Umm, which one?anatech said:
I worked a hydrogen belt furnace for die attach: using indium based alloys, gold tin, gold germanium.
Die attach scrubbers using gold silicon, gold ge.
Nitrogen belt for hermetic sealing, 95-5 lead tin, indium types.
Vapor phase reflow, two stage, pure tin first stage, 60/40 second.
Hot air, focussed infrared, dap vacuum sealing, resistance soldering, induction heated continuous reflow, solder pot.
All solder joint processes, materials and design for cryogenic (liquid helium) superconductor magnet assembly at work, all those using tin/silver..strength, lack of creep...unfortunately, the stainless vacuum bellows within are 6 to 8 mil thick walls, so are susceptible to halide corrosion (chlorine, flourine, bromine, iodine), so activated fluxes are not allowed...we are stuck using R type flux, with tighter control of the processes.
Oh, I also do regular soldering on wires, and all my own plumbing work and repair.
Cheers, John
Anybody know about tin whiskers... the dendrites that grow from high tin alloys?
I do a lot of SMT stuff... the parts keep getting smaller... the distance between pins is pitiful. Cant even breadbaord anymore because not all silicon even comes in thru-hole versions. First pass on a design is with a real pcb and robots ($$$$$$).
I know I have switch to Pb free... been avoiding it so far. The dendrite thing seems to be at the center of genuine controversy (here we go!).
The manufacturers are dodging the issue (where's the recommendations)... while the SMT assembly shops are tearing their hair out.
Experts????
I do a lot of SMT stuff... the parts keep getting smaller... the distance between pins is pitiful. Cant even breadbaord anymore because not all silicon even comes in thru-hole versions. First pass on a design is with a real pcb and robots ($$$$$$).
I know I have switch to Pb free... been avoiding it so far. The dendrite thing seems to be at the center of genuine controversy (here we go!).
The manufacturers are dodging the issue (where's the recommendations)... while the SMT assembly shops are tearing their hair out.
Experts????
The manu's don't know..poobah said:
In the last coupla months, some big military contractors have contacted me about this issue, it seems the requirements for lead free are now being instituted at the mil vendors. I am being asked because of my experience in using tin/silver at work.
The two issues associated with tin are whiskers and tin pest.
In the literature, I have seen no indicaton that a tin alloy suffers from whisker formation. I've also seen no indication that it does not, unfortunately. In the application I am experienced with, we have to keep a minimum of 200 mils gap between soldered surfaces and anything conductive, as this gap is required for our operation in a liquid helium environment..there are places in the helium phase diargram where it is conductive..so by design, it is possible we bypassed the issue?.
Tin pest is the powdering breakdown of pure tin as a result of cold. From what I recall, this is a atomic level phase change thing.
This I can certainly speak of fluently. I have made solder joints ranging from #32 awg copper up to 12 inch lap joints an inch wide that carries 7 kiloamps in liquid helium, all of them using tin silver eutectic.
In the five years that the machine has been in operation, there has been no indication of tin pest or joint failure (with 20 to 30 thousand joints, if it were even a low level problem, we'da had some failures). And I note that it is not possible to get much colder than liquid helium. In addition, high temp superconductors operating at liquid nitrogen level have also not shown any pest. So that issue, I wouldn't worry about.
Whiskers, I think the jury is still out, but I suspect that as long as the solder is an alloy of tin, whiskers are not an issue. At least, I have found nothing to indicate alloy's are a problem in this regard.
Cheers, John
Thanks John,
I'll have dig up some of the stuff I've read and post links...
Oddly, I recall some dialogue that said that tin whiskers was an ancient problem in early electronics... cured by the adoption of lead. That's NOT a statement guys! just a recollection.
It might have been some BS from someone with magic solder to sell...
7000 amps huh? That's almost enough for the diesel powered bass guitar amp I want to build...
I'll have dig up some of the stuff I've read and post links...
Oddly, I recall some dialogue that said that tin whiskers was an ancient problem in early electronics... cured by the adoption of lead. That's NOT a statement guys! just a recollection.
It might have been some BS from someone with magic solder to sell...
7000 amps huh? That's almost enough for the diesel powered bass guitar amp I want to build...
OK... back to the subject of Pb free solder/parts and the growth of tin whiskers:
Here's a link with some great info, this wasn't available last time I searched:
http://nepp.nasa.gov/whisker/background/#q6
They don't offer much comfort in the way of solutions though.
I would have to think that this will be especially important to the tube guys considering the higher voltages involved.
Are we going to see good ole "Kester 44" go black market?
Here's a link with some great info, this wasn't available last time I searched:
http://nepp.nasa.gov/whisker/background/#q6
They don't offer much comfort in the way of solutions though.
I would have to think that this will be especially important to the tube guys considering the higher voltages involved.
Are we going to see good ole "Kester 44" go black market?
Lets hope this board doesnt have to start covering diy smelting.
I live near a coal burning powerplant built in 1954. It puts out ~5,400,000 pounds of toxic pollution ino the air each year. This includes an admitted 361 pounds of mercury. Also emitted are 750 pounds of lead, 800 pounds of arsenic, 635 pounds of chromium compounds, and 1,300 pounds of barium compounds.
There was action about this, but thats stopped with the Clear Skies act. Its absurd we have to worry about solder with stuff like this in our backyards.
As an aside, coal contains over 1ppm of uranium and 3ppm of thorium.
I live near a coal burning powerplant built in 1954. It puts out ~5,400,000 pounds of toxic pollution ino the air each year. This includes an admitted 361 pounds of mercury. Also emitted are 750 pounds of lead, 800 pounds of arsenic, 635 pounds of chromium compounds, and 1,300 pounds of barium compounds.
There was action about this, but thats stopped with the Clear Skies act. Its absurd we have to worry about solder with stuff like this in our backyards.
As an aside, coal contains over 1ppm of uranium and 3ppm of thorium.
Hi poobah,
That article agrees with everything else I've read on the subject. The conclusions reached in general was to make sure the alloying substance was a higher concentration. One of the things that came out of this was the exclusion for lead in high rel applications.
Joint failures were another common problem, and wetting (related). So this will be in the air until the Mil complex is happy with an alternative. Skews from the manufacturers are a problem here. Can you imagine your audit trail with a statement "May contain nuts" (substitute lead).
Oh well. The real problem as I see it is they don't want electronic products ending up in land fill. All other options are unpopular (an anti junk law) and trying to run down manufacturers to reclaim the product won't work either. So, they stuck it to everyone at the source.
RoHS is here to stay folks. "It sounded good in the board room"
-Chris
That article agrees with everything else I've read on the subject. The conclusions reached in general was to make sure the alloying substance was a higher concentration. One of the things that came out of this was the exclusion for lead in high rel applications.
Joint failures were another common problem, and wetting (related). So this will be in the air until the Mil complex is happy with an alternative. Skews from the manufacturers are a problem here. Can you imagine your audit trail with a statement "May contain nuts" (substitute lead).
Oh well. The real problem as I see it is they don't want electronic products ending up in land fill. All other options are unpopular (an anti junk law) and trying to run down manufacturers to reclaim the product won't work either. So, they stuck it to everyone at the source.
RoHS is here to stay folks. "It sounded good in the board room"
-Chris
Related to this ( or it might deserve its own post);
Europe brings in the Reduction of Harmful Substances (RoSH) legislation from 1st July 2006. From that date, no new leaded electronics will be allowed to be manufactured or imported into Europe. (and its not just lead). What are the regulations around the rest of the world?
I believe that Japan went this way years ago.
By the way. For the SMT guys; we had our chinese guys try MULTICORE LF318 solder paste and Heraeus F620. The heraeus won.
You can solder any lead free part with 60/40, but leaded parts might not take the extra heat required for lead free solder. The exception is BGA components. You shouldn't mix them.
Europe brings in the Reduction of Harmful Substances (RoSH) legislation from 1st July 2006. From that date, no new leaded electronics will be allowed to be manufactured or imported into Europe. (and its not just lead). What are the regulations around the rest of the world?
I believe that Japan went this way years ago.
By the way. For the SMT guys; we had our chinese guys try MULTICORE LF318 solder paste and Heraeus F620. The heraeus won.
You can solder any lead free part with 60/40, but leaded parts might not take the extra heat required for lead free solder. The exception is BGA components. You shouldn't mix them.
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