1. Solder paste printing
Paste is printed through a stencil; SPI measures volume and alignment. This is the highest-leverage control point.
2. Placement
Pick-and-place mounts SMDs from feeders. Feeder setup and component verification decide whether the right part lands in the right place.
3. Reflow
The profile follows the paste alloy. Too little heat leaves cold joints; too much damages parts and the laminate.
4. Inspection
AOI checks placement and solder fillets; X-ray examines hidden joints such as BGAs and QFNs.
5. Through-hole and test
Selective or wave solder, cleaning where required, then ICT, flying probe or functional test according to the test plan.
6. Final
Depanel, clean, inspect against IPC-A-610, pack with traceability records. Each of the six stages is a place where a pcb assembly services supplier should be able to name the control point, not only the machine.
