01How the process works
Solder paste is printed through a stencil, components are placed by pick and place machines and the board is reflow soldered. Through hole parts are wave or selective soldered. Automated optical inspection (AOI), X-ray for BGAs, in-circuit and functional tests follow.
Most defects start at paste printing. Component traceability, moisture sensitive device handling and ESD protection are process controls auditors look for, alongside workmanship to IPC-A-610.
- Solder paste printing. Paste printed and inspected (SPI).
- Placement. Components placed by machine.
- Reflow. Controlled temperature profile.
- Inspection. AOI, X-ray, manual to IPC-A-610.
- Testing. ICT, functional test, conformal coat.
02What typically goes wrong
| Defect | Typical cause | How it is found |
|---|---|---|
| Solder bridges | Paste volume, stencil | AOI |
| Insufficient solder and opens | Printing, coplanarity | AOI, X-ray, ICT |
| Tombstoning | Pad design, reflow | AOI |
| BGA voids | Profile, paste | X-ray |
| Wrong or reversed components | Feeder set-up | AOI, first article |
| ESD damage | Handling | Functional test, audit |
03Where an inspector should look
01
Before production
- Gerber, BOM and first article
- Stencil and reflow profile
- MSD and ESD controls
02
During production
- SPI and AOI results
- Reflow profile checks
03
After production
- IPC-A-610 visual sampling
- Functional test results
- Packaging (ESD, moisture)
04Standards and references
IPC-A-610 (acceptability of electronic assemblies), IPC J-STD-001 (soldering), IPC-7711/7721 (rework), IEC 61340-5-1 (ESD).
Standards are named for orientation. The applicable edition and acceptance criteria are those in your contract and specification.
05How we support buyers of pcb assembly parts
Electrical and Instrumentation InspectionInspection of electrical panels, switchgear, cables, instrumentation and control systems, with electrical test witnessing.
Manufacturing and Special Process AuditsProcess audits of casting, machining, welding, heat treatment, plating and moulding, with VDA 6.3 style evaluation.
Pre-Shipment InspectionFinal random or complete inspection of finished goods before shipment: quantity, conformity, workmanship, packing and marking.