In a message dated 9/15/98 17:50:43, SteveZeva wrote:
>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-
Hi Steve,
You are not off base, as long as you profile a solder joint nearest the center
of the BGA. The original message I responded to talked about a general profile
peaking at 219C, which of course would mean that internal BGA solder joints
would never see those temperatures.
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]
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