Part Attrition in Electronics Manufacturing

What is Part Attrition

When manufacturing electronic devices, a certain percentage of the electronic components used will be lost or discarded in the process. This is known as part attrition.

Reasons for Attrition

Attrition occurs due to a variety of reasons:

  • Components are damaged during assembly (bent pins, cracked packages, etc.)
  • Extra parts are lost or misplaced
  • Some parts fail testing or inspection
  • Engineering changes require rework which consumes additional parts
  • Assemblers make mistakes requiring scrapped PCBs and parts

The attrition rate is the percentage of parts that are lost for every product built. For example, if a product's BOM (bill of materials) specifies 100 resistors, but on average 105 resistors are actually used per unit built, the attrition rate would be 5%.

Attrition Rates

Attrition rates vary depending on the component type, package, and assembly process:

  • Through-hole parts generally have lower attrition than surface-mount
  • Smaller parts and fine-pitch ICs have higher attrition
  • Manual assembly has higher attrition than automated
  • Complex, multi-stage assembly has higher attrition than simple, single-stage

Typical attrition rates range from 1% for simple through-hole assembly to 10% or higher for complex surface-mount products with many small parts.

When planning material requirements for production, the expected attrition must be factored in. If 1000 units are to be built, and part attrition averages 5%, then 1050 of parts should be purchased.

Managing Component Attrition in PartsBox

Inventory management software like PartsBox can automatically account for attrition. The user can set attrition percentage and minimum quantity values per part. PartsBox will then calculate the total quantity of each part needed to cover the expected losses.

For example, consider a product that uses 5 of resistor R1 per unit. To build 1000 units:

  • With 0% attrition, 5000 pcs of R1 are needed
  • With 5% attrition, 5250 pcs are needed:
  • With 5% attrition and a minimum of 300, 5300 pcs are needed:
    • 5% of 5000 is 250, rounded up to the minimum 300 is 300
    • So an extra 300 pcs are required to cover the expected 5% loss

By planning for attrition, manufacturers can ensure they will not run out of parts mid-production. PartsBox makes this easy by automatically adjusting required quantities based on the user's attrition settings.