Symmetrical switching of multiple power SiC dies (chips) enables high power applications for 1200V and up to 580 A or more. Conventional molded power semiconductor package designs provide a symmetrical connection for the high-side and low-side switching node connection but the gate contacts for the high side and low side are not symmetrical, which results in different maximal possible switching speeds for the high side and low side. This can lead to oscillations at increased frequencies which can destroy the modules due to high inductive connection of the gate contacts, unless a strong derating is applied for the application.
Hence, there is a need form an improved molded power semiconductor package design suitable for high power applications for 1200V and up to 580 A or more.
According to an embodiment of a molded power semiconductor package, the molded power semiconductor package comprises: a mold compound; a plurality of first power semiconductor dies embedded in the mold compound; and a first lead frame embedded in the mold compound above the plurality of first power semiconductor dies, wherein a first part of the first lead frame comprises a plurality of branches electrically connected to a first load terminal of the first power semiconductor dies, wherein a second part of the first lead frame is spaced inward from the branches of the first part, and electrically connected to a gate terminal of the first power semiconductor dies, wherein the first part of the first lead frame has a protrusion that juts out from a first side face of the mold compound to form a first lead of the molded power semiconductor package, wherein a longitudinal axis of the second part of the first lead frame intersects the first lead, wherein the second part of the first lead frame is physically disconnected from the first lead by a severed region of the first lead frame.
According to an embodiment of a method of producing a molded power semiconductor package, the method comprises: positioning a first lead frame above a plurality of first power semiconductor dies, the first lead frame comprising a first part and a second part integrally connected to one another, wherein the first part comprises a plurality of branches and the second part is spaced inward from the branches; electrically connecting the plurality of branches to a first load terminal of the first power semiconductor dies; electrically connecting the second part of the first lead frame to a gate terminal of the first power semiconductor dies; molding the first lead frame and the plurality of first power semiconductor dies with a mold compound, wherein the first part of the first lead frame has a protrusion that juts out from a first side face of the mold compound to form a first lead of the molded power semiconductor package and a longitudinal axis of the second part of the first lead frame intersects the first lead; and after the molding, severing the integral connection between the first part and the second part of the first lead frame such that the first lead becomes physically disconnected from the second part of the first lead frame.
Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.
The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts. The features of the various illustrated embodiments can be combined unless they exclude each other. Embodiments are depicted in the drawings and are detailed in the description which follows.
The embodiments described herein provide a molded power semiconductor package having a connection frame that overlies the power semiconductor dies included in the package and which provides power and gate connections to the power semiconductor dies. A first group of the power semiconductor dies may form a low-side switch of a half-bridge and a second group of the power semiconductor dies may form a high-side switch of the half-bridge. The high-side and low-side power semiconductor dies are mounted to the metallized surface of separate insulative substrates to reduce stray inductance. The connection frame that provides power and gate connections to the power semiconductor dies may have a uniform thickness or regions of different thicknesses to further reduce stray inductances, enabling even higher switching speeds. Further structural features are described for reducing the stray inductance of the connection frame.
A gate contact structure inside the molded power semiconductor package extends along the centerline of the molded power semiconductor package. The gate contact structure may be part of a metal clip frame, a PCB (printed circuit board), an insulative substrate having a metallized surface, or as an additional metal strip insulated from the connection frame, e.g., by mold compound, insulation, glue, insulation foil, etc. Press-fit connectors may be connected to the gate contact structure and partially overmolded to provide external gate connections.
The molded power semiconductor package with the connection frame described herein may have a stray inductance of 7 nH or less, a mostly symmetrical contact structure for multiple power semiconductor dies with low gate inductance, and high symmetry between the high-side switch and low-side switch of a half bridge. The molded power semiconductor package may include four or more power SiC dies (chips) to enable high power applications for up to 1200V or more and up to 580 A or more.
Described next, with reference to the figures, are exemplary embodiments of the molded power semiconductor package and methods of producing such a power semiconductor package. Any of the connection frame and molded power semiconductor package embodiments described herein may be used interchangeably unless otherwise expressly stated.
The molded power semiconductor package 100 includes at least one first power electronics carrier 102 having a metallization layer 104 disposed on an electrically insulating substrate 106. First power semiconductor dies 108 are attached to the metallization layer 104 of the at least one first power electronics carrier 102. The molded power semiconductor package 100 also includes at least one second power electronics carrier 110 having a metallization layer 112 disposed on an electrically insulating substrate 114. Second power semiconductor dies 116 are attached to the metallization layer 112 of the at least one second power electronics carrier 110. A mold compound 118 encases the first power semiconductor dies 108 and the second power semiconductor dies 116, and at least partly encases the at least one first power electronics carrier 102 and the at least one second power electronics carrier 110. In one embodiment, the surface (out of view in
The outline of the mold compound 118 is shown in
Each at least one first power electronic carrier 102 and each at least one second power electronics carrier 110 may be, e.g., a DCB (direct copper bonded) substrate, an AMB (active metal brazed) substrate, an IMS (insulated metal substrate), etc. The first power semiconductor dies 108 and the second power semiconductor dies 116 may be power Si or SiC power MOSFET (metal-oxide-semiconductor field-effect transistor) dies, HEMT (high-electron mobility transistor) dies, IGBT (insulated-gate bipolar transistor) dies, JFET (junction filed-effect transistor) dies, etc.
As shown in
The first power semiconductor dies 108 may be attached to the metallization layer 104 of a single first power electronics carrier 102, with a first subset 120 and a second subset 122 of the first power semiconductor dies 108 being symmetrically arranged on the single first power electronics carrier 102 about a longitudinal centerline A-A′ of the molded power semiconductor package 100. The second power semiconductor dies 116 similarly may be attached to the metallization layer 112 of a single second power electronics carrier 110, with a first subset 124 and a second subset 126 of the second power semiconductor dies 116 also being symmetrically arranged on the single second power electronics carrier 110 about the longitudinal centerline A-A′ of the molded power semiconductor package 100.
The first and second subsets 120, 122 of the first power semiconductor dies 108 instead may be attached to separate first power electronics carriers 102 as shown in
In the example illustrated in
The first power semiconductor dies 108 and the second power semiconductor dies 116 may be electrically coupled as a half bridge, with the first power semiconductor dies 108 forming a low-side switch of the half bridge and the second power semiconductor dies 116 forming a high-side switch of the half bridge. For the vertical die arrangement shown in
At least one lead 136, 138, 140 protrudes from a first side face 142 of the mold compound 118 and at least one lead 144 protrudes from a second side face 146 of the mold compound 118 opposite the first side face 142. The longitudinal centerline A-A′ of the molded power semiconductor package 100 extends between the first and second side faces 142, 146 of the mold compound 118.
In
A switch node lead 144 protrudes from the second side face 146 of the mold compound 118 and is electrically connected to the switch node ‘SW’ between the high-side power semiconductor dies 116 and the low-side power semiconductor dies 108 of the half bridge. In this case, the switch node lead 144 is the output lead for the molded power semiconductor package 100.
The internal electrical connections between the package leads 136, 138, 140, 144 and the power semiconductor dies 108, 116 encased in the mold compound 118 may be provided by a connection frame overlying the power semiconductor dies 108, 116. In
In
In either case, the first structured metal frame 148 is electrically connected to the source terminal 130 of each first (low-side) power semiconductor die 108, e.g., by bumps or stamped features 152 at the backside of the first structured metal frame 148, or by solder, electrically conductive adhesive, etc. The second structured metal frame 150 is electrically connected to the source terminal 134 of each second (high-side) power semiconductor die 116, e.g., by bumps or stamped features 154 at the backside of the second structured metal frame 150, or by solder, electrically conductive adhesive, etc.
A first subset 120 and a second subset 122 of the first power semiconductor dies 108 may be arranged on opposite sides of the longitudinal centerline A-A′ of the molded power semiconductor package 100, as previously described herein. A first subset 124 and a second subset 126 of the second power semiconductor dies 116 similarly may be arranged on opposite sides of the longitudinal centerline A-A′.
As shown in
Further as shown in
The first branches ‘2’ of the connection frame are vertically connected to the source terminal 130 of each power semiconductor die 108 included in the first subset 120 of first power semiconductor dies 108. The second branches ‘3’ of the connection frame are vertically connected to the source terminal 130 of each power semiconductor die 108 included in the second subset 122 of first power semiconductor dies 108. The third branches ‘5’ of the connection frame are vertically connected to the source terminal 134 of each power semiconductor die 116 included in the first subset 124 of second power semiconductor dies 116. The fourth branches ‘6’ of the connection frame are vertically connected to the source terminal 134 of each power semiconductor die 116 included in the second subset 126 of second power semiconductor dies 116.
The first structured metal frame 148 of the connection frame may include a first additional ‘7’ branch that connects the first branches ‘2’ at a distal end of the first branches ‘2’, and a second additional branch ‘8’ that connects the second branches ‘3’ at a distal end of the second branches ‘3’. The second structured metal frame 150 of the connection frame may include a third additional branch ‘9’ that connects the third branches ‘5’ at a distal end of the third branches ‘5’, and a fourth additional branch ‘10’ that connects the fourth branches ‘6’ at a distal end of the fourth branches ‘6’.
The first structured metal frame 148 of the connection frame may include a first gate metallization ‘12’ disposed in an opening 156 formed in the first central part ‘1’ of the first structured metal frame 148 and that is electrically insulated from the first central part ‘1’, the first branches ‘2’, and the second branches ‘3’. The first gate metallization ‘12’ is electrically connected to the gate terminal 128 of each first power semiconductor die 108, e.g., by bond wires 158. The second structured metal frame 150 of the connection frame may include a second gate metallization ‘14’ disposed in an opening 160 formed in the second central part ‘4’ of the second structured metal frame 150 and that is electrically insulated from the second central part ‘4’, the third branches ‘5’, and the fourth branches ‘6’. The second gate metallization ‘14’ is electrically connected to the gate terminal 132 of each second power semiconductor die 118, e.g., by bond wires 162.
The first and second gate metallizations ‘12’, ‘14’ may be part of a lead frame, as explained above. The first and second gate metallizations ‘12’, ‘14’ instead may be part of respective first and second PCB disposed in the corresponding openings 156, 160 formed in the first central part ‘1’ and the second central part ‘4’ of the connection frame. In yet another example, the first and second gate metallizations ‘12’, ‘14’ may be part of respective first and second additional power electronics carriers disposed in the corresponding openings 156, 160 formed in the first central part ‘1’ and the second central part ‘4’ of the connection frame.
A first press-fit pin 164 may be attached to the first gate metallization ‘12’ and protrude through the front (top) surface of the mold compound 118. A second press-fit pin 168 may be attached to the second gate metallization ‘14’ and protrude through the front surface of the mold compound 118. The molded power semiconductor package 100 may include additional press-fit pins 170 one or more of which may be attached to the first structured metal frame 148 and/or the second structured metal frame 150 and protruding through the front (top) surface of the mold compound 118, e.g., for external current sensing, temperature sensing, etc.
The second structured metal frame 150 of the connection frame may include an additional branch ‘16’ at the end of the second central part ‘4’ of the second structured metal frame 150 and that faces the first structured metal frame 148. The additional branch ‘16’ extends in parallel with both the third branches ‘5’ and the fourth branches ‘6’ of the second structured metal frame 150. The additional branch ‘16’ is vertically connected to the metallization layer 104 of the at least one first power electronics carrier 102, e.g., by bumps or stamped features 172 at the backside of additional branch ‘16’, or by solder, electrically conductive adhesive, etc.
In
In
An end of the first structured metal frame 148 may protrude from the first side face 142 of the mold compound 118 to form the low-side phase/ground lead 140 of the molded power semiconductor package 100. An end of the second structured metal frame 150 may protrude from the second side face 146 of the mold compound 118 to form the switch node lead 144 of the molded power semiconductor package 100.
In
In
In
For example, the first lead frame 300, which includes the first and second structured metal frames 148, 150, may have a thickness less than 0.5 mm, e.g., of about 0.25 mm. The second lead frame 302, which includes the package leads 136, 138, 140, 144, may have a thickness greater than 0.5 mm and less than 1 mm, e.g., of about 0.8 mm. Other lead frame thickness combinations may be used, with the second lead frame 302 being thicker than the first lead frame 300. The multi-layer lead frame 304 is then attached to the power electronics carriers 102, 110 and the power semiconductor dies 108, 116, as previously described herein and as shown in
In
Placing the metal strips or a single metal sheet 400 over the power contacts inside of the molded power semiconductor package 100 reduces the stray inductance by about 28%, e.g., from about 9.1 nH for the embodiment in
As shown in
In
In
For the molded power semiconductor package and production embodiments described above and according to which the die gate connections ‘12’, ‘14’ are provided by part of the lead frames 148, 150, the following embodiments describe how the lead frame gate connections ‘12’, ‘14’ may be realized. In the following embodiment, the gate metallizations ‘12’, ‘14’ are initially part of the respective lead frames 148, 150 which also provide power leads 136, 138, 140, 144 and therefore cannot be used electrically until disconnected from the leads 136, 138, 140, 144. The gate metallization part ‘12’, ‘14’ of the lead frames 148, 150 are fixed through the molding process to ensure proper assembly. The gate metallization part 12′, ‘14’ of the lead frames 148, 150 are separated after the molding process to ensure no shorting between the gate metallizations ‘12’, ‘14’ and the power leads 136, 138, 140, 144 of the molded package 100.
The second part 502 of the first lead frame 148 corresponds to the first gate metallization ‘12’ shown in
As shown in
In
In
In
In
In one embodiment, the integral connection between the first part 500 and the second part 502 of the first lead frame 148 is severed by drilling the second part 502 of the first lead frame 148 inside the perimeter of the mold compound 118, e.g., using a micro drill. In another embodiment, the integral connection between the first part 500 and the second part 502 of the first lead frame 148 is severed by machining the second part 502 of the first lead frame 148 inside the perimeter of the mold compound 118, e.g., using a saw blade. In the case of severing the integral connection by drilling or machining, a stop may be used based on the lead frame thickness, e.g., as used in PCB (printed circuit board) machining or drilling processes. In another embodiment, the integral connection between the first part 500 and the second part 502 of the first lead frame 148 is severed by laser cutting the second part 502 of the first lead frame 148 inside the perimeter of the mold compound 118. In each case, the resulting severed region 1100 of the first lead frame 148 includes a plurality of interconnected drilled regions, a machined region, or a laser cut region inside the perimeter of the mold compound 118.
The severed region 1100 of the first lead frame 148 is shown as a plurality of interconnected drilled regions in
For the severing region embodiment shown in
Although the present disclosure is not so limited, the following numbered examples demonstrate one or more aspects of the disclosure.
Example 1. A molded power semiconductor package, comprising: a mold compound; a plurality of first power semiconductor dies embedded in the mold compound; and a first lead frame embedded in the mold compound above the plurality of first power semiconductor dies, wherein a first part of the first lead frame comprises a plurality of branches electrically connected to a first load terminal of the first power semiconductor dies, wherein a second part of the first lead frame is spaced inward from the branches of the first part, and electrically connected to a gate terminal of the first power semiconductor dies, wherein the first part of the first lead frame has a protrusion that juts out from a first side face of the mold compound to form a first lead of the molded power semiconductor package, wherein a longitudinal axis of the second part of the first lead frame intersects the first lead, wherein the second part of the first lead frame is physically disconnected from the first lead by a severed region of the first lead frame.
Example 2. The molded power semiconductor package of example 1, wherein the severed region of the first lead frame is positioned inside a perimeter of the mold compound.
Example 3. The molded power semiconductor package of example 2, wherein the severed region of the first lead frame comprises a plurality of interconnected drilled regions, a machined region, or a laser cut region.
Example 4. The molded power semiconductor package of example 2 or 3, wherein the mold compound has a reduced thickness over the severed region of the first lead frame or is completely removed over the severed region of the first lead frame.
Example 5. The molded power semiconductor package of example 1, wherein the severed region of the first lead frame is positioned outside the mold compound.
Example 6. The molded power semiconductor package of example 5, wherein the severed region of the first lead frame comprises a stamped region.
Example 7. The molded power semiconductor package of any of examples 1 through 6, further comprising: a press-fit pin attached to the second part of the first lead frame and extending outward from a front surface of the mold compound, wherein the first side face of the mold compound extends between the front surface and a back surface of the mold compound.
Example 8. The molded power semiconductor package of any of examples 1 through 7, further comprising: a plurality of second power semiconductor dies embedded in the mold compound and electrically connected to the plurality of first power semiconductor dies to form a half bridge; and a second lead frame embedded in the mold compound above the plurality of second power semiconductor dies, wherein a first part of the second lead frame comprises a plurality of branches electrically connected to a first load terminal of the second power semiconductor dies, wherein a second part of the second lead frame is spaced inward from the branches of the first part of the second lead frame, and electrically connected to a gate terminal of the second power semiconductor dies, wherein the first part of the second lead frame has a protrusion that juts out from a second side face of the mold compound opposite the first side face to form a second lead of the molded power semiconductor package, wherein a longitudinal axis of the second part of the second lead frame intersects the second lead, wherein the second part of the second lead frame is physically disconnected from the second lead by a severed region of the second lead frame.
Example 9. The molded power semiconductor package of example 8, wherein both the severed region of the first lead frame and the severed region of the second lead frame are positioned inside a perimeter of the mold compound, wherein the mold compound has a reduced thickness over the severed region of the first lead frame or is completely removed over the severed region of the first lead frame, and wherein the mold compound has a reduced thickness over the severed region of the second lead frame or is completely removed over the severed region of the second lead frame.
Example 10. A method of producing a molded power semiconductor package, the method comprising: positioning a first lead frame above a plurality of first power semiconductor dies, the first lead frame comprising a first part and a second part integrally connected to one another, wherein the first part comprises a plurality of branches and the second part is spaced inward from the branches; electrically connecting the plurality of branches to a first load terminal of the first power semiconductor dies; electrically connecting the second part of the first lead frame to a gate terminal of the first power semiconductor dies; molding the first lead frame and the plurality of first power semiconductor dies with a mold compound, wherein the first part of the first lead frame has a protrusion that juts out from a first side face of the mold compound to form a first lead of the molded power semiconductor package and a longitudinal axis of the second part of the first lead frame intersects the first lead; and after the molding, severing the integral connection between the first part and the second part of the first lead frame such that the first lead becomes physically disconnected from the second part of the first lead frame.
Example 11. The method of example 10, wherein the integral connection between the first part and the second part of the first lead frame is severed inside a perimeter of the mold compound.
Example 12. The method of example 11, wherein severing the integral connection between the first part and the second part of the first lead frame comprises: drilling the second part of the first lead frame inside the perimeter of the mold compound.
Example 13. The method of example 11, wherein severing the integral connection between the first part and the second part of the first lead frame comprises: machining the second part of the first lead frame inside the perimeter of the mold compound.
Example 14. The method of example 11, wherein severing the integral connection between the first part and the second part of the first lead frame comprises: laser cutting the second part of the first lead frame inside the perimeter of the mold compound.
Example 15. The method of any of examples 11 through 14, wherein the molding comprises: reducing a thickness of the mold compound over the integral connection to be severed; or forming an opening in the mold compound over the integral connection to be severed.
Example 16. The method of example 10, wherein the integral connection between the first part and the second part of the first lead frame is severed outside the mold compound.
Example 17. The method of example 16, wherein severing the integral connection between the first part and the second part of the first lead frame comprises: stamping the integral connection between the first part and the second part of the first lead frame outside the mold compound.
Example 18. The method of any of examples 10 through 17, further comprising: before the molding, positioning a second lead frame above a plurality of second power semiconductor dies, the second lead frame comprising a first part and a second part integrally connected to one another, wherein the first part of the second lead frame comprises a plurality of branches and the second part of the second lead frame is spaced inward from the branches of the first part of the second lead frame; before the molding, electrically connecting the plurality of branches of the first part of the second lead frame to a first load terminal of the second power semiconductor dies, electrically connecting the second part of the second lead frame to a gate terminal of the second power semiconductor dies, and electrically interconnecting the plurality of second power semiconductor dies and the plurality of first power semiconductor dies to form a half bridge; as part of the molding, molding the second lead frame and the plurality of second power semiconductor dies with the mold compound, wherein the first part of the second lead frame has a protrusion that juts out from a second side face of the mold compound opposite the first side face to form a second lead of the molded power semiconductor package and a longitudinal axis of the second part of the second lead frame intersects the second lead; and after the molding, severing the integral connection between the first part and the second part of the second lead frame such that the second lead becomes physically disconnected from the second part of the second lead frame.
Example 19. The method of example 18, wherein the integral connection between the first part and the second part of the first lead frame is severed inside a perimeter of the mold compound, and wherein the integral connection between the first part and the second part of the second lead frame is severed inside the perimeter of the mold compound.
Example 20. The method of example 19, wherein the molding comprises: reducing a thickness of the mold compound over each of the integral connections to be severed; or forming an opening in the mold compound over each of the integral connections to be severed.
Example 21. The method of any of examples 18 through 20, wherein the integral connection between the first part and the second part of the first lead frame is severed outside the mold compound, and wherein the integral connection between the first part and the second part of the second lead frame is severed outside the mold compound.
Example 22. The method of example 21, wherein severing each of the integral connections comprises: stamping, outside the mold compound, both the integral connection between the first part and the second part of the first lead frame and the integral connection between the first part and the second part of the second lead frame.
Terms such as “first”, “second”, and the like, are used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.
As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.
It is to be understood that the features of the various embodiments described herein may be combined with each other, unless specifically noted otherwise.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.