Hi Tomas,
I have no simple answer for you, as my 0402 experience is still quite
limited, but by clicking on "0201 Sized Components" from the mainpage of my
website http://www.smtinfo.net you'll get many links to articles about
assembly of small chips. I hope you'll find a good clue.
Daan Terstegge
----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, January 12, 2004 9:42 PM
Subject: Re: [TN] reflowing 0402 SMT capacitors with underside termination s
> Hi Steve,
>
> I'm honored to get a reply from such an esteemed member of the group!
>
> We actually use the 2% formulation for that very reason - this is slightly
> different from classic tombstoning - I have included some info. from the
> vendor (which we implemented in our board and stencil design) as well as a
> few pix of the resultant behavior in our design (can't imagine much
> proprietary stuff could be pried from the top-down shot but please treat
the
> photos with discretion). Note component terminations... kinda look like
> pontoons.
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> Best Regards,
>
>
>
>
>
> Tom Ochenas
> Process Engineering
> Maxtek Components Corporation
> 2905 SW Hocken Avenue
> Beaverton, OR 97005
> [log in to unmask]
> desk: 503-627-3078
> fax: 503-627-4651
>
>
>
>
> -----Original Message-----
> From: Steve Gregory [mailto:[log in to unmask] <mailto:[log in to unmask]> ]
> Sent: Monday, January 12, 2004 12:23 PM
> To: [log in to unmask]
> Subject: Re: [TN] reflowing 0402 SMT capacitors with underside
terminations
>
>
> Hi Tom!
>
> There's a few articles out there that talk about "Phased Reflow
Soldering".
> Here's a link to one:
>
> http://www.reed-electronics.com/semiconductor/index.asp?layout=article
> <http://www.reed-electronics.com/semiconductor/index.asp?layout=article&>
&
> articleid=CA274087&industryid=3026
>
> Something I've done in the past that works really well in my opinion, is
to
> use a 2%
> silver solder paste. Sn62/Pb36/Ag2...works in the same way that Phased
> Reflow
> does.
> The difference is pretty dramatic when it comes to eliminating tombstones!
>
> -Steve Gregory-
>
>
> > Greetings All,
> >
> > I am having my first experience working with an assembly design that
> > involves 0402 capacitors with underside solderable terminations (vice
> > wrap-around end terminations)... The reflow process seems to cause the
> > components to tilt and skew to highly unacceptable levels. Physically it
> > looks as if the caps floated to the top of the molten solder volume (as
if
> > on pontoons) then slid down one way or the other. The vendor made a few
> > recommendations including migration to a thinner (4 mil) stencil as well
> as
> > some pad design and nitrogen tweaks and... Even after implementing these
> > recommendations we are experiencing the same problems, just to a
slightly
> > lesser (although still unacceptable) degree... Does anyone out there
have
> > any additional thoughts on how to remedy this sort of issue?
> >
> > We do build another part [successfully] with a similar style component,
> but
> > it is a 1206 form factor and is perhaps massive enough to keep from
> floating
> > up the way the 0402 caps do...
> >
> > Your collective wisdom is greatly appreciated!
> >
> > Best Regards,
> >
> > Tom Ochenas
> > Process Engineering
> > Maxtek Components Corporation
> > 2905 SW Hocken Avenue
> > Beaverton, OR 97005
> > [log in to unmask]
> > desk: 503-627-3078
> > fax: 503-627-4651
> >
>
>
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