Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
  • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
  • F28F21/081—Heat exchange elements made from metals or metal alloys
  • F28F21/085—Heat exchange elements made from metals or metal alloys from copper or copper alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
  • B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering or brazing
  • B23K35/0244—Powders, particles or spheres; Preforms made therefrom
  • B23K35/025—Pastes, creams or slurries
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550°C
  • B23K35/302—Cu as the principal constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
  • B23K35/3612—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents
  • B23K35/3613—Polymers, e.g. resins

Definitions

• the invention relates to a flux-free brazing paste for brazing copper and copper alloys.
• coolers essentially consist of brass pipes carrying the coolant and the heat-dissipating copper fins connected to them. During the production of the cooler, the components are put together and soldered together at the joints. The use of low-melting soft solders based on lead-lead alloys with a high lead content is still widespread.
• the brass tubes of the coolers are sprayed with an aqueous flux based on zinc chloride-ammonium chloride and then pre-soldered with the soft solder. After assembling coated pipes and copper fins, the complete cooler is immersed again in the flux solution and after drying in a continuous furnace soldered. The flux residues must be removed with water after the soldering process, otherwise the finished coolers will show signs of corrosion. This manufacturing process is no longer competitive from an economic and ecological point of view.
• the use of corrosive fluxes based on zinc chloride-ammonium chloride requires a high level of technical and financial expense in the treatment of waste water and disposal of the flux residues.
• Brazing with low-melting copper solders is an alternative to the production of soft-soldered copper-brass coolers.
• copper-phosphorus solders with a melting range of 710-880 ° C or silver-containing copper-phosphorus solders with working temperatures of around 700 ° are generally used C used.
• these solder alloys can only be used to a limited extent to connect the brass tubes and copper fins of the cooler, since the copper softens at the required soldering temperatures and already loses a large part of its strength.
• suitable hard solders have been specially developed for soldering copper-brass coolers. These hard solder alloys are described in more detail in the patents US 5,178,827, US 5,130,090 and US 5,378,294.
• solder alloys consist of copper-phosphorus alloys with melting point lowering Addition of nickel and possibly tin and manganese.
• the liquidus temperatures of these solder alloys are well below 700 ° C, which enables soldering processes with peak temperatures below the softening temperature of copper.
• These solders are self-flowing due to the phosphorus content and can be used in a protective gas atmosphere, preferably under nitrogen with low residual oxygen levels, for flux-free joining of copper and brass. Further information about these brazing alloys can be found in Adv. Mater.
• solder alloys have the disadvantage that they are very brittle and can therefore only be used in the form of rapidly cooled foils (meltspinning foils) or in powder form for soldering coolers. Meltspinning foils are out of the question for mass production due to cost reasons. In addition, the application of the foils during the assembly of the cooler components is very difficult to integrate into an online production.
• solders for the alternative use of these solders in powder form, it is expedient to provide them in the form of a paste in which the solder powder is dispersed in a binder system and which can be applied in liquid or semi-liquid form to the objects to be soldered.
• Solder pastes with a wide variety of solder alloys and binder systems are known and have been used for a long time. Solder pastes are sometimes contained in a system of organic binder and organic aqueous solvents in addition to the solder powder, usually flux additives.
• the essential criteria in the selection of the components of the binder system are that the paste remains stable and usable even over a long period of time and that the solder does not sediment irreversibly, that it can be applied well, in particular without running off from vertical surfaces, and that the binder system does the soldering process not disabled .
• the binder system In the case of high-melting brazing alloys in particular, the binder system must volatilize or burn off without residue, if possible without forming toxic or environmentally hazardous products.
• solder paste An important aspect when applying the solder paste is the application speed and drying time.
• the binders usually used in solder pastes have a drying time of several minutes when using high-boiling organic solvents. More volatile solvents such as alcohols or ketones dry faster, but emit highly flammable vapors, which require complex measures to be taken on the explosion protection systems.
• the binder has thermoplastic properties.
• the binder has thermoplastic properties.
• thermoplastic behavior can be used with thermoplastic behavior.
• Humidity reacts, which is also not prevented by the embedding in the binder, and as a result, the wetting and flow behavior of the solder deteriorates after a short storage period of the paste.
• the high affinity of the solder powder for oxygen also prevents the use of conventional binders, such as Cellulose, cellulose derivatives, polyethylene glycols etc., since the solder powder reacts with the oxygen-containing decomposition products of the binders during the heating process to form slag, which makes it difficult for the solder to flow. It has also been shown that even when using oxygen - free binders such as hydrocarbon resins etc. A good soldering result can only be achieved if the solder powder used has an oxygen content of less than 150 ppm.
• the invention was therefore based on the task of developing a thermoplastic organic binder system for oxygen-sensitive low-melting copper-phosphor solder alloy powders, which protects the solder from oxidation and also excellent soldering without the addition of fluxes when using solder powders with an oxygen content of over 150 ppm
• liquid binder-solder powder mixture should solidify again within a very short time after application and decompose without residue under a protective gas atmosphere.
• a binder system consisting of a mixture of polyisobutene with a relative molecular weight of 50,000 to 500,000 and paraffin with a melting range of 40 to 90 ° C.
• the invention thus relates to a flux-free brazing paste consisting of a finely divided solder based on a copper-phosphorus alloy with a working temperature not exceeding 700 ° C and a thermoplastic organic binder system, which is characterized in that the binder system consists of a mixture of polyisobutene with relative Molecular mass from 50,000 to 500,000 and paraffin with melting range from 40 to 90 ° C.
• the binder system according to the invention effectively and permanently protects the brazing powder based on a low-melting copper-phosphorus alloy against oxidation.
• it shows flux-like properties in that it can melt already surface oxidized solder powder with an oxygen content of over 150 ppm, for example up to an oxygen content of 300 ppm, in the soldering process without problems without slag formation.
• the binder system combines the advantageous thermoplastic properties with the problem-free residue-free removal in the heating process.
• the binder system preferably consists of a mixture of polyisobutene with a relative molar mass of 60,000 to 90,000 and paraffin with a melting range of 40 to 60 ° C.
• Particularly suitable solder alloys are those which consist of 10 to 20 atom% of phosphorus, 2 to 5 atom% of nickel, 0 to 15 atom% of tin, 0 to 5.5 atom% of manganese and the rest of copper.
• solder alloys are characterized by melting ranges lying essentially at about 600 to 650 ° C., so that their working temperature does not exceed 700 ° C. and they are used without problems for soldering copper and copper alloys can be.
• the brazing paste according to the invention advantageously contains 75 to 98% by weight of finely divided solder alloy and 25 to 2% by weight of thermoplastic organic binder. It preferably contains 80 to 95% by weight of finely divided solder alloy and 20 to 5% by weight of thermoplastic binder.
• the qualitative and quantitative composition of the binder system is expediently chosen so that, when mixed with the solder powder, there results a hard solder paste which is solid at room temperature and changes into the molten state from a temperature of 40 ° C.
• thermoplastic organic binder system expediently consists of 20 to 70% by weight of polyisobutene and 80 to 30% by weight of paraffin. It preferably consists of 30 to 50% by weight of polyisobutene and 70 to 50% by weight of paraffin.
• Mixtures of 20 to 70% by weight of polyisobutene with a relative molecular weight of 50,000 to 500,000 and 80 to 30% by weight of paraffin with a melting range of 40 to 90 ° C. can advantageously be used as thermoplastic organic binder systems for brazing powder based on copper-phosphorus alloys.
• Brazing pastes according to the invention are particularly suitable for brazing components on copper and / or copper alloys. In particular, they can be used very advantageously in the production of coolers for internal combustion engines.
• the method for soldering components made of copper and / or copper alloys is carried out in such a way that a brazing paste is applied to the components at least at the points to be joined at a temperature between 40 and 90 ° C the invention applies, optionally in an intermediate step by cooling to a temperature below 40 ° C, the solder paste coating solidified and then heated for soldering to the working temperature of the solder alloy, the organic binder system being removed without residue during the heating process.
• Viscosity 70 ° C, Brookfield RVT: 50 Pa-s.
• polyisobutene 3.5% by weight polyisobutene, molecular weight 85,000 (Oppanol®B15, BASF AG);
• Viscosity 70 ° C. Brookfield RVT: 35 Pa • s.
• the solder paste according to Example 1 is applied to a brass sheet at 70 ° C. and then cooled to room temperature for solidification.
• the soldering is carried out in a continuous furnace under nitrogen at 650 ° C. A smooth, shiny solder layer is obtained.
• solder powder Cu75nl6P5Ni4 with oxygen content of 300 ppm is slurried in ethanol and spread on a brass sheet. After the solder layer has dried, the soldering is carried out in a continuous furnace under nitrogen at 650 ° C. The solder joints show insufficient solder flow and black slag residues.
• the solder powder is in a 3% aqueous solution

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Electric Connection Of Electric Components To Printed Circuits (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Nonmetallic Welding Materials (AREA)
• Powder Metallurgy (AREA)

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• 1997
  • 1997-10-24 DE DE19747041A patent/DE19747041A1/de not_active Withdrawn
• 1998
  • 1998-09-02 KR KR1020007004302A patent/KR100666836B1/ko not_active Expired - Fee Related
  • 1998-09-02 BR BR9812961-9A patent/BR9812961A/pt not_active IP Right Cessation
  • 1998-09-02 ES ES98948897T patent/ES2177061T3/es not_active Expired - Lifetime
  • 1998-09-02 CN CN98810504A patent/CN1111463C/zh not_active Expired - Fee Related
  • 1998-09-02 DE DE59804087T patent/DE59804087D1/de not_active Expired - Lifetime
  • 1998-09-02 AT AT98948897T patent/ATE217233T1/de not_active IP Right Cessation
  • 1998-09-02 WO PCT/EP1998/005564 patent/WO1999021679A1/de not_active Ceased
  • 1998-09-02 US US09/529,972 patent/US6342106B1/en not_active Expired - Fee Related
  • 1998-09-02 AU AU95355/98A patent/AU9535598A/en not_active Abandoned
  • 1998-09-02 EP EP98948897A patent/EP1032483B1/de not_active Expired - Lifetime
  • 1998-09-02 JP JP2000517819A patent/JP4215390B2/ja not_active Expired - Fee Related

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