Power semiconductor device and method of manufacturing a power semiconductor device

Abstract

The invention relates to a power semiconductor device (1) comprising a substrate (2), at least one power semiconductor chip (3) arranged on the substrate (2), and a plastic housing (4) encapsulating the power semiconductor chip (3) and at least a portion of the substrate (2), wherein on a top side (8) of the plastic housing (4) forming an outer side of the power semiconductor device (1), at least above the power semiconductor chip (3), a metal structure (10) is arranged which is applied by a plasma coating process, the metal structure (10) being electrically insulated from the power semiconductor chip (3).

Description

Technical Field

[0001] This invention relates to a power semiconductor device having a plastic housing. It also relates to a method for manufacturing such a power semiconductor device. Background Technology

[0002] For power semiconductor devices having at least one power semiconductor chip, there are different structural forms. For example, they can be configured as molded modules in which at least one power semiconductor chip is disposed on a substrate, and a molded plastic housing encapsulates the power semiconductor chip and at least a portion or region of the substrate.

[0003] To improve the performance of electronic systems, silicon devices are increasingly being replaced by silicon carbide-based devices. This enables higher power densities and, consequently, device miniaturization. This offers advantages in terms of material and cost savings. However, the area available for electrical contacts also decreases. Therefore, the requirements for current density and current carrying capacity are significantly increased for top-side contacts.

[0004] Plastic housings made of organic materials can crack due to fault conditions on the circuit carrier, triggering thermal events. Organic materials begin to decompose starting at approximately 350 °C. Housing failure means the surrounding mounting space is no longer protected from the critical temperature. The power required to reach this decomposition temperature is only a few watts in some cases, and power limitations are not feasible for all devices. Summary of the Invention

[0005] Therefore, one object of the present invention is to provide a power semiconductor device that, while having a high power density, can still limit the temperature rise in its surrounding environment during fault conditions. Furthermore, a method for manufacturing such a power semiconductor device should also be provided.

[0006] This task is solved by the subject matter of the independent claims. Preferred embodiments and improvements constitute the subject matter of the dependent claims of this invention.

[0007] According to one aspect of the invention, a power semiconductor device is provided, comprising a substrate, at least one power semiconductor chip disposed on the substrate, and a plastic housing encapsulating the power semiconductor chip and at least a portion or region of the substrate. On the top side of the plastic housing forming the outer side of the power semiconductor device, at least above the power semiconductor chip, a metal structure, applied in a plasma coating process and electrically insulating from the power semiconductor chip, is provided. The plastic housing is particularly formed of molding compound or injection molding compound, which is shaped by directly overmolding or injection molding the molding compound or injection molding compound onto the substrate or a portion thereof and the power semiconductor chip, and completely surrounds the substrate or at least a portion thereof and the power semiconductor chip.

[0008] Therefore, the power semiconductor device has a metal structure on the top side of the housing, which does not contact the power semiconductor chip or other electronic components of the power semiconductor device as a wire or other means. The metal structure is thus only arranged on the top side of the plastic housing and does not form contact with the power semiconductor chip through the plastic housing.

[0009] The power semiconductor device offers the following advantages: in the event of a rapid temperature rise in the power semiconductor chip and damage to the plastic casing, the metal structure reduces the risk of heat or flame leakage. Due to the increased thermal conductivity of the metal structure, heat is dissipated, preventing excessively high temperatures outside the plastic casing. Furthermore, it prevents flames from being ejected into the surrounding environment. Therefore, the power semiconductor device provides safety measures to protect the surrounding environment in the event of a thermal event on the power semiconductor chip.

[0010] The metal structure is applied via a plasma coating process. In this process, particularly in what is also known as Fine Powder Coating (FPC), fine metal particles are introduced into a plasma jet and thereby applied to the surface to be coated. This process allows the application of a finely structured layer composed of a thermally conductive material.

[0011] The metal structure can substantially extend to cover the entire top side of the plastic housing. Alternatively, it can be defined only a portion of the top side, such as the area above the power semiconductor chip.

[0012] For example, the metal structure can be constructed as a grid structure. It can also be constructed as a spiral structure or a tortuous structure, or have other regular or irregular shapes.

[0013] According to one embodiment, a plastic layer applied by a plasma coating process is further provided on the top side of the metal structure. This plastic layer may be made of, for example, PEEK (polyetheretherketone) or PA (polyamide). Through this plastic layer (which may also be applied in a full-coverage manner), the metal structure is insulated and protected on the outside. The plastic used is particularly likely a high-temperature resistant plastic.

[0014] The metal structure can be connected to the ground terminal of the power semiconductor device.

[0015] According to another aspect of the invention, a method for manufacturing a power semiconductor device is provided, comprising: providing a power semiconductor device having at least one power semiconductor chip disposed on a substrate and a plastic housing encapsulating the power semiconductor chip and at least a portion or region of the substrate; and applying a metal structure electrically insulated from the power semiconductor chip to the top side of the plastic housing in a plasma coating process.

[0016] This method possesses the advantages described above in conjunction with the power semiconductor device. Furthermore, the metal structure serving as a safety device can be applied particularly simply and precisely via a plasma coating process.

[0017] The temperature introduced in the FPC process is below 100°C, which is extremely low and poses no problem for the materials involved. The device is also not subjected to mechanical stress during the FPC process. Therefore, it is much gentler than, for example, cold spraying. Furthermore, the shape, extension, and thickness of the metal structure can be freely chosen and easily changed at any time. The top side of the plastic housing to which the metal structure is applied is not required to be flat; it can also be curved, inclined, or structured.

[0018] Since the metal structure is applied to the top side of the plastic housing, it has a defined insulating distance from the semiconductor chip, which does not need to be considered in the mold design.

[0019] According to one embodiment, the metal structure is structured using at least one template. By using the template, a fine structure can be produced and good edge sharpness can be achieved.

[0020] According to one embodiment, the top side of the plastic housing is pretreated by heating, grinding, sandblasting, laser roughening, and / or plasma activation to improve adhesion before plasma coating. This has the advantage that a metal structure can be applied to the plastic housing even if the adhesion to metal powder is unsatisfactory.

[0021] In particular, copper, iron, and aluminum, or other metals with good thermal conductivity and their alloys, are suitable materials for the metal structure. Attached Figure Description

[0022] The embodiments of the present invention will now be described by way of example with reference to the illustrative drawings.

[0023] Figure 1 A cross-sectional view of a power semiconductor device according to a first embodiment of the present invention is shown; Figure 2 Showing according to Figure 1 A top view of a power semiconductor device; Figure 3 A top view of a power semiconductor device according to a second embodiment is shown; Figure 4 A top view of a power semiconductor device according to a third embodiment is shown; and Figure 5 A cross-sectional view of a power semiconductor device according to a fourth embodiment is shown. Detailed Implementation

[0024] Figure 1 A power semiconductor device 1 is shown, having a substrate 2 having a lower side 5 and a top side 6. At least one power semiconductor chip 3 is disposed on the top side 6. The power semiconductor chip 3 and at least some regions of the substrate 2, particularly its top side 6, are embedded in a plastic housing 4. External terminals 7 of the power semiconductor device 1 extend from the plastic housing 4.

[0025] The top side 8 of the plastic housing 4 constitutes the top side of the power semiconductor device 1. A metal structure 10 formed by a plasma coating process is applied to the top side 8, above the power semiconductor chip 3.

[0026] The metal structure 10 is electrically insulated from the power semiconductor chip 3. Therefore, it is not used for contact with the power semiconductor chip 3. The electrically insulated metal structure 10 is made of, for example, copper or aluminum, and is arranged in an area where, in the event of accelerated heating of the power semiconductor chip 3, the plastic housing 4 may fail and potentially catch fire.

[0027] Figure 2 Showing according to Figure 1 The image shows a top view of the power semiconductor device 1. As can be seen from this view, the metal structure 10 is configured as a mesh structure. Such a mesh structure can be applied, for example, using a template in a plasma coating process with a very fine structure and clear boundaries.

[0028] In the illustrated embodiment, the metal structure 10 has dimensions a and b, which are approximately equivalent to the dimensions of the power semiconductor chip 3. Therefore, the metal structure 10 only covers the portion of the top side 8 in which the plastic housing 4 would fail in the event of overheating of the power semiconductor chip 3. This saves on material and cost for the metal structure 10.

[0029] Figure 3 A power semiconductor device 1 according to another embodiment is shown. Figure 1 and Figure 2 The illustrated embodiment differs in that the metal structure 10 substantially extends to cover the entire top side 8 of the plastic housing 4. This configuration of the metal structure 10 can be chosen when the power semiconductor device 1 has multiple power semiconductor chips 3, or when high heat is expected to be generated in other areas of the top side 8 for other reasons.

[0030] Figure 4 Another embodiment of the power semiconductor device 1 is shown. In this embodiment, the metal structure 10 is arranged only above one power semiconductor chip 3 and is in a spiral structure. Furthermore, it has contact terminals 11 for electrical contact with the spiral structure 10. In this embodiment, the metal structure 10 can be used to heat the power semiconductor chip 3 arranged below it when needed; however, in the event of accelerated heating of the power semiconductor chip 3, it, like the metal structure 10 in the previous embodiment, serves to limit the ambient temperature and prevent flames from erupting from the plastic housing 4 in the event of failure of the plastic housing 4.

[0031] Figure 5 Another embodiment of the power semiconductor device 1 is shown. In this embodiment, the metal structure 10 is also configured as a spiral structure with electrical contact terminals 11. However, an insulating layer 12 is additionally applied to the metal structure 10. The insulating layer 12 is made of plastic, which is also applied to the metal structure 10 and the top side 8 of the plastic housing 4 by a plasma coating process.

[0032] List of reference numerals 1 Power semiconductor devices 2 substrate 3 Power Semiconductor Chips 4. Plastic casing 5. Lower side 6 Top side 7 external terminals 8 Top side 10 Metal Structure 11 Contact terminals 12 Insulation layer

Claims

1. A power semiconductor device (1), comprising: - A substrate (2); - At least one power semiconductor chip (3) disposed on the substrate (2); as well as - A plastic housing (4) that encapsulates at least a portion of the power semiconductor chip (3) and the substrate (2). Wherein, on the top side (8) of the plastic housing (4) forming the outside of the power semiconductor device (1), at least above the power semiconductor chip (3), a metal structure (10) applied by a plasma coating process is provided, the metal structure (10) being electrically insulated from the power semiconductor chip (3).

2. The power semiconductor device (1) according to claim 1, wherein the metal structure (10) substantially extends to cover the entire top side (8) of the plastic housing (4).

3. The power semiconductor device (1) according to claim 1, wherein the metal structure (10) is defined in a region above the power semiconductor chip (3).

4. The power semiconductor device (1) according to any one of claims 1 to 3, wherein the metal structure (10) is formed as a mesh structure.

5. The power semiconductor device (1) according to any one of claims 1 to 3, wherein the metal structure (10) is formed as a spiral structure.

6. The power semiconductor device (1) according to any one of claims 1 to 5, wherein an electrically insulating plastic layer (12) applied by a plasma coating process is provided on the top side of the metal structure (10).

7. The power semiconductor device (1) according to claim 6, wherein the plastic layer (12) applied by a plasma coating process is formed of PEEK or PA.

8. The power semiconductor device (1) according to any one of claims 1 to 7, wherein the metal structure (10) is connected to the ground terminal of the power semiconductor device (1).

9. The power semiconductor device (1) according to any one of claims 1 to 8, wherein the metal structure (10) is formed as a heating structure and has contact terminals (11) for applying voltage.

10. A method for manufacturing a power semiconductor device (1), comprising: A power semiconductor device (1) is provided, the power semiconductor device having at least one power semiconductor chip (3) disposed on a substrate (2) and a plastic housing (4) encapsulating at least a portion of the power semiconductor chip (3) and the substrate (2); and a metal structure (10) electrically insulated from the power semiconductor chip (3) is applied to the top side (8) of the plastic housing (4) by a plasma coating process.

11. The method of claim 10, wherein the metal structure (10) is patterned using at least one template.

12. The method according to claim 10 or 11, wherein the top side (8) of the plastic housing (4) is pretreated by heating, grinding, sandblasting, laser roughening and / or plasma activation to improve adhesion prior to plasma coating.

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