While 17.4 has only been amongst you for a month, now, I’ve had a few questions regarding manipulating your layer stack-up in the new release. We covered scripting changes previously, but a quick chat about the general use model is warranted. The new model, once you understand the underlying concept, is simpler to manage without the ambiguity that lay under the covers in the past.

How Do I Add a Die Stack Layer?

This is the question that I hear most. In 17.2, if you right-clicked the top substrate layer and added a layer above this, you would get a die stack type layer above the substrate. This is reasonable in many cases… unless you were trying to add another substrate (or mask) layer to the substrate itself. To do this, you would either: 

• Add the layers below the top layer and then shift all the elements down to the new layer before doing any renaming needed

  or

• Add die stack layers before using the config substrate layers command to redefine where the substrate started.

The simple additions would give you a cross-section as below. Note that the two diestack layers are coded red, indicating they are part of the substrate. I can now change LAYER_1 to the new top using the config command, but I cannot complete my stack-up work directly in this command, where I should be operating. I also needed to add a dielectric layer between the bottom die stack and the top conductor layer for the tool to understand where the boundary between the two regions existed.

With 17.4, the rules are much simpler. To manipulate the substrate cross-section, perform actions in that area – add, delete, rename, etc. layers by selecting those in the red area. To make changes to the die stack region, operate anywhere OUTSIDE the package layers. If you have no die stack layers yet, this means working with the surface layers to add your first die stack or spacer dielectric layer. After you have the first layer, you can use it as your reference layer (or you can continue to use the surface layer).

The snapshot above highlights the different areas of the design cross-section. This removes any ambiguity about what type of layer you are trying to add or whether it contributes to the total thickness of the substrate or rather is a placeholder for a die, interposer, or spacer element in a stack.

For those of you coming from the 17.2 APD world, you will notice that the layer material, thickness, and other physical characteristics of the die stack layers are grayed out and not editable. This is intentional. You may place multiple dies side-by-side in the design; each die is apt to have its own unique thickness, material composition, etc. For this reason, each die’s thickness, material, bump geometries, adhesive, and other characteristics are managed from within the die stack editor command.

Sounds Simple. Can You Show Me a Real Example?

Absolutely! Glad you asked! Take a few short seconds to watch this video, which will show you the differences when working in the different layers. Whether you’re adding a single layer (or layer pair) through the right mouse button directly, or using the Add Layers… form, you’ll find consistent actions and results:

Is There Anything Else I Should Keep in Mind?

Most of the cross-section editor remains consistent between the two releases (17.4 looks cleaner and more modern, though). It IS important, though, to remember that the Layer ID column, under the physical section, is used by the via span labels in the main canvas. Ensure they line up with how you identify them quickly while working.  

Should you use scripts to add layers to your cross-section, these may need adjustment for the use model changes here. They need to be updated for compatibility, making now the perfect time to do it. Of course, if you will use an environment with both 17.2 and 17.4 installed side-by-side, keep a copy of your old scripts for 17.2 around as well!

Happy designing!