Method and apparatus for forming electronic device

Abstract

The invention provides a method and apparatus for forming an electronic device. The method comprises the following steps: providing a substrate; placing at least one electronic component on the substrate through soldering paste; applying microwave radiation to the substrate to reflow the solder paste; applying vacuum pressure to the substrate to remove bubbles formed in the soldering paste during reflow soldering of the soldering paste; and curing the solder paste into a solder bump between the substrate and the at least one electronic component.

Description

Technical Field

[0001] This application generally relates to semiconductor technology, and more specifically, to methods and apparatus for forming electronic devices. Background Technology

[0002] The semiconductor industry has consistently faced complex integration challenges as consumers demand smaller, faster, and higher-performing electronic devices, packing increasing functionality into single devices. Typically, electronic components are mounted onto a substrate using solder bumps. The formation of solder bumps can involve reflow soldering of solder paste formed between the substrate and the electronic components, enabling efficient electrical connections between the substrate and the electronic components. The reflow soldering process can be performed by applying heat convection heating to the entire device, where the solder paste is heated and transformed into solder bumps. However, due to the mismatch in the coefficients of thermal expansion (CTE) between different materials within the device, the heating process via convection heat transfer can cause warpage issues, which can adversely affect device performance and subsequent manufacturing processes.

[0003] Therefore, there is a need for a method to form electronic devices that have reduced warpage and improved performance. Summary of the Invention

[0004] The purpose of this application is to provide a method for forming an electronic device that has reduced warpage and improved performance.

[0005] According to one aspect of this application, a method for forming an electronic device is provided. The method includes: providing a substrate; placing at least one electronic component on the substrate using solder paste; applying microwave radiation to the substrate to reflow the solder paste; applying vacuum pressure to the substrate to remove air bubbles formed within the solder paste during reflow soldering; and curing the solder paste into solder bumps located between the substrate and the at least one electronic component.

[0006] According to another aspect of this application, an apparatus for forming electronic devices is provided. The apparatus includes: a platform configured to hold a substrate on which at least one electronic component is placed via solder paste; a microwave radiation source configured to apply microwave radiation to the substrate to reflow the solder paste; and a vacuum source configured to apply a vacuum pressure to the substrate to remove air bubbles formed within the solder paste during reflow soldering via the microwave radiation.

[0007] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and not intended to limit the invention. Furthermore, the accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with this specification, serve to explain the principles of the invention. Attached Figure Description

[0008] The accompanying drawings, which are incorporated herein by reference, form part of this specification. Unless expressly indicated otherwise in the detailed description, the features shown in the drawings illustrate only some embodiments of this application, and not all embodiments thereof, and should not be construed as implying to the reader of this specification that all embodiments are possible.

[0009] Figures 1A to 1E The various steps of a method for forming an electronic device according to a first embodiment of this application are shown.

[0010] Figure 2 An apparatus for forming an electronic device according to a second embodiment of this application is shown.

[0011] Throughout the accompanying drawings, the same reference numerals will be used to refer to the same or similar parts. Detailed Implementation

[0012] The following detailed description of exemplary embodiments of this application takes into account the accompanying drawings, which form a part of the description. The drawings illustrate specific exemplary embodiments in which this application may be practiced. The detailed description, including the drawings, describes these embodiments in sufficient detail to enable those skilled in the art to practice this application. Those skilled in the art may further utilize other embodiments of this application and make logical, mechanical, and other changes without departing from the spirit or scope of this application. Therefore, the reader of the following detailed description should not interpret the description in a limiting sense, and the scope of the embodiments of this application is defined only by the appended claims.

[0013] In this application, unless otherwise expressly stated, the use of the singular includes the plural form. In this application, unless otherwise stated, the use of “or” means “and / or”. Furthermore, the use of the term “comprising” is not restrictive. Additionally, unless otherwise expressly stated, terms such as “element” or “assembly” cover both elements and assemblies comprising one unit and elements and assemblies comprising more than one sub-unit. Furthermore, the section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described.

[0014] As used herein, for ease of description, spatial relative terms such as “below,” “under,” “above,” “upper,” “upper,” “lower,” “left,” “right,” “vertical,” “horizontal,” and “side” may be used to describe the relationship between an element or feature and another element (or feature) or feature (or feature), as shown in the diagrams. In addition to the orientations depicted in the diagrams, the spatial relative terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein shall be interpreted accordingly. It should be understood that when an element is referred to as “connected to” or “coupled to” another element, the element may be directly connected to or coupled to the other element, or there may be intermediate elements present.

[0015] As mentioned above, electronic components are typically mounted onto a substrate after a reflow soldering process, where the solder paste subsequently forms solder bumps. Currently, the reflow soldering process is performed by applying heat convection heating to the entire device with solder bumps, which can lead to warping problems due to uneven heating across the device. To address this issue, a new method for forming electronic devices has been provided. This new method uses microwave radiation to reflow solder the solder paste located between the substrate and at least one electronic component, providing more uniform and rapid heating. Furthermore, during the reflow soldering process, a vacuum pressure is applied to remove air bubbles formed within the solder paste. Therefore, after the reflow soldering process, solder bumps with a uniform structure and fewer defects can be formed, enhancing the reliability of the connection between the substrate and the electronic component.

[0016] Figures 1A to 1E The various steps of a method for forming an electronic device according to a first embodiment of this application are shown.

[0017] like Figure 1A As shown, a substrate 100 is provided, in which embedded interconnects 101 are disposed. The substrate 100 includes a front surface and a rear surface opposite to the front surface, the front surface serving as a platform for mounting electronic components. The interconnects 101 may be formed between and through the substrates 100. Thus, electronic components and other structures on one or both surfaces of the substrate 100 can be electrically coupled to each other to form an integrated electronic system. In some embodiments, a first set of conductive pads 102 may be formed on the front surface of the substrate 100 for mounting electronic components. It is also understood that the first set of conductive pads 102 may be exposed portions of the interconnects 101 formed within the substrate 100.

[0018] In some embodiments, substrate 100 includes at least one nonpolar material (such as silicon), which is the main component of the material of substrate 100. It should be noted that substrate 100 may also contain a small amount of polar material. For example, in this embodiment, substrate 100 may contain more than 99 wt.% nonpolar material and less than 1 wt.% polar material, which helps to improve the structural and electrical properties of substrate 100. In some other embodiments, substrate 100 may contain less than 2 wt.%, 5 wt.%, or 10 wt.% polar material.

[0019] Next, solder paste 105 is applied to each conductive pad in the first set of conductive pads 102 for mounting electronic components. Solder paste 105 may include a metallic solder and a flux. In some embodiments, the metallic solder may include one or a combination of metallic materials. It is understood that a combination of metallic and non-metallic materials may also be provided within the metallic solder. More specifically, the metallic material may be Al, Sn, Ni, Au, Ag, lead (Pb), bismuth (Bi), Cu, or a combination thereof. In some embodiments, the metallic solder may include metal powder, such as sintered metal powder. In some other embodiments, an adhesive material may be further provided to bind the metal powder. The adhesive material should have sufficient tack to bind the metal powder together before, during, and after subsequent heating processes of the solder paste 105. In other words, the adhesive material should not completely evaporate during the heating process of the solder paste 105. Additionally, the adhesive material may include a thermally conductive material, which allows for effective convective heat transfer within the solder paste 105 during the heating process. In some alternative embodiments, the adhesive material may include a polar material, which further facilitates the heating process of the solder paste 105 upon subsequent exposure to microwave radiation, since the adhesive material can absorb microwave energy and can be selectively heated.

[0020] Furthermore, the flux within the solder paste 105 can be used to facilitate the subsequent heating process of the solder paste 105, thereby achieving sufficient electrical connection between the substrate 100 and the electronic components mounted thereon. The flux may include a large number of one or more polar materials that can be specifically heated when exposed to microwave radiation. Additionally, in some embodiments, the flux may include one or more polar materials with a higher degree of polarization than the metal solder included in the solder paste 105. Therefore, when exposed to microwave radiation, the flux can be heated to a higher temperature than the metal solder, allowing sufficient convective heat transfer from the flux to the metal solder. In some embodiments, the flux may include one or more materials selected from the group consisting of: nonylphenol ethoxylate, glyceryl monostearate, acid activator, water, and inorganic salts. In a preferred embodiment, the flux may include between 40 wt.% and 70 wt.% nonylphenol ethoxylate, between 10 wt.% and 30 wt.% glyceryl monostearate, between 3 wt.% and 10 wt.% acid activator, between 3 wt.% and 10 wt.% water, and between 4 wt.% and 15 wt.% inorganic salt.

[0021] In some embodiments, flux may be applied to the surface of the metal solder, such as the bottom surface of the metal solder or the entire spherical surface. In some other embodiments, flux may be mixed into the metal solder to form a monolithic solder paste mixture, which further enhances convective heat transfer from the flux to the metal solder.

[0022] Next, as Figure 1B As shown, at least one electronic component 111 is provided. In some embodiments, the electronic component 111 may include various types of electronic modules, such as semiconductor chips, resistors, capacitors, etc. In alternative embodiments, at least one electronic component 111 may include a semiconductor package. It is understood that the electronic component 111 can be arranged and sized according to the actual needs of the electronic device. In some embodiments, different types of electronic components 111 may be included in a single electronic device according to actual needs. Furthermore, the at least one electronic component 111 includes at least a non-polar material. It is understood that, with Figure 1A Similar to the substrate 100 shown, the electronic component 111 may contain small amounts of polar material, such as an encapsulation layer or adhesive within the electronic component 111. For example, the electronic component 111 may contain more than 99 wt.%, 98 wt.%, 95 wt.%, or 90 wt.% of non-polar material, and therefore less than 1 wt.%, 2 wt.%, 5 wt.%, or 10 wt.% of polar material.

[0023] Next, at least one electronic component 111 is placed on the front surface of the substrate 100. More specifically, the at least one electronic component 111 may have a second set of conductive pads 112 on its rear surface. Each conductive pad in the second set of conductive pads 112 is aligned with one conductive pad in the first set of conductive pads 102, and solder paste 105 is placed therebetween. In some other embodiments, additional solder paste may be attached to the second set of conductive pads 112. The at least one electronic component 111 may then be placed on the front surface of the substrate 100, with solder paste 105 and additional solder paste placed between the first set of conductive pads 102 and the second set of conductive pads 112.

[0024] Next, as Figure 1C As shown, microwave radiation is applied to substrate 100 to reflow solder paste 105. In some embodiments, a microwave source is placed above electronic component 111, and microwave radiation is then applied from the microwave source to electronic component 111 to heat solder paste 105. Electronic component 111, which typically comprises non-polar materials, may not absorb or may absorb very little microwave energy, so microwaves can penetrate electronic component 111 and reach solder paste 105. In some other embodiments, the microwave source is placed at one or more side sides of electronic component 111. Microwave radiation can be applied from the microwave source to solder paste 105 from side to side. Therefore, microwaves can interact more directly with solder paste 105 without first passing through electronic component 111, which can improve the energy absorption efficiency of solder paste 105. It is also understood that the placement of the microwave source can vary depending on the actual layout of the electronic device. For example, one or more microwave sources may be tilted at 30 degrees, 45 degrees, 60 degrees, or any other suitable angle relative to the front surface of substrate 100.

[0025] Still referencing Figure 1C When solder paste 105 is exposed to microwave radiation, the dipoles within the polar molecules of the flux in solder paste 105 are sensitive to the electric field of the microwave, and the dipoles can rotate under the influence of the electric field to align themselves with the direction of the electric field. The electric field of the microwave is periodically changing, which may cause the dipoles to rotate frequently. Therefore, as the dipoles rotate according to the direction of the electric field, they may collide with each other, which generates heat and causes the flux to rise to a higher temperature, for example, above the melting temperature of the metal solder in solder paste 105. In addition, the metal solder in solder paste 105, especially the metal powder, may also absorb microwave energy to generate heat, which will cause a moderate rise in the temperature of the metal solder. As the temperature of the flux rises, some of the heated flux may evaporate first, and the heat generated in the flux can be transferred to the metal solder by convection, which will cause the temperature of the metal solder to rise further. Then, the temperature of the metal in the metal solder may rise above its melting temperature, causing the metal to melt and the metal solder to reform in the molten state.

[0026] During the microwave irradiation process, the flux can be heated to a high reflow soldering temperature to provide sufficient heat to the metal solder via convection, allowing the metal solder to melt and wet on the first set of conductive pads 102 and the second set of conductive pads 112. In a preferred embodiment, the reflow soldering temperature of the solder paste can reach a temperature range between 200°C and 240°C. In some other embodiments, the temperature of the solder paste can be even higher to achieve a faster reflow soldering process. In some embodiments, microwave irradiation can be applied intermittently to control the temperature of the heated flux. For example, microwave irradiation can be applied and maintained for a specific duration (e.g., 10 seconds to 2 minutes), followed by a pause in the application of microwave irradiation for another specific duration (e.g., 5 seconds to 30 seconds). Furthermore, depending on the reflow soldering process of the solder paste 105, this cycle can be repeated several times. It is understood that the specific duration can be several seconds to several minutes, depending on the actual needs of the heating process, such as the specific composition of the flux and / or metal solder, the amount of metal solder, and / or the power of the microwave irradiation. In some other embodiments, a temperature sensor (e.g., an infrared temperature sensor or an infrared image array) can be used to monitor the temperature of the flux or solder within the solder paste 105, and the real-time temperature measurement results can then be provided to the controller of the microwave source to adjust the power and / or duration of the microwave radiation. In some preferred embodiments, the substrate 100 and the electronic components 111 mounted thereon can be placed in an atmosphere with a higher ambient temperature to avoid excessive heat transfer from the flux and / or solder to the substrate 100 and / or electronic components 111 due to the significant temperature difference between the substrate 100 and / or electronic components 111 and the solder paste 105. For example, the ambient temperature can be 10°C to 150°C lower than the reflow soldering temperature of the metal within the solder paste 105, or preferably 10°C to 50°C, or more preferably 10°C to 30°C.

[0027] Furthermore, in this embodiment, microwave radiation is applied at a variable frequency during the microwave irradiation step. Compared to microwaves at a fixed frequency, rapidly scanning a range of frequencies increases the uniformity of microwave energy. Microwave radiation can be applied within a frequency range of 1 GHz to 10 GHz. The microwave source can be set at a power range of 100 W to 2000 W. In other embodiments, microwave radiation can be applied at frequencies higher than 10 GHz or at microwave source power higher than 1000 W, which allows the solder paste 105 to heat up more quickly. Additionally, microwave radiation can be sustained for a minimum duration (e.g., 1 minute) to sufficiently heat the metal solder and completely evaporate the flux. It is also understood that the frequency, power, and duration of microwave radiation can be selected according to the actual needs of the reflow soldering process of the solder paste 105.

[0028] Because molecules in nonpolar materials are insensitive to microwave electric fields, when substrate 100 and electronic components 111 are exposed to a microwave field along with solder paste 105, the substrate and electronic components may not be heated by microwave radiation or will be almost unheated. Furthermore, interconnects 101 embedded within substrate 100 and metal layers that may be included within electronic components 111 may reflect microwaves and generate almost no heat. In this way, solder paste 105 is selectively heated by microwave radiation. This heating mechanism can provide several advantages for the reflow soldering process of solder paste 105. First, since substrate 100 and electronic components 111 are almost unheated by microwave radiation, selective heating of solder paste 105 by microwave radiation (rather than a conventional heating process applied to the entire electronic device) can reduce warpage problems of substrate 100 and electronic components 111. Second, microwaves can penetrate solder paste 105 to supply energy and can therefore generate heat in a volumetric manner throughout solder paste 105, allowing for a more uniform heat distribution from the surface to the interior of solder paste 105. Third, microwaves induce molecular rotation without breaking molecular bonds (due to the low energy of photons), which can have minimal impact on the internal structure of components in electronic devices. Fourth, microwave heating can be started and / or stopped quickly, which can shorten the heating duration.

[0029] During microwave irradiation, residual gases from ambient gases and / or vaporized flux may be trapped within the molten solder paste 105, thereby forming bubbles within the solder paste 105, which subsequently transforms into solder bumps. These bubbles within the solder paste 105 can be removed by applying vacuum pressure in subsequent processes, as detailed below.

[0030] like Figure 1DAs shown, after microwave radiation is applied, a vacuum pressure is quickly applied to the substrate 100 to continue the reflow soldering process of the solder paste 105. It is important to note that the overall reflow soldering process of the solder paste 105 includes the stage of microwave radiation heating of the solder paste 105 and the stage of applying vacuum pressure to the substrate 100. Applying vacuum pressure to the substrate 100 means placing the substrate 100 in a vacuum atmosphere. More specifically, a vacuum chamber can be provided to house the substrate 100 and the structures thereon. The vacuum chamber can be fluidly connected to a vacuum pump to provide vacuum pressure within the vacuum chamber. In some embodiments, the substrate 100, at least one electronic component 111, and the solder paste 105 between them are housed within the vacuum chamber to be exposed to vacuum pressure. When vacuum pressure is applied, the solder paste 105 remains at a high reflow soldering temperature and in a molten state to allow the reflow soldering process of the solder paste 105 to continue. The molten solder paste 105 allows gases to escape from it under a vacuum atmosphere. Simultaneously, the presence of vacuum pressure may create a pressure difference between the interior of the bubbles within the solder paste 105 and the vacuum environment outside the solder paste 105. Therefore, the gas trapped within the bubbles can escape from the solder paste 105. Furthermore, by removing the gas from the bubbles, heat can be transferred more efficiently to the substrate 100 and the solder paste 105 without being hindered by gases with relatively low thermal conductivity, thereby ensuring uniform heat distribution throughout the solder paste 105. In addition, the vacuum environment surrounding the solder paste 105 eliminates convection caused by airflow, thereby reducing potential interference with heat transfer during the reflow soldering process of the solder paste 105 and resulting in uniform heat distribution throughout the solder paste 105. Therefore, although the solder paste 105 strongly absorbs microwave energy and is rapidly heated, this method can improve the uniformity of the reflow soldering process and reduce hotspots generated during the reflow soldering process. Finally, as... Figure 1E As shown, solder paste 105 is cured into solder bumps 106 to form an electrical connection between substrate 100 and at least one electronic component 111, thereby forming an electronic device. By applying vacuum pressure, the reflow soldering process of solder paste 105 can be performed more uniformly and fully. The formed solder bumps 106 have a uniform structure and fewer bubble defects, which improves the reliability of the connection between at least one electronic component 111 and substrate 100.

[0031] In some embodiments, the flux may evaporate completely, allowing the reflow soldered metal to form an electrical connection. In some other embodiments, only a portion of the flux may evaporate, and the remaining flux can eventually be removed from the metal solder, for example, by a cleaning agent. In some alternative embodiments, the remaining flux and metal solder may be fused together to form an electrical connection between the electronic component 111 and the substrate 100.

[0032] The reflow soldering process of solder paste 105 in a vacuum environment can have a sufficient duration to ensure that solder paste 105 is adequately reflow soldered. In some embodiments, a vacuum pressure can be applied for a duration ranging from 30 seconds to 10 minutes. The vacuum pressure can be less than 5 mtorr to provide a sufficient vacuum environment. Furthermore, when solder paste 105 is exposed to a vacuum environment, solder paste 105 should remain at the reflow soldering temperature, which ensures that solder paste 105 remains in a molten state, allowing air bubbles within solder paste 105 to escape. In some preferred embodiments, the reflow soldering temperature can be in the range of 200°C to 240°C, thereby ensuring that solder paste 105 (i.e., the metallic solder material) is adequately wetted on the surfaces of the first set of conductive pads 102 and the second set of conductive pads 112.

[0033] In some other embodiments, the vacuum chamber can be formed by attaching a baseless top cover to at least a portion of the front surface of the substrate 100. Therefore, vacuum pressure can be provided within the vacuum chamber defined by the top cover and the front surface of the substrate 100. The smaller volume allows the vacuum chamber to achieve the desired vacuum pressure more quickly.

[0034] In some embodiments, when a vacuum pressure is applied to the substrate 100, the temperature of the solder paste 105 can be maintained in the range of 200°C to 240°C. A heater can be provided to conserve heat and slow the cooling rate of the solder paste 105, allowing it to be maintained at a reflow soldering temperature within the vacuum environment. This reflow soldering temperature can be approximately the same as or slightly lower than the temperature of the solder paste 105 during the microwave irradiation process. In some embodiments, a carrier with a heat transfer barrier top layer can be used instead of a heater to prevent rapid cooling of the substrate 100 and the solder paste 105. In some embodiments, the duration of applying vacuum pressure to the substrate 100 can be longer than the duration of applying microwave irradiation to the substrate 100. In this way, air bubbles generated within the solder paste 105 during microwave irradiation can be sufficiently removed during the application of vacuum pressure. In some preferred embodiments, the duration of applying vacuum pressure to the substrate 100 can be two or three times the duration of applying microwave irradiation to the substrate 100.

[0035] After the solder paste 105 has been fully reflowed, vacuum pressure is no longer applied to the substrate 100, and the solder paste 105 can be cooled to a temperature below the reflow temperature, causing the solder paste 105 to solidify into solder bumps 106 to form an electrical connection between the substrate 100 and at least one electronic component 111. It is understood that external gas can be introduced to increase the pressure exposed to the substrate 100 and the reflowed solder paste 105, thereby ending the vacuum reflow process. In some preferred embodiments, the duration of the pressure increase after the vacuum reflow process can be the same as or longer than the duration of the vacuum pressure applied to the substrate 100 (e.g., two or three times longer). Alternatively, after the vacuum reflow process, the substrate 100 and the reflowed solder paste 105 can also be exposed to the atmosphere of the process environment. In some other embodiments, the solder paste 105 can be cooled and solidified into solder bumps 106 during the application of vacuum pressure to the substrate 100.

[0036] refer to Figures 1A to 1E Applying vacuum pressure to the substrate 100 after the microwave irradiation process optimizes the reflow soldering process. In this way, the vacuum pressure is applied only in the later stages of the reflow soldering process, thereby saving energy and improving process efficiency. Furthermore, the vaporized flux generated during microwave irradiation is unaffected by the vacuum environment, ensuring sufficient convective heat transfer from the flux to the solder metal.

[0037] In an alternative embodiment, a vacuum pressure is simultaneously applied to the substrate 100 while microwave radiation is applied to reflow solder paste 105. Therefore, gases generated during the microwave radiation process can be immediately expelled and pumped out of the solder paste 105 in a vacuum environment. This further reduces the amount of gas trapped within the solder paste 105 during the reflow soldering process, and thus reduces air bubbles within the subsequently cured solder bumps 106. Additionally, this also reduces the duration of the reflow soldering process, improving process efficiency and saving costs. It is understood that a vacuum pressure can be applied simultaneously when the microwave radiation source is turned on. Alternatively, the vacuum pressure can be applied after a period of time following the application of microwave radiation.

[0038] Subsequently, an encapsulation layer can be formed on the substrate 100 to encapsulate at least one electronic component 111 and solder bumps 106, thereby forming an electronic package. In some other embodiments, the method for forming an electronic device may not include the process of forming an encapsulation layer.

[0039] In some embodiments, the method can be used to form electronic devices with small size and complex structures, such as system-in-package (SIP) devices with various electronic components. In some other embodiments, the electronic devices can be applied to any device where it is desirable to reduce warpage issues and improve electrical connection reliability. The electronic devices can also be dual-sided, with the back surface of the substrate serving as another platform on which the electronic components can be mounted using solder paste. Solder paste on the front and back surfaces of substrate 100 can be microwave-irradiated and reflow-soldered in a vacuum environment to form electrical connections between the electronic components and the substrate.

[0040] Figure 2 An apparatus for forming an electronic device according to a second embodiment of this application is shown. Specifically, this apparatus can be used to perform a reflow soldering process of solder paste 105 within the electronic device. The details of the process for forming the electronic device can be similar to... Figures 1A to 1E The method for forming electronic devices is shown in the figure.

[0041] like Figure 2 As shown, the device may include three contiguous regions, namely a first region A, a second region B, and a third region C, for performing a reflow soldering process of solder paste 205 between the substrate 200 and at least one electronic component 211. The device further includes a platform 201 for placing the substrate 200. The platform 201 is a single unit that spans the first region A, the second region B, and the third region C. In some embodiments, a main chamber may be provided to include all three regions (or even more additional regions as desired), which can prevent contaminants from entering the device, thereby protecting the substrate 200 and the structures thereon during reflow soldering.

[0042] In some embodiments, the first region A is configured to apply microwave radiation to the substrate 200 via a microwave radiation source 215 to perform reflow soldering on the solder paste 205. The microwave radiation source 215 is disposed within the first region A, for example, above the platform 201.

[0043] In some embodiments, during microwave irradiation, the substrate 200 and solder paste 205 may be placed in an atmosphere with an ambient temperature of 80°C to 120°C. In some preferred embodiments, the platform 201 may be a heater, or the platform 201 may include a heater that generates additional heat. This additional heat can raise the temperature of the ambient atmosphere during microwave irradiation, thereby mitigating heat dissipation. Furthermore, since the platform 201 is in direct contact with the substrate 200, the additional heat can be transferred to the substrate 200 via convection, and thus to the solder paste 205. This allows the solder paste 205 to be heated via a hybrid heating mechanism that combines direct microwave heating with heat transferred from the platform 201 via convection, resulting in a more efficient reflow soldering process and lower energy requirements for the microwave source 215. Furthermore, with lower microwave energy applied from the microwave source 215, the total heat generated within the device can be reduced, which can prevent or mitigate the burning effect caused by excessive microwave energy. Furthermore, because the bottom portion of the solder paste 205 is less exposed to microwave radiation, it can receive more heat energy transferred from the platform 201 via convection, thereby enabling the solder paste 205 to be reflowed in a more uniform and controllable manner, and producing fewer defects.

[0044] In some preferred embodiments, platform 201 may comprise a polar material, a combination of multiple polar materials, or a combination of polar and non-polar materials, which can be subsequently heated by microwave radiation. Furthermore, platform 201 may comprise one or more thermally conductive materials, allowing sufficient convective heat transfer from platform 201 to substrate 200 and solder paste 205 after microwave heating of platform 201 during the reflow soldering process of solder paste 205, and mitigating heat dissipation from solder paste 205. In some embodiments, a significant portion of platform 201 (e.g., greater than 50 wt.%, 60 wt.%, 70 wt.%, 80 wt.%, 90 wt.%, 95 wt.%, or 99 wt.%) is formed of a polar material, which gives platform 201 better heating performance when exposed to microwave radiation. More specifically, platform 201 may comprise at least one polar material selected from silicon carbide, graphite, polar charcoal, and polar carbon. In some other embodiments, platform 201 may comprise a non-polar substrate coated with or in which a polar material is distributed, which can reduce the material requirements of platform 201 and achieve better mechanical support and lower cost during the reflow soldering process of solder paste 205 (if a suitable material is used as the material for the non-polar substrate). Specifically, the non-polar substrate may comprise a silicon wafer or silicon powder, and the polar coating may comprise at least one polar material selected from silicon carbide, graphite, polar charcoal, or polar carbon.

[0045] In these embodiments, when microwave radiation is applied, platform 201 is also exposed to microwave radiation, which can penetrate solder paste 205 and substrate 200, and ultimately reach platform 201. Simply put, excess microwave energy that cannot be absorbed by solder paste 205 can be collected by platform 201 and converted into heat, which in turn facilitates the heating and reflow soldering process of solder paste 205. In some embodiments, platform 201 may include a film or plate at its bottom capable of reflecting microwaves upwards. During microwave radiation, the reflected microwaves can penetrate platform 201 again and generate heat there, or even penetrate platform 201 and reach solder paste 205 again, thereby further heating and reflow soldering solder paste 205.

[0046] The second region B is configured to apply vacuum pressure to the substrate 200 via a vacuum source to remove air bubbles within the solder paste 205. The vacuum source includes a vacuum pump. The second region B further includes a vacuum chamber 220 fluidly connected to the vacuum pump, which provides a vacuum atmosphere within the vacuum chamber 220 for containing the substrate 200 and providing it with a vacuum environment. In some other embodiments, a heater may be placed within the second region B to heat the substrate 200 placed on the platform 201, conserve heat energy, and slow the cooling rate of the solder paste 205, allowing the solder paste 205 to be maintained at a reflow soldering temperature within the vacuum environment.

[0047] The third region C is configured to cool the solder paste 205 and cure it into solder bumps 206. In some embodiments, the third region C may include cooling elements (such as a heat sink on the platform 201, a fan adjacent to the substrate 200, or an air conditioner) to facilitate cooling of the solder paste 205. In some preferred embodiments, a cooling chamber is arranged in the third region C to accommodate the substrate 200, thereby cooling the solder paste 205 by controlling it at a relatively low temperature within the cooling chamber.

[0048] In forming the electronic device, a substrate 200, on which the structure is formed, is first placed on a platform 201 within a first region A. A microwave radiation source 215 applies microwave radiation to the substrate 200 to heat the solder paste 205 and reflow it. Next, the substrate 200 is transported to a second region B, for example, to a vacuum chamber 220, where a vacuum pressure is applied by a vacuum pump to remove air bubbles from the solder paste 205 and continue the reflow process. In some embodiments, the first region A and the second region B can be close to each other, such that the substrate 200 can be quickly transported to the vacuum chamber 220 in the second region B while the solder paste 205 is still at a high reflow temperature and in a molten state. Following the vacuum reflow process in the second region B, the substrate 200 can be transported to a third region C to cool the solder paste 205 and solidify it into solder bumps 206.

[0049] In some embodiments, a conveyor belt may extend through a first region A, a second region B, and a third region C. During the reflow soldering process, the conveyor belt is used to transport the substrate 200 from the first region A through the second region B to the third region C. The conveyor belt may include a belt or a carrier located on a track to transport the substrate 200 at a controlled speed. It is also understood that the equipment may not include a conveyor belt, and the substrate 200 may be transported by manual operation.

[0050] In some other embodiments, the device may not include the third region C. The substrate 200 and solder paste 205 may be cooled and cured in the second region B with or without vacuum pressure.

[0051] In some other embodiments, when microwave radiation is applied to reflow solder paste 205, a vacuum pressure is simultaneously applied to substrate 200. In these cases, Figure 2 The first region A and the second region B shown can be combined to form a reflow soldering chamber. The reflow soldering chamber may include a microwave radiation source 215 and is fluidly connected to a vacuum pump. When the substrate 200 is located in the reflow soldering chamber, microwave radiation is applied to the substrate 200 and vacuum pressure is applied to the substrate 200 to reflow solder the solder paste 205.

[0052] Although the method for forming electronic devices described herein has been described in conjunction with the accompanying drawings, those skilled in the art will understand that modifications and adjustments can be made to the method for forming electronic devices without departing from the scope of the invention.

[0053] Various embodiments have been described herein with reference to the accompanying drawings. However, it will be apparent that various modifications and changes can be made thereto, and other embodiments can be implemented without departing from the broader scope of the invention as set forth in the appended claims. Furthermore, other embodiments will be apparent to those skilled in the art upon consideration of the practice of one or more embodiments of the invention disclosed herein. Therefore, the embodiments in this application and herein are intended to be considered exemplary only, and the true scope and spirit of the invention are indicated by the list of exemplary claims appended.

Claims

1. A method for forming an electronic device, characterized by, The method comprises: providing a substrate; placing at least one electronic component on the substrate by solder paste; applying microwave radiation to the substrate to reflow the solder paste; applying vacuum pressure to the substrate to remove air bubbles formed within the solder paste during reflowing of the solder paste; and solidifying the solder paste into solder bumps between the substrate and the at least one electronic component.

2. The method of claim 1, wherein, The vacuum pressure is applied to the substrate while the solder paste is in the process of reflowing.

3. The method of claim 1, wherein, The vacuum pressure is applied to the substrate while the solder paste is in a reflowing temperature range of 200°C to 240°C.

4. The method of claim 1, wherein, The process of applying vacuum pressure comprises: The vacuum pressure is applied for a duration ranging from 30 seconds to 10 minutes.

5. The method of claim 1, wherein, The solder paste comprises a metal and a flux.

6. The method of claim 1, wherein, The step of solidifying the solder paste into solder bumps comprises: cooling the solder paste to a temperature below a reflowing temperature of the solder paste.

7. The method of claim 1, wherein, The vacuum pressure is applied to the substrate after the microwave radiation is applied to the substrate.

8. The method of claim 1, wherein, The vacuum pressure is applied to the substrate while the microwave radiation is applied to the substrate.

9. An apparatus for forming an electronic device, comprising: The apparatus comprises: a platform configured to place a substrate having at least one electronic component placed thereon by solder paste; a microwave radiation source configured to apply microwave radiation to the substrate to reflow the solder paste; and a vacuum source configured to apply vacuum pressure to the substrate to remove air bubbles formed within the solder paste during reflowing of the solder paste by the microwave radiation.

10. The apparatus of claim 9, wherein, The solder paste comprises a metal and a flux.

11. The apparatus of claim 9, wherein, The vacuum pressure is applied to the substrate while the solder paste is in a reflowing temperature range of 200°C to 240°C.

12. The apparatus of claim 9, wherein, The vacuum source is further configured to apply vacuum pressure for a duration ranging from 30 seconds to 10 minutes.

13. The apparatus of claim 9, wherein, The platform comprises: a first area associated with the microwave radiation source, wherein the microwave radiation source is configured to apply microwave radiation to the substrate when the substrate is located in the first area; a second area associated with the vacuum source, wherein the vacuum source is configured to apply vacuum pressure to the substrate when the substrate is located in the second area; and a third area for cooling the solder paste and solidifying the solder paste into solder bumps.

14. The apparatus of claim 13, wherein, The platform further comprises: a conveyor belt extending through the first area, the second area, and the third area, wherein the conveyor belt is configured to transport the substrate from the first area through the second area to the third area.

15. The apparatus of claim 9, wherein, The platform comprises: a chamber associated with the microwave radiation source and the vacuum source, wherein microwave radiation is applied to the substrate and vacuum pressure is applied to the substrate when the substrate is located within the chamber.

16. The apparatus of claim 9, wherein, The platform further comprises a heater configured to heat a substrate placed on the platform.

17. The apparatus of claim 9, wherein, The platform comprises at least one polar material configured to absorb microwave radiation to heat a substrate placed on the platform.

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