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Dross produced, are we in or out?

We don't know if our solder pot is producing too droos or no... - May 20, 2005 by ING  

We agree with Sr.Tech ... - May 23, 2005 by


ING

#34380

Dross produced, are we in or out? | 20 May, 2005

We don't know if our solder pot is producing too droos or not. When we get it out of the solder pot, we have to add around 50 lbs of solder bars. I think it's an important quantity. I want to know your feeling about that. We use Alpha Metal Hiflo Bar solder (63SN/27Pb). We have an Electrovert Ultrapack 650C.

Thanks

Eric

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#34383

Dross produced, are we in or out? | 21 May, 2005

We would need more info to answer. How many boards get run between de-drossings? How many days between de-drossings? Are you removing dross only or some good solder with it?

Jerry

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#34384

Dross produced, are we in or out? | 21 May, 2005

We agree with the previous poster.

50 pounds sounds like a lot. We don't know: * How often you dedross? * What method you use for dedrossing? * What portion of your dross that is dross versus solder? * How many boards do you run between drossings? * What is the duration of time that you operate your machine? * Etc etc etc

Beyond using N2, steps in reducing dross are: * Keep temperature LT 270C * Run pump speed slower * Maintain solder contaminants to BS219, ASTM B32-66T

Kleenox [Solder Saver] does not reduce dross. It reduces the amount of solder entrapped in dross. Buy it from Kester. One tiny warning, one chemical byproduct of the dross reduction process is fluorine gas. Not much of it, but enough to be irritating to the operators without breathing equipment or great ventilation.

Has anyone used a Pulsar Solder Saver [ http://www.x-axys.com/pulsar-smt/thermal/wave/dross.asp ]? There was mention of it in a SMTnet thread a while ago.

We have no relationship, nor receive benefit from the companies referenced above.

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HOSS

#34412

Dross produced, are we in or out? | 23 May, 2005

Eric,

We also have a UPK 650C. Our machine was configured for N2 and using the ConTour nozzle. If you're using this nozzle without N2 you're creating tons of dross unnecessarily not to mention probably getting tons of icicling. We found out the hard way. Now using a standard lambda nozzle and Kleenox.

We only run the pumps 2 hours or so per day and de-dross weekly. We sprinkle Kleenox across the wave once per day and then sprinkle and cut in the stuff at the end of the shift prior to our weekly de-drossing. We are adding 25-50 lbs per week.

DaveF is correct. Kleenox doesn't reduce dross but separates good solder from lead oxide (black dust). If you use Kleenox, be sure that you have your operators protected from the fumes of the Kleenox and the additional lead dust it will generate. De-drossing will be easier as there should be less material to remove.

Some tips: We only add the stuff with the pot inside the machine to take advantage of the cabinet exhaust. We also only roll the pot out about half way during de-drossing for the same reason. Operators are also fitted with particulate respirators.

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#34413

Dross produced, are we in or out? | 23 May, 2005

Dave,

Again I am going to ask: who do you mean when you say "we". I would just like to know who you are consulting with to derive your information.

I am not bantering you, I just want to know who "we" is.

Could you grace me with a response this time ?

Thnx.

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OverTheHill

#34414

Dross produced, are we in or out? | 23 May, 2005

We agree with Sr.Tech

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#34420

Dross produced, are we in or out? | 23 May, 2005

Dave,

On the SolderSaver, My business partner was given a demo on this thing back in 2000. He said: "It worked but had a tendency to kick up dross dust into the air, but it sure did separate the good solder from the dross."

Pete

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ING

#34434

Dross produced, are we in or out? | 24 May, 2005

OK, here is the answers for your questions: - 250 boards every day - We dedross every day at the end of the day - We add approx 50 lbs of solder every day - We use a standard spoon with holes

And about Kleenox, is it really toxic? Do we have any alternative? Thanks

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Rob

#34435

Dross produced, are we in or out? | 24 May, 2005

Sr. Tech,

Let's not destroy the mystique, Dave is all seeing & omnipotent, so let's leave it at that.

Sometimes the reality doesn't live up to the dream, so let's not take that risk!

Rob.

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#34436

Dross produced, are we in or out? | 24 May, 2005

OK.You are right. I don't think he is going to answer me anyway. It's just that the "we" thing disturbs me for some reason.

I just want to make sure that he is not talking about an alternate personality,pet rock, or invisible friend or something like that.

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Rob

#34438

Dross produced, are we in or out? | 24 May, 2005

Hey, If it's an imaginary friend it's a very well informed one!

Perhaps this propensity to disturbance stems from a childhood experience of yours? Were you deserted by your imaginary friend?

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#34439

Dross produced, are we in or out? | 24 May, 2005

#34442

Dross produced, are we in or out? | 24 May, 2005

How big are the boards? I havn't done a lot with wave solder and I'm just wondering, how much solder these boards would use. Also I seem to recall being told that a thin layer of dross helps prevent more dross from forming. Of course this would not be true with a turbulent wave.

At one place we paid for the kids Xmas party with the money from selling the dross.

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RDR

#34444

Dross produced, are we in or out? | 24 May, 2005

Patrick, does this stuff not smell and gag and kill operators like the kleenox does? I would be very interested if this is the case.

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pr

#34447

Dross produced, are we in or out? | 24 May, 2005

We have done exhaustive studies and found the "smell and gag and kill operators" is acceptable and is more than offset by the solder saved!

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#34448

Dross produced, are we in or out? | 24 May, 2005

Russ, The product smokes when it separates the dross from the good solder, but never heard any complaints when good local ventilation is used (the product is as toxic as a couple of burning candles). If you email your company info I can arrange for a sample in that way you can see for yourself.

Pat Patrick@no-residue.com

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RDR

#34450

Dross produced, are we in or out? | 24 May, 2005

I agree, but OSHA is starting to get curious about the high turnover rate we are having and are curious why there has been no complaints. And I just can't tell them that I am killing the operators off before they have a chance to complain.

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#34453

Dross produced, are we in or out? | 24 May, 2005

Eric: For the amount of dross that you're removing, we're concerned that you could be loosing the balance of your solder alloy, because dross consists primarily of tin oxides. It has little lead in it, beyond than the lead content of the solder that you remove with the dross. So, it's possible that you should be adding pure tin, rather than solder, when making-up for low pot level.

Consider analyzing the content of your solder pot.

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RDR

#34456

Dross produced, are we in or out? | 24 May, 2005

What would the ramifications be with a tin poor pot?

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#34458

Dross produced, are we in or out? | 24 May, 2005

Certainly, most often, the focus of pot analysis is directed at controlling impurities. Maintaining proper level of tin is important, also. When the portion of tin decreases: * Liquidous temperature increases. * Ability to wet decreases. * Solder connection looks dull. * Theoretically, it is a weaker connection along the intermetallic layer, since there is even less tin after depletion in creating the copper tin intermetallic compound.

We add this paper, because we can no longer find it on the Metcal site.

The Effect Of Metallic Impurities On The Wetting Properties Of Solder by: Dennis Bernier Vice President, Research & Development Kester Solder Company

SOURCE OF IMPURITIES

The solder used for this investigation was all from one batch with thefollowing analysis:

Element Weight % Element Weight % Sn (tin) 60.1 Fe (iron) 0.006 Sb (antimony) 0.02 Bi (bismuth) 0.006 Cu (copper) 0.004 As (arsenic) <0.01 Au (gold) <0.002 In (indium) 0.005 Cd (cadmium) 0.0003 Ni (nickel) <0.001 Zn (zinc) 0.0002 P (phosphorous) <0.001 Al (aluminum) <0.001 S (sulfur) <0.001 Ag (silver) 0.001 Pb (lead) balance

Though the purpose of this testing was to determine the effect of impurities dissolved during the soldering process, it is important to note that national specifications for solder are not strict enough to assure obtaining high purity metal. Secondary or refined metal could contain excessive impurities and shorten the usable life of the solder bath. Impurities such as copper, antimony, zinc and aluminum have an effect on soldering quality and should be kept to a minimum.

Assuming that high purity solder is being used, the impurities are introduce into the solder from parts being soldered, from holding fixtures and from the solder pot itself.

Copper - Nearly everything on a printed circuit assembly is made of or plated with copper which dissolves rather rapidly in solder. The circuit board itself, component leads and jumper wires all introduce copper into the solder in a wave soldering machine.

Gold - No longer used as an overall protective plating, gold is used on certain component leads such as nickel-iron alloy used to make transistors, diodes and integrated circuits.

Cadmium - Sheet metal chassis frames and other parts might be cadmium plated to prevent rusting and improve appearance and solderability.

Zinc - Brass is an alloy of zinc and copper; so brass terminals, lugs and bolts are sources of impurities.

Aluminum - Fixturing devices, bolts and fabricated metal parts might be made of aluminum. The tough oxide film on the aluminum will usually prevent solder wetting; but with multiple solder immersions or if abraded, aluminum can dissolve in the solder. It is doubtful that aluminum will remain in the solder under production conditions since it will dross out when combining with copper, gold or antimony.

Silver - Many parts are silver plated to preserve solderability. Like the other coinage metals, gold and copper, silver will dissolve in the solder.

Iron - Temperatures over 430 degrees C will cause the solder to dissolve iron from the solder pot itself. An improperly alloyed solder using too much heat could contain excessive iron. A new solder pot -- whether cast iron, cold-rolled steel or stainless steel -- will have exposed iron available for dissolution into the solder. Excessive cleaning of the pot walls with a wire brush can also introduce iron into the solder. The problem associated with iron contamination is excessive drossing which usually clears up as the iron compounds are removed with the dross.

Sulfur - It is very unlikely that sulfur would contaminate the solder bath during normal production. Sulfur might be present in secondary metals since it is used to remove copper during the refining process. Sulfur should be limited by national solder specifications to avoid its presence in solder.

Phosphorous - The main source of phosphorous is copper that has been deoxidized with phosphorous.

PROBLEMS ASSOCIATED WITH IMPURITIES

Phase 1 of the investigations involved a compilation of analyses performed over the last ten years for the specific purpose of solving soldering problems. The amount of impurities in the solder was related to observed defects or solder conditions. These defects, specifically cause by contaminated solder, are noted below with some discussion about the impurities which caused the problem. The table following this discussion shows the percentage range of impurities which seemingly caused the observed soldering defects.

Icicles, Shorts, Bridges Cadmium, zinc and aluminum in trace amounts increase the surface tension of the solder to cause this defect. Copper and gold increase the solder viscosity to cause the same problem.

Large Solder Fillets Copper, gold and antimony increase the melting point of the solder and the intermetallic compounds with tin or lead make the solder more sluggish. The result is larger fillets and more solder consumed to create the solder joint.

Unfilled Holes The speed of wetting is reduced by the presence of copper, gold, antimony and cadmium. Though no instance occurred with zinc and aluminum, these metals are likely to also affect wetting speed because of their ability to increase the surface tension of the solder.

Dull Solder, Gritty Solder Cadmium and zinc in trace amounts make the solder surface dull. Gold also dulls the surface but is quite often indicated by a sparkling, crystalline surface condition. Bismuth or antimony in large amounts above 2.5% also dull the surface. Copper and aluminum contamination result in a gritty-looking solder surface. Both phosphorous and sulfur have caused gritty solder though rarely are these two impurities found in solder samples.

Dross Inclusions Dross inclusions in the solder show up as visible particulate grit or hidden inside a bump or pimple in the otherwise shiny solder surface. Quite often the source of this problem is an unusual amount of iron in the solder.

Cracked Joints Inclusions in the solder such as intermetallics of tin or lead with copper, gold and antimony can provide the nucleus for crack propagation.

Dewetting Zinc, antimony and phosphorous can cause solder to dewet on copper.

By looking at the real world of wave soldering and the ten years of analytical records, we can summarize the impurity levels which traditionally caused problems.

Impurity % When Problems Occur Cu (copper) 0.250 - 0.500 Au (gold) 0.005 - 0.200 Cd (cadmium) 0.005 - 0.150 Zn (zinc) 0.001 - 0.010 Al (aluminum) 0.001 - 0.006 Fe (iron) 0.010 - 0.100 Sb (antimony) 0.100 - 1.000 Ag (silver) 0.200 - 2.000 Bi (bismuth) 0.250 - 1.000 As (arsenic) 0.030 - 0.100 In (indium) no data Ni (nickel) 0.010 - 0.030 P (phosphorous) 0.010 - 0.100 S (sulfur) 0.002 - 0.030

Immediately obvious by an examination of this list is the fact that the percentages established by experience are not precise numbers. The explanation for this is that the defects cause by the impurities may be acceptable at one company and cause for rejection at another company. Rigid inspection requirements for aerospace or military products might reject solder joints which are acceptable for consumer products. Difference between fluxes, soldering machines, circuit board density, component layout, hole sizes, solderability and amount of heat all contribute to the quality of soldering.

REFERENCES

1.Soldering Manual, 1959, New York, American Welding Society 2.C. L. Barber: Solder, 1965, Chicago, Kester Solder Company 3.H. Manko: Solders and Soldering, 1964, New York, McGraw-Hill 4.M. L. Ackroyd et al. : Tin Research Institute Publication No. 493, 1975, The Metals Society. 5.D. Mackay: Proceedings of Institute of Printed Circuits, Meeting, September, 1972, San Francisco

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steve

#34459

Dross produced, are we in or out? | 24 May, 2005

Great Thread, look if you really want to continue replacing 50lbs of bar a day. Could I offer my assistance in selling you your bar???? Just kidding!!

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RDR

#34466

Dross produced, are we in or out? | 25 May, 2005

Excellent Dave F! I was hoping that I wouldn't get "lead rich joint" for an answer.

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