PCB assembly labeling 1

[Ivan987]

Hi everyone,

As this is my first post thank you for all the useful information I've already found here.

Company where I work is in electronics design / manufacturing and my question is related to PCB assembly labeling best practices.
We start the design by opening a document number for the design (eg 100050 Rev10). Document numbers have revisions(Rev 10,11..) and we increase the revision after every release. Each revision gets tied to a part number (eg 200750) which represents the whole PCB assembly. Sometimes we keep the same part number if the change is interchangeable. By reading this forum I got the impression that this is in line with best practices mentioned by some users.

My question is what kind of label should we put on the assembly that is what should be on the label? In gerbers we only mark the PCB part number (not the same as PCBA part number). We don't print any other part number in silk screen as one PCB can be used in different PCB assemblies each having its own part number.

I see two option. One is the part number only. Second in BOM part number with revision. In this case the part number does not have the revision but when an interchangeable change is made then BOM is revised which is indexed in our ERP as "part number-001", "part-number-002 etc".

I'm really interested how other do this. What do you put on the label if you even use one? Another question is how you tie the document revisions to the part numbers? We don't have PLM and our ERP does not support it so we use the table in the design document.

Thank you.

 

[IRstuff]

You can put whatever you want on it. But, typically:
> Part number
> Revision
> Date code
> Company name

Anything else is optional, particularly since that document number is not necessarily something an end user might have or want.

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[CWB1]

Welcome Ivan.

You need a simple 4-7 digit alphanumeric p/n and your company's branding on the part. If you have multiple suppliers of the same part then you will likely also want a unique mark for each that is located separately from the p/n. If you need to track individual parts for manufacturing or otherwise, use a QR or bar code. Revisions, manufacturing date, or other nonsense should never be on the part.

The first rule of part numbering/marking is to keep them simple and clearly located. Ignore the grand ideas and focus on the customer's needs. Overly long p/ns create a host of human errors which cost customers real money every year bc they are often read/transcribed/entered into a system incorrectly. A lengthy p/n is like a lousy sales print or public website - it disqualifies you from consideration on the basis of quality before the first sample is evaluated. You also need to ensure that the customer can easily locate (only) the correct p/n on the service/purchase level part/assembly. Do not allow p/ns that aren't serviceable/purchasable to be visible to the customer, either hide them under others at the assembly level or use a QR or bar code for the internal-use ones.

The second rule of part numbering is that revisions must be backwards compatible. B might have upgraded material, coating, or other specs to improve durability, but the basic fit/form/function should be the same as A. For this reason, revisions are not marked on the part.

 

[Ivan987]

The second rule of part numbering is that revisions must be backwards compatible. B might have upgraded material, coating, or other specs to improve durability, but the basic fit/form/function should be the same as A. For this reason, revisions are not marked on the part.

Thank you for your excellent answer. Nevertheless I have a few more questions.

Does this mean that part numbering you use has revisions for the part numbers?

It's still not fully clear what to do in the case I'm about to describe. Let's say there is a PCB assembly which uses EEPROM-1. Due to the chip shortage we had to find a replacement part which is EEPROM-2. The application software is compatible unless maybe someone tries to read the EEPROM manufacturer ID.

As this looks like an interchangeable change we keep the same part number 200075. We also put the same label on boards with EEPROM-1 and EEPROM-2. The only way to see the difference is by reading the marking on the EEPROM chips.

Now, a software engineer gets the board and from the marking on the label he cannot tell which EEPROM is mounted. There are two revisions of the documentation which both point to the same part number (eg. Doc 100050 RevA and Doc 100050 RevB).

Should I tell him that it's not important as the application works with both (hence the change is interchangeable)?

Any thoughts on this?

Thanks again.

 

[IRstuff]

Revision numbers usually indicate form, fit, or function changes.

TTFN (ta ta for now)
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