Send it Steve ; will make no difference with inhouse environment .
What Werner is eluding to is :
When you have a blunt drill and not so smooth barrel wall ; the plating is
very much weaker in "rings" up the wall , than when you half fill the barrel
, which grabs strong ;
and other half with completely different "CTE" initial inertia :
the barrel snaps where solder infill ends .
Seen that on some boards from open field installations ;
mostly the barrel was faulty in copper to begin with .
Peek down the barrel ; if it is reasonably smooth you have no worries to
speak of .
Commercial reality is it will last minimum 5-10 years ;
just to play a long distance prophet .
Even that 75% "rule" I'd love to elaborate on as I often found the weakest
ring just under the pad, (may have something to do with the drill entry and
exit; pad/barrel shear; ?);
but I restrain myself this time ; Werner should know better anyhow .


see you          paul


-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Wednesday, 18 August 1999 9:43
To: [log in to unmask]
Subject: [TN] Via Fill...(I know ya'll are sick of this! BUT...)


Hey ya'll!

Well, I got about a 50/50 split about whether or not it's important that
vias
fill with solder or not...more precisely, the one's that do fill need to be
at least 75% full. To add to that, Werner jumps in and says something about
that it makes a difference whether the vias in question are at the outer
edges of the board, or in towards the center...hoo-boy, I hate it when he
confuses me with the facts!

What I once thought was fairly a non-issue, now seems to have taken on some
significance. But I'm still stuck with these boards. I don't know the
precise
operating environment, but I do know what they do. It's for a mail sorting
system...we have several boards that we build that go into a system that
sorts mail by reading the barcode on each piece of mail as it whips by at
"warp speed" and sorts it by zipcode and whatnot...don't think it's gonna
see
extreme environments (unless they'll have these systems down in Antartica,
but I don't think so because there ain't the volume of mail coming outta
that
place that needs a automated system such as this...hehehe) so I think the
temp cycling will be pretty benign...but then again, I'm really guessing.

Hate to scrap all these boards, and also hate to have to put all the labor
into masking all the damn vias just to be sure they don't fill...also hate
to
call the customer and ask them if it's okay to run with these boards...they
may, or may not have the insight that the TechNet list has about these
issues
in which case I may appear as "the boy who cried wolf" which makes me feel
real enthusiastic about this whole deal...

I'm just gonna come out and ask; what should I do?

-Steve Gregory-

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