A method for detecting the welding of a multilayer heat dissipation structure for an integrated circuit

Abstract

The application relates to the field of welding technology and discloses a multi-layer heat dissipation structure welding detection method for integrated circuits. In the brazing process, a temperature sensor is used to collect the temperature value of a packaging state vacuum cavity heat uniform layer in real time, a pressure sensor is used to collect the contact pressure between a forced cooling pressure head and the packaging state vacuum cavity heat uniform layer in real time, a control unit calculates the temperature change rate dT / dt collected by the temperature sensor and the pressure change rate dP / dt collected by the pressure sensor in real time, when the temperature change rate dT / dt is lower than a preset first threshold value and the duration exceeds a first preset time, and meanwhile the pressure change rate |dP / dt| exceeds a preset second threshold value and the duration exceeds a second preset time, the control unit determines that high-temperature cracking occurs in the packaging state vacuum cavity heat uniform layer, and thus responds. In the brazing process, detection is synchronously carried out, the temperature and pressure response time is short, the temperature change rate and the pressure change rate are used for comprehensive determination, and false positives are reduced.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a welding inspection method for multilayer heat dissipation structures used in integrated circuits. Background Technology

[0002] The most common multilayer heat dissipation structure for integrated circuits is a composite structure of a liquid cooling heat dissipation layer and a vacuum cavity heat dissipation layer. This structure is usually connected into one piece by vacuum brazing. When the vacuum cavity heat dissipation layer needs to participate in brazing in a packaged state (i.e., internally filled with dielectric and sealed), although forced cooling can be used to protect the vacuum cavity heat dissipation layer during the brazing process, there is still a risk in actual production that the vacuum cavity heat dissipation layer may crack at high temperatures due to abnormal process parameters, workpiece material defects, or problems with the initial packaging quality.

[0003] Currently, existing technologies typically use post-brazing airtightness testing to determine the integrity of the vacuum chamber's heat spreader. This method cannot detect cracks in real time during the brazing process, and any resulting media leakage may have already contaminated the furnace cavity and other workpieces. In fact, large-scale cracking may have already occurred within the brazing furnace.

[0004] Therefore, how to accurately and reliably detect high-temperature cracking of the vapor chamber in the packaged state during the brazing process, while minimizing false alarms from single-signal detection, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a welding detection method for multilayer heat dissipation structures for integrated circuits. By fusing temperature and pressure signals, the method can detect in real time and accurately whether the heat dissipation layer of the packaged vacuum cavity has cracked due to high temperature during the brazing process, and issue an alarm and take protective measures in a timely manner.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for inspecting the soldering of multilayer heat dissipation structures for integrated circuits, during the brazing process: A temperature sensor is used to collect the temperature value of the heat spreader layer in the encapsulated vacuum cavity in real time. A pressure sensor is used to collect the contact pressure between the forced cooling head and the heat spreader layer of the encapsulated vacuum cavity in real time; The control unit calculates the temperature change rate dT / dt collected by the temperature sensor and the pressure change rate dP / dt collected by the pressure sensor in real time. When the temperature change rate dT / dt is lower than a preset first threshold and the duration exceeds a first preset time, and the pressure change rate |dP / dt| exceeds a preset second threshold and the duration exceeds a second preset time, the control unit determines that the heat dissipation layer of the encapsulated vacuum cavity has ruptured at high temperature and responds accordingly. The brazing process involves welding the encapsulated vacuum cavity heat dissipation layer and the liquid cooling heat dissipation layer together in an up-down stacking order. The forced cooling head can be raised and lowered inside the brazing furnace and press against the upper surface of the encapsulated vacuum cavity heat dissipation layer during the brazing process.

[0007] According to the welding inspection method described above, the temperature sensor is a contact temperature sensor and is located at the bottom of the forced cooling head.

[0008] According to the welding inspection method described above, the pressure sensor is further disposed on the drive mechanism of the forced cooling head and / or disposed at the bottom of the forced cooling head.

[0009] According to the welding inspection method described above, the brazing method is a multi-piece furnace, in which multiple assemblies formed by stacking a vacuum cavity heat dissipation layer and a liquid cooling heat dissipation layer are clamped by the same welding fixture.

[0010] According to the welding inspection method described above, the forced cooling head has a plurality of cooling protrusions, each of which corresponds to one of the assembly. The welding fixture has a cutout that allows each cooling protrusion to pass through. After passing through the cutout, the cooling protrusion presses against the upper surface of the heat-spreading layer of the encapsulated vacuum cavity.

[0011] According to the welding inspection method described above, the temperature sensor is specifically disposed at the bottom of each or a portion of the cooling protrusions of the forced cooling head.

[0012] According to the welding inspection method described above, the pressure sensor is further provided at the bottom of each cooling protrusion on which a temperature sensor is provided.

[0013] According to the welding inspection method described above, the further aspect is that the response includes issuing a crack alarm signal and automatically executing protective actions.

[0014] According to the welding inspection method described above, the protective actions further include stopping the brazing heating process, recording the time and location of the crack occurrence, and marking it as unqualified.

[0015] According to the welding inspection method described above, the first threshold is -5℃ / s to -2℃ / s, and the first preset time is 0.2 seconds to 0.4 seconds; the second threshold is 0.15 MPa / s to 0.3 MPa / s, and the second preset time is 0.15 seconds to 0.35 seconds.

[0016] The beneficial effects of the present invention are as follows: The solution of the present invention performs simultaneous detection during the brazing process, with short temperature and pressure response times, and can detect abnormalities in a very short time after a crack occurs. At the same time, it uses two independent signals, temperature change rate and pressure change rate, for comprehensive judgment. An alarm is triggered only when both exceed a preset threshold, which minimizes the false alarms that may be caused by a single signal due to factors such as furnace airflow disturbance, cooling medium fluctuation, and cylinder pressure fluctuation.

[0017] With multiple cooling protrusions configured, each station can independently detect and pinpoint the specific workpiece that has cracked, facilitating subsequent tracing and analysis. Once a crack is detected, the system can automatically execute protective actions to minimize the impact of media leakage on the furnace cavity and other workpieces.

[0018] The solution of this invention has strong applicability. It can be applied independently to various vacuum brazing equipment with forced cooling heads, or integrated into more complex multi-layer heat dissipation structure welding systems. For equipment that has already been equipped with temperature sensors for forced cooling heads, it is easy to add pressure sensors and upgrade the control program. It is also suitable for technical updates through upgrades and modifications. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the working principle of the welding inspection method of the present invention.

[0020] Figure 2 This is a schematic diagram illustrating the specific application principle of the welding inspection method of the present invention.

[0021] The components represented by the labels in the diagram are: A: Liquid cooling heat dissipation layer; B: Encapsulated vacuum cavity heat dissipation layer; C: Solder layer. 10: Forced cooling head, 11: Cooling protrusion, 12: Temperature sensor, 13: Pressure sensor, 20: Welding fixture. Detailed Implementation

[0022] Exemplary embodiments of this disclosure will now be described in more detail.

[0023] Example 1: This example describes a welding inspection method for multilayer heat dissipation structures used in integrated circuits. The working principle utilizes... Figure 1 illustrate, Figure 1The illustration depicts a brazing process where the encapsulated vacuum cavity heat spreader layer B and the liquid cooling heat dissipation layer A are welded together in a stacked order. The liquid cooling heat dissipation layer A can be made of common materials such as copper-based or aluminum alloy, while the encapsulated vacuum cavity heat spreader layer B can be made of common materials such as copper-based, iron-based, or aluminum alloy. Above the encapsulated vacuum cavity heat spreader layer B is a forced cooling pressure head 10. The forced cooling pressure head 10 can move up and down within the brazing furnace and press against the upper surface of the encapsulated vacuum cavity heat spreader layer B during the brazing process. This is used to forcibly cool the encapsulated vacuum cavity heat spreader layer B to prevent it from being damaged by heat. This method, combined with a low-temperature brazing process, can reliably weld the encapsulated vacuum cavity heat spreader layer B and the liquid cooling heat dissipation layer A together when the medium (such as water, acetone, or special working fluid) has not been drained.

[0024] To achieve the goal of accurately and reliably detecting high-temperature cracking of the vapor chamber layer B in the encapsulated vacuum cavity during brazing, as mentioned in the background technology, and to minimize false alarms in single-signal detection, this embodiment proposes a method that uses a temperature sensor 12 to collect the temperature value of the vapor chamber layer in real time during brazing, and a pressure sensor 13 to collect the contact pressure between the forced cooling head and the vapor chamber layer in real time. Based on the collected temperature value and contact pressure, it is determined whether the vapor chamber layer has cracked due to high temperature.

[0025] To accurately collect the above two types of data, the temperature sensor 12 in this invention preferably adopts a contact temperature sensor, such as a high-temperature resistant armored thermocouple, which is set at the bottom of the forced cooling head 10. Specifically, a suitable blind hole is opened at the position where the forced cooling head 10 contacts the upper surface of the heat spreader layer B of the encapsulated vacuum cavity. The temperature measuring end of the armored thermocouple is inserted into the blind hole and fixed with high-temperature thermally conductive adhesive. When the forced cooling head 10 is in close contact with the upper surface of the heat spreader layer B of the encapsulated vacuum cavity, the temperature sensor 12 indirectly obtains the surface temperature of the heat spreader layer B of the encapsulated vacuum cavity through the metal thermal conductivity of the forced cooling head 10.

[0026] However, in alternative implementations, the temperature sensor 12 can also be a non-contact temperature sensor, such as an infrared sensor, which can be flexibly placed in the brazing furnace, as long as its sensing point can capture the heat spreader layer B of the encapsulated vacuum cavity (not limited to the upper surface).

[0027] Theoretically, it is also feasible to use a pressure sensor on the drive mechanism of the forced cooling head 10 (i.e., a sensor built into the press) for the pressure sensor 13. However, it is preferable to use a pressure sensor located at the bottom of the forced cooling head 10. Specifically, the pressure sensor 13 is a strain gauge pressure sensor. The strain gauge pressure sensor (accuracy ±0.5%FS) is embedded at the bottom of the forced cooling head 10. The pressure sensor 13 can be arranged side by side with the temperature sensor 12 to directly measure the contact pressure between the forced cooling head 10 and the heat spreader layer B of the encapsulated vacuum cavity.

[0028] The pressure sensor set at the bottom of the forced cooling head 10 is used not only because it is more timely and sensitive, but more importantly, when using a single furnace for multiple production, the pressure sensor 13 can be customized according to the position and quantity of the workpiece, thereby achieving accurate identification of damaged or failed workpieces.

[0029] The wiring of temperature sensor 12 and pressure sensor 13 is led out through the wiring channel of forced cooling head 10 to the outside to realize communication connection with control unit.

[0030] After resolving the data acquisition issues for temperature and contact pressure, the control unit can calculate in real time the temperature change rate dT / dt collected by the temperature sensor 12 and the pressure change rate dP / dt collected by the pressure sensor 13. During the determination process, if the temperature change rate dT / dt is lower than a preset first threshold and its duration exceeds a first preset time, while the pressure change rate |dP / dt| exceeds a preset second threshold and its duration exceeds a second preset time, the control unit can determine that the heat spreader layer of the encapsulated vacuum cavity has experienced a high-temperature rupture, and thus respond by issuing a rupture alarm signal and automatically executing protective actions. For example, based on extensive experimental calibration, the first threshold is set to -5℃ / s to -2℃ / s, the first preset time is set to 0.2 seconds to 0.4 seconds, the second threshold is set to 0.15 MPa / s to 0.3 MPa / s, and the second preset time is set to 0.15 seconds to 0.35 seconds. By combining these two sets of thresholds, the high-temperature rupture of heat spreaders in commonly used copper-based, steel-based, and aluminum alloy encapsulated vacuum cavities can be accurately determined. Specific values ​​can be further precisely calibrated based on the material.

[0031] The use of AND logic effectively avoids false alarms caused by factors such as airflow disturbances in the furnace, fluctuations in the cooling medium, and cylinder pressure fluctuations. For example, when a brief disturbance in the airflow in the furnace causes a small temperature fluctuation, the pressure signal is normal and will not trigger an alarm. Similarly, when the cylinder pressure fluctuates briefly, the temperature signal is normal and will not trigger an alarm. Only when both are abnormal at the same time is it determined to be a real rupture.

[0032] In addition, the protective actions mentioned above include at least one of stopping the brazing heating process, recording the time and location of the crack, and marking the workpiece as unqualified. Specifically, in this embodiment, after the control unit determines that a crack has occurred, it issues an audible and visual alarm signal and displays "The heat spreader layer B of the encapsulated vacuum cavity has cracked" on the operation interface. At the same time, it automatically stops the brazing heating process to prevent the crack from expanding further, records the time and location of the crack (such as "Workpiece No. X"), and marks the workpiece as unqualified to prevent it from flowing into subsequent processes.

[0033] Example 2, this example combines Figure 2 To provide a better industrial application scenario for the welding inspection method of the present invention, specifically, see [link to relevant documentation]. Figure 2 In this embodiment, the brazing method is a single furnace with multiple components, that is: multiple assemblies formed by stacking the encapsulated vacuum cavity heat dissipation layer B and the liquid cooling heat dissipation layer A are held together by the same welding fixture 20 and brazed together.

[0034] To achieve brazing of multiple parts in one furnace, such as Figure 2 As shown, the forced cooling head 10 has a plurality of cooling protrusions 11, each of which corresponds to one of the assemblies formed by stacking the encapsulated vacuum cavity heat dissipation layer B and the liquid cooling heat dissipation layer A. The welding fixture 20 has a cutout portion that allows each cooling protrusion 11 to pass through. After passing through the cutout portion, the cooling protrusion 11 presses against the upper surface of the encapsulated vacuum cavity heat dissipation layer B.

[0035] The welding fixture 20 here is a specialized fixture composed of upper and lower pressure plates that can be elastically clamped. It can be customized according to the production batch. The brazing furnace is an industrial vacuum brazing furnace, which can provide the vacuum degree required for brazing. The forced cooling head 10 is set on the upper side of the brazing furnace and is cooled by an internal circulating cooling channel. Its drive cylinder and cooling medium supply device are both set outside the brazing furnace. The forced cooling head 10 is connected to an external control unit and is connected to the cooling medium supply device. The cooling medium is deionized water. In a preferred embodiment, the control unit can adjust the cooling intensity of the forced cooling head 10 in real time to more reliably control the temperature of the vapor chamber B in the encapsulated vacuum chamber within a safe range.

[0036] In this embodiment, since the number of cooling protrusions 11 is the same as the number of heat dissipation structures held by the welding fixture 20, the temperature sensor 12 can be set at the bottom of each cooling protrusion 11 of the forced cooling head 10. Similarly, the pressure sensor 13 is also set at the bottom of each cooling protrusion 11. The temperature sensor 12 and the pressure sensor 13 can cooperate to provide monitoring data and judgment results for each workpiece to be welded. Specifically, in this embodiment, the temperature sensor uses an armored thermocouple. A suitable blind hole is opened at the position where each cooling protrusion 11 contacts the upper surface of the encapsulated vacuum cavity heat spreader layer B. The temperature measuring end of the armored thermocouple is inserted into the blind hole and fixed with high-temperature thermally conductive adhesive. When the cooling protrusion 11 is in close contact with the upper surface of the encapsulated vacuum cavity heat spreader layer B, the temperature sensor 12 indirectly obtains the surface temperature of the encapsulated vacuum cavity heat spreader layer B through the metal thermal conductivity of the cooling protrusion 11. Since the judgment rule of this invention mainly responds to temperature changes, the deviation between the measured temperature and the surface temperature of the encapsulated vacuum cavity heat spreader layer B has almost no effect. The pressure sensor 13 is a strain gauge pressure sensor. Specifically, a strain gauge pressure sensor (accuracy ±0.5%FS) is embedded in the bottom of each cooling protrusion 11. This pressure sensor 13 can be arranged side by side with the temperature sensor 12 to directly measure the contact pressure between each cooling protrusion 11 and the heat spreader layer B of the encapsulated vacuum cavity. The wiring of both the temperature sensor 12 and the pressure sensor 13 is led out through the wiring channels of the forced cooling head 10 to the outside to achieve communication connection with the control unit.

[0037] The control unit simultaneously monitors the temperature and pressure signals of all cooling protrusions 11, establishes an independent judgment channel for each workpiece, and calculates the temperature change rate dT / dt collected by the temperature sensor 12 and the pressure change rate dP / dt collected by the pressure sensor 13 in real time. During the judgment, when the temperature change rate dT / dt is lower than the preset first threshold and the duration exceeds the first preset time, and at the same time the pressure change rate |dP / dt| exceeds the preset second threshold and the duration exceeds the second preset time, the control unit can determine that the heat dissipation layer B of the encapsulated vacuum cavity of the corresponding assembly has ruptured at high temperature, and thus respond, including issuing a rupture alarm signal and automatically executing protection actions as described above, so as to accurately locate the specific workpiece number of the judgment result.

[0038] For example, in a batch brazing of 24 workpieces in a furnace, the control unit detects that the temperature of the 7th cooling protrusion 11 drops from 195℃ to 170℃ within 0.3 seconds (dT / dt = -83℃ / s), and at the same time, the contact pressure of the cooling protrusion 11 drops from 0.42MPa to 0.15MPa (|dP / dt| = 0.9 MPa / s). The control unit immediately determines that the 7th workpiece has cracked, issues an alarm, stops heating, and highlights "Workpiece No. 7 cracked" on the operation interface. The 7th workpiece is marked as unqualified. The remaining 23 workpieces, since no cracking signal was detected, can continue brazing or continue according to the process requirements.

[0039] In one alternative implementation, the control unit calibrates the temperature zones based on the temperature differences inside the brazing furnace, and also calibrates the temperature zone where each workpiece is located. In this way, when a workpiece is detected to be broken, heating can be stopped only for the corresponding temperature zone, while brazing continues in the remaining temperature zones.

[0040] In another optional implementation, the control unit also records process parameters and traces batches, packages and stores all temperature data, pressure data, and cooling flow data within a set time period before the rupture occurs for subsequent process analysis, and marks all products in the batch that were welded in the same furnace as the ruptured workpiece as "suspected products from the same furnace" for 100% airtightness testing in subsequent inspection stages.

[0041] Example 3: In large-scale brazing production of multiple parts in a single furnace, selective monitoring based on the number and arrangement of workpieces is a practical approach. Therefore, as an alternative implementation method, unlike Example 2, the temperature sensor 12 in this example is only installed at the bottom of a portion of the cooling protrusions 11 of the forced cooling head 10. Correspondingly, the pressure sensor 13 is also installed at the bottom of each cooling protrusion where the temperature sensor 12 is installed. For example, the two types of sensors are set every few or several rows of cooling protrusions 11, or the two types of sensors are set specifically according to the different positions or temperature zones of the furnace where the cooling protrusions 11 are located. In this case, the temperature sensor 12 and the pressure sensor 13 work together to provide monitoring data and judgment results for each selected workpiece as the monitoring object.

[0042] Apart from the difference in the correspondence between the two types of sensors and the cooling protrusion 11, all other technical aspects can be referred to in Embodiment 2. The advantage of this embodiment compared to Embodiment 2 is that, when designing a large furnace capacity, it simplifies the manufacturing cost of equipment components while ensuring sufficient monitoring samples.

[0043] It should be noted that the temperature sensor 12 and pressure sensor 13 used in the various embodiments of the present invention can be dedicated sensors designed for detecting the failure of the heat spreader layer of the encapsulated vacuum cavity of the present invention, or they can be functional extensions or data utilization of the original sensors in the equipment / system. As long as they utilize the ideas of the present invention, they should all fall within the protection scope of the present invention. For example, as mentioned above, when only single-piece brazing production is performed, the pressure sensor 13 can theoretically be a pressure sensor on the drive mechanism of the forced cooling head 10, i.e., a sensor built into the press. In the case of the forced cooling head 10 in Embodiment 1 or the cooling protrusion 11 in Embodiments 2 and 3, the temperature sensor 12 may be set at the bottom to collect temperature data to provide a basis for real-time adjustment of the cooling intensity of the forced cooling head 10. For example, in one feasible solution, the control unit adjusts the cooling intensity of the forced cooling head 10 in real time by combining the temperature of the heat spreader layer B of the encapsulated vacuum cavity collected by the temperature sensor 12 of the present invention with the temperature of the brazing area collected by the furnace temperature sensor of the brazing furnace. When the temperature of the brazing area is lower than the preset target temperature, the cooling intensity is reduced. When the temperature of the heat spreader layer B of the encapsulated vacuum cavity is close to or exceeds the preset tolerance temperature, the cooling intensity is increased. In this case, the data collected by the temperature sensor 12 can be used simultaneously for the detection and determination of the failure of the heat spreader layer of the encapsulated vacuum cavity of the present invention.

[0044] The above embodiments are merely preferred implementations of the present invention. For those skilled in the art, any modifications or improvements made without departing from the concept of the present invention should fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for inspecting the welding of multilayer heat dissipation structures for integrated circuits, characterized in that, During the brazing process: A temperature sensor is used to collect the temperature value of the heat spreader layer in the encapsulated vacuum cavity in real time. A pressure sensor is used to collect the contact pressure between the forced cooling head and the heat spreader layer of the encapsulated vacuum cavity in real time; The control unit calculates the temperature change rate dT / dt collected by the temperature sensor and the pressure change rate dP / dt collected by the pressure sensor in real time. When the temperature change rate dT / dt is lower than a preset first threshold and the duration exceeds a first preset time, and the pressure change rate |dP / dt| exceeds a preset second threshold and the duration exceeds a second preset time, the control unit determines that the heat dissipation layer of the encapsulated vacuum cavity has ruptured at high temperature and responds accordingly. The brazing process involves welding the encapsulated vacuum cavity heat dissipation layer and the liquid cooling heat dissipation layer together in an up-down stacking order. The forced cooling head can be raised and lowered inside the brazing furnace and press against the upper surface of the encapsulated vacuum cavity heat dissipation layer during the brazing process.

2. The welding inspection method according to claim 1, characterized in that, The temperature sensor is a contact temperature sensor and is located at the bottom of the forced cooling head.

3. The welding inspection method according to claim 2, characterized in that, The pressure sensor is installed on the drive mechanism of the forced cooling head, or at the bottom of the forced cooling head, or both on the drive mechanism and at the bottom of the forced cooling head.

4. The welding inspection method according to claim 3, characterized in that, The brazing method involves multiple components in one furnace, with multiple assemblies formed by stacking a vacuum cavity heat dissipation layer and a liquid cooling heat dissipation layer in an encapsulated state on top of each other and clamped by the same welding fixture.

5. The welding inspection method according to claim 4, characterized in that, The forced cooling head has multiple cooling protrusions, each corresponding to one of the assembly. The welding fixture has a cutout that allows each cooling protrusion to pass through. After passing through the cutout, the cooling protrusion presses against the upper surface of the heat-spreading layer of the encapsulated vacuum cavity.

6. The welding inspection method according to claim 5, characterized in that, The temperature sensor is specifically located at the bottom of each or a portion of the cooling protrusions of the forced cooling head.

7. The welding inspection method according to claim 6, characterized in that, The pressure sensor is located at the bottom of each cooling protrusion that is equipped with a temperature sensor.

8. The welding inspection method according to claim 1, characterized in that, The response includes issuing a rupture alarm signal and automatically executing protective actions.

9. The welding inspection method according to claim 8, characterized in that, The protective actions include stopping the brazing heating process, recording the time and location of the crack, and marking it as non-compliant.

10. The welding inspection method according to claim 1, characterized in that, The first threshold is -5℃ / s to -2℃ / s, and the first preset time is 0.2 seconds to 0.4 seconds; the second threshold is 0.15 MPa / s to 0.3 MPa / s, and the second preset time is 0.15 seconds to 0.35 seconds.

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