wire harness requirements

Introduction

Wires, cables, and wire harnesses are widely used in the electronics and electrical industry to connect equipment electrically. The reliability of these connections depends on good design and proper wire harness assembly.

The quality standards for preparing and assembling wires, cables, and wire harnesses are set by the IPC/WHMA-A-620 Requirements and Acceptance for Cable and Wire Harness Assemblies document.

This article explains what IPC/WHMA-A-620 is, its scope, and key guidelines for using it. It also highlights the most important sections of the standard.

Enjoy reading!

History of IPC/WHMA-A-620

The IPC/WHMA-A-620 standard was created in 2002 by the Global Electronics Association (IPC) and the Wire Harness Manufacturers Association (WHMA). It has been updated regularly since then. As of February 2025, the latest version is "E", released in October 2022. So the Rev.E standard symbol is IPC/WHMA-A-620E.

You can find the standard's history and details about its latest version on the IPC website in the "Document Revision Table" section.

Scope of IPC/WHMA-A-620

The IPC/WHMA-A-620 standard sets requirements and acceptance for cable and wire harness assemblies. It covers:

• General rules: product classes, conditions, order of precedence, and more.
• Materials: flux, lead-based solder, lead-free solder, adhesives, and others.
• Process control and tools management.
• Guidelines for measuring harness dimensions and basic testing.
• Requirements for crimped, ultrasound-welded or soldered connections.
• Requirements of connectors, harness marking, overmolding, potting, securing, and final assembly.
• Requirements for coaxial cables, often used for high-frequency signals.
• Requirements for electrical shielding and external harness protection.

IPC/WHMA-A-620 does not cover wire cross-section criteria or X-ray inspection rules.

IPC/WHMA-A-620 and Other Standards

Chapter two of IPC/WHMA-A-620 lists related standards from organizations like Global Electronics Association (IPC), SAE, ANSI, ISO, ESDA, DoD, IEC, AIA/NAS, EIA, ASTM, and IEEE.

When using IPC/WHMA-A-620 with other standards, conflicts may occur if requirements differ. In such cases, follow the order of precedence.

IPC/WHMA-A-620 Main Rules

IPC/WHMA-A-620 outlines rules for assembling and inspecting cables and wire harnesses. Key points are listed below. Full details are in the standard's first chapter.

• The English version takes precedence. Translation errors in IPC standards can occur. When discrepancies exist between the English and translated versions, the English text takes precedence.
• The product class is determined by the user. The inspector does not assign the IPC product class.
• Follow order of precedence. IPC/WHMA-A-620 clarifies how to handle discrepancies between the standard and customer requirements, using rules known as order of precedence.
• Ensure personnel proficiency. The standard requires that instructors, operators, and quality control personnel demonstrate proficiency in their jobs. Companies should maintain records verifying personnel qualifications, including education, experience, training, and testing to the standard. If qualifications are lacking, supervision and on-the-job training should be provided until proficiency is achieved.
• Text over illustrations. Always prioritize the text of the requirement over illustrations, as images can sometimes exaggerate or mislead.
• Use appropriate magnification tools. Depending on the wire diameter inspected, use a proper magnifier or microscope. If additional verification is needed, use higher magnification as specified in relevant tables.
• Maintain adequate lighting. Ensure surface illumination of at least 1000 lux and a light color temperature of 3000-5000 °K during inspections.
• Focus on process control. Process control is more important than inspection alone. For Class 3, it's required. Use documents like a control plan.
• Use statistical process control (SPC). SPC may be used. Ensure proper training, keep records, and describe SPC controls in the control plan.
• Calibrate tools and equipment. Crimping tools, torque tools, and test equipment must be checked and calibrated when required.
• Document rework and repair. Rework (Class 3) and repair (Class 2 and 3) shall be documented. Read more about Rework and Repair.

Main Chapters of IPC/WHMA-A-620

The "E" version of IPC/WHMA-A-620 includes the following main chapters:

• General
• Applicable Documents
• Wires
• Soldered Terminations
• Crimp Terminations
• Insulation Displacement Connection (IDC)
• Ultrasonic Welding
• Splices
• Connectorization
• Over-molding/Potting
• Measuring Cable Assemblies and Wires
• Marking/Labeling
• Coaxial and Biaxial Cable Assemblies
• Securing
• Harness/Cable Electrical Shielding
• Harness/Cable Protective Coverings
• Finished Assembly Installation
• Solderless Wrap
• Testing

Appendices: Terms and definitions, pull force tables, etc.

Summary

The IPC/WHMA-A-620 standard is a globally recognized document that specifies quality requirements for the assembly of cables, wires, and complete wire harness assemblies. It provides guidelines for material selection, process control, and visual inspection criteria. IPC/WHMA-A-620 is essential for companies involved in harness production, harness installation in products, or wire-to-PCB assembly.

IPC/WHMA-A-620 is regularly updated to meet the demands of the electronics and electrical engineering industries. It clarifies how properly assembled wire harnesses, correctly crimped terminations, or robustly soldered wires and cables to PCBs should appear. Its application enables manufacturing plants not only to meet customer requirements but also to ensure the reliability and durability of their products.

I encourage everyone involved in cable harness production and inspection to familiarize themselves with IPC/WHMA-A-620.

References

• https://www.ipc.org/ipc-document-revision-table
• "IPC/WHMA-A-620: Requirements and Acceptance for Cable and Wire Harness Assemblies," Rev. E, IPC International Inc. USA, 2022.