About interposer and spacer?

Spacers are used to represent the physical spacer objects placed between dies in a die stack. The spacer provides separation between the two die, be it for electrical/thermal/etc. reasons or to ensure there is adequate vertical spacing so that, when the upper die is mounted above the lower die, the lower die's bond wires will not be damaged. 

Interposers contain routed clines and bond fingers, normally. The fingers provide a point for bond wires coming from dies mounted above the interposer to connect to. The routing clines then connect these fingers (normally located closer to the center of the interposer) to a second set of fingers (normally around the periphery of the interposer). A second set of bond wires will connect from these peripheral fingers down to the package substrate or to another die/interposer lower down in the stack. This helps to reduce the length of bond wires (and amount of gold/copper needed for the wires) and minimizes the length of the span of the wire over a lower die in the stack that might extend a significant distance out from the edge of the die mounted above.

When you use these items will depend upon your specific flow and design requirements, however. I can't tell you when you will add them to your design. All I can say is that the more accurate your design, the more accurate the SI extraction, 3D view (and 3D bond wire DRC checks), etc. will be. 

Regards,
- Tyler

So how exactly do you create a spacer in the SIP tool?  I tried following the help files, but didn't get very far.  Is a .dra symbol created first, then saved off as something else?  I tried every different way that I know how. 

Thanks in advance

There is both a text document solution, as well as a video walking you through spacer and interposer creation in the self-help area. I don't have exact links to them, but they should be reasonably easy to find with a keyword search. 

Or, if you just want a basic, rectangular spacer, you can create it dynamically in SiP 16.6 from the Add -> Spacer form by specifying the material, thickness, size, etc. 

- Tyler

 Ah.....found it and got it to work.  Thanks for your help Tyler

Victor

And now we have a blog from Tyler on spacers: 

IC Packagers: The Spaces Between Your Dies