Two copies of same PCB, with slightly different schematic and BOM?

[brianjaod]

Hi all,

I've got a scenario that must have happened to most of you, but I can't figure out the right Altium setup for it. I have a simple LED board that I want to use in two different places in our device assembly; one pcb on the left side and one on the right side. But they're both the exact same PCBs (identical gerbers) with the same reference designators, etc. The only difference between left and right is how a couple of i2c address resistors are populated during board assembly. So this means that the system BOM should have two of each component, i.e. 2 of R1, 2 of R2, 2 of C1, etc, because one for each left and right side board. I realize that I could simply generate two different BOMs, but then I would need to manually combine part quantities for ordering, etc. Isn't there a simply way for Altium to help me automate this common scenario? My BOM should have the correct cumulative total for each part, including the duplicated ref designators.

Initially I thought that Altium's "variant" feature would do this, but it seems to only work as an "either/or" type of feature, not allowing BOTH variants to be included in a BOM/design. Thoughts? Thanks!

Brian

[mairomaster]

I suggest you look at the two boards as two separate boards - left and right. Make one variant for the left board and one for the right board, then you will have 2 different BOMs. That will help during the assembly as well, if you are using an assembly service for the purpose. For ordering purposes you can easily combine the quantities for the two BOMs, using a custom excel spreadsheet.

An alternative way would be to just populate everything for the BOM purpose and order double the amount in the BOM. Then you will have some spare resistors which were supposed to be DNP, but that's not a big issue considering how cheap they are.

[robertferanec]

Absolutely agree with mairomaster. Make just one board with two variants.

It looks to me like you may want to manufacture these boards in pairs - two boards at once. You can simply create a panel (or you can ask your PCB manufacturer to create a panel) where you place 2 same PCBs inside it. Then when you will be assembling the PCBs, just tell your assembly house to fit one PCB based on BOM1 and the other PCB based on BOM2.

[brianjaod]

Thanks for the input @mariomaster and robertferanec! I like the idea of using the "variant" feature for this, but I guess I'm not understanding how to do it with BOTH boms at once? Isn't the variant usage an either/or feature? Or can I have two variants combined into a single output BOM? For our workflow and internal process, it's really important that it's part of a single output BOM, and I'm already using an excel template with Altium for that custom format output. Thanks for your help!

[mairomaster]

To me that sounds plain wrong. It is two different PCBs, two different assemblies - left one and right one. That is especially important for the assembly - you don't solder quite the same components on both of them. And the BOM is especially important for the assembly. Hence it's quite logical to have two different BOMs.

Example:

BOM1 (R2 is DNP and not included in the BOM)
C1
C2
C3
R1
etc...

BOM2 (R1 is DNP and not included in the BOM)
C1
C2
C3
R2
etc...

Using an output file, you can easily set it up to export 2 different BOMs, using 2 different variants, exported to 2 different files.

It's sound very illogical to me to combine the two BOMs together and I can't think of a way to do it in Altium. Well apart from the option I already suggested - to not use a DNP components at all and include everything in the BOM. It will require additional communication with the assemblers though.

[robertferanec]

Maybe we do not understand each other.

brianjaod, there are several different BOMs which you may generate for your documentation. Normally we generate:
- Purchasing BOM (list of components with supplier part numbers and quantities) used to buy components for the specific board variant
- Assembly BOM (grouped) is used by assembly house. It lists reference designators and component part numbers, so they can see where for example 100nF is fitted (C2, C4, C10, ...)
- Assembly BOM (one component per line) is used by assembly house to find information about specific component e.g. they need info about C3, they will find it all in one line

I am not exactly sure what your plans are with the BOM that you are trying to make. Could you explain?

[brianjaod]

mairomaster & robertferanec, thanks for the additional info! We've typically used a single BOM for both purchasing and assembly, as well as for the entire system of several PCBs, components, screws, etc. And so shifting to more than one BOM is not ideal for us, but I think I need to chew on this a bit longer and then circle back. Stay tuned . . . . thanks!

[LulaNord]

Hi...i am a new user here. As per my knowledge you should make one variant for the left board and one for the right board, then you will have 2 different BOMs. That will help during the assembly as well, if you are using an assembly service for the purpose. For ordering purposes you can easily combine the quantities for the two BOMs, using a custom excel spreadsheet.

assembly circuit

[mairomaster]

Hi...i am a new user here. As per my knowledge you should make one variant for the left board and one for the right board, then you will have 2 different BOMs. That will help during the assembly as well, if you are using an assembly service for the purpose. For ordering purposes you can easily combine the quantities for the two BOMs, using a custom excel spreadsheet.

Tip - you could have just quoted my post, instead of repeating it