1.4 Connector Families: The Mechanical Interface

Shielding and protection transform a simple harness into a resilient system component, capable of resisting both invisible interference and harsh physical conditions. Electromagnetic shielding keeps signals clean in noisy environments, while protective layers such as sleeves, overbraids, and armor prevent wear from vibration, abrasion, and heat. The effectivenessconnector of these measures depends not just on material choice but also on terminations, routing, and clamping practices. When designed as a unified strategy, shielding and protection ensure that a harness remains both electrically quiet and mechanically durable throughout its service life.

1.4.1 Cable Harness Drawing Rules

Wire harness drawing standards are guidelines and specifications that define how wire harness drawings should be created and formatted. These standards ensure consistency, clarity, and accuracy in wire harness documentation, making it easier for designers, manufacturers, and technicians to understand and work withis the harnesses.

While specific standards can vary based on industry and application, here are some common elements found in wire harness drawing standards:

• Title Block
• Scale
• Drawing Views
• Symbol Library
• Wiring Diagrams
• Wire Routing
• Connector Information
• Wire Identification
• Bill of Materials (BOM)
• Revision Control

1.4.1.1 Title Block

A title block is typically placed at the bottom right corner of the drawing and contains essential information such as the drawing title, revision number, date,only part number, and the name of the drafter.

Key Information Found in a Title Block

The title block is divided into several smaller sections, each containing specific metadata:

• Part Name / Title: A clear, descriptive name of the assembly (e.g., "HARNESS ASSEMBLY, MAIN ENGINE").
• Drawing Number: The unique number that identifies the drawing. For a harness, this is almost always the same as the Part Number of the assembly itself.
• Revision Level: A critical field that indicates the version of the drawing (e.g., A, B, C, or 1, 2, 3). Manufacturers must always work from the latest approved revision to avoid building an obsolete part.
• Approval Block: This section contains the names or initials of the individuals who created, checked, and approved the drawing, along with the dates. This establishes accountability and a traceable record of the design process. Common fields include:
• • DRAWN BY
  • CHECKED BY
  • ENG. APPROVAL
  • MFG. APPROVAL
• Company Information: The name and address of the company that owns the design.
• Tolerances: A block that defines the default dimensional tolerances for any measurements on the drawing that do not have a specific tolerance called out (e.g., "UNLESS OTHERWISE SPECIFIED, TOLERANCES ARE: X.XX = ±0.50").
• Scale: The ratio of the size of the items on the drawing to their actual size (e.g., 1:1, 1:2). For large harnesses, this is often listed as "NTS" (Not To Scale).
• Sheet Information: The size of the drawing sheet (e.g., A, B, C, or A4, A3) and the sheet number if the drawing package contains multiple pages (e.g., "SHEET 1 OF 3").

19.3.1.2 Drawing Views

Wire harness drawings usually include multiple views, such as plan views, elevation views, and section views, connector View orientation to provide a comprehensive representation of the harness layout.designed Especiallyto be disconnected, making it the connector'sweakest view direction, you know, from the top or from the back view have different circuits, we have the traumatic experience of viewing it wrong, then making a whole order wrong.

• The graphical representation is the core of the drawing.
• Clear, Scaled View: The main drawing should show the harness laid out flatlink in a 1:1 scale if possible, or a clearly noted smaller scale. All branches, connectors, and components should be shown in their correct geometric relationship to each other.
• Dimensioning: Every critical dimension must be included. This includes the overall length, the length of each branch from its breakout point, and the locations of any labels or hardware. Tolerances are essential for all lengths.
• Connector Orientation: The "clocking" or orientation of connectors (especially angled or keyed ones) must be clearly defined in a separate detail view to ensure they are installed correctly.

19.3.1.3 Symbol Library

• A standardized library of symbols is used to represent various components, connectors, terminals, splices, and other elements within the wire harness.

19.3.1.4 Wiring Diagrams

Wiring diagrams show the electrical connectionschain. betweenIt components,is includinga wirecomplex routing,electro-mechanical branching,device that must maintain low contact resistance despite vibration, oxidation, and terminationhandling points.abuse. TheseSelection diagramsis oftennot usemerely standardizedabout symbols"fitting" andthe colorwire; codesit is about matching the contact physics to representthe differentsignal wires, connectors,type and functions.

19.3.1.5 Wiring Routing

The routing of wires within the harness should be clearly illustrated, indicating the path, bundling, and securing methods. This includes any clips, ties, or sleeves used to manage and protect the wires.

19.3.1.6 Standards and Requirements Table

The standards and requirements on a cable harness drawing are a set of notes that define the quality, testing, and manufacturing criteria for the assembly. These are typically located in a "General Notes" section on the drawing and serve as a formal instruction set for the manufacturer, ensuring the harnesshousing meetsmechanics allprevent technicalaccidental disconnects under stress.

1.4.1 Contact Physics: Plating and performance specifications.

19.3.1.7 BOM List

The BOM is a structured list of every component required to build one unit of the harness assembly. It serves as the primary document for procurement and inventory control. A comprehensive BOM must include:

• Item Number: A unique sequential identifier for each line item.
• Part Number: The specific manufacturer or internal part number for the component.
• Description: A concise technical description (e.g., "CONN, RCPT, 12 POS, DTM SERIES").
• Quantity: The total quantity of the component required per single harness assembly.
• Reference Designator: A unique identifier (e.g., P1, J2, W3) that links the component in the BOM to its location on the graphical drawing.

19.3.2 Specification Documentation

Cable harness specification documentation is the complete set of technical documents that formally defines all the requirements needed to manufacture, inspect, and test a cable harness. This package serves as the single source of truth and the contractual agreement between the design authority and the manufacturer.

Its purpose is to provide a clear, unambiguous, and comprehensive set of instructions that ensures every harness is built to the exact same standard.

These are separate documents that are referenced on the main drawing. They provide detailed instructions on how to perform specific tasks.

• Workmanship Standard: This is almost always IPC/WHMA-A-620. The drawing will specify the required class (e.g., Class 2 or Class 3).
• Crimp Specifications: For critical applications, there may be a separate document detailing the exact tooling, crimp heights, and pull-force requirements for each terminal.
• Test Procedures: A detailed procedure that outlines the steps for electrical testing, including the specific equipment to be used, the test voltage (for Hipot), and the pass/fail criteria.

19.3.2.1 Quantities

One of the important criteria for cable harness calculation and production is quantities.

In cable harness manufacturing, quantities are a fundamental input for all technical and logistical calculations. They directly influence cost, production strategy, and quality control. The two primary types of quantities are the per-harness quantity (defined by the Bill of Materials) and the total production quantity (the number of harnesses to be built).

The accuracy of a price quote is directly dependent on precise quantity calculations.

Bill of Materials (BOM) Cost Roll-up: Component pricing is heavily dependent on volume. A harness built in quantities of 100 will have a significantly higher per-unit material cost than one built in quantities of 10,000 due to price breaks from suppliers. Calculations must use the price points corresponding to the planned production volume.

Economies of Scale: Component suppliers offer tiered pricing. The total production quantity determines which price break the manufacturer can achieve. For example, the unit price for 10,000 terminals is significantly lower than for 1,000. A larger production volume allows for more aggressive material pricing.

Amortization of NRE Costs: Non-Recurring Engineering (NRE) costs include the design of the harness, creation of the manufacturing formboard, and programming of test equipment or any machine equipment investment. These are fixed, one-time costs. The total production quantity is used to amortize these costs, spreading them across all units.

Per-Unit NRE Cost = Total NRE Cost / Total Production Quantity A larger quantity dramatically reduces the per-unit NRE cost.

19.3.2.2 Quantities Effects on Capacity PlanningFretting

The productionchoice quantityof contact plating is thedictated central input for capacity planning, which involves allocatingby the necessaryvoltage resourceslevel, (machines,signal labor,sensitivity, space) to meet production targets.

• Machine Hours: The total quantity determinesand the requiredexpected machine hours. For example, a runnumber of 10,000 harnesses with 20 crimps each requires 200,000 machinemating cycles. The capacity planner must calculate if the available crimping presses can perform this work within the scheduled timeframe or if additional machines or shifts are needed.
• Labor Allocation: The total labor hours are calculated by multiplying the per-unit assembly time by the quantity. The planner uses this to determine the required number of assembly technicians and to schedule their work.
• Assembly Stations: The quantity and complexity of the harness dictate the number of physical assembly boards or stations required on the production floor to meet the delivery schedule without creating bottlenecks.
• Future Resource Planning: Long-term quantity forecasts are used to make strategic decisions. If a forecast shows a sustained high volume for a new project, the company may decide to invest in new automated equipment, expand the factory floor, or hire and train more staff in anticipation of the increased workload.

		AFFORDABLE MACHINE INVESTMENTS			FULLY AUTOMATIC MACHINE
No.	NAME	CUTTING & STRIPPING	MANUAL CRIMPING	DESKTOP CRIMPING	CABLE CUTTING & STRIPPING & CRIMPING	TUBE CUTTING	TEST	SHRINKING
1	X	36.14	20.03	73.37	36.14	16.73	62.26	33.37
2	Y	152.94	33.50	333.50	152.94	89.06	244.61	222.39
3	Z	778.44	534.00	1200.67	778.44	423.56	1334.00	889.56
4	T	30.59	20.03	53.37	30.59	2.81	57.81	33.37
	TOTAL CAPACITY %	22.18%	13.50%	36.91%	22.18%	11.83%	37.75%	26.19%

In this case, specifically processes evaluated as a total amount of cable harnesses and process timing to find possible machine investment decisions. It defines the usage percentage of machines.

NAME	Cutting & Crimping(min.)	Assembly(min.)	BUTYL + OVERMOULD(min.)	Test+ Görsel & Packing(min.)	SARIM(min.)	Kablo Bağı Şek. Klips (min.)	Band Markalama	Toplam(min.)	85%
x	0.782	5.497	1.427	1.585	3.127	0.210	0.405	13.032	15.331
y	0.633	5.097	1.427	1.585	3.710	0.210	0.405	13.067	15.373
z	0.853	5.697	1.427	1.585	3.127	0.210	0.405	13.303	15.651
t	0.710	5.297	1.427	1.585	3.710	0.210	0.405	13.343	15.698
	2.978	21.587	5.707	6.340	13.673	0.840	1.620	52.745

In this case, processes calculated by the total amount of cable harnesses equal to an hour. Capacity study starting with process timing, machine capacity validation, customer transport forecast.

Braids, foils, drain wires, sleeves, and routing for noise/abrasion control.

Shielding and protection give a harness two kindsindustry ofstandards defense—against electrical noise and against the physical abuse of heat, motion, and abrasion. Foils, braids, and combination shields each have strengths for different frequency ranges and flexibility needs, while sleeves, overbraids, and armor keep insulation intact over years of service. The most effective designs terminate shields with a full 360° bond at the entry point, minimize exposed pigtails, and route cables close to chassis metal to shrink loop areas. Smart choices in clamps, grommets, and branch protection prevent mechanical wear from undoing electrical performance. When shielding and protection are planned together, the result is a harness that stays both electrically quiet and physically durable in its working environment.

1.4.1 Why shield & protect (two jobs, one harness)

• EMC job: keep noisy stuff in, keep sensitive stuff quiet. That’s about— impedance to groundTin and smallGold loop—a areas.
• Mechanicalre job:not surviveinterchangeable.
  rubs,

  A) edges,The heat,Galvanic Mandate

  Never mate Tin to Gold.

  Mixing these dissimilar metals creates a galvanic cell in the presence of humidity, leading to rapid corrosion at the interface. This oxide layer causes intermittent signal failure, often described as "No Fault Found" (NFF) because the act of unplugging and motionreplugging withouttemporarily nicking insulation orwipes the shieldoxide itself.

Design both at once—an elegant shield that frays on the first bracket is still a failure.away.

B)

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Plating

Selection

1.4.2 Picking the shield (what each does best)

Matrix

Shield typeFeature	CoverageTin Plating	High-freqGold (E-field)	Low-freq (H-field)	Flex	NotesPlating
FoilPrimary +Use	High drainCurrent / Power Circuits (Al/PET> +10V, drain> wire)100mA).	~100%	Excellent	Fair	Good	Light,Low cheap,Energy great/ broadbandLogic E-field;Signals needs/ drainData for(Dry terminationsCircuits).
CopperPhysics	Soft braidmetal; relies on high normal force (tinned/bare)wiping action) to break through its natural oxide layer.	70–95%	Good	Better	OK	LowerHard, noble metal; does not oxidize. Relies on transferlow impedancenormal force, atpreserving LF;spring stronger, heavierintegrity.
FoilMating + braid (combo)Cycles	~100%Low durability (	Best10 to 30 cycles	Best	OK). The soft tin wears through quickly.	PreferredHigh fordurability tough(100 EMI;to common1,000+ on data/power hybridscycles).
ConductiveFailure wrapMode	Fretting Corrosion: (CuMicro-motion tape)from vibration causes fresh tin to oxidize, eventually building an insulating barrier.	Pore Corrosion:Custom	Great	Good	Poor	For shortIf runs/repairs;plating watchis fortoo cutthin, edges
Discretebase drainmetal only	—	Poor	Poor	—	Notmigrates athrough shield—onlypores a(prevented bondby aidNickel for foilunderplate).

Design Rule: SignalsIf nearthe switcherscircuit voltage is too low to "punch through" an oxide layer (typically < 10V), Gold plating is mandatory. Tin is acceptable for power circuits where the arc/voltage can burn off minor oxidation.

1.4.2 Housing Selection: Locks and Keying

The connector housing provides mechanical protection and insulation. Its material and locking features determine whether the harness survives assembly and operation.

A) Material Science: Nylon vs. PBT

• Nylon (PA66): The most common connector material. It is hygroscopic (absorbs moisture).
  • Pros: Tough, resilient snap-fits.
  • Cons: Dimensions change with humidity; can become brittle if "dry as molded" before hydration.
• PBT (Polybutylene Terephthalate): Used for precision automotive/industrial connectors.
  • Pros: Dimensionally stable; does not absorb water.
  • Cons: More brittle; snap-locks can break if over-flexed during assembly.

B) Locking Mechanisms (TPA & CPA)

For high-reliability (Class 3) and automotive applications, simple friction fits are insufficient. Secondary locks are mandatory.

• Primary Lock: The plastic tang on the terminal or longhousing harnessesthat →clicks into place.
• TPA (Terminal Position Assurance): A secondary plastic wedge or comb inserted after the terminals are seated.
  • Function: It mechanically blocks the terminals from backing out. If the TPA will not seat, it indicates a terminal is not fully inserted. combo. Short sensor runs in quiet boxes → foil + drainMandate: oftenTPA suffices.is required for all high-vibration connectors.

    
    

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• 1.4.3 Termination that worksCPA (andConnector whatPosition to avoid)

  Gold standard:Assurance): 360°A bondlocking tab on the outside of the shieldmated pair.

  • Function: Ensures the two connector halves are fully mated and prevents accidental unlatching.

C) Keying and Polarization

Connectors must be keyed (shaped) to aprevent:

1. Mis-mating: Plugging connector A into header B.
2. Reverse mating: Plugging it in upside down (180˚).
   DFM Note: Use different color codes or physical keying options (Key A, Key B) for identical connectors located in the same harness area.

1.4.3 Sealing Mandates: Harsh Environments

Standard connectors are breathable. For harsh environments (automotive under-hood, outdoor, wash-down zones), the connector must be effectively sealed to meet metal backshellIP67 (Dust tight / Immersion up to 1m) or clamp—noIP68 gaps, no whiskers.ratings.

• BackshellsInterface Seals: withA springsilicone fingers/conesring givethat trueseals 360°.the mating face between the male and female housing.
• BandWire clampsSealing:
  • Single Wire Seal (SWS): orA dedicateddiscrete silicone plug crimped onto the insulation of each wire. EMI glandsMandate: doThe similarinsulation atdiameter bulkheads.must match the seal range exactly; too small leaks, too large tears the seal.
  • Mat Seal (Block Seal): A single rubber block with holes for all wires. Used in high-density connectors.
• Cavity

  Pigtails (if you must):Plugs:

  • Keep total exposed length ≤10 mm.
  • Use drain wireMandatory for foilany shields;unused braidpin pigtailsposition. areLeaving lasta resort.hole open in a sealed connector compromises the entire assembly.
  • Bond as close as physically possibleBackshells: toRigid thecovers chassisthat entry.
  screw

  Bondingonto strategy:

  circular
  • Both-ends bond when possible (best EMI).
  • If ground loops/DC offsets are a risk: bond at one end and add AC pathconnectors (e.g., MIL-DTL-38999). They provide:
    • 1–10Strain nFRelief: toTransferring chassisbending or a common-mode choke on the pair) to keep RF currents off the conductors.

    Checklist at drawing time: call out “360° shield termination at Jx backshell” or “Drain to chassis, pigtail ≤10 mm @ Jx.”

    
    

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    1.4.4 Drain wires (foil’s best friend)

    • Must touch foil continuously—factory-applied under the foil is ideal.
    • Terminate the drain with the shield (not to signal ground pins unless specified).
    • If you splice, cap and insulate the drain at the splice; don’t leave “antennas.”

    
    

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    1.4.5 Sleeves, jackets & armor (save the insulation)

    Protection	Best for	Temp	Notes
    PET braid sleeve	General abrasion, dress	125 °C	Light, expandable; add heat-shrink collars at ends
    Nylon/PA or PUR overbraid	Oily bays, drag chains	80–90 °C	Tough vs scuff; good flex life
    Heat-shrink (polyolefin)	Strain relief, branch boots	125 °C	Dual-wall (adhesive) seals against fluids
    PTFE/FEP spiral wrap	High temp, rework access	200+ °C	Slippery, clean; not sealed
    Fiberglass + silicone	Hot spots near exhaust	200–260 °C	Bulky; great radiant heat protection
    Split loom (PE/PP)	Quick dress, low cost	80–100 °C	Not sealed; add clamps to stop creep
    Stainless braid / conduit	Rocks, sharp edges	—	Heavy; use where failure is unacceptable

    Edges & pass-throughs: always use grommets/bushings and edge guards. No bare metal on insulation—ever.

    
    

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    1.4.6 Routing rules that buy dB (and years)

    • Separate power/switching from low-level signals by ≥100 mm; if they must cross, do it at 90°.
    • Hug chassis metal and clamp every 200–300 mm to shrink loop area.
    • Avoid parallel runs with antennas/RF; keep to one side of high-di/dt cables.
    • Put the bond point at the entryforce to the metalhousing, enclosurenot (don’tthe carry “RF” inside).crimps.
    • FirstEMI bend afterShielding: strain relief, not at the backshell.

    
    

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    1.4.7 Clamps, strain relief & branch points

    • Use 360˚cushioned P-clamps; size so rubber compresses slightly.
    • Place the first clamp before the first bend and within 50–80 mmtermination of the backshell.
    • Branches:cable reinforce with heat-shrink boots or molded splitters; no zip-tie cuts—use lacing tape or rounded ties over sleeves.braid.

    
    

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    1.4.8 Validating shielding & protection (quick but honest)

    • Continuity to chassis: < 0.05–0.10 Ω from backshell to chassis; verify both ends if bonded.
    • Transfer sanity check: near-field probe the noisy board, compare with/without shield bond; aim for a clearly lower trace.
    • Flex/abrasion test: cycle through expected bend radius; inspect sleeves and any braid for broken filaments or jacket scuff.
    • Ingress check (sealed families): IP test or at least soapy water spray + pressure decay on suspect connectors.
    • Pull test at clamp: the clamp should take load—not the pins.

    
    

    Final

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    Checklist:

    
    

    Connector

    1.4.9Selection Common traps → smallest reliable fixMandates

    TrapMandate	SymptomCriteria	FixVerification Action
    LongPlating shieldMatch	Never pigtailsmate Tin to Gold.	EMCAudit fail at higher freq	SwitchBOM to 360°ensure backshell;mating ifpairs not,(Plug ≤10& mmHeader) pigtail,use bondidentical atcontact entryplating.
    Signal Integrity	Gold platingShield bondedmandated onlyfor tolow-voltage/data logiccircuits ground(< 10V).	GroundPrevents bounce,"No noFault RFFound" path	Bondfailures tocaused chassis;by addoxide ACbuildup pathon ifTin DC loop is a concerncontacts.
    Retention Security	TPA (Terminal Position Assurance)PET sleevemandated endsfor frayvibration environments.	LooseVisual filaments,inspection snags	Finishconfirms withTPA heat-shrinkis collars;fully hot-knifeseated cutand sleeveslocked.
    Sealing Integrity	ZipAll tiesunused overcavities insulationin sealed connectors must have Cavity Plugs.	Cold-flow,Leak nickstesting (vacuum decay) or visual check ensures the IP rating is maintained.
    Mating Cycles	Connector durability rating must exceed the expected service life cycles.	Use cushioned clamps or tie bases; derate tension
    Foil shield broken at bend	Intermittent drain	Respect bend radius; pick combo shieldGold for tighthigh-cycle bends
    Sharptest bulkhead edges	Jacket cuts over time	Installports; grommets/edge guardsTin; routeis withlimited saddlesto approx. 30 cycles.
    Over-packed bundle	Heating, crosstalk	Split the loom; add spacing; derate current

    
    

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    1.4.10 Pocket checklists

    At design freeze

    • Shield type chosen (foil/braid/combo) per noise & flex
    • Termination called (360° backshell vs pigtail ≤10 mm)
    • Bond strategy (both ends or single + AC path) noted
    • Sleeve/armor picked for environment; grommets specified
    • Clamp spacing & first-clamp distance on drawing

    During build

    • Shield strands tidy; no whiskers; boots shrunk clean
    • Drain tied only to the intended bond point
    • Labels outside clamps; no ties over bare insulation
    • Bend radius respected at exits/branches

    Verification

    • Chassis bond resistance measured & logged
    • Quick probe/EMI sniff improved with bond on
    • Flex/abrasion spot check OK; no jacket cuts at edges

    
    

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    By combining the right shielding techniques with robust physical protection, harnesses can endure demanding environments without compromising signal integrity or longevity. The payoff is reliability in operation, reduced failures, and extended product life.