DE102005058121A1 - Producing a ceramic component forms suspension of ceramic powder in hardenable organic binder that is irradiated to harden and heated to destroy organics - Google Patents

Abstract

Producing a ceramic component comprises having a green material comprising at least 45 vol.% of ceramic powder in a suspension with hardenable organic binder, locally irradiating to harden the material into a geometric shape, removing this from the suspension and heating to below the sintering temperature but at a temperature high enough to destroy the organic material. The suspension is solvent-free, of viscosity less than 20,000 mPa.s and the ceramic is used with an electronic component for its electrically insulating characteristics.

Description

The The invention relates to a method for producing a ceramic Component in which a green body from a suspension containing at least 45% by volume of ceramic powder with an organic, hardenable Component is obtained as a binder by passing the suspension through local introduction of radiant energy to form the geometric Structure of greenware hardened and the green taken from the suspension and a heat treatment for removal supplied to the binder is, wherein the temperature is below the sintering temperature but high enough for thermal decomposition of the organic components of the green body he follows.

The method described above may, for example, the US 6,117,612 be removed. The aim is to have a process for the production of green compacts for ceramic components available, in which the green compact with a rapid prototyping method, eg. B. the method of stereolithography, can be produced. Areas of application for this process can be found not only in prototype construction but also in small series, where the production of molds for the green product is not worthwhile.

In order to be able to process the ceramic particle-produced suspensions with fill levels above 40% by volume of ceramic particles by means of rapid prototyping methods, they must have a sufficiently low viscosity. According to the US 6,117,612 the viscosity is reduced by the fact that the suspension, which must also contain components of a thermosetting resin for the generation of a preliminary bond in the green compact, is prepared on an aqueous basis. The water thus serves as a dilution for the per se viscous resin, so that the suspension to be processed, despite the high degree of filling of ceramic particles remains sufficiently fluid to be processed by rapid prototyping.

The The object of the invention is a method for manufacturing of ceramic components from green bodies indicate, in which the greenlings with a rapid prototyping process can be produced and the application of the rapid prototyping method comparatively can be done without problems.

These The object is achieved with the initially described method according to the invention thereby solved, that the suspension is substantially solvent-free, wherein the viscosity the suspension by varying the concentration of a dispersant less than 20,000 mPa · s is reduced and wherein it is the ceramic component to is a component whose electrical insulating properties to be used in conjunction with electrical components. According to the invention, the viscosity of the suspension is therefore over the Concentration of the added Disperpators set, creating a Adjustment of the required viscosity of less than 20,000 mPa · s achieved can be. With this viscosity is a processing of the suspension, for example, in commercial Stereolithography systems possible.

On an addition of diluents like Water or organic solvents can in the suspension according to the invention be waived. It has become shown that the addition of solvents to reduce the viscosity limits the processability of the suspensions thus produced. By the energy input into the suspension to produce the desired Namely, it can evaporate locally because of its three-dimensional structure of solvents in the suspension come with the effect that there is the viscosity of the suspension increases. As a result, however, the desired result, a Greenfinch with a high degree of filling on ceramic particles, endangered.

According to one Embodiment of the method is provided that the green compact for a circuit support will be produced. This means that the greenling by the following Sintering process is converted into a circuit carrier. The electrically insulating properties are known to be prerequisite for the Suitability of a material as a circuit carrier, since on this electrical Components to be mounted and contacted electrically, without that shorts between the individual components may occur. The use of ceramic circuit boards has the advantage that it mechanically even at higher temperatures to stay stable.

According to one secondary Embodiment of the invention can also be provided that the Greenfinch for a casing electrical components is produced. This results the possibility, the housing also thermally stable execute, wherein the ceramic casing can be used simultaneously as a temperature protection. It is also possible, the housing, which is primarily a encapsulation of the electrical components of to ensure the environment should, in addition as a circuit carrier to use. In this case, especially on the inside the housing walls provided electrical components and associated electrical conductors.

According to one special embodiment of the green body is provided that the housing for a MEMS (Micro electro mechanical system) is determined. When MEMS acts These are particularly delicate assemblies that are therefore effective before environmental influences protected Need to become. In particular, MEMS are produced on wafers, for example by means of etching technology. Execution of the housing as a ceramic component allows doing this advantageous with the Waver, on which the MEMS formed was hermetically sealed, for example by wafer bonding and thus to provide excellent protection for the MEMS.

A Another development of the invention is obtained when prior to training of the green body in the suspension is placed in an electrically conductive structure, the following through the resulting green body is enclosed. This advantageously achieves that the electrically insulating properties of the ceramic also for insulation from within the ceramic component to be produced electrical conductors can be used. This is advantageous the process of rapid prototyping (for example stereolithography) in a special way, since the green component forming the ceramic component um the electrically conductive structure are cured around by introducing the energy can.

The electrically conductive structure is placed on the workpiece carrier, on which the green body arise should. This workpiece carrier is provided in any case, in layers, around the green plant being formed to lower into the bath with the suspension and in this way the surface of the Suspension bath layer for Layer of the green product to be produced to create.

alternative can also be provided that the process of obtaining the green compact from the suspension (for example by a stereolithography process) interrupted before completion of the green body is connected, an electrically conductive structure with the unfinished green compact and the green subsequently is completed, wherein the electrically conductive structure enclosed becomes. In this case, therefore, the electrically conductive structure is not placed on the workpiece carrier, but on already formed parts of the green body. Here, the electric conductive structure can not be prefabricated, but for example be obtained by coating the unfinished green compact. By the subsequent one Completion of the green body is then an electrical insulation by enclosing the electrically conductive structures possible.

The Enclose the electrically conductive structure (regardless of whether this in the Suspension is inserted or connected to the unfinished green compact) takes place usually not completely, so that parts of the electrically conductive structures, for example are still accessible for contacting with other components. Enclosing the but electrically conductive structure is definitely in the Subareas in which the structure is electrically isolated should. Subsequently can on the thus formed surface of the green compact another, electrically conductive structure can be applied as a conductive trace, thereby a higher one Complexity of Circuits possible becomes.

According to one particular embodiment of the invention is a dispersant Alkylolammmoniumsalz a copolymer having acidic groups used. This is a so-called steric dispersant, which causes an effective separation of the powder particles from each other. This is achieved by the long-chain polymer molecules of the dispersant act as a separating layer between the individual powder particles. As a result, the mobility of the powder particles to each other guaranteed whereby the fluidity of the Suspension is maintained. This can be the required low viscosity to reach. Alkylolammmoniumsalze of copolymers having acidic groups for example, by the company Byk Chemie GmbH under the trade name Disperbyk 154, Disperbyk 180 or Disperbyk 190 offered.

When Advantageously, it has been found, if the above Dispersants in a concentration between 2 and 5% by weight added become. It has been shown that in this concentration range the viscosity is advantageously adjusted by targeted variations of the concentrations can, without the concentration of the dispersant other properties negatively affected by the suspension.

Farther it is advantageous if an acrylic resin is used as binder comes. Acrylic resins have in comparison to also eligible epoxy resins the advantage that they have a lower viscosity. Consequently let yourself also for the suspension achieve a relatively lower viscosity. However, when using acrylate resins, a photoinitiator must also be used for toasting the curing reactions be added. Upon irradiation of the suspension with UV radiation are formed from the photoinitiator free radicals, which subsequently a Initiate polymerization of the acrylate monomers. For example, when using a UV laser with the wavelength of 365 nanometers can be a liquid Photoinitiator from Ciba Ltd. with the trade name Darocur 4265 be used.

An additional viscosity reduction can be advantageously achieved if the particles of the ceramic powder are coated with the dispersant before being introduced into the suspension. In this case, the dispersant is not added directly to the suspension, but the particles coated with the dispersant ensure the introduction of the dispersant in the suspension. The coating of the powder particles with the disperser has the advantage that it is already at its place of action when introducing the particles into the suspension. This prevents, for example, clumping of the powder particles during introduction into the suspension. In addition, the optimal efficiency of the dispersant molecules is guaranteed.

One A particularly suitable method for curing the binder is the stereolithography method. This can be used advantageously on a proven technology become. The adjusted viscosities in the processed Ensure suspensions advantageous in that the production of green compacts without modification with commercial Stereolithography systems can be done.

According to one special embodiment of the method is provided that the heat treatment for removal of the binder with completion of oxygen at temperatures up to 600 ° C he follows. By completing oxygen during the heat treatment, the removal is done the binder, also called debinding, advantageous particularly gentle carried out. It is going to happen prevents oxidation of the binder components in the green compact. Due to such an exothermic reaction would otherwise thermal energy free, which due to local overheating of the green body could lead to tensions, tears, delaminations and delays.

Farther It is beneficial if the heat treatment for removing the binder in an oxygen-containing atmosphere at temperatures up to 1150 ° C takes place. This heat treatment is particularly advantageous downstream of the latter. The debinding in an oxygen-containing atmosphere has namely the Advantage that this is more effective and therefore shorter treatment times higher Debinding effects achieved. Is the debinding under oxygenated the atmosphere only applied in a subsequent step, so is the concentration of the binder in the green already fallen so much by the first debinding step, that local overheating effects in the green can be excluded. The mentioned quality problems can therefore no longer occur.

Further Details of the invention are described below with reference to the drawing described. Show it

1 schematically the temperature profile during debindering according to an embodiment of the method according to the invention,

2 to 4 selected process steps of the method according to the invention for producing a circuit carrier and

5 the use of a housing component produced according to an embodiment of the method according to the invention with electrically insulating properties.

in the The method parameters are given below by way of example. the for the production of a green body successfully used. For this, the manufactured green has as Layered model with a layer thickness between 20 and 200 μm as digital Dataset available.

In the preparation of the suspensions, a commercially available Al ₂ O ₃ powder (alumina) having a mean particle diameter of 0.8 μm was used. Alternatively, powders of zirconia (ZrO ₂ ) or silica (SiO ₂ ) may also be used.

Around a degree of filling to achieve the suspension of ceramic particles of greater than 45% by volume and while a relatively low Viscosity of less than 20,000 mPa · s to ensure, the ceramic particles were in the suspension before admixture with the steric dispersant from Byk Chemie GmbH with the Trade name Disperbyk 180 coated. In order to have an optimal dispersing effect To achieve the dispersant was dissolved in a solvent and then with homogenized to the powder. This suspension was in a drying oven at 60 to 80 ° C dried until all the solvent had evaporated. The dried powder was additionally ground and sieved.

in the next Step, the pretreated ceramic powder was an acrylate resin added and by intensive stirring dispersed. This suspension was additionally ground with a ball mill to any remaining Aglomarate of ceramic particles to destroy. The thus prepared suspensions are also over a period of several weeks stable.

With a use of 4% by mass of the above-mentioned dispersant, a viscosity of 2000 mPa · s resulted with a degree of filling of ceramic particles of 45% by volume. Due to the relatively low viscosity of the suspensions could Filling level of ceramic powder can be increased to up to 55% by volume without exceeding the maximum permissible viscosity of 20,000 mPa · s (the stated proportion of dispersant is based on the mass of the ceramic powder used).

In front the production of the green body in a stereolithography plant was the photoinitiator Darocur 4265 of the company Ciba Ltd. added. The proportion of photoinitiator based on the amount of suspension can be between 0.3 and 2% by mass lie, with the optimal amount in relation to the current composition the suspension is to be determined experimentally in each case. The laser power for the curing was varied between 5 and 14 mW. The hardening depth was 100 to 500 μm. Herewith could reach layer thicknesses between 50 and 100 microns.

The next step in debinding (binder removal) is in 1 shown schematically. A two-step debinding technique has been developed. First, the green compact was heated at K per minute in N ₂ atmosphere to 600 ° C (T ₁ ), and this temperature was maintained for one hour. This process took approximately 10 hours (t ₁ ). In a second step, the samples were further heated up to a temperature of 1150 ° C. (T ₂ ) in air or in an O ₂ atmosphere, and this temperature was also maintained for one hour. The second treatment step was also stopped after about 10 hours (t ₂ ), after which the green compact cooled to room temperature. Debinding errors such as distortion, cracks, delamination and the like could be avoided with this two-step process.

A subsequent sintering was carried out in a conventional manner at 1800 ° C in H ₂ atmosphere. The finished ceramic reached 99.8% of the theoretical density, so that the ceramic structure contained hardly any pores.

Further Attempts to produce green bodies yielded more possible Variations of the above procedural parameters. Instead of already mentioned Acrylate resin monomer 4017 may also include the acrylate resin monomer 4006 of Cognis GmbH be used. However, this has a higher viscosity, therefore lower filling levels Ceramic powder can be achieved. The process parameters in stereolithography can within the following areas on the particular application to be optimized: Penetration depth between 150 and 400 μm, laser power between 2 mW and 13 mW (using a 325 nm He-Cd laser) Wavelength), Focusing range of laser radiation between 45 and 90 μm and scanning speed between 50 and 200 mm / s. The stereolithographically obtained structures can in addition be exposed to an irradiation with UV light in order to improve curing to reach the binder.

Of the 2 can be taken as a green plant 11 for a circuit carrier 12 (see. 4 ) with a standard stereolithography system 13 can be produced. The stereolithography system 13 consists of a container 14 in which a suspension 15 for the desired green body 11 is filled. Furthermore, a workpiece carrier 16 for the green 11 provided for the production of the individual layers of the green body gradually into the container 14 lower. In 2 is shown schematically as a laser beam 17 the first layer 18 of the green body 11 manufactures. This is a sleeve 19 in the layer 18 installed, which on the workpiece carrier 16 was fixed.

Of the 3 can be seen how the unfinished green compact in the form of the first layer 18 from the container 14 was taken to a conductor track 20 for example, by coating (not shown in detail) on the layer 18 applied. This one comes with the sleeve 19 electrically connected, with both the sleeve 19 as well as the track 20 are to be understood as electrically conductive structures.

Of the 4 can be seen how the finished green product 11 by applying a second layer 21 can be completed, this being in the in 2 shown way. As a result, both the tracks 20 as well as the sleeve 19 largely enclosed by the green compact, with contact surfaces 22 remain free, where not shown electrical components can be contacted. The sleeve 19 thereby assumes the function of a vias and the trace 20 runs inside the circuit board. The greenling according to 4 can be subjected to a sintering treatment in a non-illustrated process step, whereby the desired circuit carrier is obtained.

In 5 is an oscillator manufactured in MEMS construction 23 shown. This is part of a Wavers 24 , To protect the oscillator from the environment is a ceramic housing part 25 provided, which by Waverbonden on the Waver 24 is fixed. This results in a hermetic conclusion of the oscillator 23 , whereby its reliable functioning is ensured.

Claims (13)

Method for producing a ceramic component, in which - a green body ( 11 ) from a minimum of 45% by volume containing ceramic powder containing an organic, curable component is obtained as a binder by the suspension is cured by local introduction of radiant energy to form the geometric structure of the green compact and - the green product ( 11 ) is removed from the suspension and fed to a heat treatment to remove the binder, wherein the temperature is below the sintering temperature but high enough for thermal decomposition of the organic constituents of the green body, characterized in that the suspension is substantially free of solvent, wherein the Viscosity of the suspension is reduced by varying the concentration of a dispersing agent to less than 20,000 mPa · s and wherein the ceramic component is a component whose electrical insulating properties are to be used in conjunction with electrical components. Process according to claim 1, characterized in that the green body ( 11 ) for a circuit carrier ( 12 ) will be produced. Method according to claim 1 or 2, characterized in that the green compact ( 11 ) for a housing ( 25 ) electrical components is produced. Method according to claim 3, characterized in that the housing ( 25 ) for a MEMS ( 23 ) is provided. Method according to one of the preceding claims, characterized in that before the formation of the green body ( 11 ) in the suspension an electrically conductive structure ( 19 ), which is then replaced by the resulting green body ( 11 ) is enclosed. Method according to one of the preceding claims, characterized in that the process for obtaining the green compact ( 11 ) is interrupted from the suspension before completion, an electrically conductive structure ( 20 ) is connected to the unfinished green compact and the green body is then completed, wherein the electrically conductive structure is enclosed. Method according to one of the preceding claims, characterized in that the dispersant used is an alkylolammonium salt of a Copolymers with acidic groups is used. Method according to claim 7, characterized in that the dispersant has a concentration between 2 and 4% by mass is added. Method according to one of the preceding claims, characterized characterized in that the binder used is an acrylate resin, the suspension further comprising a photoinitiator for initiating the curing reaction is added. Method according to one of the preceding claims, characterized characterized in that the particles of the ceramic powder before coated in the dispersion with the dispersing agent become. Method according to one of the preceding claims, characterized characterized in that for curing the binder is a stereolithography method is applied. Method according to one of the preceding claims, characterized characterized in that the heat treatment for removal of the binder with completion of oxygen at temperatures up to 600 ° C he follows. Method according to one of the preceding claims, characterized characterized in that the heat treatment for removing the binder in an oxygen-containing atmosphere at temperatures up to 600 ° C he follows.