Tutorials

SOLDERING SUPPLIES & SAFETY

by Carrie Sundra

**THIS PAGE IS STILL UNDER CONSTRUCTION**

02/09/2024 - We've made it live because it contains all of the written info we can think of for now, and we're soliticing feedback from friends, colleagues, and a few test soldering groups.  We'll be adding photos and links over the next few weeks.

Important Safety Tips!

Safety tips are interspersed throughout the following discussion of supplies, but here are the most important things to remember while soldering:

  • Wear eye protection
  • Avoid burns! Don't touch the hot metal parts of the soldering iron
  • Solder in a well ventilated area and/or use a fume extractor
  • Don't solder on a flammable surface - use a solder mat
  • Clear your work area of flammable items
  • Wash your hands after soldering

What is Soldering?

Soldering is a way of attaching components to a printed circuit board (PCB) by melting metal wire called solder.  Solder joints need to be strong so they hold the component in place, and highly conductive so that electrical energy isn’t lost between the PCB and the component.  You can make so many cool things after learning how to solder!  There are great toys (even for us middle-aged kids), wall art, signs, useful tools, robots, planes, cars, etc that you can solder together.  And did I mention LEDs?  So many beautiful colors and patterns can be made by soldering LEDs into different shapes.

SAFETY & WORK AREA

Before you get started, here are some tips that will set you up with a good workspace and help to keep you safe and free of accidental burns & damage!

Eye Protection

It may seem like eye protection is a bit overkill, but sometimes solder can splatter, especially when removing components or removing excess solder.  Solder that's heated to 700F and launched into your eyeball can actually melt through your cornea.  Yikes!  Always wear some kind of eye protection - safety glasses with side coverage are best, normal eyeglasses are the bare minimum.

Hair, Hands, & Body

Use typical workshop safety precautions - if you have long hair, tie it back.  In addition to it being a fire hazard, burning hair smells really gross.  Do not wear plastic gloves while soldering, as they can melt onto your skin if accidentally touched with an iron.  Your bare hands are best because you'll have better tactile feedback, but if you need to wear gloves because of warmth, do not wear any synthetic materials like polyester or synthetic "fleece" because they will also melt into your skin.  Wool is best because the fibers are self-extinguishing, leather is also a good choice.  Wear footwear that covers the top of your feet in case solder splatters on the floor, or in case you drop a hot component.  Don't solder over your lap because melted solder can fall onto it, always solder over your work surface.


Always wash your hands after soldering!  Even if you're strictly using lead-free solder, electronics are not 100% guaranteed to be free of lead.  Components that have a "tinned" surface can contain lead, if you're working on an old board it will absolutely contain lead, and there's just no way to see the lead and confirm that something is indeed lead-free.  Lead is toxic and while the relatively small quantities found in electronics are not immediately fatal, lead can build up in your body over time and cause health problems.  Wash your hands after soldering, and especially before eating.

Soldering Surface, Mats, & Work Area

You’ll need a flat surface that’s heat-resistant, or a soldering mat. There should be nothing flammable directly around your soldering area (no cardboard or tissues).  You can use a very thick wood surface that you don’t care about burning if that’s all you have, but never use anything that you’ll use for food preparation.  Soldering mats are made of high-temperature silicone or plastic that can resist melting and burning when the tip of the soldering iron touches it, and many have handy recesses that help you keep track of components. Thin mats will protect most desks and tables, but note that cutting mats are not soldering mats!  Cutting mats and squishy blue foam anti-static mats are NOT heat resistant and WILL melt and smell bad while doing it.

Ventilation & Fume Extractors

When you solder, visible smoke fumes are created by flux boiling off (more on flux below).  These fumes are mildly acidic and can irritate your throat and lungs if directly inhaled.  Working in a well-ventilated space with tall ceilings is helpful, or soldering near an open window so there's some air movement.  If your space has neither of these, or if you're sensitive to solder fumes, you may want to get a fume extractor.  There are varying degrees of extraction systems, but small fans with charcoal filters are frequently used by hobbyists and small workshops.  Longtime solderers also tend to develop a breathing pattern where they habitually hold their breath while soldering.

SOLDERING SUPPLIES

Successful soldering starts with having the right tools and supplies. There are lot of different types of solder, flux, and soldering iron tips out there, read on to get acquainted with these materials and to learn which ones we like for practicing and why!

Circuit Board (PCB)

You will solder to pads on either the front or back of the circuit board. Pads, and traces that connect pads, are etched out of a thin layer of copper that is bonded to a fiberglass substrate. The pads will look shiny and usually have a gold or silver finish called the "plating" or "finish". The smooth colorful coating is called the "solder mask" (black in the photo above), and it covers the traces to protect them from oxidizing, protect them from shorting if a piece of metal or cut-off from a component lead rests on top of the board, and keeps the solder from flowing down the trace and away from the pad. There is usually one color of solder mask that covers the whole board, it can be anything from green, to black, white, purple, blue, red, or even custom colors.  The writing is called "silkscreen" and is a very durable epoxy that won't wipe off if cleaned with alcohol or even acetone.  It's typically white like the photo above, but can also be different colors like blue, red, black, or yellow.  The traditional circuit board has green solder mask with white silkscreen, but black solder mask is now very common, as is white solder mask, and some boards can use various colors of mask and silkscreen and plating to be quite artistic!  


Circuit boards usually have at least two layers - the front and the back (or top/bottom).  There can also be inner layers that you can't see, which are used for connecting pads on boards with a high density of components, or running power throughout the entire board, or both.  Four layer boards are also very common, and layers can increase from there.

Components

It’s easiest to start soldering with through-hole components. They have metal legs called “leads” which go through a hole in the circuit board. They are soldered to the pad surrounding that hole on the opposite side of the circuit board. Common through-hole components for beginning soldering kits are resistors, LEDs, capacitors, switches, buttons, and battery holders.

Flux

Flux is the most important soldering supply. It’s a mildly acidic liquid that keeps solder joints and pads clean, reduces the surface tension of solder so it flows easily, prevents freshly flowed solder from oxidizing, and helps heat flow from your iron to the board. It allows you to make strong and highly conductive joints. We like flux pens the best because you can easily add just a small bit of flux to a PCB or joint, and they're portable!

There are many different types of flux, and while “no-clean” flux is very common, we think “rosin mildly activated” (rosin RMA) is better for learning. It has more working time under heat, and you can choose to clean it or not after you’re done soldering.  It does tend to leave yellow residue behind, which most people prefer to remove mostly for aesthetic reasons.  Here's more info on different types of flux:


No-Clean: Short working time, low activity, loses its power very quickly and typically only gives you one shot at making a good solder joint.  It can have a very perfumey smell.  Perfectly fine and generally preferred by more experienced solderers because it leaves less residue, the residue is typically clear, and sometimes the residue can actually help protect the joint from humidity.  Formulations specifically for lead-free solder will hold up to heat better and have slightly longer working times.


Rosin RMA: Medium working time, medium activity, usually you get a few tries at making a good solder joint before you have to reapply.  Leaves a yellowish residue and smells like pine sap.  Does not have to be cleaned off for short-term applications, though most people prefer to because the residue makes it look visually messy.  Can start to corrode over a timespans of many years, or if exposed to high humidity.


Water-soluble: Longest working time, highest activity, can have a weird fishy smell.  Great for surface mount soldering, and used by most professional circuit board factories with highly automated processes.  It MUST be cleaned with warm water because it will start to corrode joints if left for more than 24 hrs.  Because the flux is more corrosive, solder containing water-soluble flux has a shorter shelf life and tends to be more expensive, especially in lead-free formulations.

Solder

Solder is a mix of metals with a low melting point, which turns to liquid when it touches the soldering iron and turns back to a solid when the heat is removed. Solder comes in a wire form on spools and is very flexible, making it easy to position before soldering. We like using lead-free Sn/Ag/Cu (SAC) solder for low toxicity and easy use. Solder without silver (Ag) will be harder to use. 


Solder also contains a core of flux, which is why it’s possible to solder some large components without adding flux externally. No-clean is the most common type of flux core, though again, we prefer rosin RMA for beginners because of its longer working time.  See more about flux above.

Soldering Iron & Tips

A soldering iron is a handheld metal rod with removable tips that heat up. The iron should be at least 60W output, anything else will be underpowered and more difficult to use. 90W irons are very nice to use, but tend to be more expensive.  The soldering iron should also have a stand that allows you to put the handpiece down when it’s hot. Ideally the stand should store the handpiece point-down, and allow you to pick up the handpiece, solder, and put it back down without readjusting your grip. 


Tips come in many shapes and sizes both to solder a variety of components easily, and to give the solderer the ability to figure out what works best for them.  A versatile tip for starting out is small but not too pointy – like a tiny flat-head (-) screwdriver. Finer soldering may require pointier tips, or (unintuitively) larger tips that can be dragged across many small pads at once.  Very pointy conical tips can be hard to use because they oxidize easily and don't have the power output that larger tips do.  Bent tips are also versatile because they can be used in various positions depending on where you need to reach and how you want to make contact with the pad.  Some people really like using blade-style tips and will use just the point to solder a single pad, or the full edge of the blade to drag-solder many pads.  Start with a screwdriver tip or a not-too-pointy conical tip, then try other styles to see what you like best.

Brass Wool Tip Cleaner

Brass wool is increasingly replacing sponges, though either will work. Brass wool does a nice job of cleaning the tip of the soldering iron without cooling it down or building up residue. If you use a sponge instead, try to use only distilled water to wet it.

Small Cutters

For cutting through-hole component leads after soldering them.  They should be spring-loaded for easy use, have a small thin head with flush back, and be very sharp.  Note that these are ONLY FOR CLIPPING SMALL DIAMETER COPPER.  Do not use them to cut steel (music) wire, aluminum wire, or thick copper wire.  That is how you end up with dented cutters which are then very frustrating to use and should just be thrown in the garbage.  If you do this to someone else's cutters, immediately buy them a new pair and something else nice to atone for your sins.

Circuit Board & Wire Holders

The easiest and often time fastest way to keep your PCB from moving around on you while you solder is to just tape it to your work surface.  Blue "painter's" tape is great for this and many other things - no shop is complete without an ample supply of blue tape!  It can also be used to hold wires while you solder them together (splice them), and is typically on-hand in most shops and many homes.


If you're going to be soldering a lot, there are many types of small vises, circuit board holders, and "helping hands."  They run from cheap to expensive.  The cheapest $5-$10 ones with bare alligator clips and wing nut adjustment and a bonus magnifying glass are generally worthless and not worth the few dollars they cost.  They are difficult to put into position, and breathing wrong on them causes the clips to droop or fall.  The style made out of coolant hose with covered alligator jaws are better, but can still be difficult to adjust.  There are other various snakey arms that may be easier to adjust.  It's important that the base also have some weight or be able to be clamped to the work table, otherwise they tend to tip over.  The best set of helping hands we've ever used hands-down is custom built by a small local machine shop, uses professional camera arms that are easy to adjust and never slip, and I wish they had an ecommerce site up so I could link them.


Small vises abound.  Panavise makes many that are specifically for circuit boards, but their standard mini vise is quite versatile.  The Hakko vise is probably one of the easiest and sturdiest for small boards that have a good amount of flat space to clamp to.

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Happy Soldering!

Thanks for getting to the end of this quite comprehensive guide on soldering safety and supplies!  We know it's a lot of information, and there will thankfully be no quiz in the morning, we just wanted to provide the why and how behind the things we say are our preferences and choices.  We go over all of this when we teach workshops (as do many others), but we know that not everyone has the opportunity to attend in-person soldering workshops, and wanted to give you the best opportunity we could to successfully solder.  We've written this from the perspective of helping a beginner, so like anything, our advice and favorites change depending on what we're actually soldering.  Be sure to check out our How to Solder Video.  For info that's more geared toward surface mount soldering, check out our Guide to SMT Soldering Supplies


We definitely hope this guide has helped you, and if you have any feedback, please reach out via our contact form(Be warned: if you try to mansplain soldering to us, we'll viciously mock you to our friends and then ignore you.)  We hope you solder awesome things, don't forget to @ us and show us what you're up to on social media!