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December 2013

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TechNet E-Mail Forum <[log in to unmask]>, Bernard <[log in to unmask]>
Date:
Wed, 11 Dec 2013 17:19:17 -0800
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Hi Raye----
While it may be no comfort because I'm out of my area of
confidence, I believe you are correct.  If the starting thickness
is to be a requirement, the only way to inspect would be to
get a coupon from the lot number----- so it seems to me.
Otherwise, the overall thickness should be specified as the
requirement.
Enjoy!!!
Bernie

On 12/11/2013 4:48 PM, Rivera, Raye wrote:
> Hi Bernard,
>
> As a general rule, copper is copper. On this specific board our engineering team confirmed that the ratio of foil to plate does not matter.  While I am no expert, the only time I can think of that it might matter is in traces for very high frequency signals.  On these even the surface roughness of the trace and the cross-sectional profile of the trace can matter.
>
> Here is another consideration.  We determined that the foil layer the PCB fabricator used was less than 1/2 oz based on a microsection.  The PCB fabricator tell us that they did start with 1/2 oz copper and intentionally reduced it to 3/8 oz chemically. If they didn't do this,  by the time they got the right amount of plating in the through holes, they would have up to 1.7 oz surface copper.  For reasons I don't fully understand they would not be able to hold our trace and space requirements when they etched the outer layer traces.
>
> I have always thought a microsection shows the thickness of the starting foil. Apparently it only shows the thickness of what remains of the starting foil. If we can't measure it, why should we state a minimum starting thickness for the foil in the standard? I can see the value of including it in table 3-12 as a general guideline, but it does read as if it is a requirement.
>
> Best regards,
> Raye Rivera
>   
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bernard
> Sent: Wednesday, December 11, 2013 12:38 PM
> To: [log in to unmask]
> Subject: Re: [TN] IPC-6012C Total Cu thickness
>
> I ask this question just out of curiosity----- Does the cu/plated metal ratio affect in any way the signal transfer rate or electrical characteristics????  If no---- all seems academic beyond the total thickness.  If yes, then min cu seems appropriate.
> Bernie Kessler
>
> On 12/11/2013 12:23 PM, Grunde Gjertsen wrote:
>> Those tables are very educative when explaining to QA and design people why final copper thickness is what it is in relation to base copper and class and should be left well alone in my opinion, they are not that difficult to understand if you know a bit about PCB manufacture.
>> At least over here people in the industry is getting more removed from PCB manufacture since so many factories has closed down and production gone to far east, so to have the standards actually explaining stuff like that and not simply stating requirements is not a bad thing.
>>
>> Rgds
>> Grunde
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Reuven Rokah
>> Sent: 11.desember 2013 21:07
>> To: [log in to unmask]
>> Subject: Re: [TN] IPC-6012C Total Cu thickness
>>
>> Can I have the draft for comments?
>>
>>
>> On Wed, Dec 11, 2013 at 4:21 PM, Louis Hart <[log in to unmask]> wrote:
>>
>>> Raye, although not a guru, please allow me to comment.
>>>
>>>    Jason and Reuven I agree with. Further, I have put among the 6012
>>> committee comments a request to simplify those tables for inner and
>>> outer copper thickness. Most of those columns can be eliminated, I
>>> believe, allowing for easier interpretation by those charged with acceptance.
>>>
>>> IPC will circulate a draft of 6012 rev D after 1 Jan 2014 for
>>> industry review. I have already submitted some 20 requests for what I
>>> see as improvements.  Louis Hart
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
>>> Sent: Tuesday, December 10, 2013 12:13 PM
>>> To: [log in to unmask]
>>> Subject: [TN] IPC-6012C Total Cu thickness
>>>
>>> Hello technet gurus,
>>>
>>> I have a question regarding total copper thickness for external conductors.
>>>
>>> 3.6.2.13 states only a requirement for total conductor thickness,
>>> that is foil + plating, and references table 3-12 for the appropriate
>>> values. There is no requirement for the foil thickness.
>>> Table 3-12 also has a column with heading:
>>>
>>> Absolute Cu Min. (IPC-4562 less 10% reduction)
>>>
>>> Does that column heading constitute a requirement?   Would using a copper
>>> foil less than the stated minimum constitute a rejectable condition
>>> even if total copper thickness meets requirements?
>>>
>>> Engineering  states that they only care about the total thickness
>>> from a functional point of view.
>>>
>>> I ask this because I have a difference of opinion with a colleague on
>>> the interpretation of the standard.
>>>
>>> Best regards,
>>> Raye Rivera
>>>
>>> QA Manager * Canoga Perkins
>>> 20600 Prairie Street * Chatsworth * CA 91311-6008
>>> 818-678-3872  * [log in to unmask]<mailto:[log in to unmask]>
>>>
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>>
> --
> Bernard Kessler Bernard Kessler & Associates, Ltd 562-495-3221 Fax:
> 562-495-3228 "Service is our Profession"
>
>
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-- 
Bernard Kessler Bernard Kessler & Associates, Ltd 562-495-3221 Fax: 
562-495-3228 "Service is our Profession"


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