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June 2014

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Subject:
From:
Gerry Gagnon <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Gerry Gagnon <[log in to unmask]>
Date:
Wed, 11 Jun 2014 10:01:54 -0400
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Hi Richard,
 
Thanks, being a very very long time "lurker" I will jump in and contribute once in a while.
The response time is so fast now on technet that the answer comes before I have a chance. 
Always enjoy your posts.
 
By the way, before someone notices, the following paragraph does not really apply:
 
>I am assuming your supplier is a using vertical electroplating cells & racks for ENIG.
>These racks will sway in the plating solution as well as possibly using rack vibration and rack bumping to keep small >holes from filling with air bubbles. Also ENIG will have some higher than usual plating temperatures for the EN >portion of the deposit
 
The statements above have nothing to do with the issue.
I didnt have my coffee when i sent this out.
Onward through the fog,
 
Gerry

 
> Date: Wed, 11 Jun 2014 12:51:22 +0000
> From: [log in to unmask]
> Subject: Re: [TN] Plating in non-plated holes - again
> To: [log in to unmask]
> 
> Good post, Gerry!
> 
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerry Gagnon
> Sent: Wednesday, June 11, 2014 7:43 AM
> To: [log in to unmask]
> Subject: Re: [TN] Plating in non-plated holes - again
> 
> Hi Henry,
>  
> Thank you.
>  
> I apologize for asking such a simple question because it could be part of the issue you are facing.
>  
> I should have also asked what your outerlayer copper foil thickness prior to plating is, surface etch density in the area of the NPTH, and the soldermask but I'll cover this now.
>  
> I am assuming your supplier is a using vertical electroplating cells & racks for ENIG.
> These racks will sway in the plating solution as well as possibly using rack vibration and rack bumping to keep small holes from filling with air bubbles. Also ENIG will have some higher than usual plating temperatures for the EN portion of the deposit.
>  
> To keep plating from getting into a PTH, the primary plating resist needs to prevent plating solution from allowing any plating solutions into that hole. Otherwise the hole will get activated and copper plated just like the PTHs. If the plating resist partially "tents" over the NPTH, and some plating solution gets into the NPTH then some degree of partial plating will occur in the NPTH. If the resist tent protecting the NPTH completely breaks down then the NPTH plates exactly like any other PTH.
>  
> After the plating resist is removed, the board is etched, soldermask is applied, and the ENIG surface finish is applied.
> The etching process will remove some of the plating in the NPTH. The ENIG process micro-etch steps will remove some copper in the NPTH. But nothing is 100% guaranteed.
>  
> So, in theory, if you can guarantee that the plating resist tent holds up then you will have no problem.
> This is normally the case for small hole sizes such as vias and through-hole components, etc.
> The larger NPTH hole sizes can be problematic. Also, if you look at the surface edges of a freshly drilled hole they are very sharp, which can also act like a paper hole punch when racks sway in the plating solution. In the old days, resist tents for any hole over 0.060" could not be guaranteed 100% using a 1 mil thick plating resist. The sharp hole edges, combined with agitation during plating, make it more difficult for the thin resist tent to hold up. Using a thicker plating resist will make high etch density designs more difficult. Always tradeoffs in board build.
>  
> The situation is most probably better now, meaning larger diameter NPTHs and NPTH slots are possible, but the issue is still the same. There will be a NPTH diameter or NPTH slot geometry which will be large enough to cause resist tent breakdown even today. The envelope is always pushed.
>  
> Your 0.125" diameter NPTH is typically a tooling hole size, which probably gets the tight tolerance as well. This size has been around for a long time (but I remember when the limit was 0.093" tooling holes) and should be processible by good shops. Some shops successfuly tent this size, others may use rubber plugs in these holes. All shops should notice plating in the NPTHs and carefully repair it so noone would notice it was even repaired. I used to use small reamers not drills to do this. It can be done correctly, the FHS and tolerance should be as per the print after the repair. The moral here is to be careful designing large NPTH holes and slots.
>  
> Yes, IPC A610 allows some level of this but your print spec drives in this case, not A610.
> If you receive boards with plating in the NPTHs, your supplier could either repair it acceptably at your location or hire a board repair house come and repair it for you. 
>  
> Sorry for the 4 credit course.....hard to stop typing.
>  
> Best regards and good luck in your adeventure,
>  
> Gerry
> 
>  
> > Date: Tue, 10 Jun 2014 13:31:29 -0700
> > From: [log in to unmask]
> > Subject: Re: [TN] Plating in non-plated holes - again
> > To: [log in to unmask]
> > 
> > Gerry, they are 0.125" I believe.
> > ______________________________________________________________________
> > _______________
> > 
> > 
> > Henry Rekers P. Eng |   Schneider Electric   |  Global Supply Chain  |   
> > Senior Manufacturing Engineer
> > Phone: +1-250-652-7100 ext. 7510  |   Toll Free: +1-866-466-7627 ext. 
> > 7510  |   Fax: +1-250-544-2390  |   
> > Email: [log in to unmask]  |   Site: 
> > www.schneider-electric.com  |   Address: 2195 Keating Cross Road, 
> > Saanichton, BC, Canada, V8M 2A5
> > *** Please consider the environment before printing this e-mail
> > 
> > 
> > 
> > From:
> > Gerry Gagnon <[log in to unmask]>
> > To:
> > <[log in to unmask]>,
> > Date:
> > 06/10/2014 11:31 AM
> > Subject:
> > Re: [TN] Plating in non-plated holes - again Sent by:
> > TechNet <[log in to unmask]>
> > 
> > 
> > 
> > Hi Henry,
> >  
> > What is the diameter of NPTH?
> >  
> > Best regards,
> >  
> > Gerry
> >  
> > > Date: Tue, 10 Jun 2014 11:25:39 -0700
> > > From: [log in to unmask]
> > > Subject: Re: [TN] Plating in non-plated holes - again
> > > To: [log in to unmask]
> > > 
> > > That's what I think, but we're getting push back from the supplier and I 
> > 
> > > was hoping to get more specific. 
> > > 
> > > Thanks.
> > > 
> > > 
> > _____________________________________________________________________________________ 
> > 
> > > 
> > > 
> > > Henry Rekers P. Eng |   Schneider Electric   |  Global Supply Chain  | 
> > > Senior Manufacturing Engineer
> > > Phone: +1-250-652-7100 ext. 7510  |   Toll Free: +1-866-466-7627 ext. 
> > > 7510  |   Fax: +1-250-544-2390  | 
> > > Email: [log in to unmask]  |   Site: 
> > > www.schneider-electric.com  |   Address: 2195 Keating Cross Road, 
> > > Saanichton, BC, Canada, V8M 2A5 
> > > *** Please consider the environment before printing this e-mail
> > > 
> > > 
> > > 
> > > From:
> > > David Hillman <[log in to unmask]>
> > > To:
> > > <[log in to unmask]>, 
> > > Date:
> > > 06/10/2014 10:08 AM
> > > Subject:
> > > Re: [TN] Plating in non-plated holes - again
> > > Sent by:
> > > TechNet <[log in to unmask]>
> > > 
> > > 
> > > 
> > > Hi Henry - maybe I am making this too simple but if your drawing/design
> > > data shows a nonplated thru hole, then having any plating in it, partial 
> > 
> > > or
> > > complete, is a violation of the drawing and therefore a nonconformance.
> > > 
> > > Dave
> > > 
> > > 
> > > On Tue, Jun 10, 2014 at 10:26 AM, Henry Rekers <
> > > [log in to unmask]> wrote:
> > > 
> > > > Hey there technetters.  A while back, I sent a message about enig 
> > > plating
> > > > contamination in NON-plated holes.   I've bounced it back to the board
> > > > shop saying that it is unacceptable, but they claim it is due to 6012
> > > > 3.5.2
> > > > I also think it's unacceptable in the 4552 spec.   The design
> > > > documentation clearly states non-plated.   It's not plated, just 
> > > partially
> > > > plated.
> > > >
> > > > Any advice?
> > > >
> > > > Thanks.
> > > >
> > > > 
> > > 
> > _____________________________________________________________________________________
> > > >
> > > >
> > > > Henry Rekers P. Eng |   Schneider Electric   |  Global Supply Chain  |
> > > > Senior Manufacturing Engineer
> > > > Phone: +1-250-652-7100 ext. 7510  |   Toll Free: +1-866-466-7627 ext.
> > > > 7510  |   Fax: +1-250-544-2390  |
> > > > Email: [log in to unmask]  |   Site:
> > > > www.schneider-electric.com  |   Address: 2195 Keating Cross Road,
> > > > Saanichton, BC, Canada, V8M 2A5
> > > > *** Please consider the environment before printing this e-mail
> > > >
> > > > ______________________________________________________________________
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