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