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resistor color code calculator is the first band from the left represents the primary good sized figure (digit) of resistance. The 2d band represents the second one good sized digit of resistance. The 0.33 band is the multiplier. The fourth band represents the tolerance cost to which a resistance can vary. The fourth band is generally silver or golden in color.
As noted formerly the maximum vital rule which ought to be observed for studying the resistors is to begin from the primary band (that is at the left side). There are methods to become aware of the primary band from the left side.
The first band is relatively carved in the direction of the leg compared to fourth.
The fourth band of 4 band resistor is specific due to the fact that it's far silver or golden, Both those colours aren't used withinside the first band.
The four-band resistor colour code is the maximum usually used resistor. Similar to the three band resistor, the primary bands usually supply the primary 2 digits of the resistance fee. The 0.33 band represents the multiplier even as the fourth band represents tolerance.
AB × C ± D × 105 ±5% = 1,2 hundred kΩ ± 5�nds:
A: 1st band – 1st giant digit
B: 2d band – 2d giant digit
C: third band – multiplier
D: 4th band – tolerance
For a four band resistor colour code, we are able to start via way of means of first locating the tolerance band as it also includes gold or silver. The tolerance band is likewise effortlessly recognized because of the elevated hole among the tolerance band and the multiplier band. In this example, it's miles gold and as a consequence offers a tolerance of ±5% whilst we appearance up the resistor colour code chart. Starting from the alternative end, the primary band is as a consequence recognized to be brown which has a 1st giant digit of 1. The 2d band is purple and has a 2d giant digit of 2. The third band is inexperienced because of this that that the multiplier is 105. Using the formula. The resistance acquired is 12 × 105 = 1,2 hundred kΩ. Lastly, the tolerance band which we recognized to be gold offers a tolerance fee of ±5%.
Sometimes for a four band resistor colour code, the tolerance band may be left blank, ensuing in a three-band resistor. In this case, the resistance fee could stay the same, besides that the tolerance could be ±20% as though it have been a three-band resistor.
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All the electronic devices that we use in our daily life, such as cell phones, laptops, refrigerators, computers, televisions and all other electrical and electronic devices are made with simple or complex circuitry.
ZTT-4.00MG DHW components Warranty 2 years RESONATOR, CERAMIC, 100 V, 4 MHZ, 0.5%, 30 PF, THROUGH HOLE. ZTT series ceramic resonator offers wide frequency range and extended temperature range capabilities with built-in load capability.
Resonators are designed to eliminate a sound wave at a given frequency. Just like waves in the ocean, sound waves have a peak and a trough. Sound waves of a particular frequency bounce inside a resonator. The peak of a sound wave meets through another wave of the same size, canceling out. Sound wave cancellation is what eliminates those annoying noises, giving you a better exhaust note. If you like the sound of your exhaust system but hear the hum a number of turns, a resonator can help you with this problem.
A resonator is a device or system that exhibits resonance or resonant behavior. That is, it naturally oscillates with greater amplitude at certain frequencies, called resonant frequencies, than at other frequencies. Oscillations in a resonator can be both electromagnetic and mechanical (including acoustic). Resonators are used to generate waves of specific frequencies or to select specific frequencies from a signal.Musical instruments use acoustic resonators that produce sound waves of specific tones.
Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce very precise frequency oscillations. A standing wave in a rectangular cavity resonator A cavity resonator is a resonator in which waves exist in an empty space inside the device. In electronics and radio, microwave cavities made up of hollow metal housings are used in transmitters, receivers and microwave test equipment to verify frequency, in place of tuned circuits which are used at higher frequencies. bass. Acoustic cavity resonators, in which sound is produced by air vibrating in a cavity with an opening, are known as Helmholtz resonators.
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2N3904 is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin. 2N3904 has a gain value of 300; this value determines the amplification capacity of the transistor. The maximum amount of current that could flow through the Collector pin is 200mA, hence we cannot connect loads that consume more than 200mA using this 2n3904 transistor. To bias a transistor we have to supply current to base pin, this current (IB) should be limited to 5mA.
When this transistor is fully biased then it can allow a maximum of 200mA to flow across the collector and emitter. This stage is called Saturation Region and the typical voltage allowed across the Collector-Emitter (VCE) or Collector-Base (VCB) could be 40V and 60V respectively. When base current is removed the transistor becomes fully off, this stage is called as the Cut-off Region and the Base Emitter voltage could be around 600 mV.
2N3904 as switch:
When a transistor is used as a switch it is operated in the Saturation and Cut-Off Region as explained above. As discussed a transistor will act as an Open switch during Forward Bias and as a closed switch during Reverse Bias, this biasing can be achieved by supplying the required amount of current to the base pin. As mentioned the biasing current should maximum of 5mA. Anything more than 5mA will kill the Transistor; hence a resistor is always added in series with base pin. The value of this resistor (RB) can be calculated using below formulae.
The manufacture of each semiconductor product requires hundreds of processes. After sorting, the entire manufacturing process is divided into eight steps: Wafer Processing, Oxidation, Photography, Etching, Film Deposition, Interconnection, Test, and Package.
Fig 1. Semiconductor Parts Manufacturing Process
1 Wafer Processing
Fewer people know, all semiconductor processes start with a grain of sand. Because the silicon contained in sand is the raw material needed to produce wafers. A wafer is a round slice formed by cutting a single crystal column made of silicon (Si) or gallium arsenide (GaAs). To extract high-purity silicon materials, silica sand is required, a special material with a silicon dioxide content of up to 95%, which is also the main raw material for making wafers. Wafer processing is the process of making and obtaining wafers.
① Ingot Casting
First, the sand needs to be heated to separate the carbon monoxide and silicon, and the process is repeated until the ultra-high purity electronic grade silicon (EG-Si) is obtained. High-purity silicon melts into a liquid, and then solidifies into a single-crystal solid form called an "ingot", which is the first step in semiconductor manufacturing. The manufacturing precision of silicon ingots (silicon pillars) is very high, reaching the nano level.
② Ingot Cutting
After the previous step is completed, you need to cut off both ends of the ingot with a diamond saw, and then cut it into slices of a certain thickness. The diameter of the ingot slice determines the size of the wafer. Larger and thinner wafers can be divided into more units, which helps reduce production costs. After cutting the silicon ingot, it is necessary to add a "flat area" or "indent" mark on the slice, so that it is convenient to set the processing direction based on it as a standard in the subsequent steps.
③ Wafer Surface Polishing
The thin slice obtained through the above-mentioned cutting process is called a "die", that is, an unprocessed "raw wafer". The die surface is uneven, and it is impossible to directly print circuit patterns on it. Therefore, it is necessary to first remove surface defects through grinding and chemical etching processes, then form a smooth surface through polishing and then cleaning residual contaminants.
The role of the oxidation process is to form a protective film on the surface of the wafer. It can protect the wafer from chemical impurities, prevent leakage current from entering the circuit, diffusion during ion implantation, and the wafer from slipping off during etching.
Fig 2. Oxidation
The first step of the oxidation process is to remove impurities and pollutants, such as organic matter, metals and evaporation residual moisture with four steps. After the cleaning is completed, the wafer can be placed in a high temperature environment of 800 to 1200 degrees Celsius, and a layer of silicon dioxide is formed by the flow of oxygen or vapor on the wafer surface. Oxygen diffuses through the oxide layer and reacts with silicon to form oxide layers of different thicknesses, which can be measured after the oxidation is complete.
Dry Oxidation and Wet Oxidation Method
According to the different oxidants in the oxidation reaction, the thermal oxidation process can be divided into dry oxidation and wet oxidation. The former uses pure oxygen to produce a silicon dioxide layer, which is slow but the oxide layer is thin and dense. The latter requires both oxygen and high solubility. The characteristic of water vapor is that the growth rate is fast, but the protective layer is relatively thick and the density is low.
Fig 3. Dry Oxidation and Wet Oxidation Method
In addition to the oxidizer, there are other variables that affect the thickness of the silicon dioxide layer. First of all, the wafer structure, surface defects and internal doping concentration will affect the rate of formation of the oxide layer. In addition, the higher the pressure and temperature generated by the oxidation equipment, the faster the oxide layer will be formed. In the oxidation process, it is also necessary to use dummy wafers according to the location of the wafers in the unit to protect the wafers and reduce the difference in oxidation degree.
Photomask is the use of light to "print" circuit patterns onto a wafer. We can understand it as semiconductor parts drawing on the surface of the wafer. The higher the fineness of the circuit pattern, the higher the integration of the product chip, which can only be achieved through advanced photomask technology. Specifically, it can be divided into three steps: photoresist coating, exposure and development.
① Coated Photoresist
The first step in drawing a circuit on a wafer is to coat photoresist on the oxide layer. Photoresist changes the chemical properties of the wafer to become "photographic paper". The thinner the photoresist layer on the surface of the wafer, the more uniform the coating, and the finer the patterns that can be printed. In addition, this step can use the "spin coating" method.
Fig 4. Coating Photoresist
According to the difference of UV light reactivity, photoresist can be divided into two types: positive glue and negative glue. The former will decompose and disappear after being exposed to light, leaving a pattern of unreceived areas, while the latter will polymerize after being exposed to light to let the pattern of the light-receiving part appear.
After covering the photoresist film on the wafer, the circuit can be printed by controlling the light irradiation. This process is called "exposure." We can selectively pass light through the exposure equipment. When the light passes through the mask containing the circuit pattern, the circuit can be printed on the wafer coated with a photoresist film underneath.
Fig 5. Exposure
During the exposure process, the finer the printed pattern, the more components can be accommodated in the final chip, which helps to improve production efficiency and reduce the cost of individual components.
The step after exposure is to spray developer on the wafer, in order to remove the photoresist in the area not covered by the pattern, so that the printed circuit pattern can be revealed. After the development is completed, it needs to be checked by various measuring equipment and optical microscopes to ensure the quality of the drawing of the circuit diagram.
After the photolithography of the circuit diagram is completed on the wafer, an etching process is used to remove any excess oxide film and only the semiconductor circuit diagram is left. To do this, liquid, gas or plasma is used to remove the unselected parts.
There are two main etching methods, depending on the material used: wet etching that uses a specific chemical solution for chemical reaction to remove the oxide film, and dry etching that uses gas or plasma.
1) Wet Etching
Fig 6. Wet Etching Method
Wet etching that uses chemical solutions to remove oxide films has the advantages of low cost, fast etching speed, and high productivity. However, wet etching has the characteristics of isotropy, that is, its speed is the same in any direction. This will cause the mask (or sensitive film) and the etched oxide film to not be completely aligned, making it difficult to process very fine circuit diagrams.
2) Dry Etching
Dry etching can be divided into three different types:
The first is chemical etching, which uses etching gas (mainly hydrogen fluoride). Like wet etching, this method is also isotropic, which means that it is not suitable for fine etching.
The second method is physical sputtering, that is, ions in the plasma are used to strike and remove the excess oxide layer. As an anisotropic etching method, it has different etching speeds in the horizontal and vertical directions, so its fineness must exceed that of chemical etching. However, the disadvantage of this method is that the etching speed is slow, because it completely relies on the physical reaction caused by ion collision.
Fig 7. Physical Sputtering
The third method is reactive ion etching (RIE). It combines the first two methods, that is, while using plasma for ionized physical etching, and chemical etching is performed with free radicals generated after plasma activation. In addition to the etching speed exceeding the first two methods, RIE can use the characteristics of ion anisotropy to achieve high-definition pattern etching.
Fig 8. Reactive Ion Etching (RIE)
Now dry etching has been widely used to improve the yield of fine semiconductor circuits. Maintaining the uniformity of full-wafer etching and increasing the etching speed are crucial. Today's most advanced dry etching equipment is supporting the production of the most advanced logic and memory chips with higher performance.
5 Film Deposition
In order to create the micro devices inside the chip, we need to continuously deposit layers of thin films and remove the excess parts by etching, and add some materials to separate the different devices. Each transistor or memory cell is constructed step by step through the above process. The "thin film" we are talking about here refers to a "membrane" whose thickness is less than 1 micron (μm, one millionth of a meter) and cannot be manufactured by ordinary mechanical processing methods. Here the process of putting a thin film containing the desired molecular or atomic unit on the wafer is "deposition."
To form a multi-layer semiconductor structure, we need to fabricate a device stack first, that is, alternately stacking multiple thin metal (conductive) films and dielectric (insulating) films on the surface of the wafer, and then repeat the etching process to remove excess parts and form a three-dimensional structure. Technologies that can be used in the deposition process include chemical vapor deposition (CVD), atomic layer deposition (ALD) and physical vapor deposition (PVD). The methods using these technologies can be divided into dry and wet deposition.
① Chemical Vapor Deposition
Fig 9. Chemical Vapor Deposition
In chemical vapor deposition, the precursor gas chemically reacts in the reaction chamber and generates a thin film attached to the surface of the wafer and by-products that are drawn out of the chamber.
Plasma-enhanced chemical vapor deposition requires the use of plasma to generate reactive gas. This method reduces the reaction temperature and is very suitable for temperature-sensitive structures. In addition, the use of plasma can also reduce the number of depositions, which can often lead to higher quality films.
② Atomic Layer Deposition
Fig 10. Atomic Layer Deposition
Atomic layer deposition forms a thin film by depositing only a few atomic layers at a time. The key to this method is to loop the independent steps in a certain order and maintain good control. Coating the precursor on the wafer surface is the first step, after which different gases are introduced to react with the precursor to form the required substances on the wafer surface.
③ Physical Vapor Deposition
Fig 11. Physical Vapor Deposition
Physical vapor deposition refers to the formation of thin films by physical means. Sputtering is a physical vapor deposition method. Its principle is that atoms of the target material are sputtered out by the bombardment of argon plasma and deposited on the wafer surface to form a thin film.
In some cases, the deposited film can be treated and improved by techniques such as ultraviolet heat treatment.
The conductivity of semiconductors is between conductors and non-conductors (ie insulators). This characteristic allows us to fully control the current. Through wafer-based lithography, etching and deposition processes, transistors and other components can be constructed, but they also need to be connected to achieve power and signal transmission and reception.
Metal is used for circuit interconnection because of its conductivity, which is need to meet the following conditions:
Low Resistance: Since the metal circuit needs to pass current, the metal in it should have low resistance.
Thermochemical stability: The properties of the metal material must remain unchanged during the metal interconnection process.
High Reliability: With the development of integrated circuit technology, even a small amount of metal interconnect materials must have sufficient durability.
Manufacturing Cost: Even if the previous three conditions have been met, high cost is not suitable for the mass production.
The interconnection process mainly uses two substances, aluminum (Al) and copper (Co).
Fig 12. Al and Co Interconnection Process
Aluminum Interconnect Process
This process starts with aluminum deposition, photoresist application, and exposure and development, removing any excess aluminum and photoresist before entering the oxidation process through etching tech. After the foregoing steps are completed, repeat them until the interconnection is completed.
With its excellent electrical conductivity, aluminum is also easy to lithography, etch, and deposit. In addition, it has a lower cost and a better adhesion to the oxide film. The disadvantage is that it is easy to corrode and has a low melting point. In addition, in order to prevent the reaction of aluminum and silicon from causing connection problems, it is also necessary to add a metal deposit to separate the aluminum from the wafer, which is called a "barrier metal."
Aluminum circuits are formed by deposition. After the wafer enters the vacuum state, the thin film formed by aluminum particles will adhere to the wafer. This process is called "Vapour Deposition" and includes chemical vapor deposition and physical vapor deposition.
Copper Interconnection Process
With the improvement of semiconductor process precision and the shrinking of device size, the connection speed and electrical characteristics of aluminum circuits are gradually unable to meet the requirements. For this reason, we need to find new conductors that satisfy the requirements of both size and cost. With its lower resistance, so it can achieve faster connection speed. What’s more, copper is more reliable because it is more resistant to electromigration than aluminum, which is the movement of metal ions that occurs when current flows through the metal.
However, copper does not easily form compounds, so it is difficult to vaporize and remove it from the wafer surface. To solve this problem, we no longer etch copper, but the dielectric materials, so that metal circuit patterns composed of trenches and via holes can be formed, and then copper is filled into the aforementioned to help interconnection, which is called "inlaid process".
Fig 13. Copper Interconnection Barriers
As the copper atoms continue to diffuse into the dielectric, the insulation of the latter will decrease and produce a barrier layer that prevents the copper atoms from continuing to diffuse. Then a very thin copper seed layer will be formed on the barrier layer. After this step, electroplating can be carried out, that is, the high-aspect-ratio graphics are filled with copper. After filling, the excess copper can be removed by a metal chemical mechanical polishing (CMP) method. After completion, an oxide film can be deposited, and the excess film can be removed by photolithography and etching processes. The full entire process needs to be repeated continuously until the copper interconnection is completed.
It can be seen from the above comparison that the difference between the copper interconnection and the aluminum interconnection is that the excess copper is removed by metal CMP instead of etching.
The main goal of the test is to check whether the quality of the semiconductor chip meets a certain standard, thereby eliminating defective products and improving the reliability of the chip. In addition, products that are tested and defective will not enter the packaging step, which helps to save cost and time. Electronic die sorting (EDS) is a testing method for wafers.
EDS is a process for inspecting the electrical characteristics of each chip in the wafer state and thereby improving the semiconductor yield.
1) Electrical Parameter Monitoring (EPM)
EPM is the first step in semiconductor chip testing. This step will test every device (including transistors, capacitors, and diodes) that the semiconductor integrated circuit needs to use to ensure that its electrical parameters meet the standards. The measured electrical characteristic data will be used to improve the efficiency of the semiconductor manufacturing process and product performance (not to detect defective products).
2) Wafer Aging Test
The semiconductor defect rate comes from two aspects, namely, the rate of manufacturing defects (higher in the early stage) and the rate of defects occurring throughout the life cycle afterwards. Wafer aging test refers to testing the wafer under a certain temperature and AC/DC voltage to find out which products may have defects in the early stage, that is, to improve the reliability of the final product by discovering potential defects.
3) Parameters Test
a. Temp Test
High Temperatur: Verify that the chip can work at a temperature that exceeds the maximum temperature by 10% or higher.
Low Temperatur: Verify that the chip can work at a temperature that lower the minimum temperature by 10% or more.
Room Temperatur: Check whether the chip can work at room temperature (25°C).
(The high and low temperature test requirements for storage semiconductors are 85-90℃ and -5-40℃ respectively.)
b. Speed Test
Core: Check whether the core functions are valid.
Speed: Test movement speed.
c. Motion Test
DC: Apply direct current to check whether the current and voltage are normal.
AC: Apply alternating current to test movement characteristics.
Function: Check whether all functions are normal.
After the burn-in test is completed, the semiconductor chip needs to be connected to the test device with a probe card, and then the temperature, speed, and motion test of the wafer can be performed to verify the relevant semiconductor functions. Please see the table for the description of the specific test steps.
Repairing is the most important test step, because some defective chips can be repaired, and you only need to replace the defective components.
The chips that failed the electrical test have been sorted out in the previous steps, but they still need to be marked to distinguish them. In the past, we needed to mark defective chips with special inks to ensure that they can be identified with the naked eye. Today, the system automatically sorts them based on the test data values.
Square chips (also called single wafers) of equal size are formed on the wafers processed by the previous several processes. The next thing to do is to obtain individual chips by cutting. The chip that has just been cut is very fragile and cannot exchange electrical signals, so it needs to be processed separately. This process is packaging, including forming a protective shell on the outside of the semiconductor chip and allowing them to exchange electrical signals with the outside. The entire packaging process is divided into five steps, namely wafer sawing, single wafer attachment, interconnection, molding, and packaging testing.
1) Wafer Sawing
To cut countless densely arranged chips from the wafer, we must first grind the back of the wafer until its thickness can meet the needs of the packaging process. After grinding, we can cut along the scribing line on the wafer until the semiconductor chip is separated.
There are three types of wafer sawing techniques: blade cutting, laser cutting and plasma cutting. Blade cutting refers to cutting wafers with diamond blades, which is prone to generate frictional heat and debris and thus damage the wafers.
Laser cutting has higher precision and can easily handle wafers with thin thickness or small scribing line pitch.
Plasma cutting uses the principle of plasma etching, so even if the scribing line pitch is very small, this technology can also be applied.
2) Single Wafer Attachment
After all the chips are separated from the wafer, we need to attach the individual chips (single chip) to the substrate (lead frame). The role of the substrate is to protect the semiconductor chips and allow them to exchange electrical signals with external circuits. A liquid or solid tape adhesive can be used to attach the chip.
Fig 14. Bonding
After attaching the chip to the substrate, we also need to connect the contact points of the two to achieve electrical signal exchange. There are two connection methods that can be used in this step: wire bonding using thin metal wires and flip chip bonding using spherical gold or tin blocks. Wire bonding is a traditional method, and flip-chip bonding can speed up semiconductor product manufacturing.
Fig 15. Molding
After completing the connection of the semiconductor chip, it is necessary to use a molding process to add a package to the outside of the chip to protect the semiconductor integrated circuit from external conditions such as temperature and humidity. After the packaging mold is made as required, we put the semiconductor chip and the epoxy molding compound (EMC) into the mold and seal it. The sealed chip is in its final product.
5) Package Test
The chip that has the final form must pass the final defect test. All that enters the final test is the finished semiconductor chip. They will be put into the test equipment, set different conditions such as voltage, temperature and humidity, etc. for electrical, functional and speed tests. The results of these tests can be used to find defects, improve product quality and production efficiency.
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