Patent ID: 12261127

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following description of certain embodiments presents various descriptions of specific embodiments. However, the innovations described herein can be embodied in a multitude of different ways, for example, as defined and covered by the claims. In this description, reference is made to the drawings where like reference numerals can indicate identical or functionally similar elements. It will be understood that elements illustrated in the figures are not necessarily drawn to scale. Moreover, it will be understood that certain embodiments can include more elements than illustrated in a drawing and/or a subset of the elements illustrated in a drawing. Further, some embodiments can incorporate any suitable combination of features from two or more drawings.

Aspects and embodiments disclosed herein are directed to a semiconductor device module, and methods of making the same, that integrate an electromagnetic interference (EMI) shield into the device module. In one embodiment, one or more conductive posts are positioned on one or more sides of one or more devices within the module and are coupled to conductive layers above and below the one or more devices, thereby forming an EMI shield around the one or more devices. The EMI shield reduces or eliminates degradation in performance of the one or more devices within the module due to EMI received from one or more other devices in the module or from the environment.

One aspect is directed to a packaged semiconductor module having an integrated electromagnetic interference shield. In one embodiment, the packaged semiconductor module comprises a substrate having a ground plane, a plurality of electronic devices mounted on a surface of the substrate, at least one conductive post disposed on at least one side of at least one of the electronic devices and electrically coupled to the ground plane, a mold compound covering the electronic devices and at least partially covering the at least one conductive post, and a conductive layer disposed on a top surface of the mold compound and electrically coupled to the at least one conductive post, wherein the at least one conductive post, the conductive layer, and the ground plane together comprise the integrated electromagnetic interference shield.

In one example, the conductive layer comprises silver-filled epoxy. The at least one conductive post can be made from various conductive materials, such as gold, copper, solder, conductive paint, doped polysilicon, or silver-filled epoxy. The at least one conductive post may be disposed between two of the plurality of electronic devices in the semiconductor module. In one example, the plurality of electronic devices are radio frequency (RF) devices.

Another aspect is directed to a method of manufacturing a module having an integrated electromagnetic interference shield. According to one embodiment, the method comprises connecting a plurality of electronic devices to a substrate including a ground plane, providing bond pads on the substrate electrically connected to the ground plane, performing a molding process to encapsulate the plurality of electronic devices in mold compound, forming one or more conductive posts in the mold compound between adjacent ones of the plurality of electronic devices and in electrical connection with the bond pads, and disposing a conductive layer on a surface of the mold compound, the conductive layer electrically connected to the one or more conductive posts. In one example, the method further comprises ablating the surface of the mold compound, prior to disposing the conductive layer on the surface of the mold compound, to form via holes for the one or more conductive posts. The one or more conductive posts may be formed in the vias by screen printing of solder paste, electroplating, chemical vapor deposition, physical vapor deposition (evaporative deposition or sputtering), by deposition of conductive paint, or by other methods of depositing conductive material known in the art. In some examples, disposing the conductive layer on the surface of the mold compound includes painting a layer of silver-filled epoxy or conductive paint on the top and side surfaces of the mold compound.

In many modern applications, including cellular phone handsets, personal digital assistants (PDAs), media players, and other portable device that use radio frequency (RF) components, the size (length, width and thickness) and weight of the finished product can often be important design parameters. For example, particularly for cellular phone handsets, there is continuing drive toward devices that offer increased functionality and features within a given form factor. Accordingly, the size and weight of individual components used in these devices can also be important. As discussed above, the conventional approach for providing electromagnetic interference shielding for RF devices involves placing a grounded metal can over the individual RF device to be shielded, which adds size, weight and cost to the design and therefore, may be undesirable in many instances.

Aspects and embodiments disclosed herein are directed to methods and apparatuses to provide an interference shield that is integrated into individual modules during the packaging process with minimal increase in the size and/or weight of the module. As used herein, the term “EMI shield” is used to refer to both electromagnetic interference and radio frequency interference shielding. Aspects and embodiments of methods and structures for proving EMI protection for devices in an electronics device module may provide high design flexibility as well as an easier and less expensive method by which to manufacture EMI shields. In addition, an integrated “fencepost” shield according to aspects of the invention provides a way to achieve inter/intra module isolation and low package profile, which has not been achieved by conventional existing technologies. As discussed below, a fencepost cage may be formed using conductive columns disposed between or around one or more electronic devices in a module to provide a robust and practical EMI shield for various packages and process conditions.

Referring toFIG.1, there is illustrated one example of a method of packaging an electronic device or module incorporating an integrated EMI shield. Aspects and embodiments of the method are discussed below with continuing reference toFIG.1.

A first step100includes preparing a substrate to be incorporated into an electronic module. This step100may include forming metallization on the substrate that may be used to interconnect various components of the electronic module and at least some of which may become part of the integrated EMI shield, as discussed further below. In step102, an electronic module may be assembled according to methods and techniques known to those skilled in the art. This step102may include acts such as mounting a plurality of die to the substrate, forming any necessary internal or external connections or connection points (including depositing layers of metallization and/or dielectric), etc. Therefore, it is to be appreciated that although module assembly is illustrated as a single step102inFIG.1, it may comprise several steps that may be performed at the same time, at different times, and/or in different locations. Furthermore, it is to be appreciated that step100may be considered part of step102.

An example of such a module is illustrated inFIG.2. The module200comprises at least two die202mounted to a substrate204. Some examples of the die202include, but are not limited to, power amplifiers, low noise amplifiers, transceivers, linear devices, filters and other devices that may require or benefit from EMI shielding. As discussed above, EMI shielding is typically desirable for RF devices and therefore, at least one of the die202may be an RF device and the module200may be an RF module; however, it is to be appreciated that the invention is not so limited, and the die202may comprise any type of digital or analog device or component. In one example, the die202are mounted to the substrate204using wire bonds206connected to bond pads208, as illustrated inFIG.2. Alternatively, the die202may be mounted to the substrate204using flip chip bonding methods, or any other suitable technique known to those skilled in the art.

According to one embodiment, an integrated EMI shield is incorporated into the module200by forming one or more conductive posts216on one or more sides of one or more of the die202, for example, between adjacent die202during the packaging process. A plurality of these conducive posts216may be placed around the die202on the substrate204and connected to a ground plane212in the package, as discussed further below, to provide the integrated EMI shield. To form an integrated shield in a molded module, a manufacturing difficulty lies in finding a way to connect the ground plane212in the substrate to the top conductive shield layer. Embodiments of the methods of forming an integrated shield using conductive post connectors216provide a robust manufacturing process for resolving this difficulty, as discussed further below.

Referring again toFIG.1, as discussed above, step100may include forming metallization on the substrate204that will become part of the integrated EMI shield. Referring toFIG.3, this metallization may include bond pads210, a ground plane212, and vias214that connect the bond pads to the ground plane212. Conductive posts216may then be formed on the bond pads210(step108), as discussed further below. It is to be appreciated that although in the example illustrated inFIG.3, one discrete bond pad210, with associated via214, is provided for the conductive post216, aspects and embodiments disclosed herein are not so limited and many other configurations are contemplated. For example, as illustrated inFIG.4, the individual bond pads210may be replaced with a metallization track or ring218that may at least partially encircle the die(s)202. In this example, one or more vias214may be provided at points along the track218to couple the track, and therefore the conductive posts216, to the ground plane212. Furthermore, in one example, the track218may be continuous between two or more conductive posts216and therefore, each conductive post216need not have an individually associated via214and the vias214may be laterally offset from the conductive posts.

According to one embodiment, the method of forming an integrated EMI shield includes a transfer molding process (step104) to encapsulate the die(s)202in a mold compound220. During the transfer molding process the substrate204is placed in a lower mold chase, an upper mold chase is lowered onto the lower mold chase to a seal a cavity around the device, and the mold compound220is flowed into the cavity to encapsulate the die(s)202on the substrate. Transfer molding processes are well known to those skilled in the art.

Still referring toFIGS.1and3, after the transfer molding process (step104), an ablation process (step106) may be used to form via holes222for the conductive posts216through the mold compound220. The ablation process may include, for example, a laser ablation process, an anisotropic etch process, a drilling process utilizing mechanical drill bits, micro ablation (sand blasting), or other methods of forming a via through the mold compound known in the art. The ablation process exposes upper portions of the bond pads210on which the conductive posts216will be formed. The bond pads210may serve as etch stops or ablation stops during the ablation process. The via holes222may be about 100 μm wide to facilitate later filling with conductive material.

After formation of the vias holes222, the conductive posts216are formed within the via holes222and in electrical contact with the bond pads210and the ground plane212(step108). The conductive posts216may be formed by, for example, screen printing of solder paste, electroplating, chemical vapor deposition, physical vapor deposition (evaporative deposition or sputtering), by deposition of conductive paint, or by other methods of depositing conductive material known in the art. The conductive posts216may be formed of or include copper, gold, silver, solder, doped polysilicon, or any other suitable conductive material. The conductive posts216may extend from the bond pads210to the upper surface of the molding compound220and the upper ends of the via holes222, but in other embodiments may have upper ends disposed below the upper surface of the molding compound220and the upper ends of the via holes222.

After the conductive posts216have been formed, a thin conductive coating or layer224may be formed on top of the mold compound220(step110) to contact the exposed tops of the conductive posts216. The conductive layer224may be deposited on top of the mold compound220using any of various techniques known to those skilled in the art, such as, by printing, depositing, sputtering, etc. In one example, the conductive layer224comprises a metal-filled epoxy, such as a silver-filled epoxy, or a metal paint layer as disclosed in U.S. Pat. No. 10,163,814, incorporated herein by reference, that is spray-painted on top of the mold compound220. The conductive layer224contacts the exposed tops of the conductive posts216and thus electrically connects the exposed conductive posts216. The conductive layer224may also cover sides of the mold compound210and extend down to exposed positions of the ground plane212or to a conductive material layer226previously formed on sides of the mold compound210(for example, in step100) and in electrical connection with the ground plane212. The conductive posts216may thus be in electrical connection to the ground plane212both from the bottom ends through the bond pads210and vias214, and from top ends through the conductive layer224and, optionally, conductive material layer226.

As discussed above, in one embodiment, the module200includes a ground plane212disposed along a bottom surface of the substrate204, as shown inFIG.3, and connected to the conductive posts216by vias214. Through contact between the tops of the conductive posts216and the conductive layer224, an electrical connection is formed between the conductive layer and the ground plane212, thus completing an EMI shield in the module200. The conductive posts216provide a flexible (because they may be located anywhere suitable on the substrate) and fully integrated connection between the ground plane212in the substrate204and the top conductive shield layer224. Thus, one or more of the die(s)202may be substantially enclosed in a grounded EMI shield formed by the conductive layer224, the conductive posts216(and their associated metallizations, such as vias214and bond pads210) and the ground plane212. This integrated EMI shield according to embodiments of the invention may add minimal size and weight to the module200, unlike the bulky metal cans of conventional EMI shielding solutions.

The locations of the conductive posts216and associated bond pads210and vias214may be selected to minimize the number of conductive posts216utilized to minimize associated fabrications costs, while providing sufficient intra-module EMI protection between devices or die202in a module to meet specifications. For example, as illustrated inFIG.5, a high power device or die202A that may emit a relatively large amount of EMI, for example, a power amplifier, as well as a second device or die202B that may be sensitive to EMI, for example, a low noise amplifier may be present in the same module200. It may thus be desired to form one or more conductive posts216between the high power device or die202A and the EMI sensitive device or die202B. In some instances, the conductive posts216may be spaced from one another at a fraction of a wavelength of the electromagnetic radiation expected to be emitted from the high power device or die202A. In other embodiments, the conductive posts216, or even a single conductive post216, may provide sufficient amount of conduction of energy emitted from the high power device or die202A to the ground plane212such that multiple conductive posts216, or conductive posts216spaced at a fraction of the wavelength of electromagnetic radiation of concern, may not be necessary to achieve a desired attenuation of EMI. For especially EMI sensitive devices or die202C it may be desired to provide conductive posts216on each side of the device or die202C to guard against both intra-module EMI and EMI from sources external to the module200. For high power or sensitive devices or die202D located proximate an edge or corner of the module200it may be desired to provide conductive posts only on sides of the device or die202D facing other devices or die within the module.

In summary, an effective, low cost and robust integrated EMI shield can be provided in any transfer molded module using only the ground plane typically already present in the module substrate, a thin layer of conductive material deposited on top of the mold compound, and a plurality of the conductive posts discussed herein to connect the conductive layer to the ground plane, thereby forming a complete shield for some or all of the devices in the module. The conductive posts may be placed anywhere in the package, with optional redundant connections to ensure the contact to the conductive layer224meets all electrical requirements, allowing for a very flexible EMI shield design that can be easily modified to accommodate different module layouts and devices. Similarly, as discussed above with reference toFIG.4, the vias214connecting the wirebond pads210(or track218) to the ground plane need not be coincident with each pad, or with specific locations on the ground plane, allowing for flexible pad210and via214placement in the module. The number of conductive posts required to provide an adequate EMI shield depends on the operating frequency of the devices to be shielded and the level of shielding desired. For example, the density (the spacing between immediately adjacent conductive posts216in any given direction) may increase with increasing signal frequency. In one example, a spacing of about λ/20 (where λ is the wavelength of the signal to be shielded) may be used. It is to be appreciated that the post spacing need not be uniform, provided only that the minimum spacing to achieve desired shielding at a given frequency is maintained. The conductive posts discussed herein can be used to provide a completely integrated EMI shield that is highly flexible and adds minimal cost, weight and/or size to the module. The conductive posts may be processed using traditional processing techniques which are low cost, robust and do not require the procurement of any additional or specialized assembly equipment.

Aspects of this disclosure can be implemented in various electronic devices. Examples of the electronic devices can include, but are not limited to, consumer electronic products, parts of the consumer electronic products such as packaged radio frequency modules, uplink wireless communication devices, wireless communication infrastructure, electronic test equipment, etc. Examples of the electronic devices can include, but are not limited to, a mobile phone such as a smart phone, a wearable computing device such as a smart watch or an ear piece, a telephone, a television, a computer monitor, a computer, a modem, a hand-held computer, a laptop computer, a tablet computer, a microwave, a refrigerator, a vehicular electronics system such as an automotive electronics system, a stereo system, a digital music player, a radio, a camera such as a digital camera, a portable memory chip, a washer, a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, a multi-functional peripheral device, a wrist watch, a clock, etc. Further, the electronic devices can include unfinished products.

Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise,” “comprising,” “include,” “including” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to.” The word “coupled”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Likewise, the word “connected”, as generally used herein, refers to two or more elements that may be either directly connected, or connected by way of one or more intermediate elements. Additionally, the words “herein,” “above,” “below,” and words of similar import, when used in this application, shall refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the above Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word “or” in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

Moreover, conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” “such as” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.

While certain embodiments have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the disclosure. Indeed, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. For example, while blocks are presented in a given arrangement, alternative embodiments may perform similar functionalities with different components and/or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these blocks may be implemented in a variety of different ways. Any suitable combination of the elements and acts of the various embodiments described above can be combined to provide further embodiments. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.