Power module with angled metal spacing units

Abstract

The present application discloses a power module with a guide angle metal spacing unit. Between a high-power circuit component and an upper substrate, a metal spacing unit with a fixed height and a guide angle forms a space with the same height as the metal spacing unit, and exposes a control substrate for wire bonding process and a gap for glue filling process. The space can accommodate the working tools of wire bonding and glue filling processes, improve the tool operation angle, make the wire bonding and glue filling processes more efficient, and increase the yield of the production line.

Description

Technical Field

[0001] This invention relates to a power module, and more particularly to a high thermal conductivity power module with beveled metal spacer units. Background Technology

[0002] With global warming becoming increasingly severe and environmental awareness rising, governments worldwide have introduced numerous green energy subsidy policies for transportation in recent years. This has led to a growing number of consumers choosing electric vehicles to replace traditional fossil fuel-powered vehicles, such as electric cars replacing traditional cars and electric locomotives replacing two-stroke locomotives. These electric vehicles rely on high-power electric motors for power, resulting in a growing market demand for high-power power modules. This has prompted major suppliers to invest heavily in research and development to improve production line yield and output. Furthermore, the continuous innovation of light source devices such as high-brightness LEDs or LEDs has led to a sustained increase in the energy consumption of power supply devices, requiring high-power and high-heat-dissipation power modules to effectively support them.

[0003] High-power power modules inevitably convert a portion of their energy into heat due to their high energy consumption. As electronic devices become increasingly miniaturized, high-power components generate even more heat within smaller spaces. Therefore, removing excess heat and maintaining operational stability are crucial. To address this heat dissipation issue, a commonly used solution is to use ceramic materials as the insulating layer of the circuit board. Ceramic substrates, as a type of circuit board, possess a coefficient of thermal expansion close to that of semiconductors and high heat resistance. The most common ceramic material is alumina (Al₂O₃) used in direct-bonded copper (DBC) substrates. Alumina has a thermal conductivity of up to 35 W / mK in a single-crystal structure and 20 to 27 W / mK in a polycrystalline structure. Other common ceramic substrate materials include aluminum nitride (AlN), beryllium oxide (BeO), and silicon carbide (SiC). Ceramic substrates have thus become the preferred choice for high-power power module substrates.

[0004] In the selection of high-power electronic components for power modules, besides silicon, which is currently the most commonly used material in electronic components, high-power components made of silicon carbide (SiC) and gallium nitride (GaN) are gradually gaining a foothold in the market. These components have higher efficiency and operating temperature, which are extremely important performance indicators, especially in power modules that conduct high currents. Compared with silicon, SiC has 10 times the insulation breakdown electric field strength, 3 times the band gap width, and 3 times the thermal conductivity. This allows the aforementioned electronic components to be fabricated with extremely thin drift layers to produce components with very high breakdown voltages (above 600V), and the resistance per unit area can be reduced to 1 / 300 of that of silicon at the same breakdown voltage. SiC power components can operate at higher temperatures, and their thermal conductivity is three times that of silicon, which helps reduce heat dissipation requirements. Therefore, SiC high-power electronic components are the development trend for power modules.

[0005] like Figure 1 As shown, the high-power electronic component, exemplified by the power module chip 90, needs to switch between two states: conducting high current and disconnecting. To avoid direct short circuits due to high current, a pair of input / output electrodes 92 and 94 are typically distributed on the top and bottom sides of a SiC substrate. The top and bottom input / output electrodes 92 and 94 are electrically and thermally connected to two corresponding ceramic substrates 82 and 84, respectively, forming a sandwich-like structure between the power module chip 90 and the ceramic substrates 82 and 84. The high-power electronic component is thus sandwiched between the ceramic substrates, especially since the distance between the two ceramic substrates 82 and 84 in the height direction is only a few hundred micrometers, which is extremely small. Furthermore, to control the conduction or disconnection of this electronic component, a control electrode 96 is provided, such as... Figure 2 , 3 As shown, because the surface space of high-power electronic components is limited, only a few tens of micrometers of insulation gap can often be maintained between the control electrode and the input / output electrode.

[0006] The control electrode 96 of the power module chip needs to receive control signals and effectively control the flow and disconnection of large currents. Therefore, the control electrode 96 and the input / output electrodes 92 through which current flows when conducting must not be connected, and there is only a gap 98 of tens of micrometers between them. However, it is necessary to ensure that when large current flows between the two input / output electrodes, it will not flow through the control electrode 96 to cause a short circuit, so as to protect the control electrode 96 from overheating and melting. The gap between the control electrode 96 and the pads of the input / output electrodes 92 and 94 must also maintain good insulation so that no arcing will occur due to instantaneous current changes when connecting or disconnecting. One common practice is to isolate the electrodes by potting a non-conductive viscous polymer material, which remains insulating after curing. As for the control electrode 96, it is connected to the external control circuit (not shown in the figure) through wire bonding.

[0007] To accommodate the rising space of the wire bonding metal wires after the first soldering and to enable more precise potting to prevent overflow, if the gap between the ceramic substrates is too small, it will hinder the potting and wire bonding processes, or force them to be performed at an angle, resulting in longer processing time or lower yield. The objective of this invention is to ensure that high-power electronic components can conduct heat dissipation between the two ceramic substrates as expected, while simultaneously improving the operating angle and yield of the potting and wire bonding processes in narrow gaps. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the prior art, according to the embodiments of the present invention, it is desirable to provide a power module with a chamfered metal spacer unit, which aims to achieve the following objectives: (1) while maintaining good heat dissipation, it can improve the operating angle and yield of the potting process in the narrow gap between the pads; (2) while maintaining good heat dissipation, it can ensure the required operating height of the first solder joint in the wire bonding process and improve the operating angle and yield of the wire bonding process; (3) it can eliminate the right-angle protrusion at the interface between the metal spacer unit and the ceramic substrate, thereby greatly alleviating the stress concentration problem and avoiding delamination between the interfaces at the corners.

[0009] According to an embodiment, the present invention provides a power module with a chamfered metal spacer unit, comprising:

[0010] A first substrate includes at least one mounting ceramic substrate portion having a predetermined length and width dimensions, and the first substrate has a mounting surface and a mounting circuit layer formed on the mounting surface.

[0011] At least one high-power circuit component has a pair of input and output electrodes located on a top surface and a bottom surface, respectively, and a control electrode located on the top surface. The high-power circuit component is electrically connected to the mounting circuit layer of the mounting ceramic substrate via the input and output electrodes on the bottom surface, and an insulating gap is formed between the input and output electrodes located on the top surface and the control electrode.

[0012] The number corresponds to the metal spacer units of the aforementioned high-power circuit components. Each of the aforementioned metal spacer units is thermally and electrically disposed on the top surface input / output electrodes of the corresponding high-power circuit components. The aforementioned metal spacer units have a predetermined height, and each of the aforementioned metal spacer units forms a chamfer at each corner, thereby forming a projection in the direction of the aforementioned height that does not exceed the top surface input / output electrodes; and

[0013] A second substrate parallel to the first substrate and including at least one spacer ceramic substrate portion having a predetermined length and width dimension, the second substrate having a corresponding surface and a spacer circuit layer formed on the corresponding surface, the second substrate being electrically and thermally bonded to the side opposite to the high-power circuit component of the metal spacer unit through the aforementioned spacer circuit layer of the aforementioned spacer ceramic substrate portion, such that a gap corresponding to the predetermined height is formed between the control electrode of the high-power circuit component and the second substrate, and the aforementioned insulating gap is exposed.

[0014] Compared to existing technologies, this invention installs metal spacer units between the second substrate and the top surface of the high-power circuit components for each component. These metal spacer units have a predetermined height and beveled at each corner, thereby creating a projection in the direction of the aforementioned height that does not exceed the projection of the top surface entry / exit electrodes. This creates a gap between the control electrodes of the circuit components and the second substrate that can accommodate the first bonding space of the wire bonding process and exposes the aforementioned insulation gap. This allows for smoother potting, avoids overflow or insufficient bonding, improves yield, and makes the potting and wire bonding process less restrictive in terms of operating angle. In particular, the beveled corners of the metal spacer units effectively reduce stress concentration during repeated thermal expansion and contraction, preventing contact peeling.

[0015] When this invention adds a metal spacer unit to the top surface of the power module chip, thereby increasing the height difference between the ceramic substrate and the power chip module and exposing the insulation gap, the significant difference in thermal expansion coefficients between the metal spacer unit and the power module chip means that both during installation and operation, the chip will be exposed to temperatures exceeding 200 degrees Celsius. During repeated temperature fluctuations, the interface connecting the metal spacer unit and the power module chip will peel off from the corners due to stress concentration. To avoid this problem, this invention further forms chamfered corners at the corners of the metal spacer unit to prevent stress concentration and peeling caused by sharp, protruding right angles. Attached Figure Description

[0016] Figure 1 This is a 3D schematic diagram of a common high-power module.

[0017] Figure 2 This is a side view diagram of a common high-power module.

[0018] Figure 3 This is a front view schematic diagram of a common high-power module.

[0019] Figure 4 This is a perspective view of the first preferred embodiment of the power module of the present invention after the second substrate has been removed (illustrating the relative structural relationship of the metal spacer unit exposing the insulation gap).

[0020] Figure 5 This is a perspective view of a first preferred embodiment of the power module of the present invention.

[0021] Figure 6 This is a front view schematic diagram of a first preferred embodiment of the power module of the present invention.

[0022] Figure 7 This is a side view of a first preferred embodiment of the power module of the present invention.

[0023] Figure 8 This is a perspective view of a second preferred embodiment of the power module of the present invention.

[0024] Figure 9 This is a side view schematic diagram of a second preferred embodiment of the power module of the present invention.

[0025] Wherein: 1, 1' are the first substrate; 11, 11' are the mounting surfaces; 12, 12' are the mounting circuit layers; 13' is the first dielectric material layer; 14, 14' are the mounting ceramic substrate portions; 2, 2' are high-power circuit components; 21, 21' are the bottom surfaces; 211, 211', 221, 92, 94 are input / output electrodes; 22 is the top surface; 222, 222', 96 are control electrodes; 223, 98 are insulation gaps; 224' is wire bonding; 3, 3' are metal spacer units; 4, 4' are the second substrate; 41, 41' are the corresponding surfaces; 42, 42' are the spacer circuit layers; 43' is the second dielectric material layer; 44, 44' are the spacer ceramic substrate portions; 82, 84 are ceramic substrates; 90 is the power module chip. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments should be understood as illustrative only and not as limiting the scope of protection of the present invention. After reading the description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

[0027] First preferred embodiment

[0028] like Figure 4-7As shown, in a power module with beveled metal spacer units provided in the first preferred embodiment of the present invention, the first substrate 1 includes a high thermal conductivity ceramic substrate, such as aluminum nitride, which is defined here as a ceramic substrate mounting portion 14, and a circuit mounting layer 12 above the ceramic substrate mounting portion 14. For ease of explanation, the top surface of the ceramic substrate mounting portion 14 where the circuit mounting layer 12 is disposed is defined here as the mounting surface 11. The circuit mounting layer 12 is used to mount high-power circuit components 2 with operating currents of tens of amperes or more, and the direction of the thickness of the first substrate 1 is defined as the height direction.

[0029] In this embodiment, copper metal layers are formed over both the mounting surface 11 and the bottom surface opposite to the mounting surface 11 using, for example, sputtering. Then, a portion of the non-conductive areas are removed from the mounting surface 11 using photolithography to form the mounting circuit layer 12. Both of these layers can be further thickened by electroplating or similar methods as needed. Of course, those skilled in the art can also use similar methods other than sputtering to form the circuit layer.

[0030] Next, the input / output electrodes 211 of the bottom surface 21 of at least one high-power circuit component 2 are securely soldered to the mounting circuit layer 12. In this embodiment, the high-power circuit component 2 is exemplified as an STMicroelectronics automotive-grade 1200V SiC power chip. The high-power circuit component 2 includes a bottom surface 21, input / output electrodes 211 soldered to the mounting circuit layer 12 on the bottom surface 21, a top surface 22, input / output electrodes 221 located on the top surface 22, and a control electrode 222 located on the top surface 22 and separated from the input / output electrodes 221. An insulating gap 223 is formed between the input / output electrodes 221 and the control electrode 222. Since the current of such high-power circuit components can reach hundreds of amperes, even a slight impedance in the transmission path will cause a great deal of heat. Therefore, the soldering in this embodiment is achieved by applying pressure and thermal melting.

[0031] Next, a metal spacer unit 3, exemplified by copper, is soldered onto the input / output electrodes 221 of the top surface 22 of the high-power circuit component 2 after undergoing a nano-silver sintering process. This ensures good electrical and thermal conductivity while preventing the projection of the metal spacer unit 3 in the height direction from exceeding the input / output electrodes 221 of the top surface 22 of the high-power circuit component 2. This creates a predetermined gap of 400 to 1000 μm above the control electrode 222 and the insulation gap 223 on the top surface 22 of the high-power circuit component 2, ensuring that the control electrode 222 and the insulation gap 223, both located on the top surface 22, are exposed. This allows the control electrode 222 to be wired to an external control circuit. In particular, in this embodiment, each corner of the metal spacer unit 3 is formed with a rounded bevel, such as an arc, so that the stress between the joints caused by thermal expansion and cooling contraction can be effectively dispersed by the rounded bevel, whether it is the heating during welding or the temperature rise caused by the large current passing through during operation, or the repeated temperature difference of temperature drop. This avoids the joint peeling caused by thermal stress.

[0032] The second substrate 4 also includes a ceramic substrate corresponding to the ceramic substrate mounting portion 14, defined here as the spacer ceramic substrate portion 44, and a spacer circuit layer 42 of, for example, copper metal is formed on the corresponding surface 41 of the corresponding metal spacer unit 3. The spacer circuit layer 42 is soldered to the metal spacer unit 3. Therefore, in the height direction, a gap equivalent to the height of the metal spacer unit 3, for example, 400 to 1000 μm, is formed between the spacer circuit layer 42, the control electrode 222 of the top surface 22 of the high-power circuit component 2, and the insulating gap 223. Since the gap is at least 400 μm high, which is greater than the aforementioned wire diameter of 200-300 μm, it can be ensured that the wires previously connected by wire bonding will not be compressed and damaged. On the other hand, a non-conductive viscous polymer material is then poured into the insulating gap 223 and kept insulating after curing, thereby isolating the two electrodes. This can also greatly improve the problem in the prior art where the gap of the potting resin is only a closed narrow channel, making it difficult to ensure that the insulating resin material can fill the gap, thus making it impossible to ensure the insulation capability of the manufactured product.

[0033] Even after the second substrate 4 is installed, and the control electrode 222 is then wire-connected, the high-power circuit components 2 and the second substrate 4 are pulled apart in the height direction by the metal spacer unit 3, allowing the wire bonding operation to be completed smoothly. Therefore, the disclosure of this invention enables the wire bonding and potting processes to be executed more efficiently, not only improving manufacturing yield but also simultaneously increasing production efficiency, significantly reducing the assembly cost of high-power circuit components, and enhancing market competitiveness.

[0034] Second preferred embodiment

[0035] like Figure 8-9As shown, in the power module provided by the second preferred embodiment of the present invention, the parts that are the same as those in the previous preferred embodiment will not be described again here, and similar components will also use similar names and reference numerals. Only the differences will be described. This embodiment is a power module that uses multiple high-power circuit components 2' connected in parallel, such as the power supply for electric vehicles. The total current may be as high as hundreds of amperes, so multiple high-power circuit components 2' are required. The first substrate 1' is mainly a circuit board made of dielectric material to achieve thermal and electrical separation. The circuit at the dielectric material circuit board can be made more complex by using a multilayer board design. However, at the corresponding high-power circuit components 2', a plurality of corresponding through holes are formed in the first dielectric material layer 13' for mounting the ceramic substrate part 14' to be embedded therein. Since the upper surfaces of the first dielectric material layer 13' and the mounting ceramic substrate part 14' are flush, it is referred to here as the mounting surface 11', and a mounting circuit layer 12' is formed on the mounting surface 11', thereby forming an integrated circuit board with thermal and electrical separation.

[0036] Next, as described above, the bottom surface 21' and input / output electrodes 211' of the three high-power circuit components 2' in the figure are respectively soldered onto the mounting circuit layer 12', and the projection range of the high-power circuit components 2' in the height direction is within the range of the mounting ceramic substrate portion 14'.

[0037] Similarly, in this embodiment, the second substrate 4' also has a spacer ceramic substrate portion 44' embedded in the second dielectric material layer 43', and a corresponding spacer circuit layer 42' corresponding to the metal spacer unit 3' is formed on the flush corresponding surface 41', thereby soldering the spacer ceramic substrate portion 44' to the metal spacer unit 3' via the spacer circuit layer 42'.

[0038] To avoid cracks caused by thermal expansion and contraction due to the difference in thermal conductivity between the metal spacer unit 3', the spacer ceramic substrate portion 44', and the high-power circuit component 2', the side surface of the metal spacer unit 3' in this embodiment is recessed relative to the corresponding side surface of the high-power circuit component 2', so that there is a space for expansion and contraction between the two. In particular, the corners of the metal spacer unit 3' are formed with arc-shaped chamfers to buffer stress deformation during thermal expansion and contraction.

[0039] Since both the first substrate and the second substrate in the power module of this embodiment are ceramic substrates embedded in dielectric materials with thermoelectric separation, the better thermal conductivity of ceramics can be used to conduct the heat generated by the high-power circuit components to heat dissipation fins that are thermally connected to the ceramic substrate, for example, in the high-heat-generating parts corresponding to the high-power circuit components. However, the entire module can use multilayer boards in the dielectric material layer and additionally set more complex control circuits. Through the wires 224' electrically connected to the control electrode 222', the circuit is connected to the first dielectric material layer 13', making the control and operation more versatile and able to meet the needs of various situations.

[0040] In summary, this invention forms a space with the same height as the metal spacer unit between high-power circuit components and the second substrate, using a metal spacer unit of fixed height and chamfered angles. This space exposes a control substrate for wire bonding and a gap for potting. This space can accommodate the tools used for wire bonding and potting, improve the operating angle of the tools, and enable more efficient execution of the wire bonding and potting processes, effectively improving production line yield and output efficiency; thus effectively achieving the aforementioned objectives of this invention.

Claims

1. A power module with beveled metal spacer units, characterized in that, include: A first substrate includes at least one mounting ceramic substrate portion having a predetermined length and width dimensions, and the first substrate has a mounting surface and a mounting circuit layer formed on the mounting surface. At least one high-power circuit component has a pair of input and output electrodes located on a top surface and a bottom surface, respectively, and a control electrode located on the top surface. The high-power circuit component is electrically connected to the mounting circuit layer of the mounting ceramic substrate via the input and output electrodes on the bottom surface, and an insulating gap is formed between the input and output electrodes located on the top surface and the control electrode. The number corresponds to the metal spacer units of the aforementioned high-power circuit components. Each of the aforementioned metal spacer units is thermally and electrically disposed on the top surface input / output electrodes of the corresponding high-power circuit components. The aforementioned metal spacer units have a predetermined height, and each of the aforementioned metal spacer units forms a chamfer at each corner, thereby forming a projection in the direction of the aforementioned height that does not exceed the top surface input / output electrodes; and A second substrate parallel to the first substrate and including at least one spacer ceramic substrate portion having a predetermined length and width dimension, the second substrate having a corresponding surface and a spacer circuit layer formed on the corresponding surface, the second substrate being electrically and thermally bonded to the metal spacer unit opposite to the high-power circuit component through the aforementioned spacer circuit layer of the aforementioned spacer ceramic substrate portion, such that a gap corresponding to the predetermined height is formed between the control electrode of the high-power circuit component and the second substrate and the aforementioned insulating gap is exposed.

2. The power module with chamfered metal spacer unit as described in claim 1, characterized in that, It further includes at least one heat dissipation fin that is thermally mounted on the mounting ceramic substrate portion and / or the spacer ceramic substrate portion in a direction away from the aforementioned high-power circuit components.

3. The power module with chamfered metal spacer unit as described in claim 1, characterized in that, The aforementioned metal spacer unit is made of copper.

4. The power module with chamfered metal spacer unit as described in claim 3, characterized in that, The surface of the aforementioned metal spacer unit is plated with silver.

5. The power module with chamfered metal spacer unit as described in claim 1, characterized in that, The aforementioned high-power circuit component is a power management integrated circuit.

6. The power module with chamfered metal spacer unit as described in claim 1, characterized in that, The first substrate mentioned above is a circuit board with an embedded ceramic substrate.

7. The power module with chamfered metal spacer unit as described in claim 1, characterized in that, The second substrate mentioned above is a circuit board with an embedded ceramic substrate.

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