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January 2012

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Subject:
From:
Graham Naisbitt <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Graham Naisbitt <[log in to unmask]>
Date:
Tue, 31 Jan 2012 15:41:10 +0000
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Brian 

Nous sommes en très bon accord! 

I had the privilege of attending an IPC standards meeting way back in the 80's and listening to both Brian and Jack Brous roundly criticise the US DOD for:

1	Imposing a somewhat arbitrary pass/fail for cleanliness

2	Trying to introduce an equivalency factor for each machine type

3	Insisting that 75/25 was the best mix

They did NOT, however, recommend heated solution!

Brian is, as usual, right on the button, but because the industry is rather deeply entrenched, I have taken the liberty of starting afresh with a new International Standard under IEC - well advanced. It will call 50/50 and it will allow for some new test solution when dealing with no-cleans.

I do intend raising the question at the standards meetings in San Diego shortly - but the effort might prove too much.

…and Fabrice - if the equipment is made correctly, then the temperature rise through the pump circuit SHOULD be minimal. Ours is less than 5DegC through the day. Do however watch your factory temperature and pollution levels - we have to make "tweaks" in certain polluted areas of China and India.

…and Joyce - I am not sure what you meant by "sweet-spot for water" but guess you might be referring to the flash-point of the test solution? If so, I can advise that it is 19DegC for 75/25.

Brian - I would greatly appreciate any input you might be able and willing to provide, even if I have to fly to Cyprus!

Graham N

On 31 Jan 2012, at 12:51, Brian Ellis wrote:

> Je ne comprends pas!
> 
> Pure water has equal numbers of hydroxyl and hydronium ions at all temperatures. The exponent of the ion concentration falls from about 15 at 0°C to 12 at 100°C (approximations). IOW, the warmer the water the lower the ionic concentration. I don't think this is important for the solubilisation of minute quantities of contaminants which will mostly dissolve better at higher temperatures because of molecular effects (there are some exceptions). The IPA plays almost no role in the ionic dissolution process as it is very weakly ionic compared with water. Its only purpose is to dissolve rosin in the flux so as to release encapsulated ionic materials. The more IPA in the solution, ionic contamination testing becomes less sensitive. If there were no alcohol-soluble/water insoluble components in the contaminant porridge, then such testing would achieve maximum sensitivity with 0% IPA. This is why the UK and some other defence standards specify 50% IPA and not 75%; it doubles the sensitivity of the test as there is double the quantity of water, which is all that counts. The 75% was originally chosen by Hobson et al. because the original test in MIL-P-28809 employed wetting the PCB from a wash bottle and collecting the drippings, typically in less than a minute, so they needed something that dissolved RMA residues as rapidly as possible. IMO, it was, and still is, a big mistake to perpetuate the 75% IPA solution with instruments where the circuit is immersed, because of saturation of heavy metal salts. If I were to write a spec today from scratch, I would not even specify IPA but rather a non-flammable ether at 25% or 33.3%, giving 3-4 times the sensitivity of the test. I did extensive research of this idea in the mid-1990s and had very positive results. The problem was IPA was firmly entrenched and it seemed no one wanted to change the existing specs. I still have some of my lab notes dating from April/May 1996.
> 
> Brian
> 
> On 31/01/2012 13:44, Joyce Koo wrote:
>> Maximum dissociation of oh vs h3o vs vapor pressure If I am not mistaken.
>> --------------------------
>> Sent using BlackBerry
>> 
>> 
>> ----- Original Message -----
>> From: Brian Ellis [mailto:[log in to unmask]]
>> Sent: Tuesday, January 31, 2012 06:34 AM
>> To: TechNet E-Mail Forum<[log in to unmask]>; Joyce Koo
>> Subject: Re: [TN] Typical ROSE Test Duration
>> 
>> What is a "sweet spot"?
>> 
>> Brian
>> 
>> On 31/01/2012 13:22, Joyce Koo wrote:
>>> Correct me if I am wrong, 45-55C is a sweet spot for water.  Add IPA, it is a different story.  Graham, can you kindly let me know what is it?  Many thx.(from 50% - 75% IPA).
>>> --------------------------
>>> Sent using BlackBerry
>>> 
>>> 
>>> ----- Original Message -----
>>> From: PIRES Fabrice [mailto:[log in to unmask]]
>>> Sent: Tuesday, January 31, 2012 06:05 AM
>>> To: [log in to unmask]<[log in to unmask]>
>>> Subject: Re: [TN] Typical ROSE Test Duration
>>> 
>>> Graham,
>>> 
>>> I agree that the main objective of ROSE measurements should be assembly control (even for no-clean processes) and not process qualification, that SIR is the right method for process risk assessment and then process qualification, and that ion chromatography (IC) gives much more information than ionic contamination about contamination nature and then associated risks.
>>> 
>>> But these 2 techniques (SIR and IC) have as main inconveniency they cannot be used on every day base contrary to ionic contamination in addition of their higher cost. So ionic contamination IMHO keeps interesting for every day controls provided SIR test have been performed previously to qualify the assembly process.
>>> 
>>> About HOT ROSE, the first question is what would be the max T�C to avoid side effect according to you ? 30, 40 or 45C ? Moreover even with some flame retardant leaching, the most important for assembly control should be to perform ROSE measurements always the same (so with same and reasonnable leaching).
>>> At last I suppose HOT ROSE also means better temperature control whatever the workshop temperature and quantity of measurements (lots of measurements induces increase of solution T�C due to pump heating ). So HOT ROSE should allow to perform ROSE measurements in more controlled temperature (even if it is a at moderate T�C), which is IMO very important factor for measurement repeatability.
>>> 
>>> Fabrice
>>> 
>>> -----Message d'origine-----
>>> De�: Graham Naisbitt [mailto:[log in to unmask]]
>>> Envoy�: lundi 30 janvier 2012 19:05
>>> �: TechNet E-Mail Forum; PIRES Fabrice
>>> Objet�: Re: [TN] Typical ROSE Test Duration
>>> 
>>> Fabrice
>>> 
>>> What do you hope to measure by this technique?
>>> 
>>> There are just as many non-ionic contaminants in a no-clean process that will not be detected by this technique. It should ONLY be used to control the assembly process.
>>> 
>>> SIR testing is non-discriminating between ionic and non-ionic species, it simply looks for resistance changes. IF you find a problem with SIR, then use Ion Chromatography or FTIR to establish what is there causing an SIR problem.
>>> 
>>> HOT ROSE testing will, IMHO, give you a lot of cause for concern without a clear understanding of whether it means anything to the end product service reliability. It might also burn-down your facility, but that's a different issue.  :-)
>>> 
>>> No-clean ROSE testing maybe requires another route.which is what we are working on.
>>> 
>>> Graham Naisbitt
>>> 
>>> On 30 Jan 2012, at 13:47, PIRES Fabrice wrote:
>>> 
>>>> Hi,
>>>> 
>>>> As temperature is important for the contamination measurements it seems highly recommandable to perform the measurements at constant T�C and for that reason temperature-controlled equipment should appear as an interesting solution.
>>>> 
>>>> Heated solution should be also particurlarly interesting for ionic contamination measurements on no-clean PCA for those performing such measurements or on some dirty PCAs. As no-clean or some dirty PCA induce a lot more residues comparatively to cleaned PCA and requires usually much longer measuring time. It could be more than 1 or even 2 hours for asymptote. Higher temperatures (up to 45�C to limit solution evaporation or other side effects) allow to reduce significantly this duration to more industrially acceptable values.
>>>> 
>>>> So if heated solution should be used with precaution as previously noted it can also offer some advantages.
>>>> 
>>>> fabrice
>>>> 
>>>> -----Message d'origine-----
>>>> De : TechNet [mailto:[log in to unmask]] De la part de Graham Naisbitt
>>>> Envoy� : lundi 30 janvier 2012 13:21
>>>> � : [log in to unmask]
>>>> Objet : Re: [TN] Typical ROSE Test Duration
>>>> 
>>>> Hello Techies
>>>> 
>>>> The equipment Brian refers to is Contaminometer - and they are still made, by me. Sorry for the advert but.everyone keeps talking about my competitors.
>>>> 
>>>> However, as regards the issue of test time, keep-in-mind that some folk recommend testing with heated solution, and temperature has a significant effect in the measurement technique. Some systems also suffer from excess temperature deviation during the test cycle and it does make a difference to your results - false positives and/or false negatives are undesirable.
>>>> 
>>>> Hot or warm solution has been shown to increase the risk of leaching the flame retardant (Bromine) out of the laminate, through the mask and onto the board surface. (IVF, Sweden circa 1992)
>>>> 
>>>> Instruments should provide compensation for both temperature and CO2 effects.
>>>> 
>>>> Given that Rigo is working at NASA, I thought this info might be important.
>>>> 
>>>> This test method is great for controlling your assembly process. It's is NOT safe to assume that tested assemblies yielding results of<1,5microgrammes of NaCl equivalence are good because it implies that it is safe to leave UP TO 1.5 micro grammes of salt on every square centimetre of your assembly.maybe, maybe not...
>>>> 
>>>> Hope this helps - see you in San Diego?
>>>> 
>>>> Graham Naisbitt
>>>> Gen3 Systems
>>>> www.gen3 systems.com
>>>> 
>>>> On 26 Jan 2012, at 18:12, Brian Ellis wrote:
>>>> 
>>>>> Yes, it depends! In the instruments I used to make, they measured to within 1% of estimated asymptote or 15 min, whichever was the shorter. By curve fitting, the software extrapolated to asymptote and then analysed the 2 or 3 major components that made up the total curve (e.g. if there was a component due to activators in a rosin matrix, this would dissolve slowly, while salt from fingerprints would dissolve rapidly), thus determining the ug/cm� eq. NaCl for each type of contaminant and the printout gave a list of possible contaminants creating each component curve shape. Effectively, although it was limited to 15 min actual measurement, some contaminants (e.g. substrate leaching) took hours or days to asymptote and this was indicated. Of course, to have a test that long would be impossible, because CO2 absorption (which was compensated for in these instruments) would be greater than the dissolved leachates and the accuracy would be lower than a real 15 min test!
>>>>> 
>>>>> Brian
>>>>> 
>>>>> On 26/01/2012 18:46, Stadem, Richard D. wrote:
>>>>>> The minimum time is ten minutes. Read all about this in IPC-HDBK-001 section 8.3.6 and 8.3.7.
>>>>>> 
>>>>>> -----Original Message-----
>>>>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Garcia, Rigo (GSFC-300.0)[MANTECH SRS TECHNOLOGIES]
>>>>>> Sent: Thursday, January 26, 2012 10:16 AM
>>>>>> To: [log in to unmask]
>>>>>> Subject: [TN] Typical ROSE Test Duration
>>>>>> 
>>>>>> Hi everybody!
>>>>>> 
>>>>>> I have looked at several document but can't find the answer. This should be an easy one for my TechNet buddies though.
>>>>>> 
>>>>>> Does anybody know what the typical duration for the ROSE Test is?
>>>>>> 
>>>>>> Rigo Garcia
>>>>>> 
>>>>>> Sr. Quality Assurance Engineer
>>>>>> Workmanship Standards, Code 300
>>>>>> NASA, Goddard Space Flight Center
>>>>>> Greenbelt, MD  20771
>>>>>> Phone. (301) 286-6129
>>>>>> Fax.       (301) 286-6576
>>>>>> 
>>>>>> 
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