Open a cable assembly purchase order and you will usually find a line that reads something like "built to IPC/WHMA-A-620." It looks like a specification. It is not one, at least not completely. The standard says so on its own first page: it "can be used as a stand-alone document for purchasing products, however it does not specify frequency of in-process inspection or frequency of end product inspection."
That sentence explains a great many arguments. Two suppliers can both be A-620 compliant and still ship assemblies judged against different criteria, because three settings the standard deliberately leaves open — the acceptance class, the inspection regime, and the revision in force — belong to the buyer. Leave them blank and somebody else fills them in.
What IPC/WHMA-A-620 governs, and what it does not
The scope is narrow and specific. The standard "prescribes practices and requirements for the manufacture of cable, wire and harness assemblies," and for its own purposes "the terms cable and wire harness are used interchangeably." What it actually contains is "materials, methods, tests and acceptability criteria for producing crimped, mechanically secured, or soldered interconnections."
Two exclusions deserve a second reading. First, "this standard does not provide criteria for cross-section or X-ray evaluation" — microsection and X-ray judgment sit in a separate appendix rather than in the acceptance criteria themselves. Second, and far more consequential for procurement, the standard places no limit "on the number of process indicators or the number of allowable repair/rework of defects."
Read those two sentences together and the design philosophy becomes obvious. This document expects you to control the process rather than inspect your way out of a bad one: "the intent of this document is to rely on process control methodology to ensure consistent quality levels during the manufacture of products."
Diagram comparing the workmanship items that IPC/WHMA-A-620 defines against the three settings a cable assembly purchase order must define
The coverage is broad where workmanship is concerned:
Section | Subject |
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4 | Soldering: solder and flux, cleanliness, solder connections, wire preparation, insulation, sleeving, birdcaging, terminals |
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5 | Crimp terminations: open and closed barrel, insulation support, inspection window, conductor crimp, bellmouth, conductor brush, carrier cutoff tab |
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6 | Discrete wire termination: wire position, overhang, insulation crimp, D-sub and modular (RJ type) connectors |
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9 | Connector damage limits, mating surfaces, contacts, installation of contacts and sealing plugs |
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11 | Measuring cable assemblies and wires, including length tolerance and breakouts |
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12 | Marking and labeling: content, legibility, permanency, location, marker sleeves, flag and tie wrap markers |
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13 | Coaxial and biaxial assemblies: stripping, center conductor and shield termination, semirigid coax |
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14 | Securing: restraining devices, breakout spacing, routing, bend radius, wire crossover |
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15 | Electrical shielding: braid coverage, shield termination, jumper wires |
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19 | Test tables: continuity, shorts, dielectric withstanding voltage, insulation resistance, VSWR, insertion loss, reflection coefficient, pull force |
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Why the gaps cost more than the requirements
Say you buy five thousand patch cords and forty come back with crimp heights outside the window. Your incoming inspection catches them. Now ask the two questions every claim eventually reaches. Which class were these assemblies evaluated against, and how many of them should have been inspected?
If the purchase order said "A-620," neither question has an answer. The supplier inspected on its own terms, which is precisely what the standard permits when the buyer stays quiet. You are left negotiating a defect rate that was never defined as a defect rate.
There is a second-order problem too. A-620 is written in bracketed form: "where the words ‘shall’ or ‘shall not’ indicates a requirement for at least one Class, the requirements for each Class are in brackets next to the ‘shall’ or ‘shall not’ requirement." A single clause can therefore hold three different acceptance thresholds. Whether a given conductor brush length, strand damage allowance or braid coverage figure applies to your order depends on the class stamped on the drawing — and the class is not the supplier’s to choose.
The three classes are defined in section 1.3, and they are defined by context rather than by workmanship.
The three IPC/WHMA-A-620 product classes with their official definitions and the end-use environment each one assumes
Class 1 is judged on function. Class 2 buys extended life and assumes the environment will cooperate. Class 3 assumes the opposite. That is a statement about where the cable is installed, and only the buyer knows where that is.
The three decisions the standard hands back to you
Decision 1: the acceptance class
Section 1.3 is blunt about ownership. "Use of this standard requires agreement on the Class to which the product belongs. The User has the ultimate responsibility for identifying the Class to which the assembly is evaluated. If the User does not establish and document the acceptance Class, the Manufacturer may do so."
That last sentence is the one to underline. Silence does not produce a neutral position. It transfers the decision to the party with an interest in the cheaper answer. "User" here means the specifying party — you, not the factory.
Decision 2: inspection frequency and process control
The scope states the gap plainly and then names its own remedy. Because inspection frequency is not specified, "such information should be developed with a statistical process control plan (see IPC-9191)." The standard’s answer to "how much should we inspect?" is not a larger sample. It is a control plan with defined process indicators, which is a different document from the standard and therefore a different line on your purchase order.
Decision 3: the revision in effect
Standards move. The purpose section states that "the use of an amendment or newer revision is not automatically required," and then, in language marked as a requirement for all three classes, that "the revision in effect shall be as specified by the User." The publisher repeats the point in its own policy statement: when a standard is revised, applying the new revision to an existing relationship "is not automatic unless required by the contract."
A drawing that says "A-620" and nothing else is therefore a floating reference. Over a three-year program it will drift across at least one revision boundary.
Revision | Date |
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IPC/WHMA-A-620 | January 2002 |
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IPC/WHMA-A-620A | July 2006 |
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IPC/WHMA-A-620B | October 2012 |
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IPC/WHMA-A-620B with Amendment 1 | August 2013 |
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IPC/WHMA-A-620C | January 2017 |
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IPC/WHMA-A-620D | January 2020 |
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IPC/WHMA-A-620E | October 2022 |
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IPC/WHMA-A-620F | current revision |
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How to write the three decisions into a purchase order
Three purchase order clauses covering the acceptance class, the inspection plan, and the revision of record
Name the class, and justify it with the environment
Write the class number and the reason beside it. "Class 2 — indoor cabinet and rack cabling, no flexing in service, controlled temperature and humidity" gives a supplier something to disagree with, which is the point. Disagreement during quoting is cheap; disagreement after five thousand assemblies is not.
While you are there, settle how much dimensional data you want. Section 1.4.1 states that unless a measurement is specifically invoked, "actual measurements … are not required except for referee purposes." If you need crimp height readings on every lot, they have to be called out. They will not arrive by default.
Attach an inspection plan, not just a standard
The order should define first article inspection, the in-process checkpoints, and the final electrical routine. Decide explicitly whether continuity and shorts testing are performed on every unit or on a sample, and name the test tables you are working to so that "tested" cannot mean two different things to two different people.
Table | What it sets minimum requirements for |
|---|
19-1 | Continuity |
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19-2 | Shorts (low voltage isolation) |
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19-3 | Dielectric withstanding voltage (DWV) |
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19-4 | Insulation resistance (IR) |
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19-5 | Voltage standing wave ratio (VSWR) |
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19-6 | Insertion loss |
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19-7 | Reflection coefficient |
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19-8 | Pull test force values |
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19-9 | RF connector shield pull force testing |
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Because A-620 sets no ceiling on rework, also state how many repair passes you will accept on a conductor termination before the assembly is scrapped. The standard permits unlimited repair. Your reliability model may not, and the difference belongs in writing before the first lot ships.
Pin the revision and require it on the certificate
Write the full designation with its revision, and require the certificate of conformance to repeat it along with the class. If you want a vendor to adopt a newer revision automatically when one is published, write that as well. The publisher recommends the latest revision but will not assume you want it — and will not assume that it is already in force either.
Where buyers get this wrong
- Specifying "IPC-A-620" or "A-620 compliant" with no class, no revision and no inspection plan. That is three defaults, and none of them belong to you.
- Assuming the class is a supplier engineering call. By the standard’s own wording it belongs to the specifying party.
- Asking A-620 for a cross-section or X-ray acceptance criterion. It explicitly declines to provide one.
- Treating an electrical test report as acceptance criteria. The report carries a value; the class decides whether that value passes.
FAQ
Is IPC/WHMA-A-620 mandatory for cable assemblies?
No. It is voluntary and operates as part of a relationship entered into by customer and supplier. It is widely described as the industry-consensus standard for requirements and acceptance of cable and wire harness assemblies, which is why it appears on so many drawings — but quoting it is a choice, and how much of it you adopt is a choice too.
What is the difference between Class 1, Class 2 and Class 3?
Class 1 is judged on the function of the completed assembly. Class 2 adds continued performance and extended life in an environment not expected to cause failures. Class 3 covers performance-on-demand where downtime cannot be tolerated and the environment may be uncommonly harsh. The definitions are context-driven, so an identical assembly can legitimately be Class 2 in one installation and Class 3 in another.
Does A-620 require 100% continuity testing?
The standard publishes minimum requirements for continuity, shorts, dielectric withstanding voltage and insulation resistance testing. It does not specify how frequently those tests are carried out. Whether testing runs on every unit or on a sample is a decision you write into the purchase order.
Which revision of A-620 should I specify?
The one your qualification and your supplier’s process approval were built against. Name it explicitly, because neither the standard nor the publisher’s policy will move an existing relationship to a newer revision without a contractual reason.
Can I use A-620 for a simple consumer patch cord?
You can, but check whether Class 1 already says everything you need. Applying Class 3 criteria to a product whose only real requirement is that it functions adds cost without adding performance.
Conclusion
"Built to A-620" is a useful shorthand and a poor specification. The standard is explicit that it is not a complete purchasing document: it defines workmanship, and it hands three decisions back to the buyer. The class tells the supplier what to measure against. The inspection plan tells them how often to look. The revision tells them which edition of the rulebook they are holding.
Write all three down, and the argument about a defective lot becomes a question with an answer.
Working with ZONG Cable on assembly specifications
ZONG Cable manufactures cable assemblies to the class and inspection plan our customers specify — patch cords, network and HDMI assemblies, USB assemblies, cord sets and full OEM/ODM programs. If you are writing an A-620 clause into a purchase order for the first time, send us the end-use environment and the failure consequence and we will tell you which class the application actually supports, rather than defaulting to the highest one. The electrical and dimensional routines we run before shipment are documented on our test and inspection page, and the process control behind them is described under quality management. For custom constructions, OEM support covers tooling, marking and packaging options up to full private label.
Sources
- IPC/WHMA-A-620F, *Requirements and Acceptance for Cable and Wire Harness Assemblies* — front matter, scope, purpose, classification and table of contents. Global Electronics Association (IPC). https://www.electronics.org/TOC/IPC-WHMA-A-620F-TOC.pdf
- IPC/WHMA-A-620D-2020 product description and revision information, ANSI Webstore. https://webstore.ansi.org/standards/ipc/ipcwhma620d2020
- ZONG Cable test and inspection capability. https://zh-zong.com/test-inspection/
- ZONG Cable quality management. https://zh-zong.com/quality-management/
- ZONG Cable OEM/ODM support. https://zh-zong.com/oem-support/
- ZONG Cable patch cord assemblies. https://zh-zong.com/patch-cord-cable/
