JPH0724325B2 - Manufacturing method of flexible wiring board integrated with reinforcing plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of manufacturing a reinforcing plate-integrated flexible wiring board in which a reinforcing portion is formed and integrated with a flexible wiring board.

(Prior art and problems to be solved) With the development of the electronic industry in recent years, the mounting method of industrial and consumer equipment has been simplified, and printed wiring boards required to be compact, highly reliable, and have high performance. Is desired. In particular, a flexible wiring board using a plastic film as a base substrate, which is lightweight and can be mounted three-dimensionally, has been receiving attention.

However, since the flexible wiring board is a wiring board with a thickness of 50 to 200 μm, it is too flexible to mount components automatically, and mounting is difficult. A 2.0 mm reinforcing plate is partially attached.

FIG. 3 is a cross-sectional view of an example of a conventional flexible wiring board with a reinforcing plate, in which a conductor circuit (3) is formed on one surface of a base substrate (2), and an insulating layer (4) is formed on the conductor circuit (3) with a coverlay material. The flexible wiring board (1) was formed by adhering a pre-perforated reinforcing plate (6 ') through the adhesive layer (5') and curing the adhesive layer (5 ').

As the flexible base substrate (2), a heat-resistant polyimide-based film is often used, and the reinforcing plate (6 ') is deformed during soldering such as a paper phenol plate or a glass / epoxy laminated plate, A material that does not shrink is used, and as the adhesive (5 ′), an adhesive made of epoxy-based, urethane-based, acrylic-based, phenol-based, triazine-based resin, or the like is used.

However, the flexible wiring board (1) or the reinforcing board (6 ') coated with the adhesive is laminated and press-bonded at a high temperature and a high pressure to integrally form the adhesive. Those reinforcing plates (6 ') must be punched or NC-processed in advance and bonded to each product one by one with an adhesive, and if there are many, 4 to 5 must be laminated. There wasn't. Not only is this a lot of work and expense,
There were problems in performance, such as air bubbles entering the adhesive and misalignment. In addition, in order to attach it to a predetermined position,
Aligning holes are made in the flexible wiring board (1) and the reinforcing plate (6 '), they are attached using a pin jig, or the temporarily adhered ones are set so that they do not shift and the adhesive is hardened. Took time and effort.

(Means for Solving Problems) The present invention provides a method for manufacturing a reinforcing plate-integrated flexible wiring board that solves the above-mentioned problems.
After forming the required conductor circuit on the flexible base substrate, attach the heat-melting engineering plastic film to the insulating layer with solder heat resistance and the position where reinforcement of the flexible base substrate is required, excluding the terminals and lands. The engineering plastics melted at a high temperature are then injection-molded on the film, and the engineering plastics are heat-welded and integrated.

FIG. 1 is a sectional view of an example of a reinforcing plate-integrated flexible wiring board obtained by the manufacturing method of the present invention. In the drawing, (1) is a flexible wiring board on which a conductor circuit (3) is formed on one surface of a flexible base substrate (2), and an insulating layer (4) is formed on the conductor circuit (3) with a coverlay material except for terminals and lands. It is formed by applying. A heat-melting engineering plastic film (5) having an adhesive applied in advance on the back surface of the flexible base substrate (2).
Affix. These films may be adhered separately, but it is preferable that the cover lay film is adhered by a heat press at the same time as the cover lay film is adhered in the process. Thereafter, the engineering plastics melted at a high temperature is injection-molded on the engineering plastics film and heat-welded to form the reinforcing portion (6) and integrate them.

FIG. 2 is a rear view of the flexible wiring board of FIG. 1, and a reinforcing portion made of engineering plastics having an arbitrary shape and thickness can be easily formed. Conventionally flat wiring boards can be easily formed to have any thickness and shape according to the mounting method and location of the wiring board, and the shape and function of the parts. Can be planned.

Such a flexible wiring board can be used not only on one surface of the base substrate but also on a double-sided wiring board, and the reinforcing portion can be formed not only on one surface but also on both surfaces at the same time. The number of reinforcing parts can be from 1 to 10 and can be arbitrarily selected according to the shape of the mounted components.

Conventionally, as a means for integrating the flexible wiring board and the engineering plastics that form the reinforcing portion, by bonding the adhesive film in the B stage state to the flexible wiring board side in advance, It was considered to be melted and hardened by heat and integrated. After that, after-curing was performed by heating in a constant temperature bath or the like.

However, 400 on the B-stage adhesive film
1000 high temperature engineering plastics around ℃
When injection molding at a high pressure of around kg / cm ² , the adhesive film will be washed away, and the thickness will be uneven near the gate and around the mold,
The adhesive force became uneven due to the inclusion of air bubbles. When after-curing was performed in a constant temperature bath, distortion during injection molding and curing shrinkage distortion of the resin occurred, and warpage of the reinforcing plate increased.

In view of the above, the present invention solves the above-mentioned problems by processing engineering plastics similar to the injection-molded engineering plastics into a film shape in advance and adhering it to a flexible base substrate.

The engineering plastic film is formed by applying the same adhesive as the coverlay film that protects the conductor circuit and press-bonding the punched film at the same time when applying the coverlay insulating layer. It was confirmed that the film maintained its shape without being flowed or deformed even when injection-molded at a high temperature of about 400 ° C. or a high pressure of about 1000 kg / cm ² . Further, the engineering plastics injection-molded as the reinforcing plate are compatible with the film at a temperature of about 400 ° C. and can be fused.

Further, the engineering plastics to be injected should have a flat soldering heat property, and the heat distortion temperature evaluated by JIS K7207 should be at least 180 ° C or higher. Soldering heat resistance here means the heat resistance of electronic parts such as ICs, resistors and capacitors at 190 to 250 ° C, and can be soldered by hand soldering, solder dipping, solder reflow, etc. It does not shrink or warp.

Forming the flexible wiring board and the reinforcing portion integrally by injection molding in this way not only has the advantage of automatically laminating the individual laminating, but also facilitates the assembly into the electronic device, and in some cases Since it can be integrated with the equipment case, it will greatly improve productivity and functionality, and is an indispensable wiring material for weight reduction, miniaturization, and addition of functions, which will be required more and more in the future. Becomes

(Example) As a base substrate for a flexible wiring board, a solder heat resistant polyimide film, a polyparabanic acid film, a polyphenylene sulfide film, a polyether film, etc. are used, and an epoxy-based, phenol-based, acrylic-based, silicon-based, imide Apply an adhesive such as a system, attach electrolytic copper foil, rolled copper foil, print an etching resist on the copper foil or laminate a photosensitive film and etch it with iron chloride or copper chloride to form a conductor circuit. Formed.

After the conductor circuit is formed, a cover layer is formed by a solder resist or a heat resistant film so that the terminals and lands on which the components are mounted are exposed to form an insulating layer. At this time, the solder resist is formed before pasting the engineering plastics on the back surface, but the insulating film made of polyimide, polyparabanic acid, etc. is punched into a predetermined shape, positioned and temporarily fixed. .

Then, heat-melting engineering plastics such as polyetherimide, polyphenylene sulfide, polyether sulfide, and polyether ether ketone are extruded into a film having a thickness of 10 to 50 μm to form a film, epoxy, acrylic, A film of thermosetting adhesive such as urethane, silicon, or imide is applied to a thickness of 5 to 20 μm, and the film dried in a semi-cured state is temporarily fixed to a predetermined position of the flexible base substrate. Then, when the cover lay insulating film is bonded at a high temperature and a high pressure, the temporarily fused heat-melting engineering plastic film is also bonded at the same time. Note that, depending on the structure or shape of the flexible wiring board, the two films may be attached through separate steps.

The flexible wiring board forming the reinforcing portion is then set in the injection molding die. At this time, it is preferable that the engineering plastic film surface of the flexible wiring board is oriented at right angles to the gate surface to be ejected.

As the engineering plastics to be injected, polyphenylene sulfide, polyetherimide, polyether sulfide, a crystalline or non-crystalline resin such as polyether ether ketone, at least these resins at a high temperature of 300 ~ 450 ℃, the flexible Pour the wiring board into the set mold. At this time, the flexible wiring board needs to be strongly clamped in the mold so as not to be deformed by the injection pressure. Further, the engineering plastics to be injected must be at least slightly lower than the heat resistant temperature of the film of the base substrate or the conductor circuit will be deformed. Further, engineering plastics can be molded into any shape, but the shape needs to be sufficiently examined so that no stress remains on the wiring board.

(Effects of the Invention) As described above, according to the method for manufacturing a reinforcing board-integrated flexible wiring board of the present invention, since the reinforcing portion is integrally formed on the flexible wiring board by injection molding, the conventional individual bonding A lot of labor and cost are significantly reduced,
The performance of the obtained flexible wiring board is also significantly improved.

Therefore, it will be extremely effective in electronic devices that are required to be lighter, smaller, and have additional functions, which will be required more and more in the future.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of a reinforcing plate-integrated flexible wiring board obtained by the manufacturing method of the present invention, and FIG. 2 is a rear view of the flexible wiring board of FIG. FIG. 3 is a sectional view of an example of a conventional flexible wiring board integrated with a reinforcing plate. 1 ... Flexible wiring board, 2 ... Base substrate, 3 ...
Conductor circuit, 4 ... Insulating layer, 5 ... Engineering plastic film, 6 ... Reinforcement part.

Claims (3)

[Claims] 1. After forming a required conductor circuit on a flexible base substrate, a heat-melting engineering plastic is provided at a position where reinforcement of the insulating layer having solder heat resistance and the flexible base substrate is required except for terminals and lands. Reinforcing plate integrated flexible wiring board characterized by sticking each of the films, and then injection-molding the engineering plastics melted at high temperature onto the film to heat-bond the engineering plastics Production method. 2. An engineering plastic film having a softening temperature of at least 200 ° C. or higher and being softened and welded at a temperature not higher than an injection molding temperature, which is compatible with engineering plastics to be injection molded. The method for manufacturing a flexible wiring board integrated with a reinforcing plate according to claim 1. 3. The method for manufacturing a flexible wiring board integrated with a reinforcing plate according to claim 1, characterized in that the injection-molded engineering plastics have irregular thicknesses and irregular reinforcing portions are formed.