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1.1 What is Box Build?

Scope, role in manufacturing, and where it fits in the flow.

Box build—often called final assembly or system integration—is where all the finished pieces come together into a working product. It’s the stage after PCBs are soldered and harnesses are tested, where mechanical parts, wiring, firmware, and accessories are fitted, connected, and verified. This step carries the responsibility for mechanical fit, electrical performance, safety compliance, cosmetic finish, and correct labeling before shipment. Because it’s the last point before the customer sees the product, box build blends precision, variant control, and disciplined checks to ensure everything works and looks right the first time.

1.1.1 Plain-English definition

Box build (a.k.a. final assembly or system integration) is where we take finished subassemblies—PCBA(s), harnesses, displays, fans, storage, power supplies, enclosures—and turn them into a working product. It’s the last mile: mechanical fit, wiring, firmware/config, functional/safety test, labels, and pack-out.

Think: everything after soldering the boards and before the shipping label.



1.1.2 What’s in scope vs out of scope

In scope (typical)

Notes

Mechanical assembly (enclosures, standoffs, gaskets, bezels)

Torque control, thread care, adhesives/TIMs, seals

Wiring & interconnects

Harness routing, strain relief, shield bonds, panel jumpers

Sub-assembly integration

Fans, drives, displays, keypads, antennas, thermal modules

Firmware load & config

Programming, keys/calibration, variant options

Functional & safety test

Power-on checks, I/O exercise, earth/hipot/leakage if required

Cosmetic & label control

Regulatory, serials, MAC/IMEI, warnings, branding

Pack-out

Kitting accessories, foam/box selection, documents


Out of scope (usually)

Where it happens

SMT/THT soldering

PCB assembly lines (Ch. 7–13)

Cable harness build

Harness cell (Ch. 19–21)

Metal/plastic fabrication

External vendors / mech shop



1.1.3 Where it sits in the factory flow

Materials → SMT/THT → Clean/Inspect → Programming (optional) → Conformal coat (optional) → Box Build → Test → Burn-In (if used) → Final QC → Pack & Ship

Handoffs into box build

  • PCBA(s) (AOI/AXI done, function/ICT passed)
  • Harnesses (tested, serialized)
  • Enclosure (painted/plated, threads QC’d)
  • Thermal parts (TIM pads/paste, heatsinks)
  • Bought-outs (PSUs, fans, drives, displays)
  • Docs (BOM, exploded view, torque chart, routing map, label set)

1.1.4 Levels of build (what “box” means today)

Level

Example

You focus on…

Sub-assembly

PSU tray, fan wall, front I/O panel

Fixtures, torque & ESD, fast flow to final

Chassis/system

Desktop, gateway, rack unit

Harness routing, airflow, EMC seals, test

Cabinet/integration

Multi-unit rack, kiosk

Crating, cable management, site labels, safety locks



1.1.5 The Box Build “contract” (inputs & outputs)

Inputs you must have (Golden Data Pack + fixtures):

  • Exploded views, step-by-step SWI with photos, routing diagram, torque map, adhesive/TIM notes, label map
  • Test plan (limits, fixtures, scripts) and programming image
  • Variant matrix (which options/labels/accessories per SKU)
  • Acceptance criteria (cosmetics, gaps, flushness, wobble, noise)

Outputs you own:

  • A powered unit that boots, passes test, and is safe
  • Serialization (unit & subassemblies bound in MES)
  • Regulatory & customer labels applied correctly
  • Pack kit complete and documented


1.1.6 Decision gates (don’t build past a bad step)

  1. Kitting OK — all parts, correct variant, ESD-safe, torque tools in cal.
  2. Mech First Article — dry fit: standoffs heights, hole alignments, door/cover fit, gasket compression.
  3. Torque Audit — sample fasteners meet spec; threadlock/washer types correct.
  4. Cable Routing Check — clamps, bend radii, shield bonds, no pinch points.
  5. Power-On / Functional — passes scripted FCT; fans/LEDs/sensors behave.
  6. Safety Test — earth/hipot/leakage where required.
  7. Cosmetic & Label — gaps/flushness/finish; all marks/legal/regulatory in place.
  8. Pack Review — accessories, manuals, foam orientation, drop-test method.

Fail any gate → NG-QUAR the unit and fix before moving.


1.1.7 Tooling & controls that make BB smooth

  • Torque drivers with programmed setpoints + bit ID; post the torque map.
  • Locating fixtures: zero-point pins for chassis, display bezels, and PSU cages.
  • Adhesive/TIM kits: pre-cut pads, measured syringes; one bead size chart.
  • Label station: prints from MES only; no hand edits.
  • ESD discipline: mats, straps, ionizers; metalwork bonded; safe power-up routine.
  • Visual boards: routing photos, connector pin-1, gasket path, label diagrams.


1.1.8 Roles & handoffs (who does what)

Role

Key responsibilities at box build

ME/IE

Cell layout, fixtures, torque map, time study, ergonomics

PE/TE

SWIs, routing/label maps, programming image, test limits

QE

Cosmetic criteria, torque audits, safety test compliance

Operators

Assembly per SWI, ESD, torque discipline, self-checks

Tester

Program load, FCT/safety tests, result logging

Planner/Logistics

Kitting & variant control, accessories, pack materials


1.1.9 Why box build matters (and common traps)

Why: it’s where fit, finish, and function meet. A great PCBA can still fail here from bent pins, crushed gaskets, wrong labels, or cables pressed against fans.

Traps → Smallest reliable fix

  • Variant mix-ups → Scan SKU/Variant to unlock SWI, label set, and test.
  • Stripped threads → Torque map + thread repair kits; start fasteners by hand.
  • Fan/noise/thermals → Respect airflow arrows; TIM amount & placement; don’t block vents with harness.
  • EMC regressions → Ensure 360° shield bonds, gasket continuity, paint scrape points where called.
  • Cosmetic defects → Handle with gloves; use clean mats; inspect at bright, diffuse light.


1.1.10 Pocket checklist (start-of-lot)

  • Kit & Variant match traveler; accessories present
  • Fixtures & torque tools verified and in cal
  • SWI/label/test programs loaded from MES by scan
  • First Article: dry fit + torque + routing check signed
  • Safety equipment (ESD, guards) in place



Bottom line: Box build turns good parts into a good product. Define the scope, lock variants by scan, use fixtures and torque control, route cables with intent, and gate every unit through function, safety, cosmetics, and labeling. Do that, and the last mile becomes the most predictable one.


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