They (connector mfg's) specify the drilled hole size because that is
what matters. :^)
Well, that and minimum annular copper thickness is the first order
effect on pressfit hole reliability.
The goal is establishing a gas-tight joint w/out damaging the hole
wall & the via's post interconnects.
IMAO IMHO, the hierarchy of pwb specification for establishing a
pressfit connection with
a) a gas tight joint,
b) w/out damaging the pwb via/post interconnects and
c) w/out bending (aka z-ing in) pins or going over pressure on the press
Is:
1) connector mfg specified drilled hole size
2) minimum hole wall plating (typically 1.2 mil on 40 mil and larger
vias/ 1.0 mil min on less than 40 mil vias). Read the supplier's data
sheet for 1 and 2. It's usually gospel, esp for item 1.
3) minimum finished hole size (i.e. maximum hole wall plating) to
prevent stuck or bent pins during insertion
Finished hole size is secondary to the drilled hole size (as long at
the correct drill and minimum copper is met).
Finished hole diameter comes into play (only/mostly) at the low end
of the hole size range as pin insertion forces will spike. Too small
a via causes either your press to hang up or pins to collapse and "Z
in" to the pwb surface.
If you're really doing your due diligence, dust off a copy of
Bellcore "078" and read up on their spec for verifying pressfit holes
(10 sections each axis after insertion/reinsertion testing to verify
minimum retention force at end of multiple insertion cycles). That
spec is a lifesaver (and in my case perhaps a career saver 20 years or so ago).
At 06:28 AM 12/2/2013, Zilber Gil wrote:
>Press-fit manufacturer / spec /mil (i.e. mil-c-28859B) define the
>requested drill diameter and final diameter (and minimum copper and
>plating thickness). In may cases the PCBs manufacturer asked us to
>drill bigger diameter holes in order to get the requested final
>finish hole (manufacturer process standard). My question is
>(Assuming OSP finish) why press-fit manufacturer/std define drill
>hole diameter and not finish hole diameter and minimum copper
>thickness? What could be wrong if approving manufacturer request
>(bigger drill diameter, control final finish)?
>
>Thanks,
>Gil
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
>Sent: Monday, December 02, 2013 4:09 PM
>To: [log in to unmask]
>Subject: Re: [TN] Press Fit Connector Drill size/finish size
>
>What is your question?
>
>
>On Mon, Dec 2, 2013 at 2:14 PM, Zilber Gil <[log in to unmask]> wrote:
>
> > Thank Reuven,
> >
> > Assuming OSP finish then my question.
> >
> > Thanks,
> >
> > Gil
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
> > Sent: Monday, December 02, 2013 1:23 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Press Fit Connector Drill size/finish size
> >
> > Hi Gil,
> > If you have HASL finish, the final hole size does not reflect the
> > required press fit hole size.
> > I you have OSP for example, the final holes size of PCB is the same as
> > the press fit requirements.
> >
> >
> > On Mon, Dec 2, 2013 at 1:01 PM, Zilber Gil <[log in to unmask]> wrote:
> >
> > > Hi all,
> > >
> > > Press-fit manufacturer / spec /mil (i.e. mil-c-28859B) define the
> > > requested drill diameter and final diameter (and minimum copper and
> > > plating thickness). In may cases the PCBs manufacturer asked us to
> > > drill bigger diameter holes in order to get the requested final
> > > finish hole (manufacturer process standard). My question is why
> > > press-fit manufacturer/std define drill hole diameter and not finish
> > > hole diameter and minimum copper thickness? What could be wrong if
> > > approving manufacturer request (bigger drill diameter, control final
> > finish)?
> > >
> > > Thanks
> > >
> > > Gil Zilber
> > > Elta system Ltd.
> > >
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