Grant,
I am all for reducing or eliminating work-in-process, however that probably
will not fix your current issue.  The test people will see an issue if the
boards are taken directly from the wave to ICT or age for a period of time
before ICT.  Many no-clean fluxes leave a residue on the board.  Look at the
solids content of the flux that you are using.  A majority of 'no-cleans'
have < 2% of solids, however there are several that have much higher solids
contents.  The residues from a high solids content flux will be 'gummy'
immediately after the wave and will harden as the board cools down.  This
maybe the 'curing' that you refer to.  If you take the boards immediately to
ICT you will find that the 'gummy' residue will build up and eventually
cause the probes to fail and possibly the vacuum gaskets to fail also.  Most
probe vendors(IDI, QA, Everret Charles, etc...)  make a high spring force
probe and/or a 'flux buster' probe.  The 'flux busters' twist as they are
pushed down allowing them to drill through the residues.  You may need to
control the time between wavesolder and ICT so that the boards have time to
cool and the flux residues solidify. If you have the option you may need to
identify a different flux that meets all of your needs.  I have worked with
10% solids no-clean and have used a combination of these to overcome ICT
false failure issues.

Regards,
Steve


-----Original Message-----
From: Grant Emandien [mailto:[log in to unmask]]
Sent: Thursday, August 19, 1999 9:18 AM
Subject: Solder joint curing


Hi all out there,

What is the average period for a solder joint (reflow and wave) to 'cure'? I
also state that I don't quite know what cure means in this instant - but the
general problem we have is the minimum period (if there is such a thing!)
required for a solder joint to cure before introducing it to ICT under
reasonable conditions of stability.

Our test guys are complaining that the assemblies reach there machines too
late (hours later), resulting in hardened flux which the test pins have
difficulty in penetrating, causing damaged pins, retesting and hence
unnecessary wear of the test fixtures and reduction in throughput.
Introducing the assemblies too early while the joints are still in
'transition' may also result in retesting (true or false?).

As you may have guessed, we don't clean boards as a norm however, this may
be the way to go in future as will be experimenting with a cleaner shortly.

Cheers
Grant

##############################################################
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 Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################