In reality the silver content in the solder or the absence of lead doesn't make it best.
The best solder should be the best for its particular application.
If you're about to build-up a solid state equipment(or work with OpAmps or ICs) than the temperature applied to the device leads is crucial. Therefore it's not desirable to have a solder that has high temperature of melting such as tin-silver solder. Any solder has very poor conductivity compared to the cooper or silver therefore its function is to hold conducting leads together tight. A content of silver in the solder only makes it to melt under the higher temperature and so higher power device should be used to work with such.
A lead-free solder has an advantage not to be as harmfull for the human flora over the one that contains lead. Despite that any soldering job should be done with good air circulation and avoiding inhalation of the flux and solder smoke.
The "speed" is the most important factor that I value in solder. The faster I join conducting leads the less I inflict them under the high temperature the less I stress the conducting material and device I work with. Becides the above mentioned speed I also love the ability to leak. Hard tin-silver ones can't do that and can form bubbles if not sufficient time applied to melt it. Therefore I figured that spending 5x or more for Cardas or Johnson ain't worth it(too damn "slow") and chose Weller.
P.S. Always remember to join conducting leads and NOT solder to solder! |
Welborne Labs house brand is better than WBT and as good as and cheaper than Cardas (which they also sell).
http://www.welbornelabs.com/solder.htm |
I would second Nsgarch's recommendation for the Welborne Labs House brand. It's the easiest to work with that I've found, inexpensive and I certainly can't hear any difference between it and other solder. |
I'm working my way up to building a k and k phono preamp. I've been practicing soldering on a couple of circuit boards.
Somebody told me that silver has very low resistance, which they said is desirable for solder. So, as an amateur, I thought that perhaps the solder with the highest amount of silver would be the best to use. If I understand Marakanetz, it is more important to use a solder with a lower melting point than one with a higher silver content.
I also understand that when soldering you want to heat the copper trace and the lead together and then melt the solder by touching it to the heated lead and copper trace - not to the tip of the soldering iron. Am I on the right track here? In my practicing, I find that it takes two or three additional seconds to melt the solder this way. Of course, it melts faster touching it to the tip of the iron, but I understand that this is a good way to get a "cold" joint.
Thanks for all your help. |
Jj, You're definitely on the right track but the fastest melting solder consists only from lead wich has following important disdvantage:
The melting temperature is too low which means you can't use it in the power circuitry (or output tubes or transistors) affected by the heat. If heat acts on pure lead solder it will crack within the time to form a cold joint or lost of the contact.
Therefore pure lead or high content of lead solder should be used for small signal ICs that demand a very short duration of applied high temperature.
The mixture of tin lead and silver depending on quantity melts under different temperatures. Therefore it's a good practice to have at least two different kinds of solder.
You have to make shure that the power of the soldering iron is upto your application. For high-temperature solving solder you'll need higher power iron but than you'll have to make sure that you won't damage a circuit element.
2...3 seconds to melt is too slow. In my case the solder melts almost instantly and than leaks arround the soldering surfaces. This way you won't get any cold joint or bubble.
In this case I guess you'll need a more powerfull iron or different solder. For electronics applications you'll need the thin wire of solder
Having a soldering iron with variable power and number of different iron tips would help you match for a specific joint you will want to perform. Please also note that you should clean the iron tip freequently otherwise the heat transfer won't be efficient. |
Dear Marakanetz,
Are you in agreement that the solder should be touched to the heated trace and lead and not to the tip of the iron?
If so, then I would need to either turn up the heat or use a solder with a lower melting point to shorten the two or three seconds after I touch the solder to the lead and the trace?
Right now, I touch the tip of the iron to the lead and trace together for about 3 seconds before touching the solder to the other side. |
my experience has yielded good results by touching the solder to the iron-trace junction, so that some solder gets on each. Helps to speed up the initial melt at a somewhat lower junction temperature (causes less stress on the component) yet still flows well across the conducting surfaces being soldered |
Jj it's just strictly technique issue.
Whenever you feel that conducting leads are ready to be joined, pour the solder onto them.
It must be a nice shiny "hut" but not blob or bubble... |
I'm posting again since somehow this didn't go through....
So my following comments will complement some of the above notes.
Some silver containing solders require higher temperatures to melt. This can be an inconvenience specially working on printed circuits or surface mounted. There is a risk of overheating deformation or desoldering adjacent parts. In the case of cable and interconnects there can be oxidation and insulation damage.
I prefer to work with eutectic low melting point solder and do a good physical bonding (eg wire metal) between the conductors and then secure it with the solder. Cleanliness and good preparation of parts to be soldered is needed for a quality job.
Working with lead solder requires common sense : wash your hands properly after using it. Better yet use protective latex gloves ultra cheap and safe. This material to affect you has to be inside your body, in other words it doesn't jump at you and kills you. The normal hygiene practices are enough to work with the material properly.
Eutectic solder has a single temperature for melting and not a range. A non eutectic one behaves as follows: part of it starts to melt earlier and others after, likewise to solidify the same happens but in reverse order so it's slower to work and maintains more stress upon solidification that later might yield a broken soldedered part. Eutectic provides in my experience better and more important more reproducible results.
The use of a variable power soldering instrument is desirable to avoid working with too hot an iron and this way lessen damage chance.
Eutectic Sn/PB 63/37 melts at 361 F.
WBT types : Sn/Pb/Ag 62/36/2 melting range 354-372 F
One key point to remember solder has to melt, wet properly and after that solidify with the minimum stress. This requires a couple of overlooked things
1- Heat just enough and with power/soldering tip acording to size of parts to be soldered. i.e. larger pieces require more wattage iron and larger tip.
2- If you overheat the solder will "dance" over the overheated parts and not settle.
3- To avoid stress avoid sudden cooling by blowing air directly to the recently applied solder. That doesn't allow enough time for proper wetting/distribution of material.
4- Use rosin based flux not acid flux containing solders.
Hope this is helpful and not confusing
Luis |
Q: Does solder smoke contain lead? |
No lead, it's just flux vapors. Good ventilation in the area needed but no draft hitting directly the working area since heating will be more difficult. |
No it doesn't but the flux smoke is toxic so proper ventillation is required. |
I've read two variations on a single suggestion that appear to minimize risk of overheating the component and that purport to avoid a cold joint. My understanding follows, but I'm not sure I've got it right: apply the tip of the iron to about 1mm to 2mm of solder between the tip and the junction of the lead and trace; and as the solder instantly melts apply the iron tip to the junction of lead and trace and the tip of the solder to the junction of the lead, trace and instantly melted solder (not to the tip of the solder wire) and melt the amount of solder you need.
Am I understanding this right and do you recommend this technique? Does it avoid fried components?
Thanks again, Jeff |
I don't want to hijack the thread, but is there any tool you like better than a Metcal soldering tool? |
