Sorry, I'm not in the least convinced. Galden is a PFPE or
perfluorinated-polyether. Still a PFC. The new so-called HFPEs are close
to deceit. They have a hydrogen-bonded ether or similar attached to the
end of an alkane or cyclic perfluorinated ether. These are relatively
easily hydrolysed and thus the molecule decomposes, leaving the inert
and stable PFC unaltered. The residence time of the molecule is
relatively short, giving a lower GWP, while the PFC residue will have
much longer residence time and higher GWP. BTW, the GWPs quoted by the
makers are for a 100 year window. The true effect should be that figure
x the number of centuries residence time, to give a realistic window.
Brian
On 10/12/2012 16:28, Stadem, Richard D. wrote:
> Brian, the newer VPS fluids do not have the environmental issues.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: Friday, December 07, 2012 2:41 AM
> To: [log in to unmask]
> Subject: Re: [TN] Termination finishes, Cu thickness under Ag, Au-Pt-Pd
>
> I agree with you, Bev. If you lose only 1 kg of the stuff this year, on a linear scale (in reality exponential, but the difference is small), there will still be about 990 g of it floating round the earth, warming it, 100 years from now, 980 g in 2 centuries, 900 g in 3012 and 500 g in somewhere round 10012. In each year, in that time, your 1 kg will have the same effect as if you had burnt fossil fuels producing about 10 tonnes (yes, 10,000 kg) of CO2.
>
> Is that a legacy you want to leave your children, grand-children, great-grand-children up to your great^25-grand-children?
>
> The problem is that the fluid has to be stable for more than 5 minutes while boiling at the temperature of soldering and the vapour has to have high density. These factors preclude any organic substance with a C-H covalent bond or any element with a single electron missing (Group VIIB) in its outer ring other than fluorine, which has an extremely tight bond. Even chlorine, the next one down, has a weak bond which would be rapidly destroyed at soldering temperatures, so would be useless for the job. This implies that the substance must be perfluorinated, whether a complex alkane or cyclic compound. The problem starts in that the covalent bond is so darned strong that there is no widely available natural mechanism, such as hydrolysis, to break the substance down; it requires pyrolysis at >1000°C to do so. The occasional molecule may be split by a collision with a high-energy radiated particle and this is why most perfluorinated substances have atmospheric residence times of the ord
er of thousands or tens of thousands of years - without those odd collisions, the lifetime would be infinite.
>
> In practice, as the perfluorinated substances are so inert, it is unlikely they would bond with anything on a printed circuit assembly but the odd molecules could be imprisoned in the molten flux residues or simply trapped under components. This is why you lose your kg or so of fluid each year, no matter how good your machine is at recovering as much vapour as possible, either by long freeboard dwell times and/or vacuum extraction or other mechanical means. This is inevitable. OK, one well constructed machine produces a kg or so of losses per year and isn't going to make much difference to the climate change caused by the teragrams of CO2 emitted by us annually, nor is it likely to be restricting to lose a few hundred dollars-worth of the stuff. If, as has been suggested, every assembly plant in the world had one, then we are talking about hundreds of thousands of such machines, some of them cheap and highly emissive, spewing out an aggregate of many tonnes of the substances each
year. It is conceivable that this would overtake CO2 as the chief cause of the greenhouse effect, because the atmospheric residence time of CO2 is of the order of a hundredth that of the PFCs and is more easily sequestered, being ionically active in the presence of water vapour.
>
> I therefore dispute, in the strongest possible terms, the contention that vapour-phase soldering should be allowed to proliferate. Rather, it would be wise to avoid it.
>
> There is also a political aspect to the question. As we have seen at Doha recently, there is discord as to how to handle greenhouse gas emissions. It is probable that we are at a turning point and that, in a year or two, the nations will agree that something must be done to reduce GG emissions. This will involve increasing regulation. CO2 will be difficult to regulate but PFCs will be easy, just as the Montreal Protocol regulated CFCs. I foresee that PFCs could be phased out from manufacture over, say, a five or ten year period, at the end of which all the VP reflow machines will be worth only their scrap metal value.
>
> Brian
>
> On 07/12/2012 03:03, Bev Christian wrote:
>> "No self-respecting electronics manufacturer should be without a
>> vapor-phase soldering machine in the facility."
>>
>> Sorry, I cannot agree. We tried one and then sent it back. We have a
>> ton of RF cans with small holes in them for underfill application.
>> The heat transfer liquid condensed inside the cans and we couldn't get
>> it out. It was still there days, probably weeks later and as has
>> already been noted the stuff is expensive. And how many of the
>> liquids being used are still incredibly excellent global warmers? I
>> haven't looked at their tech sheets lately.
>> Bev
>>
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
>> Sent: Thursday, December 06, 2012 7:38 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Termination finishes, Cu thickness under Ag,
>> Au-Pt-Pd
>>
>> We have two vapor-phase reflow machines here at GD, and I work with
>> VPS at other companies in the area. The ones we use are from R&D.
>> http://www.rdtechnicalservices.com/System-RD2.cfm
>> We have an RD-1 and an RD-2, and I am supporting the installation of
>> an
>> RD-52 at another site, and have used all three machines at various
>> companies.
>>
>> No self-respecting electronics manufacturer should be without a
>> vapor-phase soldering machine in the facility.
>>
>> For high-mass, difficult-to-solder assemblies, VPS just cannot be
>> beat. VPS is also an excellent method for performing some of the more
>> advanced processes such as compliant lead attachment, BGA reballing,
>> CSP and flipchip reflow, etc. At one location we set up a really good
>> process for manufacturing PoP components, including the die-attach
>> where the die-bond epoxy is cured at the same time the die is
>> soldered. Having an oxygen-free atmosphere really helps.
>>
>> Also, I have found R&D to be a really good company, and the owner is a
>> real square shooter. They have great VPS machines and good service. I
>> don't have any experience with other VPS systems, so I cannot comment
>> on that. I have no financial interest in R&D, just a lot of good experience.
>>
>> As with any VPS, proper maintenance is required. With condensation
>> soldering you will get a buildup of flux on the inside of the machine
>> and it must be kept clean. I strictly enforce a monthly maintenance
>> program, and if done diligently the machines will last a long, long
>> time. For the larger VPS systems a small chiller is usually required,
>> so keep that in mind when considering purchasing a system.
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
>> Sent: Wednesday, December 05, 2012 2:37 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Termination finishes, Cu thickness under Ag,
>> Au-Pt-Pd
>>
>> Inge,
>>
>> On the VPSsubject your comments echo what I have heard.
>>
>> Did you get some actual hands on time for experimentation? If so
>> what machine?
>>
>> Thanks,
>> Bob K.
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
>> Sent: Wednesday, December 05, 2012 3:09 PM
>> To: [log in to unmask]
>> Subject: Re: [TN] Termination finishes, Cu thickness under Ag,
>> Au-Pt-Pd
>>
>> Hi Inge!
>>
>> Welcome back ol' buddy! I for one, have missed you here! Wish we could
>> get Paul to drop in once in a while. But I know that will be unlikely.
>>
>> Me a bagpipe blower? You have got to be kidding me! I don't even know
>> how to hold one of them things much less play one! They look kinda'
>> creepy to me...like an octopus or something. But when I hear "Amazing
>> Grace" being played on bagpipes, my heart pounds and I get goose bumps.
>>
>> I've not faded away, I'm still here, just don't have as much to talk
>> about as I used to. Anyways, this group has never been about any one
>> person, it's always been about all of us. Some have been here longer
>> than others, but what has made this email forum as solid and long
>> lasting as it has been, has been the contributions from everyone in
>> this group. I hope that this will continue.
>>
>> I'm dealing with what I guess you could call a "speed-bump" in my
>> life's road right now, but I plan on being here for a long time...
>>
>> Again, welcome back!
>>
>> Steve
>>
>> -----Original Message-----
>> From: Inge Hernefjord
>> Sent: Wednesday, December 05, 2012 11:55 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Termination finishes, Cu thickness under Ag,
>> Au-Pt-Pd
>>
>> Hi Wayne & collegues,
>>
>> heard from Joyce that you missed my comments. Sorry for that. When
>> Steve Gregory faded away as kind of bagpipe blower in the TN brigade,
>> I lost some contact with the troops march and became last one and with
>> time I saw the troops at distance. Well, with my old legs, seems as I
>> have to get lift with a jeep and catch up with you.
>>
>> On the theme you just discuss with Julie, I'd say to her not to mix
>> with changing the component finish immediately. Doing such things can
>> end in a never-ending-process. I am not updated with what is actually
>> going on, so my advice may not be of any help, but there is one
>> soldering method that have a very generous process window and that is
>> VPS, Vapour Phase Soldering. It has some very attractive advantages,
>> like instant and simultaneous heating, extremly low Oxygen presence
>> and is very fast. All properties that makes even many poor
>> weldable>acceptable weldable. You may not be able to try this, of some
>> reason. Just wanted to put up a finger and feel the wind direction
>>
>> Inge
>>
>> On 5 December 2012 00:41, Thayer, Wayne - IS
>> <[log in to unmask]>wrote:
>>
>>> Hi Julie-
>>>
>>> Sorry for the late response. I have a lot of experience with this or
>>> similar material. Yes, burnishing helps. I also deliberately use an
>>> iron tip that doesn't wet well. Paste with SMT works too, and is
>>> more controllable. We typically used the SnPbAg alloy with about
>>> 2%Ag, but I don't know if that helped. Our rule of thumb was you got
>>> three shots to solder to it, IF you used pre-heat and were very careful.
>>> BUT, this product is cake to solder to compared with AgPd, which most
>>> of the thick film commercial products used. That stuff would only
>>> survive a very carefully controlled single reflow.
>>>
>>> One thing we learned is that the leach rate SKYROCKETS if the
>>> designer put the PtPdAu directly on top of thick film Au where the
>>> solder was going to be. That recipe leaches just as bad as plain
>>> gold. The overlap MUST be behind a solder dam. (The thick film
>>> vendors only tell you this AFTER you figure it out on your own!) By
>>> the way, plain gold solders just fine on ceramic using SnAu eutectic
>>> solder. It is very expensive and is quite hot (270C or so). The
>>> joints are very pretty
>> shiny silver and very strong.
>>> You can also weld copper wires to thick film gold or silver.
>>> MiniCircuits
>>> sells piles of RF parts containing tiny transformers attached this
>>> way, and this technique is also used on RF inductors which are wound
>>> on an alumina mandrel.
>>>
>>> We ended up having a low temperature copper put on top of the gold
>>> whenever we could. It is much more robust--still wets horribly though!
>>>
>>> Wayne Thayer
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
>>> Sent: Wednesday, November 28, 2012 8:59 AM
>>> To: [log in to unmask]
>>> Subject: Re: [TN] Termination finishes, Cu thickness under Ag,
>>> Au-Pt-Pd
>>>
>>> Julie,
>>>
>>> Yes, the addition of a small amount of Pt does slow up the rate of
>>> the conductors leaching into the solder. From practical experience,
>>> the more Pt is added, the better the leach resistance. However, the
>>> more Pt is added, the greater are wetting problems.
>>>
>>> Thick film ink suppliers [used to] offer inks with different amounts
>>> of Pt so you could slightly 'chose your poison.'
>>>
>>> Also can depend on whether it is a fritted, or a frit-less, system.
>>>
>>> Like Mike says - BURNISH before solder IS the general rule!
>>>
>>> Never was something you really 'wanted' to solder to, unless you had
>>> no other choice.
>>>
>>>
>>> Steve Creswick
>>> Sr Associate - Balanced Enterprise Solutions
>>> http://www.linkedin.com/in/stevencreswick
>>> 616 834 1883
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
>>> Sent: Tuesday, November 27, 2012 8:02 PM
>>> To: [log in to unmask]
>>> Subject: Re: [TN] Termination finishes, Cu thickness under Ag,
>>> Au-Pt-Pd
>>>
>>> The claim of the supplier is that the Pt prevents the Au from
>>> dissolving into the solder. Hmmm. Can anyone back that up?
>>> The recent info on this is that it's looking like a wettability
>>> problem more than a dissolving-into-the-joint problem, although
>>> neither is confirmed.
>>>
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