CN113966099B - Microwave integrated circuit film thickening process suitable for solid-state product - Google Patents

Abstract

The present invention provides a microwave integrated circuit film thickening process suitable for solid-state products, comprising the following steps: performing a gold plating on a ceramic substrate with an attachment layer, and the thickness of the formed gold plating layer is 2 to 3 μm; closely attaching the mask to the surface of the substrate coated with photosensitive adhesive after the gold plating, performing development, fixing and etching of the metal layer after exposure, and completing photolithography on the gold plating layer; copper plating on the gold plating layer after photolithography, and the thickness of the formed copper plating layer is 3 to 5 μm; nickel plating on the copper plating layer, and the thickness of the formed nickel plating layer is 0.5 to 1 μm; performing a secondary gold plating on the nickel plating layer, and the thickness of the formed gold plating layer is 2 to 3 μm. The present invention solves the problem of making thicker film layer circuits through a unique film layer structure design, based on the thin film ceramic circuit board manufacturing process, and adopts the "four plating and one engraving" method, achieves higher graphic accuracy and film layer adhesion, realizes multiple functions, and meets the needs of high-power circuits.

Description

A microwave integrated circuit film thickening process suitable for solid-state products

Technical Field

The invention belongs to the technical field of microwave integrated circuits, and in particular relates to a microwave integrated circuit film thickening process suitable for solid-state products.

Background technique

Conventional thin-film circuits are made by sputtering, pattern transfer, and gold plating. The thickness of the film layer is limited by manual welding, wet etching quality control, and other factors. Currently, microwave integrated circuit microstrip products are mainly based on thin-film technology. The thickness of the Au film layer on the surface of the microstrip circuit pattern is only 4μm to 6μm, which is difficult to meet the application requirements of high-power components. In order to meet the use requirements, it is usually used to bond gold strips on the surface of the Au layer to improve the circuit power tolerance. However, this method has low reliability and a long process flow, and cannot meet the requirements of high-reliability model tasks.

With the increase in satellite launch costs and the continuous increase in satellite functional density, the original solid-state amplifier manufacturing model based on alumina ceramic substrates can no longer meet the demand. There is an urgent need to find a way to significantly improve the reliability of high-power solid-state amplifier circuits.

In order to meet the needs of high-power circuits, the Au layer can be thickened to 10-15μm during the product manufacturing process. However, since SnPb welding is involved in the product assembly process, the excessively thick Au layer cannot be completely removed through multiple tinning processes. The presence of residual gold poses a risk to the long-term reliability of the solder joints.

At present, there are few examples of film thickening related processes, specifications and product applications in publicly published documents and publications. The Chinese patent "Method for thickening the copper thickness of local graphics of printed circuit boards", publication number CN108617104A, provides a method for thickening the copper thickness of local graphics of printed circuit boards, including the following steps: material incoming step; drilling and countersinking step; first board electrification step; first dry film pasting step; first exposure and first development step; local electroplating step; first film stripping step; second board electrification step; anti-etching ink printing step; second dry film pasting step; second exposure and second development step; etching step; second film stripping step. This patent adopts "adhesive electroplating" to achieve copper layer thickening, and uses "adhesive film" to control the lateral growth of the copper layer. However, "adhesive electroplating" is difficult to control the growth of the copper layer in the height direction. At the same time, the "adhesive film" may act as a pollution source to pollute the electroplating solution system, affecting the purity of the coating, and ultimately resulting in unqualified performance of the printed circuit board product.

The Chinese patent "A production process for locally thickening copper plating in a single area of a PCB board", publication number CN106061127A, provides a production process for locally thickening copper plating in a single area of a PCB board, the process flow mainly includes: (1) cleaning the copper material, the cleaning liquid is a rosin oil cleaning liquid; (2) micro-etching, using NaPS to micro-etch the bottom copper; (3) chemical copper deposition, immersing the PCB board in a chemical plating solution for copper plating; (4) pattern electroplating; (5) shield, selecting a shield layer after processing with a plating-resistant material; (6) local thickening copper plating, using the shield layer to perform local thickening copper plating; (7) sandblasting, sandblasting the copper surface to obtain a frosted surface; (8) tin spraying, tin spraying after sandblasting; (9) water washing, controlling the temperature during water washing, and accompanied by air stirring; (10) melting the shield layer wax layer with boiling water after plating, and then washing with a water-soluble cleaning agent. This patent uses a shield to prevent the lines from growing laterally during the copper plating process. However, the shelter also has the problem of difficulty in controlling the growth of the copper layer in the height direction, and has the problem of complex manufacturing and cumbersome removal process after electroplating.

The Chinese patent "A method for manufacturing an aluminum nitride-based thin film circuit", publication number CN104037115A, provides a method for manufacturing an aluminum nitride-based thin film circuit with a soldering functional surface coating structure and a special-shaped feature, comprising the following steps: Step 101: Cleaning the aluminum nitride substrate. Step 102: Arranging the aluminum nitride substrate to form a metal seed layer film on the front and back. Step 103: Using a photolithography process on the metal seed layer film on the front to prepare a circuit pattern with special-shaped features. Step 104: Laser processing the internal rectangular through hole of the aluminum nitride-based thin film circuit, or the internal rectangular through hole and the abnormal shape part. Step 105: Dilute hydrochloric acid treatment. Step 106: Prepare a soldering functional surface coating. Step 107: Use a grinding wheel scriber to scribe the regular shape part of the aluminum nitride-based thin film circuit. This patent is aimed at the production of thin-film microwave circuit boards based on aluminum nitride ceramic substrates. The metal seed layer is prepared by physical deposition, and the finished product is obtained by pattern transfer and electroplating thickening. It does not involve a film thickening process.

The Chinese patent "Method for Making Alumina Ceramic Circuit Board", publication number CN109195338A, provides a method for making an alumina ceramic circuit board, including: step 1, ultraviolet laser etching: using an ultraviolet laser machine to etch the alumina ceramic board according to the circuit pattern to form a groove that matches the shape of the conductive part in the circuit pattern; step 2, filling with conductive copper paste: filling the conductive copper paste into the groove evenly by printing, and baking; step 3, grinding the plate: using a grinding machine to grind off the conductive copper paste remaining on the ceramic surface of the non-circuit pattern; step 4, surface brush plating: using a high-speed brush plating pen to brush copper, nickel and gold on the circuit pattern to form a high-reliability fine ceramic circuit board. This patent uses laser to etch a groove consistent with the routing on the ceramic substrate, and then prints metal slurry and sintering process to make the circuit base layer, and finally brush-plated the metal layer on the printed metal film, without involving the film thickening process.

A search of domestic and foreign papers and journal literature has been conducted, but no microwave integrated circuit film thickening process suitable for solid-state products has been found.

Summary of the invention

In order to overcome the deficiencies in the prior art, the inventors have conducted intensive research and provided a microwave integrated circuit film thickening process suitable for solid-state products. Through a unique film layer structure design and based on the thin-film ceramic circuit board manufacturing process, the "four plating and one engraving" (four long-term electroplating and one photolithography) method is adopted to solve the problem of manufacturing thicker film layer circuits, achieve higher graphic accuracy and film layer adhesion, realize multiple functions (welding functional devices, bonding gold wires/gold ribbons/functional devices), meet the needs of high-power circuits, and thus complete the present invention.

The technical solution provided by the present invention is as follows:

In a first aspect, a microwave integrated circuit film thickening process applicable to solid-state products comprises the following steps:

Performing gold plating once on the ceramic substrate with the adhesion layer, the thickness of the formed gold plating layer is 2 to 3 μm;

The mask is closely attached to the surface of the substrate coated with photosensitive adhesive after the gold plating, and after exposure, development, fixing and etching of the metal layer are performed to complete the photolithography on the gold plating layer;

Copper is plated on the gold-plated layer after photolithography, and the thickness of the formed copper-plated layer is 3 to 5 μm;

Plating nickel on the copper plating layer, the thickness of the formed nickel plating layer is 0.5 to 1 μm;

Secondary gold plating is performed on the nickel plating layer, and the thickness of the formed gold plating layer is 2 to 3 μm.

In the second aspect, a thin film thickened microwave integrated circuit board, as shown in FIG5 , comprises, from bottom to top, a ceramic substrate, an adhesion layer, a 2-3 μm Au plating layer, a 3-5 μm Cu plating layer, a 0.5-1 μm Ni plating layer and a 2-3 μm Au plating layer.

A microwave integrated circuit film thickening process suitable for solid-state products provided by the present invention has the following beneficial effects:

(1) A microwave integrated circuit film thickening process suitable for solid-state products provided by the present invention is based on the "secondary stacking" composite film layer technology route of conventional ceramic thin film circuits, which innovatively solves the problem that solid-state circuit products are difficult to withstand large current capabilities; in the "four-plating and one-carving" process flow, the thickness of the composite film layer structure and the high quality control of the crystal particles can be achieved through the selection of plating solution and electroplating process parameters;

(2) According to a microwave integrated circuit film thickening process suitable for solid-state products provided by the present invention, an optimized film layer structure is determined. On the basis of the existing thin film circuit structure, a 3-5 μm Cu layer is electroplated to ensure the normal realization of circuit performance; at the same time, in order to prevent the Cu layer from diffusing and oxidizing to the surface and meet the subsequent assembly gold wire and gold ribbon bonding requirements, 0.5-1 μm Ni and 2-3 μm Au are electroplated in sequence on the basis of the electroplated thick Cu to meet the aerospace reliability requirements; the surface gold layer thickness is controlled at 2-3 μm, and the gold can be removed by conventional tin plating to ensure the reliability of lead-tin welding;

(3) According to a microwave integrated circuit film thickening process suitable for solid-state products provided by the present invention, the process is optimized and designed according to the determined film layer structure, and the thickening process flow is optimized: the photolithography process is placed after the first gold plating, so that the lateral growth time of the microstrip is significantly shortened, thereby obtaining a microstrip with a neater side, and at the same time improving the product performance stability; the present invention controls the lateral growth of the microstrip edge in a mask-free or cover-free state, avoiding the pollution caused by the mask or cover or the complicated process.

(4) According to a microwave integrated circuit film thickening process suitable for solid-state products provided by the present invention, a "quasi-thick film" circuit product is obtained, the film adhesion is increased to more than 2kg/ ^mm2 , the gold wire bonding strength is high, the line width/spacing accuracy is good, the circuit film thickness is adjustable, the circuit film resistance accuracy is high, the circuit film can withstand many tin-lead solder times, and the current resistance is strong.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a microwave integrated circuit film thickening process applicable to solid-state products;

FIG2 is a flow chart of a microwave integrated circuit thin film thickening process when photolithography is performed first and then coating is performed;

Figures 3.1 and 3.2 are schematic diagrams of the scale of the protruding part of the microstrip after electroplating using the process flow in Figure 2; Figures 3.3 and 3.4 are side views of the microstrip after electroplating using the process flow in Figure 1;

FIG4 is a side dimensional diagram of the microstrip after electroplating using the process flow in FIG1;

FIG5 on the left is a schematic diagram of the structure of a conventional microwave integrated circuit; FIG5 on the right is a schematic diagram of the structure of a microwave integrated circuit in the present invention;

FIG6 is a SEM image of the microwave integrated circuit structure of the present invention;

Figure 7 shows the application scenario of solid-state products.

Detailed ways

The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

As shown in FIG. 1 , the present invention provides a microwave integrated circuit film thickening process applicable to solid-state products. The film thickening process is specifically described as follows.

(1) Light painting

Use photolithography equipment to make electronic graphics into negatives that are magnified several times. This process can be ignored when using laser direct writing technology.

(2) Plate making

Microphotography is used to image the enlarged electronic pattern on the glass mask. When laser direct writing is used for plate making, the pattern can be directly etched on the mask.

(3) Punching

According to the design requirements, it is decided whether to implement the drilling process on the ceramic substrate. Currently, carbon dioxide, picosecond or fiber laser processing is usually used to make holes on ceramic substrates.

(4) Sputtering

According to the difference of the selected adhesion layer, different ventilation rate, vacuum degree and power parameters are adopted to implement sputtering coating on the surface of the substrate to obtain the adhesion layer.

The structure of the sputtered film layers on the front and back of the thin film thickened microwave integrated circuit products is consistent with that of conventional thin film microwave integrated circuit products. The adhesion layer obtained by sputtering is the seed layer for the subsequent film deposition, and its adhesion will determine the adhesion of the final thin film thickened product.

(5) One-time gold plating

The gold plating adopts a neutral micro-cyanide plating system, the solution pH is 5.9-6.1, the gold content is 8-15g/L, the system temperature is 50±5℃, the current density is 1-2.3mA/ ^cm2 , and the anode: cathode (area ratio) is 2:1. The thickness of the gold plating is 2-3μm.

Subsequent operations such as copper and nickel plating are directly performed on the sputtered layer. Due to differences in microstructures such as the lattice, the copper layer will be peeled off from the bottom sputtered layer. The function of the gold layer of the first gold plating is the transition between the adhesion layer and the plating layer above it.

In the primary gold plating, the gold in the neutral micro-cyanide plating solution exists in the form of Au(CN) ₂ ^- , which has strong cathode polarization, dispersion and covering ability, and the coating is fine and bright, so the gold plating system with thickened film is selected.

(6) Photolithography

The mask produced in step (2) is tightly attached to the surface of the substrate coated with photosensitive adhesive after the gold plating. After exposure, development, fixing and etching of the metal layer are performed to complete the transfer of the pattern.

In the traditional etching concept, photolithography is generally performed first and then coating. Corresponding to the process in the present invention, step (6) should be performed before step (5). The flow chart is shown in Figure 2.

The process flow in Figure 1 and Figure 2 shows that the film thickening mainly involves four electroplating steps (the pre-plating step is extremely short and the coating thickness is extremely small, which will not be discussed here): However, it is worth noting that with each additional electroplating step, the microstrip (graphic) will further grow laterally, further amplifying the underlying defects, and even exceeding the microstrip tolerance requirements, making the microstrip edge "serrated". Using the process flow in Figure 2, after four electroplating steps, with a line width of 100μm as the standard, the protruding part can be as large as 20μm (see Figures 3.1 and 3.2).

In order to reduce the impact of electroplating on the appearance of the microstrip, the present invention optimizes the thickening process flow: the photolithography process is placed after the first gold plating. This operation reduces the chances of lateral growth of the microstrip from four times to three times, and the lateral growth time of the microstrip is significantly shortened, thereby obtaining a microstrip with a relatively neat side (see Figure 3.3 and Figure 3.4), and the line width accuracy can be controlled within ±15μm (with a line width of 100μm as the standard, see Figure 4). Therefore, the process flow is improved from "engraving first and then plating" shown in Figure 2 to "plating first and then engraving" shown in Figure 1.

(7) Copper plating

(7.1) Preparation before plating

For semi-finished circuits with a lot of surface stains, organic solvents should be used to degrease the substrate surface.

Semi-finished circuits containing isolated non-conductive patterns should first be interconnected with gold wires to connect the electrically isolated patterns to the electrodes during electroplating. As a process line, the gold wires should first ensure that all isolated patterns are conductive, while avoiding key functional areas such as thinner lines and input and output terminals.

At the same time, it can be seen that the above-mentioned method of plating first and then engraving in the present invention achieves the effect of reducing the number of electroplating amplification times of the "defect" of the process line bonding point from 4 times to 3 times, which in a certain sense further improves the appearance of the thin film thickened circuit product.

Before copper plating, the surface condition of the product and the interconnection of the gold wires should be checked, and the quantity and completeness of the process documents should be checked. The process requirements should be clarified, the plating area should be calculated, and the hangers should be cleaned.

(7.2) Hang up

Fix the substrate on the fixture. The clamping point should be selected at the blank area or the inspection point. It is required to be clamped firmly and not fall off.

(7.3) Degreasing

Degreasing is done by soaking in alkaline degreasing liquid. It is strictly forbidden to use ultrasonic degreasing.

(7.4) Cyanide copper plating

Place the substrate parts to be plated in the plating tank and fix them on the cathode rod. The top of the substrate is about 5 to 10 cm away from the surface of the plating solution. The minimum plating area of each tank is not less than ^2dm2 ; if the substrate area is insufficient, use a "companion sheet" (aluminum alloy or copper alloy can be used as the plating companion sheet) to make the total area reach ^2dm2 .

Cyanide copper plating, solution composition and process parameters are shown in Table 1.

Table 1 Cyanide copper plating solution formula and operating conditions

After the tank is lowered, a current density of 2±0.5A/dm ² is used for "impact plating" for 1±0.5min, and then the current is reduced to 1.1±0.1A/dm ² and copper plating continues. The total electroplating time is 3±1min.

(7.5) Acid bright copper plating

The precautions for copper plating are the same as above.

In the acid bright copper plating solution, the solution components and process parameters are shown in Table 2.

Table 2 Bright copper plating solution formula and operating conditions

After the tank is lowered, the current density is 2±0.5A/ ^dm2 for "impact plating" for 1±0.5min, and then the current is reduced to 1.4±0.1A/ ^dm2 and copper plating is continued. The total electroplating time is 40±5min. The copper layer thickness is 3~5μm.

The chemical copper plating system is always in a non-steady state with poor consistency. The cyanide copper plating has coarse crystal particles, which makes it difficult to ensure the straightness of the line side, but the interface bonding strength is strong after the first gold plating, so it is used as a pre-copper plating process. The acid bright copper plating has a bright coating, low porosity and good leveling, so it is selected as the formal copper plating process.

(8) Nickel plating

The selection of nickel plating system must consider the effect of internal stress on the adhesion between the film layer and the substrate, and between the film layers. After a large number of R&D tests, it was determined to choose the aminosulfonate nickel plating solution system. This system has low stress, fast plating solution deposition speed, and better dispersion ability than the nickel plating solution using sulfuric acid as the main salt.

Aminosulfonate nickel plating solution system, solution components and process parameters are shown in Table 3.

Table 3 Nickel electroplating solution formula and operating conditions

If the nickel layer thickness is too small, it cannot prevent the diffusion of the underlying copper layer, and there is a risk of circuit failure; if the thickness is too large, the stress in the film layer will be out of control, causing the circuit film layer to fall off. In order to determine this thickness, high-temperature storage tests were conducted on thin-film thickened circuit sheets with different nickel layer thicknesses, as shown in Table 4.

Table 4 Nickel layer thickness determination test

The gold layers of the three groups of test pieces all changed color, that is, no visible diffusion of the copper layer occurred. The "serial number 1" test piece was further used for gold wire and gold ribbon pressure welding tests. The destructive tensile test values of the gold wire and gold ribbon all met the relevant inspection requirements of microwave integrated circuits, and the fracture mode was "fracture at the necking point", which can be judged that the performance of the gold layer meets the standard and the purity is reliable. Considering the stress factor, the nickel layer thickness is selected to be 0.5-1μm.

(9) Secondary gold plating

(9.1) Pre-gold plating

Before pre-gold plating, the nickel-plated microwave integrated circuit product is washed with water, and then activated with a 10wt% to 15wt% citric acid solution, the activation temperature is room temperature, and the activation time is 20s to 60s.

The activated microwave integrated circuit product is pre-plated with gold for 3 to 5 minutes in a citrate gold plating tank using a citrate gold plating solution. The citrate gold plating solution, solution components and process parameters are shown in Table 5.

Table 5 Pre-gold plating (1) solution formula and operating conditions

(9.2)Gold plating

The thickness of the secondary gold plating is 2-3 microns. The specific operation method and parameters are the same as those in 5) electroplating, that is, a neutral micro-cyanide plating system is used, the solution pH is 5.9-6.1, the gold content is 8-15g/L, the system temperature is 50±5℃, the current density is 1-2.3mA/ ^cm2 , and the anode: cathode area ratio is 2:1.

So far, the specific film layer structure has been determined. That is, on the basis of the existing thin film circuit structure (substrate + adhesion layer + 2-3μm Au plating), 3-5μm Cu plating, 0.5-1μm Ni plating and 2-3μm Au plating are added, as shown in Figure 5 and Figure 6.

The setting of 3-5μm Cu plating can ensure the normal realization of circuit performance. The selection of Cu takes into account its excellent thermal and electrical conductivity. It can take into account heat dissipation and other requirements while meeting the requirements of electrical performance. The 0.5-1μm thick Ni plating prevents the Cu layer from diffusing and oxidizing to the surface, while meeting the subsequent assembly gold wire and gold ribbon bonding requirements. If the thickness of the nickel layer is too small, it cannot prevent the diffusion of the underlying copper layer, and there is a risk of circuit failure. If the thickness is too large, the stress in the film layer will be out of control, causing the circuit film layer to fall off. The thickness of the surface gold layer is controlled at 2-3μm, and the gold can be removed by conventional tin plating to ensure the reliability of lead-tin welding. The prototype product using this process condition has been tested many times and can meet the product performance requirements.

The thin film thickening microwave integrated circuit obtained by the thin film thickening process of the present invention can achieve the following technical indicators:

a. Adhesion of circuit film layer>2kg/ ^mm2 , bonding strength of 25 micron diameter gold wire≥4.5g; bonding strength of 250*25 micron gold ribbon≥50g;

b. Line width/spacing accuracy ±15μm;

c. Circuit film thickness: 10-15μm;

d. Circuit film layer resistance accuracy ±2%;

e. Number of times the circuit film layer can withstand tin-lead solder: at least 20 times, 3 seconds each time;

f. Current resistance: 0.4mm line width/5A

In summary, based on the thin film microwave integrated circuit preparation process, the present invention combines various use requirements such as welding and bonding with the physical properties of metal materials, starting from determining the composite film structure of the film thickening, confirming the thickness of each film layer through experiments, and using process optimization to improve product quality, and finally obtains a film thickening microwave circuit product whose performance indicators meet the requirements of aerospace satellite products, reaching the advanced level at home and abroad. This process method has been successfully applied to high-power solid-state amplifiers of multiple models and bands, such as Fengyun-2 L-band 220W solid-state amplifier, Fengyun-3 C-band 100W solid-state amplifier, Tiantong S-band 20W solid-state amplifier, and Tianlian S-band 43W solid-state amplifier, solving the problems of poor rework resistance and insufficient current resistance of conventional process film layers, and the application effect is good, as shown in Figure 7.

According to a second aspect of the present invention, a thin film thickened microwave integrated circuit board is provided, which is prepared by the thickening process described in the first aspect, as shown in FIG5 , and includes, from bottom to top, a ceramic substrate, an adhesion layer, a 2-3 μm Au coating, a 3-5 μm Cu coating, a 0.5-1 μm Ni coating, and a 2-3 μm Au coating.

The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, the technical solution of the present invention and its implementation methods may be subjected to a variety of equivalent substitutions, modifications or improvements, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims (11)

1. A microwave integrated circuit film thickening process suitable for a solid-state product is characterized by comprising the following steps of:

carrying out primary gold plating on the ceramic substrate with the adhesion layer, wherein the thickness of a formed gold plating layer is 2-3 mu m;

Tightly attaching the mask plate on the surface of the substrate coated with the photosensitive adhesive after primary gold plating, and performing development, fixation and corrosion of a metal layer after exposure to finish photoetching on a gold plating layer;

copper is plated on the gold plating layer after photoetching, and the thickness of the formed copper plating layer is 3-5 mu m;

nickel is plated on the copper plating layer, and the thickness of the nickel plating layer is 0.5-1 mu m;

Performing secondary gold plating on the nickel plating layer, wherein the thickness of the formed gold plating layer is 2-3 mu m; the thickness of the circuit film is 10-15 μm.

2. The process for thickening a thin film of a microwave integrated circuit suitable for a solid-state product according to claim 1, wherein in the step of performing gold plating on the ceramic substrate with the adhesion layer once, a neutral micro cyanide plating system is adopted, the ph=5.9 to 6.1 of the solution, the gold content is 8 to 15g/L, the system temperature is 50±5 ℃, the current density is 1 to 2.3mA/cm ², and the anode: cathode area ratio = 2:1.

3. The process for thickening a thin film of a microwave integrated circuit suitable for use in a solid-state product according to claim 1, wherein the step of plating copper on the gold plating layer after photolithography comprises a pre-plating preparation process:

and (3) carrying out gold wire interconnection on the circuit semi-finished product containing the non-conductive isolated pattern, so that the electrically isolated pattern is communicated with the electrode during electroplating.

4. The process for thickening a film of a microwave integrated circuit suitable for use in a solid-state product according to claim 1, wherein the step of plating copper on the gold plating layer after photolithography comprises a cyanide copper plating process as a preplating process:

Hanging the substrate part to be plated in a plating tank, fixing the substrate part on a cathode rod, and keeping the top end of the substrate 5-10 cm away from the liquid level of the plating solution; the minimum electroplating area of each groove is not lower than 2dm ², and if the area of the substrate is insufficient, the total area reaches 2dm ² by using an electroplating piece;

After the substrate part is put down in the groove, the current density of 2+/-0.5A/dm ² is firstly used for impact plating for 1+/-0.5 min, then the current is reduced to 1.1+/-0.1A/dm ², copper plating is continued, and the total electroplating time is 3+/-1 min.

5. The process for thickening a thin film of a microwave integrated circuit suitable for use in a solid-state product according to claim 1, wherein the step of plating copper on the gold plating layer after photolithography comprises a cyanide copper plating process:

Hanging the substrate part to be plated in a plating tank, fixing the substrate part on a cathode rod, and keeping the top end of the substrate 5-10 cm away from the liquid level of the plating solution; the minimum electroplating area of each groove is not lower than 2dm ², and if the area of the substrate is insufficient, the total area reaches 2dm ² by using an electroplating piece;

After the substrate part is put down in the groove, the current density of 2+/-0.5A/dm ² is firstly used for impact plating for 1+/-0.5 min, then the current is reduced to 1.4+/-0.1A/dm ², copper plating is continued, and the total electroplating time is 40+/-5 min.

6. The process for thickening a film of a microwave integrated circuit suitable for use in a solid state product according to claim 1, wherein in the step of plating nickel on the copper plating layer, the nickel plating system is a sulfamate nickel plating solution system.

7. The process for thickening a microwave integrated circuit film suitable for a solid-state product according to claim 1, wherein in the step of plating nickel on a copper plating layer, the system temperature is 55-65 ℃, the cathode current density is 1-2A/dm ², the system ph=3.8-4.2, and the anode: cathode area ratio = 2:1, a step of; the stirring mode is cathode movement or cathode rotation and air stirring; the system is filtered regularly or continuously, and the filtering precision is 1-5 mu m; the anode is a sulfur-containing nickel plate or nickel cake.

8. The process for thickening a thin film of a microwave integrated circuit suitable for a solid product according to claim 1, wherein the step of performing secondary gold plating on the nickel plating layer comprises a pre-gold plating process:

before pre-gold plating, washing a nickel-plated microwave integrated circuit product with water, and then activating by adopting 10-15 wt% citric acid solution, wherein the activating temperature is room temperature, and the activating time is 20-60 s;

And pre-plating the activated microwave integrated circuit with citrate gold plating solution in a citrate gold plating tank for 3-5 min.

9. The process for thickening a thin film of a microwave integrated circuit suitable for a solid product according to claim 1, wherein the step of performing the secondary gold plating on the nickel plating layer comprises a gold plating process:

Adopting a neutral micro-cyanide plating system, wherein the pH value of the solution is=5.9-6.1, the gold content is 8-15 g/L, the system temperature is 50+/-5 ℃, the current density is 1-2.3 mA/cm ², and the anode: cathode area ratio = 2:1.

10. A microwave integrated circuit board with thickened film, which is characterized by being prepared by the microwave integrated circuit film thickening process suitable for solid-state products according to one of claims 1 to 9, and sequentially comprising a ceramic substrate, an adhesion layer, a gold coating of 2-3 mu m, a copper coating of 3-5 mu m, a nickel coating of 0.5-1 mu m and a gold coating of 2-3 mu m from bottom to top.

11. The thin-film thickened microwave integrated circuit board according to claim 10, wherein the adhesion of a circuit film layer of the circuit board is more than 2kg/mm ², and the gold wire bonding strength with the diameter of 25 micrometers is more than or equal to 4.5g; the bonding strength of the gold ribbon of 250 x 25 microns is more than or equal to 50g; line width/pitch accuracy + -15 μm; the precision of the circuit film resistance is +/-2%; circuit film tolerates tin-lead solder times: at least 20 times, each for 3 seconds; current resistance capability: 0.4mm line width/5A.