Probe Card Thermal Stability via Buried Core Layer

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Solution Overview

Problem

Conventional probe cards experience electrical signal loss and increased component count, leading to high costs and complexity in high-frequency signal transmission, particularly due to the use of space transformers and interposers in Full Wafer Level Testing.

Innovation Solution

A probe card design featuring probes, a probe head, a substrate with a buried core layer of lower thermal expansion material, and a connecting member with through holes or zero insertion force connectors to reduce thermal expansion differences and simplify assembly, enhancing high-frequency signal transmission characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a space transformer and interposer are used to reduce thermal expansion differences, then thermal stability is improved, but electrical loss increases and transmission characteristics of high-frequency signals deteriorate

Engineering Contradiction:

Improvethermal stabilityVSAvoidelectrical loss

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The invention extracts and removes the space transformer and interposer components from the probe card structure. By eliminating these intermediate components, the patent achieves direct electrical connection between probes and the semiconductor wafer, thereby reducing electrical loss and improving high-frequency signal transmission characteristics while still addressing thermal expansion differences through alternative means

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention employs composite material structures in the probe card substrate and probe assembly that integrate different materials with complementary properties. This includes using materials with matched thermal expansion coefficients in the probe card structure to compensate for thermal effects without requiring additional intermediate components, thus maintaining thermal stability while avoiding the electrical losses associated with space transformers

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If a space transformer and interposer are provided to reduce thermal expansion differences, then thermal stability is improved, but the number of components increases and manufacturing complexity increases

Engineering Contradiction:

Improvethermal stabilityVSAvoidnumber of components

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention merges the functions of thermal compensation and electrical connection into a simplified integrated structure. By directly connecting probes to the wafer through a streamlined probe card assembly without intermediate space transformers or interposers, the patent combines multiple functions into fewer components, reducing both the number of parts and assembly complexity while maintaining thermal stability through material selection and structural design

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If probes are collectively contacted with all dies on the semiconductor wafer, then testing speed is improved, but positioning accuracy requirements increase

Engineering Contradiction:

Improvetesting speedVSAvoidpositioning accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The invention creates an equipotential reference plane between the probe card assembly and the semiconductor wafer surface. By ensuring that all probes are held at consistent heights and angles relative to the wafer, the patent enables collective contact with multiple dies simultaneously while maintaining uniform positioning accuracy across all probe contact points, thus achieving both high testing speed and adequate positioning precision

Inventive Principle:

Principle #12Equipotentiality

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

The design achieves economical and cost-effective high-frequency signal transmission with improved accuracy and reduced assembly complexity by minimizing thermal expansion differences and eliminating the need for space transformers, while maintaining probe card durability and reliability.

Implementation Method 1

the space transformer 54 serves also as a function of reducing a difference between the coefficient of thermal expansion of the semiconductor wafer and the coefficient of thermal expansion of the substrate 57

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS7772858B2Probe card

Publication Date: 2010.08.10 NHK SPRING CO LTD

AI summary

A probe card includes a plurality of probes that contacts a plurality of electrodes provided in the semiconductor wafer and that inputs or outputs an electrical signal in or from the electrodes, a probe head that holds the probes, a substrate having a wiring which is provided near the surface of the substrate facing the probe head so as to be contactable with the probe head and is connected to the probes, a core layer formed of a material which is buried in the substrate and has a coefficient of thermal expansion lower than that of the substrate, and a connecting member that electrically connects at least some of the probes with an external device via the wiring.