It is known that if a chip is damp, then when you try to solder such a chip, it will swell with bubbles and will not work properly. And taking into account the cost of chips, their delivery time and the complexity of repairs, this is very expensive. I searched a lot on the Internet. Eat different tips, from - dry on table lamp to a household oven. There is also very expensive equipment. None of the advice suited me personally (like my friend in Germany, he had been looking for something similar for a long time.). In theory, each chip should have documentation that describes at what temperature and how long it should dry before soldering. This is correct, but not always available to most repairmen.
If we summarize all the information, it turns out that for normal drying of the chip, it must be at a temperature of approximately 130 degrees Celsius. about 8-10 hours. This does not harm it, but it does remove moisture. I do not claim originality, but I want to share the device that I use myself and my friend in Germany (I did it on my advice). Perhaps it will be useful to others too. Since use of this device, I’ve never had any problems with any chip, I’ve ordered it from both China and Russia.
Oven for chips made from scrap materials over a couple of weekends. The body is made of pressed paper with lamination. These were pieces from decorative furniture finishing, 6 mm thick. Although you can use any temperature-resistant material (must keep the temperature at least up to 180 degrees C. and higher). Connections are made with M3 screws. As heating elements 20 watt ceramic resistors with a nominal value of 15 Ohms were used (you can use from 10 to 18 Ohms). Only 6 pieces, since the oven is designed for simultaneous drying of 2-3 chips.
For one chip, 3-4 resistors will be enough. An electro-mechanical thermostat at 130 degrees C was used as a temperature maintaining element. For protection (not pictured), a 10 A, 180 degree C thermal fuse is pressed to one of the resistors from below. All resistors are connected in parallel. Those. the entire circuit consists of series-connected: a thermal fuse, a thermostat, a group of resistors. For clarity, a 12 V LED (or 3.5 V through a 510 Ohm resistor) is connected in parallel with the resistors. The entire device is powered by a computer power supply (there was an old one with 200 W). Although any 12 V power source and a current of about 5 A will be suitable. A cover made of the same material as the body is placed on top of the device. This improves thermal stability and reduces switching frequency.
Pros: ease of manufacture and availability of materials. (Thermostat and resistors can be purchased at almost any radio store).
Of the minuses: The thermostat has a very large hysteresis, almost 40 degrees C. That is, it turns off at 130 degrees C, and turns on at 90 degrees C. But this does not harm the chip in any way; rather, on the contrary, it does not allow a very damp chip to swell. The photo shows the device from below (without wires and thermal fuse) and actually in operation. The device has been in use for about a year. I hope this information will be useful!
Oven for drying chips
Good day. I had to do laptop repairs. And the problem arose of how to dry the chip before soldering. It is known that if a chip is damp, then when you try to solder such a chip, it will swell with bubbles and will not work properly. I myself had it a couple of times in the beginning. And taking into account the cost of chips, their delivery time and the complexity of repairs, this is very expensive. I searched a lot on the Internet. There are different tips, from drying it on a table lamp to using a household oven. There is also very expensive equipment. None of the advice suited me personally (like my friend in Germany, he had been looking for something similar for a long time.). In theory, each chip should have documentation that describes at what temperature and how long it should dry before soldering. This is correct, but not always available to most repairmen. If we summarize all the information, it turns out that for normal drying of the chip, it must be at a temperature of approximately 130 degrees Celsius. about 8-10 hours. This does not harm it, but it does remove moisture. I do not claim originality, but I want to share the device that I use myself and my friend in Germany (I did it on my advice). Perhaps it will be useful to others too. Since using this device, there have never been any problems with any chip; I ordered it from both China and Russia.
Oven for chips made from scrap materials over a couple of weekends. The body is made of pressed paper with lamination. These were pieces from decorative furniture trim, 6 mm thick. Although you can use any temperature-resistant material (must keep the temperature at least up to 180 degrees C. and higher). Connections are made with M3 screws. 20-watt ceramic resistors with a nominal value of 15 Ohms were used as heating elements (you can use from 10 to 18 Ohms). Only 6 pieces, since the oven is designed for simultaneous drying of 2-3 chips. For one chip, 3-4 resistors will be enough. An electro-mechanical thermostat at 130 degrees C was used as a temperature maintaining element. For protection (not pictured), a 10 A, 180 degree C thermal fuse is pressed to one of the resistors from below. All resistors are connected in parallel. Those. the entire circuit consists of series-connected: a thermal fuse, a thermostat, a group of resistors. For clarity, a 12 V LED (or 3.5 V through a 510 Ohm resistor) is connected in parallel with the resistors. The entire device is powered by a computer power supply (there was an old one with 200 W). Although any 12 V power source and a current of about 5 A will be suitable. A cover made of the same material as the body is placed on top of the device. This improves thermal stability and reduces switching frequency.
Pros: ease of manufacture and availability of materials. (Thermostat and resistors can be purchased at almost any radio store).
Of the minuses: The thermostat has a very large hysteresis, almost 40 degrees C. That is, it turns off at 130 degrees C, and turns on at 90 degrees C. But this does not harm the chip in any way; rather, on the contrary, it does not allow a very damp chip to swell. The photo shows the device from below (without wires and thermal fuse) and actually in operation. Device
Modern radio-electronic devices cannot be imagined without microcircuits - complex parts into which, in fact, dozens, or even hundreds of simple, elementary components are integrated.
Microcircuits allow you to do devices light and compact. You have to pay for this with the convenience and ease of installation and the rather high price of the parts. The price of a microcircuit does not play an important role in determining the overall price of the product in which it is used. If such a part is damaged during installation, when replacing it with a new one, the cost may increase significantly. It is not difficult to solder a thick wire, a large resistor or a capacitor, all you need is basic soldering skills. The microcircuit must be soldered in a completely different way.
To avoid annoying misunderstandings, when soldering microcircuits it is necessary to use certain tools and follow certain rules based on extensive experience and knowledge.
To solder microcircuits, you can use various soldering equipment, ranging from the simplest - a soldering iron, to complex devices and soldering stations using infrared radiation.
A soldering iron for soldering microcircuits should be low-power, preferably designed for a supply voltage of 12 V. The tip of such a soldering iron should be sharply sharpened to a cone and well tinned.
To desolder microcircuits, a vacuum desoldering pump can be used - a tool that allows you to remove solder from the legs on the board one by one. This tool is similar to a syringe in which the piston is spring-loaded upward. Before starting work, it is pressed into the body and fixed, and when necessary, it is released by pressing a button and rises under the action of a spring, collecting solder from the contact.
A hot-air station is considered a more advanced equipment, which allows both dismantling of microcircuits and soldering with hot air. This station has in its arsenal a hairdryer with adjustable air flow temperature.
A piece of equipment such as a heat table is very popular when soldering microcircuits. It heats the board from below, while installation or dismantling is carried out from above. Optionally, the heating table can be equipped with top heating.
IN industrial scale soldering of microcircuits is carried out by special machines using infrared radiation. In this case, the circuit is preheated, soldered directly, and the contacts of the legs are cooled step by step.
At home
Soldering microcircuits at home may be required to repair complex household appliances, computer motherboards.
As a rule, to solder the legs of the microcircuit, use a soldering iron or soldering gun.
Working with a soldering iron is carried out using regular solder or solder paste.
Recently, lead-free solder has become increasingly used for soldering with more high temperature melting. This is necessary to reduce the harmful effects of lead on the body.
What equipment will be required?
To solder microcircuits, in addition to the soldering equipment itself, you will need some other equipment.
If the microcircuit is new and made in a BGA package, then the solder is already applied to the legs in the form of small balls. Hence the name - Ball Grid Array, which means an array of balls. These enclosures are designed for surface mounting. This means that the part is installed on the board, and each leg is soldered to the contact pads with a quick, precise action.
If the microcircuit has already been used in another device and is used as used spare parts, it is necessary to perform a reballing. Reballing is the process of restoring the solder balls on the legs. Sometimes it is also used in the case of a blade - loss of contact of the legs with the contact patches.
To carry out reballing, you will need a stencil - a plate of refractory material with holes located in accordance with the location of the microcircuit pins. There are ready-made universal stencils for several of the most common types of microcircuits.
Solder paste and flux
For proper soldering of microcircuits, certain conditions must be met. If the work is carried out with a soldering iron, then its tip should be well tinned.
For this, flux is used - a substance that dissolves the oxide film and protects the tip from oxidation before being coated with solder during soldering of the microcircuit.
The most common flux is pine rosin in a solid, crystalline form. But to solder a microcircuit, such a flux is not suitable. Its legs and contact spots are treated with liquid flux. You can make it yourself by dissolving rosin in alcohol or acid, or you can buy it ready-made.
In this case, it is more convenient to use solder in the form of filler wire. Sometimes it may contain powdered rosin flux inside. You can purchase a ready-made soldering kit for soldering microcircuits, which includes rosin, liquid flux with a brush, and several types of solder.
When performing reballing, solder paste is used, which is a base of viscous material, which contains tiny balls of solder and flux. This paste is applied thin layer on the legs of the microcircuit with reverse side stencil. After this, the paste is heated with a hairdryer or infrared soldering iron until the solder and rosin melt. After hardening, they form balls on the legs of the microcircuit.
Work order
Before starting work, it is necessary to prepare all tools, materials and devices so that they are at hand.
When installing or dismantling, the board can be placed on a thermal table. If a soldering gun is used for dismantling, then to prevent its impact on other components, you need to isolate them. This can be done by installing plates made of refractory material, for example, strips cut from old circuit boards that have become unusable.
When using a desoldering pump for dismantling, the process is more accurate, but takes longer. The desoldering pump “charges” as it cleans each leg. As it fills with pieces of solidified solder, it needs to be cleaned.
There are several soldering rules that must be followed:
- Soldering the microcircuits on the board must be done quickly so as not to overheat the sensitive part;
- You can hold each leg with tweezers during soldering to provide additional heat removal from the body;
- When installing using a hair dryer or infrared soldering iron, you must monitor the temperature of the part so that it does not rise above 240-280 °C.
Electronic parts are very sensitive to static electricity. Therefore, when assembling, it is better to use an antistatic mat that is placed under the board.
Why dry chips?
Chips are microcircuits housed in BGA packages. The name, apparently, came from an abbreviation that meant “Numerical Integrated Processor”.
Based on experience, professionals have a strong opinion that during storage, transportation, and shipment, chips absorb moisture and during soldering, it increases in volume and destroys the part.
The effect of moisture on the chip can be seen if the latter is heated. Blisters and bubbles will form on its surface long before the temperature rises to a value sufficient to melt the solder. One can only imagine what is happening inside the part.
To avoid the undesirable consequences of moisture in the chip body, when installing boards, the chips are dried before soldering. This procedure helps remove moisture from the case.
Drying rules
Chips must be dried in compliance with temperature regime and duration. New chips that were purchased in a store, from a warehouse, or sent by mail are recommended to be dried for at least 24 hours at a temperature of 125 °C. For this you can use special drying ovens. You can dry the chip by placing it on a hot plate.
The drying temperature must be controlled to prevent overheating and failure of the part.
If the chips were dried and stored in normal room conditions, it is enough to dry them for 8-10 hours.
Considering the cost of the parts, it is obviously better to dry them in order to proceed with installation with confidence, than to try to solder an undried chip. Troubles can result not only in wasted money, but also in lost time.
