nomenclature

[davepcb]

Is there any advantage to naming the top and bottom layers of a pcb stackup "Primary Component Side" and "Secondary Component Side" instead of "Top" and "Bottom"?

In the past I saw the top and bottom labeled "component" and "solder" side. I understand that because most components were thru hole. Now with smt components on both sides I would assume that the side with the most critical components would be called Primary Component Side. The use of Top and Bottom seems too generic. Any thoughts?

davepcb

[Colorado-PC-Dude]

We used to stick with the default "Top" and "Bottom" naming, until we got a board back where "Top" was on the bottom and "Bottom" was on the top. Since it was a thru-hole board it wouldn't have made any difference, except it was a PCI card. Since then we have simply called our electrical layers First, Second, Third, etc... and given them numerical indicators in the copper. Never had a problem since.

I don't think it really matters what you call them, as long as it makes sense to you and you can easily describe the stackup to your board house.

Ben

[Tom]

Dave,

IPC teaches "Primary Side / Secondary Side" as a neutral nomenclature for all CAD Tools. It's a great idea and I wish all CAD vendors would change their defaults to the standard.

But until PADS changes "Top / Bottom" to "Primary Side / Secondary Side" we will keep using the PADS default. It's the CAD vendors that need to change and when they do so will we.

I can't have a CAD database that has Top and Bottom in every menu and then put "Primary Side / Secondary Side" in all my output. I like to keep everything symmetrical.

[padmaster]

Allegro calls them 'top' and 'bottom' but I use layer ID text that says Primary side and Secondary side.

Primary side indicates the side where the majority of the components will be placed and the side where non-wavable parts should be placed. It is also typically the side from which the board is viewed in the cad program.

Secondary side is where wavable parts may go and is the prefered side for test probing.


Of course, if you have a double sided reflow board, 'primary' and 'secondary' have less technical meaning, but I think it's a good practice.

[PRoehl]

You can change the layer names in PADS to whatever you want. It defaults to Top/Bottom, so just change the name in the settings. Not sure if Mentor would address this issue.

OrCAD Layout also uses the "Top & Bottom" naming conventions. And it will stay that way forever since Cadence will never bother with it.

Paul