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Soldering Tips Video's
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Video demonstrations of common hand soldering skills, like 1206 placement or solder bridge removal.
(added on 12-Sep-2004)

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Hand Soldering cableTips & Techniques
Hand Soldering in the 21st Century
Circuits Assembly
State-of-the-art hand soldering systems offer improved temperature control, increased process speeds and repeatable process control.

Lead-Free Hand Soldering of PTH Parts
Circuits Assembly
Bob Willis explains how to solder PTH parts with leadfree solder.
(added on 11-Sep-2004)

A PRIMER ON HAND SOLDERING ELECTRICAL CONNECTIONS

by

David L. Pippen
dpippen@nmsu.edu
Assistant College Professor
New Mexico State University

ABSTRACT
Hand soldering techniques and various alloys used in the soldering process are discussed. Some guidelines for selecting soldering alloys, characteristics of various solder types, solderable metals, solder selection, the process of producing a good solder joint, and desoldering are discussed. A summary of causes for poor solder connections is given.

WHAT IS SOLDERING?
Soldering is a process by which you can join metal items together by applying heat along with special metallic alloys (solder) and allowing them to cool. This results in a metal bond between the metals that is strong and has good electrical conductivity under harsh mechanical environments.

WHAT IS SOLDER?
Solder is a metal alloy consisting of distinct percentages of two or more metals. In electrical work, the alloy is usually tin (Sn) and lead (Pb). However, Silver (Ag), Zinc (Zn), and Antimony (Sb) are used for special soldering alloys. Solder that uses lead has a lower melting point than pure lead. However, some solders contain no lead.

Each alloy composition has unique characteristics, eg., melting point, hardness, and solid-to-liquid transition properties, and may or may not be eutectic.

A eutectic alloy is a composition of one or more metals that has one sharp melting point and no intermediate "plastic" stage. Non-eutectic compositions have a semi-liquid temperature range where the metal can be "worked" due to its plastic nature.

Soldering Tips Video's
BEST
Video demonstrations of common hand soldering skills, like 1206 placement or solder bridge removal.
SOLDER JOINT BASICS

Before solder is applied, a good mechanical connection should be made between the wires by twisting the wires together. Soldering should be considered a means for making a good electrical connection, not a mechanical one.

For good heat conduction between the soldering iron and the joint, a small amount of solder should be applied to the tinned portion of the soldering-iron tip, and this surface should be applied to the joint. The solder wire is then applied to the joint, but is not brought into contact with the iron. When the solder melts into the wire, the joint is properly soldered. This procedure avoids a cold solder joint that could cause trouble at some future time. It is a good idea for the inexperienced hobbyist to practice soldering with some scrap wire. The stripped ends of high strand count power wires for the ESC should be tinned by flowing rosin-core solder onto them before soldering them to the battery, motor, or solder posts. This tinning procedure ensures a quick, clean, hot-solder joint.
Lead Free Solder

It is also important to bear in mind that the use of solders that contain tin or lead solder in plumbing that is connected to potable water systems is outlawed in many places. These materials can seep into the water supply, and have been found to pose a health risk, especially for children. Be sure to use lead free solder wire for any applications that affect a drinking water supply.
Soldering Guide
How to Solder | Advice for Components | What is Solder? | Desoldering | Burns
For information about soldering irons and other tools please see the Tools Required page.

Download PDF version of this page

How to Solder
First a few safety precautions:
Never touch the element or tip of the soldering iron.
They are very hot (about 400°C) and will give you a nasty burn.
Take great care to avoid touching the mains flex with the tip of the iron.
The iron should have a heatproof flex for extra protection. An ordinary plastic flex will melt immediately if touched by a hot iron and there is a serious risk of burns and electric shock.
Always return the soldering iron to its stand when not in use.
Never put it down on your workbench, even for a moment!
Work in a well-ventilated area.
The smoke formed as you melt solder is mostly from the flux and quite irritating. Avoid breathing it by keeping you head to the side of, not above, your work.
Wash your hands after using solder.
Solder contains lead which is a poisonous metal.
If you are unlucky (or careless!) enough to burn yourself please read the First Aid section.

Preparing the soldering iron:
Place the soldering iron in its stand and plug in.
The iron will take a few minutes to reach its operating temperature of about 400°C.
Dampen the sponge in the stand.
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment, then squeeze to remove excess water. It should be damp, not dripping wet.
Wait a few minutes for the soldering iron to warm up.
You can check if it is ready by trying to melt a little solder on the tip.
Wipe the tip of the iron on the damp sponge.
This will clean the tip.
Melt a little solder on the tip of the iron.
This is called 'tinning' and it will help the heat to flow from the iron's tip to the joint. It only needs to be done when you plug in the iron, and occasionally while soldering if you need to wipe the tip clean on the sponge.
You are now ready to start soldering:

Hold the soldering iron like a pen, near the base of the handle.
Imagine you are going to write your name! Remember to never touch the hot element or tip.
Touch the soldering iron onto the joint to be made.
Make sure it touches both the component lead and the track. Hold the tip there for a few seconds and...
Feed a little solder onto the joint.
It should flow smoothly onto the lead and track to form a volcano shape as shown in the diagram. Apply the solder to the joint, not the iron.
Remove the solder, then the iron, while keeping the joint still.
Allow the joint a few seconds to cool before you move the circuit board.
Inspect the joint closely.
It should look shiny and have a 'volcano' shape. If not, you will need to reheat it and feed in a little more solder. This time ensure that both the lead and track are heated fully before Introduction


Tin, lead and their alloys, due to their low melting temperatures and wide availability, are the most commonly used solder materials. In fact, lead has been used as a soldering metal for water pipes (also made of lead) even in Roman times, hence the scientific name for lead, Plumbum.

Mechanical Properties


Tin
(wt.%) Tensile
Strength
(MPa) Shear
Strength
(MPa) Elongation
(%) Elastic
Modulus
(GPa) Izod
Impact
Strength
(J) Stress to
produce
0.01%/day
creep rate

As can be seen from the above table, the 63% tin 37% lead solder alloy results in the maximum tensile strength, shear strength, impact strength, and resistance to creep. This 63-37 composition is also known as the eutectic point of the alloy, where the alloy behaves like a pure metal having a single melting (solidification) temperature (176ºC / 349ºF). This is a good operational feature. Once the solder melts on application of heat, it solidifies immediately on removal of heat, without going through a pasty stage like other alloys. This allows for predictable soldering and fast cycle times.