Hi,

My suggestion would be to run some tests. Create at least 4 different
configurations (pad geometries) for each component type and place about of
100 of each on a test board. Run at least 10 boards through manufacturing
and do a quantitative analysis to determine which geometry(s) produce the
fewest defects. Then no one can argue "whose fault".

Best regards,

Mario Irigoyen

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]]On Behalf Of
Matthew Lamkin
Sent: Monday, August 27, 2001 9:09 AM
To: [log in to unmask]
Subject: [DC] Capacitor pad reduction ?


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I have many documents from AVX/SYFER etc on the subject but they do not
quote any figures on reducing the width.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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