Figure 1: Remove the defective pad
and remove solder mask from the connecting circuit.
|
| 1. |
Clean the area.
|
| |
| 2. |
Remove the defective pad and a short length
of the connecting circuit. (See Figure 1).
|
| |
|
| 3. |
Use knife and scrape off any epoxy residue,
contamination or burned material from the board
surface.
|
| |
| |
Caution
Abrasion operations can generate
electrostatic charges. |
| |
| 4. |
Scrape off any solder mask or coating
from the connecting circuit. (See Figure 1). |
|
Figure 2: Select a commercially available replacement pad
that
matches the missing pad.
|
| 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
circuit 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 commercially available surface mount
pad that most closely matches the surface mount
pad to be replaced. If a special size or shape
is needed it can be custom fabricated. (See
Figure 2).
|
|
Figure 3: Cut out the new surface mount pad.
|
| 9. |
Cut out and trim the new pad. Cut the length
to provide the maximum allowable circuit overlap
for soldering. Minimum 2 times the circuit width.
(See Figure 3).
|
| |
|
| |
Note
The new replacement surface mount pad
may be trimmed from copper sheet. |
| |
|
| 10. |
Mix the epoxy and apply a small amount to the
surface where the new pad will be placed.
|
|
Figure 4: Place the new surface mount pad in place using
Kapton tape.
|
| 11. |
Place a piece of Kapton tape over the top surface
of the new pad. Place the new pad into position
on the circuit board surface using the Kapton
tape to help in alignment. (See Figure 4).
|
| |
|
| 12. |
Cure the epoxy per Procedure 2.7
Epoxy Mixing and Handling. |
| |
|
| |
Caution
Some components may be sensitive
to high temperature. |
| |
|
| 13. |
After the epoxy has cured remove the Kapton
tape used for alignment. Carefully clean the
area and inspect the new pad for proper alignment.
|
| |
|
| 14. |
If the new pad has a connecting circuit apply
a small amount of liquid flux to the lap solder
joint connection area and solder the circuit
from the new pad to the circuit on the circuit
board surface. Use minimal flux and solder to
ensure a reliable connection. Kapton tape may
be placed over the top of the new pad to prevent
excess solder overflow.
|
| |
|
| |
Note
If the configuration permits,
the overlap solder joint connection should be
a minimum of 3.00 mm (0.125") from the related
termination. This gap will minimize the possibility
of simultaneous reflow during soldering operations.
Refer to 7.1 Soldering Basics.
|
| |
|
| 15. |
Mix epoxy and coat the lap solder joint connections.
Cure the epoxy per the manufacturer's recommended
instructions.
|
| |
|
| |
Note
Additional epoxy can be applied around
the perimeter of the new pad to provide additional
bond strength
|
| |
|
| 16. |
Apply surface coating to match
prior coating as required. |
| |
|
|
Figure 5: Completed repair.
|
|
Evaluation |
| |
|
| 1.
|
Visual examination |
| |
|
| 2. |
Measurement of new pad width and
spacing. |
| |
|
| 3. |
Electrical continuity measurement. |
|
