JP2007235167A - Wiring circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring circuit board in which the cost for forming the means for connection between upper and lower circuit conductors can be reduced and which is adaptable to production of a wide variety of products with small volume for each as well as production of a narrow variety of products with large volume for each by enhancing the productivity of the wiring circuit board that possesses different circuit conductor patterns depending on the product. <P>SOLUTION: The wiring circuit board uses a number of metal protrusions 53(57), which penetrates an interlayer insulating film interposed between metal layers, as the means for connection between upper and lower conductors, wherein the protrusions 53(57) for connection between upper and lower conductors are positioned at cross points of a lattice arranged with fixed intervals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed circuit board for connecting electronic devices such as IC and LSI, and more particularly to a printed circuit board capable of realizing high-density mounting.

The applicant company has developed various manufacturing techniques for printed circuit boards, and the results have been proposed in, for example, Japanese Patent Application No. 11-229140, which is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-05139. However, an example of the relatively latest prior art will be introduced with reference to FIGS.
4 (A) to 4 (F) and FIGS. 5 (G) to 5 (I) are for explaining one conventional example related to a printed circuit board for high-density mounting. It is sectional drawing shown to A)-(I).

(A) First, an insulating base 1 made of an insulating sheet having a thickness of about 50 to 100 μm is prepared. As shown in FIG. 4 (A), holes 2 for interlayer connection are drilled or lasered in the insulating sheet 1. Formed by processing.
(B) Next, as shown in FIG. 4B, the holes 2 are filled with a conductive paste (for example, silver or copper, etc. as a main material) 3 by, for example, a printing method. As a result, the insulating base 1 becomes a semi-cured sheet A in which the holes 2, 2,... Are filled with the conductive paste 3.

(C), (D) Next, as shown in FIG. 4 (C), metal foils 4 and 4 made of copper, for example, are allowed to face both sides of the sheet A, and the metal as shown in FIG. 4 (D). The foils 4 and 4 are laminated by a pressure press. As a result, metal foils 4 and 4 are formed on both sides, and an insulating sheet 1 exists between them, and the conductive foils 3, 3. A laminate in which the four are electrically connected is formed.
(E) Next, resist films 5 and 5 having the same pattern as the conductor circuit to be formed on the metal foils 4 and 4 are formed. FIG. 4E shows a state after the resist films 5 and 5 are formed.

(F) Next, by etching the metal foils 4 and 4 using the resist films 5 and 5 as a mask, conductor circuits 6 and 6 are formed as shown in FIG. As a result, a laminated body B is formed in which conductor circuits 6 and 6 are formed on both surfaces by interlayer separation by the insulating sheet 1 and interlayer connection by the conductive paste 3 in the hole 2.
(G) Next, as shown in FIG. 5 (G), the laminate B has holes 2, 2,... On both sides, and the holes 2, 2,. The insulating sheets 1a, 1a filled with 3,... And the metal foils 4a, 4a are stacked, and then these are stacked by a pressure press. The laminated body formed by this lamination is defined as C.

(H) Next, as shown in FIG. 5H, resist films 5 and 5 are selectively formed on the metal foils 4a and 4a on both sides of the laminate C.
(I) Next, using the resist films 5 and 5 as a mask, the metal foils 4a and 4a are selectively etched to form wiring films 6a and 6a as shown in FIG. As a result, a printed circuit board 7 having four layers of conductor circuits 6, 6, 6a, 6a is formed.

FIGS. 6A to 6G are cross-sectional views illustrating another conventional example related to a printed circuit board for high-density mounting in order of steps (A) to (G). It is.
(A) A metal foil (thickness, for example, 18 μm) 10 made of, for example, copper is prepared. As shown in FIG. 6 (A), conductive protrusions 11, 11,. It is formed by screen printing of a conductive paste such as silver. The thickness of the protrusions 11, 11,... Is, for example, about 50 to 100 μm.

(B) Next, as shown in FIG. 6B, an insulating adhesive sheet 12 is bonded onto the surface of the metal foil 10 on which the protrusions 11, 11,. The adhesive sheet 12 is appropriately thinner than the thickness of the projections 11, 11,... So that the tops of the projections 11, 11,. .. Are formed on the metal foil 10, and an adhesive sheet 12 is bonded to the top of the protrusions 11, 11,.

(C), (D) Next, as shown in FIG. 6 (C), a metal foil 13 similar to the metal foil 10 is placed above the surface of the adhesive sheet 12 of the adhesive sheet 10, and a hot press method is used. 5D, the metal foil 13 is laminated on the adhesive sheet 12 and the protrusions 11, 11,. B is a laminate formed thereby.
(E) Next, a patterned resist film, for example, is formed on the metal foils 10 and 13 on both surfaces of the laminate B, and the metal foils 10 and 13 are etched using the resist film as a mask to thereby form the conductor circuit 14 and 15 is formed. FIG. 6E shows a state where the resist film used as a mask after the formation of the conductor circuit is removed.

(F) Next, two laminates a made by the same method as the laminate A shown in FIG. 6B are prepared, and the two laminates a and a are shown in FIG. 6F. Thus, it is made to face on both surfaces of the laminate B.
(G) Next, the laminated body B is sandwiched between the laminated bodies a and a from both sides thereof, and pressed and laminated by the above-described hot press method, and wiring as shown in FIG. The circuit board 16 is completed.
JP 2001-05139 A

  By the way, in the prior art shown in FIGS. 4 and 5, first, the hole 2 of the insulating sheet 1 is filled with a conductive paste 3 mainly composed of an expensive metal such as silver and used for interlayer connection. There was a problem that led to an increase in cost. In particular, as the density is increased, the arrangement density of the holes 2 increases, resulting in a cost increase that cannot be ignored. Secondly, when the hole 2 is filled with the conductive paste 3, there is a problem that a small amount of the conductive material adheres to portions other than the hole 2 and the insulation resistance decreases.

  Third, when forming the holes 2, 2,... In the insulating sheet 1 and then laminating under pressure, the sheet 1 is stretched in the lateral direction by the applied pressure, and the positions of the holes 2, 2,. As a result, there is a problem that even if a hole for correction is made, the correction cannot be completed. Such misalignment of the holes 2 causes an interlayer connection failure and becomes a serious problem that cannot be overlooked, and is particularly fatal in the case of a printed circuit board with high-density mounting. Fourth, there is a problem that the reliability of joining between the metal foils 4 and 4 made of copper or the like and the conductive paste 3 is insufficient. That is, the conductive paste 3 in which the holes 2 are filled removes the solvent so that it becomes semi-cured, but the semi-cured conductive paste shrinks due to the removal of the solvent and the like, and the volume becomes small. Often, the upper and lower surfaces of the are concave. As a result, there is a problem that poor bonding is likely to occur between the metal foils 4 and 4, yield and reliability are lowered.

  Next, there was a problem with the conventional example shown in FIG. First, since the protrusion 11 is formed of a conductive paste that is an expensive material, there is a problem that the cost increases. Secondly, the formation of the protrusion 11 with the conductive paste has a limit in increasing the thickness of the conductive paste as a result of using the screen printing method. As a result, the screen printing may be repeated a plurality of times for the formation of the protrusion 11. Often needed. And if the number of times of printing increases, there is a problem that the shape of the projection 11 is easily deformed due to misalignment, and the reliability of connection with the metal foil 4 later becomes low, and screen printing is problematic. Alignment work is very difficult, troublesome, requires skill, and requires a long alignment time. Such a tendency becomes more prominent as the diameter of the protrusion 11 becomes smaller. Incidentally, in the case of a protrusion having a diameter of 0.3 mm, it is necessary to print twice, and in the case of a protrusion having a diameter of 0.2 mm, it is necessary to print four times. This is quite troublesome and leaves a problem in dealing with high-density printed circuit boards.

  Third, there is a problem that the heights of the protrusions 11, 11,. That is, since it is difficult to make the thickness of the formed film uniform in screen printing, naturally the heights of the protrusions 11, 11,. Due to the variation in thickness, there is a possibility that the connection between the metal foil 13 and the protrusions 11, 11,... May be poor, and there is a problem that yield and reliability are lowered. Fourth, the metal foil 10 serving as the base of the printed circuit board in the manufacturing process is as thin as 18 μm, for example, and sufficient care is taken not to cause wrinkles, deformation, bending, etc. on the metal foil 13 side during the screen printing. It is necessary and has the possibility of causing a decrease in yield due to a slight mistake. Naturally, this causes a cost increase and cannot be overlooked. However, if the metal foil 10 is made thick to increase the rigidity of the base, it faces a problem that it prevents the fine patterning of the conductor circuit.

In addition, as a problem common to each of the above conventional examples, there is a limit to high density, that is, a minute interlayer connection, and in one conventional example, due to difficulty in miniaturizing the hole diameter and filling the conductive paste, In another conventional example, printing becomes more difficult as the diameter becomes smaller by bump printing, and a diameter of 200 μm or less could not be actually produced. Further, the bonding strength between the conductive paste and the copper foil is low, and when it is used as a pad-on via, the via-shaped pad strength is not sufficient, and it is necessary to take an area more than necessary.
In addition, it is required not only to deal with mass production of small varieties, but also to increase the productivity of printed circuit boards having conductor circuits with different patterns depending on the model, and to be able to cope with small production of other varieties. However, the reality is that it has not been able to meet the demand.

  The present invention has been made in order to solve such problems, and prevents bending, bending, deformation, and the like in the manufacturing process, and improving the dimensional stability in the manufacturing process, thereby improving the space between the upper and lower conductor circuits. Improves connection reliability, reduces the cost of connecting means between upper and lower conductor circuits, and not only supports mass production of small varieties, but also increases the productivity of printed circuit boards with different patterns of conductor circuits depending on the model. The purpose is to be able to cope with even small production of other varieties.

  The wired circuit board according to claim 1, wherein upper and lower conductor connecting projections made of a number of metals are arranged on each surface of the metal layer on each intersection of the lattices arranged at a predetermined interval, An interlayer insulating layer is provided on the surface on which the inter-connection connection protrusion is formed so as to penetrate the inter-conductor connection protrusion, and a metal layer is formed on the surface of the interlayer insulation layer including the upper and lower conductor connection protrusions. It is characterized by.

  According to the wired circuit board of the first aspect, the upper and lower conductor connecting projections made of a large number of metals are arranged on the surface of the metal layer on the intersections of the grids having a constant interval. Regardless of whether the two-sided conductor circuit is formed by selective etching, it is mass-produced as a standard product, and then a different pattern conductor circuit is formed depending on the model. Therefore, the productivity of various types of printed circuit boards can be increased. At the same time, the mask does not need to be changed depending on the product type, and the amount of metal etching can be reduced. Therefore, it is possible to deal with a wide range of production from low-mix production to small-product mass production, greatly contributing to economic improvement.

  In the present invention, basically, the upper and lower conductor connecting projections made of a large number of metals are arranged on each surface of the metal layer on each intersection of the lattices arranged at regular intervals, and the conductor of the metal layer An interlayer insulating layer is provided on the surface on which the inter-connection connection protrusion is formed so as to penetrate the inter-conductor connection protrusion, and a metal layer is formed on the surface of the interlayer insulation layer including the upper and lower conductor connection protrusions. The material of the metal layer forming the conductor circuit, the metal forming the protrusions for connecting the upper and lower conductors, and the metal layer formed on the surface including the protrusions for connecting the upper and lower conductors of the interlayer insulating film is preferably copper. is there.

Moreover, it is preferable to coat a film 54 for improving the connectivity or improving the reliability of the connectivity, such as a conductive paste, a noble metal such as solder or gold, or an anisotropic conductive film, on the top of the connection protrusion between the upper and lower conductors. .
The interlayer insulating film is preferably a prepreg containing glass cloth, for example.

Example 1
FIGS. 1A to 1E, 2A, 2B and 3 are for explaining a first embodiment of the wired circuit board according to the present invention. ) Is a cross-sectional view showing the method of manufacturing the printed circuit board of the embodiment in the order of steps, and FIGS. 2A and 2B are cross-sectional views showing other examples of the upper and lower conductor connecting projections. 3 is a perspective view showing the characteristics of the printed circuit board according to the embodiment.
First, a method for manufacturing a printed circuit board will be described with reference to FIGS.
(A) First, as shown in FIG. 1A, a base material 51 having a single layer structure made of a metal plate such as copper is prepared, and a resist film 52 is selectively formed on one surface thereof.

(B) Next, as shown in FIG. 1B, the base material 51 is half-etched from the surface using the resist film 52 as a mask to form the inter-conductor connection projection 53. Note that half-etching does not literally mean half-thickness etching, but means that etching is performed while leaving a portion to be a circuit layer.
(C) Next, as shown in FIG. 1 (C), the top of the protrusion 53 is improved in connection with a noble metal such as conductive paste, solder, or gold, or an anisotropic conductive film, if necessary. A film 54 that increases reliability in terms of connectivity is coated. The film 54 is not indispensable, but it is preferable to provide it when it is necessary to further improve connectivity or reliability.

(D) Next, as shown in FIG. 1D, a metal foil 56 made of copper or the like is laminated on the one surface of the base material 51 with an interlayer insulating film 55 interposed therebetween.
(E) Next, as shown in FIG. 1E, a conductive circuit is formed by selectively etching the other surface portion of the base material 51 and the surface of the metal foil 56. Thereby, a printed circuit board is completed.

  According to such a method for manufacturing a printed circuit board, it is not necessary to use a multi-layer structure having an etching barrier layer as a base material, and a process for removing the etching barrier layer is not required. Can be reduced.

In addition, after the formation of the protrusion 53, the tip end portion thereof may be roughened so that a large number of needle-like spines can be formed so as to improve the connectivity with the conductor circuit made of the metal foil 56. Roughening can be done by spray etching or CZ treatment. Moreover, it can also roughen by crushed copper plating.
Further, the entire surface of the copper including the protrusion 53 is subjected to an electrolytic chromate treatment to form an electrolytic chromate film, thereby improving the oxidation resistance of the protrusion 53 and the copper surface, and preventing the deterioration of the copper foil quality due to participation. May be.

  Although the shape of the protrusion 53 for connecting the upper and lower conductors of the printed circuit board shown in FIG. 1 is a coneide shape (Mt. Fuji shape), this is not always necessary, and FIG. It may be a drum shape as shown. (53a indicates a drum-shaped protrusion). By changing the etching conditions, the shape of the protrusion changes, and the drum-like protrusion 53a can be formed. Since the top surface of the projection 53a is wide, there are advantages that solder, conductive paste processing, etc. can be easily performed, and that the connection with the conductor circuit is easily improved.

  Further, as shown in FIG. 2B, a hook-like protrusion 57 may be formed. Thus, since the protrusion 57 has a pointed tip, it is easy to improve the penetrability of the interlayer insulating film 55, particularly the penetrability to the prepreg with glass cloth, and to easily bite into the conductor circuit. There is an advantage that it can be increased. Such hook-shaped protrusions 57 can be formed by etching with a resist film having a smaller diameter than the protrusions to be formed. Alternatively, a conical or drum-shaped protrusion is once formed by selective etching (of course half-etching) using a resist film or the like as a mask, and then the mask is removed and etching (of course half-etching) is performed again. be able to.

Next, the features of this embodiment are shown in FIG. Although this embodiment is not shown in FIG. 1, as shown in FIG. 3, the upper and lower conductor connecting protrusions 53, 57, or 25 are characterized in that they are arranged at each intersection of the lattice.
In the present embodiment, projections, for example 57, are arranged on each intersection of a grid made up of lines arranged vertically and horizontally (ideally) at predetermined intervals.

  According to such a printed circuit board, regardless of the type of the printed circuit board, mass production is carried out until the stage before the conductive circuit on both sides is formed by selective etching, and then depending on the model. Since it is possible to form conductor circuits with different patterns, only specific protrusions are used for interlayer connection, and others are unnecessary by not forming the circuit or by slightly over-etching. As a result, various protrusions can be removed by etching, and the productivity of various types can be increased.

The present invention can be applied to, for example, a printed circuit board for connecting electronic devices such as ICs and LSIs, in particular, a printed circuit board capable of realizing high-density mounting.

(A)-(E) are sectional drawings which show the manufacturing method of the 1st Example of this invention circuit board in order of a process. (A), (B) is sectional drawing which shows each another example of the protrusion for an upper-lower conductor connection of the said Example. It is a perspective view for showing the feature of the above-mentioned example. (A)-(F) is for demonstrating one conventional example regarding the printed circuit board for high-density mounting, and is sectional drawing which shows the manufacturing method of a wired circuit board to process order (A)-(F). . (G)-(I) is for demonstrating one conventional example regarding the printed circuit board for high-density mounting, and is sectional drawing which shows the manufacturing method of a wired circuit board to process order (A)-(F). . (A)-(G) is for demonstrating another prior art example regarding the printed circuit board for high-density mounting, and is sectional drawing which shows the manufacturing method of a wired circuit board to process order (A)-(G). .

Explanation of symbols

51 ... Base material, 53 ... Projection for connection between upper and lower conductors (cone shape),
53a ... drum-like protrusions, 54 ... film for enhancing connectivity, 55 ... interlayer insulating film,
55a ... Interlayer insulating film made of anisotropic conductive film, 57 ... Projection.

Claims (1)

The upper and lower conductor connecting projections made of a number of metals on the surface of the metal layer are arranged on each intersection of the lattices arranged at regular intervals,
An interlayer insulating layer is provided on the surface of the metal layer on which the inter-conductor connection protrusions are formed in a state of being penetrated by the inter-conductor connection protrusions,
A printed circuit board comprising a metal layer formed on a surface of the interlayer insulating layer including the upper and lower conductor connecting projections.

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