Before starting work every day, five mandatory hard-point inspections of the Reflow Soldering equipment must be completed, including whether the parallelism deviation between the left and right sides of the track and the center line is controlled within ±0.15mm, and whether the nitrogen supply pressure is maintained at 0.35MPa with the real-time displayed purity no less than 99.99%. Once these two parameters exceed the tolerance, it will directly lead to intensified oxidation of BGA solder joints and an increased proportion of poor wetting.

The measured temperature of each temperature zone must be verified segment by segment

Use a calibrated K-type thermocouple with a data collector to insert the standard test board three consecutive times at the middle position of each temperature zone for actual measurement. The deviation between the measured peak temperature of all temperature zones and the set value must be controlled within ±2℃. Among them, the 4th to 6th temperature zones are the main heating sections of reflow soldering. When the temperature fluctuation exceeds ±1.5℃, the melting consistency of the Solder Paste will significantly decrease, which will induce a large number of offset solder joints and incomplete reflow phenomena.

Chain speed and cooling air speed must be locked synchronously

The set value of the chain speed must strictly match the process card of the current product. After each line change, a stopwatch must be used to actually measure the 3-meter track transit time and back-calculate the chain speed, with the error not greater than ±0.02m/min. At the same time, the rotation speed of the top fan in the cooling section must ensure that the measured value of the anemometer is stable at 2.3m/s±0.1m/s. If the air speed is too low, the cooling rate of the bottom solder joints of QFN-type devices will be uneven, resulting in microcracks; if the air speed is too high, 0201 resistors will easily be blown off by the airflow.

Chain tension and guide rail cleanliness cannot be ignored

The chain tension needs to be tested with a special spring scale by applying a 20N pull force in the middle of the drive side to measure the deflection. The deflection value should be in the range of 8 to 12mm. Exceeding the range will cause PCB transmission jitter and superimpose the risk of solder joint cracking. The guide rail surface must be wiped with a dust-free cloth dipped in electronic-grade ethanol with a concentration of 99.7%. Residual solder residue or Flux carbide will form local hot spots after 8 hours of continuous operation, causing the temperature feedback distortion of adjacent temperature zones to reach more than 3℃.

The alarm log of Jia Jinyuan reflow soldering equipment must be checked item by item, especially the three types of high-frequency alarms: 'thermocouple disconnection', 'low nitrogen flow', and 'cooling fan stall'. Any record that has not been closed-loop processed means that the output batch of this shift is already in a state of quality risk exposure. Work must be suspended immediately, and production can only be resumed after completing the root cause analysis.