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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