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Product defect detection using thermal ratio analysis

  • US 5,032,727 A
  • Filed: 09/14/1990
  • Issued: 07/16/1991
  • Est. Priority Date: 09/14/1990
  • Status: Expired due to Term
First Claim
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1. A method of detecting defects in a test sample of a product, comprising the steps of:

  • generating a reference record for at least one reference sample of the product that does not have defects, comprising the sub-steps of;

    (1) making an ambient-temperature thermal record of the reference sample at ambient temperature;

    (2) making a plurality of elevated temperature thermal records of the reference sample at a plurality of respective elevated temperatures, including applying a respective thermal stimulus to the reference sample, and(3) making a first difference record for the reference sample from the ambient-temperature thermal records and one of the plurality of elevated temperature thermal records and at least a second difference record for the reference sample involving at least another of the plurality of elevated temperature thermal records,generating first and at least second difference records for the test sample by repeating sub-steps (1)-(3) with the test sample replacing the reference sample;

    deriving at least one ratio record from the difference records for the reference sample and the test sample;

    forming a composite record including at least the derived one ratio record; and

    generating a defect indication when the composite record yields a statistical significant deviation from an expected value.

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