JPH03258475A - Excimer laser beam machining method - Google Patents

Abstract

PURPOSE:To completely remove the decomposition product components of the carbon sticking to an org. material by irradiating the org. material with an excimer laser beam to decompose away the org. material, then washing the org. material with a solvent having a nitrogenous 6-memhered cyclic structure. CONSTITUTION:The small holes 4 of a polyimide film substrate 1 are irradiated with the excimer laser beam consisting of KrF to decompose away the polyimide in the parts of the small holes 4. The substrate 1 is then washed with the solvent having the nitrogenous 6-membered cyclic structure, by which a good insulating property is imparted to all of 1st electrodes 2a, 2b, 2c, 2d and 2nd electrodes 3a, 3b, 3c, 3d. The solvent having the nitrogenous 6 membered cyclic structure is a compd. contg. a nitrogen atom in the 6-membered cyclic structure.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to improvements in excimer laser processing methods.

C. Prior Art and Problems] As is well known, an excimer laser, which is a laser that oscillates in the ultraviolet region, decomposes and removes substances non-thermally through its photochemical decomposition action, so it is less likely to undergo thermal deformation. Therefore, it is applied to precision machining.

In particular, laser machining is used for precision machining of electric circuit boards whose density has been increasing in recent years. This electric circuit board is made of organic materials such as plastics, which are inexpensive and have excellent insulation properties. Since these organic materials undergo thermal deformation when exposed to high temperatures, fine precision processing is difficult with thermal processing lasers such as YAG lasers and CO2 lasers.

On the other hand, since the Ekinmercer uses its high energy to break and decompose the intermolecular bonds of the material, it generates significantly less heat than the laser, making it possible to perform precise processing such as drilling holes of 1 mm or less. However, when an organic material is irradiated with an excimer laser, soot is generated from the material and adheres to the surrounding area in black. Regarding this phenomenon, for example, the Institute of Electrical Engineers of Japan, Optical and Quantum Device Study Group, Decomposition and Removal Processing of Polyimide Using OQ D-89-54r Excimer Laser J (19
89).

This attached carbon impairs the appearance, but can be visually removed by wiping it off with alcohol or the like. However, carbon attached to the material surface is firmly attached and cannot be removed by ultrasonic cleaning using alcohol or the like. For this reason, when an electrical circuit board made of polyimide or the like is decomposed and removed using an excimer laser, the electrical resistance of the board surface near the excimer laser irradiation decreases, and in severe cases it becomes conductive. In other words, is there any problem when using excimer laser processing to form conductive paths on both sides of the board, so-called through holes? Excimer laser processing is impossible near circuit patterns that require insulation. .

Note that when the irradiation energy density of the excimer laser is increased, the deterioration in insulation properties is reduced. In addition, measures such as increasing the resistance to some extent by washing the workpiece with alcohol ultrasonic waves immediately after excimer laser irradiation have been taken, or it has been impossible to obtain complete insulation. In particular, when holes such as through holes are made in a substrate, it is extremely difficult to remove carbon adhering to the walls of the holes.

For this reason, there is a problem in applying the excimer laser to processing circuit boards with small wiring pattern gaps, such as those used in recent high-density circuits.

The present invention has been made in view of the above circumstances, and the organic material is decomposed and removed by irradiating the organic material with an excimer laser, and then washed with a nitrogen-containing six-membered ring solvent. It is an object of the present invention to provide an excimer laser processing method that can completely remove the decomposition products of attached carbon.

[Means and effects for solving the problem] The present inventors repeatedly conducted cleaning tests using various solvents on circuit boards after excimer laser processing, and found that a solvent having a nitrogen-containing six-membered ring structure was used. It was discovered that the insulating properties were completely restored by washing with water.

Although the mechanism of the above phenomenon is unclear, many of the above solvents belong to the so-called tar bases contained in coal tar obtained by coal carbonization.
It is presumed that it has a high solubility in carbon.

By the way, when a circuit board is cleaned with a solvent having a nitrogen-containing ring structure, the insulation properties are restored, but these compounds have a high boiling point and tend to remain in trace amounts even after drying, giving off a strange or foul odor. Therefore, after that, water, hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, esters, etc., which have a boiling point lower than that of the nitrogen-containing six-membered ring solvent and can be mixed with the nitrogen-containing six-membered ring solvent. It is desirable to perform secondary cleaning with a solvent.

That is, the present invention provides an excimer laser processing method, which comprises irradiating an organic material with excimer laser light to decompose and remove the organic material, and then cleaning with a solvent having a nitrogen-containing six-membered ring structure. be.

Examples of the present invention will be described below along with comparative examples.

[Example 1] Refer to FIG. 1. This figure is a schematic plan view of the ion flow recording head.

1 in the figure is a polyimide film substrate 1 (trade name: Kapton, manufactured by DuPont) with a thickness of 50 μm.

On the surface of this substrate 1, a first electrode 2 with a width of 400 μm is arranged 18
A second electrode 3 having a width of 400 μm is formed on the back surface so as to intersect with these first electrodes. Note that the interval between the first electrode and the interval between the second electrode is approximately 100 μm.
It is. The surfaces of the first and second electrodes have a thickness of 1 μm.
A Ni plating film (not shown) of m is formed. A hole with a diameter of 200μ is provided at the intersection of the first and second electrodes.
A small hole 4 of m is opened.

In the first embodiment, K is inserted into the small hole 4 of the circuit board having the above configuration.
The polyimide in the small holes 4 was decomposed and removed by irradiation with rF excimer laser light having a wavelength of 248 nm. Next, the first and second electrodes were immersed in a solvent such as pyridine (see Table 1 below) and subjected to ultrasonic cleaning for 30 minutes. Thereafter, it was dried by heating at about 1000''c.

However, for circuit boards that have been treated with solvent as described above, a tester, that is, a digital multimeter (product name: JR
-6848, manufactured by Atopan Test, maximum resistance range 30
The resistance between the first electrode and the resistance between the first and second electrodes were measured at 0 MΩ). Here, the resistance between the co-electrodes means the even-numbered grains (2a, 2b...) and the odd-numbered grains (2c, 2c, etc.) of the first electrode.
2d...) are grouped into two groups, and the total resistance between these groups is shown. Also, the first-second
The resistance between the electrodes refers to the resistance between the first electrodes 2a, 2b, 2c,
2d.= and second electrodes 3a, 3b, 3c3d...
are grouped into two groups, and the resistance between these groups is shown. Each resistor has a maximum resistance value of 300MΩ
The resistance value was above. That is, according to Example 1, it was confirmed that both the resistance between the first electrodes and the resistance between the first and second electrodes had good insulation properties. Further, when 100 V DC was applied between the electrodes in the same manner as in the above method, the current flowing was ] μA, confirming that the insulation between the electrodes had been completely restored. Further, even after cleaning with the above solvent, problems such as dissolution of the polyimide substrate and peeling of the electrodes are not observed, and only the thin carbon layer attached to the surface is removed, which is very effective in practice.

By the way, after ultrasonic cleaning with the above solvent, the colorless and transparent solvent turns yellowish brown, and if the electrode is cleaned with the same solvent that was used once, the insulation properties will be significantly reduced. It is thought that the above solvent was used to dissolve and remove carbon firmly adhered to the surface of the polyimide substrate after excimer laser processing.

Note that even if aniline, pyurine, lutidine, toluidine, cyclohexylamine, piperidine, or uridine shown in Table 1 below is used instead of the above solvent (pyridine), the resistance between the first electrode, the first When the same test as in Example 1 was conducted regarding the resistance between the two electrodes, similarly good insulation properties were obtained. In other words, in both cases 300M
It was more than Ω.

Furthermore, the resistance when using other solvents such as ethanol and benzene (see Table 2 below) was also investigated, and the results are as shown in Table 3 below. According to the same table, )L
It was confirmed that when N-dimethylformide and quinoline were used, the resistance between the first and second electrodes was only 300 MΩ or more, and good insulation was not obtained in other cases.

[Example 2''J As in Examples 1 and 1, the first and second electrodes were washed in pyridine and then ultrasonically cleaned (secondary cleaning) in methanol for 5 minutes. The insulation between the electrodes was also restored, and there was almost no bad odor.

In addition to the above-mentioned methanol, secondary cleaning solvents include water, hydrocarbons, halogenated hydrocarbons, alcohols, ethers, ketones, esters, etc.
Any material may be used as long as it is miscible with the ring member solvent.

E Example 3 Instead of the polyimide circuit board used in Example I, a first circuit board made of 18 μm thick copper foil was placed on a 75 μm thick polyimide film (trade name Ubilex, manufactured by Ube Industries, Ltd.).
A polyimide circuit board with second electrodes bonded to both sides with an acrylic adhesive was used.

Similar to Example Y, after cleaning with a solvent, secondary cleaning was performed as in Example 2, but the insulation was similarly restored and there was no bad odor.

In addition, in Example 3, only electric circuit patterns are used! However, this is because carbon removal can be easily determined based on electrical resistance, and is not limited to electrical circuit pattern materials.

In other words, it can be applied to marking materials, semiconductor materials, etc. used in excimer laser processing, as long as carbon-like decomposition products are generated.

[Comparative Example] As in Example 1, KrF excimer laser light having a wavelength of 248 nfil was irradiated to decompose and remove the polyimide in the small hole 4 portion, thereby forming a through hole. At this time, black decomposition products adhered around the first and second electrodes.

This deposit was apparently completely removed by wiping with methanol and ultrasonic cleaning.

However, with a tester, that is, a digital multimeter (product name JR-6848, manufactured by Attobanpsto, maximum resistance range 300MΩ), the
When the resistance of the electrode and the second electrode was measured, it was found that the resistance was in the range of Ω to 10
The resistance had decreased from 0 to Ω, and the insulation had been lost.

pyridine Table 1 Aniline Piyurin amine piperidine Collijin Table 2 Table 3 ethanol benzene toluene (C, eyes,)3N triethylamine C mouth, cooc20 too Ethyl acetate Amide Chinorin however, * in Table 1 is 300 Indicates a value of MΩ or more.

C Effects of the Invention] As detailed above, according to the present invention, the organic material is decomposed and removed by irradiating the organic material with an excimer laser, and then the organic material is washed with a nitrogen-containing six-membered ring solvent. It is possible to provide an excimer laser processing method that can completely remove carbon decomposition products adhering to system materials.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view of the ion flow recording head. 1... Polyimide film substrate, 2... First electrode,
3... Second electrode, 4... Small hole.

Claims (4)

[Claims] (1) An excimer laser processing method, which comprises irradiating an organic material with excimer laser light to decompose and remove the organic material, followed by cleaning with a solvent having a nitrogen-containing six-membered ring structure. (2) The excimer laser processing method according to claim 1, wherein the solvent having a nitrogen-containing six-membered ring structure is a compound containing a nitrogen atom in the six-membered ring skeleton structure. (3) The excimer laser processing method according to claim 1, wherein the solvent having a nitrogen-containing six-membered ring structure is a compound in which a nitrogen atom is directly bonded to a carbon atom in the six-membered ring skeleton structure. (4) The excimer laser according to claim 1, wherein after being washed with the solvent having a nitrogen-containing six-membered ring structure, the excimer laser is washed with another solvent having a lower boiling point than this solvent and which is miscible with the solvent. Processing method.