Matthew,
We did an investigation about 6 years ago to see if there was any correlation between the results from ROSE and ion chromatography measurements and SIR. Test boards were soldered at various companies using their ordinary soldering process. Different types of fluxes and solder pastes were used. Some companies cleaned the assemblies after soldering but the majority of the companies used a no-clean process. There was no clear correlation between IC and SIR. There was even poor correlation between two different methods for ROSE measurements. I will send a paper presenting some of the results off-line to you.
Per-Erik Tegehall
IVF
-----Ursprungligt meddelande-----
Från: Douglas O. Pauls [mailto:[log in to unmask]]
Skickat: den 5 februari 2004 18:28
Till: [log in to unmask]
Ämne: Re: [TN] Ion Chromatography
Matthew,
I will tag onto Brian's comments.
Being a backwards kind of guy, I will answer your second question first.
The place to look for information is usually the different committees in
the IPC Cleaning and Coating Committees. The SIR task group, led by Chris
Mahanna of Robisan Labs, would have knowledge of SIR studies. The Ion
Chromatography Ionic Cleanliness Task Group, led by Renee Michalkiewicz of
Trace Labs, is working on developing ion chromatography test methods and
guidelines. The two groups usually contain the same people, so there is
good co-operation between the sciences. If you really want to get into the
topic, come join us in Anaheim.
With that said, there is no "precise" correlation studies done. No studies
that say that for X micrograms of chloride you get Y decades decrease in
SIR or that Z total micrograms of Ions equals A micrograms of NaCl
equivalence increase. The reasons are largely as Brian has indicated. Not
all ions are created equal. From my own experience in running many many
(many.....) such tests, that "in general" as IC total anions increase, so
does ROSE results and you see a corresponding, but unquantified, drop in
SIR. I have seen ionic cleanliness testers completely miss huge levels of
bromide which impact SIR. I occasionally published such items in my
Circuits Assembly columns in years past. I often found that when you had
high levels of halides, you got electromigration and dendrites. Other
anions, such as sulfate or nitrate, would cause electrical leakage (low
SIR) but no dendrites.
If I recall, Delco Electronics has done work looking at the three tests and
trying to do some correlations. I am hoping they will get a chance to
share this information at Apex. They have published papers in the past
(Phil Wittmer, Hank Santfleben). The NPL in the UK has done some work in
the area (Chris Hunt). IVF in Sweden (Per-Erik Tegehall). Graham Naisbitt
of Concoat is working in the SIR area. I have published a few.
I know that everyone wants a single metric for "acceptabel cleanliness".
On one side of the line is it dirty and rejectable, and on the other side
it is clean and acceptable. Won't happen. It is far too complex an issue
for a one size fits all measure.
Doug Pauls
Rockwell Collins
Brian Ellis
<b_ellis@PROTONIQ To: [log in to unmask]
UE.COM> cc:
Sent by: TechNet Subject: Re: [TN] Ion Chromatography
<[log in to unmask]>
02/05/2004 01:34
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Please respond to
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Forum."; Please
respond to Brian
Ellis
Depends what you mean by correlation.
1) If (unlikely) all the ions present in contamination can be measured
in the chromatograph and if (equally unlikely) the extraction process is
the same, then IC and ionic contamination testing should correlate. In
practice, it won't a) because you measure only the ions that you have
tubes/detectors for and b) the extraction conditions differ (especially
the Ionograph method).
2) There cannot be any correlation between SIR and either ion testing
method, in practice. In theory, if the contamination consists only of a
single species of an ionic salt, then pure SIR will correlate
non-linearly, but ECMR (which is more commonly measured than SIR,
although it is equally commonly and mistakenly confused for SIR) will
not necessarily correlate. To illustrate: imagine an SIR test pattern
contaminated only with sugar. The SIR will be low but the ionic testing
will indicate zero. OTOH, a light contamination with some salts with a
very low hygroscopicity may indicate a high SIR but low ionic
contamination.
Brian
Matthew Park wrote:
> Dear Technet,
>
> Is there a correlation between Ion chromatography test result vs
> SIR/Ionography? I done some tests years ago and found no correlation btw
> IC vs SIR. Where can I get some info about technical studies done about
> IC/SIR.
>
> thanks
> Matthew
>
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