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October 2004

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Subject:
Re: Aperture for 0603mm chip
From:
"Tempea, Ioan" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Tempea, Ioan
Date:
Thu, 14 Oct 2004 08:54:23 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (62 lines) 
Quoc,

I don't see you mentioning land pattern design. If the gap between the pads
is bigger than 0.023", you start increasing your probability of tombstoning.
Then, in case your soldering paste (if no-clean) does not create mid-chip
balls, you could print 1:1, no homeplating, although we reliably do
homeplating on 0603s that have a good pad
design.

After this you just check your process step by step: the printing shall be
well registered, no offsets at placement and yes, the reflow recipe has an
influence, if everything else is OK. You will need longer preheating, to
make sure that the paste on both pads melts at the same time when hitting
the spike. But a good reflow recipe will not correct poor printing or
insertion.

Also there are so called anti-tombstoning pastes out there, that are worth
trying.

Good luck,
Ioan

> -----Original Message-----
> From: TechNet [SMTP:[log in to unmask]] On Behalf Of Le Ai Quoc
> Sent: Wednesday, October 13, 2004 11:32 PM
> To:   [log in to unmask]
> Subject:      [TN] Aperture for 0603mm chip
>
> Hi Technetters,
> Do you know the opening style (aperture) for stencil (metal mask) applied
> for printing solder paste on resistance, capacitor chip 0603mmm to prevent
> "Tombstone/Manhattan" after reflow. Also, pls. advise about stencil
> thickness.
> Last but not least, is the reflow profile important for this defect? Any
> suggestion?
> Thanks in advance,
> Le Ai Quoc
>
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