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Installing .025 inch centers probes is
a delicate process. Three areas require
special attention:
- Drilling straight holes of precise
diameter and location to optimize probe
registration and targeting.
- Fixturing such that the sockets do
not touch each other (the gap between
socket bodies is .005 nominal).
- Installing probes and sockets in a
controlled manner to minimize the possibility
of damage to the delicate components.
The finished mounting hole diameter is
.0205/.0215 [0.521/0.546]. Use a #75 or
.55 mm drill, depending on the material,
drill feeds and speeds, and drilling technique.
Homogeneous plate materials such as Lucite,
Nylon and Delrin are recommended. It is
difficult to drill straight holes of this
diameter in fibrous materials such as
G-10/FR4 and phenolic.
For best registration, first center-drill
the mounting holes. For the finished hole,
use a drill with the shortest flutes that
will clear the material thickness. Solid
carbide, PC-board drills with 1/8" dia.
shanks are recommended.
Chip removal is important and can be
easily done by peck drilling while a small
air stream clears chips at the top of
the hole. Check the finished hole diameter
from both sides with gage pins or part
number PG25 Go/No go tool.
A chief concern in the design of small-probe
fixtures has been eliminated since the
sockets are retained by interference fit
instead of by epoxy mounting. The major
difference between fixturing methods for
these probes and most larger center spacing
probes is that extra consideration must
be given to preventing adjacent sockets
from shorting. Three drilled plates, properly
registered, will provide this protection
as shown in the sketch.
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025-16
Series Suggested Fixturing Method |
Slide the socket into the fixture assembly
carefully by hand until the press ring
portion rests against the top edge of
the mounting hole.
If using sockets with pre-attached wire
in multi-plate fixtures, use the ST25
socket threading tool to facilitate feeding
the wire through the plates. Slide the
tool (reduced end first) into the plates
until it is flush with the top plate.
Then feed the 1.5 [38.1]long stripped
end of the wire into the tool until it
protrudes from the reduced end. Pull the
wire through with the tool and slide the
socket in as described above. (Refer also
to the illustrated instructions for using
ST25).
Install the sockets by pushing them flush
with a small press or other controlled
method of applying force perpendicular
to the mounting plate. A hard, flat pusher
(the end of a gage pin, for example) should
be used for socket installation. Install
lone sockets one at a time. Install groups
of sockets on .025 inch grid together
to avoid reducing the diameter of adjacent
mounting holes.
Insert the probes into the sockets and
push gently with a flat, non-metallic
object to seat them fully.
Steps for Installing 025-16 Series Sockets
using ST25 Tool. The ST25 helps thread
the pre-attached wire of 025-16 Series
sockets through the holes in multi-plate
fixtures.
Step One:
Slide ST25 fully into socket mounting
holes.
Step Two:
Thread 1.5 [38.1] long stripped end of
socket wire into ST25 until wire end emerges
from tail and insulation contacts top
of ST25
Step Three:
Feed wire into hole while pulling wire
end and ST25 out.
Step Four:
Slide ST25 off wire, install socket and
probe.
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