Brazing method suitable for medical implantable ceramic tube shell

Abstract

The invention provides a brazing method suitable for a medical implantable ceramic tube shell. The brazing method comprises the steps that a zirconia ceramic workpiece is cleaned; performing vacuum magnetron sputtering on the surface of the cleaned zirconia ceramic workpiece, and sequentially depositing a bottom metal layer and a surface metal layer to form a metalized layer; performing vacuum heat treatment on the zirconia ceramic workpiece with the metalized layer so as to eliminate the internal stress of the metalized layer; acid pickling is conducted on the surface of the pure titanium metal piece to remove an oxidation film, and drying treatment is conducted; placing a gold solder between the metallization layer and the pure titanium metal piece, and assembling an assembly to be welded; according to the method, a to-be-welded assembly is placed in a vacuum brazing furnace to be brazed, preset heating, heat preservation and cooling procedures are executed, and high-strength, high-airtightness and excellent-biocompatibility connection between zirconia ceramic and pure titanium is achieved through an optimized surface metallization process, stress relief treatment and a strictly-controlled full-process vacuum brazing process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ceramic package, in particular to a brazing method suitable for medical implant-grade ceramic package. BACKGROUND

[0002] In the existing field of ceramic package, the mainstream process is usually made by brazing silver copper solder between multi-layer ceramic metallized base and metal parts, through printing high-temperature conductive paste such as W and Mo as conductor, and through paste preparation, tape casting, punching and cavity forming, metallization printing, laminating, isostatic pressing, hot cutting, glue removal sintering, nickel plating, brazing and gold plating processes, which is commonly used in aerospace and precision packaging.

[0003] In the existing field of ceramic package, the conventional process can ensure the sealing, although the reliability is good, but the toxic elements (such as nickel, chromium and tin) inevitably exist in the material, and now there is a high demand for airtight packaging of medical devices, and the material safety and body fluid corrosion resistance are required in medical implantation, which needs to solve the problems of biocompatibility, wettability and joint stability, and must meet the stringent standards of medical implants, and the conventional materials and processes cannot meet the requirements. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects of the prior art, and the present application provides a brazing method suitable for medical implant-grade ceramic package.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is: a brazing method suitable for medical implant-grade ceramic package, comprising: cleaning the zirconia ceramic workpiece; vacuum magnetron sputtering the surface of the cleaned zirconia ceramic workpiece to deposit a bottom metal layer and a surface metal layer in sequence to form a metallized layer; vacuum heat treatment of the zirconia ceramic workpiece with the metallized layer to eliminate the internal stress of the metallized layer; acid pickling the surface of the pure titanium metal piece to remove the oxide film and drying treatment; placing gold solder between the metallized layer and the pure titanium metal piece to assemble a to-be-welded assembly; placing the to-be-welded assembly in a vacuum brazing furnace for brazing, executing a preset temperature rising, holding and cooling program to realize the connection of the zirconia ceramic workpiece and the pure titanium metal piece.

[0006] Preferably, the cleaning of the zirconia ceramic workpiece specifically includes: first ultrasonic cleaning with pure water, and then soaking cleaning with medical alcohol.

[0007] Preferably, the bottom metal layer is a titanium layer with a thickness of 0.2-0.5 μm; and the surface metal layer is a platinum layer deposited on the titanium layer with a thickness of 0.1-0.3 μm.

[0008] Preferably, the temperature of the vacuum heat treatment is 300-400 ℃, and the holding time is 1 hour.

[0009] Preferably, the pure titanium metal piece is pickled with a hydrochloric acid solution, rinsed with pure water after pickling, and dried with nitrogen blowing; and the pickled pure titanium metal piece is brazed on the same day.

[0010] Preferably, the purity of the gold solder is not less than 99.99%.

[0011] Preferably, the vacuum degree of the vacuum brazing furnace is not less than 1×10 -6 Pa.

[0012] Preferably, the temperature rising, holding and cooling procedure specifically comprises: rises from room temperature to 900 ℃ at a temperature rising rate of 5-8 ℃ / min; continues to rise to 1080 ℃, and then holds for 10-15 min; after the holding ends, cools from 1080 ℃ to 400 ℃ at a cooling rate of 3-5 ℃ / min; and then naturally cools to below 150 ℃.

[0013] Compared with the prior art, the present application has the following beneficial effects: through the optimized surface metallization process, stress relief treatment and strictly controlled whole-process vacuum brazing process, high-strength, high-air-tightness and excellent biocompatibility connection between the zirconia ceramic and the pure titanium is realized. DETAILED DESCRIPTION

[0016] The present application provides a high-reliability and high-biocompatibility brazing method suitable for medical implant-grade ceramic tube shells and pure titanium metal pieces, which realizes high-strength, high-air-tightness and excellent biocompatibility connection between the zirconia ceramic and the pure titanium through the optimized surface metallization process, stress relief treatment and strictly controlled whole-process vacuum brazing process.

[0017] Embodiment 1 This embodiment specifically describes a typical brazing method suitable for zirconia ceramic tube shells and pure titanium electrode leads for heart pacemakers.

[0018] S100, cleaning of the zirconia ceramic workpiece The zirconia ceramic tube to be brazed is placed in an ultrasonic cleaning machine containing high-purity deionized water, and ultrasonic cleaning is performed for 10 minutes under the conditions of a frequency of 40 kHz and a power of 100 W to remove loose contaminants such as dust and grease on the surface.

[0019] After being taken out, the surface moisture is blown dry with high-purity nitrogen, and then the workpiece is immersed in analytical pure medical alcohol for 15 minutes to further dissolve and remove organic contaminants.

[0020] The surface is blown dry again with high-purity nitrogen, and immediately transferred to the sample chamber of a magnetron sputtering device for metallization treatment.

[0021] S200, Metallization of the zirconia ceramic surface The cleaned zirconia ceramic workpiece is placed in the vacuum chamber of a multi-target magnetron sputtering coating device, and vacuumized to a base vacuum degree better than 5×10 -4 Pa.

[0022] The titanium target power supply is turned on, and sputtering is performed in an argon atmosphere (working gas pressure 0.5 Pa) to deposit a dense titanium layer on the zirconia ceramic surface as a bottom metal layer. The thickness of the titanium layer is accurately controlled to be 0.35 μm by controlling the sputtering power and time. The role of this titanium layer is to enhance the chemical bonding with the zirconia ceramic and provide a good adhesion basis for the subsequent metal layer.

[0023] Without breaking the vacuum, the platinum target power supply is switched to continue sputtering in an argon atmosphere to deposit a platinum layer on the titanium layer as a surface metal layer. The thickness of the platinum layer is accurately controlled to be 0.2 μm. The platinum layer has good chemical inertness, high temperature stability, and can effectively prevent the excessive diffusion of titanium into the filler, while providing an excellent wetting surface for the subsequent gold-based filler.

[0024] S300, Vacuum heat treatment of the metallized layer The zirconia ceramic workpiece that has completed magnetron sputtering metallization is transferred to a vacuum heat treatment furnace.

[0025] After vacuumizing to 1×10 -3 Pa, the temperature is raised to 350℃ at a rate of 10℃ / min.

[0026] The temperature is kept at 350℃ for 1 hour. This heat treatment process helps to release the residual stress accumulated in the metallized layer during the magnetron sputtering process, promotes the interdiffusion of atoms at the interface between the titanium layer and the zirconia ceramic, thereby enhancing the adhesion strength of the metallized layer and its long-term stability.

[0027] After the holding period ends, the furnace is cooled to below 100℃, and the workpiece is taken out for use.

[0028] S400, Surface treatment of pure titanium metal parts The pure titanium metal piece is immersed in a 10 vol.% hydrochloric acid aqueous solution for pickling at room temperature for 3 minutes to completely remove the natural oxide film on the surface thereof.

[0029] After pickling, the pure titanium metal piece is immediately taken out and ultrasonically rinsed with a large amount of high-purity deionized water for 2 minutes to ensure complete removal of residual acid solution, and the rinsed pure titanium metal piece is surface-dried with dry and clean high-purity nitrogen.

[0030] The surface of the pure titanium metal piece after pickling treatment is highly active, and to avoid the formation of a new oxide film in the air for a long time, affecting the quality of the brazed joint, it must be used for subsequent assembly and brazing within the same day (usually recommended within 4 hours).

[0031] S500, solder preparation and assembly of components A gold foil with a purity of ≥99.99% or a pre-formed gold-based solder sheet, such as pure Au or Au-Ge, Au-In, etc. low-vapor-pressure alloys, is selected, and in this embodiment, pure Au solder is preferred, and the thickness can be selected according to the joint gap design, usually between 20-50 μm.

[0032] The gold solder sheet is cut into a shape matching the area to be welded.

[0033] The zirconia ceramic workpiece with a metallized layer, the gold solder, and the pure titanium metal piece are stacked in the order of "zirconia ceramic workpiece with a metallized layer-gold solder-pure titanium metal piece", and the assembly is assembled into a to-be-welded assembly, and a tool clamp can be used for slight pre-tightening to ensure good contact and accurate position of each part.

[0034] S600, vacuum brazing The assembled to-be-welded assembly is smoothly placed in the uniform temperature zone of the vacuum brazing furnace.

[0035] The furnace door is closed, the vacuum system is started, and the vacuum degree in the inner cavity of the brazing furnace is pumped to a high vacuum environment of not less than 1×10 -6 Pa to maximize the avoidance of oxidation of the metal at high temperature.

[0036] The preset brazing temperature rising, holding, and cooling procedures are performed: First stage temperature rising: the furnace temperature is uniformly raised from room temperature to 900℃ at a temperature rising rate of 6℃ / min, and this slow temperature rising is beneficial to uniform temperature of each part of the assembly and allows slow escape of organic matter or adsorbed gas in the solder and the metallized layer.

[0037] Second stage heating and holding: continue to heat up to the brazing temperature 1080℃ (the melting point of pure gold solder is about 1064℃, slightly higher than this temperature to ensure full melting flow). After reaching 1080℃, hold for 12 minutes. At this temperature, the gold solder is completely melted and fully wets, spreads, capillary fills the gap between the platinum metallization layer and the pure titanium surface, and forms a strong metallurgical bond through interfacial reaction.

[0038] First stage cooling: after the holding time is over, slowly cool the temperature from 1080℃ to 400℃ at a controlled cooling rate of 4℃ / min. Slow cooling helps to reduce thermal stress caused by the difference in thermal expansion coefficient between ceramic and metal, prevent joint cracking, and promote brazing seam structure homogenization.

[0039] Second stage cooling: when the temperature drops to 400℃, turn off the heating power and let the workpiece in the furnace cool naturally to below 150℃.

[0040] When the furnace temperature drops to below 80℃, high-purity nitrogen can be filled into the furnace to normal pressure, the furnace door is opened, and the completed brazed assembly is removed.

[0041] The zirconia ceramic-pure titanium brazed joint prepared by the method of the embodiment is detected and shows that: Joint appearance: the brazing seam is uniform, continuous and smooth, without visible cracks, un-welded and other macroscopic defects.

[0042] Air tightness: tested by a helium mass spectrometer leak detector, the leakage rate is less than 1×10^-9 Pa·m³ / s, meeting the long-term implantation air tightness requirements of high-end medical implant devices (such as neural stimulators, cardiac pacemakers, etc.).

[0043] Mechanical strength: through tensile or shear testing, the joint strength is usually higher than that of the zirconia ceramic body, and the fracture usually occurs in the ceramic matrix rather than the brazing seam interface.

[0044] Biocompatibility: the materials used (zirconia, pure titanium, gold, platinum, titanium) all have good biocompatibility, and the entire process is carried out in a highly clean environment without the introduction of harmful substances, meeting the requirements of medical implant standards (such as ISO10993 series).

[0045] It is conceivable that the cleaning step can adjust the ultrasonic power, time and solvent type; in the metallization layer, the thickness of the titanium bottom layer can be selected between 0.2-0.5μm (such as 0.25μm or 0.45μm), and the thickness of the platinum surface layer can be selected between 0.1-0.3μm (such as 0.15μm or 0.25μm).

[0046] The temperature of vacuum heat treatment can be selected in the range of 300-400℃ (such as 320℃ or 380℃), and the holding time can be adjusted accordingly.

[0047] The pickling of pure titanium can use other concentrations of hydrochloric acid or mixed acid (such as dilute HF+HNO3 solution), but it is necessary to ensure that the oxide film is effectively removed and excessive corrosion is not generated.

[0048] It is necessary to ensure that the gold solder has high purity (≥99.99%) and high vacuum degree (≥1×10^-6 Pa) during brazing, which is the key to ensure the purity and performance of the joint.

[0049] The heating rate in the brazing procedure can be adjusted between 5-8℃ / min, the holding time can be adjusted between 10-15min, and the cooling rate can be adjusted between 3-5℃ / min, so as to optimize the stress state and interface reaction of components of different sizes and structures.

[0050] In summary, the present application successfully solves the technical problem of reliable connection of medical implant-grade zirconia ceramic tube shell and pure titanium metal parts by a set of systematic, precise and controllable process flow, and has extremely high industrial application value.

[0051] The technical features of the above embodiments can be combined arbitrarily, and in order to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0052] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A brazing method for medical implant-grade ceramic tubing shells, characterized in that, include: Cleaning of zirconia ceramic workpieces; Vacuum magnetron sputtering is performed on the cleaned zirconia ceramic workpiece surface to sequentially deposit a bottom metal layer and a top metal layer, forming a metallization layer. Vacuum heat treatment is performed on zirconia ceramic workpieces with metallized layers to eliminate the internal stress of the metallized layers. The surface of pure titanium metal parts is pickled to remove the oxide film and then dried. Gold solder is placed between the metallization layer and the pure titanium metal part to assemble the component to be soldered. The components to be brazed are placed in a vacuum brazing furnace for brazing, and a preset heating, holding and cooling program is executed to achieve the connection between the zirconia ceramic workpiece and the pure titanium metal part.

2. The brazing method for medical implant-grade ceramic tubing shells according to claim 1, characterized in that, The cleaning process for zirconia ceramic workpieces includes: first, ultrasonic cleaning with pure water, followed by soaking in medical alcohol.

3. The brazing method for medical implant-grade ceramic tubing shells according to claim 2, characterized in that, The bottom metal layer is a titanium layer with a thickness of 0.2-0.5 μm; the top metal layer is a platinum layer deposited on the titanium layer with a thickness of 0.1-0.3 μm.

4. The brazing method for medical implant-grade ceramic tubing shells according to claim 3, characterized in that, The vacuum heat treatment temperature is 300-400℃, and the holding time is 1 hour.

5. The brazing method for medical implant-grade ceramic tubing shells according to claim 1, characterized in that, The pure titanium metal parts are pickled using hydrochloric acid solution, rinsed with pure water after pickling, and dried with nitrogen gas; and the pickled pure titanium metal parts are brazed on the same day.

6. The brazing method for medical implant-grade ceramic tubing shells according to claim 1, characterized in that, The purity of the gold solder is not less than 99.99%.

7. The brazing method for medical implant-grade ceramic tubing shells according to claim 1, characterized in that, The vacuum degree of the vacuum brazing furnace is not less than 1×10⁻⁶. -6 Pa.

8. The brazing method for medical implant-grade ceramic tubing shells according to claim 1, characterized in that, The heating, heat preservation, and cooling process specifically includes: The temperature was increased from room temperature to 900℃ at a rate of 5-8℃ / min. Continue heating to 1080℃ and hold for 10-15 minutes; After the heat preservation is completed, the temperature is cooled from 1080℃ to 400℃ at a cooling rate of 3-5℃ / min. Then let it cool naturally to below 150°C.