Factors affecting the quality of reflow soldering by SMT chip
1. Influencing factors of solder paste
The quality of reflow soldering is affected by many factors, the most important factor is the temperature curve of the reflow soldering furnace and the composition parameters of the solder paste. The high-performance reflow soldering furnaces commonly used nowadays can more easily and accurately control and adjust the temperature. In contrast, in the trend of high density and miniaturization, the printing of solder paste has become the key to the quality of reflow soldering.
The particle shape of the solder paste alloy powder is related to the welding quality of narrow-pitch devices, and the viscosity and composition of the solder paste must also be selected appropriately. In addition, the solder paste is generally stored in a cold storage, and the lid can only be opened after it is returned to room temperature when used. Pay special attention to Avoid mixing the solder paste with water vapor due to temperature difference, if necessary, stir the solder paste with a mixer.
2. Influence of welding equipment
Sometimes, the excessive vibration of the conveyor belt of the reflow welding equipment is also one of the factors affecting the welding quality.
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3. Influence of reflow soldering process
After eliminating the abnormal quality of the solder paste printing process and the placement process, the reflow soldering process itself will also cause the following quality anomalies:
(1).Cold welding is usually a low reflow temperature or insufficient time in the reflow zone.
(2).The temperature of the tin bead preheating zone is too fast (generally, the slope of temperature rise is less than 3 degrees per second).
(3).The tin solder circuit board or components are wet, and excessive moisture can easily cause tin explosion to produce tin.
(4).The crack is generally that the temperature in the cooling zone drops too quickly (generally, the temperature drop slope of lead welding is less than 4 degrees per second).