Description
Flux: A chemical substance that can help and promote the welding process, and has a protective effect and prevents oxidation reactions. Flux can be divided into solid, liquid and gas. It mainly includes "assisting heat conduction", "removing oxides", "reducing the surface tension of the material being welded", "removing oil stains on the surface of the material being welded, increasing the welding area", and "preventing reoxidation". Among these aspects, the two most critical functions are: "removing oxides" and "reducing the surface tension of the material being welded".
Selection of flux The function of flux is to improve welding performance and enhance welding firmness. Flux can remove oxides on the metal surface and prevent it from continuing to oxidize, enhance the activity of solder and metal surface, thereby increasing wetting ability and adhesion.
Flux includes strong acid flux, weak acid flux, neutral flux and other types. Commonly used fluxes for electricians include rosin, rosin solution, solder paste and solder oil, etc. Their applicable range is shown in the table, and they can be reasonably selected according to different welding objects. Solder paste and solder oil are corrosive and cannot be used to solder electronic components and circuit boards. After soldering, the residual solder paste and solder oil should be wiped clean. Rosin should be used as flux when tinning the pins of components. If the printed circuit board has been coated with rosin solution, no flux is needed when soldering the components.
For manufacturers, there is no way to test the composition of the flux. If you want to know whether the flux solvent is volatilized, you can simply measure the specific gravity. If the specific gravity increases a lot, it can be concluded that the solvent has volatilized.
When choosing flux, there are the following suggestions for manufacturers:
First, smell the odor to preliminarily determine what kind of solvent is used. For example, methanol has a relatively small smell but is very choking, isopropyl alcohol has a heavier smell, and ethanol has a mellow smell. Although the supplier may also use a mixed solvent, if the supplier is asked to provide a composition report, they will generally provide it; however, the price of isopropyl alcohol is about 3-4 times that of methanol. If the price is severely reduced with the supplier, it may be difficult to say what is inside
Second, determine the sample. This is also the most fundamental method for many manufacturers to choose flux. When confirming the sample, the supplier should be asked to provide a relevant parameter report and compare it with the sample. If the sample is confirmed OK, the subsequent delivery should be compared with the original parameters. When abnormalities occur, the specific gravity, acidity value, etc. should be checked. The amount of smoke generated by the flux is also a very important indicator.
Third, the flux market is mixed. When choosing, you should have a clear understanding of the qualifications of the supplier. If necessary, you can go to the manufacturer to see the factory. If it is an informal flux manufacturer, it is very afraid of this set. How to use the flux Before introducing the method of use, let's talk about the classification of flux. It can be divided into a series of non-polar flux. The one sold on the market is called "solder oil". Be sure to clean it after use, otherwise it is easy to corrode and damage the welded object.
Another type is an organic series flux, which can quickly decompose and leave inactive residues. Another type is a resin active series flux. This type of flux is non-corrosive, highly insulating and has long-term stability. The most commonly used one is to add an activator to the rosin flux.
Generally speaking, the method of using aluminum flux is relatively simple. First, wipe alcohol on the weld to remove oil stains, and then you can apply the flux to the surface to be welded, and then you can weld. But you must remember to clean it after welding, and pay attention to safety during use, and don't let it enter the mouth, nose, throat and contact the skin. When not in use, just seal it and place it in a cool and ventilated place.
The key to soldering circuits with tin bars is to clean the soldering area, heat and melt the rosin on the soldering area or apply the flux on the object to be soldered, and then use the soldering iron to tin it and point it on the point to be soldered. Generally, rosin is used to solder small components, and flux is used to solder large components. Rosin is used on circuit boards, and flux is used for single-piece soldering.
Instructions:
1. The sealed shelf life is half a year. Please do not freeze the product. The best storage temperature: 18℃-25℃, the best storage humidity: 75%-85%.
2. After the flux is stored for a long time, its specific gravity should be measured before use, and the specific gravity should be adjusted to normal by adding diluent.
3. Solvent flux is a flammable chemical material. It should be operated in a well-ventilated environment, away from fire, and avoid direct sunlight.
4. When using flux in a sealed tank, pay attention to reasonably adjusting the spray volume and spray pressure according to the performance of the wave crest furnace and the characteristics of the product.
5. When the flux is continuously added in the sealed tank, a small amount of sediment will accumulate at the bottom of the sealed tank. The longer the time, the more sediment will accumulate, which may cause the spray system of the wave crest furnace to be blocked. In order to prevent the sediment from blocking the spray system of the wave crest furnace, affecting the spray volume and spray condition and causing PCB soldering problems, it is necessary to regularly clean and maintain the spray system such as the sealed tank and filter. It is recommended to do it once a week and replace the flux with sediment at the bottom of the sealed tank.
For manual soldering operations:
1. Try not to pour too much flux at one time, add and supplement according to the amount of production;
2. Add 1/4 diluent every 1 hour, and add an appropriate amount of flux every 2 hours;
3. Before lunch and evening breaks or when stopping use, try to seal the flux;
4. Before leaving get off work at night, carefully pour the flux in the tray back into the bucket and clean the tray with a clean cloth for use;
5. When using the flux used yesterday, add 1/4 diluent and more than twice the amount of new flux that has not been used, so that the flux used yesterday can be fully used to avoid waste.
6. When applying flux with spray or foaming process, please regularly inspect the air pressure of the air compressor. It is best to filter the moisture and oil in the air with more than two precision screening programs, and use dry, oil-free, and water-free clean compressed air to avoid affecting the structure and performance of the flux.
7. Pay attention to the adjustment of the spray when spraying, and make sure that the flux is evenly distributed on the PCB surface.
8. The tin wave is flat, the PCB is not deformed, and a more uniform surface effect can be obtained.
9. When the tinned PCB is severely oxidized, please perform appropriate pre-treatment to ensure quality and solderability.
10. The unsealed flux should be sealed before storage. Do not pour the used flux back into the original packaging to ensure the cleanliness of the original liquid.
11. The scrapped flux needs to be handled by a dedicated person and cannot be dumped at will to pollute the environment.
12. During the operation, the bare board and the foot of the parts should be prevented from being contaminated by sweat, hand stains, face cream, grease or other materials. Before the welding is completed and not completely dry, please keep it clean and do not contaminate it with your hands. 13. The amount of flux coating depends on the product requirements. The recommended amount of flux for single-sided boards is 25-55ml/min, and the recommended amount of flux for double-sided boards is 35-65ml/min.
14. When the flux is applied by foaming process, it is necessary to control the specific gravity of the flux to prevent the structure and performance of the flux from being affected by the volatilization of solvents in the flux, the increase of specific gravity, and the increase of flux concentration. It is recommended to detect the specific gravity of the flux after about 2 hours of foaming. When the specific gravity increases, add an appropriate amount of diluent to adjust it. The recommended range of specific gravity control is ±0.01 of the specific gravity of the original liquid specification. 15. The preheating temperature of the flux, the recommended temperature for the bottom of a single-sided board is 75-105℃ (the recommended temperature for the surface of a single-sided board is 60-90℃), and the recommended temperature for the bottom of a double-sided board is 85-120℃ (the recommended temperature for the surface of a double-sided board is 70-95℃).
16. For other precautions, please refer to the Material Safety Specification Sheet (MSDS) provided by our company.
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Post time: Aug-29-2024
