OSP and SIR

Splitting hairs, I expect SIR of all solderability protection, including OSP, to decrease after reflow. What�s more, I expect the SIR of all solderability protection to pretty much decrease over time.

The �comb pattern� test specimens meet requirements concerning surface insulation resistance ANSI/J-STD-004 after 96 h and 168 h conditioning in the humidity chamber SIR value is at least 100 MW. log Surface Insulation Resistance (SIR) ||Conditioning time in humidity chamber [hour] ||0||24||48||72||96||168 Cu any coating||12.0||11.2||11.3||11.3||11.0||11.0 Sn-Pb HASL||11.4||11.3||10.5||10.2||10.2||10.3 Electroless Ni /Immersion Au||11.9||11.0||11.2||11.2||11.4||11.4 Electroless Sn OrmeconTM CSN||10.4||9.7||10.7||10.7||10.5||10.1 OSP EnthoneTM Entek Plus||12.0||10.4||10.7||11.2||11.0||10.8 [�Lead - Free Solderability Preservative Coatings of PCBs� Zofia Morawska, Grazyna Koziol, Tele & Radio Research Institute, 03-450 Warsaw, Poland, phone (48-22) 619 22 41 X 263, fax (48-22) 619 25 10; IMAPS Advancing Microelectronics, Volume 28, No. 3, May/June 2001]

Given that it does decrease, it still is within specification [final insulation resistance greater than 5 x 10^8]. So, a straight-up decrease in SIR might not be the angle to take on this problem.

What�s your thinking about: * In-bound res on boards and parts? * Heavy handed application of yer NC? * That, er maybe it�s not so NC?

Or you could get a bit more specific, maybe?

reply »