For all of you that requested the procedure on trace repair,  Here it is. 
The graphic illustrations and tables have been left out for simplicity. 
This is the outline for the new IPC 4.2.1 procedure for trace repair 
IPC-700D (no its not published yet) We effectively repair hundreds of 
boards a week using this procedure.   


Conductor Repair, Foil Jumper, Epoxy Method
Procedure No. 4.2.1
Product Class: R/F/C
Skill Level: Intermediate
Level of Reliability: C 

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

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

REFERENCES
2.1		Handling Electronic Assemblies
2.2		Cleaning
2.5	 	Baking And Preheating
2.7		Epoxy Mixing and Handling
	

TOOLS AND MATERIALS
Buffer
Cleaner
Circuit Foil Jumpers
Color Agent, Various Colors
Epoxy
Hand Held Drill
Heat Lamp
Kapton Tape
Knife
Light
Liquid Flux
Microscope
Oven
Scraper
Solder
Soldering Iron with Tips
Wipes


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 foil jumper to match the width and thickness of the 
circuit to be replaced.  Cut a length approximately as needed.  The foil 
jumper should overlap the existing circuit a minimum of 2 times the 
circuit width.

NOTE
The new replacement may be trimmed from copper sheet.

8. Gently abrade the top and bottom surface of the replacement foil 
jumper with a buffer to remove the protective coating.

NOTE
A thin protective coating is often applied to the replacement foil jumper 
to prevent oxidation.

9. Clean the circuit foil jumper.

10. If needed, the ends of the replacement circuit foil jumper may be 
tinned with solder prior to lap soldering it in place.

11. If the circuit foil jumper is long or has bends, one end may be 
soldered prior to forming the new shape.  Place the foil jumper in 
position.  The foil jumper should overlap the existing circuit a minimum 
of 2 times the circuit width.  The jumper may be held in place with 
Kapton tape.  (See Figure 2).

12. Apply a small amount of liquid flux to the overlap joint.

13. Lap solder the foil jumper to the circuit on the PC board surface 
using solder and a soldering iron.  Make sure the foil jumper 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 foil jumper 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 foil 
jumper.  Use one stick to hold the new jumper 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. Lap solder the foil jumper to the remaining circuit on the PC board 
surface using solder and a soldering iron.  Make sure the foil jumper is 
properly aligned.  (See Figure  5).

17. Mix the epoxy.  If desired, add color agent to the mixed epoxy to 
match the PC board color.  

18. Coat the top and sides of the foil jumper with epoxy.  The epoxy 
bonds the foil jumper to the PC 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 the manufacturers instructions.

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.