PTH Creep Fatigue Under Roughness Influence

In the previous project "PTH Lifetime Predictor for TC", the lifetime predictor derived is applicable only when the strain is greater than 3.0x10-4. Below this level, the strain is mainly creep strain which does not obey the Manson-Coffin rule. This project serves to provide a better understanding of creep strain on PTH and the influence of copper plating roughness, using FEM simulations and verifying through high temperature (HT) testing. Once the creep characteristics of a typical PWB copper plating are identified, the creep consideration can be added into the AF equation of the PTH lifetime predictor.

 

Project stage: 
Lead company: 
Fujitsu

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Idea Information

Background: 
•Real test including High Temperature(HT) test has been conventionally used but is very time-consuming.
•Life prediction of cycling by FEM was established in the previous two PJs.
•AF for temperature cycling has been established in the last project.
•There’s an AF equation for cycling of PTH and solder joint, but no popular equation for creep in PCB field.

Problem: 

The PTH lifetime predictor for TC derived from the previous project is applicable if the strain experienced by the PTH is less than 3.0x10-4.  PWB takes a long time to fail when the strain is low. Low strain, comprising mainly creep strain, would still cause PTH to crack. There is currently no establish equation to predict PTH lifetime at high temperature (HT).

Definition Information

Goals / Benefits: 

This project serves to

  • Understand creep characteristics of copper plating for PWB.
  • Verify creep effect with simulations and high temperature test.
  • Add creep consideration into AF equation of PTH lifetime prediction.

 

These three objectives will be considered with PTH roughness. PTH roughness effect will be added into not only a creep equation but also the cyclic equation established in the previous project.

Approach: 

The project flow is shown below:

Key Participants: 
Fujitsu
Hitachi Chemical
NVIDIA
Panasonic
Rogers Corporation
Sanmina
Shibaura Institute of Technology
Public