Steve i'd disagree (for a change) on this one ,
finding 1) & 2) valid ; but not really relevant .

I'd say the counteracting CTE's under load are the major reasons,
as you have may have dilatations working straight against each other (worst
still in tangential twist),
very undesirable scenario (even with just differing CTE's in same direction)


Than it's the metal (copper on copper) touch/lever magnification of the
stress .

With this did have the negative, mainly on PDevelopment work ; or one of's
built .
Unfortunately ; this one is real (cracks componentry) .

Long story off line .

Never looked for standards at this point

paul

-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Wednesday, 23 February 2000 9:45
To: [log in to unmask]
Subject: Re: [TN] How many leads can you jam into a plated th


In a message dated 02/22/2000 1:09:04 PM Central Standard Time,
[log in to unmask] writes:

<< I know that it is generally "taboo" to put more than one lead in a plated
through hole, but I would like to better understand why.  I believe that it
is because:

 1) Rework:  You need to be able to remove and replace any component without
impacting another.

 2) Flux entrapment and solder defects:  The oversized hole required will
result in increased solder defects and could also lead to flux entrapment.

 Are these reasons correct and are there any other reasons?

 Are there any classifications of PCB which allow for this practice?

 Anyone out there with real experience (positive or negative)?

 Thanks,

 Lang >>

Hi Lang!

I've never it done before, most likely because I've never faced the
situation. Is this something being considered because there's a flaw in the
design that you want to be able to not have to scrap boards, or is this
something that's being looked at to be designed in? (although I can't think
of any real reason you'd want to do that intentionally)

I have though, shared holes with a jumper wire, but that can't really be
called another lead... other than that I have no other experience.

Be interested in the situation of why something like that is being
considered..

-Steve Gregory-

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