1 Design Considerations and Improvement by Using Chip and Package Co-Simulation Yeong-Jar Chang, Meng-Xin Jiang, Chen-Wei Chang, Wang- Jin Chen, Faraday Technology Corporation, Taiwan, R.O.C. Charlie Shih, Jack Lin Cadence Design Systems

2 Overview Traditional Package Design Consideration Proposed Flow Per-pin Inductance Checking and Improvement Coupling Checking and Improvement Co-simulation and Improvement

3 Traditional Package Design Consideration It is very difficult to get the good trade- off between Efficiency and Quality ! Estimated Package model Chip model Package modelChip model Package Pre-layout Simulation Package Post-layout Simulation

4 Proposed Flow and Methodologies Good Enough? Package Design Fast Checking No Good Enough? Electrical Checking No IC/PKG/PCB Co-sim Finish Yes Good Enough? No Yes Trace impedance Coupling Group delay Reference plane Per-pin inductance Power impedance Pulse response Insertion/Return loss Transient power analysis

5 Per-Pin Inductance Checking and Improvement (1/2) (a) Single Ball (b) Parallel 3 Balls (c) Effective 3 Balls The cases to compare the P/G inductance GND1 GND2 GND3 GND1 GND2 GND3

6 (a)  ~ 0.92nH (at 100MHz) (b)  ~ 0.64nH (at 100MHz) (c)  ~ 0.43nH (at 100MHz) P/G Impedance Per-Pin Inductance Checking and Improvement (2/2)

7 Design Consideration (1) Do not treat via, lead-frame or BGA ball as simple inductors only Parallel scheme can not always get the reduction as we expected The better position, case (c), can achieve 33% improvement than case (b) with the same number of ground balls

8 Result – GND layout improvement XIM-EPA can tell us 2% improvement in several minutes 4.267nH4.195nH

9 Example – GND layout improvement 50um 100um

10 Coupling Behavior - Even Mode and Odd Mode Odd Even

11 Coupling Behavior Rising delay at even pattern = ps Falling delay at even pattern = ps Rising delay at odd pattern = ps Falling delay at odd pattern = ps > 1111 faster > 0000 faster > 1010 slower > 0101 slower Lumped Circuit Take the EM (electro-magnetic field) Into consideration

12 Design Consideration (2) The coupling behavior is much different from what we think in the RC-based circuit analysis. The corner (fast/slow) simulation will be different We need to take the EM into consideration if the size is large or the speed is fast. For the rule of thumb, the critical size is /20. ( = wave length = speed of light / frequency )

13 Example - Coupling Improvement Enlarging the space from 55um to 65um can reduce the coupling coefficient from 0.11 to 0.09

14 Basic Co-Simulation Concepts 5v 4v 3v 0.5v1v 5v 3.5v 2v Global GND=0 REF1 REF2 S1 and S2 are S-parameter models S1 S2

15 The S-parameter model is a mathematic model which records the relative voltage instead of the absolute voltage. Connecting the REFs of S-parameters and the global GND (0 or ideal GND) together is correct for co-simulation. But, it does not mean that they are all 0 voltage. Chip-package co-simulation is very important to know the real behavior. Design Consideration (3)

16 Example: Chip-Package Co-Sim Chip P1 G1 P2 G2 Package Die side Ball side Chip Package Die side Ball side REF1 REF2 to other REFs and the global ground P1 G1 P2 G2 Dynamic IR drop without package model Dynamic IR drop with package model of initial design Dynamic IR drop with package model after modification 1.070~1.079v 1.022~1.031v 1.066~1.074v

17 Summary Have proposed a new flow to improve the efficiency and quality of package design The chip-level and package-level design concepts are totally different Have introduced some design considerations for improving package design Have consolidated the ground connections for chip-package co-simulation

18 Appendix

19 Case Studies for Model Extraction in Different GND Setting

20 Case 1 Case 2 Case 3

21 Delay Differences in PCB (W=6mils, D=6, L=1000, 50ohm)

22 References [1]R. Pomerleau, S. Scearce, T. Whipple, “Using Co- design to Optimize System Interconnect Paths”, DesignCon 2011 [2]Keith Felton, “Methodology and Flow Challenges in System-level Co-design of Multi-die Packaged Systems”, Article on [3]Joel McGrath, "The Need for Package-Aware Methodology for IC Design" Article on [4] M. Patil, et al, "Chip-package-board co-design for Complex System-on- Chip(SoC)", in Proc. EPEPS, pp , 2010.