As a rule, when soldering conventional radio elements with a small number of conclusions, there are no problems. But when dismantling multi-output electronic components, such as microcircuits, line transformers, multi-output variable resistors, difficulties arise even for those who can accurately and correctly solder.
To dismantle multi-pin parts, you need a tool with which you can easily remove the solder from the place of the soldered contact. To effectively remove the solder, you can use a few simple devices.
How to use a copper braid?
Using a copper braid is quite simple. It is necessary to attach a copper braid to the place where it is necessary to remove the solder and, pressing it with a heated tip of the soldering iron, wait for the moment when the solder is melted and absorbed by the braid under the action of the capillary effect. In this case, it will be clearly visible how the liquid solder is absorbed by the copper braid, and the place around the output and the printing path itself remain clean from the solder. The used piece of copper braid, filled with solidified solder, is bitten off by nippers.
It should be remembered that braid braid is different. So, for example, you can hear criticism of the quality of the copper braid, which is produced by little-known firms and the praise of the products of such firms as Weller or Goot wick. And indeed it is.
For example, I was disappointed in braiding brands such as Pro'skit or Rexant. The veins are thick and not twisted into a pigtail. You can work with such a braid, but I would not dare to use it when repairing important and expensive components.
In the photo - a copper braid coil. Marked very succinctly - SOLDER WICK. The quality is very good, but there are trifling flaws. The braid is highly compressed and elongated - probably in order to save on copper. What can be done to comfortably use this copper braid for your own purposes?
First of all, you need to “fluff” the copper braid so that there is as much free space between the copper conductors as possible. Since the action of the copper braid is based on the capillary effect, it is necessary to ensure that molten solder can rise up the copper conductors and fill the space between them. To do this, of course, you need to provide free space between the copper conductors.
It also does not hurt to impregnate the braid with liquid flux. Suitable LTI-120. Gumboil weakens surface tension and promotes uniform coating of copper conductors with liquid solder. Of course, you can use a solid, lumpy rosin, but to achieve a good effect will be more difficult.
Using a copper braid, you can easily remove solder jumpers between the terminals of the microcircuits that can form when the multi-pin chip is mounted on a printed circuit board.
Once I saw a report on TV from a Chinese electronics factory, where the installer removed excess solder between the terminals of the microcircuit, gently holding a copper braid under the soldering iron sting along the terminals of the microcircuit on the board - it looked very impressive!
Previously, a copper braid could be bought either at the radio market or at the radio store. Now copper braid is easy to buy on the Internet, for example, at the well-known Aliexpress. It turns out cheaper than in stores.
I took the Goot Wick braid for myself, which is considered one of the best. I bought immediately 5 pieces of different widths (1.5mm, 2.0mm, 2.5mm, 3mm, 3.5mm) and a length of 1.5 meters each. At that time, a little more than $ 1 apiece came out.
There are just a huge number of positions, you can even buy a coil of 20 meters. Here is the link to the Goot Wick, choose.
It is clear that the only minus of using a copper braid to remove solder is that it is a consumable item and can end at the most inopportune moment. This drawback is devoid of a special tool called desolder.
Desolder (Desoldering pump).
Word desolder come from an english word desoldering - desoldering, solder removal.
The desolder itself, or in another way a desoldering pump, is a cylindrical tube, on one side of which a narrow nose is fixed, and on the other a piston mechanism with a handle and a button. A rigid spring is placed inside this device, which pushes the piston.
The photo below shows a mechanical desolder in parsing. As you can see, this simple tool consists of a narrow nose, a hollow cylinder, a spring and a piston with a lock.
How to use a desoldering pump?
In order to remove the solder from the place of the soldered contact, we melt the solder at the contact point with a soldering iron. To give molten solder better fluidity, we use rosin or flux. Rosin and flux helps to reduce the surface tension of the metal and increases the fluidity of the molten solder.
Next, fix the desolder piston by pressing the lever until it clicks. In this case, the piston will be fixed, and the spring will be in a compressed state. Without stopping the heating of the place where you need to remove the solder, we bring the narrow tip of the desoldering pump to the place of soldering. Press the desolder lock button. In this case, the piston will move sharply due to the compressed spring and will create a vacuum of air in the cylinder, due to which the molten solder is drawn into the cylinder. The surface of the print track and the output remains clean from solder.
Using the desolder is quite convenient, but there are some disadvantages.
With frequent use of the desolder, its main negative quality is manifested - contamination of the piston mechanism with pieces of solder mixed with rosin. In this case, a mixture of solder and flux crumbs adhere to the cylinder walls and the spring. This interferes with the free movement of the piston in the cylinder and, of course, complicates the work.
To clean the desolder, it is necessary to disassemble it and clean it. As a cleaning agent, for example, a spray cleaner can be used. Degreaser. It well dissolves rosin, which interlocks pieces of solder. After applying the spray cleaner, we clean the inner walls of the hollow cylinder and the nozzle with a brush. Then the cylinder must be wiped with a cloth, removing the remnants of solder and cleaning agent. After this procedure, the desolder is ready for use again. Cleaning can also be carried out using other means, for example, isopropyl alcohol ("Universal Cleaner"). This is sold in radio stores.
A good desolder can be bought all on the same Ali. Here is the link to the extradition with desolders. It can be filtered by the number of orders, the availability of new products or the seller’s rating. Choose what you like.
The desolder is useful where it is necessary to remove radio components with large cross-section terminals from the circuit board. It can be transformers, TDKSs, line transistors in picture tubes TV, IGBT transistors in welding inverters, metal screens and radiators. In general, where a lot of solder is used for installation, it is irrational to use a copper braid.
At a time when tools like a desolder were not widely sold, radio mechanics used a rubber bulb.
The use of rose alloy.
In addition to the listed devices and materials, I want to advise one more. This is an alloy of Rose. A distinctive quality of this alloy is its low melting point (about 95. 100 0 С). This makes it an indispensable assistant in the soldering of miniature components. In addition, it can come in handy when re-installing them. For example, in the case when overheating of the component is undesirable.
In addition to the Rose alloy, there is another low-temperature alloy, the melting point of which is even lower than that of Rose. This is a Wood alloy (65-72 0 C). Surely you will want to use it in your practice. But, I want to note that Wood's alloy toxicsince it contains cadmium (about 10% alloy). therefore use him in everyday work i strongly recommend.
Rose alloy alloy soldering technology is as simple as twice two. Its essence is to dissolve the “native” solder with a lower-temperature alloy. Due to diffusion, the Rose alloy dissolves in a higher temperature solder, with which the component is soldered to the board. Due to this, its melting point decreases. Alloy Rose as if replaces the "native" solder. At the same time, an electronic component, module or even a block can be easily and safely removed with a soldering iron or a hairdryer of a hot air soldering station.
Naturally, after the electronic component is removed from the board, the remnants of solder from the contacts and the tip of the soldering iron must be removed with a copper braid. If this is not done, then the presence of residues of the low-temperature alloy will lead to degradation of the solder, especially if the electronic part or component is very hot during its operation. I think this is already clear, no need to explain.
An exception to this rule can be considered, for example, sealing a microphone module on a smartphone board. The microphone module is very sensitive to overheating, therefore, the Rose alloy can be used as the main solder. During operation, the microphone module does not heat up, and the soldering turns out to be of high enough quality so that the device will work for more than one year.
The disadvantages of the Rose alloy can only be attributed to the fact that it is quite expensive. Therefore, many initially avoid using it in their amateur radio practice. Also, do not try to search for it in Aliexpress or other Chinese online stores. The fact is that bismuth is a rather rare metal and its export from China in its pure form is prohibited. The same applies to the Wood alloy containing cadmium, which is also toxic. Its free shipment is limited.
In some cases, it is allowed to use a soldering iron for dismantling, which, by heating a large area, melts the solder at all contacts.
But using a hairdryer can be inconvenient with tight installation. It is possible to heat the solder on the legs of adjacent components.
Dismantling is ideal, in which the pads will remain clean and tinned. Mechanical and chemical methods are sometimes used.
To accurately remove the solder from the board, it is better to use a soldering iron. In this case, several options are possible:
- remove solder directly to the soldering iron tip,
- use a desoldering pump to remove excess solder,
- remove with braid.
You can mechanically remove the solder with a file or a file. This method is quick, but rude. When using the chemical method, the solder is dissolved by aggressive materials, for example, any acid solutions.
Sometimes, compressed air is used to clean the circuit board, which blows off excess material. But this method is rarely used, since it is rude and even quite traumatic.
Sting removal and desoldering pump
To remove the solder on the soldering iron tip, you must thoroughly clean it and cover it with flux. Then, when the solder is melted at the contact pads, the latter will stick to the tip and the pad will be cleaned.
This method is not very convenient in that at a time it allows you to collect only a small amount of material, and then you have to clean the sting again.
Desoldering pump - a tool, structurally consisting of a tube with a spring-loaded piston. At one end of the tube is a suction device. Before starting work, the piston is pressed into the tube and fixed using the button.
To remove the solder from the contacts, it is necessary to heat it with a soldering iron and approaching the suction device of the desoldering pump, release the piston by pressing the button.
The piston, moving under the action of the spring, will create a vacuum in the tube, which will pull in its molten solder. To remove the collected tin, it is enough to disassemble the body of the desoldering pump.
Braided copper tape
The most effective way to remove solder from the circuit board is the one that uses a braid, that is, a braided tape made of copper wires. It can be made independently by removing it from the shielded wire and cutting it into pieces of the desired length, or can be purchased in the store.
On sale there are many options for this device.
In most cases, the flux-coated braid is wound into a skein on a plastic bobbin. Sometimes such a bobbin is enclosed in a plastic case with a special bend for more convenient use of the braid.
The product can be designated in different ways - a thread for removing solder, a soldering tape, a braid for soldering. In any name, this is usually the same material, which allows you to quickly and efficiently remove solder from the board.
How to use
To use the braid when removing solder, you will need a soldering iron and a bottle with liquid flux.
If there is no liquid flux, take any other, but it will work uncomfortably. You can prepare a liquid flux yourself if you dissolve in advance pieces of pine rosin in alcohol or pieces of zinc in hydrochloric acid.
A copper braid is best for removing solder alloy. A section of the braid must be coated with a flux. This can be done with a brush, but it is better that the entire surface on which the solder will be collected is covered, and parts of the wires inside the braid will remain inaccessible.
It will be more effective to apply the flux by immersing the end of the braid into it. To do this, it is better to use a stable vessel with a wide enough throat.
After wetting the braid with flux, it is applied to the place from which it is necessary to remove the solder, and heated with a soldering iron. A heated braid transfers heat to the solder, and that, melting, sticks to the braid, leaving the contacts clean.
When a sufficient amount has been collected to prevent further collection, the end of the braid is cut off and the next section is used.
After cleaning one of the contacts, the steps are repeated with each subsequent until complete cleaning or until the component is released from the board. As a result of high-quality cleaning, the mounting holes are flat, and the contact pads remain clean and tinned.
How to do it yourself
The braid for removal is a consumable and should be in the arsenal of every electrician involved in the manufacture and repair of electronic modules.
But sometimes a situation arises when there is neither a braid nor a suitable shielded wire at hand. Then you can make such a device from any copper flexible stranded wire with thin hairs.
To do this, remove the insulation from the wire and twist the hairs a little to collect them in a bundle.
The braid produced by industry is, as a rule, already covered with flux, and the need for additional wetting disappears. Working with such material is, of course, more convenient. The segments with assembled solder can not be thrown away, but used later for tinning of contacts.