Comparison of MCA and Discrete Failure Rates
Summary
MIL-HDBK-217F is used to compare the reliability of a discrete vs an MCA
design. The system is assumed to consist of 12 2N2222A transistors,
operating in an Airborne Inhabited Fighter environment.
Discrete System: λ p = 0.81 failures/106 operating hours
MCA System: λ p = 0.32 failures/106 operating hours
Discrete Calculation
Transistor, Low Frequency, Bipolar (MIL-HDBK-217F Section 6.3)
Transistor failure rate λ p = λ bπ T π Aπ R π S π Qπ E
Base failure rate λ b = 0.00074
Temperature factor π T = 2.1 (Assume Tj = Tcase = 60°C)
Application factor π A = 1.5 (Linear Amplification)
Power Rating Factor π R = 1.0 (Power = 1W)
Voltage Stress Factor π S = 1.0 (VCE = VCEO, Vs = 1.0)
Quality factor Π Q = 1.0 (JANTX)
Environmental factor Π E = 29 (Aircraft Inhabited Fighter)
Þ λ p = 0.00074 * 2.1 * 1.5 * 1.0 * 1.0 * 1.0 * 29 = 0.06760
Number of 2N2222A die N = 12
Þ Nλ p = 12 * 0.06760 = 0.8112
MCA Calculation
Transistor, Low Frequency, Bipolar (MIL-HDBK-217F Section 6.3)
Transistor failure rate λ p = λ bπ T π Aπ R π Sπ Qπ E
Base failure rate λb = 0.00074
Temperature factor π T = 2.1 (Assume Tj = Tcase = 60°C)
Application factor π A = 1.5 (Linear Amplification)
Power Rating Factor π R = 1.0 (Assume Power = 1W)
Voltage Stress Factor π S = 1.0 (Assume VCE = VCEO, Vs = 1.0)
Quality factor Π Q = 1 (Hybrid)
Environmental factor Π E = 1 (Hybrid)
Þ λ p = 0.00074 * 2.1 * 1.5 * 1.0 * 1.0 * 1 * 1 = 0.002331
Dr D.Hinchley
12 Jul 2000
www.semelab.com Tel +44 (0)1455 556565
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Hybrid (MIL-HDBK-217F Section 5.5)
Hybrid failure rate λ p = [NC λC ](1 + 0.2π E )π F π Qπ L
Number of 2N2222A die NC = 12
2N2222A failure rate λC = 0.002331
Environmental factor π E = 5.0 (Airborne Inhabited Fighter)
Circuit function factor π F = 5.8 (Linear, f < 10MHz))
Quality factor Π Q = 1.0 (Class B)
Learning factor Π L = 1.0 (> 2yrs in production)
Þ λ p = [12 * 0.002331]* ( 1 + 0.2 * 5.0 ) * 5.8 * 1.0 * 1.0 = 0.3245
Dr D.Hinchley
12 Jul 2000
www.semelab.com Tel +44 (0)1455 556565
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