This article is about the use of flux on printed circuit boards used by the hobbyist for homemade circuit boards. You will discover the origins of flux use and its role in early circuit board development.
You will learn its role in the development of modern technology, types of flux for home use and their function, problems you may encounter while using flux and potential health dangers.
History
The earliest know use of flux was around 4000 BC. It was used to join soft metals like silver and gold for making jewelry, copper in primitive waterways and even to tin plate iron. This early flux was made from strong acids and natural resins. Though suitable for these primitive applications, it was much too corrosive to be used in modern circuit board manufacturing. However, in the twentieth century, the use and composition of flux developed as a technology.
Significance
The development of modern flux led to the invention of the printed circuit board in 1936 by Austrian engineer Paul Eisler. His invention paved the way for commercial manufactured circuit boards and the development of modern electronics.
Function
Flux is used with solder to join components to a printed circuit board. A soldering iron is used to heat the flux and solder at the solder joint. Because the flux has a lower melting point than the solder, it vaporizes first and forms an acidic cloud around the joint. This removes any oxidation present on the copper trace and wire lead. It prevents new oxidation by keeping oxygen out and helps the molten solder flow by reducing surface tension.
Types
There are two types of flux, rosin based and water soluble. Rosin-based flux, used by hobbyists, is made from pine sap and is naturally acidic. Water-based flux is used mainly in commercial circuit board production. Flux comes in different forms and packaging such as paste, liquid, foam, and rosin core soldering wire. Flux paste and rosin core soldering wire are the types used most often by hobbyists.
Problems
A common problem is using too much rosin flux. This can lead to a heavy build of rosin residue on the board under components. This residue contains acid and can damage the PCB and components over time. You should clean the solder joint thoroughly with isopropyl alcohol. Make sure the board is completely dry before going on.
Warnings
Rosin flux is corrosive and can damage your lungs with prolonged exposure. According to the material safety data sheet for Kester 44 Resin, "WARNING! Severe Irritant. Potential Sensitizer Exposures to soldering fumes and vapors may be irritating to eyes, respiratory system, and skin."
Please solder in a well ventilated area and avoid breathing fumes. Remember that flux is corrosive. If you think you have been exposed to dangerous levels, get medical attention immediately.
Summary
You should now have a better understanding of what flux is, its history and its use on printed circuit boards. Electronics is a great hobby that you can enjoy for years. Be careful and have fun!
