How To Solder and Desolder Connections

Before you begin soldering, note the following safety precautions: Never solder on devices that are powered on or plugged in. Unplug, turn off, and remove power sources before soldering. Don't solder directly to hard-shell lithium-ion batteries (such as 18650 cells)—the heat will damage the battery internals. Use a battery spot welder instead. Be extremely careful if you're soldering/desoldering lithium-polymer battery wires! You can easily short the battery with solder or your tools, resulting in battery damage and a fire hazard. Follow these precautions: Drain the battery below 25%. This reduces the battery's ability to start a fire if it was short-circuited. Work with one wire at a time to prevent shorts. Use tweezers to control movement and ensure the wire doesn't short. If you're desoldering a battery from a circuit board, use flush cutters to cut each wire one-at-a-time before desoldering to isolate the battery. Whenever possible, create an indirect path by soldering connectors onto the battery and the circuit board. This reduces the chance of an unintentional short.

Through-hole soldering ↗ refers to threading components with leads through holes on a circuit board, then securing them with molten solder. Through-hole soldering is prevalent in DIY projects and modern electronics, where it's used to secure large components (such as capacitors and ports). Common through-hole components include joystick modules, ports, capacitors, microcontrollers, batteries, and wires.

The next 10 steps will show you how to solder through-hole components onto a circuit board. In addition to a soldering iron, you'll need: A vise, clamp, or "Use an iOpener or " tool. If you're joining two wires, our Use an iOpener or is a great tool. A pair of Use an iOpener or (eyeglasses will protect your eyes, but solder spatter will damage the glasses). Rosin-core solder wire (Use an iOpener or or Use an iOpener or ) A tip cleaning tool (wet sponge or Use an iOpener or ) A fume extractor → (if you're working indoors) High concentration (>90%) isopropyl alcohol and a Use an iOpener or (like a toothbrush) A Use an iOpener or , Use an iOpener or , and Use an iOpener or

Use an iOpener or in a well-lit area, away from anything flammable. Secure the circuit board with a vise or a "helping hands" tool. Angle the board such that you can easily access the solder pads. Place the fume extractor close to the project so it'll catch the solder fumes. Wear your safety goggles.

Thread the component leads through the circuit board holes. Most components should lie flat, close to the board. Double-check the orientation if the component is electrically directional (such as diodes, LEDs, and electrolytic capacitors). Diodes normally have a bar indicating the cathode (-). LEDs have a shorter lead on the cathode (-) and a flat spot on the dome.

Bend the leads out slightly to help keep the component in place. Alternatively, you can use painter's tape to secure the component.

Turn on your Use an iOpener or . If your soldering iron has temperature control: Set it to 300 °C (~570 °F) if you're using leaded solder Set it to 375 °C (~700 °F) if you're using lead-free solder Clean the tip of your soldering iron. If you're using a sponge, wet the sponge and quickly wipe the tip across it. If you're using brass wire, stab the tip into the wire a few times.

Melt a small glob of solder onto the tip of the iron. This is called "tinning the tip" and will help with heat transfer. You'll likely see some wispy smoke as you melt solder. This is mostly the rosin-core flux that's built into the solder wire. Flux helps molten solder flow, but gets vaporized over time. Once that happens, you'll need to either melt more solder to refresh the flux, or apply flux from an Use an iOpener or . If you're new to soldering, repeat the cleaning and melting steps a few times to get a feel for how molten solder flows and how much the tip can hold.

You're going to heat the solder pad and the component lead very hot for 2 to 3 seconds. The pad and lead should readily melt the solder wire. Press the tip against the circuit board's solder pad and the component lead for about 1 second to heat them both. Angle the tip so it has maximum contact with the pad and lead. If you're using a narrow tip or working on a large solder pad, you may not be able to transfer enough heat to the area. You can try increasing the temperature by 50°C or switch to a larger tip for more effective heat transfer. Don't heat the area for more than 10 seconds, or you risk damaging solder pads, components, and loosening nearby parts. Feed the solder wire into the heated area until there's a concave pool of solder surrounding the lead. This should happen within a few seconds. If the solder doesn't adhere to the pad, apply flux to the pad or increase the temperature. Remove the solder wire, then lift the soldering iron from the pad.

Congratulations—you've created a solder joint! Inspect the joint to see if it formed correctly: Leaded solder joints should look like a shiny, concave tent surrounding the entire lead. If the joint isn't shiny, it may not have formed correctly. Reheat the joint briefly and allow it to cool. Lead-free solder joints should look like a concave tent surrounding the entire lead. They may be shiny or dull. If the solder joint doesn't surround the entire lead, reheat the joint and add more solder. If the solder looks like a round bead instead of a concave tent, it didn't bond to the component lead. Reheat the joint and try to get the lead hot enough so the solder bonds to it. Check for unintentional solder bridges between joints. If you find one, apply flux and reheat a joint to break it. If it won't separate, use solder wick → to remove the excess solder. Like any skill, practice makes perfect. If your first solder joint doesn't look picture-perfect, that's OK! It takes a few attempts to get the hang of the movement and timing.

After soldering all the leads, use a flush cutter to trim them just above each solder joint. Leave a glob of solder on the tip (tin the tip) before you turn the iron off. If you're using rosin-core solder, wait till the tip stops smoking. The solder glob protects the tip from getting dirty or oxidized and extends its life.

Apply some isopropyl alcohol to the solder joints and scrub the area with a soft-bristled brush to remove any flux residue. Wipe the solder joint with a lint-free cloth to soak up the flux and alcohol residue.

If you're soldering a component with multiple through-hole leads (such as a joystick module, microcontroller, or port), solder two opposite leads to hold the component position in place. Check the alignment, then solder the remaining joints. Alternatively, you can bend two opposite leads to secure the component to the board while you solder. If the molten solder doesn't flow or is hard to manipulate, apply more flux to the joint.

The next 8 steps will show you how to desolder through-hole components using a solder wick and desoldering pump. If you're new to soldering, be sure to read the soldering steps above first, as this builds upon that knowlege. In addition to the soldering equipment, you'll need: Use an iOpener or (aka desoldering braid) and/or a Use an iOpener or . Use an iOpener or A spudger, tweezers, and/or pliers (to help loosen stubborn components)

Hold the circuit board steady in a vise or helping hands tool. Tilt it so you can easily reach the solder pads. Wear safety goggles. If possible, use a tip with the largest surface area that can still fit between the solder joints. Turn on your soldering iron. If your soldering iron has temperature control: Set it to 350 °C (~650 °F) if you're using leaded solder Set it to 375 °C (~700 °F) if you're using lead-free solder

Clean the tip of your soldering iron. If you're using a sponge, wet the sponge and quickly wipe the tip across it. If you're using brass wire, stab the tip into the wire a few times. Melt a small glob of solder onto the tip. This will help with heat transfer. If you're desoldering with a solder wick, proceed to the next step. If you're desoldering with a desoldering pump, skip to this step →.

You're going to melt the solder joint through the wick, allowing the wick to draw the molten solder into itself. Apply a bead of Use an iOpener or to the solder joint. Place a clean portion of the solder wick on top of the solder joint. Press the soldering iron tip firmly against the wick for 2-3 seconds. You're trying to heat the wick hot enough so that it melts the solder underneath it. If you heat the circuit board continuously for more than 10 seconds, the excessive heat may damage the solder pad. If the wick doesn't draw solder, you may need to increase the temperature. The wick may also be oxidized due to age—apply more flux or try a newer roll of wick. As the solder saturates the wick, slide the wick so that a new portion touches the joint. You'll know it's saturated when the wick's color changes from copper to silver. Once most of the solder has soaked into the wick, lift the wick and tip away together from the joint.

Use tweezers to grip the component and remove it. If the leads are stuck but don't have a lot of residual solder, heat the solder pad directly and use tweezers or a spudger to gently remove it. If there is still a lot of solder left on the pad, apply more flux and try using the wick again. Use flush cutters to remove your used wick. When you're done desoldering, follow this step → to clean up your board.

To desolder with a desoldering pump, you're going to heat the solder joint and use the pump to suck up the molten solder. If this is your first time using a desoldering pump, check out this guide →. Depress the desoldering pump plunger until it locks in place.

Press the soldering iron tip against the solder joint. Once the solder melts, position the pump nozzle as close to the molten solder as possible without touching the tip. The nozzle is made of heat-resistant plastic, so don't worry if you occasionally brush the tip with it. Press the side button to activate the pump and suck up the molten solder.

Use tweezers to grip the component and remove it. If the leads are stuck but don't have a lot of residual solder, heat the solder pad directly and use tweezers or a spudger to gently remove it. If there is still a lot of solder left on the pad, heat the pad and repeat the solder sucking procedure to remove any remaining solder.

If your desoldering pump doesn't remove all the solder and you're having trouble heating the joint, apply some more solder and try again. The extra solder helps transfer heat to the pad. If you're still having trouble melting the solder, apply some Use an iOpener or to the joint to keep it liquid for longer. Clean your soldering iron after using low-temp solder to avoid brittle joints from mixing low‑temp solder with standard solder. If you desolder a lot of pins or do a lot of desoldering work, a dedicated desoldering station or Use an iOpener or is a good investment.

Surface-mount soldering ↗ attaches components directly to a circuit board's surface. Most electronics manufacturers use surface-mount technology (SMT) because it's easy to automate and cost-effective. In industrial manufacturing, a machine uses a stencil to apply solder paste to the circuit board. Robotic arms precisely place ↗ each component. The board then passes through an oven, melting the solder paste and bonding the components in place. Surface mount components are much smaller than through-hole components, so they're harder to solder by hand. But with a bit of patience, practice, and a good magnifying glass, you can become proficient in surface-mount soldering!

The next 6 steps will show you how to solder surface-mount components onto a circuit board. You'll need a fine-tipped soldering iron in addition to the following: Solder wire (Use an iOpener or or Use an iOpener or ) or solder paste Use an iOpener or Use an iOpener or and Use an iOpener or to help manipulate the tiny components A tip cleaning tool (wet sponge or Use an iOpener or ) A magnifying glass or lens A fume extractor → (if you're working indoors) High concentration (>90%) isopropyl alcohol and a Use an iOpener or (like a toothbrush)

Set up your tools in a well-lit area, away from anything flammable. Set the circuit board on a flat, non-flammable, heat-resistant surface or secure it with helping hands or a Use an iOpener or . Place the fume extractor close to the project so that it'll catch the solder fumes. Wear your safety goggles.

Apply a small bead of flux onto each solder pad. If you're using solder paste, apply a small amount of paste instead. Most solder pastes contain flux. Use tweezers and picks to carefully maneuver your component so that it straddles between the solder pads. This can be very tricky depending on the size of your component! Take your time and don't press against the component too hard, or you may fling it out of place. Double-check the component orientation if it's electrically directional (such as LEDs and diodes). These components normally have a bar indicating the cathode (-) end.

Turn on your soldering iron. If your soldering iron has temperature control: Set it to 350 °C (~650 °F) if you're using leaded solder Set it to 400 °C (~750 °F) if you're using lead-free solder Clean the tip of your soldering iron. If you're using a sponge, wet the sponge and quickly wipe the tip across it. If you're using brass wire, stab the tip into the wire a few times. If you're not using solder paste, melt a small amount of solder onto the tip. You'll transfer this solder onto the joint.

Carefully press a tweezer point or the tip of a spudger on top of the component to hold it in place. The soldering iron will spill a lot of heat around the point of contact, which can easily loosen surrounding components. Be careful not to bump the surrounding parts with your tools. Touch the soldering iron tip to the solder pad and the component. Once the pad heats up, it will draw the molten solder onto itself. This should happen within a few seconds. If the solder doesn't adhere to the pad, apply more flux to the pad or increase the temperature. Don't heat continuously more than 10 seconds at a time, or the heat may damage the component and solder pad. Allow the circuit board to cool down, then try again. Remove the tip from the solder joint. Repeat this process for the rest of the component leads.

Be gentle when you're cleaning small components as they can easily break off the board. Apply some isopropyl alcohol to the solder joints and scrub the area with a soft bristled brush to remove any flux residue. Wipe the solder joint with a lint-free cloth to soak up the flux and alcohol residue.

Many surface mount components (especially integrated circuits) have multiple leads that need to be soldered. They can be difficult to align and secure to the board: Hold the component in place and solder the corner leads to secure it in place. Alternatively, you can secure the component to the board using Use an iOpener or and then solder the corner leads.