Patent Grant
12057376
Embodiments of this invention generally relate to semiconductor packages and more particularly relate to cooling and interconnect features of semiconductor packages.
Semiconductor packages provide connective compatibility between a semiconductor die and an external apparatus such as a printed circuit board (PCB), and protect the semiconductor die from potentially damaging environmental conditions such as temperature variations, moisture, dust particles, etc. Thermal dissipation is an important design consideration in many semiconductor applications. For example, power semiconductor devices, i.e., devices that are configured to control voltages on the order of 100 V (volts) or more and/or currents on the order of 1 A (ampere) or more, generate a substantial amount of heat during operation. This heat must be efficiently removed from the semiconductor die to avoid causing damage to the semiconductor die and/or associated electrical connections. Metal heat sinks can be used to increase the cooling capability of semiconductor package arrangements. Heat sinks are mounted on one side of a semiconductor package to provide a thermal dissipation path for heat generated during operation. Since the heat sink interfaces with one side of the package, this can create asymmetric heat distribution with dangerously high temperatures at the side of the semiconductor package that is opposite from the heat sink. Current solutions for achieving balanced heat extraction are ineffective and/or cost prohibitive.
An interconnect clip is disposed. According to an embodiment, the interconnect clip comprises a die attach pad that comprises a die attach surface, a heat dissipation pad that comprises a heat dissipation surface and a lead contact pad that comprises a lead contact surface at an inner side of the interconnect clip or at an outer side of the interconnect clip,
the outer side of the interconnect clip in the lead contact pad faces and is spaced apart from the inner side of the interconnect clip in the heat dissipation pad, and the inner side of the interconnect clip in the lead contact pad faces and is spaced apart from the outer side of the interconnect clip in the die attach pad.
Separately or in combination, the die attach surface extends along a first lateral plane, the heat dissipation surface extends along a second lateral plane, and the lead contact surface extends along a third lateral plane that is between the first and third lateral planes.
Separately or in combination, the die attach pad, the heat dissipation pad and the lead contact pad are constituent parts of a single sheet of metal.
Separately or in combination, the interconnect clip further comprises a first bridge section that is connected between the die attach pad and the heat dissipation pad and a second bridge section that is connected between the die attach pad and the lead contact pad, and the inner and outer sides of the interconnect clip extend transversely to the first lateral plane in the first and second bridge sections.
Separately or in combination, the second bridge section comprises a span which extends from the die attach pad at a steeper angle than a shortest path between the die attach pad and the lead contact pad.
Separately or in combination, the second bridge section comprises a first span and a second span, the inner side of the interconnect clip in the first span intersects the die attach surface and extends along the steeper angle, and the inner side of the interconnect clip in the second span faces and is spaced apart from the outer surface of the interconnect clip in the lead contact pad.
Separately or in combination, the interconnect clip comprises a plurality of the heat dissipation pads, and each of the heat dissipations pads are laterally separated from one another by a gap.
Separately or in combination, the interconnect clip further comprises a second bridge section that is connected between the die attach pad and the lead contact pad, and the second bridge section forms one of the heat dissipation pads.
Separately or in combination, the interconnect clip further comprises a plurality of first bridge sections, and each of the first bridge sections are independently connected between the die attach pad and one of the heat dissipation pads.
A semiconductor package is disclosed. In an embodiment, the semiconductor package comprises a lead frame structure comprising a die pad, a plurality of leads extending away from the die pad, and a connection surface that is connected with one or more of the leads and is offset from a die attach surface of the die pad, a semiconductor die mounted on the die pad and comprising a first surface terminal which faces away from the die pad, an interconnect clip that electrically connects the first surface terminal to the connection surface, and an encapsulant body of electrically insulating material that encapsulates the semiconductor die, the interconnect clip comprises a die attach pad, a heat dissipation pad, and a lead contact pad, the die attach pad comprises a die attach surface that is flush against the first surface terminal, the lead contact pad comprises a lead contact surface that is flush against the connection surface, and the heat dissipation pad comprises a heat dissipation surface that is exposed from a first outer surface of the encapsulant body.
Separately or in combination, the die attach surface extends along a first lateral plane, the heat dissipation surface extends along a second lateral plane, and the lead contact surface extends along a third lateral plane that is between the first and third lateral planes.
Separately or in combination, the interconnect clip further comprises a first bridge section that is connected between the die attach pad and the heat dissipation pad and a second bridge section that is connected between the die attach pad and the lead contact pad, and the inner and outer sides of the interconnect clip extend transversely to the first lateral plane in the first and second bridge sections.
Separately or in combination, the second bridge section comprises a span which extends from the die attach pad at a steeper angle than a shortest path between the die attach pad and the lead contact pad.
Separately or in combination, the heat dissipation surface is substantially coplanar with the first outer surface of the encapsulant body.
Separately or in combination, the die attach pad, the heat dissipation pad and the lead contact pad are constituent parts of a single sheet of metal.
Separately or in combination, the interconnect clip comprises a plurality of the heat dissipation pads, and each of the heat dissipation pads are laterally separated from one another by a section of the encapsulant body.
Separately or in combination, the die pad comprises an outer surface that is opposite from the semiconductor die and is exposed from a second outer surface of the encapsulant body, wherein the second outer surface of the encapsulant body is opposite the first outer surface of the encapsulant body.
Separately or in combination, each of the leads comprise distal ends that are exposed from the encapsulant body and bend towards the first outer surface of the encapsulant body, and the distal ends of each lead comprise a contact surface that extends away from the encapsulant body.
Separately or in combination, each of the leads comprise distal ends that are exposed from the encapsulant body and bend towards the second outer surface of the encapsulant body, wherein the distal ends of each lead comprise a contact surface that extends away from the encapsulant body.
Separately or in combination, each of the leads comprise distal ends that are exposed from the encapsulant body and extend along a single plane that is vertically between the second outer surface of the encapsulant body and the first outer surface of the encapsulant body.
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.
Embodiments of an interconnect clip with an advantageous three-level design are described herein. The interconnect clip comprises a die attach pad disposed on a first lateral plane, a heat dissipation pad (or pads) disposed on a second lateral plane that is spaced apart from the first lateral plane, and a lead contact pad disposed on a third lateral plane that is between the first and second lateral planes. The interconnect clip can be arranged in a semiconductor package with the die pad flush against a semiconductor die, the lead contact pad flush against a lead connection surface that is offset from the die pad, and the heat dissipation pad (or pads) exposed at an outer surface of the package encapsulant body. The heat dissipation pad (or pads) and the die attach pad are directly connected to one another by a bridge portion (or portions) of the interconnect clip, thereby providing a direct thermal dissipation path between the surface of the semiconductor die and the outer surface of the package encapsulant body. The lead contact pad and the die attach pads are also directly connected to one another by a bridge portion, thereby providing a direct electrical conduction path between a terminal of the semiconductor die and the package lead.
The three-level design of the interconnect clip advantageously provides a solution for simultaneously providing electrical interconnect and package cooling. Moreover, an interconnect clip with these features can be formed at low cost with relatively few processing steps. For example, the interconnect clip can be formed from a single piece of sheet metal that is processed by relatively few metal processing steps such as stamping, punching, cutting, etc. An interconnect clip with advantageous geometric features can be made from this technique. For example, the interconnect clip can include multiple heat dissipation pads that are laterally spaced apart from one another by portions of the encapsulant body and occupy a substantial percentage area of the outer side of the package encapsulant body. This produces a large contact surface for interfacing with a heat sink while simultaneously providing a great degree of mold adhesion.
Referring to
The interconnect clip 100 is configured such that the outer side 110 of the interconnect clip 100 in the lead contact pad 106 faces and is spaced apart from the inner side 108 of the interconnect clip 100 in the heat dissipation pad 104 and such that the inner side 108 of the interconnect clip 100 in the lead contact pad 106 faces and is spaced apart from the outer side 110 of the interconnect clip in the die attach pad 102. In this context, the term “faces” refers to the orientation of a surface relative to the plane of another surface to which it “faces” and does not require direct overlapping of the surfaces. Due to the above described arrangement, the interconnect clip has a three-level configuration, wherein the lead contact pad 106 is disposed on an intermediate level between the level of the die pad 102 and the level of the heat dissipation pad 104.
The interconnect clip 100 comprises a die contact surface 112 that corresponds to the inner side 108 of the interconnect clip 100 in the die attach pad 102. The interconnect clip 100 additionally comprises a lead contact surface 114. In the depicted embodiment, the lead contact surface 114 corresponds to the inner side 108 of the interconnect clip 100 in the lead contact pad 106. In another embodiment, the lead contact surface 114 can correspond to the outer side 110 of the interconnect clip 100 in the lead contact pad 106. The interconnect clip 100 additionally comprises a heat dissipation surface 116 that corresponds to the outer side 110 of the interconnect clip 100 in the heat dissipation pad 104. According to an embodiment, each of these surfaces 112, 114 and 116 are substantially planar surfaces.
The interconnect clip 100 is configured such that the die contact surface 112 extends along a first lateral plane 118, the heat dissipation surface 116 extends along a second lateral plane 120, and the lead contact surface 114 extends along a third lateral plane 122. The first, second and third lateral planes 118, 120, 122 are two-dimensional reference planes that are coplanar with the inner or outer sides 108, 110 of the interconnect clip 100 in the various pads 102, 104, 106 of the interconnect clip 100. Thus, the die contact surface 112 is coplanar with the first lateral plane 118, the heat dissipation surface 116 is coplanar with the second lateral plane 120, and the lead contact surface 114 is coplanar with the third lateral plane 122. According to an embodiment, each of the first, second and third lateral planes 118, 120, 122 are parallel to one another and hence the die contact surface 112, the heat dissipation surface 116, and the lead contact surface 114 are each parallel to one another. Alternatively, at least one of the first, second and third lateral planes 118, 120, 122 can be tilted relative to the other planes so that at least one of the die contact surface 112, the heat dissipation surface 116, and the lead contact surface 114 is tilted relative to the other surfaces.
The interconnect clip 100 further comprises first and second bridge sections 124, 126. The first bridge section 124 is a span of the interconnect clip 100 that extends between the die attach pad 102 and the heat dissipation pad 104. The second bridge section 126 is a span of the interconnect clip 100 that extends between the die attach pad 102 and the lead contact pad 106. The inner and outer sides 108, 110 of the interconnect clip 100 extend transversely to the first lateral plane 118 in at least portions of the first and second bridge sections 124, 126.
In the depicted embodiment, the first bridge section 124 is tilted relative to the first lateral plane 118 such that the inner and outer sides 108, 110 of the interconnect clip 100 form an acute angle relative to the first lateral plane 118. Moreover, the first bridge section 124 is provided by a single span of the interconnect clip 100 that extends along this tilted plane.
The second bridge section 126 comprises multiple spans that extend in different directions. More particularly, the second bridge section 126 comprises a first span 128, a second span 130, and a third span 132. The first span 128 intersects the die attach pad 102 and the second span 130. The first span 128 is tilted relative to the first lateral plane 118 such that the inner and outer sides 108, 110 of the interconnect clip 100 in the first span 128 form an acute angle relative to the first lateral plane 118. The second span 130 of the second bridge section 126 intersects the first span 128. The second span 130 of the second bridge section 126 is spaced apart from the lead contact pad 106 such that the inner side 108 of the interconnect clip 100 in the second span 130 faces the outer side 110 of the interconnect clip 100 in the lead contact pad 106. As shown, the second span 130 of the second bridge section 126 may be parallel to the first and/or second lateral planes 118, 120. The third span 132 of the second bridge section 126 intersects the second span 130 and the lead contact pad 106. Thus, the first, second and third spans 128, 130, 132 of the second bridge section 126 are arranged such that the die attach pad 102 is connected with the lead contact pad 106 and such that the second bridge section 126 comprises a portion (i.e., the second span 130 in the depicted embodiment) that is further away from the die attach pad 102 than the lead contact pad 106.
According to an embodiment, the second bridge section 126 forms one of the heat dissipation pad 104. In this embodiment, the second bridge section 126 is configured such that the outer side 110 of the interconnect clip 100 in a portion of the second bridge section 126 that is furthest away from the die pad (i.e., the second span 130 in the depicted embodiment) extends along the third lateral plane 122. Thus, the second bridge section 126 comprises a heat dissipation surface 116 that is coplanar with the other heat dissipation surface 116 (or surfaces) of the heat dissipation pad 104 (or pads). Alternatively, the second bridge section 126 can be configured only for electrical interconnection. For example, the second bridge section 126 can have a substantially similar configuration to that which is shown in
According to an embodiment, the second bridge section 126 comprises a span which extends from the die attach pad 102 at a steeper angle than a shortest path between the die attach pad 102 and the lead contact pad 106. The embodiment of
According to an embodiment, the interconnect clip 100 is a monolithically formed from a single sheet of metal. That is, each of the features of the interconnect clip 100 (e.g., the die attach pad 102, the heat dissipation pad 104, the lead contact pad 106, the first and second bridge sections 124, 126) are constituent parts of a single sheet of metal. For example, the interconnect clip 100 having each of the above discussed features can be produced by initially providing an undisturbed sheet of conductive metal, e.g., a flat plate of metal such as copper, aluminum, alloys thereof, etc. that is similar or identical to a metal sheet that is used to form a package lead frame. This sheet of conductive metal can comprise or be plated with one more layers of conductive material (e.g., Cu, Ni, Ag, Au, Pd, Pt, Ni, etc.) which act as adhesion promotors, anti-corrosion layers, etc. These layers can be provided before or after the metal processing steps described below. The undisturbed sheet of conductive metal can be geometrically formed into the configuration described herein by performing metal processing steps such as punching, stamping, bending and cutting. For example, a metal piece with angled bending between the die attach pad 102 and the first and second bridge section 124, 126 can be obtained by single metal stamping or punching step. The interconnect clip 100 may be formed to include multiple separate ones of the heat dissipation pads 104 and associated first bridge sections 124 (e.g., as shown in
Referring to
The semiconductor package 200 comprises a lead frame 202. The lead frame 202 can be formed from a conductive metal such as such as copper, aluminum, nickel, iron, zinc, etc., and alloys thereof. The lead frame 202 comprises a die pad 204 and a plurality of leads 206 extending away from the die pad 204. The die pad 204 comprises a planar die attach surface 208 that is dimensioned for the mounting of a semiconductor die thereon. The leads 206 are offset from the die pad 204, meaning that connection surfaces 210 of the leads 206 are on a different lateral plane as the die attach surface 208. The connection surfaces 210 can be upper surface portions of the leads 206 that are near the die pad 204. In another embodiment, the connection surfaces 210 are disposed on a planar pad (e.g., as shown in
A semiconductor die 212 is mounted on the die contact surface 208 of the die pad 204. The semiconductor die 212 comprises a first surface terminal 214 which faces away from the die pad 204 in the mounted position. The first surface terminal 214 can be an electrically conductive bond pad which provides an I/O connection to one of the terminals (e.g., source, drain, collector, emitter, etc.) of the semiconductor die 212.
Generally speaking, the semiconductor die 212 can have a wide variety of device configurations. Examples of these device configurations include discrete semiconductor devices such as transistors, diodes, thyristors, etc., and integrated semiconductor devices such as logic devices, controllers, sensors, etc. The semiconductor die 212 can be configured as vertical device, i.e., a device that conducts across a thickness of the die 212 in a direction perpendicular to a main (upper) surface of the semiconductor body of the die 212. Alternatively, the semiconductor die 212 can be configured as lateral device, i.e., a device that conducts in a direction parallel to the main (upper) surface of the semiconductor body of the die 212. The semiconductor die 212 can comprise any of a variety of semiconductor materials including type IV semiconductors, e.g., silicon, silicon germanium, silicon carbide, etc., and type III-V semiconductors, e.g., gallium nitride, gallium arsenide, etc.
According to an embodiment, the semiconductor die 212 is configured as a power semiconductor device, i.e., a device that is configured to control voltages of 100 V or more and/or currents of 1 A or more. More commonly, power semiconductor device devices are configured to control voltages on the order of 500 V to 1500V and/or currents on the order of 10 A or more. Examples of these devices include power diodes and power transistor devices such as MOSFETs (metal-oxide semiconductor field-effect transistors), IGBTs (insulated gate bipolar transistors), HEMTs (high electron mobility transistors). In these embodiments, the first surface terminal 214 can be a load terminal of the device (e.g., source, emitter, anode, etc.). In a vertical device configuration, the semiconductor die 212 may comprise a second load terminal (e.g., drain, collector, cathode, etc.) that is disposed on a rear surface of the semiconductor die 212 and electrically connected to the die pad 204, e.g., by a soldered connection.
The semiconductor package 200 further comprises an encapsulant body 216. The encapsulant body 216 comprises an electrically insulating encapsulant material that seals and protects the semiconductor die 212. The encapsulant material may include epoxy materials, thermosetting plastics, ceramic, etc. The encapsulant body 216 can be formed by a molding technique, such as injection molding, compression molding, transfer molding, etc. The encapsulant body 216 comprises a first outer surface 218 that is opposite from the die pad 204 and a second outer surface 220 that is opposite from the first outer surface 218. The encapsulant body 216 further comprises sidewall surfaces 222 that extend between the first and second outer surfaces 218, 220. Each of the leads 206 protrudes from one of the sidewall surfaces 222. In the depicted embodiment, an outer surface 224 of the die pad 204 that is opposite from the semiconductor die 212 is exposed from the second outer surface 220 of the encapsulant body 216. In that case, the exposed outer surface 224 of the die pad 204 can be an electrical terminal and/or interface surface with a heat sink.
The interconnect clip 100 is mounted in the semiconductor package 200 so that it electrically connects the first surface terminal 214 to a connection surface 210 of the leads 206. To this end, the die contact surface 112 is flush against the first surface terminal 214 and the lead contact surface 114 is flush against one of the connection surfaces 210. A conductive adhesive, such as solder, sinter, conductive glue, etc., may be provided at the interface between the interconnect clip 100 and the first surface terminal 214 and/or at the interface between the interconnect clip 100 and the connection surface 210. The remaining leads 206 of the semiconductor package 200 may be electrically connected to other terminals of the semiconductor die 212 (not shown) using any type of interconnect structure, e.g., bond wire, ribbon, clip, etc. In addition or in the alternative, at least one of the leads 206 may merge with the die pad 204 and can be electrically connected to a rear surface terminal of the semiconductor die 212.
By configuring the second bridge section 126 to comprise a span which extends from the die attach pad 102 at a steeper angle than a shortest path between the die attach pad 102 and the lead contact pad 106 in the manner previously described, the inner side 108 of the interconnect clip 100 is moved away from a laterally overhanging portion 226 of the semiconductor die 212 that extends underneath the interconnect clip 100. That is, the steep angle means that the interconnect clip 100 does not extend close to the laterally overhanging portion 226 of the semiconductor die 212. This mitigates the electromagnetic field interaction between the interconnect clip 100 and the semiconductor die 212. This may be particularly advantageous in an embodiment wherein the semiconductor die 212 is configured as a power semiconductor die 212 and comprises an edge termination structure that is disposed in the laterally overhanging portion 226 of the semiconductor die 212. In that arrangement, there is large potential difference between the edge termination structure, which may be at drain potential (e.g. GND) as the first surface terminal 214 of the semiconductor die 212, which may be at a large voltage (e.g., 500 V or more) during operation of the device.
The interconnect clip 100 is arranged in the semiconductor package 200 so that the heat dissipation surfaces 116 the heat dissipation pad 104 (or pads) is exposed from the first outer surface 218 of the encapsulant body 216. In an embodiment, the heat dissipation surface 116 of the heat dissipation pad 104 (or pads) is substantially coplanar with the first outer surface 218 of the encapsulant body 216. One way to obtain this configuration is to initially form the encapsulant body 216 so that the heat dissipation pad 104 (or pads) protrude from the first outer surface 218 and subsequently perform a planarization process such as polishing or grinding to remove the raised portions of the interconnect clip 100. Alternatively, the heat dissipation pad 104 (or pads) may slightly protrude from the first outer surface 218 of the encapsulant body 216.
The outer perimeter of the heat dissipation pad 104 (or pads) and the associated bridge connection acts as a mold adhesion surface that enhances adhesion between the material of the encapsulant body 216. This ensures that the interconnect clip is stably formed in the proper position to provide electrical interconnect and heat dissipation.
The exposed heat dissipation surface 116 (or surfaces) of the interconnect clip 100 can interface with an external heat sink structure, e.g., by mounting a heat sink flush against the first outer surface 218 of the encapsulant body 216. In that case, the interconnect clip 100 provides a thermally conductive path between the semiconductor die 212 and the heat sink, thereby enabling efficient removal of heat from the semiconductor die 212. A second heat sink structure can interface with the outer surface 224 of the die pad 204, e.g., by mounting the second heat sink to be flush against the die pad 204. In that configuration, the semiconductor package 200 includes two thermal dissipation paths which draw heat away from the semiconductor die 212 in opposite directions. This provides balanced and efficient heat dissipation and ensures that the semiconductor package 200 does not have dangerously hot regions during operation.
Referring to
The depicted embodiment illustrates just one example of a wide variety of designs. More generally, the size, geometry, number and location of the heat dissipation pads 104 and associated bridge sections can vary. For example, the heat dissipation pads 104 can have different shapes such as L-shape, C-shape, T-shape, circular, polygon, etc. The number and geometry of these heat dissipation pads 104 can be selected based on design considerations such as compatibility with a particular package design and/or heat sink configuration. Likewise, the angle of inclination and/or distance between bridge sections can be tailored according to design factors such as electrical isolation and/or mold adhesion.
One advantage of having multiple heat dissipation pads 104 versus a single one of the heat dissipation pads 104 for one of the interconnect clips 100 is added flexibility in customizing the location and geometry of the heat dissipation pads 104 according to creepage distance requirements. For example, the heat dissipation pads 104 may be of a smaller geometry or eliminated to meet creepage distance requirements between certain leads.
Referring to
Referring to
Referring to
The semiconductor package 200 embodiments disclosed herein represent just a few of many different types of semiconductor package assemblies that may incorporate the interconnect clip 100 described herein. Examples of the semiconductor package assemblies include any type of melded semiconductor package 200 such as flat lead packages, chip carrier packages, ball grid array or pin grid array packages, etc. Additionally, these semiconductor package assemblies include so-called chip on board assemblies that do not include a lead frame.
The term “substantially” as used herein encompasses absolute conformity with the specified requirement as well as minor deviations from absolute conformity with the requirement due to manufacturing process variations, assembly, and other factors that may cause a deviation from the design goal. Provided that the deviation is within process tolerances so as to achieve practical conformity and the components described herein are able to function according to the application requirements, the term “substantially” encompasses any of these deviations.
The term “electrically connected,” “directly electrically connected” and the like as used herein describes a permanent low-impedance connection between electrically connected elements, for example a direct contact between the relevant elements or a low-impedance connection via a metal and/or a highly doped semiconductor.
Spatially relative terms such as “under,” “below,” “lower,” “over,” “upper” and the like, are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first,” “second,” and the like, are also 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.
With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6630726 | Crowley | Oct 2003 | B1 |
| 20020190397 | Kim | Dec 2002 | A1 |
| 20070161151 | Madrid et al. | Jul 2007 | A1 |
| 20090294934 | Shi | Dec 2009 | A1 |
| 20100078784 | Otremba | Apr 2010 | A1 |
| 20140110828 | Otremba | Apr 2014 | A1 |
| 20150076674 | Miyakawa | Mar 2015 | A1 |
| 20170179009 | Otremba | Jun 2017 | A1 |
| 20210074667 | Lee | Mar 2021 | A1 |
| 20210118778 | Blansaer | Apr 2021 | A1 |
| Number | Date | Country |
|---|---|---|
| 2016066700 | Apr 2016 | JP |
| 2018211686 | Nov 2018 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20220139811 A1 | May 2022 | US |
