A chemical nickel-gold process for ceramic substrates

Abstract

The invention relates to the technical field of ceramic substrates, and in particular to a chemical nickel-gold process applied to ceramic substrates, comprising the following steps: step one: firstly making a circuit on a ceramic substrate, depositing a metal layer on the ceramic substrate, and obtaining a ceramic substrate with a connected circuit by etching; step two: coating the ceramic substrate with a photoresist, and selecting a template matched with the circuit for photocuring; step three: removing excess photoresist on the ceramic substrate by cleaning, so as to form a nickel-plated substrate with a circuit mask; step four: removing excess photoresist by grinding, and obtaining a metal surface with a certain roughness for electroplating nickel-gold; step five: electroplating a palladium alloy as a nickel target, wherein a mass ratio of 0.2%-0.4% of a rare earth element is added to the palladium alloy; step six: exciting the palladium alloy, performing chemical nickel plating on the outside of the palladium alloy, and forming a nickel plating layer on the metal surface by reducing nickel oxide in a nickel plating solution; and step seven: removing the covered photoresist and the excess nickel layer.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, and in particular to a chemical nickel-gold process applied to a ceramic substrate. Background Art

[0002] With the continuous improvement of ceramic substrates, integration and density, the welding requirements and welding reliability in the surface packaging of components are getting higher and higher. At present, most ceramic substrates use chemical nickel-gold plating. To improve the welding performance of the surface packaging of components, but chemical palladium-gold plating has the following serious shortcomings: high-end ceramic substrates (such as DBC substrates) have very high requirements for their solderability and solder joint reliability, and it is also difficult to reach a certain thickness through chemical nickel-gold. When the nickel layer is thicker and the metal line spacing is small, chemical nickel-gold treatment is performed on the line surface. Nickel-gold may be deposited on the ceramic within the line spacing, causing a short circuit. The reason is that in the chemical nickel-gold process, because the line gap is too small, it is difficult to clean thoroughly, resulting in the metal ions in the gap being deposited on nickel-gold, causing a short circuit.

[0003] Therefore, it is necessary to improve the existing method of electroplating nickel-gold on the metal surface of ceramic substrates to overcome the disadvantages of chemical nickel-gold treatment on the surface of the above metal layer circuits, greatly improve the solderability of the pads and the reliability of the solder joints, and solve the problems such as plating protrusions caused by electroplating nickel-gold. Summary of the invention

[0004] The problem to be solved by the present invention is to provide a chemical nickel-gold process applied to a ceramic substrate, which has a simple process and can greatly improve the reliability of solder joints.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a chemical nickel-gold process applied to a ceramic substrate, comprising the following steps:

[0006] Step 1: First, a circuit is made on a ceramic substrate, a metal layer is deposited on the ceramic substrate, and a ceramic substrate with a connecting circuit is obtained by etching;

[0007] Step 2: coating the ceramic substrate with photoresist and performing light curing with a template matching the circuit;

[0008] Step 3: removing excess photoresist on the ceramic substrate by cleaning to form a nickel-plated substrate with a circuit mask;

[0009] Step 4: Remove excess photoresist by grinding, and obtain a metal surface with a certain roughness for electroplating nickel and gold;

[0010] Step 5: electroplating a palladium alloy as a nickel target, wherein the palladium alloy is doped with 0.2% to 0.4% by mass of a rare earth element;

[0011] Step 6: activating the palladium alloy, performing chemical nickel plating on the outside of the palladium alloy, and forming a nickel plating layer on the metal surface by reducing nickel oxide in the nickel plating solution;

[0012] Step 7: Remove the covering photoresist and excess nickel layer.

[0013] Furthermore, the nickel plating layer is doped with rare earth elements, and the mass ratio of the rare earth elements doped in the nickel plating layer is 0.2%-0.4%.

[0014] Furthermore, in step six, the nickel plating temperature is 50-85° C., and the nickel plating is performed for 3-5 minutes. The process can be repeated multiple times, preferably 2-4 times, depending on the required thickness of the coating.

[0015] Furthermore, in step six, the thickness of the nickel plating layer is 1-16 μm.

[0016] Furthermore, in step five, the sputtering power of the palladium alloy is 15-21 kw, the sputtering gas pressure is 0.3 Pa, the negative bias voltage is 450 V, the deposition temperature is 200° C., and the deposition time is 10-30 min.

[0017] Furthermore, the nickel plating solution comprises nickel oxide, a reducing agent, a complexing agent, a stabilizer and a solvent.

[0018] Further, the stabilizer is sodium thiosulfate and thiourea, and the total concentration of the stabilizer in the chemical nickel plating solution is 1-5 g / L, wherein the concentration ratio of the sodium thiosulfate to the thiourea is 1:(2-4);

[0019] The complexing agent is one of C4O6H4KNa or ethylenediamine, and the total concentration of the complexing agent in the chemical nickel plating solution is 30-100 g / L;

[0020] The reducing agent includes at least one of sodium hypophosphite, potassium hypophosphite and ammonium hypophosphite.

[0021] Furthermore, the rare earth element includes at least one rare earth element selected from the group consisting of lanthanum, cerium, erbium and yttrium.

[0022] Furthermore, it includes a pretreatment step, which includes: degreasing, polishing, pickling, water washing, drying, ion beam cleaning and preheating steps.

[0023] Furthermore, the ceramic substrate is one of aluminum oxide, aluminum nitride, silicon carbide, and beryllium oxide.

[0024] Compared with the prior art, the present invention has the following advantages and positive effects:

[0025] The chemical nickel-gold process applied to ceramic substrates provided by the present invention mainly solves the problem of small line spacing and difficulty in reaching a certain thickness of conventional chemical nickel-gold plating, further improves the solderability of pads and the reliability of solder joints, and solves the problem that product quality and reliability cannot meet the requirements of high solderability, as well as the problem of protruding edges of the plating caused by electroplating nickel-gold. It has a good service life, and the gold surface retains excellent welding performance for a long time, eliminating defects such as cold soldering, leaking soldering, and poor welding reliability, thereby improving product quality and product reliability, and the production process is pollution-free, can be used for smaller substrates, is more adaptable to the development of the industry and is suitable for industrial production. DETAILED DESCRIPTION

[0026] In order to better understand the present invention, the present invention is further described below in conjunction with specific embodiments.

[0027] High-end ceramic substrates (such as DBC substrates) have very high requirements for their solderability and solder joint reliability, and it is also difficult to achieve a certain thickness through chemical nickel-gold. When the nickel layer is thicker and the metal line spacing is smaller, chemical nickel-gold treatment is performed on the line surface. Nickel-gold may be deposited on the ceramic within the line spacing, causing a short circuit. The reason is that during the chemical nickel-gold process, the line spacing is too small, so it is difficult to clean thoroughly, resulting in the metal ions in the gap being deposited on nickel-gold, causing a short circuit.

[0028] Therefore, it is necessary to improve the existing method of electroplating nickel-gold on the metal surface of ceramic substrates, and optimize it on this basis to overcome the disadvantages brought about by the chemical nickel-gold treatment on the surface of the above metal layer circuits, greatly improve the solderability of the pads and the reliability of the solder joints, and solve the problems such as plating protrusions caused by electroplating nickel-gold.

[0029] In the prior art, copper and other metals are also used for lamination, exposure and development to make copper metal films as masks, etc. However, during the processing, since the metal mask and nickel metal have relatively similar chemical properties and also have relatively good bonding strength, when the metal mask is removed, it is easy to cause damage to the edge of the nickel metal layer, or the metal mask may not be completely removed.

[0030] Thereby, a chemical nickel-gold process for ceramic substrates is obtained, which has a simple process, can solve the problems existing in the metal mask, and improve the reliability of the pad.

[0031] According to the general inventive concept of one aspect of the present invention, a chemical nickel-gold process applied to a ceramic substrate is provided, comprising the following steps:

[0032] Step 1: First, a circuit is made on a ceramic substrate, a metal layer is deposited on the ceramic substrate, and a ceramic substrate with a connecting circuit is obtained by etching;

[0033] Step 2: Apply photoresist on the ceramic substrate and use a template that matches the circuit for light curing;

[0034] Step 3: removing excess photoresist on the ceramic substrate by cleaning to form a nickel-plated substrate with a circuit mask;

[0035] Step 4: Remove excess photoresist by grinding, and obtain a metal surface with a certain roughness for electroplating nickel and gold;

[0036] Step 5: electroplating a palladium alloy as a nickel target, wherein the palladium alloy is doped with 0.2% to 0.4% by mass of a rare earth element;

[0037] Step 6: Activate the palladium alloy, perform chemical nickel plating on the outside of the palladium alloy, and form a nickel plating layer on the metal surface by reducing the nickel oxide in the nickel plating solution;

[0038] Step 7: Remove the covering photoresist and excess nickel layer.

[0039] The chemical nickel-gold process applied to ceramic substrates provided by the present invention mainly solves the problem of small line spacing and difficulty in reaching a certain thickness of conventional chemical nickel-gold plating, further improves the solderability of pads and the reliability of solder joints, and solves the problem that product quality and reliability cannot meet the requirements of high solderability, as well as the problem of protruding edges of the plating caused by electroplating nickel-gold. It has a good service life, and the gold surface retains excellent welding performance for a long time, eliminating defects such as cold soldering, leaking soldering, and poor welding reliability, thereby improving product quality and product reliability, and the production process is pollution-free, can be used for smaller substrates, is more adaptable to the development of the industry and is suitable for industrial production.

[0040] The circuit can be effectively covered by photoresist, and the template obtained by etching the photoresist can have a relatively uniform circuit. After nickel plating, the photoresist can be directly removed by cleaning to obtain a relatively flat nickel coating. By controlling the thickness of the photoresist, a thicker nickel coating can also be obtained. There is no need to worry about the difficulty in removing the mask due to complete coverage of the nickel coating. The thickness of the photoresist can be made much larger than the thickness of the coating. The surface can then be carefully polished to obtain a flat surface and a relatively regular edge of the coating. The nickel layer on the surface of the photoresist can also be removed to expose the photoresist, making it easier to remove.

[0041] Furthermore, in step five, the mass ratio of the rare earth element doped in the nickel plating layer is 0.2%-0.4%.

[0042] Furthermore, in step five, the mass ratio of the rare earth element doped in the nickel plating layer can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, etc.

[0043] Furthermore, the rare earth element includes at least one rare earth element selected from the group consisting of lanthanum, cerium, erbium and yttrium.

[0044] Furthermore, in step five, the palladium alloy can be formed by electroplating, evaporation, sputtering, chemical plating, chemical deposition and the like.

[0045] Furthermore, in step five, when the palladium alloy is sputtered, the sputtering power of the palladium alloy is 15-21 kw, the sputtering gas pressure is 0.3 Pa, the negative bias voltage is 450 V, the deposition temperature is 200° C., and the deposition time is 10-30 min.

[0046] Furthermore, when the palladium alloy is chemically deposited, the nickel-plated substrate is placed in a chemical palladium plating solution, wherein the chemical palladium plating solution includes a palladium compound, a hypophosphorous acid compound, a boron hydride compound, ammonium chloride, ammonia water, a composite complexing agent, and a complexing stabilizer. The composite complexing agent and the complexing stabilizer can facilitate the dispersion of the palladium compound and prevent precipitation.

[0047] The target layer can increase the bonding strength of nickel and gold, making the thickness of the nickel layer controllable. A nickel layer with better bonding strength can be obtained through multiple depositions. The addition of rare earth elements can improve the compactness and coverage between nickel layers or between the nickel layer and the target layer, thereby improving the bonding ability between nickel layers, so that the thickness of the nickel layer can be controlled at will, thereby solving the problem of nickel layer protrusion. The addition of rare earth elements can also play a certain role as a stabilizer, which can save the addition of many precious metal stabilizers.

[0048] Furthermore, in step six, the nickel plating temperature is 50-85° C., and the nickel plating is performed for 3-5 minutes. The process can be repeated multiple times, preferably 2-4 times, depending on the required thickness of the coating.

[0049] Furthermore, in step six, after each nickel plating process, the substrate can be removed from the nickel plating solution, cleaned, polished, and the surface structure can be observed before continuing to nickel plate. By preparing a surface with a microstructure between multiple levels, the bonding force between the nickel layers is increased to prevent the nickel layer from peeling off, or nickel plating can be continued directly in the nickel plating solution for continuous nickel plating until the nickel plating is completed.

[0050] Furthermore, in step six, the thickness of the nickel plating layer is 1-16 μm, and the nickel plating layer is doped with rare earth elements.

[0051] Furthermore, the thickness of the nickel plating layer can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 μm.

[0052] After many tests, it can be known that the chemical nickel plating according to the present invention can achieve a nickel plating layer of up to 16μm, and a relatively good use effect can be obtained within this range. Compared with the general nickel plating layer with a thickness of less than 10μm, the present application can obtain a relatively stable nickel plating layer, and the circuit gap will not be affected by the thickness of the nickel plating layer.

[0053] Furthermore, the nickel plating solution includes nickel oxide, a reducing agent, a complexing agent, a stabilizer and a solvent.

[0054] Furthermore, the stabilizers are sodium thiosulfate and thiourea, and the total concentration of the stabilizers in the chemical nickel plating solution is 1-5 g / L, wherein the concentration ratio of sodium thiosulfate to thiourea is 1:(2-4).

[0055] Furthermore, the total concentration of the stabilizer in the chemical nickel plating solution can be 1, 2, 3, 4, or 5 g / L, and the concentration ratio of sodium thiosulfate to thiourea can be 1:2, 1:3, or 1:4.

[0056] Furthermore, the complexing agent is one of C4O6H4KNa or ethylenediamine, and the total concentration of the complexing agent in the chemical nickel plating solution is 30-100 g / L.

[0057] Furthermore, the total concentration of the complexing agent in the chemical nickel plating solution can be 30, 40, 50, 60, 70, 80, 90, or 100 g / L.

[0058] Furthermore, the reducing agent includes at least one of sodium hypophosphite, potassium hypophosphite and ammonium hypophosphite.

[0059] Furthermore, the method comprises a pretreatment step, which comprises degreasing, polishing, pickling, washing, drying, ion beam cleaning and preheating steps.

[0060] Furthermore, the pretreatment step may include: washing the ceramic substrate with water to remove the surface soil, and pickling it with acid to remove the surface oxide, washing it with acid again with acid solution to remove the acid, performing hydrogen removal treatment, washing it with water again, and then drying it with 70-85°C hot air, and then entering the nickel plating process.

[0061] Pickling can remove the oxide film on the surface, and can make the surface slightly corrosive, making the surface rough, thereby increasing the surface's ability to bond with metal or photoresist, thereby reducing stress concentration between different materials, and the phenomenon of plating or mask detachment. Hydrogen drive treatment can handle the hydrogen permeation during the pickling process, thereby reducing its stress corrosion and hydrogen embrittlement, making it have better bonding performance, thereby improving the problem of poor bonding caused by high stress in the metal layer;

[0062] Furthermore, the hydrogen driving treatment includes: heating and baking at 180-200°C for 3-4h.

[0063] Furthermore, in step five, after electroplating the palladium alloy as the nickel target, it is necessary to wash with water for 1-2 minutes at room temperature, and then dry at 50-60°C, and blow dry with hot air at 85°C for 3-4 minutes.

[0064] Furthermore, the ceramic substrate is one of aluminum oxide, aluminum nitride, silicon carbide, and beryllium oxide.

[0065] Furthermore, the ceramic substrate may also be a ceramic metallized substrate, such as a ceramic copper-plated substrate or the like.

[0066] Furthermore, the present application is mainly designed to address the problem of poor bonding between ceramic substrates and nickel plating, but the method of the present application can be used not only for ceramic substrates, but also for nickel plating of other substrates, and the specific use can be adjusted according to actual conditions.

[0067] The technical solution of the present invention is described in detail below through preferred embodiments. It should be noted that the specific embodiments below are only used for illustration and are not used to limit the present invention.

[0068] Embodiment 1:

[0069] The method comprises the steps of pretreatment and nickel plating, wherein the pretreatment comprises: washing the ceramic substrate with water to remove the surface soil, pickling it with acid to remove the surface oxide, washing it with acid again with acid washing liquid to remove the acid, performing hydrogen driving treatment, washing it with water again, drying it with hot air at 70-85°C, and then transferring it to the nickel plating process;

[0070] Wherein, the nickel plating steps are:

[0071] Step 1: First, a circuit is made on a ceramic substrate, a metal layer is deposited on the ceramic substrate, and a ceramic substrate with a connecting circuit is obtained by etching, and the ceramic substrate is aluminum oxide;

[0072] Step 2: Apply photoresist on the ceramic substrate and use a template that matches the circuit for light curing;

[0073] Step 3: removing excess photoresist on the ceramic substrate by cleaning to form a nickel-plated substrate with a circuit mask;

[0074] Step 4: Remove excess photoresist by grinding, and obtain a metal surface with a certain roughness for electroplating nickel and gold;

[0075] Step 5: electroplating a palladium alloy as a nickel target, wherein 0.2% by weight of lanthanum is doped into the palladium alloy, the sputtering power of the palladium alloy is 21 kW, the sputtering pressure is 0.3 Pa, the negative bias voltage is 450 V, the deposition temperature is 200° C., and the deposition time is 30 min;

[0076] Step 6: activating the palladium alloy, and performing chemical nickel plating on the outside of the palladium alloy, forming a nickel coating on the metal surface by reducing the nickel oxide in the nickel plating solution, the nickel coating is doped with 0.2% lanthanum, the nickel plating temperature is 50°C, the nickel plating is 3 minutes, the nickel plating is repeated 4 times, the thickness of the nickel coating is 8 μm, the total concentration of the stabilizer is 1 g / L, and the concentration ratio of sodium thiosulfate to thiourea is 1:2;

[0077] The complexing agent is C4O6H4KNa with a total concentration of 30 g / L;

[0078] Reducing agents include sodium hypophosphite;

[0079] Step 7: Remove the covering photoresist and excess nickel layer as experimental group A.

[0080] Embodiment 2:

[0081] The pretreatment steps are the same as those in Example 1;

[0082] Wherein, the nickel plating steps are:

[0083] Steps 1 to 4 are the same as those in Example 1, except that the type of the ceramic substrate is aluminum nitride;

[0084] Step 5: electroplating a palladium alloy as a nickel target, wherein 0.3% by mass of cerium is doped into the palladium alloy, the sputtering power of the palladium alloy is 17 kW, the sputtering pressure is 0.3 Pa, the negative bias voltage is 450 V, the deposition temperature is 200° C., and the deposition time is 20 min;

[0085] Step 6: activating the palladium alloy, and performing chemical nickel plating on the outside of the palladium alloy, forming a nickel coating on the metal surface by reducing the nickel oxide in the nickel plating solution, wherein the rare earth element doped in the nickel coating is 0.3% cerium, the nickel plating temperature is 85° C., the nickel plating is performed for 4 minutes, and the thickness of the coating can be repeated multiple times according to the required thickness, preferably 3 times, the thickness of the nickel coating is 12 μm, the total concentration of the stabilizer is 2 g / L, and the concentration ratio of sodium thiosulfate to thiourea is 1:3;

[0086] The complexing agent is ethylenediamine with a total concentration of 50 g / L;

[0087] Reducing agents include potassium hypophosphite;

[0088] Step 7: Remove the covering photoresist and excess nickel layer as experimental group B.

[0089] Embodiment 3:

[0090] The pretreatment steps are the same as those in Example 1;

[0091] Wherein, the nickel plating steps are:

[0092] Steps 1 to 4 are the same as those in Example 1, except that the type of the ceramic substrate is silicon carbide;

[0093] Step 5: electroplating a palladium alloy as a nickel target, wherein erbium is doped in an amount of 0.4% by mass into the palladium alloy, the sputtering power of the palladium alloy is 21 kW, the sputtering pressure is 0.3 Pa, the negative bias voltage is 450 V, the deposition temperature is 200° C., and the deposition time is 30 min;

[0094] Step 6: activating the palladium alloy, and performing chemical nickel plating on the outside of the palladium alloy, forming a nickel coating on the metal surface by reducing the nickel oxide in the nickel plating solution, wherein the rare earth element doped in the nickel coating is 0.4% erbium, the nickel plating temperature is 65° C., the nickel plating is 5 minutes, and the thickness of the coating can be repeated multiple times according to the required thickness, preferably 4 times, the thickness of the nickel coating is 16 μm, the total concentration of the stabilizer is 4 g / L, and the concentration ratio of sodium thiosulfate to thiourea is 1:4;

[0095] The complexing agent is C4O6H4KNa with a total concentration of 70 g / L;

[0096] Reducing agents include potassium hypophosphite;

[0097] Step 7: Remove the covering photoresist and excess nickel layer as experimental group C.

[0098] Embodiment 4:

[0099] The pretreatment steps are the same as those in Example 1;

[0100] Wherein, the nickel plating steps are:

[0101] Steps 1 to 4 are the same as those in Example 1, except that the type of the ceramic substrate is beryllium oxide;

[0102] Step 5: electroplating a palladium alloy as a nickel target, wherein yttrium is doped in an amount of 0.4% by mass into the palladium alloy, the sputtering power of the palladium alloy is 21 kW, the sputtering pressure is 0.3 Pa, the negative bias voltage is 450 V, the deposition temperature is 200° C., and the deposition time is 30 min;

[0103] Step 6: activating the palladium alloy, and performing chemical nickel plating on the outside of the palladium alloy, forming a nickel coating on the metal surface by reducing the nickel oxide in the nickel plating solution, wherein the rare earth element doped in the nickel coating is 0.4% yttrium, the nickel plating temperature is 85° C., the nickel plating is 4 minutes, and the thickness of the coating can be repeated multiple times according to the required thickness, preferably 4 times, the thickness of the nickel coating is 14 μm, the total concentration of the stabilizer is 5 g / L, and the concentration ratio of sodium thiosulfate to thiourea is 1:4;

[0104] The complexing agent is C4O6H4KNa with a total concentration of 100 g / L;

[0105] Reducing agents include ammonium hypophosphite;

[0106] Step 7: Remove the covering photoresist and excess nickel layer as experimental group D.

[0107] Comparative Example 1:

[0108] The pretreatment and nickel plating steps are the same as those in Example 1, except that the mask is made of copper alloy. Finally, the copper alloy used as the mask is removed, and this is used as the control group A.

[0109] Comparative Example 2:

[0110] The pretreatment and nickel plating steps are the same as those in Example 1, except that no rare earth material is added in steps 5 and 6, which is used as control group B.

[0111] Experimental Group 1:

[0112] Observe the circuit conditions of the experimental groups AD and the control group A, mainly observing the width and uniformity of the circuit, the condition of the edge of the nickel layer, and whether there is nickel or mask residue in the circuit. Through observation, it can be seen that the circuit conditions in the experimental groups AD are good, while there are several copper metal residues at the edge of the nickel layer in the control group A, and the edge of the nickel layer has slight damage. It can be seen that the circuit can be effectively covered by the photoresist, and the template obtained by etching the photoresist can have a relatively uniform circuit. After nickel plating, the photoresist can also be directly removed by cleaning to obtain a relatively flat nickel coating, and by controlling the thickness of the photoresist, a thicker nickel coating can also be obtained. There is no need to worry about the difficulty in removing the mask due to the complete coverage of the nickel coating. The thickness of the photoresist can be made much larger than the thickness of the coating, and then the surface is carefully polished to obtain a flat surface and a relatively regular edge of the coating, and the nickel layer on the surface of the photoresist can be removed to expose the photoresist, so that it can be removed more conveniently.

[0113] Experimental Group 2:

[0114] Conventional welding performance is mainly affected by damage to the metal surface, so a salt spray test and a damage test are used to characterize the effect of the product in the nickel plating process provided by the present invention.

[0115] (1) Salt spray resistance test: The ceramic substrates of Examples 1-4 were used as the experimental group, and Comparative Example 2 was used as the control group. The salt spray resistance test was performed on them. The experimental groups A to D and the control groups A and B were placed in a salt spray resistance test box, respectively, and the time when corrosion occurred on their surfaces was measured. The results are shown in Table 1.

[0116] Table 1: Salt spray resistance test results

[0117]

[0118]

[0119] As can be seen from Table 1, the chemical nickel-gold process for ceramic substrates provided by the present invention mainly solves the corrosion problem of conventional chemical nickel plating, eliminates the poor weldability of chemical nickel plating caused by corrosion, poor weather resistance, and the inability of product quality and reliability to meet the requirements of high weldability. The corrosion resistance of chemical nickel plating can be greatly improved, so that the metal surface retains excellent welding performance for a long time, and defects such as cold welding, leaking welding, and poor welding reliability are eliminated, thereby improving product quality and product reliability, and the production process is pollution-free and suitable for industrial production.

[0120] (2) Damage test: The ceramic substrates of Examples 1 to 4 were used as an experimental group, and Comparative Example 2 was used as a control group, and friction polishing and bending tests were performed on them.

[0121] The specific operation method of the friction polishing test is: place the plated part in a vibration polishing machine, and use a soapy water solution as a lubricant to perform a friction polishing test to observe whether there is any damage on the surface.

[0122] The specific operation method of the bending test is: the nickel-plated layer is subjected to a 180° bending test, and then the bent portion is checked with a magnifying glass of 100 times to observe whether there are obvious cracks or peeling. The results are shown in Table 2.

[0123] Table 2: Damage test results

[0124] Experimental Group A Experimental Group B Experimental Group C Experimental Group D Control group B Friction polishing smooth smooth smooth smooth Slightly damaged Bending test No damage No damage No damage No damage Slight shedding

[0125] The plated parts experimental groups AD obtained in Examples 1-4 have uniform surface coatings and smooth appearances, without any damage or blistering. However, compared with the control group B, there are obvious blistering or damage on the surface, indicating that the bonding strength between the nickel plating layer and the substrate does not meet the market demand.

[0126] It can be seen that the plated part obtained by the present invention has a firm and uniform surface and no blistering occurs at all, which shows that the bonding force between the nickel plating layer obtained by the present invention and the substrate is very good, thereby perfectly ensuring the compactness of the plating structure.

[0127] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of this patent.

Claims

1. A chemical nickel-gold process applied to a ceramic substrate, characterized in that: The specific steps include: Step 1: First, a circuit is made on a ceramic substrate, a metal layer is deposited on the ceramic substrate, and a ceramic substrate with a connecting circuit is obtained by etching; Step 2: coating the ceramic substrate with photoresist and performing light curing with a template matching the circuit; Step 3: removing excess photoresist on the ceramic substrate by cleaning to form a ceramic substrate with a circuit mask; Step 4: Remove excess photoresist by grinding, and obtain a metal surface with a certain roughness for electroplating nickel and gold; Step 5: electroplating a palladium alloy as a nickel target, wherein the palladium alloy is doped with 0.2%-0.4% by mass of a rare earth element; Step 6: activating the palladium alloy, performing chemical nickel plating on the outside of the palladium alloy, and forming a nickel plating layer on the metal surface by reducing nickel oxide in the nickel plating solution; Step 7: Remove the covering photoresist and excess nickel layer; The nickel coating is doped with rare earth elements, and the mass ratio of the rare earth elements doped in the nickel coating is 0.2%-0.4%; in step 6, the nickel plating temperature is 50-85°C, the nickel plating is 3-5min, and the thickness of the coating is repeated 2-4 times according to the required coating thickness, and the thickness of the nickel coating is up to 16μm; in step 5, the sputtering power of the palladium alloy is 15-21kw, the sputtering pressure is 0.3Pa, the negative bias voltage is 450V, the deposition temperature is 200°C, and the deposition time is 10-30min; the rare earth elements include at least one rare earth element of lanthanum, cerium, erbium, and yttrium; and also includes a pretreatment step of the ceramic substrate before step 1, and the pretreatment step includes: degreasing, polishing, pickling, water washing, drying, ion beam cleaning and preheating steps; The nickel plating solution comprises nickel oxide, a reducing agent, a complexing agent, a stabilizer and a solvent; the stabilizer is sodium thiosulfate and thiourea, and the total concentration of the stabilizer in the chemical nickel plating solution is 1-5 g / L, wherein the concentration ratio of the sodium thiosulfate to the thiourea is 1:(2-4); the complexing agent is one of C4O6H4KNa or ethylenediamine, and the total concentration of the complexing agent in the chemical nickel plating solution is 30-100 g / L; The reducing agent includes at least one of sodium hypophosphite, potassium hypophosphite and ammonium hypophosphite.

2. The chemical nickel-gold process for ceramic substrates according to claim 1, characterized in that: The ceramic substrate is one of aluminum oxide, aluminum nitride, silicon carbide and beryllium oxide.