A failure analysis method of a vapor chamber

Abstract

This invention provides a failure analysis method for a heat spreader, comprising the following steps: testing the temperature difference between the hot and cold ends of the heat spreader to determine if the temperature difference is within the standard range; performing a visual inspection of the heat spreader to determine if micro-leakage is caused by weld spalling or poor welding; performing a dimensional inspection of the heat spreader to determine if there is any thickness deviation affecting the internal structure and causing increased thermal resistance; performing thermal imaging tests on the heat spreader under both gravity and anti-gravity conditions to determine if the heat spreader's performance is completely lost or partially degraded; performing two-dimensional and / or three-dimensional imaging detection on the heat spreader; performing airtightness testing on the heat spreader; performing hydrophilicity testing on the heat spreader; performing capillary action testing on the heat spreader; drying the heat spreader and obtaining the quality difference before and after drying to determine if it is within the standard range; and performing material characterization tests on the heat spreader. This failure analysis method for heat spreaders enables rapid location and in-depth analysis of failure causes, improving the efficiency of failure analysis.

Description

Technical Field

[0001] This invention belongs to the field of heat dissipation technology, specifically relating to a failure analysis method for a heat spreader. Background Technology

[0002] With the widespread application of vapor chambers (VCs) in consumer electronics, smart homes, aerospace, and other fields, their quality and reliability are paramount. Numerous problems have arisen during the design and manufacturing processes of vapor chambers, such as low-temperature bulging in copper vapor chambers, non-condensable gases in stainless steel vapor chambers, discoloration in stainless steel vapor chambers, and performance degradation after aging in titanium / flexible / steel-copper vapor chambers. These problems directly lead to product non-compliance. Quickly and accurately locating the causes of vapor chamber failure has become an important, difficult, and time-consuming task. Currently, although there are some empirical analytical methods in the industry, there is still no systematic, standardized process that can improve the accuracy and efficiency of analysis. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a failure analysis method for a heat exchanger, which enables rapid location and in-depth analysis of the cause of failure and improves the efficiency of failure analysis.

[0004] This invention is achieved through the following technical solution:

[0005] A failure analysis method for a heat exchanger includes the following steps: Test the temperature difference between the hot and cold ends of the vapor chamber to determine if it is within the standard range; perform a visual inspection of the vapor chamber to determine if micro-leakage is caused by weld spalling or poor welding; perform a dimensional inspection of the vapor chamber to determine if thickness deviation affects the internal structure and increases thermal resistance; perform thermal imaging tests on the vapor chamber under both gravity and anti-gravity conditions to determine if the vapor chamber performance is completely lost or partially degraded; perform two-dimensional and / or three-dimensional imaging detection on the vapor chamber; perform airtightness testing on the vapor chamber; perform hydrophilicity testing on the vapor chamber; perform capillary action testing on the vapor chamber; dry the vapor chamber and obtain the mass difference before and after drying, obtain the mass of the liquid water working medium, and determine if it is within the standard range; perform material characterization tests on the vapor chamber.

[0006] This invention provides a failure analysis method for heat exchangers. It refines the failure diagnosis and analysis of heat exchangers from aspects such as temperature difference retesting, appearance and dimensional inspection, thermal performance testing, two-dimensional / three-dimensional detection, airtightness testing, hydrophilicity and capillary performance testing, working fluid quality inspection, and material characterization testing. Based on the results of non-destructive temperature difference retesting, appearance and dimensional inspection, thermal performance testing, two-dimensional / three-dimensional detection, and airtightness testing, the possible causes of heat exchanger failure are initially determined. Then, through destructive hydrophilicity and capillary performance testing, working fluid quality inspection, and material characterization testing, the failure cause is accurately determined, achieving rapid location and in-depth analysis of the failure cause and improving the efficiency of failure analysis.

[0007] Furthermore, thermal imaging tests were conducted on the vapor chamber under both gravity and anti-gravity conditions to determine whether the vapor chamber had completely lost its performance or experienced partial degradation. Under gravity conditions, the heat source was located below the vapor chamber, and the liquid working fluid flow direction was consistent with the gravity direction. Under anti-gravity conditions, the heat source was located above the vapor chamber, and the liquid working fluid flow direction was opposite to the gravity direction. The determination of whether the vapor chamber's performance was completely lost or partially degraded was made as follows: if completely lost, the vapor chamber experienced dry burning or leakage during manufacturing; if partially degraded, and the dead zone area under gravity and the dead zone area under anti-gravity were the same, then non-condensable gases were present inside the vapor chamber; if partially degraded, and the dead zone area under gravity was smaller than the dead zone area under anti-gravity, then the capillary performance within the vapor chamber was poor, or there was too much or too little water in the working fluid.

[0008] Furthermore, in the step of performing two-dimensional imaging inspection and / or three-dimensional imaging inspection on the heat spreader, two-dimensional imaging is used to observe the heat spreader to determine whether the solder paste is uniformly dissolved, free of bubbles, and whether there is a possibility of air leakage; three-dimensional imaging is used to determine whether there is obvious collapse, deformation or foreign matter in the internal structure of the heat spreader.

[0009] Furthermore, in the step of airtightness testing of the heat spreader, helium testing is used to determine whether the heat spreader has leaked. If the heat spreader bulges after helium testing, the cause of failure is poor welding during the heat spreader production process. If there is no change in the appearance and thermal properties of the heat spreader before and after helium testing, then hydrophilicity testing / capillary capacity testing is performed.

[0010] Furthermore, in the step of testing the hydrophilicity of the heat spreader, the heat spreader is disassembled to obtain the liquid-absorbing core, which is a capillary structure formed by the shell and the wire mesh. The liquid-absorbing core is sampled and the hydrophilicity of the capillary structure is tested with a water contact angle meter. If the contact angle is ≤10°, the hydrophilicity requirement is met; otherwise, it is necessary to check whether there are any abnormalities in the baking process and / or sintering process in the production of the heat spreader.

[0011] Furthermore, in the step of capillary capacity testing of the heat exchange plate, the heat exchange plate is disassembled to obtain the liquid absorption core, which is a capillary structure formed by the shell and the wire mesh. The liquid absorption core is brought into contact with the liquid water working medium, and the climbing process of the liquid water working medium in the liquid absorption core is recorded to determine whether the climbing of the liquid water working medium is uniform and whether the climbing speed meets ≥3mm / s.

[0012] Furthermore, in the steps of material characterization testing of the heat exchange plate, at least one of the following is performed: elemental composition analysis, surface morphology analysis, qualitative and quantitative analysis of surface compounds, and galvanic corrosion test.

[0013] Furthermore, in the material characterization test of the heat spreader, qualitative and quantitative analysis of the surface compounds of the heat spreader is performed to analyze the composition and thickness of the passivation film on the surface of the heat spreader, and to determine whether there is an incomplete passivation problem in the surface treatment process of the heat spreader.

[0014] Furthermore, in the material characterization test of the heat spreader, when the shell and the wire mesh of the heat spreader are made of different types of metals, the heat spreader is subjected to galvanic corrosion test to determine whether severe galvanic corrosion will occur between the shell and the wire mesh. When the potential difference is ≥150mV, the heat spreader is determined to be galvanically incompatible.

[0015] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a flowchart of the failure analysis method for the heat exchanger in Example 1.

[0017] Figure 2 This is a thermal imaging test image from Example 2.

[0018] Figure 3 This is a three-dimensional CT scan test image of the stainless steel heat exchanger plate in Example 2.

[0019] Figure 4 These are hydrophilicity test diagrams and climbing test diagrams of the stainless steel heat spreader in Example 2.

[0020] Figure 5 This is an electrochemical test diagram of the stainless steel heat spreader in Example 2.

[0021] Figure 6 This is a scanning electron microscope image of the stainless steel heat spreader of Example 2. Detailed Implementation

[0022] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the embodiments of the present invention, and not all structures.

[0023] Furthermore, the terms "first," "second," "third," etc., used in the specification and claims are only for the purpose of distinguishing the description of the same technical features and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated, nor necessarily the order of description or chronological sequence. Where appropriate, the terms are interchangeable. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0024] Similarly, the terms "fixed" and "connected" are used in the specification and claims and should not be construed as limited to a direct connection. Therefore, the expression "device A is connected to device B" should not be limited to device A being directly connected to device B in a device or system; it means that there is a path between device A and device B, which can be a path that includes other devices or tools.

[0025] Example 1 This embodiment provides a failure analysis method for a heat spreader. Figure 1 This is a flowchart of the failure analysis method for a vapor chamber. Please refer to it. Figure 1 The failure analysis method for a vapor chamber includes the following steps: Step S1: Test the temperature difference between the cold and hot ends of the heat spreader to determine whether the temperature difference is within the standard range.

[0026] Step S2: Visually inspect the heat spreader to determine if the micro-leakage is caused by weld spalling or poor welding. Step S3: Perform a dimensional inspection on the heat spreader to determine if there are any thickness deviations that could affect the internal structure and increase thermal resistance. Step S4: Perform thermal imaging tests on the heat exchanger under both gravity and anti-gravity conditions to determine whether the heat exchanger's performance is completely lost or partially degraded. Step S5: Perform two-dimensional imaging and / or three-dimensional imaging on the heat spreader to determine whether there are welding defects at the welding position, and / or whether there are obvious collapses, deformations or foreign objects in the internal structure; Step S6: Perform an airtightness test on the heat exchange plate; Step S7: Perform hydrophilicity testing on the temperature distribution plate; Step S8: Perform capillary capacity testing on the heat exchange plate; Step S9: Dry the temperature plate, obtain the quality difference of the temperature plate before and after drying, obtain the quality of the liquid water working medium filled in the original temperature plate, and determine whether it is within the standard range. If it exceeds the standard range, there is an abnormality in the water injection process and / or the removal process in the temperature plate production process. Step S10: Perform material characterization tests on the heat exchanger.

[0027] This embodiment provides a failure analysis method for a heat exchanger. It refines the failure diagnosis and analysis of the heat exchanger from aspects such as temperature difference retesting, appearance and dimensional inspection, thermal performance testing, two-dimensional / three-dimensional detection, airtightness testing, hydrophilicity and capillary performance testing, working fluid quality inspection, and material characterization testing. Based on the results of non-destructive temperature difference retesting, appearance and dimensional inspection, thermal performance testing, two-dimensional / three-dimensional detection, and airtightness testing, the possible causes of heat exchanger failure are initially determined. Then, through destructive hydrophilicity and capillary performance testing, working fluid quality inspection, and material characterization testing, the failure cause is accurately determined, achieving rapid location and in-depth analysis of the failure cause and improving the efficiency of failure analysis.

[0028] The purpose of step S1 is to retest the temperature difference to prevent misjudgment. In step S1, the temperature difference between the cold and hot ends of the heat spreader is tested to determine whether the temperature difference is within the standard range. If it is within the standard range, the heat spreader failure may be a misjudgment; if the temperature difference exceeds the standard range, then a visual inspection is performed.

[0029] In one implementation, a vapor chamber plate that has been manually or mechanically determined to be faulty is selected. A six-station workbench is used to re-measure the temperature difference between the cold and hot ends of the vapor chamber plate on the corresponding fixture to determine whether the judgment is false. If the temperature difference is within the standard range, it is a false judgment; if the temperature difference exceeds the standard range, proceed to step S2.

[0030] In one embodiment, in step S1, a six-station workbench is used to re-measure the temperature difference between the hot end T1 and the cold end T2 of the failed heat spreader on the corresponding fixture. The temperature difference test is performed at a temperature of 25°C for 90 seconds, and the heating source is 1 cm². 2 A copper block with a preheating power of 10W and a starting temperature of 45℃ was used. A thermal pad with a thickness of 0.3mm and a thermal conductivity of 3W / (m·K) was placed between the heat source and the heat spreader. The heat spreader includes a shell with a accommodating cavity and a wire mesh. The shell includes an upper cover and a lower cover, the edges of which are fixed by welding. The wire mesh is provided with a first capillary structure and is disposed in the accommodating cavity. The lower cover is provided with a second capillary structure and the wire mesh is welded to the lower cover, so that the first capillary structure and the second capillary structure form a liquid-absorbing core for storing liquid.

[0031] In step S2, a CCD camera is used to inspect the solder lines between the upper and lower covers to determine whether micro-leakage is caused by solder rupture or poor soldering.

[0032] In step S3, the temperature distribution plate is inspected for dimensions. Key dimensions, such as the length, width, and thickness of the shell, as well as the dimensions of other features on the shell surface, are measured using a thickness caliper to determine whether there are any thickness deviations that affect the internal structure and cause an increase in thermal resistance.

[0033] In step S4, thermal imaging tests are performed on the vapor chamber under both gravity and anti-gravity conditions to determine whether its performance is completely lost or partially degraded. In this embodiment, under gravity conditions, the vapor chamber is attached to the test heat source, with the heat source positioned below the vapor chamber, and the liquid working fluid reflux direction is consistent with the gravity direction. Under anti-gravity conditions, the vapor chamber is attached to the test heat source, with the heat source positioned above the vapor chamber, and the liquid working fluid reflux direction is opposite to the gravity direction. To determine whether the vapor chamber performance is completely lost or partially degraded, if only the temperature at the test heat source is detected in the thermal imaging test, it indicates that the vapor chamber performance is completely lost, suggesting dry burning or leakage during the manufacturing process. If there is partial degrade, and the dead zone areas under gravity and anti-gravity are the same, then non-condensable gases are present inside the vapor chamber. If there is partial degrade, and the dead zone area under gravity is smaller than the dead zone area under anti-gravity, then the capillary network performance within the vapor chamber is poor, or there is too much or too little water in the working fluid.

[0034] In step S4, the surface of the heat spreader facing away from the test heat source is covered with a protective film, the area of ​​which is smaller than the area of ​​the heat spreader.

[0035] In step S5, two-dimensional imaging is used to observe the heat spreader to determine whether the solder paste is evenly dissolved and free of bubbles, and whether there is a possibility of air leakage; three-dimensional imaging is used to determine whether there is obvious collapse, deformation or foreign matter in the internal structure of the heat spreader.

[0036] In one implementation, X-ray two-dimensional imaging is used to determine whether there are welding defects at the welding location, while three-dimensional CT scanning is used to determine whether there are obvious collapses, deformations, or foreign objects in the internal structure. X-ray two-dimensional imaging is relatively intuitive for observing heat spreaders produced by brazing processes (such as copper heat spreaders and steel-copper heat spreaders), mainly to observe whether the solder paste is uniformly dissolved, free of bubbles, and whether there is a possibility of air leakage. However, X-ray two-dimensional imaging is not very effective for heat spreaders formed by laser welding (such as stainless steel heat spreaders and titanium heat spreaders) and heat spreaders formed by diffusion welding processes (such as copper-aluminum heat spreaders and flexible heat spreaders), requiring further analysis through airtightness testing.

[0037] Step S6: Perform an airtightness test on the heat exchange plate.

[0038] Helium testing is used to determine whether the heat spreader is leaking. If the heat spreader bulges after helium testing, the failure is due to poor welding. If there is no change in the appearance and thermal properties of the heat spreader before and after helium testing, the process proceeds to step S7 (hydrophilicity test) and step S8 (capillary capacity test). The hydrophilicity test in step S7 and the capillary capacity test in step S8 are performed after disassembling the heat spreader structure.

[0039] Disassemble the heat spreader to obtain the liquid absorption core, which is a capillary structure formed by the shell and the wire mesh.

[0040] In step S7, the hydrophilicity of the heat spreader is tested. The liquid wick is sampled and the hydrophilicity of the capillary structure is tested with a water contact angle meter. If the contact angle is ≤10°, the hydrophilicity requirement is met; otherwise, it is necessary to check whether there are any abnormalities in the baking and sintering processes during the heat spreader production process.

[0041] In step S8, the capillary capacity of the temperature distribution plate is tested. The liquid wick is brought into contact with the liquid working medium, and the climbing process of the liquid working medium in the wick is recorded to determine whether the climbing of the liquid working medium is uniform and whether the climbing speed meets the requirement of ≥3mm / s. The capillary capacity is evaluated by measuring the rising speed of the liquid working medium in the capillary structure. The faster the climbing speed of the liquid working medium in the capillary structure, the stronger the capillary force.

[0042] In one embodiment, the suction core is placed on a climbing test platform, which includes a lifting platform, a tray, a metal panel, several magnets, and a scale. The lifting platform is driven to the tray, and the tray contains pure water as the working medium. The suction core is fixed vertically to the metal panel by the magnets. The lifting platform is slowly adjusted to raise the tray. When the suction core contacts the pure water in the tray, the adjustment is stopped. A video recording is started to record the climbing speed of the liquid water working medium in the capillary structure, and the climbing height is measured by the scale.

[0043] In step S9, the temperature uniform plate is dried to obtain the quality difference of the temperature uniform plate before and after drying, and the quality of the liquid water working medium filled in the original temperature uniform plate is obtained. It is determined whether the quality difference is within the standard range. If it exceeds the standard range, there is an abnormality in the water injection process and / or the removal process in the temperature uniform plate production process.

[0044] Step S10: Perform material characterization tests on the heat exchanger.

[0045] In this embodiment, at least one of the following is performed on the heat spreader: elemental composition analysis, surface morphology analysis, qualitative and quantitative analysis of surface compounds, and galvanic corrosion test.

[0046] In one implementation, elemental composition analysis is performed using inductively coupled plasma optical emission spectrometry (ICP-OES, carbon-sulfur analyzer) to analyze the elemental composition of the same batch of shell raw materials and wire mesh. If the content of metallic and non-metallic elements in the test results is within the national standard range, the raw materials meet the requirements; if it exceeds the national standard range, the supply of raw materials needs to be checked. For example, if the shell is made from SUS316L raw material strip, and the content of Cr, Ni, and Mo elements in the raw material strip is too low, it will affect the corrosion resistance of the material. Elemental composition analysis is used to determine whether there is a problem with the raw materials.

[0047] In one embodiment, surface morphology analysis uses scanning electron microscopy (SEM) to perform surface morphology and semi-quantitative elemental analysis on the top cover, screen, and bottom cover of the heat spreader to determine whether there are material defects in the product, and then analyze whether the material defects are generated at the raw material supply end or during the process production.

[0048] In one embodiment, the qualitative and quantitative analysis of surface compounds uses X-ray photoelectron spectroscopy (XPS) to analyze the composition and thickness of the passivation film on the top cover, screen, and bottom cover of the heat spreader, in order to determine whether there is an incomplete passivation problem in the product surface treatment process.

[0049] In one embodiment, when the housing of the heat exchanger and the wire mesh of the heat exchanger are made of different types of metals, an galvanic corrosion test is performed on the heat exchanger to determine whether severe galvanic corrosion will occur between the housing and the wire mesh. If the potential difference is ≥150mV, the heat exchanger is determined to be galvanically incompatible.

[0050] Example 2 This embodiment provides a failure analysis method for a heat exchanger plate. The failure analysis method for a stainless steel heat exchanger plate initially determined to have poor performance includes the following steps: Step S1: Test the temperature of the hot end T1 and the cold end T2 of the heat spreader to determine if the temperature difference is within the standard range. If it is within the standard range, the failure of the heat spreader may be a misjudgment. If the temperature difference exceeds the standard range, proceed to visual inspection.

[0051] In this embodiment, a six-station workbench is used to re-measure the temperature difference of the failed sample on the corresponding fixture. The test power is 3W, the starting temperature is 45℃, the test duration is 90s, and the test method is a reverse gravity condition test. The temperature plate is placed vertically, with the temperature plate in contact with the test heat source, and the test heat source is located above the temperature plate, simulating a reverse gravity working environment. The judgment criterion is T1-T2≤2℃. The hot end of the temperature plate is the end of the temperature plate that is directly in contact with the test heat source when the temperature plate is placed vertically, and the temperature of the hot end is recorded as T1; the cold end of the temperature plate is the end of the temperature plate that is away from the test heat source when the temperature plate is placed vertically, and the temperature of the cold end is recorded as T2.

[0052] When testing certain specific heat spreaders, it is also necessary to test the edge temperature T3. The edge temperature T3 refers to the edge position of the heat spreader that is isolated from the cavity. The criterion is that T1-T3 > 2℃.

[0053] Test results: T1-T2=4.3℃>2℃, T1-T3=8.3℃, the temperature difference exceeds the judgment standard, the stainless steel temperature riser plate has poor performance.

[0054] Step S2: Visually inspect the heat spreader to determine if the micro-leakage is caused by weld spatter or poor welding.

[0055] In this embodiment, when the welding line between the upper and lower covers of the heat spreader was observed using a CCD camera, no obvious defects were found.

[0056] Step S3: Perform a dimensional inspection on the heat spreader to determine if there are any thickness deviations that could affect the internal structure and increase thermal resistance.

[0057] In this embodiment, the thickness of the stainless steel heat spreader was measured using thickness calipers, and the thickness was within the tolerance range.

[0058] Step S4: Perform thermal imaging tests on the heat exchanger under both gravity and anti-gravity conditions to determine whether the heat exchanger's performance is completely lost or partially degraded.

[0059] Figure 2 This is a thermal imaging test image of a stainless steel temperature riser. In this embodiment, thermal imaging tests were performed on the failed sample on a six-station workbench under both gravity-fed and gravity-opposed conditions. Please refer to [link / reference]. Figure 2 The fact that the dead zones under gravity and against gravity are similar in size indicates that the performance of the stainless steel heat exchanger is partially degraded and that there is non-condensable gas inside the cavity.

[0060] Step S5: Perform two-dimensional imaging and / or three-dimensional imaging on the heat spreader to determine whether there are welding defects at the welding position, and / or whether there are obvious collapses, deformations or foreign objects in the internal structure. Figure 3 This is a 3D CT scan test image of a stainless steel heat exchanger. In this embodiment, a 3D CT scan was used to scan the stainless steel heat exchanger. Please refer to [link / reference]. Figure 3 The stainless steel heat spreader plate showed no obvious collapse, deformation or foreign objects, indicating that there were no abnormalities in its internal structure.

[0061] Step S6: Perform an airtightness test on the heat exchange plate.

[0062] In this embodiment, the stainless steel heat spreader was placed in a helium furnace for leak testing. After the helium test, there was no obvious bulging or pitting on the surface of the stainless steel heat spreader. At this time, the temperature difference was measured again, T1-T2=4.4℃>2℃, T1-T3=8.2℃, and the thermal performance of the heat spreader did not change significantly, ruling out welding or sealing leaks in the stainless steel heat spreader.

[0063] The heat spreader includes a shell with a accommodating cavity and a wire mesh. The shell includes an upper cover and a lower cover, the edges of which are fixed by welding. The wire mesh is provided with a first capillary structure and is disposed within the accommodating cavity. The lower cover is provided with a second capillary structure, and the wire mesh is welded to the lower cover, so that the first and second capillary structures form a liquid-absorbing core for storing liquid. In this embodiment, the upper cover is removed, and the lower cover and wire mesh form the liquid-absorbing core.

[0064] Step S7: Perform hydrophilicity testing on the temperature distribution plate. Figure 4 These are the hydrophilicity test diagrams and the climb test diagrams for the stainless steel temperature riser. Figure 4 (a) is a diagram before the water drips. Figure 4 (b) is a schematic diagram of measuring the contact angle of a water droplet using a water contact angle tester. Please refer to [link / reference]. Figure 4 In this embodiment, a 1×1cm sample of the disassembled absorbent core is taken. 2 For samples of various sizes, the contact angle before and after water droplet application was measured using a water contact angle tester. When the water droplet completely wets the surface of the absorbent core, the contact angle is 0°, indicating superhydrophilicity and meeting the hydrophilicity requirements.

[0065] Step S8: Perform capillary action test on the temperature distribution plate. In this embodiment, the absorbent core is brought into contact with the liquid working medium, and the climbing process of the liquid working medium in the absorbent core is recorded. Please refer to... Figure 4 , Figure 4 (c) is a climbing test diagram. In this embodiment, the liquid absorption core was obtained by removing the temperature plate. Direct observation revealed that the liquid absorption core had an abnormal color, indicating that the liquid absorption core was corroded. Combined with the test results, the liquid water working medium in the liquid absorption core climbed slowly and unevenly, and the capillary performance was poor. It was initially inferred that the inner cavity had undergone relatively serious corrosion, and further material characterization test analysis was required.

[0066] Step S9: Dry the temperature plate, obtain the quality difference of the temperature plate before and after drying, obtain the quality of the liquid water working medium filled in the original temperature plate, and determine whether it is within the standard range. If it exceeds the standard range, there is an abnormality in the water injection process and / or the removal process in the temperature plate production process.

[0067] In this embodiment, the stainless steel heat spreader plate was weighed before disassembly. After disassembling the heat spreader plate and completing the tests in steps S7 and S8, all disassembled parts were collected and placed in a 90°C oven for half an hour to dry the moisture. After drying, they were weighed using an analytical balance. The mass difference was 0.2462g (defined standard 0.24~0.26g), indicating that the water injection volume of the original heat spreader plate was within the normal range, thus ruling out abnormalities in the water injection process and / or the removal process.

[0068] Step S10: Perform material characterization tests on the heat exchanger. In this embodiment, the stainless steel heat exchanger is subjected to the following tests: (1) Electrochemical test The stainless steel heat spreader used in this study had a shell made of SUS-316L stainless steel and a wire mesh made of copper foil to analyze potential dissimilar metal galvanic corrosion behavior. Electrochemical open-circuit stability tests were conducted on the 316L stainless steel strip and copper foil in pure water for 1800 s.

[0069] Figure 5 This is an electrochemical test diagram of a stainless steel heat spreader. Please refer to it. Figure 5 The open-circuit potential of the copper foil is stable at around -2.2mV (vs. SCE), while the open-circuit potential of the 316L stainless steel strip is stable at around 181.7mV (vs. SCE). The potential difference between the two is approximately 183.9mV (vs. SCE). When the potential difference between dissimilar metals is greater than 150.0 mV, significant galvanic corrosion will be induced, and the system will be considered as a galvanically incompatible heat spreader system.

[0070] (2) Scanning electron microscopy analysis The surface morphology of the copper foil on the stainless steel heat spreader was analyzed using scanning electron microscopy. Figure 6 This is a scanning electron microscope image of the stainless steel heat spreader. Please refer to [link / reference]. Figure 6 Most of the holes in the copper foil were closed, but a few unclosed holes began to form loose corrosion products on the outer ring, indicating that there was galvanic corrosion caused by galvanic incompatibility, which led to the blockage of the copper foil micropores and thus affected the gas-liquid two-phase circulation.

[0071] Using the failure analysis method described above, the stainless steel heat exchanger was analyzed. The analysis results showed that the material selection during the design was unreasonable, which led to dissimilar metal galvanic corrosion between the copper foil, which served as the liquid absorption core, and the stainless steel, which served as the shell. The stainless steel acted as the cathode and the copper foil as the anode. The corrosion products blocked the micropores and continued to deteriorate, leading to the failure of the stainless steel heat exchanger.

[0072] The failure method in this embodiment deeply analyzes and locates the root cause of product problems through a single failed sample, covering the causes of failure from multiple aspects such as materials, design, process, and testing. This significantly shortens the time spent repeatedly finding the cause of failure, reduces time and manpower costs, and can provide effective assistance to the product development and design process and mass production process.

[0073] This invention is not limited to the above-described embodiments. If any modifications or variations to this invention do not depart from the spirit and scope of this invention, and if such modifications and variations fall within the scope of the claims and equivalent technologies of this invention, then this invention also intends to include such modifications and variations.

Claims

1. A failure analysis method for a heat exchanger, characterized in that, Includes the following steps: Test the temperature difference between the hot and cold ends of the vapor chamber to determine if the temperature difference is within the standard range; Perform a visual inspection of the heat spreader to determine if the micro-leakage is caused by a weld spatter or a poor weld. Perform dimensional checks on the heat spreader to determine if there are any thickness deviations that could affect the internal structure and increase thermal resistance. Thermal imaging tests were conducted on the vapor chamber under both gravity and antigravity conditions to determine whether the vapor chamber's performance was completely lost or partially degraded. Two-dimensional imaging and / or three-dimensional imaging are used to detect the heat spreader to determine whether there are welding defects at the welding position and / or whether there are obvious collapses, deformations or foreign objects in the internal structure. Perform airtightness testing on the temperature distribution plate; Hydrophilicity testing was performed on the temperature distribution plate; Capillary capacity testing was performed on the temperature distribution plate. Dry the temperature plate, obtain the quality difference of the temperature plate before and after drying, obtain the quality of the liquid water working medium filled in the original temperature plate, and determine whether it is within the standard range. If it exceeds the standard range, there is an abnormality in the water injection process and / or the removal process in the temperature plate production process. Material characterization tests were performed on the temperature riser.

2. The failure analysis method for a heat spreader according to claim 1, characterized in that: In the step of determining whether the temperature plate has been completely lost or partially attenuated by performing thermal imaging tests on the temperature plate under both gravity and anti-gravity conditions, the heat source is located below the temperature plate under gravity conditions, and the reflux direction of the liquid working fluid is consistent with the direction of gravity. Under anti-gravity conditions, the heat source for testing is located above the temperature equalizer, and the reflux direction of the liquid working fluid is opposite to the direction of gravity. To determine whether the performance of the vapor chamber is completely lost or partially degraded, if it is completely lost, the vapor chamber was dry-burned or leaked during the manufacturing process; if it is partially degraded and the dead zone area with gravity is the same as the dead zone area against gravity, there is non-condensable gas inside the vapor chamber; if it is partially degraded and the dead zone area with gravity is smaller than the dead zone area against gravity, the capillary performance inside the vapor chamber is poor, or there is too much or too little water in the working fluid.

3. The failure analysis method for a heat spreader according to claim 1, characterized in that: In the step of performing two-dimensional imaging inspection and / or three-dimensional imaging inspection on the heat spreader, two-dimensional imaging is used to observe the heat spreader to determine whether the solder paste is uniformly dissolved, free of bubbles, and whether there is a possibility of air leakage. Three-dimensional imaging is used to determine whether there is obvious collapse, deformation or foreign objects in the internal structure of the heat exchange plate.

4. The failure analysis method for a heat spreader according to claim 1, characterized in that: In the process of testing the airtightness of the heat spreader, a helium test is used to determine whether the heat spreader has leaked. If the heat spreader bulges after the helium test, the cause of failure is poor welding during the heat spreader production process. If there is no change in the appearance and thermal properties of the heat spreader before and after the helium test, the hydrophilicity test / capillary capacity test is then performed.

5. The failure analysis method for a heat spreader according to claim 1, characterized in that: In the hydrophilicity test of the heat spreader, the heat spreader is disassembled to obtain the liquid absorption core, which is a capillary structure formed by the shell and the wire mesh. The liquid absorption core is sampled and the hydrophilicity of the capillary structure is tested with a water contact angle meter. If the contact angle is ≤10°, the hydrophilicity requirement is met; otherwise, it is necessary to check whether there are any abnormalities in the baking process and / or sintering process in the heat spreader production.

6. The failure analysis method for a heat spreader according to claim 1, characterized in that: In the step of capillary capacity testing of the heat exchange plate, the heat exchange plate is disassembled to obtain the liquid wick, which is a capillary structure formed by the shell and the wire mesh. The liquid wick is brought into contact with the liquid water working medium, and the climbing process of the liquid water working medium in the liquid wick is recorded to determine whether the climbing of the liquid water working medium is uniform and whether the climbing speed meets the requirement of ≥3mm / s.

7. The failure analysis method for a heat spreader according to claim 1, characterized in that: In the material characterization test of the heat exchanger, at least one of the following is performed: elemental composition analysis, surface morphology analysis, qualitative and quantitative analysis of surface compounds, and galvanic corrosion test.

8. The failure analysis method for a heat spreader according to claim 7, characterized in that: In the material characterization test of the heat spreader, qualitative and quantitative analysis of the surface compounds is performed to analyze the composition and thickness of the passivation film on the surface of the heat spreader, and to determine whether there is an incomplete passivation problem in the surface treatment process of the heat spreader.

9. The failure analysis method for a heat spreader according to claim 8, characterized in that: In the material characterization test of the heat spreader, when the shell and the wire mesh of the heat spreader are made of different types of metals, the heat spreader is subjected to galvanic corrosion test to determine whether severe galvanic corrosion will occur between the shell and the wire mesh. When the potential difference is ≥150mV, the heat spreader is determined to be galvanic incompatible.

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