Articles by Microwave Journal

Bending and Forming RF/Microwave PCBs

Bending and forming RF/microwave printed-circuit boards (PCBs) around a curved shape are sometimes part of the design process, such as when fabricating conformal antennas. While this may not be commonplace, for those times that it is necessary, it is important to know several things about the high-frequency PCB material for the project. This includes the correct type of material to use, by how much the material can be flexed without damage, and what types of mechanical and electrical effects are to be expected by bending and forming an RF/microwave PCB. Quite simply, picking the wrong PCB material for bending and forming applications can result in mechanical cracks and damage to the circuit board.


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Aiming For The Perfect Wire Bond

Wire bonds keep everything in place on a printed-circuit board (PCB). They are used to attach passive and active components as well as integrated circuit (ICs) to a circuit substrate, and even to connect one circuit substrate to another. Wire bonds can be formed with a variety of different wire bonding machines, including manual and automatic models. In all cases, the goal is to achieve a low-resistance connection with good mechanical integrity and high reliability. But this seemingly simple goal depends not only on the type of substrate material and its parameters but numerous wire-bonding parameters, including the temperature, time, and applied force when making a wire bond.
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Taking A Measure Of Copper Surface Roughness

Conductor surface roughness in printed-circuit boards (PCBs) is a material parameter that should not be overlooked. As detailed in the previous Blog in this series, the surface roughness of a PCB’s conductor layer can have a great deal of impact on signal losses through the conductors. If the effects of conductor surface roughness are not accounted for at the design stage, when using a commercial computer-aided-engineering (CAE) software simulation program, the predicted performance results of the simulations can deviate. These deviations can be significant from the actual performance measured from a designed prototype circuit. The differences can add up to lost design time, added design iterations, and added time and expense when creating a new circuit.
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Sizing Up PCB Laminate Surface Roughness

Designing an RF/microwave circuit requires some knowledge of printed-circuit-board (PCB) qualities, especially when selecting a PCB material for a particular application. Modern computer-aided-engineering (CAE) simulation tools can help predict the electrical performance of circuits on different PCB materials, using material parameters such as relative dielectric constant in the calculations. But one PCB material parameter that is often overlooked in the design process is the surface roughness of the conductors. In the past, conductor surfaces were assumed to be perfectly smooth. What happens when they are not?
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Modeling A PCB’s Thermal Behavior

Temperature effects on a printed-circuit board (PCB) can make it difficult to achieve target performance goals, even with the best PCB substrate materials. Modeling these effects takes imagination—to visualize different sources of heat, for example, and thermal paths where the heat might travel. It also requires an understanding of both thermal-mechanical and electromagnetic (EM) relationships to account for the assortment of variables that can influence PCB performance with changing temperatures. As a result, modeling thermal effects on PCB performance combines predictions provided by the heat diffusion equation as much as from Maxwell’s equations for EM fields.
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Picking the right PCB for lead-free processing

The goals of the Restriction of Hazardous Substances (RoHS) directive by the European Union (EU) for lead-free printed-circuit-board (PCB) processing are worthwhile, but have impacted how electronic circuits are designed and manufactured. For one thing, lead-based solders had lower melting points than lead-free solders. The peak solder temperature for lead-free solders is typically +260°C. As a result, PCB materials must handle higher temperatures during lead-free-solder processing and rework. Understanding what happens to a PCB at those elevated temperatures can help guide the task of selecting PCB materials for lead-free-solder processing.
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Planar Resistors Build On Reliability

Planar resistors can be fabricated along with circuit patterns on selected high-frequency laminate materials. By executing processing steps not unlike those that form circuits on printed-circuit boards (PCBs), embedded planar resistors can be added to a high-frequency PCB. They can be made with precise values, with tight tolerances, and with reasonable power-handling capabilities. They can replace discrete resistors with their associated assembly and reliability issues, in many high-frequency applications. Planar resistors are well suited to compact designs, including in multilayer circuits where they can minimize or eliminate plated through holes for resistors.
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Everything I needed to know I learned at IMS2011

Play nice Share Don’t tell secrets Don’t judge a book by its cover Hard work can be really fun It’s great to have smart friends Social Media is not just for teenagers Nice people rock Mean people don’t Many hands make quick work…and a great conference The ones with the best questions often create innovations that change the world! RF/MW Geeks are the new Rock Stars Promote your peers and friends
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