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July 1997

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From:
Ted Stern <[log in to unmask]>
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Date:
Tue, 29 Jul 1997 13:54:45 -0700
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Dear Ted:

While I cannot comment on your question regarding pwb reliability, I
have performed (during a nine year peroid) close to one thousand copper
purity, tensile strength, and elongation tests; from at least 20
different manufacturers, operating brightener systems from virtually all
major vendors, and operating and maintaining their copper baths with a
variety of different methods (type of anodes, anode/cathode ratios,
filtration, frequency of carbon treat, etc.) . During this time, I have
encountered only one bath which consistently failed the WS-6536 specs. 
(This does not include failures traced to poor sample preparation.) 
This failure occured with a Lea Ronnel additive system. But to their
credit, Lea Ronnel did not dismiss the lab data as erroneous, and in a
timely fashion determined the poor copper electroplating was due to poor
rectification and not their additive system.

While I have not accumulated this data in a single data base, if I were
to segragate the data into "below average", "average", and "above
average", it would be as follows:

  		     Elongation (%)	  Tensile Strength (psi)

"below average"		< 9			< 39,000
"average"		9-15			39,000 - 42,000
"above average"		> 15			> 42,000

The best 10% of baths tested consistantly maintained greater than 20%
elongation and 44,000 psi tensile strength.

Hope you find this information useful.

Regards,
Ted Stern
Circuit Research Corp.

Edwards, Ted A (AZ75) wrote:
> 
>      At the recent IPC meeting in Tempe, AZ. on IPC 6012, Qualification and
> Performance Specification for Rigid Printed Boards, I asked if Para 3.11.8
> b), which reads as follows, is realistic given todays thicker boards and
> higher aspect ratios:
> 
>           b) When tested as specified in IPC-TM-650, method 2.4.18.1 ambient
> using 50-100 micrometer (0.002-0.004 in) thick sample, the tensile strength
> shall be no less than 245MPa (36,000 psi) and the elongation shall be no
> less than 6%.
> 
> The numbers appear to be directly from WS 6536 and unchanged over the years;
> I personally do not think a 0.125 board with 16 mil holes if it were 6%
> elongation would be very reliable.  I also do not think anyone really would
> try to be at 6%.  BUT I have no data so when I said why not change to a
> "real" number , the team members said show me the data.  That leads me to
> ask the following; anybody have any data?  Is a value of  49,000 psi and 14%
> , any better , or any worse,  than a 42,000 psi and 22%?
> 
> [log in to unmask]

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