Method for preparing substrate, method for preparing power module, and power module

Abstract

The invention discloses a method for preparing a substrate, a method for preparing a power module and a power module. The method for preparing the substrate comprises: S1, cutting a conductor by laser according to a conductive pattern to obtain a conductive part, and processing a mounting hole on the conductive part; S2, pre-fixing the conductive part on a ceramic substrate by a mixed solder paste, the shape of the mixed solder paste is adapted to the shape of the conductive part, the cross-sectional area of ​​the mixed solder paste on the projection surface in the thickness direction of the ceramic substrate is smaller than the cross-sectional area of ​​the conductive part, and part of the mixed solder paste is located in the mounting hole; S3, placing the conductive part and the ceramic substrate in step S2 as a whole in a vacuum brazing furnace for heating to obtain a conductive matrix; S4, taking out the conductive matrix after the vacuum brazing furnace is cooled, and cutting the conductive matrix to obtain a plurality of substrates. According to the method for preparing the substrate of the invention, the requirements for processing equipment are reduced, thereby reducing production costs, no chemical liquids such as etching liquid are required, pollution to the environment is reduced, and the production efficiency of the substrate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power modules, and in particular to a method for preparing a substrate, a method for preparing a power module, and a power module. Background Art

[0002] In the field of power semiconductor modules, DBC (Direct Bond Copper, ceramic copper clad laminate) is usually used as the carrier of IGBT chips to increase the heat dissipation and current carrying capacity of the device. 2 O 3 The main method of making ceramic into DBC is direct copper coating, that is, Al 2 O 3 The two sides of the ceramic are covered with copper. During the metallization process, no additional substances need to be added to achieve copper foil and Al 2 O 3 Direct connection of ceramics, and then etching the copper clad into the corresponding conductive pattern according to the circuit design or product structure.

[0003] However, the existing copper plating method often requires manufacturers to introduce related etching production lines, which increases equipment costs. Etching also requires the use of corresponding chemical liquids such as etching liquids. Improper handling of chemical liquids will pollute the environment. 2 O 3 The thick copper covered by ceramic has a slow etching efficiency and low precision, and the etching will etch away the copper except the conductive pattern, resulting in material waste. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a method for preparing a substrate, which reduces the requirements for processing equipment, thereby reducing production costs, and does not require chemical liquids such as etching liquid, thereby reducing pollution to the environment and improving the production efficiency of the substrate.

[0005] Another object of the present invention is to provide a method for preparing a power module including the method for preparing the substrate.

[0006] Another object of the present invention is to provide a power module manufactured by using the above power module manufacturing method.

[0007] A method for preparing a substrate according to a first embodiment of the present invention comprises the following steps:

[0008] S1, laser cutting the conductor according to the conductive pattern to obtain a conductive member, and processing a mounting hole on the conductive member;

[0009] S2, the conductive member is pre-fixed on the ceramic substrate by means of a mixed solder paste, the shape of the mixed solder paste matches the shape of the conductive member, wherein the cross-sectional area of ​​the mixed solder paste on the projection surface in the thickness direction of the ceramic substrate is smaller than the cross-sectional area of ​​the conductive member, and part of the mixed solder paste is located in the mounting hole;

[0010] S3, placing the conductive member and the ceramic substrate in step S2 in a vacuum brazing furnace for heating to obtain a conductive substrate;

[0011] S4. After the vacuum brazing furnace is cooled, the conductive substrate is taken out, and the conductive substrate is cut to obtain a plurality of substrates.

[0012] According to the method for preparing a substrate of the embodiment of the present invention, through the above steps S1 to S4, the directly cut conductive parts can be brazed on the ceramic substrate to obtain the substrate. Compared with the traditional etching method, the requirements for processing equipment are reduced, thereby reducing production costs, and chemical liquids such as etching liquid are not required, which reduces environmental pollution and improves the production efficiency of the substrate.

[0013] According to some embodiments of the present invention, step S1 specifically includes:

[0014] S21, printing the mixed solder paste onto the ceramic substrate through a printing screen;

[0015] S22, after the conductive member is pre-fixed on the ceramic substrate, the conductive member is placed in a tooling as a whole.

[0016] According to some embodiments of the present invention, on the projection surface in the thickness direction of the ceramic substrate, the minimum distance between the edge of the mixed solder paste and the edge of the conductive member is L 1 , wherein the L 1 Meet: 0.2mm≤L 1 ≤0.3mm; on the projection surface in the thickness direction of the ceramic substrate, the mixed solder paste covers the bottom of the mounting hole.

[0017] According to some embodiments of the present invention, on the projection plane in the thickness direction of the ceramic substrate, the minimum distance between the edge of the opening of the printing screen and the edge of the conductive member is L 2 , wherein the L 2 Meet: 0.2mm≤L 2 ≤0.3mm; on the projection surface of the ceramic substrate in the thickness direction, the opening of the printed screen covers the bottom of the mounting hole.

[0018] According to some embodiments of the present invention, the thickness of the printed screen in the thickness direction of the ceramic substrate is D, wherein D satisfies: 0.1 mm≤D≤0.2 mm.

[0019] According to some embodiments of the present invention, before step S1, the step further includes

[0020] S0, machining positioning holes on the ceramic substrate and cleaning the ceramic substrate;

[0021] Wherein, in step S22, the tooling is installed through the positioning hole.

[0022] According to some embodiments of the present invention, before step S1, the method further includes:

[0023] S20, removing oxides of the conductor.

[0024] According to some embodiments of the present invention, the mixed solder paste includes CuSnTi solder paste and cuprous oxide, the mass proportion of the cuprous oxide is ɑ, wherein the ɑ satisfies: 1%≤ɑ≤2%.

[0025] According to some embodiments of the present invention, the particle size of the cuprous oxide is d, wherein d satisfies: 45 μm≤d≤65 μm.

[0026] According to some embodiments of the present invention, in step S3, the brazing temperature is T, and the brazing time is t, wherein T and t respectively satisfy: 900°C≤T≤950°C, 20min≤t≤30min.

[0027] A method for preparing a power module according to an embodiment of the second aspect of the present invention comprises the following steps:

[0028] S1', the connection part of the power pin of the frame is pre-fixed in the mounting hole of the substrate by solder paste, and the substrate is prepared by the method for preparing the substrate of the first aspect of the embodiment of the present invention;

[0029] S2', welding the substrate and the frame.

[0030] According to some embodiments of the present invention, in step S1 ′, the solder paste is placed in the mounting hole by printing or spraying, and at least a portion of the connecting portion is located in the mounting hole.

[0031] According to some embodiments of the present invention, on a projection surface in the thickness direction of the substrate, a cross-sectional area of ​​the mounting hole is larger than a cross-sectional area of ​​the connecting portion.

[0032] According to some embodiments of the present invention, in the length direction of the substrate, the minimum distance between the edge of the mounting hole and the edge of the connecting portion is L3 , wherein the L 3 Meet: 0.05mm≤L 3 ≤0.1mm; and / or in the width direction of the substrate, the minimum distance between the edge of the mounting hole and the edge of the connecting portion is L 4 , wherein the L 4 Meet: 0.05mm≤L 4 ≤0.1mm.

[0033] According to the power module of the embodiment of the third aspect of the present invention, the power module is prepared by using the preparation method of the power module of the embodiment of the second aspect of the present invention.

[0034] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0036] Figure 1 is a flow chart of a method for preparing a substrate according to an embodiment of the present invention;

[0037] Figure 2 is a flow chart of a conductive member of a substrate according to an embodiment of the present invention;

[0038] Figure 3 is a schematic diagram of a substrate and a frame of a power module according to an embodiment of the present invention;

[0039] Figure 4 yes Figure 3 A partial enlarged view of a substrate and a frame of the power module shown;

[0040] Figure 5 is a side view of a substrate and a frame of a power module according to an embodiment of the present invention;

[0041] Figure 6 yes Figure 5 A partial enlarged view of the substrate and frame of the power module.

[0042] Reference numerals:

[0043] 100: Power module:

[0044] 10: conductor; 11: conductive pattern; 12: conductive member; 13: mounting hole; 20: mixed solder paste; 30: ceramic substrate; 31: positioning hole; 40: conductive substrate; 50: substrate; 60: frame; 61: power pin; 62: connection part; 70: solder paste;

[0045] 200: Workwear. DETAILED DESCRIPTION

[0046] Reference below Figure 1-Figure 2 A method for preparing the substrate 50 according to an embodiment of the first aspect of the present invention is described.

[0047] like Figure 1 and Figure 2 As shown, the method for preparing the substrate 50 according to the first embodiment of the present invention comprises the following steps:

[0048] S1. Laser cut the conductor 10 according to the conductive pattern 11 to obtain the conductive member 12, and process the mounting hole 13 on the conductive member 12. That is, the redundant part of the conductive member 12 is removed by laser cutting according to the conductive pattern 11 to process the conductor 10 into the conductive member 12. The conductor 10 may be a copper sheet with a thickness of 0.2 mm. The conductive member 12 may be used to install the power chip, and may also be used for heat dissipation of the power module 100.

[0049] Among them, the mounting hole 13 can be processed on the conductive part 12 by laser cutting. When the pin is assembled with the conductive part 12, one end of the pin can be fitted in the mounting hole 13 so that the pin is restricted by the mounting hole 13 to avoid large movement of the pin. At this time, the mounting hole 13 plays a better positioning role and ensures the stability of the relative position of the conductive part 12 and the power pin.

[0050] S2. The conductive member 12 is pre-fixed on the ceramic substrate 30 by means of the mixed solder paste 20. The shape of the mixed solder paste 20 matches the shape of the conductive member 12, so as to facilitate the pre-fixation of the conductive member 12 on the ceramic substrate 30 firmly and avoid leakage of the mixed solder paste 20.

[0051] In the thickness direction of the ceramic substrate 30 (for example, Figure 4 The cross-sectional area of ​​the mixed solder paste 20 on the projection surface (in the front-to-back direction) is smaller than the cross-sectional area of ​​the conductive member 12. Since the mixed solder paste 20 will be melted by high temperature in the vacuum soldering furnace, the area of ​​the mixed solder paste 20 is set smaller. While the conductive member 12 is firmly soldered to the ceramic substrate 30, the liquid mixed solder paste 20 is prevented from flowing to the outside of the conductive member 12 during the soldering process, thereby reducing the waste of the mixed solder paste 20 and ensuring the regularity of the surface of the substrate 50.

[0052] Part of the mixed solder paste 20 is located in the mounting hole 13. At this time, the mounting hole 13 can be suitable for installing the pins of the power module 100, that is, the pins can be connected to the ceramic substrate 30 through the mixed solder paste 20 in the mounting hole 13 to achieve a fixed connection between the pins and the substrate 50, and the pins can be electrically connected to the conductive part 12 through the mixed solder paste 20.

[0053] Optionally, the ceramic substrate 30 may be Al 2 O 3 Ceramic substrate 30. But not limited thereto.

[0054] S3, placing the conductive member 12 and the ceramic substrate 30 in step S2 in a vacuum brazing furnace for heating to obtain a conductive substrate 40. This step can securely braze the conductive member 12 to the ceramic substrate 30 to prevent the conductive member 12 from falling off during the processing of the power module 100.

[0055] S4, after the vacuum brazing furnace is cooled, the conductive substrate 40 is taken out, and the conductive substrate 40 is cut to obtain a plurality of substrates 50. In other words, the plurality of substrates 50 can be integrated together for processing, thereby improving the production efficiency of the substrates 50.

[0056] According to the method for preparing the substrate 50 of the embodiment of the present invention, through the above steps S1 to S4, the directly cut conductive member 12 can be brazed on the ceramic substrate 50 to obtain the substrate 50. Compared with the traditional etching method, the requirements for processing equipment are reduced, thereby reducing production costs, and chemical liquids such as etching liquid are not required, which reduces pollution to the environment and improves the production efficiency of the substrate 50.

[0057] According to some embodiments of the present invention, step S2 specifically includes:

[0058] S21, printing the mixed solder paste 20 onto the ceramic substrate 30 through a printing screen. The position of the mesh of the printing screen is the same as the position of the conductive member 12 on the ceramic substrate 30, so that only the area where the conductive member 12 is provided on the ceramic substrate 30 is provided with the mixed solder paste 20, while other areas of the ceramic substrate 30 are free of the mixed solder paste 20. In this way, the waste of the mixed solder paste 20 can be reduced, the cost can be reduced, and the normal operation of the power module 100 can be ensured.

[0059] S22, the conductive member 12 is pre-fixed on the ceramic substrate 30 and then placed in the fixture 200. The fixture 200 can limit the movement of the ceramic substrate 30 and the conductive member 12, so that the relative position change of the conductive member 12 and the ceramic substrate 30 is avoided during the process of moving the ceramic substrate 30 and the conductive member 12 to the vacuum brazing furnace, thereby improving the yield rate of the substrate 50.

[0060] Furthermore, on the projection surface in the thickness direction of the ceramic substrate 30, the minimum distance between the edge of the mixed solder paste 20 and the edge of the conductive member 12 is L 1 , where L 1 Meet: 0.2mm≤L 1 ≤0.3mm. When L 1When L is less than 0.2 mm, the minimum distance between the edge of the mixed solder paste 20 and the edge of the conductive member 12 is small, that is, the edge of the mixed solder paste 20 on the ceramic substrate 30 will be roughly flush with the edge of the conductive member 12, causing the liquid mixed solder paste 20 to flow to the outside of the conductive member 12 during the brazing process; when L 1 When L > 0.3 mm, the minimum distance between the edge of the mixed solder paste 20 and the edge of the conductive member 12 is large, and the size of the mixed solder paste 20 is small, which will reduce the connection reliability between the conductive member 12 and the ceramic substrate 30. 1 Meet 0.2mm≤L 1 ≤0.3 mm, while ensuring the connection reliability between the conductive member 12 and the ceramic substrate 30, the liquid mixed solder paste 20 can be prevented from flowing to the outside of the conductive member 12 during the soldering process.

[0061] Reference Figure 5 and Figure 6 , on the projection surface in the thickness direction of the ceramic substrate 30, the mixed solder paste 20 covers the bottom of the mounting hole 13. That is, a part of the mixed solder paste 20 on the ceramic substrate 30 is located on the conductive member 12 and the ceramic substrate 30, and this part of the mixed solder paste 20 is used to solder the conductive member 12 to the ceramic substrate 30; the other part of the mixed solder paste 20 covers the entire bottom of the mounting hole 13, and is used to firmly solder the pin to the ceramic substrate 30, so as to achieve a reliable connection between the substrate 50 and the pin.

[0062] According to some embodiments of the present invention, on the projection plane in the thickness direction of the ceramic substrate 30, the minimum distance between the opening edge of the printing screen and the edge of the conductive member 12 is L 2 , where L 2 Meet: 0.2mm≤L 2 ≤0.3mm. When L 2 When L is less than 0.2 mm, the minimum distance between the opening edge of the printing screen and the edge of the conductive member 12 is small. Since the mixed solder paste 20 is printed on the ceramic substrate 30 through the printing screen, the edge of the mixed solder paste 20 on the ceramic substrate 30 will be roughly flush with the edge of the conductive member 12, causing the liquid mixed solder paste 20 to flow to the outside of the conductive member 12 during the soldering process. 2 When L>0.3 mm, the minimum distance between the edge of the opening of the printing screen and the edge of the conductive member 12 is large, and the size of the mixed solder paste 20 is small, which will reduce the connection reliability between the conductive member 12 and the ceramic substrate 30. 1 Meet 0.2mm≤L 2 ≤0.3 mm, while ensuring the connection reliability between the conductive member 12 and the ceramic substrate 30, the liquid mixed solder paste 20 can be prevented from flowing to the outside of the conductive member 12 during the soldering process.

[0063] On the projection surface of the ceramic substrate 30 in the thickness direction, the openings of the printing screen cover the bottom of the mounting hole 13, that is, the mixed solder paste 20 printed on the ceramic substrate 30 by the printing screen can cover the bottom of the mounting hole 13, ensuring that there is enough mixed solder paste 20 in the mounting hole 13, so as to facilitate firmly fixing the pin in the mounting hole 13 and ensure the reliability of the electrical connection between the pin and the conductive part 12.

[0064] According to some embodiments of the present invention, in the thickness direction of the ceramic substrate 30 (eg, Figure 4 The thickness of the printed screen in the front-to-back direction (in the front-to-back direction) is D, where D satisfies: 0.1mm≤D≤0.2mm. That is to say, the thickness of the mixed solder paste 20 in the thickness direction of the ceramic substrate 30 is between 0.1mm and 0.2mm. In this way, the melted mixed solder paste 20 can fill the gap between the conductive part 12 and the ceramic substrate 30, so that the conductive part 12 is firmly connected to the ceramic substrate 30, and the mixed solder paste 20 can be prevented from flowing to the outside of the conductive part 12, further reducing the waste of the mixed solder paste 20.

[0065] According to some embodiments of the present invention, before step S1, the step further includes

[0066] S0, machining a positioning hole 31 on the ceramic substrate 30, and cleaning the ceramic substrate 30;

[0067] In step S22 , the tooling 200 is installed through the positioning holes 31 .

[0068] like Figure 2 As shown, a plurality of positioning holes 31 are processed on the ceramic substrate 30, and a plurality of positioning holes 31 are located in the middle of the ceramic substrate 30, and the remaining positioning holes 31 are evenly spaced along the circumference of the ceramic substrate 30. In the description of the present invention, "plurality" means two or more. By providing positioning holes 31 on the ceramic substrate 30, on the one hand, the positioning holes 31 can realize the positioning of the printing screen and the ceramic substrate 30 to ensure that the mixed solder paste 20 can be accurately printed on the ceramic substrate 30 where the conductive part 12 is placed; on the other hand, the positioning holes 31 can realize the positioning of the tooling 200 and the ceramic substrate 30, so that the ceramic substrate 30 and the conductive part 12 can be accurately installed in the tooling 200, thereby improving the production efficiency of the substrate 50.

[0069] Optionally, after processing the positioning hole 31 , the surface of the ceramic substrate 30 needs to be cleaned to ensure the cleanliness of the surface of the ceramic substrate 30 .

[0070] In some optional embodiments, before step S21, the following steps are further included:

[0071] S20, removing oxides from the conductive member 12. For example, alcohol scrubbing can be used to remove oxides on the surface of the conductive member 10, and then the conductive member 10 is cut according to the conductive pattern 11, and cleaned again after cutting, so that the surface of the conductive member 12 has neither oxide nor cutting chips, thereby ensuring the cleanliness of the conductive member 12, so that the conductive member 12 can be more stably arranged on the ceramic substrate 30, and at the same time, it is beneficial to arrange the power chip on the conductive member 12, thereby reducing the energy consumption of the power module 100.

[0072] According to some embodiments of the present invention, the mixed solder paste 20 includes CuSnTi solder paste and cuprous oxide, and the mass proportion of cuprous oxide is ɑ, wherein ɑ satisfies: 1%≤ɑ≤2%. When ɑ<1%, the content of cuprous oxide is less, and cuprous oxide cannot be evenly distributed in the CuSnTi solder paste, so that the mixing uniformity of the mixed solder paste 20 is poor, and the height of the mixed solder paste 20 is inconsistent (i.e., the weld is inconsistent) during brazing, which seriously affects the flatness of the substrate 50; when ɑ>2%, the content of cuprous oxide is more, resulting in less content of CuSnTi solder paste, which will reduce the weldability of the mixed solder paste 20, thereby reducing the connection reliability of the conductive member 12 and the ceramic substrate 30. Therefore, by making ɑ satisfy 1%≤ɑ≤2%, while ensuring the flatness of the substrate 50, the connection reliability of the conductive member 12 and the ceramic substrate 30 can be improved, and the conductive member 12 and the ceramic substrate 30 can be prevented from separating.

[0073] Further, the particle size of cuprous oxide is d, where d satisfies: 45μm≤d≤65μm. When d<45μm, the particle size of cuprous oxide is small, and the liquid mixed solder paste 20 overflows more during brazing, that is, the portion of the liquid mixed solder paste 20 overflowing the conductive member 12 is large, and the capillary filling force of the mixed solder paste 20 is large, and the welding void is relatively small, which affects the weldability of the mixed solder paste 20; when d>65μm, the particle size of cuprous oxide is large, although the liquid mixed solder paste 20 overflows less during brazing, the capillary filling force of the mixed solder paste 20 is small, and the welding void is relatively large, which also affects the weldability of the mixed solder paste 20. Therefore, by making the particle size d of cuprous oxide satisfy 45μm≤d≤65μm, the overflow of the liquid mixed solder paste 20 during brazing can be effectively avoided, the weldability of the mixed solder paste 20 is guaranteed, and thus the connection reliability between the conductive member 12 and the ceramic substrate 30 can be guaranteed.

[0074] According to some embodiments of the present invention, in step S3, the brazing temperature is T, and the brazing time is t, wherein T and t respectively satisfy: 900°C≤T≤950°C, 20min≤t≤30min. In this way, while ensuring that the mixed solder paste 20 can be melted, the mixed solder paste 20 is prevented from being excessively melted and affecting the performance of the mixed solder paste 20.

[0075] Optionally, in step S3, the vacuum degree of the vacuum brazing furnace may be controlled to be 10 -2 level.

[0076] In some optional embodiments, the substrate 50 can be a ceramic copper-clad plate. For example, a pad (i.e., a conductive member 12) is provided on one side of the ceramic substrate 30 in the thickness direction, and a power chip can be arranged on the pad; or, the pad (i.e., the conductive member 12) and the heat dissipation layer are respectively provided on both sides of the ceramic substrate 30 in the thickness direction, and a power chip can be arranged on the pad, and the surface of the heat dissipation layer away from the pad can be flush with the bottom surface of the plastic package and exposed outside the plastic package. When the power chip generates heat during operation, the heat can be transferred to the heat dissipation layer through the pad and the ceramic substrate 30, and the heat dissipation layer exchanges heat with the outside to achieve heat dissipation of the intelligent power module. For example, the materials of the pad, the ceramic substrate 30 and the heat dissipation layer can be set to a copper layer, a ceramic layer, and a copper layer, respectively, to facilitate the normal use of the substrate 50.

[0077] like Figure 2-Figure 5 As shown, a method for preparing a power module 100 according to an embodiment of the second aspect of the present invention comprises the following steps:

[0078] S1', the connection part 62 of the power pin 61 of the frame 60 is pre-fixed in the mounting hole 13 of the substrate 50 by the solder paste 70, and the substrate 50 is prepared by the preparation method of the substrate 50 of the first embodiment of the present invention. The solder paste 70 can be a Sn-based solder, but it is not limited thereto.

[0079] S2', solder the substrate 50 and the frame 60. For example, the power pin 61 can be securely fixed in the mounting hole 13 by reflow soldering. In order to ensure that the conductive part 12 and the ceramic substrate 30 are not separated during reflow soldering, it is necessary to ensure that the temperature of the solder paste 70 of the reflow soldering is lower than the soldering temperature T, while ensuring that the power pin 61 is electrically connected to the substrate 50, avoid relative displacement between the conductive part 12 and the ceramic substrate 30, so that the power module 100 is more reliable. In particular, the power pin 61 is electrically connected to the conductive part 12 through the solder paste 70 and the mixed solder paste 20.

[0080] According to the preparation method of the power module 100 of the embodiment of the present invention, through the above-mentioned steps S1'-S2', the power pin 61 is restricted by the mounting hole 13 during the welding process, thereby preventing the power pin 61 from moving significantly. At this time, the mounting hole 13 plays a good positioning role, thereby preventing the power pin 61 from moving relative to the substrate 50 when being welded, thereby ensuring the stability of the relative position of the substrate 50 and the power pin 61, improving the efficiency of one-time forming when welding the substrate 50 and the power pin 61, and reducing the risk of scrapping the power module 100.

[0081] According to some embodiments of the present invention, in step S1', the solder paste 70 is placed in the mounting hole 13 by printing or spraying, which increases the diversity of placing the solder paste 70 in the mounting hole 13 and improves the production efficiency of the power module 100. At least part of the connecting portion 62 is located in the mounting hole 13. For example, when pre-fixing the power pin 61, a part of the connecting portion 62 can be placed in the mounting hole 13; or, when pre-fixing the power pin 61, the connecting portion 62 can be placed in the mounting hole 13. In this way, the mounting hole 13 can effectively limit the movement of the connecting portion 62 and ensure the stability of the position of the power pin 61.

[0082] According to some embodiments of the present invention, in the thickness direction of the substrate 50 (eg, Figure 4 On the projection surface (in the front-to-back direction), the cross-sectional area of ​​the mounting hole 13 is larger than the cross-sectional area of ​​the connecting portion 62. This arrangement facilitates the placement of the connecting portion 62 in the mounting hole 13, and at the same time, a gap is provided between the connecting portion 62 and the mounting hole 13, which facilitates the melting solder paste to be filled between the mounting hole 13 and the connecting portion 62 during reflow soldering, and prevents the liquid mixed solder paste 20 from flowing to the connecting portion 62.

[0083] Furthermore, if Figure 3 and Figure 4 As shown, in the length direction of the substrate 50 (for example, Figure 3 In the left-right direction, the minimum distance between the edge of the mounting hole 13 and the edge of the connecting portion 62 is L 3 , where L 3 Meet: 0.05mm≤L 3 ≤0.1mm. When L 3 When L is less than 0.05 mm, the minimum distance between the edge of the mounting hole 13 and the edge of the connecting portion 62 is small. When the processing error of the mounting hole 13 and the connecting portion 62 increases, the connecting portion 62 cannot be placed in the mounting hole 13, which easily causes the power pin 61 and the substrate 50 to move relative to each other. 3 When L > 0.1 mm, the minimum distance between the edge of the mounting hole 13 and the edge of the connecting portion 62 is large, and the size of the mounting hole 13 is large. The melted solder paste 70 during reflow soldering may not fill the mounting hole 13, resulting in a depression on the surface of the substrate 50. 3 Meet 0.05mm≤L 3 ≤0.1 mm, which can improve the flatness of the surface of the substrate 50 while ensuring the relative position stability of the power pin 61 and the substrate 50.

[0084] Likewise, if Figure 5 and Figure 6 As shown, in the width direction of the substrate 50 (for example, Figure 3In the vertical direction, the minimum distance between the edge of the mounting hole 13 and the edge of the connecting portion 62 is L 4 , where L 4 Meet: 0.05mm≤L 4 ≤0.1mm. Such an arrangement can also improve the flatness of the surface of the substrate 50 while ensuring the relative position stability between the power pin 61 and the substrate 50.

[0085] Optionally, in the thickness direction of the substrate 50 , the minimum distance between the connecting portion 62 and the bottom wall of the mounting hole 13 may be between 0.1 mm and 0.2 mm.

[0086] According to the power module 100 of the embodiment of the third aspect of the present invention, the power module 100 is manufactured by using the manufacturing method of the power module 100 of the embodiment of the second aspect of the present invention.

[0087] According to the power module 100 of the third aspect of the present invention, by adopting the above-mentioned method for preparing the power module 100, the production efficiency of the power module 100 can be improved, and the yield rate of the power module 100 can be improved.

[0088] Other structures and operations of the power module 100 according to the embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0089] In the description of the present invention, it is to be understood that the terms “center”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “top”, “bottom”, “inside”, “outside”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0090] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0091] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" 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 the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0092] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a substrate, characterized in that: The following steps are involved: S1, laser cutting the conductor according to the conductive pattern to obtain a conductive member, and processing a mounting hole on the conductive member; S2, the conductive member is pre-fixed on the ceramic substrate by means of a mixed solder paste, the shape of the mixed solder paste matches the shape of the conductive member, wherein the cross-sectional area of ​​the mixed solder paste on the projection surface in the thickness direction of the ceramic substrate is smaller than the cross-sectional area of ​​the conductive member, and part of the mixed solder paste is located in the mounting hole; S3, placing the conductive member and the ceramic substrate in step S2 in a vacuum brazing furnace for heating to obtain a conductive substrate; S4, after the vacuum brazing furnace is cooled, the conductive substrate is removed and the conductive substrate is cut to obtain a plurality of substrates; Wherein, on the projection surface in the thickness direction of the ceramic substrate, the minimum distance between the edge of the mixed solder paste and the edge of the conductive member is L1, wherein L1 satisfies: 0.2mm≤L1≤0.3mm; On a projection surface of the ceramic substrate in the thickness direction, the mixed solder paste covers the bottom of the mounting hole.

2. The method for preparing a substrate according to claim 1, characterized in that: Step S2 specifically includes: S21, printing the mixed solder paste onto the ceramic substrate through a printing screen; S22, after the conductive member is pre-fixed on the ceramic substrate, the conductive member is placed in a tooling as a whole.

3. The method for preparing a substrate according to claim 2, characterized in that: On the projection plane in the thickness direction of the ceramic substrate, the minimum distance between the opening edge of the printing screen and the edge of the conductive member is L2, wherein L2 satisfies: 0.2mm≤L2≤0.3mm; On a projection surface of the ceramic substrate in the thickness direction, the openings of the printed screen cover the bottom of the mounting hole.

4. The method for preparing a substrate according to claim 3, characterized in that: The thickness of the printing screen in the thickness direction of the ceramic substrate is D, wherein D satisfies: 0.1 mm≤D≤0.2 mm.

5. The method for preparing a substrate according to claim 2, characterized in that: Before step S1, the S0, machining positioning holes on the ceramic substrate and cleaning the ceramic substrate; Wherein, in step S22, the tooling is installed through the positioning hole.

6. The method for preparing a substrate according to claim 2, characterized in that: Before step S1, the method further includes: S20, removing oxides of the conductor.

7. The method for preparing a substrate according to any one of claims 1 to 6, characterized in that: The mixed solder paste includes CuSnTi solder paste and cuprous oxide, the mass proportion of the cuprous oxide is ɑ, wherein the ɑ satisfies: 1%≤ɑ≤2%.

8. The method for preparing a substrate according to claim 7, characterized in that: The particle size of the cuprous oxide is d, wherein d satisfies: 45 μm≤d≤65 μm.

9. The method for preparing a substrate according to any one of claims 1 to 6, characterized in that: In step S3, the brazing temperature is T, and the brazing time is t, wherein T and t respectively satisfy: 900°C≤T≤950°C, 20min≤t≤30min.

10. A method for preparing a power module, characterized in that: The following steps are involved: S1', the connection part of the power pin of the frame is pre-fixed in the mounting hole of the substrate by solder paste, and the substrate is prepared by the preparation method of the substrate according to any one of claims 1 to 9; S2', welding the substrate and the frame.

11. The method for preparing a power module according to claim 10, characterized in that: In step S1 ′, the solder paste is placed in the mounting hole by printing or spraying, and at least a portion of the connecting portion is located in the mounting hole.

12. The method for preparing a power module according to claim 10, characterized in that: On a projection surface in the thickness direction of the substrate, a cross-sectional area of ​​the mounting hole is larger than a cross-sectional area of ​​the connecting portion.

13. The method for preparing a power module according to claim 12, characterized in that: In the length direction of the substrate, the minimum distance between the edge of the mounting hole and the edge of the connecting portion is L3, wherein L3 satisfies: 0.05mm≤L3≤0.1mm; and / or In the width direction of the substrate, a minimum distance between an edge of the mounting hole and an edge of the connecting portion is L4, wherein L4 satisfies: 0.05 mm ≤ L4 ≤ 0.1 mm.

14. A power module, characterized in that: The power module is prepared by the method for preparing a power module according to any one of claims 10 to 13.

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