I could not agree more with what Vladimir stated. Wetting balance tests and even dip-and-look solderability tests do not compare with the actual "test" of assembly and soldering of the board and components. If there are issues, one needs to put a TC on the PWB and find out exactly what the profile is, and if it appears to be adequate but there are still issues with wetting then those need to be determined using other means such as micro-sectioning, etc. Just because component leads and/or board pads solder up by themselves does not mean they can be eliminated. As a well-known reliability expert who occasionally contributes to this forum once said, "I can get good solder coverage on a toothpick."
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
Sent: Tuesday, August 11, 2009 8:11 AM
To: [log in to unmask]
Subject: Re: [TN] PCB wetting issue saga, final question
Hi Ioan,
Unfortunately, any of the solderabilty tests (even the wetting balance one) very often are far away from the real life (real re-flow profiles) and the level of "comfort" they can give one can be very deceptive.
I always say that in order to solve a problem, one would have to get down to its root cause.
It case of "solderabilty issues" the real root cause may have absolutely nothing to do with solderabilty of either component or the board. You can take a look at the case history on our website.
Regards,
Vladimir
SENTEC
------Original Message------
From: Ioan Tempea
Sender: TechNet
To: [log in to unmask]
ReplyTo: TechNet E-Mail Forum
ReplyTo: Ioan Tempea
Sent: Aug 11, 2009 08:51
Subject: [TN] PCB wetting issue saga, final question
Hello Technos,
I have been asking questions on Technet about some wetting issues we see on a particular board and got many useful answers. In the end we've had the boards tested for solderability by respectable labs and the bare boards passed J-STD-003 testing with flying colors.
To back track a little bit, the original doubt came from the fact that in reflow, the solder does wet very well on both the board and the component in the component pin area, but would stop spreading pretty far from the land's end. It just stops spreading, even though the wetting angles at the stop points are very low, so denoting excellent wetting.
And here comes the question: why is testing per J-STD-003 done at 235 C and with a rather aggressive flux, when the reflow soldering takes place at 205 C (HASL finish) using a milder flux (I am using WS, but it could very well be no-clean...)?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal Fabrication / Sr. Manufacturing Engineer
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