Classifications

• • 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
  • H05K3/3494—Heating methods for reflowing of solder
• • 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
  • B23K1/012—Soldering with the use of hot gas
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/08—Treatments involving gases
  • H05K2203/087—Using a reactive gas
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/09—Treatments involving charged particles
  • H05K2203/095—Plasma, e.g. for treating a substrate to improve adhesion with a conductor or for cleaning holes
• • 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
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/11—Treatments characterised by their effect, e.g. heating, cooling, roughening
  • H05K2203/1157—Using means for chemical reduction

Definitions

• the present invention relates to a soldering method by reflow of electronic components on a support such as a printed circuit board, and also relates to a soldering device for the implementation of such a method.
• soldering consists in bringing the wafers carrying the electronic components to be soldered 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 nozzle.
• the wafers are previously fluxed in an upstream zone, using a flux spray or a flow foam, then preheated so as to activate the fluxes previously deposited, in order to clean the surfaces to be brazed, to elimination of oxides, organic contaminants, etc ...
• brazing alloy there is a quantity of brazing alloy at the connection locations of the components on the circuit, for example by screen printing a solder paste containing a mixture of metallic alloy and flux on the printed circuit before depositing the components to be soldered on.
• brazing alloy had been the object of pre-deposit (s) on the support, on locations of connection of the components, pre-deposit (s) remelt (s) ("reflow "), this being generally followed by an operation of planarizing the surface of the previously remelted pre-deposits (formation of" bumps "in English, we will refer to the SIPAD TM processes or still commercially available OPTIPAD TM), or even by the fact that the brazing alloy has been pre-deposited for certain components on the terminations of the components themselves. It is only then that the components are positioned on the support.
• the support provided with the components is then inserted into a reflow oven so as to provide the 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 or pre-deposit.
• the object of the invention is to provide a technical answer to the problems mentioned above.
• the components are placed on support connection locations, and
• an actual brazing operation of the components is carried out using the said brazing alloy, by heat treatment of the support, and is characterized in that said heat treatment of the support is carried out in order to perform the brazing of the components using using the brazing alloy, by bringing the support into contact, at a pressure close to atmospheric pressure, with a treatment atmosphere comprising excited or unstable chemical species, and substantially free of electrically charged species, the atmosphere being obtained by passing an initial treatment gas through an electrical discharge, and the heat treatment of the support being obtained by means of the chemical species thus heated under the action of the discharge.
• the process according to the invention can also include one or more of the following steps:
• polymerizable glue is deposited on the bonding locations of the support, and the said adhesive is polymerized in order to bond the components to the support at the bonding locations ;
• brazing alloy is available by screen printing brazing paste on the support at the connection locations of the components;
• the brazing alloy is available by the fact that the brazing alloy had been the object on the pre-deposition support (s), on the or the connection locations of the components, pre-deposition (s) then having undergone a reflow operation, then having then advantageously undergone an operation of planarizing their surface;
• the brazing alloy is available by the fact that the brazing alloy had been pre-deposited (s) on locations / terminations of the components themselves, pre-deposit (s) having then undergone reflow operation; before or after the step of depositing adhesive on the bonding locations of the support, or even after depositing the components on the support, a fluxing operation is carried out prior to the support by treatment of the latter, at a pressure close to atmospheric pressure, by means of a fluxing atmosphere comprising excited or unstable chemical species and substantially free of electrically charged species; -
• the fluxing atmosphere of the support is obtained by passing an initial fluxing gas through an electric discharge, the initial fluxing gas advantageously comprising a reducing gas mixture comprising hydrogen.
• the initial treatment gas comprises a reducing gas mixture comprising hydrogen; the treatment atmosphere is obtained at a gas outlet from an apparatus for forming excited or unstable species, into which the initial treatment gas has been transformed;
• the fluxing atmosphere is obtained at a gas outlet from an apparatus for forming excited or unstable species, in which the initial fluxing gas has been transformed; the component placement and soldering steps are carried out on the two large faces of the support, said treatment operation being carried out by means of two apparatuses for forming excited or unstable chemical species, each arranged opposite one of the faces support; the method further comprises a step of cooling the support, after said treatment, by passing the latter through a cooling atmosphere comprising a neutral gas.
• the invention also relates to a device for brazing by reflow of electronic components on a support, for example a printed circuit board, for implementing a method as defined above, characterized in that comprises a device for conveying the supports carrying, on at least one of their faces the components to be brazed on connection locations, locations on which a brazing alloy is available, the conveying member ensuring the transfer of the supports opposite first means allowing the polymerization of glue dots present on the bonding locations of the support, and opposite the second means comprising at least one apparatus for forming a treatment atmosphere comprising excited or unstable chemical species and being substantially devoid of electrically charged species, treatment atmosphere the temperature of which makes it usable for producing, at a pressure close to the pressure atmospheric, heat treatment of the support, for the actual soldering of the components.
• the device advantageously comprises, interposed along the conveyor upstream of the first means or between the first means and the second means, at least one apparatus for forming a fluxing atmosphere comprising excited or unstable chemical species and being substantially devoid of electrically charged species, fluxing atmosphere usable for carrying out gas phase fluxing of the support.
• pressure close to atmospheric pressure is understood to mean a pressure advantageously situated in the range [0.1 ⁇ 10 ⁇ Pa, 3 ⁇
• the "support” on which the components according to the invention are soldered can be very varied in nature, depending on the different supports used in the industry, as well on the electronic components to be soldered. By way of illustration, it may be supports of the printed circuit type (whatever their surface finish or finish), or even, for example, metallized ceramic supports such as hybrid circuits, or even housing bottoms on which must be soldered. circuits in a global encapsulation process.
• the components concerned can be extremely varied, from traditional passive or active electronic components to more complex and delicate components for handling, whether they are encapsulated or bare chips (BGA, MCM, Flip Chips, etc.).
• the “components” according to the invention may also consist of circuits which must be soldered on another support or on a bottom of the housing before encapsulation.
• FIG. 1 is a diagrammatic view of a brazing device for implementing the method according to the invention.
• FIG. 1 is shown a general view of a device brazing by reflow suitable for implementing the method according to the invention.
• This device comprises a conveyor member 10 comprising a belt 12, shown in phantom, disposed in an enclosure 14 and extending between two guide rollers, 16 and 18, at least one of which is motor.
• a set of printed circuit boards such as 20, on at least one of the large faces of which are arranged a set of electronic components, such as 22, which should be brazed.
• the electronic components are arranged at connection locations to which solder paste, for example an alloy of tin and lead, is applied. Furthermore, points of a polymerizable adhesive suitable for the intended use have been deposited on suitable bonding points of the board (for example on polymeric surfaces of the printed circuit board, between two connection locations), ensuring keeping the components in place during their brazing.
• solder paste for example an alloy of tin and lead
• the mat 12 ensures the transfer of the printed circuit boards 20 carrying the components 22 opposite a first station 24 allowing, by thermal transfer, the polymerization of the adhesive deposited (for example by radiation), then through a second station 28 for heat treatment, at the level of which the actual soldering of the components 22 is carried out.
• the belt 12 ensures the transfer of the wafers 20, downstream from the second heat treatment station 28 to a cooling station 30 at the level of which the wafers are arranged in a nitrogen atmosphere.
• the second heat treatment station 28 can be considered to be confused with a fluxing station 26, both constituted by a module 32 for forming a treatment and fluxing gas comprising species excited or unstable chemicals and substantially free of electrically charged species.
• the device can comprise two modules 32 for forming excited or unstable chemical species arranged each facing one of the large faces of the plate 20.
• module 32 The function of module 32 is to pass an initial treatment gas, advantageously comprising a reducing gas mixture, for example based on nitrogen and hydrogen, supplemented, if necessary with water vapor, through an electric discharge , inside which the initial gas is transformed, so as to generate, at the gas outlet of the module, the treatment gas which comprises the excited or unstable gaseous species and which is substantially devoid of electrically charged species (situation of post-discharge).
• the temperature of the species leaving the discharge will generally be directly sufficient (> 190 ° C.). However, in certain particular cases (certain metallic eutectics for example), it may be envisaged to preheat the initial gas somewhat before it enters the landfill.
• FIG. 2 There is shown in Figure 2 a sectional view of an example of module 32 capable of generating such chemical species.
• the module 32 comprises a first tubular electrode 34, formed for example by an internal face of a metal block 36, and in which is concentrically disposed an assembly formed of a tube made of dielectric material 38, for example made of ceramic, on the internal face of which is deposited, by metallization, a second electrode 40, excessively thickened in FIG. 2, in order to improve clarity.
• the dielectric tube 38 and the second electrode 40 define, with the first electrode 34, a tubular gas passage 42, and, internally, an internal volume 44 in which a refrigerant is circulated.
• the block 36 comprises, diametrically opposite, two longitudinal slots 46 and 48, respectively forming the inlet of the initial treatment gas to be transformed (excited) in the passage 42 and the outlet of the treatment atmosphere stream comprising the excited gaseous species or unstable but substantially devoid of electrically charged species.
• the slots 46 and 48 extend over the entire axial length of the cavity 42.
• the block 36 also advantageously comprises, at the periphery of the first electrode 34, a plurality of conduits, such as 50, for the passage of a cooling fluid, for example water.
• a cooling fluid for example water.
• the gas inlet slot 6 communicates with a homogenization chamber 52 formed in a housing 54 attached to the block 36 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 gas mixture circulating in the gas passage 42 so as to cause, by ionization, an excitation of the gas molecules entering into its constitution and to thus generating excited or unstable chemical species, in particular H * or H 2 " radicals, which deoxidize and decontaminate the external surface of the printed circuit boards 20 (FIG. 1).
• the method of soldering electronic components on a wafer circuit board is done here as follows.
• wafers 20 are used on which solder paste has been screen printed, at connection locations of the components. It would also have been possible to use a brazing alloy which has been the subject of pre-deposits on the wafer on locations for connection of the components, and of a pre-reflow, in general followed by an operation of flattening of the surface. pre-deposits thus obtained (industrially available processes well known to those skilled in the art of microelectronics). It could also be components having themselves locations / terminations on which a pre-deposit of brazing alloy has been carried out.
• the latter transfers the wafers from the loading station to the first adhesive polymerization station 24, and the circuit is thus preheated.
• the platelets are transferred to the module 32 for the formation of excited or unstable chemical species, described previously with reference to FIG. 3, at which level the platelets, on the one hand, undergo an operation of fluxing, under the action of the chemical species delivered by the module 32 and, on the other hand and at the same time, under the action of the heat transmitted to these excited species under the effect of the discharge, the components are brazed on the brochure.
• the process is continued here by a step of cooling the wafers, under the action of a flow of nitrogen supplied at the level of the cooling station.
• the first step of thermal treatment of polymerization and preheating of the wafer is carried out by means of a specific station 24.
• the actual heat treatment for reflow is carried out with active species (cleaning, deoxidation, etc.) making it possible to avoid any oxidation phenomenon and therefore to substantially improve the wetting performance;
• the method according to the invention makes it possible to combine completely satisfactory brazing performance, while making it possible to avoid the subsequent cleaning operation of the supports.
• the invention has been particularly exemplified in the foregoing by positioning a module for forming the treatment or fluxing atmosphere on the path of the supports (or even one module per side), it is of course possible to envisage the presence of several modules in series and / or in parallel making it possible to obtain the required effect, but one can also consider (depending on the case of each user site) the fact of not installing, facing one or each face support, that a module (whether processing or fluxing), by performing successive ironings next to the module to obtain the desired effect.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Electric Connection Of Electric Components To Printed Circuits (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9529206

Family Applications (1)

Country Status (11)

Families Citing this family (10)

Family Cites Families (3)

• 1998
  • 1998-07-30 FR FR9809773A patent/FR2781706B1/fr not_active Expired - Fee Related
• 1999
  • 1999-07-08 JP JP2000562170A patent/JP2002521207A/ja active Pending
  • 1999-07-08 CN CN99808004A patent/CN1307508A/zh active Pending
  • 1999-07-08 KR KR1020017001258A patent/KR20010053616A/ko not_active Application Discontinuation
  • 1999-07-08 WO PCT/FR1999/001657 patent/WO2000006333A1/fr not_active Application Discontinuation
  • 1999-07-08 EP EP99929437A patent/EP1100644A1/fr not_active Withdrawn
  • 1999-07-08 CA CA002338157A patent/CA2338157A1/fr not_active Abandoned
  • 1999-07-08 AU AU46253/99A patent/AU4625399A/en not_active Abandoned
  • 1999-07-08 HU HU0104961A patent/HUP0104961A2/hu unknown
  • 1999-07-08 BR BR9912560-9A patent/BR9912560A/pt not_active Application Discontinuation
  • 1999-07-22 TW TW088112437A patent/TW416881B/zh not_active IP Right Cessation

Non-Patent Citations (1)

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