How to solder

Soldering tools

Soldering Station

We have soldering stations at the benches which allow us to control the temperature of the soldering iron. Our stations include a soldering iron stand which is where the soldering iron should be placed when not in use to prevent injury or accidental melting of other materials.

Brass sponge

The brass sponge is used to wipe excess solder off the tip of the soldering iron. Alternatively a conventional wet sponge can serve the same purpose but can shorten the lifespan of the tip.

Solder

Solder is a metal alloy that is melted to form that conductive bond, essentially it's our conductive hot glue. It looks like wire on a spool but will melt at a much lower temperature. Solder can come in different gauges and can be leaded or unleaded. Leaded solder is easier to solder with as it has a lower melting temperature but does have some health concerns. It is important to use ventilation and wash hands after use with this type of solder. 

Helping Hands

The helping hands we have in the space have four adjustable arms with alligator clips to hold your circuit board or electrical components to provide an extra hand with soldering. 

Soldering tips

The tip of a soldering iron can be replaced with different shape tips for different soldering applications. Typically we will use the conical tips for most applications. 

Tweezers and Needle Nose Pliers

Tweezers can be used for holding small components. Needle nose pliers can be used for larger components when tweezers do not work. 

Tips

Before we get started, check out these couple of tips!

Hold the soldering iron in your dominant hand and the solder in your other hand. Unspool some solder so you can easily hold it.

Try not to use too much solder! It's easy to add more solder but difficult to remove excess solder.

How to Solder

This video covers some of the steps below.

Set your iron temperature to 650°F for leaded solder or 700°F for unleaded solder.

The Weller soldering irons light solid green when heating up and flash green when at temperature. 

2. Tin the tip

Once the soldering iron is hot, wipe it on a wet sponge or brass sponge. Wait several seconds for the tip to return to the desired temperature, then touch solder to the tip ensuring it flows evenly around the tip. 

3. Mount the component

Insert your component through the top side of your circuit board. Flip the board over so the bottom side is facing up. If possible, bend the legs of your component so it will not fall out, otherwise use your helping hands to hold the component in place. It is helpful to mount the board in the helping hands.

4. Heat the joint

Use the soldering iron to touch the copper pad (metal ring) and the lead (metal leg) together known as the joint at the same time. Hold it there for several seconds to heat both the pad and the lead.

5. Apply solder to the joint

Keep the soldering iron touching the pad and lead and touch your solder to the joint. Only bring in your solder after you have heated the joint. Don't touch the solder directly to the tip of the iron. If your solder is not melting when just touching the joint, it may need to be heated more. 

6. Solder other pins

Once the first pin is soldered, the component should be fixed into place. If the component is not sitting correctly, reheat the single pin and use a tool like tweezers or needle nose pliers to fix it. Then solder the remaining pins. It is very difficult to change the orientation of the component once multiple pins are soldered.

7. Snip the leads

For components with long leads, you should cut them off with flush cutters.

8. Tin the tip

Before shutting off the soldering iron, tin the tip again by wiping it on the brass sponge and applying solder to the tip.

Examples of Good and Bad Solder Joints

Poor quality solder joints are usually because the pin and pad are not heated before solder is brought in or the solder directly touches the soldering iron. 

Remember, you are looking for a nice cone shape and trying to avoid a short which is a connection between two pins with solder. 

Soldering wires

1. Strip the wires

Using the wire strippers in the drawer, place the end of the wire in between the jaws and then squeeze on the handles to bite on the insulating cover and pull it off.

2. Tin the exposed wires

Twist the wires between your fingers to ensure they are not frayed and then apply a bit of solder to the end of each wire. You may have to hold the wire in the helping hands.

3. Add heat shrink

Slide heat shrink over one of the wires. Choose a size that is only slightly larger than the thickness of the wire.

4. Twist together the wires

Twist the ends of the tinned wires together and clamp them in the helping hands.

5. Heat the wires 

Heat the wires with the soldering iron to melt the solder and connect the wires.

6. Heat the heat shrink

Slide the heat shrink over the newly soldered joint and hold the soldering iron close to heat and shrink the rubber tube over the joint. You may have to use needle pliers to bend down the wire ends. 

Try not to touch the heat shrink with the soldering iron as it can burn. You can also use a heat gun instead.

Heat shrink is used to insulate the exposed soldered wire. This prevents it from contacting another wires and creating a short.

Alternative Method

Another, potentially easier method is to twist the wires together before adding solder.

Surface Mount Soldering

1. Add solder to one pad 

First heat the pad for several seconds then bring in the solder to melt a little onto one pad.

I recommend taping your board to the table or finding another way to keep it from sliding around.

2. Solder component to one pad

Use tweezers to hold the component in place on the circuit board with one hand and bring the soldering iron in with the other hand to melt the solder on the pad. Move the soldering iron away once the solder has melted around the pin/pad of the component. 

3. Add solder to other pads

Use the soldering iron and solder to add solder to all other pins/pads of the component.