An easy way to check for bloomed resin residues is to warm them to say 90-80C,
you can use the point of an iron, hot air, anything. If the bloom is resin it will
most likely
revert back to its normal unbloomed state, visibly shrinking/disappearing, [but still
there] and incidentally become more readily soluble in regular cleaners. This is not
guaranteed, but if it doesn't then you are only a few minutes worse off but you will
have saved a lot of investigation/lab time if it does.
Mike Fenner
BSP, OX15 4JQ, England
T: +44 1295 722 992
M: +44 789 999 7715
F: +44 1295 720 937
-----Original Message-----
From: Graham Naisbitt <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 25 August 1999 16:21
Subject: Re: [TN] BGA solder residues
>Ingemar,
>
>I may be barking up the wrong tree but, I recall IVF in Gothenburg had some
>pictures they took of Adipic Acid "Roses". In fact I may still have copies
>around here somewhere.....
>
>Try calling Per-Erik Tegehall - if he can't remember, ask Bill Brox.
>
>Eureka - and SPOOKY!
>
>As I am writing this, I just had a customer walk in with EXACTLY the same
>problem! - Yikes.
>
>Anyhow, I found the pictures, will scan them and have them available
>electronically for anyone who is interested. Let me know off line.
>
>Examining the pictures, the "problems" were: EITHER - Trapped colophane
>particles in the solder resist - OR - Sodium Carbonate - OR - Adipic Acid
>dendrites/flakes - OR - Zinc Oxide (or Hydroxide). All at micron levels.
>
>Furthermore, GEC Hirst Research Group (before they were closed down!)
>established 16 different forms of "White powder residue". The gentleman who
>was in charge at that time is Dr Brian Richards at the NPL - got your
>TechNet ears on?
>
>If any fellow Techie want more info, let me know.
>
>Regards,
>Graham Naisbitt
>
>[log in to unmask]
>
>WEB: http://www.concoat.co.uk
>
>CONCOAT Ltd
>Alasan House, Albany Park
>CAMBERLEY GU15 2PL UK
>
>Tel: +44 (0) 1276 691100 Fax: +44 (0) 1276 691227
>----- Original Message -----
>From: <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Wednesday, August 25, 1999 11:29 AM
>Subject: [TN] BGA solder residues
>
>
>Oumphf!
>You can't pronounce that? Like me not being able to see what strange
>roses we find between the balls after BGA on FR4 after 10 minutes in a
>REHM heat conveyour oven. Top temp is +230 / 1 minute. Preheat is
>included in the 10 minutes. Kester 229D is used (if a Kester man reads
>this, please give a line or two in response. The residues grow to
>something that reminds of roses or cabbage! Colour in daylight is white,
>but the residues do not seem to belong to the ordinary white residues
>(Tin Abiate, polymerized rosin and lead salts). Flakes are <<1micron
>thick and up to 50microns in diameter. EDAX gives 99%Lead and bal is
>some Tin and Carbon and other random elements. Not soluble in the usual
>solvents like Ethylene, Perclorethylene, Acetone etc. And that is
>natural, as the residues are inorganic. Kester 229D is not QPL'd. Paste
>Sn62Pb36Ag2 is screenprinted on traditional Cu/Ni/Sn-pads. We have used
>this Kester formula for years for other products without seeing cabbage
>nor roses. BGA is ceramic C4 from Mota, number of balls (bumps) approx.
>25x25 matrix.
>
>Can it be PbCO3? The flux is RMA and contains clorides.
>
>The line is stopped, nothing will be delivered until the cabbage growth
>is eliminated. Special question to SIRguru labs: can we send this job to
>you if our qualification does not cover the need?
>
>Regards
>Ingemar Hernefjord
>Ericsson Microwave Systems
>
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