JPH05253534A - Liquid material applying method - Google Patents

Abstract

PURPOSE:To provide a liquid material applying method with which a liquid material can be applied uniformly even to the edges of holes of a necessary coating surface without entering the holes. CONSTITUTION:When a liquid material is applied to form a film such as a shoulder mask, a permanent mask, an insulating film, a protective film, etc., on a printed circuit board with through holes, the through holes opposite to the side to be coated with the liquid material are colosed with a film and then the liquid material is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for applying a liquid material onto a plate having a through hole formed therein, and more specifically, a through hole which can be used in printed wiring board manufacturing, precision metal processing, etc. is formed. The present invention relates to a method of applying a liquid material on a plate.

[0002]

2. Description of the Related Art Conventionally, in the printed wiring board industry, when a solder mask, a permanent mask, an insulating film, a protective film or the like is formed on a printed wiring board, it is generally called a solder resist, which has heat resistance and insulation after curing. A liquid substance capable of forming a film having properties such as properties is applied. At this time, screen printing, roll coating, curtain coating, air spraying, airless spraying, electrostatic spraying, and the like are used as methods for applying this liquid material onto a printed wiring board.

The solder resist is mainly composed of a thermosetting resin such as an epoxy resin or an aminoplast resin or a photocurable resin such as an epoxy acrylate resin. Then, as a method of forming a resist pattern on a printed wiring board using such a solder resist, a screen printing method has been conventionally adopted.

However, in recent years, the wiring density of a printed wiring board has increased, and the requirement for electrical insulation between conductors has become strict. Therefore, a solder resist used for this is required to be a thick film with excellent dimensional accuracy. It can no longer be dealt with by the screen printing method.

Therefore, a photographic method of forming an image by development after imagewise exposure has led to a demand for a thick film, highly reliable solder resist excellent in dimensional accuracy. And
To meet this demand, for example, Japanese Patent Laid-Open No. 53-560.
No. 18, JP-A No. 54-1018, and the like, a photosensitive resin composition containing an acrylic polymer and a photopolymerizable monomer as main components, and JP-A No. 52-37996.
JP-A-58-62636, JP-A-62-
A photosensitive resin composition containing a photoreactive epoxy resin and an epoxy resin curing agent as main components, which are disclosed in Japanese Patent Publication No. 74920, Japanese Patent Publication No. 1-54390, and the like.
An isocyanate ethyl methacrylate-modified photosensitive resin composition disclosed in JP-A-61-132947 has been proposed.

As a method for forming a film by applying these photographic solder resists onto a printed wiring board, in addition to the conventional screen printing method, JP-A-58-62636 is used.
The curtain coating method, roll coating method, various spraying methods and the like disclosed in the publication are used. By these methods, a photographic solder resist is applied to the entire surface or a necessary surface of a printed wiring board, but each method has advantages and disadvantages. That is, the screen printing method or the roll coating method using a solder resist having a relatively high viscosity (tens to hundreds of poises) applies the solder resist while pressing it with a squeegee or roll. The solder resist is filled in the formed through holes, and the solder resist cannot be removed in the subsequent developing process, which causes a defect such as insufficient soldering when mounting the components.

Further, in the curtain coating method and various spraying methods using a solder resist having a relatively low viscosity (tens to hundreds of centipoise), the thickness of the solder resist applied to the printed wiring board is particularly around the through hole. As a result, the required characteristics such as heat resistance cannot be obtained, and soldering may occur at unnecessary portions during soldering when mounting components, which may cause defects such as short circuits. The reason why the thickness of the solder resist becomes thin is that the solder resist has a low viscosity and therefore flows down into the through hole after coating.
Further, as a result, the solder resist may flow out on the opposite side of the coated surface and cause the solder resist to adhere to unnecessary portions to cause a defect, and a process for removing the unnecessary solder resist may be provided. As a result, the manufacturing cost of the printed wiring board increases.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, and a liquid material coating method capable of uniformly coating a required coating surface without causing the coated liquid material to flow into a through hole. The purpose is to provide.

[0009]

The present invention has achieved the above object by sealing a through-hole on the surface opposite to the surface on which a liquid material is applied with another film-like material. That is, the present invention, when applying a liquid material to form a film on a plate in which a through hole is formed, after sealing the through hole on the opposite surface of the surface to which the liquid material is applied with a film-like material, the liquid material The present invention relates to a method for applying a liquid substance, characterized by applying.

In the present invention, the plate in which the through holes are formed is not particularly limited, and examples thereof include a printed wiring board and various precision metal working plates.

The film-like material used in the method of the present invention is preferably a film-like material having an adhesive property.
Films with adhesive layers such as HITAREX (product name of adhesive film made by Hitachi Chemical Co., Ltd.), TACKWELL (product name of adhesive film made by Sekisui Chemical Co., Ltd.), or adhesive when heat or pressure is applied. Films exhibiting properties are listed. In addition, a photosensitive dry film such as a product name Fotec (manufactured by Hitachi Chemical Co., Ltd.) can be used. The thickness of these film-like materials is not particularly limited, but is preferably several microns to several millimeters.

In the present invention, it is necessary to bring the above film-like material into close contact with the edges of the through holes. There is no particular limitation on the method of contacting, for example, a method of pressing the film-like material onto the through-holes of the plate by hand, using a roller or the like to bring it into close contact, and stacking the film-like material on the plate having the through-holes and heating. There are a method of bringing them into close contact by passing them between rolls, a method of making a plate having a through hole and a film-like material overlap each other in a vacuum chamber, and bringing them into close contact.

The portion where the film-like material is adhered is
The plate may be a part or the whole surface as long as the through hole can be completely closed.

The film-like material must be removed after the liquid material is applied, but the peeling method is not particularly limited, and it may be removed in the process until the liquid material is cured. Therefore, it is preferable to use a film-like material that can be easily peeled off by hand and that does not leave an adhesive substance. Further, when a photosensitive dry film is used, if the liquid substance is a resist using a photographic method, it can be removed at the time of development if the unexposed state is maintained. It can be easily removed at the time of development by using a dry film having only properties.

As described above, by sticking the film-like material to the through-hole portion, one side of the through-hole (the surface opposite to the surface on which the liquid material is applied) is sealed, and the through-hole is used, for example, during screen printing or roll coating. When the liquid substance is pushed into the inside, the internal pressure rises, which prevents the liquid substance from entering the holes. Similarly, during curtain coating or spray coating, liquid does not enter the through holes. Further, since the dripping does not occur in the through hole, the amount of the liquid matter attached around the through hole does not decrease, and a sufficient film thickness can be obtained up to the edge of the through hole, and at the same time, the liquid matter on the opposite surface can be obtained. Will not occur.

Further, in the case of a printed wiring board, since the liquid substance does not enter the through hole, the spray pressure at the time of development is used to remove the resist in the through hole, especially when a photographic liquid solder resist is used. Does not need to be high (for example, 2 kgf / cm ² or more), so that defects such as resist peeling between pads for QFP (quad flat package) mounting do not occur, and a highly accurate and highly reliable solder mask Is obtained.

[0017]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 A tackwell # 150AS- was formed on one side of a double-sided printed wiring board having a circuit thickness of 50 μm, in which through holes (hereinafter referred to as through holes) having a diameter of 0.3 mm to 0.8 mm were formed using a laminator. After laminating ST (manufactured by Sekisui Chemical Co., Ltd.), liquid solder resist HR-5000A is formed on the surface opposite to the surface where the TACKWELL film is laminated.
E-21 (manufactured by Hitachi Chemical Co., Ltd.) was applied by screen printing. After the application, the tackwell film was peeled off and the inside of the through hole was observed. As a result, the liquid solder resist was not contained at all. Further, after the coated substrate was dried at 80 ° C. for 20 minutes and the through hole land portion was observed, it was found that a sufficient film thickness was obtained. After that, when the formed coating film was cured under predetermined conditions and further soldered, soldering was achieved without any problems.

Example 2 The same liquid solder resist H was applied to a double-sided printed wiring board laminated with the tackwell film used in Example 1.
R-5000AE-21 was diluted with propylene glycol monomethyl ether acetate and then applied using a curtain coater. Observation after drying at 80 ° C. for 20 minutes revealed that no resist was contained in the through holes and a sufficient film thickness was obtained at the through hole lands. Further, the liquid solder resist did not adhere to the surface from which the tackwell film was peeled off. After that, when the formed coating film was cured under predetermined conditions and further soldered, soldering was achieved without any problems.

Example 3 Instead of the tackwell film in Example 1, an alkaline development type photosensitive dry film, Fotec H, was used.
-Except that a film excluding the photopolymerization initiator component of F450 (manufactured by Hitachi Chemical Co., Ltd.) was used and alkali development type HR-6060 (manufactured by Hitachi Chemical Co., Ltd.) was used as the liquid solder resist. After observing after performing the same operation as in Example 1, there was no resist clogging in the through holes. Next, after a predetermined negative film was superposed on the coating surface of HR-6060 and a predetermined exposure was performed, the supporting film of Fotec H-F450 was peeled off and development was carried out, and Fotec H-F450 was completely removed. It was After that, when the coating film of HR-6060 was cured under predetermined conditions and then soldering was performed, soldering was achieved without any problems.

Comparative Example 1 A liquid solder resist was applied in the same manner as in Example 1 except that the tackwell, which was an adhesive film, was not laminated, and the resist was clogged in all through holes.

Comparative Example 2 A liquid solder resist was applied in the same manner as in Example 2 except that the tackwell, which is an adhesive film, was not laminated. As a result, almost no resist was applied to the through-hole lands, and the through-hole was not applied. It was also found that the film thickness on the circuit near the hole was extremely thin, and the solder adhered to the part to be protected by soldering after hardening the resist, causing a short circuit.

[0023]

According to the method of the present invention, when a liquid material is applied to a plate having a through hole, the liquid material does not enter the through hole, and a uniform film thickness is obtained up to the hole. Liquid matter does not adhere to the opposite surface. Further, in coating, any method such as a screen printing method, a roll coating method, a curtain coating method, and various spraying methods can be applied. Further, by using a photographic resist, a highly accurate and highly reliable printed wiring board can be obtained, and a metal precision-processed board without defects can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Yoshida 4-13-1, Higashimachi, Hitachi, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Yamazaki Plant

Claims (2)

[Claims] 1. In order to form a film on a plate having through-holes formed therein, when applying a liquid material, the through-hole on the surface opposite to the surface on which the liquid material is applied is sealed with a film-like material, and then the liquid material is applied. A method for applying a liquid material, which comprises applying. 2. The method for applying a liquid material according to claim 1, wherein the plate having the through holes is a plate for printed wiring board production or precision metal processing.