Acceleration factor calculation method for highly accelerated life test

Abstract

The invention relates to the field of electrical variable measurement, in particular to an acceleration factor calculation method for a highly accelerated life test, which comprises the following steps: carrying out heating and cooling tests on a PCB (Printed Circuit Board) product, simultaneously carrying out vibration tests on the PCB product, and calculating an acceleration factor of the PCB product for testing the life of the PCB product: H, carrying out cyclic heating and cooling on the PCB product so as to realize rapid temperature change of the PCB product; n, high-frequency random vibration waves are applied to the PCB product, so that the PCB product is in a high-frequency random vibration state; wherein the step H and the step N are carried out synchronously, so that fatigue strength generated by the step H and the step N on the PCB product is coupled to obtain an acceleration factor A; the high-frequency random vibration wave contains energy of more than 2000Hz, so that all components on the PCB product can be vibrated. According to the acceleration factor calculation method for the highly accelerated life test provided by the invention, all failure faults can be easily found in a laboratory, and the test accuracy is improved.

Description

Technical Field

[0001] The invention relates to the field of measuring electrical variables, and in particular to a method for calculating an acceleration factor of a highly accelerated life test. Background Art

[0002] Highly Accelerated Life Test is referred to as HALT. There are three main test procedures in Highly Accelerated Life Test: random vibration test, rapid temperature change test and combined stress test. The acceleration factor refers to the ratio of the product's life under normal working stress to its life under accelerated environment.

[0003] However, the above three main test procedures are usually used as acceleration factors alone. The components of the acceleration factors are simple and it is difficult to simulate the real environment. There are technical problems in the laboratory where failures are difficult to find, and it is urgent to design a new acceleration factor calculation method.

[0004] It should be noted that the above information disclosed in this background technology section is only for understanding the background technology of the present application concept, and therefore, it may contain information that does not constitute the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the acceleration factor of a highly accelerated life test to solve the above problems.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] Calculation method of acceleration factor for highly accelerated life test,

[0008] Conduct heating and cooling tests on PCB products, perform vibration tests on PCB products, and calculate the acceleration factor of PCB products for life testing of PCB products.

[0009] In an optional embodiment, the following steps are included:

[0010] H. Cycle heating and cooling of PCB products to achieve rapid temperature change of PCB products;

[0011] N. Apply high-frequency random vibration waves to the PCB product to put the PCB product in a high-frequency random vibration state;

[0012] The step H and the step N are performed synchronously, so that the acceleration factor A is obtained by coupling the fatigue strength generated by the step H and the step N on the PCB product.

[0013] In an optional implementation, the calculation formula of the acceleration factor A is as follows:

[0014]

[0015] Random vibration equivalent conversion fatigue accumulation formula:

[0016] D(vib)=∑(N1S1 (1 / β) +…+N x S x (1 / β) );

[0017] Rapid temperature change equivalent conversion fatigue accumulation formula:

[0018] D(temp)=∑(2N1S1 (1 / β) +…+2N x S x (1 / β) ;

[0019] Composite stress equivalent conversion fatigue accumulation formula:

[0020] D(com)=D(vib)×D(temp);

[0021] Where: D(vib) = fatigue accumulation value of random vibration;

[0022] D(temp) = fatigue accumulation value of rapid temperature change;

[0023] 2N = number of cycles;

[0024] S = stress condition (rapid temperature change °C / min).

[0025] In an optional embodiment, the high-frequency random vibration wave contains energy above 2000 Hz, so that all components on the PCB product can be vibrated;

[0026] When the PCB product is cyclically heated and cooled in step H, the heating process and the cooling process are performed alternately.

[0027] In an optional embodiment, the high-frequency random vibration wave is provided by a high-frequency random vibration device;

[0028] When the PCB product is cyclically heated and cooled in step H, the PCB product is first subjected to a heating process or a cooling process.

[0029] In an optional embodiment, the high-frequency random vibration wave in step H is: 2000Hz~5000Hz;

[0030] The heating temperature in step N is: -65°C to 85°C; the first heating or cooling in step N starts from room temperature.

[0031] The beneficial effects of the present invention are as follows: a method for calculating the acceleration factor of a highly accelerated life test is provided, wherein rapid temperature change and high-frequency random vibration are used in coordination with each other, and the two together constitute the elements of the acceleration factor. The components of the acceleration factor are comprehensive, and the effect of simulating the actual use environment of PCB products in the laboratory is achieved. All failure faults can be easily found in the laboratory, thereby improving the accuracy of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A verification diagram of the relationship between vibration magnitude and stress-strain provided in an embodiment of the present disclosure.

[0034] Figure 2 A verification diagram of the relationship between temperature change rate and stress-strain provided in an embodiment of the present disclosure.

[0035] Figure 3 This is a diagram of an embodiment of the vibration parameter and fatigue accumulation calculation provided in an embodiment of the present disclosure.

[0036] Figure 4 A diagram showing the vibration magnitude and fatigue accumulation calculation results provided in an embodiment of the present disclosure.

[0037] Figure 5 This is a diagram of the temperature change cycle and fatigue accumulation calculation results provided in an embodiment of the present disclosure.

[0038] Figure 6 This is a diagram of the temperature change rate and fatigue accumulation calculation results provided in an embodiment of the present disclosure.

[0039] Figure 7 This is a diagram of the HALT test conditions and fatigue accumulation calculation results provided in an embodiment of the present disclosure.

[0040] Figure 8 An evaluation diagram of sample environmental conditions and cumulative fatigue test time provided for an embodiment of the present disclosure.

[0041] Fig. 9 This is a diagram of an acceleration factor calculation embodiment provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In this article, when it is mentioned that the first component is located on the second component, this may mean that the first component may be directly formed on the second component, or the third component may be interposed between the first component and the second component. In addition, in the drawings, in order to effectively describe the technical content, the thickness of the components may be exaggerated or reduced.

[0044] Herein, example embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as "at least one of..." when following a list of components modify the entire list of components, rather than modifying individual components in the list. For example, the expression "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0045] The terms used herein are only used to describe specific exemplary configurations and are not intended to be limiting. As used herein, the singular articles "a", "an", and "the" may also be intended to include plural forms, unless the above text clearly indicates otherwise. The terms "include", "comprise", and "have" are inclusive, thus specifying the presence of features, steps, operations, components, and / or assemblies, but do not exclude the presence or addition of one or more other features, steps, operations, components, assemblies, and / or combinations thereof.

[0046] As used herein, the phrases "in one embodiment," "according to one embodiment," "in some embodiments," and the like generally refer to the fact that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure. Therefore, a particular feature, structure, or characteristic may be included in more than one embodiment of the present disclosure, so that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example," "exemplary," and the like are used to "serve as an example, instance, or illustration." Any implementation, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. On the contrary, the use of the terms "example," "exemplary," and the like is intended to present concepts in a concrete manner.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0048] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0049] refer to Figures 1 to 9 At least one embodiment provides a method for calculating the acceleration factor of a highly accelerated life test, including: H, cyclically heating and cooling a PCB product to achieve rapid temperature change of the PCB product, using the principle of thermal expansion and contraction to deform the components on the PCB product, simulating the deformation of the components of the PCB product during actual use; N, applying a high-frequency random vibration wave to the PCB product to put the PCB product in a high-frequency random vibration state, simulating the slight displacement of the components of the PCB product when subjected to vibration during actual use; wherein the steps H and N are performed simultaneously, so that the fatigue strength coupling generated by the steps H and N on the PCB product is used to obtain an acceleration factor A; random vibration characteristics of the highly accelerated life test: the range of high-frequency random vibration is: 2000Hz~5000HZ, thereby generating a resonant induction effect on the product; all components on the tested PCB product are excited to vibrate, so that the amplitude of the product is significantly increased; the vibration spectrum diagram for high-frequency random vibration is: the X-axis is frequency (Hz), and the Y-axis is amplitude (g 2 / Hz), each frequency corresponds to an amplitude, and the curve of the vibration spectrum is obtained. The area of ​​the vibration spectrum can represent a vibration value G rms . G rms It is a value used as a control for high-frequency random vibration equipment; the spectrum diagram shows the relationship between each frequency of high-frequency random vibration and the corresponding vibration energy (amplitude). High-speed cameras and image tracking software are needed to observe and calculate: When PCB products are subjected to high-frequency random vibration: 1. The components on the PCB products move in all directions; 2. The components on the PCB products shake rapidly due to stress and strain; the following is a specific implementation example: The stress and strain at any point on the product show high-frequency and rapid periodicity, and the amplitude of shaking is quite small; the degree of stress and strain will increase with the increase of the product response magnitude (reference Figure 1 ).

[0050] In some embodiments, the rapid temperature change characteristics of the highly accelerated life test: the rapid temperature change caused by the high and low temperature cycles produces the effect of thermal expansion and contraction, so that the components on the PCB product interact quickly. High-speed cameras and stress-strain analysis software are required to observe the movement of components on the PCB product: the main indicators of the highly accelerated life test are: 1. The components on the PCB product interact (extrude) from the inside to the outside; 2. The components on the PCB product have strains due to thermal expansion and contraction; the following is a specific implementation example: the stress and strain at any point on the product changes periodically with the temperature cycle, and the amplitude of the shaking is quite small; the degree of stress and strain will increase with the increase of the product response magnitude (reference Figure 2 ).

[0051] In some embodiments, rapid temperature changes and temperature differences in temperature cycles cause shrinkage or expansion rates between different components of the system, or induce different strain rates. The coefficients of thermal expansion (CTE) of various components on the PCB product are incompatible, which may trigger defects such as: interconnection problems, solder joint problems, defective leads and ball solder joints, deformation or cracking of components on PCB products, cracking of surface coatings, sealing leakage, insulation protection failure, thermal coefficient mismatch of different materials, circuit line loss, patch quality, cracks, internal injuries, plug-in tolerances, and joint problems.

[0052] Composite stress characteristics of highly accelerated life test: In HALT test, temperature cycle and random vibration exist and work together. Rapid temperature change often causes product fracture. In order to detect fracture, random vibration is necessary. The combination of the two produces composite stress, which has a destructive force multiplication effect. If the composite stress test is missed, the product will miss more than 30% of the failure opportunity.

[0053] In some embodiments, the basic principle of HALT is fatigue accumulation: the fatigue accumulation caused by the composite stress of random vibration and temperature change rate and their combination can be explained by the fatigue accumulation index of Miller's law; this law quantifies the fatigue accumulation caused by a stress: the amount of fatigue accumulated under each stress condition is expressed as a percentage of the total life consumed, and the total life is the sum of the life consumed under all stress conditions. When the sum reaches 1, the end of the life is reached and failure occurs; and the percentage of consumed life is based on the relationship between the stress level and the number of cycles before failure (SN). The HALT test uses random vibration and temperature change rate to make the product move in all directions; so its operating principle can be explained by the relationship between stress and number of cycles (SN). If the number of cycles corresponding to the weak point of the product is N and the stress is S, then it will fail (refer to Figure 2 and Figure 3 ).

[0054] The general relationship of Miller's law is as follows: D~NSβ ; D = fatigue accumulation, normalized to 1; N = number of cycles; S = stress condition (e.g. lbf / in 2 ) ; β = material index (derived from the SN curve, experimental data concludes that for most materials, it ranges from 8 to 12; physically, it represents the negative inverse of the slope of the SN curve).

[0055] Applied in HALT, we can further explain that we can find out the operating principle of early failure: Assuming that the failure is caused by a defect in a cold solder joint in the product, we can deduce it with (defective = no defect): Defective NS β = No defect NS β ; The entire product is in HALT test; each component of the product receives almost the same number of stress cycles, so the relationship can be expressed as: defective S β = No defect S β According to the above equation, for a failure caused by a cold solder joint in a short time, it can be directly assumed that the defective material coefficient β = 1, while other components without defects; after the same period of fatigue accumulation, no failure occurs, so it can be normally assumed that the material coefficient β = 10. Therefore, the relationship can be expressed as follows: Defective S 1 = No defect S 10 ; Therefore: the defective S is much larger than the non-defective S; if the defective S is substituted into Miller's law, the defective fatigue accumulation value will increase rapidly, that is, the defective area may fail due to fatigue accumulation and damage; on the other hand, it means that the non-defective area also has fatigue accumulation in the same period of time, but it has not reached the level of damage, maintaining its lifespan.

[0056] HALT technology explores a kind of mechanically stimulated fatigue, which is an irreversible fatigue accumulation. This kind of fatigue will accumulate and cannot be eliminated. Assume that the failure is a cold solder joint in the product, and other components of the product are also suffering from fatigue accumulation at the same time, and they are not damaged.

[0057] Under different magnitudes of cyclic stress, the number of cycles required to cause material failure is also different. The relationship between stress magnitude and number of cycles can be represented by an SN diagram. The smaller the cyclic stress, the more cycles are required for material failure. What needs to be mastered in this relationship is that, for example, iron alloys and titanium alloys have a characteristic that when the cyclic stress magnitude is lower than a certain value, the material can withstand an unlimited number of cyclic stresses without causing fatigue. This value corresponds to the horizontal line on the right side of the SN diagram. For example, aluminum and copper do not have similar limiting values. Even with very small cyclic stresses, as long as the number of cycles continues to increase, the material will be fatigued and damaged.

[0058] HALT emphasizes a kind of excitation effect; it uses effective stress that helps the excitation effect; it does not mean using higher stress or overstress. The random vibration equivalent conversion fatigue accumulation formula of highly accelerated life test: based on the general relationship of Miller's law (Miner); the function of the fatigue accumulation value of random vibration is as follows: D(vib) = Σ(N1S1 (1 / β) +…+N x S x (1 / β) ); D(vib) = cumulative fatigue value of random vibration; T = process time (min); N = number of cycles (vibration frequency Hz of the spectrum); S = stress condition (vibration amplitude grms of the spectrum); β = material index (reference MIL-STD-810G: β = 4 is used, and the characteristic is expressed in inverse form: the probability of failure over time).

[0059] In some embodiments, the acceleration factor calculation method of the highly accelerated life test is further described in detail below in conjunction with the calculation process as an implementation example: Vibration data is collected through a vibration spectrum analyzer: data corresponding to the vibration frequency and the vibration amplitude; the vibration data can be directly imported into EXCEL; field A = vibration frequency Hz; field B = vibration amplitude G rms2 / Hz; the vibration amplitude unit of field B needs to be converted to field C = vibration amplitude g rms That is, take the square root of field B and multiply it by field A. Therefore, in the vibration spectrum, the fatigue accumulation D(vib) of the vibration amplitude corresponding to each vibration frequency is expressed in NS (1 / β) Calculate field E separately, and add field E to get field F: Total fatigue accumulation Sum-D (vib) of a vibration data: 2602707 (reference Figure 3 ).

[0060] Specific formula verification: Use high-speed camera and image tracking software to observe the stress-strain results to verify the random vibration equivalent conversion fatigue accumulation formula: The value of fatigue accumulation D(vib) will change in a similar proportion to the value of stress-strain (refer to Figure 4 ); Rapid temperature change equivalent conversion fatigue accumulation formula for highly accelerated life test: Based on the general relationship of Miller's law; the function of fatigue accumulation value of rapid temperature change; is as follows: D(temp) = Σ(2N1S1 (1 / β) +…+2N x S x (1 / β) ); D(temp) = fatigue accumulation value of rapid temperature change; 2N = number of cycles (number of temperature cycles; So it is defined as 2N); S = stress condition (rapid temperature change °C / min); β = material index (refer to MIL-STD-810G: β = 4 is used, and the characteristic is expressed in inverse terms: the probability of failure over time).

[0061] Specific calculation method: Collect temperature data through temperature data acquisition instrument: Assume high temperature setting = 85℃, low temperature setting = -65℃, and the entire temperature range = 150℃ (the temperature range specification can be independently determined): Enter the calculated temperature change rate = 60℃ / min into field A; field B cycle number N = 5, field E at 2NS (1 / β) The calculation result is: 28, which represents the fatigue accumulation value generated by a rapid temperature change data (reference Figure 5 ).

[0062] Specific formula verification: Use high-speed camera and stress-strain analysis software to observe stress-strain results to verify the rapid temperature change equivalent conversion fatigue accumulation formula: The value of fatigue accumulation D(temp) will change in a similar proportion with the value of stress-strain, which is consistent with the actual performance (reference Figure 6 ).

[0063] The fatigue accumulation formula of the composite stress equivalent conversion of the highly accelerated life test is: D(com) = D(vib) ╳ D(temp); the fatigue accumulation calculation of the HALT test condition (reference Figure 7 ): Fatigue accumulation calculation under environmental stress conditions: Rapid temperature changes are greater than 15℃ / min. Most IC parts and some semiconductor parts cannot withstand rapid temperature changes exceeding 15℃ / min, which leads to circuit failure. In actual environmental conditions on cars and airplanes, the temperature change rate is as high as 100℃ / min. For example: when a car accelerates into the highway, the temperature change rate under the engine cover will reach -60℃ / min; the car that has just entered the car wash will also have a temperature change of -60℃ / min; in winter, when the engine is just started, the high-temperature oil in the oil pipeline flows through the devices with a high slope temperature change rate. Electronic equipment in aircraft in the sky will be subjected to the temperature of the air, with a temperature change rate of ±100℃ / min, and it is repeated many times a day. Even if the mobile phone is exposed to the low temperature outside when the user walks out of the heated room, the temperature change rate will reach -60℃ / min; then the user gets in the car and turns on the heater, and the temperature change rate will reach +60℃ / min, which may be repeated many times a day.

[0064] On powered products; if vibration occurs, it will be above 2000Hz and 20G rmsHigh-frequency random vibration; the power unit may fail; other components are subjected to environmental stress of high-frequency random vibration; the seat cushion of a truck running on a flat road will vibrate up and down. If vibration shock occurs on the product, there will be random vibration higher than 20Grms, and it contains high-frequency random vibration.

[0065] For high-frequency random vibration in the environment, vibration data can be collected through a vibration spectrum analyzer. For example, the vibration response of the product in the actual operation of the environment can be collected; or a vibration accelerometer can be directly attached to the product, and the product can be knocked against the table continuously or dropped directly to obtain vibration data (refer to Figure 8 ).

[0066] We equate the HALT test conditions and sample environmental conditions to fatigue accumulation; according to the planned items: random vibration, rapid temperature change, combined stress, total fatigue accumulation, list (reference Fig. 9 ):The proportional relationship between the HALT test conditions and the sample environmental conditions data produces the acceleration factor Fig. 9 The example shows a highly accelerated life test; the test results are: vibration operating limit 50G, rapid temperature change setting 60℃ / min (5 cycles), plus composite stress test, the known test time is 175min. The obtained acceleration factor: 69336, represents the ratio of the life under normal working stress to the life under accelerated environment, which can be used for quantitative reliability engineering.

[0067] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0068] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0069] Although this patent document contains many details, they should not be construed as limitations on the scope of any invention or the claims, but rather as descriptions of features of particular embodiments of particular inventions. Certain features described in this patent document in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various functions described in the context of a single embodiment may also be implemented separately in multiple embodiments, or in any suitable subcombination. In addition, although the above-mentioned features may be described as working in certain combinations, or even initially claimed to be so, in some cases, one or more features in the claim combination may be removed from the combination, and the claim combination may be directed to subcombinations or variations of subcombinations.

[0070] Likewise, although operations are described in a particular order in the drawings, this should not be understood as requiring that such operations be performed in the particular order or order shown, or that all illustrated operations be performed, in order to achieve the desired results. In addition, the separation of various system components in the embodiments of this patent document should not be understood as requiring such separation in all embodiments.

[0071] Only a few implementations and examples are described, and other implementations, enhancements, and variations can be made based on what is described and illustrated in this patent document.

[0072] Although several embodiments are provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are considered to be illustrative rather than restrictive and are not limited to the details given. For example, various components or assemblies may be combined or integrated in another system, or certain features may be omitted or not implemented.

Claims

1. A method for calculating the acceleration factor of a highly accelerated life test, characterized in that: Conduct heating and cooling tests on PCB products, perform vibration tests on PCB products, and calculate the acceleration factor of PCB products for life testing of PCB products.

2. The method for calculating the acceleration factor of a highly accelerated life test according to claim 1, characterized in that: H. Cycle heating and cooling of PCB products to achieve rapid temperature change of PCB products; N. Apply high-frequency random vibration waves to the PCB product to put the PCB product in a high-frequency random vibration state; The step H and the step N are performed synchronously, so that the acceleration factor A is obtained by coupling the fatigue strength generated by the step H and the step N on the PCB product.

3. The method for calculating the acceleration factor of a highly accelerated life test according to claim 2, wherein: The calculation formula of the acceleration factor A is as follows: Random vibration equivalent conversion fatigue accumulation formula: D(vib)=Σ(N1S1 (1 / β) +…+N x S x (1 / β) ); Rapid temperature change equivalent conversion fatigue accumulation formula: D(temp)=∑(2N1S1 (1 / β) +…+2N x Sx (1 / β) ); Composite stress equivalent conversion fatigue accumulation formula: D(com)=D(vib)×D(temp); Where: D(vib) = fatigue accumulation value of random vibration; D(temp) = fatigue accumulation value of rapid temperature change; 2N = number of cycles; S = stress condition (rapid temperature change °C / min).

4. The method for calculating the acceleration factor of a highly accelerated life test according to claim 2, wherein: The high-frequency random vibration wave contains energy above 2000 Hz, so that all components on the PCB product can be vibrated; When the PCB product is cyclically heated and cooled in step H, the heating process and the cooling process are performed alternately.

5. The method for calculating the acceleration factor of a highly accelerated life test according to claim 3, wherein: The high-frequency random vibration wave is provided by a high-frequency random vibration device; When the PCB product is cyclically heated and cooled in step H, the PCB product is first subjected to a heating process or a cooling process.

6. The method for calculating the acceleration factor of a highly accelerated life test according to claim 2, wherein: The high frequency random vibration wave in step H is: 2000Hz~5000Hz; The heating temperature in step N is: -65°C to 85°C; the first heating or cooling in step N starts from room temperature.

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