I'm not an expert, Inge, but the shape and size of the molecule plays an
important role, as well as the destruction mechanism. Then there is the
effect of the residual molecule after an atom have been knocked off; in
some cases, you get new molecules that are even more stable than the
original one. It also depends on the free radicals available. For
example, monoatomic oxygen is more available in the lower stratosphere
than in the troposphere and the opposite is true of the OH radicals.
Atmospheric chemistry is quite complex but, I believe, fairly well
understood: lots of maths!
Brian
On 10/12/2012 09:43, Inge Hernefjord wrote:
> "This may take from a few seconds to a few hundred years ....etc."....
> What on earth (?) decides this ? Within many disciplins, we are extremly
> good at finding out the most complex things, and that use to satisfy
> most...until I enter with my (irritating) 'Why?' . You say there are models
> today that explain.
>
> I had a similar discussion with a biochemist about the embryonal
> nuclomatics when a cell, by means of RNA, together with millions other
> cells decide to build a penis, for instance. What stops the process so that
> you don't get a cat p. or a whale p.? And why do the amino acids named
> 'starters' suddenly begin this nuclei process and what on earth makes them
> do this absolutely simultaneously? In this case, my informant said " Noone
> knows ".
>
> Inge
>
>
>
>
> On 8 December 2012 13:43, Brian Ellis <[log in to unmask]> wrote:
>
>> The computer used to generate the text is 80 years old, without many
>> revisions after transfer to an inorganic one, less than 5 y-o. In this
>> case, it was easy-squeezy, as I have 25 years experience working for the MP
>> on solvents.
>>
>> To answer a question you addressed to Dave, determining the GWP of a
>> substance with long atmospheric residence times is fairly easy and involves
>> two parameters. We know the spectral radiation towards outer space from the
>> earth as a black body temperature equivalent to 287 K ±5 K; we can
>> empirically determine the absorption spectrum of any gas. From the two, it
>> is easy to determine the amount of radiative energy that will be absorbed
>> at any given molecular concentration of gas in the atmosphere, that energy
>> being converted to increased air temperature.
>>
>> The second parameter is the folded-e atmospheric residence time, which is
>> the time for a given mass of a gas to reach 1/e times its original mass.
>> This is a function of the mechanism by which the gas decomposes in the
>> atmosphere. Most organic gases decompose by hydrolysis, meaning that C-H
>> bond is destroyed by a hydroxyl (OH) free radical. This may take from a few
>> seconds to a few hundred years and is easily determined, in most cases,
>> empirically or theoretically, the models being fairly good. In the case of
>> PFCs, the mechanism is known and the residence time can be determined
>> reasonably accurately by statistically calculating the probability of a
>> molecule being destroyed by collisions from particles of varying energy.
>> Strangely enough, the residence time is most difficult to determine
>> accurately with molecules that destruct in times less than a few weeks
>> because of the variability of the concentration of free hydroxyl radicals
>> in the air, in turn dependent on the water vapour mass or, more simply, the
>> humidity. Methane, for example, will last longer in a desert than in a
>> tropical rain forest.
>>
>> Hope this simplification answers your question
>>
>> Brian
>>
>>
>> On 08/12/2012 12:46, Inge Hernefjord wrote:
>>
>>> Wow! What a speech. Brian, you should have a job in Brussels. Your
>>> buerocratic language is distinct and perfect. Do you stream directly from
>>> your organic computer and with no adjustments or do you sketch the text
>>> and
>>> make ready successively? You become better and better,old
>>> anglocyprofrank.
>>>
>>> /Inge
>>>
>>> On 8 December 2012 10:57, Brian Ellis <[log in to unmask]> wrote:
>>>
>>> Dave
>>>>
>>>> In theory, I agree with you but let me first recount two little anecdotes
>>>> regarding a closely allied subject, halogenated cleaning solvents.
>>>>
>>>> The first one was at a plant in China making aircon compressors. They
>>>> used
>>>> 1,1,1-TCA for degreasing and removing the residual abrasive the cylinders
>>>> after honing. As this solvent was being phased out under the Montreal
>>>> Protocol (MP), they decided that trichloroethylene (TCE) was the most
>>>> likely low-cost substitute. As the Operator Exposure Limit of TCE was 25
>>>> ppm, against 400 ppm for TCA, it was clear that their open top vapour
>>>> degreasers had to be replaced. They applied for and obtained a grant from
>>>> the MP Multilateral Fund to purchase two zero-emission vapour degreasers
>>>> which were installed in a large workshop. When I went to audit the
>>>> installation, I thought my nasal chromatograph could just detect the
>>>> odour
>>>> of TCE, which should have been impossible with zero-emission machines. I
>>>> got out the old Dräger tubes and started pumping. Sure enough, it read
>>>> about the limit at the place where the operator stood to press the button
>>>> to start a cycle; this should not have been. I investigated further and
>>>> found a tiny leak at an olive joint on a stainless steel pipe.
>>>>
>>>> Moral: can zero-emission machines be guaranteed to be just that?
>>>>
>>>> As a post script to the above, there was no way that a balance sheet
>>>> could
>>>> be made of incoming and outgoing solvent, as the volume of the latter was
>>>> twice that of the former because of the contaminants dissolved/suspended
>>>> in
>>>> it!
>>>>
>>>> The second one concerned a plant in the USA that chose nPB to replace
>>>> CFC-113 in open-top vapour phase machines for defluxing assemblies with
>>>> many wound components. The machines were fully enclosed with extraction,
>>>> high freeboard and gantry transfer, to eliminate the risk of nPB vapour
>>>> in
>>>> the workplace, as they were rightly concerned about the substance's
>>>> toxicity. After the changeover, they were surprised to find high levels
>>>> of
>>>> nPB in the workshop and this was determined to be due to drag-out from
>>>> the
>>>> assemblies, imputed to the wound components. They therefore added a stage
>>>> of vacuum oven exhaustion of the assemblies after cleaning, but still the
>>>> inspectors/retouchers complained of persistent headaches after a few
>>>> hours.
>>>> Even in a vacuum oven it was impossible to reduce the quantity of vapour
>>>> trapped in the windings of the coils to a low level, even though it was
>>>> below the odour threshold.
>>>>
>>>> Moral: can drag-out be totally eliminated?
>>>>
>>>> It is my opinion that it would be practically impossible to ensure zero
>>>> emissions from a vapour-phase reflow machine, by analogy with the above
>>>> anecdotes.
>>>>
>>>> Now, look at the political aspect. It is easy for the politicians to say,
>>>> you have five years to phase out the **production** of the perfluorinated
>>>> substances used in vapour phase reflow machines. As there are only a
>>>> handful of plants capable of producing them in the world, the control of
>>>> such a phase-out would be easy. Problem solved for the said politicians.
>>>> It
>>>> would not be possible for them to say, thou shalt use only zero-emission
>>>> machines in such a way that drag-out losses are zero, because there is no
>>>> way that companies making highly secret defence equipment in countries
>>>> like
>>>> Iran, N. Korea or in the jungles of Myanmar or Laos could be controlled.
>>>>
>>>> I therefore think that the controlled phase-out of production of PFCs, à
>>>> la MP, is the likely route of control, regrettably. Like the MP, there
>>>> may
>>>> be Essential Use Exemptions, where it can be shown to the satisfaction of
>>>> an EUE Technical Experts Committee that a) no other process is possible
>>>> and
>>>> b) every means are in place to minimise emissions and c) every effort is
>>>> made to alter the overall products to eliminate the need to use PFCs in
>>>> the
>>>> process. For example, in the case of MP-controlled solvents, we allowed a
>>>> small handful of EUEs. As I remember it, one was for the shuttle booster
>>>> solid fuel rocket assembly and I can recall a short-term EUE for a
>>>> medical
>>>> application. There may have been one or two more that I no longer
>>>> remember.
>>>> As was established for halons, a bank could be set up for PFC EUEs.
>>>> Frankly, I see no other way. Whether a production phase-out date is set
>>>> for
>>>> 2018, 2020 or 2025 or even 2030, I cannot predict but the more the
>>>> quantity
>>>> of PFCs made increases, the more the phase-out date is likely to be
>>>> nearer.
>>>>
>>>> My conclusion is that the use of VP reflow/soldering should be reduced to
>>>> an absolute minimum, using only the most advanced emissions-free
>>>> technology, and this will offer the best chance of a gentle phase-out. On
>>>> the other hand and go mad, as has been suggested in this thread, with
>>>> every
>>>> assembly shop implementing the technique, and this will be the surest way
>>>> of having restrictions placed in the shortest possible term.
>>>>
>>>> The choice is up to you, the assembly industry. I believe PFCs will be
>>>> controlled sooner or later, please make sure that the control is least
>>>> painful by the sensible use of these substances.
>>>>
>>>> Brian
>>>>
>>>>
>>>>
>>>>
>>>> On 08/12/2012 02:00, [log in to unmask] wrote:
>>>>
>>>> Hi Brian! It is rare but I disagree with you on one point in your
>>>>> details. As a society we seem to jump to the "let's ban" option far too
>>>>> often. I would offer a different approach - let's make the system more
>>>>> efficient and less wasteful. We have enough smart engineers that we
>>>>> should be able to design systems where the fluid loss is very very low
>>>>> or potentially zero. I understand that would make systems more expensive
>>>>> but then we would truly find out where Vapor Phase soldering is really
>>>>> necessary. Rockwell Collins utilizes Vapor Phase soldering as it is the
>>>>> most efficient and effective way to solder some of our thermally
>>>>> demanding designs. Condensation soldering has its place with our other
>>>>> soldering methodologies and should be used in a responsible manner. We
>>>>> have all witnessed the impact of the environmental legislation where
>>>>> many of the substitutions are more harmful to the environment than the
>>>>> material that was banned. Our goal should be a balance - ban materials
>>>>> where acceptable substitutes are available, be more controlled and
>>>>> efficient with materials that have no substitutes and submit to
>>>>> recovery/recycling practices to the largest extent possible. As a
>>>>> material engineer, I don't believe banning the use of materials is
>>>>> always the best approach. I know you are a champion the balanced
>>>>> approach so I believe the same approach could be used for Vapor Phase
>>>>> fluids.
>>>>>
>>>>> Dave Hillman
>>>>> Rockwell Collins
>>>>> [log in to unmask]
>>>>>
>>>>>
>>>>>
>>>>> From: Brian Ellis <[log in to unmask]>
>>>>> To: <[log in to unmask]>
>>>>> Date: 12/07/2012 12:26 PM
>>>>> Subject: Re: [TN] Termination finishes, Cu thickness under Ag, Au-Pt-Pd
>>>>> Sent by: TechNet <[log in to unmask]>
>>>>> ------------------------------****----------------------------**--**------------
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> 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.**rdtechnicalservic**es.com/**System-RD2.cfm<http://rdtechnicalservices.com/**System-RD2.cfm>
>>>>> <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>
>>>>> <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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>>>>> >
>>>>> >
>>>>> > ______________________________****____________________________**__**
>>>>>
>>>>>
>>>>> __________
>>>>> > This email has been scanned by the Symantec Email Security.cloud
>>>>> service.
>>>>> > For more information please contact helpdesk at x2960 or
>>>>> [log in to unmask]
>>>>> > ______________________________****____________________________**
>>>>> __**
>>>>> __________
>>>>> >
>>>>> >
>>>>> > ______________________________****____________________________**__**
>>>>>
>>>>>
>>>>> __________
>>>>> > This email has been scanned by the Symantec Email Security.cloud
>>>>> service.
>>>>> > For more information please contact helpdesk at x2960 or
>>>>> [log in to unmask]
>>>>> > ______________________________****____________________________**
>>>>> __**
>>>>> __________
>>>>> >
>>>>> > ______________________________****____________________________**__**
>>>>>
>>>>>
>>>>> __________
>>>>> > This email has been scanned by the Symantec Email Security.cloud
>>>>> service.
>>>>> > For more information please contact helpdesk at x2960 or
>>>>> [log in to unmask]
>>>>> > ______________________________****____________________________**
>>>>> __**
>>>>> __________
>>>>> >
>>>>> >
>>>>> > ______________________________****____________________________**__**
>>>>>
>>>>>
>>>>> __________
>>>>> > This email has been scanned by the Symantec Email Security.cloud
>>>>> service.
>>>>> > For more information please contact helpdesk at x2960 or
>>>>> [log in to unmask]
>>>>> > ______________________________****____________________________**
>>>>> __**
>>>>> __________
>>>>> >
>>>>>
>>>>> ______________________________****____________________________**__**
>>>>>
>>>>> __________
>>>>> This email has been scanned by the Symantec Email Security.cloud
>>>>> service.
>>>>> For more information please contact helpdesk at x2960 or
>>>>> [log in to unmask]
>>>>> ______________________________****____________________________**__**
>>>>> __________
>>>>>
>>>>>
>>>>>
>>>>> ______________________________****____________________________**__**__________
>>>>
>>>>
>>>> This email has been scanned by the Symantec Email Security.cloud service.
>>>> For more information please contact helpdesk at x2960 or
>>>> [log in to unmask]**________________
>>>> **____________________________**__**__________
>>>>
>>>>
>>> ______________________________**______________________________**
>>> __________
>>> This email has been scanned by the Symantec Email Security.cloud service.
>>> For more information please contact helpdesk at x2960 or [log in to unmask]
>>> ______________________________**______________________________**
>>> __________
>>>
>>>
>>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
|
