Patent Description:
As is known, high voltage and/or high current power semiconductor devices are widely used in applications, for example of power conversion, where they are subject to high or very high voltage biases (with values even up to <NUM>-<NUM> V) and are passed by currents that may switch rapidly.

In these devices, special measures are therefore desired for forming the package, so as to provide a high electrical insulation, a suitable separation distance between the leads associated with gate, source and drain terminals, and a high heat dissipation to the outside.

Power semiconductor devices (MOSFETs or IGBTs in case of silicon substrates) of this type are formed in a die of semiconductor material (typically silicon, silicon carbide, silicon and gallium nitride -GaN- or gallium nitride only) which has a first main surface where a drain pad extends, and a second main surface, opposite to the first main surface, where source and gate pads extend.

The die is bonded to a conductive support called "leadframe", provided with drain, source and gate leads for outer connection of the device. To this end, the drain pad is generally bonded to a bearing portion of the leadframe, which also has a heat dissipation function; gate and source leads are coupled to the gate and, respectively, source pads through bonding wires or clamps or clips. The die/leadframe assembly is packaged in a mass of resin or other package insulating material. The package insulating material may be molded or laminated.

Traditional packages for power semiconductor devices are generally arranged vertically and comprise pins projecting downwards from a single bottom side of the package structure (generally of a parallelepiped shape), for electrical coupling to a Printed Circuit Board (PCB). A suitable heat sink, typically a metal foil, is coupled to the package structure, also arranged vertically with respect to the printed circuit board.

To obtain increasingly compact size as regards thickness, horizontal packages, for example of the Surface Mounting Device (SMD) type, which allow also a Dual Side Cooling (DSC), have been developed.

For example, <CIT> (corresponding to publication <CIT>) describes a solution where the die has a plurality of projecting gate regions, mutually separated by windows having source contact regions arranged therein. A dissipative plate, formed by an insulating multilayer, is arranged above the die and comprises a bottom metal layer counter-shaped to the projecting gate regions and having contact projections extending within the windows and electrically contacting the source contact regions.

The solution described above has a very compact structure even for power devices operating at high voltage (up to <NUM>-<NUM> V), with possible cooling on both sides and electrical insulation on one or two bigger sides, but it is quite complex to manufacture and requires a specific layout for each die size.

<CIT> discloses a direct chip attach structure having a bearing structure including a base section and a transverse section. The transverse section extends for a reduced portion of the package height and has not thermal function; the connection regions are extend at a distance from the package face and holes are formed for accommodating external solder balls.

<CIT>, <CIT> and <CIT> disclose semiconductor devices having an L-shaped bearing structure and contact regions protruding from the package.

<CIT> discloses a semiconductor package having a metal clip or plate for connecting the bottom side of the chip to the outside.

<CIT> discloses a semiconductor package formed of an upper and a lower leadframe.

The aim of the present invention is to provide a high voltage and/or high power packaged device which overcomes the drawbacks of the prior art.

According to the present invention, a packaged electronic device and a manufacturing process thereof are provided, as defined in the accompanying claims.

For a better understanding of the present invention, some embodiments thereof are now described, purely by way of non-limiting example, with reference to the accompanying drawings, wherein:.

<FIG> show a power device <NUM>, of semiconductor material, such as a MOSFET or IGBT, of Dual Side Cooling (DSC) type, with a first type of leadframe, with molded package and without projecting leads (leadless solution).

The power device <NUM> is integrated in a die <NUM>, represented only schematically, and having a first and a second face 2A, 2B, opposite to each other.

The die <NUM> is formed, in a known and not-represented manner, by a semiconductor body, formed by processing a substrate of silicon carbide or silicon and/or gallium nitride, and incorporating conductive regions, insulating regions, and suitably doped regions, in a manner known to a person skilled in the art.

In the example considered, the die <NUM> integrates a transistor <NUM>, for example a MOSFET or IGBT, at high voltage, represented only through an equivalent electric diagram, and having source terminal S, drain terminal D and gate terminal G. The transistor <NUM> may for example be of superjunction type, formed by a plurality of elementary units connected in parallel with each other, in a manner not shown and known to a person skilled in the art.

The drain terminal D is formed by a drain contact region <NUM>, generally of metal such as aluminum, extending on the first face 2A of the die <NUM>. The gate terminal G is formed by a gate contact region <NUM> generally of metal such as aluminum, extending on the second face 2B of the die <NUM>. The source terminal S is formed by one or more source contact regions <NUM> (one represented dashed, as extending behind the section plane), generally of metal such as aluminum, formed on the second face 2B of the die <NUM>.

The source <NUM> and gate contact regions <NUM> may have suitable shape and arrangement, according to the desired connection scheme, with the source contact regions <NUM> electrically insulated from the gate contact region <NUM>, in an manner obvious to a person skilled in the art.

A support or bearing structure (hereinafter called "leadframe") <NUM>, of metal, is bonded to the drain contact region <NUM>. For example, a conductive adhesive layer, such as a conductive solder, not shown, may be provided, which electrically and thermally connects the drain contact region <NUM> with the leadframe <NUM>.

In the embodiment shown in <FIG>, the leadframe <NUM> has the shape of an inverted L that has a base section <NUM> and a transverse section <NUM>. Both sections may have a thickness of about <NUM>-<NUM> microns.

The base section <NUM> of the leadframe <NUM> has a generally rectangular outer shape (see also <FIG>), extending mainly in an XY-plane of a Cartesian coordinate system XYZ having a first axis X (also referred to as the longitudinal or length direction), a second axis Y (also referred to as the width direction) and a third axis Z (also referred to as the thickness or height direction, <FIG>). The base section <NUM> has a first and a second side 16A, 16B and is bonded to the drain contact region <NUM> on the first side 16A thereof through a conductive adhesive layer, not shown.

The base section <NUM> may or may not have a planar structure (for example the first side 16A thereof may be recessed), with a greater area with respect to the die <NUM> to form a carrying base for the die <NUM> itself.

The transverse section <NUM> extends transversely, in particular perpendicularly, to the base section <NUM>, next to, but spaced from, the die <NUM>. The transverse section <NUM> has a higher height (along the third axis Z of the Cartesian coordinate system XYZ, in <FIG>) than the die <NUM>, approximately equal to the overall height of the power device <NUM> (except for the thickness of the relative lead, as discussed hereinafter), to form a thermal flow path, as explained in more detail hereinafter.

The die <NUM> and the leadframe <NUM> are embedded in a package <NUM> of molded type formed by a region of resin or other electrically insulating material.

In the embodiment shown, the package <NUM> is generally parallelepiped, and has a first main surface 5A (arranged at the top in <FIG>), a second main surface 5B (arranged at the bottom in <FIG>) and four side walls 5C-5F. Here, a first and a second transverse wall 5C, 5D (parallel to a YZ-plane of the Cartesian coordinate system XYZ) are mutually spaced in the length direction of the power device <NUM> and a first and a second longitudinal wall 5E, 5F (parallel to an XZ-plane of the Cartesian coordinate system XYZ) are mutually spaced in the width direction of the power device <NUM>.

In the embodiment shown, therefore, the main surfaces 5A and 5B are rectangular with long sides parallel to the first axis X.

The package <NUM> accommodates a front thermal dissipation region <NUM> extending between the first surface 5A of the package <NUM> and the second side 16B of the base section <NUM> of the leadframe <NUM>. In the embodiment shown, the front thermal dissipation region <NUM> is level with the first main surface 5A of the package <NUM> (see also <FIG>). For example, a surface 21A of the front thermal dissipation region <NUM> is substantially coplanar with a surface of the insulating material of the package <NUM>.

The package accommodates the front thermal dissipation region <NUM> extending along the second side 16B ( e.g., surface of the support structure <NUM> facing away from the die <NUM>) of support structure. The insulating material of the package <NUM> covers sidewalls or ends 21B of the front thermal dissipation region <NUM>.

The front thermal dissipation region <NUM> is of a material with good thermal conductivity and therefore thermally connects the leadframe <NUM> with the outside; for example, the front thermal dissipation region <NUM> may be of copper, or may comprise multiple layers of different materials, for example copper and conductive solder paste. The front dissipation region <NUM> may be referred to as a conductive layer or a thermally conductive layer.

In some applications, an electrically insulating, but good thermal conductive layer, covering the metal, may be provided. In another solution, the front thermal dissipation region <NUM> may comprise a nickel and gold layer, deposited through an ENIG (Electroless Nickel Immersion Gold) process, as discussed hereinafter with reference to <FIG>.

The package <NUM> also accommodates a gate lead <NUM> and one or more source leads <NUM> of electrically conductive material. In the example considered, there are three source leads <NUM>, see <FIG>.

Furthermore, the package <NUM> accommodates a gate connection region <NUM> and one or more source connection regions <NUM> (here three, only one represented with dashed line in <FIG>, as extending behind the section plane).

In detail, the gate lead <NUM> and the source leads <NUM> face the second main surface 5B of the package <NUM> (see also <FIG>); the gate connection region <NUM> extends between the gate lead <NUM> and the gate contact region <NUM>; and the source connection regions <NUM> extend between the source leads <NUM> and the respective source contact regions (or single region) <NUM>.

In the embodiment shown, the gate <NUM> and source leads <NUM> are mutually aligned in the width direction (along the second axis Y of the Cartesian coordinate system XYZ) and are arranged in proximity to the first transverse wall 5C of package <NUM>.

The gate <NUM> and source connection regions <NUM> are also of electrically conductive material, such as copper; they may be formed in a redistribution layer RDL or in any other known way and electrically connect the gate lead <NUM> with the gate contact region <NUM> and the source leads <NUM> with the source contact region(s) <NUM>, respectively.

The transverse section <NUM> of the leadframe <NUM> extends towards the second main surface 5B of the package <NUM>, up to in proximity thereof, and is in direct contact with a rear thermal dissipation region <NUM>.

The rear thermal dissipation region <NUM> faces the second main surface 5B, in proximity to the second transverse wall 5D of the package <NUM> (see also <FIG>).

The rear thermal dissipation region <NUM> is therefore in direct physical and electrical contact with the leadframe <NUM> and forms a drain lead (hereinafter it will therefore also be referred to as the drain lead <NUM>).

The gate <NUM>, source <NUM> and drain leads <NUM> extend here level with the second main surface 5B of the package <NUM>; alternatively, they may be depressed with respect to this second main surface 5B. Furthermore, they are of electrically conductive material and may be formed by multiple layers, for example of nickel and gold, as described hereinafter with reference to <FIG>.

In practice and as visible in <FIG>, the gate <NUM> and source leads <NUM> are arranged longitudinally remote from the drain lead <NUM>, and therefore at a large creepage distance D1. For example, with a power device <NUM> operating up to <NUM> V, the creepage distance D1 may be of <NUM> and with a power device <NUM> operating up to <NUM> V, the creepage distance D1 may be of <NUM>.

As shown in <FIG>, the power device <NUM> is here intended to be bonded with the second main surface 5B of the package <NUM> to a support <NUM>, for example a printed circuit board, of insulating material, provided with conductive tracks and with contact regions at the gate <NUM>, source <NUM> and drain leads <NUM>, in a per se known manner.

Furthermore, in <FIG>, a dissipative plate 4A is bonded to the first main surface 5A of the package <NUM> through an adhesive layer <NUM>, for example a solder paste or a thin layer of a material which provides good electrical insulation and a high thermal conductivity. In this manner, the adhesive layer <NUM> allows a good thermal dissipation of the power device <NUM>, and at the same time the electrical insulation of the dissipative plate 4A and the coplanarity in case of multiple power devices <NUM> having the same dissipative plate 4A placed thereon.

The leadframe <NUM> allows the drain terminal <NUM> of the transistor <NUM> to be electrically connected to the drain lead <NUM> placed on the same side of the gate <NUM> and source leads <NUM> (second main surface 5B of the package <NUM>), and a thermal dissipation path to be created towards the front side of the transistor <NUM> (first main surface 5A of the package <NUM>) through the front thermal dissipation region <NUM>, and towards the rear side of the transistor <NUM> (second main surface 5B of the package <NUM>) through the drain lead <NUM>, thus obtaining an effective Dual Side Cooling (DSC).

The cooling effect may also be increased by the presence of the dissipative plate 4A.

Therefore, the power device <NUM> has a high thermal dissipation; furthermore, it may work at high voltage due to the large creepage distance D1 and may be formed in a simple manner, not requiring complex dissipation structures having specifically designed portions or clips, as described hereinafter.

The power device <NUM> may be obtained by mounting a plurality of dice <NUM> on respective leadframes <NUM> still connected to each other, for example aligned along a single direction (monodirectional leadframe string forming a multiple support structure <NUM>, as shown in <FIG>). The drain leads <NUM> of the several devices may also already be bonded on the single leadframes <NUM>, as described hereinafter. Furthermore, in a not-shown manner, the front thermal dissipation regions <NUM> may already have been bonded on the second side 16B of the base section <NUM> of the leadframe <NUM>.

In detail, in the multiple support structure <NUM> of <FIG>, the leadframes <NUM> are arranged side by side and mutually connected by connection arms <NUM> which connect pairs of adjacent leadframes <NUM> at their transverse section <NUM>.

In particular, here, the connection arms <NUM> extend in proximity to the top edges (in <FIG>) of the transverse sections <NUM> of the leadframes <NUM>, remote to the base sections <NUM> of the leadframes <NUM>; alternatively, in this embodiment, they may be arranged at any height of the transverse sections <NUM>, when allowed by considerations of distance between regions exposed to different voltage (creepage distance).

In <FIG> the drain leads <NUM>, bonded on the transverse sections <NUM>, are also visible.

The multiple support structure <NUM> may be obtained from a metal sheet, for example of copper, by etching the metal sheet according to known etching processes to obtain the desired configuration of the base sections <NUM> and of the transverse sections <NUM>, and bonding the drain leads <NUM>.

In this embodiment, after bonding the dice <NUM>, the single leadframes <NUM> are divided; each leadframe <NUM>, with its die <NUM>, is inserted into a mold having the gate <NUM> and source leads <NUM> and the respective gate and source connection regions <NUM>, <NUM>, placed therein. Then, the package <NUM> is molded, obtaining the power device <NUM> of <FIG>.

As an alternative to the above, the power device <NUM> may be manufactured by molding a multiple package structure, which covers all the dice <NUM> and the leadframes <NUM>, still joined, and separating the single power devices <NUM> by cutting. In this case, projections at the connection arms <NUM> may extend up to the surface of the package <NUM>.

According to yet another embodiment, not shown, the multiple support structure may have a two-dimensional extension, array-like. Also in this case, the cutting of the leadframes may occur before or after molding the package <NUM>.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, with the same first leadframe type, molded package and projecting leads. Therefore, the power device <NUM> has a structure similar to the power device <NUM> of <FIG>, and will be described only with reference to the differences, using like reference numerals for like parts.

In detail, in the power device <NUM>, the package <NUM> is molded so that the transverse section <NUM> of the leadframe <NUM> is exposed to the outside, level with the second transverse wall 5D, as also visible in <FIG>.

Furthermore, in the power device <NUM>, the gate <NUM> and source leads <NUM> extend up to the first transverse wall 5C of the package <NUM>, and therefore have an exposed side that is level with the first transverse wall 5C.

In this embodiment, therefore, since the gate <NUM>, source <NUM> and drain <NUM> leads face side walls (5C, 5D) of the package <NUM>, soldering to the support <NUM> may also occur along these side walls 5C, 5D, and the solders may be easily viewed to verify the correctness and integrity thereof, as required in some applications, for example the automotive field.

Furthermore, here again the creepage distance D1 between the source leads <NUM> and the drain lead <NUM> is large, so that the power device <NUM> may work at very high voltages.

Furthermore, this embodiment is also characterized by an optimum cooling effect.

As for the power device <NUM>, the power device <NUM> of <FIG> may be provided with a dissipative plate (also called first dissipative plate) 4A which is bonded to the first main surface 5A of the package <NUM>; furthermore, a second dissipative plate 4B may be bonded to the transverse section <NUM> through an own adhesive layer <NUM>, for example a solder paste or a thin layer of a material having the characteristics indicated above for the adhesive layer <NUM>.

The power device <NUM> of <FIG> may be formed similarly to the power device <NUM>, with a suitable configuration of the gate <NUM>, source <NUM> and drain leads <NUM> and by suitably placing it in a mold for molding the package <NUM> and/or through special techniques to increase the exposure area on the first main surfaces 5A and on the second transverse walls 5D.

<FIG> show a power MOSFET device <NUM> of Dual Side Cooling (DSC) type, with the same first leadframe type, with laminated package and without projecting leads (leadless solution). Therefore, the power device <NUM> has a general structure similar to that of the power device <NUM> of <FIG>, and will be described only with reference to the differences, using like reference numerals for like parts.

In detail, the power device <NUM> of <FIG> is obtained through a lamination process (described hereinafter with reference to <FIG>) which leads to forming a package <NUM> comprising a packaging region <NUM>, a first insulating layer <NUM> and a second insulating layer <NUM>. The package <NUM> has a first main surface 105A (arranged at the top in <FIG>) and a second main surface 105B (arranged at the bottom in <FIG>), similar to the surfaces 5A and 5B of the package <NUM> of <FIG>.

The packaging region <NUM> here surrounds the die <NUM>, the transverse section <NUM> and only the top portion (at the bottom in <FIG>) of the base section <NUM> of the leadframe <NUM> and has a main surface <NUM> (in <FIG>, at the bottom).

The gate connection region <NUM> and the source connection region <NUM> (in dashed lines in <FIG>) are also embedded in the packaging region <NUM>, but the drain <NUM>, gate <NUM> and source leads <NUM> (<FIG>) are formed in the first insulating layer <NUM> (e.g., an insulating solder) extending on the main surface <NUM> of the packaging region <NUM>.

A second insulating layer <NUM> extends partially on the second side 16B of the base section <NUM> of the leadframe <NUM> and partially on the packaging region <NUM>, where it laterally surrounds the front thermal dissipation region <NUM>.

In <FIG> connection arms <NUM> (similar to the connection arms <NUM> of <FIG>) are also visible and deriving from cutting the leadframe <NUM>, as discussed hereinafter.

The embodiment of <FIG> is also characterized by high dissipation and large creepage distance D1 (<FIG>) and is therefore suitable for high voltage applications.

The power device <NUM> of <FIG> may be formed using manufacturing steps shown in <FIG>, <FIG>and described hereinafter.

In particular, <FIG> and <FIG> refer to the simultaneous manufacturing of several power devices <NUM> which are separated in a final cutting step. In particular, <FIG> show only one part of the overall structure, that is intended to form a single power device <NUM>, while <FIG> shows the overall structure before cutting.

Specifically, <FIG> shows the overall structure for manufacturing four power devices <NUM> arranged side by side in the width direction, along the first axis X of the Cartesian reference system XYZ, but in general any number of power devices <NUM> may be formed at the same time, depending on the techniques and machines used.

In detail, <FIG> show an intermediate structure obtained after bonding a die <NUM> (already provided with the drain <NUM>, gate <NUM> and source contact regions <NUM>) to the respective leadframe <NUM>. The leadframe <NUM> is here part of a leadframe bar or string visible in <FIG> and having the shape shown in <FIG> and therefore still referred to as multiple support structure <NUM>; unlike <FIG>, however, the rear drain conductive regions <NUM> have not yet been formed in the manufacturing step of <FIG>.

Returning to <FIG>, the die <NUM> is bonded to its leadframe <NUM> with its drain contact region <NUM> arranged downwards, while the gate <NUM> and source contact regions <NUM> are arranged upwards.

Then, <FIG>, the packaging region <NUM> is formed by laminating an insulating material, depositing and pressing successive sheets of material up to reaching the height of the transverse section <NUM> of the leadframes <NUM>.

In <FIG>, the packaging region <NUM> is holed from the main surface <NUM>, for example by laser, to form gate holes <NUM> and source holes <NUM>, intended to accommodate the gate <NUM> and source connection regions <NUM>.

Then, <FIG>, the gate holes <NUM> and the source holes <NUM> are filled, for example, by plating a conductive material, such as copper. In this step, in addition to forming the gate <NUM> and source connection regions <NUM>, a conductive layer <NUM> is also formed and covers the main surface <NUM> of the packaging region <NUM>.

Subsequently, <FIG>, the conductive layer <NUM> is shaped through one or more etching steps; in particular, it is removed throughout the thickness to electrically separate the portions in contact with the gate connection regions <NUM> and with the source connection regions <NUM> as well as with the leadframe <NUM> from each other, furthermore it is reduced in thickness where the gate, source and drain leads <NUM>, <NUM> and <NUM> are not intended to be formed.

Then, <FIG>, the first insulating layer <NUM>, for example a solder mask, is deposited above the conductive layer <NUM>, separating the parts to be electrically insulated, and is then shaped to form openings <NUM> where the gate <NUM>, source <NUM> and drain leads <NUM> are intended to be formed.

Furthermore, the second conductive layer <NUM> is deposited and shaped below the base section <NUM> of the leadframe <NUM>. In particular, the second conductive layer <NUM> forms a single large opening <NUM> which exposes most of the base section <NUM> of the leadframe <NUM>.

Then, <FIG>, the leads <NUM>, <NUM> and <NUM> and the front thermal dissipation region <NUM> are formed. To this end, for example, an ENIG (Electroless Nickel Immersion Gold) process is used, including a galvanic nickel growth and formation of a thin gold layer obtained by immersion, to improve soldability and non-oxidability.

In this manner, an intermediate structure <NUM> shown in <FIG> is obtained; the intermediate structure <NUM> is formed by a plurality of power devices <NUM> arranged side by side, bonded to the multiple support structure <NUM> (still undivided) and mutually connected by parts of the packaging region <NUM> and of the first and second insulating layers <NUM>, <NUM> as well as by the connection arms <NUM>.

After possible marking operations, not shown, the intermediate structure <NUM> is cut along cutting lines represented by arrows <NUM> in <FIG> to obtain the single power devices <NUM> of <FIG>.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, with the same first type of L-shaped leadframe, laminated package and projecting leads.

Therefore, the power device <NUM> has a general structure similar to the power device <NUM> of <FIG>, but gate and source leads <NUM>, <NUM> (<FIG>) as well as transverse section <NUM> of the leadframe <NUM> arranged similarly to what has been described with reference to <FIG>.

In particular, in <FIG>, the gate and source leads <NUM>, <NUM> are arranged to face, in particular level with, a transverse wall, herein referred to as the first transverse wall 105C, by analogy to the power device <NUM> of <FIG>, and the transverse section <NUM> of the leadframe <NUM> is arranged to face, in particular level with, an opposite transverse wall, herein referred to as the second transverse wall 105D.

This solution is also characterized by a large creepage distance D1 and is particularly suitable for automotive applications and where it is desired to have leads extending also on side walls (such as the first and the second transverse walls 105C, 105D) for obtain an increase in the solder area and/or a better inspectability of the solder to a support, for example a printed circuit board, such as the support <NUM> shown in <FIG>.

The power device <NUM> of <FIG> may be formed using the same manufacturing process described above with reference to <FIG>, <FIG>, through suitable sizing and arrangement of the different regions and/or by providing suitable steps for forming transverse parts of the gate and source leads <NUM>, <NUM> and of the transverse section <NUM> of the leadframe <NUM>.

As shown in <FIG>, the surface 21A of the front thermal dissipation region <NUM> is substantially coplanar with a surface 107A of the second insulating material <NUM>. The sidewalls 21B of the front thermal dissipation region <NUM> are covered by the second insulating material <NUM>.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, with a second leadframe type, with molded package and without projecting leads (leadless solution).

The power device <NUM> has a structure similar to the power device <NUM> of <FIG>, and will be described only with reference to the differences, using like reference numerals for like parts.

In detail, in <FIG>, the leadframe, here indicated by <NUM>, has the shape of an inverted C in the section plane of <FIG>, due to the presence of a second transverse section <NUM>, in addition to the transverse section <NUM> (hereinafter referred to as the first transverse section <NUM>) already present in the leadframe <NUM> of <FIG> (see also <FIG>).

The second transverse section <NUM> extends from an edge of the base section (here indicated by <NUM>) opposite (in the length direction parallel to the first axis X) to the edge of the first transverse section <NUM> to extend adjacent to and at a distance from the die <NUM>, on the opposite side with respect to the first transverse section <NUM>, as also visible in <FIG>, which shows a plurality of leadframes <NUM>, not yet divided.

The second transverse section <NUM> has a lesser height with respect to the first transverse section <NUM>, for example approximately equal to the die <NUM>. The second transverse section <NUM> has an end surface 218A here approximately level with the die <NUM>. However, this alignment is not essential and the second transverse section <NUM> might be a little higher or lower than the die <NUM> in the height direction of the power device <NUM> (along third axis Z).

A thermal connection structure <NUM> extends between the end surface 218A of the second transverse section <NUM> and the second main surface 5B of the package <NUM>. The thermal connection structure <NUM> is electrically insulating, but thermally conductive, to create a third thermal dissipation path from the die <NUM> to the second main surface 5B of the package <NUM>, in addition to the thermal dissipation path towards the front side of the power device <NUM>, through the front thermal dissipation region <NUM> (first thermal dissipation path), and to the thermal dissipation path towards the rear side of the power device <NUM>, through the first transverse section <NUM> of the leadframe <NUM> and the drain lead <NUM> (second thermal dissipation path).

The thermal connection structure <NUM> may be formed, for example, by a DBC (Direct Bonded Copper) multilayer comprising a first and a second metal layer <NUM>, <NUM> and an intermediate insulating layer <NUM>, for example of ceramic such as alumina (Al<NUM>O<NUM>), aluminum nitride (AlN) or beryllium oxide (BeO).

In the example shown, the thermal connection structure <NUM> is bonded to the end surface 218A of the second transverse section <NUM> through an adhesive layer <NUM>; a thermal continuity region <NUM> extends between the thermal connection structure <NUM> and the second main surface 5B of the package <NUM>, facing, in particular level with, the second main surface 5B, to favor soldering with a carrying substrate, for example the support <NUM> of <FIG>. The thermal continuity region <NUM> further completes the third thermal dissipation path towards the second main surface 5B of the package <NUM>.

In the example shown, the thermal continuity region <NUM> may be formed like the gate <NUM>, source <NUM> and drain leads <NUM>, for simplicity of manufacture, even if it has no electrical function.

The power device <NUM> of <FIG> is characterized by a high thermal dissipation capacity, due to the three thermal dissipation paths, a large creepage distance (given here again by the distance D1 between the source leads <NUM> and the drain lead <NUM>). In particular, here, the second transverse section <NUM> of the leadframe <NUM>, having a lesser height with respect to the first transverse section <NUM>, terminates at a distance from the gate <NUM> and source leads <NUM>.

The power device <NUM> of <FIG> may be formed similarly to what described for the power device <NUM> of <FIG>, using the multiple support structure <NUM> of <FIG>. In detail, in <FIG>, multiple structure support <NUM> forms a monodirectional string of leadframes <NUM>, having dice <NUM> already bonded thereto, prior to molding the package <NUM> and cutting into single power devices <NUM>.

In particular, in the multiple support structure <NUM> of <FIG>, the leadframes <NUM> are arranged side by side and mutually connected by connection arms <NUM> which connect pairs of adjacent leadframes <NUM> at the transverse section <NUM> thereof.

In a not-shown manner, similarly to <FIG>, the drain leads <NUM> and the front thermal dissipation regions <NUM> may already be bonded on the multiple support structure <NUM>. Furthermore, here, in a not-shown manner, the thermal connection structures <NUM> of the different power devices <NUM> may already be bonded on the multiple support structure <NUM>.

Also for the power device <NUM> of <FIG>, the multiple support structure <NUM> with the mounted dice <NUM> may be cut prior to molding the package <NUM> or subsequently.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, having the second type of inverted C-shaped leadframe (leadframe <NUM>), molded package and projecting leads. Therefore, the power device <NUM> has a structure similar to that of the power device <NUM> of <FIG>, but the source, gate and drain leads face the side walls of the package <NUM>, similarly to the power device <NUM> of <FIG>.

In this case, as visible in particular in <FIG>, unlike the power device <NUM> of <FIG> and the power device <NUM> of <FIG>, the gate leads <NUM> face the first longitudinal wall 5E and the source leads <NUM> face the second longitudinal wall 5F.

Furthermore, here again the transverse section <NUM> of the leadframe <NUM> is arranged level with the second transverse wall 5D.

In the embodiment shown, furthermore, instead of three distinct source leads <NUM>, only one is provided.

The solution of <FIG> is also characterized by a large creepage distance D1 and high thermal dissipation; it is also particularly suitable for automotive applications, as discussed hereinabove.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, having the second type of inverted C-shaped leadframe (leadframe <NUM>), laminated package and without projecting leads (leadless solution).

The power device <NUM> has a general structure similar to the power device <NUM> of <FIG>, but is obtained through a lamination process similar to the one previously described with reference to <FIG> and <FIG>.

The power device <NUM> is then enclosed in a package <NUM> of laminated type, has the thermal connection structure <NUM> with the bonding region <NUM> extending thereon, and has gate <NUM> and source terminals <NUM> facing only the second main surface 105B of the package <NUM>.

The solution of <FIG> is also characterized by a large creepage distance D1 and high thermal dissipation.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, with the second type of inverted C-shaped leadframe (leadframe <NUM>), laminated package and with projecting leads.

Therefore, the power device <NUM> has a general structure similar to the power device <NUM> of <FIG>, but the gate and source leads <NUM>, <NUM> (<FIG>) as well as the first transverse section <NUM> of the leadframe <NUM> face the side walls of the package <NUM>, similarly to what described with reference to <FIG>. In this embodiment, the second transverse section <NUM> may also face the first transverse wall 105C, if the distance of its lower exposed edge, calculated along the side profile of the package <NUM>, from the gate and source leads <NUM>, <NUM> is larger than or equal to the creepage distance D1 (<FIG>).

In particular, here the gate and source leads <NUM>, <NUM> face a respective side wall; specifically, the gate lead <NUM> is arranged level with the first longitudinal wall, here indicated by 105E (<FIG>), and the source lead <NUM> (here only one) is arranged level with the second longitudinal wall, here indicated by 105F (<FIG>). Furthermore, the first transverse section <NUM> of the leadframe <NUM> is arranged level with the second transverse wall 105D.

<FIG> refer to a power device <NUM> of Dual Side Cooling (DSC) type, with a third type of leadframe (see also <FIG>), with molded package and without projecting leads (leadless solution).

The power device <NUM> has a general structure similar to the power device <NUM> of <FIG>, and will be described only with reference to the differences, using like reference numerals for like parts.

In detail, see in particular <FIG>, in the power device <NUM>, the leadframe, here indicated by <NUM>, has the shape of an inverted cup o C-shape with a projecting wall; in practice, with respect to the first embodiment (leadframe <NUM>, used in power devices <NUM>, <NUM>, <NUM> and <NUM>), here the leadframe <NUM> has a delimitation wall <NUM>, which extends to form a C (in plan view) from the base section, here indicated by <NUM>, and runs along three sides of the rectangular shape of the base section <NUM>. Here, the delimitation wall <NUM> connects with its ends to the transverse section (here indicated by <NUM>). In practice, together with the transverse section <NUM>, the delimitation wall <NUM> defines a recess <NUM> (<FIG>) accommodating the die <NUM> therein.

Alternatively to the above, the delimitation wall <NUM> may have ends arranged in proximity to the transverse section <NUM>, without contacting it directly.

The delimitation wall <NUM> has a smaller height than the transverse section <NUM>, for example equal to the height of the die <NUM>, even if it might be different.

A thermal connection structure <NUM>, thermally conductive but electrically insulating, extends (with reference to <FIG>) along and in contact with the delimitation wall <NUM>. The thermal connection structure <NUM> has a structure similar to the thermal connection structure <NUM> and may be formed here again by a DBC (Direct Bonded Copper) multilayer comprising (<FIG>) a first and a second metal layer <NUM>, <NUM> and an intermediate insulating layer <NUM>.

The thermal connection structure <NUM> has a C-shape of similar to the delimitation wall <NUM> (<FIG>), but shorter arms, to extend at a distance from the transverse section <NUM> and thus be electrically connected to the leadframe <NUM> only with its first metal layer <NUM> (<FIG>). Alternatively, the thermal connection structure <NUM> may be formed by disconnected portions.

Similarly to the embodiment of <FIG>, the thermal connection structure <NUM> may be bonded to the delimitation wall <NUM> through an adhesive layer <NUM>.

Thermal continuity regions 427A-427B extend in contact with the thermal connection structure <NUM> (<FIG>) and may be formed like the rear thermal dissipation region <NUM> and the gate <NUM> and source leads <NUM>.

In the embodiment shown (see in particular <FIG>) three thermal continuity regions 427A-427B are provided, one for each side of the C-shape of the thermal connection structure <NUM>. In particular, a first thermal continuity region 427A is arranged on the side of the thermal connection structure <NUM> farther from the transverse section <NUM> of the leadframe <NUM> and is similar to the thermal continuity region <NUM> of <FIG>. Two second thermal continuity regions 427B are arranged on the arms of the C-shape of the thermal connection structure <NUM> which extend longitudinally (in parallel to the first axis X), are directed toward the transverse section <NUM> and are spaced from the first thermal continuity region 427A so that the gate <NUM> and source leads <NUM> may extend in the area between the first thermal continuity region 427A and the second thermal continuity regions 427B (<FIG>).

The power device <NUM> may be generally made as previously described for the power device <NUM> of <FIG>. In particular, see also <FIG>, the thermal connection structure <NUM> may be bonded to the leadframe <NUM> when the leadframe <NUM> is still connected to adjacent leadframes <NUM> (not shown in <FIG>, but possibly arranged side by side, similarly to what described with reference to <FIG>). Similarly, <FIG>, the thermal continuity regions 427A-427B may be bonded to the thermal connection structure <NUM>, prior to cutting the multiple support structure (similar to the homonymous structure <NUM> of <FIG>) and molding the package <NUM>. Alternatively, the thermal connection structure <NUM> and the thermal continuity regions 427A-427B may be bonded to the leadframe <NUM> after cutting the multiple support structure and prior to molding the package <NUM>.

In the power device <NUM>, the creepage distance is given by the distance D2 between the second thermal continuity regions 427B and the source leads <NUM> and by the distance D3 between second thermal continuity regions 427B and the drain lead <NUM>.

Accordingly, the power device <NUM> is characterized by a very high thermal dissipation capacity, due to two further thermal dissipation paths in proximity to the longitudinal walls 5E, 5F, and formed by the arms of the C-shape of the thermal connection structure <NUM> and by the second thermal continuity regions 427B. Due to the shorter creepage distances, the power device <NUM> is suitable for low voltage applications (e.g., up to 300V), depending on the overall size of the package and the sum of the distances D2 and D3.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, having the third type of inverted cup-shaped leadframe (leadframe <NUM>), molded package and projecting leads. Therefore, the power device <NUM> has a structure similar to the power device <NUM> of <FIG>, but the source and gate leads <NUM>, <NUM> face the longitudinal walls 5E, 5F of the package <NUM> and the drain lead <NUM> faces the second transverse wall 5D, similarly to the power device <NUM> of <FIG>.

Also in this case, as visible in particular in <FIG>, the gate leads <NUM> are arranged side by side, in particular level with the first longitudinal wall 5E, and the source leads <NUM> are arranged side by side, in particular level with the second longitudinal wall 5F.

Furthermore, here again the transverse section <NUM> of the leadframe <NUM> is arranged side by side, in particular level with, the second transverse wall 5D.

In the embodiment shown, furthermore, three distinct source leads <NUM> are provided, one of which faces the second longitudinal wall 5F.

The solution of <FIG> is also characterized by a very high thermal dissipation capacity; it is also particularly suitable for automotive applications and for low voltage applications, as discussed hereinabove.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, having the third type of inverted cup-shaped leadframe (leadframe <NUM>), laminated package and without projecting leads (leadless solution).

The power device <NUM> is then enclosed in a package <NUM> of laminated type, has the thermal connection structure <NUM> thermally coupled to the thermal continuity regions 427A-427B and has gate and source terminals <NUM>, <NUM> facing only the second main surface 105B of the package <NUM> (<FIG>).

The solution of <FIG> is also characterized by a very high thermal dissipation.

<FIG> show a power device <NUM> of Dual Side Cooling (DSC) type, with the third type of inverted cup-shaped leadframe (leadframe <NUM>), laminated package and with projecting leads.

Therefore, the power device <NUM> has a general structure similar to the power device <NUM> of <FIG>, but the gate and source leads <NUM>, <NUM> (<FIG>) as well as the transverse section <NUM> of the leadframe <NUM> face the side walls of the package <NUM>, similarly to what described with reference to <FIG>.

In particular, here the gate lead <NUM> is arranged side by side with the first longitudinal wall 105E, one of the source leads <NUM> is arranged at a side of the second longitudinal wall 105F and the transverse section <NUM> of the leadframe <NUM> is arranged at a side of the second transverse wall 105D.

The solution of <FIG> is also characterized by a very high thermal dissipation; it is also particularly suitable for automotive applications, as discussed hereinabove.

<FIG> shows a variation of the power device <NUM> of <FIG>, wherein the thermal connection structure, here indicated by <NUM>, has a transverse portion <NUM> to improve the electrical insulation of the thermal connection structure <NUM> from the transverse section <NUM> of the leadframe <NUM>.

In practice, the transverse portion <NUM> extends from the longitudinal end, close to the transverse section <NUM>, of the thermal connection structure <NUM> in direction of the second main surface 5B of the package <NUM>, so that the second metal layer (here indicated by <NUM>) no longer faces the transverse section <NUM> of the leadframe <NUM>, but its end faces the second main surface 5B of the package <NUM> (as well as the corresponding ends of the first metal layer and of the intermediate insulating layer, here indicated by <NUM> and <NUM>, respectively). In this manner, the transverse section <NUM> of the leadframe <NUM> may be electrically separated, in a safe way, from the second metal layer <NUM> and from the second thermal continuity regions 427B.

This variation is also applicable to the power devices <NUM>, <NUM> and <NUM> having the cup-shaped leadframe <NUM>.

Furthermore, in <FIG>, the height of the thermal connection structure <NUM> is chosen so that the height (with respect to the base section <NUM>) of the surface of the thermal connection structure <NUM> facing the second main surface 5B of the package <NUM> (including the delimitation wall <NUM> of the leadframe <NUM>) is lower than the height of the transverse section <NUM>. In this case, the thermal continuity regions 427A-427B have greater thickness with respect to the power devices <NUM>, <NUM>, <NUM> and <NUM>.

This variation is also applicable also to power devices <NUM>, <NUM> and <NUM> having the cup-shaped leadframe <NUM>.

The characteristics and configurations described above and shown in <FIG> for the leads <NUM>, <NUM> and <NUM> arranged to form an LGA (Land Grid Array) connection are also applicable to different connection solutions, for example to BGA (Ball Grid Array) connection solutions, as shown in <FIG> for a power device <NUM> having the structure of the power device <NUM> of <FIG>.

In particular, in <FIG>, the gate <NUM> and drain leads <NUM> (as well as the source lead <NUM>, not visible) comprise a first layer <NUM>, for example of aluminum, overlaid by a second layer <NUM>, for example of gold, and by a ball <NUM>, projecting with respect to the first insulating layer <NUM>, in a per se known manner.

This variation is applicable to all power devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> described hereinabove.

Therefore, the power device described herein allows an improvement in consumption due to better thermal performances.

It allows a reduction in manufacturing costs, since it does not need the use of top clips to obtain dual side cooling (DSC).

Finally, it is clear that modifications and variations may be made to the power device described and illustrated herein without thereby departing from the protective scope of the present invention, as defined in the attached claims. In particular, the different embodiments described may be combined to provide further solutions.

For example, as indicated, even in solutions with molded package <NUM>, the cutting of the single leadframes may occur after molding, taking into account the creepage distances.

In addition, as shown in <FIG>, the transverse section <NUM>, <NUM>, and <NUM> extends to reach the second main surface 5B of the package <NUM> and thus be directly accessible from the outside. Accordingly, the rear thermal dissipation region (drain lead) <NUM> is no more present. The same solution is applicable to all the embodiments discussed herein. Thereby, the leadframe <NUM>, <NUM>, <NUM> may be monolithical with the bottom portion.

In addition, as shown in <FIG>, the transverse section <NUM>, <NUM>, and <NUM> may be done of any desired thickness, as far as allowed by the technology. Thereby the bottom drain pad may be formed of different area.

In <FIG>, the transverse section <NUM> is directly exposed on two sides (bottom or second main surface 5B and second transverse wall or second side face 5D).

Claim 1:
A packaged power electronic device, comprising:
a bearing structure (<NUM>; <NUM>; <NUM>) including a base section (<NUM>; <NUM>; <NUM>) and a transverse section (<NUM>; <NUM>; <NUM>), the base section having a first and a second face (16A, 16B) and the transverse section extending transversely to the base section;
a die (<NUM>) coupled to the first face of the base section of the bearing structure, the die having a first and a second main face (2A, 2B) and a height between the first and the second main faces;
a first, a second and a third terminal (<NUM>, <NUM>, <NUM>), the first terminal (<NUM>) extending on the first main face (2A) of the die and the second and third terminals (<NUM>, <NUM>) extending on the second main face (2B) of the die (<NUM>);
a package (<NUM>; <NUM>) of insulating material, embedding the semiconductor die (<NUM>), the second terminal (<NUM>), the third terminal (<NUM>) and at least partially the carrying base (<NUM>; <NUM>; <NUM>), the package having a first and a second main surface (5A, 5B; 105A, 105B);
a first, a second and a third outer connection region (<NUM>, <NUM>, <NUM>; <NUM>; <NUM>; <NUM>) electrically coupled to the first, the second and the third terminals respectively, the first, the second and the third outer connection regions being laterally surrounded by the package and facing the second main surface of the package,
wherein the transverse section (<NUM>; <NUM>; <NUM>) of the bearing structure (<NUM>; <NUM>; <NUM>) extends from the base section (<NUM>; <NUM>; <NUM>) towards the second main surface of the package, has a first height greater than a height of the die,
characterized in that
the transverse section
forms the first outer connection region (<NUM>) and is flush with the second main surface (5B; 105B) of the package (<NUM>; <NUM>)
and wherein the transverse section (<NUM>; <NUM>; <NUM>) of the bearing structure (<NUM>; <NUM>; <NUM>) is flush with the first main surface (5A; 105A) of the package (<NUM>; <NUM>) or is coupled to a front thermal dissipation region (<NUM>) of thermally conductive material bonded to the second face (16B) of the base section (<NUM>; <NUM>; <NUM>) of the bearing structure (<NUM>; <NUM>; <NUM>), and extends monolithically between the first and the second main surfaces (5A; 105A, 5B; 105B) of the package (<NUM>, <NUM>), without interruptions.