MEMORY DATABOOK - Al Kossow's Bitsavers

-------------------. RELIABILITY INFORMATION.Fig. 2Defect Processing FlowchartCustomerFailure report processingRequest fortechnicalimprovementr--------IReport onI results ofI investigationFailure Failure report & improvementdelivery QualityAssuranceDepartmentEngineeringDepartmentDReport onresults of: investigationL _ ~ ~~r~v.:~e~tRequest formanufacturingimprovementManufacturingDepartment11) Group A tests: appearance. labels. dimensionsandelectrical characteristics inspection(2) Group B tests: check of durability under thermaland mechanical environmentalstresses, and operating I ife characteristics(3) Group C tests: performed periodically to checkoperational life etc on long termbasis.Note: Like the reliability tests. the group B tests con·form to the following standards.MIL·STD-883B, JIS C 7022, EIAJ-IC-121Devices which pass these lot guarantee inspections arestored in a warehouse awaiting shipment to customers.Standards are also set up for handling, storage andtransportation during this period, thereby ensuringqual ity prior to delivery.5) At Oki Electric, all devices are subjected to thoroughquality checks. If, by chance, a failure does occur afterdelivery to the customer, defective devices are processedand the problem rectified immediately to minimize theinconvenience to the customer in accordance with thefollowing flowchart.3. EXAMPLE OF RELIABILITY TESTRESULTSWe have outlined the quality assurance system andthe underlying concepts employed by Oki Electric.Now, we will give a few examples of the reliability testsperformed during the developmental and productionprototype stages. All reliability tests performed by OkiElectric conform with the following standards.MIL-STD-883B, JIS C 7022, EIAJ-IC-121Since these reliability tests must determine performanceunder actual working conditions in a short period oftime, they are performed under severe test conditions.For example, the 125"C high temperature continuousoperation test performed for 1000 hours is equivalentto testing device life from 2 to 300 years of use atTa~40°C.By repeating these accelerated reliability tests, devicequality is checked and defects analyzed. The resultinginformation is extremely useful in improving the manufacturingprocesses. Some of the more common defectsin memory LSI elements and their analysis are describedbelow.27