Technical Library | 2001-04-24 10:47:02.0
Board-level circuits today routinely run at speeds of 100 MHz or more and are composed of dozens of complex interacting VLSI components. To design such circuits in a timely and correct manner it is necessary to pay close attention to circuit timing early in the design cycle. At fast clock speeds, managing component and interconnect propagation delay becomes a key aspect of circuit design. It is imperative that the critical paths on a circuit and the slack available for interconnect delay consumption be identified early, and drive subsequent stages in the design flow.
Technical Library | 2019-05-01 23:18:27.0
Moisture can accelerate various failure mechanisms in printed circuit board assemblies. Moisture can be initially present in the epoxy glass prepreg, absorbed during the wet processes in printed circuit board manufacturing, or diffuse into the printed circuit board during storage. Moisture can reside in the resin, resin/glass interfaces, and micro-cracks or voids due to defects. Higher reflow temperatures associated with lead-free processing increase the vapor pressure, which can lead to higher amounts of moisture uptake compared to eutectic tin-lead reflow processes. In addition to cohesive or adhesive failures within the printed circuit board that lead to cracking and delamination, moisture can also lead to the creation of low impedance paths due to metal migration, interfacial degradation resulting in conductive filament formation, and changes in dimensional stability. Studies have shown that moisture can also reduce the glass-transition temperature and increase the dielectric constant, leading to a reduction in circuit switching speeds and an increase in propagation delay times. This paper provides an overview of printed circuit board fabrication, followed by a brief discussion of moisture diffusion processes, governing models, and dependent variables. We then present guidelines for printed circuit board handling and storage during various stages of production and fabrication so as to mitigate moisture-induced failures.
Technical Library | 2015-04-08 11:10:47.0
An electronic schematic describes the electrical connectivity of a piece of equipment or an entire system. It is made up of symbols that represent individual components and contains electrical and mechanical information and their related connectivity, along with other important data. Information contained within the schematic is packaged into a printed circuit board (PCB) where the mechanical footprint is placed onto the board and connectivity information is graphically displayed. The more accurate the information contained in the schematic is and the clearer it is presented, the more it contributes to a robust printed circuit board.
Technical Library | 2021-03-24 01:26:05.0
In-circuit test (ICT) has remained one of the most popular and cost-effective test methods for medium and high volume printed circuit board assembly (PCBA) for many years. This is due to its component-level fault diagnosis capability- and its speed.
Technical Library | 2011-03-17 15:29:54.0
Accurate, models for vias in a multilayer circuit board are necessary to predict link performance in the GHz regime. This paper describes a methodology to build a high bandwidth, scalable first approximation circuit model using simple transmission lines o
Technical Library | 2010-12-16 16:59:09.0
This report discusses the significance of heat management in the design of printed circuit boards (PCB). After an introduction into the basics of PCBs the crucial mechanisms of heat transfer are discussed with regard to significance and typical design par
Technical Library | 2010-06-03 22:23:03.0
Strategies for successful design and manufacture of microwave multilayer printed circuit boards. All aspects from pad registration, dimensional stability, impedance fluctuation, fusion bonding, thermal ageing, z-axis expansion, reliability, to Young's mod
Technical Library | 2010-09-23 20:23:37.0
Methods of effective and ecological recycling of printed circuit boards (PCBs) are searched all over the world at this time. The material composition and temperature properties of PCB are necessary to be known for an optimal recycling technology. For thi
Technical Library | 2011-05-12 19:04:05.0
We clarify the role of signal loss measurements, aka Total Loss, in specifying and qualifying circuit board materials for high-speed electronic design. We then demonstrate the NIST Multiline measurement technique in particular by characterizing test line
Technical Library | 2021-01-06 20:28:58.0
Cavity technology in a Printed Circuit Board (PCB) has existed for many years. The methodology to create the cavity in the PCB has evolved over time as technologies have advanced and the manufacturing process varies by the individual PCB
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