Circuit Board Repair Guide > Conductor Repair Procedures > 4.2.2 How to Repair a Damaged Conductor Using a Foil Jumper & Film Adhesive

How to Repair a Damaged Conductor Using a Foil Jumper & Film Adhesive

Repair Circuit Boards | Repair SMT Pads | Repair BGA Pads | Repair Lands | Repair Edge Contacts
Repair a Conductor | Plated Hole Repair | Base Board Repair | Replace Solder Mask or Coatings

This procedure is used to replace damaged or missing circuits on the printed circuit board surface using a foil jumper bonded with film adhesive.

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

IPC Acceptability References
IPC-A-600 2.0 Externally Observable Characteristics
IPC-A-610 10.0 Laminate Conditions

Related Procedure References
CTC 1.0 Foreword - Circuit Board Repair Guide
CTC 2.1 Handling Electronic Assemblies
CTC 2.2.1 How to Clean a Circuit Board
CTC 2.2.2 Cleaning Circuit Boards, Aqueous Batch Process
CTC 2.5 Baking and Preheating of Printed Circuit Boards
CTC 2.7 Epoxy Mixing and Handling
IPC7721 4.2.2 Conductor Repair, Foil Jumper, Film Adhesive Method
Damaged conductor needs replacement
Damaged Conductor

Tools and Materials
Bonding Iron
Bonding Tips

Circuit Bonding System
Circuit Frames, Conductors      
Flux, Liquid
Soldering Station     
Surgical Knife
Tape, Kapton

4.2.2 Conductor Repair, Foil Jumper, Film Adhesive Method

Printed Board Type: N/A  |  Skill Level: Advanced  |  Conformance Level: High  |  Rev.: E  |  Rev. Date: Mar 28, 2001

Remove solder mask from connecting circuit

Fig. 1: Remove solder mask from
the connecting circuit.

Clean the area.
Remove the damaged section of 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.
Use the knife and scrape off any epoxy residue, contamination or burned material from the board surface.
Scrape off any solder mask or coating from the connecting circuit. (See Figure 1).
Clean the area.
Replacement conductors with dry film adhesive backing

Fig. 2: Sample circuit frame or replacement conductors with dry
film adhesive backing.

Apply a small amount of liquid flux to the connection area on the board surface and tin with solder. Clean the area. The length of the overlap solder connection should be a minimum of 2 times the circuit width.
7.  Select a replacement circuit with film adhesive backing that most closely matches the size of the conductor to be replaced from the Circuit Frames page. If a special size or shape is needed it can be custom fabricated. (See Figure 2).
New conductors are fabricated from copper foil. The foil is plated on the top side with solder and an epoxy bonding film is applied to the bottom side.
Scrape off epoxy bonding film

Fig. 3: Scrape off epoxy bonding
film from solder joint connection
area on back of new conductor.

8.   Before trimming out the new conductor carefully scrape off the adhesive epoxy film from the solder joint connection area on the back of the new conductor. (See Figure 3).
Scrape off the epoxy backing only from the joint connection area. When handling the new conductor avoid touching the epoxy backing with your fingers or other materials that may contaminate the surface and reduce the bond strength.
Cut out new circuit from plated side

Fig. 4: Cut out the new circuit.
Cut from the plated side.

9.  Cut out and trim the new conductor. Cut out from the plated side. Cut the length to provide the maximum allowable circuit overlap for soldering. Minimum 2 times the circuit width. (See Figure 4).
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.
Place new conductor using Kapton tape

Fig. 5: Place the new conductor
in place using Kapton tape.

Place a piece of Kapton tape over the top surface of the new conductor. Place the new conductor into position on the circuit board surface using Kapton tape to help in alignment. Leave the Kapton tape in place during the bonding cycle. (See Figure 5).
Select a bonding tip with a shape to match the shape of the new conductor.
The bonding tip should be as small as possible but should completely cover the entire width of the new conductor.
Bonding System used to bond replacement conductors

Fig. 6: Bonding System used to thermally bond dry film adhesive backed replacement conductors.

12. Position the circuit board so that it is flat and stable. Gently place the hot bonding tip onto the Kapton tape covering the new circuit. Apply pressure as recommended in the manual of the repair system or circuit board repair kit for 5 seconds to tack the circuit in place. Carefully peel off the tape. (See Figure 6).
13. Gently place the bonding tip directly onto the new circuit. Apply pressure as recommended in the manual of the repair system or repair kit for an additional 30 seconds to fully bond the new circuit. The new circuit is fully cured. Carefully clean the area and inspect the new circuit for proper alignment.
14. Apply a small amount of liquid flux to the lap solder joint connection area and solder the circuit foil jumper from the new conductor to the circuit on the PC board surface. Use minimal flux and solder to ensure a reliable connection. Kapton tape may be placed over the top of the new conductor to prevent excess solder overflow.
15. Mix liquid circuit board epoxy and coat the lap solder joint connections. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
Some components may be sensitive to high temperature.
16. Apply surface coating to match prior coating as required.
Lifted conductor repair completed

Fig. 7: Conductor repair completed.
1.  Visual examination.
2.  Measurement of new pad width and spacing.
3.  Electrical continuity measurement.

Links to Related Products

Circuit Bonding System bonds surface mount and BGA pads  
Circuit Bonding System 115-3118
The Circuit Bonding System is the best, calibrated system for bonding adhesive film backed circuits and is ideally suited for bonding small patterns including surface mount and BGA pads. This bonding press not only gives the operator better control over the bonding process, but also ensures optimal adhesion and repeatability. Includes a built-in calibration slide to maintain a regulated bonding force depending upon the circuit pattern size and shape. The digital temperature controller maintains a uniform temperature throughout the 30-second bonding cycle.

Bonding Tips
The Bonding Tips fit into the hand held Bonding Iron (part number 115-3102) and the Circuit Bonding System. The bottom machined surface of each Bonding Tip is used to apply heat and pressure to bond the adhesive backed replacement pads, edge contacts, and lands to the circuit board surface.

Circuit Frames used to replace pads, lands and conductors  
Circuit Frames
Circuit Frames allow you to replace damaged surface mount pads, lands and conductors without the mess of liquid epoxy, with a bond strength equal to the original, in just a few minutes. Circuit Frames come in a wide variety of shapes and sizes, all with a dry-film adhesive backing, activated and cured with heat and pressure. Trim out the circuit you need and bond it to the circuit board surface using a Bonding Iron or Circuit Bonding System with the appropriate Bonding Tip.

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