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4.2.1 Conductor Repair, Foil Jumper, Epoxy Method

Outline
This method is used on circuit boards to replace damaged or missing circuits on the circuit board surface.

Caution
The circuit widths, spacing and current carrying capacity must not be reduced below allowable tolerances.

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 - Medium
This procedure may have some variance with the physical character of the original and most likely varies with some of 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 4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
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
Circuit Track Kit
Kit to repair circuit board damage including lands and conductors.
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
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.
CircuitMedic Part
Micro Drill System
Versatile power tool for milling, drilling, grinding, cutting and sanding circuit boards.
CircuitMedic Part
Micro Probes
Use to dispense a minute amount of adhesive and for micro-positioning of small objects.
CircuitMedic Part
Mixing Picks
Unique mixing sticks have a paddle shape on one and sharp pick on the opposite end.
CircuitMedic Part
Scraper
Hardened stainless steel tip for scraping solder mask and removing defects.
Images and Figures
4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
Damaged Conductor
4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
Figure 1: Scrape off any solder mask or coating from the ends of the remaining circuits.
4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
Figure 2: Place the new Circuit Track in position and hold in place with Kapton tape.

4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
Figure 3: Bend Circuit Track using 2 wood sticks.
4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
Figure 4: Wide circuits that cannot be easily formed may be folded over to produce a sharp bend.
4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
Figure 5: Form the final shape of the Circuit Track then hold in place with Kapton tape while soldering.

4.2.1 Conductor Repair, Foil Jumper, Epoxy Method
Figure 6: Coat the top and sides of the Circuit Track with epoxy.
Procedure
  1. Clean the area.
  2. Remove the damaged section of circuit using a knife. The damaged circuit should be trimmed back to a point where the circuit still has a good bond to the PC board surface.

    Note
    Heat can be applied to the damaged circuit using a soldering iron to allow the circuit to be removed more easily.
  3. Use a knife and scrape off any solder mask or coating from the ends of the remaining circuit. (See Figure 1)
  4. Remove all loose material. Clean the area.

    Note
    It is essential that the board surface be smooth and flat. If the base material is damaged see appropriate procedure.
  5. Apply a small amount of liquid flux to the ends of the remaining circuit. Tin the exposed end of each circuit using solder and a soldering iron.
  6. Clean the area.
  7. Select a Circuit Track to match the width and thickness of the circuit to be replaced. (See Table 1) Cut a length approximately as needed. The Circuit Track should overlap the existing circuit a minimum of 2 times the circuit width.

    Table 1 - Common Circuit Track Sizes
    See Related Products Below

    Part No. Thickness Width
    115-2504 .002" .004"
    115-5206 .002" .006"
    115-5208 .002" .008"
    115-5210 .002" .010"
    115-5312 .003" .120"
    115-5315 .003" .015"
    115-5520 .005" .020"
    115-5530 .005" .030"

    Note
    The new circuit may be trimmed from copper sheet.
  8. Gently abrade the top and bottom surface of the Circuit Track with a buffer to remove the protective coating.

    Note
    A thin protective coating is applied to the Circuit Track to prevent oxidation.
  9. Clean the Circuit Track.
  10. If needed, the ends of the Circuit Track may be tinned with solder prior to lap soldering it in place.
  11. If the Circuit Track is long or has bends, one end may be soldered prior to forming the new shape. Place the Circuit Track in position. The Circuit Track should overlap the existing circuit a minimum of 2 times the circuit width. The Circuit Track may be held in place with High Temperature Tape. (See Figure 2)
  12. Apply a small amount of liquid flux to the overlap joint.
  13. Lap solder the Circuit Track to the circuit on the circuit board surface using solder and a soldering iron. Make sure the Circuit Track is properly aligned.

    Note
    If the configuration permits, the overlap solder joint connection should be a minimum of 3.00 mm (0.125") from the related termination. This gap will minimize the possibility of simultaneous reflow during soldering operations. Refer to 7.1 Soldering Basics.
  14. Bend the Circuit Track as needed to match the shape of the missing circuit. (See Figure 3)

    Note
    Two wood sticks can be used to make sharp bends in the replacement Circuit Track. Use one stick to hold the Circuit Track at the bend location and use the other wood stick to form the shape as needed.
  15. Wide circuits that cannot be easily formed may be folded over to produce a sharp bend. (See Figure 4)
  16. Form the final shape of the jumper and hold in place with tape. Lap solder the Circuit Track to the remaining circuit on the circuit board surface using solder and a soldering iron. Make sure the Circuit Track is properly aligned. Remove the tape used to hold the foil jumped. Clean the area. (See Figure 5)
  17. Mix the Epoxy. If desired, add color agent to the mixed epoxy to match the circuit board color.
  18. Coat the top and sides of the Circuit Track with epoxy. The epoxy bonds the Circuit Track to the circuit board surface and insulates it. A wooden stick sharpened at one end may be used to apply and spread the epoxy. (See Figure 6)
  19. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.

    Caution
    Some components may be sensitive to high temperature.
  20. Apply surface coating to match prior coating as required.
Evaluation
  1. Visual examination for alignment and overlap of foil jumper.
  2. Visual examination of epoxy coating for texture and color match.
  3. Electrical tests as applicable.
Procedure for reference only.
 

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