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October 2000

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Subject:
From:
"Ingemar Hernefjord (EMW)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 19 Oct 2000 12:33:28 +0200
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May I jump onto the train while occasionally at low speed?
Q1: Will MfVias in BGA be more sensitive to penetration of cleaners than do
plugged vias, or metallised etc vias?
Q2: anyone familiar with Vigon200? Aqueous sort of cleaner that is sprayed
with 120 psi on mounted boards with AMKOR560s. You think cleaner can
penetrate in BGAs and cause delamination in soldering operation?

Ingemar Hernefjord
Ericsson Microwave Systems


-----Original Message-----
From: Graham Naisbitt [mailto:[log in to unmask]]
Sent: den 19 oktober 2000 11:17
To: [log in to unmask]
Subject: Re: [TN] Cleaning Help Needed


Bob

I hope someone can help you locally. Certainly from what I know, you should
be able to get the job done using the HFE solvents. I have asked my
colleagues at Trek to see if they have a customer installed near you and
will let you know.

As to the issues of the SIR / residues, I have a copy of a new project
release regarding the latest data on SIR testing. It shows some alarming
results which you and others (?) might like to receive. It my shed some
light on your problem.

I have them as a .pdf file from a powerpoint presentation. If you would like
a copy - let me know off line.

Regards

Graham Naisbitt
[log in to unmask]
www.concoat.co.uk
Concoat Ltd
Alasan House, Albany Park
CAMBERLEY GU15 2PL UK
Tel: +44(0)1276691100
Fax: +44(0)1276691227
----- Original Message -----
From: "Furrow, Robert Gordon (Bob)" <[log in to unmask]>
To: <[log in to unmask]>
Sent: 18 October 2000 20:57
Subject: [TN] Cleaning Help Needed


> Hi TechNetters,
>
> I need some help regarding possible course of action and also possibly
local
> contact for cleaning.
>
> We use a BellCore compliant solderpaste on our product which we do not
> clean. Flux residues have been tested and passed for SIR and
> Electromigration (as well as other tests). This flux was chosen over
another
> candidate because although it basically performed equivalently during
> surface mount, at In-Circuit Test with via in pad product it was superior.
> This of course means a softer more penetrable residue. Unfortunately, it
> also means a more visible residue on and around the solder joints. This is
> particularly true of bottomside since after the bottomside is reflowed,
the
> board is flipped over and the topside is reflowed. This extra heat results
> in the flux residues on the bottomside flowing further out onto the
> soldermask and are very evident. This had been considered a cosmetic issue
> and a direct result of the improved pin testability.
>
> We now have some boards in prototype where under system test conditions
> (slightly elevated temperature and high humidity), there is a failure,
> possibly due to impedance variations. The test/design group feels that the
> flux residues could be causing this failure. I have been asked to clean a
> few of the boards to confirm. I don't want to hand clean as I am concerned
> all I will really accomplish is spreading the residues around. I can't go
> through my normal semi-aqueous cleaner as there are now power modules on
the
> board that would be impractical to remove entrapped liquid inside. It is
> preferred not to remove any parts so that we have the exact same boards
only
> with no flux residues. Would a vapor phase cleaner work in this
application
> since the solvent should evaporate relatively quickly. There are press fit
> connectors on the board also so I can't have anything too aggressive. I am
> looking to do just a few boards to be able to conclusively show if it is
> caused by flux residue or not. Does anyone have a better idea? Does anyone
> have a cleaning system available to do a few 14 inch by 14 inch circuit
> packs on a quick turn basis? I would prefer a local solution so I can get
> this done tomorrow. I am in North Andover, MA. If you have comments please
> respond via the TechNet. If you are able to meet my cleaning needs, please
> contact me by my email below.
>
> Thanks,
> Robert Furrow
> SMT Process Engineer
> Lucent Technologies
> 978-960-3224    [log in to unmask]
>
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