Hi Daan,
for different reasons than solder beading, I am presently evaluating
different no-clean solder pastes. And I came to realize that solder beading
might be a problem with the modern formulations, and speciffically with the
higher ranking products of the big brand names.
But until now I had no beading problem, with our stencils cut 100% and
rectangular on all the passives. I use CR36 from Multicore and get no solder
beading, regardless the pad design. I also tried the EasyProfile 256 from
Kester and F367 from Heraeus and they exhibited no solder beading. On the
other hand I got beads with Alpha's OMNIX and AIM NC251.
So, I believe too that using home plate apertures is a good thing, but there
also are pastes out there that do not produce beads. AIM just told me they
will release really soon an anti-beading paste, NC253.
So this is an alternative solution.
Regards,
Ioan
> -----Original Message-----
> From: David Fish [SMTP:[log in to unmask]]
> Sent: Monday, December 17, 2001 12:03 PM
> To: [log in to unmask]
> Subject: Re: [TN] Homeplate apertures, how to use them
>
> Dan,
>
> We do not have a standard for applying home-plate apertures.
>
> Dave
>
> ----- Original Message -----
>
> From: D.Terstegge <mailto:[log in to unmask]>
> To: [log in to unmask] <mailto:[log in to unmask]>
> Sent: Friday, December 14, 2001 2:45 PM
> Subject: Re: [TN] Homeplate apertures, how to use them
>
> Hi Dave,
>
> The goal is elimination of solder beads (the balls at the sides of
> chipcomponents). At present we're cleaning all our boards, which removes
> 99% of the solderbeads, but we want to anticipate on a no-clean process
> that we may introduce in the future. From previous Technet discussions I
> learned that the homeplate design is very effective in removing solder
> beads. Maybe I should also try some alternatives, but the question remains
> how to make an easy to use specification (to the stencil supplier, or to
> our production engineers who orders the stencil) as to what apertures
> should be changed to homeplate, and what apertures should be left
> untouched (or should be changed in another way).
>
> Daan Terstegge
> www.smtinfo.net <http://www.smtinfo.net>
>
> ----- Original Message -----
>
> From: David Fish <mailto:[log in to unmask]>
> To: [log in to unmask] <mailto:[log in to unmask]>
> Sent: Saturday, December 15, 2001 1:09 AM
> Subject: Re: [TN] Homeplate apertures, how to use them
>
>
> We do not routinely use homeplate apertures. We only use
> homeplate
> apertures in cases where we need to reduce solder balling
> when using NC
> fluxed pastes.
>
> What is your goal in using this aperture shape?
>
> Dave Fish
> ----- Original Message -----
> From: "d. terstegge" < [log in to unmask]
> <mailto:[log in to unmask]>>
> To: < [log in to unmask] <mailto:[log in to unmask]>>
> Sent: Friday, December 14, 2001 6:05 AM
> Subject: [TN] Homeplate apertures, how to use them
>
>
> > Dear Technetters,
> >
> > For our stencils I have recently introduced the homeplate
> design for the
> apertures of chipcomponents larger than 1206.
> > But now a problem occurs with the guys who have to order
> the stencils: it
> takes a lot of time, by using Gerber data, partslist and
> assembly drawing to
> figure out which components are 1206, 1210, 1812. For a coil
> or tantalumcaps
> with such a footprint I don't want a homeplate aperture
> because these parts
> need a little more solder.
> > So we end up with a nice specification, but very
> unpractical for the
> production engineers.
> >
> > How do others deal with this ? Mabe you have suggestions
> on how to make
> an easier-to-use specification ? Or ideas about easier ways
> to order a
> stencil according to my spec ?
> > Should I keep it simple and say "use homeplate-apertures
> for all
> footprints larger than 1.5 * 1.5 mm ?"
> >
> > Daan Terstegge
> > SMT Centre
> > Thales Communications
> > Unclassified mail
> > Personal Website: <http://www.smtinfo.net>
> >
> >
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