Cross net-shaped multi-layer circuit board structure and ultra-small lumped parameter device formed by same

Abstract

The invention discloses a cross net-shaped multilayer circuit board structure and a subminiature lumped parameter device formed by the same, and belongs to the field of microwave components, the cross net-shaped multilayer circuit board structure comprises at least four layers of circuit boards, a slot A used for placing a ferrite substrate is arranged between the first layer of circuit board and the third layer of circuit board, and the slot A is arranged between the first layer of circuit board and the third layer of circuit board. The second layer of circuit board is provided with a central circuit, the central circuit realizes three ports which are mutually symmetrical at 120 degrees through a crossed net structure, the fourth layer of circuit board is provided with an open slot B used for being assembled with a device shell, and the subminiature lumped parameter device is prepared by adopting the circuit board structure and adopting a stacking mode; according to the ultra-small lumped parameter device, the ultra-small size of 3 mm * 3 mm is achieved, and meanwhile the performance is not changed; mass production and manufacturing are facilitated, and the production efficiency can be improved by more than 30%; the number of parts is reduced, assembly is simplified, and production cost is reduced.

Description

Technical Field

[0001] The invention relates to microwave components, in particular to a cross-net multi-layer circuit board structure and an ultra-small lumped parameter device composed of the same. Background Art

[0002] Lumped parameter circulator / isolator is a microwave passive device with unidirectional conduction and reverse isolation. It is widely used in microwave electronic systems and can effectively improve the working efficiency, stability and reliability of the system. The current mainstream lumped parameter circulator / isolator sizes are 5mm and 7mm.

[0003] The current mainstream design schemes for 5mm and 7mm lumped parameter devices are as follows: Figure 1 As shown, it is mainly composed of seven parts, namely, an upper shell 1, a strontium constant magnet 2, a central conductor module 3, a capacitor 4, a load 5, a plastic package shell 6, and a lower shell 7. The components are connected by soldering; wherein, the central conductor module 3 is a central conductor 31 wrapped with a ferrite 32, three braided belts 33 at 120° to each other are bent and wound successively, and a polyimide film 34 is used between the braided belts for electrical isolation. Its structure is as shown in FIG. Figure 2 As shown ( Figure 2 The braided tape is a part of the center conductor, the entire metal conductor structure wrapped with ferrite is the complete center conductor, and the braided tape is a part of the center conductor); the capacitor 4 is three independent chip capacitors, which are rectangular in shape, and silver layers are printed on both the upper and lower surfaces.

[0004] At present, the lumped parameter devices on the market are mainly 5mm lumped parameter devices, and 7mm lumped parameter devices are mainly used in older systems. The process technology of the two products has been used for many years and is quite mature, but with the development of communication technology, it can no longer meet the current development needs. The reason is that there are at least the following two problems: 1. Lumped parameter devices are mostly used between power amplifiers in communication systems, mainly for inter-stage isolation. However, as the communication system has higher and higher requirements for integration, miniaturization, and low cost, the size of existing lumped parameter devices can no longer meet the demand; 2. The circuit structure of the current lumped parameter device is a central conductor module. This braided central conductor module is highly complex and requires extremely high precision and stability of the automation equipment. Any deficiency will directly affect the product's qualification rate, consistency and other indicators; 3. For the current lumped parameter devices, after the parts are purchased, some parts (center conductor, ferrite, braided tape and polyimide film) need to be woven once to form a center conductor module, and then assembled with other parts for a second time. In addition, the low weaving efficiency is also one of the important factors restricting the current center conductor module braided tape solution. Summary of the invention

[0005] One of the purposes of the present invention is to provide a cross-mesh multi-layer circuit board structure to solve the above-mentioned problem.

[0006] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: a cross-net multi-layer circuit board structure, the cross-net multi-layer circuit board structure includes at least four layers of circuit boards; Among them, a slot A for placing a ferrite substrate is provided between the first layer circuit board and the third layer circuit board, and the shape and size of the slot A are consistent with the shape and size of the ferrite substrate. The second layer circuit board is provided with a central circuit, and the central circuit realizes three ports symmetrical at 120° to each other through a cross-mesh structure, and the central circuit is distributed in two planes by means of metallized vias; the fourth layer circuit board is provided with a slot B for assembly with the device housing.

[0007] Of course, the number of layers of a circuit board is not limited to four, it can also be five, six, and so on. When a four-layer circuit board cannot meet the space size required for device design, the number of circuit board layers can be increased to expand the available space for circuit design, thereby extending the circuit and achieving a better design.

[0008] It should be noted that the cross-mesh circuit of the present invention refers to three transmission circuits that are originally 120° apart. If they are distributed in one plane, there will be overlapping interference. Therefore, the present application distributes the circuits that were originally distributed in the same plane in two planes by means of metallized vias. The advantage of this is that the parts that would originally overlap and interfere are distributed half on the upper surface of the second-layer circuit board and the other half on the lower surface of the second-layer circuit board in this way, thereby avoiding the problem of circuit overlapping interference with a spatially reconstructed structure.

[0009] As a preferred technical solution, the multi-layer circuit board structure has four layers.

[0010] As a preferred technical solution, the slot A is circular.

[0011] As a preferred technical solution, the slot B is square.

[0012] The second object of the present invention is to provide an ultra-small lumped parameter device composed of the above-mentioned cross-mesh multi-layer circuit board structure, and the technical scheme adopted is, including an upper shell, a strontium constant magnet, a special-shaped capacitor, a ferrite substrate, a load, a multi-layer circuit board and a lower shell, wherein the strontium constant magnet, the special-shaped capacitor, the ferrite substrate, the load, and the multi-layer circuit board are packaged in the upper shell and the lower shell in a stacked structure, wherein the strontium constant magnet, the special-shaped capacitor and the multi-layer circuit board are arranged in sequence from top to bottom, and the topmost layer and the second to last layer from the bottom of the multi-layer circuit board are respectively provided with a slot A for placing the ferrite substrate, and the special-shaped capacitor is provided with an opening for placing the load.

[0013] As a preferred technical solution, the special-shaped capacitor is a single-layer chip capacitor structure, and its material adopts a Class I ceramic medium with a dielectric constant of 50. That is, it is preferred to use Class I ceramic capacitors, and the dielectric constant is related to the capacitance required for the product design frequency band, and the two are positively correlated. The general rule is that the lower the frequency, the larger the capacitance required, that is, the larger the node constant. The commonly used Class I ceramic capacitor material node constant is 20 to 120, and this material is generally used in DCNS4R5B08N050P (N3) model capacitors.

[0014] As a further preferred technical solution, a silver layer A is arranged on the front side of the special-shaped capacitor, and three independent silver layers B are arranged on the back side. A soldering pad is also arranged on the back side of the special-shaped capacitor. The silver layer A is connected to the soldering pad through a metallized via and is connected to the grounding PIN pin of the multi-layer circuit board through welding.

[0015] The principle of the special-shaped capacitor of the present invention is consistent with that of the single-plate capacitor. The capacitance value is related to the surface area, thickness and dielectric constant of the capacitor electrode. In the present invention, the larger the surface area of ​​the printed silver layer, the larger the capacitance value. The example frequency band described later in the present invention is 1.8GHz, and the required capacitance value is about 4pF. Under the premise that the thickness of the capacitor substrate is 0.15mm and the dielectric constant is 50, the surface area of ​​the silver layer is about 1.1mm 2 The designed working frequency band is different and the ferrite size is different, the corresponding capacitance value will also be different, that is, the silver layer area is different.

[0016] As a further preferred technical solution, an opening for placing a load is provided on one side of the special-shaped capacitor. If a circulator design is used, this opening is not required.

[0017] In the present invention, the upper shell, lower shell structure, strontium constant magnet, etc. before and after the improvement have not undergone obvious changes, but their sizes are inconsistent. Specifically, through structural improvement, the final device size is reduced from 5mm×5mm to 3mm×3mm. Correspondingly, the sizes of the upper shell, lower shell structure, strontium constant magnet, etc. are also reduced to adapt to the overall size of the device.

[0018] Compared with the prior art, the advantages of the present invention are: 1. Compared with the existing conventional 5mm lumped parameter devices, the structure adopted by the present invention places the capacitor above the central circuit, reducing the lateral size. In short, it saves the space originally used to place the capacitor, so that the ultra-small lumped parameter device of the present invention achieves an ultra-small size of 3mm×3mm while maintaining the same performance; 2. The stacking structure adopted by the present invention greatly reduces the difficulty of production and manufacturing, is conducive to mass production and manufacturing, and the production efficiency can be improved by more than 30%; 3. Compared with the conventional 5mm×5mm device, the 3mm×3mm lumped parameter device of the present invention eliminates the use of the central conductor and the insulating film, and the number of capacitors is reduced from three to one, thereby reducing the number of parts. After the parts are purchased, only one assembly is required, thus avoiding secondary processing such as the braiding and molding of the central conductor module in the existing solution. 4. The components used in the present invention are conducive to batch manufacturing, and cost control and consistency improvement are significantly improved compared with existing solutions. Among them, the cost is expected to be reduced by about 30%, and the consistency is improved by at least 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural decomposition diagram of a lumped parameter device of the prior art of the present invention; Figure 2 for Figure 1 The structural diagram of the center conductor module in FIG. Figure 3 It is a structural exploded diagram of an ultra-small lumped parameter device according to an embodiment of the present invention; Figure 4 for Figure 3 The cross-mesh multi-layer circuit board structure diagram; Figure 5 for Figure 4 The second layer circuit board structure diagram; Figure 6 for Figure 3 The front structure diagram of the special-shaped capacitor; Figure 7 for Figure 3 The back structure diagram of the special-shaped capacitor; Figure 8 It is a simulation curve of an ultra-small lumped parameter device according to an embodiment of the present invention; Fig. 9 This is a simulation curve of a 5mm×5mm lumped parameter device according to the prior art of the present invention.

[0020] In the figure: 1. upper shell; 2. strontium constant magnet; 3. center conductor module; 31. center conductor; 32. ferrite; 33. braided tape; 34. polyimide film; 4. capacitor; 5. load; 6. plastic package shell; 7. lower shell; 8. special-shaped capacitor; 81. silver layer A; 82. silver layer B; 83. soldering pad; 84. opening; 9. multi-layer circuit board; 91. first layer circuit board; 92. second layer circuit board; 93. third layer circuit board; 94. fourth layer circuit board; 95. slot A; 96. center circuit; 97. slot B; 10. ferrite substrate. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] Example:

[0023] An ultra-small lumped parameter isolator with a size of 3mm×3mm, such as Figure 3 As shown, it includes an upper shell 1, a strontium constant magnet 2, a special-shaped capacitor 8, a ferrite substrate 10, a load 5, a multi-layer circuit board 9 and a lower shell 7, wherein the strontium constant magnet 2, the special-shaped capacitor 8, the ferrite substrate 10, the load 5, and the multi-layer circuit board 9 are packaged in the upper shell 1 and the lower shell 7 in a stacked structure, wherein the strontium constant magnet 2, the special-shaped capacitor 8 and the multi-layer circuit board 9 are arranged in sequence from top to bottom, and the topmost layer and the second to last layer from the bottom of the multi-layer circuit board 9 are respectively provided with a slot A 95 for placing the ferrite substrate 10, and the special-shaped capacitor 8 is provided with an opening 83 for placing the load 5; In this embodiment, the structure of the cross-mesh multi-layer circuit board 9 is as follows: Figure 4 and Figure 5 As shown, it includes four layers of circuit boards, which are respectively a first layer of circuit board 91, a second layer of circuit board 92, a third layer of circuit board 93 and a fourth layer of circuit board 94 from top to bottom, wherein a slot A95 for placing a ferrite substrate 10 is provided between the first layer of circuit board 91 and the third layer of circuit board 93, and the shape and size of the slot A95 are consistent with the shape and size of the ferrite substrate, and the present embodiment is circular, and the second layer of circuit board 92 is provided with a central circuit 96, and the central circuit 96 realizes three ports symmetrical at 120° to each other through a cross-mesh structure, and the central circuit 96 is distributed in two planes by means of metallized vias, half of which is distributed on the upper surface of the second layer of circuit board 92, and the other half is distributed on the lower surface of the second layer of circuit board 92, and the fourth layer of circuit board 94 is provided with a slot B97 for assembly with the lower housing 7 of the device, and the slot B97 is square; In this embodiment, the special-shaped capacitor 8 is a single-layer chip capacitor structure, and its material is a Class I ceramic medium with a dielectric constant of 50 (Guangdong Aisheng, N3 material); like Figure 6 and Figure 7As shown, the front of the special-shaped capacitor 8 is completely provided with a silver layer A81, that is, the silver layer A81 covers the entire front, and three independent silver layers B82 are provided on the back. The three independent silver layers B82 of this embodiment are "L"-shaped. A pad 83 is also provided on the back of the special-shaped capacitor 8. The silver layer A81 is connected to the pad 83 through a metallized via, and is connected to the ground PIN pin of the multi-layer circuit board through welding; an opening 84 for placing a load is also provided on one side of the special-shaped capacitor 8; In the above structure, the central circuit 96 realizes three ports symmetrical at 120° to each other through a cross-mesh structure, and uses metallized vias to realize the connection between the multi-layer circuit boards; the special-shaped capacitor 8 is placed above the multi-layer circuit board 9 to provide matching capacitance for the three ports; the strontium constant magnet is placed above the special-shaped capacitor 8 to provide the magnetic field required for the magnetization of the ferrite substrate; the upper shell and the lower shell encapsulate the strontium constant magnet, the special-shaped capacitor 8, the ferrite substrate, the load, the multi-layer circuit board 9 and other components, and play the role of magnetic circuit and magnetic shielding at the same time; Taking the common 1805-1880MHz frequency band as an example, a 1805-1880MHz isolator with a size of 3mm*3mm was simulated and designed through the above solution.

[0024] The simulation result curve is as follows Figure 8 As shown, the return loss and isolation are greater than 17dB, and the insertion loss is less than 0.43dB; Fig. 9 As shown, compared with the existing 5 mm lumped parameter device, the simulation index of the present invention has no obvious difference.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cross-mesh multi-layer circuit board structure, characterized in that: The cross-mesh multi-layer circuit board structure includes at least four layers of circuit boards, wherein a slot A for placing a ferrite substrate is provided between the first layer of circuit boards and the third layer of circuit boards, and the shape and size of the slot A are consistent with the shape and size of the ferrite substrate. The second layer of circuit boards is provided with a central circuit, and the central circuit realizes three ports symmetrical at 120° to each other through a cross-mesh structure. The central circuit is distributed in two planes by means of metallized vias, and the fourth layer of circuit boards is provided with a slot B for assembly with a device housing.

2. The cross-mesh multi-layer circuit board structure according to claim 1, characterized in that: The multi-layer circuit board structure has four layers.

3. The cross-net multi-layer circuit board structure according to claim 1, characterized in that: The slot A is circular.

4. The cross-net multi-layer circuit board structure according to claim 1, characterized in that: The slot B is square.

5. An ultra-small lumped parameter device made of the cross-net multi-layer circuit board structure according to any one of claims 1 to 4, characterized in that: It includes an upper shell, a strontium constant magnet, a special-shaped capacitor, a ferrite substrate, a load, a multi-layer circuit board and a lower shell, wherein the strontium constant magnet, the special-shaped capacitor, the ferrite substrate, the load and the multi-layer circuit board are packaged in the upper shell and the lower shell in a stacked structure, wherein the strontium constant magnet, the special-shaped capacitor and the multi-layer circuit board are arranged in sequence from top to bottom, the top layer and the second to last layer from the bottom of the multi-layer circuit board are respectively provided with a slot A for placing the ferrite substrate, and the special-shaped capacitor is provided with an opening for placing the load.

6. The ultra-small lumped parameter device according to claim 5, characterized in that: The special-shaped capacitor is a single-layer chip capacitor structure, and its material is a Class I ceramic medium with a dielectric constant of 50.

7. The ultra-small lumped parameter device according to claim 6, characterized in that: The front side of the special-shaped capacitor is completely provided with a silver layer A, and the back side is provided with three independent silver layers B. A soldering pad is also provided on the back side of the special-shaped capacitor. The silver layer A is connected to the soldering pad through a metallized via and is connected to the grounding PIN pin of the multi-layer circuit board through welding.

8. The ultra-small lumped parameter device according to claim 6, characterized in that: An opening for placing a load is also provided on one side of the special-shaped capacitor.

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