CN118081014A

CN118081014A - Welding method by adjusting temperature and gas molecular number in cavity

Info

Publication number: CN118081014A
Application number: CN202410479780.6A
Authority: CN
Inventors: 张景南; 王嘉磊; 陈明展
Original assignee: Nanjing Yili Xinchuang Semiconductor Technology Co ltd
Current assignee: Nanjing Yili Xinchuang Semiconductor Technology Co ltd
Priority date: 2024-04-22
Filing date: 2024-04-22
Publication date: 2024-05-28

Abstract

The application discloses a welding method by adjusting the temperature and the number of gas molecules in a cavity. The welding method may include: disposing a first element and a second element to be soldered within a cavity, wherein the first element and the second element are pre-connected using a soldering medium; adjusting the temperature and the gas molecular number in the chamber to realize the heat change in the chamber and the cyclic change of the gas molecular number so as to solidify the welding medium to finish the welding of the first element and the second element; wherein the thermal change causes a continuous change in temperature within the chamber between rising and falling, and the cyclical change causes a change in pressure within the chamber between positive and negative pressure.

Description

Welding method by adjusting temperature and gas molecular number in cavity

Technical Field

The application relates to the field of industrial manufacturing, in particular to a welding method and a packaged chip by utilizing the temperature and the number of gas molecules in a regulating cavity.

Background

In recent years, with the high development of chip integration, chip power consumption and power consumption density are also becoming higher and higher, and the associated heating problem is becoming a main cause of limiting chip performance and lifetime. In order to enable the chip to have good heat dissipation, a heat dissipation interface material is often used in the prior art to coat the surface of the chip and then adhere the heat dissipation cover plate. This process may be referred to as welding. At present, soldering flux is usually added during soldering, and volatilization of solvent contained in the soldering flux can cause a large amount of bubbles at a soldering interface, so that heat dissipation efficiency is finally affected.

Therefore, a new welding method is needed to solve the problem of bubbles in the welding process.

Disclosure of Invention

In order to solve the technical problems, the application provides a welding method for adjusting the temperature and the number of gas molecules in a cavity and a packaged chip prepared based on the method. The welding method can realize high coverage rate and low bubble rate of the welding medium, and excellent heat dissipation performance is obtained.

One aspect of the application provides a method of welding that utilizes a temperature and a number of gas molecules in a regulated chamber. The welding method may include: disposing a first element and a second element to be soldered within a cavity, wherein the first element and the second element are pre-connected using a soldering medium; adjusting the temperature and the gas molecular number in the chamber to realize the heat change in the chamber and the cyclic change of the gas molecular number so as to solidify the welding medium to finish the welding of the first element and the second element; wherein the thermal change causes a continuous change in temperature within the chamber between rising and falling, and the cyclical change causes a change in pressure within the chamber between positive and negative pressure.

In some possible implementations, the continuous change in temperature within the chamber between rising and falling may include the temperature rising first and then falling over time; wherein the temperature rising process comprises a constant temperature stage.

In some possible implementations, the pressure within the chamber varying at intervals between positive and negative pressures may include varying the pressure between positive and negative pressures over time.

In some possible implementations, the vacuum level in the chamber may be a multi-stage continuous variation when the pressure in the chamber is at a negative pressure.

In some possible implementations, the multiple-stage continuous variation may cause the vacuum level to continuously increase and then decrease; the continuous change resulting in the increase in vacuum may include a decrease from a starting vacuum to an intermediate vacuum and then an increase to a target vacuum.

In some possible implementations, the pressure within the chamber at the last of the interval changes may include maintaining a predetermined positive pressure until the weld is completed.

In some possible implementations, the pressure within the chamber maintains a predetermined positive pressure until the end of the weld, and the temperature may include a process that continues to drop to the end of the weld.

In some possible implementations, when the pressure within the chamber is a positive pressure, the positive pressure may be no less than 2atm.

In some possible implementations, the first element may include a chip, the second element may include a heat spreading cover plate, and the soldering medium may include a flux and a heat spreading interface material.

The application also provides a packaged chip, which can be prepared by the welding method.

The implementation of the application has the following beneficial effects:

According to the welding method for adjusting the temperature and the number of gas molecules in the cavity, the temperature and the number of gas molecules in the cavity can be adjusted to realize the regulated and controlled change of the heat and the pressure in the cavity, so that bubbles generated in the welding process of a welding medium can be effectively removed, the high coverage rate and the low bubble rate of elements are further realized, the heat dissipation effect is improved, and the product yield is improved.

Drawings

The application will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. The embodiments are not limiting, in which like numerals represent like structures, wherein:

FIG. 1 is an exemplary flow chart of a welding method utilizing regulating the number of gas molecules in a chamber according to some embodiments of the application;

FIG. 2 is an exemplary waveform diagram illustrating temperature and pressure changes according to some embodiments of the application;

FIG. 3 is a scan of a welding interface shown in accordance with some embodiments of the application;

FIG. 4 is another scan of a welding interface shown in accordance with some embodiments of the application;

FIG. 5 shows a scan of a prior art weld interface;

Fig. 6 shows another scan of a prior art weld interface.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

Unless defined otherwise, 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 application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. 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 the prior art to solder components. The vacuum reflow apparatus may be provided with a plurality of chambers. Each chamber has a preset temperature, which may also be referred to as a warm zone. The number of different vacuum reflux equipment temperature zones is different, and the vacuum reflux equipment temperature zones can be roughly divided into 7-13 temperature zones, and comprises one vacuum temperature zone and a cooling temperature zone arranged behind the vacuum temperature zone. The products to be welded are placed on a chain conveyor and enter each temperature zone in turn. The residence time of the product in each temperature zone is indirectly controlled by controlling the conveyor belt chain speed. After the product enters the vacuum temperature zone, the cavity door of the vacuum temperature zone is closed to form a closed space so as to achieve the purpose of vacuum extraction. And after the vacuum stage is finished, the cavity door is opened, and the product flows to the next temperature zone. After solidification is completed through the cooling temperature zone, the product flows out from a discharge hole of the equipment, and welding is completed.

At present, the bubble rate of a product prepared by using vacuum reflow soldering equipment is more than 6%, and the heat dissipation function of the product cannot be well realized.

On one hand, the application provides a welding method for adjusting the number of gas molecules in a cavity, which can realize high coverage rate and low bubble rate of a welded product. Referring to fig. 1, the welding method may include the following steps, as shown in fig. 1.

At step 110, a first component and a second component to be welded are disposed in the chamber.

In some possible implementations, the chamber may be hermetically sealed and the temperature and pressure within the chamber may be adjustable. Illustratively, the chamber may have an openable and closable door panel. Opening or closing the door panel may allow the chamber to communicate with the outside or may provide a hermetic seal. The chamber may have and/or be externally connected with a heating/cooling assembly and/or a gas flow path. The temperature in the chamber can be regulated by the heating/cooling assembly, and the pressure in the chamber can be regulated by the gas flow path. Or the gas flow path may be provided with a circulation line provided with a cooling device such as a condenser and a power device such as a fan or a pump. The gas in the cavity circulates in the circulating pipeline under the action of the power equipment, and the cooling equipment cools the circulating gas.

In some possible implementations, the first element and the second element may be pre-connected using a soldering medium. For example, the first element may include a chip and the second element may include a heat dissipating cover plate. The heat dissipating cover plate may be manufactured using a metal material such as copper, aluminum, iron, zinc, nickel, titanium, etc. or an alloy, a ceramic material such as alumina, zirconia, etc., a polymer material such as polyimide, polyamic acid ester, etc., a carbon material such as graphite, carbon fiber, etc., which are excellent in heat conductive properties. The heat dissipation cover plate is welded above the chip to realize quick heat conduction to the chip so as to reduce the temperature of the chip. The soldering medium may then comprise a heat dissipating interface material, for example, a silicone-based thermally conductive material such as thermally conductive silicone grease, a metal heat sink such as indium sheet, and the like. These heat dissipating interface materials are capable of fixedly connecting the first element and the second element under certain conditions while assuming a heat dissipating bridge therebetween.

In one possible implementation, the soldering medium may include a flux. The flux may be contained or coated on the heat sink 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. The pre-connection between the first element and the second element is achieved by using the welding medium, and the first welding auxiliary layer is formed by coating soldering flux on the surface of a chip. And then coating or attaching a heat dissipation interface material on the first welding auxiliary layer, and coating soldering flux on the surface of the heat dissipation interface material after finishing to form a second welding auxiliary layer. The heat sink cover plate is to be mounted on the second soldering flux layer to complete the pre-connection between the first and second components. Therefore, the welding of the element parts can be realized after the solidification of the welding medium is completed in the subsequent flow, and the heat dissipation efficiency of the first element such as a chip is effectively improved.

And 120, adjusting the temperature and the gas molecular quantity in the chamber, and realizing heat change in the chamber and cyclic change of the gas molecular quantity so as to solidify the welding medium to finish welding the first element and the second element.

In some possible implementations, the temperature within the chamber may be adjusted by adjusting the heating/cooling assembly of the chamber to achieve a change in heat within the chamber. For example, a heating coil or hot water conduit surrounding the chamber may apply heat to the chamber by means of heat conduction to effect a rise in temperature within the chamber. Meanwhile, a cooling component such as a cooling water circulation device or a gas flow path can absorb and dissipate heat in the chamber, so that the temperature in the chamber is reduced. In some possible implementations, the change in heat within the chamber may cause the temperature within the chamber to continuously change between rising and falling. For example, the temperature within the chamber may be increased and then decreased over time throughout the welding process. The temperature rise can lead the welding medium to reach a proper melting point to form a common alloy interface for more compact combination, and the temperature drop can lead the welding medium to start cooling and solidification so as to realize the fixed connection among elements.

It is understood that the solvent of the flux may volatilize during the temperature rise to generate gas and thus form bubbles inside the soldering medium. The creation of bubbles will affect the final weld quality and heat transfer efficiency. In short, the more bubbles, the lower the heat conduction efficiency. In the application, the removal of bubbles can be realized by adjusting the temperature and the number of gas molecules in the chamber. In some possible implementations, the cyclic variation of the number of gas molecules within the chamber may be achieved by filling the chamber with a predetermined amount of gas molecules through a gas flow path and/or withdrawing gas molecules from the chamber. The cyclical variation may cause the number of gas molecules within the chamber to vary between increases and decreases. That is, over time, the number of gas molecules in the chamber may be increased and then decreased, and then increased and then decreased so that the pattern changes. The pressure embodied in the chamber may then be varied over time between positive and negative pressures. In the positive pressure stage, the number of gas molecules introduced may be such that the pressure of the chamber is not less than 2atm. For example, 2atm, 3atm, 5atm, 8atm, etc. The increase in the number of gas molecules in the chamber may, on the one hand, squeeze the welding medium, thereby squeezing out gas bubbles from the welding medium. On the other hand, smaller bubbles can be dissolved in the welding medium under the extrusion of a large number of gas molecules, so that the purpose of ablation is achieved. The reduction of the number of gas molecules in the chamber can reduce the obstruction of the gas molecules in the environment, so that the gas molecules forming bubbles are more easily carried away. The two aspects realize the purpose of removing bubbles.

Referring to fig. 2, fig. 2 is an exemplary waveform diagram illustrating temperature and pressure variations inside a chamber according to some embodiments of the application. As shown in fig. 2, pc represents a pressure curve in the chamber, tc represents a temperature curve in the chamber, and P0 represents an ambient atmospheric pressure. For example, the temperature within the chamber may rise over time t. During the rise of the temperature, a phase of maintaining the temperature stable may be included. And a gas flow path through the chamber may draw gas molecules within the chamber out of the chamber. For example, when the pre-connected first and second elements are placed inside the chamber, oxygen molecules may enter the chamber. Without oxygen removal, these oxygen molecules would have an adverse effect on the welding process such as weld metal oxidation to form oxides that would affect weld quality. Therefore, the oxygen molecules can be effectively removed by the process of extracting the gas molecules in the cavity and then extracting the gas molecules after the gas molecules are introduced. In some possible implementations, the gas molecules introduced into the chamber may be shielding gas molecules, e.g., nitrogen molecules, argon molecules, etc.

The increase in temperature may preheat the welding medium. For example, the heat sink interface material is preheated and the flux is activated. Activation of the flux may volatilize the solvent and may be removed from the chamber interior during the step of adjusting the number of gas molecules (e.g., pumping away the gas molecules to cause a pressure drop in the chamber). For example, the regulation of the heat in the chamber may be first regulated so that the temperature in the chamber rises to T1, and T1 may be higher than or equal to the activation start point of the flux to activate the flux. And T1 is lower than the melting point of the heat dissipation interface material. Thus, the flux is activated while the solvent begins to volatilize, while the heat sink interface material remains in a solid state. Therefore, no bubbles enter the heat dissipation medium, and the bubbles are convenient to remove in the process of reducing gas molecules in the cavity.

Referring back to fig. 2, the heat applied to the interior of the chamber over time may continue to increase such that the temperature of the interior of the chamber continues to rise. For example, the temperature is raised to T2. T2 may exceed the melting point of the heat sink interface material so that the heat sink interface material may be transformed into a molten state, better connecting the components. For example, the indium sheet is immersed in a molten state, and a common alloy interface is formed, so that a good welding effect is achieved later.

During this process, the number of gas molecules inside the chamber may still be varied at intervals, so that the pressure inside the chamber varies between positive and negative pressure, achieving better bubble removal. In some possible implementations, the vacuum level in the chamber may be a multi-stage continuous variation when the number of gas molecules in the chamber causes the chamber to be at a negative pressure. The multiple continuous changes may be a change in vacuum level between two values, or the vacuum level may be maintained with the same trend, e.g., decreasing, increasing, and/or maintaining, in each change. In some possible implementations, the multiple continuous variations may cause the vacuum level within the chamber to continuously increase and decrease. For example, the vacuum may be increased in every segment change that is not an end segment and decreased in end segment changes. In some possible implementations, the continuous increase in vacuum may be a decrease from a starting vacuum to an intermediate vacuum and then to a target vacuum. The pressure in the chamber is expressed in Torr. It is evident that 760Torr is the ambient atmospheric pressure. In a variation, assuming the initial vacuum is 300Torr, a portion of the gas molecules may be first introduced to reduce the vacuum to an intermediate vacuum of 350 Torr. The intermediate vacuum may or may not be maintained, and then the gas molecules may be pumped out of the chamber to increase the vacuum to 250Torr to achieve the target vacuum. According to the application, the quantity of gas molecules causing the pressure in the cavity to be negative pressure is regulated, so that pollution caused by overflow of the heat dissipation interface material due to continuous gas molecule extraction is avoided, and on the other hand, the function of backfilling of the heat conduction material can be realized by the vacuum degree reduction through the differential pressure principle, so that bubbles are dissipated from the heat dissipation interface material and then removed in the process of gas molecule extraction.

In some possible implementations, the last time the interval of pressure change in the chamber caused by the adjustment of the number of gas molecules in the chamber may include a period of achieving positive pressure in the chamber and maintaining it, and continuing until the end of welding. Correspondingly, the adjustment of the heat in the chamber may be such that the temperature in the chamber comprises a process that continues to drop to the end of the welding. That is, the chamber interior remains at positive pressure during the temperature drop to solidify the melted heat sink interface material. If bubbles are also present in the thermal interface material while maintaining high pressure, these bubbles will be compressed to a minimum. And is confined to the solid structure during the subsequent cool-down curing process. On the other hand, under the action of high pressure, bubbles can be compressed to move in the melted heat dissipation interface material, so that bubbles can escape from the boundary to be further removed.

In yet another aspect, the present application provides a packaged chip that can be prepared by the above-described soldering method.

The welding method for regulating the temperature and the number of gas molecules in the cavity and the packaging chip prepared by the welding method are used for connecting elements, and can realize high heat conduction, high coverage rate of a welding medium on the surface of the element, low bubble rate and excellent heat dissipation performance.

Referring to fig. 3-6, fig. 3 and 4 are scanned views of a welding interface according to some embodiments of the present application, and fig. 5 and 6 are scanned views of a welding interface according to the prior art. As shown in fig. 3, which shows the bubble rate of the weld interface. The bubble rates for the three examples were 0.01%,0.65% and 0.20, respectively. All less than 1%. This is much less than the bubble rate of less than 10% of the weld interface of the product produced using the vacuum reflow apparatus shown in fig. 5. Meanwhile, fig. 4 shows that the coverage of the welding interface corresponding to the three examples is 98.2%,96.71% and 98.7%, respectively, which is far more than the coverage of less than 90% of the welding interface of the product obtained by the prior art shown in fig. 6.

Therefore, compared with the prior art, the welding process provided by the application can effectively remove bubbles generated in the welding process of the solvent of the soldering flux, and improves the coverage rate of the heat dissipation medium.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above-described embodiments represent only a few implementations of the present application, which are described in more detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Having described the basic concepts herein, it will be apparent to those skilled in the art that the foregoing detailed disclosure is by way of example only and is not intended to be limiting. Although not explicitly described herein, various modifications, improvements, and adaptations to the present disclosure may occur to one skilled in the art. Such modifications, improvements, and modifications are intended to be suggested within this specification, and therefore, such modifications, improvements, and modifications are intended to be included within the spirit and scope of the exemplary embodiments of the present invention.

It should be noted that in order to simplify the presentation disclosed in this specification and thereby aid in understanding one or more application embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure does not imply that the subject matter of the present description requires more features than are set forth in the claims. Indeed, less than all of the features of a single embodiment disclosed above.

In some embodiments, numbers describing the components, number of attributes are used, it being understood that such numbers being used in the description of embodiments are modified in some examples by the modifier "about," approximately, "or" substantially. Unless otherwise indicated, "about," "approximately," or "substantially" indicate that the number allows for a 20% variation. Accordingly, in some embodiments, numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and employ a method for preserving the general number of digits. Although the numerical ranges and parameters set forth herein are approximations that may be employed in some embodiments to confirm the breadth of the range, in particular embodiments, the setting of such numerical values is as precise as possible.

Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments of this specification. Other variations are possible within the scope of this description. Thus, by way of example, and not limitation, alternative configurations of embodiments of the present specification may be considered as consistent with the teachings of the present specification. Accordingly, the embodiments of the present specification are not limited to only the embodiments explicitly described and depicted in the present specification.

Claims

1. A welding method using an adjustment of the temperature and the number of gas molecules in a chamber, the welding method comprising:

disposing a first element and a second element to be soldered within a cavity, wherein the first element and the second element are pre-connected using a soldering medium;

Adjusting the temperature and the number of gas molecules in the chamber to realize the heat change in the chamber and the cyclic change of the number of gas molecules so as to solidify the welding medium to finish the welding of the first element and the second element; wherein the thermal change causes a continuous change in temperature within the chamber between rising and falling, and the cyclical change causes a change in pressure within the chamber between positive and negative pressure.

2. The welding method according to claim 1, wherein the temperature in the chamber continuously varies between rising and falling, comprising: the temperature increases and then decreases over time; wherein the temperature rising process comprises a constant temperature stage.

3. The welding method of claim 1, wherein the pressure within the chamber varies at intervals between positive and negative pressures, comprising: the pressure varies between positive and negative pressure over time.

4. A welding method according to claim 3, wherein the vacuum level in the chamber is continuously varied in multiple stages when the pressure in the chamber is at a negative pressure.

5. The welding method of claim 4, wherein the continuous variation of the plurality of segments causes the vacuum level to continuously increase and then decrease; the continuous variation that causes the vacuum degree to increase includes:

the initial vacuum level is reduced to the intermediate vacuum level and then the target vacuum level is increased.

6. A method of welding as defined in claim 3, wherein the pressure in the chamber is at the last of the interval change, comprising maintaining a predetermined positive pressure until the welding is completed.

7. The welding method of claim 6, wherein the pressure within the chamber maintains a predetermined positive pressure until the welding is completed, and wherein the temperature comprises a process that continues to drop to the end of the welding.

8. The welding method according to claim 1, wherein when the pressure in the chamber is positive pressure, the positive pressure is not less than 2atm.

9. The method of any of claims 1-8, wherein the first element comprises a chip, the second element comprises a heat spreading cover plate, and the soldering medium comprises a flux and a heat spreading interface material.

10. A packaged chip characterized by being prepared by the soldering method of any one of claims 1 to 9 using the temperature and the number of gas molecules in the regulation chamber.