BS IEC 60748-11:2000 pdf download – Semiconductor devices — Sectional specification for semiconductor integrated circuits excluding hybrid circuits.
6 Structural similarity procedures
6.1 General rules
6.1.1 Purpose
Structural similarity procedures are intended to permit a reduction in the number of inspection lots that shall be tested.
6.1.2 Principles
For a test applicable to a group of device types, the test may be performed on one type from the group and the results obtained considered as representative for all the types if the general and particular criteria for structural similarity described in this clause and applicable to this test are complied with (see Table I). The definition of these criteria shall be based on the principle that conformity and reliability verified on the representative type gives at least the same conformity and reliability assurance for the associated types. Structural similarity procedures shall not be applied for electrical and visual tests under Group A.
6.1.3 Application conditions
1) Tests and measurements specified in sequence
Structural similarity procedures described in this clause apply to a single test.
When several tests are specified in sequence, the application shall he based on the following principles:
The essential test in the sequence of tests in a sub-group shall be decisive for criteria to be used for
structural similarity grouping for the complete sequence.
NOTE For application of this principle for 8.5/CS Lest, the e.sentiaI test is ‘Rapid change of ternperature.
2) Application for quality assessment procedures
The application of the structural similarity procedures is specific to a considered quality assessment
procedure and detailed application conditions are given in Clause 7 below.
6.1.4 General criteria for structural similarity
1) The type chosen as representative for a group of types in relation to a given test may differ from one
period to another, depending on the types produced in that period.
2) For all relevant types in a group of types. the same acceleration test procedure shall be allowed.
3) If, although fulfilling the particular criteria for a group, significant difference(s) still exist in
characteristic(s), the t.ype selected for the relevant test shall be represented by the most critical device
giving the greatest risk of failure for this test.
4) If failure occurs on a device type, all the devices associated with this representative type are to be considered affected.
5) If the devices are submitted to a screening procedure in accordance with Clause 8, and if several screening sequences are applied in the same production line, the devices can only he grouped if they are screened according to the same screening sequence.
6.2 Test dependent criteria for structural similarity
The test dependent criteria for structural similarity applicable to the Group B and periodic tests are given
in Table I.
Subclauses 6.2.1 to 6.2.18 specif’ the interpretation of these criteria.
Example for the use of Table I:
Sub.group C3 requires that the test on the robustness of terminations be performed.
For this test, the following requirements for structural similarity apply (see Table I):
subclause 6.2.1 — Assembly line; suhclause 6.2.3 — Family of package; subclause 6.2.5 Encapsulation methods; subclause 6.2.6 — External terminals material:
suhclause 6.2.7 Finishing process.
Devices satisfying all the requirements of all the subclauses above are considered structurally similar for the “Robustness of terminations” test.