Created: 10/24/95 Updated: 4/18/97

Combined Temperature and Humidity Accelerated Testing of Assemblies

Project Number : C96-29

Point of Contact:

Dr. Abhijit Dasgupta
CALCE EPRC
email: dasgupta@calce.umd.edu
Phone: (301) 405-5251
Fax: (301) 314-9269


Objective Background Approach Deliverables Work Accomplished


Objective

 Illustrate the synergy between temperature cycling and humidity, for conducting accelerated stress tests cost-effectively on CCAs, to obtain maximum test-time compression. Further, illustrate quantitative approaches for assessing the damage metrics, acceleration transforms and stress margins from accelerated life testing data.


Background

CALCE EPRC is currently involved in a comprehensive multi-task, multi-year accelerated stress project (c96-13) to investigate the synergy between vibrational stresses and temperature cycling stresses for test time compression; and to develop the physics-of-failure (PoF) approach for deriving quantitative damage metrics and acceleration transforms for these stresses.

This proposed project is intended to explore similar synergy between temperature and humidity cycling, for test-time compression. Failure mechanisms which were not precipitated by temperature and vibration will be the main focus of this program. A detailed test program will be used to study the problem empirically this year. In future years, a PoF approach will be developed to quantify the damage metrics and acceleration


Approach

Based on our experience with the first years s test program, an empirical phase is proposed for the first year. Two research units will be used to test two different types of specimens this year: (i) a fully functional CCA for automotive applications, (ii) a daisy-chained CCA containing new innovative substrate materials and technologies for aerospace applications.

An L5 test matrix, developed during the previous year in project C95-13, will be used in this program, to empirically explore the synergy between combined temperature and humidity stresses for both types of specimens. All tests will be electrically monitored throughout the test for failures, using functional diagnostics or transient event detectors. Qualitative assessments of the test data will be provided at the end of this year.

A factorial test matrix is used to empirically explore the synergy between combined temperature and humidity stresses for both types of specimens. All tests are electrically monitored throughout the test for failures, using functional diagnostics or transient event detectors. Qualitative assessments of the test data will be provided at the end of this year.

In future years, PoF damage analysis will be conducted for each observed failure mode. The CALCE failure mechanism libraries will be used, whenever appropriate. Model parameters will be updated using the test data, and quantitative acceleration transforms will be illustrated using the pof approach. New models will be generated, for new mechanisms for which models are not available in the CALCE library.

The project has been subdivided into four major tasks:

  1. Determine number of pre-conditioning cycles necessary to achieve adequate test time compression. Preconditioning will also ensure that samples are cycled between extreme temperatures and have similar initial state.
  2. Apply predetermined combination of controlled temperature and moisture profiles
  3. Record and post-process failure date
  4. Qualitatively explain the synergy between moisture and humidity stresses (assess failure mechanism interaction).

Deliverables

The output during the first year will be:
(i) accelerated test methodology and test data for both types of specimens under combined temperature and humidity stresses;
(ii) qualitative assessment of the synergy between the temperature and humidity stresses for test-time compression during CCA testing.

In future years, PoF methods will be demonstrated to members, for quantitative assessments of: (i) the damage metrics and stress margins, (ii) synergy between temperature and humidity, and (iii) acceleration transforms (with supporting evidence from the case studies undertaken on the two groups of specimens).



Work Accomplished

The following tasks have been completed :


Funding

2 units