Soft Soldering

Soft soldering refers to the process of joining metals through the application of lead-based materials with the aid of a fluxing agent and a heat source.

Heat sources refer to heat that is either flame or electrically generated.

Solder refers to low temperature melt alloy metal that may be in a variety of tin and lead proportions depending on the application and can be supplied in either stick or wire form. The latter often contains a resin core flux agent.

Fluxing agents (acid or resin) may be liquid or paste.

Soft soldering can be performed in a variety of ways, including:

• liquid petroleum (LP) gas heating (irons in a confined stove or combination torch and iron)
• pressure blow torch and iron (kerosene fuel)
• electric soldering irons
• low-voltage scope soldering
• flame heating, such as air-LP or air-acetylene.

As part of the process of safety self-regulation, all persons engaging in this activity should identify the hazards, assess their significance and manage the potential risks including any additional hazards not mentioned here.

Hazards that may be encountered in soft soldering include:

• inhalation (vapour inhalation from heated fluxes and acids, and inhalation of fumes given off during soldering)
• heat (from heated materials and equipment, naked flames and fluxes)
• spillage (of corrosive liquids, such as flux)
• fire (potential risk of fire from gas heating equipment)
• superheated flux (overheated soldering iron dipped in the flux dip)
• explosion (ignited fuel gas).

The categorisation of these conditions is subjective and offered as a starting point for risk management planning. The actual degree of risk is best ascertained by persons with intimate local knowledge present at the site of the activity.

Not Applicable

The qualifications listed in this section are minimums for each type of situation. Leaders are encouraged to seek training to raise their qualification level above the minimum listed.

The leader should be:

• a registered teacher with experience (previous involvement) in using this type of equipment or similar equipment for basic applications or
• an adult with competence (demonstrated ability) or relevant qualifications and experience (previous involvement) in using this type of equipment, when a teacher with experience is not available.

Not Applicable

Suspected gas leaks should be checked by using a soapy water solution applied with a brush. Any identified leaks should be reported.

Replacement (including disconnection and reconnection of cylinders) should be carried out by the relevant authority responsible for replacing empty cylinders.

LP gas is non-toxic and odourless, but an odourant is added to give a distinctive smell. Teachers should instruct students in the responsibility of notifying the teacher if a gas leak is detected.

When LP gas is being used, the soldering benches should be situated in a position where good cross-ventilation is available.

When electric soldering irons are used, the soldering stations should be situated in a position away from any damp or wet areas and where extension leads will not be required.

Electrical equipment must have current electrical test certification.

Gas equipment should be audited each year.

It is recommended that low-voltage continuous-operation soldering equipment be used.

Soldering tips should be maintained in good working order.

Good working habits should be enforced by ensuring that:

• all flux containers do not leak and are equipped with suitable brushes
• 'dip pots' are in good order and clean, and contain sufficient solution
• a suitable container for solder is supplied
• a fire extinguisher and/or fire blanket are in the vicinity of the soldering area.

When lighting a gas oven the following procedures should be followed:

• stand to one side of the oven
• see that the flint gun is operative
• turn on gas slowly and ignite by means of the flint gun
• adjust the flame
• if difficulty is encountered in using the flint gun, turn the gas off immediately.

Teachers should be aware that in some instances excess gas build-up could occur during the use of the flint gun to light gas stoves.

Taps to gas stoves should be turned off fully. A tap should never be turned off and then turned on again as the hot stove could ignite the gas build-up with explosive force.

The soldering ovens gas main should be turned off (in most cases at the manifold position) when the soldering activity is completed.

An electric soldering iron should never be used in damp conditions.

Suitable eyewash facilities should be available in the Design Technology Workspace prior to the commencement of the activity.

Inhaling fumes or vapours from acids, fluxes or gases should be avoided when soldering.

Protective equipment may be used whenever possible to reduce the risk of burns. Heated materials should be kept in restricted areas.

Correct containers for acids and solvents and correct storage procedures should be used to minimise spillage from containers.

Safety precautions should be adopted to prevent possible fire hazards when using gas or petroleum liquids for heating. Combustible materials should not be allowed near the work area.

Correct handling methods should be used when heating oils, liquids etc. to reduce the risk of splashing. Placing hot objects or tools (soldering iron) in water or cleaning agents should be avoided.

Gas ovens should not be lit using a disposable or naked flame from a match or lighted paper.
Hot irons should be cooled in the appropriate fluid and place. Dip pots constitute a significant hazard in this respect.

An appropriate hot iron rest should be provided for the activity.

In the event of fire, turn off the gas supply at the isolation valve. The isolation switch should be situated near an exit.

Burns should be treated with clean running water.

• Maintaining a Safe Design Technology Workspace
• Gas Heating Welding and Cutting
• HLS-PR-005: Injury, Illness and Dangerous Event Recording and Reporting
• HLS-PR-003: First Aid for Schools and Non-school Locations