Force Sensor Chip Asymmetric Strain Layout

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Solution Overview

Problem

Conventional six-axis force sensors suffer from inter-axis interference and drift noise due to same-polarity arithmetic operations when detecting forces in the Z-axis direction, leading to inaccurate separation of force components and increased noise in output signals.

Innovation Solution

The improved force sensor chip features a base member with an operating part, supporting part, intermediate part, first and second connecting arm sections, and strain resistance elements on the connecting arm sections, allowing for the calculation of axial forces with different polarities and reducing drift noise through novel layout and construction of the semiconductor substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If strain resistance elements are arranged in a conventional layout on a square semiconductor substrate, then the device complexity is reduced and manufacturing is simplified, but inter-axis interference occurs and measurement precision deteriorates due to same-polarity arithmetic operations when detecting Z-axis forces

Engineering Contradiction:

Improveforce detection accuracyVSAvoidstrain resistance element layout complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by arranging strain resistance elements in non-symmetric positions on the semiconductor substrate. Specifically, the first and second strain resistance elements are positioned at different locations and orientations relative to the central through-hole, creating asymmetric strain distribution patterns that enable different polarity responses for the same applied force, thereby eliminating the need for same-polarity arithmetic operations and reducing inter-axis interference

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent utilizes the dimensional space around the central through-hole by placing strain resistance elements on both the upper and lower surfaces of the semiconductor substrate, as well as at different radial distances from the center. This multi-dimensional arrangement allows for independent control of strain responses, enabling the detection system to distinguish between different force components without interference

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of operation

If a central through-hole is added to the semiconductor substrate for probe card engagement, then ease of operation is improved, but the substrate strength is reduced and reliability deteriorates

Engineering Contradiction:

Improveprobe card engagementVSAvoidsubstrate strength

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent applies the counterweight principle by strategically positioning support structures and strain resistance elements around the central through-hole to compensate for the stress concentration and strength reduction caused by the hole. The surrounding support structures act as counterbalancing elements that distribute mechanical loads away from the hole edges, maintaining overall substrate strength despite the presence of the through-hole

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Measurement precision

If strain resistance elements are positioned to detect multiple force components, then measurement precision is improved, but drift noise increases due to same-polarity arithmetic operations

Engineering Contradiction:

Improveforce component separationVSAvoiddrift noise

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the conventional approach by designing strain resistance elements that produce opposite polarity responses to the same applied force. Instead of all elements responding in the same direction, the asymmetric arrangement causes some elements to experience tensile strain while others experience compressive strain under identical loading conditions, enabling differential measurements that cancel drift noise through natural polarity opposition rather than requiring same-polarity arithmetic operations

Inventive Principle:

Principle #13The other way round (Inversion)

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 design enables stable and precise detection of forces and moments by canceling noise and simplifying the fabrication process, effectively reducing drift noise and improving the accuracy of force and moment detection.

Implementation Method 1

at least one strain resistance element provided on each of respective deformation-generating portions of the first connecting arm section and second connecting arm section

Methodology Applied

Scientific EffectStrain resistance: Piezoresistive Effect

Data Source

PatentUS7490524B2Force sensor chip

Publication Date: 2009.02.17 HONDA MOTOR CO LTD

AI summary

In a force sensor chip, a base member, to which an external force is applied, includes: an operating part provided in a central portion of the base member and having an external-force acting area section; a supporting part provided, in an outer peripheral portion of the base member, for supporting the operating part; an intermediate part provided between the operating part and the supporting part; a first connecting arm section connecting the operating part and the intermediate section; a second connecting arm section connecting the intermediate part and the supporting part; and at least one strain resistance element provided on each of respective deformation-generating portions of the first and the second connecting arm sections.