Patent Application
20230352360
Various types of packages are available for electrical components, such as active and passive semiconductor devices, resistors, capacitors, and inductors, among others. The packages can both protect and secure the components and provide electrically conductive leads to make one or more electrical contacts with the components. Such packages can be surface mounted, through-hole mounted, or inserted into printed circuit boards, among other techniques. The type, size, lead style, structure, materials, and other characteristics of a package can be selected based on the type of components being housed within them, as well as the application for the components. For example, certain packages can be more or less suitable for components used in high power and high frequency applications.
Aspects of the present disclosure can be better understood with reference to the following drawings. It is noted that the elements in the drawings are not necessarily to scale, with emphasis instead being placed upon clearly illustrating the principles of the embodiments. In the drawings, like reference numerals designate like or corresponding, but not necessarily the same, elements throughout the several views.
A number of different packages are available for electrical components, including devices formed on semiconductor die. The packages can both protect and secure the components and provide electrically conductive leads to make one or more electrical contacts with the components. As examples, flat no-leads packages such as quad-flat no-leads (QFN) packages can be used to physically secure and electrically connect semiconductor devices and integrated circuits to printed circuit boards (PCBs). Flat no-leads packages are one of several types of packages that can be used to connect devices to PCBs without through holes. Packages including an air cavity are also used for semiconductor devices used for high power and frequency applications, because dielectric capacitances can be minimized, among other benefits. Air cavity packages can include leads and be mounted on PCBs, in through holes of PCBs, and in other configurations. Some packages are more suitable for components used in high power and high frequency applications, and the type, size, lead style, structure, materials, and other characteristics of packages can be selected and designed based on the types of components being housed within them, as well as the application for the components.
Among others, sufficient thermal dissipation is an important characteristic of high power radio frequency (RF) packages, particularly for packaging devices formed on Gallium Nitride (GaN), Silicon Carbide (SiC), and other high power density semiconductor materials. High power semiconductor die have been directly attached to package flanges or slugs made of metals. One fundamental problem with metal flanges has been the tradeoff between the thermal conductivity (TC) and the coefficient of thermal expansion (CTE) of the flanges. Typically, a higher TC for a flange material has been accompanied by a higher CTE, making the flange less compatible with the CTEs of GaN, SiC, and similar semiconductor materials.
Diamond is a unique material because it has a high TC and a low CTE. According to aspects of the embodiments, diamonds or diamond particles are incorporated into the flanges and slugs of high power RF packages. Composite materials for flanges according to the embodiments include diamonds or diamond particles and other metals, such as Silver (Ag), among others. These core materials can be tailored by modifying the diamond-to-metal ratio, diamond particle size, type of metal, total thickness, and plating metal layers above and/or below the diamond-metal core composite, to meet the needs of certain applications. The materials can be tailored for targeted TC, CTE, flatness, or roughness, producing surfaces compatible with certain die attach materials or joining processes.
A diamond composite flange is only one component of a functional RF package. Frames and conductive leads are also incorporated with the diamond composite flanges according to the embodiments, to form internal air cavities within the packages. Both pre-formed and molded frames can be used. Pre-formed window frames with conductive leads can be attached to flanges with plastic adhesives, as one example. The pre-formed frames can be sourced in different lead configurations for flexibility. Securing pre-formed frames to flanges using plastic adhesives is also a low temperature process, which can protect the diamond composite material of the flanges.
In the context outlined above, the embodiments described herein are directed to semiconductor device packages and methods of manufacture of such packages. In one example, a semiconductor device package includes a flange, a frame secured to a top surface of the flange, with the frame forming an air cavity bounded in part by the top surface of the flange, and at least one conductive lead that extends from outside the frame, through a portion of the frame, and is exposed within the air cavity for wire bonding. The flange incorporates a composite core material including diamond particles distributed in metal. The flange exhibits thermal conductivity greater than that of Copper (Cu), Aluminum Nitride (AlN), Copper Molybdenum (CuMo), Copper Tungsten (CuW), laminates of CuMo and/or CuW, and other materials. The flange also exhibits a coefficient of thermal expansion suitable for bonding semiconductor die including Gallium Nitride (GaN) and Silicon Carbide (SiC) materials to the flange.
In other examples, a leadframe and packages formed using the leadframe are described. Using the leadframe, several packages can be formed at one time. Further, electrical components can be placed within the packages by repositioning several devices at a time using the leadframe. After assembly, the packages can be separated from the leadframe. The packages can include a flange or slug incorporating the diamond composite materials described herein, a plastic frame that surrounds the flange and forms an air cavity, and a cover that encloses the air cavity. The package further includes one or more conductive leads of the leadframe that extend through the plastic frame and are exposed within the air cavity. The conductive leads can be relied upon to bond out components secured within the air cavity. Finally, a cover can be secured to enclose the air cavity.
Turning to the drawings,
Referring among
The package 10 also includes a number of conductive leads 31-34, each of which extends from outside the frame 30, through at least a portion of the frame 30, and is exposed in part within the air cavity inside the package 10. The semiconductor devices in the package 10 can be electrically coupled, using wire bonds or other means, to the exposed portions of the conductive leads 31-34 within the package 10, as described in additional detail below. The conductive leads 31-34 can be formed from Cu, Al, Tin (Sn), Ag, Au, Zinc (Zn), other metals, or any compositions thereof, and can be plated with Ag, Au, Ni, Pd, or other metals using full plating, spot-plating or other techniques.
The flange 20 can also serve as a conductive lead of the package 10, as the flange 20 is electrically conductive in some embodiments. Thus, a semiconductor device die including a transistor source metal layer on the bottom of the die can be electrically coupled to the flange 20. The flange 20 can act as a source contact or lead for the package 10 in that case. In other cases, the flange 20 can act as a heat sink but not an electrical contact, as described below.
The package 10 is designed with an aim to increase the thermal conductivity and heat dissipation from semiconductor devices packaged within the package 10. In one aspect, the flange 20 includes materials that exhibit high TC for dissipating heat more effectively than other types of materials. The materials of the flange 20 also exhibit CTE values matched for the reliable attachment of semiconductor die to the flange 20, without a large enough mismatch between the CTEs of the flange 20 and the die to result in mechanical separation under heating cycles. In one case, the materials in the flange 20 can be selected, based in part, so that the CTE of the flange 20 is matched to the CTE of a SiC substrate to the degree necessary for reliable attachment. In other cases, the materials in the flange 20 can be tailored to have a CTE matched to other substrate materials.
As described in further detail below, the flange 20 is embodied using a composite core material having a higher thermal conductivity than materials commonly used for flanges and heat slugs in semiconductor packages. The flange 20 can include a composite core material of diamond particles distributed in a metal or metal alloy. The diamond particles provide a high TC, as natural diamond has a TC of about 2200 W/mK, whereas Cu has a TC of about 398 W/mK. Enriched monocrystalline synthetic diamond has been shown to have an even higher TC than natural diamond, and the flange 20 can incorporate synthetic diamond particles. Various sizes and shapes of diamond particles can be used in the composite materials of the flange 20, to tailor the TC of the flange 20, the CTE of the flange 20, or other characteristics.
The diamond particles are mixed and distributed into a metal, such as Silver (Ag), Cu, Mo, or other suitable metals. The metal can also be selected to tailor the TC of the flange 20, the CTE of the flange 20, or other characteristics. In some cases, the diamond particles are mixed and distributed relatively evenly throughout the composite core material, although larger diamond particles can be used in some cases and placed at certain locations within the metal of the composite core material. The metal provides electrical conductivity for the flange 20, and the flange 20 can be relied upon as a conductive terminal of the package 10.
Referring to
The frame 30 is formed to have a ring or frame shape, with a central opening, as shown in
The frame 30 includes a central opening or aperture, which encircles the air cavity that is formed between the top surface 21 of the flange 20, the inner periphery of the frame 30, and the underside of the cover 40 in the package 10. The flange 20 and the frame 30 are secured together to create a seal between them. The bottom surface of the frame 30 can be secured to the top surface 21 of the flange 20 using an adhesive, such as epoxy or another plastic adhesive, using mechanical interlocks or interferences, using fasteners, or combinations thereof. In other cases, the bottom surface of the frame 30 can be secured to the top surface 21 of the flange 20 by brazing or soldering.
The bottom surface of the frame 30 can cover a periphery 21A of the top surface 21 of the flange 20. A portion of the periphery 21A is identified in
The frame 30 includes a raised platform 35 that extends around the central opening and periphery of the frame 30. As noted above, the frame 30 also includes the conductive leads 31-34, which are secured in place by the molded material of the frame 30. The conductive leads 31-34 can include apertures or openings (not shown) in the portions of the conductive leads 31-34 that are surrounded by the molded material of the frame 30. The molded material of the frame 30 can flow through the apertures during manufacture of the frame 30, to help hold the conductive leads 31-34 in place.
The conductive leads 31-34 extend from outside the frame 30, through at least a portion of the frame 30, and into the central opening of the frame 30. Portions of the conductive leads 31-34 are exposed at the level of the raised platform 35. Exposed portions 33A and 34A of the conductive leads 33 and 34 are shown in
A number of semiconductor die, including transistors, capacitor banks, and other circuit elements, can be attached and secured to the top surface 21 of the flange 20. Certain semiconductor die can be electrically coupled to the flange 20 itself. For example, a semiconductor device die including a transistor source metal layer on the bottom of the die can be electrically coupled to the flange 20. The flange 20 can act as a source contact or lead for the package 10 in that case. The semiconductor die can also be electrically coupled to the conductive leads 31-34 of the frame 30, such as to the conductive portions 33A and 34A of the conductive leads 33 and 34, using wire bonds or other means. Examples of semiconductor die in the package 10 are described below with reference to
The cover 40 can be formed from plastic or other materials similar to that of the frame 30. In other cases, the cover 40 can be formed using ceramic, glass, metal, or other materials. After the frame 30 is secured to the flange 20, the cover 40 can be secured to the frame 30. The bottom surface of the cover 40 can be secured to the top of the frame 30 using adhesives, such as epoxy or other plastic adhesives, plastic welding, heating, or melting processes, using mechanical interlocks or interferences, using fasteners, or combinations thereof. The materials used for the cover 40 can also be selected provide protection against vibrations, moisture, and other conditions for the components in the package 10, mechanical strength, adequate matching of the thermal expansion as compared to other materials in the package 10, and other relevant factors. In some cases, the cover 40 can be hermetically sealed to the frame 30, and the package 10 can be a hermetically sealed package.
In
In the example shown, the semiconductor die 60 includes a high power transistor amplifier, such as a transistor formed in GaN materials on a SiC substrate, as examples. According to the concepts described herein, the composite core materials of the flange 20 have a relatively high CT and, at the same time, a CTE that more closely matches the CTE of the SiC substrate than materials such as Cu. Thus, the flange 20 is particularly suitable for reliably dissipating heat from the transistor amplifier on the semiconductor die 60.
The semiconductor die 61 and 62 include one or more capacitors for input impedance matching. In some cases, the semiconductor die 61 and 62 can also include resistors to form resistor-capacitor networks for input impedance matching, among other circuit components. Together, the semiconductor die 61 and 62 can be relied upon for first- and second-harmonic termination, control, and input impedance matching for the transistor amplifier on the semiconductor die 60. Depending on the needs for input impedance matching, the semiconductor die 61 can be omitted, the semiconductor die 62 can be omitted, or both the semiconductor die 61 and 62 can be omitted.
After the groups of die 52 and 53 are secured to the top surface 21 of the flange 20 in the semiconductor device package 10, the die are electrically coupled to the conductive leads 31-34 of the frame 30 and to each other. Particularly, the bond wires 65 are coupled between the conductive lead 34 and bond pads on the semiconductor die 62. The bond wires 66 are coupled between bond pads on the semiconductor die 62 and bond pads on the semiconductor die 61. The bond wires 67 are coupled between bond pads on the semiconductor die 61 and bond pads on the semiconductor die 60. Additionally, the bond wires 68 are coupled between bond pads on the semiconductor die 60 and the conductive lead 32. Any suitable type and number of bond wires can be used, such as gold bond wires of suitable diameter or thickness. Additional bond wires can also be used to electrically couple the semiconductor die 60-62 in the column 50 with corresponding semiconductor die in the column 51, between stich pads on the die. In that way, the respective potentials at certain circuit nodes among the die can be matched and referenced with each other, helping to maintain stability.
The group of die 52 in the semiconductor device package 10 can operate collectively as a single three-terminal active device. Particularly, the group of die 52 can operate as a single common source transistor amplifier, with the conductive lead 34 acting as a gate input, the conductive lead 32 acting as a drain output, and the flange 20 acting as a common source. The group of die 53 can also operate collectively as another, single three-terminal active device in the semiconductor device package 10. The groups of die 52 and 53 can be used together to form a D-mode amplifier in some cases, although other amplifier configurations can be used.
In other cases, the semiconductor device package 10 can omit the group of semiconductor die 53 and conductive leads 31 and 33. In that case, the semiconductor device package 10 can appear as a single three-terminal active device having or consisting of only three terminals or package leads. In still other cases the semiconductor device package 10 can include additional columns of semiconductor die coupled together in groups. Further, the semiconductor device package 10 can include additional leads and additional groups of die, and other variations are within the scope of the embodiments.
A heatsink 72 is also positioned below the PCB 70, and the bottom surface 22 of the flange 20 is positioned against and contacts a top surface of the heatsink 72. The heatsink 72 can be embodied as a plate of Cu, Al, or other metal suitable for conducting heat away from the package 10. The flange 20 of the package 10 can be secured to the heatsink 72 in various ways. As examples, the flange 20 can be secured to the heatsink 72 using thermal paste, thermal epoxy, solder, or other suitable techniques. The package 10 can also be held in place with the flange 20 against the heatsink 72 using mechanical fasteners, clips, hold downs, or other means. Other packages incorporating flanges similar to the flange 20 can be secured to the heatsink 72 in other ways. The flange 20A shown in
The thickness “T” of the flange 20 can range among the embodiments. Example thicknesses for the flange 20 and other flanges described herein can range from 20-80 mils (i.e., thousands of an inch) as examples, although other thicknesses can be relied upon. Larger thicknesses, including over 80 mils, over 90 mils, or thicker can also be used. The thicknesses of the plating layers 83-86 can range from between 0.05-2 mils in thickness each, and other thicknesses can be relied upon. In other aspects, the ratio of diamond particles to metal in the core of the flange 20 can range, such as from a ratio of 30% diamond to 70% metal to a ratio of 70% diamond to 30% metal. These aspects of the flange 20 can be tailored by modifying the diamond-to-metal ratio, size of the diamond particles 81, type of metal 82, thickness “T,” and type and thickness of the plating metal layers 83-85, to meet the needs of certain applications. The materials can be tailored for targeted TC, CTE, flatness, or roughness, producing surfaces compatible with certain die attach materials or joining processes.
The metal 82 can be embodied as Ag, Cu, or Mo, among other metals, and Ag can be preferred for high electrical and thermal conductivity. The diamond particles 81 can be mixed and uniformly distributed into the metal 82, while the metal 82 is heated to a liquid state, and the shape of the core of the flange 20 can be established by pressing the mixture between hot plates, although other manufacturing approaches can be used.
The plating layers 83-86 can be deposited or formed over the major surfaces of the core, to help planarize the top and bottom surfaces 21 and 22. As one example, the plating layer 83 can include a layer of Nickel (Ni) deposited over a top of the core, and the plating layer 84 can include a layer of Gold (Au) deposited over the plating layer 83. Similarly, the plating layer 85 can include a layer Ni deposited over a bottom of the core, and the plating layer 86 can include a layer of Au deposited over the plating layer 84. Other metals can be used for the plating layers 83-86, however, including plating schemes using one or more layers of Ni, Au, Palladium (Pd), Cu, and other metals. The plating layers 83-86 can be formed by deposition of metal or other suitable approaches. The plating layers 83-86 can help to smooth out or planarize roughness due in part to the corners and edges of the diamonds 81 in the metal 82. A relatively large sheet of the diamond particles 81 in the metal 82 can be formed, including the plating layers 83-86, and individual flanges can be cut from the sheet. Alternatively, the diamond particles 81 and metal 82 can be formed into their final shape individually with appropriate tooling and then plating layers 83-86 can be added to all sides of the flange 20.
Due to the materials used, the flange 20 exhibits a higher TC than conventional types of materials, such as Cu, CuMo, CuMo laminates, and other materials commonly used for flanges and heat slugs in semiconductor packages. The diamond particles 81 offer very high TC, as natural diamond has a thermal conductivity of about 2200 W/mK, whereas Cu has a TC of about 398 W/mK and CuMo has a TC of about 220 W/mK. Enriched monocrystalline synthetic diamond has been shown to have an even higher TC than natural diamond, and the flange 20 can incorporate synthetic diamond particles. The metal 82 provides electrical conductivity for the flange 20, and the flange 20 can be relied upon as a terminal of the package 10 as described herein.
The flange 20 also exhibits a CTE that is better for packaging certain devices than other materials. For example, Cu has a CTE of about 17.6 ppm/° C., which is mismatched as compared to many semiconductor substrates and materials, such as GaN or SiC, which can be used to manufacture high power semiconductor devices. SiC has a CTE closer to 3 or 4 ppm/° C., and it can be difficult to reliably secure SiC die to Cu flanges, particularly when cycled in temperature. Flanges formed from CuMo, CuW, and other metals have CTEs that are more closely matched to SiC substrates but exhibit lower thermal conductivities, typically less than 250 W/mK. The CTE of the flange 20 according to the embodiments can range from 6-9 ppm/° C., which is more closely matched to that of SiC substrates, while at the same time having a TC greater than that of Cu. The flange 20 can exhibit a TC of greater than 400, 500, 600, 700, 800, 900, 1000 W/mK, or more, offering thermal benefits, depending on the amount of diamond in the flange 20, the metals in the flange 20, and other factors described below.
At reference numeral 90, the process includes forming or providing and, in some cases, preparing a flange incorporating the core materials described herein. For example, the flanges 20 or 20A can be sourced from a manufacturer or manufactured separately. The flanges 20 or 20A can also be modified or prepared in some cases, even if sourced from a vendor. For example, the periphery 21A of the flange 20 (see
At reference numeral 92, the process includes attaching one or more semiconductor die to the flange. For example, one or more semiconductor die can be secured to the top surface 21 of the flange 20 using thermal epoxy, solder, solder preforms, sintered-silver die attach, or other suitable means, as described above with reference to
At reference numeral 94, the process includes attaching or adhering a frame to the flange. For example, the bottom surface of the frame 30 can be secured to the top surface 21 of the flange 20 using an adhesive, such as epoxy or another plastic adhesive, using solder, using mechanical interlocks or interferences, using fasteners, or combinations thereof. The bottom surface of the frame 30 can cover a periphery 21A of the top surface 21 of the flange 20.
At reference numeral 96, the process includes bonding the devices attached to the flange at reference numeral 92 to the conductive leads of the flange attached at reference numeral 94. Referring again to
At reference numeral 98, the process includes adhering a cover to the frame. For example, the bottom surface of the cover 40 can be secured to the top of the frame 30 using adhesives, such as epoxy or other plastic adhesives, plastic welding, heating, or melting processes, using solder, using mechanical interlocks or interferences, using fasteners, or combinations thereof.
Turning to other examples,
The frame 130 can be formed by molding plastic or similar materials, such as polymers or polymer blends, with or without glass, carbon, or other reinforcements, among other materials. In the example shown in
The conductive leads 131 and 132 can be cut away from a larger leadframe assembly after construction of the package 100. The construction of the package 100 using a leadframe assembly is described in further detail below. The conductive leads 131 and 132 can be formed from Cu, Al, Sn, Ag, Au, Zn, other metals, or any compositions thereof, and can be plated with Ag, Au, Ni, Pd, or other metals using full plating, spot-plating or other techniques.
Similar to the package 10, a number of semiconductors devices, formed on semiconductor die, can be secured within the package 100. The semiconductor die can be secured within the package 100 either before or after the frame 130 is formed around the flange or slug 120. The semiconductor die can be secured to the top surface 121 of the flange 120 using thermal epoxy, solder, solder preforms, sintered-silver die attach, or other suitable means. Semiconductor die in the package 100 can be electrically coupled, using wire bonds or other means, to the exposed portions 131A and 132A of the conductive leads 131 and 132 within the package 100. The cover 140 can then be placed upon and secured to the raised platform 133 within the package 100, to enclose the air cavity.
Similar to the flange 20, the flange 120 includes a core of diamond particles distributed in metal, plating layers that form the top surface of the flange, and plating layers that form the bottom surface of the flange 120. The flange 120 can be formed as described above with reference to
Use of the leadframe 210 as a starting point for the manufacture of the packages 220-225 offers benefits, including higher assembly throughputs, lower cost, higher precision, and the ability to use the existing tool sets and equipment of manufacturers and suppliers. For example, the leadframe 210 can be used to grip, hold, and move a relatively large number of packages without repositioning them individually. Further, once the leadframe 210 is formed at a suitable level of precision, the relative spacing of each of the packages 220-225, once formed, is known. Thus, electrical components can be placed and interconnected within each of the 220-225 easily by automated machines, without the need to move and reposition the air cavity packages 220-225 individually.
During manufacturing, the leadframe 210 can be arranged into the correct relative position along with the flanges 230-235. Each of the flanges 230-235 can include the composite core materials and plating layers described above with reference to
The packages 220-225 can remain attached to the leadframe 210 during subsequent assembly steps. After assembly is complete, the individual packages 220-225 can be separated from the leadframe 210 by cutting or shearing the leadframe 210 at locations to separate the conductive leads 212A and 212B (and the other conductive leads) for each of the packages 220-225.
The downset facets 321A and 321B can be used to secure the flange 320 to the leadframe 310 before a mold is placed around them for the injection of the plastic frame or body of the package. In one example case, metal rivets, pins, or bolts can be inserted through the downset facets 321A and 321B to fasten the flange 320 to the leadframe 310. Other fastening means can be used, however, including solder, brazing, adhesives, and other bonds.
Once fastened together, semiconductor die can be secured to the flange 320 and wire bonded to the conductive leads 312A and 312B as described below, before a plastic frame is molded around the flange and the die. In later process steps, a mold can be placed around the leadframe 310 and the flange 320. The mold can be shaped to form a solid plastic package around the flange 320 and the semiconductor die, and plastic can be injected into the mold to form a continuous molded plastic frame or body of the package around the flange 320 and the semiconductor die to about the size of the bounding box 330. The package thus formed can be kept attached to the leadframe 310 during the remaining assembly processes. Example process steps for leadframe package device assembly or manufacturing according to this example described in further detail below with reference to
Alternatively, after the downset facets 321A and 321B are secured to the flange 320, a mold can be placed around the leadframe 310 and the flange 320. The mold can be shaped to form a plastic package around the flange 320, with an air cavity formed over the flange 320. Plastic can be injected into the mold to form a plastic frame or body of the package around the flange 230 with an air cavity formed over the flange 320. The package thus formed can be kept attached to the leadframe 310 during the remaining assembly process steps, including steps to secure semiconductor die to the flange 320 within the air cavity and to wire bond the die to the conductive leads 312A and 312B. Example process steps for leadframe package device assembly or manufacturing according to this example are described in further detail below with reference to
In
At reference numeral 402, the process includes forming a leadframe. For example, a leadframe similar to the leadframe 210 shown in
At reference numeral 402, the process can also include forming or providing flanges incorporating the core materials described herein. Flanges or slugs similar to the flanges 120, 230-235, or 320 can be sourced from a manufacturer or manufactured separately. The flanges can include the interlocking edge surface 123, and certain surfaces of the flanges can be roughened using laser etching, mechanical abrasion, chemical etching, or other techniques. For example, the peripheries of the flanges can be roughened using laser etching, mechanical abrasion (e.g., masked or unmasked sandblasting or abrasing), chemical etching, selective plating, or other techniques in some cases. The preparation of the flanges can help to strengthen bonds and connections with other materials in later process steps as described herein.
At reference numeral 404, the process includes arranging or aligning the flanges with the leadframe. As an example of that arrangement,
At reference numeral 406, the process includes securing or fastening the flanges and the leadframe together. Referring to
At reference numeral 408, the process includes placing the semiconductor die and other electrical components onto the flanges and securing the semiconductor die and electrical components to the flanges. Automated pick and place tooling can be used in this step. The process also includes wire bonding the die and components out to the exposed conductive leads within the air cavities of the packages. Automated wire bond machines can be used in this step. These steps can be performed or conducted as described above with reference to
At reference numeral 410, the process includes positioning the leadframe and the flanges, with the semiconductor die and electrical components secured to the flanges, into a mold for forming the frame of the packages. At reference numeral 412, the process includes forming a number of plastic frames or bodies around the flanges. As one example, the bounding box 330 in
At reference numeral 414, the process includes separating the packages from the leadframe. The packages can be separated by cutting or shearing the leadframe structure supports, to separate the conductive leads of each package away from the larger leadframe assembly.
At reference numeral 502, the process includes forming a leadframe. For example, a leadframe similar to the leadframe 210 shown in
At reference numeral 502, the process can also include forming or providing and, in some cases, preparing flanges incorporating the core materials described herein. Flanges or slugs similar to the flanges 120, 230-235, or 320 can be sourced from a manufacturer or manufactured separately. The flanges can also be modified or prepared in some cases, even if sourced from a vendor. For example, the flanges can be modified to include the interlocking edge surface 123, and certain surfaces can be roughened using laser etching, mechanical abrasion, chemical etching, or other techniques. The preparation of the flanges can help to strengthen bonds and connections with other materials in later process steps.
At reference numeral 504, the process includes arranging or aligning the flanges with the leadframe. As an example of that arrangement,
At reference numeral 506, the process includes securing or fastening the flanges and the leadframe together. Referring to
At reference numeral 508, the process includes positioning the leadframe and the flanges into a mold for forming the frame of the packages. The mold can be shaped to provide air cavities above or over the flanges in the resulting packages. At reference numeral 510, the process includes forming a number of plastic frames or bodies, with air cavities, around the flanges. As one example, the bounding box 330 in
At reference numeral 512, the process includes repositioning the packages formed at reference numeral 510 using the supporting leadframe. That is, once the air cavity packages are formed or molded around the leadframe and flanges at reference numeral 510, the surrounding leadframe can be used to move the packages without repositioning them individually. The leadframe and packages can be moved to machines for picking semiconductor die and other electrical components and placing the die and components into the air cavities and onto the flanges.
At reference numeral 514, the process includes placing one or more semiconductor die and other electrical components into the air cavities and onto the flanges, and securing the die and components to the flanges. Automated pick and place tooling can be used in this step. The process also includes wire bonding the die and components out to the exposed conductive leads within the air cavities of the packages. Automated wire bond machines can be used in this step. These steps can be performed or conducted as described above with reference to
At reference numeral 516, the process includes enclosing the air cavities of the packages. For example, covers can be secured over the air cavities of the packages as described herein. At reference numeral 518, the process includes separating the packages from the leadframe. The packages can be separated by cutting or shearing the leadframe structure supports, to separate the conductive leads of each package away from the larger leadframe assembly. In other cases, packages can be removed (e.g., cut or sheared away) from their surrounding leadframes before electrical components are secured and enclosed within those packages, but the leadframe offers the ability to easily move several packages at a time.
Power transistors formed on semiconductor die can be packaged using the embodiments described herein. Among other types, the transistors described herein can be formed as high electron mobility transistors (HEMTs), pseudomorphic high-electron mobility transistors (pHEMTs), metamorphic high-electron mobility transistors (mHEMTs), laterally diffused metal oxide semiconductor transistors (LDMOS), metal-insulator-semiconductor field effect transistors (MISFETs or MISHFETs), metal-oxide-semiconductor field effect transistors (MOSFETs).
The transistors described herein can be formed using a number of different semiconductor materials and semiconductor manufacturing processes. Example semiconductor materials include the group IV elemental semiconductor materials, including Silicon (Si) and Germanium (Ge), compounds thereof, and the group III elemental semiconductor materials, including Al, Gallium (Ga), Indium (In), and compounds thereof. Semiconductor transistor amplifiers can be constructed from group III-V direct bandgap semiconductor technologies, in certain cases, as the higher bandgaps and electron mobility provided by those devices can lead to higher electron velocity and breakdown voltages, among other benefits. Thus, in some examples, the concepts can be applied to group III-V direct bandgap active semiconductor devices, such as III-Nitride material devices (Aluminum (Al)-, Gallium (Ga)-, Indium (In)-, and their alloys (AlGaIn) based Nitrides), GaAs, InP, InGaP, AlGaAs, etc. devices. However, the principles and concepts can also be applied to transistors and other active devices formed from other semiconductor materials.
As used herein, the term “III-Nitride material(s)” or “Gallium Nitride material(s)” refers to any Group III element-nitride compound. Non-limiting examples of III-nitride materials include boron nitride (BN), aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), and thallium nitride (TIN), as well as any alloys including Group III elements and Group V elements, such as aluminum gallium nitride (Alx Ga(1-x) N), indium gallium nitride (Iny Ga(1-y) N), aluminum indium gallium nitride (Alx Iny Ga(1-x-y)N), gallium arsenide phosphide nitride (GaAsa Pb N(1-a-b)), aluminum indium gallium arsenide phosphide nitride (Alx Iny Ga(1-x-y) Asa Pb N(1-a-b)), among others. Typically, when present, arsenic and/or phosphorous are at low concentrations (e.g., less than 5 weight percent). The term “gallium nitride” or GaN semiconductor refers directly to gallium nitride, exclusive of its alloys.
According to certain embodiments, the substrates of the semiconductor devices described herein can include Silicon (Si) (i.e., a substrate containing the Si in any form). Examples of substrates comprising Si that can be used in various embodiments include, but are not limited to, SiC substrates, bulk Si wafers, Si-on-insulator (SOI) substrates, Silicon-on-sapphire (SOS) substrates, and separation by implantation of oxygen (SIMOX) substrates, among others. Suitable Silicon substrates also include composite substrates that include a Si wafer bonded to another material such as diamond, AlN, SiC, or other polycrystalline materials. Silicon substrates having different crystallographic orientations can be used, though single crystal silicon substrates can be preferred in certain, but not necessarily all, embodiments. In some embodiments, Silicon (111) substrates are used. A III-Nitride or GaN transistor can be a III-Nitride heterostructure FET (III-N HFET), a metal-insulator-semiconductor FET (MISFET or MISHFET), such as a metal-oxide-semiconductor FET (MOSFET). Alternatively, when implemented as an HFET, III-Nitride transistor can be a HEMT configured to produce a 2DEG.
The features, structures, and characteristics described above may be combined in one or more embodiments in any suitable manner, and the features discussed in the various embodiments are interchangeable in many cases. Although relative terms such as “on,” “below,” “upper,” “lower,” “top,” “bottom,” “right,” and “left” may be used to describe the relative spatial relationships of certain structural features, these terms are used for convenience only, as a direction in the examples. When a structure or feature is described as being “over” (or formed over) another structure or feature, the structure can be positioned over the other structure, with or without other structures or features intervening between them. When two components are described as being “coupled to” each other, the components can be electrically coupled to each other, with or without other components being electrically coupled and intervening between them. When two components are described as being “directly coupled to” each other, the components can be electrically coupled to each other, without other components being electrically coupled between them.
Terms such as “a,” “an,” “the,” and “said” are used to indicate the presence of one or more elements and components. The terms “comprise,” “include,” “have,” “contain,” and their variants are used to be open ended and may include or encompass additional elements, components, etc., in addition to the listed elements, components, etc., unless otherwise specified. The terms “first,” “second,” etc. are used only as labels, rather than a limitation for a number of the objects.
Although embodiments have been described herein in detail, the descriptions are by way of example. The features of the embodiments described herein are representative and, in alternative embodiments, certain features and elements can be added or omitted. Additionally, modifications to aspects of the embodiments described herein can be made by those skilled in the art without departing from the spirit and scope of the present invention defined in the following claims, the scope of which are to be interpreted to encompass modifications and equivalent structures.
