3.1 Printing Inspection
General rule: The amount of solder paste printed on the pad may deviate within certain limits, but the area covered by solder paste on each pad must exceed 75% of the pad area.
3.2 Dispensing Inspection
Ideal glue spot: There should be no traces of patch glue contamination visible on the pad or the lead-out end face. The glue spot should be centered on each pad, approximately 1.5 times the size of the dispensing nozzle. The quantity of glue should be determined based on the solder end of the component and should not soil the PCB pads after mounting.
3.3 Pre-Furnace Inspection
3.4 Post-Furnace Inspection
A satisfactory solder joint should be complete and well wetted, with the solder spread to the edge of the pad.
In SMT, quality defect statistics are crucial. For the quality defect statistics of reflow soldering, we employ the DPM statistical method, which stands for defects per million. The calculation formula is as follows:
Defect rate [DPM] = Total number of defects / Total number of solder joints * 10^6
Total number of solder joints = Number of tested circuit boards × Number of solder joints per board
Total number of defects = Total number of defects detected on all circuit boards
For instance, if a circuit board has 1000 solder joints, 500 boards are tested, and 20 defects are detected, the defect rate can be calculated as follows:
Defect rate [ppm] = 20 / (1000 * 500) * 10^6 = 40 ppm
General rule: The amount of solder paste printed on the pad may deviate within certain limits, but the area covered by solder paste on each pad must exceed 75% of the pad area.
3.2 Dispensing Inspection
Ideal glue spot: There should be no traces of patch glue contamination visible on the pad or the lead-out end face. The glue spot should be centered on each pad, approximately 1.5 times the size of the dispensing nozzle. The quantity of glue should be determined based on the solder end of the component and should not soil the PCB pads after mounting.
3.3 Pre-Furnace Inspection
3.4 Post-Furnace Inspection
A satisfactory solder joint should be complete and well wetted, with the solder spread to the edge of the pad.
In SMT, quality defect statistics are crucial. For the quality defect statistics of reflow soldering, we employ the DPM statistical method, which stands for defects per million. The calculation formula is as follows:
Defect rate [DPM] = Total number of defects / Total number of solder joints * 10^6
Total number of solder joints = Number of tested circuit boards × Number of solder joints per board
Total number of defects = Total number of defects detected on all circuit boards
For instance, if a circuit board has 1000 solder joints, 500 boards are tested, and 20 defects are detected, the defect rate can be calculated as follows:
Defect rate [ppm] = 20 / (1000 * 500) * 10^6 = 40 ppm
