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This study was conducted to understand seven materials’ reliability, behavior of dielectric constant and dissipation factor over medium to high frequencies. A modified version of HDPUG design was used for evaluation. This test board contains IST, CAF, thermal cycling and impedance (both microstrip and stripline) coupons. In addition to these we added HATS coupons. Materials were chosen from FR4 family and selection was made based upon our present and future needs. Dielectric constants of these materials ranged from Dk 3.6-Dk 4.2, as published, at 10GHz. This document shows the effect of Dk and Df values from 10GHz to 20GHz and also shows their performance for lead free assembly process when tested using IST and HATS test methods. In addition, CAF testing was done on five of the seven materials.
As signal speeds are getting higher, a better understanding of material performance is required. Materials which were good at low frequencies may not be good for higher frequencies. The goal of this study was to:
- Compare material reliability using HATS and IST test methods.
- CAF analysis of these materials.
- Study insertion losses for materials chosen and do a comparison of these materials for frequencies between 1GHz-20GHz.
A modified HDPUG design was adopted as a test vehicle. To keep the testing manageable, thermal cycling and water absorption coupons were not tested. However, HATS coupons were added to the panel design.Read the full article here.Editor's Note: This article originally appeared in the March 2014 issue of The PCB Magazine.