ANSI/J-STD-001A Article 9.2.1.1 (d) identifies reject criteria.

Dave Acton

> -----Original Message-----
> From: Steve Collins [SMTP:[log in to unmask]]
> Sent: Thursday, November 12, 1998 4:57 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] Spec ref for lifted pad after assy
> 
> This is not a press fit pin in this case. The hole dia. is .076 ±.003
> with
> a .150 dia. pad the part is a .072±.002 shaft with a .093 shoulder. We
> expect .0008 to .001" of copper in the hole, if there is more than
> this and
> as long as the vendor knows what his process will return for wall
> thickness
> and adjusts his start drill accordingly its not a problem for us.
> 
> Again my question:
> 
> What would be the proper specification to check to when after
> inserting a
> gold pin into a Plated through hole the pad is lifted due to stress of
> the
> assembly method. We were using an arbor press to insert the pin and
> the
> material is Glassteel's MC-3. I have looked at IPC-A610 and find no
> reference to this situation there. How will this defect effect long
> term
> reliability of the soldered connection. I'm worried about the knee of
> the
> PTH cracking due to the pad lifting.
> 
> 
> ----------
> > From: [log in to unmask]
> > To: [log in to unmask]
> > Subject: Re: [TN] Spec ref for lifted pad after assy
> > Date: Thursday, November 12, 1998 1:29 PM
> > 
> > Steve,
> > 
> > Can't help on which spec to look for, but wish to make you aware of
> another
> > issue. The sizing of the hole is extremely important. However,
> letting
> the
> > fabricator know that you are pressing pins into the holes and
> whichones
> are
> > more important. 
> > 
> > Some fabricators will allow a little more room in their over-drill
> and
> plate a
> > little extra copper in the hole to make sure that the plated barrel
> is
> very
> > ductile and will not fail under normal circumstances. Usually they
> will
> shoot
> > for 0.0012 in. in the hole instead of 0.001 in. The philospohy is
> that no
> one
> > will complain about extra copper in the hole as long as the
> component
> lead
> > fits in the hole. Unfortunately with this copper thickness, the
> bight of
> the
> > corner of the pin does not clear the coppper plating, as it should
> do.
> > Subsequently the falt of the pin presses on the plated wall and
> lifts the
> > surface land.
> > 
> > I have seen the insertion process competely push out the barrel of a
> hole
> > including lifting the lands. 
> > 
> > When you design the hole size and tolerance, you generally assume
> that
> there
> > will be no more than 0.001 in. in the hole. Here the fabricator is
> trying
> to
> > be a good guy and it bites you in the end.
> > 
> > I hope this helps a little for the future.
> > 
> > Regards,
> > 
> > Gary
> 
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