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WO1992005228A1 - Pates a braser contenant de l'acide acrylique et ses derives - Google Patents

Pates a braser contenant de l'acide acrylique et ses derives Download PDF

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Publication number
WO1992005228A1
WO1992005228A1 PCT/US1991/006470 US9106470W WO9205228A1 WO 1992005228 A1 WO1992005228 A1 WO 1992005228A1 US 9106470 W US9106470 W US 9106470W WO 9205228 A1 WO9205228 A1 WO 9205228A1
Authority
WO
WIPO (PCT)
Prior art keywords
solder
additive
solder paste
vehicle
ranges
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/US1991/006470
Other languages
English (en)
Inventor
James L. Davis
Robert W. Pennisi
Fadia Nounou
Bobby D. Landreth
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Motorola Solutions Inc
Original Assignee
Motorola Inc
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 Motorola Inc filed Critical Motorola Inc
Priority to KR1019930702031A priority Critical patent/KR930703396A/ko
Publication of WO1992005228A1 publication Critical patent/WO1992005228A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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
    • B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
    • 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, 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, 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
    • B23K35/3618—Carboxylic acids or salts

Definitions

  • the invention relates to solder paste formulations, and in one aspect, more particularly relates to solder paste formulations that contain acrylic acid, polyacrylic acid and/or derivatives thereof.
  • Solder formulations also known as solder creams or solder pastes, are homogeneous blends of a soft solder alloy typically in a powder form dispersed in a liquid medium conventionally containing a fluxing composition or flux, an organic solvent, and a thickening agent which will give the desired viscous or paste-like consistency to the solder formulation.
  • solder formulations can be applied to the surfaces or locations in a number of various ways, such as by screen printing, or by means of a dispenser such as a syringe, or simply by dipping the site to be soldered into the solder paste formulation so that the viscous paste adheres to the site, such as an electronic component lead.
  • solder paste formulations have been used increasingly by the electronics industry, particularly in the automated manufacture of printed circuits in which leadless miniature electronic components are surface mounted on a printed circuit board (PCB) to which a solder paste formulation has previously been applied, such as by screen printing.
  • PCB printed circuit board
  • the PCB is then subjected to a sufficiently high temperature, for example by means of a heated conveyor belt, to cause the flux and solder alloy in the formulation to liquefy and contact the electronic component leads so that on subsequent cooling of the PCB, the components will remain soldered on the PCB.
  • solder paste rheology is largely determined by those components of the solder paste which are collectively known as the vehicle.
  • solder paste vehicles consist of solvents to dissolve the rosin fluxes or fluxing agents and the activators, and other additives to achieve the proper rheology.
  • cyclohexanol (sorbitol) derivatives and various CellosolveTM mono- and dialkyl ethers of ethylene glycol and derivatives thereof are used in commercial solder pastes. Problems encountered with conventional solvents include poor solubility of the organic acid fluxing agents in the solvents which is sometimes addressed by using more solvent that is considered desirable, and an inability to obtain high viscosities (poor rheological control).
  • the flux composition of the solder formulation a material which is non-corrosive and which will provide, after the heating and cooling steps, flux residues which are themselves non-corrosive and non-conducting.
  • rosin-based flux compositions are widely used in the commercially available solder paste formulations specifically made for use in the manufacture of surface mounted electronic components.
  • more reactive fluxing compositions may be used, which leave residues which are corrosive and/or conductive.
  • a somewhat corrosive fluxing composition is desired so that the oxides which form on the metal surfaces to be soldered may be removed to permit the subsequently formed solder bond to be stronger both physically and electrically.
  • Corrosive fluxing compositions usually leave residues and it is necessary to remove these residues formed by means of either aqueous or organic solvent systems to ensure that the resulting soldered circuit is noncorrosive.
  • the use of solder paste formulations containing such rosin-based or more reactive fluxes has a number of disadvantages.
  • the noncorrosive residues such as rosins
  • Rosin based fluxes tend to leave copious amounts of residue on the circuit. Additionally, such residues are unsightly and therefor, as with the corrosive flux residues which are also unattractive, will need to be removed.
  • the removal step involves extra production equipment, time and material.
  • flux residues tend to be hygroscopic and may thereby cause spattering.
  • some fluxes permit solder particles in the paste to move away from the solder site and give rise to the formation of numbers of discrete small balls of soft solder around the soldered joints, which can create electrical short circuits.
  • halocarbons such as the chlorofluorocarbons (CFCs)
  • CFCs chlorofluorocarbons
  • solder fluxing compositions are less preferred, and it would therefore be advantageous to discover a new fluxing composition that would avoid one or more of these disadvantages.
  • solder pastes with fluxing agents whose residues could be easily cleanable by a relatively inexpensive organic solvent that is readily disposed of, such as formic acid.
  • Still another object of the invention is to provide a fluxing agent that is a derivative of acrylic acid that will simultaneously serve to improve the rheological properties of the solder paste formulation.
  • solder paste vehicle having a solvent and an additive having the formula:
  • R is H or lower alkyl and n ranges from 1 to 10,000 ; where the additive is present in an amount effective to perform a function selected from the group consisting of fluxing, rheology improving and mixtures thereof.
  • Acrylic acid and polymers and derivatives thereof have been found to be useful additives in solder paste vehicles and, in turn, in solder paste formulations. These materials have the formula:
  • R is H or lower alkyl and n ranges from 1 to 10,000.
  • Lower alkyl is defined as Q to C ⁇
  • this structure is acrylic acid.
  • R is hydrogen and n ranges from about 2 to about 10,000, the structure represents polyacrylic acid.
  • R is methyl, the structure represents methacrylic acid and polymethacrylic acid.
  • Polyacrylic acid and acrylic acid have been found to be particularly effective as fluxing agents for lead/tin and lead /tin /silver solders. Some of the other polymeric materials, such as polymethacrylic acid, are expected to be effective fluxing agents as well.
  • the rheological properties of solder paste dictate the dispensability of the material. Thus, in order to obtain the best line definition, the rheology of the paste must fall within a narrow process window. The higher molecular weight materials of the invention are thus useful as thixotropes and thickeners.
  • polyacrylic acid and methacrylic acids exhibit viscosity behavior similar to polymethacrylates. It is the viscosities of these nonionic acrylic solutions that make these additives attractive as rheological aids in solder pastes.
  • Important variables in providing the ultimate rheology of the end product solder paste include, but are not limited to, the process by which the paste is applied, the molecular weight and thixotropic characteristics of the thickener additive, the proportions of thickener used, etc.
  • the molecular weight of these polymer additives may range from between about 500 and 20,000, it will be appreciated that these other factors be considered. Because of these interacting factors, it is difficult to define absolute ranges for additive proportions and molecular weights.
  • acrylic based polymers As thickening agents for solder paste. First, they provide good control of solder paste rheology due to the higher viscosities of the polymer solutions. Secondly, the acrylic based polymers listed above do not contain chlorine as some other potential additives might. Hence, the possibility of ionic contamination from the polymer additives is minimized.
  • methacrylate additives tend to decompose at or near the temperatures used in soldering. Unzipping of acrylic polymers at soldering temperatures occurs rapidly by a chain reaction and produces almost exclusively the monomer. The monomer will either evaporate or decompose to other volatile compounds such as ethylene, propylene, carbon monoxide, carbon dioxide and water. Thus, residues from the thickening agents are expected to be minimal or non-existent due to unzipping and the subsequent evaporation of the acrylic polymer decomposition products.
  • the flux of this invention can be prepared in a variety of ways: (1) Acrylic acid may be added directly to the solder paste vehicle.
  • Polyacrylic acid powder, — -(CH2CHCOOH) n — , or the other polymeric powders may be added directly to the paste vehicle.
  • a solution of acrylic acid in a wide variety of solvents including, but not limited to, methanol, ethanol, ethylene glycol, isopropanol and butyl CellosolveTM, is added directly to the solder paste.
  • Polymer powders are dissolved in a wide variety of solvents including, but not limited to, methanol, ethanol, ethylene glycol, isopropanol and butyl CellosolveTM, which are then added directly to the solder paste.
  • acrylic acid or polyacrylic acid or other derived species are effective fluxing agents, resulting in solder reflow with minimum residue from the acid.
  • the addition of polyacrylic acid and the other polymers to the paste vehicle is straight forward since the materials are powders. This technology appears particularly attractive since the polyacrylic acid and other materials can function both as a fluxing agent and an additive to obtain proper rheological properties of the paste. The fluxing action of these materials appears to be derived from their ability to reduce surface oxides.
  • the use of acrylic acid, polyacrylic acid and derivatives thereof will replace current solder fluxing systems based on rosin additives.
  • the addition of either acrylic acid, polyacrylic acid and their derivatives to the solder paste will achieve excellent reflow properties and eliminate the severe residue problems that plague conventional solder pastes. In the case of the thixotropic polymers, rheological improvement will also result.
  • the additive is used in the solder paste, or is topically applied to the solder bond to serve as an effective fluxing agent by removing the oxides from the metallic surfaces to which the component is to be bonded.
  • the acrylic acid, polyacrylic acid or other additives are soluble in formic acid so that the formic add may wash away any residue after the bonding step. It is contemplated, however, that in some embodiments of the invention there will be no residues left and the use of formic add solvent would be obviated.
  • the suitable organic acids for the present invention include acrylic add, CH2CHCOOH; polyacrylic add, — (CH2CHCOOH) n — , polymethacrylic add and mixtures thereof.
  • Polyacrylic add is preferred in some aspects. Suitable coadditives in combination with those defined above include, but are not necessarily limited to polyacrylamide, poly(methyl methacrylate), polyacrylonitrile and mixtures thereof.
  • the polyacrylic add may have a molecular weight range of from about 100 to about 200,000, and in a more preferred range from about 500 to about 5000.
  • these additives have been found to serve as good fluxing agents for soldering Sn/Pb; Sn/Pb/Ag; and Sn/Pb/Ag/Sb compositions to copper over and above some of the other organic adds. It will be appredated, however, that other solders are expected to be useful in conjunction with these additives, and that other metals besides copper are expected to be effectively deaned and bonded to by formulations containing these materials.
  • solder formulations tests have shown that these adds are effective fluxing agents, resulting in solder reflow bonds having minimum residue, which can be easily removed by formic acid, water or the like.
  • the addition of the polyacrylic acid to the paste vehide is straightforward since the material is a solid powder at room temperature.
  • acrylic add and polyacrylic add can also be used directly or topically as a flux for solder balls or spheres.
  • the solder used in this process can be untreated solder powder (as in a paste formulation) or solder spheres.
  • the acid may also be applied to formated solder spheres.
  • the metals of the solder may include, but are not limited to lead, tin, antimony, silver and mixtures thereof. These types of solders were found to exhibit excellent reflow characteristics.
  • the proportion of additive in the vehicle ranges from about 0.1 to about 60 wt.% of the vehicle, and in a preferred aspert from about 0.3 to about 40 wt.% of the vehicle.
  • the proportion of additive as a proportion of the solder paste vehicle will vary depending on the particular formulation and its intended use. For example, high temperature solder pastes or pastes for highly oxidized metal surfaces may require a different additive proportion from those outlined above.
  • the minimum amount of additive needed will depend upon the molecular weight of the additive as well. For example, less of a higher molecular weight additive is needed to achieve the same viscosity than if a lower molecular weight additive is used.
  • the balance of the fluxing composition may be any of the customary materials or additives.
  • Suitable alcoholic solvents for dissolving the acrylic add and derivatives therefrom include, but are not limited to methanol, ethanol, isopropanol; 2-butanol; 1-hexanol; 1- heptanol; 1-octanol; 1-dodecanol; 2-ethoxyethanol; 2-(2- ethoxyethoxy)ethanol; 2-(2-butoxyethoxy) ethanol; n- hexadecanol; n-octadecanol; benzyl alcohol; 1,2-ethanediol; 1,2- propanediol; 1,3-propanediol; 1,2-butanediol; 1,3-butanediol; 1,4- butanediol; 1,2-pentanediol; 1,5-pentanediol; 2,4-pentanediol; 2,5-hexanediol; glycerol; 1,2,4-
  • the proposed solder pastes containing acrylic add, polyacrylic acid or other additive can replace current solder fluxing systems based on rosin additives.
  • acrylic add can replace the acid in conventional abietic add-based fluxes.
  • the addition of acrylic add to the solder pastes will achieve excellent solder reflow properties and eliminate or reduce the residue problems that plague conventional solder pastes. This lack of residue reduces the need for any board deaning with ozone-depleting CFCs after solder reflow. With any of these organic acid fluxes and methods of this invention, no retooling would be required in the existing assembly line. If the process can be one in which no residue remains, then some deaning equipment may need to be removed.
  • a low residue, formic acid cleanable solder paste was formulated with the following composition. 88.0% Solder powder
  • the rheological properties of the solder paste can be tailored to meet exacting requirements.
  • the polymeric additives have been found to serve as both fluxing agents, and as thickening agents to achieve proper rheology. In fact, no other thickening agent need be employed.
  • the use of these additives to simultaneously meet rheology and flux requirements is expected to lower the number of processing steps required in solder paste formulations.
  • the amount of additives, such as thickeners, required for acceptable screen printing the residues remaining from the solder paste following solder reflow will be significantly lowered or eliminated.
  • all additives in the vehicle should exhibit a boiling point between about 150 and about 350°C, in one aspect from between about 175 and about 270°C.
  • Lower boiling polymers will decompose and/or evaporate prior to reflow and would not provide effective fluxing action.
  • the polymers will unzip into only the monomer and harmless components, many or all of which would volatilize.
  • temperatures around 250°C. approximately 90 to 95% of the polymer has degraded.
  • These decomposition temperatures are dependent upon the type of acrylic acid polymer, its molecular weight and the chain microstructure. It should be mentioned that the viscosity of these pastes with polyacrylic add is about 260 cps, whereas without polyacrylic add the viscosity is about 100 cps.
  • Acrylic acid and polyacrylic acid are especially useful organic acid fluxing agents that performs surprisingly better than other adds, particularly in leaving low portions of residue. Additional embodiments of the invention include topical application of the additives to solder bonds, later cleaned away with organic adds, if necessary.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Electric Connection Of Electric Components To Printed Circuits (AREA)

Abstract

Pâtes à braser comportant des véhicules comprenant de l'acide acrylique, de l'acide polyacrylique ainsi que leurs dérivés utilisés comme agents de fluxage, adjuvants rhéologiques ou l'un et l'autre. En tant qu'agents de fluxage, les matières nettoient les oxydes des cartes de circuits imprimés (PCB) en cours d'assemblage et ensuite ils se volatilisent laissant peu ou pas de résidus indésirables. Les matières polymères se décomposent en matières sans danger et souvent volatiles. Les éventuels résidus peuvent être complètement éliminés par lavage à l'aide d'acide formique. On peut mélanger lesdits agents de fluxage à des composants de brasage classiques, tels que des pâtes de brasage au plomb/à l'étain, ou les appliquer localement à des matières d'apport de brasage, tel que des billes de brasage; les deux techniques permettent l'assemblage de PCB plus facilement avec des soudures de haute qualité, et avec peu ou pas de résidus. Les dérivés polymères utiles d'acide acrylique comprennent, de manière non exhaustive, le polyméthacrylate, le polyacrylamide, le poly(méthyle méthacrylate) et le polyacrylonitrile.
PCT/US1991/006470 1990-09-17 1991-09-09 Pates a braser contenant de l'acide acrylique et ses derives Ceased WO1992005228A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1019930702031A KR930703396A (ko) 1991-01-08 1991-12-16 스티렌 공중합체 수지를 함유한 개선된 열가소성 조성물

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US58312990A 1990-09-17 1990-09-17
US583,129 1990-09-17

Publications (1)

Publication Number Publication Date
WO1992005228A1 true WO1992005228A1 (fr) 1992-04-02

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5907007A (en) * 1996-03-19 1999-05-25 Denso Corporation Soldering flux
US6936115B2 (en) * 2001-06-07 2005-08-30 Fry's Metals, Inc. Soldering flux vehicle additive and fine pitch printing method
EP3040154A4 (fr) * 2013-09-12 2017-04-12 Senju Metal Industry Co., Ltd Flux de nettoyage, pâte à braser de nettoyage et jonction brasée

Citations (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3033713A (en) * 1960-04-20 1962-05-08 Air Reduction Improved-stabilized brazing fluxes and binders
US3040781A (en) * 1958-04-15 1962-06-26 Martin Marietta Corp Solderable coating
US3471310A (en) * 1965-05-24 1969-10-07 Eutectic Welding Alloys Welding process and product
US3791027A (en) * 1971-06-30 1974-02-12 Ibm Soldering method
US3832242A (en) * 1970-07-23 1974-08-27 Scm Corp Brazing and solder compositions comprising a chelating agent
US3895973A (en) * 1973-12-17 1975-07-22 Chevron Res Activated soldering flux
US3986899A (en) * 1974-06-07 1976-10-19 Scm Corporation Atomized copper brazing paste
US4113525A (en) * 1977-06-30 1978-09-12 Chevron Research Company Carboxylic acid-containing wax fluxes
US4296019A (en) * 1979-11-29 1981-10-20 The Dow Chemical Co. Solvent blends for ethylene copolymers
US4325754A (en) * 1980-12-15 1982-04-20 Gte Products Corporation Flexible brazing alloy tape and method of making same
US4541876A (en) * 1983-10-31 1985-09-17 Scm Corporation Nonaqueous powdered metal paste composition
US4554307A (en) * 1983-05-20 1985-11-19 Allied Colloids Limited Water soluble polymers and dispersions containing them
US4613639A (en) * 1983-03-12 1986-09-23 Basf Aktiengesellschaft Preparation of plastisols and organosols having a long shelf life
US4762573A (en) * 1984-07-20 1988-08-09 Ytkemiska Institutet Fluxing agent and soldering process
US4995921A (en) * 1990-05-11 1991-02-26 Motorola, Inc. Solder pastes using alcohol blends as rheological aids
US5004508A (en) * 1989-12-12 1991-04-02 International Business Machines Corporation Thermally dissipated soldering flux
US5037877A (en) * 1987-10-22 1991-08-06 Produits Chimiques Auxiliaires Et De Synthese (P.C.A.S.) Polymer based preparation for the surface protection of zinc against white rust
US5064480A (en) * 1989-08-04 1991-11-12 Quantum Materials, Inc. Water washable soldering paste
US5064481A (en) * 1990-05-17 1991-11-12 Motorola, Inc. Use or organic acids in low residue solder pastes

Patent Citations (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3040781A (en) * 1958-04-15 1962-06-26 Martin Marietta Corp Solderable coating
US3033713A (en) * 1960-04-20 1962-05-08 Air Reduction Improved-stabilized brazing fluxes and binders
US3471310A (en) * 1965-05-24 1969-10-07 Eutectic Welding Alloys Welding process and product
US3832242A (en) * 1970-07-23 1974-08-27 Scm Corp Brazing and solder compositions comprising a chelating agent
US3791027A (en) * 1971-06-30 1974-02-12 Ibm Soldering method
US3895973A (en) * 1973-12-17 1975-07-22 Chevron Res Activated soldering flux
US3986899A (en) * 1974-06-07 1976-10-19 Scm Corporation Atomized copper brazing paste
US4113525A (en) * 1977-06-30 1978-09-12 Chevron Research Company Carboxylic acid-containing wax fluxes
US4296019A (en) * 1979-11-29 1981-10-20 The Dow Chemical Co. Solvent blends for ethylene copolymers
US4325754A (en) * 1980-12-15 1982-04-20 Gte Products Corporation Flexible brazing alloy tape and method of making same
US4613639A (en) * 1983-03-12 1986-09-23 Basf Aktiengesellschaft Preparation of plastisols and organosols having a long shelf life
US4554307A (en) * 1983-05-20 1985-11-19 Allied Colloids Limited Water soluble polymers and dispersions containing them
US4541876A (en) * 1983-10-31 1985-09-17 Scm Corporation Nonaqueous powdered metal paste composition
US4762573A (en) * 1984-07-20 1988-08-09 Ytkemiska Institutet Fluxing agent and soldering process
US5037877A (en) * 1987-10-22 1991-08-06 Produits Chimiques Auxiliaires Et De Synthese (P.C.A.S.) Polymer based preparation for the surface protection of zinc against white rust
US5064480A (en) * 1989-08-04 1991-11-12 Quantum Materials, Inc. Water washable soldering paste
US5004508A (en) * 1989-12-12 1991-04-02 International Business Machines Corporation Thermally dissipated soldering flux
US4995921A (en) * 1990-05-11 1991-02-26 Motorola, Inc. Solder pastes using alcohol blends as rheological aids
US5064481A (en) * 1990-05-17 1991-11-12 Motorola, Inc. Use or organic acids in low residue solder pastes

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5907007A (en) * 1996-03-19 1999-05-25 Denso Corporation Soldering flux
US6936115B2 (en) * 2001-06-07 2005-08-30 Fry's Metals, Inc. Soldering flux vehicle additive and fine pitch printing method
EP3040154A4 (fr) * 2013-09-12 2017-04-12 Senju Metal Industry Co., Ltd Flux de nettoyage, pâte à braser de nettoyage et jonction brasée
US10259083B2 (en) 2013-09-12 2019-04-16 Senju Metal Industry Co., Ltd. Cleaning flux, cleaning solder paste, and solder joint

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