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Home > ANSYS Q3D 教學 > Q3D vs. Maxwell for TSP Application

 

本文始於2015，分別以R16的版本為例，說明Q3D與Maxwell做電容式觸控面板模擬的差異。This article is intended to discuss the difference between Q3D and Maxwell for TSP application, specially for C calculation. Use Q3D2015 and Maxwell2015 for example.

-- update section 7 on 2017.10

  1. Introduction

  2. Create TSP Model

  3. Assign Material

  4. Solution Type and Excitation

  5. Analysis Setup

  6. Result Matrix and Simulation Time

  7. Summary

  8. Q&A

    8.1 For Maxwell, how to assign "solution frequency" for C?

    8.2 Why does Maxwell solve real thickness 1um faster than Q3D?

    8.3 Can Maxwell solve R, C at AC (with skin effect) or transition region (DC~AC)?

  1. Introduction

  2. Create TSP Model

The same as Q3D, or you can copy all objects (ctrl+A, ctrl+C) from Q3D and paste (ctrl+V) them to Maxwell directly.

  1. Assign Material

the same as Q3D

  1. Solution Type and Excitation 

4.1 Set Solution Type and Design Unite

[Maxwell 3D] \ [Solution Type]，選[Electric：Electrostatic]

選[Electric：Electrostatic]，等一下步驟4.2設定Excitation會出現Voltage/Charge/Floating/Charge Density供選擇，步驟6的模擬結果才會出現[寄生電容]值。如果這裡一開始選的是[Magnetic：Magnetostatic]，步驟4.2設定Excitation會出現Voltage/Current/Current Density供選擇，步驟6的模擬結果則是[寄生電感]值。

Modeler \ Units，選[mm]

4.2 [Maxwell 3D] \ [Excitations] \ [Assign] \ [Voltage]

top-layer ITO are named as Rx, Rx_1, Rx_2,...，bottom-layer ITO are named as Tx, Tx_1, Tx_2,...

Rx=R1=0V, Rx_1=R2=0V, ..., Tx=T1=1V, Tx_1=T2=1V, ...

  對導体設定電壓或電流後，Maxwell才有辦法對object，進行靜態電場的分析。 一個design中，建議至少有兩種電壓值，比方0V, 1V；避免所有net都同一個電壓值(0V)，會導致meshing很久切不到target [Percent Error]。這是因為Maxwell是透過object的電壓/電流設定，計算能量場於design的分佈情況，如果每個object電壓相同， 彼此間沒有電位差(電力線分佈)，很難算收斂整個系統的場分佈情況

4.3 [Maxwell 3D] \ [Parameters] \ [Assign] \ [Matrix]

這裡有勾選的電壓，其所代表的net才會進行分析，模擬結果才會 在step6看到他們的自電容與互電容值。

  1. Analysis Setup 

[Maxwell 3D] \ [Analysis Setup] \ [Add Solution Setup]

Maxwell裡的[Percent Error]，就像是HFSS裡的[Maximum Delta S]，決定了模擬的精度，其數值越小，meshing refine的次數會越多，所切出的四面體(四面錐體)越多，模擬所耗的記憶體越大。

  1. Result Matrix and Simulation Time 

6.1 Maxwell 3D \ Validation Check

6.2 Maxwell 3D \ Analysis All

6.3 [Maxwell 3D] \ [Results] \ [Solutions Data]

      或是在[Project Manage]內，選Analysis\Setup1按滑鼠右鍵選[Profile] or [Convergence]即可

即使把percent error調的夠小(for example, 0.1% twice)，Maxwell解出來的Cm略大於Q3D解的值，原因是兩邊的厚度不同。

    同樣解1um真實厚度的題目，Maxwell比Q3D with HPC的速度略快，但Maxwell解real 1um比Q3D解thin conductor with HPC的速度慢 。

雖然Maxwell解靜態電場電容只用單核，但速度不會比Q3D+HPC多核慢，這是讓筆者比較surprise的

  1. Summary 

Both of Maxwell and Q3D are

-- Quasi-static solver with FEM

-- support "floating net"

Maxwell與Q3D的電容C求解結果很接近，但

-- Q3D不用設air box, Maxwell需要

-- Q3D可以by solver type或CG, AC_RL做HPC distribution求解加速, 但Maxwell不行

-- Maxwell沒有thin conductor，所以一定要放大等效厚度求解(至少1um以上厚度)

-- 對於Maxwell，CG與RL的求解結果，無法整合成SPICE或S-parameter model

-- Maxwell只能解DC電容，而Q3D可以解DC與其他頻點的電容

Maxwell比起Q3D在觸控應用上，目前的優點是

-- 可以看空間場, plot 3D E field

-- 有對稱boundary可以利用

Maxwell比起Q3D在觸控應用上，目前限制是

-- 無法export SPICE或S-parameter model (只解C@DC)

-- 沒有thin conductor技術

-- HPC在Maxwell對觸控的應用上， 目前幫不上忙。 (freq. distribute觸控用不上)

  1. Q&A 

8.1 For Maxwell, how to assign "solution frequency" for C? 

Ans：Maxwell solves [Electrostatic] at DC, so it does not need to assign solution frequency.

8.2 Why does Maxwell solve real thickness 1um faster than Q3D? 

Ans： I am not sure what is the root cause, but note that Maxwell solves static C with tetrahedra (FEM) mesh, but Q3D solves C with triangle (BEM) mesh.

8.3 Can Maxwell solve R, C at AC (with skin effect) or transition region (DC~AC)? 

Ans：Maxwell has an [Eddy Current] solve type to calculate skin effect, but it is only for Rac, not for C and transition region. In the future, maybe R19 or R20, AC solver for CG will be added in Maxwell.