Hello Roger, thanks for that but no the link didn't work.
However I have gone onto the Kemet website and downloaded it (and much more
too).
Are you saying in this that the reduced width pads are for wave soldering
and not Reflow?
We are using convection Reflow here so I would appreciate knowing if this is
the case.
If it turns out that thinner pads can be used with below soldering, should
they be extending any
longer than the IPC-SM-782-A pads?
Thankyou - Matthew Lamkin.
> -----Original Message-----
> From: Roger M. Stoops [SMTP:[log in to unmask]]
> Sent: Monday, August 27, 2001 8:17 PM
> To: [log in to unmask]
> Subject: Re: [DC] Capacitor pad reduction ?
>
> Matthew,
> Are these capacitors being wave or reflow soldered? Assume wave soldered
> if assembly dept is asking for reduction in pad width. Some have found
> that reduced pad widths are better for their process. Check out
> http://www.kemet.com/kemet/web/homepage/kechome.nsf/vapubfilesname/F3102Fc
> e.PDF/$file/F3102Fce.PDF
> . (I hope the link works.) Here a mfgr has a pad width for wave
> soldering at about 70% of the width for reflow soldering.
> Also, if wave soldering, is the dwell time too long in the wave? Preheat
> cycle too short? Parts along board edges or near connectors perpendicular
> to board surface? Rough handling? Same type of part failing each time?
> Here's a question for everybody: IPC-SM-782A has reduced width pad
> geometries for resistors, but not capacitors. Back in unused portion of
> brain a memory keeps saying that the no-rev version of SM-782 had reduced
> width for res-s and caps. Anybody care to comment? Any reason for the
> change (if it really was so)?
> Roger M. Stoops, C.I.D., PCB Designer
>
>
> Trimble
> Engineering and Construction Division
> 5475 Kellenburger Rd.
> Dayton, OH 45424-1099 USA
> Ph: +01 937.233.8921 or +01 937.233.4574 ext 288
> Fax: +01 937.233.7511
>
>
>
>
>
>
> Matthew Lamkin
> <matthew.lamkin@PROTEC-FIRE-DETECTI To:
> [log in to unmask]
> ON.PLC.UK> cc:
> Sent by: DesignerCouncil Subject:
> [DC] Capacitor pad reduction ?
> <[log in to unmask]>
>
>
> 08/27/01 10:09 AM
> Please respond to "(Designers
> Council Forum)"; Please respond to
> Matthew Lamkin
>
>
>
>
>
> Hello everyone,
> I wonder if I can tap into your experience of cracking of ceramic
> capacitors.
>
> I have a situation where the shop floor are having problems with cracked
> capacitors, due to
> several possible causes.
> However, the blame for the problem is being thrown at design with an
> instruction to reduce
> the width of the pads (1206/0805/0603 caps only) to be less than the width
> of the component.
>
> Now there are many documents out there advocating using the IPC SM-782-A
> pads, and many that
> advocate reducing the pads.
> However, I have the IPC specs which give me actual dimensions to follow
> whereas the documents
> that advocate reduced pad widths do not.
>
> Can anyone give me some advice on what size these pads should be when
> reduced to prevent MLCC cracking?
>
> Can anyone supply a URL of a document that gives any good information on
> this?
>
> I have many documents from AVX/SYFER etc on the subject but they do not
> quote any figures on reducing the width.
>
> Thankyou -
> Matthew Lamkin
> Protec Fire Detection PLC.
> England, U.K., Planet Earth.
>
> P.S. Come on Steve, I'm timing you now, to see how long it takes until you
> quote a website....he, he....
>
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