Inilah Led

Stands for "Light-Emitting Diode." An LED is an electronic device that emits light when an electrical current is passed through it. Early LEDs produced only red light, but modern LEDs can produce several different colors, including red, green, and blue (RGB) light. Recent advances in LED technology have made it possible for LEDs to produce white light as well.

LEDs are commonly used for indicator lights (such as power on/off lights) on electronic devices. They also have several other applications, including electronic signs, clock displays, and flashlights. Since LEDs are energy efficient and have a long lifespan (often more than 100,000 hours), they have begun to replace traditional light bulbs in several areas. Some examples include street lights, the red lights on cars, and various types of decorative lighting. You can typically identify LEDs by a series of small lights that make up a larger display. For example, if you look closely at a street light, you can tell it is an LED light if each circle is comprised of a series of dots.

The energy efficient nature of LEDs allows them to produce brighter light than other types of bulbs while using less energy. For this reason, traditional flat screen LCD displays have started to be replaced by LED displays, which use LEDs for the backlight. LED TVs and computer monitorsare typically brighter and thinner than their LCD counterparts.

Inilah Adapter

An adapter is a device that allows a specific type ofhardware to work with another device that would otherwise be incompatible. Examples of adapters include electrical adapters, video adapters, audio adapters, and network adapters.

An electrical adapter, for instance, may convert the incoming voltage from 120V to 12V, which is suitable for a radio or other small electronic device. Without regulating voltage through an adapter, the incoming electrical surge could literally fry the internal components of the device. Most consumer electronics have adapters attached to the plug at the end of the electrical cord. Whenever you see an plug surrounded by a large box, it is most likely an electrical adapter. You can typically find the inputand output voltage printed directly on the adapter. A device that does not have an adapter on the end of its electrical cable typically has a built-in voltage adapter. For example, desktop computers typically have the adapter built into the internal power supply.

Video adapters and audio adapters adapt one type of interface to another type of connector. For example, a DVI to VGA adapter allows you to connect theDVI output of a laptop to the VGA input of a projector. Most professional audio devices use 1/4" audio jacks, while most computers have 1/8" "minijacks" for audio input and output. Therefore, 1/4" to 1/8" audio adapters are often used to import audio into computers. Likewise, an 1/8" to 1/4" adapter can used to output audio from a computer to a professional audio system. Since a large number of audio and video interfaces exist, there are hundreds of audio and video adapters available.

Network cards, or NICs, are also called network adapters. These include Ethernet cards, internalWi-Fi chips, and external wireless transmitters. While these devices don't convert connections like audio or video adapters, they enable computers to connect to network. Since the network card makes it possible to connect to an otherwise incompatible network, the card serves as an adapter. Similarly, video cards are sometimes called video adapters because t

Inilah Usb

Stands for "Universal Serial Bus." USB is the most common type of computer port used in today's computers. It can be used to connect keyboards, mice, game controllers, printers, scanners, digital cameras, and removable media drives, just to name a few. With the help of a few USB hubs, you can connect up to 127 peripherals to a single USB port and use them all at once (though that would require quite a bit of dexterity).

USB is also faster than older ports, such as serial and parallel ports. The USB 1.1 specification supports data transfer rates of up to 12Mb/sec and USB 2.0 has a maximum transfer rate of 480 Mbps. Though USB was introduced in 1997, the technology didn't really take off until the introduction of the Apple iMac (in late 1998) which used USB ports exclusively. It is somewhat ironic, considering USB was created and designed by Intel, Compaq, Digital, and IBM. Over the past few years, USB has become a widely-used cross-platform interface for both Macs and PCs.

Inilah Touchscreen

Touchscreen

 
 
 
• 

A touchscreen is a display that also serves as an input device. Some touchscreens require a proprietary pen for input, though most modern touchscreens detect human touch. Since touchscreen devices accept input directly through the screen, they do not require external input devices, such as mice and keyboards. This makes touchscreens ideal for computer kiosks, as well as portable devices, such as tablets andsmartphones.

While a touchscreen may look like an ordinary display, the screen includes several extra layers that detect input. The first layer is a hard protective layer that protects the actual display and the touchscreen components. Beneath the protective layer is an electronic grid that detects input. Most modern touchscreens use capacitive material for this grid, in which the electrical charge changes wherever the screen is touched. Beneath the touchscreen layer is the LCD layer, which is used for the actual display.

While early touchscreens could only detect a single point of input at a time, modern touchscreens support "multi-touch" input. This technology, which was made popular by the original iPhone, enables the screen to detect multiple finger motions at once. For example, on some touchscreen devices, you can rotate an image by twisting three fingers in a clockwise or counterclockwise motion. Many touchscreen applications also allow you zoom in and out by spreading two fingers apart or pinching them together.

Thanks to multi-touch and other improvements in touchscreen technology, today's touchscreens are easier and more natural to use than they used to be. In fact, improved touchscreen technology has greatly contributed to the popularity of the iPad and other tablet PCs.

Inilah Touchscreen

Touchscreen

 
 
 
• 

A touchscreen is a display that also serves as an input device. Some touchscreens require a proprietary pen for input, though most modern touchscreens detect human touch. Since touchscreen devices accept input directly through the screen, they do not require external input devices, such as mice and keyboards. This makes touchscreens ideal for computer kiosks, as well as portable devices, such as tablets andsmartphones.

While a touchscreen may look like an ordinary display, the screen includes several extra layers that detect input. The first layer is a hard protective layer that protects the actual display and the touchscreen components. Beneath the protective layer is an electronic grid that detects input. Most modern touchscreens use capacitive material for this grid, in which the electrical charge changes wherever the screen is touched. Beneath the touchscreen layer is the LCD layer, which is used for the actual display.

While early touchscreens could only detect a single point of input at a time, modern touchscreens support "multi-touch" input. This technology, which was made popular by the original iPhone, enables the screen to detect multiple finger motions at once. For example, on some touchscreen devices, you can rotate an image by twisting three fingers in a clockwise or counterclockwise motion. Many touchscreen applications also allow you zoom in and out by spreading two fingers apart or pinching them together.

Thanks to multi-touch and other improvements in touchscreen technology, today's touchscreens are easier and more natural to use than they used to be. In fact, improved touchscreen technology has greatly contributed to the popularity of the iPad and other tablet PCs.

Inilah Touchscreen

Touchscreen

 
 
 
• 

A touchscreen is a display that also serves as an input device. Some touchscreens require a proprietary pen for input, though most modern touchscreens detect human touch. Since touchscreen devices accept input directly through the screen, they do not require external input devices, such as mice and keyboards. This makes touchscreens ideal for computer kiosks, as well as portable devices, such as tablets andsmartphones.

While a touchscreen may look like an ordinary display, the screen includes several extra layers that detect input. The first layer is a hard protective layer that protects the actual display and the touchscreen components. Beneath the protective layer is an electronic grid that detects input. Most modern touchscreens use capacitive material for this grid, in which the electrical charge changes wherever the screen is touched. Beneath the touchscreen layer is the LCD layer, which is used for the actual display.

While early touchscreens could only detect a single point of input at a time, modern touchscreens support "multi-touch" input. This technology, which was made popular by the original iPhone, enables the screen to detect multiple finger motions at once. For example, on some touchscreen devices, you can rotate an image by twisting three fingers in a clockwise or counterclockwise motion. Many touchscreen applications also allow you zoom in and out by spreading two fingers apart or pinching them together.

Thanks to multi-touch and other improvements in touchscreen technology, today's touchscreens are easier and more natural to use than they used to be. In fact, improved touchscreen technology has greatly contributed to the popularity of the iPad and other tablet PCs.

Inilah Trackball

A trackball is an input device used to enter motion data into computers or other electronic devices. It serves the same purpose as a mouse, but is designed with a moveable ball on the top, which can be rolled in any direction. Instead of moving the whole device, you simply roll the moveable ball on top of the trackball unit with your hand to generate motion input.

Trackballs designed for computers generally serve as mouse replacements and are primarily used to move the cursor on the screen. Like mice, computer trackball devices also include buttons, which can serve as left-click and right-click buttons, and may also be used to enter other commands. While trackballs are most commonly used with computers, they may also be found in other electronics, such as arcade games, mixing boards, and self-serve kiosks. These devices often have trackballs that are larger than the ones used in computer input devices.

Besides the capability to be built into various devices, trackballs have a number of other advantages over mice. Some advantages include the small footprint (since they don't require a mousepad or large area to move the mouse), fingertip control (which may offer more accuracy), and improved ergonomics (since there is less strain on the wrist). Still, many people find trackballs harder to use than mice, since they feel less natural and may require practice to get used to. For this reason, the vast majority of computers include a mouse, rather than a trackball, as the defaultinput device.

Inilah Thermistor

A thermistor (short for "thermal resistor") is a type of resistor that is used to measure temperature. While typical resistors are designed to maintain consistent resistance regardless of temperature, a thermistor's resistance varies significantly as the temperature changes. Once a thermistor is calibrated, changes in electrical resistance can be accurately translated into changes in temperature.

Thermistors are commonly used in computers to monitor the ambient temperature of internalcomponents. For example, thermistors may be used to record the temperature near the CPU, RAM slots, and the power supply. These thermistors are usually integrated into the computer's motherboard. The actual temperature of components such as the processor and memory modules is typically measured by a diode that is integrated into the chip.

Computers use the information recorded by thermistors to prevent overheating. For example, if a processor is running near capacity for an extended period of time, the temperature may gradually increase. When this happens, the computer might speed up the internal fans to increase airflow and cool the computer. In extreme circumstances, such as when a laptop is used outside on a hot day, the fans may not be able to keep the computer at a safe temperature. If the thermistors record a dangerously high temperature, the computer may shut down to avoid overheating and damaging the hardware.

Inilah Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductormaterial with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

The transistor is the mendasar building block of modern electronic devices, and is ubiquitous in modern electronic systems. Following its development in the early 1950s, the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios,calculators, and computers, among other things.

History

A replica of the first working transistor.

The thermionic triode, a vacuum tube invented in 1907, propelled the electronics age forward, enabling amplified radio technology and long-distance telephony. The triode, however, was a fragile device that consumed a lot of power. Physicist Julius Edgar Lilienfeld filed a patent for a field-effect transistor (FET) in Canada in 1925, which was intended to be a solid-state replacement for the triode.^[1][2]Lilienfeld also filed identical patents in the United States in 1926^[3] and 1928.^[4][5] However, Lilienfeld did not publish any research articles about his devices nor did his patents cite any specific examples of a working prototype. Because the production of high-quality semiconductor materials was still decades away, Lilienfeld's solid-state amplifier ideas would not have found practical use in the 1920s and 1930s, even if such a device had been built.^[6] In 1934, German inventor Oskar Heil patented a similar device.^[7]

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948.

From November 17, 1947 to December 23, 1947, John Bardeen and Walter Brattain at AT&T'sBell Labs in the United States, performed experiments and observed that when two gold point contacts were applied to a crystal of germanium, a signal was produced with the output power greater than the input.^[8] Solid State Physics Group leader William Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge of semiconductors. The term transistor was coined by John R. Pierce as a portmanteau of the term "transfer resistor".^[9][10] According to Lillian Hoddeson and Vicki Daitch, authors of a biography of John Bardeen, Shockley had proposed that Bell Labs' first patent for a transistor should be based on the field-effect and that he be named as the inventor. Having unearthed Lilienfeld’s patents that went into obscurity years earlier, lawyers at Bell Labs advised against Shockley's tawaran because the idea of a field-effect transistor that used an electric field as a "grid" was not new. Instead, what Bardeen, Brattain, and Shockley invented in 1947 was the first point-contact transistor.^[6] In acknowledgement of this accomplishment, Shockley, Bardeen, and Brattain were jointly awarded the 1956 Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect."^[11]

In 1948, the point-contact transistor was independently invented by German physicists Herbert Mataré and Heinrich Welker while working at the Compagnie des Freins et Signaux, a Westinghouse subsidiary located in Paris. Mataré had previous experience in developing crystal rectifiers from silicon and germanium in the German radar effort during World War II. Using this knowledge, he began researching the phenomenon of "interference" in 1947. By witnessing currents flowing through point-contacts, similar to what Bardeen and Brattain had accomplished earlier in December 1947, Mataré by June 1948, was able to produce consistent results by using samples of germanium produced by Welker. Realizing that Bell Labs' scientists had already invented the transistor before them, the company rushed to get its "transistron" into production for amplified use in France's telephone network.^[12]

Philco surface-barrier transistor developed and produced in 1953

The first high-frequency transistor was the surface-barrier germanium transistor developed by Philco in 1953, capable of operating up to60 MHz.^[13] These were made by etching depressions into an N-type germanium base from both sides with jets of indium sulfate until it was a few ten-thousandths of an inch thick. Indium electroplated into the depressions formed the collector and emitter.^[14][15] The first all-transistor car radio, which was produced in 1955 by Chrysler and Philco, used these transistors in its circuitry and also they were the first suitable for high-speed computers.^{[16][17][18][19]}

The first working silicon transistor was developed at Bell Labs on January 26, 1954 by Morris Tanenbaum.^[20] The first commercial silicon transistor was produced by Texas Instruments in 1954.^[21] This was the work of Gordon Teal, an expert in growing crystals of high purity, who had previously worked at Bell Labs.^[22] The first MOS transistor actually built was by Kahng and Atalla at Bell Labs in 1960.^[23]

In March 2013 American researchers at Stanford University announced they had built a transistor out of DNA and RNA molecules.^[24]

Inilah Resistor

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.

The current through a resistor is in direct proportion to the voltage across the resistor's terminals. This relationship is represented byOhm's law:

where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units ofvolts, and R is the resistance of the conductor in units of ohms.

The ratio of the voltage applied across a resistor's terminals to the intensity of current in the circuit is called its resistance, and this can be assumed to be a constant (independent of the voltage) for ordinary resistors working within their ratings.

Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel-chrome). Resistors are also implemented within integrated circuits, particularly analog devices, and can also be integrated into hybridand printed circuits.

The electrical functionality of a resistor is specified by its resistance: common commercial resistors are manufactured over a range of more than nine orders of magnitude. When specifying that resistance in an electronic design, the required precision of the resistance may require attention to the manufacturing tolerance of the chosen resistor, according to its specific application. The temperature coefficient of the resistance may also be of concern in some precision applications. Practical resistors are also specified as having a maximum power rating which must exceed the anticipated power dissipation of that resistor in a particular circuit: this is mainly of concern in power electronics applications. Resistors with higher power ratings are physically larger and may require heat sinks. In a high-voltage circuit, attention must sometimes be paid to the rated maximum working voltage of the resistor.

Practical resistors have a series inductance and a small parallel capacitance; these specifications can be important in high-frequency applications. In a low-noise amplifier or pre-amp, the noise characteristics of a resistor may be an issue. The unwanted inductance, excess noise, and temperature coefficient are mainly dependent on the technology used in manufacturing the resistor. They are not normally specified individually for a particular family of resistors manufactured using a particular technology.^[1] A family of discrete resistors is also characterized according to its form factor, that is, the size of the device and the position of its leads (or terminals) which is relevant in the practical manufacturing of circuits using them.

Resistor
A typical axial-lead resistor
Type	Passive
Working principle	Electric resistance
Electronic symbol

Axial-lead resistors on tape. The tape is removed during assembly before the leads are formed and the part is inserted into the board. In automated assembly the leads are cut and formed.

Inilah How To Solder

Soldering is defined as "the joining of metals by a fusion of alloys which have relatively low melting points". In other words, you use a metal that has a low melting point to adhere the surfaces to be soldered together. Consider that soldering is more like gluing with molten metal, unlike welding where the base metals are actually melted and combined. Soldering is also a must have skill for all sorts of electrical and electronics work. It is also a skill that must be taught correctly and developed with practice.
This tutorial will cover the most common types of soldering required for electronics work. This includes soldering components to printed circuit boards and soldering a spliced wire joint.

Soldering Equipment

The Soldering Iron/Gun

The first thing you will need is a soldering iron, which is the heat source used to melt solder. Irons of the 15W to 30W range are good for most electronics/printed circuit board work. Anything higher in wattage and you risk damaging either the component or the board. If you intend to solder heavy components and thick wire, then you will want to invest in an iron of higher wattage (40W and above) or one of the large soldering guns. The main difference between an iron and a gun is that an iron is pencil shaped and designed with a pinpoint heat source for precise work, while a gun is in a familiar gun shape with a large high wattage tip heated by flowing electrical current directly through it.

A 30W Watt Soldering Iron

For hobbyist electronics use, a soldering iron is generally the tool of choice as its small tip and low heat capacity is suited for printed circuit board work (such as assembling kits). A soldering gun is generally used in heavy duty soldering such as joining heavy gauge wires, soldering brackets to a chassis or stained glass work.

You should choose a soldering iron with a 3-pronged grounding plug. The ground will help prevent stray voltage from collecting at the soldering tip and potentially damaging sensitive (such as CMOS) components. By their nature, soldering guns are quite "dirty" in this respect as the heat is generated by shorting a current (often AC) through the tip made of formed wire. Guns will have much less use in hobbyist electronics so if you have only one tool choice, an iron is what you want. For a beginner, a 15W to 30W range is the best but be aware that at the 15W end of that range, you may not have enough power to join wires or larger components. As your skill increases, a 40W iron is an excellent choice as it has the capacity for slightly larger jobs and makes joints very quickly. Be aware that it is often best to use a more powerful iron so that you don't need to spend a lot of time heating the joint, which can damage components.

A variation of the basic gun or iron is the soldering station, where the soldering instrument is attached to a variable power supply. A soldering station can precisely control the temperature of the soldering tip unlike a standard gun or iron where the tip temperature will increase when idle and decrease when applying heat to a joint. However, the price of a soldering station is often ten to one hundred times the cost of a basic iron and thus really isn't an option for the hobby market. But if you plan to do very precise work, such as surface mount, or spend 8 hours a day behind a soldering iron, then you should consider a soldering station.

The rest of this document will assume that you are using a soldering iron as that is what the majority of electronics work requires. The techniques for using a soldering gun are basically the same with the only difference being that heat is only generated when the trigger is pressed.

Solder

The choice of solder is also important. There several kinds of solder available but only a few are suitable for electronics work. Most importantly, you will only use rosin core solder. Acid core solder is common in hardware stores and home improvement stores, but meant for soldering copper plumbing pipes and not electronic circuits. If acid core solder is used on electronics, the acid will destroy the traces on the printed circuit board and erode the component leads. It can also form a conductive layer leading to shorts.

For most printed circuit board work, a solder with a diameter of 0.75MM to 1.0MM is desirable. Thicker solder may be used and will allow you to solder larger joints more quickly, but will make soldering small joints difficult and increase the likelihood of creating solder bridges between closely spaced PCB pads. An alloy of 60/40 (60% tin, 40% lead) is used for most electronics work. These days, several lead-free solders are available as well. Kester "44" Rosin Core solder has been a staple of electronics for many years and continues to be available. It is available in several diameters and has a non-corrosive flux.

Large joints, such as soldering a bracket to a chassis using a high wattage soldering gun, will require a separate application of brush on flux and a thick diameter solder of several millimeters.

Remember that when soldering, the flux in the solder will release fumes as it is heated. These fumes are harmful to your eyes and lungs. Therefore, always work in a well ventilated area and avoid breathing the smoke created. Hot solder is also dangerous. It is surprisingly easy to splash hot solder onto yourself, which is a thoroughly unpleasant experience. Eye protection is also advised.

Preparing To Solder
Tinning The Soldering Tip
Before use, a new soldering tip, or one that is very dirty, must be tinned. "Tinning" is the process of coating a soldering tip with a thin coat of solder. This aids in heat transfer between the tip and the component you are soldering, and also gives the solder a base from which to flow from.
Step 1: Warm Up The Iron
Warm up the soldering iron or gun thoroughly. Make sure that it has fully come to temperature because you are about to melt a lot of solder on it. This is especially important if the iron is new because it may have been packed with some kind of coating to prevent corrosion.
Step 2: Prepare A Little Space
While the soldering iron is warming up, prepare a little space to work. Moisten a little sponge and place it in the base of your soldering iron stand or in a dish close by. Lay down a piece of cardboard in case you drip solder (you probably will) and make sure you have room to work comfortably.
Step 3: Thoroughly Coat The Tip In Solder
Thoroughly coat the soldering tip in solder. It is very important to cover the entire tip. You will use a considerable amount of solder during this process and it will drip, so be ready. If you leave any part of the tip uncovered it will tend to collect flux residue and will not conduct heat very well, so run the solder up and down the tip and completely around it to totally cover it in molten solder.
Step 4: Clean The Soldering Tip
After you are certain that the tip is totally coated in solder, wipe the tip off on the wet sponge to remove all the flux residue. Do this immediately so there is no time for the flux to dry out and solidify.
Step 5: You're Done!
You have just tinned your soldering tip. This must be done anytime you replace the tip or clean it so that the iron maintains good heat transfer.
Soldering A Printed Circuit Board (PCB)
Step 1: Surface Preparation:
A clean surface is very important if you want a strong, low resistance solder joint. All surfaces to be soldered should be cleaned well. 3M Scotch Brite pads purchased from the home improvement, industrial supply store or automotive body shop are a good choice as they will quickly remove surface tarnish but will not abrade the PCB material. Note that you will want industrial pads and not the kitchen cleaning pads impregnated with cleaner/soap. If you have particularly tough deposits on your board, then a fine grade of steel wool is acceptable but be very cautious on boards with tight tolerances as the fine steel shavings can lodge between pads and in holes.
Step 2: Component Placement
After the component and board have been cleaned, you are ready to place the components onto the board. Unless your circuit is simple and only contains a few components, you will probably not be placing all the components onto the board and soldering them at once. Most likely you will be soldering a few components at a time before turning the board over and placing more. In general it is best to start with the smallest and flattest components (resistors, ICs, signal diodes, etc.) and then work up to the larger components (capacitors, power transistors, transformers) after the small parts are done. This keeps the board relatively flat, making it more stable during soldering. It is also best to save sensitive components (MOSFETs, non-socketed ICs) until the end to lessen the chance of damaging them during assembly of the rest of the circuit.
Step 3: Apply Heat
Apply a very small amount of solder to the tip of the iron. This helps conduct the heat to the component and board, but it is not the solder that will make up the joint. To heat the joint you will lay the tip of the iron so that it rests against both the component lead and the board. It is critical that you heat the lead and the board, otherwise the solder will simply pool and refuse to stick to the unheated item. The small amount of solder you applied to the tip before heating the joint will help make contact between the board and the lead. It normally takes a second or two to get the joint hot enough to solder, but larger components and thicker pads/traces will absorb more heat and can increase this time.
Step 4: Apply Solder To The Joint
Once the component lead and solder pad has heated up, you are ready to apply solder. Touch the tip of the strand of solder to the component lead and solder pad, but not the tip of the iron. If everything is hot enough, the solder should flow freely around the lead and pad. You will see the flux melt liquify as well, bubble around the joint (this is part of its cleaning action), flow out and release smoke. Continue to add solder to the joint until the pad is completely coated and the solder forms a small mound with slightly concave sides. If it starts to ball up, you have used too much solder or the pad on the board is not hot enough.
Step 5: Inspect The Joint and Cleanup
Once the joint is made you should inspect it. Check for cold joints (described a little above and at length below), shorts with adjacent pads or poor flow. If the joint checks out, move on to the next. To trim the lead, use a small set of side cutters and cut at the top of the solder joint.

















You can also watch the tinning process on video below (requires Flash):





Soldering a PCB is probably the most common soldering task an electronics hobbyist will perform. The basic techniques are fairly easy to grasp but it is a skill that will take a little practice to master. The best way to practice is to buy a simple electronics kit or assemble a simple circuit (such as an LED chaser) on a perf-board. Don't buy that expensive kit or dive into a huge project after only soldering a few joints.

Soldering components onto a PCB involves preparing the surface, placing the components, and then soldering the joint.



Once you have cleaned the board down to shiny copper you can use a solvent such as acetone to clean any bits of the cleaning pad that may remain and to remove chemical contamination from the surface of the board. Methyl hydrate is another good solvent and a bit less stinky then acetone. Be aware that both these solvents can remove ink, so if your board is silk screened, test the chemicals first before hosing down the entire board.

A few blasts with compressed air will dry out the board and remove any junk that may have built up in the holes.

It also never hurts to give the component leads a quick wipe down as well, to remove glue or tarnish that may have built up over time.



Bend the leads as necessary and insert the component through the proper holes on the board. To hold the part in place while you are soldering, you may want to bend the leads on the bottom of the board at a 45 degree angle. This works well for parts with long leads such as resistors. Components with short leads such as IC sockets can be held in place with a little masking tape or you can bend the leads down to clamp onto the PC board pads.

In the image below, a resistor is ready to solder and is held in place by slightly bent leads.





If you see the area under the pad starting to bubble, stop heating and remove the soldering iron because you are overheating the pad and it is in danger of lifting. Let it cool, then carefully heat it again for much less time.







Once the surface of the pad is completely coated, you can stop adding solder and remove the soldering iron (in that order). Don't move the joint for a few seconds as the solder needs time to cool and resolidify. If you do move the joint, you will get what's called a "cold joint". This is recognized by it's characteristic dull and grainy appearance. Many cold joints can be fixed by reheating and applying a small amount of solder, then being allowed to cool without being disturbed.







After you have made all the solder joints, it is good practice to clean all the excess flux residue from the board. Some fluxes are hydroscopic (they absorb water) and can slowly absorb enough water to become slightly conductive. This can be a significant issue in a hostile environment such as an automotive application. Most fluxes will clean up easily using methyl hydrate and a rag but some will require a stronger solvent. Use the appropriate solvent to remove the flux, then blow the board dry with compressed air.