Welding method utilizing the regulation of temperature and gas molecule quantity within a chamber and its wafer packaging

Abstract

This invention discloses a welding method utilizing the adjustment of temperature and gas molecule quantity within a chamber. The welding method may include: placing a first component and a second component to be welded within the chamber, wherein the first component and the second component are pre-connected using a welding medium; adjusting the temperature and gas molecule quantity within the chamber to achieve cyclical changes in heat and gas molecule quantity within the chamber to solidify the welding medium and complete the welding of the first component and the second component; wherein the heat changes cause the temperature within the chamber to continuously change between rising and falling, and the cyclical changes cause the pressure within the chamber to change intermittently between positive and negative pressure.

Description

Welding method that utilizes the temperature and number of gas molecules within the chamber This invention relates to the field of industrial manufacturing, and in particular to a welding method and a wafer packaging method that utilizes the adjustment of the temperature and number of gas molecules within a chamber. In recent years, with the increasing integration of chips, chip power consumption and power density have also risen significantly. The resulting heat generation has gradually become a major limiting factor for chip performance and lifespan. To ensure good heat dissipation, current technologies often use a thermal interface material to coat the chip surface before bonding a heat sink. This process is known as soldering. Currently, flux is typically added during soldering, and the evaporation of solvents in the flux leads to numerous air bubbles at the solder interface, ultimately affecting heat dissipation efficiency. Therefore, there is a great need for a new welding method to solve the problem of air bubbles during the welding process. To address the aforementioned technical problems, this invention provides a welding method that utilizes the adjustment of temperature and gas molecule quantity within a cavity, as well as a packaged wafer fabricated based on this method. This welding method achieves high coverage of the welding medium and low bubble rate, resulting in excellent heat dissipation performance. One aspect of the present invention provides a welding method utilizing the adjustment of temperature and gas molecule quantity within a chamber. The welding method may include: placing a first element and a second element to be welded in the chamber, wherein the first element and the second element are pre-connected using a welding medium; adjusting the temperature and gas molecule quantity within the chamber to achieve cyclical changes in heat within the chamber and cyclical changes in the gas molecule quantity to solidify the welding medium and complete the welding of the first element and the second element; wherein the heat changes cause the temperature within the chamber to continuously change between rising and falling, and the cyclical changes cause the pressure within the chamber to change intermittently between positive and negative pressure. In some feasible implementations, the continuous temperature change within the chamber between rising and falling may include the temperature first rising and then falling over time; wherein the temperature rise process includes a isothermal phase. In some feasible implementations, the pressure variation between positive and negative pressure within the chamber may include the pressure varying between positive and negative pressure over time. In some feasible implementations, when the pressure inside the chamber is negative, the vacuum level inside the chamber can be continuously varied in multiple segments. In some feasible implementations, the multi-segment continuous change can cause the vacuum level to continuously increase and then decrease; the continuous change that causes the vacuum level to increase can include decreasing the initial vacuum level to an intermediate vacuum level and then increasing it to the target vacuum level. In some feasible implementations, when the pressure inside the chamber is at the last of the interval changes, a predetermined positive pressure may be maintained until the welding is completed. In some feasible implementations, the pressure within the chamber is maintained at a predetermined positive pressure until the welding is completed, and the temperature may include a process of continuously decreasing until the welding is completed. In some feasible implementations, when the pressure inside the chamber is positive, the positive pressure may be no less than 2 atm. In some feasible implementations, the first element may include a wafer, the second element may include a heat sink, and the soldering medium may include flux and a heat dissipation interface material. In another aspect, the present invention provides a packaged wafer, which can be prepared by the above-described welding method. Implementing this invention has the following beneficial effects: The welding method provided by this invention, which utilizes the adjustment of temperature and number of gas molecules within a cavity, can achieve controlled changes in heat and pressure within the cavity by adjusting the temperature and number of gas molecules. This effectively removes bubbles generated by the welding medium during the welding process, thereby achieving high coverage and low bubble rate of components, improving heat dissipation, and increasing product yield. To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific implementation of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Vacuum reflow soldering equipment is commonly used in existing technologies for soldering components. Vacuum reflow soldering equipment can have multiple chambers. Each chamber has a preset temperature, also known as a temperature zone. Different vacuum reflow systems have different numbers of temperature zones, generally ranging from 7 to 13 (including one vacuum temperature zone and a cooling temperature zone following the vacuum zone). The product to be soldered is placed on a chain conveyor belt and enters each temperature zone sequentially. The residence time of the product in each temperature zone is indirectly controlled by controlling the conveyor belt speed. After the product enters the vacuum temperature zone, the chamber door closes, forming a sealed space to achieve vacuum extraction. After the vacuum stage ends, the chamber door opens, and the product continues to the next temperature zone. After curing in the cooling temperature zone, the product flows out of the equipment outlet, and the soldering is complete. Currently, products prepared using vacuum reflow soldering equipment have a bubble rate of over 6%, which does not effectively achieve the product's heat dissipation function. This invention provides a welding method that utilizes the adjustment of the number of gas molecules within a chamber, enabling high coverage and low bubble rate in the welded product. Referring to Figure 1, as shown in Figure 1, the welding method may include the following steps. Step 110: Place the first and second components to be welded into the cavity. In some feasible implementations, the chamber can be sealed, and the temperature and pressure within the chamber can be adjusted. For example, the chamber may have an openable and closable door. Opening or closing the door can allow the chamber to communicate with the outside or achieve sealing. The chamber may have and / or be externally connected to heating / cooling elements and / or a gas flow path. The heating / cooling elements can regulate the temperature within the chamber, and the gas flow path can regulate the pressure within the chamber. Alternatively, the gas flow path may include a circulation pipe, on which a cooling device such as a condenser and a power device such as a fan or pump are installed. The gas within the chamber circulates within the circulation pipe under the action of the power device, while the cooling device cools the circulating gas. In some feasible implementations, the first and second components may be pre-connected using a soldering medium. For example, the first component may include a wafer, and the second component may include a heat sink. The heat sink may be made from thermally conductive metallic materials such as copper, aluminum, iron, zinc, nickel, titanium, or alloys; ceramic materials such as alumina and zirconium oxide; polymer materials such as polyimide and polyamide; or carbon materials such as graphite and carbon fiber. By soldering the heat sink to the wafer, rapid heat conduction to the wafer is achieved, thereby reducing its temperature. The soldering medium may include a heat dissipation interface material, such as a silicone-based thermally conductive material like thermally conductive silicone grease, or a metal heat sink like an indium foil. These heat dissipation interface materials can, under certain conditions, fix the first and second components together and simultaneously act as a heat dissipation bridge between them. In one feasible implementation, the welding medium may include flux. The flux may be contained within or coated onto the heat dissipation interface material. For example, when a metal heat sink is used as the heat dissipation interface material, the flux may be coated on the surface of the metal heat sink. One method of using the welding medium to achieve a pre-connection between the first component and the second component may involve first coating the wafer surface with flux to form a first flux layer. Subsequently, a heat dissipation interface material is coated or mounted on the first flux layer, and then flux is coated onto the surface of the heat dissipation interface material to form a second flux layer. A heat dissipation cover is then installed on the second flux layer to complete the pre-connection between the first and second components. In this way, after the welding medium has cured in subsequent processes, the components can be welded, effectively improving the heat dissipation efficiency for the first component, such as the wafer. Step 120: Adjust the temperature and number of gas molecules in the chamber to achieve changes in heat and cyclic changes in the number of gas molecules in the chamber, thereby solidifying the welding medium to complete the welding of the first component and the second component. In some feasible implementations, the temperature within the chamber can be adjusted by regulating the heating / cooling elements, thereby achieving heat variation within the chamber. For example, a heating coil or hot water conduit surrounding the chamber can apply heat to the chamber via heat conduction, causing the temperature inside the chamber to rise. Simultaneously, cooling elements, such as a cooling water circulation device or a gas flow path, can absorb and dissipate the heat inside the chamber, causing the temperature inside the chamber to fall. In some feasible implementations, the heat variation within the chamber can cause the temperature inside the chamber to continuously change between rising and falling. For example, throughout the welding process, the temperature inside the chamber can first rise and then fall over time. The temperature rise allows the welding medium to reach a suitable melting point to form a eutectic interface for a tighter bond, while the temperature fall allows the welding medium to begin cooling and solidifying, achieving a fixed connection between the components. It is understandable that the flux solvent evaporates during heating, generating gas and thus forming bubbles within the welding medium. The formation of these bubbles affects the final weld quality and thermal conductivity. In short, the more bubbles, the lower the thermal conductivity. In this invention, bubbles can be removed by adjusting the temperature and the number of gas molecules inside the chamber. In some feasible implementations, the number of gas molecules in the chamber can be cyclically varied by introducing a predetermined amount of gas molecules into the chamber and / or extracting gas molecules from the chamber through a gas flow path. This cyclical variation allows the number of gas molecules in the chamber to alternate between increasing and decreasing. That is, over time, the number of gas molecules in the chamber can first increase, then decrease, then increase again, and then decrease again in a similar pattern. The pressure within the chamber can then vary between positive and negative pressure over time. During the positive pressure phase, the amount of gas molecules introduced can ensure that the pressure in the chamber is not less than 2 atm. For example, 2 atm, 3 atm, 5 atm, 8 atm, etc. The increase in the number of gas molecules within the chamber serves two purposes: firstly, it compresses the welding medium, thereby expelling bubbles; secondly, it allows smaller bubbles to dissolve within the welding medium under the pressure of a larger number of gas molecules, achieving ablation. Conversely, the decrease in the number of gas molecules within the chamber reduces the obstruction from surrounding gas molecules, making it easier for the gas molecules constituting the bubbles to be carried away. These two aspects achieve the goal of bubble removal. Referring to Figure 2, which is an exemplary waveform diagram of temperature and pressure changes inside a chamber according to some embodiments of the present invention. As shown in Figure 2, Pc represents the pressure curve inside the chamber, Tc represents the temperature curve inside the chamber, and P0 represents the ambient atmospheric pressure. Exemplarily, the temperature inside the chamber can rise over time t. During the temperature rise, a phase of temperature stabilization may be included. Gas molecules inside the chamber can be extracted through the gas flow path of the chamber. For example, when the pre-connected first and second components are placed inside the chamber, oxygen molecules will enter the chamber. If oxygen is not removed, these oxygen molecules will adversely affect the welding process, such as affecting the welding quality due to the oxidation of the weld metal into oxides. Therefore, by including a process of extracting gas molecules from the chamber and then introducing and extracting gas molecules, effective removal of oxygen molecules can be achieved. In some feasible implementations, the gas molecules introduced into the chamber can be protective gas molecules, such as nitrogen molecules, argon molecules, etc. The increase in temperature can preheat the soldering medium. For example, it preheats the heat dissipation interface material and activates the flux. Flux activation causes solvent evaporation, which is then removed from the chamber during the gas molecule quantity adjustment step (e.g., removing gas molecules to reduce pressure within the chamber). For example, the heat within the chamber can be adjusted first to raise the temperature to T1, which can be higher than or equal to the flux activation starting point, thus activating the flux. Simultaneously, T1 is lower than the melting point of the heat dissipation interface material. In this way, the flux is activated while the solvent begins to evaporate, while the heat dissipation interface material remains in a solid state. This prevents bubbles from entering the heat dissipation medium, facilitating their removal during the process of reducing gas molecules within the chamber. Referring back to Figure 2, the heat applied to the interior of the chamber can continue to increase over time, causing the temperature inside the chamber to continue to rise. For example, the temperature can be raised to T2. T2 can exceed the melting point of the heat dissipation interface material, allowing the material to molten and better connect components. For example, indium sheets may wet in the molten state, forming a eutectic interface for better soldering results in subsequent processes. During this process, the number of gas molecules inside the chamber can still vary intermittently, causing the pressure inside the chamber to change between positive and negative pressure, achieving better bubble removal. In some feasible implementations, when the number of gas molecules in the chamber causes it to be in a negative pressure state, the vacuum level inside the chamber can be continuously varied in multiple stages. This continuous variation can be that the vacuum level changes between two values, or that the vacuum level maintains the same trend of change in each stage, for example, decreasing, increasing, and / or remaining constant. In some feasible implementations, the continuous variation in multiple stages can cause the vacuum level inside the chamber to continuously increase and then decrease. For example, the vacuum level can increase in each stage of the variation before the final stage and decrease in the final stage. In some feasible implementations, the continuous increase in vacuum level can be from an initial vacuum level decreasing to an intermediate vacuum level and then increasing to a target vacuum level. Let Torr represent the pressure inside the chamber. Obviously, 760 Torr is the ambient atmospheric pressure. In a given process, assuming an initial vacuum of 300 Torr, some gas molecules can be introduced first to lower the vacuum to an intermediate level of 350 Torr. This intermediate vacuum can be maintained or discontinued. Subsequently, gas molecules can be extracted from the chamber to increase the vacuum to 250 Torr, achieving the target vacuum. The adjustment of the number of gas molecules causing a negative pressure within the chamber in this invention serves two purposes: firstly, it avoids the overflow and contamination of the heat dissipation interface material caused by continuous extraction of gas molecules; secondly, the reduction in vacuum can achieve a "backfilling" function of the heat-conducting material through the pressure difference principle, allowing air bubbles to escape from the heat dissipation interface material and subsequently be removed during the gas molecule extraction process. In some feasible implementations, the final stage of the interval change in pressure within the chamber caused by the adjustment of the number of gas molecules in the chamber may include achieving and maintaining a positive pressure in the chamber until the welding is completed. Correspondingly, the adjustment of heat within the chamber may include a process in which the temperature within the chamber continuously decreases until the welding is completed. That is, the chamber remains under positive pressure while the temperature decreases to solidify the molten heat dissipation interface material. Under high pressure, if bubbles are still present in the heat dissipation interface material, these bubbles will be compressed to a minimum. They are then confined within the solid structure during the subsequent cooling and solidification process. On the other hand, under high pressure, bubbles can also be compressed, causing them to move within the molten heat dissipation interface material and escape from the boundaries, further debubbling. In another aspect, the present invention provides a packaged wafer, which can be prepared by the above-described welding method. The welding method disclosed in this invention, which utilizes the adjustment of the temperature and number of gas molecules within the chamber, and the packaged wafer prepared by the welding method, are used for inter-component connections. The welding medium, which has high heat conduction, has a high surface coverage of the component and a low bubble rate, thus achieving excellent heat dissipation performance. Referring to Figures 3 through 6, Figures 3 and 4 are scanned images of weld interfaces according to some embodiments of the present invention, while Figures 5 and 6 show scanned images of weld interfaces obtained in the prior art. As shown in Figure 3, it represents the bubble rate of the weld interface. The bubble rates corresponding to the three examples are 0.01%, 0.65%, and 0.20%, respectively, all less than 1%. This is significantly lower than the less than 10% bubble rate of the weld interface of the product prepared using a vacuum reflow soldering apparatus shown in Figure 5. Meanwhile, Figure 4 shows the coverage of the weld interfaces corresponding to the three examples, which are 98.2%, 96.71%, and 98.7%, respectively, far exceeding the less than 90% coverage of the weld interface of the product obtained in the prior art shown in Figure 6. Therefore, compared with the prior art, the welding process provided by the present invention can effectively remove the bubbles generated by the flux solvent during the welding process and improve the coverage of the heat dissipation medium. The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The embodiments described above merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims. The basic concepts have been described herein. It is obvious that the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, various modifications, improvements, and corrections may be made to this specification by those skilled in the art. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein. It should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the objects required by this specification have more features than those mentioned in the claims. In fact, the embodiments have fewer features than all the features of the single embodiments disclosed above. In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical fields and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible. Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein. 110, 120: Step P0: Ambient atmospheric pressure Pc: Pressure curve inside the chamber t: Time Tc: Temperature curve inside the chamber Torr: Pressure magnitude inside the chamber The present invention will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, the same reference numerals denote the same structures, wherein: FIG1 is an exemplary flowchart of a welding method utilizing the number of gas molecules in a chamber according to some embodiments of the present invention; FIG2 is an exemplary waveform diagram of temperature and pressure changes according to some embodiments of the present invention; FIG3 is a scan of a welding interface according to some embodiments of the present invention; FIG4 is another scan of a welding interface according to some embodiments of the present invention; FIG5 shows a scan of a welding interface obtained by the prior art; FIG6 shows another scan of a welding interface obtained by the prior art. 110, 120: Steps

Claims

1. A welding method utilizing the adjustment of chamber temperature and the number of gas molecules, the welding method comprising: A first component and a second component to be welded are placed in a chamber, wherein the first component and the second component are pre-connected using a welding medium; the temperature and the number of gas molecules in the chamber are adjusted to achieve heat changes and cyclic changes in the number of gas molecules in the chamber, thereby solidifying the welding medium to complete the welding of the first component and the second component; wherein the heat changes cause the temperature in the chamber to continuously change between rising and falling, and the cyclic changes cause the pressure in the chamber to change between positive and negative pressure at intervals.

2. The welding method as described in claim 1, wherein, The temperature within the chamber changes continuously between rising and falling, including: the temperature first rises and then falls over time; wherein the temperature rise process includes a constant temperature phase.

3. The welding method as described in claim 1, wherein, The pressure within the chamber varies between positive and negative pressure at intervals, including: the pressure changing between positive and negative pressure over time.

4. The welding method as described in claim 3, wherein, When the pressure inside the chamber is negative, the vacuum level inside the chamber changes continuously in multiple segments.

5. The welding method as described in claim 4, wherein, The multiple continuous changes cause the vacuum level to continuously increase and then decrease; the continuous changes that cause the vacuum level to increase include: decreasing the initial vacuum level to an intermediate vacuum level and then increasing it to the target vacuum level.

6. The welding method as described in claim 3, wherein, When the pressure inside the chamber is at the last of the interval changes, it includes maintaining a predetermined positive pressure until the welding is completed.

7. The welding method as described in claim 6, wherein, The pressure within the chamber is maintained at a predetermined positive pressure until the welding is completed, and the temperature includes a continuous decrease until the welding is completed.

8. The welding method as described in claim 1, wherein, When the pressure inside the chamber is positive, the positive pressure is not less than 2 atm.

9. The welding method according to any one of claims 1 to 8, characterized in that the first element comprises a wafer, the second element comprises a heat sink, and the welding medium comprises flux and a heat dissipation interface material.

10. A packaged wafer, characterized in that the packaged wafer is prepared by a welding method according to any one of claims 1 to 9, which utilizes the method of adjusting the temperature and the number of gas molecules within the chamber.

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