IPC 7711A.pdf - 第283页
14. After the bonding cycle remove the tape used for alignment. The new edge contact is fully cured. Carefully clean the area and inspect the new edge con- tact for proper alignment. 15. If the new edge contact has a con…
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 edge contact on the board surface must be smooth and
flat. If internal fibers of the board are exposed or deep scratches exist in the
surface they should be repaired. Refer to appropriate procedure.
8. Select a new edge contact that most closely matches the edge contact to be
replaced. (See Figure 2.)
NOTE
The new replacement edge contact may be trimmed from copper sheet.
9. Before trimming out the new edge contact carefully scrape off the adhesive film
from the solder joint connection area on the back of the new edge contact. (See
Figure 3.)
CAUTION
Scrape off the epoxy backing only from the joint connection area. When han-
dling the replacement contact, avoid touching the epoxy 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 edge contact. Cut out from the plated side. Cut the
length to provide the maximum allowable joint if lap soldering. Minimum 2 times
the conductor width. Leave the new edge contact extra long. The excess mate-
rial will be trimmed after bonding. (See Figure 4.)
11. Place a piece of tape over the top surface of the new edge contact. Position the
new edge contact on the printed wiring board surface using the tape to aid in
alignment. (See Figure 5.)
NOTE
Allow the edge contact to overhang the edge of the printed wiring board. Leave
the Tape in place during the bonding cycle.
12. Select a bonding tip with a shape to match the shape of the new edge contact.
NOTE
The bonding tip should be as small as possible but completely cover the entire
surface of the new edge contact.
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 edge contact. Apply pressure as
recommended by the manufacturer. (See Figure 6.)
CAUTION
Excessive bonding pressure may cause measling in the printed wiring board
surface or the new conductor to slide out of position.
Figure 5 Place the new edge contact
in place using tape.
Figure 6 Bonding system.
Figure 7 File overhanging piece of the
new edge contact.
Figure 8 Completed repair.
IPC-7721A
Number: 4.6.2
Revision:
Date: 2/98
Subject: Edge Contact 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
--``,``,-`-`,,`,,`,`,,`---
14. After the bonding cycle remove the tape used for alignment. The new edge
contact is fully cured. Carefully clean the area and inspect the new edge con-
tact for proper alignment.
15. If the new edge contact 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 edge contact 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 edge contact 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. Trim the extending edge of the new edge contact with a file. File parallel to the
beveled edge until the excess material has been removed. (See Figure 7.)
18. If sealing the lap solder joint connection is required, 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.
NOTE
Additional epoxy can be applied around the perimeter of the new edge contact
to provide additional bond strength.
19. Apply surface coating to match prior coating as required.
EVALUATION
1. Visual examination, measurement of new pad width and spacing.
2. Electrical continuity measurement.
IPC-7721A
Number: 4.6.2
Revision:
Date: 2/98
Subject: Edge Contact 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: 4.6.2
Revision:
Date: 2/98
Subject: Edge Contact 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
--``,``,-`-`,,`,,`,`,,`---