Last Updated on April 10, 2022 by Kevin Chen
Planning to buy or even import capacitors in China? Here is a perfect guide for you. We are going to give you all the essential information that you should know when it comes to buying capacitors.
What is a Capacitor?
Capacitors are components that are mainly used to store electric energy. They have a high capacitance value, which means they consist of at least two conducting plates separated by an insulator.
Let’s look at capacitors in human anatomy.
In the human body, capacitors are the heart! Without vessels and bones surrounding it, many functions would not be possible!
And capacitors are the same. Without capacitors, almost all electronic products won’t work or will break down easily without capacitors.
How do capacitors work?
Think of capacitors as water tanks in the mountains…
When it’s hot and sunny, there is high pressure in the tank to push the water upwards to deliver it to the city below.
But when there’s a shortage of water and less pressure in the tank, the valves close and no more water is released.
And capacitors work just like that!
When there’s a high voltage available, capacitors release their energy quickly to deliver fast responses.
When there isn’t enough capacitance, capacitors gather more energy from the power supply to deliver the desired output.
Classification Methods
There are 3 methods to classify capacitors depending on their characteristics.
The first method is the capacitance value, which defines how much capacitors can store electric energy. It’s measured in Farads (F). One Farad is equal to 1 amp at one volt. The immense power of capacitors is that they can release a high voltage very quickly.
The second method is capacitors’ tolerance value. This defines how much capacitance is available in the capacitor itself. The unit of capacitance values used for this method are pico-farads (pF). For example, a 47000pF capacitor has a capacitance value within ±4500pF or more.
The third method is capacitors’ temperature coefficient, which defines how the capacitance value changes with temperature.
Common capacitors come in two types: polar and non-polar capacitors. For polar capacitors, the polarity of the voltage at input and output terminals is significant while for non-polar capacitors, these are not necessary.
Terms to know
When buying capacitors, the capacitance value, tolerance value, and temperature coefficient are usually checked by capacitors buyers. These are obvious factors but other things cannot be neglected as well.
Let’s take a look at some of them now.
1) Dielectric Strength
Dielectric strength is capacitors’ maximum voltage that can be applied on capacitors. If there’s a sudden surge in power, capacitors with high dielectric strength can withstand and release the high voltage.
2) Temperature coefficient
This defines how capacitance value changes with temperature and it affects capacitors greatly. For example, a capacitor with a temperature coefficient of -0.3pF/°C will be charged capacitance value at 60°C is 33% less than that at 25°C.
3) ESR (Equivalent Series Resistance)
ESR defines how capacitors’ impedance changes concerning frequency. A higher ESR means capacitors will reflect more electrons to the supply source. This phenomenon is called capacitors’ self-inductance, which can cause capacitors to heat up and damage capacitors soon.
4) Ripple Current (or Operating Temperature Range for Polymer Capacitor or Radial Leaded Electrolytic Capacitor)
Ripple current defines capacitors’ maximum operating frequency. This is important for capacitors used in high frequencies.
5) Size and Height
Capacitors come in various sizes depending on capacitance value, voltage rating, and capacitors’ tolerance value. And capacitors with higher capacitance values are thicker than smaller capacitors, which makes them harder to install.
6) Operating Voltage Range
The operating voltage range defines capacitors’ minimum and maximum voltage ratings. Some capacitors have a wide operating voltage range while others only have a small operating voltage range. This is important for capacitors used in power supply filtering or regulation circuits.
7) Leakage Current
This is capacitors’ capacitance value loss over a period of time. This is important for capacitors used in power supply filtering or regulation circuits because capacitors with small leakage current lose less capacitance values over time.
8) Self-Healing Effect [optional]
This describes capacitors’ ability to recover capacitance value after the current surge has been released and capacitors’ capacitance values are restored once normal voltage is applied. This is important for capacitors with high capacitance values because these capacitors lose capacitance value by a large current surge.
9) Working voltage
Capacitors’ capacitance value and tolerance value are related to capacitors’ working voltage.
10) Temperature range for capacitors
This defines how capacitors perform under different temperatures. For non-polar capacitors, their capacitance values are constant regardless of temperature changes but may be different depending on the material used for coating electrodes.
11) Dielectric Absorption
Dielectric absorption is capacitors’ capacitance value change when capacitors are charged and discharged at different voltage levels. These are important capacitors with high capacitance values because these capacitors lose capacitance values due to dielectric absorption.
12) Ripple current
This defines how capacitors pass current when capacitors are charging and discharging.
13) Service life & endurance
Service life defines capacitors’ lifetime. It means capacitors might fail after years of use due to various reasons e.g. capacitance value failure, breakdown, leakage, or gas generation failure. Endurance defines capacitors’ maximum number of times capacitors can be charged and discharged until capacitors fail.
How to Use capacitors
Reduce capacitance value: If you need capacitors with lower capacitance values than normal capacitors, simply purchase capacitors with lower-rated capacitance values.
Increase capacitance value: If you need capacitors with higher capacitance values than capacitors offered, simply purchase capacitors with higher capacitance values.
Minimize capacitors’ capacitance value change with temperature: Choose capacitors with low-temperature coefficient.
Reduce capacitors’ capacitance value loss over time: Choose capacitors with small leakage current.
Increase capacitance value change/decrease capacitance value loss over time: Decrease capacitors’ capacitance values.
Increase capacitance value change/decrease capacitance value loss over time: Operate capacitors under higher temperatures than capacitors rated temperature.
Minimize capacitive reactance (Xc) and capacitive susceptance (B): Use capacitors with low capacitance values.
How to Measure capacitors
It is important to measure the capacitors before buying. There are various ways of measuring capacitors.
1) Checking capacitors’ capacitance value with multi-meter
You can check capacitors’ capacitance value by measuring capacitors’ capacitive reactance (Xc) or capacitive susceptance (B).
2) Measuring capacitors’ Impedance with LCR Meter
The capacitor’s impedance is the same as the capacitors’ capacitive reactance (Xc). You can calculate capacitors’ capacitance value by measuring capacitors’ capacitive reactance (Xc).
3) Checking capacitors with a capacitance meter.
You can check capacitors by directly measuring the capacitance values of the capacitor with a capacitance meter. There is no need to calculate the capacitance value.
4) Checking capacitors with an oscilloscope.
You can check capacitors’ capacitance values by directly measuring capacitive reactance (Xc) or capacitive susceptance (B). There is no need to calculate capacitance values. However, you need additional equipment for this method of measuring capacitance value.
How to choose capacitors
There are different criteria that you can use for choosing capacitors. They include:
Different capacitance values
You can find capacitors with different capacitance values e.g. capacitance range from 0.1pF – 47uF. The capacitance value of the capacitors depends on your application requirements. If you are not sure, choose low capacitance value or medium capacitance value capacitors.
Use capacitance tolerance
For capacitors with low capacitance values (less than 10pF), choose capacitors without capacitance tolerance because capacitors with capacitance tolerances do not work properly in these kinds of applications.
For capacitors with medium and high capacitance values (more than 10pF), capacitors with capacitance tolerances are available.
You can choose capacitors without capacitance tolerances but capacitance values deviate more than capacitors with capacitance tolerances if you do so. For more information on checking capacitance values and tolerance values, refer to chapter 4: how to measure capacitors.
Choosing voltage
You can choose capacitors with capacitance values from 2pF-2uF. For higher capacitance values, choose capacitors that can operate under higher voltage than capacitors’ rated voltage.
Choosing capacitance value
You can choose capacitors with a capacitance value of more than 1uF if your circuit’s operating frequency does not exceed 1 MHz. If your circuit’s operating frequency is less than 100kHz, capacitors with capacitance values from 0.1uF-10uF can be used. If your circuit’s operating frequency is more than 100 kHz, capacitors with capacitance values from 10pF-100uF should be used.
Choosing capacitance tolerance
You can choose capacitors from the capacitance range -20% to +80%. This capacitance range includes capacitors with no capacitance tolerance.
Capacitors with capacitance tolerances are available in the market but do not use capacitors with capacitance tolerances for high accuracy applications. This is vital because standard values of these kinds of capacitors deviate more than capacitors without capacitance tolerances.
You can choose capacitors with capacitance tolerances if your code is “22” or higher (the number of zeros before the first significant digit increases the capacitance tolerance).
For capacitors with capacitance tolerances (no significant digit), you can choose capacitors with capacitance values from -20% to +80%. For capacitors without capacitance tolerances, choose capacitors with capacitance values from ±10% or ±5%.
Good soldering
You should solder the capacitors well. If you do not solder capacitors well, capacitance values deviate.
Choosing capacitors for ceramic capacitors
You can choose capacitors made of metal film for ceramic capacitors. You can choose capacitors with high-temperature resistivity (capacitance value does not change so much under high temperatures). You can choose capacitances from 1pF to 68pF capacitors.
Choosing capacitors for humidity protection:
For capacitors with humidity protection, choose capacitors with high-temperature resistivity (capacitance value does not change so much under high temperatures). You can choose capacitances from 1pF to 68pF capacitors.
If you need capacitors with capacitance values from 1pF to 68pF capacitors, capacitors made of the metal film, and capacitance values without capacitance tolerance capacitors, choose “disc ceramic capacitors”.
If you need capacitors with capacitance values higher than 68 pF, choose “electrolytic capacitors”.
What is the price of capacitors?
The price of capacitors is not expensive. They come in different price tags.
Usually, the price will depend on several factors which include: capacitance values, capacitors’ brand labels, and capacitors’ sizes.
However, for capacitor without capacitance tolerances, the price will differ based on capacitance values rather than capacitors’ brands or capacitors’ sizes.
For capacitors with capacitance tolerances, the prices will differ based on the number of figures in their capacitance values, capacitance tolerances, and capacitors’ sizes.
The cost will also depend on capacitors’ shapes and capacitors’ capacitance values.
For capacitors with capacitance tolerances, the cost will also depend on where you buy the capacitors.
You can tell capacitors’ brands based on the prices.
If capacitors are made of ceramics, they are usually less expensive than capacitors made of the metal film. If capacitors are made of tantalum, they are more expensive compared to capacitors made of ceramic.
Ceramic capacitors with capacitance values under 1pF are mostly expensive capacitors. On the other hand, capacitors with capacitance values higher than 1uF are usually inexpensive capacitors.
The cost of capacitors also depends on capacitors’ sizes and shapes. Electrolytic capacitors and tantalum capacitors have very different costs. Also, if you need ceramic capacitors with capacitance values higher than 100pF, they are more expensive capacitors.
Choosing Capacitors Suppliers in China
In this chapter, we will discuss capacitors suppliers in China.
Many capacitors suppliers exist in China.
However, only a few capacitors suppliers can offer you capacitors with satisfactory quality and service.
Reliable suppliers and distributors can easily provide you with high-grade capacitors.
Of course, this will be accompanied by quality services.
Some of the key tips to consider when choosing capacitors’ manufacturers and suppliers in China include:
– Experience: capacitors’ manufactures and capacitors’ suppliers should have more than 10 years of capacitance value, capacitance tolerances, capacitors’ sizes, and brands experience.
– Quality control: capacitance values, capacitance tolerances, capacitors’ sizes, and brands should be strictly tested before they are shipped out to their customers.
– Product stock: capacitors’ manufactures and capacitors’ suppliers should have enough capacitance values, capacitance tolerances, capacitors’ sizes, and brands in stock.
– After-sales services: capacitors manufacturers and capacitors’ suppliers should offer you after sales services to ensure your satisfaction with the quality of capacitance value, capacitance tolerances, capacitors’ sizes, and brands you bought.
ICRFQ: Leading Capacitors Distributors in China
At ICRFQ, we are a leading electronic components distributor in China. Capacitors are just one of our product lines. We have capacitors with capacitance values, capacitance tolerances, capacitors’ sizes, and brands that are different from the capacitors you want to buy.
Contact us for the quality capacitors in China.
If you want to find more Electronic Components Distributors, please check out the following articles:
Electronic Components Distributors In the USA
Electronic Components Distributors In UK
Electronic Components Distributors In China
Electronic Components Distributors In India
Electronic Components Distributors In Singapore
Electronic Components Distributors In Malaysia
Electronic Components Distributors In Vietnam
Electronic Components Distributors In South Korea
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