Global Equivalent Circuit Modeling System for Substrate Mounted Circuit Components Incorporating Substrate Dependent Characteristics

• US 20040128633A1
• Filed: 04/18/2003
• Published: 07/01/2004
• Est. Priority Date: 04/18/2002
• Status: Active Grant

• Current Assignee: University of South Florida (State University System of Florida)
• Original Assignee: University of South Florida (State University System of Florida)
• Inventors: Weller, Thomas, Capwell, John
• Granted Patent: US 7,003,744 B2
• Time in Patent Office: Days
• US Class Current: 716/4
• CPC Class Codes: G06F 30/367 Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods
• CPC Class Codes: H05K 3/0005 for designing circuits by computer

Abstract

The present invention is a substrate dependent circuit modeling system for substrate-mounted components. The height and dielectric constant of a substrate have a significant impact on the frequency response of such components, and these effects cannot be treated independently from the circuit model. The equivalent circuit parameters in the model must be made to vary in accordance with changes in the substrate. The invention includes the steps of selecting a substrate mounted electrical circuit component for which an equivalent circuit model is desired, determining equivalent circuit model input parameters, wherein some of which are dependent upon characteristics of the substrate upon which the component is mounted, for the selected component, representing the selected electrical circuit component mounted upon the substrate as an equivalent electrical circuit, formulating mathematical expressions based upon the input parameters, and creating a unique equivalent circuit model for the component mounted upon the given substrate, the unique equivalent circuit model representing the mounting of the component upon the given substrate wherein the equivalent circuit model provides behavior and performance predictions of the component based upon the given substrate characteristics.

Claims

1. A method for generating an equivalent circuit model to determine the behavior and frequency performance of a substrate mounted electrical circuit component mounted upon a given substrate, the equivalent circuit model incorporating substrate-dependency parameters, the method comprising the steps of:

selecting a substrate mounted electrical circuit component for which an equivalent circuit model is desired;

determining equivalent circuit model input parameters, wherein some of which are dependent upon characteristics of the substrate upon which the component is mounted, for the selected component;

representing the selected electrical circuit component mounted upon the substrate as an equivalent electrical circuit;

formulating mathematical expressions based upon the input parameters; and

creating a unique equivalent circuit model for the component mounted upon the given substrate, the unique equivalent circuit model representing the mounting of the component upon the given substrate wherein the equivalent circuit model provides behavior and performance predictions of the component based upon the given substrate characteristics.

2. The method of claim 1 wherein the step of determining equivalent circuit input parameters comprises the steps of measuring substrate geometric properties and defining equation variables.

3. The method of claim 1 further comprising the step of expanding the unique substrate dependent equivalent circuit model over a plurality of different component values wherein the model applies to a predetermined range of values for the component thereby creating a global equivalent circuit model for accurately predicting the behavior of a range of component values.

4. The method of claim 1 wherein the model is applicable at a fundamental resonant frequency of the component.

5. The method of claim 4 wherein the model is applicable at or beyond a second harmonic of the fundamental resonant frequency.

6. The method of claim 1 further comprising the step of incorporating the equivalent circuit model into a circuit simulation tool.

7. The method of claim 1 further comprising the step of optimizing a plurality of the unique equivalent circuit models, each the model corresponding to a unique element in a circuit schematic.

8. A method for generating an equivalent circuit model to determine the behavior and frequency performance of a substrate mounted chip inductor mounted upon a given substrate, the chip inductor comprising a plurality of coil turns in a surface-mounted package, the method comprising the steps of:

determining equivalent circuit model input parameters, wherein some of which are dependent upon characteristics of the substrate upon which the inductor is mounted;

representing the inductor mounted upon the substrate as an equivalent electrical circuit;

calculating substrate dependence inductance terms based upon the input parameters; and

creating a unique equivalent circuit model for the inductor upon the given substrate, the unique equivalent circuit model representing the mounting of the inductor upon the given substrate wherein the equivalent circuit model provides behavior and performance predictions of the inductor based upon the given substrate characteristics.

9. The method of claim 8 wherein the step of calculating substrate dependent inductance terms based upon the input parameters further comprises the step of:

representing the inductance terms as a function of an effective chip inductor body width, a substrate thickness and a thickness of a metal trace upon which the inductor is mounted, wherein the step of representing the inductance terms uses the following equation;

ESL (H,W,T)=(L_nom)*(Kg_a−

Kg_b)*(In(W/(H+t)))

wherein;

ESL represents a effective series inductance of the inductor as mounted upon the substrate;

H represents the thickness of the substrate;

W represents the effective chip inductor body width;

t represents the thickness- of the metal trace to which the inductor is mounted upon the substrate;

L_nom represents a nominal inductance of the inductor; and

Kg_a and Kg_b represent fitting coefficients.

10. A method for generating an equivalent circuit model to determine the behavior and frequency performance of a substrate mounted chip resistor mounted upon a given substrate, the method comprising the steps of:

determining equivalent circuit model input parameters, wherein some of which are dependent upon characteristics of the substrate upon which the resistor is mounted;

representing the resistor mounted upon the substrate as an equivalent electrical circuit;

calculating substrate dependence inductance terms based upon the input parameters; and

creating a unique equivalent circuit model for the resistor upon the given substrate, the unique equivalent circuit model representing the mounting of the resistor upon the given substrate wherein the equivalent circuit model provides behavior and performance predictions of the inductor based upon the given substrate characteristics.

11. The method of claim 10 wherein the step of calculating substrate dependence inductance terms based upon the input parameters further comprises the step of:

representing the inductance terms as a function of an effective chip resistor body width, a substrate height and a thickness of the metal trace upon which the resistor is mounted, wherein the step of representing the inductance terms uses the following equation;

ESL (H,W,T)=ESL_a+ESL_b*freq*1e-9)*(Kg_a Kg_b*In(Wf/(H_sub+H_res+T_mtl)))

wherein;

ESL represents an effective series inductance of the resistor as mounted upon the substrate;

ESL_a, ESL_b, Kg_a and Kg_b are fitting parameters;

Wf represents the effective chip resistor body width;

H_sub represents a thickness of the substrate;

H_res represents the effective height of the resistor above a top surface of the substrate to which it is mounted; and

T represents the thickness of the metal trace to which the resistor is mounted upon the substrate.

12. A computer program stored in a computer readable medium embodying instructions to performa method for generating an equivalent circuit model to determine the behavior and frequency performance of a substrate mounted electrical circuit component mounted upon a given substrate, the equivalent circuit model incorporating substrate-dependency parameters, the method comprising the steps of:

where upon a selection of the component, determining equivalent circuit model input parameters, wherein some of which are dependent upon characteristics of the substrate upon which the component is mounted, for the selected component;

representing the electrical circuit component mounted upon the substrate as an equivalent electrical circuit;

formulating mathematical expressions based upon the input parameters; and

creating a unique equivalent circuit model for the component mounted upon the given substrate, the unique equivalent circuit model representing the mounting of the component upon the given substrate wherein the equivalent circuit model provides behavior and performance predictions of the component based upon the given substrate characteristics.

13. A circuit simulation apparatus comprising:

input circuit parameters; and

processing means for determining optimal circuit components, wherein the processing means utilize an equivalent circuit modeling system that determines the behavior and frequency performance of circuit components as a function of characteristics of a substrate upon which each circuit component is mounted.

14. The apparatus of claim 13 wherein the equivalent circuit modeling system can be expanded over a plurality of different circuit component values wherein the modeling system applies to a predetermined range of values for the circuit component thereby creating a global equivalent circuit modeling system for accurately predicting the behavior of a range of circuit component values.