Preparation method of ceramic substrate resistance heating sheet

Abstract

The invention discloses a preparation method of a ceramic substrate resistance heating sheet, and relates to the technical field of electronic components. The method specifically comprises the following steps: carrying out magnetron sputtering on the surface of a ceramic substrate, sequentially obtaining a titanium layer and a copper layer, plating a bottom copper layer, carrying out primary pattern transfer, plating a thick copper layer after development, removing a film, carrying out flash etching to remove the titanium copper layer outside a pattern, carrying out secondary pattern transfer, removing the copper layer outside a bonding pad area on the pattern, carrying out sand blasting, and then carrying out nickel blasting. And finally, a nickel layer and a gold layer are plated, and punching and cutting are carried out. According to the method provided by the invention, the nickel thin-film resistor heating sheet can be prepared on the surface of the ceramic substrate, and the nickel thin-film resistor heating sheet has good binding force.

Description

Technical Field

[0001] The invention relates to the technical field of electronic components, in particular to a method for preparing a ceramic substrate resistance heating sheet. Background Art

[0002] Ceramic substrate refers to a substrate that connects ceramic sheets and copper through special processes (such as brazing, sintering, magnetron sputtering, etc.). Compared with PCB substrates, it not only has excellent electrical insulation properties but also good thermal conductivity and reliability. It can be etched with various patterns like PCB boards and has a large current carrying capacity. Therefore, ceramic substrates have become the basic materials for high-power power electronic circuit structure technology and interconnection technology.

[0003] Nickel resistors and platinum resistors are two common resistor heating sheets, and they have some major differences in materials, performance and application range. Compared with platinum resistors, nickel resistors use nickel materials as resistor heating sheets, which are usually suitable for environments of -60℃-260℃. Based on the differences in material costs and manufacturing processes, the price of nickel resistors is usually lower than that of platinum resistors. At present, the market uses silk-screen platinum as resistors and silk-screen gold paste as pads, which has high production costs and poor pad bonding.

[0004] Combining the advantages of nickel resistors and ceramic substrates, this patent proposes a method for preparing a nickel resistor heating sheet on a ceramic substrate. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a nickel thin film resistor heating sheet on a ceramic substrate to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a ceramic substrate resistance heating sheet comprises the following steps:

[0008] Step 1: After cleaning the surface of the ceramic substrate, vacuum coating is performed to obtain a titanium copper layer, and after a base copper layer is plated on the surface of the titanium copper layer, a pattern transfer is performed to develop a photolithography pattern on the surface of the ceramic substrate;

[0009] Step 2: After the thick copper layer is plated on the surface of the ceramic substrate after development in step 1, the titanium-copper layer other than the primary photolithography pattern is removed by stripping and flash etching, and a secondary pattern transfer is performed after washing and drying, and a secondary photolithography pattern is developed on the surface of the ceramic substrate, and then etching and stripping are performed to remove the copper layer other than the pad area on the secondary photolithography pattern, exposing the titanium layer sputtered at the bottom, and then sandblasting is performed, and washing and drying is performed;

[0010] Step 3: After the ceramic substrate dried in step 2 is cleaned with a dilute hydrochloric acid solution, a nickel layer is plated on the surface, vacuum annealing is performed, and after cooling, an insulating protective layer is silk-screened on the surface of the ceramic substrate, and then a nickel layer and a gold layer are plated in sequence. After washing and drying, laser drilling and cutting are performed to obtain a ceramic substrate resistor heating sheet.

[0011] In step 1, the vacuum coating is performed by magnetron sputtering, first sputtering the titanium layer and then sputtering the copper layer; the thickness of the titanium layer is 0.1 μm-0.3 μm, and the thickness of the copper layer is 0.5 μm-3 μm; the vacuum coating pressure is 2.0×10 -1 Pa-3.0×10 -1 Pa, vacuum coating temperature is 200℃-300℃;

[0012] Furthermore, in step 1, the bottom copper layer is obtained by electroplating, and the composition of the plating solution is: 150g / L-200g / L of copper sulfate pentahydrate, 50g / L-70g / L of sulfuric acid, 40ppm-70ppm of chloride ions, 10mL / L-15mL / L of wetting agent, 0.6mL / L-1.4mL / L of brightener, and 25mL / L-35mL / L of leveling agent; the thickness of the bottom copper layer is 1.5μm-4.0μm;

[0013] Furthermore, in step 2, the thick copper layer is obtained by electroplating, and the plating solution composition is the same as the bottom copper layer electroplating plating solution; the thickness of the thick copper layer is 8 μm-18 μm;

[0014] Furthermore, in step 3, the nickel layer is obtained by electroplating or chemical plating, and has a thickness of 2.0 μm-2.6 μm; wherein the chemical plating is firstly palladium activated for 10 minutes, and then the nickel layer is plated after washing;

[0015] Furthermore, in step 3, the thickness of the insulating protective layer is 8 μm-12 μm; after silk-screen printing of the insulating protective layer, the thickness of the nickel layer is 3 μm-5 μm, and the thickness of the gold layer is 0.1 μm-0.2 μm.

[0016] Furthermore, in step 1, the surface of the ceramic substrate is subjected to low-temperature plasma treatment before vacuum coating, with a combination of 90-95wt% nitrogen and 5-10wt% oxygen as a plasma gas source, the ceramic substrate is placed directly below the plasma nozzle, aligned with the center of the specimen, with a distance of 5mm-25mm, and low-temperature plasma is sprayed for 60-100s; wherein the plasma gas source temperature is 20-30°C;

[0017] Furthermore, chemical micro-etching is performed before palladium activation, and a sulfuric acid-sodium persulfate system is used for micro-etching for 1-2 minutes; wherein the sulfuric acid-sodium persulfate system is composed of: sodium persulfate 50-60 g / L, concentrated sulfuric acid 30 mL / L, copper sulfate 100-120 g / L;

[0018] In the further step 3, a palladium barrier layer is inserted between the nickel layer and the gold layer. The palladium barrier layer adopts a chemical plating process, and the specific process parameters are: palladium chloride 2-2.5g / L, sodium hypophosphite 10-12g / L, ammonium hydroxide 150-165mL / L, ammonium chloride 30-40g / L, bismuth nitrate 50-60mg / L, isopropanolamine 20-35mL / L; adjust the pH to 9.5-10, and heat in a water bath to 45-55°C; the thickness of the palladium barrier layer is 0.1μm-0.2μm; after the chemical palladium plating is completed, heat treatment is performed, and it is kept at 200-250°C for 1-2h, and then a subsequent gold plating layer is performed.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention proposes a method for preparing a nickel resistor heating sheet on a ceramic substrate. Combining the advantages of nickel resistors and ceramic substrates, a Ti seed layer is vacuum sputtered before electroplating a Cu layer on the ceramic surface, which can not only improve the bonding strength between the ceramic and Cu layers, but also the Ni circuit deposited on the titanium surface is the heating resistor in the subsequent Ni plating. The ceramic surface is plasma treated before vacuum sputtering to enhance the hydrophilicity of the ceramic surface, improve the uniformity of the magnetron sputtered Ti / Cu layer on the ceramic surface and the bonding strength between the ceramic and Ti layers.

[0021] 2. Insert a Pd barrier layer into the chemically plated Ni / Au layer to prevent the nickel layer from diffusing to the surface of the gold layer and causing oxidation, and to prevent the nickel layer from being attacked by the solution during gold immersion and causing nickel corrosion, resulting in "black pads" during welding; optimize the palladium plating process parameters to obtain a dense coating; chemical palladium plating is accompanied by some side reactions, such as hydrogen produced by hypophosphite. As palladium is a metal with good hydrogen storage performance, the hydrogen produced by the side reaction will cause gaps between the coatings, affecting the conductivity of the coating; therefore, heat treatment is performed to eliminate hydrogen and improve the adhesion of the coating; and the quality of the coating on the pad surface is improved;

[0022] 3. The present invention strictly controls the thickness of each metal layer on the surface of the ceramic substrate to ensure that the resistor heating sheet manufactured within this parameter range can achieve good bonding between the nickel resistor and the ceramic substrate, and each metal layer has good uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The morphology of the substrate after the pattern transfer and development in step 1 of the present invention;

[0024] Figure 2 The morphology of the substrate after the secondary pattern transfer and development in step 2 of the present invention;

[0025] Figure 3 The morphology of the substrate after the secondary development and etching in step 2 of the present invention;

[0026] Figure 4 The morphology of the substrate with a layer of green photosensitive ink (solder resist) printed on the surface in step 3 of the present invention;

[0027] Figure 5 The morphology of the substrate after laser drilling and cutting in step 3 of the present invention;

[0028] Figure 6 This is the tin ball morphology on the surface of the copper-nickel-gold pad after the vertical tensile test in Experiment 1. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the experiment, the copper plating solution was provided by MacdermidAlpha; the nickel plating solution was provided by Uemura Industries;

[0031] Wetting agent MacuSpec VF-TI300 Wetter, brightener MacuSpec VF-TH300 Brightener, leveler MacuSpec V-TH300 Leveler in copper plating solution;

[0032] Composition of palladium activation solution: 2-2.5g / L palladium chloride

[0033] The composition of the plating solution for Ni / Au layer is as follows:

[0034] The nickel plating solution is composed of 45 mL / L Ni muden NPR-4-A, 150 mL / L Ni muden NPR-4-M, and the rest is water; the gold plating solution is from C.Uyemura TCL-61-M5200mL / L; Gold solution (Au: 2.0g / L) 20mL / L.

[0035] Embodiment 1: The present invention provides a technical solution, and the specific steps are as follows:

[0036] Step 1: After cleaning the ceramic substrate surface, perform alkali washing → water washing → acid washing → ultrasonic water washing → baking. Take the cleaned ceramic substrate for vacuum coating. First, sputter a Ti layer as a transition layer with a thickness of 150nm; then sputter a Cu layer as a seed layer with a thickness of 1200nm to obtain a Ti / Cu seed layer. Then place it in a copper plating solution and electroplate the bottom Cu layer using a DC electroplating method. Thicken the Cu sputtering layer to a thickness of 1μm. Perform a pattern transfer, transfer it to the substrate using a film → exposure, and develop a photolithography pattern, such as Figure 1 As shown;

[0037] Step 2: After the substrate is developed in step 1, it is degreased → washed → micro-etched → washed → acid washed → washed, and then placed in a copper plating solution to electroplate the Cu layer to a thickness of 10 μm. The Ti / Cu layer other than the primary photolithography pattern is removed, washed and dried, and then a secondary film is applied → exposed. After the secondary photolithography pattern is developed on the surface of the substrate, the copper on the pattern other than the pad is exposed, such as Figure 2 As shown; the substrate after the secondary development is etched and the film is stripped to remove the copper layer on the secondary photolithography pattern except the pad area, as shown Figure 3 As shown; the substrate after etching and film stripping is sandblasted by horizontal line wet spraying, and then washed and dried;

[0038] Step 3: Place the substrate after drying in step 2 in a 5% dilute hydrochloric acid solution for 2 minutes, wash with pure water, and then soak in a palladium activation solution for 10 minutes for activation. Take it out and place it in a nickel plating solution for chemical plating to obtain a Ni-plated layer. Place it in a vacuum annealing furnace for vacuum annealing. After cooling, screen print a layer of green photosensitive ink on the surface of the substrate, keep the pad exposed, and pre-bake at 70°C for 40 minutes before exposure and curing. Figure 4 As shown; then chemically plate Ni / Au to obtain a Ni layer with a thickness of 3μm and an Au layer with a thickness of 0.1μm, and then wash and dry as shown Figure 5 As shown, laser drilling and cutting are performed to obtain a ceramic substrate resistor heating sheet.

[0039] Wherein, in step 1, the alkali washing adopts liquid alkali with a concentration of 5% and a temperature of 50°C; the acid washing adopts dilute sulfuric acid washing with a concentration of 1.8% and a temperature of 30°C, and after washing, it is baked in an oven at a high temperature of 100°C for 60 minutes;

[0040] The vacuum coating pressure is 3.0×10 -1 Pa, vacuum coating temperature is 300℃;

[0041] When electroplating the bottom Cu layer, the composition of the copper plating solution is: 150g / L copper sulfate pentahydrate, 70g / L sulfuric acid, 70ppm chloride ion, 10mL / L wetting agent, 0.6mL / L brightener, 25mL / L leveler;

[0042] The copper plating solution is also used for thickening the electroplated Cu layer in step 2, with a current of 1.5A per substrate and electroplating for 2.5h;

[0043] During sandblasting, the blasting pressure is 1.0kg up, 1.0kg down, and the line speed is 0.5m / min;

[0044] The composition of the nickel plating solution is: Ni muden NPR-4-A 45mL / L, Ni muden NPR-4-M 150mL / L, and the rest is water; the water bath is heated to 80°C for chemical Ni plating;

[0045] The temperature in the vacuum annealing furnace is 600°C, the vacuum degree is 1.0 Pa, and the annealing is performed for 1 hour.

[0046] Example 2: Referring to Example 1, the green photosensitive ink is replaced with glass glaze, and the specific steps are as follows:

[0047] Step 1: After cleaning the surface of the ceramic substrate by alkali washing → water washing → acid washing → ultrasonic water washing → baking, the cleaned ceramic substrate is vacuum coated. First, a Ti layer is sputtered as a transition layer with a thickness of 150nm; then a Cu layer is sputtered as a seed layer with a thickness of 1200nm to obtain a Ti / Cu seed layer, and then the bottom Cu layer is electroplated in a copper plating solution by direct current electroplating. The Cu sputtering layer is thickened to a thickness of 1μm, and a pattern transfer is performed. The film is transferred to the substrate by film bonding → exposure, and a photolithography pattern is developed;

[0048] Step 2: After the substrate developed in step 1 is cleaned by degreasing → washing → micro-etching → washing → acid washing → washing, it is placed in a copper plating solution to electroplate a Cu layer to a thickness of 10 μm, and then stripping → flash etching is performed to remove the Ti / Cu layer outside the primary photolithography pattern, and after washing and drying, secondary filming → exposure is performed. After the secondary photolithography pattern is developed on the surface of the substrate, the copper layer on the pattern except the pad is exposed; the substrate after the secondary development is etched and stripped to remove the copper layer on the secondary photolithography pattern except the pad area; the substrate after etching and stripping is sandblasted by a horizontal line wet spray method, and then washed and dried;

[0049] Step 3: Place the substrate after drying in step 2 in a 5% dilute hydrochloric acid solution for cleaning for 2 minutes, wash with pure water, and then soak it in a palladium activation solution for 10 minutes for activation, take it out and place it in a nickel plating solution for chemical plating to obtain a Ni-plated layer, place it in a vacuum annealing furnace for vacuum annealing, and after cooling, screen print a layer of glass glaze on the surface of the substrate to keep the pad exposed, pre-bake at 70°C for 40 minutes, expose it, and bake it at 400°C for curing; then chemically plate Ni / Au to obtain a Ni layer with a thickness of 3μm and an Au layer with a thickness of 0.1μm, wash it with water and dry it, and then perform laser drilling and cutting to obtain a ceramic substrate resistor heating sheet.

[0050] Wherein, in step 1, the alkali washing adopts liquid alkali with a concentration of 5% and a temperature of 50°C; the acid washing adopts dilute sulfuric acid washing with a concentration of 1.8% and a temperature of 30°C, and after washing, it is baked in an oven at a high temperature of 100°C for 60 minutes;

[0051] The vacuum coating pressure is 3.0×10 -1 Pa, vacuum coating temperature is 300℃;

[0052] When electroplating the bottom Cu layer, the composition of the copper plating solution is: 150g / L copper sulfate pentahydrate, 70g / L sulfuric acid, 70ppm chloride ion, 10mL / L wetting agent, 0.6mL / L brightener, 25mL / L leveler;

[0053] The copper plating solution is also used for thickening the electroplated Cu layer in step 2, with a current of 1.5A per substrate and electroplating for 2.5h;

[0054] During sandblasting, the blasting pressure is 1.0kg up, 1.0kg down, and the line speed is 0.5m / min;

[0055] The composition of the nickel plating solution is: Ni muden NPR-4-A 45mL / L, Ni muden NPR-4-M 150mL / L, and the rest is water; the water bath is heated to 80°C for chemical Ni plating;

[0056] The temperature in the vacuum annealing furnace is 600°C, the vacuum degree is 1.0 Pa, and the annealing is performed for 1 hour.

[0057] Example 3: Referring to Example 1, low-temperature plasma treatment and chemical micro-etching before palladium activation are added. The specific steps are as follows:

[0058] Step 1: After cleaning the surface of the ceramic substrate, perform low-temperature plasma treatment. Place the ceramic substrate directly below the plasma nozzle, align it with the center of the specimen, and spray 20°C low-temperature plasma 95% nitrogen + 5% oxygen. After 100s of treatment, wash and dry it. Take the cleaned ceramic substrate for vacuum coating. First, sputter a Ti layer as a transition layer with a thickness of 150nm; then sputter a Cu layer as a seed layer with a thickness of 1200nm to obtain a Ti / Cu seed layer, and then place it in a copper plating solution and electroplate the bottom Cu layer using a DC electroplating method. The Cu sputtering layer is thickened to a thickness of 1μm. Perform a pattern transfer, transfer it to the substrate using film-sticking → exposure, and develop a photolithography pattern, such as Figure 1 As shown;

[0059] Step 2: After the substrate is developed in step 1, it is degreased → washed → micro-etched → washed → acid washed → washed, and then placed in a copper plating solution to electroplate the Cu layer to a thickness of 10 μm. The Ti / Cu layer other than the primary photolithography pattern is removed, washed and dried, and then a secondary film is applied → exposed. After the secondary photolithography pattern is developed on the surface of the substrate, the copper on the pattern other than the pad is exposed, such as Figure 2 As shown; the substrate after the secondary development is etched and the film is stripped to remove the copper layer on the secondary photolithography pattern except the pad area, as shown Figure 3 As shown; the substrate after etching and film stripping is sandblasted by horizontal line wet spraying, and then washed and dried;

[0060] Step 3: Place the substrate after drying in step 2 in a 5% dilute hydrochloric acid solution for cleaning for 2 minutes, wash with pure water, perform chemical micro-etching, use sulfuric acid-sodium persulfate system micro-etching for 2 minutes, and then place it in a palladium activation solution for 10 minutes for activation, take it out and place it in a nickel plating solution for chemical plating to obtain a Ni-plated layer, place it in a vacuum annealing furnace for vacuum annealing, and after cooling, screen print a layer of green photosensitive ink on the surface of the substrate, keep the pad exposed, and pre-bake at 70°C for 40 minutes before exposure and curing. Figure 4 As shown; then chemically plate Ni / Au to obtain a Ni layer with a thickness of 3μm and an Au layer with a thickness of 0.1μm, and then wash and dry as shown Figure 5 As shown, laser drilling and cutting are performed to obtain a ceramic substrate resistor heating sheet.

[0061] Wherein, in step 1, the alkali washing adopts liquid alkali with a concentration of 5% and a temperature of 50°C; the acid washing adopts dilute sulfuric acid washing with a concentration of 1.8% and a temperature of 30°C, and after washing, it is baked in an oven at a high temperature of 100°C for 60 minutes;

[0062] The vacuum coating pressure is 3.0×10 -1 Pa, vacuum coating temperature is 300℃;

[0063] When electroplating the bottom Cu layer, the composition of the copper plating solution is: 150g / L copper sulfate pentahydrate, 70g / L sulfuric acid, 70ppm chloride ion, 10mL / L wetting agent, 0.6mL / L brightener, 25mL / L leveler;

[0064] The copper plating solution is also used for thickening the electroplated Cu layer in step 2, with a current of 1.5A per substrate and electroplating for 2.5h;

[0065] During sandblasting, the blasting pressure is 1.0kg up, 1.0kg down, and the line speed is 0.5m / min;

[0066] In step 3, the composition of the sulfuric acid-sodium persulfate system is: 50 g / L sodium persulfate, 30 mL / L concentrated sulfuric acid, and 120 g / L copper sulfate;

[0067] The composition of the nickel plating solution is: Ni muden NPR-4-A 45mL / L, Ni muden NPR-4-M 150mL / L, and the rest is water; the water bath is heated to 80°C for chemical Ni plating;

[0068] The temperature in the vacuum annealing furnace is 600°C, the vacuum degree is 1.0 Pa, and the annealing is performed for 1 hour.

[0069] Example 4: Referring to Example 1, a Pd barrier layer is added to the chemically plated Ni / Au layer, and the specific steps are as follows:

[0070] Step 1: After cleaning the surface of the ceramic substrate by alkali washing → water washing → acid washing → ultrasonic water washing → baking, low-temperature plasma treatment is performed. The ceramic substrate is placed directly below the plasma nozzle, aligned with the center of the test piece, 20 mm apart, and low-temperature plasma 95% nitrogen + 5% oxygen is sprayed. After 100 seconds of treatment, it is washed and dried. The cleaned ceramic substrate is vacuum coated. First, a Ti layer is sputtered as a transition layer with a thickness of 150nm; then a Cu layer is sputtered as a seed layer with a thickness of 1200nm to obtain a Ti / Cu seed layer, and then placed in a copper plating solution to electroplate the bottom Cu layer by direct current electroplating. The Cu sputtering layer is thickened to a thickness of 1μm. A pattern transfer is performed, and the film is transferred to the substrate by film bonding → exposure, and a photolithography pattern is developed;

[0071] Step 2: After the substrate developed in step 1 is cleaned by degreasing → washing → micro-etching → washing → acid washing → washing, it is placed in a copper plating solution to electroplate a Cu layer to a thickness of 10 μm, and then stripping → flash etching is performed to remove the Ti / Cu layer outside the primary photolithography pattern, and after washing and drying, secondary filming → exposure is performed. After the secondary photolithography pattern is developed on the surface of the substrate, the copper on the pattern except the pad is exposed; the substrate after the secondary development is etched and stripped to remove the copper layer on the secondary photolithography pattern except the pad area; the substrate after etching and stripping is sandblasted by a horizontal line wet spray method, and then washed and dried;

[0072] Step 3: Place the substrate after drying in step 2 in a 5% dilute hydrochloric acid solution for cleaning for 2 minutes, wash with pure water, and then soak it in a palladium activation solution for 10 minutes for activation, take it out and place it in a nickel plating solution for chemical plating to obtain a Ni-plated layer, place it in a vacuum annealing furnace for vacuum annealing, and after cooling, screen print a layer of green photosensitive ink on the surface of the substrate, keep the pad exposed, and expose and bake it after pre-baking at 70°C for 40 minutes; then chemically plate Ni / Pd / Au to obtain a Ni layer with a thickness of 3μm, a Pd layer with a thickness of 0.1μm, and an Au layer with a thickness of 0.1μm. After washing and drying, laser drilling and cutting are performed to obtain a ceramic substrate resistor heating sheet.

[0073] Wherein, in step 1, the alkali washing adopts liquid alkali with a concentration of 5% and a temperature of 50°C; the acid washing adopts dilute sulfuric acid washing with a concentration of 1.8% and a temperature of 30°C, and after washing, it is baked in an oven at a high temperature of 100°C for 60 minutes;

[0074] The vacuum coating pressure is 3.0×10 -1 Pa, vacuum coating temperature is 300℃;

[0075] When electroplating the bottom Cu layer, the composition of the copper plating solution is: 150g / L copper sulfate pentahydrate, 70g / L sulfuric acid, 70ppm chloride ion, 10mL / L wetting agent, 0.6mL / L brightener, 25mL / L leveler;

[0076] The copper plating solution is also used for thickening the electroplated Cu layer in step 2, with a current of 1.5A per substrate and electroplating for 2.5h;

[0077] During sandblasting, the blasting pressure is 1.0kg up, 1.0kg down, and the line speed is 0.5m / min;

[0078] In step 3, the composition of the sulfuric acid-sodium persulfate system is: 50 g / L sodium persulfate, 30 mL / L concentrated sulfuric acid, and 120 g / L copper sulfate;

[0079] The composition of the nickel plating solution is: Ni muden NPR-4-A 45mL / L, Ni muden NPR-4-M 150mL / L, and the rest is water; the water bath is heated to 80°C for chemical Ni plating;

[0080] The temperature in the vacuum annealing furnace is 600°C, the vacuum degree is 1.0 Pa, and the annealing is performed for 1 h;

[0081] The Pd barrier layer is electroless-plated, and the plating solution composition is: 2.3 g / L palladium chloride, 10 g / L sodium hypophosphite, 160 mL / L ammonium hydroxide, 32 g / L ammonium chloride, 55 mg / L bismuth nitrate, 30 mL / L isopropanolamine; the pH is adjusted to 9.5 and heated to 50°C in a water bath; after the electroless palladium plating, heat treatment is performed at 250°C for 1 hour before subsequent gold plating.

[0082] Example 5: Referring to Example 3, a Pd barrier layer is added to the chemically plated Ni / Au layer, and the specific steps are as follows:

[0083] Step 1: After cleaning the surface of the ceramic substrate by alkali washing → water washing → acid washing → ultrasonic water washing → baking, the cleaned ceramic substrate is vacuum coated. First, a Ti layer is sputtered as a transition layer with a thickness of 150nm; then a Cu layer is sputtered as a seed layer with a thickness of 1200nm to obtain a Ti / Cu seed layer, and then the bottom Cu layer is electroplated in a copper plating solution by direct current electroplating. The Cu sputtering layer is thickened to a thickness of 1μm, and a pattern transfer is performed. The film is transferred to the substrate by film bonding → exposure, and a photolithography pattern is developed;

[0084] Step 2: After the substrate developed in step 1 is cleaned by degreasing → washing → micro-etching → washing → acid washing → washing, it is placed in a copper plating solution to electroplate a Cu layer to a thickness of 10 μm, and then stripping → flash etching is performed to remove the Ti / Cu layer outside the primary photolithography pattern, and after washing and drying, secondary filming → exposure is performed. After the secondary photolithography pattern is developed on the surface of the substrate, the copper on the pattern except the pad is exposed; the substrate after the secondary development is etched and stripped to remove the copper layer on the secondary photolithography pattern except the pad area; the substrate after etching and stripping is sandblasted by a horizontal line wet spray method, and then washed and dried;

[0085] Step 3: Place the substrate after drying in step 2 in a 5% dilute hydrochloric acid solution for cleaning for 2 minutes, wash with pure water, perform chemical micro-etching, use sulfuric acid-sodium persulfate system for micro-etching for 2 minutes, and then place it in a palladium activation solution for immersion for 10 minutes for activation, take it out and place it in a nickel plating solution for chemical plating to obtain a Ni-plated layer, place it in a vacuum annealing furnace for vacuum annealing, and after cooling, screen print a layer of green photosensitive ink on the surface of the substrate, keep the pad exposed, and expose and bake it after pre-baking at 70°C for 40 minutes; then perform chemical Ni / Pd / Au plating to obtain a Ni layer with a thickness of 3μm, a Pd layer with a thickness of 0.1μm, and an Au layer with a thickness of 0.1μm. After washing and drying, laser drilling and cutting are performed to obtain a ceramic substrate resistor heating sheet.

[0086] Wherein, in step 1, the alkali washing adopts liquid alkali with a concentration of 5% and a temperature of 50°C; the acid washing adopts dilute sulfuric acid washing with a concentration of 1.8% and a temperature of 30°C, and after washing, it is baked in an oven at a high temperature of 100°C for 60 minutes;

[0087] The vacuum coating pressure is 3.0×10 -1 Pa, vacuum coating temperature is 300℃;

[0088] When electroplating the bottom Cu layer, the composition of the copper plating solution is: 150g / L copper sulfate pentahydrate, 70g / L sulfuric acid, 70ppm chloride ion, 10mL / L wetting agent, 0.6mL / L brightener, 25mL / L leveler;

[0089] The copper plating solution is also used for thickening the electroplated Cu layer in step 2, with a current of 1.5A per substrate and electroplating for 2.5h;

[0090] During sandblasting, the blasting pressure is 1.0kg up, 1.0kg down, and the line speed is 0.5m / min;

[0091] In step 3, the composition of the sulfuric acid-sodium persulfate system is: 50 g / L sodium persulfate, 30 mL / L concentrated sulfuric acid, and 120 g / L copper sulfate;

[0092] The composition of the nickel plating solution is: Ni muden NPR-4-A 45mL / L, Ni muden NPR-4-M 150mL / L, and the rest is water; the water bath is heated to 80°C for chemical Ni plating;

[0093] The temperature in the vacuum annealing furnace is 600°C, the vacuum degree is 1.0 Pa, and the annealing is performed for 1 h;

[0094] The Pd barrier layer is electroless-plated, and the plating solution composition is: 2.3 g / L palladium chloride, 10 g / L sodium hypophosphite, 160 mL / L ammonium hydroxide, 32 g / L ammonium chloride, 55 mg / L bismuth nitrate, 30 mL / L isopropanolamine; the pH is adjusted to 9.5 and heated to 50°C in a water bath; after the electroless palladium plating, heat treatment is performed at 250°C for 1 hour before subsequent gold plating.

[0095] Detection experiment

[0096] Experiment 1: Take the copper-nickel-gold pads prepared in Examples 1-5 and conduct a vertical tensile test. Weld an aluminum wire with a diameter of 0.5 mm on the sample pad and conduct a tensile test using a tensile testing machine.

[0097] Table 1

[0098] pull Example 1 Example 2 Example 3 Example 4 Example 5 5.29kg No peeling No peeling No peeling No peeling No peeling 5.30kg No peeling No peeling No peeling No peeling No peeling

[0099] In Example 1, when the pulling force was 5.29kg and 5.30kg respectively, the aluminum wire broke, but no cracks were found in the pad, indicating that the copper-nickel-gold pad had good bonding strength. Figure 6 shown.

[0100] Experiment 2: Use an X-Ray film thickness measuring instrument (model: XDLM237) to measure the thickness of the Ni chemical plating layer of the small pieces of products cut from Examples 1-5, and record the average value data of each group of products in Table 2;

[0101] Experiment 3: Use a multimeter to measure the resistance of the small pieces of products cut from Examples 1-5, and record the average value of each group of products in Table 2;

[0102] Table 2

[0103] project Example 1 Example 2 Example 3 Example 4 Example 5 Thickness μm 2.40 2.26 2.31 2.24 2.36 Resistance Ω 15.4 16.7 16.4 l7.1 15.9

[0104] Conclusion: The thickness of the Ni layer is 2.0μm-2.4μm, showing that the chemically plated Ni layer has good uniformity; the resistance is in the range of 15±3Ω.

[0105] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a ceramic substrate resistance heating sheet, characterized in that: The following steps are involved: Step 1: After cleaning the surface of the ceramic substrate, vacuum coating is performed to obtain a titanium copper layer, and after a base copper layer is plated on the surface of the titanium copper layer, a pattern transfer is performed to develop a photolithography pattern on the surface of the ceramic substrate; Step 2: After the thick copper layer is plated on the surface of the ceramic substrate after development in step 1, the titanium-copper layer other than the primary photolithography pattern is removed by stripping and flash etching, and a secondary pattern transfer is performed after washing and drying, and a secondary photolithography pattern is developed on the surface of the ceramic substrate, and then etching and stripping are performed to remove the copper layer other than the pad area on the secondary photolithography pattern, exposing the titanium layer sputtered at the bottom, and then sandblasting is performed, and washing and drying is performed; Step 3: After the ceramic substrate dried in step 2 is cleaned with a dilute hydrochloric acid solution, a nickel layer is plated on the surface, vacuum annealing is performed, and after cooling, an insulating protective layer is silk-screened on the surface of the ceramic substrate, and then a nickel layer and a gold layer are plated in sequence. After washing and drying, laser drilling and cutting are performed to obtain a ceramic substrate resistor heating sheet.

2. The method for preparing a ceramic substrate resistance heating sheet according to claim 1, characterized in that: In step 1, vacuum coating is performed by magnetron sputtering, first sputtering the titanium layer and then the copper layer; the thickness of the titanium layer is 0.1 μm-0.3 μm, and the thickness of the copper layer is 0.5 μm-3 μm; the vacuum coating pressure is 2.0×10 -1 Pa-3.0×10 -1 Pa, vacuum coating temperature is 200℃-300℃.

3. The method for preparing a ceramic substrate resistance heating sheet according to claim 1, characterized in that: In step 1, the bottom copper layer is obtained by electroplating, and the composition of the plating solution is: 150g / L-200g / L of copper sulfate pentahydrate, 50g / L-70g / L of sulfuric acid, 40ppm-70ppm of chloride ions, 10mL / L-15mL / L of wetting agent, 0.6mL / L-1.4mL / L of brightener, and 25mL / L-35mL / L of leveling agent; the thickness of the bottom copper layer is 1.5μm-4.0μm.

4. The method for preparing a ceramic substrate resistance heating sheet according to claim 1, characterized in that: In step 2, the thick copper layer is obtained by electroplating, and the composition of the plating solution is the same as the electroplating solution of the bottom copper layer; the thickness of the thick copper layer is 8μm-18μm.

5. The method for preparing a ceramic substrate resistance heating sheet according to claim 1, characterized in that: In step 3, the nickel layer is obtained by electroplating or chemical plating, and has a thickness of 2.0 μm-2.6 μm; Before chemical plating, palladium is activated for 10 minutes, and then the nickel layer is plated after washing.

6. The method for preparing a ceramic substrate resistance heating sheet according to claim 1, characterized in that: In step 3, the thickness of the insulating protective layer is 8 μm-12 μm; the thickness of the nickel layer after silk-screening the insulating protective layer is 3 μm-5 μm, and the thickness of the gold layer is 0.1 μm-0.2 μm.

7. The method for preparing a ceramic substrate resistance heating sheet according to claim 1, characterized in that: Step 1: Before vacuum coating, the surface of the ceramic substrate is treated with low-temperature plasma, using a combination of 90-95wt% nitrogen and 5-10wt% oxygen as a plasma gas source, placing the ceramic substrate directly below the plasma nozzle, aligning it with the center of the specimen, with a distance of 5mm-25mm, spraying low-temperature plasma, and treating for 60-100s; wherein the plasma gas source temperature is 20-30°C.

8. The method for preparing a ceramic substrate resistance heating sheet according to claim 5, characterized in that: Before palladium activation, chemical micro-etching is performed, and a sulfuric acid-sodium persulfate system is used for micro-etching for 1-2 minutes; the composition of the sulfuric acid-sodium persulfate system is: sodium persulfate 50-60g / L, concentrated sulfuric acid 30mL / L, and copper sulfate 100-120g / L.

9. The method for preparing a ceramic substrate resistance heating sheet according to claim 1, characterized in that: In step 3, a palladium barrier layer is inserted between the nickel layer and the gold layer. The palladium barrier layer adopts a chemical plating process. The components of the plating solution are: palladium chloride 2-2.5g / L, sodium hypophosphite 10-12g / L, ammonium hydroxide 150-165mL / L, ammonium chloride 30-40g / L, bismuth nitrate 50-60mg / L, isopropanolamine 20-35mL / L; the pH is adjusted to 9.5-10, and the water bath is heated to 45-55°C; the thickness of the palladium barrier layer is 0.1μm-0.2μm; after the chemical palladium plating is completed, heat treatment is performed, and it is kept warm at 200-250°C for 1-2h, and then a subsequent gold plating layer is performed.

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