Patent Application
20080044637
The stretched porous PTFE material used in the present invention can be produced in accordance with, for example, the process described in Japanese Patent Publication No. 42-13560. A liquid lubricant is first mixed with unsintered powder of PTFE, and the resultant mixture is extruded into a tube or plate by ram extrusion. When a sheet having a small thickness is desired, the plate-like extruded product is rolled by pressure rolls. After the extrusion or rolling step, the liquid lubricant is removed from the extruded product or rolled product as needed. When the thus-obtained plate-like extruded product or rolled product is stretched in at least a uniaxial direction, an unsintered stretched porous PTFE material is obtained in the form of a film. When the unsintered stretched porous PTFE film is heated to a temperature of at least 327° C. that is a melting point of PTFE while fixing it so as not to cause shrinkage, thereby fixing the stretched structure by sintering, a stretched porous PTFE film having high strength is obtained. When the stretched porous PTFE material is a tube, it can be formed into a flat film by cutting it in a longitudinal direction thereof. Although a material (referred to as “stretched porous PTFE film”) in the form of a film is used as the stretched porous PTFE material in the present invention, that having any other form may also be used if desired.
The stretched porous PTFE material obtained by the stretching process has a micro-fibrous tissue comprising fibrils (very fine fibers) and nodes connected to each other by the fibrils, which are respectively formed by PTFE. In the stretched porous PTFE material, this micro-fibrous tissue forms a porous structure (referred to as “microporous structure”).
In the stretched porous PTFE material, a resin portion of the microporous structure is composed of the fibrils and nodes, while a void portion of the microporous structure is composed of spaces (referred to as “porous spaces”) formed by the fibrils and nodes. Although the stretched porous PTFE film may be used as the stretched porous PTFE material by itself, a plurality of the films may also be superimposed and pressure welded to one another to provide a multi-layer film or sheet integrally formed by fusion bonding.
The porosity of the stretched porous PTFE material is preferably at least 20%, more preferably at least 40%. It is desirable that the porosity of the stretched porous PTFE material falls within a range of preferably 20 to 90%, more preferably 40 to 80% for the purpose of reconciling low dielectric characteristics or strain-absorbing ability with shape-retaining ability.
The average pore diameter of the stretched porous PTFE material is preferably at most 10 μm, more preferably at most 5 μm, particularly preferably at most 1 μm. It is preferable that the average pore diameter of the stretched porous PTFE material be at most 1 μm, since such a material can be subjected to hyperfine working, and moreover a plated film can be firmly fixed to a wall surface of a microhole formed in the material by an anchoring effect. The average pore diameter of the stretched porous PTFE material may be made small to 0.1 μm or smaller.
The thickness of the stretched porous PTFE material may be suitably selected according to the purpose of use, a position used or the like. However, it is generally at most 3 mm, preferably at most 2 mm, and the lower limit thereof is of the order of generally 5 μm, preferably 10 μm. It is preferable that the thickness of the stretched porous PTFE material be controlled to generally 1 to 2 mm (1,000 to 2,000 μm) when a product obtained from the stretched porous PTFE material is used as a probe card for inspection of semiconductors, to generally at most 1 mm (1,000 μm), preferably at most 500 μm when used as a substrate material for flexible substrates or the like, or to at most 100 μm when used as a multi-layer high-density wiring board. As described above, the stretched porous PTFE material used in the present invention is preferably a stretched porous PTFE sheet or film (hereinafter referred to as “stretched porous PTFE film”) having a thickness ranging from 5 μm to 3 mm.
In the present invention, a process of irradiating the stretched porous PTFE material with a pulse laser beam having a pulse length of 10 picoseconds or shorter is adopted for forming a microhole in the material.
The pulse length of the pulse laser beam irradiated is preferably from 10 femtoseconds (fs) to 10 picoseconds (ps). This pulse length is more preferably 20 to 1,000 fs, particularly preferably 30 to 500 fs. When the pulse length of the laser beam is short, it is possible to conduct precise microworking on the stretched porous PTFE material.
The energy of the pulse laser beam is preferably from 10 nanojoules (nJ) to 1 millijoule (mJ). This energy is more preferably from 1 microjoule (μJ) to 1 mJ, particularly preferably 1.0 to 800 μJ. In many cases, this energy is within a range of 50 to 600 μJ. When the energy falls within the above range, precise microworking may be conducted on the stretched porous PTFE material in cooperation with the pulse length.
The fluence (time integral value of a radiant flux passing through a unit area) of the pulse laser beam irradiated is generally at least 0.1 J/cm2. The fluence of the pulse laser beam irradiated is preferably 0.1 to 20 J/cm2, more preferably 0.3 to 10 J/cm2.
The wavelength of the pulse laser beam preferably falls within a range of from 200 nm to 1 μm. This wavelength is more preferably within a range of from 300 to 900 nm. The frequency is within a range of preferably from 1 Hz to 10 kHz, more preferably from 1 Hz to 1 kHz, particularly preferably from 1 to 100 Hz. When the frequency is made high, the number of emissions (shots) of the pulse per unit time can be increased. As examples of a laser medium, may be mentioned titanium/sapphire (Ti/Saphire).
By adjusting the above various conditions, a microhole having desired opening shape and depth can be precisely wrought in the stretched porous PTFE film. In addition, in the microhole formed in accordance with the process of the present invention, the microporous structure of its wall surface is substantially retained without being destroyed. The microhole may be either a through-hole or a non-through-hole. The hole diameter of the microhole formed in the stretched porous PTFE material preferably falls within a range of from 0.1 μm to 1,000 μm. However, the hole diameter of the microhole is made greater than the average pore diameter of the stretched porous PTFE material. The sectional form of the microhole may be any of, for example, circular, star, octagonal, hexagonal, rectangular, triangular, ring and groove forms. With respect to the hole diameter of the microhole, a side or diameter according to its sectional form is made greater than the average pore diameter of the stretched porous PTFE material. Upon the irradiation of the pulse laser beam, a diaphragm or mask may be provided in an optical path to form a microhole having a desired sectional form. A beam spot size may also be changed to form a desired beam.
The hole diameter of the microhole may be controlled to preferably about 5 to 100 μm, more preferably about 5 to 30 μm in application fields for which a small hole diameter is fit. On the other hand, the hole diameter may be controlled to preferably about 100 to 1,000 μm, more preferably about 300 to 800 μm in application fields for which a relatively large hole diameter is fit. The microhole may be a single hole. However, a plurality of holes may be formed on a desired pattern as needed.
Since the stretched porous PTFE material is generally a very soft stretched porous PTFE film, it may be preferable in some cases from the viewpoint of precision working that the film be supported on a support and wrought when it is abraded by irradiation of a pulse laser beam. However, it has been found that when the stretched porous PTFE material is supported on the support, and the pulse laser beam is irradiated from the side of the stretched porous PTFE material, a through-hole formed is greatly affected on its support side by particles flown off by abrasion of the support to greatly change its form.
The thin film-abrading process described in Japanese Patent Application Laid-Open No. 2002-160079 involves such problems that the kinds of the support (substrate) and the laser beam must be selected, the material to be wrought is limited to thin films such as an ITO film formed on the support, and it is difficult to sufficiently remove the adverse influence by the abrasion of the support, and so the process is not always suitable for a working process using an organic polymeric material such as a stretched porous PTFE material as a material to be wrought.
In the present invention, may be adopted an abrasion working process comprising irradiating a stretched porous PTFE material with a pulse laser beam in a state that the stretched porous PTFE material has been supported on a support, and at this time, using, as the support, a support provided with a site coming into no contact with the stretched porous PTFE material at a region corresponding to a target region of the stretched porous PTFE material, in which a microhole is formed.
More specifically, as illustrated in
On the other hand, when a stretched porous PTFE material (material 43 to be wrought) is supported on a support 41 having no bore, and the target region is irradiated with a pulse laser beam 44 as illustrated in
More specifically, when the support provided with no bore at the region corresponding to the target working region of the material to be wrought is used to form a microhole in the stretched porous PTFE material by the irradiation of the pulse laser beam, as illustrated in
On the other hand, when the support provided with the bore at the region corresponding to the target working region of the material to be wrought is used to form a microhole in the stretched porous PTFE material by the irradiation of the pulse laser beam, as illustrated in
More specifically, when the support provided with the bore at the region corresponding to the target working region of the material to be wrought is used to form the microhole in the stretched porous PTFE material by the irradiation of the pulse laser beam, the opening portion of the microhole draws an even contour line of the prescribed form. If burr-like protuberance is formed at the opening edge of the microhole, the height thereof is generally at most 30 μm, preferably at most 20 μm, more preferably at most 15 μm, so that a microhole substantially having no burr-like protuberance is formed. Supposing that a diameter (opening diameter on the irradiation side) of the opening portion formed by the irradiation of the pulse laser beam is A, and a diameter of an opening portion formed on the other side is B, the microhole satisfies the relationship of A≧B. In addition, if fissures, irregularities and/or cracks occur at the wall surface of the microhole, the depth thereof is generally at most 0.5×A, preferably at most 0.4×A, more preferably at most 0.3×A. Accordingly, the wall surface of the microhole shows a smooth form.
No particular limitation is imposed on the material of the support. However, as examples thereof, may be mentioned quartz substrates, ceramic substrates, glass substrates, synthetic resin substrates and metal substrates. The site coming into no contact with the material to be wrought, which is provided in the support, is a bore (through-hole) as its representative example. However, it may also be a recess or groove.
The above working process is not limited to the case where the stretched porous PTFE material is used as the material to be wrought, but may be applied to an abrading method for a wide variety of materials to be wrought. In other words, the abrasion working process according to the present invention is a process for abrading a material to be wrought by irradiation of a pulse laser beam, which comprises irradiating the material to be wrought with the pulse laser beam in a state that the material to be wrought has been supported on a support, and at this time, using, as the support, a support provided with a site coming into no contact with the material to be wrought at a region corresponding to a target working region of the material to be wrought.
No particular limitation is imposed on the material to be wrought. However, it is preferably an organic polymeric material. Examples of the organic polymeric material include polyolefin resins, polyamide resins, polyester resins, liquid crystal polymers, methacrylic resins, polystyrene resins, polyvinyl chloride resins, polycarbonate resins, polysulfone resins, poly(phenylene sulfide) resins, cycloolefin resins, polyimide resins, epoxy resins, phenol resins and fluorocarbon resins.
Examples of the fluorocarbon resins include polytetrafluoroethylene (PTFE), tetrafluoroethylene/hexafluoropropylene copolymers (FEPs), tetrafluoroethylene/perfluoroalkyl vinyl ether copolymers (PFAs), polyvinylidene fluoride (PVDF), polyvinylidene fluoride copolymers and ethylene/tetrafluoroethylene copolymers (ETFEs).
The organic polymeric material may also be an organic polymeric porous material. Examples of the organic polymeric porous material include porous materials of the above-mentioned fluorocarbon resins. As the organic polymeric porous material, is preferred a stretched porous PTFE material.
The conditions for the irradiation of the pulse laser beam vary according to the kind and shape of the material to be wrought. However, the pulse length of the pulse laser beam irradiated is generally 400 picoseconds (ps) or shorter, preferably 100 picoseconds or shorter, more preferably 10 picoseconds or shorter. This pulse length is generally 10 femtoseconds (fs) or longer, preferably 20 femtoseconds or longer, more preferably 30 femtoseconds or longer.
The energy of the pulse laser beam irradiated is generally from 10 nanojoules (nJ) to 1 millijoule (mJ), preferably from 1 microjoule (μJ) to 1 millijoule (mJ), more preferably from 10 to 800 microjoules, particularly preferably from 50 to 600 microjoules. The fluence of the pulse laser beam irradiated is generally at least 0.1 J/cm2, preferably at least 0.3 J/cm2. This fluence is generally at most 20 J/cm2, more preferably at most 10 J/cm2. The fluence of the pulse laser beam is preferably from 0.3 to 10 J/cm2.
The material to be wrought may be abraded in any form of through-holes, grooves, recesses, various patterns, etc. Accordingly, a region coming into no contact with the material to be wrought, such as a bore, is formed in the support according to the target working region of the material to be wrought.
The present invention will hereinafter be described more specifically by the following Examples and Comparative Examples. However, the present invention is not limited to these examples only. Physical properties were measured in accordance with the following respective methods.
A porosity of a stretched porous PTFE material was measured in accordance with ASTM D-792.
A stretched porous PTFE film (porosity: 60%, average pore diameter: 0.1 μm) having a thickness of 60 μm was irradiated by 20 shots with a Ti/Sapphire laser beam under conditions of a wavelength of 800 nm, a pulse length of 130 fs, energy of 200 μJ and a frequency of 10 Hz to form a through-hole. As illustrated in
The same stretched porous PTFE film as that used in Example 1 was irradiated by 45 shots with an ArF laser beam having a wavelength of 192 nm, a pulse length of 9 ns, energy of 50 mJ and a frequency of 5 Hz to form a through-hole (average hole diameter: 280 pm). In the wall surface of the through-hole, it was confirmed that PTFE fibrils were fused, and the microporous structure was impaired to become non-porous.
A stretched porous PTFE film (porosity: 60%, average pore diameter: 0.1 μm) having a thickness of 60 μm was irradiated by 50 shots with a Ti/Sapphire laser beam under conditions of a wavelength of 800 nm, a pulse length of 170 fs, energy of 200 μJ and a frequency of 10 Hz in a state that the stretched porous PTFE film had been placed and supported on a quartz substrate to form a through-hole. In the quartz substrate, a bore larger than the through-hole had been formed at its region corresponding to the target region of the stretched porous PTFE film, in which the through-hole was formed, in advance before use.
As illustrated in
Abrasion working was conducted in the same manner as in Example 2 except that a quartz substrate provided with no bore was used as a support. As illustrated in
More specifically, acute irregularities and cracks, and fused marks of the resin are observed on the support side of the stretched porous PTFE film. It may be inferred that this is attributed to the fact that the matter flown off by the abrasion of the support after the pulse laser beam passes through the material to be wrought collides with the pulse laser beam to incur scattering of the laser beam, thereby adversely affecting the section of the through-hole. Burr-like protuberance is observed at the opening edge of the through-hole. The form of the through-hole is not a circle, but an indented indeterminate form.
According to the present invention, there can be provided stretched porous PTFE materials in which a microhole is formed, and a microporous structure of a wall surface in the microhole is substantially retained without being destroyed. According to the production process of the present invention, a microhole having desired form and size can also be formed in a stretched porous PTFE material by precise working substantially without destroying the microporous structure thereof. Further, according to the abrasion working process of the present invention, no particle flown off by abrasion of a support is generated, and materials to be wrought having a wrought portion excellent in form can be produced.
The microhole-formed stretched porous PTFE materials according to the present invention are suitable for use as substrate materials that are excellent in heat resistance, chemical resistance, mechanical properties and dielectric characteristics and have an even pore diameter distribution, moderate elasticity and elastic recovery property, or the like. More specifically, the materials can be suitably applied as substrate materials to, for example, technical fields of mounting members of semiconductor devices, members for inspection of electrical reliability, and the like. According to the abrasion working process of the present invention, there can be provided various kinds of products precisely and beautifully abraded.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-016286 | Jan 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/01051 | 1/20/2005 | WO | 00 | 7/21/2006 |
