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Reply To: | TechNet E-Mail Forum. |
Date: | Wed, 19 Apr 2000 13:50:14 -0500 |
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Iain,
We use a thermocouple flex probe that attaches to the edge of the board by a
small clamping mechanism. The tip of the thermocouple is held in place on
the board surface by flexing (slightly) the probe and clamping it in a fixed
position. We have had very good results with this type of probe. Contact
me off-line for more information [log in to unmask]
blm
Iain Braddock wrote:
> Cyber colleagues,
>
> I would like to get others' views on the following subject.
>
> When attempting to measure the thermal profile of a populated board
> through a forced convection reflow oven what is considered the best form
> of thermocouple attachment & why?
>
> I believe there are four general methods of attachment.
>
> 1) T/c tip bonded to the lead/pad with something like a 2 pack epoxy
> quick drying, covering the tip.
>
> 2) T/c tip touching lead/pad bedded onto a thermal compound paste
> with it covering it.
>
> 3) T/c tip soldered to lead/pad.
>
> 4) T/c embedded through board directly adjacent to lead/pad with
> compound covering tip.
>
> Option 1 - Easy to apply and as the bonding agent isn't very thermally
> conductive perhaps less likely to be influenced by the higher air
> temperature in the chamber.
>
> Option 2 - Easy to apply but perhaps influenced more with the air
> temperature although being sunk by the board.
>
> Option 3 - Difficult to achieve as the tip isn't very receptive to SnPb
> solder.
>
> Option 4 - Time consuming, destructive but perhaps less influenced than
> the others with air temperature.
>
> I appreciate that the temperature will also depend on where it is
> attached on the board power plane etc.
>
> Finally, but on a different but connected note, what would be the
> consequence if some of the joints had only just managed to get a few
> degrees above liquidus - reliability? Perhaps if you've read this one Mr
> Engelmaier it may be up your street?
>
> CIA Iain.
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