Power module and power conversion device

Abstract

This disclosure provides a power module and a power conversion device, belonging to the field of power conversion technology. The power module includes at least one power chip, a substrate, a heat sink, and a solder layer. The at least one power chip is located on the surface of the substrate, and the substrate has a first metal layer on its surface opposite to the power chip. The area of ​​the metal layer is greater than or equal to the area occupied by the at least one power chip. The surface of the heat sink is provided with a blocking structure, the area enclosed by the blocking structure being greater than or equal to the area occupied by the at least one power chip and less than or equal to the area of ​​the first metal layer. The solder layer is disposed within the area enclosed by the blocking structure, and the heat sink is fixedly connected to the first metal layer through the solder layer. Adopting this disclosure can improve the reliability and stability of the soldered interconnection between the power module and the heat sink.

Description

Technical Field

[0001] This disclosure relates to the field of power conversion technology, and in particular to a power module and a power conversion device. Background Technology

[0002] A power module is a semiconductor device that converts at least one of the voltage, current, and frequency of a power source, and is the core device for power conversion.

[0003] Power modules generate heat during operation, so they are usually used in conjunction with heat sinks. For example, after the power module is packaged, its substrate is soldered to the heat sink base plate.

[0004] However, the reliability of the welded joint is currently weak after the power module and heat sink are soldered together. Summary of the Invention

[0005] This disclosure provides a power module and a power conversion device that can improve the reliability and stability of the soldered interconnection between the power module and the heat sink.

[0006] In a first aspect, this disclosure provides a power module, which includes at least one power chip, a substrate, a heat sink, and a solder layer;

[0007] The at least one power chip is located on the surface of the substrate, and the substrate has a first metal layer on the surface opposite to the power chip, the area of ​​the metal layer being greater than or equal to the area occupied by the at least one power chip.

[0008] The surface of the heat dissipation base plate is provided with a blocking structure. The area enclosed by the blocking structure is greater than or equal to the area occupied by the at least one power chip, and less than or equal to the area of ​​the first metal layer.

[0009] The welding layer is disposed within the area enclosed by the barrier structure, and the heat dissipation base plate is fixedly connected to the first metal layer through the welding layer.

[0010] In the solution disclosed herein, because a barrier structure is fixed above the surface of the heat dissipation base plate, the molten solder is confined within the area enclosed by the barrier structure during reflow soldering, thereby preventing the molten solder from overflowing. Consequently, the thickness of the solder layer at the edges after cooling and solidification is approximately equal to the thickness inside, and the strength of the solder layer is generally consistent across all locations. This reduces or even prevents the solder layer from being weak in localized areas, especially at the edges, making it less prone to cracking at the edges and thus improving the long-term reliability and stability of the subsequent soldered interconnects.

[0011] In one possible implementation, the blocking structure protrudes from the surface of the heat dissipation base plate opposite to the heat dissipation fins.

[0012] In one possible implementation, the blocking structure includes multiple sidewalls connected to form an annular region.

[0013] In the scheme shown in this disclosure, the number of sidewalls can be three or more, which are connected in sequence, and the first sidewall is connected to the last sidewall to form a closed annular region.

[0014] In one possible implementation, at least one of the plurality of sidewalls has a plurality of exhaust slots, and the inner and outer spaces of the annular region are connected through the plurality of exhaust slots.

[0015] In the scheme disclosed herein, during high-temperature reflow soldering, the volatiles generated can be discharged through the venting grooves on the sidewall, preventing gas from accumulating in the solder, reducing the porosity in the cured solder layer, and improving the heat transfer effect of the solder layer.

[0016] In one possible implementation, the depth of the exhaust groove is less than or equal to half the height of the sidewall.

[0017] In the scheme disclosed herein, the venting groove has a relatively small depth, which helps to prevent molten solder from overflowing from the venting groove during reflow soldering of the heat sink base plate and the substrate. This size of venting groove enables the venting of gas from the molten solder while ensuring that the molten solder does not overflow.

[0018] In one possible implementation, the cross-sectional shape of the exhaust groove is U-shaped, V-shaped, or arc-shaped.

[0019] In one possible implementation, the barrier structure includes multiple sidewalls connected to form an open area, the inner and outer spaces of the area enclosed by the multiple sidewalls being connected through the open area.

[0020] In the scheme shown in this disclosure, there may be three or more sidewalls connected in sequence, with the first sidewall connected to the last sidewall but not connected, forming an area with an opening. The opening is used to connect the space inside and outside the area so that gas can be discharged outward through the opening during high-temperature reflow soldering.

[0021] In one possible implementation, the blocking structure further includes at least one first protrusion located at the opening, and the plurality of sidewalls and the at least one first protrusion forming an annular region.

[0022] In the scheme shown in this disclosure, a barrier structure with an opening is provided, and a first protrusion is arranged at the opening to prevent molten solder from overflowing from the opening.

[0023] In one possible implementation, the height of the first protrusion is equal to the height of the sidewall.

[0024] In the scheme shown in this disclosure, since the first protrusion and the sidewall have the same function, which is to prevent the molten solder from overflowing, the height of the first protrusion and the height of the sidewall are equal or nearly equal.

[0025] In one possible implementation, the surface of the heat dissipation base plate facing away from the heat dissipation fins further includes at least one second protrusion, which is disposed within the area enclosed by the blocking structure.

[0026] In the solution disclosed herein, the second protruding post located within the area enclosed by the blocking structure can prevent the molten solder from collapsing.

[0027] In one possible implementation, the second protrusion is located at the center of the area enclosed by the blocking structure.

[0028] In the solution shown in this disclosure, the center of the area enclosed by the blocking structure is supported by a second protruding post, which can prevent the molten solder from collapsing near the center.

[0029] In one possible implementation, the height of the second protrusion is equal to the height of the blocking structure.

[0030] In the scheme shown in this disclosure, the second protrusion of equal height and the sidewall together support the power module and the heat sink, which helps to make the thickness of the cured weld layer equal at all locations, so that the strength of the weld layer is basically equal at all locations, thereby improving the reliability and stability of the weld layer.

[0031] In one possible implementation, the surface of the heat dissipation base plate has a boss, and the blocking structure is disposed on the platform of the boss.

[0032] In the scheme shown in this disclosure, the boss serves as the pad of the heat dissipation base plate, and the blocking structure is arranged on the platform of the boss.

[0033] In one possible implementation, the power module further includes a molding compound, in which the at least one power chip and the substrate are both located, and the surface of the first metal layer of the substrate facing the heat dissipation base plate is exposed outside the molding compound.

[0034] In the scheme disclosed herein, the molding compound serves to protect and isolate the internal power chips, encapsulating the substrate and all the power chips on the substrate. Because the first metal layer of the substrate facing away from the power chips needs to be soldered to a heat dissipation base plate outside the molding compound, the first metal layer is exposed from within the molding compound. For example, the surface of the first metal layer facing away from the power chips is flush with the bottom surface of the molding compound, or the surface of the first metal layer facing away from the power chips protrudes from the bottom surface of the molding compound.

[0035] In one possible implementation, the power module further includes heat dissipation fins fixed to the surface of the heat dissipation base plate opposite to the substrate.

[0036] In the scheme disclosed herein, the radiator includes a heat dissipation base plate and heat dissipation fins, which can increase the heat dissipation area of ​​the radiator.

[0037] In one possible implementation, the power module further includes a heat sink, with the side of the heat sink base away from the power chip facing the heat sink, and the heat sink base in contact with the heat dissipation medium inside the heat sink.

[0038] In the solution disclosed herein, the side of the heat sink facing away from the power chip is immersed in a heat sink and comes into contact with the heat dissipation medium in the heat sink. The heat dissipation medium in the heat sink carries away the heat from the heat sink as it flows, thereby achieving the purpose of heat dissipation for the power chip.

[0039] In a second aspect, a power conversion device is provided, the power conversion device including a housing, a circuit board and a power module as described in the first aspect or any one of the first aspects;

[0040] Both the circuit board and the power module are located in the housing, and the power chip of the power module is electrically connected to the circuit board. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of a power module and a heat sink welded together, provided in an exemplary embodiment of this disclosure;

[0042] Figure 2 This disclosure provides an exemplary embodiment along... Figure 1 The diagram shows a cross-section cut along plane AA.

[0043] Figure 3 This is another exemplary embodiment provided along with the present disclosure. Figure 1 The diagram shows a cross-section cut along plane AA.

[0044] Figure 4 This is a schematic diagram of a blocking structure fixed on the surface of a heat sink base plate according to an exemplary embodiment of this disclosure;

[0045] Figure 5 This is a schematic diagram of a blocking structure fixed on the surface of a heat sink base plate, provided in another exemplary embodiment of this disclosure;

[0046] Figure 6 It is along Figure 5 A partial schematic diagram showing the sections after cutting through planes AB and AC;

[0047] Figure 7 This is a schematic diagram of a blocking structure fixed on the surface of a heat sink base plate, provided in another exemplary embodiment of this disclosure;

[0048] Figure 8 It is along Figure 7 A partial schematic diagram showing the sections after cutting through planes AB and AC;

[0049] Figure 9 This is a schematic diagram of a blocking structure fixed on the surface of a heat sink base plate, provided in another exemplary embodiment of this disclosure;

[0050] Figure 10 This is a schematic cross-sectional view along the center of the power module after the power module and the heat sink are fixed by a fixture during welding, according to an exemplary embodiment of this disclosure.

[0051] Figure 11 This is a schematic cross-sectional view along the center of the power module after the power module and heat sink are fixed by a fixture during welding, according to another exemplary embodiment of this disclosure.

[0052] Explanation of reference numerals in the attached figures

[0053] 1. Power module; 11. Power chip; 12. Substrate; 13. Molded component.

[0054] 120. Ceramic substrate; 121. First metal layer; 122. Second metal layer.

[0055] 2. Radiator; 21. Heat sink base plate; 22. Heat sink fins; 211. Boss.

[0056] 3. Welding layer.

[0057] 41. Side wall; 42. Opening; 43. First protruding column.

[0058] 51. Second convex post.

[0059] 100. Upper clamp; 200. Lower clamp. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this disclosure clearer, the embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0061] This embodiment relates to a power conversion device, which can be a device used in electric vehicles (such as a motor controller) or a device used in energy storage systems (such as an uninterruptible power supply or a transformer). This embodiment does not limit the specific application scenario of the power conversion device.

[0062] The power conversion device includes a power module, which is a device formed by packaging power chips on a substrate. Specifically, the power module can be an insulated-gate bipolar transistor (IGBT) power module or a silicon carbide (SiC) power module.

[0063] The power chips inside the power conversion equipment generate heat during operation, so a heat sink is needed to dissipate heat from the power chips. For example, the heat sink is interconnected with the power module, and the power module transfers the heat generated by the internal power chips to the heat sink, which then dissipates the heat to the outside.

[0064] Currently, one common interconnection method between power modules and heat sinks is through thermal interface material (TIM). For example, both the power module and the heat sink are mounted on the motherboard, with the heat sink pressing against the power module. The heat sink's base plate and the power module's substrate face each other, and a TIM pad is placed between the base plate and the substrate. TIM is a thermally conductive silicone grease with some elasticity, capable of absorbing the gap between the base plate and the substrate, reducing the contact thermal resistance between them.

[0065] Among these, welding and sintering interconnects, compared to TIM interconnects, offer superior heat transfer and stability, making them a hot research topic in the industry. Although sintering provides higher heat transfer and stability than welding, the material costs used in sintering remain high. Welding interconnects, on the other hand, offer the advantage of lower costs. Therefore, in the field of power module and heat sink interconnects, welding interconnects are a key area of ​​research and mass production development in the industry.

[0066] The soldering interconnection between the power module and the heat sink includes pre-soldering and post-soldering. Pre-soldering is the soldering of the substrate to the heat sink base plate before the power module is packaged. For example, after the power chip is fixed on the substrate, the substrate and the heat sink base plate are soldered together, and then the final soldering is performed. In this pre-soldering process, one power module corresponds to one heat sink. Since the size of the power module is generally relatively small, the size of the heat sink is also relatively small, resulting in a lower heat dissipation effect compared to post-soldering.

[0067] Post-soldering refers to the soldering of the substrate to the heat sink after the power module has been packaged. For example, after the power module is packaged, the surface of the substrate facing away from the power chip has an exposed metal layer, which serves as the substrate's solder pads and is soldered to the heat sink. In this post-soldering process, multiple power modules can be connected to one heat sink. The heat sink is larger in size, has a larger heat dissipation area, and its heat dissipation effect is significantly better than that of pre-soldering. Therefore, post-soldering is the most common method for interconnecting power modules and heat sinks.

[0068] However, in the post-soldering process, because encapsulation precedes soldering, and the plastic encapsulation surrounding the power module and substrate occupies a large proportion of the power module, the power module is prone to deformation, such as warping, during reflow soldering with the heatsink. This causes the solder between the power module and the heatsink base plate to easily overflow from the edges when in a molten state at high temperatures. Once the solder overflows, after cooling and solidification, the solder layer is thinner at the edges (compared to the center), resulting in weaker strength and making it prone to cracking. Once cracks form, they will propagate inwards, eventually reducing the heat transfer between the substrate and the heatsink base plate.

[0069] Additionally, deformation of the power module during soldering can create gaps between the power module and the heat sink. Volatile substances generated at high temperatures accumulate in these gaps, preventing the solder from filling them completely. After cooling and solidification, the solder layer contains numerous pores, resulting in a high porosity. Higher porosity leads to greater contact thermal resistance and consequently, poorer heat transfer.

[0070] Therefore, in the process of interconnecting power modules and heat sinks through post-soldering processes, improving the long-term reliability and stability of the interconnection is currently a major research hotspot in the industry.

[0071] This embodiment provides a power module including a power module and a heat sink. The power module and the heat sink are interconnected through a post-soldering process. Because the heat sink base plate has a blocking structure, the solder is confined to the area enclosed by the blocking structure. This can prevent the solder from overflowing during reflow soldering, so that the thickness of the solder layer at the edges after cooling and solidification is about the same as the thickness inside. The strength of the solder layer at various locations is about the same, thereby reducing stress concentration, reducing the probability of edge cracking, and improving the long-term reliability and stability of the post-soldering interconnect.

[0072] like Figure 1 The diagram shown is a structural schematic of the power module 1 and the heat sink 2's heat dissipation base plate 21 after welding. Figure 1 The diagram only shows a schematic of heat sink 2 for cooling a power module 1.

[0073] like Figure 2 and Figure 3 As shown, along Figure 1 The diagram shown is a cross-sectional view of AA after it has been cut open. Figure 2 and Figure 3 The difference lies in the different blocking structure located between power module 1 and heat sink 2. Figure 2 The blocking structure in the middle is specifically as follows Figures 4 to 8 The barrier structure shown, Figure 3 The blocking structure in the middle is specifically as follows Figure 9 The blocking structure shown.

[0074] refer to Figure 1 As shown, the power module includes a power module 1 and a heat sink 2, as referenced. Figure 2 As shown, the power module 1 includes at least one power chip 11, a substrate 12, and a molding compound 13. At least one power chip 11 is fixed to a first surface of the substrate 12. The second surface of the substrate 12, facing away from the power chip, has a first metal layer 121, which serves as a solder pad for soldering to a heat sink 2. The molding compound 13 encapsulates the power chip 11 and the substrate 12, but the first metal layer 121 of the substrate 12 needs to be exposed, i.e., exposed from the molding compound 13, to facilitate soldering to the heat sink 2.

[0075] Since the first metal layer 121 on the substrate 12 is interconnected with the heat sink 2 to transfer the heat generated by the power chip 11 to the heat sink 2, the area of ​​the first metal layer 121 is usually greater than or equal to the area occupied by all the power chips 11 on the substrate 12 in order to improve the heat transfer effect. Of course, there may also be other heat-generating components on the substrate 12, so the area of ​​the first metal layer 121 can be greater than the area occupied by all the power chips 11 on the substrate 12. The larger the area of ​​the first metal layer 121, the larger the contact area with the heat sink 2, and the better the heat transfer between the power module 1 and the heat sink 2.

[0076] The first surface of the substrate 12 on which the power chip 11 is disposed also has a metal layer, referred to as the second metal layer 122. The second metal layer 122 is used to realize electrical interconnection, for example, to realize electrical interconnection between different power chips 11, and to realize electrical interconnection between the power chip 11 and other components (such as resistors, capacitors or inductors).

[0077] In one example, the first metal layer 121 and the second metal layer 122 are made of the same material, such as copper, to avoid the difference in coefficient of thermal expansion (CTE) caused by different materials. However, the thickness of the first metal layer 121 and the second metal layer 122 can be equal or unequal, and their areas can also be equal or unequal. Usually, their areas are equal.

[0078] Since the components inside the power module 1 are generally arranged on the second metal layer 122 of the substrate 12, the area of ​​the first metal layer 121 is greater than or equal to the area of ​​the second metal layer 122. This allows the orthographic projection of each component arranged on the second metal layer 122 onto the first metal layer 121. As a result, the heat generated by each component can be quickly transferred to the heat sink 2 through the first metal layer 121. This can also reduce or even prevent the heat from spreading in the horizontal plane and affecting other nearby components.

[0079] Since substrate 12 has metal layers on both sides, substrate 12 can specifically be a double-sided copper-clad ceramic plate, see reference. Figure 2 As shown, the substrate 12 structurally includes a ceramic substrate 120, a first metal layer 121 and a second metal layer 122. Both the first metal layer 121 and the second metal layer 122 are copper layers. The ceramic substrate 120 serves as a support and provides electrical isolation.

[0080] Continue to refer to Figure 2 As shown, at least one power chip 11 is disposed on the second metal layer 122, and the first metal layer 121 is exposed from the molding compound 13.

[0081] It should be noted that power module 1 also has some pins exposed outside the molding compound 13 (not shown in the figure). These pins may be located on the surface of the molding compound 13, or they may extend beyond the molding compound 13. Power module 1 is connected to external circuitry through these exposed pins on the molding compound 13. For example, power module 1 is mounted on a motherboard (the main circuit board of the power conversion device), and the aforementioned pins of power module 1 are soldered to pads on the motherboard to achieve electrical interconnection.

[0082] refer to Figure 2As shown, the heat sink 2 includes a heat sink base plate 21 and heat sink fins 22. The heat sink fins 22 are located on the surface of the heat sink base plate 21. The surface of the heat sink base plate 21 opposite to the heat sink fins 22 generally has bosses 211. The bosses 211 serve as solder pads for soldering to the substrate 12 of the power module 1. Therefore, the area of ​​the bosses 211 is generally less than or equal to the area of ​​the first metal layer 121 of the substrate 12. Of course, the area of ​​the bosses 211 can also be greater than or equal to the area of ​​the first metal layer 121.

[0083] Since the welding of the boss 211 and the first metal layer 121 is for the purpose of transferring the heat generated by the power chip 11, the larger the welding surface of the boss 211 and the first metal layer 121, the better the heat transfer between them. For example, the welding surface of the boss 211 and the first metal layer 121 is greater than or equal to the area occupied by all the power chips 11 on the substrate 12.

[0084] It should be noted that the surface of the heat dissipation base plate 21 facing away from the heat dissipation fins 22 may not have a boss 211. In this case, the surface of the heat dissipation base plate 21 facing away from the heat dissipation fins 22 can be directly welded to the first metal layer 121 of the substrate 12. This embodiment does not limit whether the surface of the heat dissipation base plate 21 has a boss 211.

[0085] During reflow soldering of power module 1 and heat sink 2, to prevent molten solder from overflowing, a blocking structure is provided on the surface of the heat sink base plate 21 opposite to the heat sink fins 22. This blocking structure protrudes from the surface of the heat sink base plate 21 and can enclose a region (see reference). Figures 4 to 9 (As shown).

[0086] Since the area enclosed by the barrier structure is used to place solder, as mentioned above, the larger the soldering surface, the better the heat transfer and the better the heat dissipation effect for the power chip 11. Therefore, the area enclosed by the barrier structure is greater than or equal to the area occupied by all the power chips 11 on the substrate 12. Furthermore, since the first metal layer 121 of the substrate 12 is a solder pad, and the boss 211 on the heat dissipation base plate 21 is also a solder pad, the area enclosed by the barrier structure is less than or equal to the area of ​​the first metal layer 121, and also less than or equal to the surface area of ​​the boss 211.

[0087] The blocking structure on the surface of the heat dissipation base plate 21 acts as a barrier for the solder, enclosing it and preventing the molten solder from overflowing during reflow soldering. Once the solder does not overflow, the solder layer 3 (refer to the reference layer) is formed after solidification. Figure 2 and Figure 3 As shown, the thickness at the edge position is the same as the thickness of the substrate inside, which can enhance the welding strength of the welding layer 3 at the edge and improve the reliability and stability between the power module and the heat sink.

[0088] It should be noted that the blocking structure can also be recessed on the surface of the heat sink base plate 21 opposite to the heat sink fins 22; that is, the blocking structure is a groove structure provided on the surface of the heat sink base plate 21. In this design, during the welding of the heat sink base plate 21 to the substrate 12, the surface of the heat sink base plate 21 is in contact with or very close to the surface of the substrate 12. In the following description, an example is given where the blocking structure protrudes from the surface of the heat sink base plate 21, and the accompanying drawings also show an example where the blocking structure protrudes from the surface of the heat sink base plate 21.

[0089] Regarding the characteristics of the blocking structure. For example... Figure 4 The diagram shown is a schematic of a blocking structure fixed on a heat dissipation base plate 21. (Refer to...) Figure 4 As shown, the blocking structure includes multiple sidewalls 41, which are connected in sequence. The first sidewall 41 and the last sidewall 41 are connected to form a closed annular region.

[0090] For example, if the first metal layer 121 on the surface of the substrate 12 and the boss 211 on the heat sink 21 are quadrilateral (e.g., rectangular), then the blocking structure includes four sidewalls 41. These four sidewalls 41 are arranged on the platform of the boss 211 and connected vertically in sequence, forming a quadrilateral annular region on the platform of the boss 211. Solder is disposed within this quadrilateral annular region. After the solder cools and solidifies, a solder layer 3 (see reference) is formed within the quadrilateral annular region. Figure 2 (As shown).

[0091] To maximize the area of ​​the weld surface, correspondingly, refer to Figure 4 As shown, the outer surface of the sidewall 41 located outside the annular region is coplanar with the side surface of the boss 211, that is, the outer surface of the sidewall 41 is flush with the side surface of the boss 211.

[0092] In one example, the multiple sidewalls 41 of the barrier structure can be integrally formed with the heat dissipation base plate 21. In another example, the multiple sidewalls 41 of the barrier structure can also be fixed to the heat dissipation base plate 21 by welding. For example, the heat dissipation base plate 21 and the barrier structure are processed independently and then fixed together.

[0093] Because the four sidewalls 41 confine the solder within a closed area, the volatiles generated in the high-temperature environment of reflow soldering cannot be discharged. Once these volatiles cannot be discharged, they will create holes in the solder layer 3 after cooling and solidification. Therefore, venting grooves can be opened on the sidewalls 41 to discharge the volatiles generated in the high-temperature environment.

[0094] like Figures 5 to 8 The diagram shows a blocking structure with exhaust grooves fixed to a heat dissipation base plate 21 (wherein, Figures 5 to 8 (The boss 211 on the heat sink base plate 21 is not shown.) Figure 5 and Figure 7 The exhaust groove 411 in the middle has a different shape. Figure 6 For along Figure 5 A schematic diagram of a partial cross-section cut along planes AB and AC. Figure 8 It is along Figure 7 A schematic diagram of a partial cross-section cut through planes AB and AC.

[0095] refer to Figure 5 and Figure 6 As shown, at least one of the multiple sidewalls 41 has multiple exhaust grooves 411, so that the inner and outer spaces of the quadrilateral annular region enclosed by the four sidewalls 41 are connected through the multiple exhaust grooves 411.

[0096] For example, all sidewalls 41 have exhaust grooves 411, and the number of exhaust grooves 411 on a single sidewall 41 is multiple.

[0097] In one example, for ease of processing, refer to Figure 6 and Figure 8 As shown, the exhaust groove 411 is located at the top of the side wall 41 opposite to the heat dissipation base plate 21, and the opening of the exhaust groove 411 is located at the top of the side wall 41.

[0098] The cross-sectional shape of the exhaust groove 411 is as follows: Figure 6 The shape shown is an arc, but it can also be like... Figure 8 The diagram shows a U-shaped, arc-shaped exhaust groove 411, which can specifically be a semi-circular exhaust groove. Of course, the cross-sectional shape of the exhaust groove 411 can also be V-shaped. This embodiment does not limit the cross-sectional shape of the exhaust groove 411.

[0099] Although there are venting grooves on the side wall 41, the solder in the quadrilateral annular area is not easy to overflow. This is because the molten solder has a certain tension in the quadrilateral annular area. As long as the venting grooves are not too large, the molten solder will not overflow under the action of tension.

[0100] To prevent molten solder from overflowing from the venting groove 411, the depth of the venting groove 411 can be relatively small. For example, the depth of the venting groove 411 can be less than the height of the sidewall 41. For instance, the depth of the venting groove 411 can be less than or equal to half the height of the sidewall 41.

[0101] In another example, the overflow of molten solder can also be controlled by adjusting the width of a single venting groove 411. For example, the width of a single venting groove 411 can be relatively small. In this scheme, the depth of a single venting groove 411 can be equal to the height of the sidewall 41. The width of the venting groove 411 is also the dimension along the length of the sidewall 41.

[0102] Regarding the features of the exhaust grooves 411 on a single sidewall 41: Multiple exhaust grooves 411 on a single sidewall 41 can be evenly arranged along the length of the sidewall 41 so that the gas in the quadrilateral annular region can be emitted outward from the position near the end of the sidewall 41 or from the position near the middle of the sidewall 41.

[0103] like Figure 9 The diagram shown is a schematic of another type of blocking structure fixed to the heat dissipation base plate 21. (Refer to...) Figure 9 As shown, the barrier structure also includes multiple sidewalls 41, but these multiple sidewalls 41 are connected to form an area with an opening 42. For example, in the case of multiple sidewalls 41 being connected, the first sidewall 41 and the last sidewall 41 are not connected, but an opening 42 is formed between the first sidewall 41 and the last sidewall 41, and the inner and outer spaces of the area enclosed by the multiple sidewalls 41 are connected through the opening 42.

[0104] For example, refer to Figure 9 As shown, the blocking structure includes three sidewalls 41. The first sidewall 41 and the second sidewall 41 are vertically connected, and the third sidewall is vertically connected to the second sidewall 41. The first sidewall 41 and the third sidewall 41 are parallel and opposite to each other. The first sidewall 41 and the third sidewall 41 are not connected, and an opening 42 is formed between the first sidewall 41 and the third sidewall 41.

[0105] In this type of barrier structure with an opening 42, the venting groove 411 does not need to be provided on the side wall 41, while the opening 42 is used for venting during reflow soldering. Of course, the venting groove 411 described above can also be provided on the side wall 41 to improve the venting effect of the barrier structure.

[0106] It should be noted that, in order to prevent molten solder from overflowing from the opening 42, the power module 1 and the heat sink 2 can be tilted during reflow soldering, so that the opening 42 faces diagonally upward. That is, the position of the opening 42 is higher than the position of the opposite side of the opening 42, so that the molten solder is less likely to overflow from the opening 42.

[0107] To further prevent molten solder from overflowing from opening 42, please refer to the relevant documentation. Figure 9 As shown, the blocking structure includes not only sidewalls 41, but also at least one first protrusion 43, which are distributed at the opening 42 to seal it. Thus, the molten solder is confined within the annular region formed by the multiple sidewalls 41 and the at least one first protrusion 43.

[0108] The number of first protrusions 43 is related to the distance between the first sidewall 41 and the last sidewall 41. For example, if the distance is small, the number of first protrusions 43 is small, and if the distance is large, the number of first protrusions 43 can be large. Of course, the number of first protrusions 43 is also related to the diameter of a single first protrusion 43. For example, if the diameter of a single first protrusion 43 is large, the number of first protrusions 43 used can be small.

[0109] Regardless of the number of first protrusions 43, the height of each first protrusion 43 is equal to the height of the sidewall 41.

[0110] As described above, the heights of the first protrusion 43, the second protrusion 51, and the sidewall 41 are all equal. The height of the sidewall 41 is equal to the target height of the welding layer 3, which is also the desired thickness of the welding layer 3.

[0111] It should be noted that before soldering the power module and the heat sink, solid solder is placed in the area enclosed by the barrier structure. In order for the cured solder layer 3 to be equal to the height of the side wall 41, the thickness of the solid solder sheet placed needs to be slightly higher than the height of the side wall 41 (because there is a gap between the solid solder and the power module and the heat sink). In this way, the thickness of the solder layer 3 formed after high-temperature reflow soldering and cooling will not be less than the height of the side wall 41, and may even be higher than the height of the side wall 41.

[0112] It should be pointed out that, as Figure 4 The barrier structure shown may also include more or fewer sidewalls 41, as long as the multiple sidewalls 41 can enclose a closed or nearly closed region. Similarly, as Figure 9 The barrier structure shown may also include more or fewer sidewalls 41.

[0113] It should be noted that, as described above, a single heat sink 2 can dissipate heat for multiple power modules 1. In this case, multiple blocking structures described above can be fixed on the surface of the heat sink base plate 21 facing away from the heat sink fins 22. For example, the surface of the heat sink base plate 21 facing away from the heat sink fins 22 has multiple protrusions 211, and the blocking structure described above is fixed on the platform of each protrusion 211. The second protruding post 51 described above is arranged on the platform of each protrusion 211 within the area enclosed by the blocking structure. Moreover, all the blocking structures on the heat sink base plate 21 have the same height.

[0114] It should be noted that, as described above, the blocking structure can be a recessed groove set on the surface of the heat dissipation base plate. In the case where the blocking structure is a recessed groove, the side wall 41 mentioned above can be the groove wall of the recessed blocking structure.

[0115] The above is a description of the characteristics of the two blocking structures.

[0116] Whether it is Figure 4 The blocking structure shown is still as Figure 9 The barrier structure shown, when the area enclosed by the barrier structure is relatively large, may cause the molten solder to collapse in the middle during high-temperature reflow soldering. Once this collapse occurs, after cooling and solidification, the solder layer 3 will not contact the first metal layer 121 on the substrate 12 at the collapsed location, further reducing heat transfer efficiency. Therefore, refer to... Figure 4 and Figure 9 As shown, on the surface of the heat dissipation base plate 21 facing away from the heat dissipation fins 22, and within the area enclosed by the blocking structure, there is at least one second protrusion 51.

[0117] For example, there is one second protruding post 51, located at the center of the area enclosed by the blocking structure. (See reference) Figure 4 As shown, the single second protruding post 51 is located at the center of the quadrilateral annular region enclosed by the four side walls 41, for reference. Figure 9 As shown, the single second protrusion 51 is located at the center of the quadrilateral annular region enclosed by the three sidewalls 41 and the two first protrusions 43.

[0118] For example, there are multiple second protruding pillars 51, which are distributed in the area enclosed by the blocking structure.

[0119] Regardless of the number of second protrusions 51 or how they are distributed, the height of the second protrusions 51 is equal to the height of the blocking structure, that is, the height of the second protrusions 51 is equal to the height of the sidewall 41.

[0120] The above describes the features of power module 1 and heat sink 2. In one example, to accelerate heat dissipation, the power module may also include a cooling water tank with an inlet and an outlet. The cooling water tank contains a flowing cooling medium (such as water). The side of the heat sink base plate 21 facing away from the power chip 11 faces the cooling water tank. The heat sink fins 22 are immersed in the cooling medium in the cooling water tank. The side of the heat sink base plate 21 facing away from the power chip 11 can also be immersed in the cooling water tank. Thus, both the heat sink fins 22 and the heat sink base plate 21 are in contact with the cooling medium in the cooling water tank. The cooling medium continuously carries away heat from the power module as it flows, thus dissipating heat from the power chip 11 within the power module.

[0121] As mentioned at the beginning, in the post-soldering interconnection method, the power module is prone to deformation and warping during reflow soldering, which aggravates the overflow of molten solder and the porosity in the solder layer 3. In order to reduce the deformation of the power module, a welding fixture can be used in reflow soldering to firmly fix the power module and the heat sink, thereby reducing the degree of deformation of the power module.

[0122] like Figure 10 and Figure 11 The image shows a cross-sectional view through the center of the power module after the power module and heat sink are secured by a clamp during welding. Figure 10 and Figure 11 (The heat sink fins are not shown in the image). Figure 10 For example Figure 2 The diagram shown illustrates the reflow soldering of the power module. Figure 11 For example Figure 3 The diagram shown illustrates the reflow soldering of the power module. Figure 10 The blocking structure in the text can be referenced. Figure 5 and Figure 7 As shown, Figure 11 The barrier structure shown can be referenced. Figure 9 As shown.

[0123] refer to Figure 10 and Figure 11 As shown, the fixture used to fix the power module includes an upper fixture 100 and a lower fixture 200. After the upper fixture 100 and the lower fixture 200 are fixed, a receiving cavity is formed inside. The fixed power module and the heat sink are placed in the receiving cavity. The upper fixture 100 presses on the plastic seal 13 and the heat sink base plate of the heat sink. The upper fixture 100 and the lower fixture 200 are fixedly connected by bolts.

[0124] Because the upper clamp 100 is pressed against the top of the power module 1 facing away from the heat sink 2, and also pressed against the top surface of the heat sink base plate facing the power module, and the upper clamp 100 and the lower clamp 200 are fastened by bolts, the power module 1 has no deformation space, thereby limiting the deformation of the power module and making it less likely to deform and warp during high-temperature reflow soldering.

[0125] Since the power module 1 is less prone to warping under the action of the fixture, it is less likely to undergo displacement during reflow soldering. Consequently, the molten solder between the power module and the heat sink is less likely to overflow. Furthermore, the solder is located within the area enclosed by the barrier structure, further preventing solder overflow and solder ball splatter. Therefore, in this embodiment, after the power module and the heat sink are soldered, the thickness and strength of the solder layer 3 are basically consistent at all locations, reducing the likelihood of stress concentration and thus improving the reliability and stability of the solder layer.

[0126] Based on the fact that the power module 1 is not easily warped under the action of the fixture, the space between the power module and the heat sink is always filled with solder, and gaps are unlikely to appear between them. Even if slight warping occurs, creating gaps, the gas generated at high temperatures can be discharged in time because the blocking structure has openings or venting channels, preventing it from accumulating in the gaps. Once there is no gas in the gaps, the molten solder will flow into the gaps and fill them. Therefore, in this embodiment, the porosity inside the weld layer 3 is low after the power module and heat sink are welded.

[0127] It should be noted that in the design where the multiple sidewalls 41 of the blocking structure form a closed annular region, during reflow soldering, refer to... Figure 10 As shown, the power module can be placed flat on the worktable. In a design where multiple sidewalls 41 of the blocking structure enclose an open area, during reflow soldering, refer to... Figure 11 As shown, the power module is placed at an angle on the worktable with its opening facing upwards to prevent molten solder from overflowing from the opening. Furthermore, reference... Figure 11 As shown, the power module is placed at an angle on the workbench with its opening facing upwards. The gas has a lower density and can float better, exiting from the area enclosed by the barrier structure.

[0128] In addition, the aforementioned fixtures can be openwork or frame-type fixtures, so that the gases emitted from the solder can be further discharged outwards during high-temperature reflow soldering.

[0129] Alternatively, if a sealed cavity is formed after the above-mentioned fixture is fixed, then in order to release the gas, a through hole penetrating the thickness of the cavity wall needs to be opened on the cavity wall so that the gas discharged from the solder can be further discharged from the cavity.

[0130] In this embodiment, because a barrier structure is fixed above the surface of the heat sink base plate, the molten solder is confined within the area enclosed by the barrier structure during reflow soldering, thus preventing the molten solder from overflowing. Therefore, the thickness of the solder layer at the edges after cooling and solidification is essentially equal to the thickness inside, and the strength of the solder layer is essentially consistent across all locations. This reduces or even avoids situations where the solder layer is weak in localized areas, especially at the edges, making it less prone to cracking at the edges and thus improving the long-term reliability and stability of the subsequent soldered interconnects.

[0131] This embodiment also provides a power conversion device, which includes a housing, a circuit board, and the aforementioned power module. Both the circuit board and the power module are located within the housing, and the power chip of the power module is electrically connected to the circuit board. For example, the circuit board is fixed in the housing, the power module is fixed on the circuit board, and the exposed pins of the power module in the plastic package are fixedly connected to the pads on the circuit board.

[0132] The above description is merely an optional embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A power module, characterized in that, The power module includes at least one power chip (11), a substrate (12), a heat dissipation base plate (21), and a solder layer (3); The at least one power chip (11) is located on the surface of the substrate (12), and the substrate (12) has a first metal layer (121) on the surface opposite to the power chip (11), the area of ​​the first metal layer (121) being greater than or equal to the area occupied by the at least one power chip (11). The surface of the heat dissipation base plate (21) is provided with a blocking structure. The area enclosed by the blocking structure is greater than or equal to the area occupied by the at least one power chip (11), and less than or equal to the area of ​​the first metal layer (121). The welding layer (3) is disposed in the area enclosed by the barrier structure, and the heat dissipation base plate (21) is fixedly connected to the first metal layer (121) through the welding layer (3).

2. The power module according to claim 1, characterized in that, The blocking structure includes multiple sidewalls (41) that protrude from the surface of the heat dissipation base plate (21) and are connected to form an annular area.

3. The power module according to claim 2, characterized in that, At least one of the plurality of sidewalls (41) has a plurality of exhaust grooves (411), and the inner and outer spaces of the annular region are connected through the plurality of exhaust grooves (411).

4. The power module according to claim 3, characterized in that, The depth of the exhaust groove (411) is less than or equal to half the height of the sidewall (41).

5. The power module according to claim 1, characterized in that, The barrier structure includes multiple sidewalls (41) connected to form an area with an opening (42), and the inner and outer spaces of the area enclosed by the multiple sidewalls (41) are connected through the opening (42).

6. The power module according to claim 5, characterized in that, The blocking structure further includes at least one first protrusion (43) located at the opening (42), and the plurality of sidewalls (41) and the at least one first protrusion (43) form an annular region.

7. The power module according to claim 6, characterized in that, The height of the first protrusion (43) is equal to the height of the sidewall (41).

8. The power module according to any one of claims 1 to 7, characterized in that, The heat dissipation base plate (21) also includes at least one second protrusion (51), which is disposed in the area enclosed by the blocking structure.

9. The power module according to claim 8, characterized in that, The second protruding post (51) is located at the center of the area enclosed by the blocking structure.

10. The power module according to claim 8 or 9, characterized in that, The height of the second protrusion (51) is equal to the height of the blocking structure.

11. The power module according to any one of claims 1 to 10, characterized in that, The surface of the heat dissipation base plate (21) has a boss (211), and the blocking structure is disposed on the platform of the boss (211).

12. The power module according to any one of claims 1 to 11, characterized in that, The power module also includes a molding compound (13), in which at least one power chip (11) and the substrate (12) are located, and the surface of the first metal layer (121) of the substrate (12) facing the heat dissipation base plate (21) is exposed in the molding compound (13).

13. The power module according to any one of claims 1 to 12, characterized in that, The power module also includes heat dissipation fins (22), which are fixed to the surface of the heat dissipation base plate (21) facing away from the substrate (12).

14. The power module according to any one of claims 1 to 13, characterized in that, The power module also includes a heat sink, with the side of the heat sink base plate (21) facing away from the power chip (11) facing the heat sink, and the heat sink base plate (21) in contact with the heat dissipation medium in the heat sink.

15. A power conversion device, characterized in that, The power conversion device includes a housing, a circuit board, and a power module as described in any one of claims 1 to 14; Both the circuit board and the power module are located in the housing, and the power chip (11) of the power module is electrically connected to the circuit board.

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