FreeLists / pcdlist / [pcdlist] Re: Thru hole components

["Jack C. Olson" <OLSON_JACK_C@xxxxxxx>]

People still use through-hole devices? (just kidding)

I don't know if this will help much, but for what it's worth:
After comparing a gazillion data sheets at a previous company,
I realized that components with round leads generally follow the
American Wire Gage sizes.
Combined with the results of a solderability study (sorry I don't
have the reference) that solder flows best (capillary action) if the
hole is 11-14 mils over the lead size, I created a set of standard
through hole sizes based on the AWG chart. Then every time I
got a new component with round leads I just selected the appro-
priate hole size from the standard set. No one ever complained
and it sure makes that part of the puzzle a cinch.

The rest of the through holes are usually for stamped metal,
square or rectangular cross section, and as long as the hole is
around 5mils over the maximum dimension (corner to corner)
the solder can still flow up along the sides.

oh.... as a side note, the hole sizes that result for round leads
stated above fit inside the range suggested by IPC-2222
Table 9-3, but I don't know about how IPC treats rectangular.

Good luck,
Jack





"Watt, William   (sys) USX" <wwatt@xxxxxxxx>@freelists.org
9May2002 12:16 PM

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Now that I know there are a few people out there, let me ask a question.
We
are having a discussion here in our design dept about standardizing hole
sizes.  The present method of determining finished hole size is to use the
IPC 2221 formula and pick the hole in the center of the range.  This is
fine
except we end up with many holes that are within .001 of each other and our
mechanical checker or the fab house will ask to combine them into one
common
size.  I recall from a past life that I used a hole chart with drill sizes
every .003 instead of every .001 and this worked fine.  I am having trouble
convincing some of my coworkers of the wisdom of this method.  I would like
to know if anyone else has an opinion on this. I would like to standardize
by using the formula, finding the median size and rounding up to the next
drill size.  How does the rest of the world do it?

Thanks for the help.  Maybe I can use an overwhelming opinion to convince
my
department.

Bill Watt
Moog Inc
Jamison Rd
East Aurora, NY 14052
716-687-5596
wwatt@xxxxxxxx

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