Hi Dan,
can you give the exact dimensions of the round land pattern?
Thanks,
Ioan
> -----Original Message-----
> From: Dan R. Johnson [SMTP:[log in to unmask]]
> Sent: Wednesday, April 10, 2002 10:22 AM
> To: [log in to unmask]
> Subject: Re: [TN] 0402 tombstone problem
>
> Steve,
> I use round pads to decrease pad size (increase circuit density). A side
> benefit seems to be less chance of skew, I don't have numbers on
> tombstoning/drawbridging, but product hasn't yelled. I have also been
> tinkering with the idea of other geometries just haven't come across the
> right application yet.
> Dan
>
> ----- Original Message -----
> From: [log in to unmask] <mailto:[log in to unmask]>
> To: [log in to unmask] <mailto:[log in to unmask]>
> Sent: Tuesday, April 09, 2002 8:12 PM
> Subject: Re: [TN] 0402 tombstone problem
>
> I just heard something not too long ago, that round pads for 0402's
> are the way to go.
>
> Never heard of that before, but just recently received a board for
> quote that uses round pads for the 0402 components...anybody else ever
> heard of this?
>
> Guess I'll find out how it works inna little while, while pondering
> why a round pad would work better than a square pad....
>
> -Steve Gregory-
>
>
>
>
> Edward,
>
> When we do everything correct on 0402 and 0201 and still
> have components
> standing-up, we often look to the component terminations and
> find poor
> plating.
>
> Good luck
> Dave Fish
>
> ----- Original Message -----
> From: "Edward S. Wheeler" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, April 09, 2002 10:59 AM
> Subject: [TN] 0402 tombstone problem
>
>
> > Hi folks, we are running a new board with 0402 parts on
> it. It seems that
> > we are having a tombstone problem as well as a problem
> with parts not
> > staying centered on the pads. We are currently using 20
> mil square pads on
> > the board, with 20 mils of spacing between them. Our
> stencil is 6 mils
> > thick, laser cut and electro polished. The trapezoidal
> walled apertures
> are
> > slightly reduced, 17 mils square, and centered on the
> pads. It appears the
> > chip shooter is placing the parts perfectly. We are using
> eutectic solder
> > paste with an OA flux, and reflowing the parts using the
> recommended
> profile.
> >
> > Are there any suggestions any of you might have concerning
> this size of a
> > part? Is there a better stencil design, reflow profile, or
> pad design that
> > could help us out? I would appreciate any suggestions.
> >
> > Thanks.
> >
> > Ed
>
>
>
>
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