Patent Application
20230387042
The present disclosure relates to a front-end module (FEM) and a process for making the same, and more particularly to an FEM that includes a die and a circulator stacked vertically with the die, and a process for forming the circulator vertically stacked with the die by utilizing elements in the die.
A front-end module (FEM) is a very important component in radio frequency (RF) applications, which incorporates all the circuitry between an antenna and at least one mixing stage of a receiver (RX) and a transmitter (TX). Typically, the FEM may include acoustic duplexers to isolate the RX path and the TX path. However, for ultra-high frequency applications (e.g., mmWave applications), the acoustic duplexers are no longer viable. In such cases, circulators are introduced for isolation purposes.
Traditional circulators have assembly processes that are not compatible with existing FEM processes. As such, it is very challenging to integrate the traditional circulators into today's FEMs. In addition, the traditional circulators tend to have very large dimensions and in particular large heights, which cannot meet current low-profile requirements of portable communication devices.
Accordingly, there remains a need for improved FEM designs that include a circulator for signal isolation in the ultra-high frequency applications, where manufacturing the circulator can be compatible with the FEM processes without sacrificing footage/height of the final products.
The present disclosure describes a front-end module (FEM) that includes a die and a circulator stacked vertically with the die, and a process for making the same. In the disclosed FEM, a thinned flip-chip die, which resides over a module carrier, includes a device region with a metal layer, an insulating layer over a top surface of the device region, and a number of interconnects extending from a bottom surface of the device region to the module carrier. A first mold compound also resides over the module carrier, surrounds the thinned flip-chip die, and extends beyond a top surface of the thinned flip-chip die to define an opening over the top surface of the thinned flip-chip die, where the first mold compound provides vertical walls of the opening. A ferrimagnetic portion resides over the top surface of the thinned flip-chip die and within the opening, and a permanent magnetic portion resides over the ferrimagnetic portion and within the opening. Herein, the permanent magnetic portion, the ferrimagnetic portion, and the metal layer of the device region are vertically aligned. A combination of the permanent magnetic portion, the ferrimagnetic portion, and the metal layer of the device region provides a circulator vertically stacked with the thinned flip-chip die.
In one embodiment of the FEM, the metal layer in the device region has a thickness between fractions of a micrometer and several tens of micrometers, and has a horizontal area between several hundreds of micrometer-square and several millimeter-square.
In one embodiment of the FEM, the thinned flip-chip die is an active die. The device region includes an active layer and a back-end-of-line (BEOL) portion underneath the active layer, where the active layer is configured to provide one or more active devices, and the BEOL portion includes the metal layer and is configured to provide one or more integrated passive devices.
In one embodiment of the FEM, the metal layer in the BEOL includes at least three ports. Herein, the one or more integrated passive devices includes one or more passive filters and one or more programmable capacitors. Each of the one or more integrated passive devices is connected to a corresponding port of the at least three ports.
In one embodiment of the FEM, the thinned flip-chip die is formed from a silicon-on-insulator (SOI) structure. The active layer of the thinned flip-chip die is formed by integrating the one or more active devices in or on a silicon epitaxy layer of the SOI structure, and the insulating layer of the thinned flip-chip die is a buried oxide layer of the SOI structure.
In one embodiment of the FEM, the thinned flip-chip die is a passive die, where the device region includes a BEOL portion, which includes the metal layer and is configured to provide one or more integrated passive devices.
In one embodiment of the FEM, the insulating layer of the thinned flip-chip die includes at least one of a dielectric material and a polymer composite material, such as silicon dioxide, silicon nitride, emulation polymers, liquid crystal polymers, interlayer polymers, and synthetic rubber.
In one embodiment of the FEM, the ferrimagnetic portion includes one or more ferrites, such as magnetite Fe3O4, yttrium iron garnet (YIG), PbFe12O19, BaFe12O19, pyrrhotite, Fe1-xS, and iron oxides with aluminum, cobalt, nickel, manganese, and zinc. The ferrimagnetic portion has a thickness between few micrometers and several hundreds of micrometers, and has a horizontal shape of a circle, a square, a hexagon, a rectangle, or a high order polygon.
In one embodiment of the FEM, the permanent magnetic portion is formed of one or more materials that are magnetized and creates their own persistent magnetic field, such as iron, nickel, cobalt, and their alloys, alloys of rare-earth metals, and lodestone. The permanent magnetic portion has a thickness between few micrometers and several hundreds of micrometers, and a horizontal shape of a circle, a square, a hexagon, a rectangle, or a high order polygon.
In one embodiment of the FEM, the ferrimagnetic portion and the permanent magnetic portion have same horizontal dimensions as the opening.
According to one embodiment, the FEM further includes a second mold compound residing over the permanent magnetic portion to encapsulate the circulator.
According to one embodiment, the FEM further includes an underfilling layer that resides over a top surface of the module carrier and fills gaps between the bottom surface of the device region of the thinned flip-chip die and the top surface of the module carrier, such that the interconnects is encapsulated by the underfilling layer. Herein, the first mold compound resides over the underfilling layer.
In one embodiment of the FEM, the ferrimagnetic portion has same horizontal dimensions as the opening, and the permanent magnetic portion has smaller horizontal dimensions than the opening, such that a top surface of the ferrimagnetic portion is partially exposed through the permanent magnetic portion.
According to one embodiment, the FEM further includes a second mold compound residing over the top surface of the ferrimagnetic portion and fully encapsulating the permanent magnetic portion.
According to one embodiment, the FEM further includes an alignment material and a second mold compound. Herein, the alignment material resides over the top surface of the ferrimagnetic portion and surrounds the permanent magnetic portion, where a combination of the permanent magnetic portion and the alignment material has same horizontal dimensions as the opening. The second mold compound resides over the combination of the permanent magnetic portion and the alignment material to encapsulate the circulator.
In one embodiment of the FEM, the ferrimagnetic portion has smaller horizontal dimensions than the opening, such that the top surface of the thinned flip-chip die is partially exposed through the ferrimagnetic portion. The permanent magnetic portion has same horizontal dimensions as the opening.
According to one embodiment, the FEM further includes a second mold compound and a third mold compound. Herein, the third mold compound has a dielectric constant higher than 10, and resides over the top surface of the thinned flip-chip die and fills gaps laterally between the ferrimagnetic portion and the vertical walls of the opening. The second mold compound resides over the permanent magnetic portion to encapsulate the circulator.
In one embodiment of the FEM, the ferrimagnetic portion has smaller horizontal dimensions than the opening, and the permanent magnetic portion has smaller horizontal dimensions than the opening, such that the top surface of the thinned flip-chip die is partially exposed through the ferrimagnetic portion and the permanent magnetic portion.
According to one embodiment, the FEM further includes a second mold compound residing over the top surface of the thinned flip-chip die, and fully encapsulating the ferrimagnetic portion and the permanent magnetic portion.
According to one embodiment, the FEM further includes a second mold compound and a third mold compound. Herein, the third mold compound has a dielectric constant higher than 10, and the third mold compound resides over the top surface of the thinned flip-chip die and fills gaps laterally between the ferrimagnetic portion and the vertical walls of the opening. The second mold compound resides over the third mold compound, and fully encapsulates the permanent magnetic portion.
In one embodiment of the FEM, the metal layer in the device region has one of a “Y” shape with three ports, an “X” shape with four ports, and a “star” shape with five ports.
According to one embodiment, the FEM further includes a bonding material between the permanent magnetic portion and the ferrimagnetic portion.
According to an exemplary process, a precursor module, which includes a module carrier, an intact flip-chip die deposed over the module carrier, and a first mold compound over the module carrier and fully encapsulating the intact flip-chip die, is firstly provided. Herein, the intact flip-chip die includes a device region with a metal layer, a number of interconnects extending from a bottom surface of the device region to the module carrier, an insulating layer over a top surface of the device region, and a die substrate over the insulating layer. As such, a backside of the die substrate is a top surface of the intact flip-chip die. Next, the first mold compound is thinned down to expose the backside of the die substrate. The die substrate is then removed substantially to provide a thinned flip-chip die and define an opening over the thinned flip-chip die and within the first mold compound. A ferrimagnetic portion is deposed over a top surface of the thinned flip-chip die and within the opening. A permanent magnetic portion is deposed over the ferrimagnetic portion and within the opening. Herein, the permanent magnetic portion, the ferrimagnetic portion, and the metal layer of the device region are vertically aligned, and a combination of the permanent magnetic portion, the ferrimagnetic portion, and the metal layer of the device region provides a circulator vertically stacked with the thinned flip-chip die.
According to one embodiment, the exemplary process further includes applying a second mold compound over the permanent magnetic portion so as to encapsulate and isolate the circulator 34 from an external environment.
In one embodiment of the exemplary process, before deposing the ferrimagnetic portion and the permanent magnetic portion, the ferrimagnetic portion and the permanent magnetic portion are bonded together via a bonding material. Herein, the ferrimagnetic portion and the ferrimagnetic portion are deposed simultaneously.
In another aspect, any of the foregoing aspects individually or together, and/or various separate aspects and features as described herein, may be combined for additional advantage. Any of the various features and elements as disclosed herein may be combined with one or more other disclosed features and elements unless indicated to the contrary herein.
Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures.
The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.
It will be understood that for clear illustrations,
The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.
Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Embodiments are described herein with reference to schematic illustrations of embodiments of the disclosure. As such, the actual dimensions of the layers and elements can be different, and variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are expected. For example, a region illustrated or described as square or rectangular can have rounded or curved features, and regions shown as straight lines may have some irregularity. Thus, the regions illustrated in the figures are schematic and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the disclosure. Additionally, sizes of structures or regions may be exaggerated relative to other structures or regions for illustrative purposes and, thus, are provided to illustrate the general structures of the present subject matter and may or may not be drawn to scale. Common elements between figures may be shown herein with common element numbers and may not be subsequently re-described.
A circulator is a passive, non-reciprocal three, four, or multi-port device that allows a microwave or radio-frequency signal to exit through the port directly after the one it entered. By terminating one port of a three-port circulator in a matched load, it can be used as an isolator. In such case, a signal can travel in only one direction between the remaining two ports. Isolators are used to shield the input ports of a system from the effects on its output ports. One example is to provide isolation to prevent a microwave source being detuned by a mismatched load. Circulators can also be used as duplexers that route signals from the transmitter to the antenna and from the antenna to the receiver, without allowing signals to pass directly from transmitter to receiver (provide isolation between transmitter and receiver). Another circulator application is in reflection amplifiers which are a type of microwave amplifier circuit utilizing negative differential resistance diodes. A non-reciprocal component such as a circulator is needed to separate the outgoing amplified signal from the incoming input signal in the one port device (e.g. a diode has only two terminals). The output and input can be decoupled by using a 3-port circulator with the signal input connected to the first port, the biased diode connected to the second port, and the output load connected to the third port.
To realize a circulator, three types of layers are needed: one or more metal layers, one or more ferrimagnetic layers over the one or more metal layers, and one or more permanent magnetic layers over the one or more ferrimagnetic layers. The one or more metal layers may be formed of copper, aluminum, silver, gold, alloy compounds, or any combination of above. The one or more ferrimagnetic layers may be formed of one or more ferrites, such as magnetite Fe3O4, yttrium iron garnet (YIG), cubic ferrites composed of iron oxides with other elements (e.g., aluminum, cobalt, nickel, manganese, and zinc), or hexagonal ferrites (e.g., PbFe12O19 and BaFe12O19 and pyrrhotite, Fe1-xS). The materials used in the one or more ferrimagnetic layers has populations of atoms with opposing magnetic moments and comprise of different types of atoms in the material's unit cell. For the ferrimagnetic materials, these moments are unequal in magnitude, so a spontaneous magnetization remains. The permanent magnetic layers are made from one or more materials that are magnetized and creates their own persistent magnetic field, such as iron, nickel, cobalt, and their alloys, alloys of rare-earth metals, and naturally occurring minerals (e.g., lodestone).
The metal layer 12 in the circulator 10 may be implemented by strip-line structures or waveguide structures. In a case of strip-line implementation, a ground plane 18 (e.g., a metal plate) underneath the circulator 10 is needed. In some applications, one or more programable capacitors (PACs) 20 may be connected to one or more ports of the metal layer 12 (only one programmable capacitor 20 connected to each port of the metal layer 12 is illustrated for simplicity) to tune frequency responses of the circulator 10. Since each port is a portion of the metal layer 12, it is easy to have the PACs 20 connected at the port metal line(s) during the manufacturing process to tune the characteristics of the circulator 10.
Typically, the circulator 10 can intrinsically realize a duplexing function. However, the circulator 10 itself has difficulty achieving high rejections in an order of 50 dB or more. In one embodiment, the circulator 10 may be combined with passive filters 22 to achieve a high-end duplexer function (e.g., the circulator with a 30 dB attenuation combined with the passive filters 22 with 20 dB or more attenuation can achieve a total 50 dB+ attenuation), as illustrated in
The thinned flip-chip die 32 includes a device region 42, an insulating layer 44 over a top surface of the device region 42, and a number of interconnects 46 extending from a bottom surface of the device region 42 to the module carrier 36 (only one of the interconnects 46 is labeled with a reference number for clarity). Herein, the thinned flip-chip die 32 substantially has no die substrate, which is removed during a packing process (details shown below). In
Typically, the BEOL portion 50 includes dielectric layers 52 and a multi-layer metal structure 54 within the dielectric layers 52. The multi-layer metal structure 54 is used to achieve the connection function of the BEOL 50. Herein, the multi-layer metal structure 54 includes a first metal layer 54-1 configured as a metal layer for a circulator (details described below), and may include a second metal layer 54-2 configured as a ground plane (only the first metal layer 54-1 and the second metal layer 54-2 are illustrated for the multi-layer metal structure 54 for simplicity). The first metal layer 54-1 may have a “Y” shape, an “X” shape, or a star shape as illustrated in
In one embodiment, the thinned flip-chip die 32 may be formed from a silicon-on-insulator (SOI) structure. The active layer 48 of the thinned flip-chip die 32 is formed by integrating active devices (not shown) in or on a silicon epitaxy layer of the SOI structure. The insulating layer 44 of the thinned flip-chip die 32 is a buried oxide (i.e., silicon oxide, BOX) layer of the SOI structure. In addition, a silicon substrate of the SOI structure is removed substantially from the thinned flip-chip die 32 (details described below). In some applications, a top surface of the thinned flip-chip die 32 is a top surface of the insulating layer 44. The BEOL portion 50 and the interconnects 46 are formed underneath the active layer 48 after the active layer 48 is completed. The interconnects 46 may be copper pillars or solder balls.
The first mold compound 38 resides over the module carrier 36, surrounds the thinned flip-chip die 32, and extends vertically above the top surface of the thinned flip-chip die 32 to define an opening 56 within the first mold compound 38 and over the top surface of the thinned flip-chip die 32. The top surface of the thinned flip-chip die 32 is exposed at the bottom of the opening 56. In some applications, the first mold compound further fills gaps between the bottom surface of the device region 42 and a top surface of the module carrier 36 and encapsulates each interconnect 46 of the thinned flip-chip die 32. One exemplary material used to form the first mold compound 18 is an organic epoxy resin system. Notice that the first mold compound 38 does not reside over the thinned flip-chip die 32 and provides vertical walls of the opening 56. The vertical walls of the opening 56 are well aligned with edges (i.e., sides of the device region 42) of the thinned flip-chip die 32.
A ferrimagnetic portion 58 is deposed within the opening 56 and over the top surface of the thinned flip-chip die 32 (i.e., over the top surface of the insulating layer 44), and a permanent magnetic portion 60 is deposed within the opening 56 and over the ferrimagnetic portion 58. The ferrimagnetic portion 58 may be formed of one or more ferrite materials, such as magnetite Fe3O4, YIG, cubic ferrites composed of iron oxides with other elements (e.g., aluminum, cobalt, nickel, manganese, and zinc), or hexagonal ferrites (e.g., PbFe12O19 and BaFe12O19 and pyrrhotite, Fe1-xS). The ferrimagnetic portion 58 may have a thickness between few micrometers and several hundreds of micrometers, or even up to few millimeters. The permanent magnetic portion 60 may be formed of one or more materials that are magnetized and creates their own persistent magnetic field, such as iron, nickel, cobalt, and their alloys, alloys of rare-earth metals, and naturally occurring minerals (e.g., lodestone). The permanent magnetic portion 60 may have a thickness between few micrometers and several hundreds of micrometers, or even up to few millimeters.
Notice that, since the vertical walls of the opening 56 are aligned with the edges of the thinned flip-chip die 32, the ferrimagnetic portion 58 and the permanent magnetic portion 60, which are deposed within the opening 56, are capable of being self-aligned with the thinned flip-chip die 32.
As such, both the ferrimagnetic portion 58 and the permanent magnetic portion 60 can be vertically aligned with the first metal layer 54-1 in the device region 42 of the thinned flip-chip die 32. In consequence, a combination of the first metal layer 54-1 in the device region 42 of the thinned flip-chip die 32, the ferrimagnetic portion 58 over the thinned flip-chip die 32, and the permanent magnetic portion 60 over the ferrimagnetic portion 58 can provide the circulator 34, which is vertically stacked with the thinned flip-chip die 32. Herein, although the ferrimagnetic portion 58 does not directly reside over the first metal layer 54-1 in the device region 42 of the thinned flip-chip die 32 (i.e., the insulating layer 44 and portions of the device region 42 in between), a vertical distance between the ferrimagnetic portion 58 and the first metal layer 54-1 in the device region 42 of the thinned flip-chip die 32 is relatively short, no larger than couple tens of micrometers or few hundreds of micrometers.
In addition,
In some applications, the thinned flip-chip die 32 in the FEM 30 is not an active die, but a passive die without any active layer. As illustrated in
In this embodiment, the combination of the first metal layer 54-1 in the device region 42 of the thinned flip-chip die 32, the ferrimagnetic portion 58 over the thinned flip-chip die 32, and the permanent magnetic portion 60 over the ferrimagnetic portion 58 still provides the circulator 34, which is vertically stacked with the thinned flip-chip die 32. Furthermore, the thinned flip-chip die 32 may be formed by an integrated passive device process, where the insulating layer 44 includes one or more dielectric materials (such as silicon dioxide or silicon nitride) and/or one or more polymer composite materials (such as emulation polymers, liquid crystal polymers, interlayer polymers, synthetic rubber, or other synthetic compounds etc.).
In some applications, the FEM 30 may further include an underfilling layer 64, as illustrated in
In some applications, the ferrimagnetic portion 58 and the permanent magnetic portion 60 in the circulator 34 may have different shapes and/or different sizes. As illustrated in
In some applications, the permanent magnetic portion 60 in the circulator 34 may not have a self-alignment shape. As illustrated in
In some applications, when the permanent magnetic portion 60 has a smaller horizontal area compared to the opening 56 and does not conform to the horizontal dimensions of the opening 56, there may be an alignment material 68 to help the permanent magnetic portion 60 to conform to the vertical walls of the opening 56, as illustrated in
In some applications, both the ferrimagnetic portion 58 and the permanent magnetic portion 60 in the circulator 34 may not have a self-alignment shape. As illustrated in
In some applications, to enhance the saturation of the ferrimagnetic portion 58, the third mold compound 66, which has a high dielectric constant (e.g., DK=10), is utilized in the FEM 30. As illustrated in
Initially, a precursor module 72 is provided as depicted in
In one embodiment, the intact flip-chip die 32IN is an active die, where the device region 42 includes the active layer 48 and the BEOL portion 50 underneath the active layer 48, as illustrated in
When the intact flip-chip die 32IN is an active die, the intact flip-chip die 32IN may be formed from a SOI structure. The active layer 48 of the intact flip-chip die 32IN is formed by integrating active devices (not shown) in or on a silicon epitaxy layer of the SOI structure. The insulating layer 44 of the intact flip-chip die 32IN is a buried oxide (i.e., silicon oxide, BOX) layer of the SOI structure. In addition, the die substrate 74 of the intact flip-chip die 32IN is a silicon substrate of the SOI structure. The BEOL portion 50 and the interconnects 46 are formed underneath the active layer 48 after the active layer 48 is completed.
In one embodiment, the intact flip-chip die 32IN is a passive die, where the device region 42 does not include the active layer 48 but only includes the BEOL portion 50, as illustrated in
Regardless of the active die or a passive die, the intact flip-chip die 32IN always includes the BEOL portion 50. In the BEOL portion 50, the dielectric layers 52 and the multi-layer metal structure 54 may be configured to provide one or more passive devices (e.g., resistors, capacitors, inductors, transmission lines, and any combination of them, etc., not shown). The one or more passive devices in the BEOL portion 50 may be connected to the first metal layer 54-1 for tuning frequency responses of the circulator, which utilizes the first metal layer 54-1 as the circulator's metallization component (e.g., the passive devices may include passive filters and passive programmable capacitors, which are connected to the first metal layer 54-1 in a configuration as shown in
For the purpose of this illustration, the first mold compound 38 resides directly over the module carrier 36, fills gaps between the bottom surface of the device region 42 of the intact flip-chip die 32IN and the top surface of the module carrier 36, and fully encapsulates the intact flip-chip die 32IN. In different applications, the precursor module 72 may further include an underfilling layer (e.g., the underfilling layer 64 in
Next, the first mold compound 38 is thinned down to expose the backside of the die substrate 74 of the intact flip-chip die 32IN, as shown in
The ferrimagnetic portion 58 is then deposed over the top surface of the thinned flip-chip die 32, as illustrated in
After the ferrimagnetic portion 58 is deposed, the permanent magnetic portion 60 is deposed over the ferrimagnetic portion 58, as illustrated in
Herein, the permanent magnetic portion 60, the ferrimagnetic portion 58, and the thinned flip-chip die 32 are vertically aligned to each other. Therefore, the first metal layer 54-1 within the device region 42 of the thinned flip-chip die 32 will be vertically aligned with the ferrimagnetic portion 58 and the permanent magnetic portion 60. In consequence, the combination of the first metal layer 54-1 in the device region 42 of the thinned flip-chip die 32, the ferrimagnetic portion 58 over the thinned flip-chip die 32, and the permanent magnetic portion 60 over the ferrimagnetic portion 58 provides the applicable circulator 34, which is vertically stacked with the thinned flip-chip die 32.
In one embodiment, when both the ferrimagnetic portion 58 and the permanent magnetic portion 60 are in the solid block state, the ferrimagnetic portion 58 and the permanent magnetic portion 60 may be bonded together before being inserted into the opening 56. As illustrated in
Finally, the second mold compound 62 is applied to encapsulate the circulator 34, as illustrated in
It is contemplated that any of the foregoing aspects, and/or various separate aspects and features as described herein, may be combined for additional advantage. Any of the various embodiments as disclosed herein may be combined with one or more other disclosed embodiments unless indicated to the contrary herein.
Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.
This application claims the benefit of provisional patent application Ser. No. 63/124,440, filed Dec. 11, 2020, the disclosure of which is hereby incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2021/063093 | 12/13/2021 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63124440 | Dec 2020 | US |
