Patent Application
20220415763
The present invention relates to a lead frame based molded radiofrequency package, and to a Doherty amplifier and electronic device comprising the same.
Lead frame based packages are known in the art. The manufacturing process of these packages starts with providing a lead frame that comprises the leads for a plurality of packages. The leads are at that time still connected to a remainder of the lead frame. Typically, the packages are provided with heat conducting substrates, such as copper blocks, to which semiconductor dies are to be mounted. The lead frame is connected to the heat conducting substrates using connecting members. These connecting members may have a form of a metal tab extending from the remainder of the lead frame to corners of the substrate and are often referred to as tie-bars. There, a connection is made between the connecting members and the substrate, for example by means of a riveted connection, a welded connection, a glued connection or a soldered connection.
Using heat conducting substrates, the active circuitry on the semiconductor dies can be efficiently cooled. Typically, the lead frame is used for simultaneously manufacturing a plurality of packages wherein each package to be manufactured is associated with a respective substrate and a respective set of leads.
The lead frame with the substrates connected thereto is subjected to further processing. The exact sequence of processing steps depends on the type of package to be produced. A first type of packages will hereinafter be referred to as over-molded air cavity packages. In these packages, the lead frame with the substrates will be subjected to a molding step during which, for each package to be produced, a ring of solidified material is formed that provides a fixation of the leads relative to the respective substrate. As a next step, the semiconductor die(s) and optionally other electrical components for each package are mounted on the respective substrate and connection between the circuitry on the semiconductor die(s) and the leads is realized using one or more bondwires. As a final step, a lid is provided for each package to be produced, which lid is connected to the ring of solidified molding material to close off the package. In these packages, a cavity is therefore formed between the lid and the substrate in which the semiconductor die(s) and other optional electrical components are arranged.
It is noted that the steps of mounting the semiconductor die(s) and other electrical components and the step of applying the molding compound can be reversed.
In another type of package, hereinafter referred to as over-molded package, the semiconductor die(s) and other optional electrical components are mounted on the substrate and the connection between these components, die(s), and leads using one or more bondwires is realized before applying the molding material. In these packages, the semiconductor die(s), optional other electrical components, and bondwires are encapsulated or covered substantially fully by the molding material. Moreover, the solidified molding material also forms the outer surface of the package.
For both types of packages, one or more separation steps are performed to separate the individual packages from the processed lead frame. Hereinafter, the one or more separation steps will be jointly referred to as separating the package from the lead frame.
The abovementioned one or more separation steps may include punching, cutting, and/or pushing. After having separated the package from the lead frame, a part of the connecting member remains attached to the substrate. This part will hereafter be referred to as the first connecting member part, whereas the part that is still connected to the remainder of the lead frame will be referred to as the second connecting member part.
A common problem associated with packages of the abovementioned type is the limited amount of space inside the package for mounting components. The semiconductor die(s), or optional other components, are typically mounted on the substrate using a fixation material that is at least partially fluid during the mounting of these components. After mounting, the fixation material will solidify to provide an electrical, thermal, and mechanical connection to the substrate. However, the fixation material may also flow to regions outside of the placement area that was originally intended or desired for the semiconductor die or optional other electrical component(s). Consequently, different electrical components can only be arranged inside a single package if they are sufficiently far removed from each other. Otherwise, the fixation material or components thereof may flow out or bleed into other areas of the substrate. As the fixation material is typically conductive, a risk of electrical shorting components or semiconductor die(s) that are mounted or arranged in these other areas exists.
A first object of the invention is to provide a package in which the abovementioned problem associated with spreading or flowing of fixation material is eliminated or at least alleviated.
Another common problem associated with packages of the abovementioned type is the difficulty in obtaining sufficient electromagnetic shielding between different components that are mounted on the substrate. Package size requirements often dictate that the different components should be arranged as close to each other as possible. Such placement will however worsen the electromagnetic coupling between the components.
EP 2892076A2 discloses a Doherty amplifier having a main amplifier and a peak amplifier in between which an isolation wall is arranged to improve isolation between the main and peak amplifiers. As a first example of the isolation wall, the isolation wall may be an erect structure arranged on the substrate. In a further example, the isolation wall is provided with a base extending perpendicular to a main section of the isolation wall. This base can be fixedly attached to the substrate.
A drawback of this first example is that it requires an additional component in addition to the lead frame for manufacturing the semiconductor package. This additional component adds to the bill of materials and increases the number of handling steps.
In a second example, the isolation wall can be formed as a part of the lead frame. More in particular, the lead frame has a plurality of ground fingers that will be connected to a ground node in the final semiconductor package. The isolation wall is initially formed coplanar with a remainder of the lead frame. Prior to assembly of the semiconductor package, the isolation wall is bent transverse to the plane of the lead frame sheet. Links connecting the isolation wall to the ground fingers connects the isolation wall to ground.
A drawback of this second example is that it requires a complex manufacturing process for bending the isolation walls, in particular when multiple isolation walls need to be bent at the same time. Furthermore, additional ground leads are required for grounding the isolation wall. However, the lead configuration is often not dictated by the manufacturer of the semiconductor package but by the customer that incorporates the package in his or her design. Often dual source strategies are employed which would mean that multiple parties should follow the same lead design. Further to the above, adding ground leads will increase the size of the semiconductor package.
US 2015/0311131A1 discloses a semiconductor device having an isolation structure arranged between a first and second circuit to reduce electromagnetic coupling between these circuits. The device comprises a pair of ground connectors to which the isolation structure is coupled. Also in this embodiment, an additional component in addition to the lead frame for manufacturing the semiconductor package is required, thereby adding to the bill of materials and increasing manufacturing complexity and costs.
A second object of the invention is to provide a package in which the abovementioned problems are eliminated or at least alleviated.
According to a first aspect of the invention, the present invention addresses the first object of the invention by providing a lead frame based molded radiofrequency ‘RF’ package that comprises a substrate, a first electrical component arranged on the substrate, a second electrical component, and a plurality of leads that are arranged spaced apart from the substrate and fixed in position relative thereto by a solidified molding compound. At least some of the leads are preferably configured for inputting and outputting electrical signals to and from the package. Moreover, the leads were part of a lead frame prior to separating the package from the lead frame.
The substrate was physically and electrically connected to the lead frame using a plurality of spaced apart connecting members prior to separating the package from the lead frame. During the separating of the package from the lead frame each connecting member was divided, for example by means of cutting, punching or pushing, into a first connecting member part that remained connected to the substrate and a second connecting member part that remained connected to the lead frame.
The first and second electrical components are preferably each, independently from each other, a component chosen from the group consisting of a surface mounted device ‘SMD’, a dielectric having a passive component realized thereon, and a semiconductor die. Other electrical components having multiple terminals and which perform either an active function, e.g. amplification of a signal, or a passive function, e.g. impedance transformation, are not excluded. In some cases the terminals of such components are referred to as lands. The first and second electrical components could include impedance matching network components, such as capacitors and inductors, integrated, distributed or lumped, or amplifying components, such as single-stage or multi-stage amplifiers, or discrete transistors.
The first electrical component can be attached to the substrate using a fixation material that was in an at least partially liquid or fluid state during the attaching of the first electrical component to the substrate.
According to the invention, the package further comprises a frame part that physically connects to and extends from at least one first connecting member part, wherein the second electrical component is mounted and/or electrically connected to the frame part. Here, mounted to should be construed as the second electrical component being in physical contact with the frame part whereas electrically connected to should be construed as the second electrical component having an electrical connection, e.g. via a bondwire, with the frame part.
The frame part of the invention provides an elevated mounting platform relative to the substrate on which the first electrical component is arranged. Such mounting platform can be used to mount the second electrical component or to connect one or more bondwires. Consequently, the risk of the fixation material or components thereof spreading to the mounting platform of for example the second electrical component and creating undesired electrical connections between one or more terminals of the second electrical component, such as an electrical short between one of the terminals and another terminal or ground, can be prevented.
The at least one first connecting member part may be connected to the substrate using rivets, a welded connection, a glued connection, or a soldered connection. Such connections are typically made before arranging the first electrical component. More in particular, the lead frame, including the substrates and the connections between the substrates and the lead frame, typically forms an intermediate product that may be manufactured by a different company than the company that arranges the electrical components and finalizes the package.
A first connecting member part among the at least one first connecting member part may form a lead among the plurality of leads. It is noted that leads, prior to separating the package from a remainder of the lead frame, are connected to the remainder of the lead frame using connecting tabs. According to the invention, the lead(s) formed by the first connecting member part(s) may be connected to substrate using rivets, a welded connection, a glued connection, or a soldered connection. Furthermore, this lead or these leads may each comprise a downset to accommodate between the different height positions of the substrate and the leads. More in particular, all the leads of the package are typically at substantial the same height position relative to the substrate.
Additionally or alternatively, a first connecting member part among the at least one first connecting member part can be physically connected to the substrate at a corner of the substrate, although other positions are not excluded.
As stated above, connecting members may have a form of a metal tab extending from the remainder of the lead frame to corners or other parts of the substrate and are often referred to as tie-bars. In such case, one of the first connecting member parts may comprise a part of the tie-bar whereas the corresponding second connecting member part comprises another part of the tie-bar. Generally, the first connecting member part(s) will not be accessible from the outside of the package or will not extend from the outside of the package as much as the leads do. Furthermore, the first connecting member part(s), when originating from tie-bars, will generally not be physically and electrically connected on the outside of the package.
According to the present invention, an embodiment is possible wherein the frame part extends between a first connecting member part that is formed as a lead, and a first connecting member part that comprises a part of a tie-bar. Alternatively, the frame part extends between a pair of first connecting member parts that are each formed as a lead, or the frame part extends between a pair of first connecting member parts that each comprise a part of a respective tie-bar. The skilled person will appreciate that other combinations are equally possible within the scope of the invention.
The package may further comprise a space between a bottom surface of the frame part that faces the substrate and a top surface of the substrate that faces the frame part. The space may for example be a result of the bottom surface of the frame part being provided with recesses to thereby create spaces, for example in the form of cavities, in between the substrate and the frame part. Additionally or alternatively, the frame part may have an upper surface to which the second electrical component is mounted and/or electrically connected, wherein the frame part displays a step in a direction away from the substrate to allow the second electrical component to be arranged substantially parallel to the substrate.
The space(s) between the top surface of the substrate and the bottom surface of the frame part may at least be partially filed with the solidified molding compound. This provides an additional anchoring of the frame part relative to the substrate. However, it may equally occur that the fixation material or components thereof has/have at least partially spread into the space(s) between the frame part and the substrate. Even if the frame part is conductive, this need not result in undesired electrical connections. For example, if the second electrical component is a semiconductor die having a conductive substrate that needs to be grounded, it does not matter if the fixation material has spread such that it contacts the frame part. Other electrical terminals of the circuitry on the top of the semiconductor die are far removed from the fixation material or the components thereof due to elevated placement of the second electrical component by the frame part.
The frame part may comprise a plurality of stress relief slots. These slots may be at least partially filled by the solidified molding compound. This provides an additional anchoring of the frame part relative to the substrate.
The solidified molding compound may encapsulate the first and second electrical components and may form a lid or top surface of the package. This type of package corresponds to the over-molded package. Alternatively, the package may comprise a lid that is fixedly connected to the leads and/or to the solidified molding compound that fixedly connects the leads and the substrate, wherein a cavity is formed between the lid and the substrate in which the first and second electrical components are arranged. This type of package corresponds to the over-molded air cavity package. In this case, the solidified molding compound that fixedly connects the leads and the substrate may be ring-shaped.
The molding compound may comprise one or more from the materials chosen from the group consisting of thermo-harder and thermo-set materials. The fixation material may be one or more from the group consisting of solder, glue, and metallic sinter material such as silver sinter material. Other materials for the molding compound or fixation material are not excluded.
The frame part, the first connecting member part, the substrate, and the connection between the first connecting member part and the substrate may be conductive. This allows a grounded connection of one or more terminals of the second electrical component via the frame part as the substrate of the package is typically connected to a ground of the device or system the package is arranged in. Furthermore, the frame part, the first connecting member part it is connected to, and the corresponding second connecting member part may have been integrally connected prior to separating the package. For example, the frame part, the first connecting member part it is connected to, and the corresponding second connecting member part may have constituted a single metal part, such as a metal strip. Additionally or alternatively, the frame part may connect the first connecting member part to another first connecting member part. In this case, the frame part, the first and another first connecting member parts it is connected to, and the corresponding second connecting member parts may have been integrally connected prior to separating the package. In this manner, a dam or bridge is formed between the first connecting member part and the other first connecting member part.
The frame part may connect the first connecting member part to a lead among the plurality of leads. In this manner, the lead can be grounded inside the package without requiring additional internal connection such as bondwires.
The second electrical component may have a first and second terminal of which at least the first terminal is connected to the frame part. Hence, the first terminal can efficiently grounded.
The second electrical component may include a second semiconductor die that comprises a conductive substrate of which a first surface that faces the frame part forms a first terminal. A second terminal of the second semiconductor die is then formed on a second surface of the second semiconductor die opposite to the first surface. Additionally or alternatively, the first electrical component may comprise a first semiconductor die. This first semiconductor die may comprise a conductive substrate of which a first surface that faces the substrate part forms a first terminal. A second terminal of the first semiconductor die is then formed on a second surface of the first semiconductor die opposite to the first surface. One or more bondwires may be provided that extend between a bondpad or bondbar arranged on the second surface of the first semiconductor die and a bondpad or bondbar arranged on the second surface of the second semiconductor die.
The first semiconductor die may comprise an RF power transistor that is arranged on the first semiconductor die. The second semiconductor die may comprise one or more passive components, such as an integrated inductor or integrated capacitor, for example forming part of an impedance matching network for the RF power transistor.
The package may comprise a plurality of said first semiconductor dies, and a plurality of said power transistors arranged on the same or different dies among the plurality of first semiconductor dies. The plurality of RF power transistors may form a main amplifier and at least one peak amplifier of a Doherty amplifier. For example, the package may comprise two first semiconductor dies, each die having a power transistor arranged thereon. One of these transistors then forms a main amplifier and one a peak amplifier. These transistors need not be of equal size to allow an asymmetrical Doherty amplifier to be formed. However, embodiments are also possible in which the main and peak amplifiers are realized on a single first semiconductor die. The skilled person will further readily understand that this concept can be extended to multiple first semiconductor dies and multiple peak amplifiers.
The package may further comprise an auxiliary frame part that is electrically isolated from the substrate and the frame part by the solidified molding compound. The auxiliary frame part may have been connected to the lead frame prior to separating the package from the lead frame, and the second electrical component may be mounted on one side to the frame part and on another side to the auxiliary frame part. In this manner, a further mounting platform is realized for the second electrical component separate from the substrate. The auxiliary frame part may be conductive, and the second terminal of the second electrical component may be connected to the auxiliary frame part. Furthermore, the substrate may comprise a recess in which the auxiliary frame part is arranged. This recess is typically filled with solidified molding compound.
The auxiliary frame part may comprise a first frame part member and a second frame part member spaced apart from the first frame part member, wherein the first and second frame part members are electrically connected using a fourth electrical component such as a surface mounted device or a semiconductor die. Similarly, the conductive frame part may comprise a first frame part member and a second frame part member spaced apart from the first frame part member, wherein the first and second frame part members are electrically connected using a third electrical component such as a surface mounted device or a semiconductor die. In these embodiments, the conductive frame part and/or auxiliary frame part is/are not a continuous structure but display(s) a gap between the first and second frame part members. The third/fourth electrical component then spans the gap to electrically connect the first and second frame part members.
According to the first aspect, the present invention also provides a Doherty amplifier that comprises the package having the main and peak amplifiers as defined above. The Doherty amplifier may further comprise a Doherty splitter for splitting an input signal over an input of the main amplifier and an input of the at least one peak amplifier, and a Doherty combiner for combining signals outputted by the main and the at least one peak amplifiers.
The Doherty combiner may comprise an impedance inverter. The Doherty splitter and Doherty combiner may be configured to allow signals amplified by the main and the at least one peak amplifiers to be added in-phase at a combining node in the Doherty combiner. The second electrical component may form at least part of the Doherty combiner and/or Doherty splitter.
According to the first aspect, the present invention also provides an electronic device comprising the package or Doherty amplifier as defined above. This electronic device may be an RF power amplifier, preferably an RF power amplifier for a base station for mobile communications, or an RF power amplifier for a solid state cooking apparatus.
According to a second aspect of the invention, the present invention addresses the second object of the invention by providing a lead frame based molded radiofrequency ‘RF’ package, comprising a substrate, a first electrical component arranged on the substrate, a second electrical component arranged on the substrate, and a plurality of leads that are arranged spaced apart from the substrate and fixed in position relative thereto by a solidified molding compound. At least some of the leads are preferably configured for inputting and outputting electrical signals to and from the package, and they were part of a lead frame prior to separating the package from the lead frame.
The substrate was physically and electrically connected to the lead frame using a plurality of spaced apart connecting members prior to separating the package from the lead frame. Moreover, during the separating of the package from the lead frame, each connecting member was divided, for example by means of cutting, punching or pushing, into a first connecting member part that remained connected to the substrate and a second connecting member part that remained connected to the lead frame.
The first and second electrical components are preferably each, independently from each other, a component chosen from the group consisting of a surface mounted device ‘SMD’, a dielectric having a passive component realized thereon, and a semiconductor die. In addition, the first connecting member part, the substrate, and the connection between the first connecting member part and the substrate are conductive.
According to the second aspect of the invention, the package is characterized in that it further comprises a conductive frame part that physically and electrically connects at least one first connecting member part to another first connecting member part, wherein the first and second electrical components are arranged on opposing sides of the conductive frame part. The conductive frame part provides a conductive barrier that provides electromagnetic shielding between the first and second electrical components.
The Applicant has realized that the first connecting member parts, which generally have no electrical function, can serve as suitable mounting platforms for mounting the conductive frame part. A further advantage is that the first connecting member parts provide a convenient and low inductance path to ground within the package.
The conductive frame part, the at least one first connecting member part and the corresponding second connecting member part(s), the another first connecting member part and the corresponding second connecting member part were preferably integrally connected prior to separating the package. In this manner, the number of components needed for manufacturing the package does not increase. Furthermore, no additional manufacturing steps are required that are specific to the shielding and that cannot be combined with other steps that are required for manufacturing the package.
At least one first connecting member part among the at least one first connecting member part may form a lead among the plurality of leads and/or the another first connecting member part may form a lead among the plurality of leads. Additionally or alternatively, a first connecting member part among the at least one first connecting member part can be physically connected to the substrate at a corner of the substrate, although other positions on the substrate are not excluded.
The conductive frame part may comprise a central part extending from the at least one first connecting member part to the another first connecting member part. The conductive frame part may further comprise one or more side parts connected to a respective side of the central part, wherein the one or mode side parts are bent relative to the central part to provide a conductive wall between the first and second electrical components that preferably extends substantially perpendicular to the substrate.
The first connecting member parts can be connected to the substrate using rivets, a welded connection, a glued connection, or a soldered connection.
The package may further comprise a space between a bottom surface of the conductive frame part that faces the substrate and a top surface of the substrate that faces the conductive frame part. For example, the bottom surface of the conductive frame part may be provided with recesses to thereby create spaces, e.g. in the form of cavities, in between the substrate and the conductive frame part. These spaces may or may not provide a passage underneath the conductive frame part. Moreover, the space(s) between the top surface of the substrate and the bottom surface of the conductive frame part may be at least partially filled with solidified molding compound. This will provide an improved anchoring of the conductive frame part relative to the substrate.
The first and/or second electrical components may be attached to the substrate using a fixation material that was in an at least partially liquid state during the attaching of first and/or second electrical component to the substrate, wherein the fixation material or components thereof has/have at least partially spread into the space(s) between the conductive frame part and the substrate. For example, the fixation material is one or more from the group consisting of solder, glue, and metallic sinter material such as silver sinter material. It should be noted that the conductive frame part may provide a barrier to the fixation material such that the spreading of the fixation material or components thereof used for attaching the first electrical component will not extend to the second electrical component and vice versa.
The frame part may comprise a plurality of stress relief slots. These slots allow for local deformation of the conductive frame part to absorb any mechanical stress in the conductive frame part. These slots may be at least partially filled by the solidified molding compound.
The solidified molding compound may encapsulate the first and second electrical components and may form a lid or top surface of the package. Such package is referred to as an over-molded package. Alternatively, the package may comprise a lid that is fixedly connected to the leads and/or to the solidified molding compound that fixedly connects the leads and the substrate, wherein a cavity is formed between the lid and the substrate in which the first and second electrical components are arranged. Such package is referred to as an over-molded air cavity package. In this latter case, the solidified molding compound that fixedly connects the leads and the substrate may be ring-shaped.
The molding compound may comprise one or more from the materials chosen from the group consisting of thermo-harder and thermo-set materials. Additionally or alternatively, the package may further comprise one or more bondwires extending over the conductive frame part for making an electrical connection between the first and second electrical components. In this case, the conductive frame part may have a locally increased thickness to minimize a gap in between the one or more bondwires and the conductive frame part. In this embodiment, electrical connection between the first and second electrical component can be realized. Such connection does not prevent that parts of the first and second electrical component are shielded from each other. For example, the first and second electrical component may each comprise an integrated circuit, for example in the form of a semiconductor die having electrical circuitry arranged thereon. Sensitive parts of this circuitry on both electrical components may be shielded by the conductive frame part whereas other less sensitive parts of the circuitry on both electrical components may be connected to each other.
The conductive frame part may comprise a first frame part member and a second frame part member spaced apart from the first frame part member, wherein the first and second frame part members are electrically connected using a third electrical component such as a surface mounted device or a semiconductor die. Hence, in this embodiment, the conductive frame part does not comprise a single integral metal structure that spans the distance between the first connecting member parts it is connected to. Instead, a gap is intentionally created by dividing the conductive frame part in at least two frame part members. This gap can be spanned by the third electrical component to allow electrical connection between the first connecting member parts to which the conductive frame part is connected.
In the above, a first aspect and a second aspect of the invention were described. According to the first aspect, the package comprises a frame part that physically connects to and extends from at least one first connecting member part, wherein the second electrical component is mounted and/or electrically connected to the frame part. According to the second aspect, the package comprises a conductive frame part that physically and electrically connects at least one first connecting member part to another first connecting member part, wherein the first and second electrical components are arranged on opposing sides of the conductive frame part. It should be appreciated that both aspects of the invention may be combined. Put differently, the various embodiments presented above concerning the different embodiments may be combined to arrive at a new embodiment. The same holds for the dependent claims describing each aspect of the invention. For example, a dependent claim describing features corresponding to the first aspect may be combined with a dependent claim describing features corresponding to the second aspect.
For example, the conductive frame part of the second aspect may comprise a first frame part member and a second frame part member that are electrically connected using a first electrical component such as a surface mounted device or a semiconductor die. Additionally or alternatively, the package according to the second aspect may comprise a second electrical component such as a semiconductor die or surface mounted device having a first terminal and a second terminal, wherein the second electrical component is mounted with its first terminal to the conductive frame part, the first frame part member or the second frame part member.
Next, the present invention will be described by referring to the appended drawings, wherein:
Package 100 further comprises leads 102 that may be provided with slots 102A. Similarly, slots 110A may be provided in frame part 110 for stress relief purposes. Frame part 110 is preferably conductive.
In the embodiment shown in
In
When separating package 100 from lead frame body 11, dam bars 13 will be severed to mechanically isolate leads 102. In addition, connecting members 12 will be severed thereby creating first connecting member parts 103 that remain attached to a respective substrate 101 and a second connecting member parts 14 that remain connected to lead frame body 11.
As shown in
Frame part 210, which is conductive, comprises a plurality of downsets 211. Each downset 211 represents a mechanical deformation of frame part 210 to change the positioning thereof relative to substrate 201, see the side view in
As illustrated, a surface mounted device 230 is mounted such that one electrical terminal thereof is connected to frame part 210 and the other terminal thereof to a lead 202. Here, lead 202 extends from one side of package 200 to the opposing side of package 200. Furthermore, in this example, a semiconductor die 220, and more in particular circuitry arranged thereon, is connected to lead 202 using a plurality of bondwires 221.
It should be noted that
Due to downsets 211, a space 212 exists underneath frame part 210. More in particular, a space 212 exists between an upper surface of substrate 201 and a lower surface of frame part 210.
When semiconductor die 220 is mounted using a fixation material that is in an at least partially liquid state during the attaching of semiconductor die 220, a risk exists that this fixation material, or components thereof, spread(s) out to other areas in the package. As the fixation material is generally conductive, a risk of shorting other components, such as surface mounted devices or other semiconductor dies, may exist. Instead of or in addition to shorting components, other inadvertent electrical connections can result from the fixation material having spread out.
The abovementioned problem is alleviated with the embodiment in
Depending on the type of package, space 212 may be filled with fixation material or components thereof or solidified molding compound. For example, in over-molded air cavity packages, semiconductor die 220 may be mounted to substrate 201 prior to performing the molding process. In such case, space 212 may be partially filled with fixation material or components thereof and partially filled with solidified molding compound. Alternatively, when the order of molding and die attachment is reversed for over-molded air cavity packages, space 212 may be solely filled with solidified molding compound. For over-molded packages in which no lid is used, all parts and components as seen in
Using downsets 311, the vertical position of the conductive frame part 310 relative to substrate 301 can be changed from a position in which it lies directly on top of substrate 301, e.g. directly adjacent to rivet 304, to a position in which it lies in plane with leads 302. This is shown in more detail in the small cross sectional view illustrated in dashed box B1.
It should be noted that in these and other embodiments, conductive frame part 310, having been part of a lead frame is typically at least locally provided with a plating finish, e.g. an Ag spot finish, an Au finish, or a Ni—Pd—Au finish), to render the surface suitable for wire bonding.
In
Similar to
The cross sectional view of
A connection between components 620, 650 and leads 602 can be obtained using bondwires (not shown). Moreover, bondwires 622 may be used to provide an electrical connection between components 620, 650. Locally, i.e. underneath bondwires 622, second section 610B may have a locally increased thickness to minimize the gap in between bondwires 622 and second section 610B.
Also shown in
Auxiliary frame part 726 is electrically isolated from substrate 701. It may have been connected, preferably integrally, to the lead frame body prior to separating the package from the lead frame. Auxiliary frame part 726 is conductive and it contacts a first terminal of SMD 730 in
In
Packages 700A and 700B further comprise a semiconductor die 720 on which for example an RF power transistor is arranged. An input terminal of semiconductor die 720, e.g. a gate terminal of the power transistor or other electrical circuitry arranged on die 720, is connected to an input lead 702A using one or more input bondwires 760. Instead of a plurality of leads 702A, also one or two leads can be used. Similarly, an output terminal of semiconductor die 720, e.g. a drain terminal of the power transistor, is connected to an output lead 702B using a plurality of bondwires 761. At the same time, the output terminal of semiconductor die 720, or another terminal of semiconductor die 720, is connected to SMD 730. In the embodiment in
In the embodiment shown in
The series combination of SMDs 730 and the inductance associated with bondwires 762 (optional), with SMDs 730, and the connection between the second terminal of SMDs 730 and substrate 701 forms a series L-C network that is configured to act as an inductance at a given frequency in or close to the operational frequency bandwidth. Moreover, the effective inductance of the series L-C network is such that it resonates at the given frequency with the output capacitance of the power transistor arranged on semiconductor die 120. This will mitigate the influence the output capacitance has on RF performance. In this case, SMD 730 may for example be a DC blocking capacitor.
Space 812 underneath conductive frame part 810 may provide a passage, as shown in
On semiconductor die 920, which is mounted on substrate 901, an RF power transistor 920A is arranged which is represented by Q1 in
Output bondbar 971 is connected, using matching bondwires 962 to a first auxiliary bondbar 972. This latter bondbar is connected to one terminal of an integrated capacitor on semiconductor die 920, whereas the other terminal of this capacitor is grounded via the conductive substrate of semiconductor die 920.
Output bondbar 971 is also connected to output lead 902B using output bondwires 961. These bondwires are represented by L1 in
In
As can be seen, first auxiliary bondbar 972 is also connected, using matching bondwires 963, to a second auxiliary bondbar 973 that is arranged on second semiconductor die 925 wherein second semiconductor die 925 is mounted on a conductive frame part 910 that is connected to first connecting member parts 903 and to substrate 901 using rivets 904. On second semiconductor die 925, a high density integrated capacitor is provided, for example a trench capacitor. One terminal of this capacitor is connected to second auxiliary bondbar 973 and the other terminal is grounded via the conductive substrate of second semiconductor die 925 and conductive frame part 910. In
At the input side, input bondbar 970 is connected, using matching bondwires 964, to a third auxiliary bondbar 974. This bondbar is connected to one terminal of an integrated capacitor whereas the other terminal of this capacitor is connected to ground via the conductive substrate of semiconductor die 920. Third auxiliary bondbar 974 is also connected, using input bondwires 960 to input lead 902A. Bondwires 960, the integrated capacitor it is connected to, and bondwires 964 are represented by L5, C4, and L6 in
Now referring to
C2 is much larger than C1, C2 will, at a relatively low frequency, display a parallel resonance with the inductance associated with the biasing network. It should be noted that the invention is not limited to the particular position at which the biasing currents are introduced in the circuit.
The parallel resonance of C2 and inductance associated with the biasing line will introduce a first peak in the effective impedance seen at the drain of the transistor. Another resonance occurs at a higher frequency substantially corresponding to the resonance frequency of C1 and L3. By properly choosing the component values for L2, L3, C1, and C3 a desired impedance behavior can be realized in the frequency range typically associated with second order intermodulation products. In this range, the impedance seen by RF power transistor Q1 should be as low as possible to avoid performance degradation.
It should be noted that packages 900A and 900B may comprise a different matching network than the network shown in
The Doherty amplifier further comprises a Doherty combiner 981 that is connected in between a combining point C and the output of package 900A. Doherty combiner 981 comprises an impedance inverter. The inclusion of Doherty combiner 981 introduces a phase shift between signals outputted by the package 900A and package 900B. However, this phase shaft is compensated by the phase shift introduced by Doherty splitter 980 such that the signals outputted by packages 900A, 900B combine in-phase at combining point C.
In the example above, the dies on which the main and peak amplifiers were realized were housed in different packages. In an embodiment, these dies can be arranged in a package as described above. For example, these dies could be arranged in a single package wherein at least part of the circuitry required for the Doherty splitter and/or combiner is realized as a second semiconductor die or other component mounted to the conductive frame part. In a further or different embodiment, the abovementioned dies are electromagnetically shielded from each other using a conductive frame part as shown in
Package 1100 shown in
Package 1200 shown in
In package 1300 shown in
In packages 1200 and 1300, input leads 1202B, 1302B corresponding to both semiconductor dies 1320, 1350, are arranged on opposite sides of lead 1202A, 1302A that corresponds to the conductive frame part. A similar configuration of leads is used at the output side. This arrangement of leads further improves the isolation between the leads corresponding to semiconductor dies 1320, 1350.
It should be noted that packages 1200 and 1300 can also be embodied without using a molding compound. However, packages 1200 and 1300 are preferably manufactured using over-molding techniques with or without the formation of air cavities inside the package.
In the description above, the invention has been explained using a detailed description thereof. The skilled person will however understand that the prevent invention is not limited to these embodiments and that various modifications can be made without departing from the scope of the invention which is defined by the appended claims and their equivalents.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NL2019/050794 | 11/29/2019 | WO |
