I believe the apparent contradiction results from IPC-SM-840 being a
_Soldermask_ Performance and Qualification Spec. not a board/assembly spec--
it doesn't apply directly to PWBs or PWAs.
   Just because you put on a mask that meets IPC-SM-840 doesn't mean your
board will meet IPC-6012, or the assembly will meet IPC-A-610, etc. You also
have to have proper surface prep, cure, etc.
Tim Reeves
ECD

> ----------
> From:         Tom Burek
> Sent:         Tuesday, May 23, 2000 12:55
> Subject:      Help! Interpret IPC-SM-840C and IPC-A-61
>
> Hello,
> Can one of you experts out there or perhaps someone from IPC interprets
> what appears to be a contradiction.
> IPC-SM-840C 3.5.2 Adhesion states that per table 2 a high reliability
> Rigid PCB that has a surface finish of Gold or Nickel can have a maximum
> 5% loss allowed on solder mask over a coupon per TM 2.4.28.1 of IPC-TM-650
> (Tape test).
> IPC-A-610 , 7.2 Coatings states a Non-conforming Defect- Class 1,2,3
> Degradation of the mask film that permits solder bridging or exposed basis
> metal.
>
> Can someone kindly differentiate the meanings?
>
> Thank You,
> Tom Burek
> Product Engineer
> [log in to unmask]
>

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################