semiconductorThe cooling slice, also called thermoelectric cooling slice, is a kind ofheat pump。Its advantages are no sliding parts, limited application in some spaces, high reliability requirements, nocryogenPolluted occasions.utilizesemiconductor material Peltier effect, whenDCConnected by two different semiconductor materials in seriesGalvanic coupleThe two ends of the thermocouple can absorb heat and release heat respectively, which can achieve the purpose of refrigeration.It is a way of generating negativethermal resistanceOfRefrigeration technology, which is characterized byNo movementThe reliability of components is also high.
Chinese name
Semiconductor refrigeration chip
Foreign name
semiconductor chilling plate
Alias
thermoelectric cooler
Type
heat pump
Features
No sliding parts
Advantages
Places with high reliability requirements and no refrigerant pollution
The semiconductor refrigeration chip is a cooling device composed of semiconductors, which only appeared around 1960. However, its theoretical basis Peltierefect can be traced back to the 19th century.This phenomenon was first discovered by Thomas Seeback, a German scientist, in 1821. However, he made a wrong inference at that time and did not understand the real scientific principle behind it.In 1834, Jean Peltier, a French watchmaker and a physicist who also studied this phenomenon part-time, found the real reason behind this phenomenon. It was only with the development of semiconductors in modern times that this phenomenon was actually applied, that is, the invention of the [refrigerator] (note that it was called a refrigerator at this time, not yetSemiconductor cooler)。By manyN-type semiconductorandP-type semiconductorThe particles ofNPThey are connected by common conductors to form a complete line, usually copper, aluminum or other metal conductors, and finally are made of two pieces of ceramicsandwich biscuitsThe ceramic pieces must be insulated and have good heat conduction,
N-type semiconductor
Semiconductor refrigeration chip
Any substance is made up ofAtomic, atoms are composed ofNucleusAnd electrons.The electron rotates around the atomic nucleus at a high speed and is attracted by the atomic nucleus. Due to certain restrictions, the electron can only run in a limited orbit and cannot leave at will. The electrons in each layer of orbit have different energies (electronic potential energy).Electrons in the farthest orbit from the atomic nucleus can often leave the attraction of the atomic nucleus and move between atoms, calledfree electron（carrierWhich enables the material to conduct electricity.If electrons cannot leave the orbit to form free electrons, they cannot participate in conducting electricityinsulator。The conductivity of semiconductor is between conductor and insulator, which is called semiconductor.The important characteristic of semiconductors is that after a certain amount of impurities infiltrate into semiconductors, not only the conductivity can be greatly increased, but also semiconductors with different properties and different uses can be manufactured according to the types and quantities of impurities.When an impurity is doped into a semiconductor, free electrons will be released. This semiconductor is called N-type (negative)semiconductor。
P-type semiconductor
P (positive) semiconductor“hole”To conduct electricity.Under the action of an external electric field, the flow direction of the "hole" is opposite to that of the electron, that is, the "hole" flows from the positive pole to the negative pole, which isP-type semiconductorPrinciple.
Carrier phenomenon
N-type semiconductorFree electron in P-type semiconductor“hole”They are all involved in conducting electricity, and the directional movement of carriers under the action of an external electric field generates current, so they are collectively called "carriers", which are unique to semiconductors. Most carriers are the result of doping impurities (in real semiconductorsImpurity semiconductorThe carrier in the form ofIntrinsic excitationMost of the carriers come from the extra non bondingvalence electron, or cavity);aboutIntrinsic semiconductorIts carrier is determined byThermal excitationOr the role of light, participate incovalent bondA pair of free electrons and holes are produced when the valence electrons of are free electrons.
Semiconductor refrigeration
It not only needs the characteristics of N-type and P-type semiconductors, but also changes the thermoelectric electromotive force rate of semiconductors according to the impurities added,ConductivityandThermal conductivityThis special semiconductor can meet the requirements of refrigeration materials.The commonly used materials in China areBismuth tellurideTernary matrixSolid solution alloyP type is Bi2Te3-Sb2Te3, N type is Bi2Te3-Bi2Se3, and verticalZone melting methodextractCrystalline material。
principle
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In principle, semiconductor refrigeration chip is a tool for heat transfer.When a piece of N-typesemiconductor material Connected with a piece of P-type semiconductor materialThermocoupleWhen there is current in the alignment, heat transfer will be generated between the two ends, and the heat will be transferred from one end to the other, resulting in a temperature difference to form a cold and hot end.But there is resistance in the semiconductor itself. When the current passes through the semiconductor, it will generate heat, which will affect the heat transfer.In addition, the heat between the two plates will also be conversely transferred through the air and the semiconductor material itself.When the cold and hot ends reach a certain temperature difference, when the amount of these two kinds of heat transfer is equal, a balance point will be reached, and the positive and reverse heat transfer will offset each other.At this time, the temperature of the hot and cold ends will not continue to change.In order to achieve lower temperature, heat dissipation and other methods can be used to reduce the temperature of the hot end.
The fan and heat sink are mainly used to dissipate heat at the hot end of the cooling fin.Generally, the temperature difference between the cold and hot ends of the semiconductor cooling fin can reach 40~65 degrees. If the temperature of the hot end is reduced by active heat dissipation, the temperature of the cold end will also decrease accordingly, thus reaching a lower temperature.
When a piece of N-type semiconductor material and a piece of P-type semiconductor material are connected into a couple, after the DC current is connected in this circuit, energy transfer can be generated. The current flows from the N-type element to the connector of the P-type element to absorb heat and become the cold end;The joint flowing from the P-type element to the N-type element releases heat and becomes the hot end.The size of heat absorption and heat release isThrough currentAnd the number of elements of semiconductor materials N and P, the following three points areThermoelectric refrigerationOfThermoelectric effect。
Where: ES is the thermoelectric electromotive force
S is the thermoelectric electromotive force rate (Seebeck coefficient)
△ T is the temperature difference between contacts
Peltier effect
（PELTIEREFFECT）
1834 FrenchPeltier And foundSeebeck effectThe opposite effect of, that is, when the current flows through the contact formed by two different conductors, there will be exothermic and endothermic phenomena at the contact, and the magnitude of exothermic or endothermic is determined by the magnitude of the current.
When current flow existstemperature gradientExcept for those caused by conductor resistanceJoule heatIn addition, the conductor also emits or absorbs heat. Between two conductor points with a temperature difference of △ T, the amount of heat emitted or absorbed is:
Qτ=τ.I.△T
Q τ is exothermic or endothermic power
τ isThomsoncoefficient
I is the working current
△ T is the temperature gradient
Until the 1950s,Soviet Academy of SciencessemiconductorAcademician Yue Fei of the Institute conducted a lot of research on semiconductors and published research results in 1954, indicating that bismuth telluride compoundsSolid solutionIt has good refrigeration effect. It is the earliest and most important thermoelectric semiconductor material, and is still a main component of semiconductor materials in temperature difference refrigeration.
After the theory of Ioffe was applied in practice, many scholars studied the semiconductor refrigeration materials until the 1960sMerit valueThe coefficient has only reached a considerable level and has been applied on a large scale, that is, our semiconductor refrigeration chips.
China inSemiconductor refrigeration technologyIt began in the late 1950s and early 1960s, when it was one of the earlier research units in the world. In the mid-1960s, the performance of semiconductor materials reached the international level. From the late 1960s to the early 1980s, it was China's semiconductor refrigeration chiptechnological development A step of.During this period, on the one hand, the coefficient of merit of semiconductor refrigeration materials is improved, and on the other hand, itsapplication area 。Institute of Semiconductors, Chinese Academy of SciencesA great deal of manpower and material resources have been invested to obtain semiconductor refrigeration chips, so that the production of semiconductor refrigeration chips and the development and application of its two products have come into being.
1. No need for anycryogen, continuous operation, noPollution sourceThere is no rotating part, which will not produce rotary effect. There is no sliding part, which is a solid piece, without vibrationnoiseLong service life and easy installation.
2. The semiconductor refrigeration chip has two functions, which can both cool and heat. The refrigeration efficiency is generally not high, but the heating efficiency is very high, always greater than 1.Therefore, using one chip can replace the discreteheating system andrefrigeration system。
3. The semiconductor refrigeration chip is a current transducer type chip, which can achieve high-precisiontemperature controlIn addition to temperature detection and control means, it is easy to realize remote control, program control and computer control, which is convenient for compositionautomatic control system。
4. SemiconductorRefrigerating sheetThermal inertiaVery small, cooling and heating time is very fastHot endGood heat dissipationCold endNo loadThe maximum temperature difference of the cooling plate can be reached in less than one minute after power on.
5. The reverse use of semiconductor refrigeration chips isThermoelectric generationThe semiconductor refrigeration chip is generally suitable for power generation in the middle and low temperature areas.
6. The power of the single refrigeration element pair of the semiconductor refrigeration chip is very small, but it can be combined into a stack. If the same type of stack is used in series and parallel to form a refrigeration system, the power can be very large, so the refrigeration power can reach a range of several milliwatts to tens of thousands of watts.
7. The temperature difference range of semiconductor refrigeration chip, from positive temperature 90 ℃ toNegative temperatureIt can be realized at 130 ℃.
According to the above analysis, the application range of semiconductor thermoelectric devices includes: refrigeration, heating, power generation, refrigeration and heating applications are common, including the following aspects:
2. Medical treatment;Cold force, cold closingcataractRemove the tabletBlood analyzerEtc.
3. Laboratory devices:Cold trap、Cold boxCold bath, electronic low temperature testing device, various constant temperature, high and low temperature experimental instruments.
4. Special devices:petroleum productsLow temperature testerBiochemical productsLow temperature tester, bacteria incubator, constant temperature developing tank, computer, etc.
5. Daily life: air conditioner, cold and hot boxWater dispenser、E-mailEtc.In addition, there are other applications, which will not be mentioned here.
instructions
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1、 Correct installation and assembly methods:
1. Installation of one side of cooling plateHeat sink, install the cooling system on one side, and install the surfaceFlatnessNo more than 0.03mm, burr and dirt shall be removed.
2. The cooling fin is in good contact with the cooling fin and the cooling guide block, and the contact surface must be coated with a thin layerThermal conductive silicone grease。
Semiconductor refrigeration chip
3. When fixing the cooling slice, the force on the cooling slice should be uniform, and attention should be paid not to excessive force to prevent the ceramic slice from fracturing.
3. Do not switch on immediately when the cooling blade is workingReverse voltage(After 5 minutes).
4. There shall be no water ingress inside the cooling fin.
5. The humidity around the cooling fin shall not exceed 80%.
3、 Precautions in use of CDL1 series refrigeration components:
1. When using nonspecial equipmentWhen inspecting the device, the temperature of the hot end must be lower than 80 ℃ under the operating parameters (including changing the current direction from the cold end to the hot end).Under the condition that there is no heat dissipation at the hot end, the test shall be conducted by momentarily energizing, that is, touching with handsCoolerThe two end faces ofHeat sensation, just feel a little cold on one side.Otherwise, because the temperature of the hot end is too high, it is very easy to cause short circuit or open circuit of the device, and the cooler will be scrapped.
2. OnGeneral conditionsNext, identify thePolarityThe cold end of the refrigeration module can be placed upward, and the lead end faces the direction of the human body. At this time, the right lead is the positive pole, usually represented in red;The left side is the negative pole, which is usually expressed in black, blue or white. This polarity is the wiring method of the refrigeration module during operation.When heating is needed, just change the current polarity.When refrigeration works, DC power supply must be usedRipple coefficientIt should be less than 10%.
3. Refrigeration thermocouplelogarithmandLimiting voltageThe parity logarithm refers to the number of PN nodes.For example, if the refrigerator model is CDL1-12703, 127 is the couple number of refrigeration components, and 03 is the allowable current value (unitampere）, the limiting voltage of refrigeration module V;The couple number × 0.11, for example, the limit voltage of CDLl-12703 V=l27 × 0.11=13.97 (V).
4. Whether various refrigeration components are in use or in the test, the cold and heat exchange must be carried out after both ends are restored to the room temperature (generally it takes more than 15 minutes).Otherwise, the ceramic chips will be easily cracked.
5. In order to improve the service life of the refrigeration module, the exposed PN elements around the refrigeration module should be cured before use.Method 706 single group curingrubberEvenly coat the PN elements around the refrigeration module, not on the two end faces.The rubber coated is naturally cured for 24 hours, and after curing, it becomes a milky white elastic solid.The purpose of curing is to completely isolate the thermocouple of refrigeration module from the outside air.It has the function of moisture-proof and can increase the service life of refrigeration components by about 50%.
6. During installation, first use water freeAlcohol cottonWipe both ends of the refrigeration module clean and evenly apply a thin layer of thermal conductive silicone grease:Cold plate, heat dissipation plate) shall be processed, the surface flatness shall not be greater than 0.03MM, and shall be cleaned;Cold end of refrigeration module during installationfaceIt must be in good contact with the cold storage plate, and the hot end should be in good contact with the heat dissipation plate (if usedScrewTighten with even force, not excessive);The size of the cold storage plate and heat dissipation plate depends on the cooling method and cooling power, which can be determined according to the situation;In order to achieve the best cooling effectThermal insulation materialThe thickness of filling shall be 25~30mm.
7. Without special instruments, users can measure the overall dimensions and height according to the manufacturer's instructions to judge its performance.useA multimeterTest the static resistance of the refrigeration module,inaccurate, for reference only.
The high calorific value caused by frequency increase has always been a problem discussed by many overlockerswindColdwaterCold, to compressorSemiconductor refrigeration, and then the crazy liquid nitrogendry ice, use up the cooling method.CommonAir-cooled radiatorAnd water cooling have become entry-level overclocking due to their low cost and ease of useEnthusiastOfStandard configurationThe disadvantage is that even the best air cooling or water cooling can onlytemperature controlIs close to or equal toambient temperature。In order to reduce the temperature below zero,have a feverFriends have chosencompressorAnd semiconductor refrigeration.VaporChill and Mach series compressors passPhase change refrigerationCan makeevaporatorThe temperature reaches - 50 ℃, while the three-stage compressor system made by foreign enthusiasts even reaches - 196 ℃, which is equivalent to liquid nitrogenEvaporation temperature。However, due to the high price of the compressor system, it can only be accepted by a few enthusiasts. Liquid nitrogen and dry ice may be the ultimate sharp tools only used by hardcore enthusiasts, and the evaporation/sublimation speed is very fast, which can only bring about the ultimate efficiency in a short time, without practical value, so semiconductor refrigeration becomes the best choice.
The particles of an N-type and P-type semiconductor are welded with a metal connector to form a couple.WhenDC currentWhen flowing from the N pole to the P pole, heat absorption occurs on the 2.3 end, which is calledCold endThe heat release phenomenon occurs at the lower 1.4 end, which is calledHot endIf the current direction is reversed, the cold and hot ends will switch to each other.Due to a coupleheat effectIt is small (generally about IKcal/h), so it will actually be tens.Hundreds of pairsGalvanic coupleSyntagmaticThermopile。Therefore, the cooling of semiconductors, that is, heat absorption at one end and heat release at the other, is caused by the carrier（electrons and holes ）Flow through the node, caused by the change of potential energyenergy transfer, which is the essence of semiconductor cooling, namelyPartier effect。
