Capacitors Blog

The manufacture begins with the basic circuit board, primed and printed. This printed circuit board for BGA has pads made of copper and these are arranged in the grid pattern that the solder balls are designed to have.

After the solder balls have been precisely arranged on the surface of the printed circuit board, the soldering process would begin. Surface mount soldering would proceed through reflow soldering (with the aid of a reflow oven that uses infrared or vapors as the heat source). At this point, the metal alloy balls would melt due to extreme temperatures. As the whole assembly cools, the solder balls will solidify and the package will become firmly affixed to the circuit board.

There is one other common packaging for integrated circuits and this is the PGA or Pin Grid Array. The BGA looks physically similar to a Pin Grid Array package. Both are one-sided; that is, only one face of the semi-conducting substrate is used for printing and mounting of circuit components. Moreover, both have an obvious grid-like pattern. However, the Pin Grid Array uses pins - thus, the name - whereas the BGA uses balls - as it has already been mentioned above. The pins (in the PGA) or the balls (in the BGA) are the materials through which electricity is conducted between the printed surface of the semiconductor board and the surface-mounted circuit components.

A trimmer is a miniature adjustable electrical component. It is meant to be set correctly when installed in some device, and never seen or adjusted by the device's user. Trimmers can be variable resistors (potentiometers) or variable capacitors. They are common in precision circuitry like A/V components, and may need to be adjusted when the equipment is serviced. Unlike other variable controls, trimmers are mounted directly on circuit boards, turned with a small screwdriver and rated for many fewer adjustments over their lifetime. In 1952, Marlan Bourns patented the world's first trimming potentiometer, trademarked "Trimpot".

This capacitor is used when a higher tolerance is necessary than polyester capacitors offer. Polypropylene film is used for the dielectric. It is said that there is almost no change of capacitance in these devices if they are used with frequencies of 100KHz or less.

The pictured capacitors have a tolerance of ±1%.

From the left in the photograph
Capacitance: 0.01 µF (printed with 103F)
[the width 7mm, the height 7mm, the thickness 3mm]
Capacitance: 0.022 µF (printed with 223F)
[the width 7mm, the height 10mm, the thickness 4mm]
Capacitance: 0.1 µF (printed with 104F)
[the width 9mm, the height 11mm, the thickness 5mm]

• This is a "Super Capacitor," which is quite a wonder.
• The capacitance is 0.47 F (470,000 µF).
• I have not used this capacitor in an actual circuit.

Care must be taken when using a capacitor with such a large capacitance in power supply circuits, etc. The rectifier in the circuit can be destroyed by a huge rush of current when the capacitor is empty. For a brief moment, the capacitor is more like a short circuit. A protection circuit needs to be set up.

The size is small in spite of capacitance. Physically, the diameter is 21 mm, the height is 11 mm.

Care is necessary, because these devices do have polarity.

Suntan Technology Company Limited
---All kinds of Capacitors

In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons on the other terminal. A capacitor is much simpler than a battery, as it can't produce new electrons -- it only stores them.

In this article, we'll learn exactly what a capacitor is, what it does and how it's used in electronics. We'll also look at the history of the capacitor and how several people helped shape its progress.

Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting substance, or dielectric. You can easily make a capacitor from two pieces of aluminum foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work.

In theory, the dielectric can be any non-conductive substance. However, for practical applications, specific materials are used that best suit the capacitor's function. Mica, ceramic, cellulose, porcelain, Mylar, Teflon and even air are some of the non-conductive materials used. The dielectric dictates what kind of capacitor it is and for what it is best suited. Depending on the size and type of dielectric, some capacitors are better for high frequency uses, while some are better for high voltage applications. Capacitors can be manufactured to serve any purpose, from the smallest plastic capacitor in your calculator, to an ultra capacitor that can power a commuter bus. NASA uses glass capacitors to help wake up the space shuttle's circuitry and help deploy space probes. Here are some of the various types of capacitors and how they are used.

• Air - Often used in radio tuning circuits
• Mylar - Most commonly used for timer circuits like clocks, alarms and counters
• Glass - Good for high voltage applications
• Ceramic - Used for high frequency purposes like antennas, X-ray and MRI machines
• Super capacitor - Powers electric and hybrid cars

In the next section, we'll take a closer look at exactly how capacitors work.

Suntan Technology Company Limited
---All kinds of Capacitors

• The capacitor's function is to store electricity, or electrical energy.
• The capacitor also functions as a filter, passing alternating current (AC), and blocking direct current (DC).
• This symbol is used to indicate a capacitor in a circuit diagram.

The capacitor is constructed with two electrode plates facing eachother, but separated by an insulator.

When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.

When a circuit tester, such as an analog meter set to measure resistance, is connected to a 10 microfarad (µF) electrolytic capacitor, a current will flow, but only for a moment. You can confirm that the meter's needle moves off of zero, but returns to zero right away.

When you connect the meter's probes to the capacitor in reverse, you will note that current once again flows for a moment. Once again, when the capacitor has fully charged, the current stops flowing. So the capacitor can be used as a filter that blocks DC current. (A "DC cut" filter.)

However, in the case of alternating current, the current will be allowed to pass. Alternating current is similar to repeatedly switching the test meter's probes back and forth on the capacitor. Current flows every time the probes are switched.

The value of a capacitor (the capacitance), is designated in units called the Farad ( F ).

The capacitance of a capacitor is generally very small, so units such as the microfarad ( 10-6F ), nanofarad ( 10-9F ), and picofarad (10-12F ) are used.

Recently, an new capacitor with very high capacitance has been developed. The Electric Double Layer capacitor has capacitance designated in Farad units. These are known as "Super Capacitors."

Sometimes, a three-digit code is used to indicate the value of a capacitor. There are two ways in which the capacitance can be written. One uses letters and numbers, the other uses only numbers. In either case, there are only three characters used. [10n] and [103] denote the same value of capacitance. The method used differs depending on the capacitor supplier. In the case that the value is displayed with the three-digit code, the 1st and 2nd digits from the left show the 1st figure and the 2nd figure, and the 3rd digit is a multiplier which determines how many zeros are to be added to the capacitance. Picofarad ( pF ) units are written this way.

For example, when the code is [103], it indicates 10 x 103, or 10,000pF = 10 nanofarad( nF ) = 0.01 microfarad( µF ).

If the code happened to be [224], it would be 22 x 104 = or 220,000pF = 220nF = 0.22µF.

Values under 100pF are displayed with 2 digits only. For example, 47 would be 47pF.

The capacitor has an insulator( the dielectric ) between 2 sheets of electrodes. Different kinds of capacitors use different materials for the dielectric.

Suntan Technology Company Limited
---All kinds of Capacitors

This is a measure of a capacitor's ability to store charge. A large capacitance means that more charge can be stored. Capacitance is measured in farads, symbol F. However 1F is very large, so prefixes are used to show the smaller values.

Three prefixes (multipliers) are used, µ (micro), n (nano) and p (pico):

• µ means 10-6 (millionth), so 1000000µF = 1F
• n means 10-9 (thousand-millionth), so 1000nF = 1µF
• p means 10-12 (million-millionth), so 1000pF = 1nF

Capacitor values can be very difficult to find because there are many types of capacitor with different labelling systems!

There are many types of capacitor but they can be split into two groups, polarised and unpolarised. Each group has its own circuit symbol.

Suntan Technology Company Limited
---All kinds of Capacitors

A capacitor is a passive electronic component that storesenergy in theform of an electrostatic field. In its simplest form, a capacitorconsists of twoconducting plates separated by an insulating material called thedielectric. Thecapacitance is directly proportional to the surface areas of the plates, andis inverselyproportional to the separation between the plates. Capacitance alsodepends on thedielectric constant of the substance separating the plates.

The standard unit of capacitance is the farad, abbreviatedF. Thisis a large unit; more common units are the microfarad, abbreviated µF (1 µF =10-6F) and the picofarad, abbreviated pF (1 pF = 10-12 F).

Capacitors can be fabricated onto integrated circuit (IC)chips. They are commonly used in conjunction with transistors in dynamic random access memory (DRAM). The capacitors helpmaintain thecontents of memory. Because of their tiny physical size, thesecomponents have lowcapacitance. They must be recharged thousands of times per second or theDRAM willlose its data.

Large capacitors are used in the power supplies of electronicequipment ofall types, including computers and their peripherals. In these systems,thecapacitors smooth out the rectified utility AC, providing pure, battery-likeDC.

Suntan Technology Company Limited
---All kinds of Capacitors

In many ways capacitors are the hidden saving grace of the electronics world. They play an essential role in smoothing switch transitions by storing and releasing a small amount of energy over short time scales. Although inductors can play the same role, I think it is safe to say that without small, accurately valued capacitors the modern electronics industry would be a very different beast. Essentially, capacitors store charge, which means that the amount of charge they can store is related to the area available to put said charges. Over recent years, the development of better control over small scale structuring has lead to large increases in capacitance in relatively small packages. The increases have been such that there have been some thoughts of putting these supercapacitors to work as battery replacements in applications where high currents are required.

On that front we can present some good news. Last month Science reported that scientists had observed an unexpectedly large increase in capacitance in some nanoporous materials. A capacitor at its most simple is a couple of parallel metal plates, where the capacitance increases with the size of the plates and as the two plates get closer together. Unfortunately, increasing the area without too much thought is a quick way to find yourself ordering another 19 inch rack for your capacitors, while sparks, ashes, and electrical fires come from the plates getting too close together. However, an alternative is to roughen the surface and include an electrolyte, which effectively replaces the second plate. This increases the surface area of the plates without increasing the volume. The development of nanoporous materials has lead to dramatic increases in the surface area of capacitors and hence a reasonably sized supercapacitor. Exploring nanoporous carbon for capacitance is nothing new, however, previous methods had very little control over the pore size. Here the researchers developed a different fabrication process that allows them to control the pore size to within 0.05nm. The process begins with a carbide substrate, which is a metal plus carbon atoms. They then etch the metal away by reacting it with chlorine, leaving the surrounding carbon structure intact. Since the amount of metal in a carbide depends on the which metal is used, the pore size can be controlled quite accurately by a good choice of metal and the amount of etching performed.

Once the pore size reduced to that below the electrolyte ion plus surrounding solvent molecules , the effect of the pores was reduced. This is because the increased surface area only works if the distance between the electrolyte and plate remains constant and once the pores get too small the charges on the inside of the pore are too far from the nearest electrolyte ion. However, a further decrease in pore size saw the capacitance increase again. It turns out that when the material is so porous, many of the carbon atoms are just barely hanging on. As a result they can move around quite a bit, which allows the electrolyte to squeeze in. The resulting tight fit between the two means that along with an effective increase in surface area, the gap between the two plates is also decreased. Both of these factors increase the capacitance.

I would say the future looked foamy but my glass is empty.