Lee,
Werner is not incorrect but the percentage difference in current density
from the board surface to the center of the hole is relatively small.
Center-of-hole current density was extensively measured by several
electrochemical scientists working for those manufacturers trying to
fabricate outrageously thick boards for supercomputers in the 1980's. What
I should have said is that the small current density difference from surface
to hole does not account for the huge differences in plated copper
thickness. Differences in board design can of course vary but it's been
proven that if you get better through-hole solution movement you will come
close to achieving 1:1
I'm not sure what you mean in referring to your Apex paper and linier
relationship. You meant linear, right? Current density relationship to
thickness was better understood when Richard O. Hull made his simple Hull
Cell invention. I'm not disputing your Navier Stokes equations but getting
the solution to flow through the hole is the key. It is not easy. Solution
impingement has been mentioned but it is generally not successful because
it's not possible to get the same amount of solution flow in each hole of a
circuit board, especially if that board has as many as 20,000 holes.
Not only that, the composition and function of the diffusion layer varies so
greatly from the planar surface of the board to individual holes that it's
not just the copper ions that are inconsistently depleted in the holes but
the organic additives as well. Plating circuit boards spawned a whole
generation of brighteners that supposedly aided throwing power. All they
really did was improve the color and physical appearance of deposits without
improving plating thickness distribution.
Reducing overall current density to less than 8 a.s.f. or less (I've seen it
done and so probably have you) does nothing but give the solution movement
in the holes more time to equalize to that on the surface. Plating at low
CDs also equalizes the differences overall on the board but that's a subject
for another day. Copper electrolytes are much healthier when they're
operated at far higher current densities than are common today. Another
subject for another day. True to form, plating discussions on TechNet are
relatively infrequent but they can garner lots of disagreement.
Sincerely,
Roger Mouton
EIMC - Advanced Plating Technologies
(949) 481-5194
www.smartcatshield.com
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----- Original Message -----
From: "Lee parker" <[log in to unmask]>
To: "EIMCNews" <[log in to unmask]>; <[log in to unmask]>
Sent: Tuesday, July 24, 2007 10:22 AM
Subject: Re: [TN] Question on plated through holes general
> 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]
>>
>>
>> Notice of Confidentiality
>> The information contained in and transmitted with this email may be
>> confidential and is intended only for the individual or entity named
>> above.
>> If you are not the intended recipient, you are hereby notified that
>> inadvertent disclosure of this information to you does not constitute a
>> waiver of confidentiality privilege and that any review, disclosure,
>> copying, or use of the contents of the email by you is prohibited.
>>
>> ----- 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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