Tips for Better Soldering

7/31/2019 Tips for Better Soldering

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Tips for better soldering


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Safety Precautions

Caution: A soldering iron can heat to around 400C, which can burn you orstart a fire, so use it carefully.

Unplug the iron when it is not in use.

Keep the power cord away from spots where it can be tripped over.

Take great care to avoid touching the tip of the soldering iron on a power

line. If a power cord is touched by a hot iron, there is a serious risk ofburns and electric shock.

Always return the soldering iron to its stand when it is not in use.

Never put the soldering iron down on your work bench, even for amoment!

Work in a well-ventilated area.

The smoke that will form as you melt solder is mostly from the flux andcan be quite irritating. Avoid breathing it by keeping your head to the sideof, not above, your work.

Solder contains lead, which is a poisonous metal. Wash your hands afterusing solder.


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Tips

Plan before you start to solder. Identify all the parts that you will be using.

It is helpful to attach each part to a piece of paper and write what it is andits value (for example, resistor #1: 100 ohms).

Some components, such as LED's, must be placed the correct way aroundin order to function.

The following is a suggested order for the installation of variouscomponents: Integrated circuit (IC) holders (note the orientation). The IC will be added later.

Resistors

Capacitors, less than 1 micro farad

Large capacitors, 1 micro farad or greater, note the orientation.

Diodes, note the orientation.

LED's, note the orientation.

Transistors, note the orientation.

Very large capacitors above 100uf, note the orientation.


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Tips

Solid wire connections between components on the board Solid wire is fairly rigid, so it will stay in place once attached.

Stranded wire to parts that are connected by wire to thecircuit

Stranded wire is more flexible than solid wire. Integrated circuits

Connect them the correct way around.

Many IC's are static sensitive.

Leave IC's in their antistatic packaging until you need them, then

ground your hands by touching a metal water pipe or windowframe before touching the IC's.

Carefully insert IC's in their holders. Make sure all the pins arelined up with the socket, then push down firmly with yourthumb.


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Soldering

Tinning The Soldering Tip

Step 1: Warm Up The Iron Warm up the soldering iron or gun thoroughly.Make sure that it has fully come to temperature because you are about tomelt a lot of solder on it. This is especially important if the iron is new becauseit may have been packed with some kind of coating to prevent corrosion.

Step 2: Prepare A Little Space While the soldering iron is warming up, prepare

a little space to work. Moisten a little sponge and place it in the base of yoursoldering iron stand or in a dish close by. Lay down a piece of cardboard incase you drip solder (you probably will) and make sure you have room to workcomfortably.

Step 3: Thoroughly Coat The Tip In Solder Thoroughly coat the soldering tip insolder. It is very important to cover the entire tip. You will use a considerableamount of solder during this process and it will drip, so be ready. If you leave

any part of the tip uncovered it will tend to collect flux residue and will notconduct heat very well, so run the solder up and down the tip and completelyaround it to totally cover it in molten solder.

Step 4: Clean The Soldering Tip After you are certain that the tip is totallycoated in solder, wipe the tip off on the wet sponge or cloth to remove all theflux residue. Do this immediately so there is no time for the flux to dry out andsolidify.


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Soldering

Component Placement

Unless your circuit is simple and only contains a fewcomponents, you will probably not be placing all thecomponents onto the board and soldering them at once. Mostlikely you will be soldering a few components at a time before

turning the board over and placing more. In general it is best tostart with the smallest and flattest components (resistors, ICs,signal diodes, etc.) and then work up to the larger components(capacitors, power transistors, transformers) after the smallparts are done. This keeps the board relatively flat, making itmore stable during soldering. It is also best to save sensitive

components (MOSFETs, non-socketed ICs) until the end tolessen the chance of damaging them during assembly of the restof the circuit.


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Soldering

Solder needs a clean surface on which to adhere. Buff the copper foil of a PC board with steel wool before

soldering.

Remove any oil, paint, wax, etc. with a solvent, steel wool,

or fine sandpaper. To solder, heat the connection with the tip of the

soldering iron for a few seconds, then apply the solder. Heat the connection, notthe solder.

Hold the soldering iron like a pen, near the base of the

handle. Both parts that are being soldered have to be hot to form a

good connection.


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Soldering

The tip of the soldering iron heats both the

copper pad and the lead from the electronic

component. Solder melts when placed in

contact with the hot metals to be joined.


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Soldering Keep the soldering tip on the connection as the solder is applied.

Solder will flow into and around well-heated connections. Use just enough solder to form a strong connection.

Remove the tip from the connection as soon as the solder hasflowed where you want it to be. Remove the solder, then the iron.

Don't move the connection while the solder is cooling.

Don't overheat the connection, as this might damage the electricalcomponent you are soldering.

Transistors and some other components can be damaged by heatwhen soldering. A crocodile clip can be used as a heat sink to protectthese components.

Soldering a connection should take just a few seconds. If it is taking longer, see the troubleshooting section below.

Inspect the joint closely. It should look shiny.

If you are soldering a wire (called the lead) onto a PC board (on thetrack), it should have a volcano shape. See Figure in next slide.

If the connection looks bad, reheat it and try again.


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Soldering

Soldering a connection should take just a few

seconds.

Inspect the joint closely. It should look shiny.

If you are soldering a wire (called the lead) onto a

PC board (on the track), it should have a volcano

shape. See Figure in next slide.

If the connection looks bad, reheat it and tryagain.


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Quality of join


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Common Problems and

Troubleshooting

Solder will not flow. The parts to be joined may be dirty. Remove the solder and clean the parts.

The connection looks grainy or crystalline. Parts were moved before the solder was allowed to cool.

Reheat to form a good joint. You may need a larger soldering iron to heatconnections adequately.

The tip is oxidized. Soldering is much easier with a shiny, clean tip.

Clean the tip with a damp synthetic sponge while the iron is hot.

To avoid oxidizing the tip, do not leave the iron plugged in when not in use.

Do not use the iron at a higher temperature than is necessary to melt solder.

Clean the tip of the iron on a damp synthetic sponge as soon as it starts to

change from a silver color. There is too much or too little solder.

Using too much solder can cause a solder bridge, which means that twoadjacent joints are accidentally connected.

Using too little solder might result in poor electrical continuity between theboard and component. The connection should be smooth, shiny, and rigid.


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Reference

Electronics Primer: How to Solder Electronic

Components at website

http://www.sciencebuddies.org/

Documents

Tips for Better Soldering