TESTING MILITARY GRADE MICROCIRCUITS
MIL-STD-883 is the US DoD standard for test methods for microcircuits. At more than 700 pages long, it covers a wide range of testing requirements from calibration and temperature requirements to the details of methods for internal inspection of microcircuits. In addition to general requirements, there are more than 100 specific test methods. The latest revision (Rev. K w/change 2) of the full document can be downloaded from Defense Logistics Agency at: https://landandmaritimeapps.dla.mil/Programs/MilSpec/listdocs.aspx?BasicDoc=MIL-STD-883.
TEST METHODS IN MIL-STD-883
The various test methods in MIL-STD-883 are divided into 4 classes. Each class is assigned a different range of numbers:
1001-1999 – Environmental tests
2001-2999 – Mechanical tests
3001-4999 – Electrical tests
5001-5999 – Test Procedures
These test methods specify the equipment, setup and measurement techniques to be used. Because the test methods are applied to a wide range of different parts, many test methods indicate that details specific to a particular device are to be included in the detailed specification for that part. For instance, the test method 3007 for Low Level Output Voltage indicates that the test temperature, forcing current, power supply voltage(s), input levels and limits “shall be specified in the applicable acquisition document”. Since these test methods are intended to cover the entire range of microcircuits, not every test is applicable to every device. The acquisition document (a/k/a procurement specification) must indicate which tests are required for that part along with the details required for various standard tests.
OUR CLASS B MICROCIRCUITS ARE QUALIFIED FOR HIGH RELIABILITY MILITARY APPLICATIONS
However, the methods in the “Test Procedures” section are somewhat different. In particular, two of these methods require whole batteries of other standard tests to be performed: Method 5004 “Screening Procedures” and Method 5005 “Qualification and Quality Conformance Requirements”. Test method 5004 defines the various screening steps that must be performed on every military quality microcircuit. These steps can vary depending on the certified quality class level: class B – conventional high reliability military application; class S – space level application. GEM devices are screened and certified to quality class level B. For quality class level B multiple screens are required throughout the manufacturing process: Wafer Lot acceptance testing; internal visual inspection; temperature cycling; constant acceleration; external visual inspection; high temperature burn-in; Percent Defective Allowable (PDA) calculation; Final electrical test at high, low and room temperatures; hermetic package seal test. Once a production lot of parts has completed the 5004 screening requirements, it is subject to method 5005 Quality Inspection (QCI). For this test requirement, sample groups are randomly selected from the production lot for “Group Tests”. For quality class B, non-radiation assured parts, there are 4 groups: Group A (electrical tests) – 116 samples, Group B (destructive mechanical and environmental tests) – 3 samples, Group C (life test) – 45 samples, Group D (package related test) – sample size varies. Group Tests A and B are performed on every production lot. Group Tests C and D are performed on a periodic basis on representative samples of each package and wafer fabrication technology. Only after completing these rigorous 100% screens and QCI can a part be certified and delivered as “883 compliant”, “QML” or “Mil Quality” parts.