Power module

Abstract

Some embodiments of the present application provide a power module, comprising: a substrate; a first solder layer disposed on the substrate; a spacer layer disposed on the first solder layer; and a second solder layer disposed on the spacer layer, wherein the spacer layer is provided with a groove outside a lateral range of the second solder layer, and in a top view, the groove surrounds the second solder layer. The present application prevents the solder of the first solder layer and the second solder layer from forming a bridging failure mode by forming a groove on the spacer layer.

Description

Technical Field

[0001] The embodiments of this application relate to the semiconductor field, and more specifically, to power modules. Background Technology

[0002] Currently, the development trend of power modules mainly focuses on high efficiency, integration, and miniaturization. With increasing energy demands and environmental requirements, the efficiency of power modules is gradually improving. At the same time, integrated and miniaturized designs enable power modules to be used in confined spaces, meeting the needs of devices such as electric vehicles and drones. Especially for products like electric vehicles where malfunctions are unacceptable, the reliability and long lifespan of power modules have become crucial. Designs place greater emphasis on durability and stability to meet the safety requirements of electric vehicles, and the welding within the module is particularly important for reliability.

[0003] See Figures 1A to 1C ,in, Figure 1A A cross-sectional view of the power module 10 is shown. Figure 1B It shows Figure 1A The scan diagram of the power module 10 shown is shown, and Figure 1C A perspective view of the power module 10 is shown. (As shown) Figures 1A to 1C As shown, the current double-sided cooling packaging structure of the power module 10 consists of an upper substrate 11A, a spacer layer 14, a die 16, and a lower substrate 11B from top to bottom. The components are connected by solder layers 12, 13, and 15. During the soldering process, the power module 10 is placed in a reflow oven for soldering. At high temperatures, the solder in solder layers 12, 13, and 15 is in a fluid state. In the highly integrated power module 10, solder overflow may occur between the upper and lower layers (solder layers 12 and 13) of the spacer layer 14, which is called "solder overflow". This can cause bridging between the components in the upper and lower layers (solder layers 12 and 13). This phenomenon can affect the lifespan and reliability of the power module 10.

[0004] Currently, the only solutions to the problem of solder overflow are to improve the reflow profile and adjust the height of the fixture to reduce the overflow and prevent it from becoming a bridging Q. However, it is still impossible to completely avoid the problem of bridging Q, that is, it is impossible to eliminate the problem of solder overflow between the upper and lower layers (solder layers 12 and 13) of the spacer layer 14. Utility Model Content

[0005] This application prevents the solder from bridging between the upper and lower layers (first solder layer and second solder layer) of the spacer layer by forming trenches on the spacer layer.

[0006] Some embodiments of this application provide a power module, including: a substrate; a first solder layer disposed on the substrate; a spacer layer disposed on the first solder layer; and a second solder layer disposed on the spacer layer, wherein the spacer layer has a groove around the lateral extent of the second solder layer, and in a top view, the groove surrounds the second solder layer.

[0007] In some embodiments, the second solder layer extends into the trench.

[0008] In some embodiments, the second solder layer is disposed within the area enclosed by the outermost edge of the trench.

[0009] In some embodiments, the height of the outermost edge of the trench is greater than the height of the second solder layer closest to the outermost edge.

[0010] In some embodiments, in a top view, the trench extends continuously around the second solder layer and forms a closed loop.

[0011] In some embodiments, in a top view, the trench extends discontinuously around the second solder layer.

[0012] In some embodiments, the second solder layer is completely spaced apart from the first solder layer by the spacer layer.

[0013] In some embodiments, the trench is formed having a plurality of discrete segments.

[0014] In some embodiments, the power module further includes: a third solder layer disposed between the substrate and the first solder layer; and a die disposed between the first solder layer and the third solder layer.

[0015] In some embodiments, both the die and the third solder layer extend beyond the lateral extent of the first solder layer.

[0016] In some embodiments, the trench is laterally spaced from the second solder layer by a non-zero distance.

[0017] In some embodiments, the trench is further disposed outside the lateral extent of the first solder layer and suspended above the first solder layer.

[0018] In some embodiments, the trench is laterally spaced from the first solder layer by a non-zero distance.

[0019] In some embodiments, the power module further includes: a third solder layer disposed above the second solder layer; and a die disposed between the second solder layer and the third solder layer.

[0020] In some embodiments, the trench is surrounded by the sidewalls of the spacer layer.

[0021] In some embodiments, both the die and the third solder layer extend beyond the lateral extent of the spacer layer.

[0022] In some embodiments, the outermost edge of the trench is spaced apart from the outermost edge of the second solder layer.

[0023] Other embodiments of this application provide a power module including: a first solder layer; a second solder layer disposed above the first solder layer; and a spacer layer disposed between the first solder layer and the second solder layer, wherein the sidewall of the spacer layer has a groove around the lateral extent of the second solder layer, and wherein the groove faces the second solder layer and the second solder layer is disposed within the area enclosed by the outermost edge of the groove.

[0024] In some embodiments, in a top view, the trench extends continuously around the second solder layer and forms a closed loop.

[0025] In some embodiments, in a top view, the trench extends discontinuously around the second solder layer and is formed having a plurality of discrete segments.

[0026] The physical isolation method of this application enables the grooves in the spacer layer of the power module to effectively accommodate the solder overflowing from the second solder layer, preventing the solder overflowing from the second solder layer from contacting the solder overflowing from the first solder layer, thereby solving the problem of bridging between the upper and lower solder layers. Attached Figure Description

[0027] The various aspects of this utility model can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard industrial practice, the various components are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various components may be arbitrarily increased or decreased.

[0028] Figures 1A to 1C A power module of the prior art is shown.

[0029] Figures 2A to 2D , Figures 3A to 3C , Figures 4 to 5 , Figures 6A to 8B A power module according to some embodiments of this application is shown.

[0030] Figures 9 to 15 The fabrication process flow of a power module according to some embodiments of this application is shown. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art are within the scope of protection of this application. In addition, when using terms such as "approximately," "about," "substantial," or "basically" to describe numerical values ​​or numerical ranges, unless otherwise stated, the term is intended to cover values ​​within ±10% of the described value. For example, the term "about 5nm" covers a size range from 4.5nm to 5.5nm.

[0032] This application redesigns the structure of the spacer layer. In addition to making the size of the spacer layer larger than the original spacer layer, a groove-like structure (groove) is added to its upper layer (solder layer). By using physical isolation, this structure can effectively accommodate overflowing solder, preventing the overflowing solder from the upper layer (solder layer) from contacting the overflowing solder from the lower layer (solder layer), thereby solving the problem of bridging between the upper and lower solder layers leading to power module failure mode.

[0033] See Figures 2A to 2C , Figure 2A A power module 100 according to some embodiments of this application is shown. Figure 2B A top view of a portion of the power module 100 is shown, and Figure 2C A perspective view of a power module 100 according to some embodiments of this application is shown. Figures 2A to 2C As shown, some embodiments of this application provide a power module 100, which includes: a substrate 101; a first solder layer 102 disposed on the substrate 101; a spacer layer 104 disposed on the first solder layer 102; and a second solder layer 103 disposed on the spacer layer 104. Figure 2A As can be seen, the spacer layer 104 has a groove R around the lateral extent of the second solder layer 103, and from... Figure 2B As can be seen in the top view, the trench R surrounds the second solder layer 103. Figure 2BIn the top view shown, the trench R extends continuously around the second solder layer 103 and forms a closed loop. In some embodiments, the trench R is laterally spaced from the second solder layer 103 by a non-zero distance S1. In some embodiments, this non-zero distance S1 can be any suitable distance, such as in the range of several nm to several μm, which can be set according to actual conditions without any particular limitation. In some embodiments, the lateral distance between the trench R and the second solder layer 103 can also be zero, that is, the trench R is set immediately adjacent to the second solder layer 103. In some embodiments, the depth of the trench R can be any suitable depth, as long as the amount of solder (tin amount) overflowing from the second solder layer 103 does not exceed the amount that the trench R can accommodate. In some specific embodiments, the depth of the trench R can occupy 1 / 3 to 2 / 3 of the total thickness of the spacer layer 104, optionally, it can occupy 1 / 2 of the total thickness of the spacer layer 104, and the width of the trench R is also not limited, which can be determined according to actual conditions, such as in the range of several hundred nm to several hundred μm or larger or smaller dimensions.

[0034] Furthermore, from Figure 2A As can be seen, the trench R is further disposed outside the lateral range of the first solder layer 102 and suspended above the first solder layer 102. Similarly, the trench R is laterally spaced from the first solder layer 102 by a non-zero distance. In some embodiments, there may be no lateral spacing, which can be set according to the actual situation without any particular restrictions.

[0035] exist Figures 2A to 2C In the power module 100 shown, the trench R is surrounded by the sidewalls 104s of the spacer layer 104, that is, the trench R is exposed to the sidewalls 104s. Furthermore, the trench R has an outermost edge Ros defined by the sidewalls 104s of the spacer layer 104. Since the spacer layer 104 has a trench R for accommodating the second solder layer 103, the second solder layer 103 and the first solder layer 102 are completely separated by the spacer layer 104. Using this physical isolation, the trench R of the spacer layer 104 of the power module 100 can effectively accommodate the solder overflowing from the second solder layer 103, preventing the overflowing solder from contacting the overflowing solder from the first solder layer 102, thereby solving the problem of bridging between the upper and lower solder layers.

[0036] Further reference Figures 2A to 2CThe power module 100 further includes: a third solder layer 105 disposed between the substrate 101 and the first solder layer 102; and a die 106 disposed between the first solder layer 102 and the third solder layer 105. In some embodiments, both the die 106 and the third solder layer 105 extend beyond the lateral range of the first solder layer 102. In some embodiments, both the die 106 and the third solder layer 105 extend beyond the lateral range of the spacer layer 104. Furthermore, the power module 100 also includes another substrate 107 (upper substrate) disposed on the second solder layer 103. Therefore, the power module 100, from top to bottom, includes another substrate 107, a second solder layer 103, a spacer layer 104, a first solder layer 102, a die 106, and a third solder layer 105.

[0037] See Figure 2D In some embodiments, in a top view, the trench R extends discontinuously around the second solder layer 103 and is formed with multiple discrete segments. It should be noted that... Figure 2B and Figure 2D The examples shown are only some specific embodiments, and other trench R structures can be used according to actual conditions, as long as the trench R can accommodate the solder overflowing from the second solder layer 103.

[0038] In other embodiments, the die 106 and the third solder layer 105 are disposed above the second solder layer 103. For example... Figures 3A to 3C As shown, Figures 3A to 3C Another power module 200 according to some embodiments is shown, which power module 200 is related to Figures 2A to 2C The power module 100 shown is similar, except that the third solder layer 105 is disposed above the second solder layer 103, and the die 106 is disposed between the second solder layer 103 and the third solder layer 105. That is, both the third solder layer 105 and the die 106 are disposed between the second solder layer 103 and another substrate 107. In this embodiment, both the die 106 and the third solder layer 105 may extend beyond the lateral range of the spacer layer 104. In some other embodiments, the die 106 and the third solder layer 105 may not extend beyond the lateral range of the spacer layer 104, which can be configured according to actual conditions.

[0039] In the above embodiments, substrate 101 and another substrate 107 can be any suitable substrate, such as a silicon semiconductor substrate, or a substrate such as a glass substrate, ceramic substrate, etc. The first solder layer 102, the second solder layer 103, and the third solder layer 105 are made of solder such as tin. In some embodiments, the spacer layer 104 can be made of metal, including but not limited to copper.

[0040] The power module 100 / 200 provided in this application allows for more process windows in the corresponding products. Specifically, see [link to relevant documentation]. Figure 4 and Figure 5 , Figure 4 The stretching of the second solder layer 103 is shown. Figure 4 The solder (second solder layer 103) shown is stretched to maintain a certain level of cross-sectional area, that is, the surface area of ​​the second solder layer 103 in contact with the spacer layer 104. It can be seen that in... Figure 4 Under the stretching conditions shown, the insufficient contact area caused by excessive solder inflow in the groove R of the spacer layer 104 that accommodates solder can be improved, thereby maintaining a certain level of cross-sectional area. Figure 5 This illustrates the compression of the second solder layer 103 (solder), from Figure 5 As can be seen, under compression, the second solder layer 103 (solder) will not exceed the lateral range (width) of the spacer layer 104 and bridge with the underlying first solder layer 102.

[0041] Figures 6A to 8B Different embodiments are shown where the second solder layer 103 extends into the trench R. In some embodiments, the solder of the second solder layer 103 does not extend beyond the edge of the spacer layer 104 and may have microstructural features.

[0042] Figures 6A to 6B This illustrates a case where the second solder layer 103 occupies only a small portion of the trench R, where... Figure 6A A top view is shown, and Figure 6B The corresponding partial cross-sectional view is shown. For example... Figure 6A and Figure 6B As shown, the second solder layer 103 extends into the trench R and is disposed within the area enclosed by the outermost edge Ros of the trench R, and is stopped by the sidewall 104s of the spacer 104, that is, the second solder layer 103 does not extend beyond the edge of the spacer layer 104. Figure 6A and Figure 6B In the illustrated embodiment, the outermost edge Ros of the trench R is spaced apart from the outermost edge 103s of the second solder layer 103, meaning that the second solder layer 103 occupies only a small portion of the trench R. In this case, no solder overflow (solder in the second solder layer 103) will occur.

[0043] Figures 7A to 7B This illustrates a case where the second solder layer 103 occupies only a significant portion of the trench R, where... Figure 7A A top view is shown, and Figure 7B The corresponding partial cross-sectional view is shown. For example... Figure 7A and Figure 7B As shown, the second solder layer 103 extends from all four sides into the trench R, and from... Figure 7BAs can be seen, the height of the outermost edge Ros of the trench R is greater than the height of the second solder layer 103 closest to the outermost edge Ros. That is, the top surface of the trench R is higher than the top surface 103t of the second solder layer 103. In some embodiments, the top surface 103t is higher than the portion of the second solder layer 103 closest to the outermost edge Ros. In this case, no solder overflow will occur.

[0044] Figure 8A and Figure 8B The second solder layer 103 is shown under tension, wherein, Figure 8A A top view is shown, and Figure 8B A corresponding partial cross-sectional view is shown. It can be seen that when the solder of the second solder layer 103 is stretched, it is not easy for the solder of the second solder layer 103 to overflow into the trench R.

[0045] In summary, the spacer layer 104 of the power module 100-400 provided in this application has a trench R with a platform shape that is not exposed to the sidewalls (i.e., surrounded by the sidewalls 104s) and has a center (the center of the portion extending beyond the second solder layer 103) to accommodate (place) overflowing solder. Therefore, the power module 100-400 provided in this application can prevent the solder of the upper and lower layers (i.e., the first solder layer 102 and the second solder layer 103) of the spacer layer 104 from forming a bridging failure mode. This application utilizes physical isolation, so as long as the amount of overflowing solder does not exceed the amount that the trench R can accommodate, there will be essentially no (or certainly no) bridging.

[0046] Return to reference Figures 2A to 2C Other embodiments of this application provide a power module 100, including: a first solder layer 102; a second solder layer 103 disposed above the first solder layer 102; and a spacer layer 104 disposed between the first solder layer 102 and the second solder layer 103, wherein the sidewall 104s of the spacer layer 104 is provided with a groove R around the lateral extent of the second solder layer 103, the groove R facing the second solder layer 103, and the second solder layer 103 is disposed within the area enclosed by the outermost edge Ros of the groove R. Figure 2B In the top view shown, the trench R extends continuously around the second solder layer 103 and forms a closed loop. In the example shown... Figure 2D In the top view shown, the trench R extends discontinuously around the second solder layer 103 and is formed as having multiple discrete segments.

[0047] The following will refer to Figures 9 to 15 To introduce and Figures 3A to 3C The manufacturing process of the power module 200 shown is similar to that of the power module 200', wherein, Figure 9 The corresponding flowchart is shown.

[0048] First, refer to Figure 9 and Figure 10 In step S1, a spacer layer 104 is fabricated or provided, and a groove R is formed on the spacer layer 104 (upper layer) to form a trench structure. In step S2, the substrate 101, the first solder layer 102, the spacer layer 104, and the second solder layer 103 are fixedly stacked in the order of substrate / first solder layer / spacer layer / second solder layer using a fixture commonly used in the art, wherein the groove R of the spacer layer 104 faces the second solder layer 103. Then, referring to... Figure 9 and Figure 11 In step S3, a method commonly used in the art is employed to... Figure 10 The stacked substrate / first solder layer / spacer layer / second solder layer structure is placed in a formic acid furnace for reflow P1.

[0049] See Figure 12 The die 106 is bonded to another substrate 107 via the third solder layer 105. Then, see... Figure 13 ,Will Figure 12 The resulting structure is refluxed to P2, for example, by being placed in a formic acid furnace. See also Figure 14 After the die 106 is reflowed in the stacked structure, the die 106 leads are bonded to a lead frame 111, such as copper metal, by wire bonding.

[0050] Next, see Figure 9 as well as Figure 15 In step S4, Figure 10 The resulting stacked structure of substrate / first solder layer / spacer layer / second solder layer and Figure 14 The resulting reflowed die / third solder layer / another base are stacked, as follows: Figure 15 As shown, Figure 14 The resulting structure is flipped to bond the die 106 to the second solder layer 103 to form a stacked structure of the power module 200'. Then, the stacked structure of the power module 200' is placed in a formic acid furnace for reflow P3. After reflow, in step S5, the power module 200' is successfully fabricated, that is, the power module 200' is obtained.

[0051] In summary, this application prevents bridging failure modes of solder between the upper and lower layers (first solder layer 102 and second solder layer 103) of the spacer layer 104 by forming a trench R on the spacer layer 104. This application utilizes a trench R of a specific shape on the surface of the spacer layer 104 to ensure that, under compression, the solder (solder) of the second solder layer 103 does not exceed the width of the spacer layer 104 and thus does not bridge. Under tension, it improves the problem of insufficient contact area caused by excessive solder flowing into the trench R of the spacer layer 104 that accommodates the solder.

[0052] The power module of this application has the following advantages over the prior art:

[0053] (1) This application utilizes physical isolation, so as long as the amount of overflow solder (solder of the second solder layer 103) does not exceed the amount that the trench R can accommodate, there will be basically no (or certainly no) bridging.

[0054] (2) The power module provided in this application allows the product to have more process windows.

[0055] (3) It can be applied to high-power products, such as high-end servers, computer rooms, charging piles, etc.

[0056] The features of several embodiments have been summarized above to enable those skilled in the art to better understand aspects of the present invention. Those skilled in the art should understand that they can readily use the present invention as a basis to design or modify other processes and structures for implementing the same purposes and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the present invention, and that various changes, substitutions, and alterations can be made therein without departing from the spirit and scope of the present invention.

Claims

1. A power module, comprising: substrate; The first solder layer is disposed on the substrate; A spacer layer is disposed on the first solder layer; as well as The second solder layer is placed on the spacer layer. The spacer layer has grooves around the lateral extent of the second solder layer, and in the top view, the grooves surround the second solder layer.

2. The power module according to claim 1, wherein, The second solder layer extends into the trench.

3. The power module according to claim 2, wherein, The second solder layer is disposed within the area enclosed by the outermost edge of the trench.

4. The power module according to claim 3, wherein, The height of the outermost edge of the trench is greater than the height of the second solder layer closest to the outermost edge.

5. The power module according to claim 1, wherein, In the top view, the trench extends continuously around the second solder layer and forms a closed loop.

6. The power module according to claim 1, wherein, The second solder layer is completely separated from the first solder layer by the spacer layer.

7. The power module according to claim 1, wherein, The trench is laterally spaced from the second solder layer by a non-zero distance.

8. The power module according to claim 1, wherein, The trench is further disposed outside the lateral range of the first solder layer and suspended above the first solder layer.

9. The power module according to claim 1, wherein, The groove is surrounded by the sidewalls of the spacer layer.

10. A power module, comprising: First solder layer; The second solder layer is disposed above the first solder layer; as well as A spacer layer, located between the first solder layer and the second solder layer. The spacer layer has a groove on its sidewall surrounding the lateral range of the second solder layer, and the groove faces the second solder layer and the second solder layer is disposed within the range enclosed by the outermost edge of the groove.

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