Power module packaging method and power module

Abstract

The invention provides a power module packaging method and a power module. The method comprises the following steps: providing a copper-clad ceramic substrate, wherein the copper-clad ceramic substrate is provided with a plurality of first regions provided with a silver sintering material and a plurality of second regions except the first regions; a chip is attached to the first area of the copper-clad ceramic substrate; sintering the silver sintering material, and fixing the chip on the copper-clad ceramic substrate; and cooling the copper-clad ceramic substrate on which the chip is fixed, and performing first pressurization treatment on the second region of the copper-clad ceramic substrate. By means of the method, the warping degree of the copper-clad ceramic substrate in the silver sintering process can be effectively improved, the quality of the power module is improved, and the warping degree of the copper-clad ceramic substrate improved through the method is 0.1 mm or below.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a power module packaging method and a power module. Background Art

[0002] According to the process, copper-clad ceramic substrates can be generally divided into DBC (Direct bonded copper), DPC (Direct plated copper), AMB (Active metal brazing), etc. Among them, DBC and AMB copper-clad ceramic substrates are widely used in semiconductor power modules.

[0003] The copper-clad ceramic substrate is a sandwich structure of copper foil / ceramic / copper foil. Different materials have different thermal expansion coefficients, Young's modulus, and thermal conductivity. In the packaging process of IGBT / SiC power modules, especially in the chip silver sintering process, the copper-clad ceramic substrate is easily affected by the thermal parameters, pressure parameters, and thermal expansion coefficients of different materials, which can easily cause warping of the copper-clad ceramic substrate, leading to some common problems, such as welding voids, plastic packaging delamination, and even ceramic cracking in severe cases. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one object of the present invention is to provide a power module packaging method, which can effectively improve the problem of warping of copper-clad ceramic substrates in the silver sintering process and improve the quality of the power module.

[0005] In one aspect of the present invention, a power module packaging method is provided. The method comprises: providing a copper-clad ceramic substrate, the copper-clad ceramic substrate having a plurality of first areas provided with silver sintering materials and a second area other than the first area; attaching a chip to the first area of ​​the copper-clad ceramic substrate; sintering the silver sintering material and fixing the chip on the copper-clad ceramic substrate; cooling the copper-clad ceramic substrate with the chip fixed thereon, and performing a first pressurization treatment on the second area of ​​the copper-clad ceramic substrate.

[0006] Furthermore, the pressure of the first pressurization treatment is 1-10 MPa, and the time of the first pressurization treatment is 1-5 min.

[0007] Furthermore, the pressurizing device includes a support plate with a pressure head installed and a clamping structure connected to the support plate. Using the pressurizing device to perform the first pressurizing treatment on the second area of ​​the copper-clad ceramic substrate includes: mounting the copper-clad ceramic substrate with the chip fixed on the clamping plate; clamping and fixing the clamping plate using the clamping structure; and performing the first pressurizing treatment on the second area of ​​the copper-clad ceramic substrate using the pressure head.

[0008] Furthermore, the pressure head performs the first pressurization process by being driven by a motor, air pressure or spring.

[0009] Furthermore, a plurality of pressure heads are installed on the support plate, and the second area of ​​the copper-clad ceramic substrate has a plurality of pressure points, which are located at the center and around the second area. When the first pressure treatment is performed, each pressure point corresponds to a pressure head.

[0010] Furthermore, the cross-section of the pressure head is I-shaped, cross-shaped, W-shaped or field-shaped, and the second area of ​​the copper-clad ceramic substrate has multiple pressure points, and the multiple pressure points are located at the center and around the second area, and the multiple pressure points correspond to one pressure head.

[0011] Furthermore, a plurality of groups of the pressure heads are installed on the support plate.

[0012] Furthermore, when the silver sintering material is sintered, the chip and the second area of ​​the copper-clad ceramic substrate are simultaneously subjected to a second pressurization treatment.

[0013] Furthermore, the pressure of the second pressurization treatment is 5-30 MPa, and the time of the second pressurization treatment is 2-10 min.

[0014] The method of the present invention has the following advantages:

[0015] The present invention can effectively improve the degree of warping of the copper-clad ceramic substrate during the silver sintering process and improve the quality of the power module by applying pressure to the second area of ​​the copper-clad ceramic substrate during cooling, or by simultaneously applying a second pressure treatment to the chip and the second area of ​​the copper-clad ceramic substrate during sintering and applying a first pressure treatment to the second area of ​​the copper-clad ceramic substrate during cooling. The warping degree of the copper-clad ceramic substrate improved by the method of the present invention is less than 0.1 mm.

[0016] In another aspect of the present invention, a power module is provided. The power module is packaged by the above-mentioned method. The copper-clad ceramic substrate of the power module has a small warpage, which improves the quality of the power module and prolongs the service life of the power module. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram showing a process flow of a power module packaging method according to an embodiment of the present invention is shown;

[0019] Figure 2 A schematic diagram showing the warping of a copper-clad ceramic substrate after a chip is silver-sintered on the copper-clad ceramic substrate using the prior art;

[0020] Figure 3 A schematic diagram showing a first pressurizing treatment of the second area of ​​a copper-clad ceramic substrate according to an embodiment of the present invention is shown;

[0021] Figure 4 A schematic structural diagram of a pressurizing device for performing a first pressurizing treatment on the second area of ​​a copper-clad ceramic substrate according to an embodiment of the present invention is shown;

[0022] Figure 5 shows a schematic diagram of pressure head distribution according to an embodiment of the present invention;

[0023] Figure 6 shows a schematic diagram of pressure head distribution according to another embodiment of the present invention;

[0024] Figure 7 A schematic diagram showing a second pressurizing treatment of a chip and a second region of a copper-clad ceramic substrate simultaneously according to an embodiment of the present invention is shown.

[0025] Reference numerals:

[0026] 1: Chip; 2: Copper-clad ceramic substrate; 3: Substrate press head; 4: Support plate; 5: Clamping plate; 6: Clamping mechanism; 7: Chip press head. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in the art or the product specifications are used.

[0028] The inventors found that in the existing power module packaging process, the chip silver sintering process only applies pressure to the chip, and the copper-clad ceramic substrate is always in a free state. Due to the difference in thermal expansion coefficients of different materials, the copper-clad ceramic substrate 2 will show obvious warping after cooling (refer to Figure 2), the warpage H is 0.4-0.5 mm. It is well known to those skilled in the art that the warpage is numerically defined as the distance between the two points on the warping plane that are farthest apart in the height direction, i.e. Figure 2 The H shown in FIG. Large warpage can easily cause welding voids, plastic packaging delamination problems, and even ceramic cracking problems.

[0029] In order to solve the above technical problems, in one aspect of the present invention, the present invention proposes a power module packaging method. In some embodiments of the present invention, reference is made to Figure 1 , the method comprising:

[0030] S100: Provide copper-clad ceramic substrates

[0031] In this step, a copper-clad ceramic substrate is provided. The copper-clad ceramic substrate has a plurality of first areas and a second area other than the first area, and a silver sintering material can be pre-arranged in the first area of ​​the copper-clad ceramic substrate. The first area is used to place the chip, and the chip is subsequently fixed on the copper-clad ceramic substrate by silver sintering technology. There is no particular restriction on the specific state and arrangement of the silver sintering material. For example, silver paste can be printed or dotted in the first area of ​​the copper-clad ceramic substrate. The copper-clad ceramic substrate can be an AMB copper-clad ceramic substrate.

[0032] S200: Bonding the chip to the first area of ​​the copper-clad ceramic substrate

[0033] In this step, the chip is bonded to the first area of ​​the copper-clad ceramic substrate, that is, the chip is bonded to the silver sintered material on the copper-clad ceramic substrate.

[0034] S300: Sintering the silver sintering material to fix the chip on the copper-clad ceramic substrate

[0035] In this step, the silver sintering material is sintered, and the chip is fixed on the copper-clad ceramic substrate. That is, the chip is fixed on the copper-clad ceramic substrate using silver sintering technology. The silver sintering process in this step can adopt pressurized silver sintering technology or non-pressurized silver sintering technology. Taking pressurized silver sintering technology as an example, by heating and pressurizing the silver sintering material (that is, pressurizing the chip), the nanosilver particles in the silver sintering material are diffused between solids, so that a dense connection is formed between the chip and the copper-clad ceramic substrate. The specific temperature for heating the silver sintering material and the specific pressure for pressurizing the chip can adopt the temperature and pressure commonly used in pressurized silver sintering technology.

[0036] S400: Cooling the copper-clad ceramic substrate with the chip fixed thereon, and performing a first pressurization treatment on the second area of ​​the copper-clad ceramic substrate

[0037] In this step, the copper-clad ceramic substrate with the chip fixed thereon is cooled, and the second area of ​​the copper-clad ceramic substrate is subjected to a first pressurization treatment. Figure 3The area of ​​the copper-clad ceramic substrate 2 where the chip 1 is set is the first area, and the remaining area is the second area. During the cooling process, the second area of ​​the copper-clad ceramic substrate is subjected to a first pressurization treatment, that is, an external force is applied to the second area to alleviate the degree of warping of the copper-clad ceramic substrate during the cooling process due to the difference in thermal expansion coefficients of different materials.

[0038] In some embodiments of the present invention, the pressure of the first pressurization treatment may be 1-10MPa, for example, 1MPa, 3MPa, 5MPa, 8MPa, 10MPa, and the time of the first pressurization treatment may be 1-5min, for example, 1min, 3min, 5min. Pressurizing the copper-clad ceramic substrate under the above pressure and time can effectively alleviate the degree of warping of the copper-clad ceramic substrate after cooling, and will not cause damage to the copper-clad ceramic substrate.

[0039] In some embodiments of the present invention, a more precise pressurizing device may be used to perform a first pressurizing treatment on the second area of ​​the copper-clad ceramic substrate. For details, refer to Figure 3 The substrate pressing head 3 can be used to perform a first pressurization treatment on the second area at the edge of the copper-clad ceramic substrate 2 and the second area between the chips 1, that is, the area of ​​the copper-clad ceramic substrate other than the chip is pressurized to reduce the degree of warping of the copper-clad ceramic substrate after cooling. In this embodiment, a suitable pressurization device can be selected according to the chip spacing and chip arrangement, and the first pressurization treatment can be performed in a cooling environment.

[0040] In other embodiments of the present invention, the Figure 4 The pressurizing device shown in the figure performs a first pressurizing treatment on the second area of ​​the copper-clad ceramic substrate. The pressurizing device includes a support plate 4 equipped with a pressure head (i.e., a substrate pressure head 3) and a clamping structure 6 connected to the support plate 4. The first pressurizing treatment on the second area of ​​the copper-clad ceramic substrate using the pressurizing device can be achieved by the following steps: first, the copper-clad ceramic substrate with the chip fixed is installed on the clamping plate 5, then the clamping plate 5 is clamped and fixed by the clamping structure 6, and finally the second area of ​​the copper-clad ceramic substrate is subjected to the first pressurizing treatment by the pressure head. The pressurizing device can also effectively reduce the degree of warping of the copper-clad ceramic substrate. Among them, the clamping plate 5 can be provided with a limit block or a limit groove for limiting the position of the copper-clad ceramic substrate, and the clamping plate 5 can also be provided with a positioning block and other structures for positioning with the clamping structure 6. Through the positioning block and the limit block or the limit groove and other structures, it can be ensured that the pressure head pressurizes the predetermined area of ​​the copper-clad ceramic substrate. By fixing the clamping plate with the clamping structure, the copper-clad ceramic substrate can be kept stably pressurized. The holding plate may be a pallet or a single liner plate without particular limitation.

[0041] The pressurizing device of this embodiment can be obtained by installing a pressure head in the cooling device used in the existing silver sintering process, thereby, there is no need to use an additional pressurizing device to pressurize the second area of ​​the copper-clad ceramic substrate, and it is suitable for the current silver sintering production line. The pressurizing device can be an independent tooling, or it can be integrated in the silver sintering equipment.

[0042] The pressure head in the pressure device of this embodiment can be driven by a motor, air pressure or spring to perform the first pressure treatment. The pressure strength can be controlled in the above manner, which is easy to implement and can be applied to products of different thicknesses to reduce the degree of product warping.

[0043] In some embodiments of the present invention, a plurality of pressure heads are installed on the support plate of the pressurizing device, and the second zone of the copper-clad ceramic substrate has a plurality of pressure points, and the plurality of pressure points are located at the center and around the second zone. When the first pressurizing treatment is performed, each pressure point can correspond to a pressure head. That is, the pressure head on the support plate corresponds to the pressure point on the copper-clad ceramic substrate, and each pressure point is pressurized using an independent pressure head, thereby realizing multi-point pressurization of the copper-clad ceramic substrate, and applying the same pressure to the center and around the copper-clad ceramic substrate. The above method is easy to implement, and can reduce the degree of warping of the copper-clad ceramic substrate after cooling, while avoiding the fracture of the copper-clad ceramic substrate caused by uneven pressure, and the above method can simplify the pressure head structure of the pressurizing device. The specific shape of the pressure head in this embodiment is not particularly limited, for example, it can be round, square, etc. The specific arrangement of the pressure points in the second zone of the copper-clad ceramic substrate is not particularly limited, as long as they are located at the center and around the second zone. For example, refer to Figure 5 In (a), the four corners and the center of the copper-clad ceramic substrate 2 each correspond to a substrate pressure head 3. Alternatively, refer to Figure 5 In (b), the center of each of the four sides of the copper-clad ceramic substrate 2 and the center of the entire substrate corresponds to a substrate pressure head 3. Alternatively, refer to Figure 5 In (c), Figure 5 On the basis of (a), the centers of the four sides of the copper-clad ceramic substrate 2 also correspond to a substrate pressing head 3, which further reduces the degree of warping of the copper-clad ceramic substrate after cooling and improves the uniformity of the force on the copper-clad ceramic substrate.

[0044] Alternatively, in some embodiments of the present invention, the cross-section of the pressure head on the support plate is in the shape of an I-beam, a cross, a W-shape, or a field shape, and the second zone of the copper-clad ceramic substrate has a plurality of pressure points, and the plurality of pressure points are located at the center and around the second zone. When the first pressure treatment is performed, the plurality of pressure points correspond to one pressure head. That is, one pressure head corresponds to a plurality of pressure points on the copper-clad ceramic substrate, and a plurality of pressure points use a pressure head together for pressure application, thereby realizing multi-point pressure application on the copper-clad ceramic substrate, and applying the same pressure to the center and around the copper-clad ceramic substrate. The above method is easy to implement, and can reduce the degree of warping of the copper-clad ceramic substrate after cooling, while avoiding the fracture of the copper-clad ceramic substrate caused by uneven pressure, and the above method can simplify the pressure head structure of the pressure device. For example, referring to Figure 6 In (a), the substrate pressure head 3 is an I-shaped pressure head, in (b), the substrate pressure head 3 is a cross-shaped pressure head, in (c), the substrate pressure head 3 is a Wang-shaped pressure head, and in (d), the substrate pressure head 3 is a Tian-shaped pressure head. When performing the first pressurizing treatment, the above-mentioned pressure heads can be used to correspond to the pressure points located at the center and around the copper-clad ceramic substrate 2, and one pressure head corresponds to one copper-clad ceramic substrate.

[0045] Alternatively, in some embodiments of the present invention, a plurality of groups of the aforementioned pressure heads may be installed on the support plate, thereby pressurizing a plurality of copper-clad ceramic substrates at the same time. Specifically, a plurality of pressure heads on the support plate corresponding to a plurality of pressure points of a copper-clad ceramic substrate may be a group, for example, Figure 5 The multiple pressure heads in (a)-(c) are each a group. Alternatively, a pressure head corresponding to multiple pressure points on a copper-clad ceramic substrate on the support plate is a group, for example, Figure 6 The I-shaped indenter, cross-shaped indenter, king-shaped indenter or field-shaped indenter in (a)-(d) are each a group. Figure 4 , multiple groups of pressure heads can respectively pressurize multiple copper-clad ceramic substrates 2. It should be noted that, in order to illustrate the corresponding relationship between multiple groups of pressure heads and multiple copper-clad ceramic substrates, Figure 4 In the figure, only one pressure head is shown in each group of pressure heads corresponding to each copper-clad ceramic substrate. The pressure heads in each group and in each group may be arranged the same or different. Preferably, the pressure heads in each group on the support plate are arranged the same.

[0046] In other embodiments of the present invention, before performing this step, that is, in step S300, when the silver sintering material is sintered, the second pressure treatment is performed on the chip and the second area of ​​the copper-clad ceramic substrate at the same time. That is to say, during the sintering process, the second area of ​​the copper-clad ceramic substrate is also pressurized to reduce the internal stress of the copper-clad ceramic substrate caused by the difference in thermal expansion coefficients of different materials during the heating process, and further reduce the degree of warping of the copper-clad ceramic substrate after cooling. The existing device for pressurizing the chip can be used to pressurize the chip and the second area of ​​the copper-clad ceramic substrate at the same time, and the pressure points of the second area of ​​the copper-clad ceramic substrate can be around the second area. Or, refer to Figure 7 , the chip is pressed by the chip pressing head 7, and the second area located at the edge of the copper-clad ceramic substrate 2 and the second area located between the chips 1 are pressed by the substrate pressing head 3. This embodiment is a scheme in which the second pressure treatment is performed on the chip and the second area of ​​the copper-clad ceramic substrate at the same time when the silver sintering material is sintered, and then the first pressure treatment is performed on the second area of ​​the copper-clad ceramic substrate when the copper-clad ceramic substrate is cooled.

[0047] In some embodiments of the present invention, the pressure of the second pressurization treatment performed on the chip and the second area of ​​the copper-clad ceramic substrate can be 5-30MPa, such as 5MPa, 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, and the time of the second pressurization treatment can be 2-10min, such as 2min, 4min, 6min, 8min, 10min. The above pressure and time are not only conducive to the diffusion of nanosilver particles between solids, but also conducive to reducing the internal stress in the copper-clad ceramic substrate, and further reducing the degree of warping of the copper-clad ceramic substrate after cooling.

[0048] The present invention can effectively improve the degree of warping of the copper-clad ceramic substrate during the silver sintering process and improve the quality of the power module by applying pressure to the second area of ​​the copper-clad ceramic substrate during cooling, or by simultaneously applying a second pressure treatment to the chip and the second area of ​​the copper-clad ceramic substrate during sintering and applying a first pressure treatment to the second area of ​​the copper-clad ceramic substrate during cooling. The warping degree of the copper-clad ceramic substrate improved by the method of the present invention is less than 0.1 mm.

[0049] The packaging method of the present invention also includes subsequent steps such as electrically connecting the chip, setting pins, setting a sealing layer and a shell, etc., to complete the packaging of the power module. Regarding the above steps, those skilled in the art can implement them using conventional methods, which will not be repeated here.

[0050] In another aspect of the present invention, a power module is provided, which is packaged by the method described above. The copper-clad ceramic substrate of the power module has a small warpage, which improves the quality of the power module and prolongs the service life of the power module.

[0051] According to the embodiment of the present invention, the warping degree of the copper-clad ceramic substrate in the power module is less than 0.1 mm, which improves the quality of the power module and prolongs the service life of the power module.

[0052] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of this specification. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0054] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A power module packaging method, It is characterized in that include: A copper-clad ceramic substrate is provided, wherein the copper-clad ceramic substrate has a plurality of first areas provided with a silver sintering material and a second area other than the first areas; Bonding a chip to the first area of ​​the copper-clad ceramic substrate; Sintering the silver sintered material to fix the chip on the copper-clad ceramic substrate; The copper-clad ceramic substrate on which the chip is fixed is cooled, and a first pressurizing treatment is performed on the second area of ​​the copper-clad ceramic substrate.

2. The method according to claim 1, It is characterized in that The pressure of the first pressurization treatment is 1-10 MPa, and the time of the first pressurization treatment is 1-5 min.

3. The method according to claim 1, It is characterized in that The pressurizing device includes a support plate with a press head installed thereon and a clamping structure connected to the support plate, and using the pressurizing device to perform the first pressurizing treatment on the second area of ​​the copper-clad ceramic substrate includes: Mounting the copper-clad ceramic substrate with the chip fixed thereon on a clamping plate; Using the clamping structure to clamp and fix the clamping plate; The first pressurizing treatment is performed on the second area of ​​the copper-clad ceramic substrate by using the press head.

4. The method according to claim 3, It is characterized in that The pressure head performs the first pressurizing process by being driven by a motor, air pressure or a spring.

5. The method according to claim 3, It is characterized in that A plurality of pressure heads are mounted on the support plate, and the second area of ​​the copper-clad ceramic substrate has a plurality of pressure points, which are located at the center and around the second area. When the first pressure treatment is performed, each pressure point corresponds to a pressure head.

6. The method according to claim 3, It is characterized in that The cross section of the pressure head is in an I-shape, a cross-shape, a W-shape or a field-shape. The second area of ​​the copper-clad ceramic substrate has a plurality of pressure points, which are located at the center and around the second area. The plurality of pressure points correspond to one pressure head.

7. The method according to claim 5 or 6, It is characterized in that A plurality of groups of the pressure heads are installed on the support plate.

8. The method according to claim 1, It is characterized in that When the silver sintering material is sintered, the chip and the second area of ​​the copper-clad ceramic substrate are simultaneously subjected to a second pressurization process.

9. The method according to claim 8, It is characterized in that The pressure of the second pressurization treatment is 5-30 MPa, and the time of the second pressurization treatment is 2-10 min.

10. A power module, It is characterized in that The power module is packaged using the method described in any one of claims 1 to 9.

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