JPS62240187A - Piercing method using laser light - Google Patents

Abstract

PURPOSE:To maintain the temp. around a piercing part at a gentle gradient and to prevent cracking by irradiating low-density laser light below the energy density for piercing to the periphery of the piercing part. CONSTITUTION:The low-density laser light 12 is irradiated on the periphery of a through-hole 2 and the high-density laser light 13 is irradiated on the piercing part at the time of piercing a through-hole having about 0.1mm diameter to a circuit board 1. The energy density of the low-density laser light 12 is made lower than the energy density to pierce the through-hole 2 to the board 1. The ambient temp. of the through-hole 2 is heated to about the intermediate temp. of the boring temp. and room temp. by irradiating such low-density laser light 12, by which the temp. gradient around the piercing part is made gentle. The generation of microcracks around the piercing part is, therefore, prevented and the reliability of the circuit board 1 is improved.

Description

[Detailed Description of the Invention] “ [Summary] When perforating a ceramic substrate, etc. using a laser beam, the temperature gradient around the perforation is reduced by irradiating the area around the perforation with a low-density laser beam that is less than the perforation energy density. This is done by making the hole gentler so that no cranking occurs around the perforation.

[Industrial application field]

The present invention relates to a drilling method using a laser, and particularly to an improvement in a method of drilling holes in ceramic substrates and the like that are prone to cranking during drilling.

For example, when providing a through ball in a hybrid integrated circuit board, the through hole provided in the board made of glass or ceramic must be made of extremely difficult-to-process material, or have a diameter of 0.
．． Laser machining is used because micromachining of about 1 mm is required.

[Conventional technology]

FIGS. 4(a) and 4(o) are diagrams for explaining a conventional drilling method using laser light.

In FIG. 4(a), a substrate l for a hybrid integrated circuit made of glass, ceramic, or resin has through-holes connecting circuit elements formed and mounted on its upper surface and circuit elements formed and mounted on its lower surface. For example, to provide a diameter of 0
．． A through hole 2 of about 1 mm is bored.

As shown in FIG. 4 (TI), where the vertical axis is the energy density Ed of the laser beam and the horizontal axis is the distance d from the center of the hole, the laser beam 3 for drilling can reduce variations in the hole diameter and improve efficiency. Because of the drilling, etc., energy is concentrated facing the through hole 2, resulting in a density distribution with a peak exceeding the drilling energy density.

The ceramic substrate 1 irradiated with the laser beam 3 is partially
When the temperature reaches 000° C. or more, it melts and scatters, forming a through hole 2. A conductive layer is coated on the inner wall of the through hole 2, and the through hole is completed.

[Problem that the invention seeks to solve]

2. When drilling the through hole 2, the energy density of the laser beam 3 is concentrated in the hole where the through hole 2 is formed. As a result, the temperature gradient between the through hole and its surroundings becomes extremely steep, generating large internal strain, which may cause microcracks to occur around the through hole 2, and residual strain that causes microcranks to develop and grow over time. There was a problem that remained.

The reliability of the hybrid integrated circuit is impaired because the conductor layer attached to the inner wall may be cut, or the processing liquid in the post-process that has permeated the microcrank may corrode the conductor layer of the through ball.

[Failure to solve the problem]

FIG. 1 is a diagram for explaining a basic method of forming a through hole 2 in a circuit board 1 to which the present invention is applied.

In FIG. 1, a circuit board 1 is irradiated with a low-density laser beam 12 that irradiates the area around a through-hole 2 and a high-density laser beam 13 that irradiates the perforated portion of the through-hole 2 .

The energy density of the low-density laser beam 12 is
The energy density of the high-density laser beam 13 is set to be equal to or higher than the drilling energy density for drilling the through hole 2 in the substrate 1.

Therefore, when the substrate l is irradiated with laser light 12.13, the low-density laser light 12 heats the area around the through-hole 2 to a temperature intermediate between the laser drilling temperature and room temperature, and the high-density laser light 13 heats the area around the through-hole 2. is heated to a laser drilling temperature, and a through hole 2 is drilled.

[Effect]

According to the above means, the area around the perforation is heated with a low-density laser beam, and the temperature gradient around the perforation becomes gentle, thereby eliminating the generation of microcracks and reducing residual strain to a harmless level. Therefore, when the method of the present invention is applied to the formation of through holes in a hybrid integrated circuit, the reliability of the hybrid integrated circuit is improved.

〔Example〕

EMBODIMENT OF THE INVENTION Below, the Example which applies this invention and drills the through-hole 2 in the circuit board 1 is demonstrated using drawing.

Fig. 2 is a diagram for explaining an embodiment of the present invention in which the heating around the perforation part and the heating for the perforation are performed in separate steps, and Fig. 3 is a diagram for explaining an embodiment of the present invention in which the heating around the perforation part and the heating for the perforation are performed in separate steps. It is a figure for explaining an example.

In the embodiment shown in FIGS. 2 and 3, a through hole 2 with a diameter of 0.1 mm is drilled in a substrate 1 made of ceramic porcelain. The energy density of the laser beam irradiated twice is approximately 0.3 Joule/pulse. In Figure 2 (C) and Figure 3 (El) and (+1) showing the energy density characteristics of the laser beam used, the vertical axis is the energy density Ed of the laser beam, and the horizontal axis is the distance d from the center of the through hole. .

Fig. 2 (a) is a side view for explaining the preheating state of heating the surroundings of the perforation, Fig. 2 (rl) is a side sectional view for explaining the state of drilling the perforation, and Fig. 2 (c) 2 is a diagram showing the energy density distribution of the laser beam used, and in FIG. 2(C), the vertical axis is the energy density distribution Ed of the laser beam, and the horizontal axis is the distance d from the center of the through hole.

In FIG. 2(A), prior to drilling a through hole 2 in a ceramic substrate 1, a low density laser beam 12 is irradiated onto the through hole portion and its surroundings. The low-density laser beam 12 has a drilling energy density of less than A, for example, about 0.15 units/pulse, as shown by the dotted line in FIG. The area to be heated and its surroundings are preheated to, for example, several hundred degrees Celsius.

In FIG. 2 (■), immediately after completing the irradiation with the low density laser beam 12, the high density laser beam 13 is irradiated.

The high-density laser beam 13 has a drilling energy density A or higher, for example, 0.3 joules/pulse, as shown by the solid line in FIG.

FIG. 3(A) is a side sectional view for explaining the drilling state of the hole, FIG. 3(II) is a diagram showing the energy density distribution of the laser beam shown in FIG. 3(A), and FIG. C) is a diagram showing the energy density distribution of the low-density laser beam irradiated to the transparent hole, and in FIGS. It is the distance d from the hole center.

In FIG. 3(a), the low-density laser beam 12 that is irradiated to the hole-piercing portion and its surroundings and the low-density laser beam 14 that is irradiated to the hole-boring portion are synchronized and irradiated at the same time.

The low-density laser beam 14 that is irradiated onto the center of the aforementioned low-density laser beam 12 and directed in the direction λj toward the perforated portion is, for example, 0.15 µm under the perforation energy density distribution as shown in FIG. The energy density distribution of the synchronized laser beams with the low-density laser beams 12 and 14 is about 1.5 mm/pulse, and the energy density distribution of the laser beam synchronized with the low-density laser beams 12 and 14 is more than the drilling energy density Δ, facing the through hole 2, as shown in FIG. 3 (b).
For example, the amount is 0.3 Joule/pulse, and the through hole 2 is bored.

〔Effect of the invention〕

As explained above, the present invention heats the periphery of the hole by irradiating it with a low-density laser beam that is less than the drilling energy density.
The temperature gradient (internal stress gradient) around the through hole becomes gentler than in the conventional method, eliminating the occurrence of microcracks and reducing residual strain to a harmless level. As a result, when the present invention is applied to a through hole for a through pole of a hybrid integrated circuit board, the effect of improving the reliability of the hybrid integrated circuit is remarkable.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the basic method of drilling a through hole in a circuit board by applying the present invention, FIG. 2 is a diagram for explaining an embodiment of the present invention, and FIG. Figure 4 is a diagram for explaining another embodiment of the present invention. Figure 4 is a diagram for explaining a conventional drilling method using laser light. In the figure, 1 is a circuit board, 2 is a through hole, 12 and 14 are low-density laser beams, and 13 is a high-density laser beam. (C) Azuto Akira, f1 i7zuC square color combination jΣsayu 1st day Kao song dtsu Figure 3 Gesai Uhe table * tnm 昂2 Zusakira kei Σ theory Moesu 5 people Zuko ArTr7'1

Claims (1)

[Claims] During drilling using a laser beam, the area around the drilling area is treated with a low-density laser beam (12) that is less than the drilling energy density.
A drilling method using laser light, characterized in that heating is performed so that the temperature gradient between the drilling part and the surroundings of the drilling part becomes gentle.