JPH10163633A - Multi-layer circuit board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low cost substrate in good productivity, by connecting any via hole, at a multi-layer circuit board where a conductor circuit layer of 3 or more layers which is electrically connected with a via hole is provided through an insulation layer, to at least a conductor circuit in outer-most layer. SOLUTION: A recess reaching up to an insulation layer is formed at a specified position of a conductor circuit 2 with a drill, etc., then, an insulation 5 is melted by various laser light ray or chemical drilling to remove a portion from the conductor circuit 2 to a desired conductor circuit including an insulation layer, so that, generally, a column-like recess is formed on the bottom part of recess, for forming a via hole 1. For via hole's electric connection method, a conductive material coats an inner wall or bottom part or recess by plating, etc., or such conductive material as a conductive paste is filled in the recess. As a result, forming of the via hole 1 is done in a single process for higher productivity, thus a multi-layer circuit board comprising a conductor circuit of 3 or more layers in manufactured at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer circuit board having three or more layers and a method of manufacturing the same, by forming each of the via holes so as to be connected to the outermost conductive circuit layer.
The present invention relates to an inexpensive multilayer circuit board having extremely high productivity and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, as the power of semiconductor devices has increased, the circuit board has been required to be further reduced in size and density, and a multilayer circuit board in which conductive circuits are stacked in multiple layers has been expected. Are getting stronger. However, in the conventional multilayer circuit board, as the number of circuit layers increases, the number of through holes or via holes (hereinafter simply referred to as via holes) increases, and the number of processes for forming these increases. There is a problem that the productivity of the circuit board is remarkably reduced, and the resulting multilayer circuit board is also expensive.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-layer circuit board having three or more conductor circuits, which is excellent in productivity and therefore inexpensive, and a method of manufacturing the same.

[0004]

According to the present invention, three or more conductive circuit layers are provided on a substrate with an insulating layer interposed therebetween, and via holes for electrically connecting the conductive circuit layers are provided. A multilayer circuit board, wherein each of the via holes is provided to be connected to at least the outermost conductive circuit, preferably, the board is aluminum or an aluminum alloy, Alternatively, the multilayer circuit board is made of copper or a copper alloy.

Further, according to the present invention, the insulating layer is made of an epoxy resin containing at least one of aluminum oxide, silicon oxide, aluminum nitride, boron nitride and silicon nitride, or an epoxy resin containing glass fiber. The multilayer circuit board is made of resin. Further, the present invention is the multilayer circuit board, wherein the diameter of the via hole is at least 1/3 of the depth of the via hole, wherein the inner surface of the via hole is plated with copper. The multilayer circuit board.

In addition, the present invention provides a multi-layer circuit comprising three or more conductive circuit layers provided on a substrate via an insulating layer, and via holes for electrically connecting the conductive circuit layers to each other. A method of manufacturing a substrate, wherein after a step of forming a circuit from the conductor circuit layer after joining the conductor circuit layer via an insulating layer has been performed at least twice or more, a step of forming a via hole is performed. This is a method for producing a multilayer circuit board.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. 1 and 2 are cross-sectional views simulating an example of the multilayer circuit board of the present invention. FIG. 1 shows that three conductive circuits 2, 4, and 7 are insulated on an electrically insulating base material 6. The via holes 1 are provided through the layers 3 and 5, and each of the via holes 1 is connected to the outermost conductive circuit 2. or,
In FIG. 2, three conductive circuits 2, 4, and 7 are provided on a metal plate 9 via insulating layers 3, 5, and 8, and via holes 1 are all connected to the outermost conductive circuit 2. Having a structure. As described above, the via hole 1 of the present invention only needs to be connected to at least the outermost conductive circuit, and connects three or more conductive circuits, for example, the conductor circuit 2, the conductor circuit 4 in FIG. One that connects any of the conductor circuits 7 may be included. Although not shown, an electronic element may be mounted on the conductor circuit 2 as necessary, or may be connected to another component by wire bonding or the like.

In the case where the structure of the present invention is not used, the formation of via holes is limited after the formation of the lower layer circuit and before the step of laminating the conductor circuit of the upper layer, and a desired number of via holes are formed by repeating the formation of a small number of via holes several times. Via holes had to be formed. In the present invention, as described above, each of the via holes 1 is characterized in that it is connected to at least the outermost conductor circuit 2. By adopting this structure, the formation of the via holes is assembled in the final step. This makes it possible to reduce the labor and time loss required for the process switching according to the conventional method to a minimum, thereby achieving an effect of significantly increasing the productivity.

The via hole 1 of the present invention can be obtained by removing the conductor circuit 2 from the conductor circuit 2 to the desired conductor circuit including the insulating layer therebetween, and forming a generally cylindrical recess. More specifically, after forming a dent reaching the insulating layer by a drill or the like at a predetermined position of the conductive circuit 2, various laser beams such as an excimer laser, a CO ₂ laser, and a YAG laser are used at the bottom of the dent. ,
A method in which the insulating layer is patterned by exposing the insulating layer to light using a photosensitive resin and then dissolving the via hole portion or chemically dissolving the insulating layer 5 by chemical drilling.

The via hole may be electrically connected by coating the inner wall and bottom of the recess with a conductive material by plating or the like, filling the recess with a conductive material such as a conductive paste, or A known method such as wire bonding using the bottom of the recess can be used, but a copper plating method is preferable because a highly reliable electrical connection can be achieved.

In the present invention, the diameter of the via hole 1 is preferably at least one third of its depth. When the diameter of the via hole is less than 1/3 of the depth, the penetration of the copper plating or the filling of the conductive paste may not be performed stably. Also, the diameter of via hole 1 is preferably 0.25 mm or more. If the diameter is less than 0.25 mm, it may be difficult to insert copper plating or fill the conductive paste. Since the upper limit of the diameter of the via hole 1 is limited by the circuit width, it is not necessary to particularly define the upper limit in the present invention, but is generally about 5 mm or less.

Regarding the material of the substrate and the metal plate of the present invention,
Although there is no particular limitation, the better the heat dissipation property is, the more preferable it is to supply a large current to the via hole 1. That is, a known insulating substrate having electrical insulation properties is used as the base material 6, such as a polyimide resin, a paper-phenol resin,
Glass-epoxy resin and the like can be mentioned. Examples of the metal plate include metals such as iron, aluminum and copper and alloys containing these as main components. Among them, copper and copper alloys, aluminum and aluminum alloys are said to be excellent in heat dissipation and workability. Aluminum and aluminum alloys are most preferably used because they are industrially supplied at low cost. In the present invention, an aluminum alloy refers to an alloy containing one or more elements of Cu, Mn, Si, and Mg in aluminum, and a copper alloy refers to one of Pb, Fe, Sn, and Zn in copper. An alloy containing more than one element.

The material of the insulating layer is not particularly limited, and may be epoxy resin, phenol resin, polyimide resin, BT resin,
An organic resin such as a Teflon resin is generally used. The organic resin is filled with various inorganic ceramics singly or plurally, or with glass fiber or the like for the purpose of enhancing thermal conductivity. Various types of epoxy resins filled with glass fibers are commercially available, and can be selected according to various uses of the multilayer circuit board, and are preferably used. Further, as the inorganic ceramic, aluminum oxide, silicon oxide, aluminum nitride, silicon nitride, nitrided nitride, or the like can be used because the thermal conductivity can be extremely increased without impairing the electrical characteristics of the obtained insulating layer, particularly, withstand voltage. Boron or the like is preferably used. The insulating layers do not necessarily have to be the same type and have the same composition, but generally, the same layer is used.
The thickness of the insulating layer is not particularly limited, and is generally 50 μm or more.

The material of the conductor circuits 2, 4, and 7 may be any of copper, aluminum, nickel, iron, tin, silver, and titanium, an alloy containing two or more of these metals, and each metal or alloy. Can be used. At this time, the foil may be produced by an electrolytic method or a rolling method, and the foil may be plated with a metal such as Ni plating, Ni + Au plating, or solder plating. It should be noted that the conductor circuits need not necessarily be made of the same material and configuration, but generally the same material is used. The thickness of the conductor circuits 2, 4, and 7 is also not particularly limited, and is generally 500 μm or less.

The multilayer circuit board of the present invention can be obtained by obtaining a multilayer circuit board without via holes formed by combining conventionally known methods and forming via holes in the multilayer circuit board. As a combination of known methods for obtaining a multilayer circuit board in which the via hole is not formed, for example, (1) bonding a metal foil via an insulating layer on at least one main surface of a metal plate and etching the metal foil A method in which a circuit is formed by processing such as a method to obtain a metal-based circuit board, and a circuit is formed by joining a metal foil via an insulating layer on the circuit board twice or more, (2) at least A method of using an insulating substrate having one or more layers of conductive circuits, and repeating at least one or more times forming a circuit by bonding a metal foil on at least one of the conductive circuits via an insulating layer; A method of bonding an insulating substrate having at least one or more conductive circuits on both sides thereof via an insulating layer on a metal-based circuit board having a conductive circuit provided on at least one main surface of the plate via an insulating layer, And more Serial (1)
To (3). Further, instead of the method of joining metal foils to form a post-circuit, a method of joining metal foils on which circuits are formed in advance may be used. Among these methods, according to the study of the present inventor, according to the study of a metal-based circuit board or an insulating substrate, a conductor circuit is bonded on the substrate via an insulating layer, and after the insulating layer is cured, the circuit is formed. The method of forming a via hole after performing the forming step two or more times is because a method of forming a via hole can stably obtain a multi-layer circuit board with good insulation properties and few electric connection failures at the via hole portion and with high productivity. This is the preferred method.

Hereinafter, the present invention will be described in more detail based on examples.

【Example】

Example 1 CEM-1 (R1790Y, manufactured by Matsushita Electric Works) having a copper foil thickness of 35 μm and a substrate thickness of 1.6 mm.
After a predetermined circuit is formed on the copper foil of No. 1, an epoxy-based prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.15 mm and an electrolytic copper foil having a thickness of 35 μm are sequentially laminated on the circuit side surface, and hot pressing is performed. Pressed by After a predetermined circuit is formed on the copper foil on the outer layer side, a thickness of 0.1
5mm epoxy prepreg (Matsushita Electric Works; R166)
1) and an electrolytic copper foil having a thickness of 35 μm were sequentially laminated, pressed by hot pressing, and then a predetermined circuit was formed on the outermost copper foil. Drill from the outermost circuit side of the board by φ
A 0.1 mm dent was formed, and a via hole having a thickness of 20 μm was formed by copper plating to electrically connect the outermost layer circuit and each inner layer circuit. With respect to this multilayer circuit board, the filling property of copper plating into the via holes and the productivity were measured by the following methods, and the results were good as described in Table 1.

<Evaluation Method for Filling of Copper Plating> (1) The presence / absence of electrical connection between conductor circuits connected by via holes, and (2) the conductor section when the cross section of via holes was observed after polishing. Regarding the presence / absence of a defect, ○ when both (1) and (2) are good, △ when only (1) is good and (2) is bad, and when both (1) and (2) are bad Was evaluated as x.

<Evaluation Method of Productivity> Evaluation was made based on the time required to manufacture 10,000 substrates of business card size (90 mm × 50 mm) in each of the manufacturing methods.

[0020]

[Table 1]

Example 2 CEM-1 (Matsushita Electric Works; R1790Y) having a copper foil thickness of 35 μm and a substrate thickness of 1.6 mm
After a predetermined circuit is formed on the copper foil of No. 1, an epoxy-based prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.15 mm and an electrolytic copper foil having a thickness of 35 μm are sequentially laminated on the circuit side surface, and hot pressing is performed. Pressed by After a predetermined circuit is formed on the copper foil on the outer layer side, an epoxy-based prepreg having a thickness of 0.15 mm (manufactured by Matsushita Electric Works; R
1661) and an electrolytic copper foil having a thickness of 35 μm were sequentially laminated and pressed by hot pressing, and then a predetermined circuit was formed on the outermost copper foil. A recess of φ0.1 mm was opened from the outermost layer circuit side of this substrate by a YAG laser, a via hole having a thickness of 20 μm was formed by copper plating, and the outermost layer circuit and each inner layer circuit were electrically connected. With respect to this multilayer circuit board, the filling property of the copper plating into the via holes and the productivity were measured by the method described in Example 1, and the results were good as described in Table 1.

Example 3 An epoxy prepreg having a thickness of 0.15 mm (R1661 manufactured by Matsushita Electric Works) and an electrolytic copper foil having a thickness of 35 μm were sequentially laminated on an aluminum plate having a thickness of 1.5 mm. After pressing, a predetermined circuit is formed. Again, an epoxy-based prepreg (Matsushita Electric Works; R1661) having a thickness of 0.15 mm and electrolytic copper foil having a thickness of 35 μm are sequentially laminated on the circuit-side surface, and pressed by hot pressing. did. After forming a predetermined circuit on the copper foil on the outer layer side, a further 0.1
5mm epoxy prepreg (Matsushita Electric Works; R166)
1) and an electrolytic copper foil having a thickness of 35 μm were sequentially laminated, pressed by hot pressing, and then a predetermined circuit was formed on the outermost copper foil. From the outermost layer circuit side of this substrate, a dent of φ0.1 mm is opened by a YAG laser, and a thickness of 2 mm is formed by copper plating.
Via holes of 0 μm were formed to electrically connect the outermost layer circuit and each inner layer circuit. About this multilayer circuit board,
The filling properties and productivity of the copper plating into the via holes were evaluated, and the results were good as described in Table 1.

Example 4 CEM-1 having a copper foil thickness of 35 μm and a substrate thickness of 1.6 mm (R1790Y, manufactured by Matsushita Electric Works)
After a predetermined circuit is formed on the copper foil of No. 1, an epoxy-based prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.15 mm and an electrolytic copper foil having a thickness of 35 μm are sequentially laminated on the circuit side surface, and hot pressing is performed. Pressed by After a predetermined circuit is formed on the copper foil on the outer layer side, an epoxy-based prepreg having a thickness of 0.15 mm (manufactured by Matsushita Electric Works; R
1661) and an electrolytic copper foil having a thickness of 35 μm were sequentially laminated and pressed by hot pressing, and then a predetermined circuit was formed on the outermost copper foil. A hole having a diameter of 0.1 mm is made from the outermost layer circuit side of the substrate by a YAG laser, and a via hole is formed by injecting a copper paste (manufactured by Asahi Kaken Corporation; ACP-052) into the opening by a printing method. The outermost layer circuit and each inner layer circuit were electrically connected. With respect to this multilayer circuit board, the filling property of the copper plating into the via holes and the productivity were evaluated. The results were good as described in Table 1.

Example 5 CEM-1 having a copper foil thickness of 35 μm and a substrate thickness of 1.6 mm (R1790Y, manufactured by Matsushita Electric Works)
After a predetermined circuit is formed on the copper foil of No. 1, an epoxy-based prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.15 mm and an electrolytic copper foil having a thickness of 35 μm are sequentially laminated on the circuit side surface, and hot pressing is performed. To form a predetermined circuit on the copper foil on the outer layer side. Further, an epoxy-based prepreg having a thickness of 0.15 mm (Matsushita Electric Works; R
1661) and an electrolytic copper foil having a thickness of 35 μm were sequentially laminated and pressed by hot pressing, and then a predetermined circuit was formed on the outermost copper foil. From the outermost circuit side of this substrate, a hole of φ0.08 mm was made at a predetermined position with a YAG laser,
A via hole having a thickness of 20 μm is formed by copper plating,
A multilayer circuit board was obtained. With respect to this multilayer circuit board, the filling property of copper plating into via holes and the productivity were evaluated. The results were good as described in Table 1.

Example 6 CEM-1 (R1790Y, manufactured by Matsushita Electric Works) having a copper foil thickness of 35 μm and a substrate thickness of 1.6 mm.
After a predetermined circuit is formed on the copper foil of No. 1, an epoxy-based prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.15 mm and an electrolytic copper foil having a thickness of 35 μm are sequentially laminated on the circuit side surface, and hot pressing is performed. Pressed by After forming a predetermined circuit on the copper foil on the outer layer side, a thickness of 0.1
5mm epoxy prepreg (Matsushita Electric Works; R166)
1) and an electrolytic copper foil having a thickness of 35 μm were sequentially laminated, pressed by hot pressing, and then a predetermined circuit was formed on the outermost copper foil. A recess of φ0.08 mm was opened from the outermost layer circuit side of the substrate with a YAG laser, and a via hole having a thickness of 20 μm was formed by copper plating to electrically connect the outermost layer circuit and each inner layer circuit. With respect to this multilayer circuit board, the filling property of the copper plating into the via hole and the productivity were evaluated. As shown in Table 1, the result was good although the filling property of the copper plating was slightly difficult. Was.

Example 7 510 mm × 510 mm ×
A bisphenol A type epoxy resin (manufactured by Yuka Shell Co., Ltd .; Epicoat 828) containing 53% by volume of boron nitride (manufactured by Denki Kagaku Kogyo KK; GP) was used as an insulating adhesive on a 1.5 mm aluminum plate. Add an amine-based curing agent and apply to a thickness of 150 μm.
A 5 μm copper foil was bonded by a lamination method. Next, after etching the copper foil to form a shield pattern, an amine-based curing agent was added to the insulating adhesive on the surface on the copper foil side, and applied so as to have a thickness of 150 μm. A copper foil was laminated by a lamination method and cured by heating. This operation was repeated again, a hole of φ0.1 mm was opened from the outermost circuit side of the obtained substrate with a YAG laser, a 20 μm-thick via hole was formed by copper plating, and an electric connection was established between the outermost layer circuit and each inner layer circuit. Connected. With respect to the multilayer circuit board obtained by the above operation, the filling property of the copper plating into the via holes and the productivity were evaluated, and the results were good as described in Table 1.

[Comparative Examples 1 and 2] The copper foil thickness was 35 μm.
m, CEM-1 having a substrate thickness of 1.6 mm (manufactured by Matsushita Electric Works; R
After a predetermined circuit is formed on the copper foil of 1790Y), an epoxy-based prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.15 mm and an electrolytic copper foil having a thickness of 35 μm are sequentially laminated on the circuit surface, and hot pressed. Pressed by After a predetermined circuit was formed on the copper foil on the outer layer side, a hole having a diameter of 0.10 mm was formed at a predetermined position by a YAG laser, and a via hole having a thickness of 20 μm was formed by copper plating. Thereafter, an epoxy-based prepreg (R1661 manufactured by Matsushita Electric Works) having a thickness of 0.15 mm and an electrolytic copper foil having a thickness of 35 μm are sequentially laminated again on the circuit side surface, and pressed by a hot press. A predetermined circuit was formed on the foil. From the outermost layer circuit side of this substrate,
Holes of 0.1 mm (Comparative Example 1) and 0.04 mm (Comparative Example 2) were formed, and via holes having a thickness of 20 μm were formed by copper plating to obtain a multilayer circuit board (see FIG. 3). With respect to this multilayer circuit board, the filling property of the copper plating into the via hole and the productivity were evaluated as follows. As shown in Table 1, the results were not satisfactory in the productivity.

[0028]

According to the present invention, since each of the via holes has a structure connected to at least the outermost conductive circuit, the step of forming the via hole can be reduced to one step, unlike the related art. As a result, a multilayer circuit board having three or more conductor circuits can be obtained at low cost, which is industrially beneficial.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a multilayer circuit board of the present invention.

FIG. 2 is a sectional view showing another example of the multilayer circuit board of the present invention.

FIG. 3 is a cross-sectional view of a known multilayer circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Via hole 2 Conductor circuit 3 Insulating layer 4 Conductor circuit 5 Insulating layer 6 Base material 7 Conductor circuit 8 Insulating layer 9 Metal plate

Claims (7)

[Claims] 1. A multilayer circuit board comprising: a substrate; and three or more conductive circuit layers provided on the substrate with an insulating layer interposed therebetween, and via holes for electrically connecting the conductive circuit layers to each other. A multilayer circuit board, wherein each of the via holes is provided so as to be connected to at least an outermost conductor circuit. 2. The multilayer circuit board according to claim 1, wherein the board is made of aluminum, an aluminum alloy, copper, or a copper alloy. 3. The multilayer circuit board according to claim 2, wherein said insulating layer is made of an epoxy resin containing at least one of aluminum oxide, silicon oxide, aluminum nitride, boron nitride, and silicon nitride. . 4. The multilayer circuit board according to claim 1, wherein said insulating layer is made of an epoxy resin containing glass fiber. 5. The multilayer circuit board according to claim 1, wherein the diameter of the via hole is at least 1/3 of the depth of the via hole. 6. The via hole according to claim 1, wherein the diameter of the via hole is at least 1/3 of the depth of the via hole, and the inner surface of the via hole is plated with copper. The multilayer circuit board according to claim 3 or 4. 7. A method for producing a multilayer circuit board, comprising three or more conductive circuit layers provided on a substrate via an insulating layer, and via holes for electrically connecting the conductive circuit layers to each other. A step of forming a via hole after at least twice a step of forming a circuit from the conductive circuit layer after joining the conductive circuit layer via an insulating layer, and a step of forming a via hole. Manufacturing method.