Denis,
Get yourself a copy of the IPC-TR-476A, Sixth working draft, Published in
April 1995. Just about everything you want to know is within this document.
Also get a copy of the new IPC-9201 SIR Test Handbook
Otherwise contact Professor Laura Turbini at Georgia Tech:
[log in to unmask]
Hope this helps
Graham Naisbitt
------------------------------------------------------------------
Concoat Ltd Email: [log in to unmask]
Alasan House, Albany Park Tel: + 44 (0)1276 691100
Camberley GU15 2PL England Fax: + 44 (0) 1276 691227
-----Original Message-----
From: TechNet Mail Forum On Behalf Of Denis Meloche
Sent: Tuesday, August 05, 1997 2:31 PM
To: [log in to unmask]
Subject: Re: [TECHNET] No-clean flux query
Dear Graham,
Could you possibly send me a copy or direct me to where I could get a copy of
Professor Laura Turbini's papers on CAF - glycol wetting agents initiating
Cathodic Anodic Filamentation?
Thanks,
Denis Meloche
Heraeus Cermalloy
610-825-6050
Fax 610-825-7061
At 10:28 PM 8/4/97 UT, you wrote:
>In reply to Thomas Lepsche
>
>Thank-you for your explanation - that makes sense.
>
>I would however, like to point out that the solution (if you will forgive the
>pun), may harbour issues that fundamentally affect your bottom line.
>
>Think of it this way:
>
>A good old fashioned rosin flux used a solids content at around 15%. A
modern
>no-clean or no-solids, may have NO solids or at least less than 2%. So how do
>you get it to wet the board without dripping everywhere? By adding wetting
>agents - that's how.
>
>BUT - during the pre-heat to soldering, like everything that gets hot, the
>surface of the board expands and it becomes hydroscopic - it becomes
absorbant
>to these lower solids products. Furthermore, the epoxy mask is generically
>more hydroscopic and no-cleans typically require a higher pre-heat. Thus
these
>extra liquids are better able to be absorbed into the board through the mask
>and once in, and the surfaces cooled down, will be almost impossible to
>extract by whatever means. This may also be why some suggest hot ionic
extract
>testing. (If you do that, watch out carefully for bromine flame retarder
>leaching thru to the surface).
>
>AND this is not going to be cleaned?? Check out Professor Laura Turbini's
>papers on CAF - glycol wetting agents initiating Cathodic Anodic
>Filamentation?
>
>All fluxes leave residues - there is fluxless soldering but not zero residue
>fluxing. Are these residues benign? You are running no-clean therefore ionic
>extract testing/cleaning should not be used? How will you test?
>
>Check out IPC-TM-650 and the newish IPC-9201 for SIR testing. There are many
>new developments in this area alone as a direct result of the above.
>
>NOW - I am not going to suggest that no-clean must not be cleaned but I am
>strongly commending that more thorough process validation be done to better
>determine the reliability potential of the product and thus - reduce field
>failure and reduce corporate risk. Either clean "cleanables" or don't clean
>no-cleans.
>
>By the way, we do have some belt and suspender personnel - and they are hotly
>pursued! In merry olde England, in the county of Yorkshire, the expression is
>"belt, braces and a piece of string" but I know what you mean.
>
>Graham Naisbitt
>
>
>Concoat Ltd Email: [log in to unmask]
>Alasan House, Albany Park Tel: +44 (0)1276 691100
>Camberley, Surrey GU15 2PL UK Fax: +44 (0)1276 691227
>
>
>-----Original Message-----
>From: TechNet Mail Forum On Behalf Of Lepsche, Thomas G (NM75)
>Sent: Monday, August 04, 1997 2:46 PM
>To: [log in to unmask]
>Subject: Re: [TECHNET] No-clean flux query
>
>Graham,
> You, obviously do not have any belt and suspender personnel at your
>facility. At my facility we do have such persons and the theory goes
>something like this " We really don't trust the performance of no-clean
>fluxes on our CCA's. We really want clean boards for maximum
>performance, but if we err in cleaning, we want to leave a residue that
>really didn't need to be cleaned off anyway." We are therefore covered
>with an explanation for the customer no matter what happens and have the
>best of all worlds. Quality and acceptability of the product and CYA is
>of most importance, cost and process difficulty is of minor importance.
>Semper Fi
>Tom
>
>>----------
>>From: Graham Naisbitt[SMTP:[log in to unmask]]
>>Sent: Sunday, August 03, 1997 5:21 PM
>>To: [log in to unmask]
>>Subject: Re: [TECHNET] No-clean flux query
>>
>>In reply to Yuan's message on Friday, I am baffled.
>>
>>Why do you want a "No-Clean" flux that you can clean? Do you mean a low
or no
>>solids product instead?
>>
>>From our experience, trying to clean no-clean is not good news. Finding the
>>right chemistry to work for you can be a time consuming and difficult
>>project.
>>I therefore strongly suggest that whatever trials you conduct, make sure
they
>>are as close as possible to production conditions. I.e. run minimum 4 hour
>>tests with largest possible number of assemblies not just 10 or 12.
>>
>>Yuan correctly indicates that there will be residues. The issue is not so
>>much
>>visual appearance but whether any remaining residues could impair circuit
>>reliability.
>>
>>So when you do get to your trials, try producing through J-STD-001, and
>>testing to IPC-TM-650 (and IPC9201) with inspection to IPC-610
>>
>>I would love to hear from others, their views on this topic.
>>
>>Graham Naisbitt
>>
>>
>>Concoat Ltd Email:
[log in to unmask]
>>Alasan House, Albany Park Tel: +44 (0)1276 691100
>>Camberley, Surrey GU15 2PL UK Fax: +44 (0)1276 691227
>>
>>
>>-----Original Message-----
>>From: TechNet Mail Forum On Behalf Of [log in to unmask]
>>Sent: Friday, August 01, 1997 5:31 PM
>>To: [log in to unmask]
>>Subject: [TECHNET] No-clean flux query
>>
>> Hello,
>>
>> My company would like to move to No Clean flux for rework of PCBA's.
>>
>> The main criteria we are looking for is the following:
>>
>> 1. High Quality Solder Joint
>> 2. Easy to work with
>> 3. Low residue
>> 4. Capability to be water washed
>> 5. Capability to be not cleaned
>> 6. The residue be contained at the location of the solder joint.
>> 7. The residue be formulated in such a way that it will not collect
>> dust and debris.
>>
>> Any information about such fluxes are appreciated.
>>
>> Thanks,
>>
>> Yuan
>> (303)417-5655
>>
>
>
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