JP2009094330A - Substrate for wiring board and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a wiring board, which forms a protruding paste of a desired height without a printing faulty, to enhance an interlayer connection reliability. <P>SOLUTION: The substrate for the wiring board comprises a releasable resin film 4 on at least one face of an insulating substrate 2 and a metal layer 3 on a face opposite to the insulating substrate 2 of the releasable resin film 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wiring board substrate and a method for manufacturing a wiring board substrate.

  With recent miniaturization and high-density mounting of electronic devices, multilayer wiring boards are widely used. The multilayer wiring board has an advantage that the surface area of the substrate can be reduced by making the conductor pattern into a multilayer. For this reason, it is widely used for motherboards of various small electronic devices such as mobile electronic devices. Recently, a further developed IVH (Innner Via Hole) type multilayer wiring board has been developed.

  In the IVH type multilayer wiring board, via holes for interlayer conduction are formed in each layer. Unlike the through holes, the via holes do not have to be all in a straight line. Therefore, it is possible to further reduce the substrate surface area.

  In such a multilayer wiring board, inner via hole connection is possible, and in order to realize a highly reliable and high-quality substrate for a wiring substrate, a desired position of a porous substrate having a release film on both sides is provided. There is disclosed a substrate for a wiring board that has a through hole and is filled with a conductive paste up to the surface of the release film (for example, see Patent Document 1).

In addition, the masking metal foil can be peeled off on at least one surface of the insulating substrate to prevent uneven filling of the conductive paste and non-uniformity of the protrusion shape due to the conductive paste when the masking film is peeled off. Also disclosed is a substrate for a wiring board affixed to (see, for example, Patent Document 2).
Japanese Patent No. 2587596 JP 2004-152882 A

  However, in the technique according to Patent Document 1, the release film is also etched in the process of removing smear generated when the through-hole is opened, and the release film is peeled off after printing the conductive paste. However, there is a problem that the height of the convex paste becomes low or varies.

  Moreover, in the technique by patent document 2, since metal foil was used as a masking film, there existed a problem that it was easy to generate | occur | produce a wrinkle before paste printing, and a printing squeegee was damaged and a printing defect was easy to generate | occur | produce.

  In view of the above-described problems, the present invention provides a wiring board substrate and a method for manufacturing a wiring board substrate that form a convex paste having a desired height without defective printing and improve interlayer connection reliability. With the goal.

  A first feature of the present invention is that a release resin film is provided on at least one surface of an insulating substrate, and a metal layer is provided on a surface opposite to the insulating substrate of the release resin film. The gist of the present invention is the wiring board substrate.

  According to the wiring board substrate according to the first feature, a convex paste having a desired height can be formed without defective printing by providing a metal layer on the surface opposite to the insulating substrate of the releasable resin film. In addition, the interlayer connection reliability can be improved.

  A second feature of the present invention is that a release resin film is provided on one surface of an insulating substrate, a conductor layer for forming a circuit pattern is provided on the other surface of the insulating substrate, and the release resin film It is a substrate for a wiring board provided with a metal layer on the surface opposite to the insulating substrate.

  According to the substrate for a wiring board according to the second feature, a convex paste having a desired height can be formed without defective printing by providing a metal layer on the surface of the release resin film opposite to the insulating substrate. In addition, the interlayer connection reliability can be improved.

  In the wiring board substrate according to the second feature, the metal layer is preferably made of the same type of metal as the conductor layer.

  According to this wiring board substrate, etching for opening a metal layer and chemical etching for forming a circuit pattern of a conductor layer can be performed in the same process.

  A third feature of the present invention is a method for manufacturing a wiring board substrate in which holes formed in an insulating substrate are filled with a conductive paste, and the conductive paste protrudes in a convex shape from the surface of the insulating substrate. A step of forming a release resin film having a metal layer on one surface of the insulating substrate and a conductor layer for forming a circuit pattern on the other surface of the insulating substrate; Using a releasable resin film with a metal layer on the surface as a masking film, forming a hole in the insulating substrate, removing smear remaining in the hole, and removing the metal layer and the oxide film on the surface of the hole The gist of the present invention is a method for producing a substrate for a wiring board, including a step of performing, a step of filling a hole with a conductive paste, and a peeling step of peeling the release resin film from the insulating substrate.

  According to the method for manufacturing a wiring board substrate according to the third feature, a convex paste having a desired height is printed by providing a metal layer on the surface opposite to the insulating substrate of the releasable resin film. It can be formed without defects and the interlayer connection reliability can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the convex paste of desired height can be formed without printing defect, and the manufacturing method of the base material for wiring boards which improves interlayer connection reliability, and the base material for wiring boards can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the descriptions of the following aspects, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Configuration of substrate for wiring board)
As shown in FIG. 1, the substrate for a wiring board according to this embodiment includes a releasable resin film 4 on one surface of the insulating substrate 2. A conductive layer 1 for forming a circuit pattern is provided on the other surface of the insulating substrate 2. A metal layer 3 is provided on the surface of the releasable resin film 4 opposite to the insulating substrate 2.

  The insulating substrate 2 is configured in a rigid type or a flexible type by using a glass epoxy prepreg, a thermoplastic polyimide film, a thermoplastic polyimide film provided with a thermosetting function, or the like.

  The releasable resin film 4 can be a plastic film such as polyethylene terephthalate, polyethylene naphthalate, polyfinylene sulfite, polyimide, polypropylene, polyethylene, epoxy resin, silicone resin, phenol resin, melamine resin.

  The metal layer 3 is made of the same kind of metal as the conductor layer 1, for example, copper foil. The metal layer 3 is formed as a thin film having a thickness of 600 mm or less. The metal layer 3 may be attached to the releasable resin film 4 by sputtering metal on the releasable resin film 4 or by an adhesive made of a thermoplastic resin such as polyvinyl acetate or acrylate. You may go.

(Manufacturing method of substrate for wiring board)
Next, the manufacturing method of the base material for wiring boards which concerns on this embodiment is demonstrated using FIG.2 and FIG.3.

  First, as shown in FIG. 2A, a release resin film 4 provided with a metal layer 3 on the surface is provided on one surface of the insulating substrate 2, and a circuit is provided on the other surface of the insulating substrate 2. A conductor layer 1 for pattern formation is formed. For the lamination of the releasable resin film 4, a roll laminator, a parallel plate press or the like can be used. These methods may be performed in a vacuum.

  Next, as shown in FIG. 2B, the circuit pattern 1A and the small-diameter hole 11 of the conductor layer and the mask hole 13 of the metal layer 3 are formed in the same process by the same etching method by the chemical etching method. As the etchant, a ferric chloride aqueous solution may be used, and processing can also be performed by using a cupric chloride aqueous solution or an alkali etchant. Here, it is necessary to align the patterns of the metal layer 3 and the conductor layer 1 with each other. In this alignment, the both surfaces are aligned by photolithography before the etching process.

  Next, as shown in FIG. 2C, a mask hole is formed in the releasable resin film 4 by laser processing. Next, a hole (via hole) 5 of the insulating base material 2 is formed by laser light irradiation using the opening of the releasable resin film 4, that is, the mask hole as a conformal mask. As the laser light, a carbon dioxide laser or excimer laser can be used. In addition, the holes 5 can be formed by chemical etching or plasma etching.

  Next, the desmear process which removes the smear (organic contaminant) which remained in the hole 5 is implemented. A desmear process is performed by irradiating the atmospheric pressure plasma which uses argon gas, for example.

  Next, as shown in FIG. 3A, soft etching for removing the oxide film on the surfaces of the metal layer 3 and the holes 5 is performed. An aqueous solution such as hydrochloric acid or sulfuric acid can be used to remove the metal layer 3 and the oxide film.

  Next, as shown in FIG. 3B, the conductive paste 6 is filled in the holes 5 by a printing method by squeezing. As the conductive paste, any conductive material having fluidity such as a silver paste, a carbon paste, a solder paste, and a solder can be used in addition to a copper paste. In that case, the hole diameter and hole shape of the small-diameter hole 11 can be changed according to the viscosity and thixotropy of the conductive paste.

  Next, as shown in FIG. 3C, the conductive paste 6 is protruded from the surface of the insulating substrate 2 in a convex shape by peeling the release resin film 4 from the insulating substrate 2. Can do.

  An IVH substrate can be manufactured by stacking and aligning several layers of the substrate for a wiring substrate manufactured as described above, aligning the substrates, and then applying pressure by heating and pressing.

(Function and effect)
When the desmear treatment is performed on the wiring board base material described in Patent Document 1, a part 4 ′ of the releasable resin film 4 is also etched as shown in FIG. Therefore, in-plane variation occurred in the thickness of the releasable resin film 4.

  In addition, in the wiring board base material described in Patent Document 2, when the conductive paste is filled by the squeezing printing method, the squeegee 8 is shaved by the masking metal foil 7 as shown in FIG. As a result, printing defects occurred due to the scraps and scratches on the squeegee 8.

  On the other hand, in the wiring board base material according to the present embodiment, the metal layer 3 is provided on the surface opposite to the insulating base material 2 of the releasable resin film 4, so that it occurs during drilling. In the step of removing the smear and the like, the releasable resin film 4 is not etched. For this reason, it can suppress that the height of convex paste becomes low or varies. Moreover, since the height of the convex paste is maintained at a desired height, the filling density of the holes can be stabilized, and the interlayer connection reliability is improved.

  Further, when the conductive paste 6 is filled, the metal layer 3 on the surface of the base material is removed, so that the squeegee is not scraped, and the occurrence of printing defects due to scraps or scratches on the squeegee is suppressed. Can do.

  Furthermore, in the wiring board substrate according to the present embodiment, the metal layer 3 is made of the same kind of metal as the conductor layer 1, so that etching for drilling the metal layer 3 and the circuit pattern of the conductor layer 1 are performed. It is possible to perform chemical etching for formation in the same process. For this reason, the number of processes can be reduced.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

For example, in the above embodiment, the hole 5 formed in the insulating substrate 2 has been described as having a bottomed hole shape, but it may be a through hole.

  In the above embodiment, the substrate for a wiring board provided with the releasable resin film 4 having the metal layer 3 provided on one surface of the insulating substrate 2 has been described. Moreover, you may provide the release resin film 4 which provided the metal layer 3 on the surface.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  Hereinafter, the substrate for a wiring board according to the present invention will be specifically described with reference to examples, but the present invention is not limited to those shown in the following examples, and the gist thereof is not changed. In the range, it can implement by changing suitably.

(Example)
The substrate for a wiring board according to the example was manufactured through the steps of laser processing, desmear treatment, soft etching, conductive paste printing, and masking film peeling according to the manufacturing method described in the above embodiment.

  Here, a conductor layer 1 was obtained by bonding a 12 μm thick copper foil to the surface of an insulating substrate 2 made of 25 μm thick polyimide. The size of the circuit pattern was 50 μm × 50 μm. As the metal layer 3, copper was used, and a releasable resin film 4 obtained by sputtering copper having a thickness of 600 mm was used. That is, as the masking film for printing, a releasable resin film 4 having a metal layer 3 on the surface was used. Moreover, the thickness of the releasable resin film 4 sputtered with copper was 20 μm.

  The conductive paste 6 was printed at a vacuum of 0.8 Torr, a squeegee pressure of 0.4 MPa, and a squeegee speed of 20 mm / sec. Although copper was sputtered as the metal layer 3, this copper can be removed simultaneously with the oxide film of the copper circuit as the conductor layer 1 during the soft etching. An evaluation board according to this example was manufactured by stacking two layers of the substrate for a wiring board manufactured as described above, aligning the layers, and applying pressure by heating and pressing.

(Conventional example 1)
As disclosed in Patent Document 1, the substrate for a wiring board according to Conventional Example 1 used a releasable resin film as a masking film for printing. The thickness of the releasable resin film was 20 μm as in the example. Other configurations and other processes are the same as those in the example, and two layers of the wiring board base material manufactured in this way are overlapped, aligned, and then heated and pressed to pressure-bond the conventional example 1 The evaluation board which concerns on was manufactured.

(Conventional example 2)
As disclosed in Patent Document 2, the substrate for a wiring board according to Conventional Example 2 used a metal foil as a masking film for printing. The thickness of the metal foil was 20 μm as in the example. Other configurations and other processes are the same as those of the example. Two layers of the wiring board base material manufactured in this way are overlapped, aligned, and then heated and pressed to pressure-bond them. The evaluation board which concerns on was manufactured.

(Evaluation)
As an evaluation method, the height of the convex shape of the conductive paste of the evaluation substrate according to Example, Conventional Example 1 and Conventional Example 2 was measured, and the average height and variation were obtained. The result is shown in FIG.

  Further, the resistance value between the conductor layer and the conductive paste layer (interlayer conductive portion) of the evaluation substrate according to the example, the conventional example 1, and the conventional example 2 was measured, and the average resistance value and the variation were obtained. Specifically, as a cooling cycle test, the treatment of leaving at −40 ° C. for 30 minutes and then leaving at 125 ° C. for 30 minutes was defined as one cycle, and a thermal shock was repeated 1000 times. And the resistance value of the interlayer conduction | electrical_connection part was confirmed with the tester for every cycle. The result is shown in FIG.

  As shown in FIGS. 6 and 7, in the evaluation substrate according to Conventional Example 1, the height variation of the convex paste was large, and the resistance value and the resistance value variation were also large. In the evaluation substrate according to Conventional Example 2, the shape of the convex paste was good, but the resistance value was high. In the evaluation board | substrate which concerns on an Example, the favorable value was able to be acquired with respect to the shape and resistance value of convex paste. Therefore, by providing a metal layer on the surface opposite to the insulating substrate of the release resin film, a convex paste having a desired height can be formed without printing defects, and the interlayer connection reliability can be improved. Was confirmed.

It is sectional drawing which shows the structure of the base material for wiring boards which concerns on embodiment. It is sectional drawing for demonstrating the manufacturing method of the base material for wiring boards which concerns on embodiment (the 1). It is sectional drawing for demonstrating the manufacturing method of the base material for wiring boards which concerns on embodiment (the 2). It is sectional drawing for demonstrating the effect | action and effect of the base material for wiring boards which concern on embodiment (the 1). It is sectional drawing for demonstrating the effect | action and effect of the base material for wiring boards which concern on embodiment (the 2). It is a graph which shows the shape of the convex paste which concerns on an Example. It is a graph which shows the resistance value of the interlayer conduction | electrical_connection part which concerns on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conductor layer 1A ... Conductor layer circuit pattern 2 ... Insulating substrate 3 ... Metal layer 4 ... Release resin film 5 ... Hole 6 ... Conductive paste 7 ... Masking metal foil 8 ... Squeegee 11 ... Small diameter hole 13 ... Mask hole

Claims (4)

  A wiring comprising a release resin film on at least one surface of an insulating substrate, and a metal layer provided on a surface opposite to the insulating base of the release resin film Substrate for substrate.   A release resin film is provided on one surface of the insulating substrate, a conductor layer for forming a circuit pattern is provided on the other surface of the insulating substrate, and the insulating base material of the release resin film is A substrate for a wiring board, wherein a metal layer is provided on the opposite surface.   The wiring board substrate according to claim 2, wherein the metal layer is made of the same kind of metal as the conductor layer. A method of manufacturing a wiring board substrate in which a hole formed in an insulating substrate is filled with a conductive paste, and the conductive paste protrudes in a convex shape from the surface of the insulating substrate,
Forming a release resin film having a metal layer on one surface of the insulating substrate, and forming a conductor layer for forming a circuit pattern on the other surface of the insulating substrate;
A step of forming a hole in the insulating substrate, using a releasable resin film provided with a metal layer on the surface as a masking film,
Removing smear remaining in the holes;
Removing the metal layer and the oxide film on the hole surface;
Filling the holes with a conductive paste;
And a peeling step of peeling the release resin film from the insulating substrate.

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