JP2013211477A - Manufacturing method of printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unfailingly remove a seed layer so as to prevent an undercut part from occurring below a wiring pattern even when the seed layer includes a metal other than copper.SOLUTION: A printed wiring board is manufactured in a method described as follows. A seed layer 2 is formed on a surface 1a of a resin base material 1, and a plating resist 3 is patterned. Then, plating process is performed on the exposed seed layer 2 to form a wiring pattern 4. The plating resist 3 is removed to expose unwanted seed layer 2. A laser beam L is radiated to an entire surface 1a of the resin base material 1 to remove the unwanted seed layer 2.

Description

  The present invention relates to a method for manufacturing a printed wiring board used in an electronic device.

  Conventionally, a semi-additive method has been frequently used as a method of manufacturing a printed wiring board (see Patent Document 1). In the semi-additive method, a seed layer is formed by electroless plating on an insulating resin substrate, a conductor circuit is formed on the seed layer by electrolytic copper plating, and then the seed layer is removed by unnecessary electroless plating. This is a method of forming a wiring pattern of a conductor circuit. When the seed layer is removed, the seed layer may be removed excessively due to the difference in film quality between the seed layer and the electrolytic copper plating layer, and the conductor circuit may be undercut.

  In Patent Document 1, when removing a seed layer by unnecessary electroless plating, the etching rates of the electroless copper plating layer and the electrolytic copper plating layer match so that an undercut portion does not occur below the formed wiring pattern. An etchant prepared to do so is disclosed.

JP 2009-149971 A

  However, since the etching agent disclosed in Patent Document 1 is used for removing a seed layer formed by electroless copper plating, it is suitable for removing a seed layer containing a metal other than copper. There is no problem.

  The present invention eliminates the problems caused by the prior art described above, and can reliably remove a seed layer containing a metal other than copper without causing an undercut portion below the wiring pattern. It aims at providing the manufacturing method of.

  The method for manufacturing a printed wiring board according to the present invention includes a step of forming a seed layer on a main surface of a resin base, a step of patterning a plating resist on the seed layer, and the seed other than the plating resist forming portion. A method of manufacturing a printed wiring board, comprising: a step of plating on a layer; a step of removing the plating resist; and a step of removing the seed layer where the plating resist has been removed. In the step of removing the layer, the seed layer is removed by irradiating with laser light.

  According to the method for manufacturing a printed wiring board according to the present invention, the seed layer is removed by irradiating a laser beam excellent in straightness, so that the seed layer is securely formed without an undercut portion below the wiring pattern. Can be removed. Thereby, the adhesiveness of the seed layer under the wiring pattern and the resin base material can be improved, and problems such as peeling starting from these can be prevented.

  In one Embodiment of this invention, the process of forming an contact bonding layer or a coating layer on the said resin base material is provided after the process of removing the said seed layer.

  In another embodiment of the present invention, in the step of removing the seed layer, the entire surface of the resin substrate is irradiated with the laser light.

  In still another embodiment of the present invention, the shape of the laser beam irradiated in the step of removing the seed layer is a square shape.

  In still another embodiment of the present invention, the energy density distribution of the laser light irradiated in the step of removing the seed layer is a top hat type.

  In still another embodiment of the present invention, in the step of removing the seed layer, the laser beam is irradiated according to a pattern shape on the main surface side of the resin base material.

  According to the present invention, a seed layer containing a metal other than copper can be reliably removed without causing an undercut portion below the wiring pattern.

It is a flowchart which shows the manufacturing process by the manufacturing method of the printed wiring board which concerns on one Embodiment of this invention. It is sectional drawing which shows the printed wiring board by the manufacturing method for every manufacturing process. It is sectional drawing which shows the printed wiring board by the manufacturing method for every manufacturing process. It is a top view which shows the irradiation range of the laser used for the manufacturing method. It is a figure which shows the energy distribution of the laser used for the manufacturing method. It is sectional drawing of the printed wiring board manufactured by the manufacturing method. It is sectional drawing which shows the one part manufacturing process of the printed wiring board which concerns on other embodiment of this invention.

  Hereinafter, a printed wiring board manufacturing method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a flowchart showing manufacturing steps according to a method for manufacturing a printed wiring board according to an embodiment of the present invention. 2 and 3 are cross-sectional views showing the printed wiring board according to this manufacturing method for each manufacturing process. FIG. 6 is a cross-sectional view of a printed wiring board manufactured by this manufacturing method.

  First, a method for manufacturing a printed wiring board according to the present embodiment will be described with reference to FIG. As shown in FIG. 2A, the seed layer 2 is formed on the surface (main surface) 1a of the resin substrate 1 (step S100). The resin substrate 1 is made of an insulating resin such as a polyimide resin.

  The seed layer 2 is made of a material containing at least one kind of metal selected from, for example, copper, nickel, chromium, titanium, tungsten, an alloy of titanium and tungsten. For example, the resin base material 1 is formed by sputtering, electroless plating, or the like. It is formed in a state with high adhesion on the surface 1a.

  Next, as shown in FIG. 2B, a plating resist 3 is patterned on the seed layer 2 (step S102), and a plating process such as electrolytic copper plating is performed on the exposed seed layer 2 (step S102). S104), as shown in FIG. 2C, the wiring pattern 4 is formed. When the wiring pattern 4 is formed, as shown in FIG. 2D, the plating resist 3 is removed by peeling or the like (step S106), and the unnecessary seed layer 2 around the wiring pattern 4 is exposed.

  Thereafter, as shown in FIG. 3E, the unnecessary seed layer 2 is removed by irradiating the entire surface of the resin substrate 1 on the surface 1a side with the laser beam L (step S108).

  The laser light L irradiated on the entire surface of the resin base material 1 in step S108 has a square shape, for example, a short wavelength (wavelength 400 nm or less) UV laser or a short pulse time width with less heat propagation. A laser (pico, femto laser, etc.) is preferred. In general, the shorter the wavelength of the laser light, the higher the proportion of the laser light absorbed by the metal. Therefore, even if the seed layer 2 contains a metal other than copper by irradiating the laser light with a short wavelength. It can be removed reliably.

  Moreover, even if the complicated wiring pattern 4 is formed by irradiating the entire surface of the resin substrate 1 with the laser light L and removing the seed layer 2, an undercut portion is generated below the wiring pattern 4. The seed layer 2 can be removed without any problem. When the area of the resin substrate 1 is larger than the irradiation area of the laser light L, the irradiation position of the laser light L is moved in the vertical and horizontal directions by a step-and-repeat method as shown in FIG. It ’s fine.

  Since it is conceivable that energy is reduced at the end of the irradiation region, it is desirable that the irradiation ranges slightly overlap in order to move the irradiation region. In order to remove the seed layer 2 uniformly, the energy density distribution of the irradiated laser beam L is not a Gaussian focused beam as shown in FIG. 5A, but as shown in FIG. It is desirable that the top hat type can be uniformly irradiated.

  In addition, as shown in FIG. 6, you may make it form the contact bonding layer 5 on the surface 1a of the resin base material 1 after the removal of the seed layer 2 by said step S108, for example. Further, instead of the adhesive layer 5, a cover layer such as a coverlay film or a liquid resist (not shown) may be formed.

  According to the manufacturing method according to the present embodiment, since the seed layer 2 is removed by irradiating the laser beam L as described above, the seed layer 2 is surely formed without an undercut portion below the wiring pattern 4. It can be removed. And since an undercut part does not arise, the adhesiveness of the seed layer 2 under the wiring pattern 4 and the resin base material 1 improves, and peeling etc. which originated in both do not generate | occur | produce. Further, in step S108, when the unnecessary seed layer 2 is removed by irradiating the entire surface on the surface 1a side of the resin base material 1 with the laser light L, the resin base material 1 from which the unnecessary seed layer 2 is removed. The surface 1a and / or the upper surface 4a of the wiring pattern 4 may be roughened or surface-modified. For this reason, it is necessary to form the wiring pattern 4 thick in advance so that the thickness after irradiation with laser light becomes the designed thickness. When the surface 1a of the resin substrate 1 and / or the upper surface 4a of the wiring pattern 4 is roughened or surface-modified, the adhesion with the adhesive layer 5 and the coating layer is improved.

  FIG. 7 is a cross-sectional view showing a part of the manufacturing process of a printed wiring board according to another embodiment of the present invention. As shown in FIG. 7, instead of irradiating the entire surface of the resin base material 1 with the laser beam L in step S108, the seed layer 2 may be removed by irradiating according to the pattern. In order to remove the seed layer 2 with certainty, it is desirable to irradiate the laser beam L so as to slightly overlap the pattern as shown. When the pattern is not complicated, it is more efficient to irradiate the laser beam L according to the pattern as described above without waste of laser energy or the like. Also in this case, the shape of the irradiated laser light L is preferably a square shape. For example, a UV laser with a short wavelength (wavelength of 400 nm or less) or a laser with a short pulse time width with little heat propagation ( Pico, femto laser, etc.) are preferred. Furthermore, in order to remove the seed layer 2 uniformly, the energy density distribution of the irradiated laser beam L is not a Gaussian focused beam as shown in FIG. 5A, but as shown in FIG. It is desirable that the top hat type can be uniformly irradiated. Further, in step S108, when the unnecessary seed layer 2 is removed by irradiating the portion corresponding to the pattern on the surface 1a side of the resin base material 1 with the laser beam L, the unnecessary seed layer 2 is removed. The surface 1a of the resin substrate 1 and / or the upper surface 4a of the wiring pattern 4 may be roughened or surface-modified. For this reason, it is necessary to form the wiring pattern 4 thick in advance so that the thickness after irradiation with laser light becomes the designed thickness. When the surface 1a of the resin substrate 1 and / or the upper surface 4a of the wiring pattern 4 is roughened or surface-modified, the adhesion with the adhesive layer 5 and the coating layer is improved.

DESCRIPTION OF SYMBOLS 1 Resin base material 1a Surface 2 Seed layer 3 Plating resist 4 Wiring pattern 4a Upper surface 5 Adhesive layer

Claims (6)

Forming a seed layer on the main surface of the resin substrate;
Patterning a plating resist on the seed layer;
A step of plating on the seed layer other than the plating resist forming portion;
Removing the plating resist;
A method of manufacturing a printed wiring board comprising a step of removing the seed layer where the plating resist is removed,
In the step of removing the seed layer, the seed layer is removed by irradiating a laser beam.   The method for producing a printed wiring board according to claim 1, further comprising a step of forming an adhesive layer or a coating layer on the resin base material after the step of removing the seed layer.   3. The method for manufacturing a printed wiring board according to claim 1, wherein, in the step of removing the seed layer, the laser beam is irradiated on the entire main surface side of the resin base material.   The method of manufacturing a printed wiring board according to any one of claims 1 to 3, wherein the shape of the laser beam irradiated in the step of removing the seed layer is a square shape.   The method for manufacturing a printed wiring board according to claim 1, wherein the energy density distribution of the laser light irradiated in the step of removing the seed layer is a top hat type.   3. The method for manufacturing a printed wiring board according to claim 1, wherein, in the step of removing the seed layer, the laser light is irradiated according to a pattern shape on a main surface side of the resin base material.

Images