A low-stress and high-thermal-conductivity IGBT power module packaging structure

Abstract

A low-stress and high-thermal-conductivity IGBT power module packaging structure. It includes a substrate, an insulating substrate, and a chip bonded in sequence from bottom to top; the insulating substrate includes an upper metal layer, an insulating substrate, and a lower metal layer bonded in sequence from top to bottom; the insulating substrate includes a plurality of first insulating substrate wafers and second insulating substrate wafers; a plurality of the first insulating substrate wafers are respectively in a rectangular structure and are arranged at equal intervals; the second insulating substrate wafers are embedded between adjacent first insulating substrate wafers and their sides are in contact. The present invention not only provides an effective heat dissipation channel, reduces the device junction temperature and its influence on the device characteristics, but also can effectively release the structural stress and strain, avoiding the performance deterioration and failure of the device caused by its action on the insulating substrate, the chip, and the solder layer.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic devices, and particularly to an IGBT power module packaging structure with low stress and high thermal conductivity. Background Art

[0002] IGBT (Insulated Gate Bipolar Transistor) power devices are applied in a wide range of fields from the inverters of hybrid electric vehicles to the power converters of wind turbines, and have evolved from conventional IGBT power devices to IGBT power modules or IGBT intelligent power modules with continuously increasing application requirements. To improve the current handling capacity of IGBT power modules, multiple IGBT chips are connected in parallel in the IGBT power module, and freewheeling diodes are integrated according to application requirements. In the current technology, an insulating substrate is used for electrical isolation between the silicon chip, substrate, and heat dissipation layer of the power module. According to different device rated powers, different insulating substrate materials and module manufacturing technologies are adopted for IGBT power modules.

[0003] The stress generated in the packaging structure due to temperature changes during the bonding process and power cycling during application will cause strain in the insulating substrate, resulting in warping and even fracture of the insulating substrate, and acting on the chip and chip solder layer, leading to deterioration and even failure of device performance. In the current technology, the directly bonded copper (DBC) insulating substrate substrate containing an insulating substrate can achieve a smaller substrate size, which is only suitable for low-power IGBT devices or power modules. Large-size insulating substrate substrates required for high-power IGBT devices or power modules generally adopt the insulating metal substrate (IMS) technology, and its insulating substrate uses polymer materials. The disadvantages are low thermal conductivity of the polymer material, capacitive crosstalk problems related to thin polymer layers, etc.

[0004] Insulating substrate materials suitable for IGBT power modules in the current technology are alumina ceramics, aluminum nitride ceramics, silicon nitride ceramics, etc. Alumina is the most commonly used insulating substrate material, which has mature technology, low cost, and is easy to metallize and machine. However, for high-power applications, the thermal conductivity of alumina is too low, and the thermal expansion coefficient is seriously mismatched with silicon materials. The thermal conductivity of aluminum nitride is 6 times higher than that of alumina, the thermal expansion coefficient is more matched with silicon materials, and it is easy to process, having advantages in high-power applications. However, the cost of aluminum nitride is 4 times higher than that of alumina. The thermal expansion coefficient of silicon nitride is very well matched with silicon and has a high thermal conductivity, and it is easy to metallize and machine, but the cost is 2 times higher than that of alumina. Summary of the Invention

[0005] In view of the above problems, the present invention provides a structure including a composite insulating substrate, which can not only provide an effective heat dissipation channel, reduce the device junction temperature and its influence on device characteristics, but also effectively release the structural stress and strain, and avoid the performance deterioration and failure of the device caused by its action on the insulating substrate, chip and solder layer. A low-stress and high-thermal-conductivity IGBT power module packaging structure and preparation method are provided.

[0006] The technical solution of the present invention is: a low-stress and high-thermal-conductivity IGBT power module packaging structure, including a substrate, an insulating substrate and a chip bonded in sequence from bottom to top;

[0007] The insulating substrate includes an upper metal layer, an insulating substrate and a lower metal layer bonded in sequence from top to bottom;

[0008] The insulating substrate includes a plurality of first insulating substrate wafers and second insulating substrate wafers;

[0009] A plurality of the first insulating substrate wafers are respectively in a rectangular structure and are evenly spaced;

[0010] The second insulating substrate wafer is embedded between adjacent first insulating substrate wafers and their sides are in contact.

[0011] The second insulating substrate wafer is in a cross-shaped structure.

[0012] The second insulating substrate wafer includes a plurality of first cross-shaped insulating wafers;

[0013] The first cross-shaped insulating wafer includes four short arms, which are embedded in the middle of the insulating substrate and are located between adjacent first insulating substrate wafers.

[0014] It further includes a plurality of second cross-shaped insulating wafers;

[0015] The second cross-shaped insulating wafer includes three short arms and one long arm, which are embedded in the side part of the insulating substrate and are located between adjacent first insulating substrate wafers;

[0016] The long arm of the second cross-shaped insulating wafer extends to the outer edge of the insulating substrate.

[0017] It further includes four third cross-shaped insulating wafers;

[0018] The third cross-shaped insulating wafer includes two short arms and two long arms, which are embedded between four first insulating substrate wafers at the four corners of the insulating substrate, and the two long arms of the third cross-shaped insulating wafer extend to the outer edge of the insulating substrate.

[0019] The thickness of the first insulating substrate wafer is the same as that of the second insulating substrate wafer.

[0020] The top and bottom surfaces of the first insulating substrate wafer and the second insulating substrate wafer are respectively in the same plane.

[0021] The length of each short arm of the first cross-shaped insulating substrate is equal to one half of the length of each side of the first insulating substrate wafer that it fits against.

[0022] The length of each short arm of the second cross-shaped insulating substrate is equal to one half of the length of each side of the first insulating substrate wafer that it fits against;

[0023] The length of one long arm of the second cross-shaped insulating substrate is equal to the length of the side of the first insulating substrate wafer that it fits against.

[0024] The length of each short arm of the third cross-shaped insulating substrate is equal to one half of the length of each side of the first insulating substrate wafer that it fits against, and the length of each long arm of the third cross-shaped insulating substrate is equal to the length of each side of the first insulating substrate wafer that it fits against.

[0025] The present invention uses a number of first insulating substrate wafers and second insulating substrate wafers to be mutually embedded and fitted to form a large-sized insulating substrate wafer, and is bonded to an upper metal layer and a lower metal layer to form an insulating substrate. Among them, the sides of each insulating substrate wafer are only closely fitted to each other instead of being fixedly connected, and the first insulating substrate wafer uses an insulating material with a conventional thermal conductivity and low cost, while the second insulating substrate wafer uses an insulating material with a high thermal conductivity. When applied to an IGBT power module that bears a large thermal load and power load, compared with a single large-sized insulating substrate, the composite insulating substrate of the present invention can effectively release the stress generated in the insulating substrate due to the thermal load and power load, avoid the warping or fracture of the substrate caused by thermal stress, and avoid the deterioration and even failure of the device performance due to its effect on the welding layer and the chip. At the same time, it provides an effective heat dissipation channel, reduces the device junction temperature and its influence on the device characteristics, and can be applied to large-sized and high-power IGBT devices or power modules. Description of the Drawings

[0026] Figure 1 is a schematic diagram of the overall structure of the packaging structure of the present invention,

[0027] Figure 2 is a schematic diagram of the square insulating substrate structure of the present invention,

[0028] Figure 3 is a top view of the square insulating substrate structure of the present invention,

[0029] Figure 4 is a side view of the square insulating substrate structure of the present invention,

[0030] Figure 5It is a schematic structural diagram of the rectangular insulating substrate of the present invention.

[0031] Figure 6 It is a top view of the rectangular insulating substrate structure of the present invention.

[0032] Figure 7 It is a side view of the rectangular insulating substrate structure of the present invention.

[0033] In the figure, 1 is the substrate, 2 is the insulating substrate, 21 is the upper metal layer, 221 is the first insulating substrate chip, 222 is the second insulating substrate chip, 2221 is the first cross-shaped insulating chip, 2222 is the second cross-shaped insulating chip, 2223 is the third cross-shaped insulating chip, 23 is the lower metal layer, 3 is the insulating substrate solder layer, 4 is the chip solder layer, and 5 is the chip. Specific embodiments

[0034] As shown in the present invention Figure 1-7 A low-stress and high-thermal-conductivity IGBT power module packaging structure, including a substrate 1, an insulating substrate 2, and a chip 5 bonded in sequence from bottom to top.

[0035] The upper metal layer 21 and the lower metal layer 23 are respectively bonded to the upper top surface and the lower bottom surface of the insulating substrate, that is, the upper top surfaces of the respective first insulating substrate chips 221 of the insulating substrate and the upper top surfaces of the respective second insulating substrate chips 222 are respectively bonded to the lower bottom surface of the upper metal layer 21, and the lower bottom surfaces of the respective first insulating substrate chips 221 of the insulating substrate and the lower bottom surfaces of the respective second insulating substrate chips 222 are respectively bonded to the upper top surface of the lower metal layer 23.

[0036] The insulating substrate 2 includes an upper metal layer 21, an insulating substrate, and a lower metal layer 23 bonded in sequence from top to bottom.

[0037] The insulating substrate includes a plurality of first insulating substrate chips 221 and second insulating substrate chips 222.

[0038] A number of the first insulating substrate wafers 221 are in a rectangular structure and are evenly spaced in the same plane both horizontally and vertically (there are equal-width gaps between the first insulating substrate wafers 221); by using a certain number of the first insulating substrate wafers 221 and embedding a certain number of the second insulating substrate wafers 222 of three basic configurations, a large-sized insulating substrate is formed; the first insulating substrate wafers 221 are wafers with the simplest shape and the most convenient production, in the form of a rectangle (square or rectangle), and a number of the first insulating substrate wafers 221 are evenly arranged in the same plane both horizontally and vertically, and there are equal-width gaps between the first insulating substrate wafers 221; the first insulating substrate wafers 221 in the form of a rectangle or square have a simple structure and are easy to prepare, and are easy to be combined with the second insulating substrate wafers 222 of the above three basic configurations into a conventional rectangular or square insulating substrate, while circular or other special-shaped wafers are inconvenient or difficult to achieve this purpose.

[0039] The second insulating substrate wafers 222 are embedded between four adjacent first insulating substrate wafers 221 and are attached to their sides.

[0040] The present invention uses a number of first insulating substrate wafers 221 in a rectangular configuration and three basic configuration cross-shaped second insulating substrate wafers 222 to cross-embed and form a large-sized insulating substrate wafer. The sides of each wafer are attached to each other, and each wafer meshes with each other due to the frictional force between the sides. Moreover, when the insulating substrate is bonded to the upper metal layer 21 and the lower metal layer 23, due to the high coefficient of thermal expansion of the copper material commonly used for the upper metal layer 21 and the lower metal layer 23, the insulating substrate is compressed and closely attached at room temperature, which can increase the mechanical strength of the insulating substrate and the insulating substrate substrate 2.

[0041] Embedding the second insulating substrate wafers 222 into the first insulating substrate wafers 221 can obtain the following advantages:

[0042] 1. Provide a heat dissipation channel. The second insulating substrate uses an insulating material with a high thermal conductivity, such as aluminum nitride.

[0043] 2. The wafers that cross-embed and are attached to each other on the sides mesh with each other due to the frictional force, improving the mechanical strength of the insulating substrate.

[0044] 3. The large-sized substrate formed by embedding and attaching multiple wafers is easier to release the stress and strain generated by the thermal load or power load than a single large-sized insulating substrate.

[0045] For further optimization, the second insulating substrate wafers 222 are in a cross-shaped structure.

[0046] For further expansion, the second insulating substrate wafers 222 include a first cross-shaped insulating wafer 2221.

[0047] The first cross-shaped insulating substrate 2221 includes four short arms of equal length (the part extending between the two first insulating substrate substrates 221), which are embedded in the middle of the insulating substrate, that is, in the gap at the intersection of the four first insulating substrate substrates 221, as Figure 2 and Figure 5 shown, the exact middle part.

[0048] Furthermore, it further includes a number of second cross-shaped insulating substrates 2222;

[0049] The second cross-shaped insulating substrate 2222 is located on the side of the first cross-shaped insulating substrate 2221 and includes three short arms of equal length and one long arm;

[0050] The long arm of the second cross-shaped insulating substrate 2222 is embedded between adjacent first cross-shaped insulating substrates 2221 with one side close to the edge, that is, one long arm of the second cross-shaped insulating substrate 2222 extends towards the outer edge of the insulating substrate. As Figure 2 and Figure 5 shown, a total of 8 second cross-shaped insulating substrates 2222 are provided in the figure, up, down, left, and right, and are respectively located on both sides of the first cross-shaped insulating substrate 2221.

[0051] Furthermore, it further includes a number of third cross-shaped insulating substrates 2223;

[0052] A number of the third cross-shaped insulating substrates 2223 are respectively located at the four corners of the insulating substrate and are embedded in the intervals between the four first insulating substrate substrates 221;

[0053] The third cross-shaped insulating substrate 2223 includes two short arms of equal length and two long arms of equal length;

[0054] The two long arms of the third cross-shaped insulating substrate 2223 extend towards the outer edge of the insulating substrate.

[0055] Furthermore, the thickness of the first insulating substrate substrate 221 is the same as the thickness of the second insulating substrate 222, and the side of the second insulating substrate 222 is attached to the side of the adjacent first insulating substrate substrate 221.

[0056] Furthermore, the top and bottom surfaces of the first insulating substrate substrate 221 and the second insulating substrate 222 are respectively in the same plane. That is, the upper top surfaces of the second insulating substrates 222 are flush with the upper top surfaces of the first insulating substrate substrates 221, and the lower bottom surfaces of the second insulating substrates 222 are flush with the lower bottom surfaces of the first insulating substrate substrates 221.

[0057] Further optimization: The lengths of the four short arms of the first cross-shaped insulating substrate 2221 are equal to half of the side length of the first insulating substrate 221 to which it is attached. The second insulating substrate 222 embedded between the first insulating substrates 221 can be unified into three basic configuration substrates. The substrate configuration is simple, easy to fabricate, can be modularized, and is easy to expand.

[0058] Further optimization: The lengths of the three short arms of the second cross-shaped insulating substrate 2222 are equal to half of the side length of the first insulating substrate 221 to which it is attached;

[0059] The length of one long arm of the second cross-shaped insulating substrate 2222 is equal to the side length of the first insulating substrate 221 to which it is attached.

[0060] Further optimization: The lengths of the two short arms of the third cross-shaped insulating substrate 2223 are equal to half of the side length of the first insulating substrate 221 to which it is attached, and the lengths of the two long arms of the third cross-shaped insulating substrate 2223 are equal to the side length of the first insulating substrate 221 to which it is attached.

[0061] The above three basic configuration second insulating substrates 222 are respectively embedded between adjacent first insulating substrates 221 at corresponding parts of the insulating substrate. Among them, the first cross-shaped insulating substrate 2221 is respectively embedded between adjacent first insulating substrates 221 in the middle of the insulating substrate, the second cross-shaped insulating substrate 2222 is respectively embedded between adjacent first insulating substrates 221 on the side of the insulating substrate, and the third cross-shaped insulating substrate 2223 is respectively embedded between adjacent first insulating substrates 221 at the four corners of the insulating substrate. The present invention uses four basic configuration insulating substrate substrates to be mutually embedded and combined to form a large-sized rectangular (square or rectangular) insulating substrate. Insulating substrates of different sizes are composed of a corresponding number of first insulating substrates 221 embedded with a corresponding number of second insulating substrates 222 of three basic configurations, and have the advantages of modularization, expandability, simple substrate configuration, and easy fabrication.

[0062] In this case, the upper metal layer 21 and the lower metal layer 23 are square or rectangular metal foils having the same shape and size as the first insulating substrate 221, and the outer edge of the insulating substrate in the insulating substrate substrate 2 is flush with the outer edges of the upper metal layer 21 and the lower metal layer 23.

[0063] The first insulating substrate substrate 221, which is the main body of the insulating substrate structure, is made of alumina material. Although its thermal conductivity is poor, its cost is low. The second insulating substrate substrate 222 embedded between each first insulating substrate substrate 221 uses high-thermal-conductivity aluminum nitride or silicon nitride material as the heat conduction channel to improve the heat dissipation effect of the insulating substrate substrate 2, reduce the device junction temperature and its influence on device characteristics. Although its cost is high, due to its small area proportion, the impact on the overall cost is limited.

[0064] A preparation method of a low-stress and high-thermal-conductivity IGBT power module packaging structure includes the following steps:

[0065] 1) Prepare a number of first insulating substrate substrates 221 with rectangular structures (including squares or rectangles);

[0066] 2) Prepare a number of cross-shaped second insulating substrate substrates 222 (including a number of first cross-shaped insulating substrates 2221, a number of second cross-shaped insulating substrates 2222, and a number of third cross-shaped insulating substrate substrates);

[0067] 3) Generate thin oxide films on the bottom surface of the upper metal layer 21 and the top surface of the lower metal layer 23 respectively;

[0068] 4) Arrange the first insulating substrate substrates 221 at equal intervals along the horizontal and vertical directions on the top surface of the lower metal layer 23 where the thin oxide film is generated;

[0069] 5) Embed the second insulating substrate substrate 222 in the intersection gap of every four first insulating substrate substrates 221;

[0070] 5.1) Embed the first cross-shaped insulating substrate 2221 in the intersection gap of four first insulating substrate substrates 221 located in the middle of the insulating substrate;

[0071] 5.2) Embed the second cross-shaped insulating substrate 2222 in the intersection gap of four first insulating substrate substrates 221 located on the four sides of the insulating substrate;

[0072] One long arm of the second cross-shaped insulating substrate 2222 extends towards the outer edge direction of the insulating substrate;

[0073] 5.3) Embed the third cross-shaped insulating substrate 2223 in the intersection gap of four first insulating substrate substrates 221 located at the four corners of the insulating substrate;

[0074] Two long arms of the third cross-shaped insulating substrate 2223 extend towards the outer edge direction of the insulating substrate;

[0075] The side part of the first cross-shaped insulating substrate 2221 is attached to the side part of the adjacent second cross-shaped insulating substrate 2222, and the side part of the second cross-shaped insulating substrate 2222 is attached to the side part of the adjacent third cross-shaped insulating substrate 2223;

[0076] 6) Cover the upper metal layer 21 so that its bottom surface fits against the top surface of each insulating substrate wafer, and align the outer edges of the insulating substrate, the upper metal layer 21, and the lower metal layer 23;

[0077] 7) Place the above structure into a reaction furnace, heat it up to 1066 - 1078 °C, hold for 45 - 60 min, and gradually cool it down to room temperature to obtain the insulating substrate wafer 2;

[0078] 8) Bond the chip 5 with a metallized back surface to the top surface of the insulating substrate wafer 2 through the chip solder layer 3;

[0079] 9) Bond the insulating substrate wafer 2 in the above structure after step 8) to the top surface of the substrate 1 through the insulating substrate wafer solder layer 4.

[0080] In this case, the material of the first insulating substrate wafer is silicon oxide, the material of the second insulating substrate wafer is aluminum nitride or silicon nitride, and the materials of the upper metal layer 21, the lower metal layer 23, and the substrate 1 are copper respectively.

[0081] This case adopts a composite insulating substrate in which an insulating substrate of a conventional thermal conductivity insulating material is embedded with a high - thermal - conductivity insulating material, so as to overcome the problems that when the IGBT power module bears a large thermal load and power load, the insulating substrate of the conventional insulating material has poor heat dissipation effect, the substrate warping or fracture caused by thermal stress of the conventional single - substrate wafer, and the deterioration and failure of device performance caused thereby.

[0082] The insulating substrate includes a number of uniformly arranged first insulating wafers, with second insulating wafers embedded therein. The insulating wafers are laterally fitted together to form a composite insulating substrate with a large size and high - thermal - conductivity channels. The top and bottom surfaces of the insulating substrate are respectively bonded to the upper metal layer 21 and the lower metal layer 23 to form a large - size insulating substrate wafer 2. The insulating substrate wafer 2 is bonded to the substrate through the insulating substrate wafer solder layer 3, and the chip 5 is bonded to the insulating substrate wafer 2 through the chip solder layer 4, constituting a low - stress and high - thermal - conductivity GBT power module packaging structure. When the IGBT power module bears a large thermal load and power load, compared with a single - piece large - size insulating substrate wafer that may cause substrate warping or fracture due to thermal stress and lead to device failure, at the same time, the second insulating wafer provides an effective heat dissipation channel, reduces the device junction temperature and its influence on device characteristics, and can be applied to large - size and high - power IGBT devices or power modules.

Claims

1. A low-stress and high-thermal-conductivity IGBT power module packaging structure, comprising a substrate, an insulating substrate, and a chip bonded in sequence from bottom to top; characterized in that, The insulating substrate includes a top metal layer, an insulating substrate, and a bottom metal layer bonded in sequence from top to bottom; The insulating substrate includes a plurality of first insulating substrate wafers and second insulating substrate wafers; The plurality of first insulating substrate wafers are respectively in a rectangular structure and are arranged at equal intervals; The second insulating substrate wafer is embedded between adjacent first insulating substrate wafers and their sides are in contact; The plurality of first insulating substrate wafers and second insulating substrate wafers are mutually embedded and in contact to form a large-sized insulating substrate wafer, and are bonded to the top metal layer and the bottom metal layer to form an insulating substrate. Among them, the sides of each insulating substrate wafer are only in close contact with each other, rather than being fixedly connected.

2. The low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 1, characterized in that The second insulating substrate wafer is in a cross-shaped structure.

3. A low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 1 or 2, characterized in that, The second insulating substrate wafer includes a plurality of first cross-shaped insulating wafers; The first cross-shaped insulating wafer includes four short arms, which are embedded in the middle of the insulating substrate and are located between adjacent first insulating substrate wafers.

4. A low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 3, characterized in that It also includes a plurality of second cross-shaped insulating wafers; The second cross-shaped insulating wafer includes three short arms and one long arm, which are embedded in the side part of the insulating substrate and are located between adjacent first insulating substrate wafers; The long arm of the second cross-shaped insulating wafer extends to the outer edge of the insulating substrate.

5. A low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 3, characterized in that, It also includes four third cross-shaped insulating wafers; The third cross-shaped insulating wafer includes two short arms and two long arms, which are embedded between four first insulating substrate wafers at the four corners of the insulating substrate. The two long arms of the third cross-shaped insulating wafer extend to the outer edge of the insulating substrate.

6. The low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 1, characterized in that The thickness of the first insulating substrate wafer is the same as that of the second insulating substrate wafer.

7. A low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 1, characterized in that, The top and bottom surfaces of the first insulating substrate wafer and the second insulating substrate wafer are respectively in the same plane.

8. The low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 3, characterized in that The length of each short arm of the first cross-shaped insulating wafer is equal to one-half of the length of each side of the first insulating substrate wafer that it contacts.

9. A low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 4, wherein The length of each short arm of the second cross-shaped insulating wafer is equal to one-half of the length of each side of the first insulating substrate wafer that it contacts; The length of one long arm of the second cross-shaped insulating wafer is equal to the length of the side of the first insulating substrate wafer that it contacts.

10. A low-stress and high-thermal-conductivity IGBT power module packaging structure according to claim 5, characterized in that, The length of each short arm of the third cross-shaped insulating wafer is equal to one-half of the length of each side of the first insulating substrate wafer that it contacts, and the length of each long arm of the third cross-shaped insulating wafer is equal to the length of each side of the first insulating substrate wafer that it contacts.

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