Flux Designations and Composition

Here are some answers to my questions after a good research. I also added more definitions that could help understand this esoteric language used in assembly, specially surrounding fluxes and their use. In blue italics are comments and extracts from other sources (Sorry but this forum does not accept italics or colour. You can contact me at at my E-mail info@microniks.com if you want an original in Word, WordPerfect or pdf file).

Rosin fluxes with colophony: Fluxes containing colophony, a natural substance extracted from the sap of pine trees and distilled to be in a liquid state for easier applications. Rosin is a natural product derived from the resinous excretion of trees. It is a glassy mix of abietic acid with some related (isomorphic) compounds and numerous hydrogenated modifications of that acid. Note that while rosin is distilled from resin, resin is not rosin.

Resin fluxes or synthetic Resin fluxes: Fluxes made with synthetic components. Most synthetic fluxes are based on organic acids like rosin, although other materials are used - primarily in low solids formulations - such as polyvinyl acetate, pentaerythritol tetrabenzoate, and bile acids.

No Clean flux: Those fluxes are mainly made up of synthetic resins and their residues are non-corrosive and non-sticky. They were designed to be left on the board for applications where such residues are acceptable. However there are many occasions in which their residue must be cleaned to comply with their application, such as High Frequency applications etc. See the following comments: � Flux residue effects on circuit performance? But according to our own experience through a modification for more than 1000 boards, the flux residues remaining after manual rework are very critical. Tens of faulty boards passed all normal & burn-in tests just by cleaning the residues of the No Clean Flux. � No-clean flux residues can be either cleanable or not cleanable. The not cleanable type leave a milky white residue on the solder connection after suitable soaking in water. Your flux supplier will have suggestions on the appropriate flux. � Clean the (no-clean) assembly (post wave). The less on there to begin with, the less cleaning required. sidebar: Why clean no clean? Use water soluble flux!!!

Low Residues: This is another way of naming the �No Clean� family of fluxes. Those fluxes are mainly made up of synthetic resins and their residues are non-corrosive and non-sticky. Comments: � With a proper thermal profile and wave dwell time the interflux was the leader in remaining residue (lowest). Also keep in mind the above statement is true for ALL fluxes (including your current flavor).

VOC-Free: A flux having no Volatile Organic Compounds such as alcohol.

Halide-Free: A flux having no halides (free chlorine ions). Those halides are normally added to increase the duration of activeness of flux during the whole process of oven reflow. When the flux composition needs to be altered to meet certain requirements, such as increased corrosion, activators are added. These are organic acids, halogenated compounds and amides, or subsequent mixes of these chemicals that assort: organic halide salts, organic mono-basic and organic di-basic acids. Their primary role in this sense is to extend the oxide reduction capacity, as opposed to increasing reaction rates as is often thought.

Water Washable with alcohol base: A flux made up of a base of alcohol which�s residues can be cleaned off with water.

Water Soluble: A water soluble flux is one that its base is made up of water and by so can be cleaned easily with water.

Resin-Free No Clean: A �No Clean� flux containing no Rosin elements. It is mostly a synthetic resin which residues are non-corrosive and non-sticky.

No Residue Flux: A flux which has no residues left on the board after the soldering process. The residues are evaporated.

High Solids Flux: A flux containing a large quantity of solids such as resins. Those fluxes leave larger quantities of residues on the board. They are designed where stronger activity is required.

Halogenated and Organic Acid Activated: A flux containing halides and activators in a rosin type flux.

Activator: Agents also called catalysts which increase the reaction without interfering with the process. They are found in most Rosin fluxes and are designed as RA for Rosin Activated (strong) and RMA for Rosin Mildly Activated.

Corrosive: That attack surfaces such as metal by an acid or a base.

Organic Acid: Organic acidic elements such as the ones found in Rosin. It is made-up of long chain of organic acid molecules which are broken down during the normal heat process of soldering. Once heated and broken-down those acids are normally non-corrosives.

Inorganic Acid: Non-organic acidic elements which are corrosive in their natural state and remain also corrosive after being through the soldering process. It has to be cleaned right away after the soldering process or it might corrode the solder and unprotected conductors.

Organic Compound: A natural compound made up of a long chain molecule which are often broken up in particles during normal heat-up process of soldering.

Aqueous Cleaner: Water base cleaner.

Solvent: A liquid that dissolves an element or a compound.

Surfactant: Also called Surface Active Agent. A substance which lowers the surface tension of the medium in which it is dissolved, and/or the interfacial tension with other phases, and, accordingly, is positively adsorbed at the liquid/vapour and/or at other interfaces.

Saponifier: A compound that transforms a residue (flux in this case) into soap. Once transformed into soap, this latter can be washed off easily with water.

Neutralizer: Agents such as an acid or a base (alkali) used to neutralize or de-activated a base or an acid. The acid will neutralize a base and a base will neutralize an acid.

reply »