METHOD FOR FORMING A PARTIAL SHIELDING FOR AN ELECTRONIC ASSEMBLY

Provided is a method for forming a partial shielding for an electronic assembly, comprising: providing an electronic assembly mounted on a mother board, wherein the electronic assembly comprises a substrate, and at least one electronic component and a conductive pattern mounted on a top surface of the substrate; disposing a mask onto the substrate to cover the at least one electronic component; forming an encapsulant layer on the mother board to encapsulate at least the electronic assembly; forming a trench through the encapsulant layer to expose at least a portion of the conductive pattern and at least a portion of lateral surfaces of the mask; forming a shielding layer on the mother board to cover the encapsulant layer and fill in the trench; and detaching the mask from the mother board.

TECHNICAL FIELD

The present application generally relates to semiconductor technologies, and more particularly, to a method for forming a partial shielding for an electronic assembly.

BACKGROUND OF THE INVENTION

Semiconductor devices are commonly found in modern electronic products, which perform a wide range of functions, such as signal processing, high-speed computing, transmitting and receiving electromagnetic signals, controlling electronic devices, and creating visual images for television displays. Various electronic components can be fabricated within a semiconductor device to perform certain functions such as calculation or memory. In order to protect the electronic components inside an electronic assembly or a semiconductor device from electromagnetic interference (EMI), a conformal shielding can be conventionally coated over the entire semiconductor device, which can reduce the magnitude of EMI radiation entering and exiting the semiconductor device. Some semiconductor devices that perform wireless communication functions are also equipped with a transceiver module for receiving signals from and/or transmitting signals to exterior devices. In such devices, the afore-mentioned conformal shielding blocks desired electromagnetic radiation from/to the exterior devices. Therefore, for an electronic assembly integrated with a transceiver module, a partial shielding that selectively and effectively performs EMI shielding is desired.

Conventionally, a laser ablation process can be used to remove solid materials at intended locations of a conformal shielding to obtain a partial shielding. For example, for an antenna module under a conformal shielding that needs to be exposed, an encapsulant layer and/or a shielding layer may be partially removed by the laser ablation process to form a cavity for the antenna module, which at least partially exposes the antenna module. Yet, the laser ablation process may be complicated since a successful laser ablation process for forming the partial shielding depends on various factors. For example, the laser energy of the laser ablation process needs to be compatible with the material to be removed to achieve a desired cavity. Further, the beam energy density, the laser pulse duration, and the laser wavelength, etc. are also other factors to be considered for a specific application. A wrong configuration profile may cause undesired damage to the electronic component, thereby, the yield of such electronic assembly may be reduced.

Therefore, a need exists for an improved method for forming a partial shielding for an electronic assembly.

SUMMARY OF THE INVENTION

An objective of the present application is to provide a method for forming a partial shielding for an electronic assembly, which achieves low lost and high yield.

According to one aspect of the present application, a method for forming a partial shielding for an electronic assembly is provided, comprising: providing an electronic assembly mounted on a mother board; wherein the electronic assembly comprises a substrate, and at least one electronic component and a conductive pattern mounted on a top surface of the substrate; disposing a mask onto the substrate to cover the at least one electronic component; forming an encapsulant layer on the mother board to encapsulate at least the electronic assembly; forming a trench through the encapsulant layer to expose at least a portion of the conductive pattern and at least a portion of lateral surfaces of the mask; forming a shielding layer on the mother board to cover the encapsulant layer and fill in the trench; and detaching the mask from the mother board.

The same reference numbers will be used throughout the drawings to refer to the same or like parts.

DETAILED DESCRIPTION OF THE INVENTION

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

In this application, the use of the singular includes the plural unless specifically stated otherwise. In this application, the use of “or” means “and/or” unless stated otherwise. Furthermore, the use of the term “including” as well as other forms such as “includes” and “included” is not limiting. In addition, terms such as “element” or “component” encompass both elements and components including one unit, and elements and components that include more than one subunit, unless specifically stated otherwise. Additionally, the section headings used herein are for organizational purposes only, and are not to be construed as limiting the subject matter described.

In semiconductor devices, multiple electronic components of various functions may be integrated in a single assembly. For example, semiconductor dice, semiconductor packages, integrated passive components, discrete active or passive electrical components as well as antennas may be integrated together as an electronic assembly. On the one hand, some electronic components may be susceptible to electromagnetic interference (EMI), radio frequency interference (RFI), harmonic distortion, or other inter-device interferences, such as capacitive, inductive, or conductive coupling, also known as cross-talks, which can interfere with the operation of these components. Such interferences may be generated both from exterior devices outside the assembly and from such as high-speed switching of digital circuits inside the same assembly. Therefore, for protection purpose, a shielding, especially an EMI shielding, may be desired. On the other hand, a shielding may be undesired, for example, for some electronic components such as an antenna module used to convert between an electromagnetic radiation signal sent or received over the airwaves and an electrical signal within the electronic assembly. The transceiver functionality of the electronic assembly will be facilitated by not having a full shielding formed over the antenna module, which could block desirable signals.

As can be seen, different electronic components in an electronic assembly may require different shielding configurations. To solve the problem, a partial shielding may be desired to selectively shield the electronic assembly, thereby providing different shielding configurations as needed by different electronic components of the assembly. Conventionally, a partial shielding may be formed by performing a laser ablation process to an electronic assembly that is conformally shielded. Yet, as illustrated above, the laser ablation process may be complicated, and of low yield and high cost.

According to some embodiments of the present application, a method for forming a partial shielding for an electronic assembly is provided. Instead of using laser ablation, the method adopts a mask with easy attachment to and detachment from the electronic assembly, which reduces the cost and improves the yield.

Referring toFIG.1A, an electronic assembly100formed with a partial shielding according to an embodiment of the present application is illustrated.

As shown inFIG.1A, the electronic assembly100includes a mother board102and multiple electronic components mounted on the mother board102. In an embodiment, the electronic component mounted on the mother board102may be a semiconductor package103, which includes a substrate104, an encapsulated semiconductor die105mounted on a bottom surface of the substrate104, and an antenna module106mounted on a top surface of the substrate104. A conductive pattern120is formed on the top surface and around the antenna module106, and the conductive pattern120may be electrically connected to the antenna module106via interconnect structures (not shown) within the substrate104. In some embodiments, the conductive pattern120surrounding the antenna module106is formed as a conductive ring. An additional conductive pattern121may be optionally disposed on top of the conductive pattern120.

The antenna module106may include an antenna106a, which provides transmission function and may take the form of inductive coil, and an encapsulant or molding compound106bdeposited around and optionally over the antenna106a. Note that the encapsulant or molding compound106bmay not be present in some other embodiments. Both the semiconductor die105and the antenna module106may be electrically and mechanically coupled to the substrate104via such as solder balls, and the substrate104may be further electrically coupled to the mother board102via solder balls107.

Further referring toFIG.1A, a partial shielding is formed on the mother board102using a method according to an embodiment of the present application. In particular, an overall structure of the semiconductor package103is encapsulated with a partial encapsulant140to provide the electronic assembly100with structural support and protection against external contaminants. Furthermore, a partial shielding layer110is formed over the electronic assembly100, or particularly over the partial encapsulant140, to protect the electronic components from being affected by such as exterior radiation.

Referring toFIG.1B, a top view of the electronic assembly100shown inFIG.1Ais illustrated. As shown inFIG.1B, the antenna module106includes the antenna106aand the encapsulant or molding compound106b, and is exposed to the exterior environment. Surrounding the antenna module106is the ring-shaped conductive pattern120. The partial shielding layer110covers an area outside the conductive pattern120. The antenna106ais disposed within the center of the cavity of the partial shielding layer110and the partial encapsulant layer (not shown).

FIG.2is a flowchart illustrating a method200for forming a partial shielding for an electronic assembly. The method200can be used to manufacture an electronic assembly with an open cavity such as the electronic assembly100shown inFIGS.1A and1B, which enables selective shielding for electronic components integrated within such electronic assembly.

Firstly, in block201, an electronic assembly to be processed is provided, wherein some electronic components of the electronic assembly are desired to be unshielded, e.g., an antenna module. Then, in block202, a mask is disposed onto a substrate of the electronic assembly to cover at least part of the electronic components desired to be unshielded. Further, in block203, an encapsulant layer is formed on a mother board for the electronic assembly to encapsulate the electronic assembly. In block204, a trench is formed through the encapsulant layer to expose at least a portion of a conductive pattern on the substrate and at least a portion of lateral surfaces of the mask. In block205, a shielding layer is formed on the mother board to cover the encapsulant layer and fill in the trench. Finally, in block206, the mask is detached from the mother board. Each step is illustrated below in more details.

FIGS.3A-3Fshow cross-sectional views of the steps of the method depicted inFIG.2according to an embodiment of the present application.

Referring toFIG.3A, an electronic assembly300includes a mother board302and multiple electronic components mounted thereon. In particular, a semiconductor package303, which includes a substrate304, an encapsulated semiconductor die305and an antenna module306, is mounted on the mother board302. In the embodiment, the semiconductor die305is mounted on a bottom surface of the substrate304, facing towards a top surface of the mother board302, while the antenna module306is mounted on a top surface of the substrate304and facing away from the mother board302. However, in some other embodiments, the semiconductor die305may be disposed on the top surface of the substrate304, i.e., on the same side as the antenna module306. The substrate304may include conductive structures on its top and bottom surfaces, and interconnect structures within the substrate304to achieve electrical connection between the respective conductive structures on the top and bottom surfaces (not shown). The semiconductor die305and the antenna module306are electrically and mechanically coupled to the substrate304via such as solder balls (for the antenna module306not shown). The substrate304is electrically coupled to the mother board302via for example solder balls307.

In one embodiment, the antenna module306may be a transceiver device that may include an antenna and some other electronic components, such as an amplifier, to convert between a desirable electromagnetic radiation signal sent or received over the airwaves and an electrical signal within the electronic assembly. In another embodiment, the antenna module306may be a discrete antenna module that provides radio frequency (RF) communications by transmitting and receiving RF signals. The discrete antenna module may include one or more antennas and optionally interleaving conductive layers, conductive vias and insulating layers, depending on the design and function of the discrete antenna module. In some embodiments, the antenna module306may be formed using a printed circuit board (PCB) manufacturing process. For example, the antenna module306may be embedded into a PCB-like plate or substrate using a build-up process used in the PCB manufacturing process.

Further referring toFIG.3A, the antenna module306may include an antenna306a, which provides transmission function and may take the form of inductive coil, and an encapsulant or molding compound306bdeposited around and optionally over the antenna306a. The encapsulant or molding compound306bmay be formed by paste printing, compressive molding, transfer molding, liquid encapsulant molding, vacuum lamination, spin coating, or other suitable processes. The encapsulant or molding compound306bcan be a polymer composite material, such as epoxy resin with filler, epoxy acrylate with filler, photoresist or polymer with proper filler. In some embodiments, the encapsulant or molding compound306bmay include no filler. The encapsulant or molding compound306bmay be non-conductive, provides structural support, and environmentally protects the functional module306afrom external elements and contaminants.

The antenna module306is electrically connected to the substrate304via certain interconnect structures which may be bond wires, conductive paste, stud bump, micro bump, or the like. For example, electrically conductive bump (not shown) may be deposited using evaporation, electrolytic plating, electroless plating, ball drop, or screen printing process. The bump material can be Al, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, and combinations thereof, with an optional flux solution.

Preferably, as shown inFIG.3A, a conductive pattern320is formed around the antenna module306. The conductive pattern320may be electrically connected to the antenna module306via interconnect structures (not shown) within the substrate304. In some embodiments, the conductive pattern320surrounding the antenna module306is formed as a conductive ring, which may be, as will be illustrate below, further electrically connected to a shielding layer and preferably a ground node, so as to aid the interference blocking capability of the shielding layer. Preferably, the conductive pattern320surrounding the antenna module306can be formed as a continuous or discontinuous ring. It can be appreciated that a height of the antenna module306and a height of the conductive pattern320are only illustrative, not representing the actual proportion. It can also be appreciated that the conductive pattern320can be formed as any predefined pattern. In some embodiments, the antenna306aand the conductive pattern320may be formed in a single process.

Further referring toFIG.3A, on top of the conductive pattern320, an additional conductive pattern321may be optionally disposed. In an embodiment, the additional conductive pattern321may be shaped as a ring or a rectangle, which may enclose a cavity above the antenna module306to position the mask to be mounted therein. An area of the additional conductive pattern321may be equal to or smaller than an area of the conductive pattern320. In some embodiments, both the conductive pattern320and the additional conductive pattern321are formed on the substrate304using a Solder-on-Pad (SOP) process. Preferably, the conductive pattern320and/or the additional conductive pattern321may be formed using plating such as Au plating, so as to enhance electrical connection between a shielding layer to be formed on the substrate304and the substrate304. The plating process may further improve the yield. Preferably, the additional conductive pattern321may be constructed that an inner periphery of the additional conductive pattern321and an inner periphery of the conductive pattern320vertically align with each other. Preferably, the additional conductive pattern321surrounding the antenna module306can be formed as a continuous or discontinuous ring. It can be appreciated that the forming of the afore-mentioned conductive pattern may adopt other suitable processes. In the next step, the additional conductive pattern321may serve as an anchor point for a mask to be disposed on the antenna module306, as will be elaborated below. As aforementioned, in some embodiments, the conductive pattern320and the additional conductive pattern321may be formed by a built-up process used in a PCB manufacturing process. It can be appreciated that the structure of the semiconductor package303is exemplary, which may be modified depending on the actual needs for the electronic assembly300.

Referring toFIG.3B, a mask330is then disposed onto the antenna module306. The shape and size of the mask330may be configured according to the shape and size of the antenna module306which is desired to be exposed in the finalized electronic assembly. In some embodiments, the mask330may cover an entirety of the antenna module306, while in some alternative embodiments, the mask330may cover a portion of the antenna module306. Preferably, the mask330may have an area larger than or equal to an area of a top surface of the antenna module306. Preferably, the mask330may have an area equal to an area delineated by the additional conductive pattern321on top of the conductive pattern320. In some embodiments, the mask330may be one or more of an adhesive tape, an ultraviolet (UV) tape, a thermal tape, metal without adhesive, metal with adhesive, polymer without adhesive, and polymer with adhesive. Optionally, a metal foil film, a metal foil tape, a polyimide film, or any other suitable flexible mask can be used as mask330. In some other embodiments, the mask330may be a metal, plastic, or silicon mask or other rigid mask. The mask330can include adhesive to provide a mechanical attachment of the mask330to the antenna module306, yet, the mask330may also attach to the antenna module306in other ways. Preferably, the mask330may be a polymer with adhesive. The adhesive can be UV release, thermal release, or otherwise configured to allow for convenient removal of the mask330from the antenna module306. The mask330can also be any suitable insulating, passivation, or photoresist layer deposited by any appropriate thin film deposition technique. It can be appreciated that the adhesive may cover any surface(s) of the mask, preferably all outer surfaces or a bottom surface of the mask330to achieve desired attachment and detachment. In some embodiments, the mask330may be placed on the electronic assembly via a pick and place machine or any other suitable mechanism.

Referring toFIG.3C, an encapsulant layer340may be formed on the mother board to cover the electronic assembly. Preferably, the encapsulant layer340may have a height equal or greater than a height of the electronic assembly (including the mask). That is, the mask topmost of the electronic assembly can be exposed from the encapsulant layer340. In some embodiments, the encapsulant layer340may be formed having a height greater than the height of the electronic assembly, thereby the mask is also fully encapsulated. Then the encapsulant layer340, which fully encapsulates the mask, may then be grinded to expose a top surface of the mask. The encapsulant layer340may be deposited via paste printing, compressive molding, transfer molding, liquid encapsulant molding, vacuum lamination, spin coating, or another suitable applicator. Preferably, the encapsulant layer340is formed using an injection molding process. The encapsulant layer340can be a polymer composite material, such as epoxy resin, epoxy acrylate, or any suitable polymer with or without filler. The encapsulant layer340may be non-conductive, provides structural support, and environmentally protects the electronic assembly from external elements and contaminants.

Referring toFIG.3D, a trench350is formed through the encapsulant layer340and adjacent to the mask330. In the case that only the conductive pattern320is disposed and the additional conductive pattern321is not disposed on the substrate, the trench350has a depth such that at least a portion of the conductive pattern320can be exposed through the trench350. Also, the trench350can expose at least a portion of lateral surfaces of the mask330. The trench350exposing the lateral surfaces of the mask330can avoid encapsulant material attached to the mask330, which may increase the difficulty of detachment the mask330from the antenna module306in the subsequent process. In the case that both the conductive pattern320and the additional conductive pattern321are disposed on the substrate, as shown inFIG.3D, the trench350has a depth that at least a portion of the additional conductive pattern321is exposed through the trench. Similarly, at least a portion of lateral surfaces of the mask330can be exposed through the trench350. Preferably, the trench350may be formed at a boundary where a conductive pattern is in contact with the mask330. In this case, the shielding layer (usually conductive) to be disposed into the trench350may electrically connect to the conductive pattern. Furthermore, there may be clearances around the mask330for further detachment of the mask330. The trench350may be continuous or discontinuous around the mask330. In the case that the position of the trench350is not aligned with the position of the conductive pattern underneath, the trench350may expose the substrate304.

In this case, the trench350may not be aligned to a circuitry that cannot be grounded/connected to a shielding layer. The trench350can be formed by chemical etching with a photolithographic mask, laser ablation, saw cutting, reactive ion etching, or another suitable trenching process.

Referring toFIG.3E, a conformal shielding layer310is then formed on the mother board to cover the encapsulant layer340and fill in the trench350. The shielding layer310is formed by spray coating, plating, sputtering, or any other suitable metal deposition process. Preferably, the shielding process is performed using sputtering. The shielding layer310can be formed from copper, aluminum, iron, or any other suitable material for EMI shielding. Preferably, the shielding layer310is thick enough such that the trench350may be filled to electrically connect the shielding layer310with the underneath conductive pattern. Specifically, all exposed surfaces of the encapsulant layer340and the trench350are coated by a shielding material, which is generally conductive. Since that the trench350is deep enough to expose the conductive pattern on the substrate, the shielding layer310, which includes the shielding layer over the encapsulant340and the shielding layer in the trench350, are all electrically connected to the conductive pattern on the substrate. Preferably, in the case that the conductive pattern is to be grounded in operation, for example, electrically coupled to a ground node, the shielding layer is thereby grounded, which enhances the shielding performance for the electronic assembly.

Referring toFIG.3F, the mask330is detached from the electronic assembly, along with a portion of the shielding layer thereon, such that the antenna module306is exposed from the encapsulant layer and the shielding layer. As shown inFIG.3F, other electronic components, such as the semiconductor die mounted on the bottom surface of the substrate, remain shielded by the shielding layer. As a result, a partial shielding is formed. Preferably, the same pick and place machine that places the mask330onto the electronic assembly can be used to detach the mask330from the electronic assembly. In some other embodiments, a tool capable of freely rotating the electronic assembly around any and all axes may be adopted, such that the mask330may drop outside the electronic assembly.

Referring toFIGS.4A and4B, it shows an electronic assembly400according to an embodiment of the present application. In some embodiments, a mask430may adopt a dummy die with adhesive430, which include a dummy die430aand an adhesive film430battached thereto with a same area, separated from a dummy wafer with adhesive film470.FIG.4Aillustrates a dummy wafer470including multiple dummy dice with an adhesive film attached to its backside. After singulating the dummy die with adhesive430from the dummy wafer with adhesive film470at the inter-die wafer area or saw street460, the dummy die with adhesive430may be disposed onto an antenna module406to serve as a mask430, wherein the adhesive film430bis in contact with the antenna module406, so as to provide intimate engagement between the mask430and the antenna module406. In particular, the adhesive film430bmay attach the dummy die430ato the antenna module406such that in a further encapsulation of the electronic assembly, minimal encapsulation material may be permeated on the surface of the antenna module406, which may lead to undesired shielding effect. The adhesive film430bcan be ultraviolet (UV) release, thermal release, or otherwise configured to allow for convenient removal of the adhesive film430b. The adhesive film430bcan also be any suitable insulating, passivation, or photoresist layer deposited by any appropriate thin film deposition technique. Removal of the adhesive film430bmay facilitate the removal of the entirety of the mask430.

Referring toFIG.5, for multiple antenna modules506located in an adjacent area, the present method with a single mask may also apply. In some embodiments, there may also be other electronic components580mounted on the mother board. In such cases, for the electronic components580, the partial shielding layer formed with the present application may at least partly shield the radiation from the antenna modules506, in addition to shielding EMI from exterior environment.

It can be appreciated that the antenna module referred to in the above embodiments can be any electronic components that desire to be not shielded. Aspects of the present application are not limited thereto.

The discussion herein included numerous illustrative figures that showed various portions of a method for forming a partial shielding for an electronic assembly. For illustrative clarity, such figures did not show all aspects of each example assembly. Any of the example assemblies and/or methods provided herein may share any or all characteristics with any or all other assemblies and/or methods provided herein.

Various embodiments have been described herein with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. Further, other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of one or more embodiments of the invention disclosed herein. It is intended, therefore, that this application and the examples herein be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following listing of exemplary claims.