JP3506194B2 - Adhesive film for plating mask - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating mask used for masking a non-plated portion when a connection terminal portion of a printed circuit board or a flexible printed circuit board is partially plated. And a pressure-sensitive adhesive film. 2. Description of the Related Art Conventionally, as a method of partially plating a connection terminal portion or the like of a printed circuit board or a flexible printed circuit board, a method of pasting an adhesive film on a non-plated portion, masking the film, and then plating. Commonly used.
However, since the surface of the printed circuit board or flexible printed circuit board to which the adhesive film is attached has complicated irregularities of the previously formed circuit, the adhesive film follows and adheres to these irregularities, preventing plating liquid from entering the mask part. There is a need to. Poor adhesion of the adhesive film causes infiltration of a plating solution, resulting in poor plating finish accuracy, resulting in malfunction of printed circuit boards and flexible printed circuit circuits. As the pressure-sensitive adhesive film used in such applications, a pressure-sensitive adhesive film using a soft vinyl chloride-based resin as a support is generally used. This is because the soft vinyl chloride-based resin can adjust the film hardness depending on the amount of the plasticizer contained, and can provide a flexible film having good followability of unevenness to the circuit surface. On the other hand, in recent years, it has been pointed out that a vinyl chloride resin has an adverse effect on the environment when incinerated, and there is a problem in final disposal, and conversion to a polyolefin material is required. [0003] Therefore, conversion to an adhesive film using a polyolefin film such as polyethylene or polypropylene as a support was examined. However, the flexibility of the support was poor, so that the adhesion to irregularities on the circuit surface was poor, and the plating solution was poor. There is a problem that immersion occurs and plating accuracy is poor, and it can be used only for a printed circuit board and a flexible printed circuit board having a relatively smooth circuit surface. Furthermore, in recent years, the automation of the equipment has been advanced in order to save labor in the plating work, and the printed circuit board on which the adhesive film is adhered and the flexible printed circuit board have been automatically conveyed. There is a demand for the slipperiness of the back surface of the pressure-sensitive adhesive film when it comes into contact with a transport guide or the like. If the slipperiness of the back surface of the pressure-sensitive adhesive film is poor, automatic conveyance cannot be performed, and workability is significantly deteriorated. In the conventional soft vinyl chloride resin adhesive film, there is a problem that the soft vinyl chloride resin has tackiness and the slipperiness of the back surface of the adhesive film is poor. In addition, polyethylene or polypropylene pressure-sensitive adhesive films have good back slipperiness, but have the problem that plating infiltration occurs as described above. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances.
It is an object of the present invention to provide a polyolefin-based pressure-sensitive adhesive film having good adhesion to surface irregularities of a printed board, no infiltration of a plating solution, good plating finish accuracy, and good slipperiness on the back of the pressure-sensitive adhesive film. That is, the present invention provides a low-density polyethylene layer having a density of 0.91 to 0.93 g / cm ³ and an ethylene-vinyl acetate copolymer layer, and has a 10% strain. Has a film tensile stress of 0.20 kg / cm ^{2 to} 0.
The present invention relates to a pressure-sensitive adhesive film for a plating mask, wherein a pressure-sensitive adhesive layer is provided on the ethylene vinyl acetate copolymer layer side of a multilayer film of two or more layers having a weight of 80 kg / cm ² . DETAILED DESCRIPTION OF THE INVENTION The support used in the present invention is a multilayer film composed of two or more layers composed of a low-density polyethylene layer and an ethylene-vinyl acetate copolymer layer. The film can be formed by a multilayer extrusion film forming apparatus such as the T-die method. The low-density polyethylene resin used in the present invention has a density of 0.91 to 0.93 g / cm ³ . When the density is lower than this range, tackiness is generated in the resin itself, and slipperiness is deteriorated. On the other hand, if the density is higher than this range, the flexibility as a film is insufficient. The ethylene-vinyl acetate copolymer resin used in the present invention preferably has a vinyl acetate content of 10 to 25% by weight. If the vinyl acetate content is low, the flexibility required for the film cannot be obtained,
If the amount is too large, the swelling with respect to the organic solvent increases, which causes a problem when applying a pressure-sensitive adhesive diluted with the organic solvent. Further, the above-mentioned support may optionally contain additives such as an antioxidant, a lubricant, and a coloring agent generally used for the polyolefin-based resin film. Further, the above-mentioned support can adjust the film tensile stress at 10% strain by adjusting the thickness ratio of the low-density polyethylene layer and the ethylene-vinyl acetate copolymer layer and the vinyl acetate content of the ethylene-vinyl acetate copolymer resin. 0.20kg / ^cm 2 ~0.80kg / c
It is necessary to m ^2. Further, if necessary, a low-density polyethylene resin may be added to the ethylene-vinyl acetate copolymer layer to adjust the film tensile stress at the time of 10% strain. The surface of the printed circuit board or the flexible printed circuit board to which the pressure-sensitive adhesive film of the present invention is attached has irregularities of up to about 50 μm because a circuit is formed first. In order to adhere to the irregularities, it is necessary that the pressure-sensitive adhesive film be easily stretched and adhered without any gap at the time of sticking, and then the adhesive force of the pressure-sensitive adhesive film suppresses the film from shrinking and floating. That is, it is necessary to minimize the stress during film stretching. Therefore, as a result of examining the relationship between the film tensile stress and the adhesiveness of the adhesive film, the film tensile stress at 10% strain was 0.80 k.
It was found that if the g / cm ² or less, no floating occurred and the adhesion was good. On the other hand, at the time of peeling the adhesive film, the workability of peeling is better if the film is as hard and hard to stretch as possible. That is, when the relationship with the film tensile stress at the time of 10% strain is examined in the same manner, 0.20 kg /
It was found that cm ² or more was required. Note that the above 1
The film tensile stress at 0% strain is JIS K-71.
13 is a value measured according to “Plastic tensile test method”. The thickness of the support is not particularly limited, but is about 50
Those having a size of μm to 150 μm are preferred. If the film thickness is less than 50 μm, sufficient strength of the film cannot be obtained,
When the film is peeled, the film is stretched, the peelability is poor, and problems such as breakage of the film occur. On the other hand, if the thickness of the film is larger than 150 μm, there arises a problem that the conformability of the film is reduced, and the plating easily penetrates. The pressure-sensitive adhesive used for the pressure-sensitive adhesive film of the present invention, commonly used acrylic pressure-sensitive adhesive, natural rubber-based pressure-sensitive adhesive,
Synthetic rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, and the like, and mixed pressure-sensitive adhesives thereof can be used.
It is appropriate to set it to 20 μm. Further, as a method of forming the pressure-sensitive adhesive layer, a method of applying a pressure-sensitive adhesive having a viscosity adjusted by being dissolved in an organic solvent is generally used,
In addition, a known method such as a method of melting and applying an adhesive or a method of dispersing and applying in water can be used. Furthermore,
The pressure-sensitive adhesive film of the present invention may be subjected to a surface treatment of the support such as a corona treatment or a plasma treatment, or the application of a primer, if necessary, in order to obtain the adhesion between the support and the pressure-sensitive adhesive. Further, a back surface treatment agent may be applied to the back surface of the adhesive film for the purpose of adjusting the rewinding property of the adhesive film. The technical points of the pressure-sensitive adhesive film of the present invention are that it has good adhesion to the surface irregularities of a printed circuit board or a flexible printed circuit board, does not infiltrate a plating solution, has good plating finish accuracy, and has a good plating finish. An object of the present invention is to obtain a polyolefin-based pressure-sensitive adhesive film having good slipperiness. For this purpose, the support has a density of 0.91 to 0.93.
g / cm ³ , a two- or more-layer film composed of a low-density polyethylene layer and an ethylene-vinyl acetate copolymer layer, and a film tensile stress at 10% strain of 0.1%.
Was ^{20kg / cm 2 ~0.80kg / cm 2} , by adhesive film back is low density polyethylene layer, it is possible to obtain the plating mask pressure-sensitive film. Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 4 Using a three-layer coextrusion inflation apparatus, four types of films having the constitutions shown in Table 1 were formed. Film thickness is 6
It was set to 0 μm. Next, a corona treatment was performed on the surface to which the pressure-sensitive adhesive was applied, and an acrylic pressure-sensitive adhesive diluted with a solvent was applied and dried so that the thickness after drying was 5 μm, thereby producing a pressure-sensitive adhesive film. Table 2 shows the properties of this pressure-sensitive adhesive film. Comparative Examples 1 to 5 Except for the constitution shown in Table 1, extrusion film formation of a film, application of a pressure-sensitive adhesive and the like were carried out in the same manner as in the examples. Table 2 shows the properties of this pressure-sensitive adhesive film. By making the pressure-sensitive adhesive film having the structure as in Examples 1 to 4, the film tensile stress at 10% strain is 0.20 kg / cm ^{2 to} 0.80 kg / cm.
^{2 and} a polyolefin-based adhesive film with good adhesion to the surface irregularities of printed circuit boards and flexible printed circuit boards, no penetration of plating solution, good plating finish accuracy, and good slipperiness on the back of the adhesive film. Can be In Comparative Example 2, since the vinyl acetate content of the ethylene-vinyl acetate copolymer was small and the film tensile stress at the time of 10% strain was large, penetration of the plating solution was observed. On the contrary, in Comparative Example 5, the film tensile stress at the time of 10% strain was small, and the adhesive film peelability was poor. Comparative Examples 3 to
In No. 5, since the back surface of the adhesive film is an ethylene vinyl acetate copolymer layer, the back surface has poor slipperiness. [Table 1] Note) 1. 1. LDPE low density polyethylene (MFR 2.0 g / 10 min, density 0.92 g / cm ³ ) EVA (5%) Ethylene vinyl acetate copolymer (vinyl acetate content 5%, M
2. FR 2 g / 10 min, density 0.92 g / cm ³ ) EVA (10%) Ethylene vinyl acetate copolymer (vinyl acetate content 10%,
3. MFR 1.5 g / 10 min, density 0.93 g / cm ³ ) EVA (15%) Ethylene vinyl acetate copolymer (vinyl acetate content 15%,
4. MFR 1.5 g / 10 min, density 0.94 g / cm ³ ) EVA (25%) Ethylene vinyl acetate copolymer (vinyl acetate content 25%,
MFR ³ g / 10 min, density 0.95 g / cm ³ ) Note) 1. Tensile stress at 10% strain JIS K-7113 "Plastic tensile test method"
Measured according to. 2. Plating test Adhesive film on glass epoxy printed circuit board (circuit unevenness 25 μm) with rubber roll heated to 80 ° C. 2
m / min, a test piece stuck at a stuck pressure of 6 kg / cm
H ₂ SO ₄ aqueous solution (PH = 1) heated to 60 ° C.
Immerse for 0 minutes, then wash with water and observe for penetration. 3. Back side slipping property Two test pieces were prepared by applying an adhesive film to a 0.5 mm thick stainless steel plate with a rubber roll at an application speed of 2 m / min and an application pressure of 6 kg / cm so that the back surfaces of the adhesive films were in contact with each other. Observe if they overlap and slide out at an angle of 50 degrees. 4. In the table, the symbol *: the film is stretched when the adhesive film is peeled, and the workability for peeling is poor. It is possible to obtain a polyolefin-based pressure-sensitive adhesive film having no plating solution infiltration and high plating finish accuracy.
Further, the adhesive film of the present invention has a good sliding property on the back surface of the adhesive film, and therefore has a good transportability and is suitable for automation of a plating apparatus. Furthermore, since the adhesive film of the present invention contains polyethylene and ethylene-vinyl acetate copolymer as main components, there is a feature that the problem of environmental pollution in incineration does not easily occur. It can be used as an excellent plating mask adhesive film instead of an adhesive film using a vinyl resin for the support.

Claims (1)

(57) Claims 1. A film having a low-density polyethylene layer having a density of 0.91 to 0.93 g / cm ³ and an ethylene-vinyl acetate copolymer layer and having a 10% strain. 0.20 stress
adhesive film for plating mask characterized by comprising providing an adhesive layer on ethylene-vinyl acetate copolymer layer side of kg / ^{cm 2} ~0.80kg / ^cm 2 and 2 or more layers film with no.