February 5, 2016

Some reflow soldering machines use the machine software to determine
profile settings without actually instrumenting the circuit card assembly
(CCA).  The solder paste manufacturer/paste part number, physical size and
weight of the CCA are entered into the machine and the machine software
then determines the machine settings.  However, in my opinion, this method
does not meet J-STD-001F paragraph 4.17 which requires, in part,  "a
reproducible time/temperature envelope".  I know of at least one major OEM
that claims that this method does not violate J-STD-001.

If you do not actually instrument a production CCA, or an equivalent test
CCA with multiple TC, to obtain a temperature versus time profile graph how
can one assure that the requisite temperatures are being achieved at the
actual solder joints for complex parts such as BGA and BTC and that the
TAL, ramp rates and coverage for both high and low mass components is
achieved.  Using multiple TC also provides an indication of whether there
is even heat distribution across the surface of the CCA since the graphs
for each different TC will all normally fit within the same basic envelope
and if they do not there may be some type of problem.

I would like folks opinion on whether J-STD-001, 4.17 mandates an actual
time versus temperature graph or not.

On Fri, Feb 5, 2016 at 5:22 AM, Nigel Burtt <[log in to unmask]> wrote:

> There are modelling software packages based on a 3D thermal profile of the
> PCB which gets you close to the profile you will need and then just needs
> some fine tuning once you have a PCB to play with.
>
> eg http://support.fluke.com/find_it.asp?SRC=DPQ&Document=9290428
>


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