Overview of Soldering 271

Overview of Soldering defines soldering, describes the tools used in soldering, and discusses the various soldering processes. Soldering is a low-heat joining process used in applications where the heat of welding or brazing would be too great or where precise control is required. There are a number of manual and automatic soldering processes. Soldering is particularly useful in electronics and jewelry fabrication as well as in creating air and watertight seals in plumbing and other systems.

After this class, users will be able to define soldering, identify the important tools involved in soldering, list soldering safety concerns, and describe the various soldering processes. It is essential for any operator who may be required to solder materials to understand the basic soldering equipment, processes, and practices.

  • Difficulty Intermediate

  • Format Online

  • Number of Lessons 19

  • Language English


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Course Outline
  • Introduction to Soldering
  • Soldering Safety Precautions
  • Advantages of Soldering
  • Disadvantages of Soldering
  • Basics of Soldering Review
  • Types of Solder
  • Flux
  • Types of Flux
  • Solder and Flux Review
  • Soldering Iron
  • Soldering Tools and Accessories
  • Heat Transfer in Soldering
  • Heat Transfer Processes
  • Hand Soldering
  • Properly Soldered Joints
  • Pipe Soldering
  • Hand Soldering and Heat Transfer Review
  • Automated Soldering
  • Automated Soldering Review
  • Define soldering.
  • List important safety considerations for soldering.
  • Describe advantages of soldering.
  • Describe disadvantages of soldering.
  • Describe solder.
  • Define flux.
  • Distinguish between types of flux.
  • Describe types of soldering irons and their components.
  • List important soldering tools and accessories.
  • Describe heat processes involved in soldering.
  • Describe the hand soldering process.
  • Distinguish between properly and improperly soldered joints.
  • Describe the pipe soldering process.
  • Describe automated soldering processes.
Vocabulary Term


A material or tool consisting of hard particles used to clean, wear down, rub away, or machine material. Abrasive cleaning can prevent defects from forming in a soldered joint.


Corrosive due to chemical properties. Acidic residue is left by some soldering fluxes.


A corrosive chemical compound. Acids can remove impurities from the surface of a workpiece.


A substance that chemically reacts with other materials under certain conditions. Activators in flux require the heat of soldering to begin reacting.


The measure of flux cleaning strength. The more active the flux, the more effectively it cleans.

adhesive bonding

A process that binds materials together using a non-metallic material. Adhesive bonding uses materials such as epoxy, polyurethane, and glue to join materials.


A basic substance that has a pH greater than 7 when dissolved in a solution. Alkaline materials are often used in cleaning products.


A mixture of two or more metals. Alloys take advantage of the beneficial properties of multiple metals.


A toxic and corrosive compound with a characteristic pungent odor. Ammonia helps clean metals during soldering.


A brittle, silvery-white metal use as an alternative to tin in soldering alloys. Antimony is less expensive than tin, but its wetting capability is poorer and it is toxic.


A substance that contains water or is similar to water. Aqueous cleaners spread easily over a workpiece.


Overheating that occurs when electricity flows from one surface to another. Arcing is dangerous because it can cause electric shock as well as burns from ultra-violet radiation.


The smallest distinguishable unit of a material that maintains the same characteristics. The energy level of atoms determines the state of matter of a material.


A mechanical system that, once established, operates without any human intervention. Automated systems can increase the efficiency of industrial processes.

base metal

One of the two or more metals to be fused together in a joining process. Base metals do not melt in soldering applications.


An interchangeable tip for tools. Bits for soldering irons are specialized for different applications.

brass sponge

A sponge made of thin threads of brass. Brass sponges clean without using water, which helps prevent rust from forming on metallic objects like soldering irons.


A process in which a filler metal is melted at a temperature above 842° F (450°C), but below the melting point of the base metals, to form a joint. Brazing differs from welding because only the filler metal is melted.

capillary action

The process of an object or substance drawing a liquid upwards against the force of gravity. Capillary action occurs in pipe soldering as well as wave soldering applications.


A covering or coating on a structure or a material. Cladding some non-metallic materials in a thin layer of metal allows them to be soldered.


A device used to join, grip, support, locate, or compress mechanical or structural parts. Clamps are often used to hold delicate work pieces.

cold joints

A dull, poorly soldered joint that does not provide good electrical conductivity. Cold joints must be removed and resoldered.


A form of heat transfer that occurs when neighboring atoms vibrate against each other. Conduction allows heat to pass from a solid object to an adjacent object or area where there is a difference in temperature.

conical bits

A soldering tip with a wide, cylindrical bit narrowing to a fine point. Conical bits are good for precise soldering work and are also known as pyramid bits.


The transfer of heat as hot particles move to cooler areas. Convection occurs most easily with liquids and gasses.


A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper is often used as an alloy in solders.


A chemical solid, liquid, or gas capable of irreparably harming living tissue or damaging material on contact. Some soldering fluxes leave corrosive residues.

desoldering iron

A tool used to heat applied solder in order to remove it. Desoldering irons are used with solder wicks or solder pumps to remove improperly applied solder.

desoldering pump

A device that pulls liquid solder away from a workpiece surface. Desoldering pumps are also known as solder suckers.

drag soldering

A joining process where a soldering technician runs the soldering iron over a series of joints in a row without stopping. Drag soldering is often used to place surface mount chips on circuit boards.


A metal's ability to be drawn, stretched, or formed without breaking or cracking. Soldered joints generally have good ductility.

electrical assembly

A component made of a frame, an electrical connector, and a self-contained part known as a module. Printed circuit boards are a type of electrical assembly.

electrical conductivity

The ability to effectively convey an electric current with low resistance. Good electrical conductivity is a often a desired property in soldered joints.

electromagnetic waves

An oscillating wave from a magnetic field that is produced by the motion of electric charges such as electric current. Light, x-rays, and microwaves are all forms of electromagnetic waves.

electronic assemblies

A component made of a frame, an electrical connector, and a self-contained part known as a module. Common electrical assemblies include printed circuit boards (PCBs).

exhaust system

The collection of various devices used to remove harmful fumes at the source of contamination. Exhaust systems for soldering include fume extractors.

filler metal

A type of metal added to a joint during a fusing process like soldering, brazing, or welding. Filler metals for soldering are known as solders.


A substance that facilitates soldering, brazing, and welding by chemically cleaning the base metals. Flux also helps solders flow more evenly.

flux pen

A flux application tool, usually shaped like a marker pen, that channels controlled amounts of water-soluble flux onto metal surfaces. Flux pens can be used to supplement or replace flux in a solder.

fume extractor

A fan or vent that diverts toxic fumes away from the soldering work area. Fume extractors are the most common type of exhaust system used in soldering.

fume extractors

A fan or vent that diverts toxic fumes away from the soldering work area. Fume extractors are especially critical in lead-based soldering applications.


A cloud of particles suspended in a gas. Applications such as soldering that emit fumes require proper ventilation.


Formed into small, distinct particles. Granulated substances have a coarse texture and feel.

hand soldering

The process of soldering manually with the use of a soldering iron. Hand soldering is usually the method of choice for repair work or particularly sensitive jobs.

heat transfer

The passage of thermal energy from a hot material to a cold material. There are three forms of heat transfer: conduction, convection, and radiation.

hydrochloric acid

An acidic, highly corrosive chemical compound. Hydrochloric acid removes oxides from metal.


Composed of matter other than plant or animal. Inorganic water-soluble fluxes are the most active of all fluxes.

isopropyl alcohol

A colorless, flammable chemical compound with a strong odor used to sterilize surfaces. Isopropyl alcohol is also known as rubbing alcohol.


The point at which two pieces of material are joined together. Soldered joints are entirely composed of filler metal unlike joints in some other joining processes.

lap joints

A joint formed by two overlapping pieces of metal. Lap joints are often used with electrical components to allow electrical conductivity between the metals.


A soft, heavy, toxic, and malleable metal often used in solder. Lead has a very low melting point.


A thin wire that protrudes from an electronic component and provides an easy path for electricity to flow. Leads are also known as pins.


A material containing some percentage of lead. Lead-based materials are toxic and must not be used in applications that will come in direct contact with food or people.

lock seam joints

A joint formed by folding thin sheets of metal together. Lock seam joints add strength to the joint by interlocking the base metals and relying on solder to stiffen and seal the assembly.

mechanical fastening

The joining of materials through the use of objects such as nails rivets, bolts, or screws. Mechanically fastened joints have a high degree of strength.

melting point

The temperature at which a material changes from a solid to a liquid. Soldering is done with filler metals that have low melting points.


Derived from a living organism. Organic water-soluble fluxes are more active than rosin-based fluxes but less active than inorganic water-soluble fluxes.


The process of a material chemically reacting with oxygen. Oxidation causes rust and tarnish to form on metal surfaces and prevents solder from bonding.


A copper platform to which surface mount components are soldered. Mounting components on pads is one of the most common soldering tasks.

personal protective equipment

PPE. Any clothing or device worn to minimize exposure to hazards and prevent injury. Personal protective equipment for soldering should include safety glasses, gloves, and flame resistant clothing.


A compound made from petroleum or natural gas. Petrochemicals can be used to make cleaning solvents.

photo sensors

An electrical component that detects objects using an infrared light transmitter and a photoelectric receiver. Photo sensors are used in a wide array of devices such as optical scanners and remote controls.


An elementary particle of electromagnetic radiation. Photons carry the energy that composes light and other types of radiation.


A thin wire that protrudes from an electronic component and provides an easy path for electricity to flow. Pins are also known as leads.


The application of heat to a base metal immediately before welding. Preheating base metals for soldering provides the heat that melts the solder.

printed circuit boards

PCB. An object that mechanically supports and electrically connects electronic components through conductive pathways, or traces, etched onto copper sheets laminated with a non-conductive surface. Printed circuit boards are often used in computers and computer accessories.

propane torches

A tool that uses a gas-fueled flame to generate heat. Propane torches can reach high temperatures.

pyramid bits

A soldering tip with a wide, cylindrical bit narrowing to a fine point. Pyramid bits are good for precise soldering work and are also known as conical bits.


An energy emission process that takes the form of waves or particles. Radiation is used in reflow soldering.

reflow soldering

An automated joining process in which PCBs are passed through an oven on a conveyor belt. In reflow soldering, radiant heat from the oven causes granules of solder to melt and form a joint.


A substance deposited or left behind by a reaction or event. Residue can cause functional issues if left on workpieces after soldering.


A component on a circuit board that resists the flow of electricity. Resistors can be smaller than a quarter of an inch.


A machine that does routine mechanical tasks on command. Robotic systems are a form of automation.


A material-handling device that can be programmed to perform a variety of complicated, repetitive tasks. Robots often have extendable arms with grippers.

rosin fluxes

A flux made of rosin, a substance derived from the sap of pine trees. Rosin-based fluxes have a range of activity levels.


A reddish-brown impurity caused by a reaction between metal, moisture, and oxygen. Rust must be removed from a workpiece prior to soldering to ensure formation of a quality joint.

safety glasses

Protective eyewear, usually made of thick plastic, which shields the eyes from flying debris and other potentially hazardous irritants. Safety glasses should always be worn while soldering.


A chemical compound with a crystalline structure. Salts are one of the active ingredients is some soldering fluxes.


The fluid that flows through the vascular system of a plant. Sap contains compounds that help clean workpieces before soldering.


An alkaline cleaning material. Saponifiers react with rosin to form water washable soaps.

screwdriver bits

A soldering tip with a wide blade. Screwdriver bits, also known spade bits, are good for soldering multiple joints at once.


A substance that is slightly water-like or contains a small amount of water. Semi-aqueous substances are slightly less fluid than aqueous substances.

short circuits

An interruption in the intended flow of electricity, particularly when current flows "short" of reaching a device. A short circuit causes excess current flow, which can destroy electronic components, cause fires, or electrocute soldering technicians.


A soft metal that has the highest electrical conductivity of all metals. Silver is used in soldering alloys and creates strong joints.

solder sucker

A device that pulls liquid solder away from a workpiece surface. Solder suckers are also known as desoldering pumps.

solder wick

A braid of flux-coated copper designed to soak up liquid solder. Solder wicks are used with soldering irons to remove improperly placed solder.


A material that can be soldered. Solderable metals include silver, copper, and tin.


A process in which a filler metal is melted at low temperatures to form a joint between two base metals. Soldering is often used for delicate projects such as jewelry and electronics.

soldering guns

A type of soldering device with a pistol-type grip and a wide work tip. Soldering guns are generally not used for delicate electronic components because regulating the temperature can be difficult.

soldering iron

A tool used to transfer heat to a metal surface in order to melt solder and form a joint. Soldering irons are typically powered by electricity.

soldering iron

A tool used to transfer heat to a metal surface in order to melt solder for a joint. Soldering irons transfer heat through conduction.

soldering iron stand

A non-flammable stand upon which to rest a hot soldering iron. Soldering iron stands also usually have a place to hold the cleaning sponge.

soldering station

A combination of common soldering accessories, including a soldering iron, iron stand, desoldering iron, cleaning pad, and energy source. Some soldering stations also include fume extractors.

soldering technicians

A person who solders. Soldering technicians help manufacture items like circuit boards and jewelry.

soldering torch

A type of soldering device that uses a flame rather than a soldering iron tip to heat solder. Soldering torches are often used when connecting pipes in a plumbing system.


A fusible metal or alloy, which is melted to join materials, with a melting point or melting range below 842°F (450°C). Solders are filler metals specific to soldering.


A mixture in which a minor component is evenly distributed in a major component. Solutions are usually liquids.


A chemical used to dissolve another material. Solvents are often used to remove surface contaminants.

spade bits

A soldering tip with a wide blade. Spade bits, also known screwdriver bits, are good for soldering multiple joints at once.

staked joint

A joint formed when a piece of metal runs through another. Staked joints are often used to hold electrical equipment in place and are also known as swaged joints.

steel wool

An abrasive material made by bundling fine strands of steel. Steel wool is used to clean work surfaces before soldering.


A material's ability to resist outside forces that are trying to break or deform it. Types of strength include yield, tensile, and creep.

swaged joints

A joint formed when a piece of metal runs through another. Swaged joints are often used to hold electrical equipment in place and are also known as staked joints.


A thin layer of corrosion. Tarnish on a workpiece can interfere with the formation of a quality soldering joint.

thermal conductivity

A physical property that indicates how well heat energy transfers through a material. Materials with high thermal conductivity work well in applications requiring high thermal control.


A silvery-white metal that is very soft and has poor strength. Tin helps prevent corrosion in solders.


The action of applying a trace amount of solder to the tip of a soldering iron. Tinning helps facilitate the heat transfer process.


Poisonous or harmful. Toxic materials, such as lead and acid, are sometimes used as components in soldering or flux.

vapor-phase soldering

An automated low-heat joining process in which a chamber of boiling volatile chemicals melt solder paste on PCBs. Vapor-phase soldering works through convection heat transfer.


The gaseous form of a substance that is a liquid or solid at normal temperatures. Water vaporizes into steam when heated.


The ability of a substance to dissolve in water. Water-soluble flux is easily cleaned with water.

wave soldering

An automated joining process in which a conveyor belt loaded with PCBs passes over a vat of molten solder. Wave soldering works through convection heat transfer and capillary action.


The joining of two pieces of metal together through the application of heat or pressure. Welding generates temperatures hot enough to melt the base metal of the workpiece when using heat to join metals.


The behavior of a liquid when it contacts a solid surface. Liquids with poor wetting ability tend to form droplets while liquids with good wetting ability spread out evenly over the solid surface area.


A crystalline growth of tiny hair-like structures in a metal. Whiskers can cause electrical malfunction.


A part that is subjected to a manufacturing process such as soldering or cutting. Any metals or materials being soldered are referred to as workpieces.

zinc chloride

A salt composed of zinc and chlorine. Zinc chloride reacts with oxides and removes them from the surface of metals.