ID - Inside Diameter
The eyelet inside diameter should be a .075 - .500 mm (.003"-.020")
greater than the component lead diameter
LUF - Length Under Flange
The length of the eyelet barrel under the flange should be .630
- .890 mm (.025" - 035") greater than the thickness of the circuit
board. This added length allows for proper protrusion when setting
the eyelet.
FD - Flange Diameter
The eyelet flange diameter should be small enough to prevent
interference with adjacent lands or circuits.
OD - Outside Diameter
The clearance hole drilled through the circuit board should
allow the eyelet to be inserted without force but should not
exceed .125 mm (.005") greater than the eyelet outside diameter.
Note
Be sure to select an eyelet meeting the proper criteria. An
eyelet with an oversize flange may interfere with adjacent circuits.
An eyelet that is too short will not protrude through the circuit
board for proper setting.
Figure 1: Precision Drill System
shown with circuit board pinned
in place.
|
| 1. |
Clean the area.
|
| |
| 2. |
Select an eyelet using the Eyelet Selection
Criteria. Use a pin gauge and caliper to measure
the existing plated hole dimensions.
|
|
|
| 3. |
Pin the circuit board to the base
of the Precision Drill System. (See Figure 1). |
|
Figure 2: Mill down to and expose
inner layer signal or plane.
|
| 4.
|
Insert the appropriate ball mill,
end mill or drill into the chuck of the drill press. |
| |
|
| 5. |
Mill or drill out the hole. The drilled hole
should be approximately .030 mm (0.001") larger
than the eyelet O.D. Inspect to ensure no metallic
particles or burrs remain.
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| |
|
| 6. |
Select the side of the assembly that will have
a counterbored hole milled into it. This side
preferably would have no surface connection.
|
| |
|
| 7. |
Select an end mill approximately .050 - .075
mm (.020" - .030") larger than the eyelet diameter.
Insert into the Precision Drill System and mill
down to and expose the inner layer signal or
plane. (See Fig. 2).
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| |
|
| |
Caution
Great care must
be taken to control the depth of the milled
hole to prevent damage to the inner layer signal
or plane.
|
|
Figure 3: Solder the eyelet barrel
to the exposed inner layer signal
or plane. |
| 8.
|
Clean the area. |
| |
|
| 9. |
Apply a small amount of flux to
the exposed signal or plane and tin with solder. |
| |
|
| 10. |
Clean the area. |
| |
|
| 11. |
Insert the eyelet into the hole
from the side opposite the milled hole, then apply
a small amount of flux into the milled hole. |
| |
|
| 12. |
Solder the eyelet to the exposed inner layer
signal or plane by applying heat from a soldering
iron to the barrel of the eyelet. (See Figure
3).
|
| |
|
| 13. |
Completely remove any solder flux
residue by spray rinsing with cleaner. |
| |
|
| 14. |
Use a microscope and inspect the solder fillet
from the eyelet to the inner connection and
perform electrical tests as required.
|
| |
|
|
Figure 4: Fill the milled hole with
the epoxy up to, and level with,
the surface of the board.
|
| 15.
|
Mix the epoxy as required. |
| |
|
| 16. |
Fill the milled hole with the epoxy up to, and
level with, the surface of the board. (See Figure
4). The epoxy filler material should be free
of voids and air bubbles.
|
| |
|
| 17. |
Cure the epoxy per Procedure 2.7
Epoxy Mixing and Handling. |
|
Figure 5: Set the eyelet using an
Eyelet Press.
|
| 18.
|
Select the proper setting tools and insert them
into the eyelet press. (See Figure 5).
|
| |
|
| 19. |
Turn the circuit board over and
rest the eyelet flange on the lower setting tool. |
|
Figure 6: Eyelet barrel formed
flat to circuit board surface.
|
| 20.
|
Apply firm even pressure to form
the eyelet barrel. (See Figure 6). |
| |
|
| 21. |
Install the component lead and solder, if required.
|
| |
|
| 22. |
Clean the area. |
| |
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| |
|
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Evaluation |
| |
|
| 1.
|
Visual examination, dimensional requirement
of land diameter and inside diameter.
|
| |
|
| 2. |
Electrical continuity as required. |
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