local pressure on the board surface starting at the fill hole, slowly proceeding to the vent hole.
    - Apply vacuum to the vent hole to draw the epoxy through the void.
  8. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling. Scrape away any excess epoxy using a knife or scraper.
    Note: If needed, apply an additional thin coating to seal any scrapped areas.
Evaluation
  1. Visual examination for texture and color match.
  2. Electrical tests to conductors around the repaired area as applicable.
Procedure for reference only.