This method is used to add a jumper at a BGA site by running
the jumper through a hole in the board. This method is normally
used for engineering changes or modifications.
Note
This procedure requires precision milling equipment and highly
trained technicians. This method is used when there is a buried
via, and other methods of terminating to the opposite side are
not an option.
Figure 1: Mill a hole through the board
and insert a Teflon sleeve.
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| 1. |
Clean the area.
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| |
| 2. |
Remove the BGA component if installed, remove
excess solder from the pads, and clean and inspect
the site.
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|
| 3. |
Remove solder mask from the via pad terminating
to the subject BGA pad. Do not remove any solder
mask from the "dog bone" area.
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|
| 4. |
Mill a hole through the board at the precise
coordinates using a Precision Drill System and
End Mill of the appropriate size. (See Figure
1 and 5).
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| |
|
| |
Note
Although both power and ground planes may be
cut, inner layer signal traces must be avoided.
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|
| 5. |
Carefully inspect the milled hole
and clean the area. |
| |
|
| 6. |
Insert an appropriately sized Teflon sleeve
into the milled hole. This sleeve will insulate
the new conductor and prevent shorting to the
inner layers. (See Figure 1).
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| |
|
|
Figure 2: Insert a copper Circuit Track into the plated
hole and Teflon sleeve.
|
| 7. |
Select a Circuit Track to match the width of
the circuit to be installed. Cut a length approximately
as needed. The overlap solder connection should
be a minimum of 2 times the circuit width. (See
Table 1).
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| |
|
Table 1 - Common Circuit Track Sizes
|
Part No. |
Thickness |
Width |
| 115-5204 |
.002" |
.004" |
| 115-5206 |
.002" |
.006" |
| 115-5208 |
.002" |
.008" |
| 115-5210 |
.002" |
.010" |
| 115-5312 |
.003" |
.120" |
| 115-5315 |
.003" |
.015" |
| 115-5520 |
.005" |
.020" |
| 115-5530 |
.005" |
.030" |
|
| 8. |
Gently abrade the top and bottom of the new
Circuit Track with the buffer to remove any
oxidation and clean.
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| |
|
| |
Note
If needed, the ends of the Circuit Track may
be tinned with solder prior to lap soldering
in place.
|
| |
|
| 9. |
Insert one end of the Circuit Track into the
plated hole connected to the BGA pad. Insert
the opposite end through the Teflon sleeve.
(See Figure 2).
|
|
Figure 3: Solder the Circuit Track to the plated hole connected
to the BGA pad.
|
| 10.
|
Apply a small amount of liquid flux and lap
solder the Circuit Track to the plated hole
connected to the BGA pad using solder and a
soldering iron. Make sure the new circuit is
properly aligned. (See Figure 3).
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|
Figure 4: Overcoat the new connection with epoxy.
|
| 11.
|
Clean the area. |
| |
|
| 12. |
Mix epoxy per procedure 2.7. |
| |
|
| 13. |
Coat the top and sides of the new circuit with
epoxy. The epoxy bonds the new circuit to the
base board material and insulates the circuit.
(See Figure 4).
|
| |
|
| |
Note
Keep the epoxy height below
the BGA pad level.
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| |
|
| |
Caution
Some components may be sensitive
to high temperature. |
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|
| 14. |
Clean the board as required. |
| |
|
| 15. |
Install a new BGA per applicable
procedures. |
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|
| 16. |
Solder a jumper wire to the exposed Circuit
Track on the opposite side of the circuit board.
Route and terminate the jumper wire as needed.
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| |
|
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Figure 5: Precision Drill System used
for milling the teflon sleeved hole.
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Evaluation |
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|
| 1.
|
Visual examination for alignment
and overlap of new circuit. |
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|
| 2. |
Visual examination of epoxy coating
for texture and color match. |
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|
| 3. |
Electrical tests as applicable. |
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