Layer misregistration in PCB and its effects on signal propagation
Layer misregistration is one of the common issues in PCB manufacturing processes. In addition to physical limitations of manufacturability (large via pad/anti-pad), it may also have impact on the electrical performance of signal lines running through via fields with anti-pad openings. In order to quantify its effects on signal propagation, comprehensive test vehicles were designed, measured, and analyzed. Significant increases in layer-to-layer crosstalk and common-to-differential mode conversion were observed, when corresponding layers were misaligned. The results helped understand the mechanisms, validate modeling methodology, and define design rules.
How detrimental could a via be?
The vertical interconnects used in printed circuit boards, known as vias, are becoming increasingly critical to interconnect performance with ever increasing system data rates. To explore the effects of vias on system link performance, both simulations and measurements on test structures were implemented in a wide frequency range. The results indicate that proper via management is vital to the success of interconnect designs operating at multi-Gb/s data rates.
Physical Ageing of the Research Reactor Core Structural Materials Due to Neutron Irradiation Exposure: a Review
A research reactor (RR) is a  nuclear reactor that has function to generate and utilize neutron flux and radiation ionization for  research purposes and industrial applications. More than 60% of current operating RRs have  been operated for 30 years or more. As the time passes, the functional capabilities of structures,  systems and components (SSCs) of those RRs deteriorate by physical ageing, which can be  caused by neutron irradiation exposure such as irradiation induced dislocation and  microstructural changes. To extend the lifetime and/or to avoid unplanned outages, ageing on  the safety related SSCs of RRs need to be properly managed. An ageing management is a  strategy to engineer, operate, maintenance, and control SSC degradation within acceptable limits. The purpose of this study is to review physical ageing of the core structural materials of  the RRs caused by neutron irradiation exposure. In order to achieve this objective, a wide range  of literatures are reviewed. Comprehensive discussions on irradiation behaviors are limited only  on reactor vessel and core support structure materials made from zirconium and beryllium as  well as their alloys, which are widely used in RRs. It is found that the stability of the mechanical  properties of zirconium and beryllium as well as their alloys was mostly affected by the neutron  fluences and temperatures.