Cable and wire harnesses transmit power and signals throughout electronic equipment. They rarely get the same attention as PCBs or semiconductors — but poor harness reliability drives product-wide failure rates. This guide covers specifications, IPC/WHMA-A-620 class selection, manufacturer criteria, and quality testing in practice.
This article covers the four main harness types and their applications, the specification items required for a complete purchase order, IPC/WHMA-A-620 class selection, manufacturer evaluation criteria, the four essential quality tests, and practical guidance on inventory standardization and cost optimization.
A cable or wire harness is an assembly of wires, terminals, connectors, protective materials, and bundling components that transmits electrical signals or power within and between devices. The right type depends on signal characteristics, available space, and environmental requirements.
Cable and wire harnesses involve many interacting components. Every item left unspecified becomes a decision the manufacturer makes for you — and may not make the way you expect. Specify completely in four categories:
The range of harness manufacturers spans from small manual assembly shops to highly automated facilities. Match the manufacturer to your volume, complexity, and quality requirements.
IPC/WHMA-A-620 (Requirements and Acceptance for Cable and Wire Harness Assemblies) is the primary international standard for harness quality. It defines three classes with progressively stricter acceptance criteria. You must specify the applicable class in your purchase order.
Require these four tests from your manufacturer — and specify the acceptance criteria and sampling frequency for each in your work instructions or quality agreement.
Harness procurement becomes complex quickly when every product variant uses a different wire gauge, connector family, or assembly configuration. Standardizing wire gauges and connector series across product lines increases the manufacturer's effective production quantities, reduces tooling investment, and simplifies your incoming inventory management.
Reliable cable and wire harness procurement requires complete specifications (wire, connector, assembly, compliance), explicit IPC/WHMA-A-620 class designation, manufacturer verification including genuine connector sourcing, and systematic quality testing (100% continuity, crimp verification, insulation resistance, pull-force sampling). A golden sample agreed before production eliminates the most common causes of rework and dispute. Standardize where possible to reduce variety and control inventory complexity.
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