JP2894997B2 - Manufacturing method of printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board using a built-up method.

[0002]

2. Description of the Related Art A conventional method of manufacturing a built-up substrate will be described below. First, as shown in FIG. 3 (a), a photosensitive epoxy resin layer 23 serving as an insulating layer on both sides of a substrate serving as a core layer 21 of FR-4 having copper conductors 22 patterned on both sides.
Is formed to a thickness of 80 μm, and the surface of the photosensitive epoxy resin layer 23 is partially irradiated with UV light of 4 J / cm ² through a patterned exposure mask. Next, development is performed with a solvent containing gamma butyl lactone to remove the UV light-irradiated portions of the photosensitive epoxy resin layer 23, thereby forming a photo via 24 as shown in FIG. Next, the photosensitive epoxy resin layer 23 is cured by performing post-baking at 130 ° C. for 2 hours. Next, the surface of the photosensitive epoxy resin layer 23 is
The entire surface is polished to a thickness of 0 μm, and a photo-cured layer having a thickness of 5 μm on the surface is removed as shown in FIG. Then, FIG.
As shown in FIG. 2A, the surface of the photosensitive epoxy resin layer 23 is plated with copper, and is then patterned by etching to form the outermost conductor 25. Further, by repeating the steps from the formation of the photosensitive epoxy resin layer 23 to the copper plating and the etching, multilayering is possible. In this example, after the built-up layers are formed on both sides one by one, FIG.
(B) Solder resist 2 of modified epoxy resin as shown in FIG.
6 is applied to both sides of the substrate in a thickness of 35 μm, and 400 mJ /
Irradiation with UV light 27 cm ² and post-baking at 150 ° C. for 1 hour
6 was cured to produce a built-up substrate.

As for the application of the solder resist 26, Japanese Patent Laid-Open No. 3-4595 discloses a multi-layer substrate which is baked to evaporate moisture in the substrate before the step of applying the solder resist 26 to both surfaces of the laminate. A manufacturing method is described.

[0004]

In the above-mentioned prior art, the surface of the photosensitive epoxy resin layer is plated with copper, and after patterning by etching, a solder resist is immediately applied. -65 to 125
When a MIL thermal shock test with a thermal cycle of ° C. is performed, resin cracks occur in the photosensitive epoxy resin layer.
The location where the resin crack occurs is generated in the resin layer immediately below the opening edge of the solder resist. The cause is that the photosensitive epoxy resin layer is locally exposed only at the opening of the solder resist by UV light irradiation after the formation of the solder resist, the part covered with the solder resist by the photosensitive epoxy resin layer and the solder resist This is because the thermal expansion coefficient differs between the opening and the opening. Stress is generated at a boundary portion having a different thermal expansion coefficient, and a resin crack is generated at a boundary portion of a portion having a different thermal expansion coefficient during repeated thermal cycles.

An object of the present invention is to prevent a resin crack due to a thermal cycle of a photosensitive epoxy resin layer and to improve the reliability of a printed wiring board.

[0006]

According to the present invention, there is provided a method of manufacturing a printed wiring board, comprising the steps of forming a photosensitive insulating resin layer on a core layer serving as a base, and exposing and developing the photosensitive insulating resin layer to form a photo via. Forming the surface, polishing the surface of the photosensitive insulating resin layer to remove the photocured layer , applying copper plating to the polished surface of the photosensitive insulating resin layer ,
The photosensitive after only set the patterned conductor by etching
The method of manufacturing a printed wiring board and a step that form the solder resist sexual insulating resin layer surface, and characterized by performing the UV irradiation in the photosensitive insulating resin layer surface before you form the solder resist I do.

According to the present invention, the surface of the outermost photosensitive insulating resin layer is irradiated with UV light before the step of applying a solder resist. Therefore, at this point, the exposed portion of the outermost photosensitive insulating resin layer is exposed, and the opening of the solder resist is not locally exposed by UV light irradiation after the formation of the solder resist.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1 (a) to 1 (c), FIGS. 2 (a) and 2 (b)
3A to 3C are cross-sectional views illustrating a method of manufacturing a printed wiring board using a built-up method according to an embodiment of the present invention in the order of steps. A method of manufacturing a printed wiring board according to an embodiment of the present invention is described in the following. First, as shown in FIG. 1A, a FR-4 core layer 11 having copper conductors 12 patterned on both sides is formed on both sides of a substrate. The photosensitive epoxy resin layer 13 serving as an insulating layer is
After forming a thickness of 0 μm, 4 J is partially applied to the surface of the photosensitive epoxy resin layer 13 through a patterned exposure mask.
/ Cm ² of UV light. Next, development is performed with a solvent containing gamma butyl lactone, and a portion of the photosensitive epoxy resin 13 not irradiated with UV light is removed, thereby forming a photo via 14 as shown in FIG. 1B. Next, the photosensitive epoxy resin layer 13 is cured by performing post-baking at 130 ° C. for 2 hours, and the entire surface of the photosensitive epoxy resin layer 13 is polished to a thickness of 40 μm from the surface thereof, as shown in FIG. Remove micron thick photocured layer. Thereafter, copper plating is applied to the surface of the photosensitive epoxy resin layer 13 to be the photosensitive insulating resin layer 15 as the outermost layer, and the surface is patterned by etching to form the conductor 16 as the outermost layer. Further, by repeating the steps from the formation of the insulating layer to the copper plating and the etching, multilayering is possible. Next, in the present embodiment, FIG.
As shown in (a), the outermost photosensitive insulating grease layer 15 has 500
The entire surface of the substrate is irradiated with UV light 17 of mJ / cm ^{2 to} expose the outermost photosensitive insulating resin layer 15 and to have a coefficient of thermal expansion near room temperature of from 8.0 × 10 ⁻⁵ / ° C. to 1.2 ×. Change to 10 ^-4 / ° C. Thereafter, as shown in FIG. 2 (b), a solder resist 18 is applied to both sides of the substrate, and 400 mJ / cm ² of U
The solder resist 18 is hardened by irradiating the entire surface with the V light 19 and post-baking at 150 ° C. for 1 hour to manufacture a built-up substrate.

According to the embodiment of the present invention described above, since the outermost photosensitive insulating resin layer 15 is exposed to light before the formation of the solder resist 18, the solder resist 1
Even when the UV light 19 is irradiated after the formation of the resist 8, the photosensitive insulating resin layer 15 as the outermost layer at the opening of the solder resist 18 is not locally exposed. Accordingly, there is no difference in the coefficient of thermal expansion between the portion of the outermost photosensitive insulating resin layer 15 covered with the solder resist 18 and the opening of the solder resist 18, and the coefficient of thermal expansion of the outermost photosensitive insulating resin layer 15 does not differ. Is 1.2
It is constant at × 10 ^-4 / ° C.

[0011]

According to the present invention, the photosensitive epoxy resin layer is heated at 120.degree.
The thermosetting component is polymerized by baking for more than 0 minutes, and UV
The photocurable component also has the property of polymerizing by light irradiation.
The coefficient of thermal expansion of the photosensitive epoxy resin is increased by curing, and baking at 150 ° C. for 4 hours is 8.0 × 10 ^−5.
/ ° C to 1.1 × 10 ^-4 / ° C.

Since the built-up substrate uses an epoxy resin having the above-described properties, in the conventional method of manufacturing a printed wiring board, only the opening of the solder resist is exposed by UV light irradiation after the formation of the solder resist. epoxy resin layer is locally exposed to light, at the opening point and the solder resist covered with solder resist of the photosensitive epoxy resin layer
Have different coefficients of thermal expansion. When the MIL thermal shock test is performed on such a printed wiring board, since the thermal expansion coefficient is partially different in the insulating resin layer, a stress is generated at the boundary thereof,
As the thermal cycle is repeated, resin cracks occur at the boundary between portions having different coefficients of thermal expansion.

However, according to the present invention, since the outermost photosensitive insulating resin layer is exposed to light before the formation of the solder resist, the outermost layer of the opening of the solder resist can be irradiated by ultraviolet irradiation after the formation of the solder resist. The photosensitive insulating resin layer is not locally exposed to light, so that cracks do not occur in the insulating layer resin even in the thermal shock test.

Further, even if baking is performed before the step of applying a solder resist as in the conventional example disclosed in JP-A-3-4595, the photocurable component has not reacted, so Due to the UV light irradiation, the outermost photosensitive insulating resin layer is locally exposed only at the opening of the solder resist, and the portion of the outermost photosensitive insulating resin layer covered with the solder resist and the opening of the solder resist. The thermal expansion coefficient differs between the portions, and curing preventing the occurrence of resin cracks cannot be expected.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views illustrating a method of manufacturing a printed wiring board using a built-up method according to an embodiment of the present invention in the order of steps.

FIGS. 2A and 2B are cross-sectional views illustrating a method of manufacturing a printed wiring board using a built-up method according to an embodiment of the present invention in the order of steps.

FIGS. 3A to 3C are cross-sectional views sequentially illustrating steps of an example of a method for manufacturing a printed wiring board using a conventional build-up method.

FIGS. 4A and 4B are cross-sectional views sequentially illustrating steps of an example of a method for manufacturing a printed wiring board using a conventional build-up method.

[Explanation of symbols]

 11, 21 Core layer 12, 22 Conductor 13, 23 Photosensitive epoxy resin layer 14, 24 Photo via 15 Outermost photosensitive insulating resin layer 16, 25 Outermost conductor 17, 19, 27 UV light 18, 26 Solder resist

Claims (1)

(57) [Claims] 1. A step of forming a photosensitive insulating resin layer on a core layer serving as a base, a step of exposing and developing the photosensitive insulating resin layer to form a photo via, and polishing the surface of the photosensitive insulating resin layer. Removing the photo-cured layer, and performing copper plating on the polished surface of the photosensitive insulating resin layer.
Wherein after only set the etching to patterned conductor
The method of manufacturing a printed wiring board and a step that form the solder resist photosensitive insulating resin layer surface, the photosensitive insulating resin layer surface before you form the solder resist U
A method for manufacturing a printed wiring board, comprising irradiating V light.