How to

How to Solder Electronics Learning to solder through-hole components is an

essential skill for any amateur hobbyist or electronic

professional. You can learn what equipment and

skills you'll need to get started soldering electronics

properly.

Getting the Necessary Equipment

1 Use a soldering iron with the appropriate heat

control. For soldering electrical components into

printed circuit boards, the best soldering irons are

Electrostatic Discharge (ESD) safe, temperature-

controlled, high-power irons. These will let you

solder for hours, and are good for complex amateur

radio projects. For simple kits, an inexpensive pencil

iron will do just fine.

Use a fixed power soldering iron, 25W for small jobs,

and 100W for larger jobs with heavy cabling.

If possible, variable temperature irons are available,

which will make for the safest treatment of the

boards. The tip temperature can be controlled to suit

the size of the job.

2 Use solder wire of an appropriate alloy. The most

common solder alloy used in electronics is 60% tin

and 40% lead, sometimes notated as 60/40. This

alloy is recommended if you are new to soldering,

though it is somewhat hazardous, requiring proper

ventilation, breathing protection, or a soldering iron

with a vacuum attachment.

Various lead-free alloys are becoming popular

recently. These require higher soldering

temperatures and do not "wet" as well as Tin-Lead

alloys. However they are safer and can be more

effective. 96.5 % tin to 3.5% silver is the most

successful and will produce a joint with less

electrical resistance than any tin-lead alloy.

Both lead and lead-free formulations are available

online at places like solderdirect.com and in your

local Radioshack or Home Depot store.

3 Try to get flux-cored wire if possible. Flux is an

additive in solder that facilitates the soldering

process by removing and preventing oxidation and

by improving the wetting characteristics of the liquid

solder. There are different types of flux cores

available for solder wire.

Rosin is most commonly used by hobbyists. After

soldering, it leaves a brown, sticky residue which is

non-corrosive and non-conductive, but can be

cleaned if desired with isopropyl alcohol. There are

different grades of Rosin flux, the most commonly

used is "RMA" (Rosin Mildly Activated).

No-clean flux leaves a clear residue after soldering,

which is non-corrosive and non-conductive. This flux

is designed to be left on the solder joint and

surrounding areas.

Water-soluble flux usually has a higher activity that

leaves a residue which must be cleaned with water.

The residue is corrosive and may also damage the

board or components if not cleaned correctly after

use.

4 Get the necessary board and

components. Mostly, electrical soldering deals with

"through-hole" components, which are pressed into

printed circuit boards (PCBs). Through-hole

components have leads (wires or tabs) that pass

through a hole in the board and are soldered to the

pad of metal plating around the hole. The hole may

be "plated through" or not.

Soldering other electrical items such as wires or

lugs, have slightly different techniques, but the

general principles of operating the solder and iron

are the same.

5 Get a clamp to hold the components. Electrical

components are usually quite small, and you'll need

tongs, needle-nosed pliers, or tweezers to hold them

in place while you operate the soldering iron and

negotiate the solder. It can be a balancing act.

Some kind of clamp or stand is usually best to hold

the board in place while you solder the components.

Soldering the Components

1

Prepare the components for soldering. Select the

correct component by checking it's type and value

carefully. With resistors, check their color code.

Bend leads correctly, if necessary, being careful not

to exceed the stress specs, and clinch leads to fit

the board.

2 Be extremely careful and solder in an

appropriate location. Always solder in a well-

ventilated area, using breathing and eye protection.

Make sure to prop up the iron when it is on but not in

use. Irons can start fires quite easily by burning into

your workbench.

Seven to twelve inches of space should be between

the electronic components and your face, or it may

jump into your eyes. Solder may splatter.

3 "Tin" the solder. Melt a small blob of solder on end

of the soldering iron. This process is called tinning

and it helps to improve heat flow from the iron to the

lead and pad, keeping the board safe from the heat.

Carefully place the tip (with the blob) onto the

interface of the lead and pad. The tip or blob must

touch both the lead and the pad.

The tip of the soldering iron should not be touching

the nonmetallic pad area of the PCB, or any of the

fibreglass area surrounding. This area can be

damaged by excessive heat.

4 Feed the solder onto the interface between the

pad and lead. Flux from the solder wire is only

active for about one second maximum after melting

onto the joint as it is slowly burned off by heat. The

lead and pad should be heated enough for the

solder to melt not the connection point. The molten

solder should "cling" to the pad and lead together by

way of surface tension. This is commonly referred to

as wetting.

If the solder does not melt onto the area, the most

likely cause is insufficient heat has been transferred

to it, or the surface needs to be cleaned of grease or

dirt.

5 Stop feeding the solder interface is filled. No

more than a drop or two of solder should be

necessary for each joint, though it will vary slightly

for different components. The correct amount of

solder is determined by:

On plated-PCBs, you should stop feeding when a

solid concave fillet can be seen around the joint.

On non-plated PCBs, you want to stop feeding when

the solder forms a flat fillet.

Too much solder will form a bulbous joint with a

convex shape, while too little solder will form a

concave joint.

Soldering Well

1 Move quickly. Unfortunately, it's quite easy to

damage a component or the board with too much

heat. For the most part, however, you can keep the

components and the board safe by moving swiftly.

Keep a finger on the board nearby to ensure that it

doesn't get too hot.

Try to err on the side of irons that are slightly less

powerful than you think you might need. Use a 30

watt iron and practice soldering quickly so as to

avoid excessive heating.

If working with a double-sided circuit board check

both sides for good solder joints. A good joint will

look shiny and cone shaped. if it looks frosty and dull

then it is a cold joint.

2 Consider using heat sinks for sensitive

components. Some components (diodes,

transistors, etc.) are quite susceptible to heat

damage and require a small aluminum heat-sink

clipped on to their leads on the opposite side of the

PCB. Small aluminum heat sinks can be purchased

through electronics supply houses. Hemostats

(small) can also be used.

3

Learn to recognize when there is enough solder

present. After a proper application of solder, the

solder will be shiny and not dull. Visible indications

are the best way to know if your solder joint is good.

The solder needs to melt with the surface of the

electronic components, rather than the tip of the

soldering iron. This way, when the solder cools, it

forms an alloy with the surface of the metal.

The solder joint should coat the surface of the

component evenly, not too much such that it forms a

glob, nor too little such that it does not completely

coat the surface.

4 Keep the soldering iron clean. Burnt flux, rosin

from the core of the solder, or plastic sheaths from

wires may all burn onto the soldering iron. Such

contaminants prevent the formation of a clean alloy

between the electronic components. This is

undesirable, because it raises the electrical

resistance and also reduces the mechanical strength

of the solder joint. A clean tip is shiny all the way

around, without burnt gunk on it.

Clean the iron in between each component that you

solder. Use a damp sponge or steel wool to clean it

thoroughly. Tip thinner may also be used.

5 Make sure to let the solder cool completely

before moving the components. This cooling

should only take five to ten seconds. If the

components are too hot to handle, use needle nose

pliers, or a tool called helping hands which consists

of two alligator clips attached to a little articulated

stand. If you watch carefully, the cooling solder will

settle right before your eyes.

6

Practice on junk components. It's important to

practice on throwaway stuff before you move straight

to trying to solder something important. Gather some

old junk boars and burnt out components from a

junked radio or other electronic device to practice

on.

Nobody is perfect, not even the professionals. Don't

be ashamed to repeat a bit of soldering work. It will

save you time in troubleshooting later.

Introduction To Basic Electronics Hands-

on Mini Course

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