Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
• • 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
  • C23G5/02—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents
  • C23G5/032—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents containing oxygen-containing compounds
• • 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
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/26—Cleaning or polishing of the conductive pattern
• • 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
  • H05K2203/07—Treatments involving liquids, e.g. plating, rinsing
  • H05K2203/0756—Uses of liquids, e.g. rinsing, coating, dissolving
  • H05K2203/0766—Rinsing, e.g. after cleaning or polishing a conductive pattern
• • 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
  • H05K2203/07—Treatments involving liquids, e.g. plating, rinsing
  • H05K2203/0779—Treatments involving liquids, e.g. plating, rinsing characterised by the specific liquids involved
  • H05K2203/0783—Using solvent, e.g. for cleaning; Regulating solvent content of pastes or coatings for adjusting the viscosity
• • 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
  • H05K2203/15—Position of the PCB during processing
  • H05K2203/1518—Vertically held PCB

Definitions

• This invention relates to a method of cleaning electronic components using a solvent system in a manner to minimise emission of (in)organic compounds and particulate materials into the environment. It is well known to use various solvents and solvent blends as a cleaning agent for the removal of oil and other contaminants from substrates such as drill cuttings etc. Most of these solvents cannot be used for the removal of inorganic/organic fluxes or other contaminants encountered on electronic circuit boards and printed circuit boards. Removal of flux from such circuit boards is not only necessary for cosmetic reasons but also to prevent corrosion by such fluxes on the boards and to allow automatic testing of such boards.
• An extension of all such cleaning baths can be achieved in two ways: (a) by increasing the number of tanks (effectively increasing the degree of dilution of the contamination thereby adding significantly to the size and cost of the equipment, or, (b) by removal of contamination from the final rinse thereby increasing the running costs.
• the latter method whilst preferred by the electronics industry is not so simple.
• the solvents is usually mixed with substantial amounts of rinse water and the solvent/rinse water mixture is difficult to separate not only from each other but also from other suspended impurities since use of absorbents to achieve this have invariably results in said absorbent removing the solvent at the same time as the other suspended impurities thereby resulting in loss of valuable solvents.
• some of the conventional absorbents such as the commercial water purification carbons have little capacity for flux residues.
• the present invention is a method of cleaning electronic components comprising the steps of: a. cleaning said component(s) in a water-miscible organic solvent followed by rinsing said components so cleaned at least once with water to generate an aqueous effluents comprising the solvent, water and suspended impurities from the cleaning and rinsing stages; and b. passing the aqueous effluent through an absorptive medium capable of removing the suspended impurities but not the aqueous solvent.
• aqueous effluent is meant here and throughout the specification the effluent comprising the water- miscible cleansing solvent and water whether generated during cleaning or rinsing cycles of the method which may or may not include suspended impurities, whether they be particulate, colloids or emulsions, and dissolved impurities including soluble cationic and anionic impurities.
• the electronic components may be cleaned either by immersion of the soiled components in the water-miscible solvent for a suitable duration and/or by spraying the components with such water-miscible solvents.
• the components thus cleaned may also be rinsed one or more times with water either by immersion and/or by spraying.
• the water used for this purpose may be de-ionised water although the initial rinsing steps may be carried out with tap water.
• the water-miscible solvents and rinse water emergent from the respective cleaning and rinsing steps respectively can be combined or treated separately for the recovery of the solvent with a view to recylcling such solvents/water.
• solvents include inter alia alcohols, glycol ethers, glycol ether esters and natural terpenoids. More specifically these include one or more of ethoxy propanol, butyldiglycol ether, ethyldiglycol ether, ethoxypropoxy propanol, ethoxy propyl acetate and butyldiglycol acetate.
• Formulations containing these types of compounds are commercially available as PROZONE® and HYKLEEN® (both ex BP Chemicals Ltd) .
• the water-miscible solvent and/or water may be subjected to moderate heating before being used for the respective cleaning/rinsing steps. Wherever such heated solvents/water is used, the temperature should not be above the flash point of the water- miscible solvent.
• the electronic components thus cleaned and rinsed can then be subjected to a drying stage and will then be ready for use, storage or being packaged for despatch to a wholesale or retail outlet.
• the cleaned aqueous effluent may also be further treated eg by evaporation to recover the solvent.
• a feature of the present invention is that the aqueous effluent streams are passed through an absorptive medium which selectively removes the suspended impurities without absorbing and removing any of the valuable water-miscible solvent.
• absorptive media include certain forms of carbon such as eg those derived from coal, coconut shells or wood; clays such as eg Attapulgite, Montmorillonite and Fullers Earth; polymeric fibres such as polypropylene fibres; or a combination of these.
• a particularly suitable absorptive medium is Attapulgite clay ODA (ex OIL-DRI) which has a particle size of 16-30 mesh (US Standard) .
• absorptive media can be made in the form of permeable and replaceable filter cartridges with or without a mixed bed of deionising resin admixed therewith.
• the aqueous effluent may also contain dissolved impurities which may be cationic or anionic, it is preferable that the aqueous effluent is treated with a de-ionising resin.
• the de ⁇ ionising resin used may be a either a cationic resin or an anionic resin or a mixture of both, depending upon the nature of the dissolved impurities in the effluent. This treatment with the de ⁇ ionising resin may be carried out either before passing the effluent through the absortive medium or by passing said effluent through a mixed bed of such de-ionising resin and the absorptive medium.
• the treated effluent comprises only the water-miscible solvent and water.
• This cleaned effluent can either be recycled as such or after concentration to reduce the water content thereof to one or more of the washing stages whereas the recovered water can be recycled to one or more of the rinsing stages.
• PROZONE® a mixture of butyldiglycol ether (80%) + ethyldigylcol ner (15%) + ethoxypropoxy propanol (5%) .
• HYKLEEN®100 Ethoxypropanol
• HYKLEEN®140 Ethoxy propyl acetate
• HYKLEEN®300 Ethoxypropoxy propanol
• HYKLEEN®340 Butyldiglycol acetate
• the granular absorptive media were evaluated in e-circulating system to simulate the way they would be used in practice.
• the flow rate used was set at 20 bed volumes per hour (the exact flow rate being different for each absorbent depending on the density of the material being used, cf Table 1). This gave a relatively low contact time of 3 minutes.
• the contaminated solvent was flowed from bottom to top through the column of the absorbent. To make the flow through the column as even as possible, a sintered glass distribution disc was used.
• the tests were carried out using a dilute solution (0.5% w/w) of contaminated Prozone®.
• the contaminant used for the evaluation was an unknown mixture of flux residues which had been generated during customer trials. Each absorbent was exposed to the same total volume of contaminants.
• the level of contamination of the Prozone® solvent was determined visually and by the use of a Lovibond® comparator to measure the Hazen colour and this measurement was then used to determine the level of flux present in the solvent.
• Fulcat® 22B this was evaluated by treating a known weight of contaminated Prozone® with 1% w/w of Fulcat®22B, due to the very fine particle size of this absorbent which made re-circulating in this laboratory test virtually impossible. The treatment was carried out by the so-called “total contact method" between the solvent and the absorbent by agitation using rollers for 150 minutes. For a strict comparison, the Attapulgite and Carbon 207A samples were also tested in this manner. Results:
• Fulcat®22B proved to be the most effective with a capacity of about 40% w/w for the flux.
• Fulcat®22B ca. 0.1 2.5 70 NSX
• Carbon 207A ca. 0.3 10 100-150 NSX

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Detergent Compositions (AREA)
• Cleaning By Liquid Or Steam (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=10743436

Family Applications (1)

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Family Cites Families (5)

• 1993
  • 1993-10-13 GB GB939321067A patent/GB9321067D0/en active Pending
• 1994
  • 1994-10-12 AU AU78193/94A patent/AU7819394A/en not_active Abandoned
  • 1994-10-12 WO PCT/GB1994/002223 patent/WO1995010343A1/en not_active Application Discontinuation
  • 1994-10-12 GB GB9420574A patent/GB2282749B/en not_active Expired - Fee Related
  • 1994-10-12 EP EP94928973A patent/EP0723472A1/de not_active Withdrawn
• 1996
  • 1996-04-12 FI FI961633A patent/FI961633A0/fi unknown

Non-Patent Citations (1)

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