Wire Harness and Cable Assembly in China: What to Specify Before You Source

Wire Harness · Cable Assembly · EMS Integration Wire Harness and Cable Assembly in China: What to Specify Before You Source How a harness is built, what belongs on the drawing, which tests to demand, and when to integrate it into a box build — with QA-managed assembly through vetted partners in Dongguan, no MOQ. Request a quoteSee services What a wire harness is — and how it differs from a cable assembly A wire harness bundles many conductors — wires, cables and sometimes splices — into one organized assembly that routes power and signal through a product. A cable assembly is usually the simpler object: a cable terminated at one or both ends with a connector. The two terms get used interchangeably in RFQs, and that is exactly where quotes go wrong, because a harness and a cable assembly carry different tooling, different test plans and different prices. The practical question a sourcing manager should ask is not which word is correct but what the drawing actually requires. A 40-pin branched harness with mixed gauges, splices, sleeving and eight connectors is a different job from a single-jacketed cable with a JST on each end, even when both get filed under "cable assembly." Name the complexity up front and the quote stops hiding behind the word. AttributeWire harnessCable assembly Typical formMany conductors, branched, sleeved, often splicedOne or few conductors, connector-terminated Primary jobRoute power and signal across a systemCarry one signal or power between two points ComplexityHigh — branches, mixed gauges, breakoutsLow to medium ProtectionLoom, wrap, braided sleeving, heat-shrinkOuter jacket, overmold, heat-shrink Test emphasisContinuity per net, hipot, pull-test on every crimpContinuity, hipot, connector retention The assembly process: cut to test, in order A harness is built through a fixed sequence, and each step has a failure mode the next step cannot fix. Understanding that sequence is what lets you read a supplier's quote and know whether the price reflects the work or skips it. Cutting. Wire is cut to length from the reel. Length tolerance matters here — a harness cut 10 mm short gets stretched across a heatsink later, and one cut 30 mm long gets folded against a sharp edge. Neither fails on the bench; both fail after a year of vibration. Stripping. Insulation is removed to expose the conductor for termination. The strip length is set by the terminal; strip too deep and you nick strands, too shallow and the insulation sits inside the crimp barrel. Crimping. A terminal is compressed onto the conductor with a calibrated tool, forming a gas-tight mechanical and electrical joint. For production harnesses, crimping is the default over soldering — it is faster, more repeatable and, done correctly, more resistant to vibration than a solder joint that can wick and harden the strands into a stress point. Soldering. Used where the design or the connector calls for it — some splices, shielded drain wires and certain terminals. Soldering is a controlled process here, not a fallback for a crimp that would not hold. Sleeving. Heat-shrink, braided sleeving and loom are applied to protect, insulate and organize the bundle, and strain relief is anchored at the connectors. Testing. The finished harness passes continuity, hipot and pull-test — covered below — before it is bagged, labeled and shipped. In our Dongguan box-build line the harness is the part we check hardest at incoming, because a harness that passes its own test in isolation is not guaranteed to survive being routed, dressed and fastened into an enclosure. That is the step most suppliers never see. The components that make up a harness A harness is only as reliable as its weakest part, and most field failures trace to a component decision made at the drawing stage. These are the pieces you will see itemized on a BOM. Wire. Specified by AWG gauge, conductor stranding and insulation rating. Larger gauge numbers mean smaller cross-section, so current-carrying capacity falls as the number rises. Stranded conductors flex; solid conductors do not, which makes stranding the default for anything that moves. Insulation is matched to the environment — PVC such as UL1007 or UL1015 for general use, cross-linked materials for higher temperature, and tinned copper where corrosion resistance matters. Terminals. The metal contacts crimped onto each conductor — ring, spade, blade, pin and socket, in open-barrel or closed-barrel form. The terminal and the wire must be sized to each other, because a terminal stamped for one gauge range will not crimp a conductor outside it. Connectors. The plastic or metal housings that make the harness pluggable — Molex, JST, TE and Deutsch families among them, plus circular M8 and M12 for industrial I/O. Look for keying and polarization so a connector cannot be mated the wrong way, and a positive latch so it cannot vibrate apart. Heat-shrink. Polyolefin tubing that shrinks onto the joint for insulation and strain relief. Adhesive-lined, dual-wall heat-shrink adds a seal against moisture where the harness lives outdoors or in a washdown area. Braiding. Expandable PET sleeving that bundles and protects against abrasion, and metal braid that adds electromagnetic shielding over signal pairs. Braiding is chosen for the environment — a harness routed past a sharp chassis edge earns its sleeving the same way a signal pair near a motor earns its shield. Wire approvals and the environment: temperature, UL and sealing The insulation on the wire is the harness's first line of defense, and it is chosen against the environment, not just the gauge. The common PVC insulations — UL1007 (80°C) and UL1015 (105°C) — are rated for general use; where the harness runs hot, cross-linked insulation steps the rating up, and silicone or FEP/PTFE take the high-temperature and flex-life cases. A wire that looks fine and degrades in the heat is a failure that returns from the field, so match the insulation rating to the hottest point the harness will see in service, not the ambient the bench happens to run at. Flammability and sealing are the other two environment calls. A flame-retardant rating such as VW-1 matters wherever the harness lives in a product that carries a UL listing; halogen-free insulation matters in confined spaces where the fumes of a burning jacket matter as much as the fire. For moisture or washdown, adhesive-lined dual-wall heat-shrink over the splice or the connector backshell turns an open joint into a sealed one, and a sealed connector or an overmolded transition finishes the job. The environment picks the insulation, the flammability rating and the sealing — the drawing just has to say so. Testing: what each test actually catches Three tests do the heavy lifting on a harness, and each catches a different class of defect. Asking for "testing" without naming them leaves the door open for a continuity-only pass that ships a harness with a weak crimp. TestWhat it appliesWhat it catches ContinuityLow-voltage point-to-point check against the netlistMis-wiring, opens, shorts between nets Hipot (dielectric withstand)High voltage between conductors and to groundInsulation damage, pin-to-pin leakage, breakdown under voltage Pull-testAxial force on each crimp to a specified valueUnder-crimped or poorly stripped terminations that would pull free in service Continuity proves the harness is wired correctly; it says nothing about whether the insulation will hold voltage or whether a terminal will stay on the wire. Hipot proves the insulation survives its working voltage plus margin, which matters on anything that carries mains, motor or high-voltage battery lines. Pull-test proves the crimp has the mechanical retention its wire gauge demands — the pull-force values are set by gauge in IPC/WHMA-A-620, so a 20 AWG crimp is held to a different number than a 14 AWG one. A harness that passes all three is wired right, insulated right and terminated right. DFM rules that decide cost and field reliability Harness cost and reliability are set at the drawing, not at the bench. Five rules settle most of it. Wire gauge. Size conductors for the current they actually carry, not the next size up out of caution. Oversizing adds copper, weight and stiffness, and the stiffness is what breaks things. Undersizing is worse — it heats, and heating degrades the insulation over time. Match the gauge to the load, then add margin only where the derating table says so. Bend radius. Every wire has a minimum bend radius, commonly quoted as a multiple of the cable's outer diameter. Tighter bends concentrate stress in the insulation and the strands, and a harness routed around a tight chassis corner is a harness that fatigues. Leave the radius on the drawing and the routing will respect it. Strain relief. Tension must never reach a crimp or a solder joint. A clamp, a gland, an anchored cable tie or a dedicated strain-relief tab at each connector takes the pull instead of the terminal. The failure strain relief prevents is the one that takes a year of vibration to surface — the most expensive kind, because it returns from the field, not from the bench. Color coding. A consistent color scheme across the harness — and documented in the drawing — is what lets an assembler build it without error and a field technician service it without a schematic in hand. Inconsistent or undocumented colors turn every repair into a tracing exercise. Connector orientation. Keyed and polarized connectors remove the mis-mating failure entirely, and orientation should be fixed on the drawing so two operators build the same harness the same way. A connector that can be installed 180 degrees out will be, eventually — by someone on a tight schedule. IPC/WHMA-A-620: name the workmanship standard The standard that governs cable and wire harness assemblies is IPC/WHMA-A-620, Requirements and Acceptance for Cable and Wire Harness Assemblies, published by IPC. It defines the acceptance criteria for crimps, soldered terminations, sleeving, routing and strain relief, across three classes — Class 1 for general products, Class 2 for dedicated service, and Class 3 for high-reliability applications where a failure is not an option. Naming the standard and the class in your RFQ does two things. It tells the supplier exactly what "good" looks like, and it tells you, at inspection time, whether the harness was built to a recognized criteria set or to whatever the bench happened to produce. A supplier that works to IPC/WHMA-A-620 can show you a crimp-height chart and a pull-test log; a supplier that cannot is guessing. Ask which class the harness is inspected to, and hold them to it. Crimp inspection and traceability The crimp is the point where a harness most often fails, so it is the point where inspection earns its cost. Crimp quality is checked three ways: crimp height measured with a micrometer against the terminal's specification, a cross-section of sample crimps examined for strand fill and barrel closure, and a pull-test on every production lot. A crimp that is under-compressed is weak and will pull free; one that is over-compressed can cut strands and leave a joint that looks fine and fails under load. Traceability runs alongside inspection. Each lot is tied to its wire, terminal and connector batches, and each finished harness carries a label that points back to that record. When a field return lands eighteen months later, you isolate a batch instead of recalling a population — the same discipline our EMS side applies to every board, so a harness and the box it goes into share one traceable story. Source the harness separately, or with the box build? The decision is really about where the integration risk lives. A harness sourced alone from a specialist is fine when the harness is a standalone spare or a drop-in for an existing product — you buy it to a drawing, test it at incoming, and install it yourself. The economics are clean because a harness house amortizes its tooling and labor across many customers. The risk appears when the harness must fit a specific enclosure. A harness that is 10 mm short gets stretched; one that is 30 mm long gets folded; a connector that faces the wrong way forces a bend no drawing intended. None of these show up in the harness's own test report, because the harness passes in isolation. When the harness is built and tested by one supplier and installed by another, the fit problem lands on your dock, and two vendors point at each other. The rule: if the harness must mate with a machined enclosure, a board and a set of connectors you are already having someone else assemble, bundle it into that box build. One partner owns the fit, routes the harness against the approved dress, tests it in situ and ships a finished product — the failure mode that costs a year of field returns is caught at the bench instead. Why China for wire harness and cable assembly China is where the wire, terminals, connectors, heat-shrink and sleeving are made, which means a harness built in the Pearl River Delta sits next to its own supply chain. That proximity shortens lead times on the exact items that delay a build — a connector family and a terminal range — and it keeps the cost structure honest, because the harness house is not importing the components it terminates. The second reason is labor at the step that is genuinely labor: cutting, stripping, crimping and sleeving scale with touch time, and Dongguan's electronics workforce does this all day, every day. The third is integration. A Dongguan EMS that also builds the box can pull the harness partner, the board and the enclosure into one program, so the harness is specified, procured, tested and installed by people who answer to one quality system rather than three. What drives harness cost and lead time Harness cost is mostly labor, and the labor follows the complexity, not the wire price. The big drivers are the number of cut-and-crimp operations, the connector and terminal families, and the test coverage you demand. Terminations. Every cut, strip, crimp and sleeve is a touch-time step. A 40-conductor branched harness has dozens of them; a two-wire jumper has four. Fewer breakouts and a cleaner netlist mean fewer operations and a lower quote. Connectors and terminals. Gold plating, sealed connectors and specialty terminals cost more than tin, unsealed and standard parts — and a rare connector family that is not on the shelf adds a lead-time hit you can avoid by standardizing on what the partner stocks. Testing. Continuity-only is fast; adding hipot and per-crimp pull-test to the plan adds fixturing and cycle time. Name the test coverage up front so the quote prices it, not skips it. Volume. Setup, tooling and fixturing are near-fixed, so a harness is cheapest per unit at production volume. No MOQ means the prototype costs what it costs without a minimum-run penalty — but the per-unit price falls as the run rises. How Nex-G runs harness: vetted partners, QA-managed, box-build integration Nex-G does not own a harness line, and we are direct about that — we are an EMS, not a harness house. What we do is source wire harness and cable assembly through vetted partners and manage the quality the way we manage every other subassembly, then integrate the result into the box build where it actually has to fit. That split is deliberate: the partner brings the crimping tooling and the touch labor, and we bring the incoming inspection, the drawing control and the integration that a standalone harness supplier cannot. The anchor is our Dongguan Hengli facility — 6,800 m², 100+ staff, building since 2006 — running EMS that covers PCBA, SMT, component sourcing, box build and testing through EVT → DVT → PVT, with no MOQ. Quality runs on ISO 9001, IATF 16949 (build-to-print — design excluded under clause 8.3) and ISO 14001, with URS certification to 2027. Every harness that enters our line is checked against the drawing and its test report before it is dressed, fastened and functionally tested inside the finished unit, so a harness problem is caught before it ships, not after a year in the field. See how box build catches integration faults. What to put in your RFQ A complete harness RFQ lets us quote fast and flag the risks early. Send the drawing or the harness spec with the netlist, wire gauges and colors, the connector and terminal part numbers, the length and bend-radius requirements, the standard and class (IPC/WHMA-A-620 Class 2 or 3), and the test coverage you expect — continuity, hipot and pull-test. Add the volume and the stage — prototype, small batch or production — and whether the harness installs into a box build we are also quoting. The more the drawing specifies, the tighter the quote and the fewer surprises at inspection. Start an RFQ. Frequently asked questions What is the difference between a wire harness and a cable assembly?A wire harness bundles many conductors into one branched, sleeved assembly that routes power and signal through a product. A cable assembly is usually a single cable terminated at one or both ends with a connector. The difference changes the tooling, test plan and price, so name the complexity in the RFQ. Do you manufacture harnesses in-house?No — we are an EMS, not a harness house. We source wire harness and cable assembly through vetted partners, manage incoming inspection and drawing control, and integrate the harness into our box build. The partner brings the crimping and touch labor; we bring the quality system and the integration. What is your MOQ for harness and cable assemblies?No MOQ — we work from a single unit to mass production, so EVT and DVT builds get the same documentation as the production run. Per-unit cost is higher at low volume because setup and tooling are near-fixed. What tests do you run on harnesses?Continuity against the netlist, hipot for insulation withstand, and pull-test on every crimp lot, with the pull values set by wire gauge per IPC/WHMA-A-620. We also functionally test the harness once it is installed in the box build. What standard do you build harnesses to?IPC/WHMA-A-620, the acceptance standard for cable and wire harness assemblies from IPC. Tell us the class — Class 2 for dedicated service or Class 3 for high-reliability — and we hold the partner to that criteria set. Can you integrate the harness into a box build?Yes — that is the point of the model. We route, dress and fasten the harness into the enclosure, test it in situ against the approved dress, and ship a finished product. The fit problem a standalone harness supplier never sees is caught at our bench. What are your lead times?Roughly 3 days for a prototype, 7 days for a small batch and 30 days for production, with the harness sourced in parallel with the board and enclosure so it does not become the long pole in the build. Do you handle UL-listed wire and flame-rated insulation?Yes — we specify UL1007/UL1015 and cross-linked or high-temperature insulations to match the environment, and can source flame-retardant and halogen-free wire where the listing requires it. State the temperature rating and flammability class on the drawing. What drives the cost of a harness most?Labor — every cut, strip, crimp and sleeve is a touch-time step, so the number of terminations and the connector families drive the quote more than the wire price. Fewer breakouts and a clean netlist mean fewer operations. Ready to source a harness and the box it fits into?Send the drawing, netlist and connector part numbers — we will quote the harness through a vetted partner and the box build together.Request a quote Related articlesBox Build Assembly GuideEMS Cost & TCO in ChinaComponent Sourcing Guide