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Soldering- where to start?

Craft & Design Technology
Soldering- where to start?

Certainly there are lots of electronics and kits that have entered Makers’ lives lately. Some people already know how to solder, but many people are just getting started. Amy posted a comment voicing her frustration at learning the seemingly guild like skill of soldering.

Below are my notes to Amy, which seemed like it would be handy information to others as well.

It can be done, this soldering thing.

Here are a few things that I try to keep in mind.
Setting up on a reusable board or thick cardboard (not the corrugated kind) is good, because cleanup will be easy, and you won’t run the risk of messing up the table.

Soldering iron
A decent iron is nice, but a cheap one can do. Turn off the cheap irons when not in use, because the tip seems to dissolve if left on. You don’t need to spend lots of money on a fine expensive tool if you are just figuring it out. You can learn how to do it on a cheap or borrowed iron, then when and if you can recognize the difference and value, then spend the money or talk somebody into gifting you a good one. Lots of people like the temperature controlled ones from Weller.

Keep the tip clean. A wet sponge works, but I like steel wool better. Wipe the tip periodically. The sponge will cool the tip when you want it to be hot.

A soldering iron stand is good, but at least keep the business end of the iron from burning a hole through the board and onto the table.

Thin, lead free solder is good. Try to stay away from the lead based stuff. See the earlier comment about metals and the badness they cause.

Safety glasses
Most people only get one set of eyes. Replacements are difficult to have installed. You are better off to take care of the pair or one you have, than to get them repaired later. Wear your safety glasses while doing dangerous stuff.

Recognize the components:
Pretty much all electronic components have markings on them. Mostly they are done in small white print, but resistors are indicated with color bands. Look at the parts list, and search the markings on any components you are not familiar with. If you put a single diode or LED in backwards, that could be the problem that makes your circuit not work. Check and double check. Search for the things you have, and look at pictures of them. Check the documentation that comes with any kit you have for notes about what the components look like and how to handle them.

Looking at the pdf for the kit Amy mentioned, there are a few things that could slip you up. LEDs, transistors and capacitors are all polarized in this circuit. Make sure they are all in the right orientation. The transistor might be exotic, here is a page that has datasheets for it. l According to this page, you could use a 2N3904 to replace the BC547. The 3904 is a pretty common transistor, you should be able to harvest one out some junk device like a radio or toy.

Resistors are not polarized, but the color bands are completely essential to get right. Resistors regulate the flow of the current in the circuit. Electricity will always follow the path of least resistance. If you have a high value resistor in a place that calls for a low value one, electricity will not flow where it should. You can read them by looking at the colors. There are lots of great resistor color code calculators. Here is one that looks good, but there are many more online.

Resistance is measured in Ohms, often symbolized by an upside horseshoe, greek symbol for omega. If you can get your hands on a meter, you can set it for Ohms, and check your color band calculations against the numbers the meter will show. A multimeter is also handy to be able to check continuity and voltage. See this page for some info on how to use a multimeter.

You are heating up the parts, not the solder. When the parts are hot enough, the solder will flow onto them. Touch the iron to the junction between the board and the component, let it heat up, then touch the solder to either the board or the component. Dumping it onto the tip will melt the solder, but often results in a cold solder joint.

Less is better in soldering
You should have the very least amount of solder needed to hold the component to the board. If you have blobby solder joints, you will likely have trouble with bad connections called cold solder joints.

Practice soldering
Sometimes it is a good idea to practice on junk. You can try soldering a wire onto a coin, US pennies work pretty good for that, they are mostly zinc with a bit of copper. Lots of other countries have other alloys, often with lots of aluminum in them, so I don’t know about that. Aluminum wicks the heat too fast, so it probably wouldn’t work.

You can also break apart an old radio or other device, cut some wires, get some parts and just solder some stuff together. After a bit you get the hang of it.

If you use the search box on any of the Maker Media sites and put in the word soldering, there are loads of resources that should help you get started.
You can watch the Make Weekend projects podcast on soldering, which is great.
Make Volume 1 had a primer on soldering.
Check out the post about a photo gallery of soldering basics.
Check out this great project for building your own fume extratctor.

There is lots of great information on soldering at Instructables.

This is not some mystical skill that people get handed to them from the tinkering gods. You learn it by doing it. You do it because you want to make something. You keep doing it because you want to make more interesting things. Learning this is just a process of getting some skills, and improving them by using them. Eventually, you can get to the point of designing your own circuits, but you can do lots of great things by following the path established by others. There are a small handful of tools that you can use with soldering and electronics. This kit has pretty much everything you need to get started.

Good luck, keep at it, and by all means, let us know about your progress.

You may have other tips for people who are new to electronics, kits and soldering. Please contribute your techniques and ideas in the comments. If you have photos and video, add them to the Make Flickr pool.

24 thoughts on “Soldering- where to start?

  1. Anonymous says:

    Lead-based solder is much better as a solder and presents about the same level of personal danger as “lead-free” solder. All the “lead-free” craziness of late stems from a) political stuff, b) negative consequences of lead collecting in garbage dumps. It’s not related in any way to manual soldering in small quantities. So it’s highly recommended to use lead-based solder in personal projects and especially for learning how to solder.

    1. Anonymous says:

      The “hype” around lead referred to in several comments comes from children being poisoned by lead, not your hobbies – it is necessarily political because that is where regulation happens. The vast majority of documented lead poisoning cases in children arise from lead paint hazards in homes and child occupied facilities, not adult hobbies.

      The is does NOT mean that lead is safe for adults to work with. It is still a poison, and there is no known benefit of lead in the human body. Adults can be and are lead poisoned through hobby work. If you work with lead solder without proper precautions there are two potential risks.

      First, you may become lead poisoned. Second, your child may become lead poisoned. If you have lead products in the house please be conscious about your work, clean-up/storage, and the project itself in which you utilize lead.

      Adult symptoms of lead poisoning include and begin to be observable at a blood lead level of 15 ug/dl in women:
      * Elevated blood pressure
      * Headaches
      * Muscle aches
      * Reduced Hemoglobin
      * Anemia
      * Reproductive function
      * Nerve dysfunction

      Symptoms of lead poisoning in children also include:
      * Lower IQ
      * Behavior problems and aggression
      * Kidney problems
      * Death

      The developmental effects of lead in children are not reversible.

      The only way to diagnose lead poisoning in either children or adults is a blood lead level test – it is not diagnosable through symptoms. Just because one has been working with lead solder for 30 years without individually identifiable symptoms does NOT necessarily mean one’s BLL is at a safe level. The ONLY way to know is through a blood lead level test easily performed by a doctor.

      It is strongly recommended that adults who work with lead either on the job or as a hobby be tested, as well as their children.

  2. anachrocomputer says:

    Some of the best advice I received when beginning soldering was “The soldering iron is not a spoon”. That is, you should not use the iron to carry solder to the joint. The soldering iron should heat the joint, but the solder should be applied to the component leads, not the tip of the iron. Of course, you’ll need some solder on the tip of the iron, just to help form a good thermal contact with the joint.

  3. Phillip Torrone says:

    @Anonymous – i tend to agree, for adult hobbyists i think lead is fine too.

  4. Xmas says:

    “The transistor might be exotic, here is a page that has datasheets for it. l According to this page, you could use a 2N3904 to replace the BC547. The 3904 is a pretty common transistor”

    The BC547 isn’t exotic. It is as common and general-purpose as the 2N3904 or 2N2222. The BC547 is a marking used more frequently outside of the US, so might seem to be uncommon.

    Again, for troubleshooting at least the LED portion of the circuit, temporarily shorting the collector and emitter leads of the transistor would light 4 of the LEDs if they are soldered in correctly. Or, as I mentioned in the other thread, a temporary touch of a wire from 9V negative to each lead on the LEDs should light one or more of the LEDs. Take for example LD4 in the diagram – touching the wire to one of the leads of that LED has no effect, the other lead will light the LED. Then move on to LD5. This troubleshooting will at least help discover issues with >50% of the components in this circuit.

  5. signal7 says:

    I’ve been soldering with lead based solder *and* without a fume extractor for 30 years. I don’t show any signs of lead poisoning despite what many of these websites would tell you. The only reason to use lead-free solder today is for manufacturing or if you happen to be concerned about the environment. The risk to your health is pretty low so long as you aren’t eating at the same time you’re soldering or something like that. Use a fume extractor if you feel the need, but it’s not an absolute requirement unless you’re spending 40+ hours a week with a soldering iron in one hand.

  6. Aud1073cH says:

    Keep the tip of your soldering iron clean.
    I wish I had been told this early on.

    Flux and other impurities in the solder cooks on the tip of your iron and leaves a layer of black and brown oxidization. This will tend to insulate the tip, making it difficult to easily transfer heat to the parts.

    Use a damp soldering sponge (not wet) to wipe the crud off of the tip of the hot iron to get it clean and shiny again.

    A soldering sponge will resist more heat. A regular sponge may tend to melt or scorch faster.
    I like the sponges with the little holes in them, so the solder blobs have somewhere to go.
    A tip cleaner using metal wool will clean without cooling the iron (like Jameco P/N 156777)
    Or you can use a metal scouring pad. Pick a soft metal like copper to make your tip last longer.

  7. chic says:

    .. is to ‘tin’ the individual components before making the connection. and making a mechanically good joint before applying solder.

  8. says:

    About lead…

    Yes, you’re not supposed to eat, drink or smoke while soldering or cleaning your PCB with isopropyl alcohol. It’s also good idea to wash hands before going to toilet. Even some christmas lights carry notice “may have traces of lead – wash hands after touching”.

    Just basic hygiene. Wash hands often. Can’t be too hard.

    But well, fumes… It’s unlikely that you could get lead fumes. Dangerous fumes come from flux. Lead-free solder generates more fumes due to more aggressive fluxes. With lead-free, it’s also more important to use soldering station (for right temperature).


  9. Steve Anderson says:

    Since I discovered this (I can’t remember where I first read it or who told me it) I’ve passed it on to anyone with soldering to do: use the (steel) side panel of a junked PC as your work surface. Not only will it help dissipate heat, protecting the surface underneath, it also means you can use magnets to hold things in position. It’s not hard to find these panels either!

  10. ketemphor says:

    Fume extractors are (or should be) designed to remove resin fumes from the air, not lead fumes. Lead gives off next to no vapors even at its boiling point at normal atmospheric pressures (I did the calculation once, it was somewhere in the parts per trillion range). Prolonged exposure to resin vapors (from the flux that is in most most solder) can lead to asthma-like conditions.

    My biggest suggestion to anyone learning to solder is to skip the super-cheap irons. In my not so humble opinion, a temperature-controlled iron is absolutely essential.
    Even the lowest-wattage uncontrolled iron will reach 800+ Fahrenheit after a few minutes. This is WAY too hot to solder efficiently.
    First: an iron that is that hot will vaporize any flux in your solder instead of just melting it. If you’re getting little puffs of heavy white smoke when soldering, that’s why. The flux vaporizing and not doing its job of cleaning the interface surfaces like it should.
    Second: Your tip will oxidize like crazy (say within 2 to 3 minutes) at those higher temperatures. An oxidized tip will not transfer heat properly and will make soldering very difficult. Even using steel or copper wool (which was a good suggestion over the standard wet sponge), it is difficult to clean this combination of oxidation and burnt flux off of the tip.
    You can get a cheap temperature-controlled iron for ~$50 if you look around a bit. Make sure it is really temperature controlled and not just “power”-controlled. The first iron I ever bought with a ‘control’ on it was simply using a TRIAC before its rectifier to reduce the power going to the tip. As I said before, even at low power, the tip will eventually heat up to very near its max temp when not being actively used.
    With a temp-controlled iron, shoot for 500-550F for soldering and 600-625F for desoldering.

  11. ketemphor says:

    This is a very nice starting iron for $50:

    I ordered one from this site about 3 years ago and since their shipment was a week late, they upgraded me to the digital readout version for free. That was the Xytronic 137ESD, which I believe is discontinued now.

    And it comes with a nifty stand with a brass/copper wool cleaner in the base. Thought I’d share … :)

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