JPS60207138A - Image forming method - Google Patents

Abstract

PURPOSE:To easily prevent overhang at the time of thick electrode plating by attaching a new photopolymerizable compsn. layer only on the hardened parts of a photopolymerizable compsn. layer patternwise formed at the first image forming step. CONSTITUTION:The first photopolymerizable compsn. layer is formed on a transparent support is laminated on the surface of an image forming base 2 with the support upside, patternwise exposed, stripped of the uppermost support, and dissolved with a developing soln. to remove the unexposed part and to form an image pattern composed of the hardened parts 3 of the first photopolymerizable compsn. layer. Further, the second photopolymerizable compsn. layer 5 attached to a support 4 is laminated, raised in affinity between the layers 3 and 5, then, stripped of the support 4 to leave the layer 5 only on the hardened parts 3 of the first photopolymerizable compsn. layer. An image increased in thickness is obtained by exposing the surface of the remaining attached photopolymerizable compsn. layer 5 to harden it.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method applied to manufacturing printed circuit boards and the like.

Generally, an image forming material called a dry film resist in which a photopolymerizable composition layer is provided on a transparent support is used as a nosetan forming means when manufacturing printed circuit boards.
This was laminated on the surface of the image forming substrate so that the photopolymerizable composition side was the contact surface, and after exposure in a predetermined pattern, the unexposed part of the photopolymerizable composition layer was removed after peeling off the support. A method of forming an image pattern consisting of a photopolymerizable composition layer that has been cured by exposure to light on the surface of a substrate, by dissolving and removing it with a developer, or by peeling and removing it as a part attached to the support in the process of peeling the support. has been adopted.

However, in the above-mentioned dry film resist, resolution is particularly important among the required characteristics, so the thickness of the photopolymerizable composition layer is generally 1.0 mil, 1.5 mm, 2.0 mil, 3.0 mil. There are many things that are limited to. For this reason, if the electrode plating is applied thicker than the above thickness after forming the image pattern, the plating metal 1 will form on the cured portion 3 of the photopolymerizable composition layer formed on the substrate 2, as shown in FIG. Oparts 1 that is cast onto the surface and becomes like a pine mushroom
There is a problem in that a phenomenon called ``singing'' occurs.

Therefore, as a method of preventing such a phenomenon, it is conceivable to increase the thickness of the cured portion 3 by repeating the image forming process using a dry film resist twice. However, this method complicates the process and is prone to problems, especially in wet development methods.Moreover, it is necessary to precisely match the exposure patterns of the two times, making it extremely difficult to align the photomask during the second exposure. It is expected that this will occur.

From the above point of view, the inventors have worked hard to find a method for increasing the thickness of the cured portion of the photopolymerizable composition layer in order to make it possible to thicken the electrode plating without causing the overparting phenomenon. As a result of repeated studies, we found that by adopting a specific method that attaches a new photopolymerizable composition layer only to the cured area formed by the first image forming process, it is possible to increase the thickness of the cured area with a simple operation. The present inventors have discovered that the second exposure can be carried out over the entire surface, eliminating the need for the difficult alignment of the photomask during the two-time edge turning in the image forming process described above, and have thus come up with this invention. Ta.

That is, this invention laminates a first photopolymerizable composition layer provided on a transparent support on the surface of an image forming substrate,
After patterned exposure, the unexposed portions of the photopolymerizable composition layer are removed by dissolving them in a developer after peeling off the support, or are removed together with the support when peeling off the support, thereby forming a layer on the surface of the substrate. After forming an image pattern consisting of the cured portion of the first photopolymerizable composition layer, and further laminating and blending the second photopolymerizable composition layer adhered to the support on the image pattern, By peeling off this support, the second photopolymerizable composition layer is deposited only on the cured portion of the first photopolymerizable composition layer.
The present invention relates to an image forming method characterized by allowing a photopolymerizable composition layer to remain attached and then exposing the entire surface to light.

The material used in this invention, on which the first photopolymerizable composition layer is provided on the transparent support, is a material that is conventionally known as an image forming process, that is, a general method in which development is performed using a developer such as an organic solvent. Both dry film resists and peel-and-develop dry film resists can be used. Specific examples of such image-forming materials include organic solvent-developed dry film resists such as Liston manufactured by DuPont, Laminar manufactured by Dynachem, etc.
There are products such as Fotec made by Hitachi Chemical Co., Ltd., and there are also products such as Peel-off type dry film resists such as NeoDrock made by Nitto Electric Industries Co., Ltd.

Formation of an image pattern using such an image forming material may be performed in the same manner as a conventional image forming method according to each developing method. That is, the image forming material is laminated on the surface of the image forming substrate with the photopolymerizable composition layer side as the bonding surface, and then exposed to light in a pattern. By dissolving and removing the unexposed portion of the polymerizable composition layer with a developer, in the peeling development method, in the process of peeling off the transparent support, the unexposed portion is simultaneously peeled off and removed while being adhered to the support. Then, an image pattern consisting of the cured portion of the first photopolymerizable composition layer is formed on the surface of the substrate.

In this invention, the second photopolymerizable composition layer adhered to the support is laminated and blended onto the image pattern thus formed, and then the support is peeled off. The second photopolymerizable composition layer is left attached only on the cured portion of the photopolymerizable composition layer, and then the entire surface is exposed to light. That is, as shown in FIG. 2, the second photopolymerizable composition is deposited on the support 4 on the cured portion 3 of the first photopolymerizable composition layer formed on the image forming substrate 2. After the layers 5 are laminated and the second photopolymerizable composition layer 5 and the cured portion 3 are sufficiently blended together by, for example, pressure bonding under heating, so that the second photopolymerizable composition layer 5 and the cured portion 3 are firmly bonded, the layer 5 shown in FIG. By peeling off the support 4 as shown in , the second photopolymerizable composition layer 5 is stuck and remains only on the cured portion 3 . Next, when the entire surface is exposed to light and the remaining second photopolymerizable composition layer 5 is cured, the thickness of the image pattern increases by the amount of the cured portion 5a, resulting in an overhang phenomenon as shown in FIG. The plated metal 1 can be thickened without causing any damage.

In order to realize the above method, as shown in FIG. 2 and FIG. Let F2 be the adhesive force of the photopolymerizable composition layer to the cured portion 3, F8 be the adhesive force to the substrate 2, and F4 be the force required to cut the second photopolymerizable composition layer 5 due to cohesive failure.
> Fl > Fa and F2 > Ft + F4. Therefore, as the second photopolymerizable composition layer, a composition that satisfies the above conditions is appropriately selected depending on the type of the support, the first photopolymerizable composition layer, and the substrate, and
It is desirable to appropriately set the pressure and temperature conditions to allow the second photopolymerizable composition layer to blend into the cured portion of the first photopolymerizable composition layer.

As such a second photopolymerizable composition layer, the photopolymerizable composition layer of a dry film resist, which is a general image forming material, is mainly an acrylic or methacrylic polymer or a copolymer thereof and addition polymerizable. Since it contains an addition-polymerizable compound having at least one unsaturated bond in the molecule and a copolymerization initiator, when it is used as the first photopolymerizable composition layer, it has good compatibility with the cured part. In order to ensure strong adhesion, it is preferable to use a composition similar to that described above within a range that satisfies the above conditions.

As a guideline for this composition, the first photopolymerizable composition layer is composed of an organic solvent development type or peel development type dry film resist, for example, although it varies to some extent depending on the type of support and substrate. In the case of photopolymerization, the amount of the addition polymerizable compound is about 100 to 1,000 parts by weight, and the other polymer components are about 25 to 400 parts by weight, per 100 parts by weight of the acrylic or methacrylic polymer or its copolymer. The amount of the initiator is preferably about 3 to 8 parts by weight based on 100 parts by weight of the addition polymerizable compound.

Among these components, acrylic or methacrylic polymers or their copolymers, addition polymerizable compounds, and photopolymerization initiators are all various types that are used in the photopolymerizable composition layer of conventional dry film resists. Can be used. Other polymer components include components similar to those used in peel-and-develop dry film resists,
Examples include chlorinated polyethylene, saturated polyethylene chlorinated polypropylene, chlorinated rubber, etc., and the amount of these used greatly influences the anchoring force of the second photopolymerizable composition layer to the support, that is, the above-mentioned Fl. It is determined to some extent whether or not a pattern of adhesion remains due to peeling.

On the other hand, the support on which the second photopolymerizable composition layer is applied does not need to be transparent, but it has low elongation and strength, such as polyethylene terephthalate film used in ordinary dry film resists. Large thickness is 1
Approximately 2 to 50 txm is suitable.

In addition, from these points, as the material for applying the second photopolymerizable composition layer to the support, a normal peel-and-develop type dry film resist can generally be used as a material that satisfies the above conditions. A dry film resist using a developer is said to be unsuitable because the anchoring force of the photopolymerizable composition layer to the support is insufficient.

As described above, according to the method of the present invention, a new photopolymerizable composition layer adhered to a support is laminated on top of an image pattern formed in the same manner as a normal image forming method. By a simple operation of peeling off the support and then exposing the entire surface to light, it is possible to thicken the electrode plating without causing an overhang phenomenon on the substrate having an image pattern. Note that the present invention can be applied not only to the production of printed circuit boards as described above but also to the production of decorative boards and the like.

Next, the present invention will be specifically illustrated with examples. In the following, parts mean parts by weight.

Example 1 A peel-and-developable dry film resist (trade name: Neoto Yotsuku, manufactured by Nitto Electric Industries, Ltd.; photopolymerizable composition layer thickness: approximately 1.5 mils) was applied to the cleaned copper surface of a copper-clad laminated board at 60°C.
The substrate was laminated under a pressure of 15 kg/lJ1 under heating at °C, a photomask with a patterned light-transmitting part was attached, and after exposure with an ultra-high pressure mercury lamp, the substrate temperature was lowered to 30 °C.
The transparent support consisting of a 16 .mu.n@2 thick polyethylene terephthalate film was peeled off while maintaining the temperature at .about.35 DEG C. to form an image pattern consisting of the cured portions of the first photopolymerizable composition layer.

Next, on this image pattern, the same peelable developable dry film resist as above was applied at a rate of 15 kq/distance at 60°C.
After laminating under pressure using ctA and maintaining this state for 60 minutes to blend the resists together, the support was peeled off at room temperature, and the first photopolymerizable composition layer constituting the image pattern was cured. The second photopolymerizable composition layer remained attached only on some portions. Full-surface exposure to an ultra-high pressure mercury lamp then resulted in an image pattern consisting of a 3 mil thick cured portion of the photopolymerizable composition layer. This board has a thickness of 2.5
Although the copper plating of the mill was thickened, no overhang phenomenon occurred.

Example 2 An organic solvent-developed dry film resist (product name: R15t manufactured by DuPont) was applied to the cleaned copper surface of a copper-clad laminate.
on 1220; A photopolymerizable composition layer with a thickness of 2 mm was laminated under pressure at 15 kti/ca under heating at 110°C, a photomask having a patterned light-transmitting part was attached, and ultra-high pressure was applied. After exposure with a mercury lamp, 25 μm
The transparent support made of a thick polyester film was peeled off, and the unexposed portion was dissolved and removed with 1-1-1-trichloroethane to form an image pattern consisting of the cured portion of the first photopolymerizable composition layer. .

Next, on top of this pattern, a second photopolymerizable composition layer having the following composition, which was adhered to a support made of a polyethylene terephthalate film with a thickness of 25μ772, was heated to 15 kg/Cd at 60°C. The resists were laminated under pressure, and this state was maintained for 60 minutes to fully blend the resists together.

<Composition of second photopolymerizable composition layer> Benzophenone...5 parts Michler's ketone...0.5 part P-methoxyphenol...0.1 part Next, when the support was peeled off at room temperature, The second photopolymerizable composition layer remained only on the cured portion of the first photopolymerizable composition layer constituting the image pattern. Thereafter, the entire surface was exposed to light using an ultra-high pressure mercury lamp, resulting in an image pattern consisting of a cured portion of the photopolymerizable composition layer having a thickness of 3.5 mils. This board was plated with copper to a thickness of 3 mils, but no overhang occurred.

Comparative Example After forming an image pattern consisting of the cured portion of the first photopolymerizable composition layer in the same manner as in Example 2, the same organic solvent developable dry film resist was applied on this image pattern in the same manner as the first time. After lamination, pattern exposure, peeling off of the support, and development using IJ chloroethane were carried out. Although this method yields an image pattern consisting of a cured portion of the photopolymerizable composition layer having a thickness of 2 mils, it is a complex process, requires a great deal of labor and time, and also - It was very difficult to align the mask due to the unevenness caused by the first image pattern.

Furthermore, in the thin wire areas, scum (a state in which the resist remains attached to an extent that cannot be seen with the naked eye) was generated on the copper surface after development, and when the electrode plating was later applied thicker, the adhesion was poor. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a state in which thick electrode plating has been applied to a substrate having an image pattern obtained by a conventional image forming method, and FIGS. 2 and 3 show an image forming method according to the present invention. FIG. 4 is a schematic cross-sectional view showing the operation of adhering and remaining the second photopolymerizable composition layer in FIG. FIG. 2... Image forming substrate, 3... Cured portion of first photopolymerizable composition layer, 4... Support, 5... Second photopolymerizable composition layer, 5a... - Cured portion of the second photopolymerizable composition layer. Patent applicant Nitto Electric Industry Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] (1) After laminating the first photopolymerizable composition layer provided on the transparent support on the surface of the image forming substrate and exposing the photopolymerizable composition layer in a pattern, Forming an image pattern consisting of the cured portion of the first photopolymerizable composition layer on the surface of the substrate by dissolving and removing the exposed portion with a developer after peeling off the support, or removing it together with the support when peeling the support. Then, after laminating and blending the second photopolymerizable composition layer adhered to the support on the image pattern, the first photopolymerizable composition layer is peeled off. An image forming method characterized by leaving a second photopolymerizable composition layer only on the cured portion of the layer and then exposing the entire surface to light.