US 5,327,437 A · Method for testing electronic assemblies in the presence of noise

Abstract

An iterative test method which is operable in the presence of measurement noise uses the result of a particular measurement on a device to decide whether to pass or fail the-device or to take another measurement. The pass/fail decision is made by computing certain statistical values which "compare" the measurement result to a predefined pass/fail limit. Another test measurement is made if the result of the present measurement is too "close" to the pass/fail limit to make an accurate decision. If the result is not too "close" to the limit then a pass/fail decision is made based on whether the measurement is on the pass or fail side of the limit. The statistical values used to compare the measurement value to the limit can be Z-statistics or Student-t statistics depending on the test environment and the noise characteristics. Overall feedback can be added to dynamically adjust the statistical values in order to bring overall error rates into alignment with predetermined error rate targets.

Claims38

Dependent claims

A method for pass/fail testing an electronic assembly with a desired confidence target level by measuring a parameter in the presence of noise with known noise characteristics and comparing said measurement with a predetermined limit, said method comprising the steps of:

A. calculating at least one statistical limit value from said confidence target level;
B. obtaining a test value which represents a measured value of said parameter;
C. calculating an average measurement value from all test values of said parameter including the test value obtained in step B;
D. calculating a statistical value from said predetermined limit, said average measurement value calculated in step C and said noise characteristics;
E. repeating steps B through D when said statistical value calculated in step D has a predetermined relationship to said statistical limit value calculated in step A;
F. resolving the pass/fail status of said assembly by comparing said average measurement value to said predetermined limit when said statistical value calculated in step D has a relationship other than said predetermined relationship to said statistical limit value calculated in step A.

3 more elements

A method for testing an electronic assembly by measuring a parameter in the presence of noise with known noise characteristics, said method comprising the steps of:

A. establishing an acceptable range of values for said parameter;
B. establishing a desired confidence target for passing said assembly and a desired confidence target for failing said assembly;
C. calculating a first statistical limit value from said confidence target for passing said assembly and calculating a second statistical limit value from said confidence target for failing said assembly;
D. estimating the standard deviation of said noise;
E. measuring a value of said parameter;
F. calculating an average measurement value from all measured values of said parameter including the value measured in step E;
G. calculating a first statistical value and a second statistical value from said acceptable range of values established in step A, said average measurement value calculated in step F and said estimated standard deviation from step D;
H. comparing said first and said second statistical values calculated in step G to said first and said second statistical limit values calculated in step C;
I. repeating steps E through H when said first statistical value or said second statistical value calculated in step G is less than said first statistical limit value calculated in step C and said both first statistical value and said second statistical value are greater than said second statistical limit value calculated in step C;
J. passing said assembly when said first statistical value and said second statistical value calculated in step G are greater than said first statistical limit value calculated in step C;
and
K. failing said assembly when said first statistical value or said second statistical value calculated in step G are less than said second statistical limit value calculated in step C.

9 more elements

A. calculating a statistical limit value from said confidence target level;
B. selecting a measurement technique from a first measurement technique and a second measurement technique;
C. measuring a value of said parameter by means of a measurement technique selected in step B;
D. calculating an average measurement value from all measured values of said parameter including the value measured in step B;
E. calculating a statistical value from said predetermined limit, said average measurement value calculated in step C and said noise characteristics;
F. repeating steps B through E when said statistical value calculated in step E is less than said statistical limit value calculated in step A;
and
G. resolving the pass/fail status of said assembly by comparing said average measurement value to said predetermined limit when said statistical value calculated in step E is greater than or equal to said statistical limit value calculated in step A.

5 more elements

A method for pass/fail testing electronic assemblies with a desired confidence target level by making repeated measurements of at least one test parameter in the presence of noise and comparing said measurements with at least one predetermined pass/fail limit, said method comprising the steps of:

A. selecting a measurement method for measuring said test parameter which produces a set of measurement values in which the mean value of said set of measurement values approximates a true value of said test parameter;
B. obtaining a set of measurements by making repeated measurements of said test parameter on at least two electronic assemblies;
C. calculating an estimated standard deviation from said set of measurements obtained in step B;
D. selecting a statistical test method based on predetermined characteristics of said estimated standard deviation calculated in step C;
E. calculating at least one statistical limit value appropriate to the statistical test method selected in step D by using said confidence target level;
F. making at least one measurement of a value of said test parameter on a selected electronic assembly using the measurement method selected in step A;
G. calculating a weighted average measurement value from all measurements of said test parameter including the test value obtained in step F;
H. calculating a statistical value from said predetermined limit and said weighted average measurement value calculated in step G;
I. repeating steps F through H when said statistical value calculated in step H has a predetermined relationship to said statistical limit value calculated in step E;
and
J. resolving the pass/fail status of said electronic assembly by comparing said average measurement value to said predetermined limit when said statistical value calculated in step H has a relationship other than said predetermined relationship to said statistical limit value calculated in step E.

8 more elements

Dependencies are inferred from the claim text.

Method for testing electronic assemblies in the presence of noise

Life of this patent

Method for testing electronic assemblies in the presence of noise

Life of this patent

Abstract

Claims38