DE102020204989B3 - Process for the additive manufacturing of a circuit carrier and circuit carrier - Google Patents

Abstract

A method for additive manufacturing of a circuit carrier is described. First, a ceramic substrate (16) and a metallic powder (17) are provided. A conductive structure (15) connected to the ceramic substrate (16) is then produced by applying a powder layer (P1) of the metallic powder (17) to the ceramic substrate (16) and selectively melting it to produce a first metallization layer (M1) and at least one further powder layer (P2, P3) of the metallic powder (17) is applied and selectively melted to produce at least one further metallization layer (M2, M3). To improve the method, it is proposed that the metallic powder (17) comprise a material which has a density anomaly, and / or that the ceramic substrate (16) is heated during the creation of the conductor structure (15). A circuit carrier is also described.

Description

The invention relates to a method for additive manufacturing of a circuit carrier, in particular a circuit carrier for power electronics. The invention also relates to a circuit carrier, in particular for power electronics.

Circuit carriers are used for the attachment and conductive connection of electronic components. Circuit boards are exemplary circuit carriers. In power electronics in particular, good heat dissipation by means of the circuit carrier is necessary. Ceramic substrates with a conductor structure formed thereon have proven useful for this. Circuit carriers of this type are produced, for example, by means of direct copper bonding (DCB) or by means of active metal brazing (AMB). Both processes are based on a material bond between the ceramic substrate and a metallization using high-temperature firing processes. Subsequent lithography, etching and washing processes are required to produce the conductor structure from the flat metallization. These processes are complex and require extensive hardware adjustments, for example in the form of lithography masks, printing stencils and corresponding tools. The production of such circuit carriers is therefore complex and is not suitable for the production of small series or prototypes. Circuit carriers and their production are known from, for example CN 104 822 223 A , US 2015/0 096 788 A1 , US 6,346,317 B1 and JP 2002- 33 566 A .

It is the object of the present invention to specify an improved method for producing a circuit carrier, in particular to specify a method that can be carried out easily and flexibly and is also suitable for the production of small series or prototypes.

This object is achieved by a method with the steps specified in claim 1. First, a ceramic substrate and a metallic powder are provided. A powder layer of the metallic powder is applied to the ceramic substrate and selectively melted to produce a first layer of metallization. At least one further powder layer of the metallic powder is applied and selectively melted to produce at least one further metallization layer. By means of the selective melting of the metallic powder, a conductor structure that is cohesively connected to the ceramic substrate is produced in layers. After the conductor structure has been completely produced on the ceramic substrate, the circuit carrier is completed. Due to the thermal conductivity of the ceramic substrate, the manufactured circuit carrier is ideally suited for power electronics. Such circuit carriers are also referred to as power electronic substrates.

The metallic powder includes a material that has an anomaly in density. Suitable materials are, for example, antimony, bismuth, gallium, germanium, lithium, silicon and / or tellurium. The corresponding material is also referred to below as a stabilization component of the metallic powder. Because of the density anomaly, the resistance to temperature changes of the metallization layers produced is increased. In addition, stresses in the metallization layers are reduced, in particular avoided. The stabilizing component is preferably added as an alloy component to further components of the metallic powder. A proportion of the stabilization component in the metallic powder can be up to 10% by weight, for example.

This object is also achieved by a method with the steps specified in claim 2. The ceramic substrate is heated during the creation of the conductor structure. The heating of the ceramic substrate has the advantage that melting of the metallic powder applied to it is simplified. In particular, less energy input is required to melt the metallic powder. In addition, the heating has a positive influence on the low thermal shock resistance of the ceramic substrate. In addition, the metallic powder bonds better with the heated ceramic substrate. The process is stable and efficient. In particular, the ceramic substrate is heated to a temperature between 200 ° C and 700 ° C. The ceramic substrate is particularly preferably heated to just below the melting temperature of the metallic powder.

According to the invention, it was recognized that the application of layers and selective melting of the metallic powder is suitable for producing a reliable metallization of the ceramic substrate. The selective melting of the powder advantageously enables the conductor structure to be manufactured directly. Complex post-processing of the metallization to produce the conductor structure, in particular complex lithography, etching and washing processes, are not required. The method enables an efficient and simple production of the circuit carrier. In particular, this also enables small series and prototypes of circuit carriers to be produced. The process has a high degree of flexibility.

Another advantage of the method is that a circuit layout of the Conductor structure can be designed flexibly. In particular, the method enables the generation of a three-dimensional structure of the metallization, which is also referred to as 3D metallization. When manufacturing in layers, different surface areas can be melted in different layers. The different metallization layers are therefore not necessarily congruent. Two or more metallization layers can have different geometries in a plane running parallel to the surface of the substrate. The method is not limited to the production of two-dimensional conductor structures, as is the case, for example, with lithography and etching processes.

The conductor structure has, for example, conductor tracks and / or contact areas for electrical components. The 3D metallization allows not only horizontal, but also vertical integration options for active and / or passive components. Furthermore, subsequent assembly steps can be dispensed with, for example in that load connections are not assembled separately, but rather are produced as part of the metallization layers. Cooling bodies and / or a housing can also be manufactured integrally.

The ceramic substrate provided can be an oxide ceramic or a non-oxide ceramic. The ceramic substrate is preferably an aluminum oxide ceramic, beryllium oxide ceramic, silicon nitride ceramic or aluminum nitride ceramic. These ceramics have a low coefficient of thermal expansion and high thermal conductivity. They are particularly well suited for applications with high temperature differences and high temperature loads.

The ceramic substrate provided is in particular plate-shaped. Alternatively or additionally, more complex shapes of the ceramic substrate are also possible. The method is not limited to plate-shaped ceramic substrates. The application possibilities of the method are further increased. The provision of the ceramic substrate can also include the production of the ceramic substrate and / or parts thereof. For example, it is possible to additively manufacture at least parts of the ceramic substrate.

The provided metallic powder forms the material from which the metallization layers and thus the conductor structure are manufactured. The metallic powder can comprise one or more components, in particular one or more materials. The metallic powder preferably has different functional components. For example, different functional components can promote, in particular ensure, high electrical conductivity of the metallization layers, good wettability of the ceramic substrate and / or high thermal shock resistance of the conductor structure. Various components of the metallic powder can be provided in the form of different starting powders which are mixed to form the metallic powder. In addition or as an alternative to this, various components can be present as alloy constituents in the metallic powder. Various components of the metallic powder can preferably be flexibly combined. In particular, it is possible that the metallic powder for producing various of the metallization layers has a different composition, as will be described in detail below.

At least two or more metallization layers are produced. The method is not restricted to a specific number of metallization layers to be produced.

After the conductor structure has been created, excess metallic powder that has not been melted can be removed. Excess metallic powder can be reused.

According to a preferred aspect of the method, the metallic powder is selectively melted by selective laser melting (SLM for short). With selective laser melting, the powder particles are completely melted. This leads to a particularly dense and homogeneous metallization of the ceramic substrate. In addition, wetting of the ceramic substrate is improved by the selective laser melting.

With selective laser melting, a focused laser beam is guided over the areas of the respective powder layer to be melted. The laser radiation can be continuous or pulsed.

Laser radiation with different wavelengths can be used for laser melting. Depending on the wavelength used, different absorption mechanisms play an important role in the metallic powder and the ceramic substrate. For example, laser radiation with wavelengths from the infrared range to the UV range can be used. Wavelengths between 380 nm and 750 nm, that is to say in the range of visible light, are preferably used. Laser radiation with wavelengths from approx. 490 nm to approx. 575 nm (green light) or from approx. 420 nm to approx. 490 nm (blue light) has proven to be particularly suitable. These wavelengths are optimal suitable for processing preferred metallic powders, especially metallic powders with a high copper content.

Parameters that can be set during laser melting are, in particular, the laser power, the focus diameter and / or the laser speed with which the laser beam is guided over the surface. The parameters can be adapted to one another in order to ensure complete melting of the metallic powder. In particular, the further parameters can be selected as a function of the wavelength of the laser radiation. The laser power is, for example, between 30 W and 1000 W, in particular between 50 W and 500 W. The focus diameter can be, for example, between 20 μm and 200 μm. Exemplary laser speeds are between 15 mm / s and 7000 mm / s, in particular between 50 mm / s and 1500 mm / s.

Any laser types can be used to generate the laser radiation, in particular fiber lasers, disk lasers or diode lasers. Due to their high beam quality, fiber lasers have proven to be particularly suitable.

Another advantage of selective laser melting is that the size of a weld pool generated during melting is defined by a beam diameter of the laser beam. As a result, the minimum structure size that can be achieved is only limited by the process parameters for selective laser melting. The weld pool width depends, among other things, on the beam power, the beam diameter, a laser speed with which the beam is guided over the powder layer and the material properties of the powder particles. With the help of selective laser beam melting, small structure sizes are possible. For example, structure sizes between 50 µm and 80 µm can be achieved.

The selective melting of the powder can also take place by means of selective electron beam melting (EBM for short). Here, a focused electron beam is guided over the areas of the respective powder layer to be melted. The advantages of selective electron beam melting are the same as those of selective laser beam melting.

The metallization layers can also be produced by means of laser metal deposition (LMD). Here, a processing head is guided over the surface of the ceramic substrate. The metallic powder is applied via nozzles on the machining head and melted using a laser beam. The metallic powder is only applied in each powder layer in the areas that are also melted. The metallic powder is selectively applied and melted. The metallic powder does not need to be applied over a large area. Subsequent removal of unmelted powder is avoided.

According to a further preferred aspect of the method, the metallic powder contains at least one of the metals gold, aluminum, copper and / or silver. These metals and the metallization layers produced with them have a high electrical conductivity. These metals can form a basic component of the metallic powder. In particular, the metallic powder can be an alloy based on one or more of these metals. Copper or a copper alloy has proven to be a particularly suitable basic component. To achieve a high electrical conductivity of the conductor structure, it is advantageous to use a metallic powder with as high a proportion of the basic component as possible. A proportion of the basic component in the metallic powder can, for example, be between 80% by weight and 100% by weight, in particular between 85% by weight and 99% by weight, preferably between 90% by weight and 95% by weight. be. The proportion of the basic component can also be different in different metallization layers. For example, the proportion in the first metallization layer can be smaller, in particular zero. The proportion of the basic component can increase in further metallization layers. For example, further metallization layers can also essentially consist of the basic component, in particular of copper.

According to a further preferred aspect of the method, the metallic powder has a wetting component, the wetting component comprising at least one of the elements titanium, hafnium, zirconium, niobium, cerium, chromium, vanadium, yttrium and scandium. These materials have good wetting properties on ceramic surfaces. The wetting component is therefore particularly suitable for wetting the ceramic substrate. The materials that can be used as wetting components are also referred to as active materials. The active materials are very reactive and can combine with the oxide of an oxide ceramic or the nitrogen of a non-oxide ceramic when exposed to temperature. With the help of the wetting component, a particularly stable material connection between the conductor structure and the ceramic substrate can be produced. Titanium has proven to be a particularly suitable wetting component.

A proportion of the wetting component in the metallic powder is preferably as low as possible. The proportion of is particularly preferred Wetting component selected just as high as necessary to achieve a desired degree of wetting. As a result, the proportion of the wetting component can be reduced in favor of other components, in particular the basic component. A proportion of the wetting component in the metallic powder can be, for example, between 0.5% by weight and 15% by weight, in particular between 0.5% by weight and 10% by weight. A proportion of the wetting component less than or equal to 10% by weight is preferred. The proportion of the wetting component can also vary from metallization layer to metallization layer. For example, the proportion of the wetting component can be higher in the first metallization layer. In particular, the first metallization layer can essentially consist of a wetting component, for example titanium. The proportion of the wetting component can decrease in further metallization layers. In particular, further metallization layers cannot contain any wetting components.

The metallic powder preferably comprises a basic component made of a metal of high conductivity, in particular made of copper, and a wetting component. For example, the two components can be in the form of two powders that are mixed to form the metallic powder. Depending on the mixing ratio, the proportion of the wetting component can be varied.

According to a further preferred aspect of the method, the metallic powder has an alloy comprising the wetting component. Further powder components, in particular a basic component of the metallic powder, can be present in the form of further alloy constituents. The combination of different powder components in one alloy ensures a particularly homogeneous composition of the metallic powder. Separation of different powder components is avoided. The metallization layers produced from the metallic powder also have a homogeneous composition, in particular a uniform distribution of the wetting component. This ensures reliable and uniform wetting of the ceramic substrate and a reliable material connection with it.

The wetting component is preferably alloyed to form a metal with high conductivity, in particular to copper. Copper-titanium alloys have proven to be particularly suitable.

According to a further preferred aspect of the method, the wetting component is provided in the form of a coating of primary powder particles. The coating of the primary powder particles has the advantage of a homogeneous distribution of the wetting component in the metallic powder. The primary powder can in particular have a basic component of the metallic powder. The primary powder preferably has a basic component and a stability component of the metallic powder. The primary powder particles can, for example, be or will be coated with the wetting component. As a result, a proportion of the wetting component in the metallic powder can be flexibly adjusted.

According to a further preferred aspect of the method, the metallic powder has a particle size distribution of d ₅₀ between 10 μm and 100 μm. A corresponding particle size distribution enables a uniform and compact application of the powder layers and thus a high density and homogeneity of the metallization layers produced. The metallic powder particularly preferably has spherical powder particles. This improves the flowability of the powder.

According to a further preferred aspect of the method, a different composition of the metallic powder is used to produce different ones of the metallization layers. As a result, the properties of various components of the metallic powder can be flexibly combined. As a result, metallization layers with different properties can be produced. The metallization layers can be adapted even better to the respective requirements. The conductor structure can have a material gradient.

According to a further preferred aspect of the method, at least the first metallization layer is produced with an increased proportion of a wetting component, in particular an increased titanium proportion, compared to at least one further metallization layer. An increased proportion of the wetting component in at least the first metallization layer causes particularly good wetting of the ceramic substrate. The material connection between the conductor structure and the ceramic substrate is particularly stable.

The metallic powder preferably has a pure titanium powder at least for producing the first metallization layer. Titanium has proven to be a particularly suitable wetting component. The use of a pure titanium powder at least for the production of the first metallization layer causes optimal wetting of the ceramic substrate.

The stability of the circuit carrier produced is increased. For example, the metallic powder is at least for the production of the first metallization layer made of a pure titanium powder. The metallic powder preferably consists of a pure titanium powder and an alloyed stabilization component, in particular silicon, at least for the production of the first metallization layer. By adding alloy to the stabilization component, stresses in the generated metallization layer are reliably avoided.

According to a further preferred aspect of the method, at least one of the further metallization layers is produced with an increased proportion of gold, aluminum, copper and / or silver compared to the first metallization layer, in particular an increased proportion of copper. The at least one further metallization layer can have an increased proportion of a basic component of the metallic powder. These metals have a high conductivity, but do not wet a ceramic surface as well as one of the above-mentioned wetting components, in particular as titanium. An increased proportion of these metals, in particular an increased copper proportion, in at least one of the further metallization layers ensures a high conductivity of the conductor structure produced. At the same time, optimal wetting of the ceramic substrate can take place through at least the first metallization layer.

In a preferred variant, at least the first metallization layer is produced essentially from a wetting component, in particular from a pure titanium powder. At least one further metallization layer can be produced from a basic component, in particular from copper. In this way, the advantageous wetting properties of the wetting component, in particular of titanium, can be combined particularly well with the high electrical conductivity of the basic component, in particular of copper.

According to a further preferred aspect of the method, the conductor structure is produced on the ceramic substrate under a protective gas atmosphere, in particular under an inert protective gas atmosphere, preferably under an argon atmosphere. Oxidation of the conductor structure produced in layers is thereby reliably avoided. The metallization layers are of high quality.

According to a further preferred aspect of the method, there is an aftertreatment step for heat treatment of the circuit carrier. The heat treatment increases the adhesive strength of the metallization on the ceramic substrate. In addition, this can reduce stresses in the metallization. The heat treatment is carried out in particular in the form of an oven treatment. A post-treatment temperature is selected in particular as a function of the material composition of the metallization layers. The post-treatment temperature is preferably about 10 ° C. to 20 ° C. below the melting point of the metallization layers. For example, depending on the material, the circuit carrier is heated to an aftertreatment temperature between 200 ° C and 1080 ° C. The aftertreatment is preferably carried out under an inert, evacuated or reducing atmosphere.

According to a further preferred aspect of the method, the provision of the ceramic substrate comprises the additive manufacturing of at least parts of the ceramic substrate. For example, additional structures on the ceramic substrate, in particular ceramic heat sinks, can be manufactured additively. The entire ceramic substrate can also be manufactured additively. In particular, ceramic substrates with a three-dimensional structure can also be produced and provided in this way. As a result, 3D circuit carriers can be manufactured in a simple and flexible manner.

The additive manufacturing of at least parts of the ceramic substrate can be done, for example, by processing a ceramic powder. The processing of the ceramic powder takes place in particular with the same processing processes and / or machines as the processing of the metallic powder for producing the metallization layers. For example, ceramic powders can be processed using selective laser melting. For example, higher preheating temperatures can be selected for this, in particular preheating temperatures of 1000 ° C. or more.

At least parts of the ceramic substrate and the conductor structure can preferably be produced by different methods of additive manufacturing. For example, parts of the ceramic substrate or the ceramic substrate as a whole can be manufactured by means of a method optimized for processing ceramic powders, in particular a 3D printing method optimized for this purpose. Due to the combination of different processes, high-quality processing of the respective materials is guaranteed. Suitable 3D printing processes are, in particular, light-curing processes. Here, for example, resins in which there are ceramic particles are polymerized by means of light, in particular laser radiation. Particularly suitable 3D printing processes are in particular stereolithography (short: SLA), digital light processing (short: DLP), binder jetting or “NanoParticle Jetting” (short: NPJ) developed by XJET. These methods are known to the person skilled in the art, in particular for the additive manufacturing of ceramic components, as is the case, for example, in the Article "3D printing with ceramics: A revolution in additive manufacturing?" (See https://www.3dnatives.com/de/3d-druck-mit-keramik-featured-170420191/ accessed on April 16, 2020) . Information on the SLA and DLP processes can also be found in the article "3D printing with stereolithography - read how it's done here!" .

According to a further preferred aspect of the method, the additive manufacturing of at least parts of the ceramic substrate takes place by lithography-based ceramic manufacturing (LCM for short). The LCM process allows the additive manufacturing of high quality ceramic components. Particularly preferably, at least parts of the ceramic substrate are first additive manufacturing using the LCM method and then the metallization layers are manufactured using an additive manufacturing method suitable for processing metallic powders, in particular using selective laser melting or selective electron beam melting.

It is a further object of the invention to provide an improved circuit carrier.

This object is achieved by a circuit carrier according to claim 18. The circuit carrier is produced as described above. The method produces an improved circuit carrier, in particular a circuit carrier with a flexible layout of the conductor structure. In particular, the circuit carrier can have a 3D metallization.

This object is also achieved by a circuit carrier with the features specified in claim 19. The circuit carrier has a ceramic substrate and a conductor structure that is firmly bonded to the substrate. The conductor structure has a plurality of metallization layers applied to the ceramic substrate. The circuit carrier can be manufactured using the method described above. The circuit carrier has a high adhesive strength of the metallization layers on the ceramic substrate.

According to a preferred aspect of the circuit carrier, at least two of the metallization layers are not congruent in a plane running parallel to the surface of the substrate. The circuit carrier has a 3D metallization. In particular, the conductor structure has regions which have no direct connection to the ceramic substrate in the direction perpendicular to a surface of the ceramic substrate. Such areas can also be referred to as free-floating areas. For example, two conductor track structures can be connected via a free-floating area in the form of a bridge.

The circuit carrier has, in particular, horizontal and / or vertical integration options for active and / or passive components. Load connections are preferably formed by the metallization layers. The metallization layers can also form heat sinks and / or housing parts. Additional assembly steps are reduced.

• 1 eine schematische Schnittdarstellung einer Vorrichtung zur schichtweisen Fertigung eines Schaltungsträgers,
• 2 einen schematischen Verfahrensablauf zur schichtweisen Fertigung eines Schaltungsträgers,
• 3 eine schematische Darstellung eines metallischen Pulvers zur Verwendung in dem Verfahren gemäß 2,
• 4 eine schematische Darstellung eines Zwischenschritts bei der Fertigung nach dem Verfahren gemäß 2,
• 5 eine schematische Darstellung eines weiteren Zwischenschritts bei der Fertigung nach dem Verfahren gemäß 2,
• 6 eine schematische Darstellung eines weiteren Ausführungsbeispiels eines Schaltungsträgers,
• 7 eine schematische Darstellung eines weiteren Ausführungsbeispiels eines metallischen Pulvers zur Verwendung in dem Verfahren gemäß 2,
• 8 eine schematische Darstellung eines weiteren Ausführungsbeispiels eines metallischen Pulvers zur Verwendung in dem Verfahren gemäß 2, und
• 9 eine schematische Darstellung eines Zwischenschritts gemäß einem weiteren Ausführungsbeispiel des Verfahrens.

Further advantages and details of the invention are explained in more detail below with reference to the drawings. In these show:

• 1 a schematic sectional view of a device for the layer-by-layer production of a circuit carrier,
• 2 a schematic process sequence for the layer-by-layer production of a circuit carrier,
• 3 a schematic representation of a metallic powder for use in the method according to FIG 2 ,
• 4th a schematic representation of an intermediate step in the production according to the method according to FIG 2 ,
• 5 a schematic representation of a further intermediate step in the production according to the method according to FIG 2 ,
• 6th a schematic representation of a further embodiment of a circuit carrier,
• 7th a schematic representation of a further embodiment of a metallic powder for use in the method according to FIG 2 ,
• 8th a schematic representation of a further embodiment of a metallic powder for use in the method according to FIG 2 , and
• 9 a schematic representation of an intermediate step according to a further embodiment of the method.

In 1 is a device 1 for the additive manufacturing of a circuit carrier 2 shown. The device 1 is for the layer-by-layer production of a circuit carrier 2 using selective laser melting (SLM).

The device 1 is in an interior 3 a gas-tight housing not explicitly shown arranged. It includes a space 4th with a component platform 5 and a powder reservoir 6th with a powder dosing platform 7th . The component platform 5 and the powder dosing platform 7th are along a stroke direction 8th movable. This allows the powder metering platform 7th and the component platform 5 be raised or lowered.

There is also a squeegee 9 available. The squeegee 9 is in a plane perpendicular to the stroke direction 8th above the powder reservoir 6th and the installation space 4th movable. There is also a laser 10 for generating laser radiation 11 available. The laser radiation 11 can by means of an adjustable scanner mirror 12th targeted to individual areas of the installation space 4th be radiated.

The device 1 also includes an overflow shaft 13th for excess powder. With the help of a space heater 14th can the installation space 4th be heated to a melting of powder by means of the laser radiation 11 to simplify.

With the device 1 becomes the circuit carrier 2 manufactured by a ladder structure 15th in layers on a ceramic substrate 16 is applied. The ladder structure 15th is made from a metallic powder 17th made that in the powder reservoir 6th is in stock. The metallic powder 17th is shown schematically by means of dotted areas. For the production of the conductor structure in layers 2 is done first with the help of the squeegee 9 metallic powder 17th from the powder reservoir 6th as a powder layer (not shown) on the component platform 5 placed ceramic substrate 16 applied. Excess metallic powder 17th is done with the squeegee 9 removed and in the overflow shaft 13th collected. That in the overflow shaft 13th collected metallic powder 17th can return to the powder reservoir at a later point in time 6th are fed.

For forming a layer of the conductor structure 15th corresponding areas of the powder layer are created by targeted laser radiation 11 melted. The laser radiation 11 is passed over the areas to be melted. Various exposure strategies are known and can be used for this purpose.

After all areas of a powder layer to be solidified have been melted at least once, another powder layer is applied. For this purpose, the component platform 5 along the stroke direction 8th lowered and the powder dosing platform 7th in stroke direction 8th raised. That over the top of the powder reservoir 6th upscale metallic powder 17th is made by moving the squeegee 9 removed and as a new powder layer in the installation space 4th distributed. The application of the new powder layer is followed by selective melting by means of laser radiation 11 at. The method steps described in this way are repeated until the conductor structure 15th is completed.

In order to simplify the melting of the metallic powder, the installation space heater is used 14th the ceramic substrate 16 heated. The heating has a positive influence on the low thermal shock resistance of the ceramic substrate 16 and causes better bonding of the melted powder 17th with the ceramic substrate 16 . The ceramic substrate 16 is heated to a temperature between 200 ° C and 700 ° C.

To ignite the metallic powder 17th to avoid being the interior 3 the gas-tight housing with a protective gas 18th flooded. Argon is used as the protective gas. This also causes a reaction, in particular an oxidation, of the melt of the metallic powder 17th prevented by the oxygen content of the ambient air. The protective gas 18th ensures a stable process.

The selective melting of the areas of the powder layers to be solidified determines the geometry of the conductor structure to be manufactured 15th . The layered structure of the ladder structure 15th can be designed, for example, by means of a CAD program and sent to a control computer (not shown) for adjusting the scanner mirror 12th to get redirected.

With reference to the 2 until 5 the manufacturing process is explained in detail. In 2 is a schematic sequence of a manufacturing process 20th shown. With the help of 3 until 5 intermediate steps of the procedure are explained. The manufacturing process 20th can with the in 1 device shown 1 be performed. Alternatively, other devices that apply layer by layer and selective melting of metallic powder can also be used 17th allow to be used.

First of all, in a deployment step 21 the ceramic substrate 16 and the metallic powder 17th provided. The ceramic substrate 16 is a substrate plate with a thickness of, for example, 1 mm. Ceramic substrates have good thermal conductivity and are ideal for circuit carriers for power electronics. Any ceramic material that can be used in such circuit carriers can serve as the ceramic substrate. For example, oxide and non-oxide ceramics with different purities can be used.

In 3 is schematically the provided metallic powder 17th shown. The metallic powder 17th exhibits powder particles 19th on. The powder particles 19th are spherical. With the metallic powder 17th it is a spherical powder. the Powder particles 19th have a diameter D. The diameter D varies from powder particles 19th to powder particles 19th . The metallic powder 17th has a particle size distribution of d 50 between 10 µm and 100 µm. The value of dso is defined as the mean particle size.

The metallic powder 17th has several components. The metallic powder 17th is an alloy based on copper. Copper has a high electrical conductivity and is ideal for creating the conductor structure. The copper content in the alloy forms a basic component of the metallic powder 17th . Another alloy component is titanium. Titanium shows very good wetting of ceramic surfaces. The titanium content in the alloy therefore forms a wetting component of the metallic powder 17th . A proportion of the wetting component in the metallic powder is between 0.5% by weight and 10% by weight. With the metallic powder 17th it is a copper-titanium alloy. For example, a copper-titanium alloy can be melted in a crucible and turned into the metallic powder 17th be atomized.

The metallic powder 17th also has a stabilizing component. The stabilization component is one of the other components of the metallic powder 17th and comprises a material that has a density anomaly. This improves the thermal shock resistance of the conductor structure 15th during operation of the circuit carrier to be manufactured 2 . Suitable materials with anomalous density are, for example, antimony, bismuth, gallium, germanium, lithium, silicon and / or tellurium.

In further exemplary embodiments not shown, further metals and / or alloys with high conductivity can also be used for the basic component. Particularly suitable metals are, for example, copper, aluminum, silver and / or gold.

In further exemplary embodiments, not shown, other materials that enable high wetting of ceramic surfaces can also be used as wetting components. Suitable materials are titanium, hafnium, zirconium, niobium, cerium, chromium, vanadium, yttrium and / or scandium.

To the deployment step 21 several metallization steps follow 22nd at. A first metallization step 22nd is schematically in 4th shown. 4th shows a section of the installation space 4th and the ceramic substrate 16 . In one powder application step 23 of the metallization step 22nd becomes a first powder layer P _{1 of} the metallic powder 17th onto the ceramic substrate 16 applied. The powder _{layer P 1} has a layer thickness d which is, for example, between 20 μm and 50 μm. In one melting step 24 the metallic powder is used to produce a first metallization layer M ₁ 17th selectively with the help of laser radiation 11 melted.

In the melting step 24 becomes the laser radiation 11 guided over the powder layer P ₁ at a laser speed v _L. The laser speed v _L is between 15 mm / s and 7000 mm / s. The laser radiation 11 has a laser power P _L between 30 W and 1000 W and a focus diameter F _L between 20 μm and 200 μm. The wavelength of the laser radiation 11 is preferably in the green or blue visible range. The parameters of the laser radiation 11 are so attached to the metallic powder 17th adjusted that the metallic powder 17th is completely melted in the areas covered by the laser. The laser radiation 11 creates a weld pool 25th . In 4th is also a border area 26th between the metallic powder 17th and the weld pool 25th shown.

In the melting step 24 all areas of the powder layer P _{1 to be} melted are melted. The melt in the weld pool 25th wets the ceramic substrate 16 . After melting, the melt cools down and solidifies to form the first metallization layer M ₁ . The metallization layer M ₁ is cohesive with the ceramic substrate 16 tied together.

The geometry of the ladder structure 15th in the first metallization layer M ₁ corresponds to the entirety of the areas to be melted on. After all areas to be melted in the melting step 24 have been melted at least once, is the metallization step 22nd completed. The metallization step 22nd is then repeated until the ladder structure 15th is completely applied to the ceramic substrate. In every metallization step 22nd first becomes a powder layer of the metallic powder 17th in one application step 23 applied and then in a melting step 24 selectively melted.

In 5 a metallization step for producing the third metallization layer M _{3 is} shown by way of example. On the ceramic substrate 16 the powder layers P ₁ to P ₃ have already been applied. The metallization layers M ₁ and M ₂ are each completely produced by selectively melting _{the powder layers P 1} and P _2. With the help of laser radiation 11 the metallization _{layer M 3 is} produced. The conductor structure is created by applying the metallization layers M ₁ to M _{3 in layers} 15th generated. The ladder structure 15th is firmly bonded with the ceramic substrate 16 tied together.

The ladder structure 15th is on a substrate surface 27 of the ceramic substrate 16 upset. The metallization layers M ₁ to M ₃ are in a plane parallel to the substrate surface 27 not congruent. So shows the ladder structure 25th for example steps 28 on. The differently shaped metallization layers M ₁ to M ₃ bring about a 3-D metallization. The manufacturing process 20th allows increased design freedom in the manufacture of the conductor structure 15th . After completing all metallization steps 22nd is the ladder structure 15th total generated. There are generally at least two metallization steps 22nd carried out, so at least two metallization layers produced. The method is not limited to a specific number of metallization layers to be produced.

After completing all metallization steps 22nd is the circuit carrier 2 finished in itself. In one step of removal 29 becomes excess, unmelted metallic powder 17th removed. When using the device 1 can the circuit carrier 2 for example from the installation space 4th removed and cleaned of powder residue with the aid of compressed air.

This is followed by a post-treatment step 30th . In the post-treatment step 30th there is a heat treatment of the circuit carrier 2 in an oven process. The circuit carrier 2 is used in the post-treatment step 30th heated to an aftertreatment temperature. The post-treatment temperature is about 10 ° C to 20 ° C below the melting temperature of the metallization layers. For example, the post-treatment temperature is between 200 ° C and 1080 ° C, depending on the material. With the help of the post treatment step 30th become tensions in the conductor structure 15th reduced.

In 6th is a schematic representation of a further embodiment of a circuit carrier 2a shown. Components that are used in connection with the exemplary embodiment according to FIGS 1 until 5 have already been described bear the same reference numerals. Parts that are structurally different but functionally identical are given the same reference numerals with an a after them.

6th shows a section of the circuit carrier 2a . The circuit carrier 2a is using the manufacturing process 20th manufactured. The circuit carrier 2a has a ceramic substrate 16 and a conductor structure connected to it in a materially bonded manner 15a on. The ladder structure 15a has a plurality of on the ceramic substrate 16 applied, superimposed metallization layers M ₁ to M ₃ . The ladder structure 15a is a 3D metallization. In the ladder structure 15a are two conductor tracks 31 over a bridge 32 connected with each other. The bridge 32 is a floating metallization area. The ceramic substrate 16 averted top of the bridge 32 forms a contact surface for applying electronic components. Under the bridge 32 is another track 33 guided. The conductor track 33 is from the conductor tracks 31 electrically isolated. Using the manufacturing process 20th complex conductor structures can be manufactured.

In 7th is schematically another embodiment of a metallic powder 17b shown. The metallic powder 17b has spherical powder particles 19b on. The spherical powder particles 19b exhibit primary powder particles 35 and one the primary powder particles 35 surrounding sheath 36 on. The primary powder particles 35 comprise the basic component of metallic powder 17b . The basic component is in particular made of copper or a copper alloy. The primary powder particles 35 also have a stabilization component made of a material that shows a density anomaly. The sheath 36 contains a wetting component made of a suitable material that wets the ceramic substrate well, in particular made of titanium. The wetting component in the form of the casing 36 is uniform in the metallic powder 17b distributed. The sheath 36 can for example by coating the primary powder particles 35 be generated. As a result, the proportion of the wetting component can be flexibly adjusted.

In 8th is another embodiment of a metallic powder 17c shown. The metallic powder 17c has spherical powder particles 19c on. The metallic powder 17c is a powder mixture. The powder mixture includes basic component powder particles 37 , in the 8th are shown without hatching. In the case of the basic components powder particles 37 it is preferably a copper powder. The metallic powder 17c also has wetting components powder particles 38 on that in 8th are shown with hatching. In the case of the wetting component powder particles 38 it is preferably a pure titanium powder.

With the metallic powder 17c the basic component and the wetting component are provided and mixed in the form of different powders. In this way, a composition of the metallic powder 17c can be varied particularly flexibly.

The different powder particles 37 , 38 of metallic powder 17c are in the reflow step 24 melted. The different materials merge here, so that it too an in-situ alloy of the different components of the metallic powder 17c comes.

In further exemplary embodiments, not shown, the metallic powder also has a stabilization component in the form of stabilization component powder particles. Alternatively, a stabilizing component can also be added to the basic component powder particles 37 and / or the wetting component powder particles 38 be alloyed.

In 9 is schematically a further embodiment of an intermediate step in the layer-by-layer production of a conductor structure 15d shown.

The intermediate step shows the production of a third metallization layer and essentially corresponds to that in FIG 5 Intermediate process step shown. Components that are used in connection with the exemplary embodiment according to FIGS 1 until 5 have already been described bear the same reference numerals. Parts that are structurally different but functionally identical are given the same reference numerals with a subsequent d.

The in 9 The embodiment shown is a different composition of the metallic powder for producing different of the metallization _{layers M 1} to M ₃ 17d used. The different composition of the metallic powder 17d is in 9 shown schematically by different puncturing of the powder layer P ₁ on the one hand and the powder layers P ₂ and P ₃ on the other hand. Accordingly, the metallization layer M _{1 also has} a different material composition than the metallization layers M ₂ and M ₃ , which is characterized by different hatching.

To produce the first metallization layer M ₁ , an increased proportion of a wetting component is used compared to the further metallization layers M ₂ , M _3. In the exemplary embodiment shown, a pure titanium powder, to which a stabilizing component made of silicon has been alloyed, is used to produce the first metallization _{layer M 1.} A composition of the metallic powder is used to produce the further metallization layers M ₂ , M ₃ 17d is used with an increased proportion of a basic component compared to the first metallization layer M _1. In the exemplary embodiment shown, the metallization layers M ₂ , M _{3 are} produced by applying powder layers P ₂ , P ₃ from a copper powder and melting them selectively.

With the help of the varying composition of the metallic powder 17d material properties of the different powder components can be applied and combined in a targeted manner. The increased proportion of a wetting component in the first metallization layer M ₁ results in optimal wetting of the ceramic substrate 16 causes. The use of an increased proportion of a basic component, in particular an increased copper proportion, in the further metallization layers M ₂ , M ₃ results in a high electrical conductivity of the conductor structure produced 15d guaranteed.

To produce the various metallization layers M ₁ to M ₃ with a different composition of the metallic powder 17d can be used between the sequential metallization steps 22nd an in 2 Composition change step shown in dashed lines 40 take place. In the composition change step 40 becomes the composition of the metallic powder 17d changes. This can be done, for example, by changing a proportion of an alloy component. Alternatively, a powder mixture, as is the case with the powder, for example 17c in 8th shown can be varied. It can also be provided that only the wetting component of the metallic powder is used to produce at least the first metallization layer M _1. In the composition change step 40 the wetting component is then exchanged for other components of the metallic powder.

In further exemplary embodiments, not shown, the powder is not melted by means of selective laser melting, but rather by means of selective electron beam melting. In yet other exemplary embodiments, the metallization layers are produced by means of laser deposition welding.

In further exemplary embodiments (not shown), additive manufacturing of at least parts of the ceramic substrate takes place in the preparation step. For this purpose, a ceramic powder can first be applied in layers to the component platform and selectively melted. In particular, three-dimensional structures of the ceramic substrate, for example heat sinks, can be manufactured easily and flexibly. In yet other exemplary embodiments (not shown), parts of the ceramic substrate or the entire ceramic substrate are first produced by means of what is known as lithography-based ceramic manufacturing (LCM). The LCM process allows the additive manufacturing of high quality ceramic components. The conductor structure is then manufactured using a method suitable for processing metallic powders, in particular selective laser melting or selective electron beam melting. In further exemplary embodiments, at least parts of the ceramic substrate are produced using one of the 3D printing processes stereolithography (SLA for short), digital light processing (DLP for short), binder jetting or “nano-partide jetting” (NPJ for short) to provide the ceramic substrate.

Claims (20)

Method for additive manufacturing of a circuit carrier, in particular for power electronics, with the following steps: - providing - a ceramic substrate (16) and - a metallic powder (17; 17b; 17c; 17d), - producing a materially bonded with the ceramic substrate (16) connected conductor structure (15; 15a; 15d) by - a powder layer (P ₁ ) of the metallic powder (17; 17b; 17c; 17d) is applied to the ceramic substrate (16) and for the production of a first metallization layer (M ₁ ) is selectively melted and - at least one further powder layer (P ₂ , P ₃ ) of the metallic powder (17; 17b; 17c; 17d) is applied and selectively melted _{to produce at least one further metallization layer (M 2} , M _3), characterized in that the metallic powder (17; 17b; 17c; 17d) comprises a material having a density anomaly. Method for additive manufacturing of a circuit carrier, in particular for power electronics, with the following steps: - providing - a ceramic substrate (16) and - a metallic powder (17; 17b; 17c; 17d), - producing a materially bonded with the ceramic substrate (16) connected conductor structure (15; 15a; 15d) by - a powder layer (P ₁ ) of the metallic powder (17; 17b; 17c; 17d) is applied to the ceramic substrate (16) and for the production of a first metallization layer (M ₁ ) is selectively melted and - at least one further powder layer (P ₂ , P ₃ ) of the metallic powder (17; 17b; 17c; 17d) is applied and selectively melted _{to produce at least one further metallization layer (M 2} , M _3), characterized in that the ceramic substrate (16) is heated while the conductor structure (15; 15a; 15d) is being produced. Method according to one of the preceding claims, characterized in that the selective melting of the metallic powder (17; 17b; 17c; 17d) takes place by selective laser melting or selective electron beam melting. Method according to one of the preceding claims, characterized in that the metallic powder (17; 17b; 17c; 17d) comprises at least one of the metals gold, aluminum, copper and / or silver. Method according to one of the preceding claims, characterized in that the metallic powder (17; 17b; 17c; 17d) has a wetting component, the wetting component of at least one of the elements titanium, hafnium, zirconium, niobium, cerium, chromium, Includes vanadium, yttrium and scandium. Procedure according to Claim 5 , characterized in that the metallic powder (17; 17b; 17c; 17d) has an alloy comprising the wetting component, in particular a copper alloy, preferably a copper-titanium alloy. Procedure according to Claim 5 or 6th , characterized in that the wetting component is provided in the form of a casing (36) of primary powder particles (35). Method according to one of the preceding claims, characterized in that the metallic powder (17; 17b; 17c; 17d) has a particle size distribution of d ₅₀ between 10 µm and 100 µm. Method according to one of the preceding claims, characterized in that the metallic powder (17; 17b; 17c; 17d) comprises antimony, bismuth, gallium, germanium, lithium, silicon and / or tellurium. Method according to one of the preceding claims, characterized in that a different composition of the metallic powder (17d) is used to produce different ones of the metallization layers (M ₁ , M ₂ , M _3). Procedure according to Claim 10 , characterized in that at least the first metallization layer (M ₁ ) is produced with an increased proportion of a wetting component, in particular with an increased titanium proportion, compared to at least one further metallization layer (M ₂ , M _3). Procedure according to Claim 10 or 11 , characterized in that at least one of the further metallization layers (M ₂ , M ₃ ) is produced with an increased proportion of gold, aluminum, copper and / or silver compared to the first metallization layer, in particular an increased proportion of copper. Method according to one of the preceding claims, characterized in that the conductor structure (15; 15a; 15d) is produced on the ceramic substrate (16) under a protective gas atmosphere (18), in particular under an inert protective gas atmosphere, preferably under an argon atmosphere . Method according to one of the preceding claims, characterized in that the ceramic substrate (16) is heated to a temperature between 200 ° C and 700 ° C while the conductor structure (15; 15a; 15d) is being produced. Method according to one of the preceding claims, characterized by an aftertreatment step (30) for heat treatment of the circuit carrier (2; 2a), in particular in a temperature range between 200 ° C and 1080 ° C. Method according to one of the preceding claims, characterized in that the provision of the ceramic substrate (16) comprises the additive manufacturing of at least parts of the ceramic substrate (16), in particular of ceramic heat sinks. Procedure according to Claim 16 , characterized in that the additive manufacturing of at least parts of the ceramic substrate (16) takes place by lithography-based ceramic manufacturing. Circuit carriers, in particular for power electronics, produced according to one of the Claims 1 until 17th . Circuit carrier, in particular for power electronics, comprising - a ceramic substrate (16) and - a conductor structure (15; 15a; 15d) connected to the ceramic substrate (16) in a materially bonded manner, the conductor structure (15; 15a; 15d) having a plurality of _{has metallization layers (M 1} , M ₂ , M ₃ ) applied to the ceramic substrate (16), the metallization layers (M ₁ , M ₂ , M ₃ ) comprising a material which has an anomaly in density. Circuit carrier according to Claim 19 , characterized in that at least two of the metallization layers (M ₁ , M ₂ , M ₃ ) are not congruent in a plane running parallel to the surface (27) of the substrate (16).

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