A three-dimensional interconnect structure for microwave module metal packaging and a method of fabrication

Abstract

The application provides a three-dimensional interconnection structure manufacturing method for a microwave module metal package, and the three-dimensional interconnection structure comprises a module shell, an upper cover plate, a lower cover plate, a substrate, a bolt and a nut. The multilayer substrate is placed in a vertical direction in the module and is supported by a boss on the inner side wall of the shell. A countersunk hole is formed at the edge of the substrate, coaxial with a through hole on the boss, and a hexagonal bolt and a nut are used to penetrate the upper and lower substrates to fix the two layers of substrates in the cavity. The internal structure of the hexagonal bolt comprises a signal connection metal column, an insulating ceramic ring and an outer shell metal layer from inside to outside. The hexagonal bolt not only fixes the upper and lower substrates but also forms a signal transmission path for the interconnection of the two layers of substrates in the three-dimensional vertical direction. The shell, the upper and lower cover plates, the internal substrate and the hexagonal bolt form a gas-tight package module with devices and bare chips.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit micro-assembly technology, and in particular to a method for fabricating a three-dimensional interconnect structure for metal packaging of microwave modules. Background Technology

[0002] With the increasing demand for miniaturization and multifunctionality of modules, the number of components and integration within modules are also constantly increasing. The number of substrates within modules is gradually increasing from one to multiple. The intricate internal signal connections place higher demands on structural design, especially in the RF or power supply fields, where there are special requirements for grounding effects and spatial distribution. The large number of substrates stacked within modules makes three-dimensional packaging design very difficult.

[0003] Traditionally, signal input and output between modules are mostly achieved through internal connectors via cables or jumper wires. That is, within the module, one end of a connector or enameled wire is connected to the input or output terminal on one substrate, and the other end of the cable is connected to another substrate to complete signal transmission. Therefore, both signal input and output ports are inside the module. This transmission method reduces signal stability and increases the module's footprint, failing to meet the high reliability and stability requirements of microwave modules, as well as the trends towards miniaturization and lightweight design. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a three-dimensional interconnect structure and manufacturing method for metal packaging of microwave modules, aiming to optimize the signal transmission method within the module, transforming traditional cable transmission into transmission via connection support pillars, thereby stabilizing the signal and greatly saving structural design space.

[0005] The solution of the present invention is: a three-dimensional interconnection structure for metal packaging of microwave modules, including a shell, an upper cover plate, a lower cover plate, a substrate, bolts, and nuts; wherein the substrate has two or more layers;

[0006] The housing has an internal cavity that is vertically connected. The inner cavity sidewall has multiple steps for supporting and fixing the substrate. The steps have through holes for placing metal connecting posts. The upper and lower surfaces of the housing have recessed steps for placing the upper cover plate and the lower cover plate. The upper cover plate and the lower cover plate are placed on the recessed steps respectively. The upper surface of each cover plate is flush with the outer surface of the housing. After encapsulation, a sealed cavity structure is formed.

[0007] Devices are attached to the surface of the substrate and are horizontally stacked on the steps inside the housing cavity. Adjacent substrates are parallel and have a reserved gap. Countersunk holes are opened on the edges of the substrates and are coaxial with the through holes on the steps. The pads on the surface of the substrate for signal connection correspond one-to-one with the countersunk holes and are distributed around the countersunk holes.

[0008] The core of the bolt is a metal connecting post, and an insulating ring is wrapped around the outside of the connecting post. An insulating ceramic ring is filled between the bolt shell and the metal connecting post. The metal connecting post, the insulating ring, and the bolt shell are flush at both ends. The bolt is used to fix two substrates that require signal communication to the side wall step and form a signal connection channel. The bolt and nut cooperate to fasten the two substrates.

[0009] Preferably, the thickness of the cover material is between 0.5mm and 2mm, the assembly gap is controlled between 0.03mm and 0.05mm, and the upper surface of the cover is flush with the surface of the housing after assembly.

[0010] Preferably, the substrate is thicker than 1 mm, has multiple interconnected circuits inside, and has pads on its surface for surface mounting of devices and connection of signals.

[0011] Preferably, the shell material is a metal encapsulation material, including aluminum alloy, silicon-aluminum alloy, and Kovar alloy; the cover plate material is a material whose welding compatibility with the shell material meets the requirements; the substrate is a resin material; and the nut material is the same as the bolt shell material.

[0012] Preferably, the outer shell of the bolt is made of metal that meets strength requirements, and its thickness is greater than 60% of the overall thickness. The bolt is equipped with corresponding threads, the thread length of which is half the length of the bolt. The inner insulating ring is made of ceramic, and the core metal connecting post is made of a material with good electrical conductivity, with a conductivity > 4 × 10⁻⁶. 7 S / m, surface is gold plated.

[0013] The method for fabricating the aforementioned three-dimensional interconnect structure includes the following steps:

[0014] Components in the three-dimensional interconnect structure are fabricated: the machined housing and upper and lower cover plates are treated with colored conductive oxidation; the overall bolt structure adopts an integrated sintering process, which sintersperses the core metal connecting column, the insulating ceramic ring and the bolt shell together to form a bolt that meets the requirements of packaging airtightness and assembly strength.

[0015] Surface-mount devices are bonded to the substrate using a reflow soldering process;

[0016] Place the substrate with the surface-mount device on the step of the housing, ensuring that the countersunk holes on the substrate are coaxial with the through holes on the step.

[0017] The bolt is used to connect the two substrates with signal communication requirements to the nut; the head plane and tail plane of the bolt are connected to the metal pads of the bolt core and the pads on the substrate by gold wire bonding.

[0018] Laser sealing is used to seal the upper and lower cover plates onto the housing, achieving airtight encapsulation.

[0019] Preferably, the input or output pads on the upper substrate are connected to the pads of the metal connecting post inside the bolt head using a thermo-ultrasonic bonding process, and then the pads of the metal connecting post inside the bolt tail are connected to the input or output pads on the lower substrate, thereby realizing signal communication between the two substrates within the module; the upper and lower substrates are defined by their relative positions within the housing; if it is a multi-layer substrate, the other two substrates required for signal communication are connected in the same way.

[0020] Preferably, the bolt head and tail after installation should not be more than 0.5mm higher than the plane of the upper and lower base plates.

[0021] Preferably, the reflow soldering temperature is between 180℃ and 240℃, and the strength of the bolts after sintering meets the requirements of GB / T5782-2000.

[0022] Preferably, when the housing is made of aluminum alloy, the peak power of the laser pulse waveform is adjusted based on the pre-peak wave for sealing aluminum alloy; when the housing is made of silicon-aluminum alloy, the peak power is adjusted based on the preheating and heat preservation wave. The horizontal axis of the laser pulse waveform is time, and the vertical axis is peak power. The adjustment setting is a floating adjustment of the peak power.

[0023] Based on the linear relationship between fusing current and gold wire diameter: I = aD c Where I is the fusing current of the gold wire (A); D is the wire diameter (in); a is the fusing coefficient (12675 for gold wire); and c is a constant (1.46 for gold wire). Calculate and select the appropriate wire diameter, which can be 25μm, 50μm, or 75μm. Ultrasonic thermocompression welding is used to connect the substrate to the metal connecting post inside the bolt.

[0024] The advantages of this invention compared to the prior art are:

[0025] This invention utilizes specially structured bolts and nuts installed in the inner wall of a module to replace connectors and cables for signal connection and bolts for fixing the substrate. Through gold wire bonding technology, the metal pillars inside the bolts are connected to the pads on the upper and lower substrates. This achieves both vertical signal transmission within the module and fixation of the upper and lower substrates, significantly reducing the space occupied by signal transmission and improving the stability and reliability of signal transmission. It also enables metal packaging to become more miniaturized and more integrated.

[0026] This invention achieves internal multi-channel signal interconnection in the three-dimensional vertical direction of the multi-layer substrates within a single packaging system through a metal package that is stacked between multiple substrates. This avoids the signal instability (interference / crosstalk) problems that are prone to occur when connecting via connector cables or flying wires. It saves space and improves system integration, meeting the development trend of microwave modules towards miniaturization and lightweight design. Attached Figure Description

[0027] Figure 1 This is an overall sectional view of the present invention;

[0028] Figure 2 This is a top view of the substrate mounting. Detailed Implementation

[0029] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the preferred embodiments are only for illustrating the present invention and are not intended to limit the scope of protection of the present invention.

[0030] A three-dimensional interconnect structure for metal packaging of microwave modules includes a housing, an upper cover, a lower cover, a multilayer substrate, bolts, and nuts.

[0031] The housing has an internal cavity that connects the upper and lower parts. The inner cavity sidewalls are provided with multiple steps (or protrusions, bosses) for supporting and fixing the substrate. The steps are provided with through holes for placing metal pillars. The upper and lower surfaces of the housing are provided with recessed steps for placing cover plates.

[0032] The upper and lower cover plates are placed on the upper and lower surfaces of the housing, respectively. The upper surface of each cover plate is flush with the outer surface of the housing, forming a sealed cavity structure after encapsulation.

[0033] Devices are mounted on the substrate surface and horizontally stacked within the housing cavity, supported by pre-installed bosses in the housing. Adjacent substrates are parallel and spaced apart. Countersunk holes are formed at the edges of the substrates, coaxial with the through holes on the bosses. The pads for signal connections on the upper and lower substrate surfaces correspond one-to-one with the countersunk holes and are distributed near the countersunk holes.

[0034] The bolt is an external hexagonal bolt with threads at the tail. The bolt core is a metal connecting post, and an insulating ceramic ring is wrapped around the outside of the connecting post. The insulating ceramic ring fills the space between the bolt shell and the metal connecting post, ensuring airtightness. The metal connecting post, the insulating ceramic ring, and the bolt shell are flush at both ends.

[0035] The external hex bolts are used to fix the double-layer substrate to the side wall boss and form a signal connection channel. The number of external hex bolts is determined by the number of signal connections between the substrates.

[0036] If the number of substrates exceeds two, the two substrates requiring signal connectivity are generally arranged adjacently, with their relative positions within the housing serving as the upper and lower substrates. The bolts are used to establish signal connectivity between them and to secure them to the step. If it is impossible to arrange the two substrates requiring signal connectivity adjacently, then the substrate located between them needs to be designed to avoid interference.

[0037] The nut is matched with the external hexagonal bolt and is used to screw the base plate in from the bottom of the bolt.

[0038] The housing material is a common metal packaging material such as aluminum alloy, silicon aluminum alloy, and Kovar alloy. Steps are provided at the top and bottom of the housing for placing the top and bottom cover plates. Bosses and through holes are provided on the internal sidewalls for overlapping and fixing the upper and lower substrates.

[0039] The cover plate material is aluminum alloy or the like, which has good welding compatibility with the shell material. The thickness is between 0.5mm and 2mm, and the assembly gap is controlled between 0.03mm and 0.05mm. After assembly, the upper surface of the cover plate is flush with the surface of the shell.

[0040] The double-layer substrate is made of resin material with a thickness greater than 1 mm. It has multiple interconnected circuits inside and solder pads on the surface for surface mounting of devices and connection of signals.

[0041] The aforementioned hexagonal bolts can be selected and customized in diameters of 1.6mm and above. The outer shell is made of high-strength metals such as stainless steel, with a thickness greater than 60% of the overall thickness. The bolts are equipped with corresponding threads, the thread length of which is half the length of the bolt. The internal insulating ring is made of ceramic. The core metal connecting post is made of materials with good conductivity such as Kovar and copper, and the surface is gold-plated.

[0042] The nut specifications match the bolts, and the nut material is the same as the bolt material.

[0043] The method for fabricating the above-mentioned three-dimensional interconnect structure includes the following steps:

[0044] Components in the three-dimensional interconnect structure are fabricated: the machined housing and upper and lower cover plates are treated with colored conductive oxidation; the overall bolt structure adopts an integrated sintering process, which sintersperses the core metal connecting column, the insulating ceramic ring and the bolt shell together to form a bolt that meets the requirements of packaging airtightness and assembly strength.

[0045] Surface mount devices are bonded to the upper and lower substrates using a reflow soldering process.

[0046] Place the upper and lower substrates after surface mount devices onto the double-layer steps of the housing, ensuring that the countersunk holes on the upper and lower substrates are coaxial with the through holes on the steps.

[0047] The bolt passes through the upper and lower substrates and is connected to the nut; the bolt head plane and tail plane are connected to the metal pads on the substrate by gold wire bonding.

[0048] Laser sealing is used to seal the upper and lower cover plates onto the housing, achieving hermetic sealing that meets the requirements of GJB548B.

[0049] Example

[0050] Combination Figure 1The three-dimensional interconnection structure for metal packaging of microwave modules in this embodiment includes a module housing 1, an upper cover plate 2, a lower cover plate 3, a double-layer substrate 4, 5, a bolt 6, and a nut 9.

[0051] The housing 1 is made of aluminum alloy 6063, with external dimensions of 30mm×30mm×30mm and a wall thickness of 1.5mm. The four internal side walls are provided with bosses for overlapping the upper and lower substrates. The bosses have a wall thickness of 2mm and are divided into upper and lower layers, 10mm apart. Each boss has a through hole with a diameter of 2.2mm, and the through holes of the upper and lower layers are coaxial.

[0052] The upper cover plate 2 and the lower cover plate 3 are made of aluminum alloy 4047, and both are 1mm thick. After the cover plates are fitted onto the housing 1, the surface of the upper cover plate 2 is flush with the upper surface of the housing, and the surface of the lower cover plate 3 is flush with the lower surface of the housing.

[0053] The double-layer substrates 4 and 5 are made of FR-4 material with a thickness of 1mm. They are built into the inner cavity of the module and stacked parallel to each other on the boss of the housing 1. A countersunk through hole is opened at the position where the substrate and the boss through hole are coaxial. The through hole diameter is 2.2mm, the countersunk hole diameter is 6.2mm, and the countersunk hole depth is 0.5mm.

[0054] The bolt 6 has a diameter of 2mm, a body length of 15mm, a hexagonal bolt head with a diagonal length of 4.2mm, and a thickness of 1mm.

[0055] The bolt 6 consists of a three-layer structure: an outer layer 1.2 mm thick, made of stainless steel; an inner insulating ring 7 0.5 mm thick, made of 90% Al2O3 ceramic; and a core metal post 8 0.3 mm in diameter, made of Kovar alloy. The three layers are flush with the head and tail planes of the bolt.

[0056] The nut 9 is matched with the bolt 6, with an inner diameter of 2mm, an outer hexagonal diagonal length of 4.2mm, and a thickness of 1mm, and is made of stainless steel.

[0057] The above-mentioned method for fabricating a three-dimensional interconnect structure for microwave module metal packaging includes the following steps:

[0058] Step 1, Fabrication of module housing 1 and upper and lower cover plates 2 and 3: Housing 1 and upper and lower cover plates 2 and 3 are machined using machining processes. The fitting clearance between housing 1 and upper and lower cover plates 2 and 3 is controlled between 30μm and 50μm. Through holes and bosses for fixing and supporting the substrate are machined on the four side walls of the inner cavity of housing 1. The inner and outer sides of housing 1, as well as upper and lower cover plates 2 and 3, are all treated with colored conductive anodizing.

[0059] Step 2, Fabrication of Bolt 6 and Nut 9: The bolt's overall structure employs an integrated sintering process, sintering the core metal connecting post, insulating ceramic ring, and outer shell together to form a specially designed bolt that meets the requirements of hermetical sealing and assembly strength. Nut 9 is manufactured using a machining process, ensuring it can be screwed properly into bolt 6.

[0060] Step 3, assembly of upper and lower substrates 4 and 5: as follows Figure 2 As shown, the plastic-encapsulated device 11 is surface-mounted onto the upper and lower substrates using a reflow soldering process. The reflow temperature is 235°C, and the solder paste is a tin-silver-copper alloy (Sn96.5 Ag3Cu0.5). The substrates 4 and 5 with the surface-mounted device are placed on the upper and lower bosses of the housing 1, ensuring that the countersunk holes on the four sides of the substrates 4 and 5 are coaxial with the through holes on the bosses.

[0061] Insert the bolt 6 made in step 2 into the coaxial hole on the substrate and the boss, and tighten it with nut 9. The head and tail of the bolt are 0.5mm higher than the plane of the upper and lower substrates 4 and 5, respectively.

[0062] Step 4, Gold wire bonding: Select 25μm gold wire 10 and use thermo-ultrasonic bonding process to connect the input or output pads on the substrate 4 to the pads of the metal pillar 8 inside the bolt head, and then connect the pads of the metal pillar 8 inside the bolt tail to the input or output pads on the substrate 5 to realize the signal communication of the double-layer substrate in the module.

[0063] Step 5, Laser Sealing: Place the assembled module into the oven provided with the laser sealing machine and vacuum bake at 120℃ for 24 hours. After the module cools, place it on the worktable and clamp it with the tooling. Use the laser sealing process to seal the upper and lower cover plates 2 and 3 onto the housing 1, achieving hermetic sealing. The hermetic sealing performance is higher than that of ceramic packaging modules of the same size, reaching 5×10. - 9 Pa·m 3 / s.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

[0065] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A three-dimensional interconnect structure for metal packaging of microwave modules, characterized in that: It includes a shell, an upper cover plate, a lower cover plate, a base plate, bolts, and nuts; the base plate has two or more layers. The housing has an internal cavity that is vertically connected. The inner cavity sidewall has multiple steps for supporting and fixing the substrate. The steps have through holes for placing metal connecting posts. The upper and lower surfaces of the housing have recessed steps for placing the upper cover plate and the lower cover plate. The upper cover plate and the lower cover plate are placed on the recessed steps respectively. The upper surface of each cover plate is flush with the outer surface of the housing. After encapsulation, a sealed cavity structure is formed. Devices are attached to the surface of the substrate and are horizontally stacked on the steps inside the housing cavity. Adjacent substrates are parallel and have a reserved gap. Countersunk holes are opened on the edges of the substrates and are coaxial with the through holes on the steps. The pads on the surface of the substrate for signal connection correspond one-to-one with the countersunk holes and are distributed around the countersunk holes. The bolt is an external hexagonal bolt manufactured using an integrated sintering process. The core of the bolt is a metal connecting post, with an insulating ring wrapped around the outside of the connecting post. An insulating ceramic ring fills the space between the bolt shell and the metal connecting post. The metal connecting post, the insulating ring, and the bolt shell are flush at both ends. The bolt is used to fix two substrates with signal communication requirements to the side wall step and form a signal connection channel. The bolt and nut cooperate to fasten the two substrates. The input or output pads on the upper substrate are connected to the pads of the metal connecting post inside the bolt head using a thermo-ultrasonic bonding process. Then, the pads of the metal connecting post inside the bolt tail are connected to the input or output pads on the lower substrate, realizing signal communication between the two substrates within the module.

2. The three-dimensional interconnect structure for microwave module metal packaging according to claim 1, characterized in that: The thickness of the cover material is between 0.5mm and 2mm, the assembly gap is controlled between 0.03mm and 0.05mm, and the upper surface of the cover is flush with the surface of the shell after assembly.

3. The three-dimensional interconnect structure for microwave module metal packaging according to claim 1, characterized in that: The substrate is thicker than 1 mm and has multiple interconnected circuits inside. The surface is covered with pads for surface mounting of components and connection of signals.

4. A three-dimensional interconnect structure for metal packaging of microwave modules according to claim 1, characterized in that: The shell material is a metal encapsulation material, including aluminum alloy, silicon-aluminum alloy, and Kovar alloy; the cover plate material is a material whose welding compatibility with the shell material meets the requirements; the substrate is a resin material, and the nut material is the same as the bolt shell material.

5. The three-dimensional interconnection structure according to claim 1, characterized in that: The bolt's outer shell is made of metal that meets strength requirements, with a thickness greater than 60% of the overall thickness. The bolt is equipped with corresponding threads, the thread length of which is half the length of the bolt. The internal insulating ring is made of ceramic, and the core metal connecting post is made of a material with good electrical conductivity, >4×10⁻⁶. 7 S / m, surface is gold plated.

6. A method for fabricating a three-dimensional interconnect structure according to any one of claims 1-5, characterized in that, Includes the following steps: Components in the three-dimensional interconnect structure are fabricated: the machined housing and upper and lower cover plates are treated with colored conductive oxidation; the overall bolt structure adopts an integrated sintering process, which sintersperses the core metal connecting column, the insulating ceramic ring and the bolt shell together to form a bolt that meets the requirements of packaging airtightness and assembly strength. Surface-mount devices are bonded to the substrate using a reflow soldering process; Place the substrate with the surface-mount device on the step of the housing, ensuring that the countersunk holes on the substrate are coaxial with the through holes on the step. The bolt is used to connect the two substrates with signal communication requirements to the nut; the head plane and tail plane of the bolt are connected to the metal pads of the bolt core and the pads on the substrate by gold wire bonding. Laser sealing is used to seal the upper and lower cover plates onto the housing, achieving airtight encapsulation.

7. The manufacturing method according to claim 6, characterized in that: The input or output pads on the upper substrate are connected to the pads of the metal connecting post inside the bolt head using a thermo-ultrasonic bonding process. Then, the pads of the metal connecting post inside the bolt tail are connected to the input or output pads on the lower substrate, thereby achieving signal communication between the two substrates within the module. The upper and lower substrates are defined by their relative positions within the housing. If it is a multi-layer substrate, the other two substrates required for signal communication are connected in the same way.

8. The manufacturing method according to claim 6, characterized in that: After installation, the bolt head and tail must not be higher than 0.5mm above the plane of the upper and lower base plates.

9. The manufacturing method according to claim 6, characterized in that: The reflow soldering temperature is between 180℃ and 240℃, and the strength of the bolts after sintering meets the requirements of GB / T5782-2000.

10. The manufacturing method according to claim 6, characterized in that: When the housing is made of aluminum alloy, the peak power of the laser pulse waveform is adjusted based on the pre-peak wave for sealing aluminum alloy. When the housing is made of silicon-aluminum alloy, the peak power is adjusted based on the preheating and heat preservation wave. The horizontal axis of the laser pulse waveform is time, and the vertical axis is peak power. The adjustment setting is to make a floating adjustment to the peak power.

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