There are more than one way to secure the TC on the board. In some
cases the boards are very expensive and scraping one is not an option.
Based on posts on the list and personal experience the best way is using
higher temperature than eutectic solder to secure the TC.. Another way is
using Kapton tape. If you are careful and run a board, after it has been
reflowed and cooled off, a second time with the TC attached at the places of
interest, a very close representation of the profile will result. It is
important that the TC do lay flay on their own on the board. In other words
form them so they stay on the board without having to force them down on the
board. The Kapton tape gets soft with heat and the adhesion gets weakened.
If there is any springing on the TC, the TC will win and it will pull away
from the board. The thermocouples wires have to be routed so they will not
interfere with components, specially BGA. Since everything will reflow
again, It is very important that all wires stay clear of components and not
move them. Either way kapton or high temp solder, it is easier if you run a
board that has all the parts reflowed and has cooled off, this way you don't
have to worry about disturbing parts as you place the TCs. As long as you
run the board only two times is still usable.
Regards,
Ramon
> -----Original Message-----
> From: McCall,Doug [SMTP:[log in to unmask]]
> Sent: Tuesday, July 29, 2003 3:34 AM
> To: [log in to unmask]
> Subject: [TN] Attaching mole thermocouples to PCBA's being profiled
> at reflow
>
> Hi all,
>
> When profiling a PCB assembly through a reflow oven process
> how do you guys actually attach the thermocouples. The reason
> for asking this question is that if you attempt to put the wires
> (x6) over the wet solder paste then the components & devices will
> be moved by the loose thermocouple wires.
>
> Therefore, I have been using a scrap PCB assembly and profiling a
> number of times, but this means having a scrap one out of the batch.
>
> Any thoughts appreciated.
>
> Thanks,
>
> Douglas I McCall,
> PCB Manufacturing Engineer
>
> BOC EDWARDS,
> Marshall Road,
> Eastbourne,
> East Sussex,
> BN22 9BA UK
> Tel: +44 (0) 1323 501 147
> Fax: +44 (0) 1323 509 824
> mailto:[log in to unmask]
>
>
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