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WO1999030865A1 - Method and apparatus for laser surface cleaning - Google Patents

Method and apparatus for laser surface cleaning Download PDF

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Publication number
WO1999030865A1
WO1999030865A1 PCT/SG1997/000071 SG9700071W WO9930865A1 WO 1999030865 A1 WO1999030865 A1 WO 1999030865A1 SG 9700071 W SG9700071 W SG 9700071W WO 9930865 A1 WO9930865 A1 WO 9930865A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser beam
solvent
laser
component
cleaning
Prior art date
Application number
PCT/SG1997/000071
Other languages
French (fr)
Inventor
Isao Yamanouchi
Original Assignee
Unique Technology International Pte 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 Unique Technology International Pte Ltd. filed Critical Unique Technology International Pte Ltd.
Priority to PCT/SG1997/000071 priority Critical patent/WO1999030865A1/en
Publication of WO1999030865A1 publication Critical patent/WO1999030865A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
    • B08B7/0035—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like
    • B08B7/0042—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like by laser
    • 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
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/12—Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure
    • B23K26/1224—Working by laser beam, e.g. welding, cutting or boring in a special atmosphere, e.g. in an enclosure in vacuum

Definitions

  • This invention relates to a method and an apparatus for cleaning of a material by directing a pulsed laser irradiation onto the surface of the material, while it is submerged in a solvent, particularly for electronics-related components such as hard disks, magnetic head sliders, silicon wafers and LCD glass panels to remove surface contaminants.
  • Another limitation in the use of pulsed laser cleaning in dry condition is that the properties of laser-sensitive materials adjacent to the surface to be cleaned may be affected.
  • One such example is the magnetic slider head where the slider surface is fixed by epoxy resin which is easily affected by laser abrasion.
  • an apparatus for removing contaminants from a surface of a component includes a laser source for directing a laser beam towards the surface and at least one medium between the surface and the laser beam; characterized in that the medium is a solvent in which the surface is immersed such that the laser beam penetrates a distance in the solvent before impinging on the surface.
  • the component is immersed in a reservoir of the solvent whereby the solvent is allowed to flow relative to the surface of the component.
  • the solvent used is selected according to the particular contaminant to be removed such that it weakens adhesive forces of contaminant particles to the surface improving ejection of the particles, thus saving on the irradiation time of the laser and promoting increased throughput
  • the surface of the component, from which contaminants are to be removed faces the side of the reservoir on which a crystal glass is mounted.
  • the laser beam is directed to penetrate the crystal glass before travelling through a distance in the solvent and impinging on the surface.
  • a method for removing contaminants from a surface of a component including: submerging the component with the surface in a solvent; characterized in that the method includes directing the laser beam to penetrate a distance in the flowing solvent before the laser beam impinges on the surface.
  • the method for cleaning a surface of a component by removing surface contaminants involves submerging the component in a reservoir of a suitable liquid that is allowed to flow relative to the surface of the component; and exposing the surface to a laser beam that passes through a crystal glass in the side of the reservoir that faces the laser source.
  • the component is positioned a distance before the crystal glass such that the laser beam passes through a thickness of the solvent before impinging the surface of the component.
  • the position of the component is variable through moving a handling device that holds the component in place before the crystal glass. The thickness of the solvent between the crystal glass and the surface of the component is thus variable.
  • the present invention provides the use of a solvent which serves to absorb the heat from the laser beam which affects the properties of the surface of the component in a dry condition.
  • a solvent minimize the risk of affecting laser-sensitive material in a component.
  • the solvent also absorbs the heat of the particles such that the surface property of the particles is maintained and therefore prevents the particles from disintegrating and spreading over the surface of the component as in a dry condition.
  • the amount of solvent between the surface and the laser beam vary as the distance between the surface of the component and the crystal glass is allowed to vary. As the solvent absorbs the laser energy, this makes it possible to protect the laser-sensitive surfaces from the laser irradiation.
  • the solvent may be water, alcohol, or a detergent depending on the type of contaminant to be removed.
  • the use of crystal glass in the preferred embodiment allow laser beam to pass through without diminishing the laser energy.
  • the component is submerged into a reservoir of solvent and the laser beam is directed through the solvent to impinge on the surface of the component to be cleaned, without the crystal glass.
  • Figure 1 is a perspective view of an embodiment of the present invention which shows an assembly of the apparatus for laser surface cleaning where the solvent is allowed to flow.
  • Figure 2 is a perspective view of another embodiment of the present invention for laser surface cleaning which shows a reservoir of solvent which is not made to flow.
  • Figure 3 is a perspective view of another embodiment of the present invention for laser surfacing cleaning which shows a laser beam directed to the surface without passing through a convex lens.
  • Figure 4 is a perspective view of another embodiment of the present invention for laser surface cleaning which shows a laser beam directed at the surface without passing through a crystal glass window.
  • Figure 5 is a photograph of a contaminated magnetic head slider.
  • Figure 6 is a microscopic photograph of the contaminant in Figure 2.
  • Figure 7 is a photograph of the magnetic head slider after dry laser cleaning.
  • Figure 8 is a photograph of the magnetic head slider after cleaning by the method of the present invention.
  • a preferred embodiment of the present invention includes a Krf excimer laser as the laser source (2).
  • This laser source (2) generates a laser pulse beam (4) of laser wavelength 248nm and pulse duration of 20ns.
  • the laser beam (4) is directed to the cleaning surface through an energy homogenizer (6), a convex lens and then a crystal glass window (10).
  • the homogenizer (6) is used to make a profile of laser energy of uniform intensity at the beam area as the laser beam (4) generated by the excimer laser (2) does not have even intensity energy over the beam area.
  • the convex lens is used if the surface of the component has an area smaller than the laser beam (4) area which is usually 30mm x 10mm.
  • the glass window (10) allows the laser beam (4) to maintain a uniform intensity when the laser beam (4) passes through.
  • the component (12) with surface to be cleaned is submerged in the solvent (13) where a continuous flow into (17) and out (18) of a liquid tank (14) is maintained to provide a clean supply of the solvent.
  • a mechanical handling device (16) is provided to pick up the cleaned component (12a) and exchanges it with another one to be cleaned.
  • the solvent in the liquid tank is allowed to remain unchanged as shown in Figure 2.
  • the laser beam is directed to the surface of the component and passes through the solvent immediately from the homogeniser without passing through a convex lens.
  • the laser surface cleaning apparatus excludes the crystal glass window.
  • Figure 5 shows the typical contaminants on a magnetic head slider and Figure 6 is a microscopic photograph of a contaminant. Analysis of the contaminant particle shows organic contents like carbon and nitrium. After laser cleaning in the air atmosphere (100mJ/cm2, 1000 pulse), the contaminants had remained on the surface as shown in Figure 7. When the slider head was placed under a solvent (De-ionized water + 1% detergent) and cleaned again with small number of pulses (50 pulses), the surface was thoroughly cleaned as shown in Figure 8.
  • a solvent De-ionized water + 1% detergent

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Cleaning In General (AREA)

Abstract

This invention provides a method and a wet laser cleaning apparatus for the cleaning of material surfaces without changing the surface property. In this invention, the contaminants, including sub-micron particles, are removed from the material surfaces without causing as much damage and change to the material surface properties as compared to the case when conventional cleaning methods are used. The improvement is provided by applying a pulsed laser beam onto the surface of materials submerged in liquid.

Description

Method & Apparatus for Laser Surface Cleaning
TECHNICAL FIELD
This invention relates to a method and an apparatus for cleaning of a material by directing a pulsed laser irradiation onto the surface of the material, while it is submerged in a solvent, particularly for electronics-related components such as hard disks, magnetic head sliders, silicon wafers and LCD glass panels to remove surface contaminants.
BACKGROUND OF INVENTION
Electronics products have been reducing in size whilst increasing in function and capacities therefore the components used are required to be very precise in the micron scale. Under such restrictions, the presence of contaminants on the surfaces of such components, even sub-micron particles, may pose a very serious problem which affects production yield and product reliability. In order to overcome this problem, these products are manufactured in a highly controlled clean-room environment. In addition to manufacturing the products in a clean-room environment, the components are also required to be cleaned in such an environment.
In the industry, two cleaning methods are commonly used - mechanical cleaning, and wet cleaning using ultrasonic microwave effect. Mechanical contact cleaning, which typically uses foam sponge-like materials and cotton buds, has an advantage over the ultrasonic cleaning method in terms of cleaning efficiency. However, mechanical cleaning may cause damage on the surfaces as a result of the particles being removed from the surfaces, and it may also create secondary contamination caused by the cleaning material itself. In addition, the mechanical forces applied to the components during cleaning may cause mechanical damage to the force-sensitive precision components, in particular, to magnetic head suspensions.
Another method of cleaning materials of surface contaminants is the pulsed laser cleaning method as illustrated in prior art patent US 5,151 ,134. Although this cleaning method is a feasible and reliable alternative solution to the current mechanical contact and ultrasonic cleaning methods, it has its limitations in a dry condition. One of these limitations is the change in the surface properties of materials as a result of the heat generated by the laser energy. The laser energy creates forces that eject the particles from the surface. However, some particles, typically organic particles, are destroyed and spread over the surface by means of the laser energy before the laser energy can reach a level strong enough to eject the particles. The vibration force of the particles created by the pulsed laser is one of the factors for cleaning. However, this is absorbed by the particles due to the damping effect created and these particles are softened which lead to an increased in the adhesion force of these particles to the surface thus compromising the level of cleaning achieved.
In prior art patent US 5,531 ,587, a neutral medium in the form of an inert gas is allowed to flow over the surface of the component to sweep ejected particles away from the surface of the component. Although this assists in the prevention of the re-attachment of the particles to the surface, the problem of strongly adhesive particles remains a problem in laser cleaning method in a dry condition.
In another prior art, IBM Zapka et al, a thin layer of liquid is introduced to the surface to be cleaned by condensation of water vapor to prevent adhesion of particles due to the absorption of laser energy. The explosive evaporation of the super heated liquid film expels even the strongly adherent sub-micron particles. Despite the improvements of these prior arts, there are still limitations.
Another limitation in the use of pulsed laser cleaning in dry condition is that the properties of laser-sensitive materials adjacent to the surface to be cleaned may be affected. One such example is the magnetic slider head where the slider surface is fixed by epoxy resin which is easily affected by laser abrasion.
SUMMARY OF THE INVENTION
According to the present invention, an apparatus for removing contaminants from a surface of a component includes a laser source for directing a laser beam towards the surface and at least one medium between the surface and the laser beam; characterized in that the medium is a solvent in which the surface is immersed such that the laser beam penetrates a distance in the solvent before impinging on the surface.
In a preferred embodiment of the present invention, the component is immersed in a reservoir of the solvent whereby the solvent is allowed to flow relative to the surface of the component. The solvent used is selected according to the particular contaminant to be removed such that it weakens adhesive forces of contaminant particles to the surface improving ejection of the particles, thus saving on the irradiation time of the laser and promoting increased throughput The surface of the component, from which contaminants are to be removed, faces the side of the reservoir on which a crystal glass is mounted. The laser beam is directed to penetrate the crystal glass before travelling through a distance in the solvent and impinging on the surface.
According to the present invention, a method for removing contaminants from a surface of a component, the method including: submerging the component with the surface in a solvent; characterized in that the method includes directing the laser beam to penetrate a distance in the flowing solvent before the laser beam impinges on the surface.
In another aspect of the invention, the method for cleaning a surface of a component by removing surface contaminants involves submerging the component in a reservoir of a suitable liquid that is allowed to flow relative to the surface of the component; and exposing the surface to a laser beam that passes through a crystal glass in the side of the reservoir that faces the laser source. The component is positioned a distance before the crystal glass such that the laser beam passes through a thickness of the solvent before impinging the surface of the component. The position of the component is variable through moving a handling device that holds the component in place before the crystal glass. The thickness of the solvent between the crystal glass and the surface of the component is thus variable.
The present invention provides the use of a solvent which serves to absorb the heat from the laser beam which affects the properties of the surface of the component in a dry condition. The use of a solvent minimize the risk of affecting laser-sensitive material in a component. The solvent also absorbs the heat of the particles such that the surface property of the particles is maintained and therefore prevents the particles from disintegrating and spreading over the surface of the component as in a dry condition.
The amount of solvent between the surface and the laser beam vary as the distance between the surface of the component and the crystal glass is allowed to vary. As the solvent absorbs the laser energy, this makes it possible to protect the laser-sensitive surfaces from the laser irradiation.
The solvent may be water, alcohol, or a detergent depending on the type of contaminant to be removed. The use of crystal glass in the preferred embodiment allow laser beam to pass through without diminishing the laser energy.
In another embodiment of the invention, the component is submerged into a reservoir of solvent and the laser beam is directed through the solvent to impinge on the surface of the component to be cleaned, without the crystal glass.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a perspective view of an embodiment of the present invention which shows an assembly of the apparatus for laser surface cleaning where the solvent is allowed to flow.
Figure 2 is a perspective view of another embodiment of the present invention for laser surface cleaning which shows a reservoir of solvent which is not made to flow.
Figure 3 is a perspective view of another embodiment of the present invention for laser surfacing cleaning which shows a laser beam directed to the surface without passing through a convex lens.
Figure 4 is a perspective view of another embodiment of the present invention for laser surface cleaning which shows a laser beam directed at the surface without passing through a crystal glass window.
Figure 5 is a photograph of a contaminated magnetic head slider.
Figure 6 is a microscopic photograph of the contaminant in Figure 2.
Figure 7 is a photograph of the magnetic head slider after dry laser cleaning.
Figure 8 is a photograph of the magnetic head slider after cleaning by the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention, shown in Figure 1 , includes a Krf excimer laser as the laser source (2). This laser source (2) generates a laser pulse beam (4) of laser wavelength 248nm and pulse duration of 20ns. The laser beam (4) is directed to the cleaning surface through an energy homogenizer (6), a convex lens and then a crystal glass window (10). The homogenizer (6) is used to make a profile of laser energy of uniform intensity at the beam area as the laser beam (4) generated by the excimer laser (2) does not have even intensity energy over the beam area. The convex lens is used if the surface of the component has an area smaller than the laser beam (4) area which is usually 30mm x 10mm. The glass window (10) allows the laser beam (4) to maintain a uniform intensity when the laser beam (4) passes through. The component (12) with surface to be cleaned is submerged in the solvent (13) where a continuous flow into (17) and out (18) of a liquid tank (14) is maintained to provide a clean supply of the solvent. A mechanical handling device (16) is provided to pick up the cleaned component (12a) and exchanges it with another one to be cleaned.
In another embodiment of the invention, the solvent in the liquid tank is allowed to remain unchanged as shown in Figure 2.
In another embodiment of the invention, as shown in Figure 3, the laser beam is directed to the surface of the component and passes through the solvent immediately from the homogeniser without passing through a convex lens.
In another embodiment, as shown in Figure 4, the laser surface cleaning apparatus excludes the crystal glass window.
Figure 5 shows the typical contaminants on a magnetic head slider and Figure 6 is a microscopic photograph of a contaminant. Analysis of the contaminant particle shows organic contents like carbon and nitrium. After laser cleaning in the air atmosphere (100mJ/cm2, 1000 pulse), the contaminants had remained on the surface as shown in Figure 7. When the slider head was placed under a solvent (De-ionized water + 1% detergent) and cleaned again with small number of pulses (50 pulses), the surface was thoroughly cleaned as shown in Figure 8.

Claims

1 An apparatus for removing contaminants from a surface of a component, the apparatus including: a laser source for directing a laser beam towards the surface and at least one medium between the surface and the laser beam; characterized in that the medium is a solvent in which the surface is immersed such that the laser beam penetrates a distance in the solvent body before impinging on the surface.
2. An apparatus of claim 1 further including: a reservoir for holding the medium; characterized in that a side of the reservoir through which the laser beam is directed has a second medium that allows the laser beam to maintain constant laser energy when the laser beam passes through the second medium.
3. An apparatus according to any one of the preceding claims further including a means of varying the distance travelled by the laser beam in the solvent.
4. An apparatus according to any one of the preceding claims further including a continuously flowing solvent into and out of the reservoir.
5. A method for removing contaminants from a surface of a component, the method including: submerging the component with the surface in a solvent ; characterized in that the method includes directing the laser beam to penetrate a distance in the solvent before the laser beam impinges on the surface.
6. A method of claim 4 further including: submerging the component into a reservoir for the solvent, the reservoir having a second medium at one side; characterized in that the method includes directing the laser beam to penetrate the second medium at the side of the reservoir and a distance in the solvent before the laser beam impinges on the surface.
7. A method according to any one of the preceding claims further including varying the distance travelled by the laser beam in the solvent.
8. A method according to any one of the preceding claims further including having a continuously flowing solvent into and out of the reservoir.
PCT/SG1997/000071 1997-12-16 1997-12-16 Method and apparatus for laser surface cleaning WO1999030865A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/SG1997/000071 WO1999030865A1 (en) 1997-12-16 1997-12-16 Method and apparatus for laser surface cleaning

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/SG1997/000071 WO1999030865A1 (en) 1997-12-16 1997-12-16 Method and apparatus for laser surface cleaning

Publications (1)

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WO1999030865A1 true WO1999030865A1 (en) 1999-06-24

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003061861A1 (en) 2002-01-24 2003-07-31 Proanalysis As Laser-based cleaning method and system
EP1524041A1 (en) * 2003-10-17 2005-04-20 Heineken Technical Services B.V. Laser removal method for labelled containers
WO2014113293A1 (en) * 2013-01-15 2014-07-24 Lawrence Livermore National Security, Llc Laser-driven hydrothermal processing
CN104526158A (en) * 2014-11-29 2015-04-22 陈磊 Laser cleaning device for annular magnetic steel
US10280558B2 (en) 2012-07-10 2019-05-07 Woodrow Scientific Limited Methods and apparatus for laser cleaning of fabric materials
US10407821B2 (en) 2012-07-10 2019-09-10 Woodrow Scientific Ltd. Methods and apparatus for laser cleaning
CN119406852A (en) * 2024-12-20 2025-02-11 福州大学 Wet high-power combined laser cleaning method for heavily corroded steel structures

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD217738A1 (en) * 1983-10-03 1985-01-23 Ilmenau Tech Hochschule PROCESS FOR SURFACE TREATMENT OF PARTS
JPS62224688A (en) * 1986-03-26 1987-10-02 Toshiba Corp Processing equipment that uses laser
JPH01286425A (en) * 1988-05-13 1989-11-17 Hitachi Ltd Deposit removal method and equipment

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD217738A1 (en) * 1983-10-03 1985-01-23 Ilmenau Tech Hochschule PROCESS FOR SURFACE TREATMENT OF PARTS
JPS62224688A (en) * 1986-03-26 1987-10-02 Toshiba Corp Processing equipment that uses laser
JPH01286425A (en) * 1988-05-13 1989-11-17 Hitachi Ltd Deposit removal method and equipment

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Vol. 12, No. 92, 1988; & JP 62224688 A (TOSHIBA). *
PATENT ABSTRACTS OF JAPAN, Vol. 14, No. 67, 1990; & JP 01286425 A (HITACHI). *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003061861A1 (en) 2002-01-24 2003-07-31 Proanalysis As Laser-based cleaning method and system
EP1524041A1 (en) * 2003-10-17 2005-04-20 Heineken Technical Services B.V. Laser removal method for labelled containers
US10280558B2 (en) 2012-07-10 2019-05-07 Woodrow Scientific Limited Methods and apparatus for laser cleaning of fabric materials
US10407821B2 (en) 2012-07-10 2019-09-10 Woodrow Scientific Ltd. Methods and apparatus for laser cleaning
US10968562B2 (en) 2012-07-10 2021-04-06 Woodrow Scientific Ltd. Methods and apparatus for laser cleaning of fabric materials
WO2014113293A1 (en) * 2013-01-15 2014-07-24 Lawrence Livermore National Security, Llc Laser-driven hydrothermal processing
US10583526B2 (en) 2013-01-15 2020-03-10 Lawrence Livermore National Security, Llc Laser-driven hydrothermal processing
US10870173B2 (en) 2013-01-15 2020-12-22 Lawrence Livermore National Security, Llc Laser-driven hydrothermal processing
US11358237B2 (en) 2013-01-15 2022-06-14 Lawrence Livermore National Security, Llc Laser-driven hydrothermal processing
CN104526158A (en) * 2014-11-29 2015-04-22 陈磊 Laser cleaning device for annular magnetic steel
CN119406852A (en) * 2024-12-20 2025-02-11 福州大学 Wet high-power combined laser cleaning method for heavily corroded steel structures

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