Reticulated Surface Pad Impedance Matching

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Solution Overview

Problem

Existing circuit board signal/ground plane structures face issues with impedance mismatch between surface pads and microstrip traces, leading to signal reflections and loss at high frequencies due to large pad clearances, which cause noise coupling and routing difficulties.

Innovation Solution

The introduction of reticulated pads with internal linear features and inductively-coupled ground plane spokes reduces pad clearance, decreases capacitance, and enhances impedance matching by using dielectric-filled gaps and orthogonal features to improve solder bonding and reduce high-frequency noise coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If large pad clearances are used in ground plane, then manufacturing is easier, but impedance matching deteriorates and noise coupling increases

Engineering Contradiction:

Improvepad clearanceVSAvoidimpedance matching

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The ground plane is segmented into multiple regions: a first ground plane region with larger clearance for manufacturing ease, and a second ground plane region with smaller clearance for impedance control. This segmentation allows different areas to serve different functions - the first region facilitates manufacturing while the second region maintains signal integrity and reduces noise coupling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different clearance dimensions are applied to different locations of the ground plane. The first ground plane region uses a first clearance dimension optimized for manufacturing, while the second ground plane region uses a second clearance dimension optimized for impedance matching. This local differentiation resolves the contradiction by allowing each region to have the quality it needs.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If large pad clearances are used in ground plane, then manufacturing is easier, but noise coupling increases

Engineering Contradiction:

Improvepad clearanceVSAvoidnoise coupling

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The ground plane is divided into manufacturing-friendly regions and noise-sensitive regions. The first ground plane region with larger clearance eases manufacturing, while the second ground plane region with smaller clearance acts as a noise barrier, preventing noise coupling to the pad.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second ground plane region with smaller clearance serves as an intermediary barrier between the pad and external noise sources. This intermediate region with restricted clearance prevents noise from coupling into the pad while allowing the first ground plane region to maintain larger clearances for manufacturing ease.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If pad size is increased for solder bonding, then solder bonding improves, but capacitance increases and impedance matching deteriorates

Engineering Contradiction:

Improvesolder bondingVSAvoidimpedance matching

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The pad structure is segmented into a pad region with larger area for solder bonding and a ground plane region with controlled clearance for impedance management. This segmentation allows the pad to have sufficient size for mechanical strength and solder attachment while the ground plane clearance is controlled to maintain electrical impedance characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different areas of the pad-ground structure are assigned different clearance characteristics. The pad region has larger dimensions to ensure adequate solder bonding area, while the adjacent ground plane region has smaller clearance to control capacitance and maintain impedance matching. This local quality differentiation resolves the contradiction between mechanical strength and electrical performance.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively reduces crosstalk, allows easier trace routing, and maintains desired impedance characteristics across signaling frequencies, improving signal integrity and reducing noise interference.

Implementation Method 1

decreases capacitance

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

inductively-coupled ground plane spokes reduces pad clearance, decreases capacitance, and enhances impedance matching by using dielectric-filled gaps and orthogonal features to improve solder bonding and reduce high-frequency noise coupling

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS9003652B2Method of fabricating a circuit board

Publication Date: 2015.04.14 DELL PROD LP

AI summary

The characteristic impedance of a surface pad is manipulated by reticulating the pad and filling the spaces with a dielectric material, providing an inductive element in the coupling of the surface pad to an underlying ground pad of a ground plane, or a combination of these approaches. In appropriate embodiments, acceptable signal trace routing paths will exist in an embedded signal layer under the ground plane and crossing under the surface pad. Other embodiments are also described and claimed.