JPS6020920B2 - Printed circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method of manufacturing a printed circuit board with a cover coat.

In general, a printed circuit board with a cover coat is a printed circuit body in which predetermined printed circuits are formed at regular intervals on a base, and the printed circuit surface of the printed circuit body is covered with a cover coat, leaving exposed parts such as terminal outlets. Each printed circuit is cut into pieces.

There are several methods of cover coating, but
One of the methods is to make holes in a cover coat film made of an appropriate material to correspond to the exposed areas.
This is superimposed on the corresponding position on the printed circuit surface of the aforementioned printed circuit body via a heat-resistant adhesive layer, and is bonded and integrated using a heating pressure press that heats the printed circuit while applying large pressure over the entire surface of the printed circuit. Are known. As the film for the cover coat used above, polyimide film, polyparabanic acid film, polyamide film, polyamide vapor, etc. are used because they have good heat resistance.

However, these films are generally expensive and have poor moisture and water resistance compared to polyester films and the like, making them somewhat difficult to use for general purposes. Therefore, in recent years, polyester films, which are cheaper than the above-mentioned films and have relatively good moisture and water resistance, have begun to be used. On the other hand, the present inventors used the above polyester film and produced industrially useful heat. An attempt was made to obtain a printed circuit board with a cover coat by a continuous production method using a roll laminator, but since the film described above has the disadvantage of being easily heat-shrinkable, warpage and voids ( Not only does this create gaps (between the printed circuit surface and the cover coat), but it also tends to cause misalignment, and it is not possible to cover coat the desired position of the printed circuit surface accurately, such as partially blocking exposed parts such as terminal openings. I have a problem. That is, unlike the lamination method described above (heated pressure press method), which heats the entire surface of the printed circuit while applying a large pressure, the heat roll laminator applies a relatively small amount of linear pressure to the center of the base. It is used to bond and integrate the material by heating it in the state.

Therefore, if the cover coat film applied to this film is easily heat-shrinkable, it is difficult to prevent the heat shrinkage even with external pressure (linear pressure) when bonding and bonding, and it is difficult to prevent the heat shrinkage when bonding and bonding together using a hot roll laminator. Even if the both ends of the base in the center direction are preliminarily bonded in a dotted manner beforehand, the heat shrinkage force easily overcomes the adhesive force in these parts, and it becomes difficult to apply the cover coat to the predetermined position. By the way, commercially available polyester films are generally made by melting a polyester resin, extruding it by an inflation method, etc., and then stretching it uniaxially or biaxially to improve its tensile strength, initial elastic modulus, etc.
They are made using methods that increase mechanical strength, such as impact strength.

The heat shrinkability of this film is due to the fact that internal stress tends to remain due to molecular orientation during the above manufacturing process. The inventors have made extensive studies in order to overcome these drawbacks of polyester film and to obtain a polyester film that does not cause the above-mentioned problems when the printed circuit surface is continuously covered with a hot roll laminator. As a result, they found that when a commercially available polyester film was subjected to a specific heat treatment, its heat shrinkability was significantly reduced, making it possible to obtain a film suitable for a continuous cover coat method using external heat roll lamination. This led to the completion of this invention.

That is, the present invention provides terminal protection for the printed circuit surface of a printed circuit elongated body formed by forming predetermined printed circuits continuously at regular intervals in the longitudinal direction of the base, leaving an exposed portion such as an opening. For cover coating, as a film for cover coating, heat treatment is performed at 150 to 240 q○ without applying tension to the processed film after extrusion molding and stretching. A polyester film with a dimensional change rate of 1% or less in both length and width is used, and this film is perforated to correspond to the exposed portion, and this is made to correspond to the printed circuit surface of the elongated body. This relates to a method for manufacturing a printed circuit board, which is characterized in that the printed circuit boards are laminated in position with a heat-resistant adhesive layer interposed therebetween and continuously bonded and integrated using a 50 to 150 q0 hot roll laminator.

Below, a method for manufacturing a printed circuit board according to the present invention will be explained based on the drawings.

Note that FIGS. 1 and 2 show the state in which the printed circuit elongated body and the cover coat film are not superimposed or temporarily bonded before being bonded and integrated using a hot roll laminator.
FIG. 1 is a plan view, and FIG. 2 is a sectional view taken along the line 0--Ro of FIG. In both figures, 1 is etched in the longitudinal direction of the base 2.
A printed circuit elongated body is formed by forming predetermined printed circuits 3 (3A, 3B, 3C) continuously at regular intervals by an appropriate means such as plating, and 4 is a printed circuit surface of the elongated body 1 as a terminal. This is a cover coating film for cover-coating leaving an exposed part 5 such as a take-out port, and is perforated to correspond to the exposed part 5, and each perforated part 6 corresponds to the exposed part 5. The printed circuit surface of the elongated body 1 is overlapped at a predetermined position with a heat-resistant adhesive layer 7 interposed therebetween.

For this overlapping, both ends of the center opening of the base are temporarily glued in a dotted manner. Temporary adhesion may be performed by pressing a heating jig (not shown) onto the stacked cover coat films to activate the adhesive force of the heat-resistant adhesive layer 7, or by using a different type of adhesive. Alternatively, the adhesive may be attached. What is particularly important in this invention is that as the above-mentioned cover coat film 4, a processed film after extrusion molding and stretching treatment, that is, a polyester film obtained by heat-treating a commercially available polyester film at a specific temperature without applying tension, is used. This is the point.

That is, the above heat treatment has been found to significantly reduce the thermal shrinkage rate and to greatly suppress shrinkage during bonding and integration using a hot roll laminator. Furthermore, among commercially available polyester films, those that have been heat-treated during extrusion molding and stretching are
Already known. However, this heat treatment is originally carried out under a condition where a certain tension is applied vertically to the rattan in order to eliminate wrinkles in the processed film after stretching. That is, with such heat treatment, it is not possible to significantly reduce the heat shrinkage rate, and the shrinkage rate tends to increase in a heated atmosphere at or above the heat treatment temperature. Normally, the secondary purpose is to increase the number of employees. Therefore, a film subjected to such heat treatment is even more unsuitable as a film for cover coating using a hot roll laminator. The processed film used to obtain the cover coat film 4 according to the present invention is obtained by extrusion processing and stretching treatment (usually 2-mall stretching) of a polyester resin by a conventional method, and is a commercially available Lumirror film. (trade name manufactured by Toray Industries, Inc.), Mylar film (trade name manufactured by DuPont), etc. are all included in the above-mentioned processed films.

A typical example of these processed films is a polyethylene terephthalate film as seen in the above-mentioned commercial products, but the film may contain other ingredients or polyhydric alcohol components that are different from those mentioned above. The thickness is usually 6 to 10
It is about 01. However, it may be thinner or thicker than the above thickness. The heat treatment temperature when heat treating this processed film without applying tension is 1
Set from 50 to 240 p.m. In this temperature range, the higher the heat treatment temperature is, the more remarkable the effect of the present invention becomes.
On the other hand, heat treatment below 150 degrees Celsius is less effective, and above 240 degrees Celsius approaches the softening point of the film.
Both are inappropriate. The heat treatment time varies depending on the heat treatment method as well as the treatment temperature. It is best to keep the film within a reasonable range.Such heat treatment causes a change in the crystal structure of the film, but the physical properties that appear due to this change include a decrease in thermal adhesion and an increase in the refractive index in the thickness direction. can be mentioned.

Regarding the refractive index in the thickness direction, taking polyethylene terephthalate film as an example, before heat treatment, the refractive index measured by an Atsbe refractometer is 1.4 pseudo-0 or less, but after heat treatment, it is 1.4
990 or more, usually increasing to 1.4995-1.5020. The polyester film for cover coat of the present invention thus obtained is characterized by a dimensional change rate of 1% or less in both length and width under conditions of 150 qo and 30 minutes. Next, the heat-resistant adhesive 7 is generally applied to one surface of the above-mentioned cover coat film 4, and any known one can be used.

Examples include polyester resins, thermosetting epoxy resins, thermosetting polyacrylate copolymer compositions, and the like. In this invention, the printed circuit elongated body 1 and the cover coat film 4, which have been superimposed as described above, are continuously guided to a hot roll laminator 8 (see FIG. 2) and bonded together. let The heat roll laminator 8 used here is composed of two rolls 8A and 8B on the upper and lower sides or the left and right sides, and the heating temperature thereof is set to 50 to 15,000 degrees depending on the type of the heat-resistant adhesive layer 7. It is undesirable for this temperature to be higher than 150qo in terms of preventing thermal shrinkage, and lower than 50qo because it is not possible to increase the adhesive strength. Roll 8A,
The linear pressure applied by 8B is usually 0.2 to 5k9/
It is at a suppressive level.

The types of rolls 8A and 8B are not particularly limited, and may be appropriately combined with conventionally known rolls such as silicone rubber rolls, Teflon-coated iron rolls, and stainless steel rolls. Particularly preferred is a combination of a silicone rubber roll and a Teflon-coated iron roll. In addition, when sufficient adhesive strength cannot be obtained by only making conduction between the rolls 8A and 8B once, the same operation may be repeated 2 to 5 times as necessary.

Also, after making this hot roll laminator 8 conductive,
For a predetermined period of time, for example, 50
A post-heat treatment may be performed at ~60qo for 5~lq hours and further at 100~110qo for 5~1 hour to completely cure the adhesive layer 7. Furthermore, after these are bonded and integrated, it may be cooled for a short time by passing between cooling rolls. According to the above-mentioned method, since the cover coat film 4 used has extremely low heat shrinkage compared to conventional ones, the overlapping and temporary adhesion state shown in FIGS. 1 and 2 is maintained as is. Therefore, the cover coat can be accurately applied to a predetermined position without causing any positional shift when passing through the hot roll laminator 8 or during subsequent heat treatment.

Moreover, the printed circuit elongated body 1 cover-coated in this way
The printed circuit board of the present invention, which is obtained by cutting the printed circuits 3A, 3B, and 3C into predetermined lengths in a subsequent process, has no voids or voids between the printed circuit surface and the cover coat layer, and is insulated. It has very good characteristics such as moisture characteristics and tree moisture characteristics.

As detailed above, according to the present invention, by using a specific polyester film as a cover coat film using a hot roll laminator, it is possible to overcome problems such as blockage of the terminal outlet due to misalignment, and to accurately It is possible to provide a printed circuit board with good insulation and moisture resistance that is covered with a cover coat.

Examples of this invention will be described below.

The refractive index in the film thickness direction shown below was calculated using a sodium light source with an Atsbe refractometer (type 1), using a test piece with a refractive index of 1.7400, and using monobromnaphthalene as an intermediate liquid, in accordance with the usual method. Measurements were taken using acid and wearing glasses with polarizing plates attached. Example 1 30% of 75mm Lumirror film (previously commercially available polyethylene terephthalate film) was placed in a 240qo dryer.
Heat treatment was performed by leaving it for a minute.

Next, a heat-resistant adhesive solution was applied to one side using an applicator so that the dry thickness was 20 peaks, and dried at 12,000 for 5 minutes to obtain a base polyester film having a heat-resistant adhesive layer. . The heat-resistant adhesive solution was prepared by dissolving Vylon-30 (polyester resin) manufactured by Toyobo Co., Ltd. in toluene, and adding Coronate L (trade name manufactured by Nippon Polyurethane Co., Ltd.) as a curing agent per 100 parts by weight of the resin. A toluene solution with a solid content of 3% by weight, which was prepared by uniformly dissolving and mixing 5 parts of a polyfunctional isocyanate compound, was used. Next, a copper foil was superimposed on the adhesive layer side of the base polyester film having the heat-resistant adhesive layer obtained in this way, and this was layered with a silicone rubber roll set to 12 mm 0.3 x 9/cm and Teflon. The polyester film for the base was placed between the coated iron roll and the silicone rubber roll, and the film was bonded and integrated with the roll.

Then, leave it in the dryer at 50℃ for 6 hours and 10 minutes.
Completely cured with heat treatment after feeding Terama with Pi○
did. Thereafter, predetermined printed circuits were continuously formed on the copper foil at regular intervals in the longitudinal direction by etching or the like to obtain a printed circuit elongate body. On the other hand, 23〆 Lumirror film (
The commercially available polyethylene terephthalate film mentioned above) was
Heat treatment was performed by leaving each piece in a dryer at 40°C for 3 minutes.

The refractive index in the thickness direction was 1.4964 before heat treatment and 1.4996 after heat treatment. Also, 150qo, 30
The dimensional change rate under the condition of 1.8% in the longitudinal direction before heat treatment;
The width was 0.7%, but the heat treated rice was 0.17% vertically and 0 horizontally.
．． It was 10%. A heat-resistant adhesive solution of the same type as above was applied to one side of the heat-treated film to a dry thickness of 20 mm, and dried to obtain a cover coat film having a heat-resistant adhesive layer according to the present invention. . After this cover coat film is perforated to correspond to the terminal outlet of each printed circuit, a heat-resistant adhesive layer is placed on the inside at the corresponding position on the printed circuit surface of the printed circuit elongated body. They were overlapped in a manner similar to the above, and predetermined positions on both ends in the middle direction were temporarily adhered in a dotted manner.

This was guided between a silicone rubber roll set to 120qo, 3k9/a and a Teflon-coated iron roll so that the cover coat film was positioned on the silicone rubber roll side, and then bonded and dried by heating. After feeding in the machine for 6 hours at 50 pm, and 1 feeding period at 100 pm, heat treatment was performed to completely cure the fish. The printed circuit board with a cover coat according to the present invention, which is obtained by cutting the integrated adhesive and the printed circuit to the length, shows no displacement of the cover coat film, and it is easy to take out the terminals of the printed circuit. It was covered with a precise cover coat, leaving only the exposed parts like the mouth.

Furthermore, the adhesive strength between the cover coat layer and the printed circuit surface is 1.
5k9/skin, no pimples or voids were observed between the two, and no wrinkles were observed. Example 2 A base polyester film having a heat-resistant adhesive layer was obtained in the same manner as in Example 1, except that the heat treatment conditions in the heating dryer were 150 qo for 30 minutes.

Using the thus obtained base polyester film having the heat-resistant adhesive layer, a printed circuit elongate body was produced in the same manner as in Example 1. On the other hand, a film for force bar coating according to the present invention having a heat-resistant adhesive layer was obtained in the same manner as in Example 1, except that the heat treatment conditions during heat drying were 150 qo and 3 whiskers as above. .

The refractive index of this film in the thickness direction before forming the heat-resistant adhesive layer is 1,4991, and the dimensional change rate under the condition of 15"0.3 powder is 0.22% vertically and 0.17% horizontally. %Met. This cover coat film is perforated to correspond to the terminal outlet of the elongated printed circuit body, and then the heat-resistant adhesive layer side is placed on the inside at the corresponding position on the printed circuit surface of the elongated body. They were overlapped so that the two ends were overlapped, and predetermined positions on both ends in the middle direction were temporarily adhered in a dotted manner.Then, the sheets were passed through a hot roll laminator in the same manner as in Example 1, and then heated and bonded together.

Note that the temperature of the hot roll lamination was 150°C. The printed circuit board with a cover coat according to the present invention obtained by cutting the above-mentioned adhesive-integrated printed circuit to a predetermined length for each printed circuit shows no displacement of the cover coat film at all.
The cover coat was precisely applied, leaving exposed parts such as the terminal outlets of the printed circuit.

In addition, the adhesive strength between the cover coat layer and the printed circuit surface is 1
．． At 6 kg/toga, no pimples or poids were observed between the two, and no wrinkles were observed. Example 3 A polyester film for a base having a heat-resistant adhesive layer was obtained in the same manner as in Example 1, except that a heat roll was used as the heat treatment means and the heat treatment was performed under sand conditions of 240:00.6.

Using the thus obtained base polyester film having the heat-resistant adhesive layer, a printed circuit elongate body was produced in the same manner as in Example 1. On the other hand, as a means of heat treatment, a heat roll was used in the same manner as above, and 240 qo, 6
A cover coat film according to the present invention having a heat-resistant adhesive layer was obtained in the same manner as in Example 1, except that the heat treatment was carried out under the conditions of 1.5 seconds.

The refractive index of this film in the thickness direction before forming the heat-resistant adhesive layer is 1.4994, and the dimensional change rate under the conditions of 150 pm and 30 minutes is 0.18% vertically and 0.12% horizontally. It was hot. After this cover coat film is perforated to correspond to the terminal outlet of the elongated printed circuit body, a heat-resistant adhesive layer is placed on the inside at the corresponding position on the printed circuit surface of the elongated body. They were overlapped in the same manner, and predetermined positions on both ends in the middle direction were temporarily bonded in a dotted manner, and then passed through a hot roll laminator in the same manner as in Example 1 and then subjected to post-heat treatment to be bonded and integrated.

The temperature of the hot roll laminator was 150°C. The printed circuit board with a cover coat according to the present invention obtained by cutting the above-mentioned adhesive-integrated printed circuit into a predetermined length for each printed circuit has no displacement of the cover coat film, and the terminals of the printed circuit It was accurately covered with a cover coat, leaving exposed parts such as the outlet.

Furthermore, the adhesive strength between the cover coat layer and the printed circuit surface is 1.
At 6k9/cm, no voids or voids were observed between the two, and no wrinkles were observed. Example 4 Copper clad plate (product name: Piralux (similar to pMa) manufactured by DuPont (thickness: 25 mm)
A printed circuit elongated body was obtained by forming a predetermined printed circuit continuously in the longitudinal direction of a printed circuit board (made by adhering steel foil to a polyimide film) by etching or the like.

Using this printed circuit elongated body and the polyester film for cover coating having a heat-resistant adhesive layer obtained in Example 1, the present invention will be relied upon under the same operating conditions and conditions as in Example 1. A printed circuit board with a cover coat was fabricated.

This circuit board showed no displacement of the cover coat film, and the cover coat was accurately applied leaving exposed parts such as the terminal outlet of the printed circuit. In addition, the adhesive strength between the cover coat layer and the printed circuit surface is 1.8k9/m,
No voids or voids were observed between the two, and no wrinkles were observed. Comparative Example 1 A heat-resistant adhesive solution similar to that in Example 1 was applied to one side of the 23-inch Lumirror film (described above) to a dry thickness of 20 mm, and dried to form a heat-resistant adhesive layer. It was made into a film for cover coat.

Using this film for cover coating and the printed circuit elongated body obtained in Example 4, a printed circuit board with a cover coat was produced using the same operation and conditions as in Example 1.
In this circuit, the cover coat film becomes misaligned during the process of passing it through a hot roll laminator and the subsequent heating process, and some of the protruding parts such as the terminal outlet are blocked, so that it is not precisely placed at the specified position. could not be covered with a coat. In addition, voids and voids were formed between the cover coat layer and the printed circuit surface, and wrinkles were also observed. Comparative Example 2 The printed circuit elongated body obtained in Example 1 and the cover coat film having the heat-resistant adhesive layer obtained in Comparative Example 1 were subjected to the same operations and conditions as in Example 1. A printed circuit board with a cover coat was fabricated using the same method.

In this circuit board, almost the same as in Comparative Example 1, the cover coat film was misaligned, and the occurrence of blemishes, pores, and wrinkles was noticeable.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the stacked state of the printed circuit elongated body and the cover coat film according to the present invention before they are bonded and integrated using a hot roll laminator. FIG. 1...Printed timespan long body, 2...Base, 3 (3A,
38,3C)...Printed circuit 4...Film for cover coat, 5...Given part, 6...Perforated part, 7
... Heat-resistant adhesive layer, 8 (8A, 88) ... Heat roll laminator, A ... Longitudinal direction. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. Covering the printed circuit surface of a printed circuit elongated body formed by forming predetermined printed circuits continuously at regular intervals in the longitudinal direction of the base, leaving exposed parts such as terminal outlet openings. When coating, the film for cover coating is obtained by heat-treating the processed film after extrusion molding and stretching at 150 to 240 °C for 30 minutes without applying tension. A polyester film with a dimensional change rate of 1% or less in both length and width is used, and this film is perforated in correspondence with the exposed portion, and this is placed in the corresponding position on the printed circuit surface of the elongated body. A method for manufacturing a printed circuit board, which comprises stacking the printed circuit boards with a heat-resistant adhesive layer interposed therebetween and continuously bonding and integrating them using a hot roll laminator at 50 to 150°C. 2. The method for producing a printed circuit board according to claim 1, wherein the polyester film is a polyethylene terephthalate film, and the refractive index in the thickness direction (as measured by an Atsube refractometer) is 1.4990 or more.