Electrical Soldering

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Key Questions

The following key questions are answered in this module:

What is the composition of solder?
Commonly used lead-based solder is typically an alloy of approximately 60% tin and 40% lead. Some countries have made the use of lead-containing solders illegal. Non-lead containing solders have a higher melting point and are made up of tin, silver and copper.

What is the role of flux in soldering?
Flux is a chemical agent applied to a joint at the same time as the solder. Its role is to remove and prevent the formation of metal oxides that would interfere with solder bonding.

How should a soldering iron be prepared?
Due to the high temperatures at which they operate, soldering irons easily develop an oxide layer that interferes with solder wetting and heat transfer. Soldering iron tips should be cleaned and covered with a thin layer of solder, which should then be maintained as it is used. This process is called tinning.

What is a cold solder joint?
If solder fails to bond to all or part of a joint due to the presence of oxides, or due to movement of a part as a solder joint is cooling, a poor physical or electrical connection will result. This low quality connection is called a cold solder joint.

How can solder be removed from a joint?
Unwanted solder can be removed from a joint by melting the solder with a soldering iron and then using a desoldering pump, which is a spring-loaded syringe that generates suction to remove molten solder. Alternatively, woven metal desoldering braid that uses capillary action to pull molten solder away from a joint can be used.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

Soldering is a technique for joining two pieces of metal together by melting and flowing a filler metal into the area where the pieces are to be joined. The filler metal, or solder, is an alloy which melts at a lower temperature than the parts being joined. Soldering differs from welding, another common method of joining metals together, in that soldering occurs at lower temperatures than welding and does not involve melting of the parts being connected. A soldered connection is not as strong as a welded connection but it does create a bond which is electrically conductive and is gas and water tight. Soldering is commonly used in electronics, plumbing, certain types of metalwork, and jewelry. This module will focus primarily on soldering as applied to electronics.

Additional Resources

Use the additional resources and links below to learn more about this topic:

• Soldering Definition
• Soldering Guide