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ADDA Fan Life Test

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SCOPE

1.MTTF Definition

2.MTTF Condition & Procedure

3.Temperature Acceleration Factor

4.MTTF Calculation & Expect

5.Test Result

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MTTF: Mean Time To Failures

It should be used in a non-repairable system setting.

In ADDA life report, ADDA will not repair the failed fans during life experiment.

1.MTTF Definition

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2.MTTF Condition & Procedure

Condition

AB0705HX-LB(X1A) life expectancy = 20000 Hrs at 60 , ℃

and ADDA expect:

1.Sample number: 200 pcs

2.70 Burn-in test time: 2160 hrs ℃

3.Failure number: 1 pcs

Formula Calculation:

(T / r) × e = 20543 hrs(ΔH / K) x ( — ) 1

273+Tl 1273+Th

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2.MTTF Condition & Procedure

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2.MTTF Condition & Procedure

Procedure

1.Sampling Plan

1.1 Use set-up test time and sample to do the MTTF test before mass production.

1.2 From start to the end of test about 2000 hrs and sample used 100 ~ 200 pcs.

2.Operation Step

2.1 Assign numbers to sample with 01~100 or 01~200.

2.2 Measure their character first. Shall be current and RPM for 3min.

2.3 Put the samples into the oven. Operated fan to rated voltage.

2.4 Set the temperature 70 then operating the oven.℃

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2.MTTF Condition & Procedure

2.5 Checking the test fan if they were acting normally to time Am 08:00 everyday, and recorded.

2.6 When the test time till 2000hrs and complete the test, turn off fan and oven power, carried out all the samples, make final character test, current and RPM for 3 min.

Note: The test time completes in the working time (08: 00~17:00) and

more than 2000 hrs at least.

• Failure Definition

1.The fan doesn’t work.

2.RPM overtakes 30%.

3.The current overtakes 30%

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3.Temperature Acceleration Factor

ΔH = Acceleration coeffient

K = Botltzmann’s coeffient = 8.623 x 10-5

Tl = 30 、 40 、 50 、 60 and Th=70 input (1)

A.F TEMP = e …..(1)

 

go in the 30 、 40 、 50 、 60 to 70 accelerate level number℃. 

(ΔH / K) x ( — ) 1273+Tl

1273+Th

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4 .MTTF Calculation & Expect

• 70℃, 90 % Confidence Level MTTF calculation

T (Total test time) = (Sample - r)×Test time(Hrs) + r1+ r2+ r3 +……

Note: Present the fan failure numbers, r1 、 r2 、 r3 、… ..present the fan first failure time, second failure time, third failuretime, ……

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The probability of fan failure 10% (L10)

Reliability function R(t) = e (-λt )

Unreliability function F(t) = 1- R(t)

e = expontial index, t = time, λ= 1 / MTTF,

Take t = L10, F(L10) = 1- R (L10)

so 10% = 1 - e (-λL10)

90% = e (-λL10)

ln(90%) = ln [ e (-λL10)]

-0.105361 = -λL10

get L10 = MTTF * 0.105361

L10≒ MTTF / 9.5

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5.Test Result

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5.Test Result