JPH0716092B2 - Small-diameter hole processing method for substrate material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly efficient processing method for smoothing mechanical inner wall roughness in small-diameter holes in a substrate material used for electronic equipment.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of substrates used in electronic equipment, drilling or the like is performed to make through holes in a glass fiber-containing epoxy resin or polyimide resin plate. At this time, although depending on the sharpness of the drill blade, fine resin chips and defective glass fiber cutting occur, and the defect occurrence rate is particularly high when the hole diameter is 0.3 mmφ or less. Such chips and defective cutting cannot be removed by normal ultrasonic cleaning. If the substrate is plated with defects still occurring, only the fiber tips will be plated while the plating solution is immersed in the gaps between the glass fibers, and the bridge will be formed at the same time as crystal growth by plating.
Since the whole is plated, it often causes corrosion during productization, resulting in product defects. Of course, when the chips are clogged, the plating solution does not penetrate, which causes voids in the holes.

[0003]

SUMMARY OF THE INVENTION Therefore, the present invention provides a method capable of removing chips in a small diameter hole and smoothing an inner wall surface at high speed, efficiently and surely to prevent generation of defective products. It is a thing.

[0004]

According to the present invention, a substrate material to be processed having a small diameter hole is wetted with a liquid in which a rare earth fine powder having a high oxidative exothermic property is suspended to remove only the liquid adhering to the substrate surface. After that, by irradiating the small-diameter hole with laser light to oxidize and heat the rare-earth fine powder, the chips in the small-diameter hole are treated, and the small-diameter hole treatment method of the substrate material is performed to smooth the inner wall roughness.

As the above-mentioned fine powder of rare earth, La, Ce,
Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, E
Lanthanides such as r, Tm, Yb, Lu, Ac, T
A simple substance, an alloy or a mixture of actinoids such as h, U and Pu is used.

As the liquid for suspending the rare earth fine powder, a liquid containing ethylene glycol, a polyhydric alcohol, an ether, a halogenated hydrocarbon, a hydrocarbon such as benzine or hexane as a main component is preferable.

The amount of the rare earth fine powder used is appropriately selected depending on the type of substrate material and the size of the through hole.

When the substrate material to be processed is wetted with a suspension of rare earth fine powder, the suspension penetrates into the small-diameter holes.
When the suspension attached to the upper and lower surfaces of the substrate is removed using a brush or the like, the suspension remains only within the small diameter. Therefore, when the small-diameter hole is irradiated with laser light, the rare earth fine powder oxidizes and generates heat, the cutting dust is burned, and the roughness of the glass on the inner wall of the small hole is melted and smoothed. The conditions for laser light are also determined by the substrate material, the size of the small holes, and the like. Usually, it is performed in the range of 5 to 8W.

[0009]

Example: Length 200 mm, width 300 mm, thickness 0.7 m
m epoxy resin substrate, each with a diameter of 0.2
Holes of 5 mm, 0.2 mm, and 0.15 mm were punched on the entire surface with an NC drilling machine at 5 mm intervals. 230 holes
It was 0 hole. The chips were clogged, the inner wall of the hole was roughened, and burrs were generated as usual.

Such a substrate is prepared by adding 10 g of Ce fine powder to 1000 g.
It is dipped in a solution suspended in cc of ethylene glycol, taken out, and the upper and lower surfaces of the substrate are wiped with a brush and set in a laser processing device (trade name: excimer laser). The hole position is fixed by NC, and laser processing is performed for a fixed time.

The structure of the discharge part of the laser device used is shown in FIG.
Shown in. The excitation circuit using a capacitive transitional, by closing the main capacitor C gap switch DC electric charge charged in _1, moves to the capacitor C _2, in the circuit of C ₁ and C ₂ 2
An arc discharge is generated at a distance of mm between the electric charges, and the laser light between the main electrodes is preionized by UV light from the arc discharge. When the voltage between the main electrodes reaches the discharge breakdown voltage due to the charges transferred to the capacitance C ₂ , discharge is caused to excite the laser gas and cause laser oscillation. Gas composition is HCl
Was 0.15%, Xe 1.5%, He 98.35%, the pressure was 3 atm, and the charging voltage was 30 kV. The output at this time was 170 mJ.

The line width can be changed by changing the angle of the incident diffraction grating of the oscillation optical system or the reflection mirror for wavelength selection, and the width of the oscillation wavelength. The range can be changed from 10 mm to 0.02 nm. In the present embodiment, control was performed so as to match each hole diameter. All the laser light irradiation time is 0.
It went in 1 sec.

FIG. 2 is a diagram in which a Cd photodetector is used, an output voltage depending on the light transmittance of a hole in a substrate is taken, and the degree of chip removal in the hole is examined. The vertical axis represents the output voltage of the photovoltaic power, 2
It is the voltage of the photovoltaic power proportional to the average light transmission amount of 300 pieces.

For example, in the case of a hole diameter of 0.25 mm, the output voltage is 5 mV if the hole is completely drilled and 100% good, but it is 28% at 1.4 mV when there is no cutting treatment. According to the present invention, the light transmittance is 9 at 4.97 mV.
It is 9.4%, which is extremely high efficiency. Hole diameter is 0.15
In mm, the light transmittance is 92%, while
In the conventional method, it was only 11.4%.

[0015]

According to the present invention, the diameter of the laser beam may be larger or smaller than the hole diameter, and the rare earth fine powder adhering to the tip of the burr or the glass may be ignited or adhered to the edge of the hole when wiping the brush. Due to the ignition of the rare earth fine powder generated, the heat generation of the rare earth fine powder between the glass fibers on the inner wall of the hole or between the hollow holes causes high speed removal of chip clogging and smoothing of the inner wall surface of small holes. Can be done reliably.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of processing a small-diameter hole in a substrate by using a high-brightness laser oscillator.

FIG. 2 is a graph showing the results of testing the average light transmission amount after processing in order to see the effect of the present invention in comparison with the conventional example in the relationship between the hole diameter and the voltage of the photovoltaic power.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshinori Shima 768, Ozenji, Aso-ku, Kawasaki-shi, Kanagawa 15 (72) Inventor Akira Ohba 3-1289 Miyato, Asaka-shi, Saitama

Claims (2)

[Claims] 1. A substrate material having a small diameter hole is wetted with a liquid in which a rare earth fine powder having a high oxidative exothermicity is suspended to remove only the liquid adhering to the substrate surface, and then a laser beam is applied to the small diameter hole. A method for treating a small-diameter hole in a substrate material, which comprises irradiating and heating the rare-earth fine powder to oxidize heat to treat the chips in the small-diameter hole to smooth the inner wall roughness. 2. The rare earth fine powder is La, Ce, Pr, N.
d, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
Lanthanoids such as m, Tb and Lu, Ac, Th,
The method for treating a small hole in a substrate material according to claim 1, which is a simple substance, an alloy or a mixture of actinides such as U and Pu.