Microwave multi-cavity system-in-package integrated brazing and heat sealing method

Abstract

The invention discloses a microwave multi-cavity system-in-package integrated brazing and heat sealing method, which comprises the following steps: preparing a product to be brazed and heat-sealed, the product being composed of more than two functional layers; a limiting base is prepared, a first open hole is formed in the middle of the limiting base, grooves are formed in the middle areas of the four sides of the limiting base, and the to-be-brazed fusion-sealed product is put into the limiting base; a limiting cover plate is prepared, a second opening is formed in the middle of the limiting cover plate, a first boss is arranged in the middle area of the four edges of the limiting cover plate, and a second boss is arranged between the first boss and the second opening; the limiting cover plate is assembled and positioned through cooperation of the first boss and the open groove and cooperation of the second boss and the first open hole. The assembled product is placed according to the positioning scribed line, and pressure is applied to the product through a controllable pressure device; and welding the product. According to the invention, brazing interconnection and airtight fusion sealing of a plurality of functional layers can be synchronously realized through integrated brazing, and microwave multi-cavity system-level packaging is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-power microwave system-level packaging, and particularly relates to a microwave multi-cavity system-level packaging integrated brazing and sealing method. BACKGROUND

[0002] High-power microwave system-level packaging is gradually transitioning from the research and demonstration stage to the engineering application exploration stage in the research of high-integration board-level vertical interconnection, and has become a key development direction of engineering application in this direction. Traditional system-level packaging is to bond a bare chip inside a cavity, and realize signal interconnection through wire bonding technology, which belongs to single-cavity integration, and the air tightness is mainly realized through parallel seam welding technology, which cannot realize brazing interconnection of electrical and microwave signals; and the brazing sealing technology is mainly used in products of cavities and cover plates in the industry. For multi-cavity integration, the internal multi-layer board-level vertical interconnection and air tightness guarantee of bare chips and wire bonding have many difficulties in engineering implementation, which not only realizes brazing interconnection between multiple layers of signals, but also guarantees the air tightness after brazing sealing, and becomes a problem to be solved in the engineering popularization and application of high-power and high-integration microwave system-level packaging. SUMMARY

[0003] The purpose of the present application is to provide a microwave multi-cavity system-level packaging integrated brazing and sealing method, which can realize brazing interconnection and air tight sealing of multiple functional layers through integrated brazing at the same time, and realize system-level packaging of microwave multi-cavity.

[0004] One aspect of the present application provides a microwave multi-cavity system-level packaging integrated brazing and sealing method, comprising: Preparation of a product to be brazed and sealed, the product being composed of two or more functional layers, the metal to be welded inside the product and the peripheral frame of the functional layer being pre-coated with solder; Preparation of a limiting base, the limiting base being provided with a first opening in the middle for accommodating the functional layer at the bottom of the product, and the middle area of the four sides of the limiting base being slotted, the product to be brazed and sealed being placed in the limiting base, and the limiting of the product from the bottom being realized through the limiting base; Preparation of a limiting cover plate, the limiting cover plate being provided with a second opening in the middle for accommodating the functional layer at the top of the product, the middle area of the four sides of the limiting cover plate being provided with a first boss for cooperating with the slot of the four sides of the limiting base, the height of the first boss being less than the depth of the slot, the length of the first boss being less than the length of the slot, and a second boss being provided between the first boss and the second opening for cooperating with the first opening of the limiting base, the limiting cover plate being buckled on the product to be brazed and sealed, the assembly and positioning of the limiting cover plate being realized through the cooperation of the first boss and the slot and the cooperation of the second boss and the first opening, so as to realize the limiting of the product from the top; A controllable pressure device is prepared and installed on the upper part of the frame, and a positioning scale is arranged on the lower part of the frame, and the assembled product is placed according to the positioning scale, and the product is pressed by the controllable pressure device. The product is welded, the interconnection between different functional layers is realized by welding the metal inside the product, and the air tightness of different functional layers is realized by welding the peripheral frame of the functional layer.

[0005] Preferably, the functional layer includes an electrical layer with a bare chip and a wire bond and a structural layer.

[0006] Preferably, the cross section of the product, the limiting base and the limiting cover plate is rectangular, the size of the first opening and the second opening is processed according to the design size of the product, the length of the first boss of the adjacent two sides of the four sides of the limiting cover plate is different, and the length of the slot of the adjacent two sides of the four sides of the limiting base is different.

[0007] Preferably, the height of the internal cavity of the limiting base and the limiting cover plate after assembly is less than the height of the product, so that the product after assembly provides the pressure required for welding by the controllable pressure device and the frame.

[0008] Preferably, the controllable pressure device includes a spring needle, an external thread column and a pressing block, the controllable pressure device is installed on the upper part of the frame through the external thread column, the up and down movement of the pressing block is realized by the extension and contraction of the spring needle, so that the assembled product is pressed by the pressing block.

[0009] Preferably, the spring needle is a high-temperature resistant spring needle, and the controllability of the pressure is realized by replacing different high-temperature resistant spring needles.

[0010] Preferably, a vacuum sintering furnace, a tube furnace or a hot air welding furnace is used, and the brazing temperature curve and the atmosphere flow curve of the corresponding product are selected to complete the welding.

[0011] Preferably, after welding, the product is cooled to room temperature, the pressure applied to the product is released, the whole of the product with the limiting base and the limiting cover plate is taken out, and then the limiting cover plate and the limiting base are removed.

[0012] According to the microwave multi-cavity system level packaging integrated brazing and sealing method of the above aspect of the present application, the brazing interconnection and air tight sealing of multiple functional layers can be realized simultaneously by integrated brazing, and the system level packaging of microwave multi-cavity is realized. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the description of the embodiments of the present application will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work. Figure 1 is the front view of the limiting base of one embodiment of the present application; Figure 2 is the top view of the limiting base of one embodiment of the present application; Figure 3 is the state diagram of the completed assembly of the limiting base of one embodiment of the present application; Figure 4 is the front view of the limiting cover plate of one embodiment of the present application; Figure 5 is the top view of the limiting cover plate of one embodiment of the present application; Figure 6 is the state diagram of the completed assembly of the limiting cover plate of one embodiment of the present application; Figure 7 is the combined diagram of the controllable pressure device and the surrounding frame of one embodiment of the present application; Figure 8 is the sectional view of the surrounding frame of one embodiment of the present application; Figure 9 is the state diagram of the completed assembly of the controllable pressure device and the surrounding frame of one embodiment of the present application; Figure 10 is the temperature curve diagram of one embodiment of the present application. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below in combination with the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0015] One embodiment of the present application provides a microwave multi-cavity system-level packaging integrated brazing and fusion sealing method, which can realize vertical signal electrical interconnection and air-tight packaging by brazing for multiple different functional layers such as electrical layers and structural layers with bare chips and wire bonds. The method of the embodiment of the present application includes steps S1-S5.

[0016] In step S1, a product to be brazed and fused is prepared, which is characterized by being composed of 2 or more functional layers, and the interconnection between different layers is realized by internal metal welding, and the air-tightness of different functional layers is realized by welding of the peripheral frame of the functional layer, and the inside of the product to be brazed (including the metal to be welded and the peripheral frame) is pre-coated with solder. In the embodiment of the present application, it is assumed that the cross section of the product is rectangular.

[0017] In step S2, a limiting base 1 is prepared, the front view of which is as shown inFigure 1 The top view of the limiting base 1 is shown as Figure 2 The main function of the limiting base 1 is to limit the size of the product to be soldered and sealed according to the functional layer of the product, mainly to limit the size of the multi-layer circuit board at the bottom of the product (such as electrical layer + structural layer + electrical layer, and the design value of the size of each layer is the same), and to support the bottom surface pressure during welding in cooperation with the limiting cover plate and the controllable pressure device.

[0018] The limiting base 1 is provided with a first opening in the middle for accommodating the functional layer at the bottom of the product. The length, width and height of the limiting base 1 and the size of the first opening should be designed and processed according to the design size of the product substrate. Figure 1 The length and width of the first opening of the limiting base are 1.4 and 1.5, and the design and processing size should be larger than the length and width of the product, and it is usually appropriate to just put down the product, so as to limit the length and width of the product from bottom to top through the length and width of the first opening after the product is put into the limiting base 1. The depth of the first opening of the limiting base 1 is 1.6, and the design and processing depth is also determined according to the design height of the product. The opening depth is usually smaller than the height of the product. The specific design and processing depth size needs to be determined in combination with the height of the limiting cover plate 2. It is necessary to ensure that the height of the internal cavity of the limiting base 1 and the limiting cover plate 2 after assembly is smaller than the height of the product, so as to provide the welding pressure required by the controllable pressure device 3 and the surrounding frame 4 after the product is assembled. The limiting base 1 is slotted in the middle of the four edges. The length of the slot is generally in the middle area of the current edge of the limiting base. The width of the slot is consistent with the width 1.7 of the reserved edge of the limiting base. The lengths of the slots of the adjacent two edges of the limiting base 1 are 1.2 and 1.3. The length of the slot should be greater than the length of the first boss of the limiting cover plate 1, and it is appropriate that the first boss is just put into the slot. The depth of the slot is 1.1, which should be greater than the height of the first boss of the limiting cover plate. The lengths of 1.2 and 1.3 should not be consistent, which is an anti-error design. The product to be soldered and sealed is placed in the limiting base 1 in sequence according to the design drawing requirements, as shown in Figure 3 After the product to be soldered and sealed 5 is put in, the limiting base 1 realizes the limitation of the length and width of the product from bottom to top.

[0019] In step S3, the limiting cover plate 2 is prepared, Figure 4 The front view of the limiting cover plate is Figure 5 The top view of the limiting cover plate. The main function of the limiting cover plate 2 is to limit the size of the product to be soldered and sealed according to the functional layer of the product, mainly to limit the size of the multi-layer circuit board at the top of the product (such as electrical layer + structural layer + electrical layer, and the design value of the size of each layer is the same), and to support the top surface pressure during welding in cooperation with the limiting base 1 and the controllable pressure device 3.

[0020] A second opening is provided in the middle of the position limiting cover plate 2 for accommodating the functional layer on the top of the product. The length, width and height of the position limiting cover plate 2 and the size of the second opening should be designed and processed according to the design size of the product substrate. Figure 5 In the figure, 2.6 and 2.7 are the length and width of the second opening of the limit cover 2, which are consistent with 1.4 and 1.5 of the limit base 1. The design processing dimensions should be larger than the length and width of the product, usually just enough to fit the product. This ensures that the length and width of the second opening limit the product from top to bottom after the limit cover 2 is fastened. Figure 4 and Figure 5 In the figure, 2.2 and 2.5 are respectively the first bosses on two adjacent sides of the four sides of the limit cover plate 2. The lengths of 2.2 and 2.5 should be less than the lengths of the slots 1.2 and 1.3 of the limit base 1. When the limit cover plate 2 and the limit base 1 are assembled, it is appropriate for the limit cover plate 2 to just fit into the limit base 1. The widths of the first bosses 2.2 and 2.5 are consistent with the width 2.8 of the reserved edge of the limit cover plate 2. 2.3 is the height of the first bosses 2.2 and 2.5, and the height of the first bosses is less than the depth 1.1 of the slot of the limit base 1. The inconsistent lengths of the first bosses 2.2 and 2.5 serve as an error-proofing design.

[0021] 2.1 is the second boss, whose bottom is on the plane formed by 2.6 and 2.7. 2.4 is the height of second boss 2.1. The length and width of second boss 2.1 should be consistent with those of the product. This ensures that after the limit cover 2 is assembled with the limit base 1, the length and width of second boss 2.1 ensure the assembly and positioning of the limit cover 2. The height of 2.4 should be determined based on the height of the internal cavity after the limit base 1 and limit cover 2 are assembled. This ensures that the height of the internal cavity after the limit base 1 and limit cover 2 are assembled is less than the height of the product. This ensures that the controllable pressure device 3 and the surrounding frame 4 provide the required welding pressure after the product is assembled.

[0022] According to the above process, assemble the limit base 1 and the finished product in the direction corresponding to 2.2 and 2.5, and assemble the limit cover 2. Figure 6 As shown, during the assembly process, the limit cover plate 2 is buckled onto the product to be brazed and sealed, and the length, width and height of the second boss and the first opening, as well as the length of the slots 1.2 and 1.3 are precisely matched with the length of the first bosses 2.2 and 2.5. The limit base 1 is used to limit the length and width of the product from bottom to top, and the limit cover plate 2 is used to limit the length, width and height of the product from top to bottom, that is, the product is positioned in both directions.

[0023] In step S4, the controllable pressure device 3 and the surrounding frame 4 are prepared, as shown in FIG. Figure 7The main function of the controllable pressure device is to provide pressure when the product is soldered and sealed. For different products, different high-temperature resistant spring needles can be replaced to achieve controllable pressure. The controllable pressure device includes a spring needle 3.1, an external threaded column 3.2, and a pressure block 3.3, wherein the spring needle 3.1 is a high-temperature resistant spring needle, and the pressure of the spring needle is usually between 0.5 kg and 10 kg. The upper part of the frame 4 is provided with a threaded hole 4.1, and the size of the external threaded column of the external threaded column 3.2 is matched with the size of the threaded hole 4.1 of the frame 4, so that the controllable pressure device is installed on the upper part of the frame 4. The spring needle 3.1 and the external threaded column 3.2 are combined into a spring pressure needle, and the pressure block 3.3 is connected with the spring pressure needle through internal threads. By controlling the extension and retraction of the high-temperature resistant spring needle 3.1, the up and down movement of the pressure block 3.3 can be achieved. The threaded hole 4.1 should be consistent with the external threads of the external threaded column 3.2. Figure 8 The frame is a sectional view, and 4.2 is a positioning line, which is convenient Figure 6 for positioning and placing during assembly, and the size of the line should be greater than the length and width of the limiting base 1 in step 6. Figure 7 When the controllable pressure device 3 and the frame 4 are combined, the distance between the bottom surface of the pressure block 3.3 and the surface of the positioning line 4.2 changes with the extension and retraction of the spring, Figure 9 The height of the limiting base 1 and the limiting cover plate 2 should be such that the distance between the bottom surface of the pressure block 3.3 and the surface of the positioning line 4.2 changes within the extension and retraction range of the spring, so that the spring can provide the required pressure.

[0024] By compressing the high-temperature resistant spring needle 3.1 of the controllable pressure device 3, the entire assembly with the limiting base 1, the product to be soldered and sealed, and the limiting cover plate 2 is placed according to the limiting of the positioning line 4.2 of the frame 4, and the high-temperature resistant spring needle 3.1 of the controllable pressure device 3 is loosened, and the assembly is completed, as shown in Figure 9

[0025] In step S5, welding is performed. Vacuum sintering furnace, tube furnace, hot air welding furnace, etc. can be used, and the brazing temperature curve and atmosphere condition program of the corresponding product are selected, for example Figure 10 the temperature curve and the welding protective gas atmosphere (99.99% argon) flow curve, to complete the welding. The internal metal to be welded and the peripheral frame are pre-coated with solder under the protection of the protective atmosphere, and after melting, wetting, spreading, and cooling, the vertical interconnection between the multiple substrates and the electrical pins is realized, and the gas-tight sealing welding between the substrate frame and the substrate is realized.

[0026] After welding is completed, cool to room temperature, compress the high-temperature resistant spring needle 3.1 of the controllable pressure device 3 to release the pressure applied to the product, and take out the entire assembly with the limiting base 1, the soldered and sealed product, and the limiting cover plate 2, and then remove the limiting cover plate 2 and the limiting base 1. ​

[0027] According to the above production process, the integrated brazing and fusion sealing of the microwave multi-cavity system-level package is completed.

[0028] To sum up, the method of the embodiment of the application realizes two-way positioning by placing the product in the limiting base and buckling the limiting cover plate on the limiting base; the pressure adjustment is realized by adjusting the spring of the controllable pressure device; the assembled limiting base, limiting cover plate and product are placed according to the positioning line of the frame, and welding is performed in combination with the brazing temperature curve and the control of the brazing cavity atmosphere, thereby realizing the integration of the microwave multi-cavity system-level package.

[0029] The method of the embodiment of the application realizes the synchronous brazing interconnection and airtight fusion sealing between the layers by two-way positioning, controlling pressure and other measures, realizes the system-level packaging of the microwave multi-cavity, and has the advantages of simple operation, accurate positioning, controllable pressure, and the airtightness of the fused product meeting the requirements, which can effectively reduce the process rejection rate and improve the one-time qualification rate of batch production, and provides a solution for the realization of high-power and high-integration microwave system-level packaging.

[0030] The above only describes certain exemplary embodiments of the application by way of illustration, and it is needless to say that the described embodiments can be modified in various ways without departing from the spirit and scope of the application for those skilled in the art. Therefore, the above drawings and descriptions are illustrative in nature and should not be understood as limiting the scope of protection of the claims of the application.

Claims

1. A microwave multi-cavity system-level packaging integrated brazing and sealing method, characterized in that: include: Prepare the product to be brazed and sealed. The product consists of two or more functional layers. The metal to be welded inside the product and the outer frame of the functional layer are pre-coated with solder. Prepare a limiting base. The limiting base has a first opening in the middle for accommodating the functional layer at the bottom of the product. The middle areas of the four sides of the limiting base are grooved. The product to be brazed and sealed is placed in the limiting base. The limiting base limits the product from bottom to top. Prepare a limiting cover plate, wherein a second opening is provided in the middle of the limiting cover plate for accommodating the functional layer on the top of the product, and first bosses are provided in the middle areas of the four sides of the limiting cover plate for cooperating with the slots on the four sides of the limiting base, wherein the height of the first boss is less than the depth of the slot, and the length of the first boss is less than the length of the slot, and a second boss is provided between the first boss and the second opening for cooperating with the first opening of the limiting base, and the limiting cover plate is buckled on the product to be brazed and sealed, and the assembly and positioning of the limiting cover plate is achieved through the cooperation between the first boss and the slot and the cooperation between the second boss and the first opening, thereby achieving the limitation of the product from top to bottom; Prepare a controllable pressure device and a frame. The controllable pressure device is installed on the upper part of the frame. Positioning lines are set on the lower part of the frame. Place the assembled product according to the positioning lines and apply pressure to the product through the controllable pressure device. The product is welded to achieve interconnection between different functional layers through internal metal welding of the product, and the airtightness of different functional layers is achieved through welding of the outer frames of the functional layers.

2. The method according to claim 1, wherein The functional layers include electrical layers with bare chips and wire bonds and structural layers.

3. The method according to claim 1 or 2, wherein: The cross-sections of the product, the limiting base and the limiting cover are all rectangular. The sizes of the first opening and the second opening are processed according to the design sizes of the product. The lengths of the first bosses on the adjacent two sides of the limiting cover are different, and the lengths of the slots on the adjacent two sides of the limiting base are different.

4. The method according to claim 1 or 2, wherein: After the limiting base and the limiting cover are assembled, the height of the internal cavity is smaller than the height of the product, so that after the product is assembled, the pressure required for welding is provided by the controllable pressure device and the surrounding frame.

5. The method according to claim 1 or 2, wherein: The controllable pressure device includes a spring pin, an external threaded column and a pressure block. The controllable pressure device is installed on the upper part of the frame through the external threaded column. The pressure block is moved up and down by the extension and contraction of the spring pin, thereby applying pressure to the assembled product through the pressure block.

6. The method according to claim 5, wherein The spring pin is a high-temperature resistant spring pin. By replacing different high-temperature resistant spring pins, the pressure can be controlled.

7. The method according to claim 1 or 2, wherein: Use vacuum sintering furnace, tubular furnace or hot air welding furnace, select the brazing temperature curve and atmosphere flow curve of the corresponding product to complete the welding.

8. The method according to claim 1 or 2, wherein: After welding is completed, cool to room temperature, release the pressure on the product, take out the entire product with the limit base, brazed and sealed product and limit cover, and then remove the limit cover and limit base.

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