A manufacturing method of a microwave ferrite isolator substrate

Abstract

The present invention discloses a manufacturing method for a microwave ferrite isolator substrate, comprising: magnetron sputtering a nickel-chromium-iron alloy target to deposit a bottom layer composite film on the surface of the ferrite substrate. By customizing a nickel-chromium-iron alloy target with a specific ratio, the present invention deposits a nickel-chromium-iron composite film on the ferrite substrate by magnetron sputtering. This composite film can be etched in one step with the copper plating layer. Compared with the conventional chromium or nickel-chromium bottom etching method, the plasma etching process is omitted, the production steps of the ferrite isolator substrate are simplified, and the processing efficiency of the ferrite isolator substrate is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave device manufacturing, and particularly relates to a method for manufacturing a microwave ferrite isolator substrate. Background Art

[0002] An isolator, also known as a unidirectional device, is designed to achieve unidirectional transmission of microwave power in a microwave circuit. An ideal isolator completely absorbs microwave power in one direction and transmits microwave power in the opposite direction without loss. Utilizing the Faraday rotation effect that the polarization plane rotates when electromagnetic waves propagate in a gyromagnetic ferrite material with an externally applied DC magnetic field, through appropriate design, a ferrite isolator can have very low attenuation when the microwave propagates forward, while being almost completely absorbed when propagating backward.

[0003] Isolators are mainly applied in several aspects: wide application frequency range, and the thin-film microwave load can operate normally under high-frequency signals; good resistance stability: the resistance of the thin-film load changes little during a long working time; good chemical stability: it can be used normally in a variety of complex environments; high power density: it can absorb a large amount of power. Due to its good properties, tantalum nitride material has become the most widely used power thin-film material at present. The thin-film microwave load based on a ferrite substrate sacrifices the power density requirement of the microwave load while increasing the miniaturization and integration degree of the device. The most important application of the tantalum nitride thin-film microwave load based on a ferrite substrate is to connect a load inside one port of a three-port circulator to form a two-port isolator. The isolator can achieve the signal isolation function, and the tantalum nitride thin-film microwave load plays a key role in it. Isolators and circulators solve a series of technical problems such as inter-stage isolation, impedance, and antenna sharing in radar equipment, improving the tactical performance of the radar system. They are indispensable key units in TR components, and preparing a ferrite thin-film circuit substrate is a very important link in manufacturing isolators and circulators.

[0004] However, in the prior art, when using chromium or nickel-chromium as the metallization underlayer, it is relatively difficult to remove chromium in the subsequent processes. For example, if wet etching is used, serious side etching of the circuit will occur. If dry etching is used, both the gold plating layer and tantalum nitride will be etched, and a dry etching process needs to be added after the wet etching process, which lengthens the manufacturing process and increases the manufacturing cost. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for manufacturing a microwave ferrite isolator substrate to simplify the manufacturing process of the microwave ferrite isolator substrate and improve the production efficiency of the microwave ferrite isolator substrate.

[0006] To solve the above problems, the present invention provides a method for manufacturing a microwave ferrite isolator substrate, including:

[0007] A nickel-chromium-iron alloy target is deposited on the surface of a ferrite substrate by magnetron sputtering to form a bottom layer composite film.

[0008] Further, before the step of depositing a bottom layer composite film on the surface of a ferrite substrate by magnetron sputtering a nickel-chromium-iron alloy target, it includes:

[0009] A nickel-chromium-iron alloy target is made according to the mass ratio of Ni:Cr:Fe = 67:21:12;

[0010] The ferrite embryo is cut into ferrite substrates with corresponding thicknesses by inner circle cutting, then the ferrite substrates are precisely polished by diamond abrasives, and then water polishing is carried out with pure water as the medium and swept-frequency complex-frequency ultrasonic cleaning is adopted;

[0011] A tantalum nitride target is magnetron sputtered on the surface of a ferrite substrate to deposit a tantalum nitride thin film for isolation resistance, forming an isolation resistance with a sheet resistance value of 48 - 50 Ω / sq.

[0012] Further, while magnetron sputtering a tantalum nitride target on the surface of a ferrite substrate to deposit a tantalum nitride thin film for isolation resistance, it includes:

[0013] Tantalum nitride circular pads with a diameter of 0.5 mm and a true roundness of 100% are generated at the four corners of the ferrite substrate for positioning, and then laser repeated processing is carried out on the front surface of the ferrite substrate multiple times to form through holes with a diameter of 0.2 mm and a depth of 0.4 mm.

[0014] Further, the magnetron sputtering process parameters for magnetron sputtering a tantalum nitride target on the surface of a ferrite substrate to deposit a tantalum nitride thin film for isolation resistance are: N2:Ar = 2:50, sputtering power 300 W, sputtering time 15 min, obtaining an isolation resistance with a sheet resistance value of 48 - 50 Ω / sq.

[0015] Further, the magnetron sputtering process parameters for magnetron sputtering a nickel-chromium-iron alloy target on the surface of a ferrite substrate to deposit a composite film are: under a vacuum degree of 6.0×10 -4 Pa, the ferrite substrate is preheated to 180 °C, the argon gas flow rate is controlled at 35 SCCM, and the target sputtering power is controlled at 300 W.

[0016] Further, after the step of depositing a bottom layer composite film on the surface of a ferrite substrate by magnetron sputtering a nickel-chromium-iron alloy target, it includes:

[0017] A copper target is magnetron sputtered to form a copper film on the bottom layer composite film of the ferrite substrate, and then the ferrite substrate is electroplated with copper to thicken the copper film to the required thickness of the isolator substrate.

[0018] Further, for the magnetron sputtering copper target, a copper film is formed on the composite film of the underlayer of the ferrite substrate, and then the ferrite substrate is electroplated with copper until the copper film is thickened to the required thickness of the isolator substrate, including:

[0019] Graphic transfer, acid etching, electroplating thick gold production, and forming production.

[0020] Further, the graphic transfer includes: performing photolithographic graphic transfer on the ferrite substrate with the copper film thickened to the required thickness, adjusting the dispensing amount and rotation speed of the photoresist by means of static dispensing and high-speed rotary dispersion, and performing dynamic etching compensation design on the pattern.

[0021] Further, the acid etching includes: adopting a wet etching process and using chemical corrosion to perform vacuum etching on the area not protected by the photoresist, etching the copper layer while corroding the composite film of the underlayer.

[0022] Further, the electroplating thick gold production includes: after etching the circuit, laying leads between the circuits to make a conductive grid, gold-plating the five sides of the circuit, and then removing the gold-plated leads by laser etching.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. When the present invention uses the photoresist mask method to pattern sputter and process the tantalum nitride isolation resistor, tantalum nitride round pads are generated at the four corners of the ferrite substrate as positioning to achieve the output of low-power laser. Multiple repeated processing can be performed from the front of the ferrite substrate to form through holes, thus replacing the existing single laser drilling, and effectively avoiding the yield decline and quality risks brought by the slag at the hole mouth of the through hole.

[0025] 2. In the present invention, a composite film of the underlayer is formed by magnetron sputtering deposition on the ferrite substrate. Since iron elements are added to the underlying nickel-chromium alloy, the corrosion resistance of the alloy is reduced, and the composite film of the underlayer can also be corroded while etching the copper layer, thereby realizing one-time mixed etching of the copper plating layer. It is not necessary to perform plasma etching after acid etching like pure chromium or nickel-chromium etching, which simplifies the production process of the ferrite isolator substrate and improves the processing efficiency of the ferrite isolator substrate.

[0026] 3. The adhesion of nickel-chromium-iron in the present invention is between that of chromium and nickel-chromium, superior to nickel-chromium and titanium-tungsten, and the adhesion fully meets the requirements of the microstrip isolator. Description of the Drawings

[0027] Figure 1 It is a process flow chart of the production of the microwave ferrite isolator substrate of the present invention. Detailed Embodiments

[0028] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] An embodiment of the present invention provides a method for manufacturing a microwave ferrite isolator substrate, including the following steps:

[0030] S1. Customize a nickel-chromium-iron alloy target, which is a nickel, chromium, and iron alloy target composed according to a specific mass ratio, and the purity of the target is 99.5%.

[0031] Among them, the nickel-chromium-iron alloy target is composed according to the mass ratio of Ni:Cr:Fe = 67:21:12, and is used to sputter the nickel-chromium-iron composite film underlayer.

[0032] S2. Ferrite blanking and surface treatment. The ferrite embryo is cut into thin slices of corresponding thickness by inner circle cutting to obtain a ferrite substrate. After the ferrite substrate is precision polished with diamond abrasive, a water polishing process using pure water as the medium is added, and a sweep frequency complex frequency ultrasonic cleaning is used to remove the polishing agent.

[0033] S3. Production of tantalum nitride. The isolation resistance tantalum nitride film is obtained by magnetron sputtering to obtain an isolation resistance with a sheet resistance value of 48 - 50 Ω / sq.

[0034] Among them, the isolation resistance tantalum nitride film is made by magnetron sputtering. After verification, the best process parameters for tantalum nitride sputtering are N2:Ar = 2:50, sputtering power: 300W, sputtering time: 15min, and an isolation resistance with a sheet resistance value of 48 - 50 Ω / sq is obtained.

[0035] S4. Ferrite drilling production. When using photoresist mask method for pattern sputtering to process tantalum nitride, positioning PADs are made. Multiple laser repetitions are processed from the front of the ferrite substrate to form through holes, specifically through holes with a diameter of 0.2mm and a depth of 0.4mm.

[0036] For ferrite drilling production, when using photoresist mask method for pattern sputtering to process the tantalum nitride isolation resistance, tantalum nitride circular Pads with a diameter of 0.5mm and a true roundness of 100% are generated at the four corners of the ferrite substrate for positioning at the same time. Low-power laser is output, and multiple repetitions are processed from the front of the ferrite substrate to form through holes, specifically through holes with a diameter of 0.2mm and a depth of 0.4mm. This process can replace the existing single laser drilling, and can effectively avoid the yield decline and quality risks caused by the slag at the hole mouth of the through hole.

[0037] S5. Sputter nickel-chromium-iron and copper. The nickel-chromium-iron alloy target customized in a specific ratio shows that the adhesion of nickel-chromium-iron on the ferrite substrate after magnetron sputtering composite film is between that of chromium and nickel-chromium, superior to nickel-chromium and titanium-tungsten. The adhesion fully meets the requirements of the microstrip isolator substrate. Then, magnetron sputter copper and electroplate copper to thicken it to the requirements of the isolator substrate.

[0038] The process parameters for magnetron sputtering composite film on the ferrite substrate: Under a vacuum of 6.0×10 -4 Pa, preheat the ferrite substrate to 180 °C, control the argon flow rate at 35 SCCM (partial pressure 0.21 Pa), and control the target sputtering power at 300 W for chromium-copper, nickel-chromium-copper, nickel-chromium-iron-copper, and titanium-tungsten-copper respectively.

[0039] Vertically weld a φ2 mm copper bar on the sputtering surface of the ferrite, then design a fixture to fix it on the tensile testing machine, and then measure the tensile force for the separation of the sputtered film layer from the ferrite substrate, and calculate the adhesion of the film layer based on the welding area. The measurement shows that the adhesion of nickel-chromium-iron is between that of chromium and nickel-chromium, superior to nickel-chromium and titanium-tungsten, and the adhesion fully meets the requirements of the microstrip isolator.

[0040] S6. Pattern transfer. The glue application adopts the methods of static drop glue and high-speed rotation dispersion. By adjusting the glue drop amount and rotation speed, dynamic etching compensation design is carried out for the pattern.

[0041] Pattern transfer. For the ferrite substrate with the copper film thickened to the required thickness, lithographic pattern transfer is carried out. The glue application adopts the methods of static drop glue and high-speed rotation dispersion. By adjusting the glue drop amount and rotation speed, dynamic etching compensation is carried out. Taking a copper thickness of 4 - 6 μm as an example, for the positive design in line compensation, a square box (2 μm * 2 μm), and for the negative design, a triangle (1.5 μm * 1.5 μm * 1.5 μm).

[0042] S7. Acid etching. Adopt the wet etching process and use chemical corrosion to carry out vacuum etching on the areas not protected by photoresist to achieve high-precision line etching. Since iron elements are added to the underlying nickel-chromium alloy, the corrosion resistance of the alloy is reduced, and the composite film of the underlying layer is also corroded while etching the copper layer.

[0043] S8. Electroplating thick gold production. After etching the lines, make a conducting grid by laying leads (width 0.1 mm) between the lines to achieve the method of five-sided gold edge wrapping for the lines, and then remove the gold-plated leads by laser etching.

[0044] S9. Forming production. Adopt high-speed resin knife dicing to cut and form the finished ferrite microstrip isolator substrate. Use a blade with a thickness of 0.15 mm and a diamond particle size of 400 meshes to cut the ferrite substrate at a spindle speed of 26000 rpm.

[0045] The working principle of the present invention is as follows: When fabricating a ferrite by punching and manufacturing a tantalum nitride isolation resistor through graphic sputtering using a photoresist mask method, tantalum nitride circular pads with a diameter of 0.5 mm and a true roundness of 100% are generated at the four corners of the ferrite substrate for positioning. A low-power laser is output and processed repeatedly from the front side of the ferrite substrate to form through holes with a diameter of 0.2 mm and a depth of 0.4 mm. Using this process to replace the existing single laser drilling can effectively avoid the yield reduction and quality risks caused by the slag at the hole mouth of the through hole.

[0046] The process parameters of the magnetron sputtered composite film on the ferrite substrate: Under a vacuum of 6.0×10 -4 Pa, the ferrite substrate is preheated to 180 °C, the argon flow rate is controlled at 35 SCCM (partial pressure 0.21 Pa), the target sputtering power is controlled at 300 W, and they are respectively chromium-copper, nickel-chromium-copper, nickel-chromium-iron-copper, and titanium-tungsten-copper. A copper rod with a diameter of φ2 mm is vertically welded on the sputtering surface of the ferrite, and then a fixture is designed to fix it on a tensile testing machine. Then, the tensile force for the separation of the sputtered film layer from the ferrite substrate is measured, and the adhesion of the film layer is calculated based on the welding area. The measurement shows that the adhesion of nickel-chromium-iron is between that of chromium and nickel-chromium, superior to nickel-chromium and titanium-tungsten, and the adhesion fully meets the requirements of the microstrip isolator.

[0047] The specific embodiments of the invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modification or substitution of the invention is also within the scope of the present invention. Therefore, equivalent transformations, modifications, improvements, etc. made without departing from the spirit and principles of the present invention should all be covered within the scope of the present invention.

Claims

1. A manufacturing method of a microwave ferrite isolator substrate, characterized in that, Including: Fabricate a nickel-chromium-iron alloy target with a mass ratio of Ni:Cr:Fe = 67:21:12; Cut the ferrite embryo into ferrite substrates with corresponding thicknesses by means of inner circle cutting, then conduct precision polishing on the ferrite substrates with diamond abrasives, then conduct water polishing with pure water as the medium and adopt sweep-frequency complex-frequency ultrasonic cleaning; Deposit a tantalum nitride isolation resistance thin film on the surface of the ferrite substrate by magnetron sputtering a tantalum nitride target to form an isolation resistance with a sheet resistance value of 48 - 50 Ω / sq; Deposit a bottom layer composite film on the surface of the ferrite substrate by magnetron sputtering a nickel-chromium-iron alloy target; wherein the magnetron sputtering process parameters are: N2:Ar = 2:50, sputtering power 300 W, sputtering time 15 min, to obtain an isolation resistance with a sheet resistance value of 48 - 50 Ω / sq; at the same time, generate tantalum nitride circular pads with a diameter of 0.5 mm and a true roundness of 100% at the four corners of the ferrite substrate for positioning, and then conduct multiple laser repetitions on the front of the ferrite substrate to form through holes with a diameter of 0.2 mm and a depth of 0.4 mm; Deposit a copper film on the bottom layer composite film of the ferrite substrate by magnetron sputtering a copper target, and then electroplate the copper on the ferrite substrate to thicken the copper film to the required thickness of the isolator substrate.

2. The manufacturing method of the microwave ferrite isolator substrate according to claim 1, characterized in that The magnetron sputtering process parameters for depositing a composite film on the surface of a ferrite substrate using a magnetron sputtering nickel-chromium-iron alloy target are as follows: under a vacuum of 6.0×10 -4 Pa, preheat the ferrite substrate to 180°C, control the argon gas flow rate at 35 SCCM, and control the target sputtering power at 300 W.

3. The manufacturing method of the microwave ferrite isolator substrate according to claim 1, characterized in that, After depositing a copper film on the bottom layer composite film of the ferrite substrate by magnetron sputtering a copper target and then electroplating the copper on the ferrite substrate to thicken the copper film to the required thickness of the isolator substrate, including: Graphic transfer, acid etching, electroplating thick gold production, and forming production.

4. The manufacturing method of the microwave ferrite isolator substrate according to claim 3, characterized in that The graphic transfer includes: conducting photolithographic graphic transfer on the ferrite substrate with the copper film thickened to the required thickness, and adjusting the dispensing amount and rotation speed of the photoresist by means of static dispensing and high-speed rotation dispersion, and conducting dynamic etching compensation design on the graphics.

5. The manufacturing method of the microwave ferrite isolator substrate according to claim 4, characterized in that The acid etching includes: adopting a wet etching process, and using chemical corrosion to conduct vacuum etching on the area not protected by the photoresist, etching the copper layer and corroding the composite film of the bottom layer at the same time.

6. The manufacturing method of the microwave ferrite isolator substrate according to claim 5, characterized in that, The electroplating thick gold production includes: after etching the circuit, using the leads designed between the circuits to fabricate a conductive grid, gold-plating the five sides of the circuit, and then removing the gold-plated leads by means of laser etching.

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