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uid metal is called a gallium-indium alloy.Gallium alloy materials with different melting points are formed by adding other elements to the "liquid metal material-gallium".Are Gallium Alloy Liquid Metal Materials Safe?Gallium ions are toxic. If taken in excess, it can have adverse effects on the human body. For example, short-term exposure to large doses of gallium chloride can cause throat inflammation and chest pain, and severe cases may cause adverse reactions such as partial paralysis.However, elemental gallium and gallium alloys are non-toxic, and liquid metals are gallium alloy materials. Liquid metal has a boiling point of up to 2000 ° C, and its physical and chemical properties are very stable, which means that it will not be volatile in the air like mercury, so it will not directly harm people.In addition, gallium is also used in some medical diagnostic processes, such as tumors, anti-osteoporosis, and immunosuppression. In some medical devices and medical materials, gallium is also used, for example, as a dental filling material, a thermometer and the like.Before using a variety of materials, you must fully understand the properties of the material itself and use the correct method.Application of liquid metal batteriesA liquid metal battery is composed of two liquid metal electrodes and a molten salt electrolyte. The positive electrode material is usually a transition metal element or alloy such as tin, and the negative electrode material is usually an alkali metal or alkaline earth metal element or alloy. When the battery is discharged, the electrons lost by the negative metal material work on the external circuit, and the cations generated by the lost electrons move to the vicinity of the positive electrode of the battery through the molten salt, a reduction reaction occurs, and a new alloy is formed with the positive metal. When the battery is charging, the above process is reversed.
November 1, 2003 Daniel Blazej, Ph.D.Articles, Design, Materials, Compounds, Adhesives, Substrates, TIMsThermal Interface Materials, TIMIt doesn’t take long for an electronics assembler to realize that a thermal interface material (TIM) is essential when two or more solid surfaces are in the heat path. Standard machined surfaces are rough and wavy, leading to relatively few actual contact points between surfaces. The insulating air gaps created by multiple voids of “contacting” hard surfaces are simply too large a thermal barrier for even modest power applications. The first tactic in overcoming this barrier is to fill the voids and eliminate air by introducing a third material to the heat path that is fluidic and wets the surfaces. For more demanding thermal applications, the second tactic is to use a composite TIM containing fillers that enhance the conduction process of the third material. Yovanovich et al. have calculated that simply replacing air with grease can reduce the thermal resistance by a factor of five or so (depending on the surfaces and contact pressure). As shown in Figure 1, a thermal interface material essentially changes the thermal path between rough-surfaced solids from conduction through point contacts and air to conduction entirely through solids.Figure 1a. Conduction through point contacts and air between hard surfaces.Figure 1b. Conduction through TIM filling gaps.An important property of any TIM is its thermal conductivity, kTIM. Unfilled polymers have a thermal conductivity of about 0.1 W/mK. All modern TIMs are composites containing particulate fillers that push thermal conductivity up to the 7 W/mK range. Inorganic particulate fillers include aluminum oxide, magnesium oxide, aluminum nitride, boron nitride, and diamond powder. Metal fillers, notably silver, are also used. Unfortunately, high thermal conductivity alone is not enough to guarantee optimal system performance, as we will show later. In the descriptions of specific material classes, we will characterize performance with thermal resistance (normalized to a unit area on one square cm) that has units Kcm2/W, obtained from a one-dimensional heat flow calculation. In this way, we can account for the interfacial thickness. The specific value in any given application is highly dependent on the contact surfaces and pressures applied. Nevertheless, the ranges provided are representative of each material class. (Note: Many suppliers report resistance values in the mixed unit of Kin2/W. These need to be multiplied by 6.45 to match the units in this paper.)In addition to thermal performance, TIMs are selected on several other critical criteria as well. Ease of use in assembly and rework are important in high-end applications, as is long-term stability (reliability). The manufacturing process flow often dictates the material selection. In many cases, for example, the TIM is attached to a heat sink in one location while final module assembly occurs in another. Elastomeric pads were developed as an alternative to early grease solutions, largely for the manufacturing advantages they offered. Phase change materials emerged as a technology that captured the thermal performance advantage of grease and combined it with the assembly ease of a solid pad. Often overlooked in the TIM selection process are adhesives and solders. Both offer the unique advantage of secure mechanical bonding, eliminating the need for clamping hardware that the greases, pads, and phase change materials require.
low melting pointAt present, the main cooling technology is air cooling, heat pipe, water cooling and so on.Air cooling technology has limited thermal conductivity and can only be applied to low-power electronic products.The heat pipe is better than the air cooling, but there is the burning limit, and even the pipe rupture failure phenomenon;Due to evaporation, leakage and other problems in the process of operation, water-cooled cooling is easy to lead to device aging, and the requirements for liquid and flow pipe are also high.The radiator that liquid metal makes has the advantage that this traditional radiator cannot compare, that is collect efficient, compact, safe, quiet in an organic whole.It has good thermal conductivity and specific heat capacity, but the volume does not increase at all. The same volume brings better performance, and the compactness is vividly reflected.Liquid metal will not leak, not easy to evaporate, will not deteriorate, safe operation, long service life.Due to the built-in electromagnetic pump in the heat dissipation pipeline, the pressure gradient is generated by the electromagnetic force to push the liquid forward without any noise, so that users can enjoy the silent radiator.The alloy of gallium metal is used as the heat conducting agent of radiator, with low melting point, non-toxic and harmless, fast heat absorption and high boiling point.Liquid metal cooling technology can not only be applied toCPUcooling, its core technology can be extended to more aspects, including the instrument industry, steel manufacturing, solar energy capture, national defense, etc. Due to the wide application of various kinds of chips and optoelectronic devices, the corresponding cooling technology has a huge market demand.According to the data, the world market for manufacturing components such as fans and fins used in computer cpus, for example, is about $5 billion to $10 billion a year. With the increasing power consumption, the price of chipcoolingsolutions has also increased dramatically, and the corresponding market demand has also increased. This undoubtedly provides the broad development space for the liquid metal heat dissipation technology.
CPUThermal conductivity of passive means without other auxiliary way of thermal conductivity of thermal conductivity, by conducting strip their contact with the chip, heat conduction take away heat gathering on the chip, but the present computer parts and components manufacturing more and more complex, the instant heat, only a passive thermal far cannot satisfy the needs of CPU heat conduction, so now we can only in the low calorific value control motherboard north and south bridge chip or some graphics display chip calorific value is not high to see this kind of way of thermal conductivity.Air cooling heat conduction is now the most common and the highest utilization of a heat conduction, belongs to the active heat conduction, this heat conduction can solve our usual heat conduction needs, the technology is mature and the price is moderate, so it is widely used in the market. The air-cooled heat conductor is simple in structure, cheap in price, safe and reliable. However, it also has some disadvantages, such as not being able to lower the temperature below room temperature, noise due to the rotation of the fan, and the improper installation of the fan will cause vibration, which will damage the computer components in the long run, and the fan life is also limited.Water cooling heat conduction is the use of water to replace air, through the movement of water in the heat between the heat convection to take away the excess heat.The water cooling system works simply by using pumps to pull water out of the water storage unit, which is then piped into a heat exchanger that covers the CPU. The water then comes out of another opening in the heat exchanger and flows back through the water pipe to the storage tank. The whole water cooling system includes heat exchanger, circulation system, water tank, water pump and so on. The thermal conductivity of the water-cooling system is very strong, which is very suitable for some overclocking enthusiasts. The principle of liquid cooling heat conduction is the same as that of water cooling heat conduction, and the heat conduction method adopted by them is the same. The difference is that the flow in the circulation system is thermal silicone oil instead of water, which has obvious benefits. It will not cause the computer hardware damage due to the damage of the circulation system to the silicon oil flowing out. At present the market for the sale of the aokma liquid cooling thermal conductivity belongs to this type of thermal conductivity. In addition to the above mentioned methods of active heat conduction, there are heat conduction of heat pipe, heat conduction of semiconductor refrigerator, heat conduction of compressor refrigeration, heat conduction of liquid nitrogen, etc.
How to use thermal paste correctly?In case of the CPUA. Clean the CPU core and radiator surface with a high purity solvent such as high purity iso-amyl alcohol or acetone and a flurry-free cloth such as a cloth used for wiping lenses (a fingerprint may be about 0.005 inches thick).If the surface is clean without oil, this step can be skipped, if there is more difficult to clean the oil, can use precision electrical cleaner cleaning, will not be in conflict with thermal paste.B. Determine the area where the CPU is in contact with the heat sink and squeeze enough thermal paste into the center of the area.C. Using a clean tool, remove a small amount of thermal paste and transfer it to the corner of the CPU core. You only need a small piece, about half the size of a grain of rice.D. Slip your fingers into the plastic bag, then rub the thermal paste on the bottom of the radiator with your fingers until the thermal paste evenly covers the entire area in contact with the CPU.Ensure that the thermal paste can fill the bottom of the radiator gap and uneven places.Note: do not apply directly with your fingers.E. With no flannelette will be wiped off the heat conduction paste at the bottom of the radiator, at this time you can see the heat conduction paste at the bottom of the radiator and other areas color is not the same, indicating that heat conduction paste has evenly filled the gap in the base.F. Start with the tool at the corner of the CPU core and spread the thermal paste evenly throughout the core.The flatter the surface to be contacted, the thinner the need for thermal paste.For an ordinary radiator underside, the thermal paste is about the thickness of a piece of regular paper (0.003-0.005 inches). If the radiator underside is bright and flat, the thermal paste can be as thin as translucent. G. Make sure there are no foreign bodies on the radiator base and CPU core surface. Place the radiator on the CPU. At this point, only press lightly and do not rotate or shift the radiator.Otherwise, it may lead to uneven thickness of thermal paste between the radiator and CPU.If there is no metal thermal paste on the CPU, which problems will occur?Metal Thermal paste is the heat conduction material of electronic components, such as the gap between the processor CPU and the radiator, the filling of the gap between the high-power transistor, SCR element diode and the material (copper, aluminum), the assembly of transistors, CPU;Temperature sensor;Automotive electronic parts, automotive refrigerator, power module, printer head, electronic appliances, audio crystal cooling, reduce the operating temperature of heating components, increase the life of the crystal.Thermal paste has excellent heat resistance, electrical insulation, thermal conductivity, damping, and viscosity is not sensitive to temperature.Its chemical properties are stable, volatile, non - toxic and tasteless. If there is no metal thermal paste on the CPU, some serious problems will occur as below:A. If there is no heat conduction paste between the CPU and the radiator, although the computer can be turned on, but the full load temperature is very high, resulting in the running speed will become very slow, believe that now basically everyone has a computer, under the same conditions, the CPU temperature, the operation of the computer light and easy to see can be seen.B. It is recommended to apply thermal paste, because the difference between thermal paste and no thermal paste can be up to 30℃, the stability of the system is greatly affected.C. The material of thermal paste also affects the thermal conductivity, such as ordinary thermal paste and gallium based alloy thermal paste, thermal conductivity difference will directly affect the service life of the heating original. However, heat conduction paste also has service life, the service life of general heat conduction paste can reach more than a year.When found that the CPU began to heat, it means that the heat dissipation performance of thermal paste began to decline, in order to CPU life safety, thermal paste is essential.
Metals are excellent choices for electrical and thermal-current conducting. However, either the stiffness of solid metals or the fluidity of liquid metals could be troublesome when flexibility and formability are both desired. To address this problem, a reliable two-stage route to improve the functionalities of gallium-based liquid metals is proposed. A series of stablesemiliquid/semisolid gallium-based liquid metal amalgams with well-controlled particle packing ratios. Through effectively packing the liquid metal with copper particles (which are found to turn into intermetallic compound, CuGa2, after dispersing), remarkable enhancements in electrical conductivity (6 × 106 S m–1, ∼80% increase) and thermal conductivity (50 W m–1 K–1, ∼100% increase) are obtained, making the CuGa2 stand out from current conductive soft materials. The CuGa2 also exhibit appealing semiliquid/semisolid mechanical behaviors such as excellent adhesion, tunable formability, and self-healing ability. As a class of highly conductive yet editable metallic mixtures, the CuGa2 demonstrate potential applications in fields like printed and/or flexible electronics and thermal interface materials, as well as other circumstances where the flexibility and conductivity of interfaces and connections are crucial.
The atomic structure is the most striking characteristic of the Liquidmetal alloys as it fundamentally differentiates Liquidmetal alloys from ordinary metals.The atomic structure of ordinary or conventional metals and alloys is periodic, where the layout of atomic elements shows repeating patterns over an extended range. This atomic structure is called "crystalline" and limits the overall performance of conventional metals.Liquidmetal alloys possess an "amorphous" atomic structure, which is truly unique. By contrast to the crystalline structure, no discernable patterns exist in the atomic structure of the unique Liquidmetal alloys. As such, properties superior to the limits of conventional metals can be achieved.Properties of Liquid metalThis amorphous atomic structure leads to a unique set of characteristic properties for the family of Liquidmetal alloys.These characteristic properties are:• High Yield Strength• High Hardness• Superior Strength/Weight Ratio• Superior Elastic Limit• High Corrosion Resistance• High Wear-Resistance• Unique Acoustical Properties One of the direct results of the unique atomic structure of Liquidmetal alloys is very high yield strength, which approaches the theoretical limit and far exceeds the strength currently available in crystalline metals and alloys.
Liquid metal may look like nothing more than a small ball of metal, but it will have shape-shifting and self-propulsion abilities.The device is made from a drop of metal alloy consisting mostly of gallium, which is a liquid at just under 30 degrees Celsius. Last year they discovered that an applied electrical current causes the gallium alloy to drastically alter its shape. Changing the voltage applied to the metal allowed it to 'shape-shift' into different formations. When the current was switched off, the metal returned to its original drop shape. The machine has two processes. One is to create gases like hydrogen. Part of these gases form the propulsion. There's also something important, in fact very important, which is the electricity generated behind the alloy. So this galvanic battery creates an internal electrical power, and this type of electricity will very easily lead to stretching of the surface of the liquid metal in an asymmetrical pattern, and this pattern leads to rotations inside the liquid metal, and the process of these rotations will set the liquid metal in motion in a certain direction.
Metal thermal pad 's typical structure of the combination onto the fan is that a number of sheet heat conducting fins are engaged in a certain process on the heat-absorbing bottom with a certain thickness.Disadvantages: the airflow needs to change the direction in the thermal plate, which is easy to form a "no wind zone". Moreover, the overhead type of the traditional axial flow fan is easy to form a dead Angle -- "wind blind zone" -- in the part of the inter-bearing, but the thermal plate is in the center of the contact is the heating equipment (CPU core, etc.). A typical metal thermal pad design, with a solid copper column as the main shaft, radiates the thermal fin outward from the inside, and inversely bends the fin towards the fan to increase contact with the airflow. With this kind of design, the blind area of the axial flow fan just corresponds to the copper core of the thermal conductor, and the copper core itself has a small exposed surface area, which is difficult to improve the thermal conductivity with the aid of airflow. Meantime, some of the outer fins are just under the fan's strong wind, the thermal effect of nature excellent. Its design can be said to be an "evasive" approach: the wind blind area is avoided by clever design, minimizing the negative impact brought by it; And compared to the "conventional turbo" fan mentioned later, the copper core has a larger contact area with the thermal fins, which can better transfer heat to all parts of the fins.
The production technology of metal thermal pad includes cutting, aluminum extrusion, metal powder jet forming and so on.A. cutting: turning, drilling, milling and grinding. In the forming process of thermal conductive sheet, cutting technology is required to obtain some special and fine shapes.The advantage is that according to different ways, cutting tools, can be applied to a variety of purposes.The disadvantage is the tool wear fast, most of the need for manual participation or automation control, high cost.Suitable for all heat conducting sheet: sheet (heat absorbing bottom, fin, etc.) forming, heat conducting sheet grooving, bottom dressing, special carving, etc.B. Aluminum extrusion: heat the original ingot of aluminum alloy to about 520~540℃, use mechanical pressure, make the aluminum liquid flow through the extrusion mold made of mold steel, cool the aluminum liquid at the outlet of the mold, make it solidified quickly, and become the first embryo of thermal conductive sheet with continuous parallel structure. Advantages are less investment, low technical threshold, short development cycle, easy to put into production; Mold cost, low production cost, large output; It can be used in a wide range of applications. It can be used to manufacture either individual heat sink or the fin part of the combined heat conductor. The disadvantage is that the fin shape is relatively simple and it is not possible to obtain a large (> 20) lane-to-length ratio. Suitable for heat sink processing, aluminum extrusion technology is mainly used to produce the initial blank of sheet fin or cylindrical fin. C. Metal powder jet forming: mainly using materials with high melting point and high heat conduction (such as copper). The metal powder is sprayed at high speed to make the first embryo of thermal conductive sheet directly, and then sintered at high temperature to make the finished product with considerable strength and density. The advantage lies in the metal powder sintering in one, high thermal conductivity; Heat conducting sheet with complex shape can be machined, the designer has less limitation. Disadvantages for raw materials, equipment, mold cost, complex process, low yield, not easy to mass production. It is mainly applied to electronic products with high calorific value and space limitation. The manufacturing cost and price are very high.
