Fatigue

There are a few basic types of fatigue test. The sample can be subjected to repeated shear, pull or push loads. In the case of shear these can also be applied with a low rate of load application or with a high “Impact” rate. These tests can simulate many fatigue loading conditions with advantage that the load, energy and strain can be selected and recorded for every load cycle. Finally the number of cycles to failure is recorded.

One example is the fatigue loading of a BGA solder ball when the board it is mounted to bends either due to CTE miss match or mechanical loading. For low load rate applications like CTE miss match the shear component of the oscillating load can be simulated with a tubular or double (fork) shear tool. The tool deflects the ball under test through repeated alternate strains until failure occurs. Failure being defined by a minimum peak load resistance on the tool for each load application. For high load rates an impact tool can be used.

High speed video of one impact fatigue loading

Oscillating Pull and Push test have many applications, one example being button life tests. With such tests a force displacement graph can be recorded providing useful information on the actuation characteristics and how these may change after multiple operations.

Test features

• Impact and low load rate fatigue
• Crack propagation analysis
• Button testing
• Sensor accuracy ±0.075%
• Simulation of
  • Fatigue effects of thermal cycling and CTE miss match
  • Board drop/bend/vibration