JP2022139923A - Method for manufacturing workpiece - Google Patents

Abstract

To provide a method for manufacturing workpiece capable of effectively removing an affected layer and microcracks generated when workpiece is processed by laser processing.SOLUTION: A method for manufacturing workpiece obtained by carrying out laser processing of a base material includes: a laser processing step S2 of irradiating the base material with a laser beam, and forming a laser processed part in the base material; an affected layer removal step S3 of processing the affected layer generated in the laser processed part with a first treatment liquid in which the base material is slightly soluble, and dissolving and removing the affected layer; and an etching step S4 of etching the surface of the laser processed part with a second treatment liquid in which the base material is soluble after the affected layer removal step.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a workpiece processed by laser irradiation.

2. Description of the Related Art There is known a method of processing an object to be processed (hereinafter referred to as a work) by irradiating the work with a laser beam to form a through hole in the work, cut the work, or the like. Laser processing is processing that utilizes a photochemical reaction (ablation), a photothermal reaction, or a combination thereof by irradiating a workpiece with a laser beam, and is widely used in various fields. For example, Japanese Unexamined Patent Application Publication No. 2002-100003 describes a wiring board having via electrodes in which through holes are filled with conductors, and the through holes of the via electrodes are formed by laser processing.

In laser processing, debris scattered on the surface of the material and dross of the melted material adhere to the processed site and the surroundings of the processed site, microcracks in the processed site due to heat influence, heat affected zone (processed deterioration layer) , areas where the hardness changes due to laser processing). In order to suppress such problems, a processing method has been proposed in which the power density of the laser beam and the position of the focal point of the laser beam are specified (for example, see Patent Document 2).

JP 2012-216583 A Japanese Patent No. 5901178

For example, in a wiring board provided with via electrodes as described in Patent Document 1, debris and dross adhere around through-holes of the substrate, and microcracks or process-affected layers are formed on the inner wall surfaces of the through-holes. If it is, it will hinder the filling of the wiring on the substrate surface and the conductors of the via electrodes, resulting in a decrease in the reliability of the electrical connection of the wiring substrate. Furthermore, since the work-affected layer and the microcracks have minute voids, it may not be possible to maintain airtightness between the front and back surfaces after the through holes are filled with conductors as via electrodes.

Considering the processing principle of laser processing, it is impossible to completely avoid the adhesion of debris and dross, the formation of microcracks, and the process-affected layer. Therefore, after laser processing, the workpiece is cleaned by brush cleaning, rinse cleaning, ultrasonic cleaning, high-pressure water cleaning, vacuum drying, plasma cleaning, polishing, and other methods. It is difficult to reliably remove cracks or work-affected layers, and in particular, it is not easy to remove microcracks and work-affected layers generated on the inner wall surfaces of through-holes.

The present invention was completed in view of the above problems, and its object is to provide a work manufacturing method that can effectively remove a work-affected layer and microcracks that are generated when a work is processed by laser processing. It is a thing.

A method for manufacturing a workpiece obtained by laser processing a base material, comprising: a laser processing step of irradiating the base material with a laser beam to form a laser-processed portion on the base material; and a process-affected layer generated on the laser-processed portion. is treated with a first treatment liquid in which the base material is hardly soluble, and after the work-affected layer removal step of dissolving and removing the work-affected layer, the surface of the laser-processed portion is removed. and an etching step of etching the base material with a second treatment liquid in which the base material is soluble.
Further, the work manufacturing method may further include a polishing step of removing debris or dross adhered to the surface of the base material by the laser processing step by polishing the surface of the base material.
Furthermore, the polishing step may be performed before the process-affected layer removing step.
The substrate may be aluminum nitride, the first treatment liquid may be hydrofluoric acid, and the second treatment liquid may be a solution of potassium hydroxide.
Further, the work may be a flat substrate, and the work manufacturing method may include forming a through hole in the substrate in the laser processing step.

According to the work manufacturing method of the present invention, it is possible to effectively remove the work-affected layer and microcracks generated by laser processing.

It is process drawing which shows the manufacturing method of the workpiece|work which concerns on this embodiment. FIG. 4 is an enlarged cross-sectional view schematically showing the periphery of a through hole after laser processing;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a wiring substrate having via electrodes is used as an example to describe the work manufacturing method of the present invention. FIG. 1 is a process chart showing a method for manufacturing a workpiece according to this embodiment. A wiring board is manufactured by the following steps.

[Laser processing step: S1]
First, a base material for a wiring board is prepared, and a laser beam is irradiated to the base material to form a through-hole extending through the front and back surfaces of the base material. In this embodiment, the base material is aluminum nitride, and a YAG laser is irradiated from above the surface side of this base material to form the through-holes. Through this process, debris, dross, cracks, and a heat-affected layer (work-affected layer) are formed around the opening of the through-hole of the base material and on the inner wall surface of the through-hole, which is a processed portion in the laser processing. FIG. 2 is an enlarged sectional view schematically showing the periphery of the through hole after laser processing. Debris 101 dispersed by laser processing adheres to the periphery of the opening of the through hole 11 on the front side of the base material 10, and the base material 10 melts and flows to the back side around the opening of the through hole 11 on the back side. A solidified dross 102 is formed. In addition, on the inner wall surface of the through-hole 11, a process-affected layer 103 is formed due to the thermal effect of laser processing, and cracks 104 are formed. The crack 104 extends from the work-affected layer 103 formed on the inner wall surface of the through-hole 11 to the base material 10 .

The debris 101, the dross 102, and the work-affected layer 103 are formed by decomposing or melting aluminum nitride constituting the base material 10 by irradiation with laser light, and the decomposed and melted aluminum nitride is cooled in the atmosphere. Since it is oxidized during the process, its main component is considered to be aluminum oxide (Al ₂ O ₃ ).

[Polishing step: S2]
Next, the front and back surfaces of the substrate are polished. Polishing is carried out by applying an abrasive to a smooth surface such as a platen and rubbing the substrate against the smooth surface. This step removes debris and dross formed around the opening of the through-hole. The work-affected layer and cracks formed on the inner wall surface of the through-hole remain on the inner wall surface of the through-hole.

[Work-affected layer removal step: S3]
Next, the substrate is immersed in a treatment liquid in which the substrate (aluminum nitride) is sparingly soluble and the work-affected layer (aluminum oxide) is soluble. Here, "the base material is poorly soluble" means that the main component of the base material does not dissolve in the processing solution at all. This includes dissolving to the extent that the shape of the base material does not change during the immersion time to the extent that it impairs the function of the work. Further, the phrase "the work-affected layer is soluble" means that the main component of the work-affected layer can be dissolved in the treatment liquid for a reasonable immersion time for manufacturing the workpiece. In this step, the work-affected layer and cracks formed in the work-affected layer are removed from the substrate by dissolving the work-affected layer in the treatment liquid. At this time, the substrate is hardly dissolved. Therefore, cracks formed in the base material are not removed either. In this embodiment, hydrofluoric acid is used as the treatment liquid.

In this embodiment, the polishing step S2 is performed before the work-affected layer removing step S3 to remove debris and dross, but the polishing step S2 is not necessarily required. Since the debris and dross are composed of the same components as the work-affected layer, the polishing step S2 is not performed, and in the work-affected layer removal step S3, the debris and dross are dissolved with the treatment liquid and removed together with the work-affected layer. may However, debris and dross are often formed with a thickness greater than the work-affected layer, and in that case, it is necessary to take a longer immersion time in the treatment liquid than when only the work-affected layer is removed. preferably implemented. In addition, when the substrate is immersed in the treatment liquid by applying ultrasonic waves to the treatment liquid, the work-affected layer can be removed more effectively.

[Etching step: S4]
Next, the base material (aluminum nitride) is immersed in a processing liquid in which the base material is soluble, and the surface of the base material is etched. Here, "the base material is soluble" means that the main component of the base material can be dissolved to the extent that cracks formed on the surface of the base material can be removed for a reasonable immersion time for manufacturing the workpiece. In this step, the substrate is immersed in the treatment liquid to etch the surface of the substrate and remove cracks formed in the substrate on the inner wall surfaces of the through-holes. In this example, a potassium hydroxide (KOH) solution was used as the treatment liquid.

The etching step S4 is performed after the work-affected layer removing step S3. This is because the cracks formed in the substrate by the laser processing step S1 are almost always covered with a work-affected layer, debris, or dross, and the etching step S4 is performed prior to the work-affected layer removal step S3. This is because the etching of the portion of the base material covered with the work-affected layer does not progress, making it difficult to remove cracks. By sequentially performing the work-affected layer removing step S3 and the etching step S4, it is possible to solve such problems and effectively remove cracks formed in the work-affected layer and the substrate. Furthermore, cracks can be removed more effectively by immersing the substrate in the treatment liquid while applying ultrasonic waves to the treatment liquid.

Although the polishing step S2 may be performed after the work-affected layer removing step S3, it is preferable that the polishing step S2 be performed before the etching step S4 is performed. By performing the polishing step S2 before the etching step S4, even cracks generated in the base material by the polishing step S2, which are not caused by laser processing, can be removed in the etching step S4.

[Washing step: S5]
The substrate is then washed. The cleaning is performed by washing with pure water, which is a cleaning liquid, ultrasonic cleaning, or high-pressure cleaning, and removes residues such as the processing liquid, debris, and dross attached to the substrate in each of the above-described steps.

[Drying step: S6]
Next, the cleaned substrate is dried with warm air to remove the cleaning liquid. Through the above steps, a base material (work) having through holes free from debris, dross, process-affected layers, and cracks generated by laser processing is manufactured. A wiring board having via electrodes is manufactured by forming a metal film on the inner wall surface of the wiring board and filling the through holes with a conductor.

Although the present invention has been described above based on the embodiments, the present invention is not limited to these embodiments, and various modifications and changes are possible without departing from the scope of the present invention. For example, in the embodiments, the substrate is made of aluminum nitride, but the substrate may be made of other ceramic materials, metal materials, resin materials, etc., or may be a processing object other than the substrate. The present invention is applicable as long as the layer and the base material are different materials.

In addition, the laser processing has been described as an example of hole processing for forming a through hole in a base material, but the present invention can also be applied to other types of laser processing such as cutting and trimming. Furthermore, the laser light source in laser processing is not limited to the YAG laser, and a light source such as a CO ₂ laser or a fiber laser may be appropriately selected depending on the type of substrate and processing.

Further, in the examples, the washing process is explained as washing with a washing liquid and the drying process as hot air drying.

10 base material 11 through hole 101 debris 102 dross 103 work-affected layer 104 crack

Claims (5)

A method for manufacturing a workpiece obtained by laser processing a base material,
a laser processing step of irradiating the base material with a laser beam to form a laser-processed portion on the base material;
A process-affected layer removing step of treating the process-affected layer generated in the laser-processed portion with a first treatment liquid in which the base material is difficult to dissolve, and dissolving and removing the process-affected layer;
After the work-affected layer removing step, an etching step of etching the surface of the laser-processed portion with a second treatment liquid in which the base material is soluble;
A method of manufacturing a workpiece, comprising: 2. The method of manufacturing a workpiece according to claim 1, further comprising a polishing step of removing debris or dross adhering to the surface of the base material by the laser processing step by polishing the surface of the base material. 3. The method of manufacturing a workpiece according to claim 2, wherein the polishing step is performed before the work-affected layer removing step. The workpiece according to any one of claims 1 to 3, wherein the base material is aluminum nitride, the first treatment liquid is hydrofluoric acid, and the second treatment liquid is a potassium hydroxide solution. Production method. 5. The method of manufacturing a workpiece according to claim 1, wherein the workpiece is a flat substrate, and a through hole is formed in the substrate in the laser processing step.

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