The transient electrical test method of liquid cold plate thermal resistanceTechnical field
The invention belongs to the thermo-resistance measurement methods in electronic equipment thermal control field.
Background technique
With the progress of science and technology, the complexity of electronic equipment is continuously improved, and displacement volume increases with benefit, from bodyProduct sharply reduces, and with the sharp increase of electronic component summation watt rating, the type of cooling of natural cooling and forced air cooling has been difficult to fullThe needs of sufficient electronic component thermal design.A kind of heat exchange equipment of the cold plate as efficient maturation, obtains in Electronic coolingIt is widely applied.Currently, the development of electronic device gradually tend to micromation and it is integrated.Micromation and integrated electronic deviceProcessing and assembly difficulty are not only increased, while increasing the heat dissipation difficulty of electronic device.According to statistics, most electronics devicePart damage is due to caused by temperature overheating.The heat flow density of pyrotoxin (chip) in electronic equipment is higher and higher, in engineeringApplication have reached 300W/cm2Magnitude, it is contemplated that 1000W/cm will be reached quickly2This order of magnitude.The especially integrated electricity of siliconThe appearance on road, so that the integrated level of circuit sharply increases.For chip higher for these integrated levels, the heat generated is anxiousIncrease severely and add, lead to the raising of heat flow density, and then electronic equipment temperature is caused to increase, so that electronic equipment be made to fail.
With semiconductor devices power, the continuous improvement of frequency, integrated level, the high power consumption of generation can make the work of device chipIt is sharply increased as temperature rise.According to arrhenius model, device lifetime exponentially declines with temperature.Temperature rise not only can be to semiconductor deviceThe part service life has an impact, and also will affect the characteristic of device and causes other failure mechanisms.Therefore, precise measurement semiconductor deviceThe temperature rise of part and thermal resistance have very important meaning to device performance is improved.Common thermal characteristics heat technique can be divided into physics and connectTouching method, optical method, electric method three categories.Physical contact method, which refers to, carries out direct physical contact temperature sensor and measured deviceTo carry out temperature measurement.Optical method is the technological means for carrying out temperature measurement to semiconductor devices using the characteristic of light, is usually surveyedMeasure the characteristics such as its natural exciting radiation, reflected radiation and scattering.The larger limitation of one of physical contact method and optical means is exactlyIt can only obtain the Temperature Distribution in device surface direction, the Temperature Distribution and thermal resistance that can not but obtain device longitudinal direction constitute distribution.ElectricityMethod is the powerful for measuring the thermal characteristics such as temperature rise and the thermal resistance of semiconductor devices.Many electrical parameters of semiconductor devices are allThere are very strong temperature dependency, such as PN junction forward conduction voltage, threshold voltage, leakage current and gain etc..Therefore, by rightThe careful measurement of more temperature sensitive parameters of electricity, the operating temperature of available semiconductor devices.
In existing electronic device cooling mode, even if traditional forced air cooling technology is big using Advanced Fan and optimizationWhen area is heat sink, cooling capacity also only can reach 20W/cm2, and such heat-removal modalities can occupy very large space and wasteA large amount of material.And liquid cold plate is widely used as a kind of efficient heat exchange equipment, in the cooling of some electronic devicesIn the middle, heat conductive efficiency is high, and heat power is 20 times or more of traditional air cooling way.Not only heat conductive efficiency is high for liquid cold plate, andAnd it is reliable and stable, just because of its numerous advantage in electronic component thermal control, become current electronic device thermal designOne research hotspot in field.Cold plate is a kind of single fluid heat exchanger, is made of substrate, fin and baffle, between fin in channelCooling fluid is passed to, electronic device (i.e. the heat source of cold plate) is then fixed on the substrate of one or both sides, and heat is by electronic deviceIt is transmitted to substrate and fin by thermally conductive, is then taken away by cooling fluid.Fin is mainly used to expand heat transfer area, reduces fluidThermal-boundary-leyer thickness reduces thermal resistance, and then improves heat conductive efficiency.The form of common liquid cooling cools down heating device at presentSpecific method be: the heat of device is conducted to cold plate, exchanges heat by the working medium run in convection current and cold plate, then by working mediumHeat is taken away.
Cold plate thermal resistance is very important parameter in liquid cooling design, only accurately obtains cold plate thermal resistance, could preferablyIt optimizes.The entire thermal resistance of device junction to cooling fluid consists of three parts, i.e. internal thermal resistance, external thermal resistance and system heatResistance.Internal thermal resistance refers to device heating area to the thermal resistance between device mounting surface；External thermal resistance refers to device mounting surface to substrateThermal contact resistance；System thermal resistance refers to the thermal resistance between substrate and cooling fluid.Liquid cold plate thermal resistance can reflect chip, weldingThe sintering of layer and shell or bonding and other issues, heat resistance characteristic has vital shadow to the reliability of semiconductor devicesIt rings.Therefore, the accuracy of thermo-resistance measurement is particularly significant, and associated Study on Test Method is also by attention.
Traditionally, the semiconductor devices of encapsulation be considered as the series resistances being made of compositions such as chip, solder, shells,Thermal capacitance network, the crust thermal resistance of device are the sum of each composition thermal resistance on heat conduction path, and the transient prediction response curve of device isEach composition thermal resistance, the coefficient result of thermal capacitance.The prior art generally determines thermal resistance by testing the temperature difference of cold plate two sides.ItsTest method is: heat source or array of heat sources being mounted on cold plate, heat source is made steadily to generate heat as far as possible, it is close to calculate its hot-fluidDegree is measured the temperature difference of cold plate two sides below heat source using one group of thermocouple at this time, can be obtained with this temperature difference divided by heat flow densityTo the thermal resistance value of cold plate.But conventional method has the following problems:
A) heat source is equipped with due to cold plate on one side, the temperature on the face vertical direction at the subpoint of cold plate is veryHardly possible measurement；
B) method of traditional test thermal resistance is tested generally by the way of stable state, to make liquid cold plate under normal conditionsHeating reaches stable state, generally requires 1~2 hour.And generally require the special test heat source of customization, such as resistance or dedicatedSemiconductor, it is necessary to cold plate individually be disassembled test, the period is longer, and testing efficiency is low；
C) error: if the fixation position of 1, thermocouple not on theoretical fixed point, can generate large error due to distance；2, the heat source that conventional method uses is generally resistance, if fever is uneven, also directly influences the measuring and calculating of hot road transmission range；3,Since cold plate itself is three-dimensional heat transfer structure, the heat flow density in one-dimensional square is difficult to estimate, this will lead toIt is larger to the calculating error of heat flow density；4, due to calibration or instrument error, it will lead to the accumulated error of test macro.
To sum up, cold plate thermal resistance is measured using conventional method has that measurement is difficult and error is big, and due to cold plateBe mounted in fine and close electronic equipment in most cases, the condition without installation conventional heat sources, thus conventional methodCold plate is individually disassembled and is tested, and needs to introduce new method to measure.
Thermal transient tester T3Ster is a kind of transient state for measuring encapsulation semiconductor devices and other electronic equipmentsThe semiconductor apparatus of heat resistance test of thermal characteristics, basic function are that transformation by the test method of electricity and mathematically calculates knotStructure function, directly measurement thermal resistance curve, isolate the thermal resistance of semiconductor.T3Ster can provide nondestructive Thermal test sideMethod, test philosophy are: for general semiconductor devices, on-load voltage is always presented decline and becomes with the rising of junction temperatureGesture.Moreover, for common diode (due between the PN junction of triode equally with the characteristic of diode, can also be withIt is common triode), generally in (25~125) DEG C this temperature range, present between on-load voltage and junction temperature such as Fig. 1 instituteThe inverse proportion linear relationship shown, (in Fig. 1, the voltage temperature coefficient of straight line is known as k-factor).After obtaining k-factor, pass through firstChange the power input of electronic device；Changed later by the transient temperature that the hot relevant parameter of test equipment tests out electronic deviceCurve；Numerical value processing is carried out to temperature variation curve, structure function is obtained by mathematic(al) manipulation；Heat is isolated from structure functionThe thermal physical property parameters such as resistance and thermal capacitance.
Summary of the invention
The purpose of the present invention is place in view of the shortcomings of the prior art, provide it is a kind of convenient, flexible quick, without fixedTest heat source processed and disassembly cold plate, thermo-resistance measurement is high-efficient, can be improved the transient electrical test liquid cooling of thermo-resistance measurement precisionThe method of cold plate thermal resistance, to solve the problems, such as the thermal resistance measurement of the electronic equipment liquid cold plate of high heat flux density.
The present invention realizes a kind of method of electrical testing liquid cold plate transient thermal resistance of above-mentioned purpose, it is characterised in that including such asLower step:
Thermal transient tester T3Ster instrument is electrically connected computer, and semiconductor devices and its adapter are connected to T3SterIt tests on the corresponding interface of host；Then in the test software of built-in computer T3Ster, according to semiconductor devices and cold plateCharacteristic, setting heating time, cooling time, heated current, test electric current and voltmeter range major parameter；It is opened using T3SterThe test of beginning transient electrical obtains the cooling curve of tested semiconductor device and saves as test file；The quilt tested out before inputThe coefficient value of the voltage temperature coefficient k of semiconductor device is surveyed, and saves file；Remove the noise in test curve；Calculate semiconductorThe differential structrue function of device is isolated cold plate thermal resistance, thermal contact resistance, device from multiple extreme points of differential structrue function and is dissipatedHot device thermal resistance, the information of packaging thermal resistance and junction of semiconductor device thermal resistance；It is last bent according to the differential structrue function for being tested semiconductorCurve is successively pressed R from right to left using the maximum point in curve as burble point by line1、R2、R3…RnIt is a different to be divided into nRegion, with the region R of the rightmost side1For represent immediate environment in entire heat-transfer path system last at thermal resistance value, by R1AsLiquid cold plate thermal resistance.
Present invention test method compared with the prior art, has the advantages that.
Without customizing test heat source.The present invention is not necessarily in addition to using T3Ster and common diode or triodeAdditional customized or buying device, test period are short.Solving conventional method, to generally require the special test heat source of customization (dedicatedResistance or dedicated semiconductor, such as customization and the matched thick-film resistor of cold plate etc.), test period longer problem.The present invention adoptsIt is real without additional customized or buying device in addition to using common diode or triode with thermal transient tester T3SterIt is short to test the preparatory period.It solves conventional method and generally requires the special test heat source of customization, such as resistance or dedicated semiconductor,Preparatory period longer problem.
Thermo-resistance measurement is high-efficient.The present invention can generally complete test in several minutes, and at a terrific speed after progressReason, and then cold plate thermal resistance is isolated, accelerate thermo-resistance measurement speed.And product designer comparatively can easily carry out it is moreSecondary iteration tests directly shorten the design optimization period of electronic equipment.Liquid cold plate will be made by avoiding in conventional methodHeating reaches stable state under normal conditions, generally requires 1~2 hour (according to the regulation of MIL-STD-810D, by the temperature of test productUntil degree reaches balance, allow to be reached soaking time required for equalized temperature by according to the selection of its outer dimension by test product, it is testedProduct outer dimension is in 100mm, soaking time 1.5h), testing time longer problem.
Improve thermo-resistance measurement precision.The present invention can be accurately obtained semiconductor devices using structure function curve very muchLongitudinal thermal resistance is constituted, and provides extraordinary condition for device design and thermal characteristics test.According to the computational theory of T3Ster, testError essentially consist in the structure function in later period mathematical processes separation error, the error can control within ± 2% (due toIt can provide extremely accurate temperature measurement, use the measuring accuracy that can reach 0.01 DEG C when diode-transducer；Assuming that 50mVUnder the premise of temperature causes stepped voltage to change, sensitivity can arrive 2mV/ DEG C), the test far below conventional test methodologies missesDifference directly enhances and improves thermo-resistance measurement precision.Therefore, product designer can get more accurate liquid cold plate thermal resistance numberAccording to the temperature of crucial heating device preferably being controlled, no matter for promoting main performance or the lifter service life of electronic equipmentThere is more active influence.
Non-destructive testing.Semiconductor device chip temperature rise and thermal resistance the present invention is based on electric method longitudinally constitute analytical technology,Point thermal resistance that can accurately measure in semiconductor devices heat-transfer path is constituted, and can nondestructively detect to be layered in the hot road of cold plateThe position of failure.This method has many advantages, such as that test speed is fast, harmless to cold plate and device architecture.
Detailed description of the invention
Fig. 1 is relation curve schematic diagram of the present invention about semiconductor devices on-load voltage and junction temperature.
Fig. 2 is output current curve schematic diagram of the present invention about constant-current source when testing.
Fig. 3 is the present invention about tested semiconductor devices on-load voltage versus time curve schematic diagram.
Fig. 4 is the present invention about the semiconductor devices cooling curve schematic diagram being extracted.
Fig. 5 is variations injunction temperature curve synoptic diagram of the present invention about semiconductor devices.
Fig. 6 is thermal resistance curve schematic diagram of the present invention about semiconductor devices.
Fig. 7 is differential structrue function curve schematic diagram of the present invention about semiconductor devices.
Fig. 8 is circuit connection diagram of the present invention about semiconductor devices.
Fig. 9 is the present invention about cold plate test semiconductor installation diagram.
Specific embodiment
- Fig. 9 refering to fig. 1.According to the present invention, the connected computer of thermal transient tester T3Ster instrument, by semiconductor devicesAnd its adapter is connected on the corresponding interface of T3Ster test host；Then in the test software of built-in computer T3SterIn, according to semiconductor devices and cold plate characteristic, heating time, cooling time, heated current, test electric current and voltmeter amount are setJourney major parameter；Start transient electrical using T3Ster to test, obtain the cooling curve of tested semiconductor device and saves as testFile；Voltage temperature coefficient (k-factor) value of the tested semiconductor device tested out before input, and save file；Remove testNoise in curve；The differential structrue function for calculating semiconductor devices, is isolated from multiple extreme points of differential structrue functionCold plate thermal resistance, thermal contact resistance, device radiator thermal resistance, the information of packaging thermal resistance and junction of semiconductor device thermal resistance；Finally according to quiltCurve is successively pressed R from right to left using the maximum point in curve as burble point by the differential structrue function curve for surveying semiconductor1、R2、R3…RnN different regions are divided into, with the region R of the rightmost side1To represent immediate environment in entire heat-transfer path systemLast at thermal resistance value, by R1As liquid cold plate thermal resistance.Can specifically following steps be used:
T3Ster connection computer is used first, carries out the test of voltage temperature coefficient (k-factor): in certain temperature sectionInterior semiconductor on-load voltage of testing saves file with the relationship of semiconductor mounting surface temperature.Next, installing tested cold plateWith tested semiconductor devices, start thermo-resistance measurement.By built-in constant-current source, thermal transient tester T3Ster imposes measured deviceThe output current curve value changed as shown in Figure 2.High current in figure is heating current, it is therefore an objective to make semiconductor device heating；Low current is test electric current, it is therefore an objective to make its both ends on-load voltage by applying constant current to it, which will not makeThere is fuel factor in tested semiconductor devices.Then, T3Ster instrument will record load as shown in Figure 3 at semiconductor devices both endsThe curve that changes over time of voltage.When test starts, junction temperature T0, the low current (test electric current) of load can be in semiconductor devicePart both ends apply test steady state voltage VF,sense,0；Once high current (heated current) is opened, then semiconductor devices both end voltage meetingIt flies up to heating initial voltage VF,drive,1, as experiment carries out, high current can make the junction temperature of device be gradually increasing, and pass throughAfter crossing heating time t, each structure sheaf in hot-fluid approach reaches thermal equilibrium state, and junction temperature rises to T at this time1, load in semiconductorThe voltage at device both ends gradually can slightly decline, until semiconductor devices junction temperature is kept constant, on-load voltage at this time is heatingSteady state voltage VF,drive,0；When heating finishes, T3Ster instrument can cut off heated current, impose again test electric current to device intoRow test.When just switching to test electric current, since semiconductor device temperature is higher, before on-load voltage at this time is slightly belowVoltage when low current is loaded, voltage at this time is test medium voltage VF,sense,1.As semiconductor devices gradually cools down, addOriginal test steady state voltage V can be gradually returned to by carrying voltageF,sense,0Level, measured device forward voltage in the case where testing electric currentVF,sense(t) versus time curve, referred to as cooling response curve (abbreviation cooling curve).Thermal transient tester T3Ster willIt extracts the continuous mathematic(al) manipulation of this section of cooling curve (being also possible to heating curves sometimes) progress out, and obtains test result, becomeIt is as follows to change mode:
Thermal transient tester T3Ster is according to the cooling curve for extracting semiconductor devices as shown in Figure 4, by taking-upThe ordinate of cooling curve, is converted using k-factor as denominator, obtains the variations injunction temperature of semiconductor devices as shown in Figure 5Curve.Thermal transient tester T3Ster carries out the variations injunction temperature curve in Fig. 5 using semiconductor devices power as denominator againTransformation, can obtain the thermal resistance curve of semiconductor devices as shown in FIG. 6, and abscissa is timeconstantτ=RC in figure, and R is thermal resistance,C is thermal capacitance, and ordinate is thermal resistance.
Thermal transient tester T3Ster is according to the transverse and longitudinal coordinate of thermal resistance curve in obtained thermal resistance curve interchange graph 6, and againSecondary carry out mathematic(al) manipulation, can obtain differential structrue function curve as shown in Figure 7, and in figure, abscissa is thermal resistance, and ordinate is thermal capacitance CTo the differential of thermal resistance R.As can see from Figure 7, the differential structrue function curve of semiconductor devices generally has multiple maximumPoint, in multiple maximum points, the distance between every two maximum point is a certain layer in the semiconductor devices heat-transfer pathThermal resistance.
Embodiment 1
Since the transistor of SOT-93 encapsulation, such as triode can satisfy the test encapsulation requirement of T3Ster, therefore canTo use the triode of SOT-93 encapsulation as tested semiconductor devices, and carry out following steps:
Refering to fig. 1.First, it measures the k-factor of triode: the triode and its adapter is connected to thermal transient testerT3Ster is tested on the corresponding interface of host；Then triode merging T3Ster is carried in thermostat, and keeps well connecingTouching；Then in the T3Ster test software of built-in computer, according to the dynatron performance, test temperature section is set；It is givingDetermine to carry out k-factor test in temperature range and saves test result；
Refering to Fig. 8.Second, according to semiconductor device circuit connection figure as shown in Figure 8, by the triode and its adapterIt is connected on the corresponding interface of T3Ster test host；
Refering to Fig. 9.Third tests semiconductor installation diagram according to cold plate, triode 1 is bonded in liquid cooling using conductive silver pasteOn cold plate 2, connection entrance liquid cooling connector 3 and outlet liquid cooling connector 4.Cold plate 2 is connected in liquid cooling system, by triode 1 withThermal transient tester T3Ster is connected, and T3Ster is connected with computer；
4th, it is powered on liquid cooling piping connection cold plate and transfer tube, and to transfer tube, works normally liquid cooling system；
5th, according to triode and cold plate characteristic, heating time, cooling time, heated current, test electric current and electricity are setThe major parameters such as meter-pressing amount journey；
6th, start to measure, when measuring the thermal resistance of triode, obtains three pole using the experimental method of heating-coolingThe cooling curve of pipe, and save result；
7th, it carries out data analysis: a) using the mathematical way of square root fitting built in T3Ster analysis software, removing coldBut the front end noise of curve, b) according to cooling curve, mathematic(al) manipulation is carried out, the differential structrue letter of the triode heat-transfer path is calculatedNumber, c) thermal resistance section different in the differential structrue function curve is separated, separation method is as follows: 1) finding differential as shown in Figure 7Maximum point in structure function curve, 2) differential structrue function is successively divided into n difference according to extreme point from right to leftRegion, 3) with the region R of the region rightmost side1Represent the thermal resistance value of tested liquid cold plate.