Learning objectives
- Fit hardware and box build items using torque controlled tools and the build documentation
- Run a final visual audit against the accept criteria of IPC A 610
- Verify labels, serial numbers and traceability records before release
- Pack finished assemblies in ESD safe, moisture protective packaging to specification
Lesson
### Lesson 1: Final assembly and final inspection
The last stage turns a tested board into a shippable product and then proves, one final time, that the whole chain did its work. Where the product includes box build, operators fit heatsinks, apply staking and adhesive where the drawing calls for them, and drive fasteners with torque controlled tools set to the values in the product documentation. Under torqued hardware loosens in service. Over torqued hardware cracks boards and strips threads. The tool setting is part of the product, not a matter of feel. Labels and serial numbers are applied and verified, because the serial is the thread that ties this physical unit to its material lots, its test results and its build revision.
Final inspection then audits the finished assembly against the accept criteria of IPC A 610, taught on this platform in our own words and judged with properly licensed or customer supplied reference images, supported by any final functional audit the product requires. Sampling follows the product audit plan, findings are recorded, and nothing that fails is quietly passed because the order is urgent. James Onsomu ends his PCB quality chapter on thorough inspection and testing to verify functionality and reliability. This stage is where that promise is signed. A failure caught here is embarrassing and cheap. The same failure caught by the customer is neither.
### Lesson 2: Packing and traceability
Packing is a quality process, not a warehouse afterthought. Finished assemblies go into ESD shielding bags, because a static discharge in a delivery van can undo seventeen stages of discipline in a millisecond. Where the product requires it, the pack includes desiccant and a humidity indicator card so the assembly travels dry, with foam or formed protection against shock and the correct labels on the outside. The packing specification is followed exactly: bag type, moisture pack, label content and box quantity are all specified, and substitutions are engineering decisions, not bench improvisations.
The stage also closes the traceability record. Lot and date codes of materials, test logs, build revision and inspection results are complete and retrievable for every serial number shipped. The classic traceability break is a swapped or duplicated label: two products claiming one identity, or one product claiming another’s history. When a customer reports a field failure years later, that record is how a manufacturer answers with facts instead of apologies. The operator who verifies the label against the unit, and the unit against the record, is guarding the company’s memory of everything it shipped.
Key numbers
- Fastener torque: set to the values in the product documentation using calibrated, torque controlled tools
- Label and serial accuracy: verified 100 percent against the unit and the record before release
- Audit sampling: performed to the product audit plan, with all findings recorded
- Packing: ESD shielding bags for 100 percent of assemblies, with desiccant and humidity card included where the specification requires them
Defects to spot
- Wrong or missing hardware: kitting errors or attention lapses at box build
- Under torqued fasteners: tool setting wrong or tool skipped, leaving hardware to loosen in service
- Over torqued fasteners: cracked boards and stripped threads from wrong settings
- Swapped or duplicated labels: the traceability break, two units claiming one identity
- Cosmetic damage in packing: protection skipped or boxes overfilled
- Non ESD packaging: ordinary plastic used at the last step, undoing the ESD discipline of the whole chain
Stage check, self test
Answer each question, then open the answer to check yourself. Passing standard: 80 percent, at least 4 of 5 correct.
1. Why are fasteners driven with torque controlled tools at final assembly?
A. They are quieter than ordinary tools
B. Both under torque and over torque damage the product, so the setting is part of the product
C. They use less electricity
D. They make labels stick better
Show answer
Answer: B
2. Two shipped units are found carrying the same serial number. What has broken?
A. The packing tape supply
B. The humidity card stock
C. Traceability, because two products now claim one identity and one test history
D. Nothing important
Show answer
Answer: C
3. What is the correct packaging for a finished assembly leaving the line?
A. A plain cardboard box with no bag
B. An ordinary plastic bag from the canteen
C. Newspaper wrapping for cushioning
D. An ESD shielding bag, with desiccant and a humidity card where the specification requires them
Show answer
Answer: D
4. Final audit finds a defect on a unit and the order is shipping within the hour. What is correct?
A. Pass it quietly, the customer probably will not notice
B. Record the finding and hold the unit to the audit disposition, urgency does not change the criteria
C. Swap its label with a passing unit
D. Remove the audit page from the record
Show answer
Answer: B
5. What does the traceability record for a shipped serial number contain?
A. Only the shipping date
B. Material lot and date codes, test logs, build revision and inspection results for that unit
C. The operator’s lunch order
D. The customer’s marketing plan
Show answer
Answer: B
Previous: Stage 16: Depaneling