TECHNET Archives

June 1998

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 30 Jun 1998 09:53:59 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (60 lines)
Hi Kathy,

Water sol fluxes are *INDEED* ionic materials and can/will cause serious
reliability problems if not thoroughly removed.

Surface resistivity (also known as SIR or Surface Insulation Resistance) is
a good "localized" test as a special layout  (opposing interlocked comb
patterns) must be present on either the assy or a coupon. These are not
always practical for production as PCB real estate value increases. (
Doncha' wish Calif real estate value followed suit?!) This test is a good
barometer for process qualification and localized evaluation, such as
underneath micro-BGA, etc.

The more common method for production is the solution extract method
commonly known as "Omegameter" or "Ionograph", depending on the manufacturer
of choice. I know of a few good used machines in the area if you're
interrested. This method essentially starts with de-ionized water-alcohol
solution then the assy is immersed for a period (typical 10 min) so the
contaminants dissolve into the solution. The volume resistance is then
measured and based on the volume of solution and surface area of the
assembly, one can determine the ionic residue in terms on micrograms of nacl
per sq. in. Typical industry standards for high quality commercial product
is 14 micrograms/sq. in. The reason nacl (salt) is mentioned is that the
test is not selective, but is an equivalent conductivity (or resistivity) to
salt, which the effects can be readily quantified. The drawback of this
method is that it will not identify a potential problem in a "trouble area"
such as underneath a daughterboard because it averages the results over the
entire surface of the assembly. It is, though, a reasonable "barometer" *IF*
in a case of a known potential trouble spot, SIR was done to first determine
the effectiveness of the cleaning process and further correlated to
Omegameter measurements for prodution confirmation.

I can help you set up these tests in house and would love to stop by to
discuss it with you.

Regards,




Ed Popielarski
QTA Machine
10 Mc Laren, Suite D
Irvine, Ca. USA 92618
Ph: (949)581-6601
Fx: (949)581-2448
E-Mail: [log in to unmask]

################################################################
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 web site (http://jefry.ipc.org/forum.htm) for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################


ATOM RSS1 RSS2