IPC 7711A - 第243页

OUTLINE This method is used on printed wiring boards to replace damaged or missing con- ductors on the printed wiring board surface. A length of standard insulated or non- insulated wire is used to repair the damaged con…

PROCEDURE

1. Clean the area.

2. Select a section of Kovar ribbon of the same width as the conductor pattern

being repaired ± .050 mm.

3. Cut the ribbon approximately 3.0 mm longer than the section being repaired.

4. Clean the ribbon conductor and base material surrounding the repair area.

5. Place and center the ribbon over the section to be repaired leaving equal ribbon

end lengths on each side and parallel to the conductor pattern.

6. Place the printed wiring board under the weld electrodes so that the electrodes

are depressed to the area of the weld.

7. Hold the ribbon in place with tweezers until the weld is completed. Weld in place

using settings based on the accepted test samples.

8. Clean the area.

9. Carefully inspect the joint for weld quality and alignment.

10. If required, apply a small amount of flux and tin the entire area with solder.

11. Clean the area.

12. Coat the repaired area with epoxy if needed.

EVALUATION

1. Visual examination, dimensional measurement of conductor width and spacing,

and electrical continuity measurement.

NOTES

IPC-7721A

Number: 4.2.3

Revision:

Date: 2/98

Subject: Conductor Repair, Welding Method

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Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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OUTLINE

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

ductors on the printed wiring board surface. A length of standard insulated or non-

insulated wire is used to repair the damaged conductor.

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

TOOLS AND MATERIALS

Cleaner

Cleaning Wipes

Epoxy

Heat Lamp

Polyimide Tape

Knife

Light

Liquid Flux

Microscope

Oven

Scraper

Solder

Soldering Iron with Tips

Wire

Wire Guide Tool

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.

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.

Figure 1 Scrap off any coating from

the ends of the conductors.

Figure 2 Lap solder the wire to one

end of the conductor.

Figure 3 Form wire using wire guide

tools.

Figure 4 Form the ﬁnal shape of the

wire and solder in place.

7721A

Repair and

Modification of

Printed Boards and

Electronic Assemblies

Revision:

Date: 2/98

Conductor Repair,

Surface Wire Method

Number: 4.2.4

Product Class: R, F, C

Skill Level: Intermediate

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.

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Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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7. Select a wire to match the width and thickness of the conductor to be replaced.

Cut a length approximately as needed. See Table 1 for Solid Wire Equivalents.

8. Strip the wire and tin the ends if needed. Non-insulated wire may be used for

short repairs if conductors are not crossed.

9. Clean the wire.

10. If the wire is long or has bends, one end may be soldered prior to forming the

new shape. Place the wire in position. The wire should overlap the existing con-

ductor a minimum of 2 times the conductor width. The wire may be held in

place with Polyimide tape during soldering.

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. Refer to 7.1 Sol-

dering Basics.

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

12. Lap solder the wire to one end of the conductor on the printed wiring board

surface. Make sure the wire is properly aligned. (See Figure 2.)

13. Bend the wire as needed to match the shape of the missing conductor. (See

Figure 3.)

NOTE

Wire guide tools can be used to form the wire as needed.

14. Lap solder the other wire end to the remaining conductor on the printed wiring

board surface using solder and a soldering iron. Make sure the wire is properly

aligned. (See Figure 4.)

15. Remove any Polyimide tape and clean the area.

NOTE

It may be necessary to encapsulate the solder joint connection if electrical spac-

ing is reduced or the connection is beneath a component.

16. If desired bond the wire to the printed wiring board surface with adhesive, epoxy

or tape dots. (See Figure 5.)

Figure 5 Bond the wire to the surface

with adhesive or tape.

Table 1 Solid Wire Equivalents

Conductor Width

2 oz. Copper

Equivalent Solid

Wire Diameter

0.25 mm #34, 0.15 mm

0.38 mm #32, 0.20 mm

0.50 mm #31, 0.23 mm

0.78 mm #29, 0.28 mm

2.08 mm #26, 0.46 mm

3.18 mm #23, 0.58 mm

When using solid wire to repair a conductor, there should be no reduction in the

cross sectional area.

IPC-7721A

Number: 4.2.4

Revision:

Date: 2/98

Subject: Conductor Repair, Surface Wire Method

Page2of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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