A method for manufacturing a radio frequency LC filter

Abstract

The present application belongs to the field of radio frequency LC filter manufacturing, and particularly relates to a radio frequency LC filter manufacturing method; the method comprises the following steps: selecting a printed board strip from pre-prepared printed board strips according to a designed LC filter circuit diagram, arranging the printed board strip on a carrier board, and fixing the printed board strip on the carrier board; manufacturing auxiliary tool holes on the carrier board on both sides of positions of components in the circuit diagram; applying soldering paste on the printed board strip at positions corresponding to the components; placing the components on the soldering paste, inserting the auxiliary tool into the auxiliary tool holes, and completing component mounting; reflow soldering the components after the component mounting is completed, removing the auxiliary tool after the reflow soldering is completed, and obtaining a circuit board; mounting and fixing the circuit board in a shell, connecting input and output pins on the shell with signal ends of the circuit by using silver-plated copper wires or pure silver wires, and completing radio frequency LC filter manufacturing; the present application has the advantages of low processing cost, short manufacturing period, and suitability for mass production.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency LC filter manufacturing, and specifically relates to a method for manufacturing radio frequency LC filters. Background Technology

[0002] Filters are key components in weaponry and play a crucial role in electronic weaponry. Radio frequency (RF) LC filters, in particular, are widely used in electronic and communication equipment due to their simple structure, high reliability, and low manufacturing cost. The rapid development and widespread application of modern microwave communication technology have spurred research progress in microwave devices, prompting the pursuit of higher performance and quality RF LC filters. How to manufacture LC filters at low cost and in a short timeframe remains a hot research topic.

[0003] Generally, RF LC filters consist of an inductor (L) and a capacitor (C), utilizing the impedance characteristics of inductors and capacitors to selectively pass or suppress signals at different frequencies. Due to the influence of distributed parameters such as parasitic effects in the filter, adjustable wire-wound inductors are often selected. In actual manufacturing, it is often necessary to find a printed circuit board (PCB) manufacturer to customize a special PCB, then manually solder the capacitors and inductors, and finally perform adjustments. Custom PCB manufacturing requires a certain time and cost, and manual soldering is inefficient, placing significant cost and time pressure on product development and production, which is detrimental to the widespread application of RF LC filters. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a method for manufacturing an RF LC filter, which includes:

[0005] S1: Design the LC filter circuit diagram, which includes the LC circuit board dimensions, pad dimensions and distribution, component selection and soldering positions;

[0006] S2: Select printed circuit board strips from the pre-made printed circuit board strips according to the LC filter circuit diagram and arrange them on the carrier board; fix the selected printed circuit board strips on the carrier board according to the arranged position relationship; the upper surface of the printed circuit board strips is provided with solder pads;

[0007] S3: Create auxiliary tooling holes on both sides of the corresponding component positions in the circuit diagram on the carrier board;

[0008] S4: Apply solder paste to the corresponding positions of the components on the printed circuit board strip;

[0009] S5: Place the component on the solder paste, insert the auxiliary fixture into the hole of the auxiliary fixture, and complete the component mounting;

[0010] S6: Reflow soldering is performed on the components that have been mounted. After the reflow soldering is completed, the auxiliary fixture is removed to obtain the circuit board.

[0011] S7: Install and fix the circuit board in the housing, and use silver-plated copper wire or pure silver wire to connect the input and output pins on the housing to the signal terminals of the circuit to complete the RF LC filter fabrication.

[0012] Preferably, the printed circuit board strip is an I-type or L-type printed circuit board, and its size is such that the solder ends of the components can be completely located on the strip.

[0013] Preferably, in step S2, if the printed circuit board strip is fixed to the carrier board by reflow soldering, then the lower surface of the printed circuit board strip is provided with solderable metal pads.

[0014] Preferably, the auxiliary tooling hole is either through or non-through, used to ensure that the auxiliary tooling is inserted and remains upright.

[0015] Preferably, the auxiliary tooling is a U-shaped structure made of rigid material. The inner width of the U-shaped structure is the same as the width of the component, so that the component can be fixed when the auxiliary tooling is inserted into the hole of the auxiliary tooling.

[0016] Preferably, the carrier plate is provided with a U-shaped notch to avoid the guide pin and facilitate the vertical placement of the carrier plate into the housing.

[0017] Preferably, in step S6, the temperature for reflow soldering is at least 30°C higher than the melting point of the solder paste.

[0018] Preferably, the material of the printed circuit board strip is FR4 or Rogers 5880, and the material of the carrier board is a copper plate with good solderability and double-sided gold plating.

[0019] Preferably, the components of the RF LC filter include capacitors and inductors, wherein the inductor is a wound coil inductor with adjustable inductance.

[0020] The beneficial effects of this invention are as follows: It reduces the manufacturing cycle and cost of circuit boards; by utilizing the holes and auxiliary tooling on the mounting plate, reflow soldering of chip components and wire-wound inductors can be achieved, solving the problems of cost, cycle time, efficiency, and consistency issues associated with manual soldering of components in RF LC filter substrate manufacturing. Furthermore, the isolation provided by the circuit board dielectric material effectively reduces signal crosstalk between components caused by the substrate material, improving the overall electrical performance of the devices. This invention has significant advantages such as low processing cost, short manufacturing cycle, and suitability for mass production. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the carrier plate after the printed circuit board strips are arranged and fixed in this invention;

[0022] Figure 2 This is a schematic diagram of the overall device after the components are mounted in this invention.

[0023] Figure 3 This is a partial enlarged view of the device after the components are mounted in this invention;

[0024] Figure 4 This is a schematic diagram of the radio frequency LC filter fabricated in this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention proposes a method for fabricating an RF LC filter. This method involves assembling printed circuit board strips onto a carrier board to create the circuit board substrate. Through-holes and auxiliary tooling on the carrier board are used to reflow solder chip capacitors and wire-wound inductors, thus providing a low-cost, short-cycle, and mass-production-suitable method for fabricating RF LC filters. The method includes the following:

[0027] S1: Design the LC filter circuit diagram, which includes the LC circuit board dimensions, pad dimensions and distribution, component selection and soldering positions.

[0028] The circuit design is carried out according to the required electrical performance specifications, which includes selecting chip capacitors and wire-wound inductors, arranging component positions, and completing the LC filter circuit diagram. The circuit diagram includes information such as the LC circuit board dimensions, pad dimensions and distribution, component selection, and soldering positions.

[0029] S2: Select printed circuit board strips from the pre-made printed circuit board strips according to the LC filter circuit diagram and arrange them on the carrier board; fix the selected printed circuit board strips on the carrier board according to the arranged position relationship; the upper surface of the printed circuit board strips is provided with solder pads.

[0030] like Figure 1 As shown, printed circuit board strips are selected from the prefabricated printed circuit board strips according to the LC filter circuit diagram for arrangement, that is, printed circuit board strips of different shapes and sizes are selected for assembly according to the pad distribution in the LC filter circuit diagram.

[0031] The printed circuit board strip should have at least one side of solder pads. If the printed circuit board strip is fixed to the carrier board by reflow soldering, the lower surface of the printed circuit board strip is provided with solderable metal pads.

[0032] Printed circuit board (PCB) strips are pre-fabricated in batches by PCB manufacturers, using materials such as standard FR4 and Rogers 5880. In certain situations, such as during urgent R&D, if there is no time to outsource strip production or if suitable strips are unavailable, mechanical processing can be used to cut a whole double-sided PCB to create PCB strips of the appropriate size. When creating PCB strips, copper PCBs can be cut to achieve the desired shape and size; the cutting method is not limited and can be laser or mechanical.

[0033] In some preferred embodiments of the present invention, for ease of assembly, the printed circuit board strip is an I-shaped or L-shaped printed circuit board; its size must be such that the solder ends of the components can be completely located on the strip.

[0034] After the printed circuit board strips are assembled on the carrier board, they should be the same size as the designed LC circuit board, especially in terms of pad placement, to meet the needs of subsequent component installation.

[0035] The selected printed circuit board strips are fixed onto the carrier board according to the pre-arranged positional relationship. The fixing method is not limited and can include adhesive bonding, reflow soldering, etc. When using reflow soldering, the printed circuit board strips should have a double-sided pad structure, and the carrier board should be made of metal or a solderable circuit board material. Preferably, the carrier board material is a double-sided gold-plated copper plate with good solderability; the melting point of the solder used should be higher than the peak temperature of the reflow profile during component mounting and soldering.

[0036] In situations where reliability requirements are not high or product application space is limited, the aforementioned printed circuit board strips can also be directly assembled and fixed on the metal casing of the filter or on the circuit of the next level system.

[0037] The carrier board should be a rigid, thin plate used to support and fix the printed circuit board strips. It should be able to withstand a soldering temperature of not less than 250°C to meet the requirements of subsequent reflow soldering of capacitors and inductors. If the carrier board itself is mounted and fixed to the outside (such as a metal housing or the next level system circuit board) by reflow soldering, its bottom should have metal pads or a solderable plating.

[0038] S3: Create auxiliary tooling holes on both sides of the corresponding component positions in the circuit diagram on the carrier board.

[0039] Auxiliary tooling holes are fabricated on the carrier plate on both sides corresponding to the mounting positions of capacitors and inductors using laser or mechanical processing.

[0040] The auxiliary tooling holes can be through or non-through, and are used to ensure that the auxiliary tooling is inserted and remains upright.

[0041] S4: Apply solder paste to the corresponding component positions on the printed circuit board strip.

[0042] Apply an appropriate amount of solder paste to the printed circuit board strips using stencil printing, dispensing, or spray soldering. The solder paste material is not limited, but 63Sn37Pb and SAC305 are recommended.

[0043] S5: Place the component onto the solder paste, insert the auxiliary fixture into the hole of the auxiliary fixture, and complete the component mounting.

[0044] The auxiliary fixture has a U-shaped structure and is made of wear-resistant rigid material. The inner width of the U-shape is consistent with the outer dimensions of the capacitor and inductor.

[0045] like Figure 2 , Figure 3 As shown, after the components are placed on the solder paste, the two leads of the fixture are inserted into the auxiliary fixture holes on the carrier board to fix the chip capacitor and the wire-wound inductor, so as to prevent the capacitor from tombstoning or shifting during reflow, and at the same time to ensure that the inductor remains upright during reflow, so as to facilitate soldering.

[0046] The components of the radio frequency LC filter of the present invention include capacitors and inductors, wherein the inductor is a wound coil inductor with adjustable inductance.

[0047] The U-shaped auxiliary tooling is reusable. When the components have the same external dimensions, the auxiliary tooling can be interchanged and reused.

[0048] S6: Reflow soldering is performed on the components that have been mounted. After the reflow soldering is completed, the auxiliary fixture is removed to obtain the circuit board.

[0049] The reflow soldering temperature should ensure good melting and wetting of the solder paste. Preferably, the reflow temperature is at least 30°C higher than the solder melting point.

[0050] During reflow soldering, the auxiliary fixture ensures the correct positioning of components. After reflow soldering is complete, the auxiliary fixture can be removed for future use.

[0051] S7: Install and fix the circuit board in the housing, and use silver-plated copper wire or pure silver wire to connect the input and output pins on the housing to the signal terminals of the circuit to complete the RF LC filter fabrication.

[0052] The circuit board is mounted and fixed inside the casing. Silver-plated copper wire or pure silver wire is used to connect the input and output pins on the casing to the signal terminals of the circuit, completing the fabrication of the RF LC filter. Figure 4 As shown.

[0053] When assembling the final circuit into the housing, a U-shaped notch should be left on the carrier board to allow it to be placed vertically into the housing, avoiding the pins, thus improving space utilization.

[0054] For mounting, reflow soldering can be used. The solder used should be a low-melting-point solder to ensure that the reflow peak temperature does not exceed the melting point of the solder used for component mounting and fixing printed circuit board strips. Silver-plated copper wire or pure silver wire is used to solder the input and output pins on the housing to guide the signal. This type of housing is commonly used in the RF LC filter field and is not specifically described. The carrier board should be slightly smaller than the inner cavity of the housing to meet installation requirements.

[0055] In some preferred embodiments of the present invention, when the printed circuit board strip is fixed by reflow soldering, the solder is SAC305 solder (solder 1, high melting point); when the components are assembled by reflow soldering under the action of auxiliary tooling, the solder is 63Sn37Pb (solder 2, second melting point); when the carrier board is installed and fixed in the housing by reflow soldering, the solder is 52In48Sn (solder 3, low melting point).

[0056] In summary, this invention utilizes pre-fabricated printed circuit board strips with pads of specific shapes and sizes on a carrier board to assemble the inductor (L) and capacitor (C) connection links, thereby realizing the fabrication of an LC circuit board substrate. Holes are machined on the carrier board at the capacitor and inductor mounting locations, and auxiliary tooling is used to fix the chip capacitors and wire-wound inductors to achieve reflow soldering of components, avoiding component displacement or misalignment during soldering. This solves the problems of cost, cycle time, efficiency, and consistency issues associated with manual component soldering in RF LC filter substrate fabrication, and has significant advantages such as low processing cost, short manufacturing cycle, and suitability for mass production.

[0057] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing an RF LC filter, characterized in that, Includes the following steps: S1: Design the LC filter circuit diagram, which includes the LC circuit board dimensions, pad dimensions and distribution, component selection and soldering positions; S2: Select printed circuit board strips from the pre-made printed circuit board strips according to the LC filter circuit diagram and arrange them on the carrier board; fix the selected printed circuit board strips on the carrier board according to the arranged position relationship; the upper surface of the printed circuit board strips is provided with solder pads; S3: Create auxiliary tooling holes on both sides of the corresponding component positions in the circuit diagram on the carrier board; S4: Apply solder paste to the corresponding positions of the components on the printed circuit board strip; S5: Place the component on the solder paste, insert the auxiliary fixture into the hole of the auxiliary fixture, and complete the component mounting; S6: Reflow soldering is performed on the components that have been mounted. After the reflow soldering is completed, the auxiliary fixture is removed to obtain the circuit board. S7: Install and fix the circuit board in the housing, and use silver-plated copper wire or pure silver wire to connect the input and output pins on the housing to the signal terminals of the circuit to complete the RF LC filter fabrication.

2. The method for manufacturing an RF LC filter according to claim 1, characterized in that, The printed circuit board strip is an I-type or L-type printed circuit board, and its size is such that the solder ends of the components can be completely located on the strip.

3. The method for manufacturing an RF LC filter according to claim 1, characterized in that, In step S2, if the printed circuit board strip is fixed to the carrier board by reflow soldering, then the lower surface of the printed circuit board strip is provided with solderable metal pads.

4. The method for manufacturing an RF LC filter according to claim 1, characterized in that, The auxiliary tooling holes can be through or non-through, and are used to ensure that the auxiliary tooling is inserted and remains upright.

5. The method for manufacturing an RF LC filter according to claim 1, characterized in that, The auxiliary tooling is a U-shaped structure made of rigid material. The inner width of the U-shaped structure is the same as the width of the component, so that the component can be fixed when the auxiliary tooling is inserted into the hole of the auxiliary tooling.

6. The method for manufacturing an RF LC filter according to claim 1, characterized in that, The carrier plate is provided with a U-shaped notch to avoid the guide pin and facilitate the vertical placement of the carrier plate into the housing.

7. The method for manufacturing an RF LC filter according to claim 1, characterized in that, In step S6, the temperature for reflow soldering is at least 30°C higher than the melting point of the solder paste.

8. The method for manufacturing an RF LC filter according to claim 1, characterized in that, The printed circuit board strip is made of FR4 or Rogers 5880, and the carrier board is made of double-sided gold-plated copper plate with good solderability.

9. A method for manufacturing an RF LC filter according to claim 1, characterized in that, The components of the radio frequency LC filter include capacitors and inductors, wherein the inductor is a wound coil inductor with adjustable inductance.

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