IPC 7711A - 第234页

5. Apply a small amount of liquid flux to the ends of the remaining conductor. Tin the exposed end of each conductor using solder and a soldering iron. 6. Clean the area. 7. Select a conductor foil jumper to match the wi…

OUTLINE

This method is used on printed wiring boards to replace damaged or missing con-

ductors on the printed wiring board surface.

CAUTION

The conductor 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

2.6 Epoxy Mixing and Handling

TOOLS AND MATERIALS

Buffer

Cleaner

Conductor Foil Jumpers

Color Agent

Various Colors

Epoxy

Hand Held Drill

Heat Lamp

Polyimide Tape

Knife

Light

Liquid Flux

Microscope

Oven

Scraper

Solder

Solder Iron

with Tips

Wipes

PROCEDURE

1. Clean the area.

2 Remove the damaged section of conductor using a knife. The damaged con-

ductor should be trimmed back to a point where the conductor still has a good

bond to the printed wiring board surface.

NOTE

Heat can be applied to the damaged conductor using a soldering iron to allow

the conductor to be removed more easily.

3. Use a knife and scrape off any solder resist or coating from the ends of the

remaining conductor. (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.

Figure 1 Scrape off any coating from

the ends of the remaining conductors.

Figure 2

Place the new foil jumper in

position, hold in place with tape conductor.

Figure 3 Bend foil jumper using 2

wood sticks.

Figure 4 Wide conductors may be

folded over.

7721A

Repair and

Modification of

Printed Boards and

Electronic Assemblies

Revision: A

Date: 11/99

Conductor Repair, Foil

Jumper, Epoxy Method

Number: 4.2.1

Product Class: R, F, C

Skill Level: Advanced

Level of Conformance: Medium

Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use

or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material.

Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment

referenced is for the convenience of the user and does not imply endorsement by IPC.

Page1of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

--``,``,-`-`,,`,,`,`,,`---

5. Apply a small amount of liquid flux to the ends of the remaining conductor. Tin

the exposed end of each conductor using solder and a soldering iron.

6. Clean the area.

7. Select a conductor foil jumper to match the width and thickness of the conduc-

tor to be replaced. Cut a length approximately as needed. The foil jumper

should overlap the existing conductor a minimum of 2 times the conductor

width.

NOTE

The new conductor 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 pre-

vent oxidation.

9. Clean the conductor foil jumper.

10. If needed, the ends of the replacement conductor foil jumper may be tinned with

solder prior to lap soldering it in place.

11. If the conductor 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 conductor a minimum of 2 times the conductor

width. The jumper may be held in place with Polyimide tape. (See Figure 2.)

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

13. Lap solder the foil jumper to the conductor on the printed wiring 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 from the related termination. This gap will minimize the

possibility of simultaneous reflow during soldering operations.

14. Bend the foil jumper as needed to match the shape of the missing conductor.

(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 conductors 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

foil jumper to the remaining conductor on the printed wiring board surface using

solder and a soldering iron. Remove the tape used to hold the foil jumper. Clean

the area. (See Figure 5.)

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

printed wiring board color.

Figure 5 Form the ﬁnal shape of the

jumper and hold in place with tape.

Figure 6 Coat the top and sides of the

foil jumper with epoxy.

IPC-7721A

Number: 4.2.1

Revision: A

Date: 11/99

Subject: Conductor Repair, Foil Jumper, Epoxy Method

Page2of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

--``,``,-`-`,,`,,`,`,,`---

18. Coat the top and sides of the foil jumper with epoxy. The epoxy bonds the foil

jumper to the printed wiring 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.

IPC-7721A

Number: 4.2.1

Revision: A

Date: 11/99

Subject: Conductor Repair, Foil Jumper, Epoxy Method

Page3of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

--``,``,-`-`,,`,,`,`,,`---