Compliant Electrical Probe with Interlocking Cantilever Arms

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Solution Overview

Problem

Conventional spring-loaded contact probes face challenges in impedance matching for high-frequency signals during integrated circuit testing, as the minimal spacing between probes results in increased interconnect length, leading to signal attenuation, while reducing spring volume compromises operating life and force.

Innovation Solution

The design incorporates four flexible cantilever arms with interlocking tabs and compliant helical springs or non-conductive structures to maintain stable contact resistance and minimize interconnect length, ensuring high-frequency response and self-contained assembly without external housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the spring length is minimized to reduce interconnect length and avoid signal attenuation, then high-frequency signal transmission is improved, but the spring volume is reduced compromising operating life and spring force

Engineering Contradiction:

Improveinterconnect lengthVSAvoidspring operating life

Core Design Contradiction:

Length of moving objectVSDuration of action of moving object

Solution Approach 1:

The probe is divided into separate components: a barrel, a plunger, and a spring. This segmentation allows each component to be optimized independently - the spring can be made longer to provide adequate operating life and force, while the overall probe length is controlled by the compact arrangement of these segmented parts.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spring is nested within the barrel, and the plunger is positioned within the barrel as well. This nested arrangement allows the spring to have sufficient length and volume for adequate operating life while the overall probe structure remains compact to minimize interconnect length for high-frequency signaling.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Duration of action of moving object

If the spring length is increased to provide adequate operating life and force, then spring volume is improved, but the interconnect length increases causing signal attenuation

Engineering Contradiction:

Improvespring operating lifeVSAvoidinterconnect length

Core Design Contradiction:

Duration of action of moving objectVSLength of moving object

Solution Approach 1:

By segmenting the probe into distinct functional components (barrel, plunger, spring), the spring can be optimized for length and volume without directly increasing the overall probe length, as each component serves a specific function and can be compactly arranged.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spring is arranged in a compressed configuration within the barrel, utilizing three-dimensional space efficiently. The spring force is transmitted axially through the plunger, allowing the spring to have adequate volume and length while the overall probe maintains a compact form factor suitable for high-frequency applications.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If multiple probes are used in small area for testing, then testing capability is improved, but impedance matching becomes difficult to maintain

Engineering Contradiction:

Improvetesting capabilityVSAvoidimpedance matching

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

Each probe is designed with localized optimization for impedance control. The probe structure includes features such as a tapered plunger and specifically designed spring compression that create consistent electrical characteristics at each probe location, enabling multiple probes to be used in close proximity while maintaining impedance matching.

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 configuration maximizes mechanical compliance, maintains stable contact resistance, and optimizes AC transmission by minimizing interconnect length, thereby reducing signal attenuation and enhancing the operational life of the spring while maintaining consistent assembled length.

Implementation Method 1

The compliance of the interconnect is maximized in order to accommodate mechanical tolerances in the interconnect application

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

the helical spring(s) or compliant non-conductive structures of the contact provide adequate normal force to the part under test and PCB in order to provide electrical contact that maintains stable contact resistance

Methodology Applied

Scientific EffectSpring force: Spring

Implementation Method 3

four flexible cantilever arms that interconnect with each other. During the deflection of the components during the stroke of the probe, the interlocking cantilever arms are always in intimate contact with the mating arm

Methodology Applied

Scientific EffectMechanical interference: Mechanical Force

Data Source

PatentUS7256593B2Electrical contact probe with compliant internal interconnect

Publication Date: 2007.08.14 XCERRA CORP

AI summary

A compliant electrical interconnect having a first component and a second component interlockingly engaged with the first component. Each component has two cantilever arms lockingly engaged and continuously biased against each other. Contact springs are captivated by the cantilever arms providing a contact force for the first and second components.