Thin Cu Stress Test

The reliability of plated through hole copper (Cu) in Printed Wiring Boards (PWB) is typically evaluated using air-to-air thermal cycling.  This takes a long time, and does not provide material data that can be used for finite element modeling of the structure.  This project will evaluate the use of rapid cycle stress testing to evaluate thin Cu and provide good material properties.

Project stage: 
Lead company: 
Fujitsu

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Idea Information

Background: 

A quick method to determine the reliability of PWB plated through holes is needed, and accurate data on the properties of thin Cu is not available.

Problem: 

Thickness of plated copper in a small through hole or in a through hole with a high aspect ratio of a PWB may be critical to securing adequate reliability for temperature cycling.  The reliability of thin Cu has been carried out using ATC. However, it takes long time to get the result.  Furthermore, finite element modeling is desireable to estimate reliability, but accurate data on the properties of thin Cu, which differ from bulk Cu, is needed.

Definition Information

Goals / Benefits: 
  • Propose how to measure stress-strain and creep properties of thin Cu.

 

  • Find out the similarities and differences between temperature cycling test and FEM simulation with the above properties for thin Cu in order to decide adequate thickness for designated life time of a PWB.
High level objectives: 
  • To characterize material property of plated thin Cu
  • To study the relationship between material properties and thickness for plated Cu by mechanical stress testing and FEM simulations
Approach: 
  • Determine the stress-strain characteristics of thin Cu after 260C reflow stress 2x using a low cycle fatigue test.
  • Compare ATC test result of a board and FEM simulation result with measured Cu properties