I would be interested to know which solder paste vendor recommends a 30
second reflow time?
Can you actually achieve a 15 second reflow time with a peak temp. of 215 to
225? What type of assemblies are these parameters achieved on and with what
equipment?
It's hard to see how 30 seconds is suited to modern complex assemblies? Is
this paste aimed at people producing panelised boards for pagers, sensors,
etc..?

The issues I suppose are down to tolerance, (I know I don't have any). A
paste with a wide process window is of great advantage. Some pastes (fluxes)
will be problematic if you aren't 'bang on the money' with your profile,
while other pastes (such as the one we use), let you away with blue bloody
murder!
In general it isn't a good idea to let the reflow time go longer than the
recommended time, but then usually this is only a guideline rather than an
exact rule. As the reflow time extends yes I'm sure the intermettalic growth
increases, and the grain size increases. But I don't think it's of
consequence for 15 seconds more of reflow time, but more in the order of 30
to 45 seconds extra.


Regards






At 16:30 27/01/98 -0500, you wrote:
>I would like to know what are the drawbacks of increasing or decreasing
>the reflow time for BGA assemblies due to the actual thickness of the
>PWB, and the thermal loading due to the number an type of
>components...If the reflow time is 15 seconds rather than the solder
>vendor recommended profile fo 30 seconds, how does that affect the
>metalurgy of the joint and its reliability?  What if the reflow time is
>45 seconds? And if I have to verify the intermettalics, how is that done
>u sing X-sectioning and SEM...Is there a recommended approach for doing
>this?
>
>thanks,
>
>Marcelo
>
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