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82 PCB007 MAGAZINE I APRIL 2024 how they are bonded together. When an elec- tric field is applied to a dielectric material, its internal dipoles align with the field, resulting in polarization of the material. is polarization allows the material to store electric charge by creating an electric field opposing the applied field. e higher the dielectric constant, the more the material can polarize and the more charge it can store. In contrast, materials with lower dielectric constants exhibit weaker inter- actions with the applied field (storing less charge), allowing for electrical signals to prop- agate faster throughout the material. Another way to contextualize the dielectric constant is to imagine a highway where cars are moving. ink of the PCB as that highway but with tiny signals instead of cars. e dielectric constant can be thought of as analogous to the road surface: some roads are smooth, allowing cars to move faster, while others are bumpy, slowing them down. In a somewhat similar sense, the dielectric constant is a measure of how easily the signals on a PCB can move. A material with a low dielectric constant indi- cates that signals can move smoothly through- out the substrate. is next equation equates signal propagation speed to dielectric con- stant, where v is the propagation speed of a sig- nal throughout the material, c represents the speed of light, and ε r is the dielectric constant of the substrate material: It is the job of the formulation scientist to create new kinds of PCB materials that will achieve the target dielectric constant of the desired application. is is achieved by com- bining different materials with different dielec- tric constants. Ceramic fillers and polymer res- ins are two important classes of materials used in creating PCB bondply that will contribute to the overall dielectric constant of the final product. It is imperative to consider the dielec- tric constant of every material used to success- fully achieve the target properties of the final product. PCB007 Preeya Kuray, PhD, is a materials scientist. To read previous columns, click here. By Matt Stevenson Realistic PCB designs should prioritize manufac- turability and reliability of the PCB as well as meet the other design requirements. To do so, one must account for the production variables associated with individual manufacturing partners. Understanding and creating robust PCB designs, especially in terms of board manufacturing, requires a lot of attention to detail. When more detail is included in the design, the manufacturing process goes more smoothly, and process yields are higher. Product development professionals with limited PCB design experience get tasked with designs. Not immersed in the PCB design discipline, they don't know all the unwritten rules, best practices, techniques, and design requirements. I recently sat down with Nolan Johnson for the first in a series of discussions about designing PCBs for the reality of manufacturing. By sharing les- sons learned over a long career in the PCB indus- try, we hope to shorten learning curves and help designers produce better boards with less hassle and rework. PCB Manufacturing 101 PCB manufacturing is the physical manifestation of a digital design, and to design manufacturable boards, it's important to understand how they are produced. At a high level, these are the steps asso- ciated with PCB manufacturing. Continue reading here. CONNECT THE DOTS Designing for Reality: Prioritizing Manufacturability