Ah but you see, I look a lot younger than I really am...

...I stayed away from all that flux - it ages you old boy.

You should see Brian Ellis - and he's only 36!

Kindest regards,

Graham

[log in to unmask]



On 30 May 2007, at 18:06, [log in to unmask] wrote:

>
> Yes I do.  And you don't have THAT many years on me.
>
> I am currently surrounded by engineering co-op students and interns  
> who all frequently remind me that they were not even born when I  
> started my career.  They delight in pointing out to me that I am  
> older than dirt.   When I launch into those lessons learned stories  
> they all roll their eyes with the "here comes another old guy  
> story", same as I did to my first mentors.
>
> I now fully appreciate how absolutely annoying I was when I was a  
> college graduate.
>
> Doug Pauls
>
>
>
> Graham Naisbitt <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 05/30/2007 12:00 PM
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> Graham Naisbitt <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
> Subject
> Re: [TN] [NTC] Flux residue, burnt flux
>
>
>
>
>
> Doug Pauls describes himself as an "Old War Horse".
>
> That's pretty depressing as I know I have quite a few years on him!
>
> When it comes to fluxes and flux residues and how they might impact
> on electro-chemical reliability - you really should test to find out
> if your production process will be give you acceptable or
> unacceptable reliability. The latest IPC-TM-650 2.6.3.7 method will
> help...
>
> Kindest regards,
>
> Graham
>
> [log in to unmask]
>
>
>
> On 30 May 2007, at 15:53, Douglas O. Pauls wrote:
>
> > Wee Mei,
> > It would not be accurate to say that flux residue is never a good
> > thing to
> > leave behind on an assembly.  We make military product and in select
> > cases, we leave flux residue intact.  But, we know exactly what the
> > residue is, we know its characteristics in the end use environment,
> > have a
> > ton of test data behind us, and have many measures in place to
> > control the
> > manufacturing process surrounding those flux residues.  The military
> > position on RMA fluxes and cleaning are largely due to inertia or  
> old
> > school mind sets.  On the other hand, military programs often have
> > to take
> > low bids and have been severely bit many times from assemblers who
> > do NOT
> > know what they are doing, or where "cost" is the only driver.
> >
> > There is no such thing as a good flux or a bad flux.  No flux is
> > "safe".
> > Many of the horror stories that we old war horses can (and do) tell
> > can
> > usually be traced back to one root cause - a failure to understand
> > precisely the materials of manufacture and how the end use  
> environment
> > effects the residues on the assemblies.  Or the corollary cause -
> > cost is
> > the only consideration.  I would say that someone like Bill Kenyon
> > could
> > take Superior 30 flux and make a reliable heart pacemaker.  But for
> > the
> > rest of the world, nooooooo way.
> >
> > Military programs today, at least the ones that I deal with, are
> > more open
> > to something other than RMA fluxes (which technically have not been
> > around
> > since 1995), IF you have the test data and demonstrated expertise
> > to back
> > it up.  We use low residue fluxes with aqueous cleanings.  There are
> > programs doing true no-clean (not here though).  There are programs
> > doing
> > water soluble flux.  Granted, it often takes a tremendous amount of
> > effort
> > to educate a customer with an RMA mind set, but it can be done.
> >
> > Doug Pauls
> > Rockwell Collins
> >
> >
> >
> > Lum Wee Mei <[log in to unmask]>
> > Sent by: TechNet <[log in to unmask]>
> > 05/30/2007 07:57 AM
> > Please respond to
> > TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> > Lum Wee Mei <[log in to unmask]>
> >
> >
> > To
> > [log in to unmask]
> > cc
> >
> > Subject
> > Re: [TN] Flux residue, burnt flux
> >
> >
> >
> >
> >
> >
> > Hello,
> >
> > From what have discussed, I gathered that flux residue is never a  
> good
> > thing to leave behind on the PCBA. Regardless whether it is water
> > soluble,
> > no clean or RMA flux, the chemical compounds in the flux residue
> > can react
> > with whatever present in its surrounding over period of time and
> > "mutate".
> > This mutated power is so powerful that it "eats" away connector
> > housing,
> > give rise to dendrites and cause short, etc.
> >
> > Is that the reason why military products only use RMA flux with  
> IPA or
> > Ensolve or other cleaning agent and never no clean and water
> > soluble flux?
> >
> > Thanks and regards,
> >
> > Wee Mei
> >
> >  
> ----------------------------------------------------------------------
> > ---------------------------
> >
> > I have seen many, many cases of electrical failure due to flux being
> > left on the board, including no-clean, water soluble, and RMA.
> > I have had to perform as an industry consultant for several  
> companies
> > that had field returns and cancelled contracts due to flux issues
> > causing performance problems (crosstalk, etc.)
> >
> > The worst one I ever had to deal with was many years ago (mid-'80s)
> > when
> > a contract manufacturer used a no-clean flux to add (build-around) a
> > printer connector on a computer motherboard. They liberally  
> spread the
> > flux over the SMT pads and hand-soldered the connector in place.  
> They
> > did not realize that the field returns they were getting shortly
> > afterwards were due to the use of the no-clean flux.
> > The chemicals in the no-clean flux attacked the connector housing
> > material, turning it into a grey powder. Some of the motherboards  
> came
> > back with no connector body left, only the connector leads  
> soldered to
> > the pads, and a grey powder where the body used to be. This company
> > brought me in to find out why the connectors were deteriorating.  
> Upon
> > reviewing the original process travelers, I found that the build-
> > around
> > was approved without qualifying the hand-soldering of the  
> connectors,
> > whereas they had been reflow soldered with water-soluble flux  
> prior to
> > that.
> > This company was forced to take back more than 100,000 computer
> > motherboards, remove the connector, remove all traces of the no- 
> clean
> > flux, assemble a new connector using water-soluble flux, wash the
> > boards, re-test the boards, and replace them into the computers,
> > all on
> > their own nickel. They nearly went bankrupt.
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Kathy Kuhlow
> > Sent: Tuesday, May 29, 2007 1:52 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Flux residue, burnt flux
> >
> > Inge,
> >
> > When NAFTA first came into play, the company I worked for ran to the
> > border for cheaper products to be built. We built industrial  
> computing
> > products at the time so it needed to be pretty durable. We ended up
> > within 9 months scrapping everything built south of the border  
> due to
> > two reasons. One was a dendrite growth on all of the gold (simm
> > sockets
> > mainly) due to water quality (said it was DI but apparently our
> > definitions of DI differed a bit). The second reason was flux under
> > the
> > older 386 and 486 chip sets.
> > There was flux underneath that never was cleaned up. We found  
> that the
> > flux was eating through the traces underneath the chips. I  
> suspect it
> > was due to a solder issue and the boards were flooded for rework but
> > insufficiently cleaned up. About 2000 boards were scrapped  
> because it
> > was impossible to determine the extent of both problems. Left  
> south of
> > the border shortly after that and only used them for cables
> > afterwards.
> >
> > Kat
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord  
> Ingemar
> > Sent: Wednesday, May 23, 2007 3:11 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Flux residue, burnt flux
> >
> > What I say now may cause some to think that I'm member of Ku-Flux-
> > Klan,
> > which is not the case. So, we follow the general habit of removing
> > 'all'
> > flux residues. However, I can't deny, that I think this flux removal
> > hysteria is little exaggerated. I've been in the business for so
> > long a
> > time, and I have not seen many reported failures that have been  
> caused
> > by flux residues. In theory, flux residues have many ingredients  
> that
> > can cause corrosion, leakage current, decreased insulation etc,  
> but it
> > seems as that does not happen in reality. 100% cleanliness is
> > satifying
> > and beautiful, but costs a lot to obtain.
> > Just a thought. Would be very interesting if anyone could describe a
> > case with flux residues causing massive failures.
> > Inge
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> > Sent: den 23 maj 2007 09:38
> > To: [log in to unmask]
> > Subject: Re: [TN] Flux residue, burnt flux
> >
> > I'm sure that an eminent co-contributor to this forum will tell
> > you, "it
> > depends". If the flux is truly burnt, i.e., black, this indicates
> > pyrolysis, which is a fancy word meaning decomposed by heat.  
> Pyrolysis
> > indicates that the residues have split apart into numerous  
> compounds,
> > leaving carbon-rich stuff. Elemental carbon can be an electrical
> > conductor; do you want conducting particles in your assembly?  
> They may
> > appear fixed in place now, but will they remain so during the  
> life of
> > the equipment?
> >
> > More important, WHY are they there? It may be because the operators
> > don't keep the bits of their irons clean. Do they wipe them on a wet
> > sponge before each joint is made? It may be that the time/ 
> temperature
> > conditions of the joint being made are far from optimal. It may be
> > lack
> > of adequate training of the operators. I can't tell. Whatever,
> > prevention is better than cure; a lttle research into the causes may
> > give you the answer.
> >
> > As to flux flow, maybe your solder wire simply has too much flux.  
> Some
> > manufacturers allow you to choose the percentage. Yes, it is  
> easier to
> > solder with an excess. It's a compromise.
> >
> > What you have not told us is the essential information: what kind of
> > assemblies are you making. You can obviously be more tolerant of
> > imperfections if you are making toys than if you are making inertial
> > guidance or satellite systems. Probably you are somewhere between  
> thes
> > extremes. "It depends"!
> >
> > Brian
> >
> > Sue Powers-hartman wrote:
> >> We fight a constant battle with operators leaving burnt flux in
> >> joints. Maybe only a small speck, but drives the inspectors nuts.
> >> The
> >
> >> way I read JStd-001D, if they can not see it at referee inspection
> > power, they have to accept it.
> >> How dangerous is this burnt flux to the PWB?  If it's not seen at
> >> inspection power and left on the board, what happens.  Also, what
> > about no clean flux?
> >> Our solder training video says that if no clean flux runs out to  
> far
> >> and is not heat activated, it can cause problems. Operators watch
> >> this
> >
> >> video, but somehow do not get this. They say that it's no clean,  
> they
> > can leave it all on.
> >> I keep saying that this can be a problem, and then they ask me, how
> >> far out can the flux be away from the joint before it's  
> unacceptable.
> >>
> >> Wow, I'm glad I found this forum, I have so many questions to  
> ask you
> > guys.
> >> Anyway, thanks for the help on this subject.
> >>
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