Brian, you are like whisky, you become better and better with time...
Inge
On 7 December 2012 09:41, Brian Ellis <[log in to unmask]> wrote:
> 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 order 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<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<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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