Methods for preventing condensation during thermal cycling tests of aerospace electronic products

Abstract

This invention provides a method for preventing condensation during thermal cycling testing of aerospace electronic products. The method includes: designing a control flow for the anti-condensation method during thermal cycling testing, providing methods for acquiring parameters in the flow, and a control algorithm for dry air or nitrogen. The steps include: during the product's temperature rise from low to high, first acquiring the product surface temperature and the dew point temperature of the circulating air inside the chamber, then comparing the deviation between the two with a safety margin, and controlling the on / off state of dry air or nitrogen and adjusting the charging rate of dry air or nitrogen according to the control algorithm to maintain a reliable safety margin between the product surface temperature and the dew point temperature until the product temperature rise is complete.

Description

Technical Field

[0001] This invention relates to the technical field of environmental and reliability testing, and in particular to a method for preventing condensation during thermal cycling testing of aerospace electronic products. Background Technology

[0002] Aerospace electronic products need to undergo thermal cycling tests according to GJB1027 to verify the robustness of the product design and its reliable operation in a given environment. During the thermal cycling test, it was found that condensation easily forms on the product surface, causing malfunctions such as surface blackening, water stains, pin corrosion, and mis-connection.

[0003] Currently, the main method to prevent condensation is to fill the test chamber (container) with dry air or nitrogen during testing of non-sealed components to reduce the moisture content inside the chamber, thereby lowering the dew point temperature and preventing condensation from forming on the product surface. However, during the heating process of thermal cycling tests, due to the large heat capacity of the product, the surface temperature of the product lags behind the temperature of the circulating gas inside the test chamber. When the humidity of the gas inside the test chamber is high, the dew point temperature is high, making it easy for condensation to form on the product surface, which affects the product performance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preventing condensation during thermal cycling tests of aerospace electronic products. Using this invention, condensation on the product surface can be effectively prevented during thermal cycling tests, and it can serve as a reference for product quality analysis, improvement of test equipment, and improvement of on-site drying air facilities.

[0005] To achieve the above objectives, the present invention provides a method for preventing condensation during thermal cycling testing of aerospace electronic products. This method, used for thermal cycling testing of aerospace electronic products, specifically includes:

[0006] Design a control process for an anti-condensation method in a thermal cycling test, and provide the method for obtaining parameters and the control algorithm for dry air or nitrogen. During the process of product temperature rise from low temperature, first obtain the product surface temperature and the dew point temperature of the circulating air in the chamber, then compare the deviation between the two with the safety margin, and control the on / off of dry air or nitrogen and adjust the charging rate of dry air or nitrogen according to the control algorithm to ensure that the product surface temperature and dew point temperature always maintain a reliable safety margin until the product temperature rise is completed.

[0007] (1) The dew point temperature of dry air or nitrogen should be lower than the low temperature limit temperature in the product test conditions, and the maximum ventilation rate should be able to match the anti-condensation requirements of the test chamber.

[0008] (2) The surface temperature Tp of the product is obtained by measuring the surface temperature sensor of the product, and the dew point temperature Td of the circulating gas in the box is obtained by measuring the dew point or by looking up the phase diagram of the dew point temperature.

[0009] (3) The deviation between the air outlet temperature change value and the product surface temperature change value is used to approximately fit the product surface temperature T. p With dew point temperature T d The safety margin C of the deviation between them is expressed by equation (1):

[0010] C = (v a -v p )×V / v dmax (1)

[0011] In the formula: C is the safety margin; v a v is the rate of change of air outlet temperature. p V represents the rate of change of the product surface temperature; V is the gas volume of the test chamber, including the air duct and the sample area; v dmax The maximum charging rate for dry air or nitrogen is calculated by v. dmax The gas filling should not cause temperature fluctuations in the test chamber;

[0012] (4) Calculate the deviation between the current product surface temperature and the dew point temperature, and compare it with the safety margin to determine whether there is a risk of condensation on the product surface. If there is a risk of condensation, control the on / off of dry air or nitrogen and adjust the charging rate of dry air or nitrogen to reduce the dew point temperature of the circulating gas in the chamber; otherwise, continue to heat up, and obtain the product surface temperature and dew point temperature in the chamber in real time during the heating process until the product reaches the target value of the product surface temperature without condensation throughout the process.

[0013] The control algorithm is used to control the on / off state of dry air or nitrogen and to adjust the charging rate of dry air or nitrogen. The expression is:

[0014] ε=ε(v d ,t,k) (2)

[0015] In the formula, v d t represents the rate of dry air or nitrogen supply; t represents the time of dry air or nitrogen supply, t = 0 indicates gas supply interruption; k represents the on / off state of dry air or nitrogen supply, k = 1 indicates supply, k = 0 indicates gas supply interruption.

[0016] The control algorithm flow is as follows:

[0017] (1) During initial inflation, ε = ε(v d0 ,t0,k0),v d0 The initial inflation rate can be taken as v. dmax t0 is the initial inflation time, taken as t minutes before the temperature changes from low to high, t = V / v d0 ;

[0018] k0 = 1;

[0019] (2) When T p -Td When C ≤ C, adjust the inflation rate v d , making v d =v dmax ,but

[0020] ε=ε(v dmax ,t i ,1);

[0021] (3) When T p -T d When >C, inflation stops, then ε=ε(0,0,0).

[0022] The present invention has the following beneficial effects:

[0023] This invention includes: designing a control process for an anti-condensation method in a thermal cycling test, providing a method for obtaining parameters in the process and a control algorithm for dry air or nitrogen; during the process of raising the product temperature from low to high, first obtaining the product surface temperature and the dew point temperature of the circulating air in the chamber, then comparing the deviation between the two with a safety margin, and controlling the on / off of dry air or nitrogen and adjusting the charging rate of dry air or nitrogen according to the control algorithm, so that a reliable safety margin is always maintained between the product surface temperature and the dew point temperature until the product temperature rises to the end.

[0024] This method can accurately and effectively prevent condensation on the product surface during thermal cycling tests. Compared to methods that involve continuous aeration throughout the test or aeration during the heating phase, it makes full use of test resources, saves test costs, and improves test efficiency. Furthermore, the collected information on vent temperature, relative humidity, and product surface temperature can completely reproduce the condensation or non-condensation process, providing valuable reference for product quality analysis, test equipment improvement, selection of on-site drying air or nitrogen, and facility improvements.

[0025] The method proposed in this invention can effectively control condensation by controlling the on / off state and inflation rate of dry air or nitrogen, ensuring that the product surface temperature is always higher than the dew point temperature of the gas inside the chamber. Simultaneously, the information collected during the experiment, such as vent temperature, relative humidity, and product surface temperature, can completely reproduce the condensation or non-condensation process, providing valuable reference for product quality analysis, improvement of testing equipment, and improvement of on-site dry air or nitrogen facilities.

[0026] The method for preventing condensation during thermal cycling testing of aerospace electronic products of the present invention obtains and compares the product surface temperature and dew point temperature, and calculates and determines parameters such as the on / off time of dry air and the filling rate based on the difference between the two, thereby controlling the product surface temperature to always be higher than the dew point temperature, which can effectively prevent condensation. Attached Figure Description

[0027] Figure 1 This is a flowchart of the automatic control process for preventing condensation according to the present invention;

[0028] Figure 2 The diagram shows the control results provided in a preferred embodiment of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described and discussed below with reference to the accompanying drawings. Obviously, what is described here is only a part of the examples of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0030] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments, and these embodiments do not constitute a limitation on the embodiments of the present invention.

[0031] Figure 1 This is a flowchart illustrating the automatic control process for preventing condensation in aerospace electronic products according to the present invention. The method for preventing condensation during thermal cycling testing of aerospace electronic products provided in this embodiment, which operates during thermal cycling testing of aerospace electronic products, specifically includes:

[0032] The thermal cycling test conditions for a certain aerospace electronic product were as follows: temperature range -40℃ to 60℃; temperature holding time 4 hours; temperature change rate 5℃ / min; surface temperature control was used. During the test, a cast aluminum block was used as a simulated load, with a simulated load weight of 20kg, similar to the product weight, thus simulating the product's condition. The dry air pressure at the test site was 0.4 kPa, the dew point temperature was -50℃, the ambient temperature was 28℃, and the relative humidity was 65%. During the low-temperature to high-temperature transition phase of the test, the dry air was controlled according to the control method, and the control parameters are shown in Table 1.

[0033] Table 1: Control Parameter Table

[0034] Serial Number Control parameter values Data source 1 <![CDATA[v a =11℃ / min]]> Calculated based on product test curves 2 <![CDATA[v p =5℃ / min]]> Calculated based on product test curves 3 V = 1200L Obtain from device parameters 4 <![CDATA[v dmax =180L / min]]> Maximum allowable dry gas flow rate of the test chamber 5 C＝40℃ Calculate according to formula (1) 6 <![CDATA[v d0 =in dmax ]]> The initial inflation rate is taken as the maximum flow rate of dry air. 7 t = 7min <![CDATA[t=V / v d0 ]]>

[0035] The control flow is as follows:

[0036] ①At the initial time, ε=ε(180,t) 转 -7,1), that is, 7 minutes before the transition from low temperature to high temperature, dry air is introduced into the test chamber at a flow rate of 180L / min to ensure that all circulating gas in the chamber is replaced by dry air.

[0037] ② Obtain T p and T d T p = -40℃, T d = -62℃, T p -T d =22℃≤40℃,ε=ε(180,ti ,1);

[0038] ③ Obtain T p and T d The values ​​are Tp = 23.5℃, Td = -17.5℃, and Tp-Td = 41℃ > 40℃, respectively. That is, after about 13 minutes of dry air introduction, ε = ε(0,0,0), and the introduction of dry air is stopped.

[0039] Control results are shown Figure 2 , Figure 2 The test curve includes two states: condensation and non-condensation. The condensation state is the test curve with a dry air inflation rate of 120 L / min, while the non-condensation state is the test curve using an automatic control method. In the condensation state, because the low-rate dry air cannot quickly displace the ambient atmosphere inside the test chamber, and as the temperature rises, the frost on the condenser melts rapidly, leading to a sharp increase in the water molecule content in the air and a rapid rise in the dew point temperature, exceeding the product surface temperature in a short period of time, thus producing a large amount of condensation. In the non-condensation state, the dry air controlled by the algorithm can quickly displace the gas inside the test chamber, ensuring that the dew point temperature is always lower than the sample surface temperature. Even after the inflation stops, the dew point temperature gradually stabilizes, although it rises slightly, it still remains at a low level, maintaining a safe margin with respect to the product surface temperature.

[0040] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions made to the present invention by those skilled in the art within the technical scope disclosed herein should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preventing condensation in a thermal cycle test of space electronic products, for a thermal cycle test of space electronic products, characterized in that Air or nitrogen, comprising: The dew point temperature of the dry air or nitrogen is set to be lower than the low temperature limit in the product test condition, and the maximum ventilation rate matches the requirement of preventing condensation in the test chamber; The surface temperature Tp of the space electronic product is measured by using the temperature control sensor on the surface of the space electronic product, and the dew point temperature Td of the circulating gas in the chamber is measured by using a dew point meter or a dew point temperature calculation phase diagram; The safety margin of the first deviation between the surface temperature Tp of the product and the dew point temperature Td is approximately fitted by using the deviation between the temperature change value of the air port and the temperature change value of the surface of the space electronic product; The second deviation between the surface temperature of the space electronic product at the current time and the dew point temperature is calculated, and the second deviation is compared with the safety margin to determine whether there is a risk of condensation on the surface of the space electronic product, If there is a risk of condensation, the on-off of the dry air or nitrogen is controlled, and the ventilation rate of the dry air or nitrogen is adjusted to reduce the dew point temperature of the circulating gas in the chamber; The safety margin of the first deviation between the surface temperature Tp of the product and the dew point temperature Td is approximately fitted by using the deviation between the temperature change value of the air port and the temperature change value of the surface of the space electronic product, comprising: C = (v a -v p ) x V / v dmax (1) where C is the safety margin; v a is the rate of change of the air temperature at the air nozzle; v p is the rate of change of the product surface temperature; V is the volume of the test chamber, including the air duct and the sample area; v dmax is the maximum rate of air charge, either dry air or nitrogen, in v dmax The air charge should not cause temperature fluctuations in the test chamber.

2. The method for preventing condensation of space electronic product thermal cycle test according to claim 1, characterized in that, After determining whether there is a risk of condensation on the surface of the space electronic product, further comprising: If there is no risk of condensation, the temperature continues to rise, and the surface temperature of the space electronic product in the chamber and the dew point temperature are obtained in real time during the temperature rising process until there is no condensation on the surface of the space electronic product throughout the process, and the target value of the surface temperature of the space electronic product is reached.

3. The method of claim 1, wherein the method is characterized by: The on-off of the dry air or nitrogen is controlled, and the ventilation rate of the dry air or nitrogen is adjusted, comprising: According to the control algorithm expression (2), the on-off of the dry air or nitrogen is controlled, and the ventilation rate of the dry air or nitrogen is adjusted: ε = ε(v d t,k) (2) where v d is the rate of the dry air or nitrogen gas; t is the time of the dry air or nitrogen gas ventilation, t = 0 indicates the off ventilation; k indicates the on-off of the dry air or nitrogen gas, k = 1, ventilation, k = 0, off ventilation.

4. The method for preventing condensation of space electronic product thermal cycle test according to claim 3, characterized in that, According to the control algorithm expression (2), the on-off of the dry air or nitrogen is controlled, and the ventilation rate of the dry air or nitrogen is adjusted, comprising: ε = ε(v d0 , t0, k0), v d0 = initial inflation rate, preferably v dmax ; t0 = initial inflation time, taken as tmin before the low temperature to high temperature change, t0 = V / v d0 ; k0 = 1.

5. The method of claim 3, wherein the method is characterized by: According to the control algorithm expression (2), the on-off of the dry air or nitrogen is controlled, and the ventilation rate of the dry air or nitrogen is adjusted, comprising: When T p -T d ≤ C, adjust the inflation rate v d such that v d = v dmax , then ε = ε(v dmax , t1,1).

6. The method for preventing condensation of space electronic product thermal cycle test according to claim 3, characterized in that, According to the control algorithm expression (2), the on-off of the dry air or nitrogen is controlled, and the ventilation rate of the dry air or nitrogen is adjusted, comprising: According to the control algorithm expression (2), the on-off of the dry air or nitrogen is controlled, and the ventilation rate of the dry air or nitrogen is adjusted, comprising: When T p -T d >C, stop inflating, then ε = ε(0,0,0).

Images