JPH02226793A - Manufacture of flexible printed board - Google Patents

Abstract

PURPOSE:To improve the curing efficiency of a flexible printed board by a method wherein a release film formed by laminating a release layer and a retaining layer, whose tensile strength is higher than the release layer are used, and pressing and heating are performed while the release layer is made to run toward the cover-lay film side. CONSTITUTION:On the circuit forming surface of a flexible printed board(FPC) 1, a cover-lay film 2 and a release film 3 are arranged in order; on the opposite side, a release film 4 constituted in the same manner as the release film 3 is arranged; both of them are rolled out from the rolls 2A, 3A, 4A, introduced in the gap between rolls 5, 5, and piled up in a body by a heating press 6, 6. The FPC 1 covered with the cover-lay film 2 is wound up by a winding roll 1B, and the release films 3, 4 are wound up by winding rolls 3A, 4B. The release films 3 and 4 are formed by unifying the following in a body via an adhesive agent layer; a release layer A used on the FPC side and a retaining layer B which is used on the heating press side and exhibits tensile strength larger than the release layer in the heating state.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to a method for manufacturing a flexible printed circuit board (hereinafter referred to as FPC), and in particular, a method for manufacturing a flexible printed circuit board (hereinafter referred to as FPC), and in particular, a 111 m thick film called a coverlay is attached to the surface of an FPC on which a predetermined circuit pattern is formed.
The present invention relates to a manufacturing method in which a release film having a specific cross-sectional structure is interposed between a press means and an FPC in a pressing process.

``Prior art'' In general, the FPC described above consists of: 1) laminating a conductor foil on the surface of a substrate made of a synthetic resin film, 2) covering the surface of the conductor foil with a resist film corresponding to the circuit pattern, and 2) applying the resist to the substrate. The conductive foil is etched to form a predetermined circuit pattern, and (2) the surface is covered with a protective film called a coverlay, and this coverlay is pressed under heat to make it adhere tightly. It is manufactured through a process called (cure treatment).

In addition, generally, the above steps 1 to 2 are performed in a so-called roll-to-roll process, in which each process is performed while being unrolled from a roll, and then the product is wound up again onto a roll. After these processes are completed, It has been common practice to cut a long FPC into a predetermined length and then perform the step (2) above in a batch process.

``Problem to be solved by the invention'' By the way, in order to streamline the FPC manufacturing process, it is possible to make all processes roll-to-roll, or to merge some processes and move them online. Although it is desirable to reduce the number of times of repeated winding as much as possible, it has been difficult to perform roll-to-roll processing in the coverlay curing process (2) above for the following reasons.

In other words, in the step (2) above, when pressing a coverlay on the surface of the FPC under heat, the FP
Apply the coverlay to the unevenness of the surface of C (the unevenness between the areas where the pattern is present and the areas where it is not).

A cushion material made of EVA etc. is interposed, and further,
In order to ensure the releasability between the cushion material and the coverlay, it is necessary to interpose a fluororesin-based organic film between them.

However, this type of organic film inevitably loses its tensile strength due to heating during pressing, and may be cut or wrinkled due to the tension that inevitably occurs during the roll-to-roll process, or wrinkles may form on the surface of the coverlay. There is a risk of adverse effects.

The present invention has been made in view of the above circumstances, and it is possible to obtain a release film that can withstand the tension associated with roll-to-roll processing and exhibit good mold release properties, and to achieve coverlay curing with roll-to-roll processing. The purpose is to

[Means for Solving the Problems] In order to achieve the above object, the present invention forms a conductive pattern on the surface of a flexible printed circuit board, and compresses a coverlay film overlaid on the patterned surface under heating. In the method for manufacturing a flexible printed circuit board that is brought into close contact with the pattern-forming surface, the flexible printed circuit board, the coverlay film, and the release film stacked on the coverlay film are all formed into long shapes, and and a step of compressing them under heat.The release film necessary for this process includes a release layer with one side facing the coverlay film. , a support layer is adhered to the other surface of the release layer and exhibits a tensile strength greater than that of the release layer in a heated state.

1. With the above structure, the presence of the support layer allows it to withstand the tension generated by continuous movement between the rolls, and the release layer overlaid on the support layer acts against the coverlay film. Good mold releasability can be exhibited.

"Example" Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a heating and compression processing apparatus applied to the manufacturing method of the present invention.

The code l is FPC. This FPCI is made by etching metal stones laminated on the surface of a flexible plastic base material to form a predetermined circuit pattern on its side (lower side in the figure). This circuit pattern is repeatedly formed at predetermined intervals. In addition, the FPCI is arranged from an unwinding roll LA to a winding roll IB for so-called roll-to-roll processing.
It is designed to be able to run along a route that leads to .

A coverlay film 2 and a release film 3 are sequentially arranged on the circuit forming surface side of the FPCI, and a release film 4 having the same structure as the release film 3 is arranged on the opposite side. These are each unwound from unwinding rolls 2A, 3A, and 4A, guided between rolls 5 and 5, and then stacked together by heating presses 6 and 6 facing each other across the running path. After being matched,
It is adapted to be wound up on take-up rolls IB, 3B, and 4B, respectively. Naori Barley Film 2 is F
It is laminated and integrated on the surface of the PCI, and is wound together with the FPCI onto a winding roll IB.

The FPCI coated on the coverlay 2 by heating and compression in the heating breaths 6.
After passing through the rolls 7 and 7 at the rear of 6, it is wound up on the take-up roll IB, while the cover layer F covered with the coverlay 2
The release films 3 and 4 stacked on the PCI pass through the rolls 7 and 7 behind the heating presses 6 and 6, and then the release films 3 and 4 are placed on the FPC.
It is separated from I and wound onto winding rolls 3B and 4B, respectively.

Further, on the surfaces of the upper and lower heating braces 6, suppressing surfaces each having the following structure are formed.

First, a stainless steel plate 9 called a mirror plate with a predetermined flatness is attached to the surface of the lower heating breath 6 via an elastic layer 8 made of silicone rubber. A glue such as cardboard that can be deformed into an uneven shape corresponding to the unevenness on the surface of the FPCI (unevenness due to the presence of a printed pattern),
John material 10 is provided. Further, support members 6a are provided on both sides of the upper heating brace 6, and the guide rod 11 connected to the stainless steel plate 9 is supported by the support members 6a in a suspended state so as to be movable up and down.

Furthermore, an elastic layer 8 is provided between the lower surface of the upper heating brace 6 and the stainless steel plate 9, similar to the lower heating brace 6, so as to realize uniform pressurization.

In the manufacturing apparatus having the above configuration, the unwinding rolls IA to 4A and the winding rolls IB, 3B, and 4B are driven intermittently, and when these rolls are stopped, the heating breath 6 is driven.
・By operating 6 and maintaining it at a predetermined temperature and pressure, the coverlay 2 is cured.
CI is wound onto a take-up roll IB. Then, the FPC as a final product is cut by cutting the FPC unwound from the roll into a predetermined size using a shear or the like.
You can get a PC.

In addition, when pressing by the heating presses 6, 6, since the cushioning material 8 is interposed between the pressing surfaces of the upper and lower heating presses 6 and the stainless steel jM [9, the heating press 6 and the stainless steel plate 9 are It is possible to apply uniform pressure by filling the gap between the two due to the difference in flatness of the two. Further, the upper stainless steel plate 9 can be moved to the upper heating brace 6 while being supported by the guide Orad 11 during pressing.

Note that the cushion material 10 provided on the lower stainless steel plate 9 deteriorates due to heating and compression a predetermined number of times (or time) and loses its ability to follow the unevenness of the surface of the FPCI. ) Replacement of this is required.

The operating time of the presses 6 and 6, that is, the time to maintain the heated and compressed state, is determined depending on the press processing conditions such as heating temperature and pressure, so depending on these conditions, It is necessary to change the running speed of the line or the time it is stopped and held under pressure.

Next, the materials used for the release films 3 and 4 will be explained.

As shown in Figure 2, this mold release film is made of a mold release layer A consisting of a fluororesin film with a thickness of 10 to 50 μm that is embossed on one side, and a silicone resin coated on one side. 10-50μm treated
A support layer B made of a thick PET film (generally has a higher tensile strength at high temperatures than a fluororesin film) is placed with the non-processed surfaces facing each other for 3 to 10 minutes.
They have a cross-sectional structure in which they are bonded together via a μm-thick adhesive layer C.

The release film with the above structure has the embossed surface of the release layer made of fluororesin film on the FPC side (more precisely, the coverlay side of that surface), and the release treated side of the support layer B made of PET film. Cushion material side (heat press side)
By being used in a state aimed at ensuring mold release between the FPC and the cushioning material, it also exhibits sufficient tensile strength and firmness (high rigidity and wrinkle resistance) under heating. can do. In addition, since the embossed fluororesin film surface is superimposed on the coverlay film and heated and compressed, it is possible to exhibit good mold releasability after that.

In the above embodiment, the reciprocating press device is operated intermittently, but it goes without saying that, for example, a roll press device may be used to perform the pressing process continuously.

In addition, in the above embodiment, the FPC running line and the coverlay running line were made to merge immediately before pressing, but for example, the FPC and coverlay were run in advance (or if necessary) on a line separate from the press processing line. If necessary, add release film, etc.) and wind up into a roll.
These may be pressed while running. By employing such a system, it is possible to simplify the complicated control of driving a large number of rolls intermittently while synchronizing them, which is required for the illustrated apparatus. On the other hand, the cushion material installed in the heating press,
Of course, it is also possible to run the cushioning material in a roll-to-roll manner in parallel with the FPC, coverlay, release film, etc. to streamline the work of replacing the cushioning material.

"Effects of the Invention" As is clear from the above explanation, according to the present invention, a release film in which a release layer and a support layer having a higher tensile strength than the release layer are laminated is used. Since pressing and heating are performed while the release layer of the film is running toward the coverlay film, the cured FPC
The release layer exhibits good releasability between the two, and the support layer can support tension and protect the release layer. This is realized in a continuous process, and has the effect of increasing the efficiency of the process.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a side view of a press device, and FIG. 2 is a perspective view of a part of a release film in cross section. 1...FPC, 2...Coverlay film, 3, 4...Release film, 7...
・Heat press, 9...Stainless steel plate, 10...
... Cushion material, lA~4A... Unwinding roll, IB~4B... Winding roll. Figure 1

Claims (1)

[Scope of Claims] A flexible printed circuit board in which a conductive pattern is formed on the surface of the flexible printed circuit board, and a coverlay film stacked on the patterned surface is compressed under heat so as to be brought into close contact with the patterned surface. In the manufacturing method, the flexible printed circuit board, a coverlay film,
The release film layered on the coverlay film is formed into a long shape, and includes the steps of moving the release film in the length direction, and compressing the release film under heat. comprises a release layer with one side facing the coverlay film, and a support layer that is adhered to the other side of the release layer and exhibits a tensile strength greater than that of the release layer in a heated state. A method for manufacturing a flexible printed circuit board, characterized in that: