radiator

2021-08-18
A computer company radiator
If the temperature of your books is soaring in the hot summer, are you in a hurry? Tell you the easiest way to dissipate heat: put a thicker book under the book, which can make the air under the book more Circulation. But the size of the book must be smaller than that of a notebook computer, because the largest heat dissipation components of the notebook are the notebook's CPU and hard disk. The hard disk and CPU are generally on both sides of the computer, or you can find the most heat-generating part by touching it with your hands. So if you want to avoid developing parts with high heat, you can put your thick books in the middle, and if your books are small, then you need to find a smaller book if you have a book by your side. If you use an electric fan, you can also fan the books together, so the temperature of the books has dropped a lot.

Relatively simple article (the pad has good heat dissipation effect)

Some computers may have a large heat dissipation area, or the computer itself is relatively small, and the last method cannot be used to dissipate heat. Then I will introduce a simple method. It is also a pad under the notebook. Of course, the pad must have good thermal conductivity.

Don’t be surprised. Some people’s computers have a marble slab, which is said to work well. Of course, you have to be able to find a small stone slab.

Cushion a water bag, buy a water bag if you can’t find a slate You can find it by shopping in the market. After you buy it, put it under the book. You're done.

Expenses (buy cooling facilities)

If you are not very satisfied with the heat dissipation, you are also adding some auxiliary facilities. But these equipment will cost your money. You can buy a cooling base or a special cooling fan for notebooks. The price is between 80 and 200, but I do not recommend everyone to buy an expensive radiator. You might as well use the money to buy a household electric fan. The wind can be too big. If you fan it, the books are scattered too. If you emptied the books in advance , The heat dissipation effect is definitely better than those low-power radiators.

Collapse edit this paragraph material to conduction
The Die of the CPU is usually less than 2 square centimeters, but the power consumption reaches tens or hundreds of watts. If the heat cannot be conducted out in time, once the heat accumulates in the Die, it will cause serious consequences.

For the radiator, the most important thing is that its base can absorb as much heat as possible from the CPU in a short time, that is, the ability to absorb heat instantly. Only metals with high thermal conductivity can be competent. For metal thermally conductive materials, specific heat and thermal conductivity are two important parameters.

The thermal conductivity coefficient is defined as: per unit length, per K, how much energy can be transmitted in W, the unit is W/mK. Among them, "W" refers to the unit of thermal power, "m" represents the unit of length in meters, and "K" is the unit of absolute temperature. The larger the value, the better the thermal conductivity. The following is a table of the thermal conductivity of several common metals:

Thermal conductivity (unit: W/mK)


Silver 429 Copper 401

Gold 317 Aluminum 237

Iron 80 Lead 34.8

1070 type aluminum alloy 226 1050 type aluminum alloy 209

6063 type aluminum alloy 201 6061 type aluminum alloy 155

It can be seen that silver and copper are the best thermally conductive materials, followed by gold and aluminum. But gold and silver are too expensive, so the heat sink is mainly made of aluminum and copper. However, due to the high copper density, complex process and relatively expensive price, the usual fans are mostly made of lighter aluminum. Of course, for air-cooled radiators, in addition to thermal conductivity, heat dissipation must be considered when considering the material. Combining these two parameters, the heat capacity of the heater shows the superiority of aluminum. However, this article only discusses the heat conduction aspects, for those we will discuss in detail in the next section.

To improve the thermal conductivity of the radiator base, the choice of materials with higher thermal conductivity is on the one hand, but on the other hand, it is also necessary to solve the problem of the tightness of the heat source such as the combination of the CPU and the radiator base. According to the law of heat conduction, under the premise of a fixed material, the conductivity is proportional to the contact area and inversely proportional to the contact distance. The larger the contact area, the faster the heat can be dissipated, but the Die is fixed for the CPU, so the bonding distance is more important.

Although theoretically speaking, the heat sink base can be in close contact with the CPU, but objectively speaking, no matter how smooth the two contact surfaces, there is still a gap between them, that is, there is air, and the thermal conductivity of air is very poor. , This requires a well-designed and strong gripping fastener to tightly buckle the heat sink to the CPU. In addition, it is necessary to replace air with something with better thermal conductivity and deformability to fill these gaps, such as thermal grease or Thermal tape. The ideal situation is that the buckle tightly fixes the heat sink to the CPU. The contact between the heat sink and the CPU is completely parallel to keep the contact area to the maximum. Some tiny gaps between them are completely filled with silicone grease to keep the contact thermal resistance to a minimum.

However, it must be clear that no matter what kind of thermal grease or heat dissipation tape, its role can only be auxiliary. Compared with the copper heat dissipation base material, its thermal resistance is many times larger. To maximize the thermal conductivity of the radiator base, it is also necessary to ensure that the radiator base is smooth and flat, so that the gap between the contact surface of the radiator and the CPU can be truly reduced.

Radiator bottom surface treatment process / Feihai Chemical passivation

Commonly used bottom surface treatment processes include:

Wire drawing process (grinding)

The wire drawing process is also the most used bottom surface treatment process. When drawing, use a tool with a certain degree of roughness and hardness, such as sandpaper, files, etc., to perform one-way, repeated or rotating friction on the surface of the object, and remove the processed surface with the help of the shearing effect of the rough surface of the tool. Of course, polishing the protrusions will also cause scratches on the originally flat surface. Therefore, a gradual process from coarse to fine should be adopted to gradually reduce the roughness of the processed surface.

Characteristics of wire drawing process: Parallel wear marks

Disc milling process (cutting)

The disk milling process refers to cutting the surface of the radiator with a high-speed rotating cutter after fixing the bottom surface of the radiator. The cutter always rotates in the same plane, so the cut bottom surface is very flat. Similar to the wire drawing process, the finer the cutter used in the disc milling process, the higher the flatness of the cut bottom surface. The manufacturing cost of the disc milling process is relatively high, but it only needs two or three procedures relative to wire drawing, which is time-saving and the effect is relatively ideal.

Disc milling process characteristics: arc-shaped wear marks

CNC machine tools

The main process used by CNC machine tools to flatten the bottom surface of the heat sink is still milling. But unlike traditional disc milling, the relative distance between the cutter of the CNC milling machine and the heat sink can be precisely controlled by the single-chip microcomputer. After the tool touches the bottom surface of the heat sink, the two move relative to each other in the horizontal direction to cut the unprocessed part left by the tool gap in traditional disc milling, and achieve a complete planar effect. No subsequent processing is allowed to obtain a mirror-like effect. , The flatness can be less than 0.001mm.

Other crafts

In addition to the above, there are other processes for the bottom treatment of the radiator, such as polishing. The polishing treatment of "Feihai Chemical Passivation" is more for the aesthetics of the radiator, which improves the flatness of the bottom surface of the radiator. Quality performance is better.

As we said before, no matter how to deal with the bottom surface of the radiator, this kind of mechanical process cannot make a completely standard flat surface, and the gap or gap between the CPU and the radiator is always inevitable. The air in these gaps has a great influence on the conduction ability of the radiator. It is well known that the thermal resistance of air is very high. Therefore, other substances must be used to reduce the thermal resistance, otherwise the conduction performance of the radiator will be large. At a discount, it can't even work. This is the origin of the heat transfer medium. Its function is to fill the large and small gaps between the heat source such as the CPU and the heat sink, and increase the contact area between the heat source and the heat sink.

Fold to edit the performance parameters of this paragraph
Since thermal grease is a chemical substance, it also has relevant performance parameters that reflect its own working characteristics. As long as you understand the meaning of these parameters, you can judge the performance of a thermal grease product.

Operating temperature

Operating temperature is an important parameter to ensure that the thermal grease is in a solid or liquid state. If the temperature is too high, the thermal grease will become liquid due to the decrease in viscosity; if the temperature is too low, it will become solid due to the increase in viscosity. Neither situation is conducive to heat dissipation. The working temperature of thermal grease is generally -50℃~180℃. Regarding the working temperature of thermal grease, generally don’t worry, after all, it is difficult to get the CPU temperature outside this range by conventional means, unless you plan to use liquid nitrogen for cooling-at that temperature most thermal grease will lose its effect.

Thermal conductivity

Compared with commonly used radiator materials, the thermal conduction system of thermal grease is much smaller. In the current general specification, the thermal conductivity of thermal grease is required to be 1.13W/mK, which is not the same as copper’s 401W/mK. The language, but compared with the air, is still much higher. It can also be seen how important it is that the bottom surface of the radiator is smooth. Some manufacturers claim that the bottom surface of the radiator is not flat enough to be filled with thermal grease without affecting its heat dissipation capacity.

Thermal resistance coefficient

The thermal resistance coefficient represents the hindering effect of an object on the conduction of heat. The concept of thermal resistance is very similar to resistance, and the unit is similar to it (℃/W), that is, the temperature difference between the two ends of the heat conduction path when the object's continuous heat transfer power is 1W. Obviously, the lower the thermal resistance, the better, because under the same ambient temperature and thermal power, the lower the thermal resistance, the lower the temperature of the heating object. The size of the thermal resistance has a great relationship with the material used in the thermal grease.

Dielectric constant

For some CPUs that are not protected by a metal top cover, the dielectric constant is a very important parameter, which is related to whether there is a short circuit inside the computer. Ordinary thermal conductive silicone grease is made of materials with better insulation, but some special silicone greases (such as silver-containing silicone grease, etc.) may have a certain degree of electrical conductivity. Of course, the current CPU is equipped with a metal top cover for heat conduction and protection of the core, so there is no need to worry about the short circuit caused by the overflow of thermal grease, but you must also be careful not to misapply thermal grease to others when applying it. Place like on the motherboard.

The dielectric constant of thermal grease used in mainstream heat sinks is greater than 5.1.

Viscosity

Viscosity refers to the viscosity of hot silicone grease. Generally speaking, the viscosity of thermal grease is around 68.

Precautions for using thermal grease

When applying thermal grease, the most important thing is to be uniform. It can cover the CPU core. There is no need to apply too much or even a thick layer, which will affect the performance of the radiator. It should be clear that the thermal conductivity of the so-called thermal grease is high. But compared to air, it is much lower than the radiator material such as copper or even aluminum.

In addition, most common thermal grease will "dry" or "harden" after being used for a year or longer, which will greatly affect the heat dissipation effect. Therefore, to ensure the long-term stable operation of the system, regular cleaning and reapplying of silicone grease is also necessary.

Collapse edit this paragraph optional fit
Especially in summer, using the computer for a long time often makes the computer "high fever". As the "good medicine" for cooling computers, radiators are becoming more and more popular with consumers. Many businesses said that as the weather gets hotter, computer radiators have entered a period of hot sales.

Most consumers who buy computer radiators are laptop users. Some people use laptops mainly for stock trading. They often drive them from the morning to more than 3 in the afternoon. They feel hot with their hands, so they think of buying a radiator to cool the computer. In 2007, the price of radiators for laptops of various brands ranged from 40-200 yuan. Industry insiders said that for laptop users, it is necessary to use high-end radiators as much as possible.

According to reports, some consumers who buy computer radiators want to buy more powerful products. They believe that the greater the power of the radiator fan, the stronger the wind and the better the heat dissipation effect. In fact, as long as you can ensure that the computer's CPU is below the safe temperature, you don't need to overemphasize the power of the fan. Using a fan with too much power will create an additional burden on the power supply and may cause some hidden failures.

Notes for editing this paragraph
Look at the shape The fin-shaped radiator is made by bending a thin aluminum plate, which looks like the bellows of an accordion; each radiating blade of the vortex radiator is inclined in one direction to facilitate air circulation. The heat dissipation efficiency of these two products is relatively strong.

Look at the material The radiator of aluminum extrusion profile is the lowest price, but the heat dissipation effect is not good; the radiator of gold, silver, and copper material has good heat dissipation effect, but the cost is high and the weight is heavy. The most cost-effective is the aluminum alloy radiator.

Look at the area The radiator dissipates heat in the form of convection. The larger the surface area, the better the heat dissipation effect. When choosing a radiator, attention should also be paid to the heat dissipation area of ​​the radiator.

Others: When choosing an aluminum radiator, pay attention to the bottom of the radiator not to be too thick, because the thermal conductivity of aluminum is not very good, and too thick will affect the heat transfer; in addition, the diversion groove on the surface of the radiator should be denser , This can ensure that the radiator can have a larger contact area with the air, thereby enhancing the heat dissipation effect. It is not recommended to buy a silent passive notebook radiator, because the contact surface between the bottom of the notebook and the radiator is actively small, and it is difficult to conduct heat from the body to the radiator
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