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What are the factors of PCBA processing through tin?
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- Date : 2022-08-14
In the process of PCBA processing, where the choice of tin permeability is very important. In the through-hole plug-in process, the PCB board through the tin is not good, easy to cause false solder, tin crack or even drop parts and other problems. So what aspects need to be grasped in the tin permeability?
A, PCBA through the tin requirements
According to the IPC standards, through-hole solder joints pcba tin permeability requirements are generally above 75% on it, that is to say, the appearance of the opposite side of the welded board inspection tin permeability standard is not less than 75% of the height of the aperture (board thickness), pcba tin permeability in 75%-100% are appropriate. And plating through-hole connected to the heat sink layer or play a role in heat dissipation of the thermal conductivity layer, pcba tin permeability is required more than 50%.
Second, the factors that affect the tin permeability of pcba
pcba through the tin is mainly affected by the material, wave soldering process, flux, manual welding and other factors.
On the specific analysis of the factors affecting pcba through tin.
1、Material
High-temperature melting tin has a strong permeability, but not all the soldered metal (PCB board, components) can be penetrated, such as aluminum metal, its surface will generally automatically form a dense protective layer, and the internal molecular structure of the difference also makes it difficult for other molecules to penetrate into. Second, if the surface of the soldered metal has an oxide layer, it will also prevent the penetration of molecules, we generally use flux treatment, or gauze brush clean.
What are the factors of PCBA processing through the tin?
2、Flux
Flux is also an important factor that affects the pcba through the bad tin, flux mainly plays a role in removing the PCB and components of the surface oxide and the welding process to prevent re-oxidation, flux selection is not good, uneven coating, too little will lead to bad tin through. Can use well-known brands of flux, activation and wetting effect will be higher, can effectively remove the difficult to remove the oxide; check the flux nozzle, the damaged nozzle needs to be replaced in a timely manner to ensure that the PCB board surface coated with the right amount of flux to play the flux flux effect.
3、Wave soldering
pcba through the tin bad natural directly with the wave soldering process has a direct relationship, re-optimize the tin through the bad welding parameters, such as wave height, temperature, welding time or moving speed, etc.. First of all, the appropriate angle of the track down a little, and increase the height of the wave, improve the amount of liquid tin contact with the solder end; then, increase the temperature of wave soldering, in general, the higher the temperature of tin permeability, but this should consider the tolerable temperature of the components; finally, you can reduce the speed of the conveyor belt, increase preheating, welding time, so that flux can fully remove the oxide, wetting the solder end, improve the amount of tin eaten.
What are the factors of PCBA processing through the tin?
4、Manual welding
In the actual plug-in welding quality inspection, there is a considerable part of the solder only after the formation of the surface solder taper, and no tin penetration in the hole, functional test to confirm that many of these parts are false solder, this situation is mostly in the manual plug-in welding, the reason is that the temperature of the soldering iron is not appropriate and welding time is too short. pcba poor tin penetration can easily lead to false soldering problems, increasing the cost of repair. If the requirements for pcba through the tin is relatively high, the welding quality requirements are more stringent, you can use selective wave soldering, can effectively reduce the problem of bad pcba through the tin.
A, PCBA through the tin requirements
According to the IPC standards, through-hole solder joints pcba tin permeability requirements are generally above 75% on it, that is to say, the appearance of the opposite side of the welded board inspection tin permeability standard is not less than 75% of the height of the aperture (board thickness), pcba tin permeability in 75%-100% are appropriate. And plating through-hole connected to the heat sink layer or play a role in heat dissipation of the thermal conductivity layer, pcba tin permeability is required more than 50%.
Second, the factors that affect the tin permeability of pcba
pcba through the tin is mainly affected by the material, wave soldering process, flux, manual welding and other factors.
On the specific analysis of the factors affecting pcba through tin.
1、Material
High-temperature melting tin has a strong permeability, but not all the soldered metal (PCB board, components) can be penetrated, such as aluminum metal, its surface will generally automatically form a dense protective layer, and the internal molecular structure of the difference also makes it difficult for other molecules to penetrate into. Second, if the surface of the soldered metal has an oxide layer, it will also prevent the penetration of molecules, we generally use flux treatment, or gauze brush clean.
What are the factors of PCBA processing through the tin?
2、Flux
Flux is also an important factor that affects the pcba through the bad tin, flux mainly plays a role in removing the PCB and components of the surface oxide and the welding process to prevent re-oxidation, flux selection is not good, uneven coating, too little will lead to bad tin through. Can use well-known brands of flux, activation and wetting effect will be higher, can effectively remove the difficult to remove the oxide; check the flux nozzle, the damaged nozzle needs to be replaced in a timely manner to ensure that the PCB board surface coated with the right amount of flux to play the flux flux effect.
3、Wave soldering
pcba through the tin bad natural directly with the wave soldering process has a direct relationship, re-optimize the tin through the bad welding parameters, such as wave height, temperature, welding time or moving speed, etc.. First of all, the appropriate angle of the track down a little, and increase the height of the wave, improve the amount of liquid tin contact with the solder end; then, increase the temperature of wave soldering, in general, the higher the temperature of tin permeability, but this should consider the tolerable temperature of the components; finally, you can reduce the speed of the conveyor belt, increase preheating, welding time, so that flux can fully remove the oxide, wetting the solder end, improve the amount of tin eaten.
What are the factors of PCBA processing through the tin?
4、Manual welding
In the actual plug-in welding quality inspection, there is a considerable part of the solder only after the formation of the surface solder taper, and no tin penetration in the hole, functional test to confirm that many of these parts are false solder, this situation is mostly in the manual plug-in welding, the reason is that the temperature of the soldering iron is not appropriate and welding time is too short. pcba poor tin penetration can easily lead to false soldering problems, increasing the cost of repair. If the requirements for pcba through the tin is relatively high, the welding quality requirements are more stringent, you can use selective wave soldering, can effectively reduce the problem of bad pcba through the tin.
