In a message dated 3/3/99 11:50:49 AM Pacific Standard Time, [log in to unmask]
writes:

<< Can anyone respond with a formula for reflowing a double sided board
 with active parts on both sides (specifically .0020 TSOP's)?
 I have seen such a formula with a weight vs. lead area in solder ratio
 but can not locate. Thanks
 Patrick Malone >>

Hey Patrick!

    Seems what I remember floating around was 30-grams of surface tension for
every square inch of pad surface. So then I guess you total up the pad surface
area available for the part, weigh it, and then go to town...(if the part
weight to surface area ratio is oakie dokie)

    But instead of going through that drill, I'll just tell ya' I haven't met
a gull-wing part out there that won't hang upside down for me in
reflow...'cept maybe some 6 & 8 leaded filters that are out there. I'm sure
some of you have seen those...ya' know, the ones with the big plastic body,
pretty tall ones...and anything with a heatsink too. Almost all your passives
are okay...'cept them rolly-poly MELF's. Most J-leaded parts are okay 'cept
for ceramic parts and your larger PLCC packages...

     That being said, you gotta have good solderability, a decent reflow
profile, a smooth running oven conveyer (no jerks or anything like that...and
no, I'm not talking about people jerks either...although that DOES help things
if there's none of those around either....hehehe), and a board that doesn't
wanna bow during reflow. You should be okay..

-Steve Gregory-

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