Paste chemicals that are the two main functions of “removing oxides” and “reducing the surface tension of the material being welded”. Widely used in watch instruments, precision parts, medical equipment, stainless steel crafts, tableware, mobile communications, digital products, air conditioning and refrigerator refrigeration equipment, glasses, knives, automotive radiators and various PCB boards and BGA solder balls brazing.

How to use solder paste _How to use solder paste

How to use solder paste _How to use solder paste

can be divided into stainless steel Solder paste, aluminum copper solder paste, etc.

(1) Inorganic Series Flux Inorganic series flux has strong chemical action, very good fluxing performance, but high corrosion effect and is an acidic flux. Because it is dissolved in water, it is also known as water-soluble flux, which includes inorganic acids and inorganic salts.

The main component of the flux containing inorganic acid is hydrochloric acid, hydrofluoric acid, etc. The main components of the flux containing inorganic salts are zinc chloride, ammonium chloride, etc., which must be carried out immediately after use. Strict cleaning, because any halides remaining on the parts to be welded can cause severe corrosion. Such fluxes are usually only used for the soldering of non-electronic products, and such inorganic series of fluxes are strictly prohibited in the assembly of electronic equipment.

(2)Organic Series Flux (OA)

The flux of organic series flux is between inorganic series flux and resin series flux. It is also acidic. Water soluble flux. The water-soluble flux containing organic acid is based on lactic acid and citric acid. Since its solder residue can be retained on the soldered material for a period of time without serious corrosion, it can be used in the assembly of electronic equipment, but generally it is not used. SMT solder paste, because it does not have the viscosity of the rosin flux (to prevent the movement of the patch components).

(3) Resin Series Flux

A resin type flux is used in the soldering of electronic products. Since 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 the solid state and is active only in liquid form. Its melting point is 127 ° C and its activity can last up to 315 ° C. The soldering temperature is 240-250 ° C, so it is in the active temperature range of rosin, and its welding residue does not have corrosion problems. These characteristics make rosin a non-corrosive flux and are widely used in the welding of electronic equipment. .

How to use solder paste_How to use solder paste

How to use solder paste_How to use solder paste

Because of atmospheric oxygen The reason is that various substances are actually surrounded by a layer of oxide, and the thickness is about 2 & TImes; 10-9 ~ 2 & TImes; 10-8 m. When soldering, the oxide film will inevitably prevent the solder from wetting the base material, and the soldering will not proceed normally. Therefore, it is necessary to apply a flux on the surface of the base material to reduce the oxide on the surface of the base material, thereby achieving the purpose of eliminating the oxide film. .

On the other hand, the high temperature of soldering tends to oxidize the surface of the solder material. The solder paste helps to prevent the oxidation process.

The surface tension of the material affects the quality of the solder, and the other role of the solder paste reduces the tension of the material. The surface tension of the molten solder prevents it from flowing to the surface of the base material, affecting the normal progress of wetting. When the flux covers the surface of the molten solder, the surface tension of the liquid solder can be lowered, and the wetting performance is remarkably improved.

Wipe the solder joints first, apply a little solder paste, then use a soldering iron to eat solder, and use a pinch to press the wires or pins on the solder joints. Use the tip of the soldering iron to gently press the soldering point to allow enough tin to flow to the solder joint and quickly remove the soldering iron. After the soldering iron is removed, wait until the tin is cooled and then release the pinch.

In order to match the use of solder, the melting point of the selected solder paste should be lower than the melting point of the solder by 10-30 °C. If the melting point of the solder paste is too low than the melting point of the solder, it will melt too early and lead to premature failure of the flux active ingredient.

For alkaline oxide films, an acidic solder paste should be selected; for acidic oxide films, an alkaline flux should be selected.

Select different types of solder paste according to the specific process. For example, liquid solder paste should be selected for wave soldering, paste flux should be selected for high frequency or medium frequency induction brazing, and powder solder should be selected for flame brazing. Flux or paste flux, etc.

Different matrix materials have different types of solder pastes due to their different surface oxide films, especially some difficult-to-weld metals, such as magnesium-containing aluminum alloys, stainless steels, and hard alloys. In order to ensure the welding performance of the magnesium-containing aluminum alloy, a flux having a stronger activity is usually selected.