A ceramic-metal integrated housing for a pressure sensor and a method of manufacturing the same

Abstract

This invention belongs to the field of special electronic packaging technology, specifically a ceramic-metal integrated housing for pressure sensors and its preparation method. The housing comprises an alumina ceramic component, with a metal ring surrounding it. One end of the alumina ceramic component has a chip bonding area and several bonding areas, while the other end has several lead-out soldering areas, which are interconnected and connected to leads. An oil injection tube also runs through the alumina ceramic component. This invention utilizes a multi-layer ceramic and metal ring welded together to form an integrated structure, achieving an operating temperature up to 550℃. It also features lightweight design, high pressure resistance, high operating temperature, good chip compatibility, high reliability, and excellent sealing performance.

Description

Technical Field

[0001] This invention belongs to the field of special electronic packaging technology, and particularly relates to an integrated ceramic-metal housing for pressure sensors and its preparation method. Background Technology

[0002] Existing pressure sensor housings use glass as insulators, with the glass, chassis, and leads encapsulated into a cavity-based integral structure through a fusion sealing process. These glass-insulator metal housings offer advantages such as low cost, high reliability, suitable operating temperature, and diverse structural forms, and are widely used in the pressure sensor field.

[0003] However, the upper limit of the operating temperature for this type of enclosure is only 300℃. Once this temperature is exceeded, the internal pressure of the enclosure will exceed the bonding force between the glass and the metal, easily causing them to separate and leading to enclosure failure. Simultaneously, increased temperature will decrease the viscosity of the glass, thereby reducing its compressive strength; the decrease in the dielectric constant of alkali metals and the increase in ionic activity will also reduce their insulation performance. As the pressure resistance and operating temperature requirements of pressure sensor chips continue to increase, traditional metal enclosures for glass insulators can no longer meet industry development trends and new technical requirements.

[0004] Furthermore, its pressure resistance decreases as temperature increases. After optimization, the housing has a pressure resistance range of 100 MPa at room temperature, making it suitable only for low- to medium-range pressure sensors. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides an integrated ceramic-metal housing for pressure sensors and its manufacturing method. This invention employs a multi-layer ceramic layer welded to a metal ring to form an integrated structure, achieving an operating temperature up to 550℃. It also features lightweight construction, high pressure resistance, high operating temperature, good chip compatibility, high reliability, and excellent sealing performance.

[0006] To achieve one of the above objectives, the present invention adopts the following technical solution: A ceramic-metal integrated housing for a pressure sensor includes a cylindrical alumina ceramic component. A metal ring is fitted around the outer periphery of the alumina ceramic component. One end of the alumina ceramic component has a chip bonding area and several bonding areas, while the other end has several lead-out soldering areas. These lead-out soldering areas and bonding areas are interconnected and connected to leads. An oil injection tube also passes through the alumina ceramic component. This housing is an assembly component for a pressure sensor and is used in specialized electronic packaging fields such as silicon-on-insulator (SOI) piezoresistive pressure sensors.

[0007] Preferably, the alumina ceramic part is made by stacking several alumina cast sheets and then co-firing them at high temperature. The co-firing temperature is 1500±50℃ and the holding time is 60±10h. The mass ratio of alumina in the alumina cast sheets is 90%-99%. The thickness of a single alumina cast sheet is 0.283mm±0.01mm.

[0008] Preferably, the lead wire is a nail-head lead wire, that is, the welding end face of the lead wire is round, which can increase the welding size and the welding strength; and the lead wire is pre-filled with solder, which is Ag72Cu28 silver-copper solder.

[0009] Preferably, the lead wire (4J29 or 4J50), the oil injection tube (4J29), and the metal ring (4J29) are all Kovar alloys.

[0010] Preferably, the chip bonding area is a groove embedded in the middle of the input end of the alumina ceramic component. The depth of the groove is adapted to the thickness of the chip, usually 0.8 mm, and the groove is used to install the chip.

[0011] Preferably, the alumina ceramic component has a through-hole for oil injection, an oil injection tube is welded into the oil injection hole, several bonding areas are symmetrically distributed on both sides of the oil injection hole, and the oil injection hole and several bonding areas surround the periphery of the chip bonding area; the alumina ceramic component also has a conductor channel, which is filled with tungsten paste, and the lead-out welding area is connected through the tungsten paste bonding area.

[0012] Preferably, the metal ring is integrally machined from two connecting rings, which can increase the stress of the metal ring. The top of the upper connecting ring (2mm) extends towards the center with a step, which facilitates the formation of a cavity in the metal ring and facilitates subsequent laser welding. The surface of the shell is plated with a nickel layer, and the leads and bonding areas are also plated with a gold layer.

[0013] To achieve the second objective mentioned above, this invention provides a method for preparing an integrated ceramic-metal housing for a pressure sensor, the specific steps of which are as follows: S1. Preparation of alumina ceramic parts: Several alumina casting sheets are sequentially subjected to drilling, filling, printing, cavity punching, stacking, isostatic pressing, side printing, sintering and plating to obtain alumina ceramic parts in which the bonding area and the lead-out welding area are interconnected one by one. S2. The oil injection pipe and metal ring are machined, and solder is pre-made at the welding end of the lead wire. S3. The above-mentioned components are installed into the mold for positioning, and the mold is placed in a brazing furnace and co-fired in a nitrogen-hydrogen mixed atmosphere to obtain the shell preform. After the shell preform cools, the entire shell preform is nickel plated, and then the lead wire and ceramic bonding area are gold plated to obtain an integrated ceramic-metal shell.

[0014] Preferably, in step S1, both the slurry used for filling holes and the slurry used for printing are tungsten pastes, and the sintering environment is hydrogen.

[0015] Preferably, in step S1, the plating material is nickel, and the phosphorus (P) content in the nickel is <5%, and the thickness of the plating layer is 2-5 μm.

[0016] The advantages of this invention are: (1) This invention uses ceramic components as pressure-bearing structural components, with conductor channels inside, and ceramic as the insulating medium between the channels. The shell made using this solution can reach a maximum operating temperature of 550℃, which is far higher than the operating temperature of existing pressure sensors. At the same time, all components in the structure of this invention adopt mature silver-copper welding technology, which does not require special brazing conditions such as vacuum, resulting in low welding cost, high strength, simple operation, high production efficiency, and easy mass production.

[0017] (2) This invention provides an integrated ceramic-metal shell, which features lightweight, high pressure resistance, high operating temperature, good chip compatibility, high reliability, and excellent sealing performance. Specifically, the integrated shell is fabricated by positioning the processed ceramic parts, oil injection pipes, metal rings, pre-made solder nail leads, and other components in a mold, and then brazing them at high temperature with silver-copper solder in a nitrogen-hydrogen mixed atmosphere. This process is simple to operate, has high production efficiency, and is suitable for mass production.

[0018] (3) The ceramic-metal integrated shell of the present invention can maintain its pressure resistance at 550°C without decreasing. In the temperature range of -65°C to 550°C, the pressure resistance range can reach more than 150MPa, which can meet the requirements of low, medium and high full range of pressure sensor use. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the bottom structure of the present invention.

[0021] Figure 3 This is a schematic diagram of the metal ring structure of the present invention.

[0022] Figure 4 This is a schematic diagram of the alumina ceramic component structure of the present invention. Figure 1 .

[0023] Figure 5 This is a schematic diagram of the alumina ceramic component structure of the present invention. Figure 2 .

[0024] Figure 6 This is a schematic diagram of the oil injection pipe structure of the present invention.

[0025] Figure 7This is a schematic diagram of the lead structure of the present invention.

[0026] The meanings of the symbols in the diagram are as follows: 1-Alumina ceramic component, 2-Metal ring, 3-Chip bonding area, 4-Bonding area, 5-Oil injection tube, 6-Lead wire, 7-Oil injection hole, 8-Lead end welding area. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] like Figure 1-2 As shown, a ceramic-metal integrated housing for a pressure sensor, which improves the pressure resistance and service temperature, specifically includes the following structure: (1) Alumina ceramic parts 1 (e.g.) Figure 4-5 As shown, the alumina ceramic component 1 is a hollow cylinder, formed by multi-layer stacking and high-temperature co-firing of 90%-99% alumina cast sheets (HTCC). Alumina has low density, high strength, and high service temperature, and its coefficient of linear expansion matches that of the chip. It provides signal input / output and insulation functions. The alumina ceramic component 1 can withstand temperatures up to 550℃ and pressures up to 200MPa. A groove for chip mounting, the chip bonding area 3, is embedded in the center of one end of the alumina ceramic component 1. Several bonding areas 4 surround the chip bonding area 3. Several lead-out soldering areas 8 are provided at one end of the alumina ceramic component 1, and the lead-out soldering areas 8 and bonding areas 4 are interconnected. Oil injection holes 7 are also provided through the alumina ceramic component 1, with several bonding areas 4 symmetrically distributed on both sides of the oil injection holes 7. Conductor channels filled with tungsten paste are also provided inside the alumina ceramic component 1. The lead-out soldering areas 8 are connected through the tungsten paste bonding areas 4. (2) Metal ring 2 (e.g.) Figure 3 As shown), oil injection pipe 5 (as shown) Figure 6 (as shown) and nail head lead wire 6 (as shown) Figure 7 (As shown); the metal ring 2 is fitted onto the outside of the alumina ceramic part 1, the oil injection tube 5 is welded to the oil injection hole 7 by solder, and the lead wire 6 is welded to the lead-out welding area 8. The lead wire 6, the oil injection tube 5, and the metal ring 2 are all machined from Kovar alloy. Specifically, the oil injection tube 5 and the metal ring 2 can be 4J29, and the lead wire 6 can be 4J29 or 4J50. The alumina ceramic part 1 is connected to the lead wire 6, the oil injection tube 5, and the metal ring 2 by silver-copper soldering.

[0029] Furthermore, the most important component of the housing of this invention is the alumina ceramic part 1, which realizes pressure resistance, insulation, and sensor assembly area in the housing, and includes a metallized area for welding with the oil injection pipe 5, metal ring 2, and lead wire 6. Specifically, a method for preparing an integrated ceramic-metal housing for a pressure sensor is described, with the following specific steps: S1. Using a 0.283mm±0.01mm thick 90%-99% alumina casting sheet, the alumina ceramic part 1 is prepared by sequentially drilling, filling, printing, punching, stacking, isostatic pressing, side printing, sintering, and plating. The above-mentioned filling and printing paste is tungsten paste, the sintering environment is hydrogen (protective atmosphere), the plating material is nickel, and the phosphorus (P) content in the nickel is <5%, and the plating thickness is 2-5 μm. After preparation, the bonding region 4 and the lead-out welding region 8 are interconnected one by one.

[0030] S2. The oil injection pipe 5 and metal ring 2 are machined by mechanical processing. Both are made of Kovar alloy (4J29). After the lead wire 6 is processed, silver-copper solder (Ag72Cu28) is pre-applied to the nail head of the lead wire 6.

[0031] S3. The above-mentioned components are installed into the mold and positioned. The mold is placed in the brazing furnace and co-fired in a nitrogen-hydrogen mixed atmosphere to obtain the shell preform. At high temperature, the above four main components are melted by pre-formed solder and wetted at the material interface by capillary action. After the temperature drops, the solder solidifies and connects all the components together.

[0032] The parameters of the brazing furnace must be matched with the eutectic silver-copper brazing process. The entire outer shell and oil injection hole are nickel-plated, and the lead wire 6 and the ceramic bonding area 4 are both nickel-plated and gold-plated.

[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ceramic-metal integrated housing for a pressure sensor, characterized by: The housing includes an alumina ceramic component (1), with a metal ring (2) fitted around the outer periphery of the alumina ceramic component (1). One end of the alumina ceramic component (1) is provided with a chip bonding area (3) and several bonding areas (4). The other end of the alumina ceramic component (1) is provided with several lead-out welding areas (8), and the lead-out welding areas (8) and bonding areas (4) are interconnected one by one. The lead-out welding areas (8) are also connected to leads (6). An oil injection pipe (5) is also provided through the alumina ceramic component (1).

2. The ceramic-metal integrated package for a pressure sensor according to claim 1, wherein: The alumina ceramic part (1) is made by stacking several alumina cast sheets and firing them together at a temperature of 1500±50℃ and holding for 60±10h; and the mass ratio of alumina in the alumina cast sheets is 90%-99%; the thickness of a single alumina cast sheet is 0.283mm±0.01mm.

3. The ceramic-metal integrated package for a pressure sensor according to claim 1, wherein: The lead wire (6) is a nail-head lead wire, and solder is pre-applied on the lead wire (6).

4. The ceramic-metal integrated package for a pressure sensor according to claim 1, wherein: The lead wire (6), the oil injection pipe (5), and the metal ring (2) are all Kovar alloys.

5. The ceramic-metal integrated package for a pressure sensor according to claim 1, wherein: The chip bonding area (3) is a groove embedded in the middle of the input end of the alumina ceramic part (1), and the depth of the groove is adapted to the thickness of the chip.

6. The ceramic-metal integrated package for a pressure sensor according to claim 1, wherein: The alumina ceramic part (1) is provided with an oil injection hole (7) through which an oil injection tube (5) is welded. Several bonding areas (4) are symmetrically arranged on both sides of the oil injection hole (7), and the oil injection hole (7) and several bonding areas (4) surround the periphery of the chip bonding area (3). The alumina ceramic part (1) is also provided with a conductor channel, which is filled with tungsten paste. The lead-out welding area (8) is connected through the tungsten paste bonding area (4).

7. The ceramic-metal integrated package for a pressure sensor according to claim 1, wherein: The metal ring (2) is integrally formed from two connecting rings, and the top of the upper connecting ring extends towards the center with a step; the surface of the shell is plated with a nickel layer, and the lead wire (6) and bonding area (4) are also plated with a gold layer.

8. A method of producing a ceramic-metal integrated housing for a pressure sensor as claimed in any one of claims 1 to 7, characterized by, The specific steps are as follows: S1. Preparation of alumina ceramic parts (1): Several alumina casting sheets are successively subjected to drilling, filling, printing, cavity punching, stacking, isostatic pressing, side printing, sintering and plating to obtain alumina ceramic parts (1) in which the bonding area (4) and the lead-out welding area (8) are interconnected one by one. S2. The oil injection pipe (5) and metal ring (2) are machined by means of mechanical processing, and the solder is pre-made at the welding end of the lead wire (6); S3. The above-mentioned components are placed into the mold for positioning, and the mold is placed in the brazing furnace and co-fired in a nitrogen-hydrogen mixed atmosphere to obtain the shell preform. After the shell preform is cooled, the entire shell preform is plated with nickel, and then the lead wire (6) and the ceramic bonding area (4) are plated with gold to obtain the ceramic-metal integrated shell.

9. The method of claim 8, wherein the ceramic metal integrated housing for a pressure sensor is prepared by the steps of: In step S1, both the slurry used for filling holes and the slurry used for printing are tungsten pastes, and the sintering environment is hydrogen.

10. The method of claim 8, wherein the ceramic metal integrated housing for a pressure sensor is prepared by the steps of: In step S1, the plating material is nickel, and the phosphorus content (P) in the nickel is <5%, and the thickness of the plating layer is 2-5 μm.

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