Hi Keith:

If you remember when AT&T and also Northern Telecom first came 
out with the SIR requirements, all PCBs were required to meet a 
SIR of 10000 megohms.  It wasn't until AT&T started using water 
soluble hot air soldering leveling fluids and fusing fluids and 
they found out their HASL and fusing processes could not always 
meet this requirement that AT&T reduced the requirement to 3000 
megohms even though the original supporting data suggested that 
10000 megaohms was limit at which electromigration occurred.  
Bellcore reduced their requirement in 1984, following AT&Ts lead. 
Bellcore still requires that bare boards before applying solder 
mask meet the 10000 megaohm requirement.  Some of your customers 
may be basing their requirements on the original AT&T 
specification.  Give me a call sometime Keith 

Harry




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______________________________ Reply Separator 
_________________________________ Subject: SIR and SEC
Author:  [log in to unmask] at SMTPLINK Date:    3/7/96 12:29 PM


I am interested in finding out if many of the board shops, or OEM's 
subscribed to Technet are seeing an requirement for SEC and SIR 
significantly tighter than the current Bellcore requirement. ie

                SEC.......1 micro gramme per sq. cm. NaCl equivelant

                SIR.......3000 megohms after HASL

I have seen requests almost an order of magnitude tighter for both 
parameters and am wondering if this in response to an industry trend or just 
isolated cases. I am interested in finding out where our industry is 
heading, in this regard, and if any of the subscribers could suggest why a 
customer may need such tight controls.

                                                Keith Lumley, RexCan Circuits