Electronic package and method of forming same

Abstract

An electronic package and a method of forming the same are provided. The method comprises: providing a substrate having a front surface and a back surface, where at least one electronic component is attached to the front surface of the substrate, and the substrate comprises at least one non-polar material; forming a mold cover on the front surface of the substrate to encapsulate the at least one electronic component; loading the substrate onto a carrier, wherein the carrier comprises at least one polar material; and applying microwave radiation to the mold cover and the carrier to cure the mold cover at least partially through the carrier.

Description

Technical Field

[0001] This application generally relates to semiconductor technology, and more particularly, to an electronic package and a method of forming the same. Background Art

[0002] The semiconductor industry has been facing complex integration challenges as consumers want their electronic devices to be smaller, faster, and more performant while packing more and more functionality into a single device. Typically, a semiconductor package may include main functional modules such as semiconductor chips and interconnect structures, as well as a mold cap encapsulating the modules. During the molding process, the molding material is first liquefied and forced into a molding die. Then, a heating process is employed to cure the molding material so as to encapsulate the modules. However, it should be noted that the traditional heating process in the curing step has high energy consumption and low efficiency, which results in high manufacturing costs.

[0003] Therefore, there is a need for a method of forming an electronic package that can improve the energy efficiency of the process. Summary of the Invention

[0004] An object of this application is to provide a method of forming an electronic package that can improve the energy efficiency of the process.

[0005] According to one aspect of this application, there is provided an electronic package and a method of forming the same. The method includes: providing a substrate having a front surface and a back surface, wherein at least one electronic component is attached to the front surface of the substrate, and the substrate includes at least one non-polar material; forming a mold cap on the front surface of the substrate to encapsulate the at least one electronic component; loading the substrate onto a susceptor, wherein the susceptor includes at least one polar material; and applying microwave radiation to the mold cap and the susceptor to cure the mold cap at least in part through the susceptor.

[0006] It should be understood that the foregoing general description and the following detailed description are merely exemplary and explanatory, and do not limit the present invention. In addition, the drawings incorporated in this specification and constituting a part of this specification illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. Brief Description of the Drawings

[0007] The drawings referred to herein form a part of this specification. The features shown in the drawings illustrate only some embodiments of this application, not all embodiments of this application, unless the specific implementation clearly indicates otherwise, and the reader of this specification should not make an opposite inference.

[0008] Figures 1A to 1D Illustrates the various steps of a method of forming an electronic package according to a first embodiment of this application.

[0009] Figure 2 Illustrates a step of a method of forming an electronic package according to a second embodiment of the present application.

[0010] Throughout the drawings, the same reference numerals will be used to refer to the same or similar parts. Detailed Description

[0011] The following detailed description of exemplary embodiments of the present application refers to the accompanying drawings that form a part of the description. The drawings illustrate specific exemplary embodiments in which the present 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 the present application. Those skilled in the art may further utilize other embodiments of the present application and make logical, mechanical, and other changes without departing from the spirit or scope of the present application. Accordingly, the reader of the following detailed description should not interpret the description in a limiting sense, and only the appended claims define the scope of the embodiments of the present application.

[0012] In the present application, unless otherwise expressly stated, the use of the singular includes the plural form. In the present application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "comprising" is not restrictive. Further, unless otherwise expressly stated, terms such as "element" or "component" cover both elements and components that include one unit and elements and components that include more than one sub-unit. Additionally, the section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described.

[0013] As used herein, for ease of description, spatial relative terms such as "under", "below", "above", "over", "on", "upper", "lower", "left", "right", "vertical", "horizontal", "side", etc. may be used to describe the relationship of one element or feature to another element(s) or feature(s) as shown in the drawings. Except for the orientation depicted in the drawings, the spatial relative terms are intended to cover different orientations of the device during 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 may 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 intervening elements may be present.

[0014] As mentioned above, a semiconductor package may include main functional modules such as semiconductor chips and interconnect structures, as well as a mold cap that encapsulates the modules. During the molding process, the molding material is first liquefied and forced into a molding die. Then, a heating process is used to cure the molding material to encapsulate the modules. However, it should be noted that the traditional heating process in the curing step of the current technology has high energy consumption and low efficiency, which results in high manufacturing costs. To solve this problem, a new method for forming an electronic package is provided, which cures the molding material by using microwave heating and the thermal energy of convection heat transfer via a susceptor. The method can be used to form electronic packages such as system-in-package (SIP) devices or package-in-package (PIP) devices.

[0015] Figures 1A to 1D FIG. shows the respective steps of a method for forming an electronic package according to a first embodiment of the present application. Hereinafter, the method will be described in more detail with reference to Figures 1A to 1D FIG.

[0016] As Figure 1A shown, a plurality of substrates 100 (or referred to as substrate units 100) may be disposed in a substrate strip such that each of the plurality of substrates 100 can serve as a platform for forming an electronic package. In this embodiment, the substrate strip may further include a plurality of connecting portions 102, each of the plurality of connecting portions 102 being located between two adjacent substrates 100, thereby connecting the plurality of substrates 100 into a substrate strip. In this embodiment, each of the substrates 100 may have the same or similar structure. For simplicity, the steps of forming an electronic package will be described hereinafter with reference to one of the plurality of substrates 100. It can be understood that the same processing process can be used on the plurality of substrates 100 to form a plurality of electronic packages. And, it can be understood that in some embodiments, both the connecting portion 102 and the substrate 100 are originally formed together in the substrate strip and do not need to be assembled together into the substrate strip.

[0017] Still referring to Figure 1A FIG., the substrate 100 includes embedded interconnect lines 101. The substrate 100 may include a front surface 100a and a rear surface 100b that face each other. The front surface 100a of the packaged substrate 100 can serve as a platform for mounting electronic components. A plurality of sets of conductive pads (not shown) may be formed on the front surface 100a of the substrate 100 for mounting electronic components. It can be understood that the plurality of sets of conductive pads may be exposed portions of the interconnect lines 101 formed in the substrate 100.

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

[0019] As Figure 1B shown, a solder material is deposited on the front surface of the substrate 100 to form a plurality of solder bumps on multiple sets of conductive pads. The solder material can be Al, Sn, Ni, Au, Ag, Pb, Bi, Cu, or a combination thereof.

[0020] Next, at least one electronic component 110 is attached to the front surface 100a of the substrate 100 via the solder bumps, thus forming an electrical connection between the interconnecting line 101 and the electronic component 110. In some embodiments, the electronic component 110 can be a semiconductor chip or a smaller semiconductor package. It can be understood that more electronic components 110 can be mounted on the front surface 110a according to the actual needs of the electronic package to be formed.

[0021] Next, a mold cover 114 is formed on the front surface 100a of the substrate 100 to encapsulate the at least one electronic component 110. As Figure 1C shown, a substrate strip having a plurality of substrates 100 is loaded between a bottom mold 111 and a top mold 112, wherein the plurality of rear surfaces 110b of the plurality of substrates 100 are in contact with the bottom mold 111. Next, a molding material can be provided. First, the molding material is liquefied by heating and pressurization, and then forced into the mold cavity defined by the bottom mold 111 and the top mold 112, thereby covering the surfaces of the electronic components 110 on each of the plurality of substrates 100, thus forming the mold cover 114. The molding material includes thermosetting materials such as epoxy resin, polyester resin, etc. In some embodiments, various other molding techniques including transfer molding process, compression molding process, or film-assisted molding (FAM) process can be used to form the mold cover 114.

[0022] Next, as Figure 1DAs shown, the substrate strip and the electronic components 110 thereon can be removed from the top mold 112 and the bottom mold 111. Then the substrate strip can be transferred to a chamber for a subsequent microwave curing process. In this embodiment, before the microwave curing process, the substrate strip is loaded onto a carrier 120 such that the plurality of rear surfaces 100b of the plurality of substrates 100 are in contact with the carrier 120. The carrier 120 can comprise a polar material, a combination of a plurality of polar materials, or a combination of a polar material and a non-polar material, which can be heated by microwave radiation in a subsequent curing step of the mold cover 114. In addition, the carrier 120 can comprise one or more thermally conductive materials, and during the curing process of the mold cover 114, after the carrier 120 is heated by microwave radiation, there can be sufficient convective heat transfer from the carrier 120 to the substrate 100 and the mold cover 114, and the heat dissipation of the mold cover 114 can be slowed down. In some embodiments, a large portion (e.g., greater than 50 wt.%, 60 wt.%, 70 wt.%, 80 wt.%, 90 wt.%, 95 wt.% or 99 wt.%) of the carrier 120 is formed of a polar material, which gives the carrier 120 good heating performance when exposed to microwave radiation. More specifically, the carrier 120 can comprise at least one polar material among silicon carbide, graphite, polar charcoal, and polar carbon. In some other embodiments, the carrier 120 can comprise a non-polar substrate coated with a polar material or in which a polar material is distributed, which can reduce the requirements for the material of the carrier 120 and achieve better mechanical support and lower cost (if an appropriate material is used as the material of the non-polar substrate) during the curing step of the mold cover 114. Specifically, the non-polar substrate can comprise a silicon wafer or silicon powder, and the polar coating can comprise at least one polar material among silicon carbide, graphite, polar charcoal, or polar carbon.

[0023] Next, still referring to Figure 1D , microwave radiation is applied to the mold cover 114 and the carrier 120 to cure the mold cover 114. In some embodiments, the microwave source is placed above the top surface of the mold cover 114, so that microwave radiation is applied from the microwave source to the mold cover 114. The mold cover 114 can be heated by microwave radiation because it contains a polar material, whereby the mold cover 114 can be cured to encapsulate the electronic components 110 on the substrate 100.

[0024] At the same time, the susceptor 120 is also exposed to microwave radiation, which can penetrate the mold cover 114 and the substrate 100 and ultimately reach the susceptor 120. In addition, the microwave radiation can also directly reach the susceptor 120 from the lateral and bottom surfaces of the susceptor 120 that are not blocked by the substrate 100. Since the susceptor 120 is at least partially formed of a polar material, the susceptor 120 has dipoles within its polar molecules that are sensitively induced by the electric field of the microwave, and the dipoles can rotate under the action of the electric field to align themselves with the direction of the electric field. The electric field of the microwave changes periodically, which can cause the dipoles to rotate frequently. Therefore, when the dipoles rotate according to the direction of the electric field, they may collide with each other, thereby generating heat energy in the susceptor 120. Then, the heat generated in the susceptor 120 can be transferred to the substrate 100 and the mold cover 114 by heat convection, thus providing additional heat energy to the mold cover 114 during the curing process. In this way, the mold cover 114 can be cured via a hybrid heating mechanism that combines the direct microwave curing of the mold cover 114 and the heat energy transferred from the susceptor 120 by convection. During the curing process, by transferring additional heat energy to the mold cover 114, the curing process of the mold cover 114 can have higher energy efficiency, and thus the energy demand for the microwave source is lower. In addition, in the case where the microwave energy applied from the microwave source is low, the total heat energy generated within the device can be reduced, which can prevent or mitigate the burning effect caused by excessive microwave energy. In addition, since the bottom portion of the mold cover is less exposed to microwave radiation, it can receive more heat energy transferred from the susceptor 120 by convection, thereby enabling the mold cover 114 to be cured in a more uniform and controllable manner and with fewer defects present. Simply put, the excess microwave energy that cannot be absorbed by the mold cover 114 can be collected by the susceptor 120 and converted into heat, which in turn contributes to the curing process of the mold cover 114. In some embodiments, the susceptor 120 may include a film or plate at its bottom that can reflect microwaves upward. During the curing process, the reflected microwaves can penetrate the susceptor 120 again and generate heat energy there, or even penetrate the susceptor 120 and reach the mold cover 114 to contribute to curing the mold cover 114.

[0025] In addition, in this embodiment, during the microwave radiation step, microwave radiation is applied at a variable frequency. Compared with fixed-frequency microwaves, the uniformity of the microwave energy of the microwave radiation process is better by quickly sweeping through a certain frequency range of microwaves. In some embodiments, microwave radiation is applied at a frequency between 1 GHz and 10 GHz. During the step of applying microwave radiation to the mold cover 114 and the susceptor 120, the mold cover 114 is heated by the microwave radiation, and there is also sufficient convective heat transfer energy transferred from the susceptor 120 to the substrate 100 and the mold cover 114. Further, the heated susceptor 120 can help slow down the heat dissipation of the mold cover 114 and help keep the mold cover 114 at a relatively high temperature, thus facilitating the mold cover 114 to be fully heated.

[0026] In some embodiments, when the mold cover 114 is cured by microwave radiation heating, the heated mold cover 114 can reach a temperature within the range of 60 °C to 180 °C. At the same time, the susceptor 120 heated by microwave radiation can reach a temperature within the range of 50 °C to 100 °C, which enables the mold cover 114 to relieve the warping of the device in the most controllable manner while being fully cured. In some other embodiments, it can also be understood that microwave radiation can be applied at a frequency lower than 1 GHz, which can further reduce the warping of the device, or microwave radiation can also be applied at a frequency higher than 10 GHz, which can cure the mold cover 114 more quickly. The selection of the frequency of microwave radiation also depends on the materials of the mold cover 114 and the susceptor 120.

[0027] After the curing process of the mold cover 114, each of the plurality of substrates 100 can be separated from the substrate strip by singulation with the electronic component 110 and the mold cover 114. Singulation can be performed along the connecting portion 102. The singulation process may include: first removing the mold cover 114 above the connecting portion 102; then removing the connecting portion 102 to separate the plurality of substrates 100 from each other. After singulation, each substrate 100 with the electronic component 110 and the mold cover 114 becomes an electronic package. In some other embodiments, the singulation process of the plurality of substrates 100 can be performed before the step of applying microwave radiation to the mold cover 114 and the susceptor 120 shown in Figure 1D or even before the molding step shown in Figure 1C .

[0028] As mentioned above, in Figure 1DIn the embodiment shown, the microwave source is placed above the top surface of the mold cover 114. In some other embodiments, a flipping mechanism may be provided in the chamber and configured to flip the substrate 100 and the components thereon. The curing of the mold cover 114 can be divided into two consecutive heating steps. In the first heating step, the mold cover 114 and the carrier 120 can be heated by the microwave source placed above the mold cover 114. Therefore, compared with the bottom part of the mold cover 114 that contacts the substrate 100, the top part of the mold cover 114 can be heated more effectively due to being closer to the microwave source. Then, the substrate 100 and the components thereon can be flipped by the flipping mechanism for the second heating step. In the second heating step, the carrier 120 and the bottom part of the mold cover 114 that contacts the substrate 100 can be heated more effectively than the top part of the mold cover 114. In this way, the overall curing process of the mold cover 114 can be more uniform and effective.

[0029] In some other embodiments, the microwave source can be placed at the side of the mold cover 114 and the carrier 120, which can be closer to the carrier 120. Microwave radiation can be applied laterally to the mold cover 114 and the carrier 120 from the mold cover 114 and the carrier 120. Therefore, the mold cover 114 is directly cured by the microwave radiation, and at the same time, the carrier 120 can be heated more efficiently by the microwave radiation, so that the thermal energy can be more fully transferred to the mold cover 114 by convection and the heat dissipation of the mold cover 114 can be slowed down.

[0030] In some alternative embodiments, the substrate 100 with the carrier 120 and the mold cover 114 thereon can be fixed in the middle of the chamber. In addition to the microwave source placed above the top surface of the mold cover 114, an additional microwave source can also be placed below the carrier 120, and thus the carrier 120 can receive direct microwave radiation from the additional microwave source, which makes the heating of the carrier 120 more efficient. Therefore, the energy applied from each microwave source can be adjusted according to the actual layout of the electronic packaging device, which makes the heating process of the mold cover 114 more efficient and uniform.

[0031] In Figures 1A to 1D the embodiment shown, the substrate strip is loaded onto the carrier 120 such that the plurality of rear surfaces 100b of the plurality of substrates 100 are in contact with the carrier 120. In alternative embodiments, the substrate strip is loaded onto the carrier such that the top surface of the mold cover is in contact with the carrier, which will be described in detail below.

[0032] Figure 2 Shows a step of a method for forming an electronic package according to a second embodiment of the present application. Figure 2 The step shown can be implemented after the step shown in Figures 1A to 1C has been performed to replace the step shown in Figure 1D and serve as Figures 1A to 1DAlternative embodiments of the embodiments shown in

[0033] Specifically, the substrate strip and the electronic components 110 thereon can be removed from the Figure 1C top mold 112 and bottom mold 111 used in the steps shown in. Subsequently, the substrate strip can be transferred to a chamber for a subsequent microwave curing process. In this embodiment, before the microwave curing process, the substrate strip is first flipped and loaded onto a carrier 220 such that the top surface of the mold cover 114 contacts the carrier 220, where the top surface of the mold cover 114 is the surface away from the substrate 100. The material and function of the carrier 220 are similar to those of the carrier 120 shown in Figure 1D and will not be described in detail below.

[0034] Next, microwave radiation is applied to the mold cover 114 and the carrier 220 to cure the mold cover 114. In Figure 2 the embodiment shown, the microwave source is placed above the substrate 100, and then microwave radiation is applied from the microwave source to the mold cover 114 and the carrier 220. The material of the mold cover 114 is heated by the microwave radiation, enabling the mold cover 114 to cure to encapsulate the electronic components 110 on the substrate 100. At the same time, the carrier 220 can also be heated by the microwave radiation. Since the carrier 220 is in direct contact with the top surface of the mold cover 114, the convective heat transfer from the carrier 220 to the mold cover 114 can be more efficient, and the effect of slowing down the heat dissipation of the mold cover 114 is also more efficient, which will provide additional heat energy to the mold cover 114 during the curing process, making the curing process more energy-efficient. In some other embodiments, the microwave source can be placed at the bottom of the chamber, for example, below the carrier 220, and thus the carrier 220 can receive direct microwave radiation from the microwave source, which can transfer heat energy to the mold cover 114 more efficiently and also slow down the heat dissipation of the mold cover 114 more efficiently. In an alternative embodiment, the substrate 100 and the structures thereon can be heated by flipping and then by microwave radiation from a microwave source placed at the top of the chamber.

[0035] In some other embodiments, in addition to the carrier 220 on the top surface of the mold cover 114, the substrate 100 can also be loaded onto an additional carrier (not shown) such that the multiple rear surfaces 100b of the multiple substrates 100 contact the additional carrier, thereby providing convective heat transfer to the mold cover 114 from both the top surface and the bottom surface of the mold cover 114, thus achieving a more uniform and effective curing process. In addition, at least one microwave source can be placed at least at one of the following positions according to the actual layout of the device: above the additional carrier, below the carrier 220, or laterally to the substrate 100.

[0036] In some embodiments, an electronic package formed by implementing any one of the above methods can be applied in any semiconductor packaging device, such as a system-in-package (SIP) device or a package-in-package (PIP) device, etc.

[0037] Although the exemplary methods for forming an electronic package of the present application are described in conjunction with the corresponding figures, those skilled in the art will understand that the electronic package can be modified and adapted without departing from the scope of the present invention.

[0038] Various embodiments have been described herein with reference to the accompanying drawings. However, it will be understood that various modifications and changes can be made thereto without departing from the broader scope of the invention as set forth in the appended claims, and additional embodiments can be implemented. In addition, other embodiments will be apparent to those skilled in the art by considering the specification and practice of one or more embodiments of the invention disclosed herein. Accordingly, it is intended that the present application and the examples herein be considered as exemplary only, with the true scope and spirit of the invention being indicated by the list of exemplary claims appended hereto.

Claims

1. A method for forming an electronic package, characterized in that, The method includes: providing a substrate having a front surface and a back surface, wherein at least one electronic component is attached to the front surface of the substrate, and the substrate includes at least one non-polar material; forming a mold cover on the front surface of the substrate to encapsulate the at least one electronic component; loading the substrate onto a susceptor, wherein the susceptor includes at least one polar material; and applying microwave radiation to the mold cover and the susceptor to cure the mold cover at least partially through the susceptor.

2. The method according to claim 1, wherein The susceptor includes one or more thermally conductive materials.

3. The method according to claim 2, wherein The susceptor includes at least one polar material selected from silicon carbide, graphite, polar charcoal, and polar carbon.

4. The method according to claim 2, wherein The susceptor includes a non-polar substrate coated with a polar material.

5. The method according to claim 4, wherein The non-polar substrate includes a silicon wafer or silicon powder, and the polar coating includes at least one polar material selected from silicon carbide, graphite, polar charcoal, or polar carbon.

6. The method according to claim 1, wherein The process of loading the substrate onto the susceptor includes: loading the substrate onto the susceptor such that the back surface of the substrate contacts the susceptor.

7. The method according to claim 1, wherein The process of loading the substrate onto the susceptor includes: loading the substrate onto the susceptor such that the top surface of the mold cover contacts the susceptor.

8. The method according to claim 7, characterized in that, After loading the substrate onto the susceptor such that the top surface of the mold cover contacts the susceptor, the method further includes: loading the substrate onto an additional susceptor such that the back surface of the substrate contacts the additional susceptor.

9. The method according to claim 1, characterized in that, The applied frequency range of the microwave radiation is between 1 GHz and 10 GHz.

10. The method according to claim 1, wherein During the step of applying microwave radiation to the mold cover and the susceptor, the temperature range of the susceptor is between 50°C and 100°C.

11. The method according to claim 1, characterized in that During the process of applying the microwave radiation, the microwave radiation is applied at a variable frequency.

12. An electronic package, characterized in that, The electronic package is formed using the method according to any one of claims 1 to 11.

Images