High-reliability high-power-density ceramic surface-mounted airtight packaging structure and packaging method

Abstract

The invention discloses a high-reliability high-power-density ceramic surface-mounted airtight packaging structure and packaging method, and the structure comprises a ceramic housing, and the top of the ceramic housing is provided with a chip sintering region. A large electrode plate and a small electrode plate are respectively arranged on the side wall of the ceramic shell, the large electrode plate is used for being electrically connected with a source electrode of the chip, the small electrode plate is used for being electrically connected with a grid electrode of the chip, and a heat dissipation piece is arranged at the top of the ceramic shell; and the working temperature of the chip is reduced, so that the good working performance of the chip is guaranteed, and the normal operation of the whole system is facilitated.

Description

Technical Field

[0001] The invention relates to the field of airtight packaging shells, and in particular to a high-reliability and high-power density ceramic surface-mount airtight packaging structure and a packaging method. Background Art

[0002] The airtight surface mount package shell currently available on the market is composed of a tungsten copper base, a ceramic shell, a copper lead and a Kovar cover plate, which are fired at high temperature. It is usually used for packaging power devices such as IGBT, MOS, and BJT. Taking MOS as an example, when using this shell to package a device, refer to Figure 3 First, the drain of the MOS chip 11 is sintered on the tungsten copper base 15 through the solder 12, and then the gate and source of the chip are led to the electrode lead-out terminal 14 with aluminum wire 13 through the ultrasonic bonding process, and finally the tube shell is sealed through the parallel seam welding process.

[0003] When the packaged device is used in a circuit, it is often installed on a PCB circuit board through reflow soldering, which greatly alleviates the stress caused by the deformation of the PCB circuit board and effectively ensures that the device will not have problems such as cracks and air leaks, thereby improving the reliability of the device.

[0004] However, this structure also has some problems. The bottom of the device is both an electrode and a heat dissipation surface. For power devices, the heat emitted by the chip is introduced into the PCB circuit board through the tungsten copper base 15 and then dissipated outward. However, due to the large thermal resistance and poor thermal conductivity of the PCB circuit board, the heat dissipation effect is poor. At the same time, the heat emitted by the chip will also cause the overall temperature of the PCB circuit board to be very high, causing the components around the power device that have low heat generation to increase their operating temperature due to the increase in the temperature of the PCB circuit board, and their performance deteriorates at high temperatures, which in turn has an adverse effect on the operation of the entire system. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a high-reliability and high-power density ceramic surface-mount airtight packaging structure and packaging method.

[0006] The present invention is achieved through the following technical solutions.

[0007] The present invention provides a high-reliability and high-power density ceramic surface-mount airtight packaging structure, comprising a ceramic shell, wherein a chip sintering area is arranged on the top of the ceramic shell;

[0008] The side walls of the ceramic shell are respectively provided with a large electrode sheet and a small electrode sheet, the large electrode sheet is used to be electrically connected to the source of the chip, and the small electrode sheet is used to be electrically connected to the gate of the chip. A heat sink is provided on the top of the ceramic shell.

[0009] Preferably, the heat sink is configured as a connecting plate, which is "L"-shaped, with the horizontal portion of the connecting plate being fitted on the top of the inner side of the ceramic shell, and the vertical portion of the connecting plate being fitted on the inner wall of the ceramic shell, and the vertical portion of the connecting plate extending to the bottom of the ceramic shell.

[0010] Preferably, a top heat sink is provided on the top of the outer side of the ceramic shell.

[0011] Preferably, the bottom of the ceramic shell is opened.

[0012] Preferably, a kovar metal frame is provided at the open end of the ceramic shell, and a cover plate is attached to the kovar metal frame.

[0013] Preferably, the connecting piece is made of tungsten copper.

[0014] Preferably, the top heat sink is made of tungsten copper.

[0015] Preferably, the cover plate is provided with a "convex" platform shape.

[0016] Another aspect of the present invention provides a packaging method for packaging a chip, which uses a high-reliability and high-power density ceramic surface-mount airtight packaging structure for packaging, and includes the following method steps:

[0017] S1: Before packaging the chip, the ceramic shell is sintered through the HTCC process, and tungsten slurry is applied to the local area on the surface of the ceramic shell that needs to be connected to the metal, and a metallization layer is formed after a high-temperature sintering process;

[0018] S2: installing the top heat sink, the Kovar metal frame, the connecting piece, the large electrode sheet and the small electrode sheet on the ceramic housing by silver-copper welding, and plating nickel or gold on the surface of the top heat sink, the Kovar metal frame, the connecting piece, the large electrode sheet and the small electrode sheet by electroplating;

[0019] S3: When packaging the chip, the chip is placed in the chip sintering area, solder is laid on the drain side of the chip, and it is welded together with the connecting piece through a sintering process;

[0020] S4: Chip packaging process, the gate of the chip is installed on the side close to the small electrode sheet, and the gate of the chip is connected to the small electrode sheet through an aluminum wire ultrasonic bonding process;

[0021] S5: Chip packaging process, the source electrode of the chip is also connected to the large electrode sheet through the aluminum wire ultrasonic bonding process;

[0022] S6: Place the ceramic shell with the chip installed in an oven at 180° C. and bake for more than 24 hours to remove moisture inside the ceramic shell;

[0023] S7: After baking, the ceramic shell is quickly transferred to a parallel seam welding device filled with a dry nitrogen environment, and the cover plate is bonded and connected to the Kovar metal frame through a parallel seam welding process, so that the cover plate, the Kovar metal frame and the vertical part of the connecting piece are connected together to form an airtight package, and at the same time, the cover plate is electrically connected to the drain of the chip.

[0024] Preferably, in S5, the diameter of the aluminum wire lead used to connect the source electrode of the chip and the large electrode sheet is 380 μm.

[0025] The beneficial effects of the present invention are:

[0026] 1. By encapsulating the chip on a ceramic shell, the drain of the chip is flipped upside down and close to the top surface of the ceramic shell, so that the connecting piece and the top heat sink on the top of the ceramic shell can dissipate the heat generated by the chip from the top of the ceramic shell. At the same time, the conductivity of the chip is enhanced when it is electrically connected to the large electrode sheet and the small electrode sheet, which reduces the packaging resistance and the operating temperature of the chip, thereby ensuring the good working performance of the chip, which is beneficial to the normal operation of the entire system.

[0027] 2. Under the same package size, the rated design power of the chip can be fully utilized, which greatly improves the application power density of the device and effectively reduces the system volume; and because the heat dissipation path does not pass through the PCB, it will not cause the temperature rise of the PCB, nor will it affect other devices placed on the PCB. Users can install and use it with PCB patch welding like existing packages, which is convenient to install and protect the chip, making it less likely to be damaged, thereby extending the service life of the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a cross-sectional structural schematic diagram of the present invention;

[0029] Figure 2 It is a partial structural schematic diagram of the present invention mainly used to show the structures of the chip sintering area, large electrode sheet, small electrode sheet and ceramic shell;

[0030] Figure 3 The present invention is mainly used to illustrate the overall structural schematic diagram of the MOS chip package in the background technology;

[0031] Explanation of the reference numerals: 1-chip sintering area; 2-large electrode sheet; 3-small electrode sheet; 4-top heat sink; 5-ceramic shell; 6-connecting sheet; 7-kovar metal frame; 8-cover plate; 9-first perforation; 10-second perforation; 11-MOS chip; 12-solder; 13-aluminum wire; 14-electrode lead end; 15-tungsten copper base. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0034] In the embodiments of this application, refer to Figure 1 and Figure 2 The ceramic shell 5 comprises a ceramic shell 5 made of Al2O3 material, and the bottom of the ceramic shell 5 is open, which is convenient for installing the chip and also convenient for subsequent overall packaging. The top of the ceramic shell 5 is provided with a chip sintering area 1.

[0035] In the embodiments of this application, refer to Figure 1 A top heat sink 4 is arranged on the top of the outer side of the ceramic shell 5. The top heat sink 4 is made of tungsten copper and has high thermal conductivity. At the same time, the expansion coefficient of the top heat sink 4 is close to that of the ceramic shell 5, so as to avoid deformation during the heat conduction process as much as possible. It is installed on the ceramic shell 5 by silver-copper welding, which is helpful for dissipating heat from the chip.

[0036] In the embodiments of this application, refer to Figure 1 and Figure 2 The side walls on the same side of the ceramic shell 5 are respectively provided with a first through hole 10 and a second through hole 11, a large electrode sheet 2 is passed through the first through hole 10, and a small electrode sheet 3 is passed through the second through hole 11, both the large electrode sheet 2 and the small electrode sheet 3 are made of pure copper material, the large electrode sheet 2 is used to be electrically connected to the source of the chip through an aluminum wire, and the small electrode sheet 3 is used to be electrically connected to the gate of the chip through an aluminum wire; it can enhance the conductivity of the packaged chip to a certain extent, and at the same time reduce the package resistance, thereby ensuring that the good working performance of the chip is not affected by the packaging process.

[0037] In the embodiment of the present application, a heat sink is provided on the top of the ceramic shell 5, and the heat sink is configured as a connecting piece 6. The connecting piece 6 is "L"-shaped and is made of tungsten copper material with high thermal conductivity. The connecting piece 6 can also be made of materials with high thermal conductivity such as CPC and CMC, so that the expansion coefficient of the connecting piece 6 is close to that of the ceramic shell 5, thereby avoiding deformation of the connecting piece 6 during conductive heat dissipation as much as possible; the horizontal portion of the connecting piece 6 is fitted on the top of the inner side of the ceramic shell 5; the vertical portion of the connecting piece 6 is fitted on the inner side wall of the ceramic shell 5, and the vertical portion of the connecting piece 6 extends to the bottom of the ceramic shell 5, so that the connecting piece 6 can guide the drain current of the chip to the bottom of the ceramic shell 5.

[0038] In the embodiment of the present application, a kovable metal frame 7 is provided at the open end of the ceramic shell 5, and a cover plate 8 is fitted on the kovable metal frame 7. The cover plate 8 is provided with a "convex" platform shape, and the protruding side of the cover plate 8 faces away from the open end of the ceramic shell 5, which is conducive to the installation of the cover plate 8 on the ceramic shell 5. When the device is used later, the effect of mechanical stress on the opening of the ceramic shell 5 is effectively reduced, and stress fatigue damage and the like of the device during use are avoided as much as possible.

[0039] In the embodiment of the present application, the cover plate 8 is also in contact with the vertical portion of the connecting plate 6, which facilitates the welding, installation and use of the PCB patch and the packaged device. The heat dissipation path of the chip does not pass through the PCB patch, thereby preventing the increase in chip temperature from affecting the increase in PCB patch temperature, thereby avoiding affecting other devices on the PCB.

[0040] The working principle of this embodiment is as follows: by packaging the chip on the ceramic shell 5, the drain of the chip is flipped upside down and closely attached to the top of the inner side of the ceramic shell, so that the connecting piece 6 and the top heat sink 4 on the top of the ceramic shell 5 dissipate the heat generated by the chip from the top of the ceramic shell 5, and at the same time, the conductivity of the chip is enhanced when it is electrically connected to the large electrode sheet 2 and the small electrode sheet 3, thereby reducing the packaging resistance and the operating temperature of the chip; at the same time, the heat dissipation path of the chip does not pass through the bottom of the ceramic shell 5, so that when the packaged ceramic shell 5 is connected and installed with the PCB, the temperature generated by the chip will not affect the PCB patch and other devices around the PCB patch, thereby ensuring the good working performance of the chip and avoiding affecting the normal operation of the PCB patch, thereby facilitating the normal operation of the entire system.

[0041] The preferred embodiment of the present invention further provides a packaging method for packaging a chip, which uses a high-reliability and high-power density ceramic surface-mount airtight packaging structure for packaging, and includes the following method steps:

[0042] S1: Before packaging the chip, the ceramic shell 5 is sintered by the HTCC process, and tungsten paste is applied to the local area on the surface of the ceramic shell 5 that needs to be connected to the metal by the screen printing process, and a metallization layer is formed after a high-temperature sintering process;

[0043] S2: Install the top heat sink 4 on the top of the outer side of the ceramic shell 5 by silver-copper welding, install the kovar metal frame 7 on the open end of the bottom of the ceramic shell 5 by silver-copper welding, install the large electrode sheet 2 and the small electrode sheet 3 in the first through-hole 10 and the second through-hole 11 respectively by silver-copper welding, and fit the connecting sheet 6 to the inner side of the ceramic shell 5 by silver-copper solder welding, and plate nickel on the surface of the top heat sink 4, the kovar metal frame 7, the connecting sheet 6, the large electrode sheet 2 and the small electrode sheet 3 by electroplating process, and then plate gold. The parts processing is completed, which is convenient for the subsequent connection and contact of various components with the chip.

[0044] S3: When packaging the chip, place the chip in the chip sintering area 1, lay solder on the drain side of the chip, the solder is lead-tin-silver solder, and the size of the solder is the same as the chip size. Through the sintering process, the back of the chip is welded to the connecting piece 6; the sintering process temperature is controlled at about 340°C.

[0045] S4: During the chip packaging process, the gate of the chip is installed on the side close to the small electrode sheet 3 to avoid the bonding aluminum wire being too long, thereby avoiding affecting the reliability of the device; the PAD area of ​​the chip gate is small, and an aluminum wire with a lead cross-sectional diameter of less than 250μm is used. The gate of the chip is connected to the small electrode sheet 3 through an aluminum wire ultrasonic bonding process.

[0046] S5: During the chip packaging process, the source of the chip is also connected to the large electrode sheet 2 through an aluminum wire ultrasonic bonding process; the source of the chip needs to pass a larger current, and the diameter of the aluminum wire lead used to connect the source of the chip and the large electrode sheet 2 is 380μm, and the number of aluminum wires is determined according to the specific rated current of the chip.

[0047] S6: placing the ceramic shell 5 with the chip installed in an oven at 180° C. for baking for more than 24 hours to remove moisture inside the ceramic shell 5 , so as to enhance the airtightness of the ceramic shell 5 and the chip during the packaging process.

[0048] S7: After baking, the ceramic shell 5 is quickly transferred to a parallel seam welding device filled with a dry nitrogen environment, and the cover plate 8 is bonded and connected to the Kovar metal frame 7 through a parallel seam welding process, so that the cover plate 8, the Kovar metal frame 7 and the vertical part of the connecting piece 6 are connected together to form an airtight package, and at the same time, the cover plate 8 is electrically connected to the drain of the chip, so that the circuit remains unobstructed when the chip encapsulated in the ceramic shell 5 is connected to the PCB patch.

[0049] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A high-reliability, high-power density ceramic surface-mount airtight packaging structure, characterized in that: The invention comprises a ceramic shell (5), wherein a chip sintering area (1) is arranged on the top of the ceramic shell (5); a large electrode sheet (2) and a small electrode sheet (3) are arranged on the side walls of the ceramic shell (5), wherein the large electrode sheet (2) is used for electrically connecting to the source electrode of the chip, and the small electrode sheet (3) is used for electrically connecting to the gate electrode of the chip; and a heat sink is arranged on the top of the ceramic shell (5).

2. A high-reliability, high-power density ceramic surface-mount airtight packaging structure as claimed in claim 1, characterized in that: The heat sink is configured as a connecting piece (6), the connecting piece (6) is in an "L" shape, the horizontal portion of the connecting piece (6) is fitted on the top of the inner side of the ceramic shell (5), the vertical portion of the connecting piece (6) is fitted on the inner side wall of the ceramic shell (5), and the vertical portion of the connecting piece (6) extends to the bottom of the ceramic shell (5).

3. The high-reliability, high-power-density ceramic surface-mount airtight packaging structure according to claim 1, characterized in that: A top heat sink (4) is provided on the top of the outer side of the ceramic shell (5).

4. The high-reliability and high-power density ceramic surface-mount airtight packaging structure according to claim 1, characterized in that: The bottom of the ceramic shell (5) is open.

5. The high-reliability and high-power density ceramic surface-mount airtight packaging structure according to claim 1, characterized in that: The open end of the ceramic shell (5) is provided with a kovable metal frame (7), and a cover plate (8) is attached to the kovable metal frame (7).

6. A high-reliability, high-power density ceramic surface-mount airtight packaging structure as claimed in claim 2, characterized in that: The connecting piece (6) is made of tungsten copper.

7. The high-reliability and high-power density ceramic surface-mount airtight packaging structure according to claim 3, characterized in that: The top heat sink (4) is made of tungsten copper.

8. The high-reliability and high-power density ceramic surface-mount airtight packaging structure according to claim 5, characterized in that: The cover plate (8) is configured to be in the shape of a "convex" platform.

9. A packaging method for packaging a chip, using the high-reliability and high-power density ceramic surface-mount airtight packaging structure as described in any one of claims 1 to 8 for packaging, characterized in that: The method comprises the following steps: S1: before packaging the chip, the ceramic shell (5) is sintered by the HTCC process, and tungsten paste is applied to the local area on the surface of the ceramic shell (5) that needs to be connected with the metal, and a metallization layer is formed after a high-temperature sintering process; S2: The top heat sink (4), the Kovar metal frame (7), the connecting piece (6), the large electrode sheet (2) and the small electrode sheet (3) are mounted on the ceramic housing (5) by means of silver-copper welding, and the surfaces of the top heat sink (4), the Kovar metal frame (7), the connecting piece (6), the large electrode sheet (2) and the small electrode sheet (3) are plated with nickel and then gold by means of an electroplating process; S3: When packaging the chip, the chip is placed in the chip sintering area (1), solder is laid on the drain side of the chip, and the chip is welded together with the connecting piece (6) through a sintering process; S4: Chip packaging process, the gate of the chip is installed on the side close to the small electrode sheet (3), and the gate of the chip is connected to the small electrode sheet (3) through an aluminum wire ultrasonic bonding process; S5: Chip packaging process, the source electrode of the chip is also connected to the large electrode sheet (2) through an aluminum wire ultrasonic bonding process; S6: placing the ceramic housing (5) with the chip installed in it in an oven at 180° C. and baking it for more than 24 hours to remove moisture inside the ceramic housing (5); S7: After baking, the ceramic shell (5) is quickly transferred to a parallel seam welding device filled with a dry nitrogen environment, and the cover plate (8) is bonded and connected to the Kovar metal frame (7) through a parallel seam welding process, so that the cover plate (8), the Kovar metal frame (7) and the vertical part of the connecting piece (6) are connected together to form an airtight package, and at the same time, the cover plate (8) is electrically connected to the drain of the chip.

10. The packaging method of the high-reliability and high-power-density ceramic surface-mount airtight packaging structure according to claim 9, characterized in that: In the above S5, the diameter of the aluminum wire lead used to connect the source electrode of the chip and the large electrode sheet (2) is 380 μm.

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