What are the causes of voids in PCBA solder joints after solder paste soldering?

fromSMTFrom the perspective of surface mount technology (SMT) processing, the porosity rate is inevitable. No manufacturer can claim that there is not a single void in the solder joints of its surface mount technology. So how does the void come into being? What is the reason for the emptiness? Through JJYSolder paste manufacturerThe engineer explained that the main reasons for the formation of the cavity are as follows:

The main reason for the formation of voids at solder joints is that the bubbles produced by the decomposition of organic substances in the flux when heated cannot be discharged in time. After cooling in the solder joints, voids will occur. The influencing factors of solder joint voids are as follows:

1Flux activity. Due to the high-temperature cracking of the organic substances in the flux, the bubbles are difficult to escape, resulting in the gas being trapped in the alloy. If the buoyancy of the gas produced by the organic matter is less than the surface tension of the solder, the gas will be trapped inside the solder joint, thereby forming a vowel phenomenon.

2Welding time.Sn63-Pb37The impregnation time of the solder is very short, approximately0.6sAndSnAgCuThe impregnation time of the solder is approximately1.5sIn these cases, the gases produced by the pyrolysis of organic matter are difficult to escape and will be completely enclosed in the alloy layer.

3Moisture in the solder paste. After the solder paste is taken out of the refrigerator, it should be at room temperature(25℃±3℃)Save at least4Avoid inhaling moisture from the air. Solder paste must be stirred before use. During the manual stirring process, the time should not be too long(about3min-5min)The stirring force should not be too strong. It is recommended to use a centrifuge for stirring. Solder paste should not be left in the air for too long after printing(Generally2Within an hour)Otherwise, excessive water absorption of the solder paste will increase the probability of cavity formation.

4Solder pad oxide.PCBThe higher the degree of oxidation and dirt on the surface of the solder pad, the more it will be after weldingPCBAThe more cavities are produced by the solder joints. The greater the degree of oxidation of the solder pad, the stronger the active agent is needed to deal with the oxide on the surface of the welded object. Solder paste and oxides on the surface of the metal to be welded must be avoided. Otherwise, there is no other way to reduce the formation of cavities.

JJY Solder Paste Manufacturer mainly engages in lead-free solder paste.SMTSurface mount solder pasteLEDWe are engaged in the research and development, production and supply of solder pastes, lead-free solder wires, wave soldering rods and other solder solders. For more knowledge about electronic soldering, you can follow and contact us. Welcome to interact with us.