Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
• • 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
  • B23K1/00—Soldering, e.g. brazing, or unsoldering
  • B23K1/20—Preliminary treatment of work or areas to be soldered, e.g. in respect of a galvanic coating
  • B23K1/206—Cleaning
• • 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
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/36—Electric or electronic devices
  • B23K2101/42—Printed circuits
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
  • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
  • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
  • H05K3/3489—Composition of fluxes; Methods of application thereof; Other methods of activating the contact surfaces

Definitions

• the present invention relates to a method of surface treatment by the dry route of at least one portion of metal surface, of the kind where the portion is treated at a pressure close to atmospheric pressure with a treatment gas comprising excited or unstable.
• Such surface treatments can, for example, occur during the production or recovery processes for flat products or hollow bodies, in the production of electronic circuits such as printed circuit boards, to perform cleaning or fluxing, degreasing or still surface activation, often before a subsequent process, which may for example be annealing, 1 * plating of zinc, aluminum, tin or their alloys, soldering (for example of electronic components on the wafer circuit board), or the deposition of organic coatings such as varnishes or paints, or inorganic coatings such as nitrides or films based on silicon.
• these steps for treating metal surfaces include pickling, cleaning, deburring of connection holes (“desmearing”) or fluxing before tinning or soldering.
• a solder paste containing a mixture of metal alloy and flux is deposited on the printed circuit at the component connection locations, then the components are placed on the plate.
• the plate provided with the components is then inserted into a reflow oven so as to provide an amount of heat necessary to allow the melting of the metal alloy, as well as the activation of the fluxing element contained in the paste.
• Wave soldering consists in bringing the plates carrying the electronic components to be brazed into contact with one or more waves of liquid solder alloy obtained by circulation of a solder bath contained in a tank, by means of a buzzard.
• the circuits are previously fluxed in an area upstream of the wave soldering machine, using a flux spray or a flow foam, then preheated so as to activate the previously deposited fluxes, so as to clean the surfaces to be brazed, to remove oxides, organic contaminants.
• One of the objectives of the present invention is to propose such improvements.
• this objective is achieved in that the excited or unstable species have a speed component substantially perpendicular to the surface.
• the subject of the invention is therefore a method of surface treatment by the dry route of at least one portion of metal surface, according to which the portion is treated at a pressure close to the pressure atmospheric by a flow of process gas comprising excited or unstable species, characterized in that the pressure of the process gas on the metal surface is increased locally so as to force the chemical species to move in a direction substantially perpendicular to said surface.
• the process according to the invention can also include one or more of the following characteristics: - the treatment gas is substantially free of electrically charged species; the treatment gas is obtained from a primary gas mixture and, where appropriate, from an adjacent gas mixture, the primary gas mixture being obtained at the gas outlet of at least one apparatus for forming excited gas species or unstable, in which an initial gas mixture comprising an inert gas and / or a reducing gas and / or an oxidizing gas has been transformed, the adjacent mixture not having passed through the apparatus; the flow of treatment gas being emitted in the direction of the surface in a direction generally perpendicular thereto, and comprising, at the periphery of the excited or unstable particles animated by a movement in a direction substantially tangent to the surface, the pressure the flow of process gas on the surface is increased at the periphery of the flow;
• the pressure of the treatment gas on the surface is increased by means of at least one flow of entrainment gas injected perpendicular to the surface; - the entrainment gas comprises nitrogen;
• the surface portion to be treated being arranged " in a treatment chamber, the pressure of the treatment gas on the surface is increased by means of at least one fan turned towards the surface so as to force the flow of gas of treatment to strike the surface in a direction substantially perpendicular to the latter;
• the treatment gas comprising the excited or unstable chemical species is produced from an initial reducing gas mixture comprising nitrogen and hydrogen.
• An example of an apparatus for forming excited or unstable gaseous species is described in the document EP-658391 already cited.
• the invention also relates to a method of wave soldering of electronic components on an electronic circuit, during which:
• the components are placed on connection locations provided on the circuit,
• a circuit fluxing operation is carried out by treatment of the latter, at a pressure close to atmospheric pressure, by means of a flow of treatment gas comprising excited or unstable chemical species, and
• the circuit carrying the components is brought into contact with at least one wave of a solder alloy, characterized in that during the fluxing operation of the electronic circuit, the pressure of the treatment gas is locally increased on the circuit so as to force the chemical species to move in a direction substantially perpendicular to the circuit.
• the invention also relates to an apparatus for treating at least a portion of metal surface by the dry route, "for the implementation of a method as defined above, characterized in that it comprises a source of treatment gas comprising excited or unstable chemical species, a device for conveying parts comprising said at least one portion of metal surface, making it possible to bring the parts into contact with a flow of treatment gas, characterized in that it comprises means for locally increasing the pressure of the treatment gas on each part, so as to force the chemical species to move in a direction substantially perpendicular to the latter.
• the invention also relates to a wave soldering device of electronic components on an electronic circuit, for the implementation of a method as defined above, characterized in that it comprises a device for conveying circuits through at least one device for fluxing circuits, by treatment of the latter by means of a flow of treatment gas comprising excited or unstable chemical species, said circuits carrying on at least one of their faces the components to be brazed on connection locations for the latter, then through a tank containing a solder alloy for soldering the components, and in that at least one of said fluxing devices includes means for locally increasing the pressure of the gas flow from treatment on each circuit, so as to force the chemical species to move in a direction substantially perpendicular to the latter.
• FIG. 1 is a schematic representation of a wave soldering apparatus according to l 'invention
• FIG. 2 is a schematic sectional view of a device for forming excited or unstable chemical species used in the constitution of fluxing device of the wave soldering apparatus of Figure 1;
• FIG. 3 represents a first embodiment of the means for locally increasing the pressure of the treatment gas on a part;
• FIG. 4 illustrates a second embodiment of the means for locally increasing the pressure of the treatment gas on a part.
• a wave soldering device comprises for the embodiment shown a device 10 for conveying circuits 12 (here for example printed circuit boards), a first station 14 for preheating the wafers, to a device 16 for processing the wafers 12 before brazing, by treatment of the latter with excited or unstable chemical species, then to a station 18 for wave soldering at the level of which the wafers, carrying the electronic components to be soldered, are brought into contact with at least one wave of a solder alloy.
• the conveying device 10 comprises one or more transfer belts, such as 20, illustrated in phantom in this figure, on which the printed circuit boards 12 are arranged.
• Each plate 12 is here provided with a set of through holes in which are inserted the tabs of the electronic components, such as 22 and 24, which should be soldered. As can be seen in Figure 1, the carpet
• the plates 12, disposed on the mat 20 are first transferred from the first preheating station 14 at which an appropriate heat treatment device 28 is disposed, then to the second fluxing station 16 at which the wafers undergo a decontamination and deoxidation operation by bringing the wafers into contact with excited or unstable gaseous species.
• the plates thus flowed are then brought into contact with at least one wave 30 of solder alloy, at the level of the soldering station 18, which wave 30 is obtained by pumping a solder bath contained in a tank 32, through of a nozzle 34.
• the excited or unstable gaseous species, coming to treat the wafers 12 at the fluxing station 16, are here obtained by passing an appropriate initial gas, for example a reducing gas mixture containing for example nitrogen and hydrogen, through a device, such as 36, for forming excited or unstable chemical species, by passing the initial gas through an electrical discharge.
• an appropriate initial gas for example a reducing gas mixture containing for example nitrogen and hydrogen
• each device 36 for forming excited or unstable chemical species comprises, for the embodiment shown, a first tubular electrode 37, formed for example by an internal face of a metal block 38, and in which is concentrically arranged an assembly formed of a tube of dielectric material 40 for example ceramic, on the internal face of which is deposited, by metallization, a second electrode 41 excessively thickened in Figure 2, to improve clarity.
• the dielectric tube 40 and the second electrode 41 define, with the first electrode 37, a tubular gas passage 42, and, internally, an internal volume 44 in which a refrigerant is circulated.
• the block 38 comprises, diametrically opposite, two longitudinal slots 46 and 48 respectively forming the inlet of the initial gas to be excited in the passage 42 and the output of the treatment gas flow comprising the excited or unstable gaseous species.
• the block 38 also advantageously comprises, at the periphery of the first electrode 37, a plurality of conduits, such as 50, for the passage a refrigerant, for example water.
• the gas inlet slot 46 communicates with a homogenization chamber 52 formed in a housing 54 attached to the block 38 and comprising a pipe 56 for supplying initial gas.
• the module is completed by an electric generator 58 at high voltage and high frequency intended to generate a discharge in the gaseous mixture circulating in the gas passage 42 so as to cause, an excitation of the gaseous molecules entering into its constitution and thus generating at output 48, a treatment gas mixture comprising excited or unstable chemical species but being substantially free of electrically charged species, which deoxidize and decontaminate the external surface of the printed circuit boards 20 (FIG. 1).
• an electric generator 58 at high voltage and high frequency intended to generate a discharge in the gaseous mixture circulating in the gas passage 42 so as to cause, an excitation of the gaseous molecules entering into its constitution and thus generating at output 48, a treatment gas mixture comprising excited or unstable chemical species but being substantially free of electrically charged species, which deoxidize and decontaminate the external surface of the printed circuit boards 20 (FIG. 1).
• the wafers are here in a post-discharge situation.
• each device 36 for forming excited or unstable chemical species generates, at the outlet, a gas flow comprising chemical species emitted in a direction generally perpendicular to the surface of the wafers 12 to be treated.
• the gas flow comprising the chemical species intended to ensure the fluxing of the wafer naturally tends to flare, so that the particles located in periphery of the flow tend to move in a direction substantially parallel to the surface of the wafer.
• this portion of flux has a lower efficiency for the treatment of holes made in the plate for mounting the components.
• the excited particles are forced to propagate substantially perpendicular to the wafer so as to come to engage in the holes.
• the pressure is increased locally, on each plate 12, of the flow of gas containing the chemical species. More preferably, insofar as the particles in question are located at the periphery of the treatment flow, the pressure of the treatment flow is increased at the periphery of the flow.
• the pressure of the activated gas flow is increased by using a jet of auxiliary driving gas (not passing through the electrical discharge), for example nitrogen or a gas identical to that used to generate the excited particles, for example nitrogen mixed with hydrogen and, where appropriate, steam.
• auxiliary driving gas for example nitrogen or a gas identical to that used to generate the excited particles, for example nitrogen mixed with hydrogen and, where appropriate, steam.
• the jet of drive gas is generated by means of a drive device 60, adapted to project the drive gas, taken from an enclosure 62, in a direction substantially parallel to the axis of the holes, that is to say perpendicular to the surface to be treated, as shown by the arrows F, and this with a relatively high speed, for example between 10 and 100 m / s.
• the means 60 could for example consist of a knife with a venturi effect or a flow amplifier.
• the width of the area treated by the flow of excited particles is thus considerably improved.
• each plate being located at the level of the fluxing station 16, in a preferably sealed enclosure, the pressure of the treatment gas on the plate is increased by means of at least one fan. 64 turned towards the wafer and disposed at the periphery of the gas flow so as to force, in this zone, the flow of treatment gas to move in a direction substantially perpendicular to the wafer.
• the entrainment gas is taken from the treatment gas present in the enclosure.

Applications Claiming Priority (3)

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• 1998
  • 1998-05-04 FR FR9805603A patent/FR2778190B1/fr not_active Expired - Fee Related
• 1999
  • 1999-04-19 EP EP99914612A patent/EP0996770A1/fr not_active Withdrawn
  • 1999-04-19 WO PCT/FR1999/000916 patent/WO1999057334A1/fr not_active Application Discontinuation
  • 1999-04-19 BR BR9906414-6A patent/BR9906414A/pt not_active Application Discontinuation
  • 1999-04-19 CN CN99800674A patent/CN1266463A/zh active Pending
  • 1999-04-19 KR KR1020007000012A patent/KR20010015531A/ko not_active Application Discontinuation
  • 1999-04-19 CA CA002293610A patent/CA2293610A1/fr not_active Abandoned
  • 1999-04-19 ID IDW991635A patent/ID24519A/id unknown
  • 1999-04-19 JP JP55497899A patent/JP2002509583A/ja active Pending
  • 1999-05-03 TW TW088107136A patent/TW548346B/zh active

Non-Patent Citations (1)

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