Suntan Blog

In aluminum electrolytic capacitors, the layer of insulating aluminum oxide on the surface of the aluminum plate acts as the dielectric, and it is the thinness of this layer that allows for a relatively high capacitance in a small volume. This oxide has a dielectric constant of 10, which is several times higher than most common polymer insulators. This layer can withstand an electric field strength of the order of 25 megavolts per meter which is significant fraction of that of common polymers. This combination of high capacitance and reasonably high voltage result in high energy density.

The above are the most common schematic symbols for electrolytic capacitors. Some schematic diagrams do not print the "+" adjacent to the symbol. Older circuit diagrams show electrolytic capacitors as a small positive plate surrounded below and on the sides by a larger dish-shaped negative electrode, usually without "+" marking.

Today electrolytic capacitors or as they are more correctly termed, Aluminium Electrolytic Capacitors are used in huge quantities. They are very cost effective and able to provide a larger capacitance per volume than other types of capacitor. This gives them very many uses in circuits where high currents or low frequencies are involved. Aluminium Electrolytic Capacitors are typically used most in applications such as audio amplifiers of all types (hi-fi to mobile phones) and in power supply circuits.

The plates of an electrolytic capacitor are constructed from conducting Aluminium foil. As a result they can be made very thin and they are also flexible so that they can be packaged easily at the end of the production process. The two plates, or foils are slightly different. One is coated with an insulating oxide layer, and a paper spacer soaked in electrolyte is placed between them. The foil insulated by the oxide layer is the anode while the liquid electrolyte and the second foil act as cathode.

In order to package them the two Aluminium foils with the electrolyte soaked paper are rolled together to form a cylinder, and they are placed into an Aluminium can. In this way the electrolytic capacitor is compact while being robust as a result of the protection afforded by the can.

There are two geometries that are used for the connection leads or tags. One is to use axial leads, one coming from each circular face of the cylinder. The other alternative is to use two radial leads or tags, both of which come from the same face of the cylinder.

The lead styles give rise to the descriptions used for the overall capacitors. Descriptions of axial and radial will be seen in the component references.

A thermocouple must be attached to the capacitor body as in:

The temperature is measured in unloaded (Tamb) and maximum loaded condition (TC).
The temperature rise is given by ΔT = TC - Tamb.
To avoid radiation or convection, the capacitor should be tested in a wind-free box.

Capacitance is the ability to store electric charge. In its simplest form a capacitor consists of two parallel plates or electrodes that are separated from each other by an insulating dielectric. It is found that when a battery or any other voltage source is connected to the two plates as shown a current flows for a short time as it charges up. It is found that one plate of the capacitor receives an excess of electrons, while the other has too few. In this way the capacitor plate or electrode with the excess of electrons becomes negatively charged, while the capacitor electrode becomes positively charged.

If the battery is removed the capacitor will retain its charge. However if a resistor is placed across the plates, a current will flow in the resistor until the capacitor becomes discharged.

Safety

The Gold Capacitor should be distant from fire , high temperature or high humidity environment.

Do not compress, crush, throw down or heat the Gold Capacitor. In addition, do not take the Gold Capacitor apart.
Do not throw the Gold Capacitor in any liquid.

Precautions in use

Do not apply voltage higher than rated voltage. Over the rated voltage will cause the Gold Capacitor to explode.

Since the Gold Capacitor is polarized; do not apply a reverse voltage.
Reversing charge the Gold Capacitor will decrease the capacitance and cause ill effects in circuit.

The Gold Capacitor is not suited to AC circuit. It can not perform rectification and filter function.

Reduce the time during soldering operation. The recommend soldering conditions is: temperature below 250, the longest operating time should be less than 5 sec.

Do not bend the lead terminal too frequently to split.

The reason for the continued use of silver mica capacitors is the fact that they can offer very high levels of performance, better in many areas than any other type of capacitor. However in many applications, other more modern technologies provide levels of performance that meets the needs for that particular requirement.

The particular properties of the silver mica capacitor are summarised below.

• High accuracy: Silver mica capacitors can be obtained with tolerance figures of +/- 1%. This is much better than virtually every other form of capacitor available today.
• Temperature co-efficient: The temperature co-efficient of silver mica capacitors is much better than most other types of capacitor. The temperature coefficient is positive and is normally in the region 35 to 75 ppm / C, with +50 ppm / C being an average value
• Value range: Values for silver mica capacitors are normally in the range between a few picofarads up to two or possibly three thousand picofarads.
• Low capacitance variation with voltage: Silver mica capacitors exhibit very little voltage dependence.
• High Q: Silver mica capacitors have very high levels of Q and conversely small power factors. These are both almost independent of frequency.

Although silver mica capacitors have a high tolerance and low temperature co-efficient they are known to jump in value on occasions.

A metal oxide varistor, or MOV, is a voltage dependent, nonlinear device that provides excellent transient voltage suppression. When exposed to high transient voltage, the metal oxide varistor clamps voltage to a safe level. A metal oxide varistor absorbs potentially destructive energy and dissipates it as heat, thus protecting vulnerable circuit components and preventing system damage.

Varistors are non-linear, voltage-dependent resistors whose value of resistance decreases with increasing voltage. Varistors are mainly used for over-voltage protection. Varistors are utilized in low-voltage electronic equipment for absorbing high-voltage pulsative noise while bypass capacitors are utilized for removing low-voltage and high-frequency alternating noise.

An advanced device having both the functions is a ceramic capacitor with varistor performance. Varistors are commonly made by sintering particulate metal oxides, with or without minor amounts of other inorganic materials, as in disk or rod form. Metal oxide varistors (MOV) are semiconductor devices that are fabricated using technology from the ceramic capacitor industry. Zinc oxide varistors are ceramic semiconductor devices based on zinc oxide. Varistors are produced by a ceramic sintering process which gives rise to a structure consisting of conductive zinc oxide grains surrounded by electrically insulating barriers. These barriers are attributed to trap states at grain boundaries induced by additive elements such as bismuth, cobalt, praseodymium, manganese and so forth. A monolithic chip varistor is generally provided with a varistor body including a plurality of varistor layers composed of a zinc oxide-based ceramic material and at least one pair of internal electrodes opposed to each other with one of the varistor layers there between , and a pair of external electrodes.

Suntan metal oxide varistor devices are made primarily of zinc oxide with small amounts of bismuth, cobalt, manganese, and other metal oxides. They can be connected in parallel for increased energy-handling capabilities. MOVs can also be connected in series to provide higher voltage ratings or to provide voltage rating between the standard increments.

Variable Electrical parameters are those that the Design Engineer must specify when selecting a Quartz Crystal device for any particular application.

a. Package Type: Will the package be Through Hole or Surface Mount, and are there size constraints with either.

b. Frequency

c. Load Capacitance: The specified Load Capacitance is dependent on the Resonance Mode required in the application . For Series resonance, no Load Capacitance is required. For Parallel Resonance, the Load Capacitance specified by the Design Engineer will be used to calibrate the Quartz Crystal thereby effecting the major operating characteristics of the device, including initial Frequency Tolerance.

d. Frequency Tolerance: At 25 degree Celsius, an amount of initial frequency deviation acceptable for the application is required. Tighter specifications of Frequency Tolerance lower yield in Quartz Crystal Blank production thereby serving to increase production costs.

e. Stability: Over the Operating Temperature Range, an amount of total deviation acceptable for the application. Tighter specifications of Stability lower yield in Quartz Crystal Blank production thereby serving to increase production costs.

f. Operating Temperature: Standard Operating Temperature ranges are generally considered as -20-+70 degrees Celsius (considered "commercial" Operating Temperature), and -40-+85 degrees Celsius (considered "Industrial" Operating Temperature) Other Operating temperature ranges are available and should be specified .

(1) Ceramic Trimmer Capacitor series can be soldered by flow soldering method and soldering iron. Do not use reflow soldering method.

(2) Soldering condition If the soldering conditions are not suitable, e.g., excessive time and/or excessive temperature, the trimmer capacitor may deviate from the specified characteristics.

(3) The dimension of mounting hole should be Murata's standard mounting hole used at flow soldering. The amount of solder is critical. Insufficient amounts of solder can lead to insufficient soldering strength on PCB. Excessive amounts of solder may cause bridging between the terminals or contact failure due to flux wicking up.

(4) When using soldering iron, the string solder should be applied to the lower part of the terminal only. Do not apply flux except to the terminals. Excessive amounts of solder and/or applying solder to the upper part of the terminal may cause fixed rotor or the contact failure due to flux invasion into the movable part and/or the contact point. The soldering iron should not come in contact with the plastic case of the trimmer capacitor. If such contact does occur, the trimmer capacitor may be damaged.

(5) Our recommended chlorine content of string solder is 0.5wt% max.

(6) Do not use water-soluble flux (for water cleaning). To prevent the deterioration of trimmer capacitor characteristics, apply flux only to terminals.

For all capacitor technologies that do not have the ability to recover after a partial breakdown, the current flow is continuous.

However metallized film capacitors have the property to recover after an instantaneous breakdown (partial breakdown) due to the fact that the metallized electrodes (capacitor plates) act as a fuse. For fusing a small current is needed, but is not continuous. This effect is defined as “self healing” and not as breakdown.

Therefore in testing these capacitors on a proof voltage, it is always possible that the capacitors have the self healing effect, taking temporarily a peak current, but are completely isolated again after this phenomenon is stopped. To take this in account for qualifying capacitors, in all IEC standards of metallized film capacitors a breakdown is defined only when it is “permanent”.

Therefore a note is added for explanation.

Requirement: There shall be no permanent breakdown or flashover during the test.

Note: The occurrence of self-healing breakdowns during the application of the test voltages is allowed.

To detect if the behavior is a self healing or permanent breakdown, it is recommended to measure the remaining charging current only after one minute of charging and to neglect the small current peaks (arcing) before that time. Modern “high pot” test equipments have the function to allow arcing currents before the final permanent breakdown current.