Power-level device clamping piece

Abstract

The present disclosure relates to a clip for a power stage device. The clip includes a first portion defining a first planar surface, and a second portion connected to the first portion. The second portion includes a second planar surface, a cavity defined in the second planar surface, and at least one notch in a perimeter of the second planar surface, wherein the at least one notch extends into the cavity. Power driver devices including clips of the present disclosure, methods of forming clips, and methods of forming power driver devices are further described.

Description

Technical Field

[0001] The present invention relates to a clip for a power stage device and a method of forming the clip. Background Art

[0002] Power stage devices such as DrMOS and eFuse devices may require a driver component in the form of an IC die and at least one component (such as a MOSFET) connected to the driver. If large die components are used in a power stage device, the die and MOSFET components may have a relatively large footprint on the board on which they are disposed, resulting in a larger overall integrated circuit package. This may be undesirable if the electrical device in which the integrated circuit package is to be incorporated has limited space to accommodate its circuitry.

[0003] In addition, maintaining the integrity of the components in the circuitry of the device is also a key factor in optimizing the lifespan of the electrical device. If components such as a die or MOSFET in an integrated circuit package are worn or damaged over time, the electrical device may malfunction (or stop working altogether), thus requiring repair or replacement of the device.

[0004] The present invention seeks to eliminate or at least mitigate the problems associated with known devices, whether indicated herein or otherwise. Summary of the Invention

[0005] In a first aspect of the present invention, there is provided a clip for a power stage device. The clip includes a first portion defining a first flat surface and a second portion connected to the first portion. The second portion includes a second flat surface, a cavity defined in the second flat surface, and at least one notch in the periphery of the second flat surface, wherein at least one notch extends into the cavity.

[0006] The first portion and the second portion may define a frame for arranging components of a circuit or an integrated circuit package, such as a package for a driver MOSFET (DrMOS) or an electronic fuse (eFuse); this may require the use of multiple semiconductors in their assembly. In addition, such components may be provided in or arranged relative to the surface features of the first portion and the second portion. For example, a semiconductor may be provided in the cavity of the second portion of the clip. During the manufacturing process, the cavity may help to hold the die in place on the clip, thus preventing the die from moving from its intended position; ultimately improving the quality and consistency of the final IC package / power stage device. When attaching the die to the clip, the cavity may also help to accommodate solder (or any other conductive adhesive that may be used, such as a conductive epoxy, acrylic, or siloxane-based adhesive), which also helps to improve the quality of the final IC package incorporating the clip.

[0007] The clip formed in this way can also help to minimize the circuit board space occupied by the final IC package / power stage device in which the clip is incorporated. For example, the clip can allow the die and the MOSFET to be "stacked" one on top of the other while also being electrically connected. During the assembly of the power stage device, the second part can be arranged on top of the MOSFET, with the lower side of the cavity in contact with the MOSFET. Then the die can be set and attached in the cavity, resulting in a vertical "stacking" of the MOSFET and the die, thus reducing the footprint required for these components.

[0008] When the power stage driver is assembled with the vertically "stacked" components, notches are provided in the perimeter of the second part, where the notches extend into the cavity, which can also provide many advantages. For example, during the manufacture and use of the power stage driver, sharp or pointed vertices (which can be provided on conventional power stage driver clips) may provide areas of high stress concentration on the underlying MOSFET. Thus, over time, such high stress concentrations may damage the MOSFET, ultimately leading to MOSFET failure or complete cessation of operation. Therefore, the notches in the second part of the clip relieve this high stress concentration point, helping to extend the life of the MOSFET and improve the reliability of the power stage driver and any device to which it may be incorporated.

[0009] In addition, the notches in the perimeter of the second part can also allow a larger die to be placed in the cavity than can be used with a conventional power stage driver clip of the same size, as parts of the die may be able to overhang the edge of the cavity in which the die is set.

[0010] At least one of the first part and the second part can be formed of or include a wettable material. At least one of the first part and the second part can be formed of or include a metal wettable material. If the clip is formed of or includes a wettable material, this can allow the die to be directly soldered to the clip. In addition, since the die can be set in the cavity, the cavity is used to accommodate the solder used when attaching the die to the clip, ultimately helping to improve the manufacturing quality of the power stage device. Further, if the power stage device is assembled using the vertical "stacking" method described above, the second part of the clip can be directly soldered to the top contact area of the MOSFET (e.g., through the lower side of the cavity of the second part).

[0011] By forming the clip of a metal wettable material, electrical connectivity can be allowed between the MOSFET and the die of the power stage device through the clip. The clip can be formed of any suitable metal wettable material understood by those skilled in the art, such as tin, copper, nickel, aluminum, their alloys, etc.

[0012] The cavity can define a third flat surface. The third flat surface of the cavity can be configured to house a die. As described above, the combination of the third flat surface and the cavity can assist in housing and aligning the die during the manufacturing process while holding the die in place during subsequent manufacturing steps, thereby ultimately improving the manufacturing and product quality of the power stage driver.

[0013] The cavity defined in the second flat surface can be square. Alternatively, the cavity defined in the second flat surface can be rectangular.

[0014] At least one notch can include one of a curved notch, a triangular notch, and a right-angled notch.

[0015] According to a second aspect of the present invention, there is provided a power stage device. The power stage device includes:

[0016] A MOSFET,

[0017] A clip including a first portion defining a first flat surface and a second portion connected to the first portion; wherein the second portion includes a second flat surface, a cavity defined in the second flat surface, and at least one notch in the perimeter of the second flat surface, wherein at least one notch extends into the cavity,

[0018] wherein the cavity is disposed on the MOSFET such that the cavity is in electrical communication with the MOSFET; and

[0019] A die disposed in the cavity of the clip.

[0020] According to a third aspect of the present invention, there is provided a method of forming a clip for a power stage device. The method includes: providing a frame including a first flat portion and a second flat portion connected to the first flat portion, stamping a cavity into the second flat portion, and cutting at least one notch in the perimeter of the second portion, wherein at least one notch extends into the cavity.

[0021] The method provides a simple and cost-effective way to produce clips for power stage drivers and the like, while also providing clips with the additional advantages described above. By using simple manufacturing processes, such as stamping (to form a cavity in the second portion of the clip), high-quality clips can be manufactured quickly and at low cost.

[0022] The method can include stamping one of a square cavity and a rectangular cavity into the second flat portion

[0023] The method can include forming at least one of a curved notch, a triangular notch, and a right-angled notch in the perimeter of the second portion.

[0024] The frame can be a metal frame. The frame can be a wettable metal frame.

[0025] According to a fourth aspect of the present invention, a method of forming a power driver device is provided. The method includes: forming a clip by providing a frame including a first flat portion and a second flat portion connected to the first flat portion, stamping a cavity into the second flat portion, and forming at least one notch in a perimeter of the second portion, wherein the at least one notch extends into the cavity; disposing the cavity of the clip on a MOSFET such that the cavity is in electrical communication with the MOSFET; and attaching a die within the cavity of the clip.

[0026] It should be understood that the advantages described above with respect to the first aspect of the present invention apply, mutatis mutandis, to this aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments of the present invention will now be described with reference to the drawings, in which:

[0028] Figure 1A and Figure 1B shows a perspective view of a clip for a power stage device;

[0029] Figure 2A and Figure 2B show a plan view and a side view, respectively, of a power stage device including the Figure 1A and Figure 1B clip; and

[0030] Figure 3A and Figure 3B show a perspective view and a plan view of a power stage device assembled on a lead frame. DETAILED DESCRIPTION

[0031] Figure 1A and Figure 1B show a perspective view of a clip 10 for a power stage device according to the present disclosure.

[0032] First, as Figure 1AAs shown, the clip 10 includes a first part 20 and a second part 30, which are connected by a connecting part 40. The first part 20 defines a first flat surface 22 on its upper side. As shown in this example, a flat surface can also be defined on the lower side 24 of the first part 20. The first flat surface 22 can provide a surface for setting on / attaching to the components of the power stage during assembly, or provide an attachment surface for connecting the power stage device to other components of the circuit. In other examples, one or more surface features can extend from or be defined in the first flat surface 22. The flat surface defined on the lower side 24 of the first part 20 also provides a surface for setting on / attaching to the components of the power stage device, or provides an attachment surface for connecting the power stage device to other components of the circuit. Additionally, one or more surface features can extend from or be defined in the flat surface of the lower side 24 of the first part 20.

[0033] The second part 30 is connected to the first part 20 by a connecting member 40. The second part defines a second flat surface 31 on its upper side. A cavity 32 is defined within the second flat surface 31. During the manufacturing process, the clip can initially be provided with a substantially flat first part 20 and second part 30, or include substantially flat regions. In subsequent manufacturing steps, surface features such as the cavity 32 in the second part 30 of the clip 10 can be formed by stamping or machining (for example) the clip 10. In this example, the cavity 32 formed in the second part 30 of the clip 10 also defines a third flat surface 36. Thus, the cavity 32 can be used to house components of the final power stage device, which will be explained in more detail below. In this example, the cavity 32 is configured to house an integrated circuit die. In other examples, the cavity 32 can be used to accommodate or house other components of the power stage device in which the clip 10 is incorporated.

[0034] The second part 30 also includes an outer perimeter 35. In this example, the outer perimeter 35 defines a substantially rectangular shape, but in other examples, the perimeter 35 can define different shapes (e.g., substantially square, circular, or triangular). A plurality of notches 34 are defined in the perimeter 35 of the second part 30. In this example, four notches 34 are provided, where the notches 34 are disposed at the corners of the second part 30. In this example, the notches 34 are curved, but depending on the application, other examples can include notches 34 of different shapes / configurations.

[0035] In Figure 1A and Figure 1B , the notches 34 also extend into the cavity 32, the advantages of which will be outlined in more detail below. The extension of the notches 34 into the cavity 32 can vary according to the technical requirements of the various components of the power stage device in which the clip 10 is incorporated.

[0036] AsFigure 1B As shown, the cavity 32 of the collet 10 defines a lower surface or bottom surface 38. Since this example includes a cavity 32 that has been stamped into the second portion 30 of the collet 10, the lower surface or bottom surface 38 of the cavity 32 extends from the lower side of the second portion 30. This can be beneficial during the assembly of the power stage collet because the bottom surface 38 of the cavity can engage additional components of the power stage collet, such as a MOSFET (the bottom side 38 of the cavity engages and connects to the contact surface of the MOSFET, which will be explained in more detail below), and serves as an attachment surface.

[0037] Figure 1A and Figure 1B The collet 10 can be formed of any suitable material understood by those skilled in the art. For example, the collet 10 can be formed of a wettable material. Forming the collet 10 of a wettable material can allow components such as integrated circuit chips (e.g., by soldering) to be attached to the collet 10. Additionally, if the collet 10 is formed of a wettable material, this can allow the surface of the collet 10 (such as the lower surface 38 of the cavity 32, or the upper surface 22 and lower surface 24) to be attached (e.g., by soldering) to other components, such as other components of a circuit or an integrated circuit package.

[0038] The wettable material used to form the collet 10 can be a metal wettable material. Examples of metal wettable materials that can be used are tin, nickel, copper, aluminum, alloys including these wettable metals, and the like.

[0039] Figure 2A and Figure 2B shows Figure 1A and Figure 1B an example of the collet 100 assembled with the die 150 and the MOSFET 160 (e.g., the basic structure of a power stage device). Similar to the components of Figure 1A , Figure 1B and Figure 2A , Figure 2B the same reference numerals are used and incremented by 100.

[0040] The die 150 is assembled within the cavity 132 of the collet 100. As described above, if the collet 100 is formed of a wettable material, the die 150 can be soldered within the cavity 132 of the collet 100. In other examples, the die 150 can be attached to the collet 100 by any alternative means understood by those skilled in the art.

[0041] As Figure 2AAs shown, the cavity 132 formed in the second portion 130 is square and matches the shape of the die 150 disposed within the cavity 132. Thus, during the manufacturing process, the shape of the cavity 132 can be matched to the component to be disposed within the cavity 132. This may assist in aligning the die 150 on the clip 100 during the assembly / manufacturing process and in holding the die 150 in place during subsequent manufacturing steps (e.g., preventing the die from rotating within the cavity). In other examples, during the manufacturing process, the shape of the cavity 132 can be different (e.g., formed as rectangular) to match different components to be accommodated within the cavity 132.

[0042] When attaching the die 150 within the cavity 132, the cavity can also assist in accommodating excess solder (or any other conductive adhesive that may be used, such as a conductive epoxy, acrylic, or silicone-based adhesive). This can further assist in improving manufacturing / product quality as excess solder / adhesive can be prevented from spreading to other areas of the clip (which may otherwise have to be removed, thereby reducing the efficiency of the manufacturing process).

[0043] As Figure 2A shown, the die 150 extends into the notch 134 of the clip 100. In this example, the notch 134 has been formed in the corner of the second portion 130 to align with the corner 152 of the die 150 disposed within the cavity 132. Specifically aligning the notch 134 and the corner 152 of the die 150 disposed within the cavity 132 in this manner allows for the use of a larger die 150 than would typically be used in a clip 100 of the same size (but without a notch aligned with the corner of the die 150). Since the die 150 must be protected from damage or wear during the manufacturing process, if the die is disposed within a cavity, it is generally desirable to leave sufficient space between the walls of the cavity and the die to provide room for the die to move during manufacturing, thereby reducing collisions between the die and the surrounding walls. Collisions between the corners of the die and the walls of the cavity can cause particularly significant damage to the die during the manufacturing process, ultimately affecting product quality. By positioning the notch 134 within the cavity 132 to align with the corner of the die 150, a larger die can be used with a clip 100 of this design as collisions between the corner 152 of the die 150 and the walls of the cavity are no longer a concern. This can allow for the manufacture of more powerful power stage devices without the device occupying a larger footprint (since a larger IC driver can be used).

[0044] As Figure 1A shown, the notch 134 of this example is formed by rounded edges. However, the geometry of the notch can vary depending on the requirements of the clip 100. For example, the notch can be generally triangular, square, etc. Those skilled in the art will understand that the notch 134 can be any suitable geometry that will produce the advantages associated with these features described herein.

[0045] Within the understanding of those skilled in the art, the notch 134 can be formed in the second part 134 in any suitable manner. For example, the notch 134 can be formed by one or a combination of punching, cutting, machining, electrical discharge machining, and laser cutting, etc.

[0046] The notch 134 can be formed in the second part 130 at any suitable manufacturing stage of the clip 100. For example, the notch 134 can be formed in the second part 130 before the cavity 132 is formed in the second part 130. Alternatively, the notch 134 can be formed after the cavity 132 has been formed in the second part 130.

[0047] In Figure 2B , the lower surface 138 of the clip 100 has been connected to the second component 160 of the power stage device. In this example, the lower surface 138 of the cavity 132 of the second part 130 has been connected to the contact surface (not shown) of the MOSFET 160 by welding 112 (although as described above, other attachment methods can be used in other embodiments of the present invention). Since the second part 130 includes the cavity 132 and the lower surface 138 of the cavity 132 extending from the second part 130, this allows for a vertical "stacking" of the components of the power stage device. As Figure 2B shown, by aligning the lower surface 138 of the cavity 132 with the contact surface of the MOSFET 160 and disposing the die 150 in the cavity 132, the "stacking" is achieved. This allows the MOSFET 160 and the die 150 to be electrically connected to each other, while also minimizing the footprint of the final power stage device (since conventionally the die and its associated MOSFET can be arranged side by side on a circuit board, lead frame, or clip).

[0048] As described above, the notch 134 of the second part 130 can extend into the cavity 132 of the second part. In Figures 1A to 3B the example, the notch extends into the cavity 132 such that the corners of the cavity are removed. During the assembly or use of the power stage device, the corners of the cavity may create concentrated stress regions on the MOSFET to which the cavity (through its lower surface) is connected. Over time, these concentrated stress regions may damage the MOSFET, resulting in abnormal functioning of the power stage clip. By including the notch 134 that extends into the cavity 132 of the clip 100 of the present invention, the notch 134 is disposed at and extends into the corners of the cavity 132, alleviating such concentrated stress regions on the MOSFET 160, thereby helping to extend the life of the MOSFET 160 and ultimately the life of the power stage clip.

[0049] The notch 134 can extend into the cavity 132 as needed for the clip 100 and the MOSFET 160 connected to the lower side 138 of the cavity 132.

[0050] As described above, since the cavity 132 of this example has been stamped into the second portion 130 of the clip 100, the cavity 132 extends from the second portion 130. In addition to forming the lower surface 138 of the cavity 132, this also defines a plurality of attachment surfaces 135 for use in connecting the cavity 132 to the MOSFET 160. During assembly, solder can be applied to the attachment surfaces 135 and the lower surface 138 of the cavity to provide a strong and reliable connection between the clip 100 and the MOSFET 160. The attachment surfaces 135 are also used to accommodate any solder that may be used to attach the MOSFET 160 to the clip 100, ultimately helping to improve the manufacturing efficiency and quality of the power stage device using the clip 100 of the present invention.

[0051] Figure 3A and Figure 3B shows the clip 200 being assembled onto the lead frame 270 before encapsulation to create the final integrated circuit package. Figures 1A to 2B

[0052] In Figure 3A , the MOSFET 260 has been connected to the lead frame 270. Then, the die 250 has been wire bonded to the contact pad 271 of the lead frame 270 via the bonding wire 280. The first portion 220 of the clip 200 has also been connected to the lead frame 270. After connecting the clip 200 to the lead frame 270 and wire bonding the die 250 to the contact pad 271 of the lead frame 270, the assembly can be encapsulated in a protective encapsulant to form an integrated circuit package.

[0053] Although specific embodiments of the present invention have been described above, it should be understood that the present invention can be practiced in a manner different from that described. The above description is intended to illustrate and not limit. Therefore, it will be apparent to those skilled in the art that the present invention described can be modified without departing from the scope of the following claims.

Claims

1. A clip for a power stage device, the clip comprising: a first portion defining a first planar surface, and A second part, the second part being connected to the first part, the second part comprising: a second planar surface; a cavity defined in the second planar surface; and At least one notch in a perimeter of the second planar surface, wherein the at least one notch extends into the cavity.

2. The clip of claim 1, wherein at least one of the first portion and the second portion is formed of a wettable material.

3. The clip of claim 2, wherein at least one of the first portion and the second portion comprises a metal wettable material.

4. The clip of any one of claims 1 to 3, wherein the cavity defines a third planar surface.

5. The clip of claim 4, wherein the third planar surface of the cavity is configured to seat a die.

6. A clip according to any preceding claim, wherein the cavity defined in the second planar surface is square.

7. The clip of any one of claims 1 to 5, wherein the cavity defined in the second planar surface is rectangular.

8. A clip according to any preceding claim, wherein the at least one notch comprises; curved notches; triangular notch; and Right angle notch.

9. A power driver device comprising: MOSFET A clip according to any preceding claim, wherein the cavity is disposed on the MOSFET such that the cavity is in electrical communication with the MOSFET; and A tube core is disposed in the cavity of the clip.

10. A method of forming a clip for a power stage device, comprising: A framework is provided, the framework comprising: a first flat portion; and a second flat portion connected to the first flat portion; punching a cavity into the second planar portion; and At least one notch is provided in a periphery of the second portion, wherein the at least one notch extends into the cavity.

11. The method of claim 10, comprising stamping one of the square cavities into the second planar portion.

12. A method according to claim 10 or 11, comprising providing in the periphery of the second portion at least one of: curved notches; triangular notch; and Right angle notch.

13. The method according to any one of claims 10 to 12, wherein the frame is a metal frame.

14. A method according to any one of claims 10 to 13, wherein the frame is a wettable metal frame.

15. A method of forming a power driver device, comprising: Forming a clip according to any one of claims 10 to 14, Disposing the cavity of the clip on a MOSFET so that the cavity is in electrical communication with the MOSFET; as well as A tubing core is attached within the cavity of the clip.

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