I. Soldering Iron
A soldering iron is a hand tool commonly used for welding, which heats the solder and the metal to be welded.
Molten solder wets the surface of the metal to be welded and forms an alloy. The soldering iron is an indispensable tool in the assembly process of electronic products, and the types commonly used are as follows.
1. Direct heating soldering iron
(1) Externally heated soldering iron
The externally heated soldering iron consists of an iron tip, iron core, shell, wooden handle, power cord and plug. Because the iron tip is installed inside the iron core, it is called an externally heated soldering iron.
Specifications
External heat soldering irons come in various specifications, including commonly used ones such as 25W, 45W, 75W and 100W. The higher the power, the higher the temperature of the soldering tip.
soldering iron core
The soldering iron core is a critical component of the soldering iron. It is constructed by winding electrical heating wire in parallel around a hollow ceramic tube, with insulating sheets of mica in between, and two wires extended for connection to a 220V AC power supply.
(2) Internally heated soldering iron
The internal heating soldering iron is composed of a handle, connecting rod, spring clip, soldering iron core and soldering iron tip. As the iron core is installed inside the tip, it heats up quickly and offers high thermal efficiency, which is why it is called an internally heated soldering iron.
Specifications
Common specifications for internally heated soldering iron are 20W and 50W. Due to its high thermal efficiency, a soldering iron with internal heating of 20W is equivalent to a soldering iron with external heating of approximately 40W.
Characteristics
The rear end of the internally heated soldering iron is hollow, designed to fit the connecting rod, and is secured with a spring clip. When it is necessary to replace the iron tip, the spring clip must first be removed. Then, using pliers, grasp the front end of the iron tip and gently pull it out. It is crucial not to use excessive force to avoid damaging the connecting rod.
(3) Differences between internally heated and externally heated soldering irons
1. Their structures differ, resulting in different heating methods.
2. Internal heating irons have less heat loss and shorter preheating time; External heating irons have greater heat loss, lower heating efficiency and a slightly longer preheat time.
3. The shape of the soldering iron tips they use is different; the former is a hollow cylinder while the latter is a solid rod.
4. Internally heated soldering iron tips have a shorter service life and the iron core is prone to breakage; External heating soldering iron tips have a longer service life.
5. Internal heating irons are lower power, available in 20W, 35W and 50W specifications, mainly used for soldering small components. External heating irons have higher power, with specifications ranging from 25W, 30W, 50W to 75W, 100W, 150W and 300W, suitable for soldering small and large components.
2. Thermostatic soldering iron
Requirements:
When soldering integrated circuits and transistor components, the temperature cannot be too high and the soldering time cannot be too long.
Otherwise, components may be damaged due to excessive heat. Therefore, the temperature of the soldering iron must be regulated.
Principle:
The thermostatic soldering iron contains a magnetic temperature controller that controls the on time to achieve temperature control. When the soldering iron is turned on, its temperature increases.
Upon reaching the set temperature, the strong magnetic sensor reaches its Curie point, losing its magnetism, causing the contact of the magnetic core to break and thus interrupting the power supply to the soldering iron.
When the temperature drops below the Curie point of the strong magnetic sensor, magnetism is restored, attracting the permanent magnet in the magnetic core switch, thereby making control switch contact and continuing to power the soldering iron. This cycle repeats itself, achieving the objective of temperature control.
Benefits:
1. Intermittent heating not only saves energy, but also prevents the soldering iron from overheating, prolonging its service life.
2. Fast heating time, requiring only 40 to 60 seconds.
3. The soldering iron tip uses a tinning quenching process, ensuring a longer service life.
4. Constant temperature is not affected by power supply voltage and ambient temperature. For example, a 50W 270°C thermostatic soldering iron can maintain a constant temperature with a supply voltage between 180V-240V and can reach 270°C after being turned on for 5 minutes.
3. Temperature controlled soldering iron
The temperature-controlled soldering iron comes equipped with a power controller, which allows adjustments to the input power during use. The temperature can be regulated within a range of 100 to 400 degrees Celsius.
The maximum power of the temperature-controlled soldering iron is 60 W and is combined with a copper-plated iron soldering tip, colloquially known as a long-life tip.
4. The Solder Sucker Soldering Iron
A solder sucker is a desoldering tool that combines a piston-driven solder sucker with a soldering iron.
The operation of the solder sucker soldering iron is as follows: Connect the power to preheat for 3 to 5 minutes, then push down and lock the piston handle; Position the tip of the solder sucker soldering iron towards the solder joint to be desoldered, wait for the solder to melt, and then press the button on the handle of the solder sucker soldering iron, the piston will automatically rise and the solder will be sucked in by the tip, allowing the component cable to disconnect from the solder pad.
Additionally, the solder sucker comes with two or more tips of different diameters, which can be selected based on the thickness of the component terminals.
Characteristics
The solder sucker soldering iron is known for its ease of use, flexibility and wide range of applications. One disadvantage of this type of solder-sucking soldering iron is that it can only desolder one solder joint at a time.
The solder sucker soldering iron comes with its own power source, making it suitable for desoldering entire integrated circuits in situations where speed is not a high priority. The durability of the iron tip is determined by the materials used in the solder sucking nozzle, heating tube and sealing ring.
(1) Long-lasting electric soldering iron
The long-lasting electric soldering iron shares the same structure and principle as the common type. The difference lies in the special process applied to the iron tip of the long life model, which involves a coating of pure iron or nickel on the copper surface.
This treatment significantly extends its lifespan, typically making it about 20 times longer than a normal soldering iron. When using this type of soldering iron, the tin must always be kept at the tip of the iron.
(2) Long infrared welding torch
The heating principle of the infrared welding torch involves infrared radiation. The infrared light source is placed on the reflective side of an ellipsoid, where the light rays converge to another focal point, reaching the temperature required for welding.
This torch is suitable for welding components such as surface-mounted devices, particularly in thermal forming and other hot welding operations of internally mounted tube pins and heat-shrinkable plastics.
(3) Electric soldering iron with long energy storage
Energy storage electric soldering iron is used for integrated circuits, especially for charge-sensitive MOS circuits. The soldering iron itself does not connect to a power source.
When inserted into the corresponding power source, the soldering iron enters an energy storage state. During welding, the iron is removed and the energy stored in it is used to complete the welding process, capable of welding several joints at the same time.
(4) LongOthers
There are also other types of soldering irons, such as the rechargeable battery-powered carbon arc soldering iron, the ultrasonic soldering iron that can remove the oxide layer from the welded parts, and the automatic soldering iron equipped with an automatic soldering device. welding wire feed. .
5. Precautions when using a soldering iron
1. Select the appropriate soldering iron type (power, shape) based on the object to be soldered.
2. It is best to use a three-pin plug for the soldering iron. Ensure adequate grounding of the box.
3. Before use, carefully inspect the power plug and cord for damage. Check whether the soldering iron tip is loose. Measure the resistance at the plug to ensure it meets the requirements.
4. Avoid hitting the soldering iron hard during use. Prevent it from falling. Excess solder on the tip of the iron can be removed with a cloth. Do not throw it away to avoid burning others. Regular tinning must be carried out during use.
5. The soldering iron should not be left randomly during use. When not soldering, place it on the soldering iron holder. Be careful not to let the power cord touch the tip of the soldering iron to avoid damage and accidents to the insulation layer.
6. After use, immediately disconnect the power and unplug the iron. Once cool, store the soldering iron back in the tool box.
II. Other auxiliary tools
1. Soldering iron holder
The soldering iron stand is used to support the soldering iron. The sponge located below the soldering iron holder is used to clean the soldering iron tip.
Careful:
1. Place the heated soldering iron on the soldering iron holder to avoid burns or fire hazard.
2. When using the water absorbent sponge, make sure the water content is sufficient to keep it upright without dripping. Excess water can accelerate the oxidation of the soldering iron tip at high temperatures, thus reducing its useful life.
2. Solder Sucker
A solder sucker is a tool used for desoldering.
Operational steps:
1. First, push the weld sucker piston rod down until it locks.
2. Use a soldering iron to heat the solder joint until the solder melts.
3. When removing the soldering iron, quickly place the solder sucker mouth on the solder joint and press the solder sucker button.
4. If the solder is not completely removed at once, repeat the operation as necessary.
3. Tweezers
Tweezers can be divided into pointed tip tweezers and round tip tweezers. Pointed tip tweezers are used to hold thin wires, facilitating assembly and soldering.
On the other hand, round-tip tweezers are used to grasp bent component cables and assist in soldering processes. Using tweezers to hold components during soldering can also serve as a means of heat dissipation.
4. Diagonal Pliers
Diagonal pliers, also known as “side cutters”, can be used to cut the rubber or plastic insulation of soft electrical wires, as well as to cut iron wires and wires. They are commonly used to trim excess extended cables from components after soldering.
5. Screwdriver
The screwdriver, also known as a rotary screw or screwdriver, comes in two types: flat head and Phillips. It is specifically used for turning screws, and the appropriate size should be chosen based on the size of the screw.
When adjusting inductive components such as magnetic cores, a non-inductive screwdriver must be used.
6. Needle-nose pliers
Needle-nose pliers, also known as pointed-nose pliers, are mainly used for cutting thin wires, bending wire joints, and removing plastic insulation. Its cutting edges can meticulously cut small components.
III. Welding Materials
Welding materials refer to the general term for materials consumed during welding.
1. Soldering
Benefits:
The use of solder as a welding flux has benefits such as low melting point, excellent fluidity and adhesion, corrosion resistance, high mechanical strength, convenience of use and low cost.
2. Flow
When a metal surface comes into contact with air, an oxide film forms. The higher the temperature, the more severe the oxidation will be.
This oxide layer prevents molten solder from wetting the metal, much like the oil on glass prevents water from wetting it. Flux is a specific material used to remove this oxide film. Therefore, in tin-lead welding, flux is an indispensable material.
Flow Functions
- Cleans the weld surface, removing the oxide film
- Prevents oxidation during heating
- Reduces surface tension, improving solder flow, which helps wetting
- Makes solder joints attractive while maintaining the surface shine of the solder point.
3. Weld resistance
During welding, only a small part is welded and the rest is left unsoldered to avoid damage to the remaining components. Therefore, it is essential to apply welding resistance.
Weld resistance serves the following purposes:
Helps avoid or reduce bridges and whiskers during welding, ensuring complete solder joints, improving welding quality, ensuring product reliability and reducing rework.
After using resistance welding, welding cannot be applied to all lines except the welding pad, thus saving a significant amount of welding material. Furthermore, due to less heat exposure and rapid cooling, the temperature of the printed circuit board can be reduced, which provides protection to the components and integrated circuits.
4. Cleaning agent
Flux residues that leave traces after welding must be cleaned. The function of the cleaning agent is to remove flux, oil stains and the like around the welding area.
Following are some types of cleaning agents:
- Trichloroethylene
- Alcohol
- Hexane
What harm can cleaning agents cause to the human body?
- Trichloroethylene: Mainly, it has an anesthetic effect on the human central nervous system and is toxic. Furthermore, it can cause water and air pollution.
- Alcohol: As it is a highly volatile liquid, when it comes into contact with the skin it removes moisture, accelerating skin aging.
- Hexane: Has an anesthetic and irritating effect. Long-term exposure can cause headaches, dizziness, fatigue and decreased appetite. It is considered a toxic substance.
