JPH04356387A - Eliminating method for adherent fragment - Google Patents

Abstract

PURPOSE:To eliminate the fragment by a dry type at a low cost by executing an ozone processing or a plasma processing with respect to the fragment which is generated and adheres at the time when a high polymer substance is irradiated with a laser light. CONSTITUTION:When a hole 5 is made by irradiating a high polymer substance 1 with a laser light 2, a fragment 4 is generated and adheres to the periphery of the hole 3. When the high polymer substance 1 to which this fragment 1 adheres is subjected to oxidation treatment in an ozone atmosphere 7, the adherent fragment is oxidized to volatile molecules of CO, CO2, NO, etc., by an oxidation effect which ozone has, and the adherent flagment can be scattered and eliminated from the surface of a high molecule substance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for removing fragments that are generated and adhere to a polymeric substance when it is irradiated with a laser beam for processing or the like.

0002

[Prior Art] Since the appearance of lasers in the 1960s,
Its oscillation wavelength ranges from vacuum ultraviolet region (10 nm) to millimeter wave (
It covers a wide area up to 10mm) and can be used for measurement, analysis,
It is used in a wide range of fields such as medicine, optical communications, and processing. When laser light is irradiated onto metals, ceramics, or polymeric materials, various types of microprocessing such as drilling, cutting, marking, and trimming are possible.
3 to 0.308 μm), YAG laser (oscillation wavelength is 1
．． 06 μm), CO2 laser (oscillation wavelength is 10.6 μm), CO2 laser (oscillation wavelength is 10.6
.mu.m), and research on these lasers and their practical application in industry are currently actively progressing.

[0003] Polymer materials generally exhibit strong light absorption in the infrared to ultraviolet region, and the reason for this is that light in this region corresponds to the absorption wavelength region of the chemical bonds that make up the polymer material. . Therefore, when a polymer substance is irradiated with a laser beam with a strong energy value in this region, a photochemical reaction occurs, and the molecular bonds between carbon, hydrogen, nitrogen, chlorine, etc. that make up the polymer substance are broken due to strong light absorption. As a result, so-called fragments such as molecules or atoms with smaller masses are generated.

[0004] Since the fragments generated by the cleavage of molecular bonds have a larger specific volume than the original molecules, most of them are dispersed as volatile molecules such as CO2 and NO, but some are dispersed as volatile molecules. It remains as carbon, carbon compounds, nitrogen compounds, etc. attached to the periphery of the processed parts of the polymeric material. For example, as shown in Figures 2 to 4, when a hole 3 is made in a polymer material 1 with a laser beam 2, fragments 4
is generated and remains attached around the hole 3 (see Fig. 2). The adhering fragments remaining on the polymer material not only damage the appearance of the workpiece, but also scatter and re-adhere to the surrounding area, reducing workability and, in some cases, potentially having a negative impact on subsequent processing steps. Therefore, various methods have been studied to remove the adhered fragments, such as wiping with an organic solvent, and as shown in FIG. In addition to the method of sonic cleaning, as shown in FIG. 4, a method of processing without adhering fragments 4 by irradiating laser light 2 while spraying gas (referred to as assist gas) 6 is also being considered.

[0005]

[Problems to be Solved by the Invention] As mentioned above, various methods have been proposed for removing adhering fragments that have adhered to the periphery of processed parts, but although the method using an organic solvent is simple and has a high removal effect, When drilling holes or processing minute shapes, adhering fragments cannot be wiped off, and there is a risk that the polymeric substance will be attacked by the organic solvent, which limits the types of polymeric substances and organic solvents that can be used. However, since it is a wet method, there are problems such as the need for a drying process after removing the attached fragments. On the other hand, the method of irradiating laser light while spraying assist gas has the advantage of being able to remove fragments in a dry manner, but although it reduces the amount of fragments adhering, it cannot completely prevent adhesion.As an assist gas, air is effective in preventing adhesion. There is a problem that spraying special gas such as helium gas is disadvantageous in terms of cost.

[0006]

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned conventional problems by focusing on the fact that ozone has an oxidizing effect or that gaseous plasma activates molecules and causes chemical reactions. The gist of this is a method for removing adhering fragments, which is characterized in that fragments generated when a polymer substance is irradiated with a laser beam and adhering thereto are removed by ozone treatment or plasma treatment. The method of the present invention will be explained below with reference to the drawings.As shown in FIG. Adheres to the surrounding area. When the polymer material 1 with these fragments and 4 attached is treated in an ozone atmosphere 7 as shown in (b), a processed product with the attached fragments and 4 completely removed is obtained as shown in (c). A polymer substance 1 is obtained.

[0007] It is widely known that ozone has strong oxidizing power and easily reacts with organic substances and organometallic compounds. When a polymer substance with the above-mentioned attached fragments is oxidized in an ozone atmosphere, the oxidation effect of ozone oxidizes the attached fragments into volatile molecules such as CO, CO2, NO, etc. It becomes possible to scatter and remove it from the surface. The ozone atmosphere here refers to a gas containing ozone, and there is no particular limit to the ozone concentration, but it is between 10 and 100,000 p.
pm is preferred. The reason is that the ozone concentration is 10 ppm.
This is because if it is less than 100,000 ppm, it will take a long time to remove the attached fragments, and if it exceeds 100,000 ppm, there will be a risk of explosion, or if high-concentration ozone leaks, it will have an adverse effect on the human body. There are various ways to create an ozone atmosphere, but the most common methods include irradiating air or oxygen with ultraviolet rays or corona discharge, or using a device called an ozonizer to create a silent discharge in dry air or oxygen. There are several ways to do this, and these methods may be combined.

Regarding the mechanism of ozone generation, as shown in the following equations (1) and (2), 184.9n
The ultraviolet rays of m are absorbed by oxygen molecules to generate excited oxygen atoms O, and since the generated excited oxygen atoms are highly reactive, they immediately act on oxygen molecules and become ozone O3. O2 → O+O (1)O
+O2 → O3 (2) Ozone generated in this way has a strong oxidizing effect because it has a strong electron affinity, and the excited oxygen atoms generated in the process of generating ozone also have an oxidizing effect, so the oxidizing effect is even stronger. This makes it possible to oxidize, decompose, and vaporize the attached fragments to remove them.

On the other hand, plasma is an aggregate of positively and negatively charged movable particles, and is used as an electron and ion source for heat treatment, bonding, thin film formation, and etching of various materials such as metals, inorganic substances, and polymeric substances. . It can also be used to activate materials such as organic substances and cause chemical reactions, with the plasma activating and isomerizing molecules, causing the elimination of constituent elements and the collapse of molecules. Applying this reaction, when the attached fragments are introduced into a plasma atmosphere containing gaseous plasma and subjected to plasma treatment, the attached fragments on the surface of the polymer material are excited and activated, the molecular structure collapses, and the gaseous The attached fragments can be easily removed by oxidation. Gas plasma can be easily obtained by dissociating gas by, for example, maintaining a reaction vessel of a plasma generator at a low pressure of 1 to 0.1 Torr and applying high frequency power. Since the present invention is a dry method, there is no need for a drying process.
Even micro-machined workpieces can be completely removed, and adhering fragments can be removed at low cost.

The laser beam used in the present invention is not particularly limited, and includes laser beams such as solid-state lasers, gas lasers, semiconductor lasers, and dye lasers. Examples of solid-state lasers include YAG lasers, YLF lasers, ruby lasers, etc. Gas lasers include Ar laser, He-Ne laser, He-
Examples of semiconductor lasers include Cd lasers and excimer lasers, and GaAs lasers and GaAlAs lasers.

[0011] Furthermore, harmonics of the above laser light may be used. A harmonic is light generated when a nonlinear optical material is irradiated with a laser beam. For example, a laser beam whose angular frequency of the incident laser beam is doubled or tripled while propagating through a nonlinear optical material, i.e. The wavelength is 1/2 or 1/2
3, which are called the second harmonic and the third harmonic, respectively. In the present invention, higher harmonics higher than the fourth harmonic can also be applied, but since the optical energy decreases as the order becomes higher, in many cases, it is preferable to use the second harmonic or the third harmonic. good. Specifically, for example, YA
The laser beam oscillated by the G laser is 1.06 μm,
The second harmonic is 0.532 μm, and the third harmonic is 0.532 μm.
It is 355 μm. Furthermore, examples of the nonlinear optical substance mentioned here include potassium titanate phosphate (KTP), barium borate (BBO), and the like.

[0012] Although there is no particular restriction on the wavelength of the laser beam, since polymeric substances generally have strong light absorption in the infrared to ultraviolet range, it is difficult for fragments to be generated when a polymeric substance is irradiated with a laser beam. It is widely known that the wavelength of laser light is most noticeable in the range of 0.05 to 20 μm, particularly in the range of 0.1 to 2 μm. Therefore, the present invention has great effects when applied to lasers that emit wavelengths in this range. As a processing laser having a wavelength in this range, an excimer laser (oscillation wavelength of 0.193 to 0.05 cm) is used.
308μm), YAG laser (oscillation wavelength is 1.06μm)
m ), CO2 laser (oscillation wavelength is 10.6 μm)
Examples include.

[0013] Examples of the polymeric substance include thermoplastic resins, thermoplastic elastomers, thermosetting resins, and thermosetting rubbers. Specific examples of these polymeric substances include thermoplastic resins such as polyester resins, polymethyl methacrylate resins, vinyl chloride resins, and polycarbonate resins, and thermosetting resins such as epoxy resins, unsaturated polyester resins, and thermosetting resins. Thermoplastic elastomers include styrene-ethylene-styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers, and thermoplastic polyester elastomers, which can be thermoset. Examples of the rubber include isobutylene rubber, butyl rubber, silicone rubber, etc., and these rubbers may be used alone or in a mixture of two or more types, and are not particularly limited. Among these polymeric substances, thermosetting resins such as polyimide resins, which are thermally stable polymeric substances and are subjected to microfabrication by laser beam irradiation, are particularly suitable. Further, the polymer substance may be a laminate of metals, ceramics, etc., and examples of the laminate of polyimide resin and metal include flexible printed circuit boards and TAB tape.

Fillers may be added to these polymeric substances for the purpose of improving absorption of laser light, and examples of fillers include ultraviolet absorbers and carbon black. Specific examples of UV absorbers include benzophenone UV absorbers such as 2,4-dihydroxybenzophenone, and benzotriazole UV absorbers such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. Specific examples of carbon black include acetylene black, Ketjen black, and natural or artificial graphite. Furthermore, plasticizers, stabilizers, antioxidants, antistatic agents, flame retardants, lubricants, and the like may be added to the polymeric substance as necessary.

When the above-mentioned polymeric substance is irradiated with laser light, there is strong light absorption because the wavelength of the laser beam corresponds to the absorption wavelength region of the chemical bonds constituting the polymeric substance, and a photochemical reaction occurs. Carbon, hydrogen, and
Bonds between atoms such as nitrogen, fluorine, chlorine, and silicon are broken to generate molecules or atoms with lower mass, so-called fragments. The fragments generated by bond cleavage have a much larger specific volume than the original molecule and are mostly volatile molecules, such as CO2,
It scatters as HCHO, NO, etc., but some of it is not completely dispersed and becomes carbon, carbon compounds, nitrogen compounds, etc. and remains as attached fragments around the processed parts of the polymeric material.

[0016]

【Example】

(Example 1) The laser beam used was krypton fluoride (
KrF) gas is used to oscillate with an excimer laser, the wavelength is 0.248 μm, and the energy density is 100 μm.
It was mJ/cm2. After focusing this laser beam with a lens to increase the energy density to 900 mJ/cm2, it was irradiated onto a polyimide resin film with a thickness of 50 μm to create 100 through holes with a hole diameter of 100 μm. Black adherent fragments were deposited. When this polyimide resin film with attached fragments attached was subjected to ozone treatment in an ozone irradiation device, the attached fragments on the inner wall of the hole were completely removed after 3 minutes.

(Example 2) Second harmonic of YAG laser (
A so-called marking process was performed in which characters and numbers were created on the surface of the polyurethane resin by irradiating the wire coated with the polyurethane resin with oscillation wavelength 0.532 μm. Since adhering fragments had adhered around the processed area, when it was put into a plasma generator and plasma treatment was performed, the adhering fragments were completely removed in 1 minute.

(Comparative Example 1) In Example 1, the polyimide resin film in which 100 holes were made by irradiating laser light and black adhered fragments were deposited around the processed area was ultrasonically cleaned in alcohol. It took 20 minutes to completely remove the adhered fragments, and an additional 2 minutes to dry and remove the alcohol on the film surface. (Comparative Example 2) In Example 2, when marking the polyurethane resin coating of the wire using the second harmonic of the YAG laser, the laser beam was irradiated while blowing helium gas onto the processed area. was reduced by half, but the adhesion could not be completely prevented.

[0019]

[Effects of the Invention] Since the present invention is a dry method, there is no need for a drying process after removing attached fragments, and even finely processed shapes can be completely removed.Furthermore, it can be removed at low cost, so it has no industrial effect. Extremely large.

[Brief explanation of drawings]

FIG. 1 shows the removal step of the method of the present invention, (a)
FIG. 6 is an explanatory diagram showing each state during laser beam irradiation, (b) during removal of attached fragments in an ozone atmosphere, and (c) each state after removal of attached fragments.

FIG. 2 is a perspective view of a polymer material with fragments attached around the processed portion when a hole is formed using a laser beam.

FIG. 3 is a cross-sectional view of a conventional method for removing adhered fragments during ultrasonic cleaning in an organic solvent.

FIG. 4 is a cross-sectional view showing a state in which laser light is irradiated while gas treatment is performed in a conventional method for removing adhered fragments.

[Explanation of symbols]

1. Polymer substances 2 Laser light 3 Hole 4 Adhering fragment 5 Organic solvent 6 Assist gas 7 Ozone atmosphere

Claims (1)

[Claims] 1. A method for removing adhered fragments, which comprises removing fragments generated when a polymer substance is irradiated with a laser beam and adhered to the same through ozone treatment or plasma treatment.