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I prefer to cut the leads before I solder them - this way there's no risk of unsettling the contact while you cut the soldered lead, so this gives you nice soli
by Florin_Andrei 16y ago
I prefer to cut the leads before I solder them - this way there's no risk of unsettling the contact while you cut the soldered lead, so this gives you nice solid reliable contacts. This requires you to hold the component with one finger while you're soldering it (otherwise it may fall off), which may get tricky as the component becomes pretty hot, but with enough kung-fu you'll be able to do it easily (e.g., hold it with the fingernail). I soldered thousands of components this way.
Another tip: when in doubt, put a little rosin on the pad and lead before soldering them, even though the alloy is supposed to contain rosin already. Again, this reduces the risk of a poor contact.
Never use cheap unstabilized soldering irons - those are only for rough jobs like soldering the lid on a tin can, and then just use the biggest iron you can find. For electronics, only use stabilized (regulated) irons (soldering stations), that allow you to finely tweak the temperature. Working at the right temperature is crucial; too hot and you burn components and oxidize pads before they get soldered; too low and again you may burn components because you're fiddling with the iron too long; or you make weak unreliable contacts. You'll figure it out with experience.
I actually prefer to use a soldering gun instead of an iron for anything except very sensitive multi-pin components that don't like EM pulses. Again, it's a bit of kung-fu to know when to push the trigger and when to release it; essentially, your brain becomes the thermal stabilizer. :) You need to "wax on, wax off" many hours before you obtain the skills, but then it's awesome. The gun allows you to do neat tricks like transport large drops of solid rosin, because you heat it up or cool it down instantly, as needed; a station, OTOH, is always at the same temperature.
Heating up both lead and pad at the same time is crucial. It bears repeating - crucial. Push the iron or gun against both parts. Don't push too hard, but make sure the thermal contact is good and firm.
Whether you wait 1 second before touching the heated pad+lead with the alloy, or you don't wait, depends on the technique. Whether you wait 1 more second before you retract the iron, or you don't wait, again depends on the technique. But once the liquid alloy has spread out, pull the iron at once, don't tarry. Then blow air over the hot area.
Nail clippers work just fine for cutting leads.
Sometimes you don't want to solder components too close to the PCB. This is true for those resistors, transistors, etc. that dissipate a lot of heat while working. Give them some breathing room. In general, don't push 3-pin components (such as transistors) too close to the PCB; when they begin to resist, you need to stop pushing. But soldering them might be tricky if they're not sitting stable in that position.
All that stuff about toxic metals and rosin fumes - I should probably be a brain dead zombie by now, I never washed my hands afterwards. Rosin smells kind of nice actually, similar to incense, but breathing the smoke directly is not pleasant; I doubt the smoke is more toxic than any other kind of smoke.
Finally: 2 hands are sometimes not enough. It helps if you're an octopus.
- drblast 16y agoAmen. You need a minimum of four hands to solder easily. "Then blow air over the hot area." I'm no expert, but I've always heard this is a bad idea. (A "cold solder joint")
- Florin_Andrei 16y agoBlow air after you remove the iron (not before), when the alloy is pasty or even full solid, to lower the temperature quickly. If it's a resistor or something like that, then don't bother, but with expensive semiconductors this is a good precaution. If failure is absolutely no option, then hold the lead on the other side of the PCB (between the soldered area and the component) really tight with some mini-pliers, to prevent too much heat from reaching the component (some heat is leeched by the mini-pliers). But this is very tricky. Sometimes I also keep a finger on the component, to remove some more heat, but I got burned more than once, since I was daydreaming instead of paying attention. As a teenager, my finger tips were always burned from the rather brash soldering technique I was using. I'm a little more cautious now. Blowing before you remove the iron is a bad idea - if not for making bad contacts (once the liquid has managed to wet the lead and the pad all around, there's no risk of cold joint anymore), then at least because there's a risk you may blow the liquid alloy away. :) Cold solder joints can often be recognized if you know how to "read" the shape of the solidified alloy. It's not a foolproof technique, but it does reveal the more egregious mistakes. If the alloy makes a round cone-like shape, uniform, symmetric, without interruptions, if the alloy seems to "merge" into the pad and the lead (or seems to "wet" both surfaces), as opposed to appearing to repeal the metal ("non-wetting" material) then chances are the contact is good.
- calloc 16y agoDon't inhale solder and flux fumes ... you end up coughing up a lung or two, and if you do inhale enough of it (i've got some stupid friends) then your poop may turn black for a day or two. In other words, make sure you have some way of moving the fumes out of your workspace, preferably having a wide open area, and or a fume extractor (Weller makes a great one).
- 16y ago