Please understand that a Plated-Through Hole (PTH) should not be under 
compression.  We use a surface pad routed to the PTH connection (dog bone). 
 Sure this requires two holes, but their is not a question of reliability of 
the PTH since the majority of the compression is relatively local to the 
shadow of the component hardware.

You must be using a large thread size.  Our values of torque for stud 
mounted components are:
     #4:  2.0 to 4.0 in-lbs.
     #6:  4.0 to 6.5 in-lbs.
     #8:  6.5 to 9.5 in-lbs.
     #10:  10 to 15 in-lbs.
     1/4":  17 to 25 in-lbs.
     1/2":  180 to 220 in-lbs.

These values are reduced depending on the thread coating; multiplied by .6 
for dry film.
 ----------
From: TechNet-request
To: TechNet
Cc: cblevins
Subject: Torque
Date: Friday, October 13, 1995 7:36AM

 Dear Scholars,

 I would like to know if there is information available, or opinions that
 address this subject of torque.
 September 20, 1995

Our design engineers have requested a torque specification for a
circuit board. This is a two layers board, FR-4 material, thickness
0.062", and copper is 2oz. This torque requirement is due to a
mechanical assembly operation. We are inserting a threaded SCR
through the circuit board, where we will secure this device with a
lock washer and nut. This assembly operation is very similar to
your (IPC'S) description on page 10, fig. 2-10 of the
"Acceptability of Electronic Assemblies," the only difference is
there is no insulating washer.

I do have the torque specification for the part being assembled
which is 22 Lb.in (US-units), and I found no problems with this
pressure.

Still the design engineer is requiring the torque specification for
the FR-4 product.

Can you please assist me in qualifing this torque requirement.

My first concers are, could an assembler tighten this part tight enough to
crush the barrels or feed-throughs. "I will answer that myself," if no
constraints are given, sure with a big enough vise or lever damage would
occur.


Sincerely your,
Medar Inc,
Michael Cussen