Hi Nancy

1.  (a.) placement of the thermocouple depends on what you want to measure.
Since the prime interest are the conditions the solder paste will see,
embedding it in a joint provides the closest simulation.

2.  (a.) reflow profiles depend on a number of factors, but assuming an
'easy' board on HASL, the widest process window lies between the max and min
meaning 'typical' profile.

3.  (d. none of the above) the largest reason for a soldering profile (but
not the only) is the flux vehicle.  The profile needed for the flux is
dependent on the manufacture of that flux and they will call out the
profile.  There are reasons for ignoring the solder paste manufacture's
profile, but as long as those 'special' reasons don't apply, their profile
should be followed.

Kind Regards

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Nancy Reynolds/MKT/HQ/KEMET/US [SMTP:[log in to unmask]]
> Sent: Thursday, November 08, 2001 1:25 PM
> To:   [log in to unmask]
> Subject:      [TN] Reflow Process Profiling Methods
>
> Hi Technet,
>
> I need some help to identify the most common methods of thermocouple
> placement when profiling reflow processes.  And while we are on the
> subject, I would also like to collect information on targeting for typical
> or recommended profiles versus absolute min/max boundaries.  Just three
> easy multiple choice questions....
>
> 1. Where do you put the thermocouple?
>    a. Embedded in a solder joint?
>    b. On top surface of a component? (If so - how do you attach the TC to
>    the part?)
>    c. On surface of the PWB?
>    d. In air?
>
> 2. Do you target reflow profiles to fit a "typical" curve or do you just
> try to stay below a maximum?
>    a. Target for typical?
>    b. Stay below maximum?
>
> 3. How do you specify that Typical or Maximum condition?
>    a. Peak Temperature and Maximum Time at that Peak?  (Please define
>    conditions.)
>    b. Total time above a fixed value (usually 183?C or 200?C)? (Please
>    define conditions.)
>    c. Solder Paste Alloy composition for above values?  (If you are
> running
>    both SnPb and Pb-free, please reply for both)
>
> If any of you would like to share soft copies of actual time/temp profiles
> that you use for targeting or specifying an acceptable range of reflow,
> please email to me off-line.
>
> Thanks in advance for your help.
> Nancy Reynolds
> KEMET Electronics
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