JP3706512B2 - Processing method of through hole of resin substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for processing a through hole of a resin substrate by laser processing.
[0002]
[Prior art]
Some semiconductor devices have a resin substrate as a core substrate, a required wiring pattern is formed on both surfaces of the core substrate, and semiconductor elements are mounted. FIG. 5 shows a method of forming a wiring board having wiring patterns formed on both sides of the core board.
FIG. 5 (a) is a cross-sectional view of a core substrate in which a copper layer 12 is formed on both surfaces of the resin substrate 10 by adhesion of copper foil or copper plating, and FIG. 5 (b) shows through holes 14 formed in the core substrate. Shows the state. FIG. 5C shows a state in which the core substrate is then plated to form a conductor layer 16 by plating on the inner surface of the through hole 14 and the surface of the core substrate. FIG. 5D shows a state in which the conductor layer 16 on the surface of the core substrate is etched to form a wiring pattern 18 on the surface of the core substrate. FIG. 5E shows a state in which the insulating layer 20 is further formed on the surface of the core substrate by applying a resin, and the wiring pattern 22 of the next layer is formed by being electrically connected to the wiring pattern 18 by the via 24. The wiring patterns 18 and 22 formed on both surfaces of the core substrate are electrically connected via the conductor layer 16 formed on the inner surface of the through hole 14.
[0003]
Thus, in a method for manufacturing a semiconductor device in which a semiconductor element is mounted by forming a wiring pattern on both surfaces of a core substrate, it is necessary to first form through holes in the core substrate. As a method for forming a through hole in the core substrate, drilling is generally used. However, since there is a limit to the hole diameter of the through hole 14 that can be formed by drilling, a method using a laser beam has come to be performed as a method of forming the smaller diameter through hole 14.
[0004]
[Problems to be solved by the invention]
According to the method using laser light, it is possible to form through holes having a diameter of about 0.1 mm, and it is possible to form through holes at a higher density in the core substrate than in the case of drilling. Is possible.
However, the method of forming a through hole using laser light has the following problems. FIG. 6 shows a conventional method for forming a through-hole 14 by irradiating a workpiece having a copper layer 12 on both surfaces of a resin substrate 10 with laser light. 6A shows a state in which the workpiece is supported on the base plate 26 and is irradiated with laser light, and FIG. 6B shows a state in which the through hole 14 is formed in the workpiece. As shown in the figure, when the through-hole 14 is formed using laser light, for example, a core substrate having a thickness of 200 μm, the diameter of the through-hole 14 on the upper surface of the core substrate is 120 μm, and the diameter on the lower surface is 120 μm. As in the case of 60 to 70 μm, there is a problem that the diameter dimension is greatly different between the top and bottom of the through hole. Conventionally, there is a large variation in diameter at the bottom of the through hole, and there is a variation of about ± 30 μm.
[0005]
Thus, when the hole diameter of the through hole is different between the upper surface and the lower surface of the core substrate, it is difficult to deposit the plating on the inner surface of the through hole, and the conductor layer is not reliably formed on the inner surface of the through hole. A conduction failure occurs in the wiring pattern formed on both surfaces.
Further, as shown in FIG. 6B, since the lower surface of the through hole 14 irradiated with the laser light is closed by the base plate 26, the inner surface of the through hole 14 is contaminated by the scattered matter due to the laser light. Also, it is difficult to deposit the plating on the inner surface of the through hole.
FIG. 6B shows a state in which the flash 12a is attached to the periphery of the opening of the through hole 14 when the laser beam is irradiated. As described above, when the flash 12a is generated, the copper layer 12 is etched to prevent a fine wiring pattern from being formed.
[0006]
When the through hole is formed by irradiating the core substrate with the laser beam as described above, if the copper layer 12 is on the surface of the resin substrate 10, the etching rate by the laser beam is slowed down and the processing time is increased. Therefore, in order to increase the processing efficiency, a method of forming the through hole 14 by laser processing after removing the copper layer 12 on the surface of the resin substrate 10 can be considered. FIG. 7 shows a state in which the resin substrate 10 from which the copper layer 12 has been removed is irradiated with laser light to form a through hole 14. However, as shown in the figure, when only the resin substrate 10 is irradiated with laser light, the peripheral edge of the opening of the through hole 14 is damaged by the laser light 14a and cannot be processed into the required shape of the through hole 14. is there.
[0007]
The present invention has been made to solve these problems, and the object of the present invention is to process through holes having a smaller diameter while suppressing variations in the diameters of the through holes formed in the resin substrate by laser processing. It is possible to provide a method for processing a through hole of a resin substrate by laser processing, which can be performed and can improve the processing efficiency of the through hole formed in the resin substrate.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises the following arrangement.
That is, in a method for processing a through hole of a resin substrate in which a through hole is formed by irradiating a workpiece having a conductive layer on both surfaces of a resin substrate with laser light from one surface side, the conductor layer is covered. A resin layer that can be etched by a laser beam and that forms a resist pattern that forms a wiring pattern by patterning the conductor layer into a predetermined pattern is deposited on the surface of the attached workpiece. Irradiating the workpiece with laser light from the side opposite to the surface on which the resin layer is deposited , etching the resin layer together with the workpiece, and forming a through hole in the workpiece Features. In the case of this method, by etching the resin layer together with the workpiece, the through hole can be easily removed and the through hole can be easily processed.
[0009]
Further, in a method for processing a through hole of a resin substrate, wherein a laser beam is irradiated from one surface side to a workpiece having a conductor layer deposited on both surfaces of the resin substrate, a laser beam is applied to the resin substrate. As a pre-process for irradiating light, the conductor layer deposited on both surfaces of the resin substrate is etched over the entire surface to reduce the thickness of the conductor layer, and then the surface of the workpiece on which the conductor layer is deposited Further, a resin layer for forming a resist pattern that can be etched by a laser beam and that forms a wiring pattern by patterning the conductor layer into a predetermined pattern is deposited, and the resin layer is deposited. The workpiece is irradiated with laser light from the side opposite to the surface to be etched, and the resin layer is etched together with the workpiece to form a through hole in the workpiece. The processing efficiency of laser processing can be improved by reducing the thickness of the conductor layer, and the through hole can be processed with higher accuracy by reducing the irradiation time of the laser beam .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory view showing a first embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention. FIG. 1A shows a state in which a core substrate 30 as a workpiece is supported on a base plate 26 for laser processing. In this laser processing apparatus, a workpiece is air-adsorbed and supported on a processing stage (not shown), and the processing stage is moved relative to the laser light source to form a through hole at a predetermined position. The base plate 26 is a support substrate for setting the core substrate 30 on the processing stage, and is provided with suction holes that communicate with air suction holes provided in the processing stage.
[0011]
The structure characterized by the processing method of the present embodiment is to perform laser processing by supporting the core substrate 30 that is a workpiece on a pattern plate 32 in which escape holes 32a are formed in advance in accordance with positions where the through holes 14 are formed. It is in the point which did. FIG. 1A shows a state in which the core substrate 30 is supported on the base plate 26 via the pattern plate 32 and the laser beam is irradiated. FIG. 1B shows the through hole 14 formed in the core substrate 30 by laser processing. Shows the state.
[0012]
As shown in FIG. 1B, the escape hole 32a formed in the pattern plate 32 is formed larger than the diameter of the through hole 14, and the core substrate 30 is irradiated with laser light to form the through hole 14. The through hole 14 is formed so as to penetrate completely. Since the arrangement of the through holes 14 formed in the core substrate 30 is determined in advance, escape holes 32 a are formed in the pattern plate 32 in accordance with the planar arrangement of these through holes 14. The material of the pattern plate 32 is not particularly limited. For example, a metal plate made of copper, aluminum, iron, or the like is etched to form the escape hole 32a, or a resin plate is etched to form the escape hole 32a. Further, the pattern plate 32 and the base plate 26 are not formed separately, but a resin layer such as polyimide is applied to the base plate 26, and the resin layer is etched to form a relief hole 32a. An integrally attached base plate 26 can also be used.
[0013]
The base plate 26 is a part that receives laser light when the through hole 14 is formed through the core substrate 30. The reason why the core substrate 30 is supported by the base plate 26 in this embodiment is to prevent the laser beam from being directly irradiated onto the processing stage of the laser processing apparatus.
Further, in this embodiment, the pattern plate 32 is used separately from the base plate 26, but the escape hole 32a is completely penetrated by the through hole 14 on the lower surface side when the core substrate 30 is irradiated with laser light. Since it is for opening the through hole 14 on the lower surface side, the pattern plate 32 and the base plate 26 are integrated, and a pattern plate in which a recess-shaped escape hole 32a is formed in accordance with the position where the through hole 14 is formed. It is also possible to use 32 and not use the base plate 26. Thus, the escape hole 32a formed in the pattern plate 32 may be a through-hole penetrating the pattern plate 32 or a concave hole. The depth of the escape hole 32a may be set as appropriate, but in this embodiment, it is set to a depth of about 100 μm.
[0014]
Thus, according to the method of forming the through hole 14 by irradiating the core substrate 30 with the laser beam using the pattern plate 32 in which the escape hole 32 a is formed, the through hole 14 is easily formed. Variations in the hole diameters of the through holes 14 on the upper and lower surfaces can be reduced. In the example in which the through holes 14 are actually formed in the core substrate 30 by the method of the present embodiment, when the thickness of the core substrate is 200 μm and the hole diameter is 100 μm on the upper surface of the core substrate 30, the hole diameter on the lower surface of the core substrate 30 is 80 μm. It became about. Thus, according to the method of the present embodiment, the difference in the hole diameters of the through holes 14 on the upper and lower surfaces of the core substrate 30 can be reduced, and the variation in the hole diameters on the lower surface of the through holes 14 is about ± 10 μm. There is an effect that the through hole 14 can be formed with extremely high accuracy. If the through holes 14 can be formed with high accuracy without variation in hole diameter, the through holes 14 can be formed in the core substrate 30 with high density.
[0015]
In addition, since the difference in the hole diameters of the through holes 14 between the upper and lower surfaces of the core substrate 30 is small, a conductor layer can be reliably formed on the inner surface of the through holes 14 by plating, and poor conduction in the through holes 14 can be prevented. It becomes possible to do. In addition, since the escape hole 32a is formed and the lower surface of the through hole 14 is opened, dirt scattered when the core substrate 30 is etched by the laser beam is less likely to adhere to the inner surface of the through hole 14, and this also causes plating. As a result, the conductor layer can be reliably deposited on the inner surface of the through hole 14.
[0016]
FIG. 2 is an explanatory view showing a second embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention. The present embodiment is characterized in that the core substrate 30 which is a workpiece is supported on the base plate 26 via the mesh sheet 34. The mesh sheet 34 of the present embodiment is made of a wire made of metal such as stainless steel woven in a mesh shape, and has a wire diameter of about 30 to 70 μm and a mesh interval of about 300 μm. The core substrate 30 is supported via the mesh sheet 34 so that the bottom surface of the through-hole 14 is not closed when the through-hole 14 is formed by irradiating the core substrate 30 with laser light as in the above embodiment. This is to facilitate the formation of the through hole 14. If a mesh sheet having a mesh interval larger than the hole diameter of the through hole 14 is selected as the mesh sheet 34, the lower surface of the through hole 14 is not closed by the mesh sheet 34, and the lower surface of the through hole 14 is opened to open the core substrate 30. Can be laser processed.
[0017]
When the mesh sheet 34 is used, the wire constituting the mesh sheet 34 may be located at the same position as the position where the through hole 14 is formed. However, since the wire has a circular cross-sectional shape, a gap is not generated between the wire and the lower surface of the through hole 14, and the through hole 14 is not completely closed by the wire.
Also in this embodiment, when the through hole 14 is formed in the core substrate 30, the lower surface of the through hole 14 is not closed, and the through hole 14 can be formed with high accuracy.
[0018]
In the present embodiment, the mesh sheet 34 formed of a metal wire is used. However, a porous sheet formed of chemical fibers or natural fibers can be used in the same manner as the mesh sheet.
The mesh sheet 34 allows the core substrate 30 to be adsorbed to the base plate 26 by air and allows the through holes 14 to be easily processed in the core substrate 30 by laser processing. When a porous sheet such as paper or nonwoven fabric is used, the core substrate 30 can be adsorbed to the base plate 26 in the same manner as the mesh sheet, and the through hole 14 can be easily processed.
Examples of materials that can be used as these mesh sheets or porous sheets are as follows.
As for using metal fibers (wires), mesh bodies formed of stainless steel, aluminum, iron, etc., as for using chemical fibers, woven fabrics using nonwoven fabrics such as polyester and nylon, nonwoven fabrics or sponges, Nonwoven fabrics and woven fabrics using hemp, cotton, silk, pulp (paper), etc. can be used as those using natural fibers.
[0019]
These mesh sheets and porous sheets only need to have a degree of mesh or porosity that allows the workpiece to be adsorbed and supported on the base plate 26 by air adsorption. In the case of using a metal mesh sheet, it is necessary to use one having a mesh interval wider than the hole diameter of the through hole 14, but in the case of a mesh sheet or porous sheet using chemical fibers or natural fibers, However, it is not necessary to consider the degree of mesh or the degree of porosity in relation to the hole diameter of the through hole 14 because it can be easily processed by laser light and does not hinder laser processing.
[0020]
FIG. 3 is an explanatory view showing a third embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention. In the present embodiment, a resin layer 36 that is easily etched by laser light is formed on the lower surface of the core substrate 30 that is a workpiece, and the core substrate 30 is supported on the base plate 26 via the resin layer 36 to perform laser processing. It is characterized by doing.
3A shows a state in which the core substrate 30 is irradiated with laser light, and FIG. 3B shows a state in which the through holes 14 are formed in the core substrate 30. FIG. In the through hole processing method of the present embodiment, when the core substrate 30 is irradiated with laser light and penetrates the through hole 14, the resin layer 36 on the lower surface of the through hole 14 is etched with laser light to pass through the through hole 14. Is processed. Since the resin layer 36 is easily etched with laser light, the resin layer 36 is etched when the through hole 14 is penetrated, and a recess 36 a is formed on the lower surface of the through hole 14.
[0021]
In this way, when the through hole 14 is formed so that the resin layer 36 is etched, the inner surface of the through hole 14 is etched straight, and variation in the diameter of the through hole 14 is suppressed. The reason why the resin layer 36 that is easily etched by the laser beam is interposed between the core substrate 30 and the base plate 26 is to allow the through hole 14 to be easily penetrated without being closed.
[0022]
As a method for interposing the resin layer 36 between the core substrate 30 and the base plate 26, a method of setting a resin film having a thickness of about 0.1 mm on the surface of the base plate 26, A method in which a resin film is applied in advance to form the resin layer 36 is possible. The copper layer 12 deposited on the lower surface of the core substrate 30 is formed into a predetermined wiring pattern by etching. Therefore, in the manufacturing process of the wiring substrate using the core substrate 30, a resin layer for forming a resist pattern for etching the copper layer 12 with a predetermined pattern is formed on the lower surface of the core substrate 30. Since the resin layer is formed by attaching a resin film such as a dry film, it is possible to use a resin film previously attached to the core substrate 30 in order to pattern the copper layer 12 as the resin layer 36.
[0023]
The method of forming the through hole 14 using the resin layer 36 for forming a resist pattern for etching the copper layer 12 is effective in that the resin layer used in the manufacturing process of the wiring board can be used.
As a method of forming the resin layer 36, the surface of the copper layer 12 of the core substrate 30 can be formed by coating a resin material. This resin layer 36 can be used as a resin layer 36 for forming a resist pattern, and can be used when the through hole 14 is formed.
[0024]
FIG. 4 is an explanatory view showing a fourth embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention. In this embodiment, an etching process for reducing the thickness of the copper layer 12 deposited on the surface of the core substrate 30 is performed as a pre-process for irradiating the core substrate 30 that is a workpiece with laser light. And The thickness of the copper layer 12 applied to both surfaces of the resin substrate 10 of the core substrate 30 is usually about 10 μm to 20 μm. In the present embodiment, first, the thickness of the copper layer 12 deposited on both surfaces of the resin substrate 10 is reduced to a thickness of about 5 to 7 μm by chemical etching, and then the core substrate is formed in the same manner as in the above-described embodiment. A through hole 14 is formed at 30.
[0025]
FIG. 4A shows the core substrate 30 in which the copper layer 12 is deposited on both surfaces of the resin substrate 10. FIG. 4B shows a state in which the copper layer 12 is etched by chemical etching to reduce the thickness of the copper layer 12. FIG. 4C shows a state in which the core substrate 30 is supported on the base plate 26 via the resin layer 36 and the through holes 14 are formed in the core substrate 30 by irradiating laser light.
According to the processing method of the through hole 14 of the present embodiment, the thickness of the copper layer 12 deposited on the surface of the resin substrate 10 is further reduced, and then the through hole 14 is formed by laser processing. 14 processing efficiency can be increased. When the through hole 14 is formed by laser processing, the metal layer such as the copper layer 12 is difficult to be etched by the laser beam. Therefore, if the copper layer 12 is thick, the processing efficiency of the through hole 14 is lowered. On the other hand, in this embodiment, the through-hole 14 can be processed more efficiently by reducing the thickness of the copper layer 12.
[0026]
Further, when the through hole 14 is processed, the reason why the hole diameter is different between the upper surface and the lower surface of the core substrate 30 is that when the through hole 14 is etched to the lower surface side of the core substrate 30, the lower copper layer 12 is formed. If the thickness of the through hole 14 is large, it takes time to etch the copper layer 12. At this time, the inner surface of the through hole 14 may be etched and the shape of the through hole 14 may deviate from the predetermined shape. In this respect, if the laser processing is performed by reducing the thickness of the copper layer 12 as in this embodiment, the copper layer 12 on the lower surface of the through hole 14 can be easily etched, and the hole shape of the through hole 14 is Deviating from the predetermined shape can be effectively prevented.
Also, leaving the copper layer 12 on both surfaces of the resin substrate 10 prevents the peripheral edge of the opening of the through hole 14 from being etched by laser light, and the through hole as shown in FIG. There is an effect of preventing a recess from being formed on the peripheral edge of the 14 openings.
[0027]
In FIG. 4C, the resin layer 36 is interposed between the core substrate 30 and the base plate 26 to form the through holes 14 in the core substrate 30, but the copper layer 12 deposited on both surfaces of the resin substrate 10. When the laser processing is performed with a reduced thickness, the workability of the through hole 14 is improved, so that the conventional processing method can be applied regardless of the processing method shown in FIGS. Is possible. Of course, it is possible to form the through-hole 14 with higher accuracy by utilizing the above-described method of using the pattern plate 32 provided with the escape hole 32a.
[0028]
Moreover, after forming the through-hole 14 in the core substrate 30, the scattered matter and the burrs adhering to the surface of the copper layer 12 and the inner surface of the through-hole 14 can be removed by etching the copper layer 12 again. By reducing the thickness of the copper layer 12 (3 to 5 μm), it is possible to form a wiring pattern at a higher density. Of course, the copper layer 12 may be completely etched and removed from the surface of the core substrate 30. These operations may be appropriately selected as processing steps for forming wiring patterns on both surfaces of the core substrate 30.
[0029]
【The invention's effect】
According to the method for processing a through hole in a resin substrate by laser processing according to the present invention, as described above, it is possible to form a through hole with high accuracy in the resin substrate. As a result, it is possible to arrange extremely small diameter through holes at a high density in the resin substrate, and it is possible to suitably cope with downsizing of the semiconductor device. Further, since the through hole can be formed with high accuracy, it is possible to reliably form the conductor layer on the inner surface of the through hole by plating, and it is possible to prevent the problem of poor conduction at the through hole portion. In addition, it is possible to improve the processing efficiency for forming the through hole in the resin substrate.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a first embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention.
FIG. 2 is an explanatory view showing a second embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention.
FIG. 3 is an explanatory view showing a third embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention.
FIG. 4 is an explanatory view showing a fourth embodiment of a method for processing a through hole of a resin substrate by laser processing according to the present invention. It is explanatory drawing which shows the manufacturing method of a semiconductor device.
FIG. 5 is an explanatory view showing a method of manufacturing a wiring board having wiring patterns on both surfaces of a core board.
FIG. 6 is an explanatory view showing a conventional method of forming a through hole in a resin substrate by laser processing.
FIG. 7 is an explanatory view showing a conventional method of forming a through hole in a resin substrate by laser processing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Resin board | substrate 12 Copper layer 14 Through-hole 16 Conductive layer 18 Wiring pattern 20 Insulating layer 22 Wiring pattern 24 Via 26 Base board 30 Core board 32 Pattern board 32a Escape hole 34 Mesh sheet 36 Resin layer 36a Recessed part

Claims (2)

In the processing method of the through hole of the resin substrate, the laser beam is irradiated from one surface side to the workpiece in which the conductor layer is attached to both surfaces of the resin substrate.
Resin layer for forming a resist pattern that can be etched with a laser beam on the surface of the workpiece on which the conductor layer is deposited, and that forms a wiring pattern by patterning the conductor layer into a predetermined pattern Depositing and forming
A laser beam is irradiated to the workpiece from the side opposite to the surface on which the resin layer is deposited, and the resin layer is etched together with the workpiece to form a through hole in the workpiece. A method for processing a through hole of a resin substrate. In the processing method of the through hole of the resin substrate, the laser beam is irradiated from one surface side to the workpiece in which the conductor layer is attached to both surfaces of the resin substrate.
As a pre-process of irradiating the resin substrate with laser light, the conductor layer deposited on both surfaces of the resin substrate is etched over the entire surface to reduce the thickness of the conductor layer,
Resin layer for forming a resist pattern that can be etched with a laser beam on the surface of the workpiece on which the conductor layer is deposited, and that forms a wiring pattern by patterning the conductor layer into a predetermined pattern Depositing and forming
A laser beam is irradiated to the workpiece from the side opposite to the surface on which the resin layer is deposited, and the resin layer is etched together with the workpiece to form a through hole in the workpiece. A method for processing a through hole of a resin substrate.

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