Measurement-Simulation Correlation of High Frequency PCB Interconnects Pranav Balachander, Anand Ursekar, Dr. Eric Bogatin, Dr. Melinda Piket-May Department of Electrical, Computer and Energy Engineering University of Colorado, Boulder

Agenda Motivation & Objective Project Outline Simulation Model & Results Measurement – Simulation Correlation

Motivation & Objective Problem : Inaccurate values of material properties. Objective : Establish best practices in simulation tool for good correlation with measurements. What this means? – Reduced Design Cycle time + No. of board spins  Lower Cost & Time 4.32 mils

Project Outline PHASE 1 PHASE 2 PHASE 3 PHASE 4 Model test structure ( Beatty Std.) in HFSS with adjacent return plane PHASE 2 Perform VNA Measurements from DC to 30 GHz PHASE 3 Dead Reckoning Simulation vs Measurement PHASE 4 1. Adjust Dk to match Phase S21. 2. With corrected Dk, adjust Df to match Mag S21. 3. With corrected Df, adjust H to match Mag S11.

WRT CMP 28/32 platform Source: CMP 28/32- Channel Modeling Platforms. www.wildrivertech.com Contains 27 MS/SL structures for systematic validation of 3D - EM solver in freq. & time domains up to 40-50 GHz. Test Structure : Series Resonant Beatty Standard.

Beatty Standard Simulation Model Copper Trace FR408 HR Constructed by increasing trace width by 3X for a 1” distance at the center. Materials: Copper Trace (σ = 5.8 x 107 S/m) Dielectric : FR408 HR (Dk = 3.67, Df = 0.012)

Simulation & Measurement Model HFSS Model Measured Structure vs Add Picture of SPARQ Network Analyzer. BS Photo says stripline while we are measuring the microstrip. Teledyne LeCroy SPARQ Network Analyzer

Dead Reckoning vs Measurement FR408 Manufacturer Specs. Dk = 3. 67 Df = 0.012 H = 7.4 mils Measured Simulated Phase S11(Deg) Mag S11(dB) Mag S21(dB) Phase S21(Deg) TDR_Z(ohms)

Extraction of Dielectric Constant Dk Dk = Variable Df = 0.012 H = 7.4 mils 3.67 Phase S21 matched at Dk = 4.1 3.80 4.00 4.10

Extraction of Dissipation Factor Df Dk = 4.10 Df = Variable H = 7.4 mils Mag S21 matched at Df = 0.020

Extraction of Dielectric Thickness H For 3X width, TDR_Z (Measured) = 25.49 Ω TDR_Z(H = 10 mils) = 25.33 Ω TDR_Z (default) = 19.06 Ω Dk = 4.10 Df = 0.020 H = Variable TDR Z matched at H = 10 mils

Extraction of Dielectric Thickness H Dk = 4.1 Df = 0.02 H = Variable Mag S11 matched at H = 10 mils

Improvement in Meas. – Sim. Correlation Initial Dk = 3.67 Df = 0.012 H = 7.4 mils Final Dk = 4.10 Df = 0.020 H 10 mils Mag S11 Mag S11 Phase S11 Phase S11 Mag S21 Mag S21 Phase S21 Phase S21

Conclusion Cannot rely on manufacturer data to build accurate 3D EM simulations. Material properties can be extracted using a test structure such as Beatty Standard. Better Measurement-Simulation Correlation. Improve ability of simulation to predict measured performance.

Acknowledgement Dr. Eric Bogatin for his guidance and valuable discussions throughout the project duration. Al Neves and Jim Bell from Wild River Technology for providing the CMP 28/32 board and continued support. Dr. Melinda Piket-May for valuable suggestions along the way. CCN Lab for use of testing and measuring equipment.