Additional Resources > Windchill Risk and Reliability Practitioner’s Guide > Reliability Prediction Methods > Parts Stress Analysis Methods > Microelectronic Devices (Excluding Hybrids) > Examples of Application of Models
Examples of Application of Models
Four examples of the use of the failure rate models and the data tables follow.
Example SSI/MSI Device
Task
A TTL digital bipolar device with 10 gates and 16 package leads is being used in an air protected environment at 60°C ambient temperature. It was procured under BS 9000 screening level S2. Predict its failure rate.
Solution
1. Identify the appropriate failure rate model from Table A-40. Because the device has less than 100 gates, the SSI/MSI digital model applies. The failure rate is given by:
2. Determine the appropriate values of KQ, KE and KT from Table A-41 through Table A-43 respectively:
▪ From Table A-41, KQ=1.0 (Screening level S2).
▪ From Table A-42, KE=4.0 (Air protected, Al).
▪ From Table A-43, Note 1,KT1 is the appropriate factor for the device (TTL digital bipolar).
From Table A-43, Note 3:
3. Determine the appropriate values for C1, C2 and Kp. With 10 gates, the device is SSI/MSI and so, from Table A-47
4. Calculate λp by inserting the values derived above into the mode in Step 1:
Example Linear Device
Task:
A monolithic linear bipolar device with 23 transistors is being used in a ship protected environment at 60°C ambient temperature. It was procured under BS 9000 screening level S2. Predict its failure rate.
Solution
1. From Table A-40, the failure rate model for linear devices is:
2. The appropriate values of KQ, KE and KT are:
▪ From Table A-41, KQ=1.0 (Screening level S2).
▪ From Table A-42, KE=4.0 (Ship protected, Sl).
▪ From Table A-43, Note 1, KT2 is the appropriate factor for the device.
From Table A-43, Note 3:
3. From Table A-45, entering with 23 transistors:
4. Calculate λpby inserting the values derived above into the model in Step 1.
Example LSI Device
Task
A bipolar digital TTL LSI device is being used in a ground fixed environment at 40°C ambient temperature. The logic diagram of the device shows 128 package leads, 164 gates and 8 flip-flops (each flip-flop = 8 gates), making a total of 228 gates. It was procured under BS 9000 screening level S3. Predict its failure rate.
Solution
1. From Table A-40, the failure rate model for LSI devices is:
2. The appropriate values of KQ, KE and KT are:
▪ From Table A-41, KQ=2.5 (Screening level S32).
▪ From Table A-42, KE=1.0 (Ship protected, S3).
▪ From Table A-43, Note 1, KT1 is the appropriate factor for digital TTL devices.
From Table A-43, Note 3:
3. From Table A-45, entering with 228 transistors:
4. Calculate λp by inserting the values derived above into the model in Step 1.
Example Memory
Task
A 512 bit Bipolar PROM using 16 package leads is being used in a ground fixed environment at 40°C ambient temperature. It was procured under BS 9000 screening level S4. Predict its failure rate.
Solution
1. From Table A-40, the failure rate model for memory devices is:
2. The appropriate values of KQ, KE and KT are:
▪ From Table A-41, KQ=5.0 (Screening level S32).
▪ From Table A-42, KE=1.0 (Ship protected, S3).
▪ From Table A-43, Note 1, KT1 is the appropriate factor for digital TTL devices.
From Table A-43, Note 3:
3. From Table A-47, entering with 512 bits:
4. Calculate λp by inserting the values derived above into the model in Step 1.