Abstract: A lead-free solder preform includes a core layer and adhesion layer coated over surfaces of the core layer, where the preform delivers the combined merits from constituent solder alloys of the core and adhesion layers to provide both high temperature performance and improved wetting in high-temperature solder applications such as die attach. The core layer may be formed of a Bi Alloy having a solidus temperature above 260° C., and the adhesion layer may be formed of Sn, a Sn alloy, a Bi alloy, In, or an In alloy having a solidus temperature below 245° C. The solder preform may be formed using techniques such as: (1) electroplating a core ribbon with an adhesion material, (2) cladding an adhesion material foil onto a core ribbon, and/or (3) dipping a core ribbon in a molten adhesion alloy bath to allow thin layers of adhesion material to adhere to a core ribbon.

Abstract: An exhaust manifold comprises a plurality of exhaust intake conduits structured to be fluidly coupled to an engine and receive exhaust gas from a corresponding cylinder of the engine. At least one exhaust intake conduit provides a reduction in an exhaust intake conduit cross-sectional area from an inlet to an outlet. A plurality of bends are each defined by a respective one of the exhaust intake conduit outlets. An exhaust intake manifold is fluidly coupled to the exhaust intake manifold and defines an exhaust intake manifold flow axis. Each of the plurality of bends is shaped so as to define an angle of approach of exhaust gas flowing therethrough. A first angle of approach of the first bend relative to the exhaust intake manifold flow axis is smaller than a second angle of approach of an inner second bend.

Abstract: An electrode for use in instruments capable of measuring the electrophoretic mobility of particles in solution is disclosed. The electrode is comprised of an inexpensive support member, generally made of titanium, onto a flat surface of which has been connected, generally by microwelding, a flat electrically conductive but chemically inert foil member, preferably platinum. A uniform texture can be generated on the exposed surfaces of the electrode by various means including tumbling the electrode with an abrasive. An oxide layer can be generated on the support member by soaking the composite electrode in an appropriate medium, protecting the exposed surface of the support member from fluid contact with the sample solution, while the foil member, unaffected by the oxidation process, is able to contact the sample solution.

Abstract: A method of manufacturing a piezoelectric element includes: forming a patterned mask layer over a substrate, in which the patterned mask layer has an opening exposing a portion of the substrate; forming a piezoelectric element in the opening; and removing the patterned mask layer to obtain the piezoelectric element, in which the piezoelectric element has a central portion and a peripheral portion adjacent to the central portion, and the peripheral portion has a maximum height greater than a height of the central portion.

Abstract: A balance shaft for balancing forces of inertia and/or moments of inertia of a reciprocating-piston internal combustion engine, including: at least one elongate main body; at least one bearing seat, disposed on the elongate main body for the mounting of a radial bearing. In the center point of the bearing seat there is provided the rotational axis of the balance shaft. The elongate main body may be formed of an integral tubular element, and the center of mass of the elongate main body may lie outside the rotational axis of the balance shaft.

Abstract: In one aspect, the present subject matter is directed to a gas turbine sealing assembly that includes a first static gas turbine wall and a second static gas turbine wall. A seal is disposed between the first static gas turbine wall and the second static gas turbine wall. The seal includes a first seal layer defining a first seal layer aperture extending therethrough. A second seal layer defines an elongated slot extending therethrough. The elongated slot includes a first end and a second end. A third seal layer defines a third seal layer aperture extending therethrough. The second seal layer is positioned between the first seal layer and the third seal layer such that the first seal layer aperture is in fluid communication with the first end and the third seal layer aperture is in fluid communication with the second end.

Abstract: An electrode for use in instruments capable of measuring the electrophoretic mobility of particles in solution is disclosed. The electrode is comprised of an inexpensive support member, generally made of titanium, onto a flat surface of which has been connected, generally by microwelding, a flat electrically conductive but chemically inert foil member, preferably platinum. A uniform texture can be generated on the exposed surfaces of the electrode by various means including tumbling the electrode with an abrasive. An oxide layer can be generated on the support member by soaking the composite electrode in an appropriate medium, protecting the exposed surface of the support member from fluid contact with the sample solution, while the foil member, unaffected by the oxidation process, is able to contact the sample solution.

Abstract: A semiconductor component includes a semiconductor package having a mountable face, a bump, and a coating part. The bump is made of first solder and is formed on the mountable face. The coating part formed of a first composition containing solder powder made of second solder, a flux component, and a first thermosetting resin binder coats the top end of the bump.

Abstract: A welding method, including: forming a molten solder in a solder bath, forming a dynamic flow of the molten solder from the solder bath, and contacting an object to be welded with the dynamic flow of the molten solder and conducting welding. The surface of the molten solder includes a reduction layer. The oxygen content of the molten solder is below 10 ppm.

Abstract: A method of forming a metal bonding layer includes forming first and second bonding metal layers on one surfaces of first and second bonding objects, respectively. The second bonding object is disposed on the first bonding object such that the first bonding metal layer and the second bonding metal layer face each other. A eutectic metal bonding layer is formed through a reaction between the first and second bonding metal layers. At least one of the first bonding metal layer and the second bonding metal layer includes an oxidation prevention layer formed on an upper surface thereof. The oxidation prevention layer is formed of a metal having an oxidation reactivity lower than an oxidation reactivity of the bonding metal layer on the upper surface which the oxidation prevention layer is disposed.

Abstract: A process for joining two parts by braze-welding, including forming a joint, between two surfaces to be joined, and a fillet. The composition of the filler metal used to form the fillet is different from that used to form the joint, to provide the joint with a higher ductility. The method can, for example, be applied to production of high-pressure compressor guide-vane sectors for a turbomachine.

Abstract: The invention relates to a method for carrying out solder connections in a technologically optimized manner, in particular lead-free solder connections. At least one of the joining partners provides the solder required for the connection. A flux is used in order to activate the solder, and the electric and mechanical connection is carried out by means of a soldering process under the effect of heat and by melting the solder/flux mixture with the inclusion of a subsequent cooling phase. According to the invention, the joining partners and the solder are heated to a temperature below the activation temperature of the solder and the flux in a first temperature treatment phase. Another heating process is then carried out to a temperature above the activation temperature of the flux up to the upper melting range of the solder in a second temperature treatment phase, wherein the solder melts and begins to connect to the respective joining partners.

Abstract: The present invention ensures a good bonding state between the electrode terminals of electronic components and the electrodes of a substrate, and achieves an increase in productivity and a downsizing of the substrate. The present invention includes: an applying step of applying a metal fine powder paste on each of multiple electrodes that are provided on a substrate; a component placing step of placing multiple electronic components with different heights, on the multiple electrodes, respectively; an organic film placing step of placing an organic film on the multiple electronic components; an organic film compressing step of applying a first pressure to the electronic component side with a pressing member and equalizing the height of the organic film; and a bonding step of applying a second pressure to the electronic component side with a compressing member on heating for a predetermined time and sintering the metal fine powder paste.

Abstract: A bonded body made of an aluminum alloy and a copper alloy and obtained by employing the aluminum alloy as one member to be bonded and the copper alloy as the other member to be bonded, the one bonded member and the other bonded member being bonded to each other through metallic connection, wherein the one bonded member is made of comprising an aluminum alloy containing Cu: 3.0 mass % to 8.0 mass % and Si: 0.1 mass % to 10 mass % with balance being Al and unavoidable inevitable impurities, and satisfying the chemical formula: C+2.4×S?7.8 where C (mass %) is a Cu concentration and S (mass %) is a Si composition concentration is satisfied, and the other bonded member comprises a copper alloy having a higher solidus temperature than the one bonded member. A bonding method for the bonded body is provided.

Abstract: Disclosed herein is a printed circuit board, including: a substrate including an insulation layer in which a cavity is formed; an electronic component mounted in the cavity of the substrate and having connection terminals; an insulation material layer formed on one side of the substrate to bury the electronic component; a first circuit layer formed on the other side of the substrate and including a connection pattern connecting with the connection terminals of the electronic component; and a second circuit layer formed on the insulation material layer. The printed circuit board is advantageous in that it can prevent the warpage thereof and ensure the reliability of electrical connection between an electronic component and a circuit layer by adjusting the thickness, thermal expansion coefficient and elastic modulus of insulation layer or the insulating material.

Abstract: A copper nanorod thermal interface material (TIM) is described. The copper nanorod TIM includes a plurality of copper nanorods having a first end thermally coupled with a first surface, and a second end extending toward a second surface. A plurality of copper nanorod branches are formed on the second end. The copper nanorod branches are metallurgically bonded to a second surface. The first surface may be the back side of a die. The second surface may be a heat spread or a second die. The TIM may include a matrix material surrounding the copper nanorods. In an embodiment, the copper nanorods are formed in clusters.

Abstract: A soldering method capable of alleviating positional displacement between substrates even though a step of removing flux can be omitted is provided. A temporary bonding agent 55 is applied onto multiple substrates 50a, 50b, and a heater 33 heats the substrates while the substrates are temporarily bonded with the temporary bonding agent 55 interposed therebetween, and before the solder 54 is melted or while the solder 54 is melted, the temporary bonding agent 55 is evaporated, and the substrates 50a, 50b are bonded with solder with the melted solder 54 interposed therebetween.

Abstract: A method for bonding a heat-conducting substrate and a metal layer is provided. A heat-conducting substrate, a first metal layer and a preformed layer are provided. The preformed layer is between the heat-conducting substrate and the first metal layer. The preformed layer is a second metal layer or a metal oxide layer. A heating process is performed to the preformed layer in an oxygen-free atmosphere to convert the preformed layer to a bonding layer for bonding the heat-conducting substrate and the first metal layer. The temperature of the heating process is less than or equal to 300° C.

Abstract: A composition may have metal nanoparticles having a diameter of 20 nanometers or less and have a fusion temperature of less than about 220° C. A method of fabricating the metal nanoparticles may include preparing a solvent, adding a precursor with a metal to the solvent, adding a first surfactant, mixing in a reducing agent, and adding in a second surfactant to stop nanoparticle formation. Copper and/or aluminum nanoparticle compositions formed may be used for lead-free soldering of electronic components to circuit boards. A composition may include nanoparticles, which may have a copper nanocore, an amorphous aluminum shell and an organic surfactant coating. A composition may have copper or aluminum nanoparticles. About 30-50% of the copper or aluminum nanoparticles may have a diameter of 20 nanometers or less, and the remaining 70-50% of the copper or aluminum nanoparticles may have a diameter greater than 20 nanometers.

Abstract: Method for producing coated assembly parts for chemical device elements including the following steps: (a) the formation of an initial assembly including a steel support part, a zirconium or zirconium alloy coating, and at least one brazing material between the support part and the coating; (b) the insertion of the initial assembly into a brazing chamber with a controlled atmosphere; (c) the formation of a controlled atmosphere in said chamber; and (d) the reheating of said assembly to a temperature at least equal to the melting temperature of said brazing material.

Abstract: A method of welding alloys having a ductility drop temperature range to limit strain-age cracking. The method involves the use of a welding device to weld a weld area of an article while maintaining temperatures throughout the weld area and a heat affected zone adjacent the weld area within a non-crack sensitive temperature range that is above a ductility drop temperature range of the alloy being welded. During welding, the temperatures of the weld area and the heat affected zone are predominantly controlled with heat input from the welding device. Once the welding has been terminated, the weld area and the heat affected zone are cooled from the non-crack sensitive temperature range through the ductility drop temperature range to a temperature below the ductility drop temperature range of the alloy.

Abstract: The aim of the invention is to provide a fluxing agent for soldering components, which creates one or more specific surface characteristics during the soldering process itself, thus obviating the need for the surface treatment process that is conventionally carried out after the soldering process. To achieve this, nanoparticles are added to a base substance.

Abstract: A method of bonding two members including an aluminum alloy material as one member, and an aluminum alloy material or a pure aluminum material as the other member, the method being characterized in: that the aluminum alloy material for the one member and the aluminum alloy material for the other member are composed of an aluminum alloy containing Mg of not more than 0.5 mass %; and that a bonding process is carried out in a furnace having a non-oxidizing atmosphere at a temperature, at which a ratio of a mass of liquid phases generated in the aluminum alloy material defined as the one member to the total mass of the aluminum alloy material falls within a range from 5% to 35%, on the condition that there is either a coated fluoride-based flux or a coated chloride-based flux between both of the members to be bonded.

Abstract: The present invention relates to a method of joining a hub 11 and a shroud 12 of an impeller 10, either one of which has blades 13 integrally formed thereon, by welding. During the welding, in an upright state in which the hub 11 is placed to face a mount surface, the hub 11 and the shroud 12 are placed on top of each other to form an assembled body 10. Welding is performed on the assembled body 10 covered with a heat insulating jacket 30(a to g), the jacket 30 covering the assembled body 10 except an open region (OP) and an inflow port 14IN required for welding. When welding of one open region OP is completed, a new open region OP is formed by moving the heat insulating jacket 30 with respect to the assembled body, and then the next welding is performed.

Abstract: An exemplary heat dissipation device includes a fin assembly, a heat pipe, and a protective member. The fin assembly includes stacked fins and air passages between fins. Each fin includes a main body, an extending hole defined in the main body, and a flange extending from the main body around the extending hole. The heat pipe is received in the extending holes of the fins and abuts the flanges of the fins. The protective member includes a plurality pairs of elastic arms. Each pair of elastic arms is sandwiched between a free end of the flange of a corresponding fin and the main body of a corresponding adjacent fin to prevent solder associated with the heat pipe from flowing into the corresponding air passage.

Abstract: A semiconductor device is provided which has internal bonds which do not melt at the time of mounting on a substrate. A bonding material is used for internal bonding of the semiconductor device. The bonding material is obtained by filling the pores of a porous metal body having a mesh-like structure and covering the surface thereof with Sn or an Sn-based solder alloy.

Abstract: A method for manufacturing a rotor by welding a plurality of elements together is described. The elements have a body with cavities and surfaces to be welded to surfaces of adjacent elements. According to the method, the elements are vertically stacked one above the other to form a pile with facing surfaces to be welded together defining slots. The cavities of adjacent elements define bores that extend within the pile. Then, adjacent elements are welded together within the slots. The bore is purged with an inert gas or mixture during welding. The slots are welded at an upper part of the bore before the slots at a lower part of the bore, and a slot at the upper part of the bore is welded last.

Abstract: The present invention relates to a brazing method for a component (100) of an air-conditioning circuit comprising a fluid refrigerant receiver (200), said receiver containing a desiccator (210) for said fluid refrigerant. Said method includes the steps consisting of: equipping said receiver (200) with confinement means (221, 222) capable of insulating said desiccator (210) from said component (100); assembling and brazing together said receiver (200) and said component (100); releasing said confinement means (221, 222). The invention also relates to a fluid receiver intended in particular for implementing such a method, with application to the air conditioning of motor vehicles.

Abstract: A method of joining at least two parts includes steps of dispersing a joining material comprising a multi-phase magnetic metal-aluminum powder at an interface between the at least two parts to be joined and applying an alternating magnetic field (AMF). The AMF has a magnetic field strength and frequency suitable for inducing magnetic hysteresis losses in the metal-aluminum powder and is applied for a period that raises temperature of the metal-aluminum powder to an exothermic transformation temperature. At the exothermic transformation temperature, the metal-aluminum powder melts and resolidifies as a metal aluminide solid having a non-magnetic configuration.

Abstract: A flux composition includes an alditol (A) and a polymer (B) which has a repeating structural unit represented by Formula (1): (wherein R1 is a hydrogen atom or a methyl group, and Z is a hydroxyl group, an oxo group, a carboxyl group, a formyl group, an amino group, a nitro group, a mercapto group, a sulfo group, an oxazoline group, an imide group, a group having an amide structure, or a group having any of these groups). The flux composition allows substrates with bumps such as pillar bumps to be electrically connected to each other by reflowing of such bumps without causing any exposure of the bumps from the flux during reflowing, thus resulting in a satisfactory electrically connected structure.

Abstract: A reflow oven chamber assembly includes a housing disposed within a reflow oven chamber, heating elements disposed in the housing, and compression box assemblies disposed in the housing. The compression box assembly includes a compression box housing having an intake port located adjacent the heating element, an intake duct disposed in the compression box, and a diffuser plate disposed above the intake duct. The intake duct has an inlet opening in fluid communication with the intake port of the compression box housing and an outlet opening. The compression box assembly draws heated air into the compression box housing from the reflow oven chamber through the intake port and into the inlet opening of the intake duct and exhaust air out of the outlet opening of the intake duct to the diffuser plate. A method of distributing heated air within a reflow soldering oven is further disclosed.

Abstract: A reflow apparatus, where formic acid is used for cleaning a surface of a solder electrode on a processing target, is disclosed. The reflow apparatus includes a processing chamber, a formic acid introduction mechanism for supplying an atmosphere gas containing formic acid to the processing chamber, and a shielding member that is made of a material having corrosion resistance against formic acid. The shielding member is arranged between a reflow processing section of the processing chamber and an inner wall of the processing chamber. In place of or in addition to the shielding member, the reflow apparatus may include a heater for decomposing residual formic acid.

Abstract: A billet includes a solid steel body and an alloy cladding. The cladding may include a square tube in which the body is inserted with an interface at which the cladding becomes bonded to the body when the billet is heated and rolled or otherwise worked into a ferrous product. At least one element composed of a mass of finely divided scavenging aluminium, titanium or magnesium, is placed in the tube adjacent the body and separate from the interface. The elements are advantageously compressed into briquettes which scavenge oxygen from residual air at the interface to prevent oxidation of the cladding at the interface. The tube may be closed to prevent gases outside the billet from penetrating to the interface. Alternatively, reliance may be placed on the briquettes to scavenge oxygen from the residual air and also from atmospheric air and furnace gases before they can penetrate to the interface.

Abstract: A solder-flux composition is sprayed onto a substrate by rotating the solder-flux composition inside a spray cap, and before the solder-flux liquid exits the spray cap, perturbing the flow thereof with a fluid.

Abstract: One embodiment of the present invention is a unique method for brazing an assembly. Another embodiment is a unique method of heat treating an object. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for heat treating and/or brazing. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith.

Abstract: A surface treatment process for a circuit board is provided. The circuit board includes a substrate, a first circuit layer disposed on an upper surface of the substrate, and a second circuit layer disposed on a lower surface of the substrate. The first circuit layer is electrically connected to the second circuit layer. In the surface treatment process for the circuit board, a first oxidation protection layer and a second oxidation protection layer are respectively formed on a portion of the first circuit layer and a portion of the second circuit layer by immersion. Afterwards, the first circuit layer exposed by the first oxidation protection layer is subjected to black oxidation to form a black oxide layer. The thickness of the first oxidation protection layer is thinner than or equal to the thickness of the black oxide layer.

Abstract: A method of joining at least two parts includes steps of dispersing a joining material comprising a multi-phase nanocrystalline magnetic metal-aluminum powder at an interface between the at least two parts to be joined and applying an alternating magnetic field (AMF). The AMF has a magnetic field strength and frequency suitable for inducing magnetic hysteresis losses in the metal-aluminum powder and is applied for a period that raises temperature of the metal-aluminum powder to an exothermic transformation temperature. At the exothermic transformation temperature, the metal-aluminum powder melts and resolidifies as a metal aluminide solid having a non-magnetic configuration.

Abstract: A soldering preform for soldering in a reducing atmosphere is substantially disc-shaped and has two soldering surfaces each for being in contact with an object to be soldered, respectively, and with at least one recess on at least one soldering surfaces for constituting a channel open to a surface of the object.

Abstract: Electronic assemblies including coreless substrates and their manufacture using electrolytic plating, are described. One method includes providing a core comprising a metal, and forming a dielectric material on the core. The method also includes forming vias in the dielectric material, the vias positioned to expose metal regions. The method also performing an electrolytic plating of metal into the vias and on the metal regions, wherein the core is electrically coupled to a power supply during the electrolytic plating of metal into the vias and delivers current to the metal regions. The method also includes removing the metal core after the electrolytic plating of metal into the vias. Other embodiments are described and claimed.

Abstract: A packaged electronic device includes a submount, a bonding pattern on the submount, and an electronic chip on the bonding pattern. A periphery of the electronic chip defines a die mounting region of the submount. The bonding pattern includes a bonding area within the die mounting region and at least one channel that extends from within the die mounting region to a region of the submount outside the die mounting region.

Abstract: In the soldering method, metal-powder-contained flux is disposed between bumps and circuit electrodes when electronic parts are mounted by soldering, the metal powder comprising a core metal formed of metal such as tin and zinc and a surface metal covering surfaces of the core metal formed of noble metal such as gold and silver. Accordingly, metal powder will not remain as residue that is liable to cause migration after the reflow process, and it is possible to assure both soldering effect and insulation effect.

Abstract: A method for manufacturing an electronic component module is performed such that a shield layer can be formed as a thin film and an electronic component can be effectively shielded. A collective substrate including a plurality of electronic component modules including a plurality of electronic components is batch-sealed with a resin. A cut section is formed from a top surface of the sealed resin to a position that reaches a grounding electrode arranged in the substrate at a boundary section of the electronic component module so as to expose the grounding electrode. A conductive paste is applied on side surfaces and the top surface. Then, a conductive thin film is formed by spin coating, and the electronic component module is cut.

Abstract: The aim of the invention is to provide a fluxing agent for soldering components, which creates one or more specific surface characteristics during the soldering process itself, thus obviating the need for the surface treatment process that is conventionally carried out after the soldering process. To achieve this, nanoparticles are added to a base substance.

Abstract: A method is provided for bonding a die comprising a solder layer which has a melting point Tm. A bond head is heated to a bond head setting temperature T1, which is higher than Tm, and a substrate is heated to a substrate setting temperature T2, which is lower than Tm. The bond head then picks up the die and heats the die towards temperature T1 so as to melt the solder layer. The solder layer of the die is pressed onto the substrate so as to bond the die to the substrate, and thereafter the bond head is separated from the die so that the solder layer is cooled towards T2 and solidifies.

Abstract: Soldering with lead-free alloys is enhanced by use of two additives to a molten solder bath. One additive is an oxygen barrier fluid that floats on or envelops a bath. Another additive is an oxygen or metal oxide scavenger in the bath. Exemplary scavengers include metals with a higher free energy of oxide formation than oxide of tin, reducing gas, or an electrode immersed in the bath. The oxygen barrier may be an organic liquid, preferably polar in nature, which forms at least a monomolecular film over static surfaces of the bath. An exemplary soldering process is wave soldering of printed circuit boards.

Abstract: Provided is a soldering flux in which the volatilized amount in reflowing is reduced to enable soldering with a small environmental load while suppressing the stickiness of the flux residue to ensure a high reliability, as well as a solder paste composition and a soldering method using the same. The soldering flux comprises a base resin, an activating agent, and a solvent, wherein the solvent comprises an organic acid anhydride being liquid form at 20° C. or higher and a polyhydric alcohol being liquid form at 20° C. or higher, and when the acid value and the content of the organic acid anhydride is AV (mgKOH/g) and WA(g), respectively, and the hydroxyl value and the content of the polyhydric alcohol is OHV (mgKOH/g) and WOH(g), respectively, then AV×WA:OHV×WOH=1:0.4 to 0.6.

Abstract: A guide wire includes a wire member having a first wire disposed on the distal side of the guide wire, and a second wire disposed on the proximal side from the first wire. The second wire is made from a material having an elastic modulus larger than that of the first wire. For example, the first wire is made from a superelastic alloy, and the second wire is made from a stainless steel. The first wire is joined to the second wire at a welded portion by welding. A coil is disposed on the distal side from the first wire. A cover layer is formed on the outer peripheral surface of the wire member in such a manner as to cover at least the welded portion. The cover layer is made from a material capable of reducing the friction of the cover layer, for example, a fluorocarbon resin or a hydrophilic material, to thereby improve the sliding performance of the guide wire. Such a guide wire is excellent in operationality and kink resistance.

Abstract: A method for setting a protective coating on the inner wall of a tube includes providing a cylindrical sleeve, then setting on the outer surface of the sleeve a layer of a thermo fusible material, then machining the sleeve to provide it with an external diameter corresponding to the tube internal diameter, positioning the sleeve in the tube, and finally soldering the sleeve on the tube by applying heat.

Abstract: Avoiding contaminant generation within a hard disk drive due to increased temperatures during a solder reflow process is described. Energy from a beam of energy that is directed toward a plurality of polyimide regions is received. Each of the plurality of polyimide regions are disposed adjacent to at least one solder pad. The plurality of polyimide regions and the at least one solder pad comprises a first component of a hard disk drive. Then, a portion of the energy is reflected away from the plurality of polyimide regions to prevent an absorption of the portion by the plurality of polyimide regions and a burning of the plurality of polyimide regions.

Abstract: An engine wall structure includes an inner wall to which hot gas is admitted during engine operation, an outer wall, which is colder than the inner wall during engine operation, and at least two webs that connect the inner wall with the outer wall and delimit a cooling duct between the walls. The webs are mainly formed by a first material and the inner wall is mainly formed by a second material of other composition and other heat conductivity than the first material.