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Publication Title | How to Solder-The Basics

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Richard Perez

©2002 Richard Perez

Weller TCP-12

oldering ensures permanent, low loss, electrical connections. A soldered electrical connection is

not difficult to make. It only requires a little practice and the right tools.

If you’re making your own electricity, your system’s wiring and its maintenance are critical. Without good electrical connections, even the finest system will perform poorly or not at all. Here’s what you need to know to make effective soldered connections for your system.

Electrical wiring is made of copper and aluminum because both metals have low resistance to electron flow (electric current). The major problem with mechanical connections is the formation of oxides on the copper or aluminum. These oxides are poor conductors of electricity, and they cause the resistance of a mechanical connection to increase.

The pure copper or aluminum on the surface of the wire gradually changes to copper oxide or aluminum oxide by chemical reaction with the oxygen in the air and water. It only takes one weak or bad link in the electrical chain to render the

wire connections. But these

mechanical connections will not prevent oxidation

within the electrical connection. As the wires that make up the mechanical connection oxidize, the electrical resistance of the connection increases. This results in a voltage loss across the connection.

A well-made soldered connection will have lower resistance than a new mechanical connection, and will not oxidize with time. Years down the road, the soldered connection will have many times less resistance than the oxidized mechanical connection.

In 120 volt wiring, the voltage loss due to oxidized mechanical connections is negligible because the input voltage is so high—120 VAC—so the current is low. Here, mechanical connections are standard and perfectly acceptable. In 12 volt systems, however, the voltage loss in poor connections can make a system fail.

The table opposite shows voltage drop and power losses for a hypothetical 120 watt load in a circuit with 0.2 ohm resistance over a variety of voltages. Poor connections really hurt in low voltage systems!

Soldering a connection ensures that it will not oxidize and increase in electrical resistance. Do it right once, and it will work for a long, long time. But you must do it right. A bad soldered connection can have more resistance than a mechanical connection.

When to Solder

Any low voltage electrical connection involving copper wire, where oxidation or corrosion is a potential problem, is a candidate for soldering. Obviously, there will be some purely mechanical con-nections in any system. It’s not prudent or possible to solder to battery terminals, inverters, and controls—here mechanical connections are appropriate. Aluminum wires can’t be


Here is a list of appropriate places for soldered connections.

• Any connection that lives outside in the weather, especially connections between wire and ring or spade connectors.

make insulated, twisted

entire circuit in- operative.

Why Solder?

Mechanical connections are

made by twisting

the bare wires together or by compressing a wire into a connector or terminal. Wire nuts can be used to

Weller D550

74 Home Power #88 • April / May 2002

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