-
- December 1, 2022
- PCB knowledge
- (0)
- 06 mins
What are PCB capacitors and why do we need them
PCB capacitors are an essential component for PCB design. Every person with a basic knowledge of electronics has heard about them, but few know what they are. PCB capacitors are used to smooth out the current flow, filter out high-frequency noise and store energy for the following circuit.
Let’s dive deep to know what PCB capacitors are and what components they contain.
What is a PCB capacitor?
A PCB capacitor is a type of electronic capacitor that is used in printed circuit board. These capacitors are made up of two conductive plates, separated by an insulating material known as the dielectric. The plates are then connected to the power source through wires.
The plate size and the type of dielectric material used determine the capacitance value of the PCB capacitor. Farads (F) measure their capacitance.
Various types of PCB capacitors are available today, but they all serve the same purpose: to store an electrical charge and release it when needed. This allows them to be used as filters or regulators that keep electrical signals steady during power surges.
What are PCB capacitors made of?
In PCB capacitors, there are two foil plates separated by a dielectric. The foil plates are called the “plates” or “electrodes,” and the dielectric is called the “dielectric.”
The plates are usually made from aluminium or copper foil, although other materials may be used to improve performance. The thickness of the plates can vary depending on the manufacturer and application. Thicker plates will have higher capacitance values, while thinner plates will have lower ones.
Different types of PCB capacitors
There are many types of PCB capacitors, each with a different purpose. Some are used for power supplies, some for filtering, and others for timing applications.
Film capacitors
Film capacitors are made of polypropylene, polyester, or polycarbonate. They have a low cost and good stability. They have a low voltage rating, so they can’t be used for high-voltage applications.
Ceramic capacitors
Ceramic capacitors are made from ceramic materials such as barium titanate or lead zirconium titanate (PZT). They usually have an even higher capacitance per unit volume than film capacitors but with a lower tolerance to temperature and humidity changes. This makes them more resistant to aging effects than film-type electrolytic capacitors.
Electrolytic capacitors
Electrolytic capacitors are today’s most common type because of their low cost and high capacity values (up to several thousands of microfarads). They were invented by Georges Righi around 1900 and are still produced in many different sizes by manufacturers like AVX, Murata, Panasonic, etc.
Supercapacitors
These are special devices that can deliver large amounts of current for a short time. They’re often used to store energy during peak load times, such as when the sun is shining on solar panels.
Dielectric capacitors
These devices use two conductive plates separated by an insulator (a dielectric) to store charge. They are used with other components to form larger assemblies, such as filters and resonators.
How does a PCB capacitor work? Why is it important?
Working:
A PCB capacitor is two parallel plates with a dielectric material between them. This material acts as an insulator that prevents any current from flowing until a voltage is applied across its terminals. A charge is stored on one plate relative to another when no voltage is applied. The more charge you can store on one plate compared to another, the greater your capacitance and the more current you can pass through without damaging or overloading it.
Importance:
●They are used to store energy in an electric field and release it as needed (or as directed).
●They remove noise from signals.
●They smooth out fluctuations in voltage levels.
How to measure PCB capacitance?
A simple way is to use an PCB oscilloscope, which displays the voltage waveform across a capacitor. You can see how long it takes for the voltage to charge or discharge and calculate the value from this.
You can also use an impedance analyzer, which displays a capacitor’s impedance as a frequency function. Impedance is defined as resistance (R) plus reactance (X), where X is inductance (L) or capacitance (C). Resistance and inductance are purely real quantities, whereas reactance is imaginary. By measuring impedance, you can tell if it has any reactive components.
How do I identify a PCB capacitor?
The best way to identify a PCB capacitors is by looking at its value. The value is the number of pico-farads (pF) or nano-farads (nF) that the capacitor can hold. A PCB capacitor’s value will always be stated in the units of pF or nF.
If you have a multimeter, it can also be used to identify capacitors. Some capacitors have markings that tell you what their values are, but most don’t have any markings. In this case, you’ll need to use your multimeter to read the resistance of each capacitor and use that information to calculate its value.
How to choose a PCB capacitor?
Choosing the right PCB capacitors for your electronic circuit can be challenging. There are a lot of factors that should be taken into consideration, but this guide will make it easier to find the right PCB capacitors for your project.
Frequency and capacitance
The frequency of the circuit will determine what kind of capacitor you need. There are many different types of capacitors with different characteristics, so it’s important to select the right one for the circuit.
Voltage rating
The voltage rating determines how much voltage can pass through a capacitor before it fails. The higher the voltage rating, the more you have to pay. If you are using DC voltages, then there is no need to buy high-voltage-rated capacitors since most DC circuits operate at low voltages (5V or 3.3V). However, if you use AC voltages, one must use capacitors with higher voltage ratings (up to 470V).
Temperature coefficient (TC)
The temperature coefficient indicates how much a capacitor changes its value at different temperatures. This specification is important, especially when designing circuits where temperature changes may occur (like in automobiles or refrigerators).
How to solder PCB capacitors on a circuit board?
Soldering PCB capacitors is a simple task. Here are the steps:
1. Clean the pads and component leads with a de-soldering braid. De-solder the leads of the component from the board.
2. Use flux to clean and prepare the pads for soldering. Make sure that there is enough flux on each pad so that when you place the component, it will be held securely by capillary action.
3. Heat one pad at a time using your soldering iron, then touch it with the solder until it melts and flows into the pad. Do this for all four pads, ensuring they are properly filled with solder paste.
A PCB capacitor is a type of electronic capacitor that is used in printed circuit boards. These capacitors are made up of two conductive plates, separated by an insulating material known as the dielectric. The plates are then connected to the power source through wires.
- Film capacitors
- Ceramic capacitors
- Electrolytic capacitors
- Supercapacitors
- Dielectric capacitors, etc
A simple way is to use an oscilloscope, which displays the voltage waveform across a capacitor. You can also use an impedance analyzer, which displays a capacitor’s impedance as a frequency function.
Conclusion
All in all, PCB capacitors are a handy component to have in your electronics toolbox. Not only do they come in handy for fixing leaky capacitors or replacing caps that have failed on a production board, but they’re also good to have around just in case. All it takes is failing one capacitor on a board before you learn how important these little things can be.
