In a message dated 9/15/98 2:49:29 PM Pacific Daylight Time,
[log in to unmask] writes:

<<  For BGAs, particularly CBGAs, a reflow profile with a
 peak temperature of 219C is too low even for eutectic Sn/Pb solder.
 Even with high-melt solder balls you should get nice fillets because of the
 eutectic solder paste.
 The reliability of the solder joints goes up roughly with the square of the
 stand-off height. >>



Really? Hmmmmm...I've always tried to peak out between 210 - 220
degrees...have I been wrong in doing that? What I thought defined a good
generic profile was;

1.) Ramp no more than 2-4 degrees per second.
2.) Dwell for around 1-1.5 minutes at roughly 150 degrees C. to activate the
flux and allow everything to come up to temperature together and stabilize.
3.) Ramp a second time to reach 20-30 degrees above the liquidous and hold
that for at least 30 seconds, but try to limit it to 1-minute, and don't peak
over 220-degrees C..

That's REAL general...but that's what I've always understood to be good basic
guidelines for a reflow profile. What should I be peaking at? Is what I
thought to be good guidelines passe' now? Am I really hosed up?

I have read lately, that "stepped" profiles really aren't necessary. I've
read, that you'll get better results with just a gradual, linear rise to peak
temperature, then cool. 'Course I know everything depends on your paste
formula and ingrediants, but speaking in general terms where am I off-base?

-Steve Gregory-

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