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This is a beginner's guide to building circuits that will talk about the "proper" way to install components (resistors, ICs, capacitors, etc), and also a little bit about soldering. It'll cover things like recommended tools, how far and which direction components should be inserted, pre-bending and clinching leads along with some tips and tricks. We'll be using a power supply kit made by David at uCHobby.com that plugs into a bread board for demonstration. Yep, we're commercial and sell all this stuff, but the advice should apply equally well to anyone's tools and circuits.
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Signing UpStep 1Recommended Tools and Supplies
- Soldering iron and solder: Just about any 25-30 Watt soldering iron will do. Ideally, the temperature of you iron would be between 600-700 degrees F (for lead-free solder, 700-800 is recommended). How temperature relates to wattage depends a lot on the iron (watch a video testing the temperature of cheap RadioShack irons), and some high wattage irons have too high of a temperature. Avoid "solder guns" as these are meant for pipe soldering. Not only can these be too hot, but they work by running high current through a resistive heating element, and this could apply dangerous voltages to your circuit.
For solder, we recommend starting out with a lead-based solder, usually called 63/37 (63% tin, 37% lead by weight) or 60/40 rosin cored solder. Get whatever's cheaper; there's unnoticeable difference in hand soldering between 63/37 and 60/40. The rosin is a flux that cleans parts so solder will bond with them. Avoid solid wire (no flux core) and acid cored solder (for plumbing, too aggressive for circuits). We recommend solder that's about .031" in diameter for most through-hole components. Water-soluble flux is much more aggressive than rosin, and these residues must be cleaned. Lead-free solder melts at a higher temperature, and doesn't wet or spread out as readily, so it will be slightly harder to use.
- Needle Nose Pliers: Useful for pre-bending leads, pulling out components during de-soldering, and a lot of other things.
- Wire Strippers: Two types are shown: the yellow ones can be adjusted to strip any size wire (good for small 28-30 AWG ribbon cable wires) whereas the red handled ones have several fixed hole sizes.
- Flush Cutters: Used to trim leads close to the board after soldering .
- Clamps: Oftentimes just resting your board on a table will be fine, but the clamps are especially helpful when desoldering parts or soldering wires together.
- Solder Sucker and Solder Wick: Both are inexpensive ways to remove solder. The sucker is a spring loaded tube that vacuums out solder and the wick is a fine braid of flux coated copper that soaks up solder.
- Multimeter: Some multimeters have a continuity check that beeps if there is a complete circuit. This is very useful for making sure parts are connected or disconnected when there're a lot of wires and parts.
-Pink Erasor: (not shown) A pink eraser can be used to rub off oxides from older components and boards without risking damage to the parts.
For solder, we recommend starting out with a lead-based solder, usually called 63/37 (63% tin, 37% lead by weight) or 60/40 rosin cored solder. Get whatever's cheaper; there's unnoticeable difference in hand soldering between 63/37 and 60/40. The rosin is a flux that cleans parts so solder will bond with them. Avoid solid wire (no flux core) and acid cored solder (for plumbing, too aggressive for circuits). We recommend solder that's about .031" in diameter for most through-hole components. Water-soluble flux is much more aggressive than rosin, and these residues must be cleaned. Lead-free solder melts at a higher temperature, and doesn't wet or spread out as readily, so it will be slightly harder to use.
- Needle Nose Pliers: Useful for pre-bending leads, pulling out components during de-soldering, and a lot of other things.
- Wire Strippers: Two types are shown: the yellow ones can be adjusted to strip any size wire (good for small 28-30 AWG ribbon cable wires) whereas the red handled ones have several fixed hole sizes.
- Flush Cutters: Used to trim leads close to the board after soldering .
- Clamps: Oftentimes just resting your board on a table will be fine, but the clamps are especially helpful when desoldering parts or soldering wires together.
- Solder Sucker and Solder Wick: Both are inexpensive ways to remove solder. The sucker is a spring loaded tube that vacuums out solder and the wick is a fine braid of flux coated copper that soaks up solder.
- Multimeter: Some multimeters have a continuity check that beeps if there is a complete circuit. This is very useful for making sure parts are connected or disconnected when there're a lot of wires and parts.
-Pink Erasor: (not shown) A pink eraser can be used to rub off oxides from older components and boards without risking damage to the parts.
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Anyone knows how to remove some shiny black laquer often found on top of components, probably to obscure their make?
Michael
You can see the schematics and parts lists here
Acid core is not too aggressive for circuits, in fact for aged parts it is the preferred solution but it absolutely must be completely cleaned off later. In fact, with today's lead free soldering the industry is using more aggressive fluxes than the old rosin core was, BUT for a hobbyist using new parts I agree rosin core (or no-clean, depending on the project requirements) would be the best choice for typical soldering.
Another *tool* to have is liquid flux. Usually, people apply too much solder to a joint just trying to get enough flux on to make it flow good. There are solders with 3% flux instead of 1 or 2% that will do better or using a separate liquid flux will be the best result. Liquid flux also is very handy when using desoldering braid, allowing excess solder to be removed more quickly and gently by reducing the amount of heat applied, even if the braid had a little flux in it already.
Solder guns do not apply dangerous voltages to a circuit. Not possible. They use an isolating transformer and very low (isolated) voltage. However they are too hot running for most hobbyist electronic work and yet for some jobs, there is no way a 25-30W iron would get the job done so either a heftier iron with stouter tip or a gun would be required.
The aggressiveness of a flux is independent of it's form, whether paste or liquid. The two main choices for electronics are rosin-based (comes from pine sap, actually) and water-soluble (you can also call this an "acid" type). All water-soluble fluxes need to be cleaned with warm water to prevent corrosion, and are generally used for older / corroded parts. Rosin-based fluxes are generally less aggressive, which means it won't be able to remove as tough of oxides, but it will also be less likely to corrode the board later. There's a large range of rosin-based fluxes varying from "no-clean" types (although "no-clean" can apply to anything, it's more of an ad than a scientific standard) to very aggressive "activated" fluxes.
In the end, if it's water-soluble, you need to clean it, and if it's rosin-based, you need to know how aggressive it is to decide on cleaning.
Neat idea for home-brew wick.
I could be wrong on this, but doesn't "acid-core" usually refer to copper pipe solder? I'm used to seeing "water-soluble" as the electronics version that is certainly safe to use if it's cleaned thoroughly.
Good stuff about using liquid flux with braid.
On solder guns, I guess the first question to answer is "How much voltage could damage a circuit?" The Weller WES51 brags about having a grounded tip with 2 mv RMS or less voltage, and also zero power switching. What kind of a circuit would be affected by, say, 5mV? 20mV? 1V? Certainly the solder guns don't have 120V at the end, but I'd bet it's in the single digits... correct me if that's off.
Even if an isolation transformer is being used, isn't there some risk that the current would go through your parts instead of the resistive heating element? The ColdHeat brand soldering iron doesn't even have a heating element, you have to complete the circuit with your component (The tip is shaped like a fork).
You may also want to check out sites of manufactures like Kester.
Kester Knowedge Base
Here is some info on lead-free hand soldering. (I have difficulty with most lead free solders because it does not wet well)
Lead Free Hand Soldering (the pdf link was broken, this one seems ok)
MIT also has some info:
http://web.mit.edu/6.270/www/contestants/workshops/1-Soldering.pdf
For folks who are starting out or who want to improve their skills, practice more. I think three weeks of class were spent soldering wires together, then having it inspected by the instructor, being rejected and starting over. That's a lot of rejection but eventually we all got it right. The best part of the class was learning what a good solder joint looks and feels like. It has helped me A LOT as an engineer.
http://engr.nmsu.edu/~etti/fall97/electronics/solder.html
But back to the question... what would be an ideal heat delivery and / or temperature? So we want to heat the joint without heating the component or damaging the board...
As shown in this video, using a small 25 Watt iron on a large wire results in high temperatures far away from the end of the wire (where you don't want them), since most of the heat is "sucked" away before it actually goes into heating the end.
One thought is to use an extremely hot iron all the time, so you can get the connection above the melting point of solder before the heat has a chance to spread.
But this goes against the advice from a lot of reputable sources (IPC soldering instructors) I've heard stating that lower temperatures are almost always better. In fact, most high end soldering stations can be locked to prevent operators from using too high of a temperature.
I suppose every different situation would have it's own ideal heat / temperature...
One more thought: in industry, entire boards are elevated above the solder melting point for more than a minute or two as they travel through reflow ovens.