Cable-free microcircuit module structure and assembling method

Abstract

The invention discloses a cable-free microcircuit module structure and an assembling method, the cable-free microcircuit module structure comprises a plurality of layers of PCB substrates installed in a frame, a plurality of components are welded or bonded on each layer of PCB substrate, based on a plastic package BGA device and a bare chip double-sided SMT assembling technology, the PCB substrates adopt a rigid-flexible cable-free design, and a plurality of components are welded or bonded on each layer of PCB substrate. According to the structure, interconnection and supporting of multiple layers of PCB substrates are achieved in a pin interconnection mode, the size of a servo drive complete machine system of the same level is reduced by more than 70%, the weight is reduced by more than 80%, the problems of application requirements of miniaturization, light weight and the like of an existing military motor drive system are solved, electrical signals of all the layers of PCB substrates are communicated through flexible belts and connectors, and the service life of the servo drive complete machine system is prolonged. And cable-free communication of the internal structure of the module is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of hybrid integrated circuits, and in particular relates to a cable-free microcircuit module structure and an assembling method. Background Art

[0002] With the rapid development of integrated circuit and microcircuit assembly technology, high integration, high power density, and high quality reliability have become important development directions in the field of weapons and equipment. Currently, servo drive system mostly adopts multi-layer printed circuit board structure based on discrete devices, and the internal interface is interconnected by cables. This structure is simple in process and easy to implement.

[0003] However, the above structure is heavy and bulky, and the cabled design not only increases the complexity of the structural design, but also makes maintenance difficult and has low reliability, making it difficult to meet the requirements of miniaturization, lightness, high power density, and low parasitic inductance of the servo system. Therefore, how to achieve system-level packaging of the two relatively independent systems of high-speed signal processing control circuit and power drive circuit in the servo system has become an important research direction. Summary of the invention

[0004] The object of the present invention is to provide a cable-free microcircuit module structure and an assembly method to overcome the problems of the prior art servo drive system being heavy, bulky and complex.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions: A cableless microcircuit module structure comprises a frame, wherein a multi-layer PCB substrate is installed in the frame, wherein each layer of the PCB substrate adopts a laminated structure, components are welded or bonded to the front and back sides of the PCB substrate, wherein the components include finished devices and bare chips, wherein the bare chips adopt a potting process, wherein each layer of the PCB substrate of the same PCB substrate is connected via a flexible board, and each layer of the PCB substrate of different PCB substrates is connected via a connector, wherein the each layer of the PCB substrates adopts cableless communication.

[0006] Furthermore, the bare chip includes an AD converter, a digital isolator, a gate driver and a MOS tube.

[0007] Furthermore, the components also include resistors, capacitors and transformers.

[0008] Furthermore, the finished device includes SOC, DDR3, FLASH, communication transceiver, DC / DC converter, current sensor and transistor.

[0009] Furthermore, thermally conductive pads are installed on the components on the PCB substrate.

[0010] In a second aspect, a method for assembling a cable-free microcircuit module structure is provided, comprising the following steps: Weld and bond finished components, MOS tubes, resistors, capacitors and connectors on each layer of PCB substrate; Bond the bare chip to each layer of PCB substrate; Bonding the bare chips through bonding wires; Potting is performed after bonding is completed; After potting is completed, three-conformal coating is carried out; Each layer of PCB substrate is installed in the frame, and finally the cover plate is added to complete the module assembly.

[0011] Furthermore, the connector is used for connecting different PCB substrates.

[0012] Further, the welding steps are: First, solder the side with fewer components on the back of the PCB substrate, mainly resistors and capacitors; Secondly, solder the front side of the PCB substrate, which is the side containing the BGA components and bare chips, and clean it after soldering.

[0013] Furthermore, the bare chip is bonded using insulating glue, and the bonding area is partially plated with nickel-palladium-gold; the welding uses nickel-palladium-gold pads, and the bonding uses gold wire, silicon-aluminum wire or aluminum wire bonding.

[0014] Further, potting includes the following steps: After the bare chip is bonded, a dam is formed using dam glue; The bare core area is potted with potting glue, and black glue is used for potting glue.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a cable-free microcircuit module structure, comprising a multi-layer PCB substrate installed in a frame, a plurality of components are welded or bonded on each layer of the PCB substrate, and the interconnection and support of the multi-layer PCB substrate is realized by a pin interconnection mode in structure. Meanwhile, a rigid-flexible cable-free PCB substrate design is adopted, and a stacked 3D assembly is performed to break through the concept of traditional planar packaging, form a three-dimensional package, greatly improve the assembly density, and realize the high power density and high integration of a multi-axis servo drive system; the layers of the PCB substrates of the same PCB substrate are connected by a flexible board, and the layers of the PCB substrates of different PCB substrates are connected by connectors, thereby ensuring the cable-free communication of the internal structure of the module, and effectively solving the problem of miniaturization and lightweight of the existing motor drive system.

[0016] Through the connection of laminated PCB substrates, flexible boards and connectors, cable-free communication between multi-layer PCB substrates is realized. This structure greatly reduces the use of cables and connectors, improves the integration and reliability of circuits, and reduces weight and cost. In addition, the front and back welding or bonding of components increases the space utilization of the circuit board and improves the overall performance.

[0017] Preferably, installing thermally conductive pads on the components on the PCB substrate can effectively improve the heat dissipation performance and service life of the module.

[0018] The present invention provides a double-sided SMT assembly technology based on plastic-encapsulated BGA devices and bare chips. The PCB substrate adopts a cable-free design combining rigid and flexible components. The interconnection and support of the multi-layer PCB substrate are realized by pin interconnection in structure. The volume of the servo drive system of the same level is reduced by more than 70% and the weight is reduced by more than 80%. The difficult problems of the current application requirements of miniaturization and lightweight of military motor drive systems are solved. The invention has important practical significance for realizing the integrated design of motor drivers and the application in military high-reliability occasions. The microcircuit module realized by the method has broad application prospects in military servo control systems such as ships, aerospace, and weapons, and has important strategic significance and social benefits.

[0019] Preferably, the back side with fewer components is welded first, and then the front side containing BGA components and bare chips is welded. This welding sequence reduces thermal stress and mechanical stress during welding, and improves welding quality and component reliability.

[0020] Preferably, the cofferdam glue is used to form a barrier, which effectively protects the bare chip from interference and damage from the external environment and improves the waterproof, dustproof and corrosion-resistant capabilities of the module. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing the internal structure of a cable-free microcircuit module in an embodiment of the present invention; Figure 2 A three-dimensional model diagram of a cable-free microcircuit module in an embodiment of the present invention; Figure 3 This is a flow chart of a cable-free microcircuit module structure assembly method according to an embodiment of the present invention; Figure 4 This is a process flow chart of assembling a cable-free microcircuit module structure in an embodiment of the present invention; Figure 5 Schematic diagram of the morphology of the PCB-1 substrate after assembly.

[0022] Figure 6 Schematic diagram of the frame used for assembly.

[0023] Figure 7This is the first step of assembling the PCB-1 substrate and frame.

[0024] Figure 8 Schematic diagram of the second step of assembling the PCB-1 substrate and frame.

[0025] Fig. 9 Schematic diagram of the assembly of PCB-2 substrate and frame.

[0026] Fig.10 Schematic diagram of adding thermal conductive pads to components on the PCB-1 substrate.

[0027] Fig.11 Schematic diagram of installing screws on the front of the circuit.

[0028] Fig.12 Schematic diagram of adding thermal conductive pads to components on the PCB-2 substrate.

[0029] Fig.13 Diagram of the screw installation on the back of the circuit. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0032] Glossary BGA packaged IC is an integrated circuit that uses ball grid array packaging technology.

[0033] BGA (Ball Grid Array) is a surface mount packaging technology. At the bottom of the BGA package, the pins are spherical and arranged in a grid-like pattern to connect to the pads on the circuit board. This packaging method can provide more pins than other packages such as dual in-line packages (DIP) or quad flat packages (QFP) because the entire bottom surface of the device can be used as pins instead of only the surrounding area. In addition, the BGA package also has a shorter average wire length, which has better high-speed performance.

[0034] BGA packaged IC is an integrated circuit packaging technology with high-density pins, excellent electrical performance and heat dissipation performance, and is widely used in various electronic devices.

[0035] Bonding is an important connection and assembly technology, which is widely used in many fields. Bonding is a technology that directly combines two homogeneous or heterogeneous semiconductor materials (or other materials) with clean and atomically flat surfaces under certain conditions after surface cleaning and activation treatment, and bonds the wafers (or other materials) into one through van der Waals force, molecular force or even atomic force. This technology uses physical or chemical effects to make the material surface closely contact at the atomic level to form a stable structure. The advantages are: High precision: Bonding technology can achieve close contact of materials at the atomic level, so it has high precision.

[0036] Strong bonding force: The bonding structure formed by physical or chemical action has a strong bonding force, which can ensure the stability and reliability of the connection.

[0037] Diversity: Bonding technology can be applied to the connection between a variety of materials, including metals, semiconductors, ceramics, etc.

[0038] Flexibility: With the development of science and technology, new bonding technologies continue to emerge, such as ultrasonic bonding and light-curing bonding, providing more options for applications in different fields.

[0039] Example 1 The present invention provides a cable-free microcircuit module structure, such as Figure 1 As shown, it includes a frame and a multi-layer PCB substrate installed in the frame, wherein each layer of the PCB substrate of the same PCB substrate is connected through a flexible board, and each layer of the PCB substrate of different PCB substrates is connected through a connector, thereby reducing the cable connection between each layer of the PCB substrate, and each layer of the PCB substrate in the frame adopts a stacked 3D assembly, and a finished device is welded on each layer of the PCB substrate, and a bare chip is bonded, wherein the bare chip is kept sealed in the form of local potting.

[0040] Specifically, the frame used for assembly has a shape such as Figure 6 As shown, the components welded or bonded on each layer of the PCB substrate include finished devices, bare chips, resistors and capacitors, and transformers. The finished devices include SOC, DDR3, FLASH, communication transceivers, DC / DC converters, current sensors, and transistors; the bare chips include AD converters, digital isolators, gate drivers, and MOS tubes.

[0041] A method for assembling the above-mentioned cable-free microcircuit module structure is proposed. Figure 3 As shown, the following steps are included: Step 1: solder finished devices, MOS tubes, resistors, capacitors and connectors on each layer of PCB substrate; Finished devices, power chips, namely MOS tubes, transformers, resistors and capacitors are assembled using the reflow process, and connectors are also manually soldered on the PCB substrate. The function of the connectors is to connect different PCB substrates. After soldering, they are cleaned and inspected.

[0042] Step 2: Bond the bare chip to each layer of PCB substrate: All bare chips except MOS tubes are bonded to the PCB substrate with insulating glue and inspected after bonding.

[0043] Step 3: Bond the bare chip with bonding wire: The bare chip needs to be bonded with gold wire, silicon aluminum wire and aluminum wire to achieve electrical connection. Therefore, the bonding area adopts a local nickel-palladium-gold plating process. After the bonding is completed, a non-destructive tensile test is performed to ensure the firmness of the wire bonding, and finally a pressure welding inspection is performed.

[0044] Step 4: Potting after bonding is completed: After assembly is completed and the test is normal, the bare chip is partially potted. The potting process adopts two steps. First, the cofferdam glue is applied on the cofferdam frame and turned upside down in the cofferdam area. After curing, the cofferdam frame is bonded. After pre-sealing inspection and AOI inspection, the bare core area is potted with potting glue. Glue is applied from the area without bonding wires in the cofferdam frame. After the colloid is naturally leveled, it is cured. Black glue is used as the local potting material for the bare chip.

[0045] Step 5: After potting, perform three-conformal coating: After potting is completed, "three-proof coating" is required. "Three-proof coating" usually refers to applying a layer of three-proof paint on electronic equipment, circuit boards or other surfaces that need protection to achieve the effect of moisture-proof, mildew-proof and salt spray-proof (referred to as three-proof). The following is a detailed explanation of three-proof coating: 1. Definition and function of conformal coating Conformal coating is a special coating with waterproof, moisture-proof, dust-proof, anti-corrosion, and chemical-proof properties. When it is applied to the surface of an object, it forms a transparent protective film that can effectively protect the object from erosion or damage from the surrounding environment. Specifically, conformal coating is not only moisture-proof, salt spray-proof, and mildew-proof, but also provides good protection for the entire external environment, such as leakage-proof, dust-proof, anti-static, anti-aging, and anti-corrosion, and also has good high temperature resistance.

[0046] 2. The purpose of three-proof coating The main purpose of coating is to reduce or eliminate the adverse effects of complex environments on the performance of electronic devices, thereby extending their service life and reliability. In electronic devices, circuit boards are one of the components most susceptible to environmental influences. Environmental factors such as moisture, mold, and salt spray may damage circuit boards, leading to oxidation, rust, and short circuits of electronic components. By coating with conformal coating, a protective film can be formed on the surface of the circuit board to prevent damage from these environmental factors.

[0047] 3. Advantages of three-proof coating Improve equipment reliability: By applying conformal coating, the damage of environmental factors to electronic equipment can be reduced, thereby improving the reliability and stability of the equipment.

[0048] Extend the service life of the equipment: The protective film formed by the three-conformal paint can effectively protect electronic equipment from erosion by environmental factors, thereby extending the service life of the equipment.

[0049] Reduce maintenance costs: Due to the protective effect of the three-conformal paint, the failure rate and maintenance times of electronic equipment can be reduced, thereby reducing maintenance costs.

[0050] Step six: install each layer of PCB substrate in the frame, and finally install the cover to complete the module assembly.

[0051] Example 2 The invention discloses a structure and an assembly method of a servo drive microcircuit module. The module adopts a plastic-sealed BGA device and a bare chip double-sided SMT assembly technology. The internally integrated components include SOC, DDR3, FLASH, AD converter, digital isolator, communication transceiver, DC / DC converter, current sensor, gate driver, MOS tube, transistor and resistor and capacitor elements. The AD converter, digital isolator, gate driver and MOS tube are bare chips, which are integrated and sealed in a cofferdam. The microcircuit module structure includes 57 active devices (referring to components other than resistors, capacitors and transformers), 86 chip resistors, 74 capacitors, and a PCB substrate is designed with 14 layers, including 6 layers of flexible boards, and the substrate thickness is 2.0 mm.

[0052] The module is assembled with finished devices and bare chips. The bare chips are partially potted. The finished devices, power chips (MOS tubes), resistors and capacitors are assembled using the reflow process. The remaining chips (bare chips except MOS tubes) are assembled using insulating adhesive. The bonding wires include gold wires, aluminum wires, and silicon aluminum wires. The schematic diagram of the internal structure of the module is as follows: Figure 1 The package is a non-hermetic package of an aluminum alloy shell. The three-dimensional model is shown in Figure 2 shown.

[0053] According to the temperature gradient requirements of the process assembly, the welding process is carried out at 230℃ first, and then the bonding process is carried out at 150℃. In order to facilitate the bonding of the bonding tooling, the connector is manually welded after all the bare chips are assembled and temporarily protected. Welding includes ICs such as SOC, resistors and capacitors, and transformers. The welding is divided into two times. First, the side with fewer components on the back is assembled, mainly resistors and capacitors. After welding, they are not cleaned, and the residual rosin protects the welded components. Secondly, the SOC side is welded, mainly BGA packaged ICs and a small number of resistors and capacitors. After welding, they are cleaned, and the bare chips are bonded with insulating glue. The curing temperature is 150℃.

[0054] The present invention adopts a hybrid circuit process for local bare chip assembly, bonding is performed after bonding is completed, and the bonding area adopts a local gold plating process, using Φ25μm gold wire, Φ80μm silicon aluminum wire, and Φ250μm aluminum wire for bonding. For example, the structure after PCB-1 substrate assembly is as follows Figure 5 shown.

[0055] After the assembly is completed, the test is normal and local potting is performed. The potting process adopts two steps. The first step is to apply the cofferdam glue on the cofferdam frame and turn it upside down in the cofferdam area. After curing, the cofferdam frame is bonded. The second step is to pot the bare die area with potting glue. The local potting material of the bare chip is black glue, which has the characteristics of high viscosity and easy molding. After experiencing temperature shock, the deformation of the polymer material will not cause the stress of the potting part to be pulled off. The specific assembly process is as follows Figure 4 shown.

[0056] The specific assembly process of the module is as follows: Figure 7-Figure 13 First, install PCB-1 on the housing, then install PCB-2 on the housing with PCB-1 installed, reinforce it with 6 M2 washers and 6 M2 screws, then install thermal pads A, B, C, D, and finally install the upper and lower covers with screws to complete the module assembly.

[0057] The installation of thermal conductive pads is aimed at high-power consumption components on the PCB substrate, including: SOC, DC / DC converter and MOS tube surface.

[0058] like Figure 4As shown, the specific assembly of the complete cable-free microcircuit module is as follows: first, the components on the first layer of PCB substrate are welded and assembled, specifically, the components on the back of the PCB substrate are welded first, and then the components on the front; the second step is to weld the connector to connect it with other layers of PCB substrates; the third step is cleaning and welding inspection; the fourth step is to bond and inspect the magnetic ring on the front of the PCB substrate, and to manually weld and clean the magnetic ring; the fifth step is to bond the bare chip, and after the bonding is completed, non-destructive, pressure welding inspection and mid-test are carried out; the sixth step is potting, firstly, the potting area of ​​the PCB substrate is bonded with a cofferdam, and the inspection and AOI (automatic optical inspection) before potting are carried out, and finally glue is poured; after the glue is poured, the sixth step is to apply three-proof coating to the PCB substrate; like the assembly of the first layer of PCB substrate, after the second and third layers of PCB substrates are assembled, the first, second and third layers of assembled PCB substrates are respectively installed on the shell, and finally the upper and lower cover plates are installed on the shell to complete the assembly of the entire module structure. After the module is assembled, the overall function is tested.

[0059] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A cable-free microcircuit module structure, characterized in that: The invention comprises a frame, in which a multi-layer PCB substrate is installed, each layer of the PCB substrate adopts a stacked structure, components are welded or bonded on the front and back sides of the PCB substrate, the components include finished devices and bare chips, the bare chips adopt a potting process, each layer of the PCB substrate of the same PCB substrate is connected through a flexible board, each layer of the PCB substrate of different PCB substrates is connected through a connector, and the each layer of the PCB substrates adopts cableless communication.

2. A cable-free microcircuit module structure according to claim 1, characterized in that: The bare chip includes an AD converter, a digital isolator, a gate driver and a MOS tube.

3. The cable-free microcircuit module structure according to claim 1, characterized in that: The components also include resistors, capacitors and transformers.

4. A cable-free microcircuit module structure according to claim 2, characterized in that: The finished devices include SOC, DDR3, FLASH, communication transceiver, DC / DC converter, current sensor and transistor.

5. The cable-free microcircuit module structure according to claim 1, characterized in that: Thermally conductive pads are installed on the components on the PCB substrate.

6. An assembly method based on the cable-free microcircuit module structure according to claim 1, characterized in that: The following steps are involved: Weld and bond finished components, MOS tubes, resistors, capacitors and connectors on each layer of PCB substrate; Bond the bare chip to each layer of PCB substrate; Bonding the bare chips through bonding wires; Potting is performed after bonding is completed; After potting is completed, three-conformal coating is carried out; Each layer of PCB substrate is installed in the frame, and finally the cover plate is added to complete the module assembly.

7. The method for assembling a cable-free microcircuit module structure according to claim 6, characterized in that: The connector is used for connecting different PCB substrates.

8. The method for assembling a cable-free microcircuit module structure according to claim 6, characterized in that: The welding steps are: First, solder the side with fewer components on the back of the PCB substrate, mainly resistors and capacitors; Secondly, solder the front side of the PCB substrate, which is the side containing the BGA components and bare chips, and clean it after soldering.

9. The method for assembling a cable-free microcircuit module structure according to claim 6, characterized in that: The bare chip is bonded with insulating glue, and the bonding area is partially plated with nickel-palladium-gold. The welding uses nickel-palladium-gold pads, and the bonding uses gold wire, silicon-aluminum wire or aluminum wire.

10. The method for assembling a cable-free microcircuit module structure according to claim 6, characterized in that: Potting includes the following steps: After the bare chip is bonded, a dam is formed using dam glue; The bare core area is potted with potting glue, and black glue is used for potting glue.

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