IPC 7711A - 第275页
CAUTION Excessive bonding pressure may cause measling in the printed wiring board surface or the new conductor to slide out of position. 14. After the bonding cycle remove the tape used for alignment. The land is fully c…
PROCEDURE
1. Clean the area.
2. Remove the defective land and a short length of the connecting conductor if
any. (See Figure 1.)
3. Use the knife and scrape off any epoxy residue, contamination or burned mate-
rial from the board surface.
CAUTION
Abrasion operations can generate electrostatic charges.
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.
7. The area for the new pad on the board surface must be smooth and flat. If
internal fibers of the board are exposed or if there are deep scratches in the
surface they should be repaired. Refer to appropriate procedure.
8. Select a replacement land that most closely matches the land to be replaced.
(See Figure 2.)
NOTE
The new replacement land may be trimmed from copper sheet.
9. Before trimming out the new land carefully scrape off the adhesive film from the
solder joint connection area on the back of the new land. (See Figure 3.)
CAUTION
Scrape off the epoxy backing only from the joint connection area. When han-
dling the replacement land avoid touching the adhesive backing with your fin-
gers or other materials that may contaminate the surface and reduce the bond
strength.
10. Cut out and trim the new land. Cut out from the plated side. Cut the length to
provide the maximum allowable conductor overlap for soldering. Minimum 2
times the conductor width. (See Figure 4.)
11. Place a piece of tape over the top surface of the new land. Place the new land
into position on the printed wiring board surface using the tape to aid in align-
ment. Leave the tape in place during the bonding cycle. (See Figure 5.)
12. Select a bonding tip with a shape to match the shape of the new land.
NOTE
The Bonding Tip should be as small as possible but should completely cover the
entire surface of the new land.
13. Position the printed wiring board so that it is flat and stable. Gently place the hot
bonding tip onto the tape covering the new land. Apply pressure as recom-
mended in the manual of the repair system or repair kit of the manufacturer.
(See Figure 6.)
Figure 5 Place the new land in place
using tape.
Figure 6 Bonding systems.
Figure 7 Completed land repair.
IPC-7721A
Number: 4.5.2
Revision:
Date: 2/98
Subject: Land Repair, 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
--``,``,-`-`,,`,,`,`,,`---
CAUTION
Excessive bonding pressure may cause measling in the printed wiring board
surface or the new conductor to slide out of position.
14. After the bonding cycle remove the tape used for alignment. The land is fully
cured. Carefully clean the area and inspect the new land for proper alignment.
15. If the new land has a connecting conductor apply a small amount of liquid flux
to the lap solder joint connection area and solder the conductor from the new
land to the conductor on the printed wiring board surface. Use minimal flux and
solder to ensure a reliable connection. Tape may be placed over the top of the
new land to prevent excess solder overflow.
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.
16. Remove tape and clean the area.
17. Mix epoxy and coat the lap solder joint connections. Cure the epoxy per the
manufacturers instructions.
NOTE
Additional epoxy can be applied around the perimeter of the new pad to pro-
vide additional bond strength.
CAUTION
Some components may be sensitive to high temperature.
18. Carefully remove any excess bonding film inside the plated hole using ball mill
or drill bit. Turn the ball mill or drill bit by hand to prevent damage to the wall of
the plated through hole.
19. Install the proper component and solder in place.
NOTE
This method is used to replace a damaged or missing land, but the new land
will not have an intermetallic connection to the remaining plated hole. The sol-
der joint of the replaced component will restore the integrity of the electrical
connection or an eyelet or buss wire may be used. See Plated Hole Repair Pro-
cedures.
20. Apply surface coating to match prior coating as required.
EVALUATION
1. Visual examination.
2. Measurement of new pad width and spacing.
3. Electrical continuity measurement.
IPC-7721A
Number: 4.5.2
Revision:
Date: 2/98
Subject: Land Repair, Film Adhesive Method
Page3of4
Copyright Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
--``,``,-`-`,,`,,`,`,,`---
NOTES
IPC-7721A
Number: 4.5.2
Revision:
Date: 2/98
Subject: Land Repair, Film Adhesive 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
--``,``,-`-`,,`,,`,`,,`---