JPH09172261A - Manufacture of multilayered printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the working manhour of a via-hole, by almost coaxially forming small holes having smaller diameters in order from the surface side of a laminate, in lands except lands of the lowermost layer, and forming via- holes with laser which penetrate the small holes of a plurality of lands from the surface of the laminate and reach the lands of the lowermost layer. SOLUTION: In a copper foil 52 of a laminate wherein a board 50 is laminated, a small hole 56 is formed by eliminating a position for forming a via-hole by photo etching or the like. In the position where the via-hole is formed, lands 12B, 16B of circuit patterns 12A, 16A formed on boards 10, 14 are superimposed in the thickness direction of the laminate. Excepting the land 12B of the circuit pattern 12A which turns to the bottom of the via-hole, in the land 16B above the land 12B and in the outermost copper foil 52, a small hole 58 and the small 56 are so formed that the diameter becomes larger toward the surface side. Thereby via-holes 60, 62 are formed at the same time when the small hole 56 is irradiated perpendicularly to the laminate surface with laser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board in which different layers are connected by via holes.

[0002]

2. Description of the Related Art In a multilayer printed wiring board, a via hole (also referred to as a via hole) is provided for making electrical connection between different layers. It is conventionally known to use a laser to form this via hole.

4 and 5 are views showing an example of a conventional via hole processing process using a laser. This method connects adjacent inner layer circuits of three or more layers. In these figures, (A) to (H) show processing steps in order. First, the insulating substrate 10 is prepared (step (A) in FIG. 4). This substrate 1
0 may include a base material such as glass fiber which is impossible or difficult to process by laser. Copper foils 12, 12 are adhered to both surfaces of the substrate 10.

Circuit patterns 12 are formed on both sides of the substrate 10.
A and 12A are formed by a known method, for example, a photoetching method (step (B) in the figure). Other substrates 14 and 14 or copper foils are adhered and laminated with an adhesive sheet or the like on both surfaces of the substrate 10 (step (C) in FIG. 4). The adhesive sheet used here does not contain glass fibers.
Like the substrate 10, the substrates 14 and 14 are preferably resin plates containing no glass fiber. Both boards 1
Copper foils 16 and 16 are adhered to the outer surfaces of 4 and 14, respectively.

The copper foils 16 and 16 of the laminated body 18 have small holes formed by removing the positions where via holes are to be formed, for example, by photoetching. This via hole is
It is located at a position overlapping the land of the circuit pattern formed on the copper foils 12, 12 of the substrate 10. Then, a drilling process is performed on the laminated body 18 using a laser (step (D) in FIG. 4).

The laser used here is applied to the portion of the small hole for removing the copper foils 16, 16 of the laminated body 18 for the via hole. The irradiation of the laser causes the resin of the substrates 14 and 14 to disappear under the small holes of the copper foil 16, and the via hole 20 is formed. When the laser reaches the land formed on the circuit pattern 12A of the substrate 10, the land cannot be perforated because the land is a copper foil. Therefore, the via hole 20 has a depth up to this land and does not affect the substrate 10 below it. The actual via-hole 20 has a conical shape whose diameter gradually decreases toward the lower layer, but in FIGS. 4 and 5, it is shown as a column for simplicity.

After the via hole 20 is formed in this manner, electroconductivity is applied to the inner surface of the via hole 20 to provide conductivity, and then electrolytic copper plating is performed. Then, the circuit pattern 16A is formed on the outer surface of the laminate 18 (see FIG. 4).
Step (E)). The circuit pattern 12A of the substrate 10 and the circuit pattern 16A of the substrate 14 by this copper plating process
And different layers are electrically connected. That is, the via hole 20A is formed.

The laminated body 18 in which the via holes 20A are formed in this manner is further laminated with another substrate 22, 22 or a copper foil to form a laminated body 18A. The adhesive sheet used at this time does not contain glass fiber. The adhesive contained in the adhesive sheet flows into the via hole 20A to fill the via hole 20A (step (F) in FIG. 5).
The substrates 22 and 22 are also provided with copper foils 24 and 24 on one side like the substrate 14, and the copper foils 24 are laminated outside.

Small holes are formed in the copper foil 24 by removing the portions corresponding to the positions of the via holes formed in the substrate 22 by, for example, photoetching. Then, a laser is used to form a via hole 26 in the substrate 22 (step (G) in FIG. 5). The bottom of the via hole hole 26 is a land of the circuit pattern 16A of the substrate 14. Then, after electroconductivity is applied to the through-holes 26 of the laminate 18A by electroless plating, electroplating is performed to form the outermost circuit pattern 24A (step (H) in FIG. 5). As a result, the via hole 26A connecting the circuit pattern 24A and the inner layer circuit pattern 16A
Is formed.

FIG. 7 is a diagram showing a conventional method of processing a via hole for connecting two layers which are not adjacent to each other. In this figure, 100 is an insulating substrate serving as a core, 102, 104,
Reference numeral 106 denotes a substrate laminated on the substrate 100. Inner layer circuit patterns 108, 110 and 112 are formed on these substrates 100, 102 and 104, respectively, and outer layer circuit pattern 114 is formed on the uppermost substrate 106.

Here, the inner layer circuit patterns 108 and 110 are connected by via holes 116, and the inner layer circuit patterns 110 and 112 are connected by via holes 118. The inner layer circuit patterns 112 and 114 are connected by the via hole 120. Via hole 116 is substrate 1
It is formed by forming a small hole from the side of the circuit pattern 110 of the substrate 102 using a laser in a state where the substrate 102 is laminated on the substrate 00, and performing copper plating treatment.

Similarly, the via hole 118 is processed in a state in which the substrates 104 are laminated, and the via hole 120 is formed in the substrate 106.
Are processed in a laminated state. As described above, conventionally, in order to make a connection between two layers that are not adjacent to each other, the layers are connected in order between layers, so that the substrates 102, 104,
The via holes 116, 118, 12 are formed every time 106 is laminated.
It was necessary to process 0.

[0013]

As described above, in the conventional method, each time a substrate is laminated, the via holes 20, 26, 66, 68, 70 are formed on the newly laminated substrate by laser. Also, the via hole holes 20, 26, 66, 6
It was necessary to copper-plat the inner surface of each of the layers 8 and 70 to form an electrical connection between adjacent layers. Therefore, there has been a problem that the number of manufacturing steps significantly increases in response to the increase in the number of laminated substrates.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to improve the productivity by reducing the number of man-hours for processing a via hole and remarkably reducing the number of manufacturing steps particularly when the number of laminated substrates is large. An object of the present invention is to provide a method for manufacturing a multilayer printed wiring board.

[0015]

According to the present invention, an object of the present invention is to provide a multilayer structure in which a plurality of insulating substrates having circuit patterns are laminated and pressure-bonded via insulating layers, while circuit patterns between three or more different layers are connected by via holes. In the method for manufacturing a printed wiring board, each of the plurality of inner layer circuit patterns has a land that overlaps in the thickness direction of the laminated body, and the lands other than the land of the lowermost layer among these lands have smaller diameters in order from the surface side of the laminated body. A small hole is formed substantially coaxially, a via hole hole that penetrates the small holes of a plurality of lands from the surface of the laminated body and reaches the land of the lowermost layer is formed by using a laser, and the via hole hole is copper-plated. And a circuit pattern between different layers are connected to each other to achieve a multilayer printed wiring board manufacturing method.

Further, the same purpose is to laminate a plurality of insulating substrates on which circuit patterns are formed by laminating and pressing into three or more layers through insulating layers, while connecting circuit patterns between different layers which are not adjacent to each other by via holes. In the manufacturing method of 1., the inner layer circuit patterns of the two layers that are not adjacent to each other have lands that overlap in the thickness direction of the laminated body without overlapping the inner layer circuit patterns between these two layers. A small hole is formed, a via hole hole that penetrates the small hole of the land of the upper layer and reaches the land of the lower layer from the surface of the laminated body is formed by using a laser, and copper plating is applied to the via hole hole to form different layers. And a method for manufacturing a multilayer printed wiring board, which is characterized in that the circuit patterns are connected.

[0017]

1 and 2 are views showing a processing step according to an embodiment of the present invention, and FIG. 3 is an enlarged view of a portion viewed from an arrow II which is a part of step F in FIG. In this embodiment, via holes for connecting circuit patterns of three or more layers are formed. Since steps (A) to (C) in FIG. 1 are the same as those shown in FIG. 4, the same reference numerals are given to the same portions and the description thereof will not be repeated.

In this embodiment, the circuit patterns 16A and 16A are formed (in FIG. 1) after the substrates 14 and 14 each having copper foil on one side are laminated on both sides of the substrate 10 (step (C) in FIG. 1). Step (D)). That is, the circuit pattern 16A is first formed without processing the via hole. Further, the other substrates 50, 50 are provided on both surfaces of the laminated body 18.
Alternatively, copper foils are laminated via an adhesive sheet or the like (step (E)). This board 50, 50 also has copper foils 52, 5 on one side.
It is a stretch of 2.

In the copper foils 52, 52 of the laminated body 54 in which the substrates 50, 50 are laminated in this way, the positions where the via holes are formed are removed by photoetching or the like to form the small holes 56.
(See FIG. 3). The lands 12B and 16B (FIG. 3) of the circuit patterns 12A and 16A formed on the substrates 10 and 14 are overlapped in the thickness direction of the laminated body 54 at the positions where the via holes are formed. Except for the land 12B of the circuit pattern 12A which is the bottom of the via hole, small holes 58 and 56 are formed in the land 16B above and the copper foil 52 of the outermost layer so that the diameter becomes larger toward the surface side. (Fig. 3).

Therefore, when the laser is irradiated perpendicularly to the surface of the laminated body 54 toward the small hole 56, the substrate 50 is provided with the via hole hole 60 having substantially the same diameter as that of the small hole 56, and the substrate 1 also.
For 4, the via holes 62 having substantially the same diameter as the small holes 58 are formed coaxially and continuously at one time. (Step (F) in FIG. 2).

After processing the via hole holes 60 and 62 in this way, copper plating is performed to form the via hole holes 60 and 62.
Conductivity is given to the inner surface of and the circuit pattern 5 is applied to the outermost layer.
2A is formed (step (G) in FIG. 2). As a result, a via hole 64 connecting the inner layer circuit patterns 12A and 16A and the outer layer circuit pattern 52A is formed. Of course, at this time, the via hole 64A penetrating only the outermost substrate 50 may be simultaneously formed.

In this embodiment, the three-layer circuit pattern 12 is used.
The via hole 64 connecting A, 16A, and 52A is formed, but a via hole connecting circuit patterns of four layers or more can of course be formed. The small holes 56 and 58 formed in the outermost layer circuit pattern 52A and the inner layer land 16B have a small diameter in order from the front surface side. However, if the positioning accuracy of each layer at the time of stacking is high, the difference in diameter between these small holes is small. it can.

FIG. 6 is a view showing another embodiment, in which two non-adjacent layers shown in FIG. 7 are connected. That is, when the circuit patterns 108A and 114A on the lowermost layer and the uppermost layer are connected, the circuit patterns 110A and 112A sandwiched between the two layers are the circuit patterns 108A and 1A, respectively.
It is formed so as not to be sandwiched between the lands of 14A.

The via hole that reaches the circuit pattern 108A in the lowermost layer from the small hole provided in the circuit pattern 114A in the uppermost layer is processed by laser and plated. Via hole 1 formed in this way
22 can be formed by one-time processing.

The excimer laser such as XeCl or KrF is suitable for the laser used in the drilling process of the present invention. The laser used is not limited to the excimer laser, but may be a CO ₂ laser, a YAG laser, or the like.

[0026]

As described above, according to the first aspect of the present invention, a via hole for connecting a circuit pattern between three or more layers is formed by using one laser drilling process and one copper plating process. Therefore, unlike the conventional method, it is not necessary to perform the drilling process and the copper plating process every time one substrate is laminated, and the processing man-hour can be remarkably reduced. Therefore, the productivity of the multilayer printed wiring board is improved.

According to the second aspect of the present invention, the circuit pattern is formed in advance so that the circuit pattern between the two layers does not come into contact with the via hole that connects the non-adjacent layers.
Since the via hole is formed by one-time laser drilling and plating after stacking, the number of processing steps can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a processing step (first half) of an embodiment of the present invention.

FIG. 2 is a diagram showing a processing man-hour (second half) according to an embodiment of the present invention.

FIG. 3 is a partially enlarged view of step F in FIG.

FIG. 4 is a diagram showing a conventional processing step (first half).

FIG. 5 is a diagram showing a conventional processing step (second half).

FIG. 6 is a diagram showing a processing method according to another embodiment of the present invention.

FIG. 7 is a diagram showing a conventional processing method.

[Explanation of symbols]

10, 14, 22, 50, 100, 102, 104, 1
06 substrate 12, 16, 24, 52 copper foil 12A, 16A, 24A, 52A, 108A, 110
A, 112A, 114A Circuit pattern 20, 26, 60, 62 Beer hole hole 20A, 26A, 64, 64A, 122 Beer hole

Claims (2)

[Claims] 1. A method for manufacturing a multi-layer printed wiring board, wherein a plurality of insulating substrates having circuit patterns are laminated and pressure-bonded via insulating layers, while circuit patterns between three or more different layers are connected by via holes. The inner layer circuit pattern of each has lands overlapping in the thickness direction of the laminated body,
Small lands having a smaller diameter are formed on the lands other than the land of the lowermost layer of these lands in order from the surface side of the laminated body substantially coaxially, and through the small holes of a plurality of lands from the surface of the laminated body, A method of manufacturing a multilayer printed wiring board, comprising forming a via hole hole reaching a land of the lowermost layer by using a laser, and performing copper plating on the via hole hole to connect circuit patterns between different layers. 2. A method for manufacturing a multilayer printed wiring board, wherein a plurality of insulating substrates having a circuit pattern formed thereon are laminated and pressure-bonded in three or more layers with an insulating layer interposed therebetween, and circuit patterns between different layers which are not adjacent to each other are connected by via holes. , The inner layer circuit patterns of two layers which are not adjacent to each other have lands that overlap in the thickness direction of the laminated body without overlapping the inner layer circuit pattern between these two layers, and small holes are formed in the lands of the outer layer of these lands. Then, a via hole hole is formed from the surface of the laminated body through the small hole of the land of the upper layer to reach the land of the lower layer using a laser, and copper plating is applied to the via hole hole to form a circuit pattern between different layers. A method for manufacturing a multi-layer printed wiring board, which comprises connecting.