DOES THE NEW REVISION OF IPC-A-600 PENDING RELEASE BY SEPTEMBER ACCEPT 
EXPOSE COPPER AND TO WHAT EXTEND ?

AUGUSTINE 8/21

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To		: [log in to unmask],[log in to unmask]
Cc		: 
From		: [log in to unmask] (R_R_HOLMES)
Date		: Sunday, March 5, 1995  04:31:39 HKT 

AT&T allows exposed Cu on PWB's, and do not consider it a reliability 
threat. 
This issue has been a topic of some discussion with Bellcore who controls 
specifications for domestic tele-communications equipment.  They now 
accept 
the fact that exposed Cu is not a reliability threat.  One of the best 
papers 
on the subject was written by two Bellcore scientists:

"THE SURFACE COMPOSITION OF COPPER WITH INDOOR EXPOSURES RANGING FROM 3 TO 
49 
YEARS	;  Rudolf Schubert and Susan M. D'Egidio;  Corrosion Science, Vol 
30 
No 10 pp999-1008, 1990

Thia paper discusses the use of Ager spectrocopy to investigate surface 
films 
on copper bus bars that had been installed as early as 1939.  They found 
films 
of 10 to 100 nanometers.  These films differ chemically and in thickness 
from 
fils formed in accelerated atmosphere corrosion chambers.

I hope this reference is of use.
 
R. R. Holmes
AT&T

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Did anyone have any idea where I could find any article or reference about 
the copper expose on the PCB (GOOD OR BAD) ? 

thanks