adequately with technical uncertainties
& Quality Management
How much does MTBF
The effort of a MTBF calculation
depends strongly on the quality
of the data provided by the customer.
Since most MTBF calculations are based on BOMs (bill of materials), the
BOM quality is a significant factor.
Good BOMs meet the following criteria:
- All BOM items have a unique identifier
All BOM items have a useful description
- Typically the manufacturer part number or an in-house part
The BOM must be available in an editable tabular format, eligible
for import into dedicated reliability software.
- This should include typical component parameters, Examples:
- "470 nF X7R",
- "Schottky diode"
- "TSOP16 quad D-flip-flop"
- "14 pin header"
The more comprehensive the BOM, the
more important the criteria. For small BOMs (50 ... 100 BOM items)
however, these criteria are less important.
- One row per BOM item.
- Some ERP systems generate BOMS in strange and clumsy formats
(e.g. BOM items distributed over multiple rows, with empty rows and
columns in between, etc.) This would require massive manual work before
Criterion 1 (unique identifier for each BOM item) is very efficient for
- Modern MTBF calculation
software use component libraries to store all component parameters that
are relevant for MTBF calculation. These libraries use the part number
as the primary key (unique identifier). When a BOM is being imported
and the software recognizes a known part number, it will assign all
MTBF relevant parameters from the library item to the BOM item
- The more often customers
return, the more efficient these libraries get. This makes
MTBF calculations cheaper in the long run.