WO1994023888A1 - Brasage sans plomb dans une atmosphere sensiblement exempte d'oxygene - Google Patents

Brasage sans plomb dans une atmosphere sensiblement exempte d'oxygene Download PDF

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Publication number
WO1994023888A1
WO1994023888A1 PCT/CA1994/000040 CA9400040W WO9423888A1 WO 1994023888 A1 WO1994023888 A1 WO 1994023888A1 CA 9400040 W CA9400040 W CA 9400040W WO 9423888 A1 WO9423888 A1 WO 9423888A1
Authority
WO
WIPO (PCT)
Prior art keywords
soldering
element according
solder
lead
circuit board
Prior art date
Application number
PCT/CA1994/000040
Other languages
English (en)
Inventor
Michael T. Mittag
Donald A. Elliott
Original Assignee
Electrovert Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Electrovert Ltd. filed Critical Electrovert Ltd.
Priority to AU58776/94A priority Critical patent/AU5877694A/en
Publication of WO1994023888A1 publication Critical patent/WO1994023888A1/fr

Links

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
    • B23K35/38—Selection of media, e.g. special atmospheres for surrounding the working area
    • B23K35/383—Selection of media, e.g. special atmospheres for surrounding the working area mainly containing noble gases or nitrogen
    • 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
    • B23K1/008—Soldering within a furnace
    • 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
    • B23K35/38—Selection of media, e.g. special atmospheres for surrounding the working area
    • 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
    • H05K3/3457—Solder materials or compositions; Methods of application thereof
    • H05K3/3468—Applying molten 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
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/36—Electric or electronic devices
    • 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
    • B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400 degrees C
    • 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
    • H05K2203/086—Using an inert gas

Definitions

  • the present application relates to lead free or substantially lead free soldering and more specifically to lead free soldering of elements in a substantially oxygen free atmosphere.
  • Soldering has been used for many years to coat and/or join metal surfaces together. Elements such as printed boards in the electronic industry are one of the known uses of lead and tin based solders. Components are assembled to boards by solder joining, and joining surfaces are sometimes solder plated or solder coated. Circuit boards without components thereon are referred to as "unpopulated" circuit boards. Circuit boards having components assembled thereon are referred to as
  • solder alloys used today has lead as one of the main constituents, usually in the range of 37 to 40% by weight of lead alloyed with tin.
  • Other metals or alloys for solder coating or joining metallic surfaces have existed for special cases which do not contain lead but these are only used in a few specific cases, primarily because of the availability and numerous advantages of lead based solders which include strength, reliability and cost. For example, silver solder is available but is only used infrequently and in special circumstances because of the expense. These special solders have become known as "lead free" alloys.
  • solder coating and solder joining of electronic assemblies which presently utilizes lead solder alloys must now find a substitute lead free solder.
  • solder alloys There are a great number of lead free solder alloys, however, most of them are expensive and they all have different properties to commercially available lead solder alloys. At the present time the costs of some of these solders make them prohibitive for use with electronic assembly production.
  • lead free solder alloys include tin based alloys, bismuth alloy solders and indium alloy solders. These solders contain small quantities of silver, gold, antimony, copper or zinc. Discussions of such solders occur in publication SMC-WP-002 of August, 1992, entitled “Surface Mount Council White Paper, An Assessment of the Use of Lead in Electronic Assembly", pages 14 to 18.
  • Some of the alternate solder alloys produce excessive amounts of dross or oxide while solder coating or solder joining occurs.
  • the presence of dross tends to inhibit soldering. Dross can cause defects in soldering including bridges or links across terminals, unfound joints, oxide inclusions, incomplete solder joining and incomplete solder coverage. Therefore, it is desirable to eliminate oxygen from the process either entirely or partially in order to limit the amount of dross.
  • Wave soldering of tin bismuth alloys has been carried out under a liquid flux as disclosed in IBM Technical Disclosure Bulletin, Vol. 23, No. 5, October 1980.
  • Acceptable quality soldering of lead alloy coating or joining on elements such as populated and unpopulated electronic circuit boards is achieved with reflow soldering or wave soldering machines operating in normal atmospheric conditions including normal air. Fluxes are applied to the surfaces to be coated or joined to ensure solder wetting.
  • a flux is defined as a chemically active compound which, when heated, removes minor surface oxidation, minimizes oxidation of the basis metal, and promotes the formation of an intermetallic layer between solder and basis metal (IPC Standard 1989 - ANSI/IPC-T- 50D) .
  • wave soldering has been performed using an inert gas blanket such as a nitrogen blanket or at least in an atmosphere which is substantially oxygen free.
  • inert gas blanket such as a nitrogen blanket or at least in an atmosphere which is substantially oxygen free.
  • reflow soldering under special atmospheres has been undertaken on printed circuit boards using reduction gas mixtures or inert gases to substantially, totally or partially exclude oxygen to provide improved reflow soldering results.
  • solder In reflow soldering, solder is applied to metal surfaces in a paste form and then heated to melt the solder to solder wet the surfaces.
  • the solder paste is applied to at least one of the surfaces to be joined and then heated to melt the solder on the surfaces and form a solder joint.
  • the present invention provides a process of soldering an element, comprising the steps of supplying solder having a lead content less than 37% by weight to surfaces on the element to be solder coated or solder joined, and blanketing the surfaces to be solder coated on the element during soldering in a substantially oxygen free atmosphere.
  • solder alloys When using lead free solder alloys, or alloys which have a reduced quantity of lead therein (i.e., less than 37%), it may be necessary in at least one embodiment to apply a flux either before soldering or at the time of soldering. Fluxes improve solder wetting and are used extensively with lead base solders. They are added generally prior to soldering preferably in a substantially oxygen free atmosphere. Any flux residues remaining after soldering are preferably not toxic, not electrically conductive and are non-corrosive.
  • tin based lead free solder includes tin, in some cases with a small amount of lead (trace residual impurities of 0.003% lead are presently known to be acceptable, but this may change in the future), in other cases with no lead at all. Small quantities of silver and copper are included in a tin based solder alloy.
  • lead free solders include tin and- bismuth, tin and indium, tin and gold, tin and antimony, and tin, copper and gold, as well as tin and zinc.
  • the melting temperature may be somewhat higher than that of the commonly used types of lead tin solders but the temperature is not sufficiently high to damage the circuit boards.
  • 95% tin, 5% lead was used as a solder
  • a second example 96.5%, 3.5% silver was used, and another example 95.5% tin, 4% copper and 0.5% silver were used.
  • a further example 42% tin and 58% bismuth was used and in a still further example 48% tin and 52% indium was used. All of these solders are known and are disclosed in the article entitled "Surface Mount Council White Paper, An Assessment of the Use of Lead in Electronic Assembly". Another candidate in a lead free solder is phosphorous included with other components.
  • one or two solder waves are used, the soldering occurs in a tunnel or an arrangement to blanket the solder wave and elements which in one embodiment are unpopulated circuit boards or populated circuit boards, passing therethrough, pass through an atmosphere that is substantially oxygen free.
  • the solder wave and the circuit boards passing through the solder wave are blanketed to prevent air contacting the surface of the solder and the surface or surfaces being soldered during solder coating or solder joining.
  • nitrogen was included as the gas blanket with the oxygen content being kept down to as low as 5 ppm to 10 ppm.
  • controlling the oxygen content up to about 20% by volume provides satisfactory soldering.
  • oxygen is in the range of 1 ppm to 100,000 ppm (10%) in nitrogen used for blanketing the solder reservoir and solder wave as a circuit board passes therethrough.
  • a carbon dioxide gas is provided as a substantially oxygen free atmosphere.
  • Some lead free solders may have residual impurities of lead in the amount of up to 0.003%, but this is minimal compared to the 37% present in known types of lead solder.
  • solder paste is applied to metallic surfaces to be either coated or joined and the circuit board is heated in air or in an inert atmosphere.
  • the inert gas is preferably nitrogen, however, other inert gases such as carbon dioxide may suffice.
  • the inert atmosphere is substantially oxygen free to prevent oxidation occurring on the solder as the solder paste melts.
  • flux is generally included in the solder paste.

Landscapes

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

Abstract

Les métaux d'apport de brasage existants commencent à être remplacés par des métaux d'apport de brasage sans plomb de manière à éviter l'utilisation du plomb. L'invention concerne un procédé de brasage d'un élément qui consiste à appliquer un métal d'apport de brasage contenant moins de 37 % en poids de plomb sur les surfaces de l'élément à étamer ou à assembler par brasage, et à recouvrir lesdites surfaces dans une atmosphère sensiblement exempte d'oxygène pendant le brasage. Lesdits éléments peuvent être des cartes de circuits imprimés garnies ou non et le brasage peut consister en un brasage tendre à la vague ou par fusion.
PCT/CA1994/000040 1993-02-05 1994-01-26 Brasage sans plomb dans une atmosphere sensiblement exempte d'oxygene WO1994023888A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU58776/94A AU5877694A (en) 1993-02-05 1994-01-26 Non lead soldering in a substantially oxygen free atmosphere

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US1442793A 1993-02-05 1993-02-05
US08/014,427 1993-02-05

Publications (1)

Publication Number Publication Date
WO1994023888A1 true WO1994023888A1 (fr) 1994-10-27

Family

ID=21765422

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA1994/000040 WO1994023888A1 (fr) 1993-02-05 1994-01-26 Brasage sans plomb dans une atmosphere sensiblement exempte d'oxygene

Country Status (2)

Country Link
AU (1) AU5877694A (fr)
WO (1) WO1994023888A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0999730A2 (fr) * 1998-11-02 2000-05-10 Lucent Technologies Inc. Procédé de soudage sans plomb pour des panneaux à circuit imprimé
DE19816671C2 (de) * 1997-04-16 2003-09-18 Fuji Electric Co Ltd Verwendung von Legierungen als bleifreie Lötmittel-Legierungen

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0109892A1 (fr) * 1982-11-17 1984-05-30 Piezo-Ceram Electronique Four continu de brasure de composants électroniques
EP0361507A1 (fr) * 1988-09-30 1990-04-04 Praxair Technology, Inc. Procédé pour revêtir par refusion dans une atmosphère à oxydation contrôlée
EP0389218A1 (fr) * 1989-03-20 1990-09-26 The Boc Group, Inc. Procédé de soudage tendre à refusion
US5009725A (en) * 1990-03-30 1991-04-23 Air Products And Chemicals, Inc. Fluxing agents comprising β-diketone and β-ketoimine ligands and a process for using the same
WO1991007248A1 (fr) * 1989-11-22 1991-05-30 Electrovert Ltd. Soudage a la vague en atmosphere gazeuse inerte
US5121875A (en) * 1991-02-22 1992-06-16 Union Carbide Industrial Gases Technology Corporation Wave soldering in a protective atmosphere enclosure over a solder pot

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0109892A1 (fr) * 1982-11-17 1984-05-30 Piezo-Ceram Electronique Four continu de brasure de composants électroniques
EP0361507A1 (fr) * 1988-09-30 1990-04-04 Praxair Technology, Inc. Procédé pour revêtir par refusion dans une atmosphère à oxydation contrôlée
EP0389218A1 (fr) * 1989-03-20 1990-09-26 The Boc Group, Inc. Procédé de soudage tendre à refusion
WO1991007248A1 (fr) * 1989-11-22 1991-05-30 Electrovert Ltd. Soudage a la vague en atmosphere gazeuse inerte
US5009725A (en) * 1990-03-30 1991-04-23 Air Products And Chemicals, Inc. Fluxing agents comprising β-diketone and β-ketoimine ligands and a process for using the same
US5121875A (en) * 1991-02-22 1992-06-16 Union Carbide Industrial Gases Technology Corporation Wave soldering in a protective atmosphere enclosure over a solder pot

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
L.A.GUTH ET AL: "No-Clean Soldering Processes", AT & T TECHNICAL JOURNAL, vol. 71, no. 2, April 1992 (1992-04-01), NEW YORK US, pages 37 - 44 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19816671C2 (de) * 1997-04-16 2003-09-18 Fuji Electric Co Ltd Verwendung von Legierungen als bleifreie Lötmittel-Legierungen
EP0999730A2 (fr) * 1998-11-02 2000-05-10 Lucent Technologies Inc. Procédé de soudage sans plomb pour des panneaux à circuit imprimé
EP0999730A3 (fr) * 1998-11-02 2001-12-05 Lucent Technologies Inc. Procédé de soudage sans plomb pour des panneaux à circuit imprimé

Also Published As

Publication number Publication date
AU5877694A (en) 1994-11-08

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