JP2994295B2 - Build-up printed wiring board and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a build-up printed wiring board having a laser via hole formed by laser processing on the same layer of a printed wiring board and a photo via hole formed by photolithographic processing, and a method of manufacturing the same. is there.

[0002]

2. Description of the Related Art In a method of manufacturing a multilayer printed wiring board, there is known a build-up method in which a circuit pattern and an insulating layer are sequentially stacked on at least one surface of an insulating substrate. In this case, via holes (via holes, via holes) are provided to electrically connect the circuit patterns of each layer.

FIG. 2 and FIG. 3 are views showing a process of manufacturing this via hole. FIG. 2 shows a step of forming a via hole using a laser, and FIG. 3 shows a step of forming a via hole by photolithographic processing. First, a method for forming the laser via hole in FIG. 2 will be described.

In FIG. 2, reference numeral 10 denotes a copper-clad laminate, which is an insulating plate (laminate) obtained by laminating a sheet (prepreg) impregnated with a resin on a reinforcing base material such as paper or glass fiber and subjecting the sheet to pressure and heat treatment. A copper foil 12 is adhered to both sides or one side of a plate. Here, a glass cloth impregnated with an epoxy resin, for example, a double-sided copper-clad laminate of NEMA standard FR-4 is used. An appropriate circuit pattern is formed on the copper foils 12, 12 by a known photo etching method.

[0005] Reference numerals 14 and 14 denote thermosetting resin layers, which are formed by applying an epoxy-based thermosetting resin to both surfaces of the copper-clad laminate 10 and heating the same. Copper foils 16, 16 are laminated on these thermosetting resin layers 14, 14. Small opening portions 18 for via holes and a predetermined circuit pattern are formed in these copper foils 16 and 16 by a known photoetching method (FIG. 2A).

[0006] The laminated body 20 thus manufactured is sequentially irradiated with a laser beam directed toward each small opening 18. Since the laser does not pass through the copper foil 16 on the surface, the thermosetting resin layer 14 is heated and disappears through the small opening 18 without the copper foil 16. As a result, a small hole 22 for a laser via hole is formed below the small opening 18. Laser is copper foil 1 below
2 cannot be reached, the lower copper foil 12 appears at the bottom of the small hole 22. FIG. 2B shows this state.

Next, the laminate 20 is plated with copper. That is, after the surface including the inner surface of the small hole 22 is given conductivity by electroless copper plating, electrolytic copper plating is performed, and a copper plating layer 24 having a predetermined thickness is formed. The copper plating layer 24 formed on the inner surface of the small hole 22 becomes a via hole (laser via hole) 26 connecting the circuit pattern of the lower copper foil 12 and the circuit pattern of the upper copper foil 16 ((C in FIG. 2). )).

It is needless to say that a circuit pattern is formed on the surface of the copper foil 16 by photo-etching or the like, if necessary. Further, another thermosetting resin layer 14 or copper foil 16 is further laminated thereon by the same procedure as above, and the laser via hole 26 is formed, whereby the number of laminations can be increased.

Next, a method of forming a photo via hole will be described with reference to FIG. First, a copper-clad laminate 10 similar to that used in FIG. 2 is prepared. Then, a photosensitive resin, for example, an epoxy acrylate-based photocurable resin is applied to both surfaces (FIG. 3A). The coating layer (photo-curable resin layer) 30 of the photo-curable resin is placed in a low-temperature constant-temperature bath, dried except for the volatile organic solvent contained in the solvent of the resin, and the film quality is appropriately cured.

Next, a photomask 34 having a via hole pattern printed thereon is closely attached to or slightly separated from the surface of the laminated body 32 to perform alignment, and light of an appropriate wavelength (usually ultraviolet (UV) light is used). ) For exposure (FIG. 3B). As a result, the resin layer 30 under the pattern of the via hole is not cured, and the resin layer 30 other than the pattern is cured.

Then, by developing with a developing solution of an alkaline solvent to remove an uncured portion (soluble portion), the photomask 34 is removed.
Small holes 3 matching the pattern of via holes baked in
6, that is, small holes 36 for photo via holes are formed (FIG. 3C). If copper plating is applied to this surface to form a copper plating layer 38, a via hole, that is, a photo via hole 40 connecting the lower copper foil 12 and the surface copper plating layer 38 is obtained (FIG. 3D).

An appropriate circuit pattern can be formed on the surface of the copper plating layer 38 by a photo-etching method or the like. The same procedure can be repeated to increase the number of layers.

[0013]

In the method of forming the photo via hole 40 described with reference to FIG. 3, since a photolithographic method is used, a large number of photo via holes 4 are formed by one exposure and development.
0 can be formed efficiently and productivity can be increased.

However, light (usually ultraviolet light) used for exposure has a large spread due to a diffraction phenomenon or the like. For this reason, there is a limit to the processing accuracy.
There is a problem that it is difficult to form a via hole of 0 μm or less.

On the other hand, the laser via hole 26 shown in FIG.
In the method of forming a laser beam, the straightness (directivity) of the laser used for processing is good and the spread is small, so that the processing accuracy is good. Usually, processing at the level of 100 μm in diameter is possible. However, in this method, it is necessary to separately irradiate the laser to each of the small openings 18 that have been photoetched, and the small holes 22 must be processed one by one while moving the laser. For this reason, there arises a problem that the number of steps for processing the small holes 22 by the laser increases and productivity is poor.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object a build-up printed wiring having the advantages of a photo-via hole with good productivity and the advantages of a laser via hole with a high processing accuracy and an ultra-small diameter. A primary object is to provide a board. A second object is to provide a method of manufacturing the same.

[0017]

SUMMARY OF THE INVENTION The present invention focuses on the fact that it is generally not necessary for a printed wiring board to make all via holes ultra-small, and it is sufficient to make only some of the via holes ultra-small.
Only via holes requiring ultra-small diameters are used as laser via holes to minimize the increase in the number of processing steps, and the other via holes are photo via holes having good productivity, and two types of via holes are mixed.

Therefore, in the present invention, the photosensitive resin layer used for forming the photo via hole is baked and cured after the formation of the photo via hole, so that the photosensitive resin layer can be directly used for forming the laser via hole.

According to the present invention, a first object is to provide a build-up printed wiring board having via holes for connecting circuit patterns of different layers, an insulating substrate having a circuit pattern formed on at least one surface thereof, Characterized by having a photosensitive resin layer laminated thereon, a photo via hole formed in the photosensitive resin layer, and a laser via hole formed in the photosensitive resin layer cured by baking. This is achieved by a printed wiring board.

A second object of the present invention is to provide a method for manufacturing a build-up printed wiring board having holes, comprising: a) laminating a photosensitive resin on a copper-clad laminate on which a circuit pattern is formed; A small hole for a photo via hole reaching the circuit pattern is formed by lithographic processing, c) the photosensitive resin remaining on the copper-clad laminate is cured by baking, and d) the photosensitive resin is plated with copper. Forming a first copper plating layer; e) forming a small opening for a laser via hole by photo-etching in the first copper plating layer; and f) irradiating a laser to the first copper plating layer to form the laser via hole. Forming a small hole for a laser via hole reaching the circuit pattern from a small opening for the photosensitive resin; g) a first copper plating layer and a laser via hole; And forming a second copper plating layer by applying copper plating to the small holes for use in the build-up printed wiring board.

The second object can also be achieved by the following method. That is, in a method of manufacturing a build-up printed wiring board having via holes, a) a photosensitive resin is laminated on a copper-clad laminate having a circuit pattern formed thereon, and b) the photosensitive resin reaches the circuit pattern by photolithographic processing. C) curing the photosensitive resin remaining on the copper-clad laminate by baking, and d) reducing the laser diameter of the cured photosensitive resin layer to a sufficiently small value.
By irradiating Ku focused laser to form a small hole for laser via hole reaching the circuit pattern, e) the circuit is subjected to copper plating to the small hole for the small hole and laser via hole photo via hole in the photosensitive resin layer Forming a via hole reaching the pattern.

The photosensitive resin used here is a mixture of a photosensitive resin and a thermosetting resin, and is subjected to a baking step (c).
It is desirable to accelerate the curing of the resin in the above.

[0023]

FIG. 1 is a view showing one embodiment of a manufacturing method according to the present invention. In this embodiment, the laser via hole is processed after the photo via hole is processed by the photolithographic method.

Firstly prepared similar copper-clad laminate 10 as those used in FIG 2. This is a circuit pattern formed by attaching copper foil 12 to both surfaces of an insulating substrate.
A photosensitive resin, for example, an epoxy acrylate-based resin is applied to both surfaces of the copper-clad laminate 10, dried and cured appropriately to form a photosensitive resin layer 30 (FIG. 1).
(A)). Steps (A) to (D) are almost the same as the steps of forming photovia hole 40 shown in FIG. 3, and thus the same portions are denoted by the same reference characters and description thereof will not be repeated.

The difference from the step of FIG . 3 is that baking is performed after the development in step (C) to sufficiently cure the resin layer 30. In this baking, for example, heating is performed in a thermostat at about 150 ° C. for 30 to 60 minutes. This baking makes it possible to accurately process small holes for laser via holes when processing the laser via holes described later.

[0026] The laminate 3 to form a photo via hole 40
2 are entirely covered with a copper plating layer 38 (first copper plating layer). A small opening 18A for a laser via hole is formed in the copper plating layers 38 on both sides by photoetching.
Is formed. First, as a preparation, a photoresist 50 is formed.
Apply or paste. A liquid photoresist can be used as the photoresist 50, but it is a matter of course that a dry photoresist may be used instead of the liquid photoresist.

On this photoresist 50, a photomask 52 having a laser via hole pattern printed thereon is aligned and overlaid. Then, exposure is performed with ultraviolet light or the like, so that a latent image of a pattern of a laser via hole is formed in the photoresist 50 (FIG. 1E). The photomask 52 is removed, developed with a developing solvent, and the photoresist 50 in an unexposed portion (pattern portion of the laser via hole) is removed. After hardening the remaining photoresist 50, the first
A small opening 18A for a laser via hole is formed in the copper plating layer 38 by etching (FIG. 1 (F)).

[0028] Then the laser is irradiated sequentially to each small opening portion 18A to form the small hole 22A to the resin layer 30 (in FIG. 1 (G)). Then, copper plating is further performed to form a copper plating layer (second copper plating layer) 24A (FIG. 1 (H)). This copper plating layer 24A is also formed on the inner surface of the small hole 22A for the laser via hole.
Laser via hole 26A is formed to connect to copper plating layers 24A and 38.

The photosensitive resin 30 used in this embodiment baking is desirable that cures well in (as d (C)), is a mixture of for example a thermosetting resin and photosensitive resin desired. As the photosensitive resin 30, photocurability is suitable.

[0030]

[Other Embodiments] In the above embodiment, the first copper plating layer 38 is formed when the photo via hole 40 is formed, and then the second copper plating layer 24A is formed by overlapping with the formation of the laser via hole 26A. I have. Therefore, the first and second
A portion where the copper plating layers 38 and 24A overlap is generated.

[0031] Therefore it is possible to thinly form the first copper plating layer 38 to shorten the time of copper plating treatment. If the first copper plating layer 38 is excessively thin, it is not preferable because the laser processes the periphery of the small opening 18A when the small hole 22A is processed by the laser (step (G)). Also, by narrowing the laser diameter sufficiently small during laser processing, the small holes 22A can be formed immediately after the step (C).
And the step of the first copper plating layer 38 can be omitted.

[0032]

According to the first aspect of the present invention, as described above, a laser via hole is formed by using the photosensitive resin layer used for forming a photo via hole. By using laser via holes and other via holes as photo via holes with good productivity, photo via holes and laser via holes can be mixed on the same printed wiring board. For this reason, the advantages of the laser via hole and the photo via hole can be utilized while compensating for the disadvantages.

According to the second aspect of the present invention, there is provided a method for manufacturing a printed wiring board. Although the manufacturing method of the same printed wiring board according to the invention of claim 3 is obtained, sufficiently small laser diameter by the invention as claimed in claim 3
Since small holes for laser via holes are directly formed in the photosensitive resin layer using a narrowed laser, the number of copper plating processes can be reduced. Here, a thermosetting resin is mixed with the photosensitive resin, and it is desirable that the photosensitive resin be sufficiently hardened by a baking process to have a hardness suitable for laser processing.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process of the present invention.

FIG. 2 is a diagram showing a conventional photo via hole forming process.

FIG. 3 is a diagram showing a conventional laser via hole forming process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Copper clad laminated board 12 Copper foil 16 Copper plating layer 18 and 18A Small opening 20 and 32 Laminated body 22 and 22A Small hole for laser via hole 24 Copper plating layer 24A 2nd copper plating layer 26 and 26A Laser via hole 30 Photosensitive resin Layer 34 Mask film 36 Small hole for photo via hole 38 First copper plating layer 40 Photo via hole 50 Photo resist 52 Mask film

Claims (4)

(57) [Claims] 1. A build-up printed wiring board having via holes connecting circuit patterns of different layers,
An insulating substrate having a circuit pattern formed on at least one surface thereof, a photosensitive resin layer laminated on the circuit pattern, a photo via hole formed in the photosensitive resin layer, and the photosensitive cured by baking; A build-up printed wiring board having a laser via hole formed in a resin layer. 2. A method of manufacturing a build-up printed wiring board having a via hole, comprising: a) laminating a photosensitive resin on a copper-clad laminate having a circuit pattern formed thereon; b) photolithographically processing the photosensitive resin on the circuit board. Forming small holes for photo via holes reaching the pattern; c) curing the photosensitive resin remaining on the copper clad laminate by baking; d) applying a copper plating to the photosensitive resin to form a first copper plating layer E) forming a small opening for a laser via hole by photo-etching in the first copper plating layer; and f) irradiating a laser to the first copper plating layer to form a small opening for the laser via hole. G) forming a small hole for a laser via hole reaching the circuit pattern from the photosensitive resin, and g) forming a copper hole in the first copper plating layer and the small hole for the laser via hole. Subjected to come to form a second copper plating layer, the manufacturing method of build-up printed wiring board, characterized in that. 3. A method of manufacturing a build-up printed wiring board having a via hole, comprising: a) laminating a photosensitive resin on a copper-clad laminate having a circuit pattern formed thereon, and b) photolithographically processing the photosensitive resin on the photosensitive resin. Forming small holes for photo via holes reaching the pattern; c) curing the photosensitive resin remaining on the copper-clad laminate by baking; and d) reducing the laser diameter of the cured photosensitive resin layer to a sufficiently small value.
By irradiating Ku focused laser to form a small hole for laser via hole reaching the circuit pattern, e) the circuit is subjected to copper plating to the small hole for the small hole and laser via hole photo via hole in the photosensitive resin layer A method of manufacturing a build-up printed wiring board, wherein a via hole reaching a pattern is formed. 4. A photosensitive resin method according to claim 2 or 3 buildup printed circuit board is a mixture of a photosensitive resin and a thermosetting resin.