Multilayer Wiring Board Capacitance Testing Without Grounded Layer

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Solution Overview

Problem

Conventional methods for testing multilayer wiring boards cannot measure electric capacitance between a signal line and a grounded layer without an overall grounded layer, limiting the ability to detect breaks or short circuits in the wiring.

Innovation Solution

A multilayer wiring board with an internal conductor layer within the base substrate serves as an electrode for capacitance measurement, allowing for the calculation and comparison of measured electric capacitance values between the three-dimensional wiring path and the internal conductor layer, enabling the detection of defects without an overall grounded layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an overall grounded layer is used in the multilayer wiring section, then electric capacitance measurement between signal line and grounded layer is enabled, but the design flexibility and adaptability to different wiring board configurations is reduced

Engineering Contradiction:

Improveelectric capacitance measurement capabilityVSAvoidapplicability to wiring boards without overall grounded layer

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent divides the grounded layer function into two parts: an overall grounded layer in the base substrate and local grounded patterns in the multilayer wiring section. This segmentation allows capacitance measurement while accommodating designs without complete overall grounded layers, resolving the contradiction between measurement capability and design flexibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an internal conductor layer as an intermediary element within the base substrate that serves as a reference electrode for capacitance measurement. This intermediary structure enables measurement functionality without requiring an overall grounded layer in the multilayer wiring section, thus maintaining adaptability to various wiring board configurations.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conventional capacitance measurement method is used, then wiring defects can be detected in boards with overall grounded layer, but testing is impossible for boards without overall grounded layer

Engineering Contradiction:

Improvewiring defect detection capabilityVSAvoidcompatibility with different multilayer wiring board types

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal testing structure where the internal conductor layer in the base substrate serves as a common reference for capacitance measurement across different multilayer wiring board configurations. This universal approach enables defect detection reliability while accommodating both boards with and without overall grounded layers in the multilayer wiring section.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If multilayer wiring section without overall grounded layer is used, then design flexibility and material reduction are achieved, but the ability to perform electric capacitance measurement for defect detection is lost

Engineering Contradiction:

Improvedesign flexibility for different wiring configurationsVSAvoidelectric capacitance measurement capability

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent moves the grounded reference function from the vertical dimension (overall grounded layer in multilayer wiring section) to the base substrate dimension (internal conductor layer). This dimensional shift allows designs without overall grounded layers while preserving capacitance measurement capability through the test pad connected to the internal conductor layer.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 allows for accurate detection of wiring defects, such as breaks or short circuits, even in multilayer wiring boards without an overall grounded layer, enhancing the reliability of testing and reducing material waste by enabling early identification and repair or removal of defective sections.

Implementation Method 1

measuring, with a measuring device 28, an electric capacitance between the test pad 78 and the uppermost wiring pattern 60

Methodology Applied

Scientific EffectElectric capacitance: Capacitance

Data Source

PatentUS7656166B2Multilayer wiring board and method for testing the same

Publication Date: 2010.02.02 NIHON MICRONICS KK

AI summary

A multilayer wiring board has a ceramic substrate, on which a multilayer wiring section is formed. The ceramic substrate has an internal conductor layer, which is connected to a test pad. The first conductor layer is formed, and then an electric capacitance is measured between the test pad and a wiring pattern of the first conductor layer. On the other hand, an electrical capacitance is calculated under the normal wiring pattern condition. The measured value is compared to the calculated value to determine whether the wiring pattern is good or bad. Similar measurements and comparisons are carried out for each of the second through fifth conductor layers to determine whether a three-dimensional wiring path is good or bad. As the ceramic substrate has an internal conductor layer, the electric capacitance of the wiring can be measured without an overall grounded layer in the multilayer wiring section, which is a characteristic part different from others among a variety of the multilayer wiring boards.