Hi Techies:

My twopenneth:-

1      Ionic testing is designed to detect harmful ionics residues. However
there are many non-ionic additives used in various process chemistries.

2      Present standards recommend that you "clean" to a level of less than
1.5 microgrammes per square centimeter (10 microgrammes per square inch) of
NaCl equivalence.

This also means that it is acceptable to leave UP TO 10 microgrammes of salt
on every square inch of your assembly! If you make anything with
fine-line/fine pitch, use modern chip scale packaging or put the assembly
into a hostile environment, this level will almost certainly be too high!

For this reason, many now use an empirical value that we have found to be
typically, less than 0.2 microgrammes per square centimeter.

3     The main issue is "How clean is clean"? Well, it may be better and
easier to establish the reliability of the assembly because no-one can
answer that question, how clean is clean.

The alternatives are: Ion Chromatography - this will tell you what is on the
surface, but it won't tell you whether the circuit is reliable - OR
Surface Insulation Resistance (SIR) which will tell you if the circuit is
reliable but it will not tell you what is on the surface.

I go back to the point: Many modern process chemistries now use non-ionic
additives that MAY be harmful contaminants but are non detectable using
ionic testing. Others have also pointed out the issues regarding no-clean
and reactions with alcohol - whartever the concentration! No-clean generally
means just that - don't clean and ionic testing is a cleaning process!

Regards, Graham Naisbitt

[log in to unmask]

Concoat Ltd             Phone: +44 1276 691100
Alasan House          Fax:      +44 1276 691227
Albany Park
CAMBERLEY
GU15 2PL UK

Any opinions expressed are those of this employer.

-----Original Message-----
From: John Barton <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 10 August 1998 14:57
Subject: [TN] No-clean Fluxes + Omegameters


>Technetters,
>Can anyone help with 2 questions that were sent my way re no-clean fluxes?
>
>> >>
>> >> Question 1         Is the Omegameter used on No-Clean PCAs.  If so
what are
>the
>> >> typical ug of NaCl levels found on the PCBs and what would be the
>> >> frequency of inspection be.
>> >>
>> >> Question 2         If you dont use an Omegameter, what process control
do you
>
>> >> have in place for the control of contamination on No-Clean PCAs.
>>
>Thanks,
>John Barton
>
>___________________________________________________________
>John Barton AKA JohnnyB
>NMRC, Lee Maltings,               Phone : +353-21-904088
>Prospect Row,                     Fax   : +353-21-270271
>Cork, Ireland.                    e-mail: [log in to unmask]
>"Whenever I'm faced with a difficult problem, I always think to
>myself 'How would MacGyver deal with this?'"
>---------------------------------------------------------------------------
-
>---
>
>################################################################
>TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section
for additional information.
>For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
>################################################################
>
>

################################################################
TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################

################################################################
TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################