>>1) What types of thermocouples are you currently using?

Type K

>>2) If standard wire (Type K), what gage wire?

.003 and .005 and ?? embedded in a probe.

>>3) If standard wire, do you buy preassembled or 'roll your own'?

Both, as well as the mounted type inside of a metal probe.  If you do make
your own Tc, try inerting the atmosphere these are formed in and you'll get
much stronger and smaller junction beads.


>>4) What is your method of attachment for profiling?

It depends on what is being profiled.....

-Bare PWBs have lots of options, but taped wires with the junctions exposed
on the pads seems to be the easiest and least invasive.

-CCAs with parts and wet paste (the real thing) require mechanical probe
thermocouples  placed in the soon to be formed solder connections (without
disturbing the component).

-oven verification uses the widest possible board with six thermocouples
permanently mounted (use any method that works for you).

-The most accurate method is to use the mechanical properties of the wire
itself to form the tension required to hold it down to the location being
profiled.  Anotherwards no tape, no solder, no glue, no thermal or
convective resistance at all covering up the wire junction.  This can be a
lot of trouble but it will show the true temperature differences that the
surfaces being profiled actually have (again, this may give you data you
might wish you didn't know about).

>>5) What specific material/mfr/part #?

Buy the ones which have the strain relief blocks and rubber bushings and
the grey plastic handle which allows you wrap up the Tc excess length.
These are much better than just the wire.

For probes, try Saunders.  They are expensive but more durable than they look.

>>6) Do you use a fully loaded board for profiling?

Depends what is being checked.  A bare board is never the same as a fully
loaded board except when the fully loaded only has small chip caps and
resistors on it.  As soon as you add large mass components to the board,
the thermal load connected to the solderpaste increases.


>>7) How often do you get to use a fully loaded board?

Whenever it is necessary to validate the reflow profile.  It is important
to be competent and fast when profiling so that production does not have to
shut down for fear of jamming the oven due to stuck thermocouples.
>
Phil Bavaro

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