JP2009060016A - Printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mounting configuration capable of easily actualizing size reduction and height reduction adaptive to high-function/multi-pin configurations of a semiconductor needed to make mobile equipment compact, thin, lightweight, highly fine, multifunctional, etc. <P>SOLUTION: The printed circuit board 1 is composed of an insulating layer 2 formed by dispersing an inorganic filler in thermosetting resin and has a via hole 5 formed by boring a through hole 3 in the insulating layer 2 at a predetermined position and charging conductive paste 4 in the through hole 3. T the printed circuit board is characterized in that the via hole 5 is compressed along the thickness and secures conduction while maintaining the shape of the through hole 3 and the insulating layer contains no core material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a printed wiring board widely used in various electronic devices such as a personal computer, a mobile communication telephone, and a video camera.

  In recent years, with the downsizing and higher performance of electronic devices, multilayer wiring boards capable of mounting LSI chips and other semiconductor chips at a high density have been supplied at a low cost not only for industrial use but also in the field of consumer equipment. Has been strongly requested. In such a multilayer wiring board, it is important that a plurality of wiring patterns formed at a fine wiring pitch can be electrically connected with high connection reliability.

  In response to such market demand, instead of the metal plated conductor on the inner wall of the through-hole, which has been the mainstream for interlayer connection of multilayer wiring boards in the past, any electrode on the multilayer wiring board can be placed at any wiring pattern position. There is an inner via hole connection method that can be connected, that is, an all-layer IVH structure resin multilayer substrate.

  This is because a conductive paste as a conductor is filled in a via hole of a multilayer wiring board and only necessary layers can be connected, and an inner via hole can be provided directly under a component land. Size reduction and high-density mounting can be realized.

For example, Patent Documents 1 and 2 are known as prior art document information related to the application of the present invention.
Japanese Patent Laid-Open No. 06-268345 JP 2002-208763 A

  Since conventional multilayer printed wiring boards generally include core materials such as woven fabric, nonwoven fabric, and film, when a through hole is provided and a via is formed by filling the through hole with a conductive paste, it is particularly printed. When the wiring board is pressurized, the conductive paste filled in the via easily flows to the base material, and as shown in FIG. 7, deformation of the via is likely to occur as shown in (A) → (B). There was a problem. As the conductive paste flows, the connection stability of the vias decreases, and the diameter of the upper and lower vias increases due to the deformation of the vias. As a result, it becomes difficult to form fine vias, so fine and high-density printed wiring It had the subject that it will become difficult to form a board.

  The present invention has been made in view of the above problems, and provides a printed wiring board that has stable via connectivity and can also increase the wiring density in the substrate.

  In order to achieve the above object, the present invention comprises an insulating layer in which an inorganic filler is dispersed in a thermosetting resin. A through hole is formed at a predetermined position of the insulating layer, and a conductive paste is formed in the through hole. A printed wiring board having filled vias, wherein the vias are compressed in the thickness direction while maintaining the shape of the through holes, and the insulating layer does not include a core material. With such a configuration, the printed wiring board is characterized in that the inorganic filler particles can be prevented from flowing even when a mixture of a thermosetting resin and an inorganic filler is used for the connection layer. Since the shape of the hole can be maintained, it is possible to realize a printed wiring board having stable via connectivity and capable of increasing the wiring density in the substrate.

  As described above, the present invention enables multi-pin connection between substrates and increases the wiring density in the substrate, so that the mobile device is small, thin, lightweight, high-definition, multifunctional, etc. Therefore, it is possible to provide a printed wiring board that can easily realize a small size and a low profile corresponding to high functionality and high pin count of a semiconductor necessary for realizing the above.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a printed wiring board according to an embodiment of the present invention. The printed wiring board 1 of the present embodiment is composed of an insulating layer 2 in which an inorganic filler is dispersed in a thermosetting resin, and a conductive paste 4 is inserted into a through hole 3 formed at a predetermined position of the insulating layer 2. As a result, the via 5 is formed. In the present invention, the insulating layer 2 of the printed wiring board 1 does not include a core material such as a woven fabric, a nonwoven fabric, or a film, the via 5 is compressed in the thickness direction, and the shape of the through hole 3 is substantially cylindrical. Alternatively, conduction is ensured while maintaining a shape close to a truncated cone shape.

  At this time, since the printed wiring board 1 is filled with an inorganic filler at a high density of 70 to 90% by weight, the inorganic filler does not flow even in heat and pressure, so the via wall is maintained on the wall surface of the via 5. The conductive paste 4 filled in the via 5 by the via wall does not flow to the insulating layer 2, and stable conduction can be ensured. Since the conductive paste 4 does not flow to the insulating layer 2 and the via 5 is difficult to deform, the shape of the through hole 3 forming the via 5 can be maintained in a substantially cylindrical shape or a shape similar to a truncated cone shape. it can.

  In the present invention, the inorganic filler in the insulating layer 2 is preferably composed of at least one of silica, alumina, and barium titanate. Moreover, it is preferable that the particle size of the inorganic filler in the insulating layer 2 is 1 to 15 μm, and the content of the inorganic filler is 70 to 90% by weight. If the content of the inorganic filler is less than 70%, the amount of the inorganic filler that forms the connection layer 3 is less than the amount of the thermosetting resin, and is in a rough state, and the thermosetting resin flows during the press. At the same time, the inorganic filler also flows, and if it exceeds 90%, the amount of the resin of the connection layer 3 becomes too small, and the embeddability and adhesion of the wiring are impaired, which is inappropriate.

  The conductive paste 4 used for the printed wiring board of the present invention is composed of copper, silver, gold, palladium, bismuth, tin, and alloys thereof, and preferably has a particle size of 1 to 20 μm.

  Moreover, the average particle diameter of an inorganic filler is comprised by the particle size larger than the average particle diameter of an electrically conductive paste.

  In the printed wiring board 1 of the present invention, an elastomer component may be dispersed in the thermosetting resin used for the insulating layer 2 in addition to the inorganic filler. In this case, since the elastomer component segregates on the surface of the inorganic filler, the fluidity of the inorganic filler can be further suppressed, which is more effective in the present invention.

  The elastomer component in the present invention is composed of either an acrylic elastomer or a thermoplastic elastomer. Specifically, for example, polybutadiene or butadiene-based random copolymer rubber or a copolymer having a hard segment and a soft segment is used. The content of the elastomer component is preferably 0.2 to 5.0% by weight with respect to the total amount of the epoxy resin composition.

  Next, the manufacturing process of the printed wiring board of this Embodiment is demonstrated in detail using FIG.

  First, as shown in FIG. 2A, a PET film 6 is attached to both sides of the insulating layer 2 by laminating.

  Subsequently, as shown in FIG. 2B, a through hole 3 penetrating all of the insulating layer 2 and the PET film 6 is formed by a laser or the like.

  Next, as shown in FIG. 2C, the through-hole 3 is filled with a conductive paste 4. This PET film 6 serves to prevent the conductive paste 4 from remaining on the surface of the insulating layer 2.

  Thereafter, the PET films 6 on both sides are peeled off (FIG. 2 (D)), and in this state, foil-like wiring material 7 is prepared from both sides of the insulating layer 2 (FIG. 2 (E)). The state shown in F) is obtained.

  Next, the wiring material 7 is bonded to the insulating layer 2 by heating and pressing. By this heating and pressing step, the via 5 filled with the conductive paste 4 is compressed by the thickness of the peeled PET film 6. By this compression, the metal fillers in the conductive paste 4 come into contact with each other at a high density, and electrical connection between the wiring material 7 and the conductive paste 4 is realized. In the present invention, since the conductive paste 4 does not flow to the insulating layer 2 because the inorganic filler does not flow even during heating and pressurization, the via 5 has a shape of the through-hole 3, that is, a substantially cylindrical shape. Alternatively, a shape close to a truncated cone shape can be maintained.

  Thereafter, as shown in FIG. 2G, the printed wiring board 1 on both sides is completed by patterning the wiring material 7.

  In the present invention, the insulating layer 2 may contain a colorant. In this case, mountability and light reflectivity are improved.

  Further, the minimum melt viscosity of the insulating layer 2 is suitably 1000 to 100,000 Pa · s as shown in the melt viscosity curve of FIG. If it is less than 1000 Pa · s, the resin flow becomes large, and if it exceeds 100000 Pa · s, there is a possibility that poor adhesion due to multilayering of the printed wiring board or poor embedding in the wiring material 5 may occur.

  In the printed wiring board of the present invention, the description has been made on the double-sided printed wiring board. However, as shown in FIG. 4, a multilayer printed wiring board may be formed by laminating a plurality of layers as shown in FIG. A multilayer printed wiring board may be formed by laminating printed wiring boards 9 formed of resin base materials of different materials on the top and bottom of the printed wiring board of the present invention. The printed wiring board 9 formed of a resin base material of a different material may be a double-sided board or a multilayer board, and is particularly limited to a board structure such as a through-hole structure or an all-layer IVH structure. The material is not particularly limited. Further, as shown in FIGS. 6A and 6B, the printed wiring boards 9 formed on the upper side and the lower side may have different shapes. Further, a multilayer printed wiring board may be formed by alternately laminating the printed wiring board 1 of the present invention and the printed wiring boards 9 made of different materials.

  The printed wiring board according to the present invention enables multi-pin connection between boards and increases the wiring density in the board, so that the mobile device is small, thin, lightweight, high definition, and multifunctional. Therefore, it is possible to provide a printed wiring board that can easily realize a small size and a low profile corresponding to high functionality and multi-pin semiconductors necessary for realizing the above.

Sectional drawing which shows an example of the printed wiring board in Embodiment 1 of this invention Manufacturing process sectional drawing of the printed wiring board in Embodiment 1 of this invention The figure which shows the melt viscosity of the connection layer of the printed wiring board in Embodiment 1 of this invention Sectional drawing which shows an example of the printed wiring board in Embodiment 1 of this invention Sectional drawing which shows an example of the printed wiring board in Embodiment 1 of this invention The perspective view which shows an example of the printed wiring board in Embodiment 1 of this invention The figure which shows the shape of the via of the conventional printed wiring board

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printed wiring board 2 Insulating layer 3 Through-hole 4 Conductive paste 5 Via 6 PET film 7 Wiring material 9 Printed wiring board

Claims (10)

The printed wiring board includes an insulating layer in which an inorganic filler is dispersed in a thermosetting resin, and a through hole is formed at a predetermined position of the insulating layer, and the through hole is filled with a conductive paste. The via is compressed in the thickness direction, and electrical conductivity is ensured while maintaining the shape of the through hole, and the insulating layer does not include a core material. The printed wiring board according to claim 1, wherein an elastomer component is dispersed in a thermosetting resin in the connection layer. The printed wiring board according to claim 1, wherein the inorganic filler has a particle size of 1 to 15 μm. The printed wiring board according to claim 1, wherein the conductive paste has a particle size of 1 to 20 μm. The printed wiring board according to claim 1, wherein an average particle size of the inorganic filler is larger than an average particle size of the conductive paste. The printed wiring board according to claim 1 or 2, wherein the content of the inorganic filler is 70 to 90% by weight. The printed wiring board according to claim 1 or 2, wherein the inorganic filler comprises at least one of silica, alumina, and barium titanate. The printed wiring board according to claim 1, wherein the conductive paste is made of copper, silver, gold, palladium, tin, and an alloy thereof. The printed wiring board according to claim 1, wherein the minimum melt viscosity is 1000 to 100,000 Pa · s. The printed wiring board according to claim 1, wherein the insulating layer contains a colorant.

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