Orthogonally stacked double-sided cooling power module and preparation method thereof

Abstract

The invention discloses an orthogonally stacked double-sided cooling power module and a preparation method thereof. The orthogonally stacked double-sided cooling power module comprises a decoupling capacitor, a copper-clad ceramic substrate, a power chip and a metal cushion block, the metal cushion blocks and the power chips are stacked and connected layer by layer in a metal cushion block-power chip-metal cushion block mode to form a series chipset, and the copper-clad ceramic substrate is connected with the two sides of the metal cushion blocks in the series chipset and is perpendicular to the power chips. According to the invention, through the cooperative effect of orthogonal stacking packaging and double-face cooling of the double copper cushion blocks, the electrical and thermal performance of the cooling power module is cooperatively optimized, the parasitic inductance of the power module is significantly reduced, the transient over-current supporting capability is significantly improved, and the packaging technology has good flexibility and is suitable for large-scale production. The method is suitable for power modules of different packaging types.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor power devices, and in particular to an orthogonally stacked double-sided cooling power module and a preparation method thereof. Background Art

[0002] Power electronics devices are primarily used in power electronics systems, including power converters, inverters, and DC-DC converters, for converting and regulating electrical energy. They play a vital role in energy conversion and energy conservation. Silicon carbide power modules, due to their high-temperature resistance and stability in high-temperature environments, have become a research focus.

[0003] As the power consumption of silicon carbide power modules increases, heat dissipation becomes a critical factor affecting their long-term stable operation. Some existing research utilizes power modules with double-sided heat dissipation, particularly in the field of high-power power transmission and conversion, with applications in power systems, automobiles, electronic equipment, and other fields.

[0004] For example, CN117497497A discloses a liquid-cooled heat dissipation package structure for a power module, comprising 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; coolant flowing through the inner and outer cooling channels; a lead with one end connected to the power chip and the other end extending 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 along the thickness direction to form a single unit. This effectively improves heat dissipation efficiency, reduces temperature differences between different surfaces, and enhances the operating reliability of the power chip. Compared to existing double-sided water-cooled heat dissipation structures, the outer copper layer can directly form the outer surface of the package structure.

[0005] CN120319736A discloses a multi-chip stacked double-sided heat dissipation silicon carbide power module. The module comprises a first and second DBC substrates, each of which is sequentially provided 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 each of the upper copper pattern layers is provided with multiple SiC chips. The module integrates two layers of DBC substrates, stacking the chips to increase the number of chips that can be connected in parallel and achieving double-sided heat dissipation, enabling more chips to be connected in parallel and improving the power density of the power module. Terminals replace most wire bonds to reduce parasitic inductance, and the terminals are designed based on the circuit topology to achieve interconnection between chips and between chips and terminals. The proposed structure effectively achieves similar stray inductance between chips and between the upper and lower sides of the chips, reducing the module's stray inductance.

[0006] Traditional double-sided cooling power modules have long current loops and large parasitic inductance in the package structure. This leads to uneven current distribution when multiple chips are connected in parallel, increasing chip switching losses and causing voltage spikes during switching transients, which impacts power device reliability. Furthermore, the limited available thermal capacity in traditional packaging structures means that under surge current conditions, the junction temperature can rapidly rise above the maximum allowable junction temperature, causing overcurrent and burnout of the device, rendering it unable to effectively support fault currents. Furthermore, the current loop design of double-sided cooling power modules is complex, and as the number of power devices connected in parallel increases, the parasitic inductance also increases rapidly, limiting the full performance of the devices.

[0007] Therefore, in 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] The present invention addresses the problems of high parasitic inductance and insufficient functional density in double-sided cooling power modules and provides an orthogonally stacked double-sided cooling power module. By adopting orthogonal stacking packaging technology and the heat dissipation effect of double-sided copper pads, the electrical and thermal performance of the double-sided cooling power module are synergistically optimized, thereby overcoming problems including large parasitic inductance, low cooling efficiency, and small package thermal capacity of the double-sided cooling power module.

[0009] To achieve the above object, the technical solution adopted by the present invention is: An orthogonally stacked double-sided cooling power module includes a decoupling capacitor, a copper-clad ceramic substrate, a power chip, and a metal pad; the copper-clad ceramic substrate includes a top copper-clad ceramic substrate and a bottom copper-clad ceramic substrate, and the decoupling capacitor is provided at both ends of the outer surface of the top copper-clad ceramic substrate; 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.

[0010] This invention utilizes the synergistic effects of orthogonal stacking and dual-copper pad double-sided cooling to collaboratively optimize the electrical and thermal performance of the cooled power module, overcoming issues such as excessive module parasitic inductance, low cooling efficiency, and insufficient package thermal capacitance. This significantly reduces the parasitic inductance of the power module and significantly improves transient overcurrent support. This packaging technology offers excellent flexibility and is applicable to power modules of different package types.

[0011] The metal pads include a quadrangular pyramid-shaped metal pad for connecting to the source electrode and a rectangular parallelepiped metal pad for connecting to the drain electrode, which can increase the insulation distance between series-connected chips, thereby avoiding voltage difference breakdown caused by too close insulation distance.

[0012] The metal pad is a copper block, a molybdenum block or a copper-molybdenum alloy block.

[0013] The thickness of the metal pad is related to the application scenario requirements of the power module, and is preferably above 3 mm, preferably 5-20 mm. The thicker the size, the more conducive to heat dissipation, but it will also increase parasitic inductance to a certain extent.

[0014] The copper-clad ceramic substrate is a ceramic substrate with copper layers on the upper and lower surfaces, and the inner copper layer is connected to the metal pad by silver sintering. Preferably, the inner copper layer is connected to the rectangular metal block by silver sintering.

[0015] The copper-clad ceramic substrate uses a through-hole copper deposition process to achieve electrical connection of the substrate.

[0016] An AC-end copper-clad ceramic substrate is provided outside the top copper-clad ceramic substrate, and the AC-end copper-clad ceramic substrate is connected to the top copper-clad ceramic substrate by reflow soldering, conductive adhesive and other processes.

[0017] The power chip includes any one of IGBT and MOSFET.

[0018] Preferably, the surface of the quadrangular pyramid-shaped metal pad connected to the power chip can completely cover the power chip.

[0019] Preferably, the capacitance value of the decoupling capacitor can achieve the effect of offsetting parasitic inductance.

[0020] The present invention also provides a method for preparing the orthogonally stacked double-sided cooling power module, comprising the steps of: Step 1: Process and manufacture metal pads according to device size and layout; Step 2: polish the surface of the metal pad and clean the surface by pickling and / or plasma ultrasonic cleaning to make the surface level deviation of the metal pad less than 20 microns; the level deviation of the metal pad of the series chip group is as small as possible, thereby improving the sintering reliability of the final module.

[0021] Step 3: Sinter the metal pads and the power chips layer by layer with silver to form a series chip group; during the step-by-step sintering process, alignment between the multiple layers is achieved through an external fixture.

[0022] Step 4: Connect the power chip to the gate, and sinter and connect the copper-clad ceramic substrate on both sides of the metal pad in a direction perpendicular to the power chip.

[0023] Step 5: reflow soldering a decoupling capacitor on the top copper-clad ceramic substrate, connecting terminals on both sides of the top copper-clad ceramic substrate to obtain the double-sided cooling power module, and using potting glue to plastic-encapsulate the module to isolate it from moisture and external vibration.

[0024] During the fabrication process, the upper and lower surfaces of the metal stack are polished to improve surface smoothness. Multiple acid washes and plasma water ultrasonic cleaning are used to remove impurities from the metal frame, ensuring surface flatness and removing oxide layers. The surface level deviation is less than 20 microns. Cleaning and surface leveling ensure the reliability of the surface-to-surface bonding during the silver sintering process. Surface leveling also minimizes horizontal deviations of the metal pads of the serial chipset during step 3, thereby improving the sintering reliability of the final module.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The power module topology of the present invention adopts an orthogonal stacking package of power chips, which greatly shortens the current loop length. Compared with traditional double-sided cooling packages, the new package 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 parasitic inductance reduction of up to 45%.

[0026] (2) The double-sided metal stack structure of the present invention can significantly increase the thermal capacitance near the chip junction and significantly reduce the transient thermal impedance of the package. When subjected to a large transient current shock, the heat generated by the power chip will increase rapidly. The double-sided metal stack structure can quickly diffuse the heat flow into the metal stack, thereby effectively reducing the peak junction temperature of the chip and significantly improving the overcurrent / overload capacity of the device.

[0027] (3) After the power module in the present invention adopts an orthogonal stacking packaging structure, the packaging current structure and the copper-clad ceramic substrate layout design can be simplified. By optimizing the thickness of the copper block, the requirements of the chip's transient overcurrent withstand capacity and steady-state thermal resistance can be met at the same time, achieving a high power density and high reliability design. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an exploded diagram of the orthogonally stacked double-sided cooling power module in Example 1, where 1 is the AC end copper-clad ceramic substrate, 2 is the decoupling capacitor, 3 is the top surface outer copper layer, 4 is the top surface ceramic substrate, 5 is the top surface inner copper layer, 6 is the power chip, 7 is the bottom surface inner copper layer, 8 is the bottom surface ceramic substrate, 9 is the bottom surface outer copper layer, 10 is a quadrangular pyramid-shaped metal pad, and 11 is a rectangular metal pad.

[0029] Figure 2 This is a schematic diagram of the orthogonal stacked double-sided cooling power module combined with the package in Example 1, wherein 1 is the AC end copper-clad ceramic substrate, 2 is the decoupling capacitor, 3 is the top surface outer copper layer, 4 is the top surface ceramic substrate, 5 is the top surface inner copper layer, 6 is the power chip, 7 is the bottom surface inner copper layer, 8 is the bottom surface ceramic substrate, 9 is the bottom surface outer copper layer, 10 is a quadrangular pyramid-shaped metal pad, and 11 is a rectangular parallelepiped metal pad.

[0030] Figure 3This is an exploded diagram of the traditional double-sided cooling power module in Comparative Example 1, where 1 is the top surface outer copper layer, 2 is the top surface ceramic substrate, 3 is the top surface inner copper layer, 4 is the metal pad, 5 is the power chip, 6 is the bottom surface inner copper layer, 7 is the bottom surface ceramic substrate, and 8 is the bottom surface outer copper layer.

[0031] Figure 4 The figure is a comparison chart of parasitic parameters of the power modules prepared in Example 1 and the comparative example. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art will make modifications or equivalent substitutions based on understanding the technical solution of the present invention, without departing from the spirit and scope of the technical solution of the present invention, and all should be encompassed within the protection scope of the present invention.

[0033] The raw materials used in the following specific embodiments are all purchased from the market. The power chip is ROHM's TK-S4611, the metal pad is made of copper, the ceramic substrate is aluminum nitride, and the silver sintering uses nano-silver paste. The power chip size is 5mm×5mm, the rectangular metal pad 11 has a size of 10mm×6mm×7mm, and the thickness is 7mm. The specific dimensions of the quadrangular metal pad 10 are: the contact surface with the chip is 5mm×5mm, the contact surface with the rectangular metal pad 11 is 8mm×5nn, and the thickness of the quadrangular metal pad 10 is 3mm. Both Example 1 and Comparative Example 1 contain a total of four chips. The capacitance value of the decoupling capacitor 2 is 0.47uF.

[0034] Example 1 like Figure 1 and Figure 2 As shown, an orthogonally stacked, double-sided cooled power module includes a decoupling capacitor, a copper-clad ceramic substrate, a power chip, and metal pads. The decoupling capacitors are located at both ends of the outer surface of the top copper-clad ceramic substrate. The metal pads include a quadrangular pyramid-shaped metal pad 10 for connecting to the source electrode and a rectangular parallelepiped metal pad 11 for connecting to the drain electrode. The copper-clad ceramic substrate uses a through-hole copper deposition process to achieve electrical connections.

[0035] The metal pads and power chips are stacked and connected layer by layer in the manner of rectangular metal pad 10-power chip 6-quadrangular pyramid-shaped metal pad 9 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 surface outer copper layer 3, a top surface ceramic substrate 4 and a top surface inner copper layer 5. The bottom copper-clad ceramic substrate includes a bottom surface inner copper layer 7, a bottom surface ceramic substrate 8 and a bottom surface outer copper layer 9.

[0036] The inner copper layers of the top and bottom copper-clad ceramic substrates are connected to both sides of the rectangular metal pads 11 in the series chip set, perpendicular to the power chip 6. The AC-terminal copper-clad ceramic substrate 1 is connected to the top copper-clad ceramic substrate via reflow soldering.

[0037] like Figure 1 and 2 The preparation of the orthogonally stacked double-sided cooling power module shown includes the following steps: Step 1: According to the device size and layout, four square pyramid-shaped metal pads 10 and four rectangular parallelepiped metal pads 11 of the same size are processed and manufactured; Step 2: polish the surface of the quadrangular pyramid-shaped metal pad 10 and the rectangular parallelepiped metal pad 11, and clean the surface by pickling and plasma ultrasonic cleaning to make the sizes between the quadrangular pyramid-shaped metal pads and the rectangular parallelepiped metal pads 11 uniform; ensure the surface flatness and remove the oxide layer, and the surface levelness deviation of a single metal pad is less than 20 microns.

[0038] Step 2: Sintering the metal pads and the power chip layer by layer with silver in the order of rectangular metal pad 10 - power chip 6 - quadrangular pyramid-shaped metal pad 9 to form a series chip group; Step 3: Connect the power chip to the gate, and sinter the top copper-clad ceramic substrate and the bottom copper-clad ceramic substrate on both sides of the rectangular metal pad 10 of the series chip group, which are perpendicular to the power chip 6; Step 4: reflow soldering the decoupling capacitor on the top copper-clad ceramic substrate, connecting terminals on both sides of the top copper-clad ceramic substrate to obtain the double-sided cooling power module, and using potting glue to plastic-encapsulate the module to isolate it from moisture and external vibration.

[0039] Comparative Example 1 like Figure 3 As shown, it includes a copper-clad ceramic substrate, a metal spacer, and a power chip stacked and electrically connected in sequence. The top outer copper layer 1, the top ceramic substrate 2, and the top inner copper layer 3 are stacked in sequence on one side of the metal spacer 4. The other side of the metal spacer 4 is sintered and connected to the power chip 5. The bottom inner copper layer 6, the bottom ceramic substrate 7, and the bottom outer copper layer 8 are stacked in sequence and connected on the other side of the power chip, forming a traditional double-sided cooling power module.

[0040] 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 is reduced by about 45%.

Claims

1. An orthogonally stacked double-sided cooling power module, characterized in that: It includes a decoupling capacitor, a copper-clad ceramic substrate, a power chip and a metal pad; the copper-clad ceramic substrate includes a top copper-clad ceramic substrate and a bottom copper-clad ceramic substrate, and the decoupling capacitor is provided at both ends of the outer surface of the top copper-clad ceramic substrate; 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.

2. The orthogonally stacked double-sided cooling power module according to claim 1, characterized in that: The metal pads include a quadrangular pyramid-shaped metal pad for connecting to the source electrode, and a rectangular parallelepiped-shaped metal pad for connecting to the drain electrode.

3. The orthogonally stacked double-sided cooling power module according to claim 2, characterized in that: The quadrangular pyramid-shaped metal pad is connected to the power chip surface and completely covers the power chip.

4. The orthogonally stacked double-sided cooling power module according to claim 1, characterized in that: The metal pad is a copper block, a molybdenum block, or a copper-molybdenum alloy block.

5. The orthogonally stacked double-sided cooling power module according to claim 1, characterized in that: The thickness of the metal pad is above 3 mm.

6. The orthogonally stacked double-sided cooling power module according to claim 1, characterized in that: The copper-clad ceramic substrate is a ceramic substrate with copper layers on the upper and lower surfaces, and the inner copper layer is connected to the metal pad by silver sintering.

7. The orthogonally stacked double-sided cooling power module according to claim 1, characterized in that: The copper-clad ceramic substrate uses a through-hole copper deposition process to perform electrical connection of the substrate.

8. The orthogonally stacked double-sided cooling power module according to claim 1, characterized in that: An AC-end copper-clad ceramic substrate is provided on the outer side of the top copper-clad ceramic substrate.

9. The orthogonally stacked double-sided cooling power module according to claim 1, characterized in that: The power chip includes either IGBT or MOSFET.

10. The method for preparing an orthogonally stacked double-sided cooling power module according to any one of claims 1 to 9, characterized in that: Including steps: Step 1: Process and manufacture metal pads according to device size and layout; Step 2: polishing the surface of the metal pad, and cleaning the surface by pickling and / or plasma ultrasonic cleaning to ensure that the deviation of the surface level of the metal pad is less than 20 microns; Step 3: Sintering the metal pads and the power chips layer by layer with silver to form a series chip set; Step 4: Connect the power chip to the gate, and sinter the copper-clad ceramic substrate on both sides of the metal pad in a direction perpendicular to the power chip; Step 5: reflow soldering a decoupling capacitor on the top copper-clad ceramic substrate, and connecting terminals on both sides of the top copper-clad ceramic substrate to obtain the double-sided cooling power module.

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