A dual-sided cooling power module in orthogonal stack and method of manufacturing the same

Abstract

The application discloses a kind of orthogonal stacked double-sided cooling power module and preparation method thereof, including decoupling capacitor, copper clad ceramic substrate, power chip and metal pad;The metal pad and power chip are connected by layer-by-layer stacking in the mode of metal pad-power chip-metal pad to form a series chip set, the copper clad ceramic substrate is connected with the two sides of metal pad in series chip set, and it is perpendicular to power chip.The synergistic effect of orthogonal stacked packaging and double copper pad double-sided cooling in the application optimizes the electrical and thermal performance of the cooling power module, significantly reduces the parasitic inductance of the power module, and significantly improves the transient overcurrent support capability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor power device technology, specifically to an orthogonally stacked double-sided cooled power module and its fabrication method. Background Technology

[0002] Power electronic devices are mainly used in power electronic systems, including power converters, inverters, and DC-DC converters, for the conversion and regulation of electrical energy. Power electronic devices play a crucial role in energy conversion and energy conservation. Silicon carbide power modules, with their advantages of high temperature resistance and high stability under high-temperature environments, have become a focus of research.

[0003] With the increasing power consumption of silicon carbide power modules, heat dissipation has become a crucial factor affecting their long-term stable operation. Some existing technologies employ power modules with double-sided heat dissipation, particularly in the field of high-power power transmission and conversion, applied in areas such as power systems, automobiles, and electronic equipment.

[0004] For example, CN117497497A discloses a liquid-cooled heat dissipation packaging structure for a power module, including a DBC ceramic substrate; a power chip; an inner copper layer forming an inner cooling channel flowing through the power chip; an outer copper layer forming an outer cooling channel; a coolant flowing in the inner and outer cooling channels; and a lead wire, one end connected to the power chip, and the other end led out through the inner copper layer and the DBC ceramic substrate. The DBC ceramic substrate, inner copper layer, power chip, and outer copper layer are stacked and connected as a whole along the thickness direction. This effectively improves heat dissipation efficiency, reduces the temperature difference between different surfaces, and enhances the operational reliability of the power chip. Compared with existing double-sided water-cooled heat dissipation structures, the outer copper layer can directly form the outer surface of the packaging structure.

[0005] CN120319736A discloses a multi-chip stacked double-sided heat-dissipating silicon carbide power module. This power module includes a first DBC substrate and a second DBC substrate, each sequentially disposed with an upper copper pattern layer, an aluminum nitride ceramic layer, and a lower conductive copper layer; a negative DC terminal; an AC terminal; and a positive DC terminal. The upper copper pattern layers of the first and second DBC substrates are arranged opposite each other, and multiple SiC chips are disposed on each upper copper pattern layer. By integrating the upper and lower DBC substrates, the chip stacking of the DBC substrates increases the number of chips connected in parallel and achieves double-sided heat dissipation, enabling more chips to be connected in parallel and improving the power density of the power module. Furthermore, terminals replace most wire bonding, reducing parasitic inductance. Terminals are designed according to the circuit topology to achieve interconnection between chips and between chips and terminals. The proposed structure effectively achieves similar stray inductance between chips and on the upper and lower sides of the chips, reducing the module's stray inductance.

[0006] Traditional double-sided cooled power modules have long current loops and large parasitic inductance in their packaging structure. Uneven current distribution among multiple parallel chips leads to increased switching losses and voltage spikes during switching transients, affecting the reliability of power devices. Furthermore, the limited available thermal capacity in traditional packaging structures causes the junction temperature to rise rapidly beyond the maximum allowable junction temperature under surge current conditions, potentially leading to overcurrent burnout and inability to effectively support fault currents. Additionally, the complex current loop design of double-sided cooled power modules means that parasitic inductance increases rapidly with the number of parallel power devices, limiting the full potential of the devices.

[0007] Therefore, for the field of high-power power transmission and conversion, power modules with lower parasitic inductance and better heat dissipation are still needed. Summary of the Invention

[0008] This invention addresses the problems of high parasitic inductance and insufficient functional density in double-sided cooling power modules by providing an orthogonally stacked double-sided cooling power module. It utilizes orthogonal stacking packaging technology and the heat dissipation effect of double-sided copper pads to achieve synergistic optimization of the electrical and thermal performance of the double-sided cooling power module, thereby overcoming problems such as excessive parasitic inductance, low cooling efficiency, and insufficient package thermal capacity.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A double-sided cooling power module with orthogonal stacking includes decoupling capacitors, a copper-clad ceramic substrate, a power chip, and metal pads; the copper-clad ceramic substrate includes a top copper-clad ceramic substrate and a bottom copper-clad ceramic substrate, and the decoupling capacitors are disposed at both ends of the outer surface of the top copper-clad ceramic substrate.

[0011] The metal pads and power chips are stacked layer by layer in a metal pad-power chip-metal pad manner to form a series chip group. The copper-clad ceramic substrate is connected to both sides of the metal pads in the series chip group and is perpendicular to the power chip.

[0012] This invention achieves synergistic optimization of the electrical and thermal performance of the cooled power module through the combined effect of orthogonal stacked packaging and double copper pads for double-sided cooling, overcoming problems such as excessively high parasitic inductance, low cooling efficiency, and insufficient package thermal capacity. This results in a significant reduction in the parasitic inductance of the power module and a significant improvement in transient overcurrent support capability. The packaging technology also offers good flexibility and is applicable to power modules with different packaging types.

[0013] The metal pads include a frustum-shaped metal pad for connection to the source and a cuboid-shaped metal pad for connection to the drain. This increases the insulation spacing between series-connected chips, thereby preventing voltage breakdown due to excessively close insulation spacing.

[0014] The metal pad is a copper block, a molybdenum block, or a copper-molybdenum alloy block.

[0015] The thickness of the metal pad is related to the application scenario requirements of the power module, preferably above 3mm, and more preferably 5-20mm. The thicker the size, the better for heat dissipation, but it will also increase parasitic inductance to some extent.

[0016] The copper-clad ceramic substrate is a ceramic substrate with copper layers on both the upper and lower surfaces, and the inner copper layer is sintered and connected to a silver metal pad. Preferably, the inner copper layer is sintered and connected to a rectangular silver metal pad.

[0017] The copper-clad ceramic substrate is electrically connected using a through-hole copper plating process.

[0018] The copper-clad ceramic substrate on the outer side of the top copper-clad ceramic substrate is connected to the top copper-clad ceramic substrate by processes such as reflow soldering and conductive adhesive.

[0019] The power chip includes either IGBT or MOSFET.

[0020] Preferably, the frustum-shaped metal pad can completely cover the power chip surface.

[0021] Preferably, the capacitance value of the decoupling capacitor is sufficient to cancel out parasitic inductance.

[0022] The present invention also provides a method for fabricating the orthogonally stacked double-sided cooling power module, comprising the following steps:

[0023] Step 1: Fabricate metal pads according to the size and layout of the components;

[0024] Step 2: Polish the surface of the metal pad, and then perform acid pickling and / or plasma ultrasonic cleaning to ensure that the horizontal deviation of the metal pad surface is less than 20 micrometers; minimize the horizontal deviation of the metal pads in the series chip group to improve the sintering reliability of the final module.

[0025] Step 3: The metal pads and power chips are sintered layer by layer to form a series chip group; during the step-by-step sintering process, the alignment between the multiple layers is achieved by external fixtures.

[0026] Step 4: Connect the power chip to the gate, and sinter copper-clad ceramic substrates that are orthogonally perpendicular to the power chip on both sides of the metal pad.

[0027] Step 5: Reflow solder decoupling capacitors onto the top copper-clad ceramic substrate, connect terminals on both sides of the top copper-clad ceramic substrate to obtain the double-sided cooling power module, and use potting compound to encapsulate the module to isolate it from the influence of moisture and external vibration.

[0028] During the fabrication process, the upper and lower surfaces of the metal stack are polished to improve surface smoothness. The metal frame surface is then repeatedly cleaned with acid and ultrasonically with plasma water to remove impurities, ensuring surface flatness and removing the oxide layer. The surface level deviation is less than 20 micrometers. Cleaning and surface level ensure the reliability of surface-to-surface bonding during silver sintering. Surface level also ensures that the horizontal deviation of the metal pads of the series-connected chipset is minimized during step 3, thereby improving the final sintering reliability of the module.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The power module topology in this invention adopts orthogonal stacked packaging of power chips, which greatly shortens the current loop length. Compared with the traditional double-sided cooling packaging, the new packaging structure adopts a straight current loop, which can effectively reduce the parasitic inductance of the power module, thereby improving the electrical performance of the module and achieving a reduction of parasitic inductance by up to 45%.

[0031] (2) The double-sided metal stack structure in this invention can significantly improve the thermal capacity near the junction of the chip and greatly reduce the transient thermal resistance of the package. When subjected to a large transient current surge, the heat generated by the power chip will increase rapidly, while the double-sided metal stack structure can quickly diffuse the heat flow into the metal stack, thereby effectively reducing the peak value of the chip junction temperature and greatly improving the overcurrent / overload capability of the device.

[0032] (3) In this invention, the power module adopts an orthogonal stacked packaging structure, which simplifies the packaging current structure and copper-clad ceramic substrate layout design. By optimizing the thickness of the copper block, the requirements of the chip's transient overcurrent withstand capability and steady-state thermal resistance can be met simultaneously, thus achieving a high power density and high reliability design. Attached Figure Description

[0033] Figure 1 This is an exploded view of the orthogonally stacked double-sided cooling power module in Example 1, where 1 is the copper-clad ceramic substrate of the AC terminal, 2 is the decoupling capacitor, 3 is the outer copper layer of the top surface, 4 is the top ceramic substrate, 5 is the inner copper layer of the top surface, 6 is the power chip, 7 is the inner copper layer of the bottom surface, 8 is the bottom ceramic substrate, 9 is the outer copper layer of the bottom surface, 10 is a frustum-shaped metal pad, and 11 is a cuboid-shaped metal pad.

[0034] Figure 2 This is a schematic diagram of the orthogonal stacked double-sided cooling power module combined with the package in Example 1. In the diagram, 1 is the copper-clad ceramic substrate of the AC terminal, 2 is the decoupling capacitor, 3 is the outer copper layer of the top surface, 4 is the top ceramic substrate, 5 is the inner copper layer of the top surface, 6 is the power chip, 7 is the inner copper layer of the bottom surface, 8 is the bottom ceramic substrate, 9 is the outer copper layer of the bottom surface, 10 is the frustum-shaped metal pad, and 11 is the cuboid-shaped metal pad.

[0035] Figure 3 This is an exploded view of a traditional double-sided cooling power module in Comparative Example 1, where 1-1 is the outer copper layer on the top surface, 2-1 is the ceramic substrate on the top surface, 3-1 is the inner copper layer on the top surface, 4-1 is the metal pad, 5-1 is the power chip, 6-1 is the inner copper layer on the bottom surface, 7-1 is the ceramic substrate on the bottom surface, and 8-1 is the outer copper layer on the bottom surface.

[0036] Figure 4 This is a comparison diagram of the parasitic parameters of the power modules prepared in Example 1 and the comparative example. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0038] All raw materials used in the following specific embodiments were purchased commercially. The power chip is a ROHM TK-S4611, the metal pad is made of copper, the ceramic substrate is aluminum nitride, and nano-silver paste is used for silver sintering. The power chip size is 5mm × 5mm. The rectangular metal pad 11 has dimensions of 10mm × 6mm × 7mm, with a thickness of 7mm. The frustum-shaped metal pad 10 has the following dimensions: the contact surface with the chip is 5mm × 5mm, the contact surface with the rectangular metal pad 11 is 8mm × 5mm, and the thickness of the frustum-shaped metal pad 10 is 3mm. Both Example 1 and Comparative Example 1 contain four chips. The decoupling capacitor 2 has a capacitance of 0.47uF.

[0039] Example 1

[0040] like Figure 1 and Figure 2 As shown, an orthogonally stacked double-sided cooled power module includes decoupling capacitors, a copper-clad ceramic substrate, a power chip, and metal pads. The decoupling capacitors are disposed at both ends of the outer surface of the top copper-clad ceramic substrate. The metal pads include a frustum-shaped metal pad 10 for connecting to the source and a cuboid-shaped metal pad 11 for connecting to the drain. The copper-clad ceramic substrate is electrically connected using a via-plated copper plating process.

[0041] Metal pads and power chips are stacked and connected layer by layer in the manner of cuboid metal pad 11-power chip 6-frustum metal pad 10 to form a series chip group. The copper-clad ceramic substrate includes a top copper-clad ceramic substrate and a bottom copper-clad ceramic substrate. The top copper-clad ceramic substrate includes a top outer copper layer 3, a top ceramic substrate 4 and a top inner copper layer 5. The bottom copper-clad ceramic substrate includes a bottom inner copper layer 7, a bottom ceramic substrate 8 and a bottom outer copper layer 9.

[0042] The inner copper layers of the top and bottom copper-clad ceramic substrates are connected to both sides of the cuboid metal pad 11 in the series chipset, and are perpendicular to the power chip 6. The AC terminal copper-clad ceramic substrate 1 of the top copper-clad ceramic substrate is connected to the top copper-clad ceramic substrate by reflow soldering.

[0043] like Figure 1 and 2 The fabrication of the orthogonally stacked, double-sided cooled power module shown includes the following steps:

[0044] Step 1: Based on the device size and layout, process and manufacture four identical frustum-shaped metal pads 10 and four identical cuboid-shaped metal pads 11.

[0045] Step 2: Polish the surfaces of the frustum-shaped metal pad 10 and the cuboid-shaped metal pad 11, and then perform acid pickling and plasma ultrasonic cleaning to ensure uniformity in size between the frustum-shaped metal pads and between the cuboid-shaped metal pads 11; ensure surface flatness and remove the oxide layer, with the surface levelness deviation of a single metal pad being less than 20 micrometers.

[0046] Step 2: The metal pads and power chips are sintered in silver layer by layer in the manner of cuboid metal pad 11-power chip 6-frustum metal pad 10 to form a series chip group.

[0047] Step 3: Connect the power chip to the gate, and sinter the top copper-clad ceramic substrate and the bottom copper-clad ceramic substrate, which are perpendicular to the power chip 6, on both sides of the rectangular metal pad 11 of the series chip group.

[0048] Step 4: Reflow solder decoupling capacitors onto the top copper-clad ceramic substrate, connect terminals on both sides of the top copper-clad ceramic substrate to obtain the double-sided cooling power module, and use potting compound to encapsulate the module to isolate it from the influence of moisture and external vibration.

[0049] Comparative Example 1

[0050] like Figure 3As shown, the module includes a copper-clad ceramic substrate, a metal pad, and a power chip that are stacked and electrically connected in sequence. The top outer copper layer 1-1, the top ceramic substrate 2-1, and the top inner copper layer 3-1 are stacked on one side of the metal pad 4-1. The other side of the metal pad 4-1 is sintered and connected to the power chip 5-1. The bottom inner copper layer 6-1, the bottom ceramic substrate 7-1, and the bottom outer copper layer 8-1 are stacked and connected to the other side of the power chip, forming a conventional double-sided cooling power module.

[0051] The module was simulated using Ansys, and parasitic inductance tests were performed on the power modules obtained in Example 1 and Comparative Example 1. The results are as follows: Figure 4 As shown, the parasitic inductance decreases by approximately 45%.

Claims

1. A orthogonally stacked, double-sided cooled power module, characterized in that, It comprises a decoupling capacitor, a copper-clad ceramic substrate, a power chip and a metal pad; the copper-clad ceramic substrate comprises a top-layer copper-clad ceramic substrate and a bottom-layer copper-clad ceramic substrate, and the decoupling capacitor is arranged at both ends of the outer surface of the top-layer copper-clad ceramic substrate. The metal pad and the power chip are connected in a metal pad-power chip-metal pad manner to form a series chip set, and the copper-clad ceramic substrate is connected to both sides of the metal pad in the series chip set and is perpendicular to the power chip.

2. The orthogonally stacked, double-sided cooled power module of claim 1, wherein, The metal pad comprises a quadrangular prism-shaped metal pad for connecting to a source electrode and a cuboid-shaped metal pad for connecting to a drain electrode.

3. The orthogonally stacked, dual-sided cooling power module of claim 2, wherein, The quadrangular prism-shaped metal pad is connected to the power chip to completely cover the power chip.

4. The orthogonally stacked, dual-sided cooling power module of claim 1, wherein, The metal pad is a copper block, a molybdenum block or a copper-molybdenum alloy block.

5. The orthogonally stacked, dual-sided cooling power module of claim 1, wherein, The thickness of the metal pad is greater than 3 mm.

6. The orthogonally stacked, dual-sided cooling power module of claim 1, wherein, The copper-clad ceramic substrate is a ceramic substrate with copper layers on the upper and lower surfaces, and the inner copper layer is silver-sintered to the metal pad.

7. The orthogonally stacked, dual-sided cooling power module of claim 1, wherein, The copper-clad ceramic substrate is electrically connected by a via hole copper plating process.

8. The orthogonally stacked, dual-sided cooling power module of claim 1, wherein, The top-layer copper-clad ceramic substrate is provided with an AC end copper-clad ceramic substrate on the outer side.

9. The orthogonally stacked, dual-sided cooling power module of claim 1, wherein, The power chip comprises any one of IGBT or MOSFET.

10. The method of making a orthogonally stacked, dual-sided cooling power module of any of claims 1-9, wherein, The method comprises the following steps: Step 1: according to the device size and layout, the metal pad is processed and made; Step 2: the surface of the metal pad is polished, and the surface is cleaned by acid washing and / or plasma ultrasonic cleaning, so that the surface levelness deviation of the metal pad is less than 20 microns; Step 3: the metal pad and the power chip are silver-sintered to form a series chip set; Step 4: the power chip is connected to the gate electrode, and the copper-clad ceramic substrate perpendicular to the power chip is sintered and connected to both sides of the metal pad; Step 5: the decoupling capacitor is reflow soldered on the top-layer copper-clad ceramic substrate, and the terminal is connected to both sides of the top-layer copper-clad ceramic substrate to obtain the double-sided cooling power module.

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