JP2021093492A - Manufacturing method of print circuit board - Google Patents

Abstract

To provide a manufacturing method of a print circuit board, which suppresses inclination caused in a cavity inner wall and reduces processing time for forming its cavity in the print circuit board that forms the cavity by blast processing.SOLUTION: In a manufacturing method of a print circuit board, when providing a cavity of a preset XYZ dimension to an insulation layer exposed on a front surface of a substrate material in which a predetermined wiring is formed, pre-processing for forming a temporal cavity having size included in the cavity at a position of the cavity by laser processing or router processing is performed, and the cavity is formed by performing the processing to the XYZ dimension by blast processing after that.SELECTED DRAWING: Figure 1

Description

The present invention relates to the formation of a cavity structure in a method for manufacturing a printed wiring board.

A recess called a cavity is formed, and the number of printed wiring boards on which a semiconductor element is mounted is increasing in the cavity.
When this cavity is formed on a printed wiring board, it is generally formed by a single method of laser processing, router processing, or blasting.
For example, in Patent Document 1, since laser processing for forming vias one by one has a problem in productivity, it is described that vias are formed by sandblasting.

In recent years, miniaturization and low profile of printed wiring boards are required, and when a semiconductor element is mounted in a cavity, a printed wiring board having a large cavity area or a deep cavity depth is required. In particular, when machining with a deep cavity depth, there is a problem that the machining time becomes long even in sandblasting. In addition, since the processing time is long, the processing accuracy varies, and problems such as defects in finished dimensions occur.

In Patent Document 2, by performing wet blasting or sandblasting after laser processing, vias composed of inner wall portions having different taper angles are formed to improve the connection reliability between the vias and the upper conductor layer. Is described.

Japanese Unexamined Patent Publication No. 2004-063726 JP-A-2009-200356

An object of the present invention is to provide a method for manufacturing a printed wiring board in which a cavity is formed by blasting, in which an inclination generated on an inner wall of the cavity is suppressed and a processing time for forming the cavity is shortened.

According to the first aspect of the present invention, when a cavity having a predetermined XYZ size is provided in an insulating layer exposed on the surface of a substrate material on which a predetermined wiring is formed, a temporary cavity having a size included in the cavity is provided. Is a method for manufacturing a printed wiring board, characterized in that the cavity is formed at the position of the cavity by laser processing or router processing, and then processed to the XYZ dimensions by blasting.

A second invention of the present invention is a method for manufacturing a printed wiring board, characterized in that the edge bottom portion of the temporary cavity by preprocessing in the first invention is processed deeper than the central bottom portion of the temporary cavity.

A third aspect of the present invention is a step of preparing a substrate material in which a predetermined wiring is formed on a copper layer, and an XYZ-sized temporary cavity in which an insulating layer exposed on the surface of the substrate material is contained in a predetermined cavity. In addition, a pre-processing step of processing by laser processing or router processing, a step of forming a resist mask for blast having a portion forming the cavity open on the surface of the substrate material, and a step of being exposed from the opening of the resist mask. A method for manufacturing a printed wiring board, which comprises a step of forming the cavity having a predetermined XYZ size by blasting the insulating layer and a step of removing the resist mask for blasting.

A fourth invention of the present invention is a method for manufacturing a printed wiring board, characterized in that the bottom portion of the temporary cavity formed by preprocessing in the third invention has a pool bottom portion processed deeper than the central portion. ..

According to the present invention, the machining time can be shortened as compared with the case of forming a cavity by a single method of blasting, and it is possible to easily obtain a printed wiring board having a small inclination generated on the inner wall of the cavity formed by blasting and having excellent machining accuracy. Is.

It is a figure which shows the process flow of the manufacturing method which concerns on this invention, (1) is a substrate preparation process, (2) is a resist mask forming process, (3) is a copper layer etching process, (4) preprocessing process (laser processing). Alternatively, a temporary cavity is formed by router processing), (5) is a resist mask forming step for blasting, and (6) is a cavity forming step (blasting).

First, the outline of the production method of the present invention will be described, and then, a specific flow of the production method of the present invention will be described with reference to FIG.
In the present invention, a resist layer is formed on a surface copper layer such as a three-layer substrate having an insulating layer and a copper layer, and a resist mask having an opening is formed at a position where a cavity is formed. This opening is formed to be larger than the XY dimension and not in contact with the wiring formed from the surface copper layer when the size of the opening required for the cavity is set to the "XY dimension".
The "XY dimension" is the size of the opening of the cavity when the surface of the substrate A is the "xy surface" in the coordinate system "xyz system" of FIG. 1 shown in FIG. It is provided in the shape of a square, rectangle, etc.).

Next, the copper layer exposed from the opening of the resist mask is removed by etching.
Then, the resist mask is removed. If the resist mask is not removed here, it may be removed after performing laser processing or router processing in the next step.

Next, the insulating layer exposed by etching is laser-processed or router-processed to have a dimension smaller than the XYZ dimension required as a cavity (the depth direction of the cavity is z and the size is "Z dimension"), that is, a predetermined dimension. It is processed into a "temporary cavity" of the size contained in the cavity. At this time, the XY dimension is processed to be about 0.005 to 1 mm smaller on one side. The Z dimension is such that the entire bottom of the temporary cavity is machined to about 40 to 70% of the required depth, and the bottom of the edge is machined to about 70 to 100%. This makes the bottom of the temporary cavity deeper than the bottom of the center.

Next, a resist mask having an opening having an XY dimension required as a cavity is formed. When this resist mask is formed from a thick resist layer or depending on the abrasive particle size used, it is preferable to form an opening wide by about 5 to 40 μm on one side with respect to the required XY size.

Next, a cavity having a predetermined size is formed by blasting, and the resist mask is removed.

By going through such a process, it is possible to obtain a printed wiring board in which the processing time is shortened as compared with the case where the cavity is formed by the single method of blasting only, and the inclination generated on the inner wall of the cavity by the processing is also reduced.

Hereinafter, a more detailed description will be given with reference to the manufacturing flow chart of FIG.
The substrate A shown in FIG. 1 (1) usually has an insulating layer 10 and an insulating layer 20 having different thicknesses, and a front surface copper layer 31, an inner layer copper layer 32, and a back surface copper layer 33 are laminated on these layers. It is a three-layer substrate.

A cavity is provided on the surface of the surface copper layer 31 of the substrate A after the resist layer is formed, and an etching resist mask serving as an opening thereof is formed. Opening w ₁ this time is larger than the XY dimensions required for a cavity, and forming an opening in a size not to contact the wiring formed from the surface of copper layer (see FIG. 1 (2)).
Further, on the surface of the back surface copper layer 33, an etching resist mask 101 covering the entire surface is formed (see FIG. 1 (2)).

Then, as shown in FIG. 1 (3), an etching process is performed to remove the exposed surface copper layer 31 from the opening (see FIG. 1 (2)) of the resist mask 100 for etching, and then, for etching on both sides. The resist masks 100 and 101 are removed.

Next, as shown in FIG. 1 (4), the temporary cavity _CT is formed here.
The bottom 200 is formed by processing the entire opening to a predetermined depth (Z dimension) with an XY dimension having a size in which the opening of the cavity is slightly reduced to the insulating layer 10 by laser processing. At that time, the edge bottom portion is processed deeper than the depth of the entire area to form the edge bottom portion 201 (see FIG. 1 (4)).

Next, as shown in FIG. 1 (5), a resist layer is formed on the surface of the surface copper layer 31. Since this resist layer is thick, a resist mask 300 for blasting having an opening having an XY dimension larger than the XY dimension of the cavity was formed.

Next, the blasting, forming a cavity _{C A} which is a predetermined XYZ dimensions, to remove the blasting resist mask 300, the printed wiring board P with a cavity _{C A} is obtained (see FIG. 1 (6)).

Hereinafter, the present invention will be described in detail with reference to examples.

It has a 240 μm-thick insulating layer 10 and a 70 μm-thick insulating layer 20 made of the glass cloth and epoxy resin shown in FIG. 1 (1), and has a 30 μm-thick surface copper layer 31, an inner copper layer 32, and a back surface copper layer. Ten three-layer substrates made of 33 were prepared as test substrates A.

Next, as shown in FIG. 1 (2), a resist layer having a thickness of 20 μm is formed on the surface of the surface copper layer 31 of the test substrate, and an etching resist serving as an opening for forming a cavity having an XY dimension of 3 mm × 40 mm. The mask 100 was formed. Opening w ₁ this time is larger than the XY dimension required as a cavity, an opening was formed in a size not to contact the wiring formed from the surface of copper layer. Specifically with respect to XY dimensions of the cavity of 3 mm × 40 mm, an opening was formed _{w 1} of 3.2 mm × 40.2 mm. Further, on the surface of the back surface copper layer 33, an etching resist mask 101 covering the entire surface was formed.

Then, as shown in FIG. 1 (3), an etching process was performed to remove the exposed surface copper layer 31 from the opening of the etching resist mask 100, and then the etching resist masks 100 and 101 on both sides were removed. ..

Next, as shown in FIG. 1 (4), the insulating layer 10 is machined to the insulating layer 10 with an XY dimension of 2.96 mm × 39.96 mm to a depth of 150 μm to form the bottom 200, and the edge portion is further formed. The edge bottom portion 201 was formed by processing to a depth of 200 μm.

Next, as shown in FIG. 1 (5), a resist layer having a thickness of 100 μm was formed on the surface of the surface copper layer 31. Since the resist layer is thick, it is set 30 μm larger on one side to form a resist mask 300 for blasting having _{an opening w 2 having an XY dimension of 3.06 mm × 40.06 mm.}

Next, as shown in FIG. 1 (6), by blasting, to form a cavity C _A which is a predetermined XYZ dimensions, to remove the blasting resist mask 300.
When the inclination of the formed inner wall of the cavity was evaluated by a value of 1/2 of the difference between the XY dimension of the upper surface of the cavity and the XY dimension of the bottom surface of the cavity, an average inclination of 19 μm was obtained.
Then, in this combined method of laser processing and blasting, the processing time was about 150 minutes.

As in Example 1, 10 3-layer substrates are prepared as test substrates, an opening of 3.2 mm × 40.2 mm is formed in the surface copper layer by etching processing, and 2.96 mm to the insulating layer 10 by router processing. With an XY dimension of × 39.96 mm, the whole was machined to a depth of 150 μm to form a bottom, and the edge was further machined to a depth of 200 μm to form a bottom.

Next, a resist mask for blasting having an opening having an XY dimension of 3.06 mm × 40.06 mm is formed, and a cavity having a predetermined XYZ dimension is formed by blasting, and then a resist for blasting is formed. The mask was removed.
When the inclination of the formed inner wall of the cavity was evaluated by a value of 1/2 of the difference between the XY dimension of the upper surface of the cavity and the XY dimension of the bottom surface of the cavity, an average inclination of 18 μm was obtained.
In the combined construction method by router processing and blast processing at this time, the processing time was about 210 minutes.

(Comparative Example 1)
As in Example 1, 10 3-layer substrates were prepared as test substrates, and an opening of 3.2 mm × 40.2 mm was formed in the surface copper layer by etching.
Next, a resist mask for blasting having an opening having an XY dimension of 3.06 mm × 40.06 mm is formed, and a cavity having a predetermined XYZ dimension is formed by blasting, and then a resist for blasting is formed. The mask was removed.
When the inclination of the formed inner wall of the cavity was evaluated by a value of 1/2 of the difference between the XY dimension of the upper surface of the cavity and the XY dimension of the bottom surface of the cavity, an average inclination of 39 μm was obtained.
In the single method by blasting at this time, the processing time was about 240 minutes.

As described above, the processing time is shortened by about 20 to 35% as compared with the single method of blasting only.
Further, the inclination generated on the inner wall of the cavity was about 40 μm in the single method of blasting only, but it was halved to about 20 μm in the combined method of router processing and laser processing and blasting of the present invention.

As confirmed on the test board this time, even in the actual product, the wiring required for each copper layer is formed, and the cavity is formed by a combined method of router processing, laser processing and blast processing, which shortens the processing time of the cavity part. The processing accuracy will be improved.

10 Insulation layer 20 Insulation layer 31 Front surface copper layer 32 Inner layer copper layer 33 Back surface copper layer 100 Etching resist mask (front surface)
101 Etching resist mask (back side)
200 Temporary cavity machining by laser machining or router machining Bottom (parts other than the bottom of the temporary cavity / bottom of the edge)
201 Temporary cavity machining by laser machining or router machining Bottom (edge bottom of temporary cavity)
300 Resist mask for blast A substrate (3-layer substrate)
Opening of the C _A cavity C _T temporary cavity P printed wiring board w ₁ opening w ₂ blasting resist mask 300 of the etching resist mask 100

Claims (4)

When a cavity having a predetermined XYZ size is provided in an insulating layer exposed on the surface of a substrate material on which a predetermined wiring is formed, a temporary cavity having a size contained in the cavity is subjected to laser processing or router processing. A method for manufacturing a printed wiring board, which comprises performing pre-machining to be formed at a cavity position and then processing to the XYZ dimensions by blasting to form the cavity. The method for manufacturing a printed wiring board according to claim 1, wherein the edge bottom portion of the temporary cavity is machined deeper than the central bottom portion of the temporary cavity by the pre-processing. The preparation process of the substrate material in which the predetermined wiring is formed on the copper layer, and
A pre-processing step of processing the insulating layer exposed on the surface of the substrate material into a temporary cavity of XYZ size contained in a predetermined cavity by laser processing or router processing.
A step of forming a resist mask for blasting in which a portion forming the cavity is opened on the surface of the substrate material.
A method for manufacturing a printed wiring board, which comprises a step of forming the cavity having a predetermined XYZ size by blasting the insulating layer exposed from the opening of the resist mask and a step of removing the resist mask for blasting. .. The method for manufacturing a printed wiring board according to claim 3, wherein the bottom portion of the temporary cavity formed by the pre-processing has a pool bottom portion processed deeper than the central portion.

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