HTCC ceramic metal shell for hybrid integrated circuit and preparation method of HTCC ceramic metal shell

Abstract

The invention discloses an HTCC ceramic metal shell for a hybrid integrated circuit and a preparation method thereof, the shell comprises a ceramic substrate, a metal upper frame, a metal lower frame, a cover plate and a lead, the ceramic substrate forms the bottom wall of the shell, the metal lower frame is located above the ceramic substrate and arranged along the periphery of the ceramic substrate, the metal upper frame is located above the metal lower frame, and the metal lower frame is located above the metal upper frame and arranged along the periphery of the ceramic substrate. The metal lower frame and the metal upper frame jointly form the side wall of the shell, and the cover plate is located above the metal upper frame; the bottom surface and the side surface of the ceramic substrate are respectively provided with a plurality of groups of horizontal grooves and vertical grooves which are communicated with each other, metalized layers are arranged on the surfaces of the horizontal grooves and the vertical grooves, and leads are welded in the horizontal grooves and the vertical grooves. The preparation method adopts a step-by-step assembly process. The reliability requirement and the electrical requirement of the device hybrid integrated circuit are met.

Description

Technical Field

[0001] The invention relates to the field of packaging of hybrid integrated circuits, in particular to a HTCC ceramic metal shell for hybrid integrated circuits and a preparation method thereof. Background Art

[0002] For hybrid integrated circuits, there are currently several mainstream packaging forms, including glass metal packaging shells, plastic packaging shells, low-temperature ceramic packaging shells, and high-temperature ceramic packaging shells. Among them, the inherent strength of glass metal packaging shells, plastic packaging shells, and low-temperature ceramic packaging shells is relatively low, so that the stability and reliability of the packaged products are relatively poor, and it is difficult to meet the requirements of high reliability and long-life stable operation of electronic devices. The high-temperature ceramic metal packaging shell uses high-temperature co-fired Al2O3 ceramics as the main body of the shell. The high-temperature resistance and strength of Al2O3 ceramics are significantly higher than glass sealing materials, plastic sealing materials, and low-temperature co-fired ceramic materials. Therefore, the use of high-temperature ceramic materials can greatly improve the stability and reliability of the product.

[0003] With the rapid development of semiconductor technology, the integration of hybrid integrated circuits is getting higher and higher, the number of internal components is increasing, the assembly density is high, the electronic circuits are complex, and the operating frequency is high, which places high demands on the reliability of the devices. The high-temperature ceramic metal packaging shell developed by the present invention is suitable for the installation of multiple sets of hybrid integrated circuits, and has a large volume, so the reliability of the shell is required to be higher. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a HTCC ceramic metal shell for hybrid integrated circuits and a method for its installation, which can meet the reliability and electrical requirements of the hybrid integrated circuits.

[0005] In order to solve the technical problem, the technical solution adopted by the present invention is: a HTCC ceramic metal shell for hybrid integrated circuits, comprising a ceramic substrate, a metal upper frame, a metal lower frame, a cover plate and leads, wherein the ceramic substrate constitutes the bottom wall of the shell, the metal lower frame is located above the ceramic substrate and arranged along the four sides of the ceramic substrate, the metal upper frame is located above the metal lower frame, the metal lower frame and the metal upper frame together constitute the side wall of the shell, and the cover plate is located above the metal upper frame; the bottom surface and the side surface of the ceramic substrate are respectively provided with a plurality of groups of interconnected horizontal grooves and vertical grooves, the surfaces of the horizontal grooves and the vertical grooves are provided with metallization layers, and the leads are welded in the horizontal grooves and the vertical grooves.

[0006] Furthermore, the thickness of the metal lower frame is greater than the thickness of the metal upper frame.

[0007] Furthermore, the ceramic substrate and the metal lower frame are provided with circular chamfers at four corners, and the center angle of the circular chamfer of the metal lower frame is greater than the center angle of the circular chamfer of the ceramic substrate.

[0008] Furthermore, the ceramic matrix is ​​formed by stacking multiple raw ceramic sheets, one or more of which are provided with a metallization layer and internal injection holes used as a conductive circuit, and the topmost raw ceramic sheet is provided with a chip sintering area and a device welding area.

[0009] Furthermore, the ceramic substrate is made of high temperature co-fired Al2O3 ceramics, and the metal upper frame, the metal lower frame and the lead wires are made of Kovar alloy.

[0010] Furthermore, the surfaces of the metallization layer of the ceramic substrate, the metal upper frame, the metal lower frame, and the leads are plated with a nickel-palladium-gold layer.

[0011] The present invention also discloses a method for preparing a HTCC ceramic metal housing for a hybrid integrated circuit, comprising the following steps: S01), take a plurality of green ceramic sheets, apply a metallization layer on the green ceramic sheets to be used as conductive circuits and open conductive holes, and fill the conductive holes with metal grouting; open horizontal and vertical grooves on the green ceramic sheets to be welded with metal leads, and pre-coat a metallization layer on the upper ceramic sheets corresponding to the green ceramic sheets with horizontal grooves; S02), stacking the green ceramic sheets processed in step S01), applying equal pressure to the ceramic sheets in all directions using an isostatic pressing device, generating a ceramic matrix through an isostatic pressing process, and then sintering to form; S03) chamfering the four corners of the ceramic substrate and the metal lower frame; S04), coating solder on the horizontal grooves and vertical grooves of the ceramic substrate, and then entering the sintering furnace for sintering; S05), sintering the metal upper frame and the metal lower frame together to form the side wall of the shell; S06), sintering the ceramic substrate, the metal lead, and the side wall of the shell together; S07), plating a nickel-palladium-gold layer on the metallization layer of the ceramic substrate and the surface of the metal upper frame, the metal lower frame, and the lead wires.

[0012] Furthermore, horizontal grooves, vertical grooves and circular chamfers are opened by laser cutting process.

[0013] Furthermore, the sintering in steps S05) to S07) is carried out in a sintering furnace, the sintering temperature is 800°C to 840°C, nitrogen-hydrogen mixed gas is used as the protective gas, and the sintering time is 2-3 hours.

[0014] Furthermore, the nickel-palladium-gold layer plated in step S08) is specifically: nickel layer 3-8 um, palladium layer 0.05-0.18 um, gold layer 0.05-0.18 um.

[0015] Beneficial effects of the present invention: The present invention adopts high temperature co-fired Al2O3 ceramic as the insulating material and the shell matrix, which has good insulation performance and high mechanical strength; adopts Kovar material as the lead wire, which has good matching performance with the ceramic material. The metal lead wire is designed with a bending structure, which plays a stress buffering role, facilitates the installation of the device and the whole machine circuit board, and increases the overall reliability.

[0016] The ceramic substrate is designed with horizontal and vertical double groove metallized welding structures at the lead brazing point to form a three-dimensional surface welding structure between the lead and the ceramic, which improves the lead brazing strength and can disperse the impact force of the shell on the lead welding point during thermal expansion and contraction, thereby improving the reliability of the shell.

[0017] The metal upper frame and the metal lower frame are made of Kovar alloy material, and are designed with a double-layer frame structure of different wall thicknesses. Kovar alloy material has good matching performance with ceramic materials, and the upper thin-wall wall structure can effectively buffer the stress generated by the cover plate and the wall on the ceramic matrix under temperature shock environment, thereby reducing the adverse effects on the shell when the ambient temperature changes. This wall structure can better buffer the stress for large-sized ceramic metal shells.

[0018] The four corners of the ceramic substrate are designed to be large rounded to replace the right-angle structure; the metal lower frame connected to the ceramic is designed to have a larger rounded corner, which is different from the ceramic rounded corner. This can disperse the stress concentration at the four corners of the large-size ceramic kovar welding structure, thereby avoiding damage to the four corners of the ceramic caused by large stress impact and improving the reliability of the shell.

[0019] The internal pads of the shell and the internal circuits of the ceramic can be designed or adjusted according to the customer's device circuit requirements. It is very flexible and can meet the assembly requirements of multiple chips and components of hybrid integrated circuits.

[0020] The pads inside the shell are designed according to the electrical performance requirements and installation requirements, including chip welding area, device welding area and lead bonding area, and the corresponding circuit connections are designed to ensure the accurate realization of various functional parameters of the circuit.

[0021] According to the electrical requirements of different circuits of the device, the ceramic layered circuits are designed as grouting hole conduction structures arranged in different matrices, and each layer of circuits is designed as metallized circuits of different widths. This circuit design has great flexibility.

[0022] The metal surface of the shell and the metallized circuit of the ceramic surface adopt the nickel-palladium-gold plating process, which can simultaneously meet the requirements of internal circuit lead bonding, chip and device welding, and the welding requirements of external leads and the whole circuit board.

[0023] The high temperature co-fired ceramic metal shell of the present invention is relatively large in size, has a total of 36 metal leads, and adopts a double-layer metal frame structure. This shell structure is relatively complex and cannot be assembled and welded in one go. It needs to be assembled and pre-burned and welded in steps, and then the components are assembled into an integral shell.

[0024] The step-by-step assembly and pre-burning welding needs to be split into three components: ceramic substrate, lead and metal frame (metal upper frame and metal lower frame) according to the shell structure design. The solder is pre-sintered and the component welding is completed in a high-temperature brazing furnace protected by a nitrogen and hydrogen atmosphere; finally, the components are assembled and welded in the brazing furnace.

[0025] The step-by-step assembly and pre-burning welding can effectively control the shell accuracy and welding quality, reduce the welding difficulty, and increase the yield rate.

[0026] The high-temperature co-fired ceramic-metal housing of the present invention is composed of materials with similar linear expansion coefficients such as Al2O3 ceramics and Kovar alloys, and is suitable for assembly and matching of large-sized hybrid circuit housings. Although the linear expansion coefficients are similar, the welding and assembly between parts of different materials will still have certain stress, especially for large-sized housings. In order to further buffer the stress, a process of step-by-step assembly pre-burning welding is adopted, soft-based silver-copper solder is used as the welding material, and processes such as controlling the amount of solder and the quality of the weld are adopted, which reduces the stress generated by different materials during the high-temperature welding process and improves the reliability of the assembly process of such products.

[0027] HTCC high temperature co-fired ceramic is a commonly used material for high reliability ceramic shells, and the manufacturing process is relatively mature. The ceramic process innovation of this shell is: the four large rounded ceramic corners and the side lead welding grooves are formed, and the laser cutting process is used instead of the conventional straight line cutting process to realize the processing of ceramic special-shaped cavities and grooves, which is especially suitable for the forming of large-sized ceramic bodies with multiple leads. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the housing of the present invention; Figure 2 This is a schematic diagram of the groove structure of the lead brazing area of ​​the ceramic substrate; Figure 3 It is a schematic diagram of the cross-sectional structure of the housing of the present invention; Figure 4 The three views of the shell structure of the present invention without the cover plate; Figure 5 The three views of the device structure behind the cover plate of the present invention; Figure 6 6a is a schematic diagram of the third layer, i.e., 3PA; and 6b is a schematic diagram of the fifth layer, i.e., 5PA. In the figure: 1. Metal upper frame, 2. Metal lower frame, 3. Ceramic substrate, 4. Metal leads, 5. Chip sintering area, 6. Internal grouting holes, 7. Cover plate, 8. Horizontal grooves, 9. Vertical grooves, 10. Metallization layer. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] Example 1 This embodiment discloses a HTCC ceramic metal shell for a hybrid integrated circuit. The ceramic metal shell is a carrier of chips and circuits, and is a device circuit lead structure and a sealing protection device. Figure 1 , 3 As shown in Figure 4, the shell includes a ceramic substrate 3, a metal upper frame 1, a metal lower frame 2, a cover plate 7 and a metal lead 4. The ceramic substrate 3 constitutes the bottom wall of the shell. The metal lower frame 2 is located above the ceramic substrate 3 and is arranged around the ceramic substrate 3. The metal upper frame 1 is located above the metal lower frame 2. The metal lower frame 2 and the metal upper frame 1 together constitute the side wall of the shell. The cover plate 7 is located above the metal upper frame 1.

[0031] like Figure 2 As shown, the bottom and side surfaces of the ceramic substrate 3 are respectively provided with a plurality of interconnected horizontal grooves 8 and vertical grooves 9, the surfaces of the horizontal grooves 8 and the vertical grooves 9 are provided with a metallization layer, and the metal leads 4 are welded in the horizontal grooves 8 and the vertical grooves 9. A three-dimensional surface welding structure of the metal leads 4 and the ceramic substrate 3 is provided in the horizontal grooves 8 and the vertical grooves 9, which improves the lead brazing strength, disperses the impact force of the shell on the lead welding point during the thermal expansion and contraction process, and improves the reliability of the shell.

[0032] In this embodiment, the metal lead 4 is made of Kovar alloy, which has good matching performance with ceramic materials. At the same time, the bending structure is designed to play a stress buffering role, facilitate the installation of the device and the whole circuit board, and increase the overall reliability.

[0033] In this embodiment, the thickness of the metal lower frame 2 is greater than the thickness of the metal upper frame 1. Both the metal upper frame 1 and the metal lower frame 2 are made of Kovar alloy material, and a double-layer frame structure with different wall thicknesses is adopted. Kovar alloy material has good matching performance with ceramic material, and the thin-walled structure of the upper layer can effectively buffer the stress generated by the cover plate and the side wall of the shell on the ceramic substrate under the temperature shock environment, thereby reducing the adverse effects on the shell when the ambient temperature changes. This shell side wall structure can better play a role in buffering stress for large-sized ceramic metal shells.

[0034] In this embodiment, the four corners of the ceramic base 3 and the metal lower frame 2 are all chamfered, and the center angle of the circular chamfer of the metal lower frame is greater than the center angle of the central chamfer of the ceramic base. This can disperse the stress concentration at the four corners of the large-size ceramic kovar welding structure, thereby avoiding damage to the ceramic four corners caused by large stress impact and improving the reliability of the shell.

[0035] like Figure 4 , 6 As shown, the ceramic matrix is ​​formed by stacking 8 raw ceramic sheets, and is designed with 7 layers of metallization layout. Each layer of ceramic layout is designed with a reasonable metallization layer 10 and a conductive hole 6 structure layout, which can not only meet the current carrying capacity required by different lead-out terminals, but also ensure the structural strength of the ceramic matrix itself. That is, the 7 raw ceramic sheets are provided with a metallization layer 10 and an internal grouting hole 6 used as a conductive circuit, and the top raw ceramic sheet is provided with a chip sintering area 5 and a device welding area. According to the electrical requirements of different circuits of the device, the ceramic layered circuits are designed as a conductive structure of grouting holes 6 arranged in different matrices, and each layer of circuits is designed as a metallization circuit of different widths. This circuit design has great flexibility.

[0036] In this embodiment, the ceramic substrate 3 is made of high-temperature co-fired Al2O3 ceramic, which has the advantages of high insulation resistance, high mechanical strength and reliable sealing.

[0037] In this embodiment, the metallization layer of the ceramic substrate 3 and the surface nickel-palladium-gold layer of the metal upper frame 1, the metal lower frame 2, and the metal lead can simultaneously meet the requirements of internal circuit lead bonding, chip and device welding, and the welding requirements of external leads and the entire circuit board.

[0038] In this embodiment, the upper frame of the housing and the cover plate 7 are welded by parallel sealing welding.

[0039] The shell of the present invention uses high temperature co-fired Al2O3 ceramic as the insulating material and the shell matrix, which has good insulation performance and high mechanical strength; uses Kovar material lead frame as the lead; increases the shell's ability to resist stress through structural design; and flexibly uses HTTC circuit structure design according to the device circuit electrical requirements in circuit design. Therefore, the shell of the invention can fully meet the device's high reliability and electrical requirements.

[0040] Example 2 This embodiment discloses a method for preparing a HTCC ceramic metal housing for a hybrid integrated circuit, comprising the following steps: S01), take a plurality of green ceramic sheets, apply a metallization layer on the green ceramic sheets to be used as conductive circuits and open conductive holes, and fill the conductive holes with metal grouting; open horizontal grooves on the green ceramic sheets to be welded with metal leads, and pre-coat a metallization layer on the upper ceramic sheets corresponding to the green ceramic sheets with horizontal grooves; S02), stacking the raw ceramic sheets processed in step S01), applying equal pressure to the ceramic sheets in all directions using isostatic pressing equipment, and generating a ceramic matrix through isostatic pressing process; the ceramic matrix produced through isostatic pressing process will have improved material density and mechanical strength.

[0041] S03), opening a vertical groove at a position where the side of the ceramic substrate is connected to the horizontal groove, and coating a metallization layer in the vertical groove; S04) chamfering the four corners of the ceramic substrate and the metal lower frame; S05), coating solder on the horizontal grooves and vertical grooves of the ceramic substrate, and then entering the sintering furnace for sintering; S06), sintering the metal upper frame and the metal lower frame together to form the side wall of the shell; S07), sintering the ceramic substrate, the metal lead and the side wall of the shell together; S08), a nickel-palladium-gold layer is plated on the metallization layer of the ceramic substrate, the metal upper frame, the metal lower frame, and the surface of the lead.

[0042] In this embodiment, horizontal grooves, vertical grooves and round chamfers are cut by laser cutting. The laser cutting process is used instead of the conventional linear cutting process to realize the processing of ceramic special-shaped cavities and grooves, which is particularly suitable for the forming of large-sized ceramic bodies with multiple lead-out terminals.

[0043] In this embodiment, the sintering in steps S05) to S07) is carried out in a sintering furnace, the sintering temperature is 800°C to 840°C, nitrogen-hydrogen mixed gas is used as the protective gas, and the sintering time is 2-3 hours. The specific steps are: 1) Heat the high-temperature nitrogen-hydrogen atmosphere protection chain brazing furnace to the silver-copper soldering temperature: 830°C, introduce nitrogen-hydrogen mixed gas (the amount of gas introduced is based on the fact that the parts and solder are not oxidized during the entire sintering process) as protective gas, and preheat for ≥30 minutes.

[0044] 2) Step-by-step assembly and sintering: According to the design process steps, assemble each step of the parts into the corresponding graphite mold, and then place the graphite mold on the brazing furnace chain belt. The sintering process takes about 2-3 hours; the shell molding step is divided into three steps. The first step is to pre-sinter the upper frame and the lower frame into a whole through silver-copper solder brazing. The second step is to pre-place silver-copper solder at the position where the lead frame needs to be brazed. The third step is to assemble the parts sintered in the first and second steps and the ceramic matrix. The sintering temperature of the first step is 825℃, and the constant temperature time is 8 minutes; the sintering temperature of the second step is 805℃, and the constant temperature time is 5 minutes. The sintering temperature of the third step is 825℃, and the constant temperature time is 5 minutes.

[0045] 3) The entire sintering process must ensure that the sintering temperature and nitrogen-hydrogen gas flow rate are constant. The temperature error in each temperature zone shall not exceed ±3°C, and the nitrogen-hydrogen mixed gas flow error shall not exceed ±5L / min.

[0046] 4) Take out the sintered assembly and check the sintering quality.

[0047] In this embodiment, the nickel-palladium-gold layer plated in step S08) is specifically: a nickel layer of 3-8 um, a palladium layer of 0.05-0.18 um, and a gold layer of 0.05-0.18 um.

[0048] According to the structural characteristics of the product, in order to ensure the long-term reliability of the product, the product has undergone many matching tests after molding, including 2000h power aging test, 100 times thermal shock (liquid-liquid) test (-55℃~125℃), 500 times temperature (-65℃~175℃) shock test, 10,000 times intermittent life test, etc. All tests have passed the assessment, thus proving that the high reliability of the product meets the national military standards.

[0049] The above description is only the basic principle and preferred embodiments of the present invention. Improvements and substitutions made by those skilled in the art based on the present invention belong to the protection scope of the present invention.

Claims

1. A HTCC ceramic metal housing for a hybrid integrated circuit, characterized in that: It includes a ceramic substrate, a metal upper frame, a metal lower frame, a cover plate and leads. The ceramic substrate constitutes the bottom wall of the shell. The metal lower frame is located above the ceramic substrate and arranged along the four sides of the ceramic substrate. The metal upper frame is located above the metal lower frame. The metal lower frame and the metal upper frame together constitute the side wall of the shell. The cover plate is located above the metal upper frame. The bottom and side surfaces of the ceramic substrate are respectively provided with multiple groups of interconnected horizontal grooves and vertical grooves, and the surfaces of the horizontal grooves and the vertical grooves are made of metallization layers. The leads are welded in the horizontal grooves and the vertical grooves.

2. The HTCC ceramic metal housing for hybrid integrated circuit according to claim 1, characterized in that: The thickness of the metal lower frame is greater than the thickness of the metal upper frame.

3. The HTCC ceramic metal housing for hybrid integrated circuit according to claim 1, characterized in that: The four corners of the ceramic substrate and the metal lower frame are all provided with circular chamfers, and the central angle of the circular chamfer of the metal lower frame is greater than the central angle of the central chamfer of the ceramic substrate.

4. The HTCC ceramic metal housing for hybrid integrated circuit according to claim 1, characterized in that: The ceramic matrix is ​​formed by stacking multiple raw ceramic sheets. One or more of the raw ceramic sheets are provided with a metallization layer used as a conductive circuit and internal grouting holes. The top raw ceramic sheet is provided with a chip sintering area and a device welding area.

5. The HTCC ceramic metal housing for hybrid integrated circuit according to claim 1, characterized in that: The ceramic substrate is made of high temperature co-fired Al2O3 ceramic, and the metal upper frame, metal lower frame and lead wires are made of Kovar alloy.

6. The HTCC ceramic metal housing for hybrid integrated circuit according to claim 1, characterized in that: The surfaces of the metallization layer of the ceramic substrate, the metal upper frame, the metal lower frame and the lead wires are plated with a nickel-palladium-gold layer.

7. A method for preparing a HTCC ceramic metal housing for a hybrid integrated circuit, characterized in that: The following steps are involved: S01), take a plurality of green ceramic sheets, apply a metallization layer on the green ceramic sheets to be used as conductive circuits and open conductive holes, and fill the conductive holes with metal grouting; open horizontal and vertical grooves on the green ceramic sheets to be welded with metal leads, and pre-coat a metallization layer on the upper ceramic sheets corresponding to the green ceramic sheets with horizontal grooves; S02), stacking the green ceramic sheets processed in step S01), applying equal pressure to the ceramic sheets in all directions using an isostatic pressing device, generating a ceramic matrix through an isostatic pressing process, and then sintering to form; S03) chamfering the four corners of the ceramic substrate and the metal lower frame; S04), coating solder on the horizontal grooves and vertical grooves of the ceramic substrate, and then entering the sintering furnace for sintering; S05), sintering the metal upper frame and the metal lower frame together to form the side wall of the shell; S06), sintering the ceramic substrate, the metal lead, and the side wall of the shell together; S07), plating a nickel-palladium-gold layer on the metallization layer of the ceramic substrate and the surface of the metal upper frame, the metal lower frame, and the lead wires.

8. The method for preparing a HTCC ceramic metal housing for a hybrid integrated circuit according to claim 7, characterized in that: Horizontal grooves, vertical grooves and rounded chamfers are cut using a laser cutting process.

9. The method for preparing a HTCC ceramic metal housing for a hybrid integrated circuit according to claim 7, characterized in that: The sintering in steps S05) to S07) is carried out in a sintering furnace at a sintering temperature of 800° C. to 840° C., with nitrogen-hydrogen mixed gas as the protective gas, and the sintering time is 2-3 hours.

10. The method for preparing a HTCC ceramic metal housing for a hybrid integrated circuit according to claim 7, characterized in that: The nickel-palladium-gold layer plated in step S08) is specifically: nickel layer 3-8um, palladium layer 0.05-0.18um, gold layer 0.05-0.18um.

Images