Memory Device Test Method for Operational Margin Assessment

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional test methods for information storage devices cannot accurately determine if a product has sufficient operational margin, leading to the risk of shipping devices that may fail due to noise, and result in either rejecting products with sufficient margin or discarding those with high reliability.

Innovation Solution

A test method and device that set conditions outside the normal use range to count faulty memory bits and determine operational margin, allowing for the identification of products with sufficient reliability and reducing the risk of noise-induced failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If testing is conducted under worst use conditions within the anticipated range, then product reliability under normal use is ensured, but products with small operational margin cannot be accurately identified and may be shipped despite noise susceptibility

Engineering Contradiction:

Improveproduct reliability under normal useVSAvoiddetection precision of operational margin

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the test parameter by setting the test condition outside the anticipated use range (e.g., lower voltage than minimum specified, or extreme temperature beyond normal operating conditions). This allows products with small operational margin to be detected as they would fail under these severe test conditions even though they might pass normal use condition tests.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs a preliminary test under extreme conditions before normal shipment. By conducting the test under conditions severer than the anticipated worst use condition, the system proactively identifies products with insufficient operational margin before they are shipped, preventing potential failures in the field.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If testing is conducted under conditions severer than worst use condition to improve reliability, then products with small operational margin are removed, but products with sufficient margin but noise susceptibility are also rejected

Engineering Contradiction:

Improveproduct reliability against noiseVSAvoidyield of shipped products

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent uses parameter changes by establishing a test condition with specific severity (outside anticipated range but controlled) and comparing the number of faulty bits against a reference value. This allows differentiation between products that fail due to insufficient margin versus those that fail due to random noise, as the reference value is set to account for expected noise-induced failures.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the traditional binary pass/fail test mechanism with a statistical evaluation system. Instead of simply rejecting all products failing the severe test, the system substitutes a comparison mechanism that evaluates the number of faulty bits against a reference value, allowing probabilistic acceptance of products with sufficient operational margin.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If all memory bits must operate normally in test to be shipped as good product, then faulty bits are removed, but products with redundant bits that can compensate for failures are incorrectly rejected

Engineering Contradiction:

Improveproduct reliabilityVSAvoidshipment of products with redundant bits

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the evaluation parameter from binary pass/fail to a count of faulty bits. By setting the test condition to generate a manageable number of expected failures and comparing against a reference value, the system can accept products where the number of faulty bits is within the acceptable range, allowing redundant bits to compensate for failures.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies partial action by not requiring perfect operation of all memory bits. Instead, it accepts a partial failure rate up to a certain threshold (defined by the reference value), allowing products with redundant bits to compensate for the failed bits and still qualify as good products for shipment.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS8984353B2Information storage device and test method of setting a test condition for information storage device outside range of presupposed real use conditions

Publication Date: 2015.03.17 RENESAS ELECTRONICS CORP

AI summary

A method of testing the operational margin of an information storage device having marked random variations, and an information storage device having the function of self-diagnosing the operational margin, are provided. The test method includes testing an information storage device including a plurality of memory bits as the test condition is set so as to be outside a range of conditions that may be presupposed in real use of the information storage device and of counting the number of memory bits that fail in operation. The test method also includes verifying the size of the operational margin of the information storage device based on the count value. The test condition is made severe and the reference value is set to a fairly large value to enable the operational margin against the noise to be tested highly accurately.