IPC A-620 Standards on Cable Lengths

When manufacturing cable assemblies I often see drawings with no specific length tolerance, and – as we all know – with anything made by hand, even with the assistance of automated tooling, the finished length can vary.

The question is, how much should a cable vary in length and what is acceptable?

IPC A-620 has a specific answer for this.  Now before we get too excited, keen followers of the IPC Standards will know that customer documentation takes preference over the standards. So, if you are unsure then it is  good practice to check with your customer / quality assurance department before assuming that the following will be acceptable for your specific requirements.

The good news is the tolerance within IPC Standards is quite good and gives the assemblers a reasonable amount of area to work within.

With the table (below) it is easy to see that you simply can’t be short but you can be long.  We always say that it is better that a cable is too long where there is spare cable rather than cable too short to connect which renders it useless.

ipc-standards

It would be good if the above tolerances were more widely adopted. With a more generous tolerance you have more scope to re-work cables in production without having to scrap the whole assembly if a mistake is made during the manufacturing process. Ultimately this reduces the overall production costs, so is well worth considering.

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