DE102007018262B4 - Method for closing ceramic capillaries on containers by means of laser - Google Patents

Abstract

Method for closing ceramic capillaries on containers by means of laser radiation, in which openings in containers are provided with one or more capillaries of ceramic material, these capillaries are provided inside with a volume enlarged space as a reservoir, subsequently a solder material for joining ceramics in the non-molten Condition is introduced into the reservoir, then the solder material is heated with a laser beam above the melting temperature and then cooled.

Description

The This invention relates to the fields of ceramics and laser technology and relates to a method of sealing ceramic capillaries on containers by means of laser, with the example heatpipes or other vessels made of ceramic or other materials with ceramic capillaries as openings be permanently closed.

Known are welding and soldering methods to Joining of Ceramics and in particular high performance ceramics (Hesse, A. et al., Ceramic Journal 3 (1994), pp. 147-150; Boretius, M. u. a., VDI reports, Volume 670, pp. 699-713, VDI-Verlag, Dusseldorf, 1988).

at this cohesive Joining method records the soldering across from the (diffusion) welding by a lower technological Effort as well as higher Reproducibility and reliability out.

At the active soldering Metallic solders produce relatively strong bonds. At the Use of this process on PVD metallised or laser treated Ceramics are especially cheap Wetting and flow properties of the solder (Wielage, B. et al., VDI Reports, Vol. 883, p. 117-136, VDI-Verlag, Dusseldorf, 1991). In this process, the ceramic is metallized and then in an oven with the solder brought into contact. This is the temperature increased to above the melting temperature of the solder. In the molten state the solders wet the metallised ceramic surface and form after cooling a solid bond.

Next but the use of metallic solders can also glass / ceramic solders for joining of ceramics (Boretius, M. et al., VDI-Verlag, Düsseldorf, 1995). In this method, the workpiece is placed in an oven and heated under pressure to above the melting temperature of the solder. The pressure is required to maintain a sufficient degree of compaction in the joint seam and to achieve a gas tightness. The process in the oven takes place under a protective gas atmosphere or in a vacuum instead. The solder forms after reaching its melting temperature a liquid Phase, which the to be joined surfaces wetted and with decreasing temperature to a solid ceramic composite leads. These Solders are mainly used when high requirements in Reference to corrosion and high temperature strength, but lower Requirements regarding transmission mechanical forces are placed.

Glass / ceramic solders wet ceramics well and can therefore unlike metallic solders without metallization of the ceramic surface be used. Another advantage of glass ceramic solders consists in that they are gas-tight. The crystalline glass / ceramic solders go into a ceramic, polycrystalline after solidifying Condition over. The soldering temperature usually corresponds to the service temperature. The special advantage of glass / ceramic solders is that they adapt the coefficient of expansion and the temperature stability the joint enable.

adversely In this method is that the workpieces in terms of their size to the are adapted to each oven that located inside a ceramic container Substances closed by joining should be, due to the relatively long and high temperature load are also heavily loaded. Low-melting substances are not be closed with these technologies in such ceramic containers.

Farther Known are methods for joining from ceramics with solders to non-high temperature resistant ceramic composites by laser, with only small components are joined and also a Vacuum or a protective gas is required.

Also known is the DE 103 27 708 A1 a method for producing gas-tight and high-temperature resistant compounds of non-oxide ceramic moldings by means of laser. According to this method, the surfaces to be joined of molded parts having a solder of 80-30 wt% yttria and / or 55-15 wt% zirconia, 5-70 wt% alumina, 0-50 wt% Silicon dioxide and 0-10% by weight of silicon, and then the temperature at the joint is raised above the melting temperature of the solder by means of a laser without the presence of a protective gas atmosphere or a vacuum. In this case, a sufficient wettability of the surfaces to be joined by the molten solder to realize the connection is realized by means of ceramic and / or solder originating and / or forming and / or additionally applied silicon dioxide on the surfaces to be joined.

Furthermore, after the DE 197 17 235 B4 a method for producing a heat pipe for transporting heat from an evaporation area to a condensation area is known. Thereafter, the housing has a capillary structure arranged therein, which is thermally coupled in the evaporation and in the condensation region with the corresponding housing walls. Furthermore, the housing has a steam channel leading from the evaporation area to the condensation area, as well as a heat transport medium. The open-pore capillary structure is made of powder particles, the are superficially melted by high-frequency plasma spraying and form a melting layer connecting the powder particles in the solidified state.

From the EP 0 607 149 B1 a method for the production of metal halide discharge lamps with ceramic discharge vessel is known in which the discharge volume is filled by a filling hole and evacuated and subsequently the filling hole is sealed gas-tight. The filling holes are attached to the different points of the discharge volume. The respective openings are closed with a fusible filler which is introduced into the opening in the form of a plug and is melted there.

all solutions is common that openings in non-oxide ceramic containers only expensive to close and there are no universal solutions.

Of the Invention is based on the object openings in non-oxidic and oxidic ceramic containers to close permanently and safely in a simple way.

The The object is achieved by the invention specified in the claims. Trainings are Subject of the dependent claims.

at the method according to the invention to close of ceramic capillaries on containers by means of laser openings in containers provided with one or more capillaries of ceramic material, these capillaries in the interior with a volume enlarged space provided as a reservoir, below a solder material for the joining of Ceramics are introduced into the reservoir in the unmelted state, then the solder material is heated above the melting temperature with a laser and subsequently cooled.

advantageously, become containers made of ceramic over closed ceramic capillaries.

Also Advantageously, containers and ceramic capillaries of the same ceramic material used.

Farther Advantageously, containers and ceramic capillaries of non-oxide ceramic used.

Also Advantageously, the ceramic used is silicon carbide ceramic.

From It is also an advantage if containers and ceramic capillaries of oxidic ceramic are used.

Advantageous It continues, if the volume-enlarged space in the middle range the capillary opening is introduced in the ceramic capillary.

It is also advantageous when the container is first evacuated and subsequently by heating of the solder in the reservoir is closed.

Farther it is advantageous if the container first with an overpressure is provided and subsequently closed by heating the solder in the reservoir becomes.

Also it is advantageous if, as solder material consisting of 80-30% by mass Yttrium oxide and / or 55-15 Ma .-% zirconium oxide, 5-70 Ma .-% alumina, 0-50 % By weight of silica and 0-10 % By weight of silicon is used.

Also It is advantageous if the solder material in the form of a powder bed or a paste or as a solid at least introduced into the reservoir.

From It is also an advantage if a diode laser is used as the laser becomes.

Also It is advantageous if a laser is an Nd: YAG laser or a CO2 laser is used.

And It is also advantageous if the area of the reservoir is at temperatures from 900 ° C up to 2000 ° C, even more advantageously heated to temperatures of 1500 ° C to 1900 ° C. becomes.

By the inventive method will it be possible in a simple and safe way, capillary openings in containers permanently closed. The inventive method is especially for Non-oxidic ceramic materials can be used for the currently No method is known to safely and permanently secure the capillary openings close. A particular advantage of the invention is that the container also can be evacuated and the closure is also gas-tight and high-temperature resistant. Likewise the containers filled with gases and gas mixtures be, then also gas-tight by the closure of the invention can be stored.

The mode of action of the solution according to the invention is that the unmolten solder is melted in the reservoir inside and possibly in the middle part of the capillary by means of laser and then pulled due to capillary action in the capillary at least on one side of the reservoir and remains there and after the Laserbe radiation solidifies. Advantageously, the molten solder is drawn into the capillary on both sides of the reservoir and remains there.

These Mode of action requires that the length of the laser irradiation and the temperature reached is thereby limited in each case upward, that the molten solder does not become so low-viscosity that the capillary forces do not more sufficient to hold the molten solder in the capillary.

The Lot can be powdered Cloth, as a paste or as a solid be introduced. After drying, the solder remains at least in the reservoir. In the case of a powder bed or a paste can but also, for example, a part of the capillary with the powder bed or be filled with the paste.

By Such procedures will be more targeted and quantified Order of the solder on the joint secured. At the same time, the process is well mechanized. and automatable.

In the subsequent process step, at least the region of the reservoir is heated with the laser radiation of a CO ₂ laser, diode laser or Nd: YAG laser. For this purpose, the laser beam is directed onto the surfaces of the capillary and the heating of the region of the reservoir is advantageously achieved by a relative movement between laser beam and capillary by, for example, deflecting the laser radiation with the aid of optics with respect to solid workpieces or by a rotation of the capillary under the laser beam. At the same time, the surface temperature is measured by a radiation pyrometer or a thermal camera. A temperature-dependent laser power control achieves a defined temperature in the region of the melting temperature of the substances used for shutter formation, as well as defined heating and cooling cycles.

The surfaces The capillary is both complete and in sections (close the reservoir) or heated successively.

Becomes only the section heated in the immediate vicinity of the reservoir, others can Portions of the capillary cooled become. This makes it possible for the Capillaries, and areas of the capillary, simultaneously with low-melting Materials in contact are to cool, so that these low-melting materials do not melt.

After reaching a temperature in the range of the melting temperature of the shuttering substances by a diode laser, a Nd: YAG laser or a CO ₂ laser shuttering occurs according to the above-described mode of action.

in the Furthermore, the invention will be explained in more detail using an exemplary embodiment.

example 1

there shows

1 a schematic representation of a container with a sealed ceramic capillary tube, and

2 a schematic representation of the reservoir space in the capillary tube during and after the laser irradiation.

A pressure-tight vessel of SiC with the dimensions of 40 mm diameter, a length of 200 mm and a wall thickness of 5 mm is open on one side. In the opening a capillary tube made of SiC with the dimensions of 6 mm outer diameter, 0.6 mm inner diameter and a length of 20 mm gas-tight fit. The capillary tube is connected to a vacuum pump which evacuates the vessel at a rate of 1 m ³ / h for a period of 5 minutes. After reaching the desired vacuum in the vessel, the capillary tube is sealed gas-tight. For this purpose, an enlargement of the otherwise tubular interior of the capillary tube is present in the interior of the capillary tube at a distance of 10 mm from the opening of the capillary tube, which projects into the vessel. This enlarged space serves as a reservoir and has the dimensions of 3 mm diameter and a length of 5 mm. It is filled with 0.5 g of a paste of a solder of composition 45.7 mass% SiO ₂ , 22.0 mass% Al ₂ O ₃ and 32.3 mass% Y ₂ O ₃ . After reaching the desired vacuum in the vessel, a laser beam of a diode laser with a power of 1,000 W in a time of 30 s is directed to the location of the capillary tube with the reservoir. During the irradiation, the vessel with the capillary tube rotates under the laser beam, so that the entire paste-like solder is heated. The heating takes place up to a temperature of 1,300 ° C, wherein the solder is molten at this temperature. Due to the capillary effect, the melt of the solder is drawn into the tubular space of the capillary tube.

After completion of the laser action, the capillary tube and the solder therein cool down and the solder solidifies in the tubular space of the capillary tube. Thus, a permanent and gas-tight closure of the capillary is achieved at least on one side of the reservoir. In most cases, however, the solder spreads to both tubular spaces adjacent to the reservoir, so that the gas-tight seal has been done practically twice.

Claims (15)

Method for closing ceramic capillaries on containers by means of laser radiation, in which openings in containers provided with one or more capillaries of ceramic material These capillaries are inside with a volume enlarged space be provided as a reservoir, hereinafter a solder material for the joining of Ceramics in the unmelted state introduced into the reservoir is, then the solder material with a laser beam over the Melting temperature heated and subsequently cooled becomes. The method of claim 1, wherein the container Ceramic over ceramic capillaries are closed. The method of claim 2, wherein the container and ceramic capillaries of the same ceramic material used become. The method of claim 3, wherein the container and ceramic capillaries of non-oxide ceramic are used. A method according to claim 4, wherein the ceramic is silicon carbide ceramic is used. The method of claim 3, wherein the container and ceramic capillaries of oxidic ceramic are used. The method of claim 1, wherein the volume enlarged space in the middle area of the capillary opening in the ceramic capillary is introduced. The method of claim 1, wherein the container is first evacuated and subsequently by heating the solder in the reservoir is closed. The method of claim 1, wherein the container is first with an overpressure is provided and subsequently closed by heating the solder in the reservoir becomes. The method of claim 1, wherein as the solder material consisting of 80-30 Ma% yttria and / or 55-15 Ma .-% zirconium oxide, 5-70 Ma .-% alumina, 0-50 % By mass of silica and 0-10% by mass Silicon is used. The method of claim 1, wherein the solder material in the form of a powder bed or a paste or as a solid at least introduced into the reservoir. The method of claim 1, wherein as a laser Diode laser is used. The method of claim 1, wherein as a laser Nd: YAG laser or a CO2 laser is used. Method according to claim 1, wherein the area of the Reservoirs to temperatures of 900 ° C to 2000 ° C is heated. The method of claim 14, wherein the region of the reservoir is heated to temperatures of 1500 ° C to 1900 ° C.