sign in sign up
<<
Home , Flux (metallurgy), Soldering, Solder paste, Tinning

SHEETMETAL FABRICATION TECHNICAL TIPS FOR

Flux

In , a (derived from Latin fluxus meaning “flow”), is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both metallurgy and metal joining.

In high-temperature metal joining processes (, and soldering), the primary purpose of flux is to prevent oxidation of the base and filler materials. - (e.g.) attaches very well to , but poorly to the various oxides of copper, which form quickly at soldering temperatures. The role of a flux in joining processes is typically dual:

1. As cleaning agents, fluxes facilitate soldering by removing oxidation from the metals to be joined by dissolving the oxides on the metal surface, which facilitates by molten solder. The flux also acts as an oxygen barrier by coating the hot surface, preventing further oxidation during the soldering process.

2. Additionally, flux allows solder to flow easily on the working piece rather than beads as it would otherwise. In some applications molten flux also serves as a heat transfer medium, facilitating heating of the joint by the soldering tool or molten solder.

FLUX TYPES

There are two types of fluxes used for soft soldering. These are organic ( based) fluxes or inorganic fluxes, usually based on halogenides and/or acids. Common fluxes are: ammonium or rosin for soldering tin; and chloride for soldering galvanized (and other zinc surfaces); and for brazing or braze-welding ferrous metals.

Rosin Flux Some of the oldest types of flux used is based off pine sap (refined and purified) called rosin. Rosin flux is still used today, mostly in electronics soldering and now typically is a blend of fluxes to optimize the flux, its performance, and characteristics. Ideally flux will flow easily, especially when hot, removes oxides quickly, and helps to remove foreign particles from the surface of the metal

SHEETMETAL FABRICATION TECHNICAL TIPS FOR SOLDERING

Rosin Flux (continued) being soldered. Rosin flux is acidic when liquid, but when it cools it become solid and inert. Since rosin flux is inert when solid, it can be left on a without harming the circuit unless the circuit will warm to the point where the rosin may become liquid and start eating away at the connection. For this reason it is always a good policy to remove rosin flux reside from a PCB. Also, if a conformal coating will be applied or PCB cosmetics are important, flux residue should be removed. Rosin flux residue can be removed with alcohol.

Express Flux #855 for Lead Free Applications Organic Acid Flux One of the more common fluxes used is water soluble organic acid (OA) flux. Common weak acids are used in organic acid flux, such as citric, lactic, and among others. The weak organic acids are combined with like isopropyl alcohol and water. Organic acid fluxes are stronger that rosin fluxes and clean the oxides off much quicker. Organic acid fluxes are most frequently used in electronics assemblies.

Inorganic Acid Flux A stronger option that organic flux is inorganic flux, which is typically a blend of stronger acids like hydrochloric acid, zinc Express’ #855 Flux does not generate toxic smoke and does chloride, and . Inorganic acid flux is targeted not contain . It can be use in all types of lead more towards stronger metals such as copper, , and free soldering on zinc, copper, tin, tinned and . Inorganic acid flux requires complete cleaning galvanized steel after use to remove all of the corrosive residue from the surfaces which will weaken or destroy the solder joint if left in place. Inorganic acid flux should not be used for electronic assembly work or electrical work.

Solder Fumes The smoke and fumes released while soldering is not great to inhale. It includes several chemical compounds from the acids and their reaction with the oxide layers. Often compounds such as formaldehyde, toluene, alcohols, and acidic fumes are present in the solder fumes. These fumes can lead to asthma and increase sensitivity to solder fumes. Cancer and lead risks from solder fumes are very low since the boiling point for solder is several times hotter than the boiling temperature of the flux and the melting temperature of the solder. The greatest lead risk is the handling of the solder itself. Care should be taken when using solder, with a focus on washing hands and avoiding eating, drinking, and smoking in areas with solder to prevent solder from entering the body.

SHEETMETAL FABRICATION TECHNICAL TIPS FOR SOLDERING

Express Fluxes

Product Item Code Appearance Type Uses Alternate uses

Soldering Flux New Copper, Zinc Coated for Clean 840E Inorganic Acid New Zinc, Lead Copper, Lead Coated materials Copper

Soldering Flux for Oxidized 845E Inorganic Acid Oxidized Zinc Oxidized Copper materials

Soldering Flux Copper, Galvanized Steel, for Natural 847E Inorganic Acid New Zinc Lead, Lead Coated Copper Zinc

Soldering Flux for Pre- 850E Inorganic Acid Pre Weathered Zinc Galvanized Steel Weathered Zinc

Premium Zinc, Oxidized Copper, Soldering Flux 851E Inorganic Acid New Copper Oxidized Zinc, Lead, Lead for Copper Coated Copper

Premium Soldering Flux 853E Inorganic Acid Stainless Steel Terne Coated Stainless Steel for Stainless Steel

Premium Galvanized Aluminum Soldering Flux 854E Inorganic Acid Aluminum (Galvalume) for Aluminum Premium Soldering Flux Organic Galvanized Steel, Terne 855E Copper, Zinc, Brass, lead for Lead Free Acid Free Coated Steel & Copper

Pre-tinning Galvanized Steel, Terne 852E Copper, Zinc and Tin Coated Stainless Steel

For more information go to www.guilbert-express.com