Devices and methods related to packaging of radio-frequency devices on ceramic substrates

Devices and methods related to packaging of radio-frequency (RF) devices on ceramic substrates. In some embodiments, a packaged electronic device can include a ceramic substrate configured to receive one or more components. The ceramic substrate can include a conductive layer in electrical contact with a ground plane. The packaged electronic device can further include a die having an integrated circuit and mounted on a surface of the ceramic substrate. The packaged electronic device can further include a conformal conductive coating implemented over the die to provide shielding functionality. The packaged electronic device can further include an electrical connection between the conformal conductive coating and the conductive layer.

BACKGROUND

Field

The present disclosure generally relates to shielding of packaged radio-frequency (RF) modules.

Description of the Related Art

Electromagnetic (EM) fields can be generated from or have an undesirable effect on a region of a radio-frequency (RF) device such as an RF module. Such an EM interference (EMI) can degrade the performance of wireless devices that use such an RF module. Some RF modules can be provided with EM shields to address such performance issues associated with EMI.

SUMMARY

According to some implementations, the present disclosure relates to a packaged electronic device that includes a ceramic substrate configured to receive one or more components. The ceramic substrate includes a conductive layer in electrical contact with a ground plane. The packaged electronic device further includes a die having an integrated circuit. The die is mounted on a surface of the ceramic substrate. The packaged electronic device further includes a conformal conductive coating implemented over the die to provide shielding functionality. The packaged electronic device further includes an electrical connection between the conformal conductive coating and the conductive layer.

In some embodiments, the conformal conductive coating can be implemented substantially directly on the die. The conformal conductive coating directly on the die can result in the packaged electronic device being a low-profile shielded device.

In some embodiments, the die can be configured as a flip-chip device. The packaged electronic device can further include an underfill implemented between the flip-chip device and the ceramic substrate. The underfill can include an edge profile configured to provide an angled transition between side walls of the flip-chip device and the surface of the ceramic substrate. The angled transition profile of the underfill can be configured to facilitate improved coverage of the conformal conductive coating between the flip-chip device and the ceramic substrate.

In some embodiments, the integrated circuit can include a radio-frequency (RF) switching circuit. In some embodiments, the die can be a silicon-on-insulator (SOI) die.

In some embodiments, the electrical connection can include a portion of the conformal conductive coating on the surface of the ceramic substrate and a plurality of conductive vias configured to provide electrical connection between the conformal conductive coating on the surface of the ceramic substrate and the conductive layer. The conductive layer can include one or more conductive strips implemented within the ceramic substrate. The conductive layer can include a plurality of the conductive strips arranged to generally form a perimeter at or near the edges of the ceramic substrate. Each of the one or more conductive strips can at least partially overlap laterally with the corresponding conductive vias.

In some embodiments, the electrical connection can include a portion of the conformal conductive coating on the surface of the ceramic substrate extending to side edges of the ceramic substrate. The conductive layer can include an edge along the corresponding side edge of the ceramic substrate such that the edge of the conductive layer is in electrical contact with the conformal conductive coating. The conductive layer can include a conductive strip along the corresponding side edge of the ceramic substrate. The conductive strip can include an edge exposed sufficiently on the corresponding side edge of the ceramic substrate to facilitate the electrical contact between the conductive strip and the conformal conductive coating. The conductive layer can include a plurality of the conductive strips arranged such that each edge of the ceramic substrate includes the corresponding exposed edge of the conductive strip in electrical contact with the conformal conductive coating.

In some embodiments, the conformal conductive coating can include a metallic paint layer or a conductive layer formed by deposition. In some embodiments, the ceramic substrate can include a low-temperature co-fired ceramic (LTCC) substrate. In some embodiments, the packaged electronic device can further include a plurality of contact pads implemented on an underside of the ceramic substrate. The contact pads can be configured to allow mounting of the packaged electronic device on a circuit board. In some embodiments, the packaged electronic device can further include an overmold implemented over the die such that the conformal coating is implemented on a surface of the overmold. The overmold can be dimensioned such that its side walls generally align with corresponding side walls of the ceramic substrate.

In a number of implementations, the present disclosure relates to a wireless device that includes a transceiver configured to generate a radio-frequency (RF) signal, and an RF module configured to process the RF signal. The RF module includes a ceramic substrate configured to receive one or more components. The ceramic substrate includes a conductive layer in electrical contact with a ground plane. The RF module further includes a die having an integrated circuit, with the die being mounted on a surface of the ceramic substrate. The RF module further includes a conformal conductive coating implemented over the die to provide shielding functionality. The RF module further includes an electrical connection between the conformal conductive coating and the conductive layer. The wireless device further includes an antenna in communication with the RF module. The antenna is configured to facilitate transmission of the processed RF signal.

In some implementations, the present disclosure relates to a method for fabricating a packaged radio-frequency (RF) module. The method includes forming or providing a ceramic substrate configured to receive one or more components. The ceramic substrate includes a conductive layer in electrical contact with a ground plane. The method further includes mounting a die on a surface of the ceramic substrate, with the die including an integrated circuit. The method further includes forming a conformal conductive coating over the die and in electrical contact with the conductive layer to thereby provide shielding functionality for the die.

In some embodiments, the ceramic substrate can include a plurality of ceramic layers arranged in a stack having an array of units defined by a grid of lines along which a singulation process results in separation of the units into a plurality of individual units. The method can further include singulating the array of units prior to the forming of the conformal conductive coating. The mounting of the die can be performed on each of the units prior to the singulating step.

According to some teachings, the present disclosure relates to a ceramic substrate for fabricating a plurality of packaged radio-frequency (RF) modules. The ceramic substrate includes a plurality of ceramic layers arranged in a stack having an array of units. Each unit is configured to receive one or more components. The array of units is defined by a grid of lines along which a singulation process results in separation of the units into a plurality of individual units. The ceramic substrate further includes a ground plane implemented within the stack. The ceramic substrate further includes a conductive layer implemented within the stack and in electrical contact with the ground plane. The conductive layer is configured so that upon the singulation process, at least one edge of each individual unit includes an exposed edge of the conductive layer.

In some embodiments, the conductive layer can include a conductive strip implemented along a corresponding one of the grid of lines, such that the singulation process along the line results in two neighboring units to be separated with each having a cut edge of the conductive strip as the exposed edge. In some embodiments, the ceramic substrate can further include one or more of a dielectric layer, a passive component, and a conductor feature. The passive component can include a resistive element, a capacitive element, or an inductive element. The conductor feature can include a conductor trace or a conductive via. In some embodiments, the ceramic substrate can include a low-temperature co-fired ceramic (LTCC) substrate.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Disclosed herein are various examples of how radio-frequency (RF) devices such as flip-chip die can be mounted on a packaging substrate such as a ceramic substrate and be shielded. Although described in the context of flip-chip die, it will be understood that one or more features of the present disclosure can be implemented in other applications, including those involving non-flip-chip die. It will also be understood that one or more features of the present disclosure can also be implemented in other types of non-ceramic substrates.

FIG. 1shows an example of a shielded packaged device100that includes an un-encapsulated device104mounted on a ceramic substrate106. As described herein, such an un-encapsulated device can be, for example, a flip-chip. As described herein, such a flip-chip104mounted on the ceramic substrate106can be shielded without use of an overmold, thereby allowing, for example, reduced height of the packaged device100. For example, the overall height of the packaged device100can be made to be less than an example specification of 0.65 mm.

In the example ofFIG. 1, the packaged device100is shown to include a conformal coating102of conductive material that substantially covers the un-encapsulated device104and some or all of an exposed portion of an upper surface108of the ceramic substrate106. Such a conformal coating can be electrically connected to a ground node110within the ceramic substrate by an electrical connection configuration112. Various examples of how such electrical connections can be implemented are described herein in greater detail.

As described herein, the un-encapsulated device102can include, for example, a die having one or more switching circuits. Die having other types of RF circuits can also be utilized. In some embodiments, such a switching die can include a silicon-on-insulator (SOI) die. Other types of process technologies can also be implemented. As described herein, the ceramic substrate106can include, for example a low-temperature co-fired ceramic (LTCC) substrate, a high-temperature co-fired (HTCC) substrate, or other types of ceramic materials and/or configurations.

FIG. 2shows an example configuration100that can be a more specific example of the packaged device ofFIG. 1. In the example, a flip-chip104such as an SOI switching die is shown to be mounted on a ceramic substrate106such as an LTCC substrate. Such a mounting of the flip-chip104on the ceramic substrate106can be facilitated by an array of solder balls120. Such solder balls120can provide mechanical mounting functionality, as well as electrical connections between the flip-chip104and contact pads formed on a mounting surface116of the ceramic substrate106.

As shown inFIG. 2, an underfill122can be formed between the flip-chip104and the ceramic substrate106. Such an underfill can be configured near the edges of the flip-chip104so as to facilitate easier formation of a conformal coating102of conductive material. For example, the peripheral portion of the underfill122is shown to provide an angled transition between the vertical edges of the flip-chip104and the horizontal surface116of the ceramic substrate106.

In some embodiments, the conformal coating102can be formed by application of conductive material by, for example, spraying or various deposition methods. Such a coating of conductive material can provide shielding functionality of portions it covers. The overall shielding performance for the packaged device100can be greatly enhanced by also providing lateral shielding at or near the edges of the ceramic substrate106, as well as a ground plane underneath the flip-chip104.

In the example shown inFIG. 2, an electrical connection configuration112can include a plurality of conductive vias138in electrical contact with the conductive coating102on the surface116of the ceramic substrate106. As shown inFIG. 3, such conductive vias can be distributed to form a perimeter; and the vias138can be spaced appropriately to provide lateral shielding between a region within the perimeter and outside of the perimeter. Although described in the context of such a perimeter, it will be understood that one or more features of the present disclosure can also be implemented in configurations where such lateral shielding does not form a complete perimeter. For example, such conductive vias can be provided so as to facilitate intra-module shielding functionality without having to form a complete perimeter about a given region.

In the example shown inFIG. 2, the electrical connection configuration112can further include one or more conductive layers (e.g.,140,142) that are implemented within the ceramic substrate106so as to be in electrical contact with the conductive vias138. Such conductive layers140,142can be in electrical contact with a ground plane that is also within the ceramic substrate106.

An example of the conductive layer140is shown inFIG. 3. Such a layer can include a plurality of conductive strips positioned along the perimeter formed by the conductive vias138. In the example shown, each of the conductive strips140is shown to be positioned laterally so as to intersect with respective vias138. For the example conductive layer142ofFIG. 2, each strip does not necessarily need to overlap completely with respective vias138, so long as it forms electrical contacts with the vias138. Other configurations of the vias138and the conductive layers140,142are also possible.

As shown inFIG. 2, the ceramic substrate106can include a plurality of layers and features130. Such layers and features can include, for example, dielectric layers, passive components (such as resistors, capacitors and inductors), conductor features (such as vias and traces), and a ground plane. In such a context, the example conductive layers140,142can be formed at selected lateral locations and/or at selected layers.

As also shown inFIG. 2, the packaged device100can include contact pads134,136that allow mounting of the packaged device100on a circuit board (e.g., a phone board) and facilitate electrical connections between the packaged device100and the circuit board.

FIG. 4shows another example configuration100that can be a more specific example of the packaged device ofFIG. 1. In the example, a flip-chip104such as an SOI switching die is shown to be mounted on a ceramic substrate106such as an LTCC substrate. Such a mounting of the flip-chip104on the ceramic substrate106can be facilitated by an array of solder balls120. Such solder balls120can provide mechanical mounting functionality, as well as electrical connections between the flip-chip104and contact pads formed on a mounting surface116of the ceramic substrate106.

As shown inFIG. 4, an underfill122can be formed between the flip-chip104and the ceramic substrate106. Such an underfill can be configured near the edges of the flip-chip104so as to facilitate easier formation of a conformal coating102of conductive material. For example, the peripheral portion of the underfill122is shown to provide an angled transition between the vertical edges of the flip-chip104and the horizontal surface116of the ceramic substrate106.

In some embodiments, the conformal coating102can be formed by application of conductive material by, for example, spraying or various deposition methods. Such a coating of conductive material can provide shielding functionality of portions it covers. The overall shielding performance for the packaged device100can be greatly enhanced by also providing lateral shielding at the edges of the ceramic substrate106, as well as a ground plane underneath the flip-chip104.

In the example shown inFIG. 4, an electrical connection configuration112can include the conformal conductive coating102extending from the upper surface116of the ceramic substrate106to generally cover the side edges of the ceramic substrate106. Such conformal conductive coating102covering the side edges of the ceramic substrate106are shown to be in electrical contact with one or more conductive layers within the ceramic substrate106and extending to their respective edges of the ceramic substrate106. For example, conductive layers160,162are shown to be implemented so that their edges generally align with respective edges (150) of the ceramic substrate106. Accordingly, the conductive layers160,162are shown to be in electrical contact with the conformal conductive coating102. Thus, combined with the ground plane (in electrical contact with the conductive layers160,162), the conformal conductive coating102provides shielding functionality for the packaged device.

As shown inFIG. 4, the ceramic substrate106can include a plurality of layers and features130. Such layers and features can include, for example, dielectric layers, passive components (such as resistors, capacitors and inductors), conductor features (such as vias and traces), and a ground plane. In such a context, the example conductive layers160,162can be formed at selected lateral locations and/or at selected layers. In some embodiments, the conductive layers160,162can be formed by, for example, patterned printing of conductive material such as silver.

As also shown inFIG. 4, the packaged device100can include contact pads154that allow mounting of the packaged device100on a circuit board (e.g., a phone board) and facilitate electrical connections between the packaged device100and the circuit board.

FIG. 5shows an example of how a conductive layer such as the example layer160(also described in reference toFIG. 4) can be implemented so as to form an exposed edge along the edge150of the ceramic substrate106. In the example, the layer160is shown to include a conductive strip along each edge150. Such strips can be positioned along cut lines between neighboring units of ceramic substrate106defined in an array (e.g., in a panel). Upon singulation of the array into individual units, the resulting edges can form the edges150of the individual ceramic substrate106. Along the edges of the ceramic substrate106, the cut portions of the conductive strips160can form exposed conductive edges for forming electrical contacts with the conformal conductive coating102. As described in reference toFIG. 4, such a conformal conductive coating can include a portion that covers some or all of the edges of the ceramic substrate106and some or all of the corresponding exposed edges of the conductive strips160.

As shown inFIG. 5, the conductive strips160do not necessarily need to form a complete perimeter around the ceramic substrate106. For example, the corner portions indicated as164can have gaps that are dimensioned sufficiently small to provide shielding functionality. InFIG. 5, a plurality of vias170can be configured to provide various electrical connections and/or heat transfer functionalities.

FIG. 6shows that in some embodiments, a ceramic substrate106can be configured to yield an electrical connection112having one or more features as described herein. As shown, such a ceramic substrate can include a plurality of layers130and/or features as described herein. As also described herein, such a ceramic substrate can include one or more conductive features160that are within the ceramic substrate106and positioned to be at least partially exposed on the edges150.

In the example ofFIG. 6, the ceramic substrate106is depicted as having a generally 90-degree cut to define vertical edges150. In some embodiments, singulating operations can yield non-vertical surfaces along such edges. For example,FIG. 7shows that in some embodiments, an array of individual units (e.g.,106a,106b) of ceramic substrate can be processed and singulated along a cut line180. Such a singulation configuration can be facilitated by, for example, a V-shaped groove182formed along the delineation line180prior to the firing process when the substrate material is relatively soft. Upon completion of the firing process, the resulting hardened ceramic substrate can be singulated by, for example, breaking the individual units along the delineation line180. Such a breaking operation can be facilitated by the V-shaped grooves.

In such singulated ceramic substrates106a,106b, exposed portions of the conductive layers160along the surfaces184a,184bof the V-groove182can form electrical contacts with their respective conformal conductive coatings.

FIG. 8shows a process200that can be implemented to fabricate a packaged radio-frequency (RF) module. In block202, a ceramic substrate having a conductive layer and a ground plane can be formed or provided. The conductive layer and the ground plane can be electrically connected. In block204, a die can be mounted on the ceramic substrate. In block206, a conformal conductive coating can be formed over the die and in electrical contact with the conductive layer to thereby provide RF shielding for the die.

In some embodiments, the ceramic substrate can be in a form of a panel during at least some of the steps of the process200ofFIG. 8. Such a panel can include a plurality of ceramic layers arranged in a stack, and the panel can include an array of units defined by a grid of lines. It will be understood that such a grid of lines does not necessarily exist physically on the panel, and can be implemented as, for example, singulating instructions and/or data. Singulation along such a grid of lines can result in separation of the units into a plurality of individual units. In the context of the examples ofFIGS. 4-7where conformal conductive coating can be applied to the side walls of a ceramic substrate, such a coating step can be performed after the singulation step. In some embodiments, the mounting of the die can be performed on each of the units prior to the singulating step.

In the example described herein in reference toFIG. 4, a die mounted on a ceramic substrate106is depicted as an un-encapsulated flip-chip104. As described herein, such a ceramic substrate can facilitate grounding of a conformal conductive coating formed over the un-encapsulated flip-chip.

FIG. 9shows that in some embodiments, a ceramic substrate106having one or more features as described herein can also be utilized in packaging applications that utilize encapsulation of one or more components mounted on ceramic substrate106. For example, a shielded packaged device100can include a die210configured to provide RF functionality, mounted on the ceramic substrate106which can be configured in a similar manner as in the example ofFIG. 4. The die210is shown to be encapsulated by an overmold212, and a conformal conductive coating102is shown to generally cover the upper surface and side walls of the overmold212and the side walls of the ceramic substrate106. As described in reference toFIG. 4, conductive layers160,162can be configured to provide electrical connection between the conformal conductive coating102and a ground plane within the ceramic substrate106.

In some implementations, a device having one or more features described herein can be included in an RF device such as a wireless device. In some embodiments, such a wireless device can include, for example, a cellular phone, a smart-phone, a hand-held wireless device with or without phone functionality, a wireless tablet, etc.

FIG. 10depicts an example wireless device400having one or more advantageous features described herein. In the context of a module having one or more features as described herein, such a module can be implemented for a number of different applications. For example, as generally depicted by a dashed box100, a shielded packaged module can be implemented as an antenna switch module. It will be understood that such a module can include more or less components than depicted inFIG. 10.

Power amplifiers (PAs)310can receive their respective RF signals from a transceiver410that can be configured and operated in known manners to generate RF signals to be amplified and transmitted, and to process received signals. The transceiver410is shown to interact with a baseband sub-system408that is configured to provide conversion between data and/or voice signals suitable for a user and RF signals suitable for the transceiver410. The transceiver410is also shown to be connected to a power management component406that is configured to manage power for the operation of the wireless device. Such power management can also control operations of the baseband sub-system408.

The baseband sub-system408is shown to be connected to a user interface402to facilitate various input and output of voice and/or data provided to and received from the user. The baseband sub-system408can also be connected to a memory404that is configured to store data and/or instructions to facilitate the operation of the wireless device, and/or to provide storage of information for the user.

In the example wireless device400, outputs of the PAs310are shown to be matched (via respective match circuits306) and routed to an antenna416through a band selection switch308, their respective duplexers412and an antenna switch414. In some embodiments, each duplexer412can allow transmit and receive operations to be performed simultaneously using a common antenna (e.g.,416). InFIG. 10, received signals are shown to be routed to “Rx” paths (not shown) that can include, for example, a low-noise amplifier (LNA).

A number of other wireless device configurations can utilize one or more features described herein. For example, a wireless device does not need to be a multi-band device. In another example, a wireless device can include additional antennas such as diversity antenna, and additional connectivity features such as Wi-Fi, Bluetooth, and GPS.