Heat-conducting silicone grease failure detection method and device

Abstract

The invention belongs to the technical field of heat dissipation, and particularly relates to a heat-conducting silicone grease failure detection method and device.The method comprises the steps that a piezoelectric sensor is arranged on the surface of the side, not coated with heat-conducting silicone grease, of a liquid cooling plate, and the piezoelectric sensor emits ultrasonic waves to a silicone grease layer and obtains echo signals reflected by the silicone grease layer; and judging whether the silicone grease layer fails or not in real time according to the change of the echo signal.

Description

Technical Field

[0001] This invention belongs to the field of heat dissipation technology, specifically relating to a method and apparatus for detecting the failure of thermal grease. Background Technology

[0002] Cold plates are typically made of highly thermally conductive materials, such as copper and aluminum. Their working principle involves close contact with the heat-generating component, transferring heat to the cold plate, and then using a coolant (such as water or ethylene glycol solution) flowing through the plate to carry away the heat, thus achieving heat dissipation. Cold plates have high heat dissipation efficiency and are widely used in electronic equipment, aerospace, new energy vehicles, and medical equipment.

[0003] A layer of thermal grease is usually applied between the liquid cooling plate and the electronic device. The thermal grease has good fluidity and filling properties. After application, it can penetrate into the tiny gaps of the contact surface, expel air, and make the liquid cooling plate and the surface of the electronic device form a tighter physical contact. This significantly reduces the contact thermal resistance of the contact surface. By optimizing the interface heat conduction path, the thermal grease allows heat to be transferred more smoothly from the electronic device to the liquid cooling plate, and then carried away by the coolant, thereby ensuring that the device operates within the normal temperature range.

[0004] The main components of thermal grease include thermally conductive fillers (such as aluminum nitride, aluminum oxide, zinc oxide, etc.) and base oils (such as silicone oil, mineral oil, etc.). When electronic devices are operating, components such as chips continuously generate heat. Prolonged high-temperature environments accelerate the evaporation of the base oil. Over time, the base oil gradually decreases, and the originally paste-like thermal grease dries out due to the loss of its "carrier." High temperatures can also cause the base oil to migrate under gravity or contact pressure (leaking from the contact interface to the edges or gaps), resulting in localized "oil deficiency" in the thermal grease layer, forming dried-out areas. Long-term thermal expansion and contraction can cause micro-cracks within the thermal grease, damaging the bonding structure between the filler and base oil. Simultaneously, minute deformations at the contact surface may compress the thermal grease, causing the base oil to be squeezed out, leaving a dense but dry filler deposit layer that loses its thermal conductivity. In scenarios with high heat dissipation requirements, it is necessary to regularly check and replace the thermal grease to maintain heat dissipation efficiency.

[0005] Existing technology 1-CN111103319B - A method for monitoring the health status of thermal grease and cooling fans, firstly establishes a second-order equivalent Cauler thermal network model based on the physical connection structure of the device, thermal grease, heat sink, and cooling fan; then, utilizing the order-of-magnitude differences between the thermal parameters of each order, establishes a mapping relationship between the thermal network time constant and the parameters of each order in the thermal network model; thereby obtaining the time constant of the health status of the thermal grease and cooling fan, and monitoring the health status of the thermal grease and cooling fan based on the time constant. This method predicts the health status and failure time of the thermal grease by fitting the heat dissipation curve of the device.

[0006] In the prior art 1, the detection of the health status of thermal grease relies on fitting the cooling curve of the heat sink. However, changes in airflow or ambient temperature around the equipment can affect the stability of this curve, leading to increased curve fitting error and affecting the accuracy of time constant extraction. This may result in misjudgment of the health status of the thermal grease. Furthermore, in continuously operating power electronic equipment, if the equipment is under dynamic load for a long time, it is difficult to obtain a stable cooling curve, resulting in low data reliability and failure to detect thermal grease failure in a timely manner, which can easily lead to overheating of the equipment. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the prior art by proposing a method and device for detecting the failure of thermal grease. By arranging a piezoelectric sensor on the surface of the liquid cooling plate that is not coated with thermal grease, the piezoelectric sensor emits ultrasonic waves toward the grease layer and acquires the echo signal reflected by the grease layer. The failure of the grease layer is determined in real time based on the changes in the echo signal.

[0008] The technical solution of the present invention: A method for detecting the failure of thermal grease includes: arranging a piezoelectric sensor on the surface of a liquid cooling plate on the side not coated with thermal grease; emitting ultrasonic waves toward the grease layer and acquiring the echo signal reflected by the grease layer; and determining in real time whether the grease layer has failed based on changes in the echo signal.

[0009] Furthermore, with the silicone grease layer intact, a fixed frequency ultrasonic pulse is emitted towards the silicone grease layer using a piezoelectric sensor, and the reflected acoustic impedance signal is received as a reference signal.

[0010] Furthermore, for the target liquid cooling plate silicone grease layer to be tested, a fixed frequency ultrasonic pulse is emitted towards the silicone grease layer using a piezoelectric sensor, and the reflected acoustic impedance signal is received as the signal to be tested.

[0011] Furthermore, with the silicone grease layer intact, the frequency of the ultrasonic pulse emitted by the piezoelectric sensor toward the silicone grease layer is 5MHz.

[0012] Furthermore, for the target liquid cooling plate silicone grease layer to be detected, the piezoelectric sensor emits ultrasonic pulses with a frequency of 10-20MHz towards the silicone grease layer.

[0013] Furthermore, the failure of the silicone grease layer is determined by comparing the acoustic impedance values ​​of the reference signal and the signal under test.

[0014] A thermal grease failure detection device, applied to the aforementioned detection method, comprising: Piezoelectric sensor or piezoelectric sensor array: The piezoelectric sensor or piezoelectric sensor array is disposed on the side of the liquid cooling plate that is not coated with thermal grease; Signal transceiver: The signal transceiver is connected to the piezoelectric sensor or piezoelectric sensor array. The signal transceiver drives the piezoelectric sensor or piezoelectric sensor array to emit sound waves and receives the echo signal of the emitted ultrasonic wave reflected by the silicone grease layer.

[0015] Furthermore, it also includes a signal amplifier, which is connected to the signal transceiver and is used to amplify the signal output by the signal transceiver.

[0016] Furthermore, an ultrasonic coupling agent is filled between the piezoelectric sensor or piezoelectric sensor array and the surface of the liquid cooling plate.

[0017] Furthermore, a filter circuit is provided between the piezoelectric sensor or piezoelectric sensor array and the signal transceiver; the signal transceiver is also connected to the data acquisition card and alarm device.

[0018] The beneficial effects of this invention are: Compared with the prior art, the beneficial effects of the present invention are: 1. It can detect the state of the thermal paste layer in real time and directly. Theoretically, it can detect air gaps much smaller than the typical thickness of the thermal paste layer. When the thermal paste layer partially delaminates, it can promptly issue an alarm signal to prevent damage to electronic components such as the CPU due to insufficient heat transfer and overheating. Existing technology determines whether the thermal paste has delaminated or failed by monitoring the CPU's overheating temperature. It usually sets an alarm when the temperature exceeds a certain threshold, which poses a safety hazard. Automatic shutdown when overheating occurs can cause significant economic losses.

[0019] 2. The amplitude of the ultrasonic echo signal at the interface can be used to determine the presence of an air layer between the cold plate and electronic components, which is associated with silicone grease debonding. High-frequency ultrasound has high sensitivity and can achieve micron-level air layer monitoring. Existing techniques that monitor thermal conductivity through temperature feedback cannot detect the existence of thin air layers.

[0020] 3. Theoretically, during prolonged high-temperature use, the liquid phase mixed within thermal grease will evaporate, causing the grease to harden. This creates air layers between the cold plate and the grease, and between the grease and electronic components. Because these air layers have poor thermal conductivity, heat from the electronic components cannot be transferred to the cold plate, ultimately leading to overheating. Early detection and intervention, such as when localized grease detachment occurs at the initial stage of grease failure, can prevent equipment overheating.

[0021] 4. Failure status can be quantitatively assessed using parameters such as the amplitude and time delay of the reflected signal, for example, determining the proportion of defects or the reduction in the thickness of the thermal grease layer. The failure area can be proportionally determined by the change in the amplitude of the ultrasonic reflected signal at the interface. Current technology can only separate electronic components and the thermal plate after the thermal grease has failed, and analyze the failure range, i.e., the debonding range, through visual inspection or image processing.

[0022] 5. Real-time monitoring is possible while the liquid cooling plate is in operation, without requiring system shutdown and disassembly, thus balancing detection accuracy and system safety. Existing temperature feedback technologies determine whether electronic components are overheating by monitoring temperature changes in real time, but they cannot quantitatively assess the failure rate of thermal grease in real time. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the device structure of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] One embodiment of the present invention provides a method for detecting the failure of thermal grease, comprising: arranging a piezoelectric sensor on the surface of a liquid cooling plate on the side not coated with thermal grease; the piezoelectric sensor emitting ultrasonic waves toward the grease layer and acquiring the echo signal reflected by the grease layer; and determining in real time whether the grease layer has failed based on the change in the echo signal.

[0026] In this embodiment, with the silicone grease layer intact, a fixed frequency ultrasonic pulse is emitted towards the silicone grease layer via a piezoelectric sensor, and the reflected acoustic impedance signal is received as a reference signal.

[0027] In this embodiment, for the target liquid cooling plate silicone grease layer to be tested, a piezoelectric sensor emits an ultrasonic pulse of a fixed frequency toward the silicone grease layer, and receives the reflected acoustic impedance signal as the signal to be tested.

[0028] In this embodiment, with the silicone grease layer intact, the frequency of the ultrasonic pulse emitted by the piezoelectric sensor toward the silicone grease layer is 5MHz.

[0029] In this embodiment, for the target liquid cooling plate grease layer to be detected, the piezoelectric sensor emits ultrasonic pulses with a frequency of 10-20MHz towards the grease layer.

[0030] In this embodiment, the failure of the silicone grease layer is determined by comparing the acoustic impedance values ​​of the reference signal and the signal under test.

[0031] A second embodiment of the present invention provides a thermal grease failure detection device, applied to the aforementioned detection method, comprising: Piezoelectric sensor or piezoelectric sensor array: The piezoelectric sensor or piezoelectric sensor array is disposed on the side of the liquid cooling plate that is not coated with thermal grease; Signal transceiver: The signal transceiver is connected to the piezoelectric sensor or piezoelectric sensor array. The signal transceiver drives the piezoelectric sensor or piezoelectric sensor array to emit sound waves and receives the echo signal of the emitted ultrasonic wave reflected by the silicone grease layer.

[0032] Signal amplifier: The amplifier is connected to the signal transceiver and is used to amplify the signal output by the signal transceiver.

[0033] In this configuration, an ultrasonic coupling agent is filled between the piezoelectric sensor or piezoelectric sensor array and the surface of the liquid cooling plate.

[0034] A filter circuit is provided between the piezoelectric sensor or piezoelectric sensor array and the signal transceiver; the signal transceiver is also connected to the data acquisition card and alarm device.

[0035] The third embodiment of the present invention provides a thermal grease failure detection system, the system comprising: A piezoelectric sensor is attached to the surface of a liquid cooling plate and faces the silicone grease layer, allowing ultrasound to be incident perpendicularly onto the silicone grease layer. An amplifier (optional) is used to amplify the signal output from the signal generator; A signal transceiver, electrically connected to the piezoelectric sensor, is used to generate a signal that drives the piezoelectric sensor to emit ultrasonic waves for receiving the reflected signal returned by the piezoelectric sensor. The piezoelectric sensor is bonded to the surface of the liquid cooling plate with low-temperature resistant adhesive.

[0036] Since the flow of coolant inside the liquid cooling plate may generate vibration noise, the piezoelectric sensor can be connected to a filter circuit (optional).

[0037] Since the thickness of the silicone grease layer is usually 50-500μm, the ultrasonic frequency can be selected from 10-20MHz to distinguish air layers of different thicknesses.

[0038] Choose to place a single piezoelectric sensor or an array of piezoelectric sensors based on the area of ​​the liquid cooling plate.

[0039] With the silicone grease layer intact, the sensor emits ultrasonic pulses at a fixed frequency (e.g., 5MHz) and receives the reflected signals as a reference signal. The reflected signals primarily originate from: the upper surface of the liquid cooling plate (sensor-liquid cooling plate interface), the interface between the lower surface of the liquid cooling plate and the silicone grease layer, and the interface between the silicone grease layer and the heating element.

[0040] In the actual testing process, the target liquid-cooled plate is periodically and repeatedly transmitted and received to acquire the signal to be tested.

[0041] Analyze the difference between the signal under test and the reference signal, and determine whether the silicone grease layer has failed by the change of characteristic parameters.

[0042] Characteristic parameter analysis and judgment of silicone grease layer status: The acoustic impedance of a normal silicone grease layer is close to that of a liquid cooling plate and a heating element (silicone grease acoustic impedance ≈ 2-3 × 10⁻⁶). 6 Rayl, aluminum ≈ 1.7 × 10 7 Rayl), with a low reflection amplitude; if air bubbles are present (air acoustic impedance ≈ 4 × 10² Rayl), the interface reflection amplitude will increase significantly (to 5-10 times the baseline value).

[0043] Changes in the thickness of the silicone grease layer (such as thinning due to drying) will alter the propagation time of ultrasound waves in the silicone grease (time = thickness / speed of sound). Abnormalities in the thickness of the silicone grease layer can be determined by calculating the time difference of the reflection peaks.

[0044] In this invention, the core function of the thermally conductive silicone grease layer is to fill the microscopic gap between the liquid cooling plate and the heating element. Its failure will lead to air gaps at the interface, drying and hardening of the silicone grease, or local peeling. These changes will alter the acoustic impedance matching relationship of the interface. By analyzing the changes in the reflection or transmission characteristics of ultrasonic echoes at different medium interfaces, it can be determined whether there are abnormalities such as bubbles, drying, or peeling in the silicone grease layer.

[0045] When the silicone grease layer is intact, the acoustic impedance difference between the cold plate (metal, such as aluminum / copper), silicone grease, and heating element (such as metal casing) is small, the ultrasonic wave transmittance is high, and the reflected signal is weak and stable. When the silicone grease layer fails (e.g., air bubbles appear), the acoustic impedance of air is approximately 400 Rayl, far lower than that of silicone grease (approximately 2 × 10⁻⁶). 6 Rayl), the interface acoustic impedance changes abruptly, the amplitude of the reflected signal will increase significantly, and multiple interface reflections may occur (such as multiple reflections inside the bubble).

[0046] The target liquid-cooled plate is periodically and repeatedly transmitted and received to acquire the signal to be measured.

[0047] Analyze the difference between the signal under test and the reference signal, and determine whether the silicone grease layer has failed by the change of characteristic parameters.

[0048] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for detecting failure of a heat-conducting silicone grease, characterized by, Comprising: A piezoelectric sensor is arranged on the side surface of the liquid cooling plate which is not coated with the thermally conductive silicone grease. The piezoelectric sensor emits ultrasonic waves towards the silicone grease layer and acquires the echo signal reflected by the silicone grease layer. The change of the echo signal is used to determine whether the silicone grease layer is defective in real time.

2. The method of claim 1, wherein, Under the condition that the silicone grease layer is in good condition, the piezoelectric sensor emits ultrasonic pulses of a fixed frequency towards the silicone grease layer, and receives the reflected acoustic impedance signal as a reference signal.

3. The method of claim 2, wherein the thermal grease failure is detected by determining whether the temperature of the thermal grease is higher than a predetermined temperature. For the target liquid cooling plate silicone grease layer to be detected, the piezoelectric sensor emits ultrasonic pulses of a fixed frequency towards the silicone grease layer, and receives the reflected acoustic impedance signal as a test signal.

4. The method of claim 2, wherein the thermal grease failure is detected by determining whether the thermal grease has failed based on the temperature of the thermal grease. Under the condition that the silicone grease layer is in good condition, the frequency of the ultrasonic pulses emitted by the piezoelectric sensor towards the silicone grease layer is 5MHz.

5. The method of claim 3, wherein the thermal grease failure is detected by determining whether the thermal grease has failed based on the temperature of the thermal grease. For the target liquid cooling plate silicone grease layer to be detected, the frequency of the ultrasonic pulses emitted by the piezoelectric sensor towards the silicone grease layer is 10-20MHz.

6. The method of claim 3, wherein the thermal grease failure is detected by the step of: The acoustic impedance values of the reference signal and the test signal are compared to determine whether the silicone grease layer is defective.

7. A device for detecting failure of a heat-conducting silicone grease, applied to the detection method according to any one of claims 1 to 6, characterized in that, Comprising: The piezoelectric sensor or piezoelectric sensor array is arranged on the side surface of the liquid cooling plate which is not coated with the thermally conductive silicone grease. The signal transceiver is connected to the piezoelectric sensor or piezoelectric sensor array. The signal transceiver drives the piezoelectric sensor or piezoelectric sensor array to emit acoustic waves, and receives the echo signal of the emitted ultrasonic waves reflected by the silicone grease layer.

8. The heat-conducting silicone grease failure detection apparatus according to claim 7, characterized by A signal amplifier is also included. The amplifier is connected to the signal transceiver and is used to amplify the signal output by the signal transceiver.

9. The heat-conducting silicone grease failure detection apparatus according to claim 7, wherein The piezoelectric sensor or piezoelectric sensor array is filled with an ultrasonic coupling agent between the piezoelectric sensor or piezoelectric sensor array and the surface of the liquid cooling plate.

10. The heat-conducting silicone grease failure detection apparatus according to claim 7, wherein A filter circuit is arranged between the piezoelectric sensor or piezoelectric sensor array and the signal transceiver. The signal transceiver is also connected to a data acquisition card and an alarm device.

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