Greg,

I'm not sure how best to interpret your wetting/dewetting results.  That question is probably best answered by Dave Hillman's Soldering/Solderability subcommittee.  I think until you have a clear definition I'd measure the area of both spread areas.  I'd also suggest that you use a standard SN63 solder paste next to your Pb-Free paste so that you can get a baseline comparison of spreading/dewetting/ etc.  I know it is extra work and one could argue that we'd never use the SN63 at the Pb-Free temperatures but it might help provide some insight to the wetting/dewetting.

Regards,
George

George M. Wenger (908)-546-4531 
Reliability Engineer
RF Power Amplifier Group
Andrew Corporation,  40 Technology Drive, Warren, NJ 07059
[log in to unmask]



-----Original Message-----
From: Munie, Gregory [mailto:[log in to unmask]]
Sent: Monday, February 10, 2003 2:40 PM
To: [log in to unmask]
Subject: [TN] IPC Test Question


Does anyone use IPC Test Method 2.4.46 for testing the wetting of solder
paste to copper coupons?

We are having an internal debate here over how to interpret "spread" for a
lead free alloy.

In general we get a "wetted area" larger than the print but there is
evidence of some pull back/dewetting, i.e. a dome of solder within a
somewhat larger dewetted circle.

As some Tin/Copper intermetallics are not easily wetted once they have
formed should the area of wetting be calculated on whole area covered or
just the solder "dome"?

At these lead free high temperatures how do I interpret wetting and
de-wetting from intermetallic formation?

Greg Munie

Kester Solder

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