JP2009253258A - Method for manufacturing wiring substrate, and wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a wiring substrate capable of easily and efficiently raising adhesiveness between an insulating layer and a conductor irrespective of a wiring pattern of the conductor, and to provide the wiring substrate. <P>SOLUTION: The method for manufacturing the wiring substrate 1 is characterized by providing: a conductor layer formation process 103 of forming a conductor layer 5 consisting of the conductor by adhesion on the surface 2a of the insulating layer 2; and a circuit formation process 104 of forming a wiring circuit 6 from the conductor layer 5 by etching, and further providing a recessed part formation process 102 of forming a recessed part 4 in an area A where the wiring circuit 6 is formed on the insulating layer 2 by a laser. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wiring board such as a printed wiring board and a manufacturing method thereof.

  A wiring board such as a printed wiring board is basically manufactured by plating a conductor such as copper on the surface of an insulating layer (conductor layer forming step) and etching it according to an arbitrary wiring pattern (circuit forming step). An electronic component or the like is connected to a wiring circuit having a wiring pattern formed by etching. In addition, when a wiring circuit is formed on both surfaces or a multilayer wiring board is formed, a through hole (through hole) for connecting other conductor layers (wiring circuits) to each other is formed in the insulating layer. (Insulating layer processing step).

Here, in the wiring board, it has been a problem to improve the adhesion between the insulating layer and the conductor. For example, as disclosed in Patent Document 1, in the process of manufacturing a printed wiring board, the surface of the insulating layer is roughened by chemical etching and then plated. By forming fine irregularities on the surface of the insulating layer to increase the surface area, the contact area between the surface of the insulating layer and the conductor is increased and the adhesion is improved.
JP 2000-88671 A

  By the way, in the circuit formation process for forming the wiring circuit, the etching progressing direction is a radial direction that is perpendicular to the surface of the insulating layer and parallel to the surface. That is, the conductor layer on the surface is etched wider as it is etched deeper.

  According to this, when a wiring circuit having a small distance between wirings is formed by etching, it cannot be etched widely, and the etching depth is limited. Therefore, in this case, in order to completely etch the conductor between the wirings, it is desirable to reduce the thickness of the plating (conductor layer) on the surface.

  However, if the thickness of the plating is reduced, the conductor on the convex portion of the roughened insulating layer surface is further thinned, and disconnection is likely to occur. Therefore, when forming a wiring circuit with a small distance between wirings, it has been necessary to reduce the surface roughness of the insulating layer surface by etching and secure the thickness of the thinnest conductor.

  Conventionally, when the surface roughness of the surface of the insulating layer is reduced as described above, there is a problem that the contact area between the surface of the insulating layer and the conductor is reduced correspondingly, resulting in a decrease in adhesion. Furthermore, in chemical etching, it is not easy to adjust the surface roughness of the insulating layer, and there is a problem in terms of manufacturing efficiency.

  The present invention has been made in view of such circumstances, and a method of manufacturing a wiring board that can easily and efficiently improve the adhesion between an insulating layer and a conductor, regardless of the wiring pattern of the conductor, and An object is to provide a wiring board.

A method of manufacturing a wiring board according to the present invention includes a conductor layer forming step of closely forming a conductor layer made of a conductor on the surface of an insulating layer, and a circuit forming step of forming a wiring circuit from the conductor layer by etching. It is a manufacturing method, Comprising: It further has the recessed part formation process which forms a recessed part in the area | region where a wiring circuit is formed on an insulating layer with a laser as a pre-process of the said conductor layer formation process, It is characterized by the above-mentioned. In addition, you may provide the other process between the said recessed part formation process and the said conductor layer formation process.

  According to this, since there is a recess formed by a laser, the contact area between the surface of the insulating layer and the conductor is increased, and the adhesion between the surface of the insulating layer and the conductor layer is improved. And this recessed part is formed in the area | region where a wiring circuit is formed in a subsequent circuit formation process on the insulating layer surface. There is no need to consider the thinning of the conductor layer by roughening the surface roughness when forming the conductor layer. Thereby, the thickness of the conductor layer can be ensured almost uniformly outside the region, and disconnection hardly occurs. Further, since the concave portion is under the wiring circuit, excellent adhesion between the insulating layer surface and the wiring circuit can be maintained even after the circuit formation step.

  Furthermore, according to the present invention, by using a laser, it becomes easy to form a concave portion (adjustment of depth and position, etc.), and a desired concave portion can be formed in a portion where adhesion is desired to be improved. That is, it is possible to easily and selectively increase the adhesion strength.

  Moreover, since the recess is formed using a laser used in another process, it can be efficiently manufactured without adding a special device for improving the adhesion. Lasers are used, for example, to form through holes that connect wiring circuits between other layers to an insulating layer.

  In the present invention, the recess is basically formed so that the entire recess fits in the region. However, the recess may be formed so that a part of the recess is outside the region. In the latter case, a part of the recess located outside the region is formed so as not to overlap the surrounding wiring region. In other words, the recess is located only under one wiring and is formed so as not to short-circuit the wirings. A plurality of recesses may be formed.

  Here, in the insulating layer processing step of the present invention, it is preferable to form a plurality of recesses along the region (wiring circuit). Thereby, the contact area between the insulating layer surface and the wiring circuit can be efficiently increased, and the adhesion is further improved. For example, it is preferable to form a plurality of recesses along the direction of current flow in the wiring circuit.

  Here, it is preferable to further include a roughening step of roughening the surface of the insulating layer including the concave surface by etching after the concave portion forming step. Thereby, fine irregularities are formed on the surface of the insulating layer including the concave surface, and the adhesion is further improved.

  The present invention is also characterized as a wiring board. That is, the wiring board of the present invention is a wiring board comprising an insulating layer and a wiring circuit made of a conductor formed in close contact with the surface of the insulating layer, and the insulating layer has a wiring circuit formed on the surface. And the wiring circuit is formed in close contact with the surface of the insulating layer including the surface of the recess. This has the same effect as described above.

  According to the method for manufacturing a wiring board and the wiring board of the present invention, the adhesion between the surface of the insulating layer and the conductor can be easily and efficiently improved regardless of the wiring pattern of the conductor.

  Next, the present invention will be described in more detail with reference to embodiments. In this embodiment, a printed wiring board having a build-up structure is taken as an example. In general, a printed wiring board having a build-up structure includes a core substrate (insulating layer) on which copper wiring circuits are formed on both sides, and a plurality of build-up layers stacked on both sides of the core substrate. Each build-up layer has an insulating layer made of resin and a wiring circuit formed on the surface of the insulating layer. The insulating layer (including the core substrate) is provided with a through hole (through hole) for connecting the wiring circuits of the respective layers.

  Hereinafter, the manufacturing method of the printed wiring board 1 in this embodiment is demonstrated with reference to drawings. FIG. 1 is a diagram showing a schematic flow of manufacturing. FIG. 2 is a plan view of the core substrate 2. FIG. 3 is a plan view of the core substrate 2 on which the copper plating 5 is formed. FIG. 4 is a plan view of the printed wiring board 1 after one layer is formed. 5 is a cross-sectional view taken along line BB in FIG. The drawings are schematically shown for convenience of explanation.

  First, as shown in FIG. 1, in the insulating layer processing step (101), the resin-made core substrate 2 is set in a laser irradiation apparatus (not shown). Then, a laser is shot a plurality of times to form through holes 3 at predetermined positions on the surface 2 a of the core substrate 2. The through holes 3 here are for connecting the wiring circuits provided on both surfaces of the core substrate 2. The through hole of the buildup layer laminated on the core substrate 2 connects the wiring circuit on the core substrate 2 and the wiring circuit on the buildup layer. That is, in the present embodiment, the through-hole 3 partially connects each layer, and has a smaller diameter than a through-hole that penetrates all layers formed by machining such as a drill. It is formed. The concave portion 4 of the present embodiment formed by the laser forming the through hole 3 can be formed with a small diameter, and can be applied to any wiring pattern. The core substrate 2 is included in the “insulating layer” in the present invention.

  Subsequently, in the recess forming step (102), the recess 4 is formed on the surface 2a of the core substrate 2 separately from the through hole 3 using the laser irradiation apparatus. Here, as shown in FIG. 2 and FIG. 5, the recess 4 has a substantially circular shape in plan view and a trapezoidal cross section in a plane orthogonal direction.

  The concave portion 4 does not penetrate the core substrate 2 and is formed in a region A (a portion surrounded by a dotted line in FIG. 2) on the surface 2 a below the wiring circuit 6. That is, in this step, the non-penetrating recess 4 is formed in the region A where the wiring circuit 6 is formed on the surface 2a by the laser. And the recessed part 4 is formed in multiple places along the area | region A (wiring circuit). One recess 4 is formed so as to be within the region A and non-penetrating depending on the laser processing conditions (adjustment of the number of shots, laser focusing, etc.).

  Subsequently, in the conductor layer forming step (103), copper plating 5 is applied on the surface 2a of the core substrate 2 as shown in FIG. Plating is performed by a known method such as electroless plating or electrolytic plating. The copper plating 5 fills the recess 4 and is formed in close contact with the surface 2a (see FIG. 5). The thickness of the copper plating 5 from the surface 2a is approximately 12 to 18 μm.

  Subsequently, in the circuit forming step (104), the wiring circuit 6 is formed from the copper plating 5 by etching. Briefly, first, a resist is laminated on the copper plating 5, and the resist is patterned according to the wiring pattern. Then, after the copper plating 5 is etched, the resist is peeled off. As a result, the copper plating 5 corresponding to the portion where the resist remains is left on the surface 2a of the core substrate 2, and a wiring circuit 6 corresponding to the wiring pattern of the resist is formed as shown in FIG. In the present embodiment, the wiring width of the wiring circuit 6 is approximately 50 μm, and the separation distance between adjacent wirings is approximately 50 μm. Thus, one layer is formed.

  Here, when a buildup layer is further formed (105: Yes), an insulating layer made of resin is laminated on the surface 2a of the core substrate 2 and the wiring circuit 6 (106). And as shown in FIG. 1, it returns to an insulating layer processing process (101), and performs the said process. By repeating this, a plurality of buildup layers are formed. In each build-up layer, as described above, a recess is formed in the insulating layer, and a wiring circuit is formed thereon.

  When the buildup layer is not formed (105: No), the manufacturing process ends. The surface on the other side (back side) of the core substrate 2 (not shown) is formed after (or at the same time or alternately) the layer formation on the surface 2a side. Even in each layer on the other side surface, the recess may be formed as described above. The printed wiring board 1 is manufactured as described above. Although not shown, electronic components may be arranged on the wiring circuit 6 or a solder resist may be formed on the core substrate 2 (insulating layer).

  Here, the effect of this embodiment will be described. According to the manufacturing method of the present embodiment, since there is the recess 4 formed by laser, the contact area between the surface 2a and copper is increased, and the adhesion between the core substrate 2 (insulating layer) and the copper plating 5 is improved. To do. And this recessed part 4 is formed in the area | region A where the wiring circuit 6 is formed in the circuit formation process (104) later on the surface 2a. Therefore, the recess 4 is located under the wiring circuit 6 and does not affect the etching depth of the portion where copper is etched (outside the region A). That is, a uniform thickness of the copper plating 5 can be secured outside the region A, and disconnection is less likely to occur. Further, since the recess 4 is below the wiring circuit 6, excellent adhesion between the core substrate 2 and the wiring circuit 6 can be maintained even after the circuit formation step (104).

  Furthermore, according to this embodiment, since the recess 4 is formed using the laser used in the insulating layer processing step (101), it is possible to efficiently perform without adding a special device for improving the adhesion. Can be manufactured. Further, by using a laser, the formation of the recess 4 (depth and position adjustment, etc.) can be facilitated, and the desired recess 4 can be formed in a portion where adhesion is desired to be improved. That is, it is possible to easily and selectively increase the adhesion strength. Even in the case of a wiring pattern having a small wiring width or inter-wiring distance as in this embodiment, the adhesion can be easily and efficiently improved by using a laser.

  In the present embodiment, the recess 4 is formed along the region A (the current path of the wiring circuit 6). Therefore, the adhesion can be improved more efficiently. Although not shown, the recess 4 may be formed intermittently along the entire region A, and the adhesion is further improved.

  Moreover, you may add a roughening process to the said manufacturing process. After the recess forming step (102), the insulating layer (including the core substrate 2) is etched to form fine irregularities on the surface including the recess 4. Thereafter, a conductor layer is formed on the surface of the roughened insulating layer (103). In this embodiment, since the adhesion is improved by the recess 4, no problem occurs in terms of adhesion even if the unevenness due to the roughening is reduced. That is, the size of the unevenness may be small without considering the adhesion, and does not require a difficult adjustment of the balance between the conductor thickness and the adhesion. That is, the adhesion can be further improved relatively easily.

  Moreover, you may replace the order of a manufacturing process in the possible range. For example, in FIG. 1, the insulating layer processing step (101) and the recess forming step (102) may be interchanged or may be performed simultaneously.

  Moreover, the shape of the recessed part 4 is not restricted above. For example, as shown in FIG. 6, the planar view shape may be an elliptical shape. According to this, adhesiveness can be improved efficiently. Further, as shown in FIG. 7, a part of the recess 4 may be outside the region A. In this case, however, the recess 4 in the wiring area A1 is formed so as not to enter the surrounding wiring area A2. That is, the recess 4 is formed so as not to short-circuit the wires. Moreover, the shape of the plane orthogonal cross section (FIG. 5) of the recessed part 4 is not restricted to the above, A semicircle shape, a rectangle, or the shape widened to the inner side may be sufficient.

  The printed wiring board 1 can be expressed as follows. As shown in FIG. 5, the printed wiring board 1 is a wiring board that includes an insulating layer 2 and a wiring circuit 6 made of a conductor formed in close contact with the surface 2 a of the insulating layer 2. In the region A where the wiring circuit 6 is formed on the surface 2a, a recess 4 is formed by laser, and the wiring circuit 6 is formed in close contact with the surface 2a of the insulating layer 2 including the surface of the recess 4. Yes. This printed wiring board 1 has the same effect as described above.

It is a figure which shows the outline flow of manufacture. 3 is a plan view of a core substrate 2. FIG. It is a top view of the core board | substrate 2 with which the copper plating 5 was formed. It is a top view of the printed wiring board 1 after 1 layer formation. It is the BB sectional view taken on the line in FIG. It is a figure which shows the modification of the recessed part. It is a figure which shows the modification of the recessed part.

Explanation of symbols

1: Printed circuit board,
2: core substrate (insulating layer), 2a: surface 3: through-hole, 4: recessed portion, 5: copper plating (conductive layer),
6: Wiring circuit
A: Area

Claims (4)

A method of manufacturing a wiring board comprising: a conductor layer forming step of closely forming a conductor layer made of a conductor on a surface of an insulating layer; and a circuit forming step of forming a wiring circuit from the conductor layer by etching,
Furthermore, the manufacturing method of the wiring board characterized by providing the recessed part formation process which forms a recessed part in the area | region where the said wiring circuit is formed on the said insulating layer with a laser as a pre-process of the said conductor layer formation process.   The method for manufacturing a wiring board according to claim 1, wherein in the recess forming step, a plurality of the recesses are formed along the region.   The method for manufacturing a wiring board according to claim 1, further comprising a roughening step of roughening a surface of the insulating layer including the surface of the concave portion by etching after the concave portion forming step. A wiring board comprising: an insulating layer; and a wiring circuit made of a conductor formed in close contact with the surface of the insulating layer,
The insulating layer has a recess formed by the laser in a region where the wiring circuit is formed on the surface;
The wiring board, wherein the wiring circuit is formed in close contact with the surface of the insulating layer including the surface of the recess.

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