The three checkpoints
IQC (incoming quality control) inspects components and materials when they arrive from suppliers, before they reach the production line. IPQC (in-process quality control) checks the process and the product during production. OQC (outgoing quality control) inspects finished, packed goods before they are released for shipment.
Many factories add FQC (final quality control) for inspection at the end of the assembly line, before packing, with OQC then covering the packed lots. Others merge the two. Names vary between factories; what matters is that each stage has a defined scope, a written instruction for your product and a record.
What each stage should cover
| Stage | When | What it checks | Records to ask for |
|---|---|---|---|
| IQC | On receipt of each lot | Part numbers, quantities, dimensions, appearance, supplier certificates, sample tests | Incoming inspection reports, certificates of conformance, reject records |
| IPQC | During production | First piece after setup, patrol checks at set intervals, process settings, station checks | First-piece records, patrol check sheets, parameter logs, line-stop records |
| FQC | End of line, before packing | Function, appearance and labeling, often on every unit | Test logs, inspection records, failure tallies |
| OQC | Packed lots, before release | Sampled inspection of finished goods, packaging, cartons, labels and quantities | OQC reports with the sampling plan used, lot release record |
IQC for electronic products
For electronics, incoming inspection deserves particular attention:
- Component authenticity. Parts bought from brokers rather than authorized distributors carry counterfeit risk. Ask how the factory sources parts and what it checks on broker purchases.
- Moisture-sensitive devices. Check that they arrive in sealed moisture barrier bags with desiccant, a humidity indicator card and the moisture sensitivity level on the label, and that broken seals are recorded. How the line then controls exposure is covered under SMT.
- Critical components. Batteries, displays, sensors and radio modules deserve product-specific checks, not just a count and a label check.
- Reduced and skip-lot inspection. A supplier with a good record may move to smaller samples, or have some lots skipped. Ask what sends it back to full inspection.
IPQC: catching problems while they are cheap
IPQC is where most defects can be stopped before they multiply. A useful IPQC system includes a first-piece check after every setup or changeover, patrol inspections on a fixed schedule, monitoring of key settings such as reflow profiles and screw torque, and clear authority to stop the line. On electronics lines, solder paste inspection and optical inspection data are part of this; see SMT. The first-piece check is a narrower, routine counterpart to formal first article inspection.
OQC and your own inspection
OQC is the factory’s release check, usually by AQL sampling. A pre-shipment inspection by your team or a third-party inspector is a separate check on your behalf. Both have a place, but neither replaces process control: by the time goods are packed, finding a problem is at its most expensive.
What to look for in a factory audit
- Independence. Does QC report to someone other than the production manager?
- Real records. Are check sheets filled in at the time, with measured values, or completed in bulk later?
- Nonconforming material. Is rejected material tagged, held in a marked area and reviewed, or does it drift back to the line?
- Feedback. Do IQC rejects and IPQC findings lead to corrective action with suppliers and on the line (CAPA, 8D), or are they only counted?
- Your critical characteristics. Are they written into the inspection instructions for your product, or is the factory using a generic checklist?
The factory audit checklist turns these points into questions you can use on site.
Common mistakes
- Relying on a third-party pre-shipment inspection as the only quality control.
- IQC that checks labels and quantities but not your critical parts.
- No first-piece check after changeovers.
- QC staff who report to production and are under pressure to pass goods.
- Inspection data that is collected but never reviewed.
Where Zefinity helps
Inspection stages look much the same on every factory’s organization chart; the difference shows in the records. During factory audits and supplier qualification, Zefinity reviews how a supplier actually runs incoming, in-process and outgoing inspection, which records it keeps and whether findings lead to change, before you commit to that supplier.
Frequently asked questions
What is the difference between QC and QA?
Quality control (QC) inspects products and processes to find nonconformities; IQC, IPQC and OQC are QC activities. Quality assurance (QA) designs the system that prevents them: quality plans, procedures, audits, training and corrective action. A factory can employ many inspectors and still have weak QA if findings never change how the work is done.
Is OQC the same as a pre-shipment inspection?
Not quite. OQC is the factory's own release inspection. A pre-shipment inspection is done by the buyer or an independent inspector on the buyer's behalf, usually against the buyer's specification and sampling plan. Many buyers use both: OQC as the factory's responsibility, and pre-shipment inspection as an independent check.