JP2622860B2 - Printed circuit board - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive layer comprising a styrene-conjugated diene block copolymer-based pressure-sensitive adhesive and containing substantially no halogen, and has a workability of bonding. The present invention relates to a printed circuit board having excellent adhesive strength and electric corrosion resistance.

2. Description of the Related Art Conventionally, there has been known a printed circuit board having an acrylic pressure-sensitive adhesive layer on the back surface thereof, which can be fixed to a main body of an electronic device or an electric device. The method of applying an adhesive such as an epoxy-based adhesive or a cyanoacrylate-based adhesive to a printed circuit board and fixing it to the main body is inferior in work efficiency, and the adhesive strength tends to vary, resulting in poor reliability of the fixing process. For this reason, a method of providing the pressure-sensitive adhesive layer has been proposed.

However, the printed circuit board provided with the conventional acrylic pressure-sensitive adhesive layer has a problem that the adhesive strength is poor and easily falls off the main body, a halogen compound contained in the pressure-sensitive adhesive layer, an acid component or an acid-based residual monomer. There is a fatal problem that the circuit is electrolytically eroded.

Means for Solving the Problems The present invention has overcome the above problems by using a special styrene / conjugated diene block copolymer pressure-sensitive adhesive.

That is, the present invention provides a styrene / conjugated diene block copolymer pressure-sensitive adhesive having a halogen content of 10 ppm.
180 ° peeling at 23 ° C and a pulling speed of 50 mm / min when bonded to a stainless steel plate surface sanded with a No. 280 sandpaper at 120 ° C under 3 kg / cm ² for 10 seconds at the following temperature: A printed circuit board provided with a pressure-sensitive adhesive layer having a value of 1.5 kg / 20 mm or more.

Action By using a styrene / conjugated diene block copolymer pressure-sensitive adhesive, the content of an acid component or an acid-based residual monomer can be avoided. Further, those having a small halogen content or containing no halogen can be easily obtained. Moreover, it is easy to form one having excellent adhesive strength. By setting the halogen content in the pressure-sensitive adhesive layer to 10 ppm or less, a printed circuit board having excellent corrosion resistance can be obtained. Further, by satisfying the adhesive force based on the above-described 180 degree peel value, a printed circuit board having an adhesive force necessary for fixing to the main body can be obtained.

Examples of Components of the Invention The pressure-sensitive adhesive layer in the printed circuit board of the present invention is formed of a styrene / conjugated diene block copolymer-based pressure-sensitive adhesive. Examples of such a pressure-sensitive adhesive include a block copolymer of styrene and a conjugated diene such as butadiene or isoprene, or a hydrogenated product thereof as a main component, which is blended with an adhesion-imparting resin.

As the styrene / conjugated diene block copolymer, an ABA block copolymer in which styrene polymer blocks and conjugated diene polymer blocks are present alternately is preferably used. From the viewpoint of durability, a styrene / butadiene / styrene block copolymer or a hydrogenated product thereof is preferred.

Rosin resins, petroleum resins,
Terpene resins, aliphatic hydrocarbon resins, aromatic hydrocarbon resins, styrene resins, xylene resins and the like are generally used. An appropriate amount of the resin for imparting adhesion is 30 to 200 parts by weight per 100 parts by weight of the styrene / conjugated diene block copolymer or its hydrogenated product. When the amount is less than 30 parts by weight, the obtained pressure-sensitive adhesive has poor adhesive strength, and when it exceeds 200 parts by weight, the obtained pressure-sensitive adhesive has poor heat resistance and cold resistance.

The pressure-sensitive adhesive may contain other combined polymers, softeners, fillers, and the like, if necessary. Those containing no halogen or acid group as a component are preferably used.

The styrene / conjugated diene block copolymer pressure-sensitive adhesive used in the present invention has a halogen content of 10 ppm or less. When the component used contains a halogen compound as an impurity, it is sufficiently purified. In addition, for example, styrene and
When mixing of a halogen compound is inevitable, as in the case of preparing a conjugated diene block copolymer by a coupling method, the product is sufficiently purified and used after removing the halogen compound. In addition, as a method for preparing the styrene / conjugated diene block copolymer, there is a sequential reaction method that does not require the use of a halogen compound.

Further, the styrene-conjugated diene block copolymer-based pressure-sensitive adhesive used in the present invention has a pressure-sensitive adhesive layer at 120 ° C., 3 kg / cm ² at 10 ° C. on a stainless steel plate surface sanded with a No. 280 sandpaper. When pressed at 23 ° C. and subjected to 180 ° peeling at a pulling speed of 50 mm / min at a tensile speed of 50 mm / min, it exhibits an adhesive strength of 1.5 kg / 20 mm or more, especially 1.5 to 5 kg / 20 mm.

The pressure-sensitive adhesive layer is formed, for example, by directly applying a styrene-conjugated diene block copolymer-based pressure-sensitive adhesive on the back surface of a printed circuit board, that is, on a surface having no circuit, or provided on a separator. An appropriate method such as a method of transferring the pressure-sensitive adhesive layer to the printed circuit board may be used.
The method of transferring the pressure-sensitive adhesive layer provided on the separator has an advantage that the pressure-sensitive adhesive layer can be easily and easily attached. In addition, since the separator is kept adhered to prevent contamination of the pressure-sensitive adhesive layer and the like, the separator can be easily peeled off when the printed circuit board is fixed to the main body. It also has the advantage that the step of applying the pressure-sensitive adhesive layer can be incorporated at an appropriate stage.

The pressure-sensitive adhesive layer attached to the printed circuit board may be reinforced with a base material made of, for example, a plastic film, nonwoven fabric, paper, or the like, as in a conventional double-sided adhesive tape. The conditions for a halogen content of 10 ppm or less in the pressure-sensitive adhesive layer are as follows:
It is necessary to be satisfied also in the case of such a reinforcing form.
Therefore, a reinforcing material containing no halogen is preferably used.

The thickness of the pressure-sensitive adhesive layer may be determined appropriately. Generally 5
500500 μm.

The printed circuit board to which the pressure-sensitive adhesive layer is provided is not particularly limited. Any printed circuit board such as paper phenolic board, glass epoxy board, glass polyimide board, glass fluororesin board, ceramic board, metal base heat sink board, copper clad composite laminate board, flexible board etc. Can be applied.

Effect of the Invention The printed circuit board of the present invention is made of a styrene / conjugated diene block copolymer-based pressure-sensitive adhesive and has a pressure-sensitive adhesive layer containing substantially no halogen, so that it has excellent corrosion resistance and a long life and reliability. As well as the efficiency of the work of fixing to the main body.

Further, since the pressure-sensitive adhesive layer has an adhesive strength equal to or higher than a predetermined value, it can be firmly fixed to a main body of an electronic device or the like.

Examples In the following, the adhesive strength was determined by adhering a pressure-sensitive adhesive layer on a 25 μm-thick polyester film, and subjecting it to a stainless steel plate surface sanded with a No. 280 sandpaper at 120 ° C., 3 kg / cm ² , 10 This is a 180 degree peel value measured at 23 ° C. and a pulling speed of 50 mm / min after bonding under a pressing condition for 2 seconds.

Example 1 A styrene / butadiene / styrene block copolymer having a weight average molecular weight of about 150,000 prepared by a sequential reaction method 10
A toluene solution containing 0 parts (parts by weight, the same applies hereinafter) and 100 parts of a hydrogenated petroleum resin is uniformly applied on a separator to a thickness of
A 100 μm pressure-sensitive adhesive layer was formed and transferred to the back surface of the substrate to obtain a printed circuit board.

The adhesive force of the pressure-sensitive adhesive layer was 2.1 kg / 20 mm, and the halogen content was 3 ppm.

The obtained printed circuit board was firmly adhered to the electric component body, and the state of adhesion was stably maintained for a long period of time. Also, 70
Even when left at ℃ for three months, the copper circuit did not produce electrolytic corrosion and was excellent in its electrolytic corrosion resistance.

Example 2 100 parts of a styrene / butadiene / styrene block copolymer prepared by a sequential reaction method and having a weight average molecular weight of about 120,000 and hydrogenated by an ordinary method, terpene resin 70
Part and a solid material consisting of 80 parts of a styrene-based resin are mixed while heating and melting, and the mixture is uniformly applied to both sides of a 25 μm-thick polyester film so that the thickness becomes 50 μm each to form a pressure-sensitive adhesive layer. Then, this was adhered to the back surface of the substrate to obtain a printed circuit board.

The adhesive force of the pressure-sensitive adhesive layer was 1.9 kg / 20 mm, and the halogen content was 6 ppm.

The obtained printed circuit board is firmly adhered to the electric component body, and the adhesion state is stably maintained for a long period of time.
Even when left at ℃ for three months, the copper circuit did not produce electrolytic corrosion and was excellent in its electrolytic corrosion resistance.

Example 3 A toluene solution containing 100 parts of a purified product of a styrene / isoprene / styrene block copolymer having a weight average molecular weight of about 75,000 prepared by a coupling method using a halogen compound and 100 parts of a hydrogenated petroleum resin was used. Uniformly apply on the separator to form a pressure-sensitive adhesive layer with a thickness of 100 μm,
This was transferred to the back surface of the substrate to obtain a printed circuit board.

The adhesive force of the pressure-sensitive adhesive layer was 2.0 kg / 20 mm, and the halogen content was 10 ppm.

The obtained printed circuit board was firmly adhered to the electric component main body, and even when left at 70 ° C. for 3 months, the copper circuit did not undergo electrolytic corrosion and was excellent in its electrolytic corrosion resistance.

Comparative Example 1 A printed circuit board was obtained according to Example 3, except that the styrene / isoprene / styrene block copolymer was used without purification.

The halogen content of the pressure-sensitive adhesive layer is 350ppm, 70 ℃
Bottom, 150μ width on printed circuit board after 7 days
m of the copper circuit was broken by electrolytic corrosion.

Comparative Example 2 A printed circuit board was obtained in the same manner as in Example 2 except that a nonwoven fabric made of rayon fiber was used instead of the polyester film.

The halogen content of the pressure-sensitive adhesive layer is 165 ppm, and the copper circuit on the printed circuit board is electrolytically eroded.
The copper circuit which had a width of 50 μm only left a width of 50 μm.

Claims (1)

(57) [Claims] 1. A styrene / conjugated diene block copolymer pressure-sensitive adhesive having a halogen content of 10 ppm or less and a stainless steel sheet sanded with a No. 280 sandpaper at 120 ° C. at 3 kg / cm ² , A printed circuit board comprising a pressure-sensitive adhesive layer having a 180 ° peel value of 1.5 kg / 20 mm or more at a temperature of 23 ° C. and a pulling speed of 50 mm / min when subjected to an adhesive treatment under a pressing condition of 10 seconds. .