Why do capacitors on the motherboard swell? The saga of capacitors or “Another blowout

Blistering capacitor A fairly common occurrence that happens due to various reasons. Eliminated by replacing the faulty capacitor and diagnosing the surrounding circuits. Ideally, it is necessary to replace not only swollen capacitor, but also its “neighbors”, even if they appear to be in good order.

Causes of capacitor swelling

The reasons for swelling can be different, but the main one is the low quality of the radio component itself. Are bloated because of " boiling over» electrolyte or its evaporation at high temperatures. Capacitors heat up, both through the external environment and from the inside. If the polarities are reversed, the capacitor instantly heats up and explodes. Also, the capacitor may heat up due to non-compliance with operating rules: voltage, capacity, maximum temperature etc. Plus to this impulses arriving at it, breakdown isolation or reducing the amount of electrolyte.

Electrolyte evaporation may occur if the capacitor has poor sealing. Over time, the electrolyte level will decrease, and the remaining one will boil, causing the capacitor to swell.

In low-quality capacitors, instead of swelling, electrolyte leaks out through the bottom. In this case, the leaking capacitor must be replaced, and the board must be cleaned of electrolyte leaks, since it can cause corrosion and damage to the elements located on the board. Therefore, if you find traces of corrosion on top of the capacitor, this means that part of the electrolyte has leaked out through the upper part, i.e. it is no longer airtight. “ Rusty capacitors” must be replaced with new ones as soon as possible.

I would like to note that not only electrolytic cells swell, but also solid capacitors.

Solid polymer capacitors also swell and open.

Replacing a swollen capacitor

Replacing a faulty capacitor with a similar one, with equal capacity, maybe a little more. The same applies to voltage, it should be equal or slightly greater.

How to avoid swelling of capacitors?

• Use quality capacitors.
• Do not allow capacitors to reach temperatures above 45 degrees (monitor the ambient temperature). Place them away from hot radiators.
• If capacitors swell in computer power supplies, use high-quality input surge protectors and voltage stabilizers.
• If the capacitors swell on the computer motherboard, use high-quality power supplies.

Sometimes I read Habr, mostly DIY. Sometimes this is rare, because work, you know... And then, not so long ago, I was surprised to come across a habratopic (I won’t point a finger) with a description, so to speak, of repairing an LCD monitor. Having glanced at it quickly, I felt first the desire to cry, and then to laugh. Why?

I have to work about 8 hours a day in just one fun organization, one of whose activities is the repair of various equipment, including LCD monitors. I wanted to say everything that could only be said in the comments, but I couldn’t. I decided to write at least to the Sandbox, because I don’t have the strength to remain silent.
A quick investigation showed that the author of that same topic dedicated to “repairing” an LCD monitor managed to publish another one, this time about repairing a TV. I must say that these topics generated a not very long thread in a closed section of one well-known technical forum. The general mood of this thread can be characterized by the following quote taken from there:

We are waiting for new opuses from the author on the topic:
“How to remove hemorrhoids using crooked hands, a mirror and scissors”
"Drill and reduction of intracranial pressure"

Often you have to repair equipment after other technicians were unable to identify the problem or were unable to fix it. And very often - after amateurs who tried to “repair” the device using yet another “instruction”, generously scattered throughout the Internet. And, to be honest, I was very surprised to find 2 such “instructions” on Habré at once.

So, let's start with the notorious “repair” of the TV, since this habratopic appeared first. To begin with, I would like to point out the presence of such a parameter as ESR. Anyone can simply google this term and get the entire theoretical basis. Therefore, we will not consider it closely. We are only interested in the fact that the troubleshooting of electrolytic capacitors is carried out not only by the fact of swelling of the aluminum jacket, but also by this very ESR parameter. In fact, this is quite important, since the capacitor swells due to excessive heat, leading to an increase in pressure inside its housing due to evaporation of the electrolyte. And the higher the ESR, the higher the heating of the capacitor. Thus, after thinking for a couple of minutes, we will understand that the power supply may well contain a fairly large number of capacitors, not yet swollen, but already with an increased ESR. Those. essentially already faulty, but not yet visible to the naked eye. To measure ESR, the simplest devices are used, accessible to any child, but many masters use them quite rarely, since the simplest solution to the problem is to replace all electrolytes in the so-called. the “cold” part of the power supply, also called the “secondary”. It is impossible to replace only swollen capacitors without checking the rest, which are not swollen. Because it is not fraught with profit, but with repeated repairs after a short period of time. Moreover, taking into account the circuit design of modern digital technology, it is quite possible that it is not only the power supply unit that is being repaired.

Another mistake the author makes is the soldering technique. For goodness sake, why tin the leads of the capacitors? Which will still have to be cut after installation?
What about the use of acid in installation work? Highly active fluxes such as “Soldering acid” are not intended for electrical installation work at all! These are fluxes for soldering ferrous metals. And they are not called acid for nothing. “Soldering acid” can rot the soldering of this same capacitor in a couple of months, even when applied in small quantities. This is why, after using such fluxes, the soldered surfaces must be washed with water, solvents, or better yet, special liquids. And they should never be used in radio installation work.

Very often, the price lists of service organizations indicate that an increasing factor is applied to the cost of repairing equipment with traces of unqualified repairs, and this is not without reason! As an example, the described TV is already quite capable of delivering an hour or two of fun entertainment to any service after an indefinite period of time. From a week to a year.

The second habratopic, dedicated to “repairing” the monitor, is also very funny. Any specialist knows that repairs begin with measurements. The author of the topic carries out measurements of such parameters as “flammability of a light bulb” - the measurement result is “not lit”, and “monitor performance” - the measurement result is “dead”. The repair method is to just as thoughtlessly replace the visually swollen electrolytes with those torn from the “ancient power supply”, and even with a lower voltage. Of course, LG designers are fools - for some reason they installed 16-volt capacitors, even if 10-volt ones work... And another miracle - the flammability of the light bulb has risen to “on”, we’ll urgently post it in Habr...

Believe me, all this was written not because I am afraid of being left without a job. On the contrary, such “obstetricians of pregnant women” provide normal craftsmen with work. Unfortunately, often, when after replacing the capacitor the monitor still does not work or does not work satisfactorily, they begin to brutally “dig” the monitor, damaging the tracks on the board, desoldering parts, etc. But repairing such a pile is a completely different matter. For example, we apply an increasing factor of 1.3 to the price for such devices.
The problem here is different. Quite recently, I was forced to give a client a “dug” monitor, due to the modest fact that the “digger” “dug” the PSU-inverter board to death, to the point of a hole in the PCB under one of the transistor assemblies. He didn’t know that the wide minus track under the assembly was laid for a reason. And the number of such examples is multiplying, precisely because of the wide distribution of various “instructions” written by various “specialists”...

Most often, the cause of swelling is the capacitor itself, which turns out to be of poor quality. The swelling itself occurs due to boiling or evaporation of the electrolyte.

Electrolyte boiling over occurs at high temperatures, the source of which is both the external environment (heating devices near equipment, objects blocking the ventilation in the device, non-compliance with the operating characteristics of the device) and internal (poor quality power supply, pulses arriving at the capacitor, breaking through the insulating layer of the capacitor, non-compliance with it). polarity, or the most common reason is a lack of electrolyte).

For capacitors, a temperature jump above 45 degrees is sufficient.

Evaporation of the electrolyte occurs if the capacitor has poor sealing (this is usually indicated by traces of corrosion from the electrolyte on the capacitor). Then, over some time, the electrolyte level will gradually decrease, which will inevitably lead to a change in the initial properties of the capacitor and, as a result, boiling of the remaining electrolyte, and then swelling of the capacitor. However, sometimes a low-quality capacitor can be so poorly sealed that the electrolyte simply leaks out through its lower part.

The electrolyte is used in electrolytic capacitors as the cathode (an electrode connected to a negative current source).

In any case, those that are swollen and even have traces of corrosion or poor sealing must be replaced. Of course, the device containing them can still serve its user for some time, but soon malfunctions will inevitably appear in its operation.

Replacing swollen capacitors

If swollen ones are detected, they must be replaced or additional high-frequency pulses must be installed to dampen the pulses. It should be taken into account that the rated operating voltage on the new ones should be no less than that of the swollen ones. The capacity of new capacitors should also not be less than those being replaced, otherwise ripples will be missed. In addition, it is worth observing the polarity if it is indicated on the board and the capacitor (otherwise, when the equipment is turned on, the newly installed capacitor may immediately break).

To change modern small capacitors, it is better to use a thin soldering iron, since a more powerful one can quickly heat the capacitors to a critical temperature, which will lead to their damage.

A capacitor is an integral part of any device that uses electricity, but sometimes it happens that malfunctions occur with this most important element of the system. In this article we will tell you why

The capacitor looks like a battery, sometimes slightly flattened vertically. Inside there is a small roll of aluminum foil, located in an electrolyte solution. Aluminum foil is isolated from the electrolyte by a dielectric made of a thin oxidized film.

The main purpose of capacitors is to convert alternating current from the outlet into direct current, which is necessary for its frequency circuit, as well as to smooth out fluctuations in the transmitted voltage.

Such oscillations are also called pulsations. They cause the capacitor to heat up, and the stronger they are, the higher the temperature will rise.

Causes of capacitor swelling

A swollen capacitor is one of the most common causes of breakdown of electrical equipment, and technically speaking, failure of an electrical circuit. Bloating most often occurs in power circuits, as well as in the power devices themselves.

There are plenty of reasons why capacitors swell - from low-quality materials and mechanical damage to the microcircuit, to wear and interruptions in the supply of electrical voltage.

Among the most obvious and frequent causes, a sequence of events can be identified: excessive heating (rather overheating) and subsequent evaporation of the electrolytic liquid from the capacitor tank.

Overheat

The most terrible phenomenon among the reasons why capacitors swell is the quality of the voltage supplied to the circuit. If it was not originally provided for a given capacitor in this particular case, it has to work in increased mode.

Therefore, the main task of manufacturers of chips, such as computer motherboards, is to calculate the base and possible load on the network and install capacitors with sufficient reactive power (analogous to bandwidth) that can withstand voltage fluctuations or turn off on their own.

And they cope with this successfully, otherwise in a matter of hours.

We cannot exclude defective parts, which, accordingly, have a much shorter service life and lower deviation limits from the basic operating mode - they heat up faster and more intensely.

Surely, if you feed such a defective capacitor with high-quality current, it will work for the entire stated period and will not show signs of malfunction, but absolutely nothing happens, and voltage surges are not something unusual.

Therefore, capacitors constantly operate in an aggressive environment. Such work will certainly lead to heating, which will gradually evaporate the electrolytic liquid from the capacitor tank, which in the near future will lead to bloating.

Electrolyte evaporation

When heated sufficiently, any liquid begins to boil. Water turns into steam and evaporates, and electrolytic fluid is no exception.

Most often, capacitors swell precisely because of a lack of electrolyte, and the reason for this may be their insufficient reactive power, poor quality of materials, as well as banal physical wear of the capacitor itself, causing it to heat up more and more.

Less commonly, external heating or incorrect polarity may also be the cause.

Replacing swollen capacitors

Any technician who understands the markings of capacitors or is able to find information on the device where it is installed will replace it within a few minutes. The process includes desoldering the old condenser and soldering the new one.

Prevention of capacitor operation

You can prevent swelling of capacitors at home, for example, on a computer motherboard, using certain measures. These include:

1. Installation of additional cooling in the system unit.
2. Installing a “voltage cut-off” at least on the socket that powers the PC.
3. Use of high-quality wires, sockets, surge protectors.
4. Use a high-quality power supply.
5. Purchasing a UPS.

There are also special silicon capacitors. They swell much less often, but their price is an order of magnitude higher, and they are not suitable everywhere, because their sinusoid alignment is different.