PCB DESIGN INTERVIEW QUESTIONS AND ANSWERS #PCB#PCBDESIGN

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Understanding PCB Materials and Specifications

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When you give a PCB for fabrication, you need to specify details on PCB materials, impedance controls, finish, copper thickness and so on. Most of the details are so common that they are always assumed. However still it is better to know them. Below is a screenshot of quotation submitted by a fabricator for a PCB design  Let us understand each term one by one and things related to them 1) 4 layer specifies NUMBER OF LAYERS - This means the number of conducting layers. The layers may be either routing layer or plane layer. The commonly used no. of layers are 1, 2, 4, 6, 8 and other even numbered layers. Odd number layer boards may be formed but they are not standard boards and doesn’t offer any savings. The PCB materials used for 3 or 4 layers would almost be same. Routing layers contains tracks while plane layer are generally used to connect power or ground. Plane layers have plane of copper from which connections are drawn up or down wherever needed. I...
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Overview of Capacitor technology

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Capacitors (and inductors) have the ability to store electrical energy, inductors store energy as a magnetic field around the component, but the capacitor stores electrical energy directly, as an ELECTROSTATIC FIELD created between two metal "plates". Basic Circuit symbols for capacitors • High Voltage Electrolytic- used in power supplies.  • Axial Electrolytic; lower voltage smaller size for general purpose where large capacitance values are needed.  • High Voltage disk ceramic; small size and capacitance value, excellent tolerance characteristics.  • Metalised Polypropylene; small size for values up to around 2µF good reliability.  • Sub miniature Multi layer ceramic chip (surface mount) capacitor. Relatively high         capacitance for size achieved by multiple layers, effectively several capacitors in parallel.  Uses of Capacitors. Decoupling --The most prevalent use of capacitors ...
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