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July 2007

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Subject:
From:
Lee parker <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Lee parker <[log in to unmask]>
Date:
Tue, 24 Jul 2007 14:22:17 -0400
Content-Type:
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text/plain (284 lines)
Roger

Werner is correct.

The paper I presented at Apex found a linier relationship between the 
current density and the cooper distribution in the hole which is often 
refered to as dog boning. My model combined the well known Navier Stokes 
equations for viscous flow and Faraday's law for electroplating. As the 
plating solution passes through the hole the copper ion concentration in the 
solution is diminished and consequently, the plating rate is reduced.

I have been in the PCB business for over 30 years and was located in the 
AT&T shop in Richmond as part of Bell Laboratories staff. This was one of 
the largest shops in the world. We constantly saw the empirical evidence of 
this relationship. My paper confirmed the existence of the relationship 
using a first principals mathematical analysis.

Best regards

Lee

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389


----- Original Message ----- 
From: "EIMCNews" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, July 24, 2007 12:55 PM
Subject: Re: [TN] Question on plated through holes general


> There seems to be a continuing misunderstanding of the forces at work in
> plating through holes.  First, you're reporting fairly thick copper at the
> knee of the hole.  The assumption is that the thickness diminishes toward
> the center of the hole.  If the hole is cross-sectioned do you find this 
> to
> be the case?  If so, this is normal but not really desirable.
>
> There's more expansion at the knee of the hole (Werner can you weigh in on
> this too please?).  If the physical properties of the deposit are poor 
> then
> there's the likelihood of cracks at the knee.
>
> As for plating thick boards at low current density, the only reason for
> doing this is that there's additional time for the electrolyte to better
> circulate through the barrel of the hole.  Contrary to some popular 
> beliefs,
> the holes of circuit boards are NOT low current density areas.  The
> thickness of the deposit in the hole is less than on the surface of the
> board because the hole doesn't see the same circulation of fresh 
> electrolyte
> as the surface.  Ogden and Tench proved this over 20+ years ago.  Numerous
> attempts have been made over the years to improve plating solution
> circulation through the hole.  It becomes more difficult with thick boards
> and/or smaller holes.
>
> Sincerely,
>
> Roger Mouton
>
> EIMC - Advanced Plating Technologies
> 949 481-5194
> www.smartcatshield.com
> [log in to unmask]
>
>
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>
> ----- Original Message ----- 
> From: "Lee parker" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, July 24, 2007 5:49 AM
> Subject: Re: [TN] Question on plated through holes general
>
>
> > Ralph
> >
> > I presented a paper at IPC this spring on the variables which affect the
> > copper uniformity in PTHs. You can probably get a copy by contacting Tom
> > Newton at IPC.
> >
> > It is difficult for me to imagine a greater copper thickness causing the
> > barrel to become more susceptible to cracks. The thicker the copper the
> > lower the stress for a given load and consequently the lower the strain.
> > What may be going on is the uniformity of the copper which causes stress
> > concentrations and the ductility of the plated copper. As I 
> > mathematically
> > demonstrated in my paper, the current density used in plating has a 
> > strong
> > impact on these parameters. The thicker the board the greater the need 
> > for
> > low current density.
> >
> > I would ask the supplier to measure the ductility of the plated copper 
> > for
> > several current densities and draw your own conclusions.
> >
> > Best regards
> >
> > Lee
> >
> > J. Lee Parker, Ph.D.
> > JLP Consultants LLC
> > 804 779 3389
> >
> >
> > ----- Original Message ----- 
> > From: <[log in to unmask]>
> > To: <[log in to unmask]>; <[log in to unmask]>
> > Sent: Tuesday, July 24, 2007 9:00 AM
> > Subject: RE: [TN] Question on plated through holes general
> >
> >
> > Lee,
> >
> > Do you also have any inromation about max Cu thickness in the PTH? In
> > the recent past we had some cracks and the min was ok but the max showed
> > values aroung .045mm. Our supplier said that the crack was caused due to
> > too thick copper. The crack location was on the top just below the Cu
> > ring.
> > Do you or anybody else has a suggestion how to handle or specify this?
> >
> > Regards
> > Ralph
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
> > Sent: Friday, July 20, 2007 10:42 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Question on plated through holes general
> >
> > David
> >
> > I always advise one mil or more in the PTH. Given the non-uniformity
> > often seen in the PTH I would also spec the drill quality and the ratio
> > of the copper at the top of the hole and in the center.
> >
> > Best regards
> >
> > Lee
> >
> > J. Lee Parker, Ph.D.
> > JLP Consultants LLC
> > 804 779 3389
> >
> >
> > ----- Original Message -----
> > From: "David Harman" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Friday, July 20, 2007 4:23 PM
> > Subject: [TN] Question on plated through holes general
> >
> >
> > I have a quick question and our standard that we have maybe an older
> > one. We currently use the ANSI/IPC-A-600 Rev E
> >
> >
> >
> >
> >
> > Page 70   Micro section:
> >
> >
> >
> > There is a table describing copper plating thickness min, requirements
> >
> >
> >
> >
> >
> >                                                Class 1
> > Class 2                         Class 3
> >
> > Average Min Thickness              .020mm (0.0008in)        0.025mm
> > (0.001 in)       0.025 mm (0.001 in)
> >
> >
> >
> > Minimum this area                     .0015 mm( .0006 in)       0.020 mm
> > (.0008 in)     0.020mm  (.0008 in)
> >
> >
> >
> >
> >
> >
> >
> > Can anyone tell me if this still is a current standards for  copper
> > plating thickness measurements.
> >
> >
> >
> > David Harman
> >
> >
> >
> >
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