Revised stress standard should improve component quality

The Automotive Electronics Council, an industry organization formed in 1992 and whose members now include most of the major automakers and many of their electronics suppliers, recently updated Q100, "Stress Qualification For Integrated Circuits." This is the first revision in more than two years and is arguably the most extensive revision to date.

According to Jerry Servais, a technical fellow (now retired) with Delphi Delco Electronics Systems (Kokomo, IN; www.delphi.com), "These changes were made to update the specification to more closely reflect the continuing evolution taking place in the manufacturing of integrated circuits. Qualification documents in particular are very conservative in nature and tend to change slowly. It was just time for this specification to be updated."

The primary changes to the main document include:

• Addition of a "Grade 0"

The operating temperature range for Grade 0 parts is –40ºC to +150ºC. The addition of Grade 0 reflects the need for electronics that can operate at higher temperatures. Grade 1, previously the grade with the widest operating temperature range, has a maximum operating temperature of +125ºC.

• Higher test temperatures

In order to test Grade 0 parts, the maximum test temperature is now +175ºC.

The new revision of Q100 requires ESD testing using the Charged Device Model (CDM) at peak voltages up to 1000 V for some parts. Shown above is a typical CDM waveform. Courtesy of Automotive Electronics Council.

The number of parts that manufacturers have to test to qualify parts has been reduced, as long as certain quality control information is available. This change recognizes that by using SPC techniques, component manufacturers have improved their process control and reduced part variation.

• Addition of the CDM ESD test

This revision requires that manufacturers now perform an ESD stress test using the Charged Device Model (CDM) to qualify their parts.

• Addition of two templates

One template covers design, construction, and qualification information, and the other outlines a quality test plan. These templates will help companies better document the qualification process.

The AEC also modified several attachments:

• –002 Human Body ESD

The AEC added a lower voltage stress and changed the acceptance criteria. Previously, the standard required components to withstand an ESD voltage of 2000 V minimum, but now components can be classified into one of seven classifications, with each classification having its own minimum withstand voltage.

• –003 Machine Model ESD

As with attachment -002, the AEC changed the acceptance criteria. Instead of a single classification with a minimum withstand voltage of 200 V, there are now five classifications, with minimum withstand voltages ranging from less than 50 V to greater than 400 V.

• –005 Nonvolatile Memory Program/Erase Endurance, Data Retention, and Operational Life Test

The AEC changed the data retention test procedure and added an operational life test to this attachment. The operational life test is a high-temperature test lasting 1008 hrs.

• –011 Charged Device Model ESD

As with attachments -002 and -003, the AEC changed the acceptance criteria. The group replaced the single classification, which had a minimum withstand voltage of 500 V, with seven classifications, which have minimum withstand voltages ranging from less than 125 V to greater than 1000 V.

The changes will help improve automotive electronics reliability in several ways. For example, the new revision requires ESD testing using the CDM. Because this model more closely approximates ESD stresses in the real world, parts that pass the ESD tests should be more robust.

The revisions also provide increased focus on the use of Q001 Part Average Testing (Ref. 2), which is designed to eliminate outlier parts (even though they meet the spec). Thus, parts will become more uniform and, consequently, more reliable. (There is something different about a part that is an outlier and therefore it represents an increased reliability risk.)

The changes to Q100 do more than just improve part reliability; they also improve and clarify the qualification process and improve the documentation of qualification test results.

Copies of all AEC documents, including Q100 and Q001, are free and can be downloaded from the AEC Web site at http://www.aecouncil.com . Engineers interested in working on future revisions of these documents can contact the AEC Technical Committee at http://www.aecouncil.com/AECRequest.html .