A heat dissipation base plate, a DCM packaging structure and a welding method thereof

Abstract

The application discloses a heat dissipation base plate, a DCM packaging structure and a welding method thereof. The heat dissipation base plate comprises a welding plane and a plurality of supporting convex points arranged on the welding plane. The plurality of supporting convex points are arranged in a radial pattern from a center position of the welding plane to a peripheral position of the welding plane, and the height of the supporting convex points gradually increases from the center position to the peripheral position. The DCM packaging structure comprises the heat dissipation base plate. The welding method uses the heat dissipation base plate. The supporting convex points of the heat dissipation base plate can continuously provide exhaust channels during welding, so as to reduce the cavity phenomenon caused by air trapping during welding, thereby reducing the cavity rate of the DCM packaging structure, ensuring the heat dissipation efficiency and long-term reliability of the module. The supporting convex point structure can also provide stable support for the welding piece during welding, effectively avoiding the inclination of the chip module after welding, and further improving the performance consistency of the DCM module and reducing the thermal resistance of the DCM module.

Description

Technical Field

[0001] This application relates to the field of packaging technology, and in particular to a heat dissipation base plate, a DCM packaging structure and its welding method. Background Technology

[0002] With the rapid development of new energy vehicles, rail transit, and new energy power generation, higher requirements are being placed on the power density, reliability, and heat dissipation performance of power semiconductor modules. DCM (Direct Cooled Module) half-bridge module packaging is an automotive-grade half-bridge power module packaging solution that utilizes innovative technologies such as direct water cooling, substrate removal, silver sintering, and copper bonding to achieve high power density, high reliability, and excellent heat dissipation performance. Furthermore, as a direct water-cooled power module, the DCM half-bridge module is widely used in high-power-density applications due to its excellent heat dissipation efficiency and compact structural design.

[0003] In existing DCM half-bridge module packaging technology, the chip and the bottom heat sink are typically connected and mechanically fixed using a large-area brazing process. The traditional bottom heat sink has a flat, flat welding surface, which presents the following technical problems in actual production:

[0004] During reflow soldering, the solder interface is prone to gas trapping. The gas cannot be discharged in time, resulting in a large number of voids and causing the void rate to exceed the standard. This seriously affects the heat dissipation efficiency and long-term reliability of the module, and also causes reliability problems such as chip tilting and stress concentration. Summary of the Invention

[0005] The purpose of this application is to provide a heat dissipation base plate, a DCM packaging structure, and a welding method thereof to improve the process defects of large-area brazing and enhance the packaging quality and reliability of DCM half-bridge modules. Furthermore, it addresses the issues of weld thickness uniformity, void ratio, and height control in DCM half-bridge modules while improving the heat dissipation base plate structure.

[0006] To achieve the above objectives, one embodiment of this application provides a heat dissipation base plate, comprising: A heat dissipation base plate body, wherein the first surface of the heat dissipation base plate body has a welding plane for welding of solder pads; The support protrusions located on the welding plane include multiple support protrusions arranged radially from the center position of the welding plane to the periphery position of the welding plane, and the height of the support protrusions gradually increases from the center position to the periphery position.

[0007] In an optional embodiment, the support bumps include a central support bump located at the center of the welding plane.

[0008] In an optional embodiment, the support bumps further include multiple groups of peripheral support bumps distributed around the central support bump. Each group of peripheral support bumps includes at least one outer support bump distributed in a ray from the central support bump to the peripheral position; When multiple groups of peripheral support bumps are included, the angles between the distribution rays of adjacent groups of the peripheral support bumps are the same or different.

[0009] In an optional embodiment, the distances between adjacent outer support bumps in each group of peripheral support bumps are equal.

[0010] In an optional embodiment, in each group of peripheral support bumps, the heights of the multiple outer support bumps gradually decrease from the peripheral position to the central position; The heights of the outermost outer support bumps in each group of peripheral support bumps are equal.

[0011] In an optional embodiment, among the multiple groups of peripheral support bumps, the number of support bumps in each group of peripheral support bumps is the same.

[0012] In an optional embodiment, the welding plane is a rectangular welding plane, and the multiple support bumps are arranged in a radial pattern from the central position of the rectangular welding plane to the peripheral position of the welding plane. This radial arrangement includes an "X" - shaped arrangement, a "rice" - shaped arrangement, or a "cross" - shaped arrangement.

[0013] In an optional embodiment, when arranged in an "X" - shaped pattern, the central support bump is located at the intersection of the "X" - shaped pattern. The peripheral support bumps include four groups, and the four groups of peripheral support bumps surround the central support bump. Each group of peripheral support bumps includes at least two outer support bumps, and the outermost outer support bumps of each group of peripheral support bumps are respectively arranged corresponding to the four azimuth angles of the rectangular welding plane.

[0014] In an optional embodiment, the height of the central support bump is 0.13 mm to 0.14 mm; Each group of peripheral support bumps includes at least two outer support bumps. Among them, the height of one outer support bump closest to the central support bump is 0.15 mm to 0.16 mm, and the height of the other outer support bump farthest from the central support bump is 0.17 mm to 0.19 mm.

[0015] In an optional embodiment, when arranged in a "rice" - shaped pattern or a "cross" - shaped pattern, the position of the central support bump is at the intersection of the "rice" - shaped pattern or the "cross" - shaped pattern.

[0016] In an optional embodiment, the welding plane of the heat dissipation base plate body further has a groove, which is disposed on the outer periphery of the support protrusion.

[0017] In an optional embodiment, the groove includes an inner ring groove and an outer ring groove that are spaced apart, with the inner ring groove located closer to the support protrusion and the outer ring groove located away from the support protrusion.

[0018] In an optional embodiment, the inner groove is a continuous groove, and the outer groove is a discontinuous groove.

[0019] In an optional embodiment, the height of the support protrusion is 0.1mm to 0.2mm; The maximum outer diameter of the support protrusion is 0.6 mm.

[0020] This application also provides a DCM packaging structure, including: Chip module; The heat dissipation base plate and solder, wherein the heat dissipation base plate is one of the heat dissipation base plates described above, and one side of the soldering plane of the heat dissipation base plate is connected to the chip module through the solder, and the solder covers the support bumps of the heat dissipation base plate.

[0021] In an optional embodiment, the solder is also provided between the top surface of the support protrusion of the heat sink base plate and the chip module.

[0022] In an optional embodiment, the thickness of the solder is greater than the height of the support bump.

[0023] In an optional embodiment, the chip module is a half-bridge chip module.

[0024] In an optional embodiment, the chip module includes a ceramic substrate and a chip disposed on the ceramic substrate, wherein the ceramic substrate of the chip module is connected to a heat sink via solder.

[0025] This application also provides a welding method for a DCM packaging structure, including the following steps: A heat dissipation base plate is provided, wherein the heat dissipation base plate is one of the heat dissipation base plates described above. A preformed solder pad is provided, which is placed on one side of the welding plane of the heat dissipation base plate and overlapped on the outermost support protrusion of the heat dissipation base plate. A ceramic substrate is provided, which is disposed on the side of the preformed solder pad away from the heat dissipation base plate. The heat dissipation base plate and the ceramic substrate are welded together. During the process of the preformed solder pad softening and melting to achieve welding, the radially arranged array of support protrusions on the heat dissipation base plate continuously provides exhaust channels.

[0026] In an optional embodiment, a molding compound is formed on the outer sides of the heat sink base plate and the ceramic substrate, respectively.

[0027] In an optional embodiment, the shape and size of the preformed solder pad are adapted to the welding plane of the heat dissipation base plate.

[0028] In an optional embodiment, a chip is further disposed on the surface of the ceramic substrate, the chip being disposed on the surface of the ceramic substrate away from the heat dissipation base plate.

[0029] In an optional embodiment, the preformed solder sheet includes a tin solder sheet, a copper-tin alloy solder sheet, or a tin-silver-copper alloy solder sheet.

[0030] In an optional embodiment, the heat dissipation base plate includes a copper plate, and the support bumps include copper support bumps.

[0031] In an optional embodiment, the heat sink and the ceramic substrate are soldered using a reflow soldering process.

[0032] In an optional embodiment, the welding temperature control for welding the heat sink base plate and the ceramic substrate includes: Control the temperature to rise to the first temperature: not exceeding 150℃, and preheat the heat dissipation base plate and preformed solder pads; Next, the temperature is raised to a second temperature: 150℃~180℃, to make the temperature of the heat dissipation base plate and the preformed solder pad uniform; Next, the temperature is raised to a third temperature: 220℃~232℃, so that the preformed solder sheet softens but does not melt and liquefy; Next, the temperature is raised to the fourth temperature: 232℃~250℃, so that the preformed solder pads are completely melted and liquefied without damaging the chip.

[0033] The beneficial effects of this application are: The heat dissipation base plate of this application features a radially arranged support bump structure on its body. The height of the support bumps gradually decreases from the outermost position to the center. This design allows the heat dissipation base plate to continuously provide venting channels as the pre-formed solder pads soften from the outside in, forming a DCM package structure. This reduces voids caused by trapped air during soldering, thereby lowering the void ratio of the DCM package structure and ensuring the module's heat dissipation efficiency and long-term reliability. The height of the outermost support bumps on the heat dissipation base plate helps determine the overall thickness of the solder after soldering. Simultaneously, the radial support bump structure provides stable support for the pre-formed solder pads and the chip module, effectively preventing tilting of the chip module after soldering, thus improving the performance consistency of the DCM module and reducing its thermal resistance. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In addition, in the following drawings, the components are not necessarily drawn to scale, and components with similar related characteristics or features may have the same or similar reference numerals.

[0035] Figure 1 This is a schematic diagram of the axial structure of a heat dissipation base plate provided in one embodiment of this application; Figure 2 This is a schematic diagram of the axial structure of a heat dissipation base plate provided in another embodiment of this application; Figure 3 This is a schematic diagram of the axial structure of the heat dissipation base plate and preformed solder pad provided in one embodiment of this application; Figure 4 This is a schematic diagram of the axial structure of the heat dissipation base plate, preformed solder pad, and chip module provided in one embodiment of this application; Figure 5 Schematic diagram of the position of the pre-formed solder pad on the heat sink during DCM package soldering. Figure 1 (correspond Figure 1 (Cross-section direction of A1-A2) Figure 6 Schematic diagram of the position of the pre-formed solder pad on the heat sink during DCM package soldering. Figure 2 (correspond Figure 1 (Cross-section direction of A1-A2) Figure 7 Schematic diagram of the position of the pre-formed solder pad on the heat sink during DCM package soldering. Figure 3 (correspond Figure 1 (Cross-section direction of A1-A2) Figure 8 This is a schematic diagram of the DCM packaging structure (corresponding to...) Figure 1 (Cross-section direction of A1-A2) Figure 9 A schematic diagram of the welding method for DCM packaging structure; Figure 10 This is a schematic diagram illustrating the effect of welding holes when the heat dissipation base plate does not have supporting protrusions. Figure 11 A schematic diagram showing the effect of welding holes when the heat dissipation base plate has 5 supporting protrusions; Figure 12A schematic diagram showing the effect of welding holes when the heat dissipation base plate has 9 supporting protrusions.

[0036] The reference numerals in the figure are as follows: 1. Heat dissipation base plate; 11. Welding plane; 12. Support bump; 121. Central support bump; 122. Outer support bump; 13. Groove; 2. Preformed solder pad; 21. Preformed solder pad located in the outer support bump area; 22. Preformed solder pad in the center position; 3. Chip module; 31. Ceramic substrate; 32. Chip; 4. Solder. Detailed Implementation

[0037] To make the technical problems, technical solutions and beneficial effects to be solved by this application clearer, the following describes this application in further detail with reference to the accompanying drawings and embodiments.

[0038] In the description of this application, it should be noted that the use of terms such as "first" and "second" to define objects (such as elements, components, regions, layers, doping types and / or parts) is merely for the purpose of distinguishing different objects and is not necessarily used to describe a specific order or sequence. Unless the context clearly indicates otherwise, it should be understood that such data can be used interchangeably where appropriate.

[0039] In the description of this application, it should be understood that the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms “compose” and / or “comprise” are used in this specification, the presence of the stated feature, integer, step, operation, element, and / or part is established, but the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups is not excluded. Meanwhile, when used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0040] In the description of this application, it should also be noted that when a component is referred to as "on another component," "connected to another component," or "in contact with another component," it can mean not only that a component is directly on, directly connected to, or directly in contact with another component, but also that an intermediate component can be inserted between the two components. Furthermore, "connection" includes not only fixed connections but also detachable connections or integral connections. Similarly, when an element is referred to as "electrically connected," "electrically contacted," "electrically coupled," or "electrically coupled to" another element, the two elements can be in direct electrical contact or point coupling, or they can be in electrical contact or point coupling through an intermediate component.

[0041] In the description of this application, it should also be noted that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0042] Furthermore, in the description of this application, spatial relation terms such as "below," "under," "below," "below," "below," "above," "on the upper surface of," "above," etc., can be used to describe the spatial positional relationship between one element or feature shown in the figures and other elements or features. It should be understood that spatial relation terms, in addition to the orientation shown in the figures, also include different orientations of elements or features in use and operation. For example, if an element or feature in the figures is flipped or inverted, an element or feature described as "below" or "below" other elements or features will be oriented "above" other elements or features. Furthermore, elements may also include other orientations (e.g., rotated by an angle or other orientations).

[0043] In the existing DCM half-bridge module packaging process, the solder interface is prone to gas entrapment during reflow soldering. The gas cannot be expelled in time, forming numerous voids and causing an excessive void ratio. This severely affects the module's heat dissipation efficiency and long-term reliability, and also leads to reliability issues such as chip tilting and stress concentration. The reasons for these problems are as follows: First, the flat heat dissipation base plate places extremely stringent requirements on welding process parameters and material properties. Due to the large welding area, it is difficult for the solder to spread evenly during the melting process, which can easily lead to inconsistent solder layer thickness after welding, resulting in localized areas that are too thin or too thick. This can then cause reliability issues such as chip tilting and stress concentration. At the same time, the large welding interface is prone to trapping gas during reflow soldering. The gas cannot be discharged in time, forming a large number of voids, resulting in an excessive void ratio, which seriously affects the module's heat dissipation efficiency and long-term reliability.

[0044] Secondly, the flat surface structure lacks an effective height control mechanism, making it difficult to accurately guarantee the welding height. During the welding process, the solder melts and is affected by gravity, surface tension, and process fluctuations, making it difficult to maintain a stable distance between the chip and the heat sink base. This can easily lead to assembly defects such as tilting and misalignment, resulting in increased module thermal resistance and poor performance consistency.

[0045] Therefore, embodiments of this application provide a heat dissipation base plate, a DCM packaging structure, and a welding method thereof, wherein... Figure 1 This is a schematic diagram of the axial structure of a heat dissipation base plate provided in one embodiment of this application; Figure 2 This is a schematic diagram of the axial structure of a heat dissipation base plate provided in another embodiment of this application; Figure 3 This is a schematic diagram of the axial structure of the heat dissipation base plate and preformed solder pad provided in one embodiment of this application; Figure 4 This is a schematic diagram of the axial structure of the heat dissipation base plate, preformed solder pad, and chip module provided in one embodiment of this application; Figure 5 Schematic diagram of the position of the pre-formed solder pad on the heat sink during DCM package soldering. Figure 1 (correspond Figure 1 (Cross-section direction of A1-A2) Figure 6 Schematic diagram of the position of the pre-formed solder pad on the heat sink during DCM package soldering. Figure 2 (correspond Figure 1 (Cross-section direction of A1-A2) Figure 7 Schematic diagram of the position of the pre-formed solder pad on the heat sink during DCM package soldering. Figure 3 (correspond Figure 1 (Cross-section direction of A1-A2) Figure 8 A schematic diagram of the soldering process for DCM package structure (corresponding to) Figure 1 (Cross-section direction of A1-A2) Figure 9 A schematic diagram of the welding method for DCM packaging structure; Figure 10 This is a schematic diagram illustrating the effect of welding holes when the heat dissipation base plate does not have supporting protrusions. Figure 11 A schematic diagram showing the effect of welding holes when the heat dissipation base plate has 5 supporting protrusions; Figure 12 A schematic diagram showing the effect of welding holes when the heat dissipation base plate has 9 supporting protrusions.

[0046] This application first provides a heat dissipation base plate, as shown in reference 1 or... Figure 2 The heat dissipation base plate includes: The heat dissipation base plate body has a first surface having a welding plane 11 for welding of solder pads; The support protrusions 12 located on the welding plane 11 include a plurality of support protrusions 12, which are arranged radially from the center position of the welding plane 11 to the periphery position of the welding plane 11, and the height of the support protrusions 12 gradually increases from the center position to the periphery position.

[0047] The heat sink 1 of this application has radially arranged support bumps on its body. This allows the heat sink 1 to form a DCM package structure by soldering the pre-formed solder pad 2 to the chip module 3. As the pre-formed solder pad 2 gradually softens from the outside in, the radially arranged support bump array continuously provides exhaust channels during this softening process. Please refer to [reference needed]. Figures 5-7 After the preformed solder pad 2 softens, the support bump array can support the preformed solder pad 2, and the area of ​​the preformed solder pad 2 that forms support does not collapse directly onto the surface of the welding plane 11, thereby forming an exhaust channel, reducing the welding void phenomenon caused by trapped gas during welding, reducing the void rate of the DCM package structure, and ensuring the heat dissipation efficiency and long-term reliability of the module (in this application, "trapped gas" refers to the phenomenon in which various gases generated during the welding process fail to escape from the molten solder in time and are trapped and retained inside the solder joint to form bubbles. These trapped gases form welding voids after the solder cools and solidifies).

[0048] In accordance with the gradually softening preformed weld sheet 2 from the outside in, the height of the support protrusion 12 is controlled to gradually decrease from the outer periphery to the center of the welding plane 11. This guides the softening and sinking of the preformed weld sheet 2, allowing the preformed weld sheet 2 at the center to easily soften and conform to the welding plane 11, while also ensuring that the preformed weld sheet 2 at the center can provide an exhaust channel. Furthermore, since both the gas at the center and the gas at the outer periphery of the welding plane 11 need to be exhausted through the exhaust channel formed by the outer support protrusion, and the closer to the outer periphery of the welding plane 11, the greater the volume of gas required to be exhausted through the corresponding exhaust channel, the outer support protrusion is higher than the one at the center, ensuring smooth exhaust.

[0049] The height of the support bumps 12 at the outermost position on the heat sink base plate body can help determine the overall thickness of the sheet solder 4 after soldering. Simultaneously, the radial array of support bumps provides stable support for the preformed solder pad 2 and the chip module 3, effectively preventing the chip module 3 from tilting after soldering, thereby improving the performance consistency of the DCM module and reducing its thermal resistance. Furthermore, multiple support bumps 12 can increase the contact area between the preformed solder pad 2 and the heat sink base plate 1 when molten, further reducing air trapping during soldering.

[0050] Please continue to refer to this. Figure 1 In one embodiment, the support protrusion 12 includes a central support protrusion 121, which is located at the center of the welding plane 11.

[0051] In one embodiment, the support protrusion 12 further includes a plurality of peripheral support protrusions distributed around the central support protrusion, each peripheral support protrusion including at least one outer support protrusion 122 radially distributed from the central support protrusion 121 to the peripheral position; When multiple sets of peripheral support protrusions are included, the included angles between the distribution rays of adjacent sets of peripheral support protrusions may be the same or different.

[0052] In one embodiment, the distance between adjacent peripheral support protrusions in each group of peripheral support protrusions is equal.

[0053] The included angle between the distribution rays of adjacent groups of peripheral support protrusions is adjusted according to the shape and size of the actual welding plane. The equal included angle between the distribution rays of adjacent groups of peripheral support protrusions forms evenly spaced exhaust channels on the welding plane surface, facilitating a reduction in void ratio. The equal distance between adjacent peripheral support protrusions in each group also ensures the uniformity and smoothness of exhaust flow through the formed exhaust channels.

[0054] Multiple support protrusions 12 are arranged radially to form a support protrusion array. When the support protrusion array includes a central support protrusion 121 and multiple sets of peripheral support protrusions, the multiple sets of peripheral support protrusions form multiple support ridges with the central support protrusion 121 as the center. The multiple support ridges, together with the central support protrusion 121, form multiple exhaust channels to assist in exhaust.

[0055] In one embodiment, the support bump array includes at least one central support bump 121 and at least three sets of peripheral support bumps, each set of peripheral support bumps having at least one outer support bump 122. At least one outer support bump 122 forms a support ridge with the central support bump 121.

[0056] In another embodiment, the support bump array includes at least three sets of peripheral support bumps, each set of peripheral support bumps having at least two outer support bumps 122, in which case the central support bump 121 may not be included. The at least two outer support bumps 122 and the central support bump 121 form a support ridge, or the at least two outer support bumps 122 form a support ridge.

[0057] In one specific embodiment, the support bump array includes a central support bump 121 and at least four sets of peripheral support bumps, each set of peripheral support bumps having at least an outer support bump 122.

[0058] Compared to a support protrusion structure in which one outer support protrusion 122 and the central support protrusion 121 form a support ridge, a support protrusion structure in which two outer support protrusions 122 and the central support protrusion 121 form a support ridge has a more stable support function, thus enabling a more stable exhaust channel.

[0059] Compared to three sets of peripheral support bumps, the design of four sets of peripheral support bumps can provide support for the preformed weldment 2 from more directions, making it easier to maintain welding stability. Depending on the size and shape of the actual welding plane 11, the multiple sets of peripheral support bumps preferably include 4 to 8 sets, and the number of supporting ridges formed is preferably 4 to 8. Because of the supporting function of the bumps, having too many sets of peripheral support bumps is not conducive to reducing voids during welding.

[0060] In one embodiment, the support bumps 12 are integrally formed or welded to the heat dissipation base body.

[0061] In one embodiment, among each group of peripheral support bumps, from the peripheral position to the central position, the heights of the plurality of outer support bumps 122 gradually decrease; The heights of the outermost outer support bumps 122 in each group of peripheral support bumps are equal.

[0062] The equal heights of the outermost outer support bumps 122 can ensure that the pre - formed solder pads and chip modules disposed on the support bumps are not tilted, the support bumps provide stable support, and ensure the overall thickness of the sheet solder 4 is uniform after welding.

[0063] In one embodiment, among multiple groups of peripheral support bumps, the number of support bumps in each group of peripheral support bumps is the same.

[0064] Please continue to refer to Figure 1 , in one embodiment, the welding plane 11 is a rectangular welding plane 11, and the plurality of support bumps 12 are radially arranged from the central position of the rectangular welding plane 11 to the peripheral position of the welding plane 11. This radial arrangement includes an "X" - shaped arrangement, a "rice" - shaped arrangement, or a "cross" - shaped arrangement.

[0065] In one embodiment, when in an "X" - shaped arrangement, the central support bump 121 is located at the intersection of the "X" - shape. The peripheral support bumps include four groups. The four groups of peripheral support bumps surround the central support bump 121. Each group of peripheral support bumps includes at least two outer support bumps 122. The outermost outer support bumps 122 of each group of peripheral support bumps are respectively arranged corresponding to the four azimuth angles of the rectangular welding plane 11, so as to provide the most stable support.

[0066] The support bumps 12 in an "X" - shaped radial arrangement can promote the discharge of gas during the reflow welding process along the four azimuth directions. And the outermost outer support bumps 122 of the four groups of peripheral support bumps respectively correspond to the four azimuth angles of the rectangular welding plane 11, forming a relatively long exhaust channel. When the welding plane 11 is square, the included angle between the distribution rays of adjacent two groups of peripheral support bumps is 90°.

[0067] The central support bump 121 primarily provides support for the center position corresponding to the preformed solder pad 2, and the central support bump 121 has the lowest height. During soldering, the array of support bumps, whose height gradually decreases from the outer periphery of the soldering plane 11 to the center position, can guide the softening and sinking of the preformed solder pad 2. The closer to the central support bump 121, the lower the height difference between the softened preformed solder pad 2 area corresponding to the support bump and the soldering plane 11. The preformed solder pad 2 (especially the area of ​​the preformed solder pad 2 that does not correspond to the support bump) can fit more closely to the soldering plane 11 of the heat sink base plate body, thereby further reducing air trapping and improving the soldering quality of the DCM package structure.

[0068] In one embodiment, the height of the support protrusion 12 is 0.1mm to 0.2mm; The maximum outer diameter of the support protrusion 12 is 0.6 mm.

[0069] In one embodiment, the height of the central support protrusion 121 is 0.13mm~0.14mm; Each set of peripheral support protrusions includes at least two outer support protrusions 122, wherein the height of the outer support protrusion 122 closest to the central support protrusion 121 is 0.15mm~0.16mm, and the height of the other outer support protrusion 122 furthest from the central support protrusion 121 is 0.17mm~0.19mm.

[0070] When the heat dissipation base plate is soldered to the chip module 3 to form a DCM package structure, the height of the outer support bump 122 furthest from the central support bump 121 corresponds to the minimum thickness of the solder layer, and the height value of 0.17mm~0.19mm is relatively moderate, which can ensure the minimum thickness of the solder layer and facilitate stable soldering.

[0071] Please refer to Figure 1 In one specific embodiment, the radial support bump array is arranged in an "X" shape. The support bump array includes a central support bump 121 and four sets of peripheral support bumps, each set of peripheral support bumps having two outer support bumps 122. The central support bump 121 has a height of 0.135 mm and an outer diameter of 0.5 mm. The height of the outer support protrusion 122 closest to the central support protrusion 121 in each group of peripheral support protrusions is 0.155mm, and the outer diameter is 0.5mm. The height of the outer support protrusion 122, which is farthest from the central support protrusion 121 in each group of peripheral support protrusions, is 0.18 mm and the outer diameter is 0.5 mm.

[0072] Please refer to Figure 2, in another embodiment, the support bump array includes a central support bump 121 and four groups of peripheral support bumps, and each group of peripheral support bumps has three outer support bumps 122.

[0073] In one embodiment, when arranged in a "rice" shape or a "cross" shape, the position where the central support bump 121 is located is the intersection position of the "rice" shape or the "cross" shape.

[0074] In one embodiment, the welding plane 11 of the heat dissipation bottom plate body further has a groove 13, and the groove 13 is arranged on the outer peripheral side of the support bump 12. The groove 13 can prevent the liquid solder 4 formed by the melting of the solder sheet during welding from overflowing.

[0075] In one embodiment, the groove 13 includes an inner ring groove and an outer ring groove arranged at intervals. The inner ring groove is arranged closer to the support bump 12, and the outer ring groove is arranged farther from the support bump 12. To form a double protection groove for preventing the liquid solder 4 from overflowing during welding.

[0076] In one embodiment, the inner ring groove 13 is a continuous groove, and the outer ring groove 13 is an intermittent groove.

[0077] During actual use, according to the size and shape of the actual welding plane 11, as well as the thickness of the corresponding preformed solder sheet 2, determine the number, width and depth of the required groove 13.

[0078] In one embodiment, the heat dissipation bottom plate 1 includes a copper plate, and the support bump 12 includes a copper support bump.

[0079] In another embodiment, the heat dissipation bottom plate 1 further includes a copper alloy plate or an AlSiC plate, and the support bump 12 includes a copper alloy support bump or an AlSiC support bump.

[0080] Please refer to Figure 8 , this application also provides a DCM package structure, including: Chip module 3; Heat dissipation bottom plate 1 and solder 4, the heat dissipation bottom plate 1 is one of the above heat dissipation bottom plates, one side of the welding plane 11 of the heat dissipation bottom plate 1 is connected to the chip module 3 through the solder 4, and the solder 4 covers the support bump 12 of the heat dissipation bottom plate 1.

[0081] In one embodiment, the solder 4 is also arranged between the top surface of the support bump 12 of the heat dissipation bottom plate 1 and the chip module 3.

[0082] In one embodiment, the thickness of the solder 4 is greater than the height of the support bump 12.

[0083] In one embodiment, the chip module 3 is a half-bridge chip module.

[0084] In one embodiment, the chip module 3 includes a ceramic substrate 31 and a chip 32 disposed on the ceramic substrate 31. The ceramic substrate 31 of the chip module 3 is connected to the heat sink 1 via the solder 4. In actual use, the chip 32 is an unpackaged chip or a packaged chip.

[0085] In one specific embodiment, the ceramic substrate 31 has a three-layer composite structure of "copper-ceramic-copper". The upper copper layer forms circuit patterns through photolithography etching, the middle ceramic layer is a highly thermally conductive insulating material (such as Al2O3 alumina, AlN aluminum nitride, or Si3N4 silicon nitride), and the lower copper layer serves as a heat dissipation surface in contact with the solder. The substrate is rectangular or square, with a thickness of approximately 0.3mm to 1mm and a surface metallization layer thickness of 0.1mm to 0.3mm. The chip 32 is a bare die with a passivation layer for protection. A gold / silver layer on the back provides a soldering surface, and the front side has metal pads for the emitter / source and gate. After the back side of the chip 32 is metallized, it is connected to the upper copper circuit of the ceramic substrate 31 through vacuum reflow soldering or sintering silver. The front electrodes are electrically interconnected through aluminum wire bonding or copper clips to form a half-bridge topology.

[0086] The support bump structure of this heat sink base plate forms an active exhaust channel network during vacuum reflow soldering, which can reduce the solder layer void ratio to below 5%. At the same time, the support bumps ensure that the chip module and the heat sink base plate maintain a uniform solder thickness, ensuring low thermal resistance and high mechanical reliability of large-area solder joints, effectively suppressing thermal cycle fatigue, and increasing the module power cycle life by 2-3 times. It is particularly suitable for the heat dissipation requirements of high power density DCM modules.

[0087] Please refer to Figure 9 This application also provides a welding method for a DCM packaging structure, comprising the following steps: Step S100: Provide a heat dissipation base plate 1, wherein the heat dissipation base plate 1 is one of the heat dissipation base plates described above; Step S200: Provide a preformed solder sheet 2, place the preformed solder sheet 2 on one side of the welding plane 11 of the heat dissipation base plate 1, and make the preformed solder sheet 2 overlap the outermost support protrusion 12 of the heat dissipation base plate 1. Step S300: Provide a ceramic substrate 31, place the ceramic substrate 31 on the side of the preformed solder pad 2 away from the heat dissipation base plate 1, and weld the heat dissipation base plate 1 and the ceramic substrate 31. During the process of the preformed solder pad 2 softening and melting to achieve welding, the radially arranged array of support protrusions on the heat dissipation base plate 1 continuously provides exhaust channels.

[0088] The steps described above are described in detail below with reference to the accompanying drawings.

[0089] First, refer to Figure 9 In conjunction with references Figure 1 Step S100 is performed to provide a heat dissipation base plate 1, wherein the heat dissipation base plate 1 is one of the heat dissipation base plates described above.

[0090] The heat dissipation base plate includes a heat dissipation base plate body and multiple support protrusions 12. The heat dissipation base plate body has a welding plane 11 for soldering. Multiple support protrusions 12 are located on the surface of the welding plane 11. The multiple support protrusions 12 are arranged radially from the center to the periphery of the welding plane 11, and the height of the support protrusions 12 gradually increases from the center to the periphery. The multiple support protrusions 12 include a central support protrusion 121 and four sets of peripheral support protrusions. Each set of peripheral support protrusions includes at least two outer support protrusions 122. The four sets of peripheral support protrusions are arranged in an "X" shape. The central support protrusion 121 is located at the intersection of the "X". The outermost outer support protrusion 122 of each set of peripheral support protrusions corresponds to the four azimuth angles of the rectangular welding plane 11.

[0091] The heat dissipation base plate 1 includes a copper plate, and the support protrusion 12 includes copper support protrusions.

[0092] In another embodiment, the heat dissipation base plate 1 further includes a copper alloy plate or an AlSiC plate, and the support bumps 12 include copper alloy support bumps or AlSiC support bumps.

[0093] Next, refer to Figure 9 In conjunction with references Figure 1 , Figure 3 and Figure 5 In step S200, a pre-formed solder sheet 2 is provided, which is placed on one side of the welding plane 11 of the heat dissipation base plate 1 and overlapped on the outermost support protrusion 12 of the heat dissipation base plate 1.

[0094] The shape and size of the preformed welding sheet 2 are adapted to the welding plane 11 of the heat dissipation base plate 1.

[0095] The preformed solder sheet 2 includes tin solder sheet, copper-tin alloy solder sheet, or tin-silver-copper alloy solder sheet.

[0096] By adding a radially arranged array of support bumps to the welding plane 11 of the heat sink base plate 1, the pre-formed solder pad 2 can be a tin solder pad, rather than necessarily a copper-tin alloy or tin-silver-copper alloy solder pad, while still maintaining a low solder void rate. This achieves the goal of reducing the complexity of the reflow process, avoiding the use of higher-grade materials, while ensuring product quality and maintaining low process costs. It is suitable for widespread use.

[0097] In actual use, the melting point of the preformed welding sheet 2 is lower than that of the heat dissipation base plate 1 and its support protrusion 12, so as to ensure that the support protrusion 12 has a supporting function.

[0098] The height of the support bump 12 is equal to or slightly less than the thickness of the solder 4 in the DCM package structure. During actual soldering, the final thickness of the solder 4 is determined by considering the thickness of the pre-formed solder pad 2 before melting and the pressure applied to the ceramic substrate 31. That is, the height of the support bump 12 is less than or equal to the thickness of the solder 4 after soldering. The height of the support bump 12 can be designed and determined based on the thickness of the solder 4 after soldering to achieve uniform solder 4 thickness in subsequent soldering processes.

[0099] Next, refer to Figure 9 In conjunction with references Figure 1 , Figure 4 and Figure 8 In step S300, a ceramic substrate 31 is provided, the ceramic substrate 31 is placed on the side of the preformed solder sheet 2 away from the heat dissipation base plate 1, and the heat dissipation base plate 1 and the ceramic substrate 31 are welded together. During the process of the preformed solder sheet 2 softening and melting to achieve welding, the radially arranged support protrusion array on the heat dissipation base plate 1 continuously provides exhaust channels.

[0100] During the welding process, please refer to the reference. Figures 5-7As the welding temperature increases, under the influence of the temperature distribution gradient and heat transfer characteristics, the preformed weld sheet 2 gradually softens from the outside to the center. Furthermore, from the outer periphery of the welding plane 11 to the center, the height of the support protrusion 12 gradually decreases. When only the outer side of the preformed weld sheet 2 softens, the preformed weld sheet 2 located in the outer support protrusion area softens first and rests on the higher outer support protrusion 122. The preformed weld sheet 2 located in the outer non-support protrusion 12 area softens first and adheres to the outer periphery of the welding plane 11. The preformed weld sheet 2 at the center, which has not softened, remains soft. The solder pad 2 is placed on the lower middle support bump 12 (outer support bump 122 or central support bump 121). When the center of the preformed solder pad 2 softens, the softened center position of the preformed solder pad 2 is placed on the central support bump 12 (outer support bump 122 or central support bump 121). The central radial support bump array continuously provides venting channels during the softening process until the preformed solder pad 2 is completely melted. The preformed solder pad 2 is used to form a solder layer between the heat sink and the chip module 3, and the solder layer 4 wraps around the support bump 12.

[0101] When the preformed welding piece 2 is attached to the welding plane 11, the exhaust channel allows the gas between the welding plane 11 and the preformed welding piece 2 to be discharged from the center position to the outer position of the welding plane 11.

[0102] A chip 32 is also disposed on the surface of the ceramic substrate 31, on the side of the ceramic substrate 31 away from the heat sink 1. The chip 32 is a half-bridge chip, and the chip 32 is either an unpackaged chip or a packaged chip. There are 2 to 3 chips 32.

[0103] The heat sink base plate 1 and the ceramic substrate 31 are soldered using a reflow soldering process. The soldering temperature control during soldering includes: Control the temperature to rise to the first temperature: not exceeding 150℃, and preheat the heat dissipation base plate 1 and the pre-formed solder sheet 2; Next, the temperature is controlled to rise to the second temperature: 150℃~180℃, so that the temperature of the heat dissipation base plate 1 and the preformed solder pad 2 is uniform. Next, the temperature is raised to the third temperature: 220℃~232℃, so that the preformed welding sheet 2 softens but does not melt and liquefy; Next, the temperature is raised to a fourth temperature range: 232℃~250℃, which completely melts and liquefies the preformed solder pad 2 without damaging the chip 32. This temperature range allows the solder to fully melt, wet, and spread, forming a good metallurgical bond, without damaging the PN junction and internal structure of the chip 32.

[0104] This step-by-step, slow heating facilitates flux evaporation and gas expulsion, minimizes residual welding stress, and extends the thermal cycle life of the power module.

[0105] Next, a molding compound is formed on the outer side of portions of the heat dissipation base plate 1 and the ceramic substrate 31.

[0106] Please refer to Figures 10-12 ,in Figure 10 This is a schematic diagram illustrating the effect of welding holes when the heat dissipation base plate does not have supporting protrusions. Figure 11 This diagram illustrates the welded void effect when the heat dissipation base plate has 5 supporting protrusions. Figure 12 This diagram illustrates the welded voids when the heat dissipation base plate has nine supporting protrusions; as can be seen from the diagram... Figure 10 When the heat dissipation base plate does not have supporting bumps, there are more voids in the corresponding encapsulation structure after soldering. Figure 11 When there are 5 support bumps, the voids in the corresponding post-weld encapsulation structure are slightly reduced. Figure 12 With nine support bumps, the voids in the post-soldering package structure are significantly reduced, almost to the point of being negligible. This demonstrates that an X-shaped arrangement of support bumps on the heat sink base plate reduces voids in the post-soldering package structure, and the more support bumps there are, the better the void-avoidance effect. In other words, the structural design provided in this application, which uses support bumps on the heat sink base plate to form a reflow channel, along with corresponding process improvements, reduces the complexity of the reflow process and avoids the use of higher-grade materials. This ensures product quality while maintaining low process costs, facilitating cost savings in production.

[0107] It should be noted that, where there is no conflict, the features in the different embodiments of this application described above can be combined with each other. Furthermore, in each of the above embodiments, the focus is on describing the differences from other embodiments; other specific descriptions of the same / similar parts between the embodiments can be referred to (or referenced) interchangeably. In addition, descriptions of well-known components and technologies have been omitted in the above description to avoid unnecessarily obscuring the concepts of this application.

[0108] Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. Any person skilled in the art can make possible changes and modifications to the technical solutions of this application by utilizing the methods and techniques disclosed above without departing from the spirit and scope of this application. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall fall within the protection scope of the technical solutions of this application.

Claims

1. A heat dissipation base plate, characterized in that, Comprising: A heat dissipation base plate body, wherein a first surface of the heat dissipation base plate body has a welding plane for solder pad welding; Support bumps located on the welding plane, the support bumps including a plurality of them, and the plurality of support bumps are radially arranged from a central position of the welding plane to a peripheral position of the welding plane, and from the central position to the peripheral position, the height of the support bumps gradually increases.

2. A heat dissipation base plate as described in claim 1, characterized in that, The support bumps include a central support bump, and the central support bump is located at the central position of the welding plane.

3. A heat dissipation base plate as described in claim 2, characterized in that, The support bumps further include multiple groups of peripheral support bumps distributed around the central support bump, and each group of peripheral support bumps includes at least one outer support bump radially distributed from the central support bump to the peripheral position; When including multiple groups of peripheral support bumps, the included angles between the distribution rays of adjacent groups of the peripheral support bumps are the same or different.

4. A heat dissipation base plate as described in claim 3, characterized in that, The distances between adjacent peripheral support bumps in each group of peripheral support bumps are equal.

5. A heat dissipation base plate as described in claim 3, characterized in that, In each group of peripheral support bumps, from the peripheral position to the central position, the heights of the multiple outer support bumps gradually decrease; The heights of the outermost outer support bumps in each group of peripheral support bumps are equal.

6. A heat dissipation base plate as described in claim 3, characterized in that, Among the multiple groups of peripheral support bumps, the number of support bumps in each group of peripheral support bumps is the same.

7. A heat dissipation base plate as described in claim 3, characterized in that, The welding plane is a rectangular welding plane, and the multiple support bumps are radially arranged from the central position of the rectangular welding plane to the peripheral position of the welding plane, and this radial arrangement includes an "X" - shaped arrangement, a "cross" - shaped arrangement or a "plus" - shaped arrangement.

8. A heat dissipation base plate as described in claim 7, characterized in that, When in an "X" - shaped arrangement, the central support bump is located at the intersection position of the "X" - shaped, the peripheral support bumps include four groups, the four groups of peripheral support bumps surround the central support bump, each group of peripheral support bumps includes at least two outer support bumps, and the outermost outer support bumps of each group of peripheral support bumps are respectively arranged corresponding to the four azimuth angles of the rectangular welding plane.

9. A heat dissipation base plate as described in claim 7, characterized in that, The height of the central support bump is 0.13 mm to 0.14 mm; Each group of peripheral support bumps includes at least two outer support bumps, wherein the height of one outer support bump closest to the central support bump is 0.15 mm to 0.16 mm, and the height of another outer support bump farthest from the central support bump is 0.17 mm to 0.19 mm.

10. A heat dissipation base plate as described in claim 7, characterized in that, When in a "cross" - shaped arrangement or a "plus" - shaped arrangement, the position where the central support bump is located is the intersection position of the "cross" - shaped or the "plus" - shaped.

11. A heat dissipation base plate as described in claim 1, characterized in that, The welding plane of the heat dissipation base plate body further has grooves, and the grooves are arranged on the outer peripheral side of the support bumps.

12. A heat dissipation base plate as described in claim 11, characterized in that, The grooves include an inner - ring groove and an outer - ring groove arranged at intervals, the inner - ring groove is arranged on the side close to the support bumps, and the outer - ring groove is arranged on the side far from the support bumps.

13. A heat dissipation base plate as described in claim 12, characterized in that, The inner - ring groove is a continuous groove, and the outer - ring groove is a discontinuous groove.

14. A heat dissipation base plate as described in claim 1, characterized in that, The height of the support bumps is 0.1 mm to 0.2 mm; The maximum outer diameter of the support bumps is 0.6 mm.

15. A DCM packaging structure, characterized in that, Comprising: A chip module; A heat dissipation base plate and solder, wherein the heat dissipation base plate is a heat dissipation base plate according to any one of claims 1 to 14, one side of the soldering plane of the heat dissipation base plate is connected to the chip module through the solder, and the solder covers the support bumps of the heat dissipation base plate.

16. A DCM packaging structure as described in claim 15, characterized in that, The solder is also provided between the top surface of the support protrusion of the heat sink base plate and the chip module.

17. A DCM packaging structure as described in claim 15, characterized in that, The thickness of the solder is greater than the height of the support bump.

18. A DCM packaging structure as described in claim 15, characterized in that, The chip module is a half-bridge chip module.

19. A DCM packaging structure as described in claim 15, characterized in that, The chip module includes a ceramic substrate and a chip disposed on the ceramic substrate. The ceramic substrate of the chip module is connected to a heat sink through the solder.

20. A welding method for a DCM packaging structure, characterized in that, Includes the following steps: A heat dissipation base plate is provided, wherein the heat dissipation base plate is a heat dissipation base plate as described in any one of claims 1 to 14; A preformed solder pad is provided, which is placed on one side of the welding plane of the heat dissipation base plate and overlapped on the outermost support protrusion of the heat dissipation base plate. A ceramic substrate is provided, which is disposed on the side of the preformed solder pad away from the heat dissipation base plate. The heat dissipation base plate and the ceramic substrate are welded together. During the process of the preformed solder pad softening and melting to achieve welding, the radially arranged support protrusions on the heat dissipation base plate continuously provide exhaust channels.

21. A welding method for a DCM packaging structure as described in claim 20, characterized in that, It also includes forming a plastic encapsulation on the outer side of the heat dissipation base plate and the ceramic substrate, respectively.

22. A welding method for a DCM packaging structure as described in claim 20, characterized in that, The shape and size of the preformed welding sheet are adapted to the welding plane of the heat dissipation base plate.

23. A welding method for a DCM packaging structure as described in claim 20, characterized in that, A chip is also disposed on the surface of the ceramic substrate, and the chip is disposed on the surface of the ceramic substrate away from the heat dissipation base plate.

24. A welding method for a DCM packaging structure as described in claim 20, characterized in that, The preformed solder sheet includes tin solder sheet, copper-tin alloy solder sheet, or tin-silver-copper alloy solder sheet.

25. A welding method for a DCM packaging structure as described in claim 20, characterized in that, The heat dissipation base plate includes a copper plate, and the support protrusions include copper support protrusions.

26. A welding method for a DCM packaging structure as described in claim 20, characterized in that, The heat sink base plate and the ceramic substrate are welded using a reflow soldering process.

27. A welding method for a DCM packaging structure as described in claim 26, characterized in that, The welding temperature control for welding the heat dissipation base plate and the ceramic substrate includes: Control the temperature to rise to the first temperature: not exceeding 150℃, and preheat the heat dissipation base plate and preformed solder pads; Next, the temperature is raised to a second temperature: 150℃~180℃, to make the temperature of the heat dissipation base plate and the preformed solder pad uniform; Next, the temperature is raised to the third temperature: 220℃~232℃, so that the preformed solder sheet softens but does not melt and liquefy; Next, the temperature is raised to the fourth temperature: 232℃~250℃, so that the preformed solder pads are completely melted and liquefied without damaging the chip.

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