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rosasl719-blog · 7 years ago

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7 TYPES OF FILM CAPACITOR DIELECTRICS THAT YOU NEED TO KNOW

Film capacitors can be broadly categorised into plastic film capacitors, metallized plastic film capacitors, and composite film capacitors. The same dielectric materials are used in the construction of these different types of film capacitors. In composite film capacitors, a combination of dielectric materials is used in the construction of the component.

Film capacitors have characteristics that make them suitable for a broad spectrum of applications including filtering, decoupling, bypassing, EMI suppression, pulse coupling, blocking, and smoothing. Plastic film capacitors deliver high reliability under extreme environmental conditions. Compared to other capacitor types, plastic film devices have lower equivalent series resistance and dissipation factor.

DIELECTRICS USED IN PLASTIC FILM CAPACITORS

Plastic film capacitors offer high stability, long shelf life, low equivalent series resistance, low self-inductance, and a high ability to absorb power surges. The dielectric material used in a film capacitor greatly determines the properties of a component. Some of the key properties of a dielectric material that determine the performance of a capacitor include dielectric constant, dissipation factor, volume resistivity, maximum application temperature, dielectric strength, and dielectric absorption. These parameters vary from one dielectric material to another.

The most common dielectric materials used in the construction of plastic film capacitors are polypropylene and polyester. Other dielectrics used in the construction of film capacitors include polycarbonate, polystyrene, polytetrafluoroethylene (PTFE), polyethylene naphthalate (PEN), polyphenylene sulphide (PPS), polyimide, and paper.

POLYESTER

Polyester has a high dielectric constant compared to polypropylene, and it is one of the most widely used dielectric materials. This high dielectric constant allows construction of capacitors with small physical sizes. Polyester capacitors, also known as mylar capacitors, have good self-healing properties and are relatively cheap.

At high temperatures, polyester capacitors dissipate more power. This characteristic makes these capacitors unsuitable for high frequency and high current AC applications. Furthermore, polyester exhibits a significant capacitance change, up to 5%, as temperature approaches low or high-temperature limits. Due to this characteristic, polyester is an unsuitable material for constructing precision capacitors. Polyester capacitors are mostly used in general purpose board level applications such as blocking, bypassing, decoupling, and some noise suppression circuits.

POLYPROPYLENE

Polypropylene is commonly used in the construction of capacitors for high frequency AC applications. This dielectric material has a low dissipation factor, high breakdown strength, low dielectric absorption, high insulation resistance, and is readily available. These properties make polypropylene a dielectric material of choice for a wide range of applications including snubber circuits, high frequency AC systems, high voltage DC & AC systems, and high current DC applications.

Polypropylene capacitors can operate over a wide temperature range. Unlike polyester capacitors, the capacitance of a polypropylene capacitor decreases with temperature. Due to its temperature characteristics, polypropylene capacitors are commonly used to complement polyester capacitors. This is achieved by connecting a polyester capacitor and a polypropylene capacitor in parallel.

Despite its impressive properties, polypropylene has a lower dielectric constant than polyester. In addition, this material is not available in thin-gauge films. Compared to polyester, polypropylene is more expensive and is not a suitable material when physical size of a component is a key consideration.

POLYPHENYLENE SULPHIDE (PPS)

Polyphenylene sulphide has excellent temperature characteristics and is commonly used for constructing precision capacitors. The capacitance of these capacitors does not vary significantly with changes in temperature. PPS capacitors are commonly used to replace polycarbonate capacitors in electronic circuits. The dielectric constants of these two materials are similar, and they both have high breakdown strength.

POLYTETRAFLUOROETHYLENE (PTFE)

PTFE capacitors, also known as Teflon capacitors, are low loss capacitors that offer excellent stability. PTFE has a relatively low dielectric constant, around 2.1, and it is, therefore, unsuitable for constructing components with small footprints. Teflon capacitors are suitable for high temperature applications and can be used in systems that expose components to temperatures of up to 200oC. PTFE capacitors have low capacitance values and are relatively expensive.

POLYSTYRENE

Polystyrene capacitors exhibit extremely low loss and high capacitance stability over temperature, typically down to ±1% 0ver the range -55°C to +85°C. It’s low dielectric constant of 2.1 makes in suitable for low capacitance, high stability applications such as timing circuits.

POLYIMIDE (KAPTON)

Polyimide has a high dielectric constant, around 3.4, and it is commonly used for constructing components for high temperature applications. Kapton capacitors can be used in systems that can expose components to temperatures of up to 250oC. Metallized polyimide capacitors have poor self-healing characteristics.

POLYCARBONATE

Polycarbonate has an average dielectric constant, around 2.7, and it is commonly used in the construction of capacitors for high temperature applications. Polycarbonate capacitors are low loss components that have good electrical characteristics over a wide temperature range. Polycarbonate capacitors were widely used in military applications. However, polycarbonate film has limited availability, and is not recommended for new designs.

The table below summarises some characteristics of common plastic film dielectrics.

#FILM CAPACITOR DIELECTRICS

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rosasl719-blog · 7 years ago

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Situation Analysis and prospects for film capacitor industry in China

Nowadays,for the capacitor market in China , the proportion of the traditional aluminum electrolytic capacitors is decreasing. Another capacitor which is more advanced environmentally friendly is becoming popular . That is film capacitors. Film capacitor is made of foil and film. Foil as electrodes and the film will be winded into a cylinder. The film are including Polyester, polypropylene, polystyrene, polycarbonate etc. So if to be sorted by the type of film , the capacitors can be sorted as Polyester capacitor (known as Mylar capacitors), polypropylene capacitors (also known as PP capacitors), polystyrene Mylar capacitors (known as PS capacitors ) and polycarbonate capacitors.

Since 1980s,the capacitor industry is becoming more and more developed . Many foreigners came to China for investment of Capacitors industry. Till now ,the capacitor industry is still going forward with high speed . After the study and test of more than 20 years , film capacitor technology is becoming more and more sophisticated . It brings new opportunities for some new products ,such as Solar car, electric car , energy storage welding and so on .

For the year 2016 ,the production value of film capacitor is approaching RMB 700 million. It is a very important part of the global capacitor industry . And with the development of the new energy automotive industry, film capacitor industry are going for a golden period of development.

Global film capacitor industry are still expanding ,and China is becoming the leading force. According to the statistics of China Electronic Components Industry Association Information Center , the global production of film capacitors are mainly concentrated in the United States, Europe, China, Japan, Korea, Taiwan and other regions. With the rapid development of Chinese economy ,China is opening the market to the buyers from all over the world . For the year 2017, the market value of the capacitor is USD 1.3 billion, covering about 42% of the global market, ranking first in the world.

Look at the market value percentage as below :

China : 42%

USA: 6.94%

Japan:4.82%

Europe:1.45%

Others:44.79%

Recently ,FARATRONIC company in China is the world's third electronic company for the output . But compared with the companies in developed countries , the capacitor industry in China is still not so competitive . As we know Nichicon in Japan ,Wima in Germany ,ICEL in Italy , CDE in USA are first class capacitor suppliers in the world .

Look at below ranking for global film capacitor industry enterprise :

1st class : Nichicon,Wima ,ICEL, CDE

2nd class : Nissei ,Panasonic, Vishay, Okaya, Philips

3rd class:Faratronic ,Weidy ,Carli,Dain,HJC,Wangbao

4th class:Tong-fong,CJE,AIDI,CG,SR

So we are facing much pressure in the global competition. But we are still trying to develop it and trying to make us more competitive .The development of the solar energy industry , LED industry and new energy vehicles in China are giving more oppotunity and market for film capacitors . In the coming few years ,the market value of film capacitor will reach a new stage .

Let’s look forward to the new development of film capacitor industry in China.

Rosa Liu

Whatsapp:+8618823758279

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