PCB Tech - Acceptable standard of tin bead size on the surface of CBA board

Acceptable standards for tin beads:

1. The diameter of the tin bead does not exceed 0.13mm

2. The number of tin beads with a diameter of 0.05mm-0.13mm within the range of 600mm2 does not exceed 5 (single side)

3. The number of tin beads below 0.05 is not required

4. All tin beads must be wrapped by the flux and cannot be moved (the flux encapsulated to more than 1/2 of the height of the tin beads is judged to be pinched)

5. Tin beads did not reduce the electrical clearance of different network conductors to below 0.13mm

Note: Except for special control areas

Rejection criteria for tin beads:

Any non-compliance of the acceptance criteria is judged to be rejected.

Remark:

1. Special control area: tin beads visible under a 20x microscope are not allowed within 1mm around the capacitor pad on the differential signal line at the golden finger end

2. The existence of tin bead itself represents a process warning. SMT chip manufacturers should continuously improve the process to minimize the occurrence of tin bead.

The PCBA appearance inspection standard is the most basic standard for the acceptance of electronic products. According to different products and customer requirements, the acceptable requirements for tin beads will be different. Generally, it is based on the national standard and combined with customer requirements. To determine the standard.