Effect of Compliant PINs on Reliability of PTHs

Project Number: C95-08

 Point of Contact: dasgupta@calce.umd.edu

Objective

The purpose of this project is to (i) validate CALCE model for compliant pin damage, (ii) evaluate pin force relaxation due to PTH damage, so that the decrease in contact reliability can be assessed, and (iii) extend the model to predict residual stresses such that the impact on PTH reliability can be evaluated using the CALCE code.
 
 

Background

Use of compliant pin interconnects presents an alternative to soldered connections. However, the insertion of compliant pin interconnects causes damage to PTHs, as evidenced by previous CALCE studies. The problem can be particularly significant in PTHs with high aspect-ratios because of high stresses and high defect-rates.

The CALCE pin-in-PTH model was developed during the previous year to predict permanent deformation in PTH and in the surrounding PWB due to the forces during pin insertion. The analytical model was based on a two-dimensional Fourier series technique. Nonlinear analysis was performed through load incrementing methods. While the elastic analysis in this model is exact, the nonlinear analysis depends on simplifying assumptions which compromise the accuracy of the model. The model therefore needs calibration for the nonlinear results.

Work Accomplished

The deformation predicted by the nonlinear analytical model has been calibrated by use of finite element analysis and empirical results. The pin force relaxation has been evaluated by using a Newton-Raphson iterative technique, and the residual stress state caused by the pin insertion forces has been evaluated. Both results have been validated using finite element analysis. 

• Added a new pin-force model to the library. The library now includes AMP pin model and AMPHENOL pin model.
• Validated CALCE pin-in-PTH model by comparing to finite element results and empirical data provided by AMP.
• The CALCE members now have access to a completely self-contained validated code that can predict the damage caused to PTH by compliant pin insertion forces, and assess the impact on long-term PTH reliability. This code is already in use at AMP.