Causes and control methods for forming pores during SMT soldering
In the SMT soldering, chip processing welding is a highly demanding process , and it is prone to various small problems. If it cannot be solved, it will also affect the product quality. Take welded pores as an example, this is a problem associated with welded joints. The presence of pores affects the mechanical properties of welded joints because the growth of pores can evolve into large cracks, increasing the burden on the solder and damaging the joints,strength, ductility and service life. So what is the reason for the formation of pores in SMT soldering? How to control the reduction of it? The following FASTPCBA technicians will introduce for everyone.
First.the reason for surface mount technology welding to form pores:
In the welding process, the formation of the pores is more complicated. Typically, voids are caused by flux venting entrained in the solder in the laminar structure during reflow . The formation of pores is mainly determined by the weld ability of the metallization zone, and decrease as the flux activity decreases, the metal load of the powder increases, and the coverage area under the lead joint changes,reducing the size of solder particles will only allow for increased porosity.
In addition, the formation of pores is also related to the coalescence of the solder powder and the elimination of the time distribution between the fixed metal oxides. The earlier the solder paste coalesces, the more pores are formed. In addition, the solder will shrink when solidified, and the layered exhaust and entrapped flux in the welding electroplating through hole are also the causes of porosity.
Second, the method of controlling pore formation in surface mount technology:
1,Use a flux with higher activity;
2, Improve the solderability of components or boards;
3, Reduce the formation of solder powder oxides;
4, Using an inert heating atmosphere;
5, Reduce the degree of preheating of remelted lead.
The reasons and control methods for forming pores in surface mount technology welding are introduced as above, hope it’s helpful for everyone. In the SMT mounting soldering process, understanding the problems and solutions that are easy to occur in each step can avoid the defects and solve the problems in time.
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