Aluminum substrate power device package

Abstract

An aluminum substrate power device package comprises a power transistor wafer, an aluminum drain electrode bonding pad is arranged on the bottom face of the power transistor wafer, and a source electrode bonding pad and a switch control electrode bonding pad are arranged on the top face of the power transistor wafer. The power transistor further comprises an L-shaped aluminum substrate, the thickness of one side of the L-shaped aluminum substrate is small, and the power transistor wafer is welded to the top face of the side, with the small thickness, of the L-shaped aluminum substrate through an aluminum drain electrode bonding pad. The insulating rubber material is filled around the power transistor wafer horizontally. The L-shaped aluminum substrate is simultaneously used as a drain electrode conductive pole piece of the power transistor wafer, a packaged drain electrode bonding pad, a packaged cooling fin and a packaged substrate; through the aluminum-aluminum welding process, the wafer is welded on the L-shaped aluminum substrate, so that the processing links are reduced, the cost is saved, the performance of a power device is improved, and high-power transistor packaging with high cost performance is realized.

Description

Technical Field

[0001] This invention relates to aluminum metal processing technology; to packaging technology and chip heat dissipation technology optimization and architecture design for power devices; and to packaging technology for silicon-based transistors, third-generation and fourth-generation semiconductor transistors. Background Technology

[0002] Power transistors (such as MOSFETs, diodes, high electron mobility transistors (HEMTs) and IGBTs) are widely used in high-power electronic devices, such as power management modules, electric vehicle drive systems, and industrial motor control.

[0003] In semiconductor manufacturing, aluminum (Al) is typically used as the main material for pads on wafers. The main reasons are: a balance between conductivity and cost, as aluminum is cheaper than copper, a commonly used conductive material; it is easy to process, and the process is very mature; the oxide is very stable and is an insulator, with higher insulation performance compared to copper oxide.

[0004] In aluminum-aluminum welding processes, laser welding and ultrasonic welding are commonly used.

[0005] Third-generation semiconductor materials GaN (gallium nitride) and SiC (silicon carbide) are representative of wide-bandgap semiconductors. Power devices made of gallium nitride have significant advantages such as fast switching speed, low on-resistance, and small chip area, and are widely used in power adapters, industrial power supplies, and automotive electronics. SiC transistors, including diodes and MOSFETs, are already widely used.

[0006] Fourth-generation semiconductor materials, mainly represented by diamond and gallium oxide, have begun to be applied to ultra-wide bandgap power devices.

[0007] Traditional power transistor packages typically employ complex lead frames and metal clip structures to achieve electrical connections between the source, gate, and drain. However, this packaging method suffers from the following problems: complex manufacturing process; large size; and limited heat dissipation, affecting device performance. The metal substrate carrying the power transistor wafer is mostly made of copper. Copper is a relatively expensive material, and copper oxide is a semiconductor with poor insulation properties. Improving the insulation of areas requiring insulation requires additional processing steps. Summary of the Invention

[0008] To address the aforementioned issues, this invention proposes a power transistor packaging structure based on an L-shaped aluminum packaging substrate. This not only simplifies the packaging process and reduces manufacturing costs, but also allows the aluminum substrate, which is made of the same aluminum metal as the wafer drain pads, to be directly welded to the aluminum substrate via an aluminum-aluminum welding process. This reduces costs while improving the power transistor's parameter specifications.

[0009] To achieve this technical objective, an aluminum-based power device package includes a power transistor wafer. The bottom surface of the power transistor wafer has an aluminum drain pad, and the top surface has a source pad and a switch control pad. The source and switch control pads on the top surface of the wafer are made of solderable materials used in surface mount technology (SMT) manufacturing and can be achieved using chemical plating or copper bumping processes. In general SMT manufacturing processes, the circuit layer of the circuit board is surface-plated copper foil, and the aluminum pads on the wafer cannot be directly soldered onto the circuit board. The package also includes an L-shaped aluminum substrate, prepared using machining or etching processes. One side of the L-shaped aluminum substrate has a smaller thickness, allowing the power transistor wafer to pass through the aluminum... The drain pad is soldered to the top surface of the thinner side of the L-shaped aluminum substrate using an aluminum-to-aluminum direct soldering process. The thicker side of the L-shaped aluminum substrate has a surface mount metal layer for easy soldering. The top surface of the power transistor wafer is flush with the thicker side of the L-shaped aluminum substrate. Insulating filler is also included, filling the top surface of the thinner side of the L-shaped aluminum substrate and the perimeter of the power transistor wafer. The insulating filler can be epoxy resin or PI engineering plastic (polyimide). For mass production, the L-shaped aluminum substrate needs to be fabricated into a multi-layered board. After the insulating filler is applied, the multi-layered board is cut into individual small packages.

[0010] Preferably, the power transistor wafer is a group of two or more transistor wafers, which are respectively soldered to the top surface of the thinner side of the L-shaped aluminum substrate via aluminum drain pads. The group of transistor wafers are packaged in the same package, and their drains are electrically connected; the finished transistor of this package can be used as a parallel transistor to expand current carrying capacity, or as the high-side circuit in a bridge circuit.

[0011] Preferably, the power transistor wafer is a diode wafer, with an aluminum anode pad on the bottom surface and a cathode pad on the top surface. The diode wafer is welded to the top surface of the L-shaped aluminum substrate on the side with the smaller thickness via the aluminum anode pad using an aluminum-aluminum direct welding process, and the top surface of the diode wafer is flush with the top surface of the L-shaped aluminum substrate on the side with the larger thickness.

[0012] Preferably, the bottom surface of the L-shaped aluminum substrate of the power transistor is plated with a surface mount metal layer that is easy to solder using a circuit board surface mount process. After the bottom surface of the L-shaped aluminum substrate is equipped with a surface mount metal layer that is easy to solder, such as nickel, silver or gold, it facilitates the soldering of the power transistor into the heat sink of electronic products.

[0013] The beneficial effects of this technical solution are: It simplifies the packaging process by directly connecting the drain pad to the L-shaped aluminum substrate, eliminating the need for metal clips and complex soldering steps in traditional packaging, thus reducing manufacturing costs. It improves heat dissipation performance, as the L-shaped aluminum substrate can directly contact an external heat sink, shortening the heat dissipation path, reducing thermal resistance, and improving the device's thermal management capabilities. Furthermore, the aluminum-aluminum soldering process, which solders the wafer onto the L-shaped aluminum substrate, reduces processing steps, saves costs, and simultaneously improves the performance of power devices. Attached Figure Description

[0014] Figure 1 This is a cross-sectional schematic diagram of a specific embodiment of the present invention.

[0015] Figure 2 This is a top view of a power transistor wafer according to a specific embodiment of the present invention.

[0016] Figure 3 This is a bottom view of a power transistor wafer according to a specific embodiment of the present invention.

[0017] Figure 4 This is a top view of the packaged structure according to a specific embodiment of the present invention.

[0018] Figure 5 This is a bottom view of the packaged structure according to a specific embodiment of the present invention.

[0019] Figure 6 This is a top view of a mass production connecting plate according to a specific embodiment two of the present invention.

[0020] Figure 7 This is a top view of a group of power transistor wafers within the same package, according to a specific embodiment three of the present invention.

[0021] Figure 8 This is a cross-sectional schematic diagram of a specific embodiment four of the present invention.

[0022] Figure 9 This is a top view of the packaged structure according to a specific embodiment five of the present invention. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1The diagram shown is a cross-sectional view of a specific embodiment of the present invention. A metal substrate power device package includes a power transistor wafer 1. The bottom surface of the power transistor wafer 1 is provided with an aluminum drain pad 11, and the top surface of the power transistor wafer 1 is provided with a source pad 12 and a switch control pad 13. The source pad 12 and the switch control pad 13 are nickel-gold pads. The thickness of the power transistor wafer 1 is 0.3 mm. It also includes an L-shaped aluminum substrate 2. The L-shaped aluminum substrate 2 is a copper substrate. The thickness of the thicker side 21 of the L-shaped aluminum substrate 2 is 1 mm, and the thickness of the thinner side 22 is 0.7 mm. The aluminum drain pad 11 of the power transistor wafer 1 is soldered to the top surface of the thinner side 22 of the L-shaped aluminum substrate 2 through an aluminum-aluminum direct soldering process. The top surface of the power transistor wafer 1 is flush with the top surface of the thicker side 21 of the L-shaped aluminum substrate 2. The source pad 12 and the switch control electrode pad 13 arranged on the top surface of the thicker side 21 of the L-shaped aluminum substrate 2 and the top surface of the power transistor wafer 1 serve as the drain pad, source pad, and switch control electrode pad for packaging. It also includes an insulating filler 3, which is made of PI engineering plastic. The insulating filler 3 is filled on the top surface of the thinner side 22 of the L-shaped aluminum substrate 2 and coated on the horizontal periphery of the power transistor wafer 1.

[0025] like Figure 2 The image shown is a top view of a power transistor wafer according to a specific embodiment of the present invention. The top surface of the power transistor wafer 1 is provided with source pads 12 and switch control pads 13. The source pads 12 and switch control pads 13 are nickel-gold pads, adapted to the SMT production requirements of electronic products.

[0026] like Figure 3 The image shown is a bottom view of a power transistor wafer according to a specific embodiment of the present invention. The bottom surface of the power transistor wafer 1 is provided with aluminum drain pads 11.

[0027] The source and drain pads of a vertical power transistor wafer are located on the top and bottom sides of the wafer, respectively.

[0028] like Figure 4 The image shown is a top view of the packaged structure according to a specific embodiment of the present invention.

[0029] The top surface 211 of the thicker side 21 of the L-shaped aluminum substrate 2 is a nickel layer that is easy to solder in SMT process; the source pad 12 and the switch control electrode pad 13 arranged on the top surface 211 and the top surface of the power transistor wafer 1 serve as the drain pad, source pad and switch control electrode pad for packaging. The insulating filler 3 is filled on the top surface of the thinner side 22 of the L-shaped aluminum substrate 2 and coated on the horizontal perimeter of the power transistor wafer 1.

[0030] like Figure 5The image shown is a bottom view of a specific embodiment of the package of the present invention. The bottom surface of the package is the bottom surface 232 of the L-shaped aluminum substrate 2. After the power transistor of this package is soldered onto the circuit board, the L-shaped aluminum substrate 2 functions as a heat sink, shortening the heat dissipation path and reducing thermal resistance.

[0031] like Figure 6 The image shown is a top view of a mass-production interconnect board according to a specific embodiment of the present invention. The interconnect board consists of two rows and three columns of individual unit packages. A group of six power transistor wafers (1-1 to 1-6) are soldered onto a metal substrate interconnect board comprising six L-shaped aluminum substrate units via aluminum-to-aluminum direct soldering pads. After insulating filler is applied to the horizontal perimeter of the group of six power transistor wafers (1-1 to 1-6), transverse cuts are made along line X-1 and longitudinal cuts are made along lines Y-1 and Y-2 to cut the interconnect board into individual packages, enabling mass production. During production, process edges are sometimes added to the metal substrate interconnect board according to equipment and production line parameters to facilitate production.

[0032] like Figure 7 The image shows a top view of a group of power transistor wafers within the same package according to a specific embodiment three of the present invention. A single package includes three power transistor wafers 1-1, 1-2, and 1-3; it includes an L-shaped aluminum substrate 2. Power transistor wafers 1-1, 1-2, and 1-3 are respectively soldered to the top surface of the side with the thinner portion of the L-shaped aluminum substrate 2 via aluminum drain pads using an aluminum-to-aluminum direct soldering process. Insulating filler is applied to the horizontal perimeter of power transistor wafers 1-1, 1-2, and 1-3. The top surface 211 of the side with the thicker portion of the L-shaped aluminum substrate 2 serves as the drain pad for the package. Top surface 211 is a solderable nickel-gold layer for SMT processes and is the parallel drain pad for power transistor wafers 1-1, 1-2, and 1-3. The power transistors in this package can be used as parallel transistors or as the high-side circuit of a bridge circuit.

[0033] like Figure 8 The diagram shown is a cross-sectional view of a specific embodiment four of the present invention. The bottom surface of the L-shaped aluminum substrate is plated with a surface-mount nickel layer 23, which is easily solderable using a circuit board surface mount process. When the power transistor is used, a metal heat sink can be directly soldered onto the nickel layer 23, further improving heat dissipation efficiency.

[0034] like Figure 9 The image shown is a top view of the packaged structure according to a specific embodiment five of the present invention.

[0035] The power transistor wafer is a diode wafer. The bottom surface of the diode wafer is provided with aluminum anode pads, and the top surface of the diode wafer is provided with cathode pads 12. The diode wafer is soldered to the top surface of the thinner side of the L-shaped aluminum substrate through the aluminum anode pads using an aluminum-aluminum direct soldering process. The top surface of the diode wafer is flush with the top surface 211 of the thicker side of the L-shaped aluminum substrate. The top surface 211 is a nickel metal layer that is easy to solder in SMT process. The insulating filler 3 is filled on the top surface of the thinner side of the L-shaped aluminum substrate 2 and coated on the horizontal periphery of the diode wafer.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A power device package based on an aluminum substrate, characterized in that: The system includes a power transistor wafer with aluminum drain pads on its bottom surface and source and switch control pads on its top surface. It also includes an L-shaped aluminum substrate with a thinner side. The power transistor wafer is soldered to the top surface of the thinner side of the L-shaped aluminum substrate via the aluminum drain pads using a direct aluminum-aluminum soldering process. The thicker side of the L-shaped aluminum substrate has a surface mount metal layer for easy soldering. The top surface of the power transistor wafer is flush with the thicker side of the L-shaped aluminum substrate. Finally, it includes an insulating filler compound that fills the top surface of the thinner side of the L-shaped aluminum substrate and the perimeter of the power transistor wafer.

2. The aluminum substrate power device package according to claim 1, characterized in that: The power transistor wafer is a group of two or more transistor wafers, which are respectively welded to the top surface of the thinner side of the L-shaped aluminum substrate through aluminum drain pads using an aluminum-aluminum direct welding process.

3. The aluminum substrate power device package according to claim 1, characterized in that: The power transistor wafer is a diode wafer. The bottom surface of the diode wafer is provided with aluminum anode pads, and the top surface of the diode wafer is provided with cathode pads. The diode wafer is welded to the top surface of the L-shaped aluminum substrate on the side with the smaller thickness through the aluminum anode pads using an aluminum-aluminum direct welding process. The top surface of the diode wafer is flush with the top surface of the L-shaped aluminum substrate on the side with the larger thickness.

4. The aluminum substrate power device package according to claim 1, characterized in that: The bottom surface of the L-shaped aluminum substrate is plated with a metal layer that is easy to solder using the surface mount technology of circuit boards.

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