A semiconductor package, a heatsink, and methods of manufacturing them

Abstract

This disclosure pertains to a semiconductor package comprising a heatsink, said heatsink, and methods of manufacturing them for thermal management of said semiconductor packages. The semiconductor package comprises a substrate, a semiconductor die mounted onto the substrate, a first terminal clip comprising at least two first clip protrusions electrically and thermally connected to the semiconductor die, and a second terminal clip comprising at least one second clip protrusion electrically and thermally connected to the semiconductor die and electrically isolated from the at least two first protrusions, wherein the at least one second clip protrusion is interleaved with the at least two first clip protrusions. The semiconductor package further comprises a first heatsink electrically and thermally mounted onto the at least two first clip protrusions and electrically isolated from the at least one second clip protrusion, wherein the heatsink is suspended above the second die surface of the semiconductor die.

Description

[0001] TITLE

[0002] A semiconductor package, a heatsink, and methods of manufacturing them

[0003] TECHNICAL FIELD OF THE DISCLOSURE

[0004] This disclosure pertains to a semiconductor package comprising a heatsink, said heatsink, and methods of manufacturing them for thermal management of said semiconductor packages.

[0005] BACKGROUND

[0006] Semiconductor packages are essential components in modern day electronics. They form the basic building blocks of most circuitry. As the semiconductor technology continues to advance, the semiconductor packages are becoming increasingly powerful. However, this increased performance often comes paired with higher power dissipation, leading to significant heat generation inside the semiconductor package.

[0007] Excessive heat in semiconductor packages can lead to the several problems, such as reduced performance or reliability issues. Namely, the high temperatures can cause (temporal) degradation of the semiconductor die, leading to lower operating speeds of even permanent damage. Therefore, heatsinks have been introduced to improve the thermal management of semiconductor packages, which increase the surface area available for heat from the heat source inside the semiconductor package towards the outside environment.

[0008] Typically, because the form factor of a semiconductor package is small, heatsinks are designed as part of the electrical circuit, such as being a terminal connected to one surface side of a semiconductor die and having the other side of the heatsink be exposed to the outside of the semiconductor package. Although effective, there is a problem in case multiple terminals are present on said same surface side of the semiconductor die. Namely, then, the heatsink would create an electrical shortage between the two terminals, making the semiconductor package useless.

[0009] Since such semiconductor dies are becoming increasingly more prominent in semiconductors packages, e.g. in Gallium Nitride power packages, and because thisproblem has not adequately been resolved, the goal of the current disclosure is to provide a semiconductor package, which offers improved thermal dissipation for semiconductor packages with semiconductors dies having at least two terminals on a same die surface.

[0010] SUMMARY

[0011] Recently, power electronic semiconductor packages utilizing Gallium Nitride (GaN) have been introduced into the market, which allow for greater operating currents, which thus also generate more internal heat. Unfortunately, however, the thermal conductivity is worse compared to Silicon (Si) and Silicon Nitride (SiN), therefore heatsinks are almost a must. Furthermore, the manufacturing process of such GaN semiconductor packages makes that at least two terminals of the semiconductor transistor are provided on the same die surface. The disclosure especially provides solution for these types of semiconductor packages.

[0012] To achieve this, the disclosure pertains in a first aspect to a semiconductor package comprising a substrate and a semiconductor die having a first die surface and a second die surface opposite to the first die surface, wherein the semiconductor die is mounted with its first die surface onto the substrate.

[0013] The semiconductor package further comprises a first terminal clip comprising at least two first clip protrusions, wherein the at least two first clip protrusions are electrically and thermally connected to the second die surface of the semiconductor die, and a second terminal clip comprising at least one second clip protrusion, wherein the at least one second clip protrusion is electrically and thermally connected to the second die surface of the semiconductor die and electrically isolated from the at least two first protrusions of the first terminal clip, the at least one second clip protrusion of the second terminal clip is interleaved with the at least two first clip protrusions of the first terminal clip.

[0014] Furthermore, the semiconductor package comprises a first heatsink electrically and thermally mounted onto the at least two first clip protrusions of the first terminal clip and electrically isolated from the at least one second clip protrusion of the second terminal clip, wherein the heatsink is suspended above the second die surface of the semiconductor die.Semiconductor packages comprising two terminals on a single die surface typically are provided with areas on the second die surface which belong to the one or the other terminal. In this disclosure, these areas are interleaved or interdigitated, meaning that they alternate between the two consecutively, such that a pattern of terminal 1-2- 1-2-1 -etc. would be obtained. This is, for instance, beneficial for turning the current flow from the first terminal to the second terminal on or off, because a third terminal could deplete or replenish the electrons at the interfaces of those interleaved areas. To have electrical connections over the maximum area of the second die surface plurality of protrusions. Each terminal clip is provided with a plurality of protrusion (at least one or at least two). These protrusions may be known as fingers and may be connected to the semiconductor die by means of solder material or conductive adhesive.

[0015] The benefit of a semiconductor package according to the disclosure is that a heatsink is provided in thermal connection suspended above the semiconductor die, therefore being closest to the source of heat in the semiconductor package. That way, the thermal management of the semiconductor package is improved. Furthermore, the first heatsink being electrically isolated from the at least one second clip protrusion of the second terminal clip ensures that the semiconductor package can still operate, while being electrically and thermally connected to the at least two first clip protrusions.

[0016] In an example of the semiconductor package, the semiconductor die is a transistor comprising a source and a drain provided on a second die surface of the semiconductor die.

[0017] In this example, the two terminals of the semiconductor transistor are explicitly chosen to be the source and the drain, since these are two terminals which are known to carry the most current and therefore generate the most heat. In this particular example, a gate or even other terminals may also be provided on the semiconductor transistor to control the flow of current between the at least two first clip protrusions and the at least one second clip protrusion.

[0018] In a subsequent example of the semiconductor package, the at least two first clip protrusions of the first terminal clip are connected to the drain, and the at least one second clip protrusion of the second clip terminal is connected to the source.

[0019] In this example, the first heatsink is directly thermally connected to the at least two first clip protrusions of the drain, since the drain may be the largest source of heatin the semiconductor package. That way, the most efficient heat subtracting can take place in the semiconductor package.

[0020] In yet another example of the semiconductor package, the semiconductor die is a Gallium Nitride (GaN) enhancement mode High-Electron Mobility Transistor.

[0021] As explained in the beginning of this summary the thermal properties GaN are worse compared to Si and SiC, therefore, the semiconductor package according to this example is particularly beneficial. Furthermore, enhancement mode (e-mode) High-Electron Mobility Transistors (HEMT)s are power electronic packages, which can handle large currents and thus internally create a lot of heat, such that the solution according to the disclosure is also especially beneficial for such semiconductor packages.

[0022] In yet another example of the semiconductor package, the heatsink comprises a plurality of elongated ridges, wherein the plurality of elongated ridges is connected to the at least two first clip protrusions, preferably a number of elongated ridges of the plurality of elongated ridges is a same number of first clip protrusions of the at least two first clip protrusions, such that each elongated ridge lines-up or is aligned or overlaps with a single distinct first clip protrusion. The alignment may be understood to be in the longitudinal direction of the elongated ridges, such that the elongated ridge is stacked substantially covering and abutting the first clip protrusion.

[0023] The benefit thereof is that a ribbed surface is obtained of the heatsink, which does not have the typical function of a heatsink of enlarging the surface area, but rather functions to ensure electrical connection to one terminal and electrical isolation to the other terminal.

[0024] In another example of the semiconductor package, the heatsink further comprises a plurality of alignment protrusions provided at a side of the heatsink oriented towards the semiconductor die.

[0025] These alignment protrusions allow for aligning the heatsink during manufacturing and could be considered as claws oriented towards the semiconductor die. Namely, these alignment protrusions are intended to abut the at least two first clip protrusions, since in that scenario it is ensured that each elongated ridge is aligned with each first clip protrusion in its longitudinal direction. One may consider that in case only one alignment protrusion, especially being on the corners of the heatsink, is abutting a first clip protrusion that the elongated ridges and first clip protrusions couldbe orientated with at an angle with respect to each other. That way, it may be possible that one elongated ridge is touching more than one first clip protrusion. When more alignment protrusions are brought into abutment with the first clip protrusions, for instance by rotation and / or translation of the heatsink, the angle between each first clip protrusion and elongated ridge will diminish and the overlapping area will increase. Eventually, by the use of these alignment protrusions each first clip protrusion will substantially be covered by an elongated ridge of the heatsink, making manufacturing easier and more reliable. Furthermore, this process may help ensuring the electric isolation of the heatsink with the at least one second clip protrusion.

[0026] In an example thereof, the plurality of alignment protrusions is aligned with the plurality of elongated ridges.

[0027] Again, it may be preferably that a number of elongated ridges of the plurality of elongated ridges is a same number of alignment protrusions of the plurality of alignment protrusions. That way, each alignment protrusion lines-up or is aligned or overlaps with a single distinct elongated ridge.

[0028] As previously explained, these alignment protrusions aid the alignment of the heatsink and ensure electrical isolation with the at least one second clip protrusion. Furthermore, having aligned alignment protrusions with the elongated ridges allows easier manufacturing of the heatsink, since the number of manufacturing step can be limited.

[0029] In another example of the semiconductor package, the elongated ridges are connected by means of solder.

[0030] And in yet another example, the elongated ridges are made of solder.

[0031] Solder can be effective means for electrically and thermally connecting the elongated ridges to the at least two first clip protrusions. Care should be taken, however, since solder is liquified for creating a connection. Therefore, channels, ridges, or other means for directing / maintaining the solder in the desired location are required on the heatsink. A particular beneficial example for this is making the elongated ridges out of solder material being partially embedded into the heatsink itself. That way, any potential flow of the solder is constricted to be along the elongated ridges, thus not creating electrical shorts between the at least two first clip protrusions and at least one second clip protrusion.In an example thereof, the solder is selected from a list of: Tin-Silver-Copper (SnAgCu) alloy, Lead-Tin-Silver (PbSnAg) alloy, Hybrid Silver (Ag) Sinter paste, Hybrid Copper (Cu) Sinter paste, or copper (Cu) in foil or strip form. Furthermore, it may be beneficial to have each elongated ridge encompass a strip of flux to improve the creation of an electrical connection.

[0032] In another example, the flux of encompassed by the solder may be selected from a list of: Rosin Flux, Water soluble flux, inorganic flux, organic acid flux, rosin mildly activate (RMA) flux, or acidic flux. These fluxes are known to improve the wettability of liquified solder onto the clip protrusions and / or the heatsink.

[0033] In a further example of the semiconductor package, the semiconductor package comprises a second heatsink electrically isolated from the first heatsink, wherein the second heatsink is mounted onto the at least one second clip protrusion, wherein the heatsink is suspended above the second die surface of the semiconductor die.

[0034] A second heat sink provided on the at least one second clip protrusion may ensure that conducted or generated heat may also be subtracted from the second terminal clip, such that the thermal management of the semiconductor clip may even further be improved.

[0035] It should be noted that the number protrusions of the at least two first clip protrusions and the at least one second clip protrusion could be limited to two and one, respectively. However, it may be preferable to have two-two, three-two, three-three, four-three, or four-four respective protrusions for the first and second clip. These are design considerations which depend on the individual semiconductor package and the requirements thereof. Furthermore, a not limited number of combined protrusions allows the semiconductor package to have a small form factor.

[0036] A second aspect of the disclosure pertains to a heatsink for use in a semiconductor package, wherein the heatsink comprises a baseplate of a first metal material having a plurality of ridges of a second metal material at least partially embedded in the base plate, wherein the second metal material is different from the first metal material, and wherein each ridge with its second metal material encompasses a flux strip. The heatsink further comprises a plurality of alignment protrusions.

[0037] It should be understood that the functionality of the plurality of elongated ridges is to ensure electrical and thermal connections with a plurality of clip protrusions orclip fingers of a semiconductor package. Even preferably, the heatsink is adapted for a plurality of alternating or digitating clip protrusions of at least two terminals of a semiconductor package. Furthermore, because of the configuration as elongated ridges, electrical isolation with neighboring clip protrusions belonging to another terminal can be ensured.

[0038] Further, the second metal material may be a solder, which can be melted to form electrical and thermal connections with a plurality of clip protrusions of a semiconductor package. While being partially encompassed in the first metal material of the baseplate it can be assured that the solder will remain in its elongated ridge configuration, such that the electrical and thermal connection can be precisely known.

[0039] To ensure that the heatsink is positioned correctly with respect to clip protrusions of a semiconductor package, the heatsink comprises alignment protrusions. These alignment protrusions allow for aligning the heatsink during manufacturing of a semiconductor package. Namely, these alignment protrusions are intended to abut the clip protrusions of a semiconductor package, since in that scenario it is ensured that each elongated ridge is aligned with each clip protrusion in its longitudinal direction. The alignment protrusions may be adapted to abut clip protrusions of a semiconductor package, such that in that case the elongated ridges substantially align / overlap with the clip protrusions of said semiconductor package.

[0040] In such case it may be preferable that a number of elongated ridges of the plurality of elongated ridges is a same number of clip protrusions of a semiconductor package, such that each elongated ridge lines-up or is aligned or overlaps with a single distinct clip protrusion.

[0041] It should be clear for the expert in the field that the heatsink according to the second aspect of the disclosure may also have any of the technical features as discussed in the first aspect of the disclosure.

[0042] In an example of the heatsink, the plurality of alignment protrusions is provided at a side edge extending perpendicular to the baseplate.

[0043] In this example, the alignment protrusions may be considered as claws oriented towards the semiconductor die. They ensure, as previously mentioned, that the heatsink may be positioned and oriented correctly with respect to clip protrusions of a semiconductor package. That way, the correct thermal dissipative property of the heatsink can be guaranteed, and furthermore it can be assured that the heatsink wouldnot create an electrical short for semiconductor packages wherein both terminals are provided on a same die surface of a semiconductor die of the semiconductor package.

[0044] Correct alignment of orientation is that regard can be considered as substantial overlap between the elongated ridges and clip protrusions of the semiconductor package.

[0045] In another example of the heatsink, the plurality of alignment protrusions is aligned with the elongated ridges.

[0046] In this particular example, it is beneficial to have the alignment protrusions to be aligned with the elongated ridges, such that the alignment protrusions ensure substantial overlap of the elongated ridges with clip protrusions of a semiconductor package. These alignment protrusions may be provided along the elongated ridges but could also be provided perpendicularly at an edge of the heatsink, such that they provide some type of clawing action.

[0047] It may even be preferably that a number of elongated ridges of the plurality of elongated ridges is a same number of alignment protrusions of the plurality of alignment protrusions. That way, each alignment protrusion lines-up or is aligned or overlaps with a single distinct elongated ridge.

[0048] A third aspect of the disclosure pertains to a method of manufacturing a semiconductor package comprising the steps of:

[0049] - providing a substrate;

[0050] - mounting at least one semiconductor die on the substrate;

[0051] - connecting a first terminal clip, comprising at least two first clip protrusions, with the at least two first clip protrusions electrically and thermally to the at least one semiconductor die;

[0052] - connecting a second terminal clip, comprising at least one second clip protrusion, with the at least one second clip protrusion electrically and thermally to the at least one semiconductor die, such that the at least two first clip protrusions are interleaved with the at least one second clip protrusion;

[0053] - connecting a heatsink, comprising elongated ridges and alignment protrusions extending perpendicular at a side edge of the heatsink, with its elongated ridges electrically and thermally to the at least two first clip protrusions.

[0054] The method according to the disclosure provides a way to manufacture semiconductor packages with improved thermal management, having at least twoterminals provided on a same die surface. Furthermore, interleaved or interdigitated clip protrusions are provided to improve the current transfer between the two terminals of the semiconductor package.

[0055] In the step of connecting the heatsink, the alignment protrusions may aid in aligning the heatsink with respect to the at least two first clip protrusions. The alignment protrusions may be considered as claws oriented towards the semiconductor die, which are intended to abut the at least two first clip protrusions. In such a scenario it is ensured that each elongated ridge is aligned with each first clip protrusion in its longitudinal direction. For this the number of elongated ridges may be equal to the number of first clip protrusions.

[0056] For alignment, more than one alignment protrusion may be present for every first clip protrusion. Alternatively, the alignment protrusions may only be present at both outermost elongated ridges. Lastly, every elongated ridge may correspond to only one alignment protrusion.

[0057] The alignment of the elongated ridges of the heatsink onto the first clip protrusions of the semiconductor package is performed during the step of connecting the heatsink. Here for, the heatsink is brought into contact with the at least two first clip protrusions and the alignment protrusions are brought into abutment. One could view the alignment protrusions to be positioned such, that (semi)automatic alignment or translation may occur during the positioning of the heatsink.

[0058] In case the alignment protrusions are provided at an edge of the heatsink oriented perpendicular to the base plate, a similar alignment action may occur as to when a rake is used to rake / pull a heavy object. First, an initial alignment protrusion may abut the one of the first clip protrusions. This will likely occur at one of the outermost alignment protrusions on the heatsink. Then because of the resistance at said initial alignment protrusion a rotation and / or translation of the heatsink will be induced when a slight force is applied to the heatsink horizontal to the baseplate, which will cause the other alignment protrusions to get into abutment with other first clip protrusions. This in turn will cause each first clip protrusion to be substantially covered by an elongated ridge of the heatsink. Subsequently, the heatsink can be attached with its elongated ridges onto the at least two first clip protrusions of the semiconductor package, ensuring electrical and thermal connection with only the at least two first clip protrusions and ensuring electrical isolation of the heatsink with the at least onesecond clip protrusion. This (semi)-automatic alignment makes manufacturing of the semiconductor packages easier and more reliable, since incorrect short circuit formation between the at least two first clip protrusions and the at least one second clip protrusion can be circumvented.

[0059] All in all, this aspect of the disclosure provides a method of manufacturing semiconductor packages which have an improved thermal management. Particularly, for semiconductor package wherein at least two terminals are provided on the same die surface.

[0060] A fourth aspect of the disclosure pertains to a method of manufacturing a heatsink for use in a semiconductor package comprising the steps of:

[0061] - providing a baseplate of a first metal material;

[0062] - creating a plurality of elongated ridges of a second metal material partially embedded into the first metal material, wherein the second metal material of each ridge of the plurality of ridges encompassing flux;

[0063] - removing first metal material from the baseplate in between the plurality of elongated ridges to create a plurality of openings;

[0064] - forming alignment protrusions oriented perpendicular to the baseplate;

[0065] The method according to this aspect of the disclosure provides a heatsink for use in a semiconductor package, which allows for effect thermal drain from a semiconductor package adapted to have two terminals on a same die surface of the semiconductor die of said semiconductor package.

[0066] To achieve this the plurality of elongated ridges are formed made of a second metal material partially embedded into the baseplate made of a first metal material. This way, the heat can be drained by making both a thermal and electrical connection with the second metal material to the semiconductor package. These elongated ridges further allow for specific connection with only one terminal of the two terminals on the same die surface of the semiconductor package, and electric isolation with the other terminal.

[0067] Furthermore, alignment protrusions are formed on the heatsink to enabling easier and faster connectivity of the heatsink onto the semiconductor package.

[0068] In an example of the method of manufacturing a heatsink the plurality of openings is created at a side edge of the heatsink, such that the step of forming maybe simple bending of the alignment protrusions along a folding line perpendicular to the plurality of elongated ridges.

[0069] In an alternative example of said method, the method further comprises the step of cutting the heatsink, after the step of removing first metal material and before the step of forming the orientation protrusions, perpendicular to the plurality of elongated ridges along the plurality of openings.

[0070] The above two examples, describe different methods of forming perpendicular alignment protrusions.

[0071] In the first example, a plurality of openings is created at a side edge of the heatsink, resulting in alignment protrusions. These openings can be chosen to be such that they fall in between the elongated ridges. That way the alignment protrusion may also comprise the second metal material and a flux core.

[0072] In the second example, the plurality of openings is formed in between elongated ridges along a perpendicular direction of the heatsink. To eventually form the alignment protrusions, it is required to cut along said perpendicular direction and through the openings. With this example two heatsinks can be formed from one starting piece of material. Again, the alignment protrusions may be made of the second metal material comprising a flux core.

[0073] In a further example of the method of manufacturing a heatsink, the step of forming the orientation protrusions is performed by means of bending.

[0074] An efficient way of forming the alignment protrusions may be by bending the initially obtained protrusions extending along the length direction of the elongated ridges along a perpendicular direction, such that all of the plurality of alignment protrusions can be bent with one single bend action.

[0075] In yet another example of the method of manufacturing a heatsink, the step of creating a plurality of elongated ridges is performed by means of skiving and cold pressure cladding.

[0076] An efficient way of forming a plurality of primary elongated ridges of a first metal material may be skiving, wherein very precise ridges can be formed at very precise interspacing. Subsequently, to create a preferable metal interface for creating a both a thermal and electrical connection, a second metal material may be cold pressure cladded in between the primary elongated ridges, thereby forming the actual elongated ridges. In another example, it may be even more beneficial to subsequently removepart of the primary elongated ridges of a first metal material, such that the elongated ridges of a second metal material obtain greater prominence (stand out more), yet still being partially embedded into said first metal material.

[0077] All in all, the semiconductor package, the heatsink, and the method of manufacturing them, provide solutions to overheating and heat control in semiconductor packages comprising a semiconductor die having two terminals provided on a same die surface. The solutions of the disclosure allow extracting heat, while maintaining electrical integrity (non-shortening).

[0078] SHORT DESCRIPTION OF THE FIGURES

[0079] The disclosure will now be discussed with reference to the drawings, which show in:

[0080] Figure 1 shows a 3-dimensional representation of a prior art semiconductor package;

[0081] Figures 2a-2b show a 3-dimensional representation of a semiconductor package according to the disclosure;

[0082] Figures 3a-3b show another 3-dimensional representation of a semiconductor package according to the disclosure;

[0083] Figures 4a-4e show steps of a method of manufacturing a heatsink for use in semiconductor packages according to the disclosure;

[0084] Figures 5a-5e show steps of another method of manufacturing a heatsink for use in semiconductor packages according to the disclosure;

[0085] Figures 6a-6b show a top view and a side view, respectively, of the internals of a semiconductor package according to the disclosure;

[0086] Figures 7a-7b show a top view and a side view, respectively, of the internals of another semiconductor package according to the disclosure;

[0087] Figures 8a-8b show two perpendicular cross-sectional side views of a semiconductor according to the disclosure;DETAILED DESCRIPTION OF THE DISCLOSURE

[0088] For a proper understanding of the disclosure, in the detailed description below corresponding elements or parts of the disclosure will be denoted with identical reference numerals in the drawings.

[0089] The drawings are intended to highlight particular elements of the disclosure for better understanding. It will be clear to the person skilled in the art that certain elements may be combined and / or removed from the various examples given, well within the scope of the claims. These figures should thus not be considered limiting the scope of the disclosure but should be considered to clarify the subject matter of the claims.

[0090] Fig. 1 shows a prior art semiconductor package 10 comprising a substrate 18 onto which a semiconductor die (not shown) is mounted. To said semiconductor die, a first clip terminal 11 and a second clip terminal 12 are electrically and thermally connected to the same die surface side. The respective clip terminal 11 / 12 are shaped such that side terminals 11-1 / 12-1 stick out of the encapsulant 15 of the semiconductor package 10. These side terminals 11-1 / 12-1 are electrically connected and at approximately the same voltage potential as the top terminals 11-2 / 12-2 of the first and second clip terminal 11 / 12, respectively. In the field, the first clip terminal 11 may be known as the drain and the second clip terminal 12 as the source. Furthermore, to switch the semiconductor die of the prior art semiconductor package 10 a third clip terminal 13 is provided, which may also be known as the gate. Additionally, the semiconductor package 10 is provided with a fourth clip terminal 14, known as a Kelvin source.

[0091] The main problem with the prior art semiconductor package 10 of Fig. 1 is that the encapsulant, which is electrically isolating and therefore also partially thermally insulation, is directly provided on top of the semiconductor die and the die’s terminal connection to the first, second, third and fourth clip terminals 11 / 12 / 13 / 14. Therefore, heat generated in the semiconductor die cannot travel outwards efficiently and would cause the semiconductor die and the connections to the clip terminals 11 / 12 / 13 / 14 to heat up, causing malfunctioning and potentially even leading to melting / breaking of the electrical connections.The goal of this disclosure is to provide an improved thermal management of such semiconductor packages, and an example of a semiconductor package 20 according to the disclosure is shown in Fig. 2a and Fig. 2b.

[0092] This semiconductor package 20i comprises, similarly to the prior art semiconductor package 10, a substrate 28 to which a semiconductor die is mounted. To a same die surface are the first clip terminal 21 and the second clip terminal 22 electrically and thermally connected. Each terminal comprises side terminals 21-1 / 22-1 and top terminals 21-2 / 22-2, respectively.

[0093] The first terminal clip 21 comprises at least two first clip protrusions, wherein the at least two first clip protrusions are electrically and thermally connected to the second die surface of the semiconductor die, and a second terminal clip 22 comprises at least one second clip protrusion, wherein the at least one second clip protrusion is electrically and thermally connected to the second die surface of the semiconductor die and electrically isolated from the at least two first protrusions of the first terminal clip. The at least one second clip protrusion of the second terminal clip is interleaved with the at least two first clip protrusions of the first terminal clip.

[0094] Furthermore, the semiconductor package 20i of Figs. 2a-2b comprises a first heatsink 30 electrically and thermally mounted onto the at least two first clip protrusions of the first terminal clip 21 and electrically isolated from the at least one second clip protrusion of the second terminal clip 22, wherein the heatsink 30 is suspended above the second die surface of the semiconductor die. More information about the internal configuration of the semiconductor package 20i and the connection of the heatsink will be discussed in the description of Figs. 6a-6b, 7a-7b, and 8a-8b.

[0095] The heatsink 30 is shown in Fig. 1 to be directly connected to the second clip terminal 22, thereby forming a uniform surface at the top of the package. However, it may also be that the heatsink 30 and the second clip terminal 22 are electrically connected internally, but at the top surface may form separate top terminals. This difference is illustrated between Fig. 2a and Fig. 2b with the encapsulant 25 separating the heatsink 30 in Fig. 2b, while being one combined heatsink / terminal 30 / 21 in Fig.

[0096] 2a.

[0097] It should be acknowledged by the expert in the field that the first and second clip terminals 11 / 12 are expected to generate the most amount of heat and that the disclosure is therefore directed to these clip terminals 11 / 12. However, placement ofheatsinks of the third or the fourth clip terminal 13 / 14 could even further improve the thermal management of a semiconductor package.

[0098] In Fig. 3a another semiconductor package 2O2 according to the disclosure is shown, being similar to the semiconductor packages of Figs. 2a / b only this time comprising a first heatsink 30-1 and a second heatsink 30-2, wherein the first heatsink 30-1 is thermally and electrically connected to the at least two first clip protrusions, wherein the first heatsink 30-1 is suspended above the second die surface of the semiconductor die, and wherein the second heatsink 30-2 electrically isolated from the first heatsink 30-1, is mounted onto the at least one second clip protrusion, wherein the second heatsink 30-2 is suspended above the second die surface of the semiconductor die.

[0099] Do note that the heatsinks 30 / 30-1 / 30-2 are exposed to the outside of the semiconductor package 20 / 20I / 202. Since these heatsinks 30 / 30-1 / 30-2 are also electrically connected to the clip terminal(s) 21 / 22, they may also be used for creating an electrical connection to further circuitry. Because of that reason, the heatsink 30 / 30-1 / 30-2 and the clip terminal 21 / 22 are also shown as an integral part in the Figs. 2a and 3a. In that regard, it may even be that they are manufactured and mounted as an integral clip part.

[0100] Alternatively, the heatsink 30 / 30-1 / 30-2 and the clip terminal 21 / 22 are separate parts such that a small channel of encapsulant 25 is provided in between the two. Note, however, that, the heatsink 30 / 30-1 / 30-2 and the clip terminal 21 / 22, respectively, are still electrically connected on the inside of the semiconductor package 2O1 / 2O2.

[0101] The Figs. 4a-4e and 5a-5f show two methods 200 for manufacturing a heatsink for use in a semiconductor package 2O1 / 2O2. The steps a-c for both Figs, are the same and are thus discussed at the same time.

[0102] In Fig. 4a / 5a, a base plate of a first metal material is provided into which a plurality of primary elongated ridges 211 is formed. This forming may be performed by cutting, CNC-ing, or skiving. Subsequently, as shown in Fig. 4b / 5b, a second metal material comprising a flux core 215 is cold pressure cladded into the trenches between the primary elongated ridges 221, thereby forming the actual elongated trenches of a second metal material 212.The resulting configuration is shown in a cross-section in Fig. 4c / 5c, wherein the elongated trench 212 made of a second metal material is shown encompassing a flux core 215, wherein the elongated trench 212 is partially embedded into the first metal material of the base plate 210. It may be beneficial to at least partially remove the primary elongated ridges 211, such that the elongated trench 212 stands outs more. This is beneficial, since the second metal material is intended to be a solder material, which would liquify during reflow. With the primary elongated ridges 211 at least partially removed, the solder will be contained to the elongated ridge 212, such that it can be assured that the electrical and thermal connection is only provided along said elongated ridge 212.

[0103] For the following steps, the two methods 201 / 202 of the Figs. 4d-4e and 5d-5f are different and will therefore be discusses separately. In the method 201 of Fig. 4d, a top view of the intermediate heatsink is shown, wherein the baseplate 210 made of a first metal material is shown to comprise elongated ridges 212 of a second metal material. Furthermore, rectangular areas are indicated with a dashed line 216, which are intended areas to be cut out of the intermediate heatsink. These areas 216 located in between the elongated ridges 216 at a side edge of the intermediate heatsink. After cutting these areas 216 out of the intermediate heatsink, protrusions are formed of the second metal material partially embedded into the baseplate 210 extending along the length direction of the elongated ridges 216. These protrusions can subsequently be bent over approximately 90 degrees, such that alignment protrusions 217 are obtained. This is depicted in Fig. 4e, wherein the alignment protrusions 217 are shown to be substantially perpendicular to the baseplate 210 of the heatsink for use in semiconductor packages. The alignment protrusions 217 also comprise a second metal material encompassing a flux core, being partially embedded into the first metal material of the baseplate 210.

[0104] The flux of encompassed by the solder (second metal material) may be selected from a list of: Rosin flux, Water soluble flux, inorganic flux, organic acid flux, rosin mildly activate (RMA) flux, or acidic flux. These fluxes are known to improve the wettability of liquified solder onto the clip protrusions 211 / 221 and / or the baseplate 210 of the heatsink 30.

[0105] An alternative method of manufacturing a heatsink for use in semiconductor packages 202 is further disclosed in Figs. 5a-5f, wherein Figs. 5a-5c have alreadybeen discussed in combination with Figs. 4a-4c. In Fig. 5d an intermediate heatsink is shown comprising elongated ridges 212 of a second metal material partially embedded in a baseplate 210 of a first metal material. Again, rectangular areas 216 are indicated to be cut out of the heatsink. This time, they are also provided in between the elongated ridges 212, but are not provided at an edge of the heatsink. Rather they are provided along a perpendicular direction to the length direction of the elongated ridges 216. These areas 216 can be removed by stamping or any other material removal tool / method. Subsequently, a perforated intermediate heatsink is obtained.

[0106] In Fig. 5e is shown that the perforated intermediate heatsink can be cut along a perpendicular direction to the length direction of the elongated ridges 212 through the created openings of Fig. 5d. This way, two heatsinks are obtained with protrusions extending in the length direction of the elongated ridges 212, thereby increasing the yield of the manufacturing by a factor of two.

[0107] Lastly, similar to Fig. 4e, in Fig. 5f, the protrusions can be bent over 90 degrees to obtain alignment protrusions. These protrusions are also made of the second metal material encompassing a flux core and partially embedded in a first metal material of the baseplate 210.

[0108] Figs. 6a-6b, 7a-7b, and 8a-8b show the internals of semiconductor packages according to the disclosure. Here the electrical and thermal connection of the heatsink for use in semiconductor packages will be explained in more detail.

[0109] Figs. 6a and 6b show an open top view and side view of a semiconductor package 2O3, respectively, meaning without encapsulant. In Fig. 6a, it can be clearly seen that a semiconductor die 25 is mounted with its first die surface onto a substrate 28, and that two clip terminals 21 / 22 are provided on the second die surface.

[0110] The semiconductor package 2O3 further comprises a first terminal clip 21 comprising at least two first clip protrusions 211, wherein the at least two first clip protrusions 211 are electrically and thermally connected to the second die surface of the semiconductor die 25, and a second terminal clip 22 comprising at least one second clip protrusion 221, wherein the at least one second clip protrusion is electrically and thermally connected to the second die surface of the semiconductor die 25 and electrically isolated from the at least two first protrusions 211 of the first terminal clip 21. In the example of Fig. 6a both the number of first clip protrusions 211 and of the second clip protrusions 221 is equal to three, which creates a largeractivation area on the semiconductor die 25, allowing for more current to be passed through. Furthermore, it is shown that the at least one second clip protrusion 221 of the second terminal clip 22 is interleaved with the at least two first clip protrusions 211 of the first terminal clip 21.

[0111] Because of this interleaving or interdigitating a simple metal plate or clip as heatsink would not suffice, since that would create an electrical short between the two clip terminals 21 / 22. Therefore, a heatsink 30 similar to Figs. 4e or 5f, is mounted onto the at least two first clip protrusions 211 of the first terminal clip and electrically isolated from the at least one second clip protrusion 221 of the second terminal clip 22, wherein the heatsink is suspended above the second die surface of the semiconductor die 25. That way, heat created in or on the semiconductor die can be transported to the outside of the semiconductor package 203efficiently, creating better thermal management of said semiconductor package 203.

[0112] To do so, the heatsink 30 comprises a plurality of elongated ridges made of a solder material partially embedded into the baseplate of the heatsink 30. The solder material elongated ridges are positioned directly on top of the at least two first clip protrusions 221, whereafter reflow solder is performed to create the electrical and thermal connection. To ensure that no solder leaks out, thereby causing electrical shortening between the first and second clip protrusions 211 / 221, small upright notches of a tougher first metal material, preferably copper, are present to contain the second metal material.

[0113] Furthermore, to ensure that the placement of the heatsink is correct, alignment protrusions 217 are provided onto the heatsink 30. In the example of Fig. 6a, the alignment protrusions 217 are provided at an edge of the heatsink 30, such that they align with the elongated ridges 212 and with the at least two first clip protrusions 211. This way, the heatsink can be placed against the ends of the first clip protrusions 211, since when all alignment protrusions 217 abut all intended first clip protrusions 211 then it is assured that the heatsink is positioned square and that the elongated ridges 212 substantially overlap the first clip protrusions 211. Otherwise, an angle between the two may be present.

[0114] Such configuration of a heatsink 30, makes the manufacturing of a semiconductor 20 according to the disclosure easier, faster, cheaper, and more reliable.In Fig. 6b, the same semiconductor package 2O3 is shown as in Fig. 6a, except for its side view is shown. In the side view, the clawing action of the alignment protrusion 217 is better visualized, abutting the first clip protrusion 211, such that the elongated ridge 212 of the heatsink 30 overlaps said first clip protrusion 211. Only then a stable and correct electrical and thermal connection can be obtained during reflow soldering of the heatsink to the first clip protrusions 211.

[0115] In the above-discussed example of the semiconductor package 2O3, the at least two first clip protrusions 211 of the first terminal clip 21 may be connected to the drain, and the at least one second clip protrusion 221 of the second clip terminal 22 may be connected to the source, since then the first heatsink 30 is directly thermally connected to the at least two first clip protrusions 211 of the drain, since the drain may be the largest source of heat in the semiconductor package 204. That way, the most efficient heat subtracting can take place in the semiconductor package 204.

[0116] In Figs. 7a and 7b, an open top view and a side view of another semiconductor package according to the disclosure are shown, respectively. The side view image of Fig. 7b is similar to the side view of Fig. 6b, wherein the clawing of the alignment protrusion 211 around the first clip protrusions 211 is nicely depicted. What cannot be seen from such a side view, is that there is also a clawing action of a second heatsink 30-2 on the second clip protrusions 221, positioned mirrored to the first heatsink 30-1.

[0117] This becomes clear in Fig. 7a, wherein the semiconductor package 204is shown to comprise a first heatsink 30-1 and a second heatsink 30-2, wherein the first heatsink is electrically and thermally connected to the first clip protrusions 211 of the first clip terminal 21 , and wherein the second heatsink 30-2 is connected to the second clip protrusions 221 of the second clip terminal 22. Both of the heatsink 30-1 / 30-2 are suspended above the semiconductor die and are electrically isolated from each other. That way, the proper working of the semiconductor package 204can be guaranteed, while still allowing heat to be subtracted from both the source and the drain.

[0118] The benefit of this semiconductor package 204according to the disclosure is that two heatsinks 30-1 / 30-2 are provided in thermal connection suspended above the semiconductor die 25, therefore being closest to the source of heat in the semiconductor package. That way, the thermal management of the semiconductor package 204is improved. Furthermore, the first heatsink 30-1 being electricallyisolated from the at least one second clip protrusion 221 of the second terminal clip 22 ensures that the semiconductor package 2O4 can still operate, while being electrically and thermally connected to the at least two first clip protrusions 211.

[0119] In Figs. 8a and 8b, two cross-sectional side views of semiconductor packages 20 according to the disclosure are shown. Fig. 8a shows a cross-sectional view along the length direction of the elongated ridges 212 of the heatsink 30. In this figure, it can be clearly viewed that the elongated ridges 212 abut the clip protrusions 211 / 221 at a top side and that the alignment protrusions 217 abut the clip protrusions 211 / 221 at a short side. That way, an effective clawing of the heatsink 30 can be obtained, wherein its position is precisely known with respect to the clip protrusions 211 / 221.

[0120] In Fig. 8b, a cross-sectional side view of a semiconductor package 20 perpendicular to the length direction of the elongated ridges 212 is shown. This figure clearly shows the electrical isolation of the heatsink 30 with one of the second or first clip protrusions 221 / 211, when the heatsink is mounted onto the first or second clip protrusions 211 / 221, respectively. Furthermore, this figure shows that the heatsink 30 comprises the elongated ridges 212 not to increase the surface area of the heatsink 30, as is typically the case in heatsinks 30, but in order to create an electrical and thermal connection with only one of the first or second clip protrusions 211 / 221. That way, the proper functioning of the semiconductor package can be guaranteed, while heat can be extracted efficiently away from the semiconductor package.

[0121] In all the above discussed examples, it may be that the semiconductor die 25 is a transistor comprising a source and a drain provided on a second die surface of the semiconductor die 25. The two terminals of the semiconductor transistor that are explicitly chosen to be the source and the drain, since these are two terminals which are known to carry the most current and therefore generate the most heat.

[0122] The examples above have also been shown to comprise a gate or even other terminals on the semiconductor transistor to control the flow of current between the at least two first clip protrusions 211 and the at least one second clip protrusion 221.

[0123] Furthermore, each semiconductor die 25 of all above-discussed examples may be a Gallium Nitride (GaN) enhancement mode High-Electron Mobility Transistor, since the thermal properties GaN are worse compared to Si. Furthermore, enhancement mode (e-mode) High-Electron Mobility Transistors (HEMT)s are powerelectronic packages, which can handle large currents and thus internally create a lot of heat.

[0124] In the examples of the Figs., the plurality of alignment protrusions has been aligned with the plurality of elongated ridges, however it should be noted that this is not necessarily needed and that the alignment protrusions 217 may even be provided at the sides perpendicular to the length direction of the elongated ridges 212.

[0125] Throughout the description of the Figs., statements have been made about both an electrical and thermal connection between the elongated ridges and the clip protrusions 211 / 221 , this may be done by means of solder. Alternatively, the elongated ridges may even be made of solder. For the latter two cases, the solder may be selected from a list of: Tin-Silver-Copper (SnAgCu) alloy, Lead-Tin-Silver (PbSnAg) alloy, Hybrid Silver (Ag) Sinter paste, Hybrid Copper (Cu) Sinter paste or copper (Cu) as a foil or strip. Furthermore, it may be beneficial to have each elongated ridge encompass a strip of flux to improve the creation of an electrical connection.

[0126] It should be noted that the number protrusions of the at least two first clip protrusions and the at least one second clip protrusion could be limited to two and one, respectively. However, it may be preferable to have two-two, three-two, three-three, four-three, or four-four respective protrusions for the first and second clip. These are design considerations which depend on the individual semiconductor package and the requirements thereof. Furthermore, a not limited number of combined protrusions allows the semiconductor package 20 to have a small form factor.

[0127] All in all, the semiconductor packages 20 according to the disclosure and as explained in Figs., the heatsink 30, and the methods of manufacturing them, provide solutions to overheating and heat control in semiconductor packages 20 comprising a semiconductor die 25 having two terminals 21 / 22 provided on a same die surface. The solutions of the disclosure allow extracting heat, while maintaining electrical integrity (non-shortening).REFERENCE LIST

[0128] 10 prior art semiconductor package

[0129] 11 first clip terminal of prior art

[0130] 11-1 side terminal of first clip terminal of prior art

[0131] 11-2 top terminal of first clip terminal of prior art

[0132] 12 second clip terminal of prior art

[0133] 12-1 side terminal of first clip terminal of prior art

[0134] 12-2 top terminal of first clip terminal of prior art

[0135] 13 third clip terminal of prior art

[0136] 13-1 side terminal of third clip terminal of prior art

[0137] 14 fourth clip terminal of prior art

[0138] 14-1 side terminal of fourth clip terminal of prior art 18 substrate of prior art

[0139] 15 encapsulant of prior art

[0140] 20 semiconductor package according to the disclosure 20I-202-203-204first, second, third, and fourth semiconductor package 21 first clip terminal of the disclosure

[0141] 21-1 side terminal of first clip terminal of the disclosure 21-2 top terminal of first clip terminal of the disclosure 22 second clip terminal of the disclosure

[0142] 22-1 side terminal of first clip terminal of the disclosure 22-2 top terminal of first clip terminal of the disclosure 23 third clip terminal of the disclosure

[0143] 23-1 side terminal of third clip terminal of the disclosure 24 fourth clip terminal of the disclosure

[0144] 24-1 side terminal of fourth clip terminal of the disclosure 28 substrate of the disclosure

[0145] 25 encapsulant of the disclosure

[0146] 30 heatsink

[0147] 30-1 first heatsink

[0148] 30-2 second heatsink200 method according to the disclosure 201 first method according to the disclosure 202 second method according to the disclosure 210 baseplate

[0149] 211 primary elongated ridge

[0150] 212 elongated ridge

[0151] 215 flux core

[0152] 216 area to be removed

[0153] 217 alignment protrusion

Claims

1. 24CLAIMS1. A semiconductor package comprising:- a substrate;- a semiconductor die having a first die surface and a second die surface opposite to the first die surface, wherein the semiconductor die is mounted with its first die surface onto the substrate;- a first terminal clip comprising at least two first clip protrusions, wherein the at least two first clip protrusions are electrically and thermally connected to the second die surface of the semiconductor die;- a second terminal clip comprising at least one second clip protrusion, wherein the at least one second clip protrusion is electrically and thermally connected to the second die surface of the semiconductor die and electrically isolated from the at least two first protrusions of the first terminal clip, the at least one second clip protrusion of the second terminal clip is interleaved with the at least two first clip protrusions of the first terminal clip;- a first heatsink electrically and thermally mounted onto the at least two first clip protrusions of the first terminal clip and electrically isolated from the at least one second clip protrusion of the second terminal clip, wherein the heatsink is suspended above the second die surface of the semiconductor die.

2. The semiconductor package according to claim 1, wherein the semiconductor die is a transistor comprising a source and a drain provided on a second die surface of the semiconductor die.

3. The semiconductor package according to claim 2, wherein the at least two first clip protrusions of the first terminal clip are connected to the drain, and the at least one second clip protrusion of the second clip terminal is connected to the source.

4. The semiconductor package according to any of claims 2-3, wherein the semiconductor die is a Gallium Nitride (GaN) enhancement mode High-Electron Mobility Transistor.

5. The semiconductor package according to any of the preceding claims, wherein the heatsink comprises a plurality of elongated ridges, wherein the plurality of elongated ridges is connected to the at least two first clip protrusions.

6. The semiconductor package according to any of the preceding claims, wherein the heatsink further comprises a plurality of alignment protrusions provided at a side of the heatsink oriented towards the semiconductor die.

7. The semiconductor package according to claims 5 and 6, wherein the plurality of alignment protrusions is aligned with the plurality of elongated ridges.

8. The semiconductor package according to any of the preceding claims, wherein the elongated ridges are connected by means of solder.

9. The semiconductor package according to any of preceding claims, wherein the elongated ridges are made of solder.

10. The semiconductor package according to claim 8 or 9, wherein the solder is selected from a list of: Tin-Silver-Copper (SnAgCu) alloy, Lead-Tin-Silver (PbSnAg) alloy, Hybrid Silver (Ag) Sinter paste, Hybrid Copper (Cu) Sinter paste.

11. The semiconductor package according to any of preceding claims, wherein the semiconductor package comprises a second heatsink electrically isolated from the first heatsink, wherein the second heatsink is mounted onto the at least one second clip protrusion, wherein the heatsink is suspended above the second die surface of the semiconductor die.

12. A method of manufacturing a semiconductor package comprising the steps of:- providing a substrate;- mounting at least one semiconductor die on the substrate;- connecting a first terminal clip, comprising at least two first clip protrusions, with the at least two first clip protrusions electrically and thermally to the at least one semiconductor die;- connecting a second terminal clip, comprising at least one second clip protrusion, with the at least one second clip protrusion electrically and thermally to the at least one semiconductor die, such that the at least two first clip protrusions are interleaved with the at least one second clip protrusion;- connecting a heatsink, comprising elongated ridges and alignment protrusions extending perpendicular at a side edge of the heatsink, with its elongated ridges electrically and thermally to the at least two first clip protrusions.

13. A heatsink for use in a semiconductor package, wherein the heatsink comprises:- a baseplate of a first metal material having a plurality of ridges of a second metal material at least partially embedded in the base plate, wherein the second metal material is different from the first metal material, and wherein each ridge with its second metal material encompasses a flux strip;- a plurality of alignment protrusions.

14. The heatsink according to claim 13, wherein the plurality of alignment protrusions are provided at a side edge extending perpendicular to the baseplate.

15. The heatsink according to claim 13 or 14, wherein the plurality of alignment protrusions are aligned with the elongated ridges.

16. A method of manufacturing a heatsink for use in a semiconductor package comprising the steps of:- providing a baseplate of a first metal material;- creating a plurality of elongated ridges of a second metal material partially embedded into the first metal material, wherein the second metal material of each ridge of the plurality of ridges encompassing flux;- removing first metal material from the baseplate in between the plurality of elongated ridges to create a plurality of openings;- forming alignment protrusions oriented perpendicular to the baseplate;17. The method according to claim 16, wherein the plurality of openings is created at a side edge of the heatsink.

18. The method according to claim 16, further comprising the step of:- cutting the heatsink, after the step of removing first metal material and before the step of forming the alignment protrusions, perpendicular to the plurality of elongated ridges along the plurality of openings.

19. The method according to any of the claims 16-18, wherein the step of forming the alignment protrusions is performed by means of bending.

20. The method according to any of the claims 16-19, wherein the step of creating a plurality of elongated ridges is performed by means of skiving and cold pressure cladding.

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