layer 25

[Dan]

Tom,

First thanks for sending all those libraries to me a few weeks back.

Another question..... what is layer 25 used for? I have parts here that have pad stacks including layer 25 in it.... why?

Thanks again,

Dan

[Tom]

Dan,

Layer_25 was introduced in PADS software in 1986 as the CAM Plane layer. This layer was used exclusively for creating all power planes because copper pour did not exist yet. CAM Planes produce a "Negative Photo Image", instead of a Positive image.

The padstack Layer_25 data produces the Anti-Pad and Thermal OD when you select CAM Plane in Setup/Layer Definitions. In the File/CAM menu for producing planes you would also have to select "Pads & Vias on Layer_25" instead of Pads on any other layer. This helps you define a special Anti-Pad and Thermal size that is more customized to your liking.

PowerPCB V4.0 is the first release on software that allows you to us "Custom Thermals" that are defined by you on the "Inner Layer" padstack. You can now use Custom Thermals with CAM Planes.

Innoveda has been trying to phase this out with their Split/Mixed Technology, however on large databases using Split/Mixed planes can bring the fastest computers to their knees. So the preference on very large boards is still CAM Plane Technology.

We have added Layer_25 to all through hole padstacks so that designers who use that technology are fully automated. Having Layer_25 defined in the padstack does not have any other effect to your database or the parts. It's just there if you need it.