IPC 7711A.pdf - 第237页
OUTLINE This method is used to replace damaged or missing conductors on the printed wir- ing board surface. CAUTION It is essential that the board surface be extremely smooth and flat. If the base board is damaged see ap…
NOTES
IPC-7721A
Number: 4.2.1
Revision: A
Date: 11/99
Subject: Conductor Repair, Foil Jumper, Epoxy Method
Page4of4
Copyright Association Connecting Electronics Industries
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 to replace damaged or missing conductors on the printed wir-
ing board surface.
CAUTION
It is essential that the board surface be extremely smooth and flat. If the base board
is damaged see appropriate procedure.
REFERENCES
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.5 Baking and Preheating
2.6 Epoxy Mixing and Handling
TOOLS & MATERIALS
Bonding Iron
Bonding System
Bonding Tips
Buffer
Conductor Foil Jumpers
with Film Adhesive
Cleaner
Cleaner Wipes
Heat Lamp
Polyimide Tape
Knife
Liquid Flux
Microscope
Oven
Scraper
Solder
Soldering Iron
Tweezers
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.
3. Use the knife and scrape off any epoxy residue, contamination or burned mate-
rial from the board surface.
4. Scrape off any solder resist or coating from the connecting conductor. (See Fig-
ure 1.)
5. Clean the area.
6. 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 conductor width.
Figure 1 Remove solder mask from
the connecting conductor.
Figure 2 Replacement conductors
with dry film adhesive backing.
Figure 3 Scrape off epoxy bonding
film.
Figure 4 Cut out the new conductor.
Cut from the plated side.
7721A
Repair and
Modification of
Printed Boards and
Electronic Assemblies
Revision:
Date: 2/98
Conductor Repair,
Foil Jumper, Film
Adhesive Method
Number: 4.2.2
Product Class: R, F, C
Skill Level: Advanced
Level of Conformance: High
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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Copyright Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
--``,``,-`-`,,`,,`,`,,`---
7. Select a replacement conductor with film adhesive backing that most closely
matches the size of the conductor to be replaced. If a special size or shape is
needed they can be custom fabricated. (See Figure 2.)
NOTE
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.
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.)
CAUTION
Scrape off the epoxy backing only from the joint connection area. When han-
dling the new conductor avoid touching the epoxy backing with your fingers or
other materials that may contaminate the surface and reduce the bond strength.
9. Cut out and trim the new conductor. Cut out from the plated side. Cut the
length to provide the maximum allowable conductor overlap for soldering. Mini-
mum 2 times the conductor width. (See Figure 4.)
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.
10. Place a piece of tape over the top surface of the new conductor. Place the new
conductor into position on the printed wiring board surface using tape to help in
alignment. Leave the tape in place during the bonding cycle. (See Figure 5.)
11. Select a bonding tip with a shape to match the shape of the new conductor.
NOTE
The bonding tip should be as small as possible but should completely cover the
entire width of the new conductor.
12. Position the printed wiring board so that it is flat and stable. Gently place the hot
bonding tip onto the tape covering the new pad. Apply pressure as recom-
mended in the manual of the repair system or repair kit. (See Figure 6.)
13. After the bonding cycle lift the bonding iron and remove the tape used for align-
ment. The new conductor is fully cured. Carefully clean the area and inspect the
new conductor for proper alignment.
14. Apply a small amount of liquid flux to the lap solder joint connection area and
solder the conductor from the new conductor to the conductor on the printed
wiring board surface. Use minimal flux and solder to ensure a reliable connec-
tion. Tape may be placed over the top of the new conductor to prevent excess
solder overflow. Clean the area.
15 Mix epoxy and coat the lap solder joint connections. Cure the epoxy per the
manufacturer’s instructions.
CAUTION
Some components may be sensitive to high temperature.
16. Apply surface coating to match prior coating as required.
Figure 5 Place the new conductor in
place using tape.
Figure 6 Repair system.
Figure 7 Completed repair.
IPC-7721A
Number: 4.2.2
Revision:
Date: 2/98
Subject: Conductor Repair, Foil Jumper, Film Adhesive Method
Page2of4
Copyright Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
--``,``,-`-`,,`,,`,`,,`---