Low-stress double-sided cooling power module and manufacturing method

Abstract

The invention provides a low-stress double-sided cooling power module and a manufacturing method thereof, the low-stress double-sided cooling power module comprises a first copper-clad ceramic substrate and a second copper-clad ceramic substrate which are oppositely arranged, the first copper-clad ceramic substrate is provided with at least two power chips, and two sides of each power chip are provided with C-shaped auxiliary support column connecting layers; and the lower surface of the second copper-clad ceramic substrate is provided with an inverted metal buffer cushion block which is arranged opposite to each power chip. The inverted metal buffer cushion block comprises a connecting frame with a groove, an auxiliary supporting column connected with the connecting frame is arranged at the position, corresponding to the auxiliary supporting column connecting layer, of the connecting frame, a protruding quadrangular frustum pyramid heat conduction structure is arranged in the groove of the connecting frame, and the bottom of the inverted quadrangular frustum pyramid heat conduction structure is connected with a power chip. The inverted metal cushion block constructs an optimized heat conduction path for the power module, so that heat generated in the working process of the chip can be efficiently conducted to an external heat dissipation environment through the metal cushion block, and the junction temperature of the chip is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a low-stress double-sided cooling power module and a manufacturing method thereof. Background Art

[0002] As a representative of the third-generation semiconductor materials, silicon carbide metal-oxide-semiconductor field effect transistors (SiC MOSFETs) break the physical performance limits of traditional Si-based power devices and can meet the application requirements of future power electronic systems for high efficiency, high power density, high-temperature reliability, and miniaturization. Therefore, due to their unique performance and broad application prospects, SiC power devices have occupied an important position in high-tech fields such as new energy vehicles, photovoltaic inverters, rail transit, and smart grids.

[0003] At the same power level, the size of SiC MOSFETs is only 1 / 6 to 1 / 4 of that of traditional Si-based power devices, and the current density per unit area is 4 to 6 times that of traditional Si-based power devices. The smaller chip size enables a more compact layout of the power module to meet the pursuit of higher power density of the power module. On the other hand, the significant reduction in the size of SiC MOSFETs results in a sharp increase in the heat flux density per unit area to 5 to 7 times that of traditional Si-based power devices. At the same time, the reduction in the packaging volume means the intensification of the thermal coupling phenomenon between chips and the reduction of the radiator size, which makes it more difficult to dissipate the heat inside the module. In addition, although SiC MOSFETs can operate under relatively harsh temperature conditions, weak links inside the power module such as bonding wires and connection layers will accelerate failure, preventing the full realization of the high-temperature operation advantages of SiC MOSFETs. The above problems have put forward higher requirements for the efficient heat dissipation design of SiC power modules.

[0004] Based on the foregoing technical challenges, a double-sided cooling structure power module design is adopted to address the technical problems of small packaging volume and high heat dissipation efficiency. However, there are still several technical bottlenecks in existing double-sided heat dissipation structure power modules, and their main technical defects are specifically manifested in the following aspects:

[0005] 1. Large thermo-mechanical stress: Existing double-sided cooling power modules introduce packaging materials with large differences in thermal expansion coefficients during the packaging process. Therefore, SiC MOSFETs and their top surface interconnect layers need to bear large thermo-mechanical stresses. In addition, during actual operation, the radiators and water cooling mechanisms at both ends of the double-sided cooling power module often require a certain pressure to ensure close fitting, which further increases the mechanical stress borne by all components inside the module. Excessive mechanical stress will cause cracks in SiC MOSFETs, resulting in insulation failure of the power module, while intensifying the thermal fatigue of the device connection layer, inducing the growth of microcracks, and causing delamination of the connection surface, resulting in thermal failure of the power module.

[0006] 2. Heat dissipation performance is not as expected: In an ideal situation, compared with a single-sided heat dissipation power module of the same size, a double-sided heat dissipation module can reduce the thermal resistance by about 50%. However, in a traditional double-sided heat dissipation power module, the structure of the metal buffer pad is mostly a cuboid, which is relatively fixed and rigid. The cross-sectional size of the top heat flow path of the SiC MOSFET is limited by the pad size of the main power source electrode of the device, resulting in a further expansion of the imbalance in heat dissipation capacity between the top and bottom of the module. Therefore, in practical applications, the thermal resistance reduction benefit obtained by adopting the double-sided cooling design is only 25% - 35%.

[0007] 3. It is difficult to balance high-efficiency heat dissipation and low thermal mechanical stress: To overcome the problem of large differences in the coefficients of thermal expansion between the materials of each layer in a double-sided cooling power module, existing solutions are to improve the structure of the metal buffer pad, such as a cylindrical structure, a hollow cylindrical structure, and a cuboid structure with grooves. However, the above-mentioned structural improvements often sacrifice a part of the heat dissipation performance of the power module and cannot fully utilize the advantage of low chip junction temperature of the double-sided cooling design. Summary of the Invention

[0008] The present invention aims to overcome the deficiencies of the prior art and provides a low-stress double-sided cooling power module and a manufacturing method.

[0009] To achieve the above object, the present invention provides a low-stress double-sided cooling power module, which includes:

[0010] A first copper-clad ceramic substrate and a second copper-clad ceramic substrate are disposed opposite to each other. At least two power chips are provided on the first copper-clad ceramic substrate, and C-shaped auxiliary support column connection layers are provided on both sides of each power chip; an inverted metal buffer pad is disposed on the lower surface of the second copper-clad ceramic substrate opposite to each power chip.

[0011] The inverted metal buffer pad includes: a connection frame with a groove, auxiliary support columns connected to the auxiliary support column connection layers are provided at positions corresponding to the auxiliary support column connection layers on the connection frame, and a raised quadrangular pyramid heat conduction structure is provided in the groove of the connection frame. The bottom of the inverted quadrangular pyramid heat conduction structure is connected to the power chip.

[0012] Preferably, the power module further includes: a DC+ power terminal, an AC power terminal, and a DC- power terminal located on one side of the power chip, and a plurality of control terminals located on the other side of the power chip. The DC+ power terminal and the AC power terminal are connected to the first copper-clad ceramic substrate, and the DC- power terminal is connected to the second copper-clad ceramic substrate; one end of the control terminal is bent and the bent end is connected to the first copper-clad ceramic substrate.

[0013] Preferably, the first copper-clad ceramic substrate is connected to the power chip, the power chip is connected to the quadrangular frustum heat dissipation structure, and the quadrangular frustum heat dissipation structure is connected to the second copper-clad ceramic substrate through corresponding connection layers.

[0014] Preferably, the power chip includes an upper-bridge power chip and a lower-bridge power chip. On the top surface side of each power chip, there is a gate pad, two sub-source pads, and a main power source pad, and on the back surface side is a drain pad; the gate pad and the two sub-source pads are respectively connected to corresponding control terminals through bonding wires.

[0015] Preferably, the first copper-clad ceramic substrate includes, from top to bottom: a first substrate upper copper layer, a first substrate ceramic layer, and a first substrate lower copper layer. The first substrate upper copper layer includes: a drain power circuit region corresponding to the power chip, a middle power circuit region corresponding to the auxiliary support column connection layer, a sub-source control circuit region, and a gate control circuit region.

[0016] Preferably, the first substrate upper copper layer further includes an NTC thermistor welding region for welding the NTC thermistor, and an NTC thermistor measurement terminal is connected to the corresponding region of the electrode of the NTC thermistor.

[0017] Preferably, the second copper-clad ceramic substrate includes, from top to bottom: a second substrate upper copper layer, a second substrate ceramic layer, and a second substrate lower copper layer. The top of each inverted metal buffer pad is connected to the second substrate lower copper layer.

[0018] The present invention also provides a manufacturing method of a low-stress double-sided cooling power module, which includes the following steps:

[0019] (a) Chip sintering: Pre-form the sintering material in the upper-bridge power chip connection region and the lower-bridge power chip connection region of the first copper-clad ceramic substrate; sequentially go through preheating, pre-sintering, and sintering to form a power chip drain connection layer connecting the power chip and the first copper-clad ceramic substrate, and interconnect the upper and lower-bridge power chips and the first copper-clad ceramic substrate through the power chip drain connection layer;

[0020] (b) Wire bonding: Connect the corresponding gate pads and sub-source pads of the upper-bridge power chip and the lower-bridge power chip to the corresponding control circuit regions through bonding wires respectively to complete the corresponding electrical connections;

[0021] (c) Interconnect the inverted metal buffer pads with the upper and lower-bridge power chips and the first copper-clad ceramic substrate: Pre-form the sintering material on the bottom surface of the quadrangular frustum heat dissipation structure and the bottom surface of the auxiliary support column; sequentially go through preheating, pre-sintering, and sintering to form an auxiliary support column connection layer and a main power source connection layer;

[0022] (d) Component welding: Weld each component by means of alloy solder welding or ultrasonic terminal welding;

[0023] (e) Co - molding and sintering of the first copper - clad ceramic substrate and the second copper - clad ceramic substrate: Prefabricate sintering materials in the upper - bridge source - electrode power loop area and the lower - bridge source - electrode power loop area, which are of the same size as the top surface of the inverted metal buffer pads. Combine the first copper - clad ceramic substrate and the second copper - clad ceramic substrate in a mold, align the printed sintering materials with the top surface of the inverted metal buffer pads, and successively go through preheating, pre - sintering, and sintering to complete the physical and electrical connection between the substrates.

[0024] Preferably, during the sintering process, the sintering process is screen printing or silver - film transfer printing; if screen printing is used, the thickness of the sintered silver paste is 10 - 100 microns; if silver - film transfer printing is used, directly pre - fabricate a sintered silver film in the sintering area.

[0025] Preferably, if the sintering process uses pressure sintering, the preheating conditions for each step are: preheating temperature 60 - 150 °C, preheating time 3 - 10 minutes, the pre - sintering conditions are: sintering temperature 100 - 150 °C, sintering pressure 1 - 5 MPa, sintering time 3 - 5 minutes, and the sintering conditions are: sintering temperature 180 - 280 °C, sintering pressure 10 - 20 MPa, sintering time 3 - 5 minutes;

[0026] If the sintering process uses pressure - less sintering, the preheating conditions for each step are: preheating temperature 60 - 150 °C, preheating time 3 - 10 minutes, the pre - sintering conditions are: sintering temperature 100 - 150 °C, sintering time 3 - 5 minutes, and the sintering conditions are: sintering temperature 180 - 280 °C, sintering time 30 - 60 minutes.

[0027] A low - stress double - sided cooling power module and manufacturing method provided by the present invention, compared with the prior art, its beneficial effects are as follows:

[0028] In the low - stress double - sided cooling power module designed by the present invention, metal buffer pads are introduced on the surface of the SiC MOSFET source electrode. This structure constructs an optimized heat - conduction path for the power module, enabling the heat generated during the operation of the chip to be efficiently conducted to the external heat - dissipation environment through the metal buffer pads, thereby effectively reducing the chip junction temperature and improving the operation reliability of the power module. In addition, the double - sided cooling structure of the present invention uses metal pads to replace the traditional source - electrode bonding wires as the conduction carrier of the power current. This structural improvement significantly reduces the parasitic inductance parameters of the module and improves the electrical performance of the power module. The specific effects are as follows:

[0029] 1. The metal buffer pad uses an inverted design. Compared with the cuboid structure of the existing pads, which has poor heat dissipation performance and large thermal stress, the bottom surface of the pad in the present invention is in the shape of a "[square]". Considering the bonding wire insulation problem and the existence of the thermal diffusion angle, the "[square]" part that fits the top main power source electrode of the SiC MOSFET adopts a frustum of a pyramid-shaped convex structure. Referring to the 45° calculation method of the microcircuit thermal resistance, the four side surfaces of the frustum of the pyramid form a 45° inclination angle with the base plane, so that the top heat flow path of the device is adapted to the thermal diffusion angle, giving full play to the heat dissipation performance of the metal buffer pad and achieving a lower chip junction temperature than that of the traditional double-sided cooling power module.

[0030] 2. The top of the frustum of a pyramid-shaped convex structure presents a flat cuboid structure, and a circle of auxiliary support columns is arranged around the cuboid, effectively overcoming the problem of poor thermal stress difference existing in the existing pads. The shape of the frustum of a pyramid-shaped convex structure is in the shape of "[" and "]". The auxiliary support columns play an important role in the power module. On the one hand, they can effectively support the current flow between the upper and lower substrates, ensuring the stability and reliability of power transmission. On the other hand, the auxiliary support columns play a good supporting role for the upper and lower substrates. In practical applications, when the power module is subjected to extrusion or impact, the auxiliary support columns can share the external force acting on the chip, thereby protecting the fragile chip and its connection layer and improving the stability and service life of the chip and its connection layer. In addition, the auxiliary support columns also greatly increase the heat exchange area between the upper and lower substrates, which effectively alleviates the problem of uneven heat dissipation capacity between the top and bottom of the power module and helps to improve the overall heat dissipation performance of the power module.

[0031] 3. After the sintering process of the inverted metal buffer pad with the SiC MOSFET and the copper-clad ceramic substrate is completed, relying on the structural advantage of integral molding, it can effectively inhibit the warping problem caused by the high and low temperature cycles during the sintering or reflow soldering process of the substrate, which helps to improve the success rate of the upper and lower substrates during mold closing and sintering.

[0032] 4. The auxiliary support columns can expand or contract freely to match the increase or decrease in the size of the power module, improving the design flexibility.

[0033] 5. The power module adopts the Kelvin connection method, which can use the Kelvin resistance measurement method to improve the test accuracy during electrical performance testing and can withstand high-power and high-current test items. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of the external structure of a low-stress double-sided cooling power module provided by the present invention;

[0035] Figure 2 is an exploded view of a low-stress double-sided cooling power module provided by the present invention;

[0036] Figure 3 Schematic diagram of the top layer structure of a low-stress double-sided cooling power module provided by the present invention;

[0037] Figure 4 Schematic diagram of the structure of an inverted metal buffer pad in a low-stress double-sided cooling power module provided by the present invention;

[0038] Figure 5 Isometric view of the structure of an inverted metal buffer pad in a low-stress double-sided cooling power module provided by the present invention;

[0039] Figure 6 Cross-sectional view of the inverted metal buffer pad A - A' in a low-stress double-sided cooling power module provided by the present invention;

[0040] Figure 7 Cross-sectional view of the inverted metal buffer pad B - B' in a low-stress double-sided cooling power module provided by the present invention;

[0041] Figure 8 Schematic diagram of the bottom layer structure of a low-stress double-sided cooling power module provided by the present invention;

[0042] Figure 9 Schematic diagram of the structure of the first copper-clad ceramic substrate in a low-stress double-sided cooling power module provided by the present invention;

[0043] Figure 10 Schematic diagram of the structure of the second copper-clad ceramic substrate in a low-stress double-sided cooling power module provided by the present invention;

[0044] Figure 11 Schematic diagram of the pad structure of the power chip in a low-stress double-sided cooling power module provided by the present invention.

[0045] Figure 12 Schematic diagram of the drain pad structure of the power chip in a low-stress double-sided cooling power module provided by the present invention.

[0046] Figure 13 Flow chart of the manufacturing method of a low-stress double-sided cooling power module provided by the present invention.

[0047] Markings in the figure: 1-first copper-clad ceramic substrate; 11-NTC thermistor; 11-1-NTC thermistor welding area; 12-first substrate upper copper layer; 12-1-upper bridge drain power circuit area; 12-2-mid-end power circuit area; 12-3-upper bridge source power circuit area; 12-4-lower bridge source power circuit area; 13-first substrate ceramic layer; 14-first substrate lower copper layer; 2-second copper-clad ceramic substrate; 21-second substrate upper copper layer; 22-second substrate ceramic layer; 23-second substrate lower copper layer; 3-power chip; 31-upper bridge power chip; 31-1-upper bridge power chip connection area; 32-lower bridge power chip; 32-1 lower bridge power chip connection area; 33-secondary source control circuit area; 33-1-upper bridge secondary source control circuit area; 33-2 lower bridge secondary source control circuit area; 33-3-secondary source pad; 3 4-3-gate pad; 3-1-main power source pad; 3-2-drain pad; 34-gate control loop area; 34-1-upper bridge gate control loop area; 34-2-lower bridge gate control loop area; 35-bonding wire; 41-auxiliary support column connection layer; 41-1-lower bridge auxiliary support column connection area; 42-power device drain connection layer; 43-main power source connection layer; 44-pad top connection layer; 5-inverted metal buffer pad; 51-connection frame; 511-auxiliary support column; 512-quadrangular pyramid thermal conductive structure; 61-DC+ power terminal; 62-AC power terminal; 63-DC- power terminal; 7-control terminal; 71-NTC thermistor measurement terminal; 72-upper bridge source control terminal; 73-upper bridge gate control terminal; 74-lower bridge source control terminal; 75-lower bridge gate control terminal; 8-groove. DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0049] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0050] In the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, horizontal, vertical, etc.) are only used to explain the relative positional relationship, movement conditions, etc. between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0051] Due to reasons such as installation errors, the parallel relationship referred to in the embodiments of the present invention may actually be an approximate parallel relationship, and the vertical relationship may actually be an approximate vertical relationship.

[0052] Embodiment 1:

[0053] As Figures 1 to 5 shown, the present invention provides a low-stress double-sided cooling power module, which includes: a first copper-clad ceramic substrate 1 and a second copper-clad ceramic substrate 2 arranged opposite to each other. At least two power chips 3 are provided on the first copper-clad ceramic substrate 1. On both sides of each power chip 3, there is a C-shaped auxiliary support column connection layer 41; on the lower surface of the second copper-clad ceramic substrate 2, there is an inverted metal buffer pad 5 arranged opposite to each power chip 3; the inverted metal buffer pad 5 includes: a connection frame 51 with a groove. At a position corresponding to the auxiliary support column connection layer 41, the connection frame 51 is provided with an auxiliary support column 511 connected thereto. In the groove of the connection frame 51, there is a protruding quadrangular pyramid heat conduction structure 512. The bottom of the inverted quadrangular pyramid heat conduction structure 512 is connected to the power chip 3.

[0054] Specifically, by setting the inverted metal buffer pad 5 on the power chip 3, and connecting the inverted metal buffer pad 5 to the C-shaped auxiliary support column connection layers 41 on both sides of the power chip 3 through the integrally formed connection frame 51, the heat exchange area between the upper and lower substrates can be significantly increased, which helps to alleviate the problem of uneven heat dissipation capacity at the top and bottom of the power module. At the same time, the auxiliary support columns 511 on both sides of the connection frame 51 and both sides of the power chip 3 are used to support the upper and lower substrates. In practical applications, when the power module is subjected to extrusion or impact, the auxiliary support columns can share the external force acting on the chip, thereby protecting the fragile chip and its connection layer. The quadrangular pyramid heat conduction structure 512 located in the connection frame 51 and at a 45-degree angle to the connection frame 51 is in contact with the top of the power chip 3, and can conduct the heat of the power chip 3 to the outside through the quadrangular pyramid heat conduction structure 512 to accelerate the heat dissipation speed. Based on this, the inverted metal buffer pad 5 forms a new heat conduction path with the external space through the space between it and the power chip 3, effectively improving the heat dissipation capacity of the device and achieving a lower chip junction temperature than traditional double-sided cooling power modules.

[0055] Among them, the copper-clad ceramic substrate can be selected from a variety of materials, including but not limited to: AlN copper-clad ceramic substrate, Al2O3 copper-clad ceramic substrate, and Si3N4 copper-clad ceramic substrate. The power chips in this embodiment can be SiC MOSFET, Si IGBT, GTO, Si MOSFET, etc.

[0056] In the present invention, the power module further includes: a DC+ power terminal 61, an AC power terminal 62, and a DC- power terminal 63 located on one side of the power chip 3, and a plurality of control terminals located on the other side of the power chip 3. The DC+ power terminal 61 and the AC power terminal 62 are connected to the first copper-clad ceramic substrate 1, and the DC- power terminal 63 is connected to the second copper-clad ceramic substrate 2; one end of the control terminal is bent and the bent end is connected to the first copper-clad ceramic substrate 1.

[0057] As Figure 6 , 7 shown, between the first copper-clad ceramic substrate 1 and the power chip 3, between the power chip 3 and the frustum heat dissipation structure 512, and between the frustum heat dissipation structure 512 and the second copper-clad ceramic substrate 2 are connected through corresponding connection layers. Specifically, the first copper-clad ceramic substrate 1 and the power chip 3 are connected through a power device drain connection layer 42, the power chip 3 and the frustum heat dissipation structure 512 are connected through a main power source connection layer 43, and the frustum heat dissipation structure 512 and the second copper-clad ceramic substrate 2 are connected through a pad top connection layer 44.

[0058] The first copper-clad ceramic substrate 1 has a groove 8, and the auxiliary support post connection layer 41 and the power chip 3 are isolated by the groove 8. Specifically, when the inverted metal buffer pad 5 is connected to the power chip 3, the groove 8 on the first copper-clad ceramic substrate 1 can increase the space of the heat dissipation channel of the inverted metal buffer pad 5, thereby accelerating the heat dissipation speed of the power chip 3. In addition, the power chip 3 and the auxiliary support post connection layer 41 are electrically isolated through the groove 8, thereby avoiding the problem that the heat generated by the power chip 3 diffuses to the auxiliary support post connection layer 41, resulting in the failure of the auxiliary support post connection layer 41, and further improving the reliability of the connection between the inverted metal buffer pad 5 and the first copper-clad ceramic substrate 1.

[0059] The power chip 3 includes an upper bridge power chip 31 and a lower bridge power chip 32. On the top surface side of each power chip, there is a gate pad 34-3, two sub-source pads 33-3, and a main power source pad 3-1. On the back side is a drain pad 3-2; the gate pad 34-3 and the two sub-source pads 33-3 are respectively connected to the corresponding control terminals 7 through bonding wires 35.

[0060] The first copper-clad ceramic substrate 1 from top to bottom includes: a first upper copper layer 12 of the substrate, a first ceramic layer 13 of the substrate, and a first lower copper layer 14 of the substrate. The first upper copper layer 12 of the substrate includes: a drain power region corresponding to the power chip 3, a mid-power loop region 12-2 corresponding to the auxiliary support column connection layer 41, a sub-source control loop region 33, and a gate control loop region 34.

[0061] The second copper-clad ceramic substrate 2 from top to bottom includes: a second upper copper layer 21 of the substrate, a second ceramic layer 22 of the substrate, and a second lower copper layer 23 of the substrate. The top of each inverted metal buffer pad 5 is connected to the second lower copper layer 23.

[0062] In the present invention, the structure corresponding to the upper-bridge power chip 31 is the same as the structure corresponding to the lower-bridge chip. Therefore, for the convenience of understanding, the structure corresponding to the upper-bridge power chip 31 is taken as an example to describe the structure corresponding to the power chip.

[0063] As Figures 8 to 9 shown, the upper-bridge power chip 31 respectively corresponds to an upper-bridge drain power loop region 12-1, a mid-power loop region 12-2, an upper-bridge sub-source control loop region 33-1, an upper-bridge gate control loop region 34-1, and an upper-bridge auxiliary support column connection region; the control terminal corresponding to the upper-bridge sub-source control loop region 33-1 is an upper-bridge source control terminal 72, and the control terminal corresponding to the upper-bridge gate control loop region 34-1 is an upper-bridge gate control terminal 73. Similarly, the lower-bridge sub-source control loop region 33-2 of the lower-bridge power chip 32 is correspondingly connected to a lower-bridge source control terminal 74, the lower-bridge gate control loop region 34-2 is correspondingly connected to a lower-bridge gate control terminal 75, and the lower-bridge power chip 32 is also correspondingly provided with a lower-bridge auxiliary support column connection region 41-1. Upper-bridge auxiliary support column connection layers are correspondingly arranged on both sides of the upper bridge.

[0064] The first upper copper layer 12 of the substrate further includes an NTC thermistor welding region 11-1 for welding the NTC thermistor 11, and an NTC thermistor measurement terminal 71 is connected to the electrode corresponding region of the NTC thermistor 11.

[0065] Specifically, the NTC thermistor welding region 11-1 is arranged between the control terminal welding regions corresponding to the upper-bridge power chip 31 and the lower-bridge power chip 32. After the NTC thermistor 11 is welded to the NTC thermistor welding region 11-1, the two electrodes of the NTC thermistor 11 are led out through the NTC thermistor measurement terminal 71 for measurement. Among them, the control terminal 7 and the NTC thermistor measurement terminal 71 in the present invention are similar in structure, are concentrated on one side of the power module and perpendicular to the substrate, and have a simple structure layout and are convenient to use.

[0066] Embodiment 2:

[0067] As Figure 13As shown in the figure, the present invention also provides a manufacturing method of a low-stress double-sided cooling power module. For the convenience of understanding, in this embodiment, the power chip 3 selects SiC MOSFET as an example to complete the manufacturing of the power module, which includes the following steps:

[0068] (a) Chip sintering: Pre-prepare the sintering material in the upper-bridge power chip connection area 31-1 and the lower-bridge power chip connection area 32-1 of the first copper-clad ceramic substrate 1; after preheating, pre-sintering, and sintering in sequence, form a power device drain connection layer 42 connecting the power chip and the first copper-clad ceramic substrate, and interconnect the upper and lower-bridge power chips with the first copper-clad ceramic substrate 1 through the power device drain connection layer.

[0069] Specifically, when pre-preparing the sintering material, the steel mesh printing method can be used to apply the sintered silver paste on the upper-bridge SiC MOSFET connection area 31-1 and the lower-bridge SiC MOSFET connection area 32-1 of the first copper-clad ceramic substrate 1; or through the silver film transfer method, directly pre-prepare the sintered silver film on the drain pad 3-2 of the SiC MOSFET. Finally, form a power device drain connection layer 42 connecting the SiC MOSFET and the first copper-clad ceramic substrate 1 through sintering.

[0070] (b) Wire bonding: Connect the corresponding gate pads and sub-source pads of the upper-bridge power chip 31 and the lower-bridge power chip 32 to the corresponding control circuit areas through bonding wires 35 respectively to complete the corresponding electrical connections.

[0071] Specifically, the electrical connection between the gate pad of the upper bridge and the upper-bridge gate control circuit area 34-1 is realized through the gate bonding wire 35, and the two sub-source pads 33-3 of the upper-bridge SiC MOSFET and the corresponding upper-bridge sub-source control circuit area 33-1 are electrically connected through two upper-bridge source bonding wires 35. The connection mode of the lower bridge is the same as that of the upper bridge.

[0072] (c) Interconnect the inverted metal buffer pads 5 with the upper and lower-bridge power chips and the first copper-clad ceramic substrate 1: Pre-prepare the sintering material on the bottom surface of the quadrangular pyramid heat conduction structure 512 and the bottom surface of the auxiliary support column 511; after preheating, pre-sintering, and sintering in sequence, form an auxiliary support column connection layer 41 and a main power source connection layer 43.

[0073] Specifically, through the method of silver film transfer printing, the sintered silver film is directly prefabricated on the bottom surface of the frustum-shaped heat conduction structure 512 and the bottom surface of the auxiliary support column 511, and then through preheating, pre-sintering, and sintering in sequence, the auxiliary support column connection layer 41 and the main power source electrode connection layer 43 are formed. In addition, the screen printing method can also be adopted to directly print the sintered silver paste similar to the shape of the bottom surface of the auxiliary support column 511 on the first copper-clad ceramic substrate 1, and then through preheating, pre-sintering, and sintering in sequence, the auxiliary support column connection layer 41 is formed. It should be noted that the descriptions of directions such as the bottom surface and the top of the frustum-shaped heat conduction structure 512 in the present invention are all described in the state when the inverted metal buffer pad 5 is buckled on the power chip. Among them, the material of the inverted metal buffer pad 5 includes but is not limited to: copper, molybdenum, molybdenum-copper, kovar alloy. The SiC MOSFET is welded to the main power source electrode pad 3-1.

[0074] During the manufacturing process of the low-stress double-sided power module, the connection step of the inverted metal buffer pad 5 with the upper and lower bridge SiC MOSFETs and the first copper-clad ceramic substrate 1 should be placed before the welding of the components. The integral molding structure of the inverted metal buffer pad 5 can effectively suppress the warping problem of the first copper-clad ceramic substrate 1 after experiencing high and low temperature cycles during subsequent sintering or reflow soldering processes, which helps to improve the success rate when the upper and lower substrates are sintered with the mold closed.

[0075] (d) Component welding: Weld each component by means of alloy solder welding or ultrasonic terminal welding.

[0076] Specifically, through alloy solder welding or ultrasonic terminal welding, the DC+ power terminal 61 is connected to the upper bridge drain power circuit area 12-1, the AC power terminal 62 is connected to the middle power circuit area 12-2, the DC- power terminal 63 is connected to the lower bridge source power circuit area 12-4, the upper bridge source control terminal 72 is respectively connected to the upper bridge sub-source control circuit area 33-1, the upper bridge gate control terminal 73 is connected to the upper bridge gate control circuit area 34-1, the NTC thermistor 11 and the NTC thermistor measurement terminal 71 are connected to the NTC thermistor welding area 11-1, and the lower bridge source control terminal 74 is respectively connected to the lower bridge sub-source control circuit area 33-2, and the lower bridge gate control terminal 75 is connected to the lower bridge gate control circuit area 34-2. In addition, the two electrodes of the NTC thermistor 11 can be electrically connected to the NTC thermistor welding area 11-1 by means of brazing solder welding. As Figures 9 to 12 shown, it is the connection area corresponding to the power chip.

[0077] (e) Clamping and sintering the first copper-clad ceramic substrate and the second copper-clad ceramic substrate: Pre-prepare sintering materials on the upper bridge source power loop area 12-3 and the lower bridge source power loop area 12-4, which are of the same size as the top surface of the inverted metal buffer pad 5. Clamp the first copper-clad ceramic substrate and the second copper-clad ceramic substrate together, align the printed sintering materials with the top surface of the inverted metal buffer pad 5, and go through preheating, pre-sintering, and sintering in sequence to complete the connection between the substrates.

[0078] Specifically, by means of stencil printing, print sintering silver paste with a size similar to the top surface of the inverted metal buffer pad 5 on the corresponding areas of the upper bridge source power loop area 12-3 and the lower bridge source power loop area 12-4. Clamp the first copper-clad ceramic substrate 1 and the second copper-clad ceramic substrate 2 together, align the printed sintering silver paste with the top surface of the inverted metal buffer pad 5, and then go through preheating, pre-sintering, and sintering in sequence to complete the physical and electrical connection between the substrates.

[0079] In this embodiment, the thickness of the sintering silver paste used is 10-100 microns. If pressure sintering is adopted for the sintering method, the preheating conditions for each step are: preheating temperature 60-150°C, preheating time 3-10 minutes, the pre-sintering conditions are: sintering temperature 100-150°C, sintering pressure 1-5 MPa, sintering time 3-5 minutes, and the sintering conditions are: sintering temperature 180-280°C, sintering pressure 10-20 MPa, sintering time 3-5 minutes. If non-pressure sintering is adopted, the preheating conditions for each step are: preheating temperature 60-150°C, preheating time 3-10 minutes, the pre-sintering conditions are: sintering temperature 100-150°C, sintering time 3-5 minutes, and the sintering conditions are: sintering temperature 180-280°C, sintering time 30-60 minutes. Among them, according to different sintering materials, the temperature, pressure, and time in the preheating, pre-sintering, and sintering processes can be adjusted to be less than or greater than the above-described indicators.

[0080] Based on the double-sided cooling power module obtained by the foregoing manufacturing method, its structure is compact, and its external dimensions are 3.2 cm × 2.5 cm × 0.4 cm. This module can be adapted to SiC MOSFETs of various sizes for packaging, and has flexible adjustability in terms of structural dimensions, so that it can be further optimized and upgraded to a multi-chip parallel module on this basis.

[0081] In other embodiments, the connection materials of all connection layers can be selected from one or more of alloy solder, sintering silver paste, sintering copper paste, and copper-silver mixed sintering paste.

[0082] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A low stress double-sided cooling power module, characterized in that: include: A first copper-clad ceramic substrate and a second copper-clad ceramic substrate are arranged opposite to each other, wherein at least two power chips are arranged on the first copper-clad ceramic substrate, and C-shaped auxiliary support column connection layers are arranged on both sides of each power chip; The lower surface of the second copper-clad ceramic substrate is provided with an inverted metal buffer block arranged opposite to each power chip; The inverted metal buffer pad includes: a connection frame with a groove, an auxiliary support column connected to the connection frame is provided at a position corresponding to the auxiliary support column connection layer, a raised quadrangular pyramid heat-conducting structure is provided in the groove of the connection frame, and the bottom of the inverted quadrangular pyramid heat-conducting structure is connected to the power chip.

2. The low stress double-sided cooling power module according to claim 1, characterized in that: The power module further includes: a DC+ power terminal, an AC power terminal, a DC- power terminal located on one side of the power chip and a plurality of control terminals located on the other side of the power chip, wherein the DC+ power terminal and the AC power terminal are connected to the first copper-clad ceramic substrate, and the DC- power terminal is connected to the second copper-clad ceramic substrate; one end of the control terminal is bent and the bent end is connected to the first copper-clad ceramic substrate.

3. The low stress double-sided cooling power module according to claim 1, characterized in that: The first copper-clad ceramic substrate and the power chip, the power chip and the quadrangular pyramid heat-conducting structure, and the quadrangular pyramid heat-conducting structure and the second copper-clad ceramic substrate are connected via corresponding connection layers.

4. The low stress double-sided cooling power module according to claim 3, characterized in that: The power chip includes an upper bridge power chip and a lower bridge power chip. A gate pad, two auxiliary source pads, and a main power source pad are distributed on the top side of each power chip, and a drain pad is distributed on the back side. The gate pad and the two auxiliary source pads are connected to corresponding control terminals through bonding wires respectively.

5. The low stress double-sided cooling power module according to claim 1, characterized in that: The first copper-clad ceramic substrate includes from top to bottom: a first substrate upper copper layer, a first substrate ceramic layer and a first substrate lower copper layer. The first substrate upper copper layer includes: a drain power circuit area corresponding to the power chip, a mid-end power circuit area corresponding to the auxiliary support column connection layer, a secondary source control circuit area and a gate control circuit area.

6. The low stress double-sided cooling power module according to claim 1, characterized in that: The copper layer on the first substrate further includes an NTC thermistor welding area for welding an NTC thermistor, and an NTC thermistor measuring terminal is connected to an electrode corresponding area of ​​the NTC thermistor.

7. The low stress double-sided cooling power module according to claim 1, characterized in that: The second copper-clad ceramic substrate comprises from top to bottom: a second substrate upper copper layer, a second substrate ceramic layer and a second substrate lower copper layer, and the top of each inverted metal buffer pad is connected to the second substrate lower copper layer.

8. A method for manufacturing a low-stress double-sided cooling power module, characterized in that: The following steps are involved: (a) Chip sintering: prefabricate sintering materials in the upper bridge power chip connection area and the lower bridge power chip connection area of ​​the first copper-clad ceramic substrate; after preheating, pre-sintering and sintering, form a power chip drain connection layer connecting the power chip and the first copper-clad ceramic substrate, and interconnect the upper and lower bridge power chips and the first copper-clad ceramic substrate through the power chip drain connection layer; (b) Wire bonding: Connect the gate pads and the auxiliary source pads of the upper bridge power chip and the lower bridge power chip to the corresponding control circuit area through bonding wires to complete the corresponding electrical connection; (c) interconnecting the inverted metal buffer block with the upper and lower bridge power chips and the first copper-clad ceramic substrate: prefabricating sintered materials on the bottom surface of the quadrangular pyramid heat-conducting structure and the bottom surface of the auxiliary support column; forming the auxiliary support column connection layer and the main power source connection layer after preheating, pre-sintering and sintering in sequence; (d) Component welding: welding of components by alloy solder welding or ultrasonic terminal welding; (e) The first copper-clad ceramic substrate and the second copper-clad ceramic substrate are molded together and sintered: a sintering material having the same size as the top surface of the inverted metal buffer pad is prefabricated in the upper bridge source power circuit area and the lower bridge source power circuit area, the first copper-clad ceramic substrate and the second copper-clad ceramic substrate are molded together, and the printed sintering material is aligned with the top surface of the inverted metal buffer pad. Preheating, pre-sintering, and sintering are performed in sequence to complete the physical and electrical connection between the substrates.

9. The method for manufacturing a low stress double-sided cooling power module according to claim 8, characterized in that: During the sintering process, the sintering process is steel screen printing or silver film transfer; if steel screen printing is used, the thickness of the sintered silver paste is 10 to 100 microns; if silver film transfer is used, the sintered silver film is directly prefabricated in the sintering area.

10. The method for manufacturing a low stress double-sided cooling power module according to claim 9, characterized in that: If the sintering process adopts pressure sintering, the preheating conditions of each step are: preheating temperature 60-150°C, preheating time 3-10 minutes, pre-sintering conditions are: sintering temperature 100-150°C, sintering pressure 1-5MPa, sintering time 3-5 minutes, sintering conditions are: sintering temperature 180-280°C, sintering pressure 10-20MPa, sintering time 3-5 minutes; If the sintering process adopts pressureless sintering, the preheating conditions of each step are: preheating temperature 60-150°C, preheating time 3-10 minutes, pre-sintering conditions are: sintering temperature 100-150°C, sintering time 3-5 minutes, and sintering conditions are: sintering temperature 180-280°C, sintering time 30-60 minutes.

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