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4.2.7 Conductor Repair, Surface Plane, Film Adhesive Method
Outline
This method is used to repair damaged circuit surface planes. The damaged areas are repaired with dry film epoxy, adhesive backed copper foil disks. They are bonded to the circuit board surface using a bonding press or bonding iron.

Caution
It is essential that the board surface be extremely smooth and flat. If the base board is damaged see appropriate procedure.

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.

Procedure References
1.0 Foreword
2.1 Handling Electronic Assemblies
2.2 Cleaning
Tools and Materials
CircuitMedic Part
Abrader
Mild abrasive for removing oxides and contaminates from conductive surfaces.
CircuitMedic Part
Alcohol Swab
Self-saturating Isopropyl alcohol swab. Squeeze handle to release alcohol.
CircuitMedic Part
Ball Mills, Abrasives, Cutting Tools
Ball mills, abrasives and cutting tools for working on circuit boards.
CircuitMedic Part
Bonding Iron, 120 VAC
Delivers the optimal heat for curing adhesive bonding film.
CircuitMedic Part
Bonding System
System designed to repair lifted and damaged conductors, pads, BGA pads, SMT pads.
Soldering Iron
Bonding Tips
Used to cure adhesive backed circuit frames for pad, land and contact repair.
Soldering Iron
Circuit Frames
Replacement circuits with a dry-film adhesive backing for conductor repair.
Cleaner
Cleaner
General purpose cleaner for removing contamination.
CircuitMedic Part
Cleaning Brushes
Disposable brushes for use with solvents for cleaning and application of coatings.
Desolder Braid
Desolder Braid
Woven copper wire designed to wick solder from surfaces and holes.
End Mills
End Mills
Designed for end cutting and hole boring.
CircuitMedic Part
Circuit Bond Packs
Clear, superior strength epoxy in two-compartment plastic packages
CircuitMedic Part
High Temp Tape Discs
High temperature polyimide tape discs, .50" diameter.
CircuitMedic Part
Knife with #16 Blades
A must-have tool for precise cutting, scraping and trimming.
Microscope
Microscope
It is a challenge to undertake precision repair without a good microscope.
Milling Machine
Milling Machine
Use for precision milling of circuit board materials.
Oven
Oven
General purpose oven for drying, baking and curing epoxies.
Precision Drill
Precision Drill
Precision drill press for accuracy and controlled depth drilling.
CircuitMedic Part
Scraper
Hardened stainless steel tip for scraping solder mask and removing defects.
Soldering Iron
Soldering Iron, Solder and Flux
A well maintained soldering iron is a must at every tech bench.
CircuitMedic Part
Tweezer, Point Tip
Fine point tweezers for precision work.
Images and Figures
4.2.7 Conductor Repair, Surface Plane, Film Adhesive Method
Damaged Surface Plane
4.2.7 Conductor Repair, Surface Plane, Film Adhesive Method
Figure 1: Milled area to remove damaged foil .
4.2.7 Conductor Repair, Surface Plane, Film Adhesive Method
Figure 2: Transplant new foil disk into milled out area.
4.2.7 Conductor Repair, Surface Plane, Film Adhesive Method
Figure 3: Bond the new adhesive backed disk using a commercially available Bonding System.
4.2.7 Conductor Repair, Surface Plane, Film Adhesive Method
Figure 4: Solder tin the area and blend in.

Procedure 
  1. Clean the area.

  2. Secure the circuit to a Precision Drill/Milling System with a microscope available for viewing. Use an end mill slightly larger than the void in the surface plane and make a counter bore through the surface plane only. Do not mill into the laminate material, you may expose inner layer circuits.

    Note

    Several adjacent counter bores may be required to fill larger areas.

  3. Clean the area with solvent.

  4. The area for the new Adhesive Backed Disk on the board surface must be smooth and flat. If internal fibers of the board are exposed or there are deep scratches in the surface they should be repaired. Refer to appropriate procedure.

  5. Select a replacement adhesive backed disk that matches the size of the end mill used to make the counter bore.

    Note

    The thickness should be selected to meet the requirements of the circuit board surface plane thickness.

  6. With the adhesive backed disk positioned film side up, carefully scrape off the adhesive film from the outer 0.005" of the disk diameter.

  7. Position the adhesive backed disk, film side down. Place a piece of High Temperature Tape over adhesive backed disk, position the adhesive backed disk into the counter bore. Press the adhesive backed disk into position. (See Figure 2)

  8. Select a bonding tip with a shape to match the shape of the adhesive backed disk.

    Note

    The bonding tip should be as small as possible but should completely cover the entire surface of the adhesive backed disk.

  9. Position the circuit board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the adhesive backed disk. Apply pressure and heat as recommended in the manual of the Repair System or Repair Kit for 5 seconds to tack the adhesive backed disk in place. Carefully peel off the tape. (See Figure 3)

  10. Gently place the hot bonding tip directly onto the new adhesive backed disk. Apply pressure and heat as recommended in the manual of the Repair System or Repair Kit for an additional 30 seconds to fully bond the new adhesive backed disk. The new adhesive backed disk is fully cured. Carefully clean the area and inspect the new adhesive backed disk for alignment.

    Note
    Several adjacent counter bores may be required to fill larger areas.

  11. Using flux and solder, carefully add a small amount of solder to a soldering iron with a "Blade" shaped tip, and flow solder over the repaired area.

  12. Using the "Blade" shaped soldering tip and desolder braid, remove any excess solder

  13. Clean the area.

  14. Using the Electric/Hand Eraser, clean and buff the soldered area to blend the repair to the circuit surface.

  15. Using High Temperature Tape, mask off an area larger than the repaired area.

  16. Using the abrasive pad, "lightly" buff the masked area to further blend the repair to the circuit surface as necessary. (See figure 4)

  17. Clean the area.
Final Finish
  1. Blend the surface type using an appropriate buffing material or abrasive pad.

  2. Matte and semi-gloss surfaces may require light abrasion in order to blend to original surface finish type. High gloss will require polishing.

  3. Remove any loose particles as necessary and clean the area.
Evaluation
  1. Visual examination.

  2. Electrical tests as applicable.

Procedure for reference only.