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Thu, 09 May 1996 16:53:55 -0400
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From [log in to unmask] Wed May 15 19:
22:26 1996
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[log in to unmask] (Janice Lund)
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American Power Conversion, West Kingston, RI 02892 USA
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Main question:

ON HIGH VOLUME DOUBLE SIDED POWER BOARDS. WHAT PERCENTAGE DIFFERENCE WOULD THE 
PRICE  INCREASE BE, OF A STANDARD MANUFACTURABLE BOARD PRICE SHOULD I SEE (of 
.001" minin the hole), IF ANY, TO A TOTAL FINISHED THICKNESS OF 2 OUNCE COPPER 
?  (please read below to find out what my  vendor says they can do without 
increasng the price)

History: 
My boards are power boards requiring a total of 2 ounce copper on the surface 
and a minimum of .001" in the holes. These are submitted to UL for approval of 
our product with the accurate requirements, because at least my prototype 
house reads my print and gives me what I require. 

My prints states:
*  .001" minimum (not average minimum) copper in the holes
*  one ounce copper foil and another ounce plated on the surface foil.

I am aware that the copper plating  process plates a ratio of 1:0 in the hole 
to 1:2 on the surface. Therefore, .001" minimum plate in the hole should 
result in .0012" plated on top of the surface foil. I would assume that no 
vendor would risk plating the absolute minimum and therefore would attempt to 
plate .0012" in the hole, resulting in .0014" plate on top of the surface 
foil. 

I am aware that 1 ounce foil has a tolerance of +/- .0002" on the foil 
thickness. I am also aware that deburring , scrub and micro-etch may remove 
another .0002" from the surface of the foil.  Based on this, the absolute 
minimum should be -> .0010" foil + .0012" plate = a total copper thickness  of 
.0022" . Whereas, my copper hole requirement is .001" minimum with the maximum 
controlled by the hole size and tolerance. I expected to receive boards with 2 
ounce finish minimum copper thickness and copper thickness in the hole in 
excess of .001" to reach the surface thickness requirement.  WAS I WRONG?? ( 
please to not reference IPC-A-600 as my print takes precedence over that spec.)

 My Production Fabrication Vendor states the best they can give us .0020" - 
.0025" on the surface for our specified 2 ounce copper .0028"  requirement.
Needless to say they were not giving us close to that before. (so I will 
believe an improvement it when I see it).
The fact is, if we accept their minimum of .0020", aren't we now still under 
the .001" minimum in the hole??
My Vendor also stated that there would be a price increase if a total of 2 
ounce total was required.
Seems to me, if they took the job, they should of been able to do the work 
requirements!

Lets just say I have a tolerance on the 2 ounce of .0004" minus and .001 plus 
(just to have a plus) which is about 15% of .0028". Aren't I really only 
asking them to produce boards that will have .0002" more that what they 
should  be giving me already.   Should that cost me??

Thanks in advance!



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