JPH02295689A - Energy beam drilling method - Google Patents

Abstract

PURPOSE:To perform drilling at high speed with high accuracy by changing repetitive frequency of an energy beam and forming drilled holes having funnel- shaped cross-sectional forms at the time of performing drilling with plural beam pulses per hole. CONSTITUTION:When materials such as ceramic and synthetic resin are irradiated with an electron beam 8 from an electron gun 1, since evaporated materials are generated and scattered at the time of machining these materials, the irradiation electron beam is scattered by those evaporated particles. The higher the repetitive frequency is, the more this scattering effect becomes remarkable. lt is considered that this cause is due to the fact that the interval of the beam irradiations becomes shorter and the particles are hardly scattered. Even if the same electron beam is projected, when the repetitive frequency is made high, the machined hole diameter is increased by the scattering effect. By this method, in energy beam drilling work to perform drilling with the plural beam pulses per hole, many holes having funnel-shaped cross-sectional forms can drilled at high speed with high accuracy by changing the repetitive frequency of the beam and using the scattering effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an energy beam drilling method that is applicable to drilling ceramics, resin plates, composite material plates, metal plates, and the like.

[Conventional technology]

Figure 3 is, for example, from the publication (Japanese Studies Wi Promotion Association Fuku, published by Nikkan Kogyo Shimbun, [Electron/Ion Beam/) End Book 2nd Edition, p. 384 (1986)) is a configuration diagram illustrating a conventional electron beam drilling method.
In the figure, (1) is an electron gun, (2) is an alignment coil, (3) is a converging lens, (4) is a deflection lens, (6) is a sample, and (8) is an electron beam.

Next, the operation will be explained. The electron beam (8) generated from the electron gun (1) is aligned by the alignment coil (2), and is focused on the sample (6) by the converging lens (3). Deflection lens <<4>> deflects the electron beam (8) to an arbitrary position on the sample.Since the electron beam (8>> is usually focused to a high power density of 106 to tosw/crr12, the irradiation of the electron beam (8) The part of the sample (6) instantly melts and evaporates, and a hole is drilled.

Figure 4 shows, for example, a publication (Ceramic Processing Handbook Compiled by the Ceramic Processing Committee, published by Construction Industry Research Group Co., Ltd., "Ceramic Processing Handbook" p. 409 (1987)).
FIG. 2 is a schematic diagram of a cross-section of a hole drilled in alumina ceramics that cannot be recorded by the conventional electron beam drilling method, as shown in FIG.

[Problem to be solved by the invention]

First of all, we will explain in detail the reason why a machined hole with a funnel-shaped cross-section as shown in Fig. 2 is necessary, using an example.

For example, LSI, PGA (pin grid array) for high-density mounting boards: For example, see publications (published by Nikkei Magnou-Hill, ``Nikkei Microdevice Seven'', No. 2, 1984).
) When attempting to apply this to the drilling of a chip carrier (a jig for inserting chips into a board) made by Lamix, the cross-sectional shape of the drilled hole had a unique "funnel" shape as shown in Figure 2. required. The reason for this is: ■ The distance between the holes in the mounting board 1 and the board is narrow. That is, the holes in the chip carrier are required to have high positioning performance (the ability to guide the electrode pins of the LSI to the holes in the substrate). Follow me,
High hole position accuracy is required, and the diameter of the hole on the back of the chip carrier should be as small as possible within a range larger than the bottle diameter.

■LSI electrode bottles are thin and easily bent. Therefore, consider the possibility that the LSI pins may be slightly bent during mounting,
The hole diameter (diameter of the hole opening) on the surface of the chip carrier should be
Bigger is better.

■When considering LSI bottles, it is best to have the ``funnel''-shaped hole opening and the hole in the guide part on the same axis as much as possible.

In order to satisfy the conditions of ■■■, a ``funnel''-shaped cross-sectional shape that is not coaxial is required, as shown in Figure 2.

Taking electron beam drilling as an example, the conventional electron beam drilling method is configured as described above, so when considering its application to an actual industrial processing method, it is important to - Since machining parameters such as repetition frequency cannot be changed arbitrarily and automatically, even if the cross section of the machined hole has a straight shape as shown in FIG. 4, it becomes tapered. Therefore, it is difficult to automatically (i.e., form a large number of holes at high speed) having a "funnel" cross-sectional shape as shown in FIG. 2.

A commonly thought method for obtaining a hole with a "funnel" cross-sectional shape is to intentionally create a hole with the power density distribution of the irradiating beam as shown in A in FIG. 5. As shown in Figure 5, a typical method for this purpose is to increase the beam diameter at the focusing lens (3) (increase the focusing angle of the beam) and increase the spherical surface of the focusing lens (3). There is a method that generates significant aberrations and obtains the power density distribution as shown in Figure 5A. However, with this method, when the beam is deflected to process a large number of holes at high speed, coma aberration (the convergence angle 6 (A), (
As shown in B) with and without coma, the axial symmetry of the beam power density distribution is lost. Therefore, there is a problem in that it is not possible to rapidly machine holes with a desired shape accuracy due to beam deflection.

Alternatively, in order to obtain a "funnel" cross-sectional shape, the hole (5) as shown in Figure 4 is machined by drilling with a power density distribution as shown in example B in Figure 5. There is also a method of re-machining with a drill etc. to enlarge only the diameter of the hole on the front side after humiliation to obtain a "funnel" shaped hole as shown in Figure 2, but the second method is Although it is true that the desired hole shape can be obtained, there are problems such as a two-step machining process, a long machining time, and a high machining cost.

The second invention was made to solve the above-mentioned problems, and it is possible to rapidly machine a large number of holes (5) with a "funnel" cross-sectional shape as shown in the example in Figure 2. The purpose is to obtain a possible energy beam drilling method.

[Means to solve the problem]

The energy beam drilling method according to the second invention is as follows:
In an energy beam drilling method in which a hole is drilled using a plurality of beam pulses per hole, the repetition frequency of the beam is changed to form a machined hole having a "funnel"-shaped cross-sectional shape.

[Effect]

For example, in the case of an electron beam, materials such as ceramics and synthetic resins generate and scatter evaporated particles during processing, and the irradiated electron beam is scattered by these evaporated particles. This scattering effect becomes more pronounced as the repetition frequency of the beam increases. The reason for this is thought to be that the interval between beam irradiations becomes shorter and the particles become less likely to diffuse. For this reason, even if the same electron beam is irradiated, if the repetition frequency is increased, the hole diameter will increase due to the scattering effect, making it possible to process a large number of holes with a "funnel" cross-sectional shape at high speed. .

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.
In Figure 1, (1) is an electron gun, <<2>> is an alignment coil, (3> is a converging lens, <<4> is a deflection lens, and (6) is a deflection lens.
>> is the sample, (8> is the electron beam, (9) is the deflection lens for vertical irradiation, <<lO>> is the evaporated material of the sample, (11) is the D/A converter and current amplifier, (l2> is the pulse generator) nelator, <13> indicates a control combinator.

Next, the operation will be explained. An electron beam <8) generated from an electron gun (1) is aligned by an alignment coil (2) and focused onto a sample (6>) by a converging lens (3). The computer (13) drives a D/A converter and a current amplifier (1l), and uses its output current to direct the electron beam (8) to the sample. 6〉
The electron beam <8> passes perpendicularly to the sample <<6>>.
Deflect it so that it is incident perpendicularly to any position above. Since the electron beam (8) is usually focused at a high power density of 106 to 108 W/cm2, the part of the sample (6) irradiated by the electron beam (8) instantly melts and evaporates, and drilling is performed. .

For example, in the case of an lmmt alumina ceramic plate, the accelerating voltage is 60 kV. Beam current 40 mA
+ Set the pulse width to 50 μs. At that time, the continuator (l3) sets the repetition frequency to l k during the first half of the drilling process.
Hz and irradiate 10 pulses, then reset the repetition frequency to 10 Hz in the second half of the drilling process, send a command to the pulse generator (l2) to irradiate lO pulses, and perform the process.

Section 22 describes the relationship between the repetition frequency of the beam pulse and the machined hole diameter. In the case of electron beams, evaporated matter (10) is generated during processing of materials such as ceramics and synthetic resins.
Due to the scattering, the irradiated electron beam is scattered by these evaporated particles. This scattering effect becomes more pronounced as the repetition frequency of the beam increases. The reason for this is thought to be that the interval between beam irradiations becomes short, making it difficult for particles to diffuse. Therefore, even if the same electron beam is irradiated, if the repetition frequency is increased, the diameter of the machined hole will increase due to the scattering effect (and the depth of the machined hole will also decrease at the same time). Experimentally, under the processing conditions of the example above, for the hole diameter at 10Hz,
The effect of increasing the hole diameter by about 70% was observed with irradiation at 500 Hz.

Due to this machining phenomenon, in the first 10 pulses, the repetition frequency is high, so the diameter of the machined hole becomes large and a hole opening is formed, and in the next 10 pulses, the repetition frequency is low, so the diameter of the machined hole becomes small and a guide part is formed. be done.

As a result, the desired "funnel" as shown in Figure 2 is created.
A hole suitable for a chip carrier with a cross-sectional shape of the mold (5)
can be processed automatically.

The advantage of the present invention compared to conventional methods that utilize spherical aberration is that the guide portion is formed by effectively utilizing processing phenomena rather than the power density distribution (shape) of the beam. Even during deflection, hole accuracy such as coaxiality between the hole opening and the guide portion can be easily maintained at a high level. In other words, the method according to the present invention is much more likely to perform corrections to maintain the beam shape during beam deflection to the same shape as when the beam is not deflected.

Note that when the beam 《8〉 is deflected, the focal length between the sample 《6〉 and the converging lens 《3》 becomes longer. It may also be used for correction.

Further, in the above embodiment, the repetition frequency is changed from 10}1K to lk}lz, but this may be another value.

In addition, in the above embodiment, the repetition frequency is first set to low to form a through hole with a relatively small diameter, and then set to high again to form a hole with a large diameter. Although we have obtained a hole with the cross-sectional shape of the mold, this employs a completely different control method to return the desired shape,
You can also program the combination to Ichiyo and have it perform the processing.
The same effects as in the above embodiment are achieved. Specifically, for example, in the first half of the drilling process, the repetition frequency is set to high in order to form a hole with a large diameter, and in the second half of the drilling process, the repetition frequency is set to high in order to form a through hole with a relatively small diameter. It is also possible to obtain a hole with a "funnel" cross-sectional shape by automatically changing the After forming multiple large-diameter large openings (or large openings), large-diameter openings (or narrow-diameter through-holes) are formed in these through-holes (or large openings) to create a "funnel"-shaped cross section. A machined hole having a shape may be obtained.

In addition, as specific means for changing the frequency, for example,
The pulse generator (l2) can be controlled by a combinatorial controller.D/A that can be controlled by a computer
Converters and pulse generators are relatively easily available.

Further, in the above embodiment, although electron optical system equipment for electron beam shaping such as a stigmator and an aperture is not added, even if it is added, the same effects as in the above embodiment can be achieved.

Further, in the above embodiments, magnetic field type concentrators and deflectors are used, but they may also be electric field type concentrators and deflectors.

Further, in the above embodiment, two sets of deflectors are used, but the number of deflectors may be one set or three or more sets, and the same effects as in the above embodiment can be obtained.

Further, although an electron beam is used in the above embodiment, other energy beams such as a laser beam may also be used, and the same effects as in the above embodiment can be obtained.

For reference, in the above embodiment, the repetition frequency is changed; however, this can be done in the same way as in the above embodiment, even if the irradiation pulse width is changed or a combination of repetition frequency change and pulse width change is used. It has the effect of Specifically, if the pulse width is increased to about 200 μs, the hole diameter can be reduced by several tens of percent.
I can do about 100% of the time.

Further, even if the irradiation beam current is changed, even if the repetition frequency is changed and the irradiation beam current is changed in combination, the same effects as in the above embodiments can be obtained. Specifically, by increasing the beam current, the hole diameter can be increased.

〔Effect of the invention〕

As described above, according to the present invention, in an energy beam drilling method in which holes are drilled using a plurality of beam pulses per hole, the repetition frequency of the beam is changed to drill holes having a "funnel"-shaped cross-sectional shape. Because it is formed, it can be processed using the scattering effect, and it has the effect of being able to process a large number of holes with a ``funnel'' cross-sectional shape with high accuracy and at high speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating an electron beam drilling method according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a cross section of a drilled hole in a sample obtained by the method of FIG. 1, and FIG. 3 is a conventional method. 4th block diagram explaining the electron beam drilling method of
The figure is a schematic diagram showing the cross section of a drilled hole in a sample obtained by the conventional electron beam drilling method, Figure 5 is an explanatory diagram showing the current density distribution at each position when there is spherical aberration, and Figure 6 (A ) and (B) are explanatory diagrams showing power density distributions with and without coma, respectively. In the figure, (1) is the electron gun, (2) is the alignment coil, <3> is the converging lens, (4) is the deflection lens, (5) is the machined hole, (6) is the sample, and (8) is the electron beam, (9) is a deflection lens for vertical irradiation, <<lO> is the evaporated material of the sample, (1
1) indicates a D/A converter and a current amplifier, <<l2>> a pulse generator, and <<l3>> a control combinator. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] An energy beam drilling method in which holes are drilled using a plurality of beam pulses per hole, characterized in that the repetition frequency of the beam is changed to form a processed hole having a "funnel" type cross-sectional shape. Energy beam drilling method.