According to the environmental requirements of flux, it can be divided into: 1. Lead flux; 2. Lead-free flux; 3. Halogen-free flux; 4. Environmental protection flux
If we make a detailed introduction to flux, it will not be as simple as the above classification. The following Guangshengde wave soldering will explain the classification of wave soldering flux in detail according to the chemical composition:
(1) Inorganic flux Inorganic flux has strong chemical action and excellent welding performance, but it is corrosive and belongs to acidic flux. Because it is soluble in water, it is also called water-soluble flux. Water-soluble flux includes inorganic acids and inorganic salts.
The main components of flux containing inorganic acid are hydrochloric acid, hydrofluoric acid, etc. The main components of flux containing inorganic salts are zinc chloride, ammonium chloride, etc. Very strict cleaning must be carried out immediately after use, because any halide left on the welded parts will lead to serious corrosion. This kind of flux is usually only used for welding non-electronic products, and it is forbidden to use this inorganic series flux in the assembly of electronic equipment.
(2) Organic Flux The soldering aid function of organic series flux is between inorganic series flux and resin series flux, and it also belongs to acidic and water-soluble flux. Water soluble fluxes containing organic acids are based on lactic acid and citric acid. Because its welding slag can remain on the welded object for a period of time without being seriously corroded, it can be used for the assembly of electronic equipment, but it is generally not used in SMT solder paste because it does not have the viscosity of rosin flux (to prevent chip components from moving).
(3) Resin-based flux is the most widely used in electronic product welding. Because it can only be dissolved in organic solvents, it is also called organic solvent flux, and its main component is rosin. Rosin is inactive in solid state, and only active in liquid state. Its melting point is 127℃, and its activity can last to 3 15℃. The optimum brazing temperature is 240 ~ 250℃, so there is no corrosion problem in the active temperature range of rosin. These characteristics make rosin a non-corrosive flux and widely used in the welding of electronic equipment.
The types of flux are far from standardized as solder alloys. At present, many manufacturers at home and abroad produce various types of flux with different functions, and the actual varieties even reach hundreds. Therefore, there are many classification methods for wave soldering flux. Traditionally, wave soldering fluxes are divided into seven types: R (rosin type), RMA (medium active rosin type), RA (high active rosin type), oA (organic acid type), IA (inorganic acid type), ws (water soluble type) and 5A (high active synthetic type).
Rosin is the main active component of R, RMA and RA wave soldering fluxes, but the chemical activity increases in turn. At present, rosin-based wave soldering flux is mostly synthetic raw materials. Rosin can be used as both an activator and a film-forming substance to cover the welding surface.
OA-type flux takes organic acid as active component, which is more active than RA-type 5 1A wave soldering flux, and takes inorganic acid as main active component, so it is the most active and corrosive wave soldering flux. Generally, it is only used when the pollution is particularly serious.
The residue of sA flux can be dissolved in fluorine and chlorine solvents. It is mainly used with Neon-Leon (cFcs) cleaning agent, but it has been replaced by water-soluble wave soldering flux.
Ws wave soldering flux and its reaction products are soluble in water, and it is convenient to clean up the residue after welding, and its activity is higher than rosin wave soldering flux. When using this flux, attention should be paid to the cleanliness of ionic residues to avoid residual corrosion.
The reaction residue of the above wave soldering flux generally needs to be cleaned after welding. In order to avoid the cleaning process, there is also an important wave soldering flux, which is no-cleaning flux. The residue of this wave soldering flux is generally considered to be benign and will not cause corrosion to solder joints and printed circuits, so it is allowed to leave the factory for assembly and welding parts. Before cleaning wave soldering flux, rabbits often use ethanol as solvent and medium, which contains a small amount of active ingredients such as rosin and even organic acids. A new type of non-cleaning wave soldering flux is water-based, which uses water instead of ethanol as solvent, thus eliminating organic volatile components. At the same time, because the active agent can be fully ionized in water, the cleaning ability of metal oxides is enhanced. The "no-cleaning" characteristic of no-cleaning flux mainly comes from the fact that its effective component content is much lower than that of ordinary wave soldering flux. Because many active agents such as rosin and halogen are solid at room temperature, the solid content of wave soldering flux is often used to indicate its activity. The solid content of non-cleaning wave soldering flux is often around 1%-3%, which is much lower than the level of ordinary wave soldering flux of 20%-35%, so the activity and solid content of its residue are very low. No-cleaning flux is also often called low solid content flux, low residue flux and so on. , mainly used for assembly and welding of electronic products with less serious oxidation and less importance.
In addition, wave soldering flux has the following categories;
(1) According to the solid content in the flux, there are wave soldering fluxes with low solid content (solid content < 2%-3%) 10%) and high solid content (> 15%). Low solid content is mainly used for solvent-free welding.
(2) According to the form at room temperature, such as in-situ wave soldering flux (such as welding wire core), paste wave soldering flux (commonly used for reflow soldering and manual soldering) and liquid wave soldering flux (commonly used for wave soldering).
(3) According to the cleaning method or medium of post-welding residue, there are water-soluble and organic-soluble wave soldering fluxes. In fact, many water-based wave soldering fluxes will still add some solvents to the water when cleaning.
(4) According to the types of active agents, there are inorganic, organic and rosin, which is also a common classification method.
Transferred from Guangshengde official website