JPH011292A - Manufacturing method of reinforced flexible wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a reinforced flexible wiring board in which a reinforcing portion is integrally formed on a flexible wiring board.

(Prior art and problems to be solved) With the development of the electronics industry in recent years, the mounting method of industrial and consumer equipment has been simplified, and printed wiring boards are required to be smaller, more reliable, and higher performance. is desired.

In particular, a flexible wiring board with a base substrate of plus 1000x film, which can be mounted three-dimensionally with light f+i, is being sold for t1S.

However, since the flexible wiring board is a wiring board with a thickness of 50 to 200 μm, it is difficult to mount components because it is too flexible for automatic mounting of components.
Because it is difficult to attach the reinforcing plate to the base, reinforcing plates with a thickness of 0.5 to 2.0 mm are attached partially.

Figure 3 is a cross-sectional view of an example of a conventional reinforced flexible wiring board, in which a conductor circuit (3) is formed on one side of a base substrate (2), and an insulating layer (4) is formed on the second side using a coverlay material. A reinforcing plate (6') with pre-perforated holes was attached to the applied flexible wiring board (1) via an adhesive layer (7), and the adhesive layer (7) was cured.

The flexible base board (2) is often based on a heat-resistant polyimide film, and the reinforcing board (6') is a paper phenol board or a glass/Epoquin laminate, which may sometimes deform when soldered. The adhesive (7) is made of Evoquin, urethane, acrylic, phenol, triazine resin, or the like.

However, the adhesive was applied to a flexible wiring board (+) or a reinforcing board (6'), which was pasted together and then press-bonded at high temperature and pressure to form an integral piece. Those reinforcement plates (
6') had to be pre-punched or NG-processed and attached to one product one by one with an adhesive, and in some cases, as many as 4 to 5 pieces had to be attached. This not only requires a lot of effort and cost, but also causes performance problems such as air bubbles entering the adhesive and misalignment. In addition, in order to bond them in the specified positions, you need to drill alignment holes in the flexible wiring board (1) and the reinforcing plate (6') and use a pin jig to bond them together, or temporarily bond them together. It took a lot of effort to set it so that it wouldn't come out and let the adhesive harden.

Means for Solving Problem C) The present invention provides a method for manufacturing a reinforced flexible flexible wiring board that solves the above-mentioned problems. A plurality of minute through holes are made in the base substrate other than the one on which the above-mentioned conductor circuits of the flexible wiring board are formed, and these are set in an injection mold and injection molded with engineered plastics to form a reinforcing section.

FIG. 1 is a sectional view of an example of a reinforced flexible wiring board obtained by the manufacturing method of the present invention. In the drawing (
1) is a flexible wiring board in which a conductor circuit (3) is formed on one side of a flexible base board (2), a terminal 11S is formed on the -L of the flexible base board (2), and an insulating layer (
4) is formed. A plurality of minute 1° I through holes (5) are provided in the base substrate (2) of the flexible wiring board (1) other than the one on which the conductor circuit (3) is formed.

The flexible wiring board (1) as described above is set in an injection mold, and engineered plastics melted at high temperature is injection molded into the reinforcement parts (6) at the positions of the base board (2) that require reinforcement. ) is formed, a part of it is press-fitted into the VR through hole (5) provided in the base substrate (2), and formed into a rivet shape (Ga) on the opposite side.

FIG. 2 is a back view of the reinforced flexible/blue wiring board shown in FIG. are firmly integrated by a rivet (6tL) formed on the opposite side through a through hole (5) provided in the base substrate (2).

Conventionally, the reinforcing part was flat, but it can be easily formed into any thickness and shape depending on the mounting method and location of the wiring board, as well as the shape and function of the part, increasing functionality. It becomes possible to aim at cost reduction.

Formation of such a reinforced flexinople wiring board is possible not only on a single-sided wiring board but also on a double-sided wiring board, and it is also possible to form reinforcement parts not only on one side of the wiring board but also on both sides at the same time. It is.

The number of reinforcing parts can range from 1 to 10, and can be arbitrarily selected according to the shape of the component to be mounted.

Various methods can be considered to integrate the flexible wiring board and the reinforcing part, but the method of the present invention does not use adhesive, but instead creates a through hole in the base board and press-fits engineered plastic into the through hole. , and are integrated by mechanical fitting formed on the ribbed rib on the opposite side to ensure sufficient mechanical and thermal characteristics during component mounting. The above-mentioned JT through holes are minute holes with a diameter of about 0.3 to 5.0 mm, and are provided in at least 4 or more places in the reinforcing part, and in most cases, 50 to 60 or more places are provided in order to be firmly integrated.

The engineered plastics to be injected are desirably resistant to soldering heat, and must have a heat distortion temperature of at least +80'C or higher as evaluated by JIS K7207. Soldering heat resistance here refers to electronic products such as ICs, resistors, and capacitors. 90~250℃
For manual soldering, solder dipping, solder reflow, etc., the heat resistance of soldering is 1, and the reinforced part does not shrink or warp significantly.

Forming the flexible wiring board and the reinforcing part integrally by injection molding in this way not only has the advantage of automatically pasting the parts that were pasted individually to the board, but also makes it easier to assemble into electronics equipment, and in some cases It is also possible to integrate it with the case of the equipment, which greatly improves productivity and functionality.It is aimed at the miniaturization of F+, small IJ9, and addition of functions, which will become increasingly necessary in the future. It becomes an indispensable wiring material.

(Function) As the base substrate of the flexible wiring board, Hirata heat-resistant polyimide film, boria rhenoacic acid film, polyphenylene sulfide film, polyether film, etc. are used, and Epoquin-based, phenol-based,
Apply an acrylic, silicone, or imide adhesive, and laminate electrolytic copper foil or rolled copper foil. Print an etching lens on the copper foil or laminate it with a photosensitive film and apply iron chloride or chloride. A conductor circuit was formed by etching with copper or the like.

After the circuit was formed, a coverlay was performed using a solder resist or a heat-resistant film so that the terminal portions and land portions on which components were to be mounted were exposed, and an insulating layer was formed to obtain a flexible wiring board.

The resulting wiring board had a 0.3 to 5 O
Holes of n+φ were drilled with 5 to 20 square pitches to facilitate fitting by press-fitting the resin. The wiring board with holes drilled in it is set in an injection mold. At this time, a depression is made especially in the part of the mold that contacts the hole part, and the press-fitted resin is formed into a billet shape on the opposite side. I took care to make sure that Note that the size and number of holes must be selected depending on the size of the reinforcing part and the stress applied during mounting.Also, the clearance between the wiring board and the mold is very important. It is necessary not to cover it.

The engineered plastics to be injected include polyphenylene sulfide, polyetherimide, polyether sulfide, etc.
At a high temperature of 'C, it is poured into a mold in which the flexinople steam wire plate has been set in advance.

At this time, it is necessary to firmly clamp the flexible wiring board in the mold so that it will not be deformed by the injection pressure. Also, the engineered plastic or plastic to be injected must be at least slightly higher than the heat resistance tQ of the base board film. If it is not too low, it is undesirable as it will cause deformation of the conductor circuit.Furthermore, engineer plastics can be molded into the shape of Ren/Yu, but the shape must be carefully considered so that stress does not remain on the wiring board. be.

(Example) Evoquin tfj on 25μm polyimide film
'? A substrate was prepared by applying the agent to a thickness of 20 μm and laminating an electrolytic copper foil to a thickness of 35 μm. Then the copper foil is dichlorinated.
Etched using copper, excluding the terminal and land parts.
A coverlay of 5f1m of polyimide film was applied to form an insulating layer, and a flexible wiring board was assembled.

11 holes of 0.5 m++φ were drilled at lOl pitch in the part where the parts were to be mounted on the flexinople wiring board so as not to cut the conductor circuit.

Place the drilled wiring board in the injection mold and press 10.
Preheated to 0'C. At this time, the above 0.5m +
A recess with a diameter of 0.7 mm was formed on the surface of iφ in contact with the iT through hole to form the top of the billet.

In the injection molding, jelly etherimide resin melted at 350° C. was injected at a pressure of 120 kg/cd to form an irregularly shaped reinforcing portion with a thickness of 0.51 to 7.01 mm. Thereafter, it was cooled to 80° C. and a reinforced flexible wiring board with a reinforcing portion integrally formed on the flexible wiring board was taken out.

The reinforced flexible flexible wiring board formed in this way has a billet of 0.75++ mφ driven into it from the back side, and the reinforcing part and the wiring board are integrated without wrinkles, deflections, warping, or other obstacles. was.

This integrated reinforced flexible wiring board was passed through a reflow oven with a peak temperature of 220"C to examine the thermal effects during component mounting. As a result, the reinforcement part integrated with the wiring board
．． Although a slight warpage of 1 to 0.3 ani was observed, there was no problem with component mounting, and it was confirmed that it could be put to practical use.

These results prove that even complex-shaped reinforcing parts can be molded in one knot, and a flexible wiring board can be obtained at high speed and at low cost.

(Effects of the Invention) As described above, according to the method for manufacturing a reinforced flexible wiring board of the present invention, the reinforcing portion is integrally formed on the flexible wiring board by injection molding. In addition to reducing labor and costs, the performance of the resulting flexible wiring board is also significantly improved.

Therefore, it will be extremely effective in electronic equipment that will increasingly be required in the future to be lighter in weight, smaller in size, and more functional.

[Brief explanation of the drawing]

1fA 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 back view of the flexible wiring board of FIG. 1. FIG. 3 is a sectional view of an example of a conventional reinforcing plate-integrated flexible wiring board. DESCRIPTION OF SYMBOLS 1... Flexible wiring board, 2... Base plate, 3... Conductor circuit, 4... Insulating layer, 5... Through hole, 5α... Billet shaped part, 6... Reinforcement part.

Claims (2)

[Claims] (1) A plurality of minute through-holes are provided in the base substrate other than the one on which the above-mentioned conductor circuit is formed of a flexible wiring board in which the required conductor circuit is formed on the flexible base substrate, and this is set in an injection mold. A method for producing a reinforced flexible wiring board, comprising forming a reinforcing part by injection molding engineered plastics, and press-fitting a part of the reinforcing part into the through hole to form a rivet shape on the opposite side. (2) The heat distortion temperature of engineered plastics is 180
The method for manufacturing a reinforced flexible wiring board according to claim 1, wherein the temperature is at least .degree.