Mean Time Before Failure
Calculations
Reverse Engineering Department
Mean Time Between Failure
-is the estimated time between inherent failures of a electronic or mechanical system
Goal is to design a product to increase the time between failures or increase the time before a failure
Mean Time Between Failure
In order to determine an effective MTBF duration is it critical to understand
the operating conditions the device is subject to in the field
Operating Conditions Include:
- Operating (Ambient) Temperature
- Component's Maximum Rating (max voltage/wattage)
- Component's Applied Rating (applied voltage/ power dissipated)
- When components are operated close to the maximum ratings, their mean time between failure can be reduced
Our Approach to Calculating A Mean Time Between Failure
- Electrical design of the prototype
- Using analog circuit design methodologies
- Develop a schematic of the design
- Generate a Bill of Materials (BOM) of components used
- Verify the alpha prototype has a mean time between failure that is greater than the specified legacy unit's value
Proceed to Design Alpha Prototype
Verify
Prototype
Meets Customer Requirement
Determine Customer
MTBF
Requirement
Perform
MTBF Analysis on the Bill of
Materials
- Using the components used on the electrical sub assemblies (ESA's)
- Perform a Failure in Time (FIT) calculation for each component using the MIL-HDBK-217F Standard
- Sum the total FIT's to get the mean time between failure of the prototype
- Technical specification defines a minimum MTBF in hours
- Or customer provides legacy documentation , that illustrates the MTBF of the legacy unit
- Kinectrics works toward a greater MTBF number than the customer imposes
Example of a Technical Specification
- Specifies an operating temperature
- Specifies a minimum MTBF requirement
Example of a Electrical Subassembly Drawing
MIL-HDBK-217F Handbook
- Developed by department of defense, with assistance with military departments
- Standard reflects the latest information on reliability prediction procedures of electronics
- Provides methods for estimating the inherent reliability of military electronic equipment
Component Failure's In Time (FIT)
Sample Calculation for Capacitor
- Has an applied Voltage of 86 VDC
- Component has a maximum voltage of 200 VDC
- Operating temperature is 50C
- Temperature rating is 125C
- Capacitance is 22 micro farads
- Capacitor material is ceramic
Following Section 10.1 of Standard
Mean Time Between Failure=