Agreed, but it is very likely that the lipophilic end of the molecule
will bond to epoxy resins, especially in the event of astoichiometry,
and the exposed hydrophilic end will play havoc with SIR, even with
non-ionic surfactants, because of its hygroscopicity. Even a good wash
cannot be guaranteed to remove it, depending on the bond strength and
the energy levels in the wash process. Furthermore, if the surfactant
contacts the epoxy above its Tg, the resin matrix is sufficiently open
to allow ingress of the molecules (cf. the Zado effect).
Note that I'm not saying that any of this WILL happen, but it COULD
happen and I counsel prudence in the form of rigorous qualification tests.
Brian
Richard Kraszewski wrote:
> One of the concerns I have is what happens if this gets onto the board. This doesn't seem as unlikely as it may seem if you let the solder level get low and start sucking the compound into the impeller. Good chance that it is based on an ionic surfactant system. Suitable choice due to their inherent heat stability, but they also tend to be rather hygroscopic. Potential for some SIR failures I suppose.
>
> When everyone used to wash, this wasn't such a big deal, but with no-cleans...?
>
> Rich K / KEDS
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: Wednesday, April 26, 2006 10:32 AM
> To: [log in to unmask]
> Subject: Re: [TN] Molten Solder Surfactant for Dross Elimination
>
> This subject was discussed at length in a thread of 10 March. Have a
> look through the archives.
>
> I contributed the following to this thread on 14 March:
>
> OK, I've had a good look at the P. Kay MS2. Framnkly, I see no grounds
> for sufficient originality for a patent to be granted. Let me go into
> the history of solder blankets. The original one was vegetable oil,
> usually peanut oil. This was effective at reducing dross formation and
> the acid decomposition products actually chemically reduced some of the
> dross back to metal. Two disadvantages: flammability and odour, which
> rendered it unpopular. Also, it had a short lifetime because of
> polymerisation, requiring skimming twice/day.
>
> To overcome this, van t'Hoen helped develop a mineral soldering oil
> which was marketed as Shell Peblum A, initially for the tinplate market
> and later for soldering. This was a pure blanket product with no
> chemical reduction. It had a reasonable lifetime of a few days.
>
> Then came the most significant development in the 1960s, by the
> erstwhile London Chemical Company in Bensenville, IL (later taken over
> by Alpha Metals). This was marketed as Lonco Fusecote 240. This was a
> blend of carboxyl alkanes and their polymers. This was popular for
> immersion reflow of electroplated tin/lead alloys, as well as being a
> clean substitute for soldering oils. It was easily cleaned with either
> water or the usual organic solvents. It was very stable with waves up to
> ~245°C and was safe with a flash point of ~265°C. Typical lifetime was
> about one week. Some of the components of this had surfactant properties.
>
> A different technique was offered by Fry's Metals, in Mitcham. They
> offered orange tablets of a hard wax blended with a reducing agent. This
> looked like a chocolate bar and I suspect that this was a deliberate
> ploy as there was also a chocolate company called Fry's. The two
> companies were founded independently by two branches of the same Quaker
> family in the 19th c. A small piece of the wax floated on a drossy
> solder bath reduced the volume of dross and some of the metal was
> recovered. The gunge resulting from this was then skimmed off, but the
> technique left no or little blanket.
>
> Other techniques used for static baths was floating pine sawdust on the
> solder. This was actually quite good at reducing dross by means of the
> slow exudation of rosin.
>
> As for machinery, the most significant was the Hollis machine which
> sucked a small volume of the "oil" and mixed it into the solder at the
> bottom of the wave, which did not oxidise. The disadvantage was that
> micro-droplets of oil were sometimes found in solder joints. This did
> not appear to affect the reliability but did cause some worry. Other
> manufacturers just offered an oil blanket so the wave itself was
> unprotected. Another technique was to drop a few drops of oil across the
> wave as each pallet or circuit approached it. Fry's recommended
> occasionally rubbing their orange "chocolate" along the nozzles with the
> wave off, of course.
>
> One of the most important factors to consider is the "cleanability" of
> the oil residues on the assembly. The vegetable and mineral oils
> required solvent cleaning, while Fusecote, being water-soluble, could
> also be water-cleaned, but was prone to foaming and additions of octylic
> alcohol and soft soap were required in the wash water.
>
> The P.Kay MS2 appears to be quite similar to Fusecote in all ways,
> except that it has a higher flash point, possibly because of longer
> chain alkane molecules. I have little doubt it is effective. What
> worries me is the toxicity to water wildlife and the long lifetime. This
> suggests (my speculation) that it may contain nonyl- or
> deca-phenoxylates or something similar which are non-ionic detergents
> that are not looked on too kindly in waste water by some authorities. If
> so, this may require the need for elimination before emission into a
> waste water stream.
>
> Hope this helps.
>
> Brian
>
> Todd, Richard wrote:
>> TechNet,
>>
>>
>>
>> I have come to the Oracle seeking wisdom. Has anyone had any experience
>> with using a molten solder surfactant for dross elimination in a wave solder
>> process? There is a (fairly) new product on the market which makes some
>> exciting claims. Although, as the adage goes, if it sounds too good to be
>> true, it probably is!
>>
>> I am not a chemist or metallurgist but, I think I understand in principal
>> how this stuff works, but I am hesitant to add anything to my solder pot for
>> fear of contamination issues, etc. Any and all comments are welcome. I am
>> especially concerned about long-term solder joint reliability issues. I
>> will do my own testing and validation both in lab and on the production
>> floor but I want to understand any process concerns, etc.
>>
>>
>>
>> Oh, by the by, I am running standard Sn/Pb in my waves; we do not solder in
>> an inert environment and we do not clean our boards (no-clean flux).
>>
>>
>>
>> Thanks in advance,
>>
>>
>>
>> Rick Todd
>>
>> Senior Engineer
>>
>> Process Quality Engineering
>>
>>
>>
>> Panasonic Automotive Systems Company of America
>>
>> Division of Panasonic Corporation of North America
>>
>> 776 Highway 74 South, Peachtree City, GA 30269
>>
>> 770-515-1087 Direct
>>
>> 678-458-2887 Cell
>>
>> 770-486-2248 Fax
>>
>> [log in to unmask] <mailto:[log in to unmask]>
>>
>>
>>
>>
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