LDPC Manufacturing Testing With Iteration-Based Error Rate Thresholds
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Solution Overview
Problem
Current methods for manufacturing testing of low-density parity-check (LDPC) codes in storage media, such as hard disk drives and Flash drives, face challenges in efficiently determining error rates and ensuring defect levels, particularly in balancing error rate reduction with processing resources and test time.
Innovation Solution
A manufacturing test system and process that uses LDPC codes to encode data written to storage media, performs iterative decoding to determine error rates, and generates an error rate function to set a passing error rate, allowing for efficient testing by optimizing the number of test iterations and error rate thresholds based on desired test time and sector coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative decoding is performed to determine error rates in LDPC codes, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies partial action by performing iterative decoding for a limited number of iterations rather than exhaustive decoding. The system determines error rates by performing a predetermined number of iterations (e.g., 10-100 iterations) which provides sufficient measurement precision for manufacturing testing purposes without requiring the full computational effort of complete convergence, thus reducing test time while maintaining adequate accuracy for defect detection
Solution Approach 2:
The patent implements preliminary action by pre-determining the number of iterations to be performed based on desired measurement precision requirements. This allows the testing system to prepare and execute a fixed number of iterations in advance, avoiding unnecessary computational steps and optimizing the balance between measurement precision and test time for manufacturing environments
2Reliability
If the number of test iterations is increased to reduce error rates, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the number of decoding iterations based on the specific testing requirements and desired reliability levels. The system can modify iteration counts as a controllable parameter to achieve different defect detection capabilities, allowing optimization between reliability and productivity by selecting appropriate iteration numbers for different product quality requirements
Solution Approach 2:
The system uses partial action by performing only the necessary number of iterations required to achieve the desired defect detection level. Rather than always performing maximum iterations, the system determines the minimum sufficient iterations needed, thereby maintaining adequate reliability for manufacturing testing while preserving productivity by avoiding excessive computational overhead
3Manufacturing precision
If error rate thresholds are set low to ensure quality, then manufacturing precision is improved, but loss of time increases due to extended testing
Solution Approach 1:
The patent implements preliminary action by pre-establishing error rate thresholds and corresponding iteration counts before manufacturing testing begins. These thresholds are determined in advance based on desired manufacturing precision requirements, allowing the testing system to efficiently evaluate products against predetermined criteria without requiring extended testing periods, thus maintaining quality control while reducing testing duration
Data Source
AI summary
An amount of time and an error rate function are received, where the error rate function defines a relationship between a number of iterations associated with iterative decoding and an error rate. A testing error rate is determined based at least in part on the amount of time. The number of iterations which corresponds to the testing error rate in the error rate function is selected to be a testing number of iterations; the testing error rate and the testing number of iterations are associated with testing storage media using iterative decoding.