Outline
This method is used on circuit boards to replace damaged or missing circuits on the circuit board surface. A length of standard insulated or non-insulated wire is used to repair the damaged circuit.
Caution: The circuit widths, spacing, and current carrying capacity, must not be reduced below allowable tolerances.
Caution: This method is not allowed when the wire will be subsequently subjected to a mass soldering operation.
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.
Microscope
Precision microscope with stand and lighting for work and inspection.
Micro Drill System
Versatile power tool for milling, drilling, grinding, cutting and sanding circuit boards.
Soldering Iron
Properly maintained soldering iron and properly sized soldering iron tips.
Wipes
Nonabrasive, low-linting wipes for cleanup.
Wire
Solid conductor wire for conductor repair and jumpers.
Wire Dots, Variety Pack
Pre-cut polymer film tape with a high performance adhesive designed for tacking wires.
Wire Guide
Use to form bends in wires and hold wires during soldering and bonding.
Wire Stripper
Sharp wire strippers for stripping insulated wire.
Images and Figures
Damaged Conductor
Figure 1: Scrape off any solder mask or coating from the ends of the remaining circuits.
Figure 2: Drill through the board adjacent to both ends of the remaining circuits.
Figure 3: Bend the stripped wire over the prepared circuits in line with the circuits.
Figure 4: Lap solder the wire to the circuits on the circuit board surface.
Procedure
Clean the area.
Remove the damaged section of the circuit using the 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.
Use a knife and scrape off any solder mask or coating from the ends of the remaining circuit. (See Figure 1)
Remove all loose material. Clean the area.
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.
Clean the area.
Select a wire to match the width and thickness of the circuit to be replaced. Cut a length approximately as needed. See Table 1 for Solid Wire Equivalents.
Table 1 - Solid Wire Equivalents
Conductor Width 2 oz. Copper
Equivalent Solid Wire Diameter
.010" (0.25 mm)
#34, .006" (0.15 mm)
.015" (0.38 mm)
#32, .008" (0.20 mm)
.020" (0.50 mm)
#31, .009" (0.23 mm)
.031" (0.78 mm)
#29, .011" (0.28 mm)
.082" (2.08 mm)
#26, .018" (0.46 mm)
.125" (3.18 mm)
#23, .023" (0.58 mm)
When using solid wire to repair a conductor, there should be no reduction in the cross-sectional area.
Strip the wire and tin the ends if needed. A non-insulated wire may be used for short repairs if conductors are not crossed.
Clean the wire.
Drill through the board adjacent to both ends of the remaining circuits. Drill the hole slightly larger than the wire diameter to be used. (See Figure 2)
Caution: Review circuit diagrams to be sure no surface or internal circuits will be damaged or shorted.
Position the wire on the opposite side from the repair and insert the stripped ends into the drilled holes.
Bend the stripped wire over the prepared circuits in line with the circuits. The wire should overlap the existing circuit a minimum of 2 times the circuit width. (See Figure 3)
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.
Apply a small amount of liquid flux to the overlap joint.
Lap solder the wire to the circuits on the circuit board surface. Make sure the wire is properly aligned. (See Figure 4)
Form the wire on the opposite side to match the shape of the missing circuit, if desired.
Clean the area.
Note: It may be necessary to encapsulate the solder joint connection if the electrical spacing is reduced.
If desired, bond the wire to the circuit board surface with adhesive, epoxy or Tape Dots. Refer to Section 6.0.
Caution: Some components may be sensitive to high temperatures.
Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling
After the epoxy has cured, clean the area.
Evaluation
Visual examination for alignment and overlap of wire.
