Ansoft Q3D Extractor
Ansoft Q3D Extractor
Ansoft Q3D Extractor
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High-Performance High Performance Packaging Designs<br />
Aaron Edwards<br />
Application Engineer<br />
Signal Integrity Tools
Time to Market<br />
� In an attempt by companies to meet time to market demands, redesigning<br />
previously laid out packages is becoming ever more appealing. Some of the<br />
largest packaging companies in the world were obsoleting package designs<br />
in less than 6 months time. Now the push to use off the shelf packages in<br />
conjunction with the ASIC design is crucial to quick turnarounds of designs.<br />
� This presentation will address the design flow of an engineer who is given an<br />
off the shelf package and tasked to redesign it to meet more stringent design<br />
specifications. Using the suite of <strong>Ansoft</strong> Signal Integrity tools, the engineer<br />
can run simulations that will provide the necessary data to enhance the<br />
package’s performance. The Signal Integrity tools will provide the engineer<br />
the means to analyzing Characteristic Impedance, Loop Inductance, and<br />
spice waveforms, which will provide enough data to make the package<br />
adhere to faster edge rate signals.
The Scenario<br />
� A big ASIC design house is asking Package Company A to<br />
provide them with a package for their layout, and meet their<br />
performance specifications. They want a quick turnaround,<br />
and also a package that will pass their measurement<br />
validation the first time through.<br />
� Management at the Package Company decides to to pull an<br />
off the shelf package to use for the high speed package<br />
design.They will verify through simulation to see if the<br />
package can handle the signal speeds.
� In a presentation given by Leah Miller of LSI Logic named<br />
“Silicon and Flip Chip Package Co-Design from a Packaging<br />
Perspective”
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~~ Joe Engineer was given a<br />
package design and told to<br />
perform various simulations for it
Design Verification List<br />
� Traces have to have Differential Impedance of 100 ohms If not,<br />
fix it<br />
� Report the findings back to management<br />
� If there are any improvements that could be made to optimize the<br />
package, present suggestions<br />
� Spice sub-circuit has to be generated for the ASIC company to<br />
perform system level simulations at 100ps risetimes<br />
� Parasitic characterization has to be performed for every net on the<br />
package<br />
� Spice subcircuit for the traces has to be generated
The Tools Needed to Perform<br />
� Joe is armed with…<br />
� <strong>Ansoft</strong>links 2.2<br />
� Spicelink 5.0 with PEEC<br />
� Optimetrics 2.5<br />
� TPA 4.0<br />
the Task
Cadence APD<br />
.SM3 File<br />
The <strong>Ansoft</strong> Solution:<br />
Reading Layout into <strong>Q3D</strong><br />
<strong>Ansoft</strong>links 2.2
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> Q2D <strong>Extractor</strong><br />
� Joe was told to verify that the differential pairs were at 100<br />
ohms. <strong>Ansoft</strong> 2D <strong>Extractor</strong> can be used to verify the<br />
transmission line characteristic impedance.<br />
� To eliminate redrawing the structure in the 2D <strong>Extractor</strong>, Joe<br />
can create a 2D cross-section from the 3D drawing. He can<br />
then simply import this cross section into the 2D <strong>Extractor</strong><br />
3D<br />
2D
The <strong>Ansoft</strong> Solution: <strong>Ansoft</strong> Q2D <strong>Extractor</strong><br />
� To determine the if the differential impedance of this these traces is 100<br />
Ohms, Joe will set up and run the nominal problem. Even though he is<br />
optimistic about obtaining 100 Ohm differential impedance from an off-theshelf<br />
package, he only wants to set up the problem once. If the package<br />
traces don’t yield the desired differential impedance he can parameterize the<br />
model to study the effect of varying trace separation and trace width
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> 2D <strong>Extractor</strong><br />
�The nominal case yields a<br />
differential impedance of 97.4<br />
ohms, it’s close but the parametric<br />
sweep will predict which values will<br />
be needed to achieve exactly 100<br />
ohm differential impedance
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> 2D <strong>Extractor</strong><br />
The results of the parametric sweep were then<br />
plotted in a graph
The <strong>Ansoft</strong> Solution<br />
� Joe has completed his first task of determining the Differential<br />
Impedance of the package<br />
� His next task is to see if there are any improvements to be<br />
made on the package to optimize performance.<br />
� He decides to study the Return Path of the package to see<br />
how it effects the Loop Inductance
The <strong>Ansoft</strong> Solution: Return Path<br />
� Loop Inductance<br />
Ground<br />
Ground<br />
Via<br />
Via
The <strong>Ansoft</strong> Solution: Return Path<br />
� The Ground Via placement is very important to minimizing the<br />
Return Loop. Using Optimetrics, we can find the best<br />
placement for those vias.
The <strong>Ansoft</strong> Solution:<br />
Optimetrics 2.5
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> Optimetrics 2.5<br />
� Variable: Position of Vias<br />
� Parameters: L1 – Self Inductance of L1 Trace<br />
H1 – Self Inductance of H1 Trace<br />
L22 – Self Inductance of the Ground<br />
L12 – Mutual Inductance between L1<br />
Trace and Ground<br />
H12 – Mutual Inductance between H1<br />
Trace and Ground<br />
� Cost Function: Loop Inductance of each Trace<br />
Loop L1 = L1 + L22 – 2*L12<br />
Lopp H1 = H1 + L22 – 2*H12
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> Optimetrics 2.5
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> Optimetrics 2.5
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> <strong>Q3D</strong> <strong>Extractor</strong><br />
� Once Joe found the optimal place to put the vias, he could<br />
view the Surface current plots. These plots allow Joe to<br />
visualize the current return path, and see where current<br />
crowding is occurring
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> <strong>Q3D</strong> <strong>Extractor</strong><br />
Differential Excitation<br />
Single Ended Excitation using<br />
Ground as Return Path
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> <strong>Q3D</strong> <strong>Extractor</strong><br />
� Now Joe can generate a PEEC subcircuit for the system level<br />
engineers to use for their system analysis. Since he has<br />
found the design specs that optimize the performance of this<br />
package, he can generate a distributed sub-circuit to see the<br />
signal through the entire signal path
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> <strong>Q3D</strong> <strong>Extractor</strong>
The <strong>Ansoft</strong> Solution:<br />
Schematic Capture
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> <strong>Q3D</strong> <strong>Extractor</strong><br />
� Happy with the simulation results, Joe tells his layout<br />
engineers to make some minor changes to the existing<br />
package layout.<br />
� The 2D <strong>Extractor</strong> determined an ideal 100 differential<br />
impedance, while Optimetrics determined an ideal via<br />
spacing.<br />
� The layout engineer made the changes, and then fed the<br />
design back to Joe.<br />
� The last thing Joe needs to perform is the characterization of<br />
every net on the package.
The <strong>Ansoft</strong> Solution:<br />
Reading Layout into TPA 4.0
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> TPA 4.0<br />
� Once the .ANF file is read into TPA, the project<br />
parameters are added.<br />
� Solderball/Solderbump profiles were added to the<br />
project. Via fill was defined, and the layer stackup was<br />
corrected
The <strong>Ansoft</strong> Solution:<br />
<strong>Ansoft</strong> TPA 4.0<br />
� After a coupling distance is given, the partitioning algorithm steps<br />
through the entire package and creates 3D models for each and<br />
every net on the package
<strong>Ansoft</strong> <strong>Q3D</strong> <strong>Extractor</strong><br />
� After the initial setup, Joe was able to let the<br />
program do the full package extraction while he<br />
went home<br />
� When he returned, a fully coupled spice deck of<br />
every net on the package was ready to be shipped<br />
off to the ASIC company for their spice simulations
Design Verification List<br />
� Traces have to have Differential Impedance of 100 ohms<br />
If not, fix it<br />
� Report the findings back to management<br />
� If there are any improvements that could be made to optimize the<br />
package, present suggestions<br />
� Spice sub-circuit has to be generated for the ASIC company to<br />
perform system level simulations at 100ps risetimes<br />
� Parasitic characterization has to be performed for every net on the<br />
package<br />
� Spice subcircuit for the traces has to be generated