PCBA Circuit Board Through the Tin Influence Factor Analysis
In the process of PCBA circuit board processing, the choice of tin permeability is very important, according to the IPC scale, through-hole solder joints pcba tin permeability requirements are generally more than 75% can be, that is, the welding of the opposite side of the board appearance overhaul the tin permeability scale is not less than 75% of the height of the aperture (thickness), PCBA tin permeability is appropriate in 75%-100%. PCBA circuit board tin permeability is mainly affected by Materials, wave soldering process, flux, hand soldering and other factors, the following with the editor to learn more about.
High-temperature melting of tin has a strong penetration of exudate, but not all of the welded metal (PCB board, components) can penetrate the exudate into, such as aluminum metal, the surface of which will generally automatically form a dense protective layer, and the internal molecular structure of the different molecules make it difficult for other molecules to penetrate the exudate into. Second, if the surface of the soldered metal has an oxidized layer, will also prevent the penetration of molecules, we generally use flux treatment, or gauze brush clean.
Flux is also an important factor affecting the PCBA through the tin bad, flux mainly play a role in removing PCB and components of the surface oxides and welding process to prevent re-oxidation of the role of flux selection is not good, uneven coating, the amount of too little will lead to poor through the tin. Can choose a famous brand of flux, activation and infiltration effect will be higher, can effectively remove the difficult to remove the oxide; check the flux nozzle, damaged nozzle need to be replaced in a timely manner to ensure that the surface of the PCB board coated with the appropriate amount of flux, flux flux effect.
PCBA through the tin bad natural directly with the wave soldering process has a direct relationship to re-optimize the tin through the bad welding parameters, such as wave height, temperature, welding time or moving speed. First of all, the appropriate angle of the track to drop a little, and increase the height of the wave crest, progress liquid tin and welding real contact; then, increase the temperature of the wave soldering, in general, the higher the temperature of the tin penetration osmosis is stronger, but this should be considered the components of the tolerable temperature; finally, you can reduce the speed of the conveyor belt, increase the preheating, soldering time, so that flux can be sufficient to remove the oxides, soak the end of the weld and progress in the tin eating quantity.
In the actual plug-in welding quality maintenance, there is a proportion of a sector of the weldment only the surface of the solder to form a cone, and no tin through the hole, the function of the test confirmed that many of this sector is a virtual weld, this situation is mostly in the manual plug-in welding, the reason is that the temperature of the iron is inappropriate and the soldering time is too short. pcba through the tin easily lead to poor soldering issues, increase the cost of repair. If the PCBA through the tin requirements are higher, the welding quality requirements are more stringent, you can use selective wave soldering, can effectively reduce the PCBA through the tin bad topic.
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