Power semiconductor modules and their heat dissipation substrates

Abstract

This invention relates to a power semiconductor module and its heat dissipation substrate. The heat dissipation substrate includes at least one textured structure disposed on a first surface of the substrate body. The at least one textured structure defines a first direction and a second direction that are intersected with each other. The at least one textured structure includes a platform area and a plurality of pits. The plurality of pits are arranged along the first direction and the second direction and are recessed at intervals on the platform area. When a row of pits is viewed in cross-section, the edge of the cross-section has a wavy structure. In this way, adhesive can be filled into the pits, increasing the contact area between the adhesive and the heat dissipation substrate, and the adhesive can be evenly distributed, thereby improving the bonding strength between the housing of the power semiconductor module and the heat dissipation substrate, while also achieving low cost and high product yield.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a power semiconductor module and a heat dissipation substrate thereof. Prior Art

[0002] Conventional power semiconductor modules comprise a heat sink substrate, a semiconductor device, a heat sink, and a housing. The heat sink substrate is a metal plate, and the semiconductor device comprises a semiconductor element disposed on the front surface of a substrate, which can be a direct bond copper substrate (DBC) or a lead frame. The back surface of the substrate is bonded to one side of the heat sink substrate. Furthermore, the heat sink is bonded to the other side of the heat sink substrate and has a heat sink fin. The housing is bonded to the heat sink substrate via an adhesive and covers the semiconductor device.

[0003] Because the shell system of the existing power semiconductor module is directly adhered to the surface of the heat sink substrate through an adhesive, the bonding strength between the shell and the heat sink substrate is insufficient, resulting in a high defect rate. When the existing power semiconductor module is pushed by external forces, the shell easily separates from the heat sink substrate, thereby losing its function of covering and protecting the semiconductor device, resulting in defective power semiconductor modules. In addition, under the action of thermal stress, the bond between the shell and the heat sink substrate gradually fails after a period of time.

[0004] Therefore, existing power semiconductor modules have the problem that the housing is easy to fall off and the product defect rate is high, and there is indeed room for improvement. Summary of the Invention

[0005] To address the problem that existing power semiconductor modules are prone to falling off and have a high product defect rate due to insufficient bonding strength between their housing and heat dissipation substrate, the present invention provides a power semiconductor module and its heat dissipation substrate to solve the above-mentioned problem, which is further described below.

[0006] The present invention provides a heat dissipation substrate, which includes: A substrate body having a first surface and a second surface opposite to each other; and At least one pitted surface structure is provided on the first surface of the substrate body. The at least one pitted surface structure defines a first direction and a second direction that intersect with each other, and the at least one pitted surface structure includes a platform area and a plurality of pits. The plurality of pits are arranged along the first direction and the second direction and are recessed at intervals on the platform area. When a cross-section of one row of pits is observed along the first direction or the second direction, the cross-sectional edge line of the pitted surface structure is a wavy structure.

[0007] The present invention provides a power semiconductor module, which includes: A heat dissipation substrate as described above; a semiconductor device disposed on the heat dissipation substrate; and A shell is combined with the first surface of the heat dissipation substrate through an adhesive and covers the semiconductor device, wherein the adhesive covers the pitted surface structure and fills the pit.

[0008] By virtue of the aforementioned technical features, the present invention provides at least one textured structure on the substrate body of the heat sink substrate. This allows the adhesive used to fill the plurality of recesses in the textured structure when the housing of the power semiconductor module is bonded to the heat sink substrate, thereby increasing the contact area between the adhesive and the heat sink substrate. Furthermore, the adhesive can be evenly distributed and conformably contact the inner surfaces of the recesses, thereby effectively enhancing the adhesive bonding strength between the housing and the heat sink substrate, preventing the housing from falling off and improving product yield. Furthermore, this achieves the benefits of high mass production and low production costs. Simple diagram description

[0009] FIG1 is a schematic side view of a partial cross section of a first preferred embodiment of the present invention. FIG2 is a partial enlarged view of the area circled in FIG1 . FIG3 is a schematic three-dimensional appearance diagram of a heat dissipation substrate according to a first preferred embodiment of the present invention. FIG. 4 is a schematic top view of the heat dissipation substrate according to the first preferred embodiment of the present invention. FIG. 5 is a schematic top view of the roughened surface structure of the heat dissipation substrate shown in FIG. 4 . FIG. 5A is an optical microscope photograph corresponding to FIG. 5 of the first preferred embodiment of the present invention. FIG6 is a partial enlarged view of the area selected by frame B in FIG5 . FIG6A is an optical microscope photograph corresponding to FIG6 . FIG7 is a side cross-sectional view taken along the CC section line of FIG6 . FIG. 7A , FIG. 7B , and FIG. 7C are photographs corresponding to FIG. 7 observed with a scanning electron microscope (SEM) at different magnifications. FIG8 is a top view of the unit area of ​​the textured surface structure of the second preferred embodiment of the present invention. FIG9 is a schematic top view of the pockmarked surface structure of the third preferred embodiment of the present invention. FIG10 is a partially enlarged side sectional view of a fourth preferred embodiment of the present invention. Implementation Method

[0010] In order to understand the technical features and practical effects of the present invention in detail and to implement them according to the contents of the specification, the preferred embodiments shown in the drawings are further described in detail as follows:

[0011] The present invention provides a power semiconductor module, a first preferred embodiment of which is shown in FIG. 1 to FIG. 4 . The power semiconductor module includes a heat dissipation substrate 1 , a semiconductor device 2 , a heat dissipation device 3 and a housing 4 .

[0012] 3 to 5 , the heat dissipation substrate 1 includes a substrate body 10 and at least one textured structure 20, wherein the substrate body 10 is a rectangular metal plate, such as a copper plate, and has a first surface 11 and a second surface 12 opposite to each other. As shown in FIG5 and FIG5A , the textured structure 20 is disposed on the first surface 11 of the substrate body 10. The textured structure 20 defines a first direction L1 and a second direction L2 that intersect with each other, and includes a platform area 21 and a plurality of pits 22. The plurality of pits 22 are arranged along the first direction L1 and the second direction L2 and are recessed at intervals on the platform area 21, presenting a checkerboard arrangement.

[0013] The textured surface structure 20 is formed by stamping, using a stamping die to form a plurality of checkerboard-shaped dimples 22 on the heat dissipation substrate 1, creating a localized surface roughening effect. In a first preferred embodiment of the present invention, the first direction L1 is perpendicular to the second direction L2. Compared to other surface roughening techniques, such as sandblasting, chemical etching, or laser treatment, stamping to roughen the surface to form the checkerboard-shaped dimples 22 allows for rapid mass production and improved production efficiency.

[0014] As shown in FIG1 , the semiconductor device 2 is disposed on the first surface 11 of the heat dissipation substrate 1. The semiconductor device 2 includes at least one semiconductor element, which may be a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), an insulated gate bipolar transistor (IGBT), etc. The heat dissipation device 3 is disposed on the second surface 12 of the heat dissipation substrate 1.

[0015] As shown in Figures 1 and 2, the housing 4 is bonded to the first surface 11 of the heat sink 1 via an adhesive 5, covering the semiconductor device 2 and enclosing the semiconductor device 2 within the housing 4 and the heat sink 1. The adhesive 5 covers the textured surface 20 and fills the recesses 22, effectively enhancing the bond strength between the housing 4 and the heat sink 1. Generally, the adhesive 5 is applied to the periphery of the bottom of the housing 4 and then bonded to the heat sink 1. A portion of the adhesive 5 is squeezed into the recesses 22. The recesses 22 increase the surface area of ​​the adhesive 5 attached to the heat sink 1, improving adhesion. The adhesive 5 is typically made of epoxy resin. The plurality of recesses 22 are arranged in a checkerboard pattern along the first direction L1 and the second direction L2, ensuring uniform distribution of the adhesive 5 between the housing 4 and the heat sink 1, enhancing bonding reliability and making the stamping die cost-effective.

[0016] Furthermore, referring to Figures 6, 6A, 7, and 7A, each of the dimples 22 of the textured surface structure 20 has a rectangular opening, thereby reducing the cost of manufacturing the stamping die. A pitch is formed between each dimple 22 and adjacent dimples 22. The pitch P1 between each dimple 22 and adjacent dimples 22 along the first direction L1, and the pitch P2 between each dimple 22 and adjacent dimples 22 along the second direction L2, are respectively between 0.05 and 1 millimeter (mm), inclusive, thereby achieving a good chewing gum bonding effect while maintaining reasonable production costs.

[0017] When the pitches P1 and P2 are less than 0.05 mm, the pitches P1 and P2 are too small, making stamping die processing difficult and resulting in high production costs. When the pitches P1 and P2 are greater than 1 mm, the surface area of ​​the heat dissipation substrate 1 on the textured structure 20 is insufficient, making it impossible to increase the adhesive bonding strength between the housing 4 and the heat dissipation substrate 1 to meet the requirements.

[0018] Further, please refer to Figures 7 and 7A. Figure 7A shows a cross-sectional image of the heat dissipation substrate 1 observed using a scanning electron microscope (SEM). The lower half of the image represents the substrate body 10, while the upper half represents the resin used to embed the heat dissipation substrate 1 test piece. The image was observed at a magnification of 500x. When a cross-sectional view of one row of pits 22 in the textured surface structure 20 is taken along the first direction L1 or the second direction L2, the cross-sectional edge of the textured surface structure 20 is wavy and has an R-shaped arc. This facilitates the adhesive 5 to fill the pits 22 and adhere to and evenly contact the inner surface of the pits 22, effectively reducing the chance of the housing 4 separating from the heat dissipation substrate 1. Each pit 22 has a depth d ranging from 0.01 to 0.15 mm, inclusive. In this way, the heat dissipation substrate 1 and the housing 4 achieve better bonding performance. When the depth d is less than 0.01 mm, the surface area of ​​the heat dissipation substrate 1 on the textured surface structure 20 is insufficient, and the bite adhesive bonding strength between the housing 4 and the heat dissipation substrate 1 cannot be increased to meet the requirements. When the depth d is greater than 0.15 mm, the deformation of the heat dissipation substrate 1 due to stamping is too large, which can easily affect the flatness of the platform area 21 and the first surface 11 of the substrate body 10, and easily cause the dimensions of the heat dissipation substrate 1 to be unstable, resulting in large dimensional differences between the heat dissipation substrates 1 after stamping, and may lead to poor yield problems. In the present invention, preferably, the depth d of each pit 22 is between 0.01 and 0.1 mm, inclusive; more preferably, the depth d of the pit 22 is 0.01 mm.

[0019] Please refer to the SEM images shown in Figures 7B and 7C. The image in Figure 7B was observed at a magnification of 300 times, and the image in Figure 7C was observed at a magnification of 200 times. By comparing the images at different magnifications, it can be seen that when a cross-sectional observation is performed on one row of pits 22 in the pitted surface structure 20, the cross-sectional edge line of the pitted surface structure 20 is a wavy structure.

[0020] Referring to Figures 5, 5A, 6, and 6A, in a first preferred embodiment of the present invention, the openings of each of the recesses 22 of the at least one textured structure 20 are square. Specifically, the length of each recess 22 in the first direction L1 is equal to the length in the second direction L2, the pitches P1 and P2 are equal, and the depth d of each recess 22 is equal. This makes the mold used to form the textured structure 20 easier to manufacture, further reducing production costs and improving production efficiency. Furthermore, this ensures a more even distribution of the adhesive 5 between the housing 4 and the heat dissipation substrate 1, further effectively enhancing bonding reliability.

[0021] As shown in Figures 3 and 4, the first surface 11 of the substrate body 10 is rectangular, and the heat dissipation substrate 1 includes four textured structures 20. Each textured structure 20 is rectangular, and the first direction L1 and the second direction L2 are respectively parallel to the length and width of the rectangle. Each textured structure 20 is correspondingly arranged near a corner of the first surface 11, thereby corresponding to the corner position of the housing 4. The adhesion at the corner position of the heat dissipation substrate 1 and the housing 4 is strengthened, thereby improving the bonding strength between the heat dissipation substrate 1 and the housing 4. Therefore, the heat dissipation substrate 1 provided by the present invention is easy to process and has the advantages of easy production and low cost. Moreover, the textured structures 20 are arranged at the corners of the first surface 11 of the substrate body 10, so that the deformation of the substrate body 10 during processing is less. By arranging the first direction L1 and the second direction L2 to be parallel to the length and width of the pitted surface structure 20, respectively, and combining the rectangular openings of the plurality of pits 22, the mold for forming the pitted surface structure 20 can be more easily and quickly processed, thereby effectively improving mass production while keeping manufacturing costs low.

[0022] The number and distribution of the pits 22 in the pitted surface structure 20 shown in FIG. 3 to FIG. 5A are for illustration only and do not limit the number of pits 22 in the first direction L1 and the second direction L2 of each pitted surface structure 20 in the first preferred embodiment of the present invention.

[0023] In other embodiments, the textured structure 20 may be distributed in other ways. For example, the heat dissipation substrate 1 has a ring-shaped textured structure 20, and the textured structure 20 surrounds a position near the periphery of the first surface 11 of the substrate body 10, thereby annularly strengthening the bonding strength with the shell 4.

[0024] Preferably, the area of ​​the textured structures 20 accounts for a ratio of 5% to 30% of the area of ​​the first surface 11 of the substrate body 10, inclusive. This ratio of the textured structures 20 ensures that the bonding strength between the housing 4 and the heat dissipation substrate 1 meets the required requirements. The "area of ​​the textured structures 20" mentioned above refers to the total area of ​​each textured structure 20. Furthermore, in the present invention, preferably, the area of ​​the textured structures 20 accounts for a ratio of 5% to 20% of the area of ​​the first surface 11, inclusive.

[0025] Preferably, referring to the second preferred embodiment of the present invention shown in FIG8 , the pitch P1 between each pit 22 and the adjacent pit 22 along the first direction L1, and the pitch P2 between each pit 22 and the adjacent pit 22 along the second direction L2, are both 0.08 mm. Thus, the textured structure 20 comprises 12 rows of pits 22 arranged along the first direction L1 within a square unit area with a side length of 1 mm. Each row comprises 12 pits 22, and each pit 22 is aligned with the corresponding pit 22 in the adjacent row along the second direction L2. For example, the seventh pit 22 in the fourth row along the first direction L1 is adjacent to and aligned with the seventh pit 22 in the third row and the seventh pit 22 in the fifth row along the second direction L2. Through the above-mentioned technical features, the pits 22 formed by stamping are smaller, and the number of pits 22 per unit area of ​​the textured surface structure 20 is greater and denser, thereby providing sufficient glue bite area, improving the bonding strength between the housing 4 of the power semiconductor module and the heat dissipation substrate 1, and being able to withstand greater loads in thrust tests, such as thrusts greater than 30 kilograms (kgf), effectively improving the problem of the housing 4 detaching.

[0026] As shown in FIG. 9 , the difference between the third preferred embodiment of the present invention and the first preferred embodiment is that the first direction L1 and the second direction L2 both obliquely intersect with the length and width of the pitted surface structure 20A, so that the plurality of pits 22A are obliquely arranged on the platform area 21A.

[0027] As shown in FIG. 10 , the fourth preferred embodiment of the present invention differs from the first preferred embodiment in that the heat dissipation substrate includes a coating 30B. This coating 30B covers at least the first surface 11B of the substrate body 10B, the terrace 21B of the textured structure 20B, and the inner surfaces of each of the recesses 22B. For example, this coating 30B is nickel-plated to enhance corrosion and oxidation resistance. When the depth d of each recess 22 is greater than 0.15 mm, plating solution is likely to remain on the heat dissipation substrate 1 during the electroplating process.

[0028] By virtue of the aforementioned technical features, the present invention provides at least one textured structure 20, 20A, 20B on the first surface 11, 11B of the substrate body 10, 10B of the heat dissipation substrate 1. When the housing 4 of the power semiconductor module is bonded to the heat dissipation substrate 1, the adhesive 5 used can fill the plurality of recesses 22, 22A, 22B of the textured structure 20, 20A, 20B, thereby increasing the contact area between the adhesive 5 and the heat dissipation substrate 1. Furthermore, the adhesive 5 can be evenly distributed and conformably contact the inner surface of the recess 22, thereby effectively improving the bonding strength between the housing 4 and the heat dissipation substrate 1. Furthermore, the adhesive 5 can achieve both low cost and high product yield, thereby providing a power semiconductor module and its heat dissipation substrate 1.

[0029] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any person having ordinary knowledge in the technical field can, without departing from the scope of the technical solution of the present invention, make partial changes or modifications to the technical content disclosed in the present invention to make equivalent embodiments, which still fall within the scope of the technical solution of the present invention and do not depart from the technical solution of the present invention.

[0030] 1: Heat dissipation substrate 2: Semiconductor devices 3: Heat dissipation device 4: Shell 5: Adhesive 10,10B:Substrate body: 11, 11B: first surface 12: Second surface 20,20A,20B: pitted surface structure 21, 21A, 21B: Platform area 22, 22A, 22B: pits 30B: plating d: depth L1: First direction L2: Second direction P1, P2: Pitch

Claims

1. A heat dissipation substrate, comprising: a substrate body having a first surface and a second surface opposite to each other; and at least one textured structure disposed on the first surface of the substrate body, the at least one textured structure defining a first direction and a second direction that intersect each other, and the at least one textured structure including a plateau region and a plurality of recesses, the plurality of recesses being arranged and spaced apart on the plateau region along the first direction and the second direction, and when a row of recesses is viewed in cross-section along the first direction or the second direction, the cross-sectional edge of the textured structure is wavy; wherein the pitch between each recess and a recess adjacent to it along the first direction, and the pitch between each recess and a recess adjacent to it along the second direction, are respectively between 0.05 and 1 mm, including endpoint values.

2. The heat dissipation substrate as claimed in claim 1, wherein each of the recesses in the at least one textured structure has a rectangular opening.

3. The heat dissipation substrate as claimed in claim 2, wherein the opening of each of the pits in the at least one textured structure is square.

4. The heat dissipation substrate as claimed in claim 1, wherein the pitch between each of the recesses and the recesses adjacent to each other along the first direction, and the pitch between each of the recesses and the recesses adjacent to each other along the second direction, are 0.08 mm.

5. The heat dissipation substrate as claimed in claim 1, wherein the depth of each of the recesses is between 0.01 and 0.15 mm, including the endpoint values.

6. The heat dissipation substrate as claimed in claim 1, wherein the depth of each of the recesses is between 0.01 and 0.1 mm, including the endpoint values.

7. The heat dissipation substrate as described in claim 1, wherein the depth of each of the recesses is 0.01 mm.

8. The heat dissipation substrate as claimed in claim 1, wherein the first surface of the substrate body is rectangular, the heat dissipation substrate includes four said textured structures, and each textured structure is disposed at a position near one corner of the first surface.

9. The heat dissipation substrate as claimed in claim 1, wherein the heat dissipation substrate includes a plating layer that at least covers the first surface, the at least one textured platform region, and the inner surface of each of the pits.

10. The heat dissipation substrate as described in any one of claims 1 to 9, wherein the first direction is perpendicular to the second direction.

11. A heat dissipation substrate, comprising: a substrate body having a first surface and a second surface opposite to each other; and at least one textured structure disposed on the first surface of the substrate body, the at least one textured structure defining a first direction and a second direction that intersect each other, and the at least one textured structure including a plateau region and a plurality of recesses, the plurality of recesses being arranged along the first direction and the second direction and spaced apart on the plateau region, and when a row of recesses is viewed in cross-section along the first direction or the second direction, the cross-sectional edge of the textured structure is wavy; wherein the first direction is perpendicular to the second direction, and the area of ​​the textured structure accounts for a proportion of the area of ​​the first surface between 5% and 30%, including endpoint values.

12. The heat dissipation substrate as claimed in claim 11, wherein the area of ​​the textured structure accounts for between 5% and 20% of the area of ​​the first surface, including endpoint values.

13. The heat dissipation substrate as claimed in claim 11, wherein the textured surface has 12 rows of said recesses arranged along the first direction in a square unit area with a side length of 1 mm, and each row has 12 said recesses, each of the recesses being directly opposite to a corresponding recess in an adjacent row along the second direction.

14. A power semiconductor module comprising: a heat dissipation substrate including a substrate body having a first surface and a second surface opposite to each other; and at least one textured structure disposed on the first surface of the substrate body, the at least one textured structure defining an intersecting first direction and a second direction, and the at least one textured structure including a plateau region and a plurality of recesses, the plurality of recesses being arranged at intervals along the first direction and the second direction and recessed in the plateau region, and when a cross-sectional view is taken along the first direction or the second direction of one row of recesses, the cross-sectional edge of the textured structure is a wavy structure; a semiconductor device disposed on the heat dissipation substrate; and a housing, the housing being bonded to the first surface of the heat dissipation substrate through an adhesive and covering the semiconductor device, wherein the adhesive covers the textured structure and fills the recesses.

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