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September 1999

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Subject:
From:
Mark Holmes <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 24 Sep 1999 09:09:21 +0100
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Hello All,

This is a question for all you board assemblers out there,

I originally sent to this message to the Designer Council list, so I
apologise in advance to anyone who subscribes to both forums.

All the data I have regarding pad sizes (e.g. IPC-2221 9.1.1) give examples
on how to calculate Minimum pad sizes, usually from a PCB fabrication
standpoint. IPC-2221 states that all lands and annular ring shall maximised
wherever feasible, consistent with good design requirements and electrical
clearance requirements.

My questions are: How do I determine the pad size that will give me the best
soldered joint?
Would the minimum pad size calculated by the formula in section 9.1.1 still
provide a good soldered connection?
Are there upper limits to the size of a solderable surface of a pad?
Would the Ideal be to maximise all the pad sizes to one size that meets the
requirements of 9.1.1 for all holes?

I am surprised there is no reference to soldering in the standard relating
to pad sizes, I am sure the pad size must have some effect on the solder
fillet.

Any information would be appreciated,

Thanks in advance,

Mark

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