Thanks for taking the time to reply.
 
Maybe it was too much eggnog this year, but I was looking in
IPC-2221 and didn't think to check IPC-2222 for the answer.
(bonehead)
Anyway, according to the latest working draft on ipc.org
(which isn't "official" yet, but it hasn't changed from the
last version which means they probably ain't gonna)
the lead-to-hole relationship should be:
 
-----
Table 9-3
-----
max.hole to min.lead   
level A-B no more than 0.7mm over min lead diameter
level C    no more than 0.6mm over min lead diameter
-----
max.hole to max.lead
level A   no less than 0.25mm over max lead diameter
level B   no less than 0.20mm over max lead diameter
level C   no less than 0.15mm over max lead diameter
-----

thanks again (everyone!)
Jack
 
 
.
On Thu, Jan 8, 2009 at 9:20 AM, Dave Schaefer <[log in to unmask]> wrote:
Jack,

I seem to recall that hole size was originally specified in MIL-275 / IPC-275D as .006" - .028" (.15mm - .71mm) over max lead depending upon classification.

At my most recent previous gig we were using max lead + .017" for thru hole sizing based upon manufacturing trials with positive results. We used thru components only in special applications and the hole size worked well for both wave and select applications, thru components were hand inserted. Mfg volume was 1K to 100K per year.

Dave Schaefer
[log in to unmask]




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