JPH07170032A - Reinforcing sheet sticking method of flexible printed wiring board - Google Patents

Abstract

PURPOSE:To stick a reinforcing sheet to a flexible printed wiring board while bubbles between them are eliminated, by a method wherein, after a work is accommodated in a vacuum box having thermal conductivity and installed in a hot pressing equipment, the inside is evacuated, and the work is thermocompression-bonded by applying pressing force and heat via the vacuum box. CONSTITUTION:A work 11 is accommodated in a vacuum box main body 14, and a lid plate 15 is mounted on the work 11. In this state, these are arranged on the lower heating plate 24 of a hot pressing equipment 13. By operating a vacuum pump 20, the inside of a vacuum box is evacuated, and a specific pressure is obtained. By making an upper heating plate 25 on the hot pressing equipment 13 descend, pressing force and heat are applied to a vacuum box 12. A reinforcing sheet 9 is bonded to a PFC 8 via the bottom plate 18 and the lid plate 15 of the vacuum box 12 and a pair of metal molds 21, 23. By the bonding in a vacuum, bubbles generated between the PFC 8 and the reinforcing sheet 9 are eliminated, the effective sticking of a reinforcing sheet is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laminating reinforcing plates by thermocompression bonding in a vacuum environment when manufacturing a flexible printed wiring board used in electronic devices such as calculators and printers. .

[0002]

2. Description of the Related Art In recent years, high-density mounting in electronic equipment has been achieved,
There are remarkable movements toward miniaturization, weight reduction, and thinning, and flexible printed wiring boards (hereinafter referred to as FPCs) are often used in such electronic devices. F
The PC is capable of mounting three-dimensionally high-density in a narrow space while mounting various electronic components and utilizing its flexibility. In addition, a reinforcing plate may be attached to one surface of the FPC in order to increase the strength of the position of the connection terminal of the FPC and a portion requiring high strength. The reinforcing plate attaching method includes a so-called vacuum pressing method in which thermocompression bonding is performed in a vacuum environment in addition to bonding with an adhesive or the like. This vacuum pressing method is performed between the FPC and the reinforcing plate. It has advantages such as good defoaming property of bubbles existing in, and good circuit embedding property.

FIG. 4 is a view showing the structure of the vacuum press apparatus 1, in which reference numeral 2 is a vacuum chamber, 3 is a hot press section, and 4 is a work. The entire hot pressing unit 3 including elements such as the upper heating plate 5 and the lower heating plate 6 is a vacuum chamber 2
The vacuum chamber 2 is installed inside, and a vacuum pumping means such as a vacuum pump 7 for vacuuming the inside is connected to the vacuum chamber 2. Further, the work 4 has a pair of molds 1 for the FPC 8 and the reinforcing plate 9 to align these with each other.
It is sandwiched between 0 and 10.

When the reinforcing plate 9 is bonded by using this vacuum press device 1, the vacuum chamber 2 is opened and the work 4 is placed between the upper hot plate 5 and the lower hot plate 6 of the hot press part 3. After that, the vacuum chamber 2 is hermetically closed, and the vacuum pump 7 evacuates the interior of the vacuum chamber 2 to a predetermined pressure. The FPC 8 and the reinforcing plate 9 are thermocompression bonded.

[0005]

However, in the conventional reinforcing plate bonding method, since the vacuum press device 1 has a structure in which the entire hot press part 3 is installed in the vacuum chamber 2, the vacuum press Since the entire apparatus 1 is very large, a large installation space is required. Since the volume of the vacuum chamber 2 is large, the evacuation time until reaching a predetermined pressure is long, and the cost of the vacuum press apparatus 1 is high. However, there is a problem that the manufacturing cost of the FPC becomes high, and the bonding of the reinforcing plate of the FPC by using such a large-scale vacuum press device 1 is inefficient in various aspects.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an efficient method for attaching a reinforcing plate of an FPC.

[0007]

In order to achieve the above-mentioned object, a method for laminating a reinforcing plate of a flexible printed wiring board according to claim 1 is such that the flexible printed wiring board and the reinforcing plate are mounted between a pair of pressing plates. In a method for laminating a reinforcing plate of a flexible printed wiring board, which is adapted to thermocompression-bond a flexible printed wiring board and a reinforcing plate by hot pressing a workpiece placed under a low-pressure environment for the work, The airtight state is maintained when the interior is evacuated, and the work is stored inside a vacuum box having heat conductivity, which is relatively movable in a direction in which the lid plate and the bottom plate approach each other. Then, after the vacuum box is installed in a hot press machine, the inside of the vacuum box is evacuated and pressing force and heat are applied through the vacuum box. And by, the workpiece is characterized in that so as to thermocompression bonding.

A vacuum box according to a second aspect is a vacuum box used in the method for laminating a reinforcing plate of a flexible printed wiring board according to the first aspect, in which a vacuum packing is attached to the upper end to evacuate the inside. A box body composed of a side plate and a bottom plate to which an exhaust pipe is connected and a lid plate, and the height from the lower end to the upper end of the side plate is smaller than the thickness of the work piece, and from the lower end of the side plate. The height to the upper end of the vacuum packing is larger than the thickness of the work.

[0009]

In the method for laminating a reinforcing plate of a flexible printed wiring board according to the present invention, air bubbles generated between the flexible printed wiring board and the reinforcing plate are removed by evacuating the inside of the vacuum box. When the pressing force and the heat are applied by the hot press device, the pressing force and the heat are respectively transmitted to the work through the vacuum box, so that the flexible printed wiring board and the reinforcing plate in the work are thermocompression bonded. To be done.

Further, in the vacuum box according to claim 2, the height from the lower end of the side plate to the upper end of the side plate of the box body is smaller than the thickness of the work, and the height from the lower end of the side plate to the upper end of the vacuum packing is the thickness of the work. Since it is set to a larger size, there is a gap between the work and the lid plate when the work is stored in the vacuum box, but the inside of the vacuum box is evacuated and a pressing force is applied by the hot press machine. Then, the work is brought into contact with the lid plate by vertically compressing the vacuum packing, and the work is vertically compressed via the bottom plate and the lid plate of the vacuum box, and at the same time, heat is conducted.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for laminating a reinforcing plate of a flexible printed wiring board (FPC) according to the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a method for laminating reinforcing plates according to this embodiment. This method is performed by using the work 11, the vacuum box 12, and the hot pressing device 13 shown in the figure.

FIG. 2 is a view showing the structure of the vacuum box 12 used in this method. In the figure, reference numeral 14 is a box body, 15 is a cover plate, and 16 is an exhaust pipe. The box body 14 is formed by using an iron plate having a thickness of 0.5 mm, and the side plate 17 and the bottom plate 18, which are formed in a cylindrical shape, are joined by welding so as to maintain the internal airtight state, and the work 11 to be described later is described. Is a size that can be stored inside. Further, the vacuum packing 1 is provided on the upper end of the side plate 17 over the entire circumference.
9 is attached, and the vacuum pump 20 is provided on one surface of the side plate 17.
An exhaust pipe 16 for exhausting the inside of the vacuum box 12 is provided by being connected to. The vacuum packing 19 and the exhaust pipe 16 are made of a material having high heat resistance. The vacuum box 12 is constituted by the box main body 14 having such a configuration and the flat plate-like cover plate 15 covering the upper portion thereof.

In the work of attaching the reinforcing plates, first,
The work 11 is produced. As shown in FIG.
Is a pin for positioning the FPC 8 and the reinforcing plate 9 (not shown)
It is placed between a lower die (pressing plate) 21 provided with, and a cushion material 22 and an upper die (pressing plate) 23 are sequentially arranged above it. The cushion material 22 is made of a highly heat-resistant material, covers the tip of the positioning pin protruding upward of the FPC 8 and uniformly transmits the pressure applied between the molds 21 and 23 to the FPC 8 and the reinforcing plate 9. It is for.

Next, as shown in FIG. 1, the prepared work 11 is housed in a vacuum box body 14 and a lid plate 15 is placed on the vacuum work body 14, and the lower hot plate 2 of the hot press machine 13 is placed thereon.
Install on top of 4. Then, the vacuum pump 20 is operated to evacuate the inside of the vacuum box 12 so that the pressure reaches a predetermined pressure, and the upper hot plate 2 of the hot press machine 13 is heated.
When 5 is lowered and pressing force and heat are applied to the vacuum box 12, the bottom plate 18 and the lid plate 15 of the vacuum box 12 are
Through the pair of molds 21 and 23, and the FPC8
And the reinforcing plate 9 are thermocompression bonded.

Therefore, when thermocompression bonding is performed, as shown in FIG.
As shown in, when the total thickness of the work 11 is t1,
The height t2 from the lower end to the upper end of the side plate 17 of the vacuum box body 14 is set to be smaller than t1, and the height t3 from the lower end of the side plate 17 to the upper end of the vacuum packing 19 is t1.
Since the size is set to be larger, a slight gap is formed between the work 11 and the lid plate 15 when the work 11 is housed in the vacuum box 12, but the inside of the vacuum box 12 is exhausted to generate heat. When a pressing force is applied by the inter-pressing device 13, t3 approaches t2, that is, the vacuum packing 19 is sufficiently compressed in the vertical direction and the lid plate 15 is pushed down, so that the work 11 and the lid plate 15 come into contact with each other.
The work 11 is vertically compressed via the bottom plate 18 and the cover plate 15 of the vacuum box 12, and at the same time, heat is conducted to the work 11 via the bottom plate 18 and the cover plate 15 of the vacuum box 12 to cause the work 11 to move. The FPC 8 and the reinforcing plate 9 therein are thermocompression bonded.

In the method for laminating the reinforcing plates of this embodiment, the space for vacuum evacuation is limited to the inside of the vacuum box 12 having a volume slightly larger than the work 11. Therefore, the inside of a large vacuum chamber surrounding the hot press part is The volume of the space in which the vacuum is evacuated can be significantly reduced compared to the conventional case where the gas is evacuated. Therefore, the time required for vacuum evacuation can be reduced, which in turn can reduce the time required for the entire bonding operation.

In this method, the apparatus used is a vacuum box 12 having a size slightly larger than the work 11.
Since only the hot press machine 13 is required, the installation space of the machine and the cost required for the machine can be reduced as compared with the conventional method which requires a large vacuum chamber. That is, according to the present method, it is more efficient than the conventional method in various aspects, such as shortening the overall working time, further reducing the installation space and cost of the device when the reinforcing plate is bonded. can do.

As a concrete example, the conventional method, the present method,
Further, as a comparative object, a sample in which a reinforcing plate was stuck was prepared by three kinds of methods, that is, an atmospheric pressure pressing method, and the defoaming property of bubbles between the FPC and the reinforcing plate was evaluated. Regarding the sample according to this method, first, a thermosetting adhesive is temporarily fixed to the FPC, and then the FPC and the reinforcing plate are positioned using a mold, and a work holding them is produced, This was placed in a vacuum box, the pressure inside the vacuum box was reduced by a vacuum pump, and thermocompression bonding was performed by a hot press machine. The hot press conditions are a temperature of 150 to 200 ° C. and a pressure of 10 to 40 Kg /
cm @ 2, time 30-60 minutes. At this time, when the pressure inside the vacuum box was monitored, a desired pressure of 130 mmHg was obtained within 1 minute after starting the vacuum pump.

Then, five samples were prepared by each of the three methods, and the presence or absence of bubbles was observed in each sample with a microscope at a magnification of 40 times. The results are shown in Table 1 below. As can be seen from these results, in all of the five samples, air bubbles were observed in the atmospheric pressure pressing method.
In addition, in the conventional method, generation of bubbles was not observed in all of the five samples. That is, it has been proved that the present method of exhausting only the inside of the vacuum box can obtain a desired pressure in a sufficiently short exhaust time and has a high bubble defoaming property as in the conventional method.

[Table 1]

In this embodiment, the vacuum box 12 is composed of the box body 14 and the flat lid plate 15. However, instead of this construction, a box body having a U-shaped cross section that fits with each other is used. The lid body may have the same shape, or the box body and the lid plate may be connected by, for example, a bellows-shaped stretchable side plate. However, in any case, it is needless to say that it is necessary to have a structure capable of maintaining an airtight state inside. Further, the pair of molds 2 in this embodiment
The configuration of the work 11 composed of 1, 23, the cushion material 22 and the like can be appropriately changed depending on the case.

[0021]

As described above in detail, the first aspect of the present invention is as follows.
In the method for laminating the reinforcing plate of the flexible printed wiring board described, since it is configured to evacuate the inside of the vacuum box, compared to the conventional case where the inside of the vacuum chamber that surrounds the entire hot press part is evacuated. The volume of the space for vacuum evacuation is remarkably reduced, the evacuation time can be shortened, and the time required for the entire bonding work can be shortened. Further, by using a vacuum box instead of the conventional vacuum chamber, the installation space of the device and the cost required for the device can be reduced. That is, when the reinforcing plate bonding work is performed, the efficiency can be improved as compared with the conventional method in various aspects such as shortening the entire working time, reducing the installation space and cost of the device, and the like.

Further, in the vacuum box according to the second aspect, when the inside of the vacuum box is evacuated and the pressing force and heat are applied by the hot pressing device, the vacuum packing is compressed in the vertical direction so that the work and the cover plate are separated. Contact and the pressing force and heat are conducted to the work through the vacuum box,
The flexible printed wiring board and the reinforcing plate can be reliably thermocompression bonded. Therefore, it is suitable for use in the reinforcing plate laminating method according to the first aspect, and the effects of the present invention can be sufficiently exhibited.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a method for laminating a reinforcing plate of a flexible printed wiring board according to the present invention.

FIG. 2 is a perspective view showing a vacuum box used in this embodiment.

FIG. 3 is a diagram showing a relationship between dimensions of the vacuum box and a work.

FIG. 4 is a view showing a vacuum press device used in a conventional reinforcing plate bonding method.

[Explanation of symbols]

8 ... Flexible printed wiring board, 9 ... Reinforcing board, 11 ...
Work, 12 ... vacuum box, 13 ... hot press machine,
14 ... Box body, 15 ... Lid plate, 16 ... Exhaust pipe, 17
... Side plate, 18 ... Bottom plate, 19 ... Vacuum packing, 21 ... Lower mold (holding plate), 23 ... Upper mold (holding plate)

Claims (2)

[Claims] 1. A work (11) having a flexible printed wiring board (8) and a reinforcing plate (9) mounted between a pair of pressing plates (21, 23) is prepared, and a low-pressure environment is applied to the work. In a method for laminating a flexible printed wiring board and a reinforcing board, wherein the flexible printed wiring board and the reinforcing board are thermocompression-bonded to each other by hot pressing below, a hermetic state is maintained when the inside is evacuated. The work is stored inside a vacuum box (12) having thermal conductivity, which is relatively movable in a direction in which the lid plate (15) and the bottom plate (18) approach each other, and then the vacuum box. Is installed in a hot press machine (13), the inside of the machine is evacuated, and pressing force and heat are applied through the vacuum box so that the work piece is thermocompression bonded. Reinforcing plate bonding method of the flexible printed wiring board, characterized in that the. 2. A vacuum box (1) used in the method for laminating a reinforcing board of a flexible printed wiring board according to claim 1.
2) which is a side plate (1) to which a vacuum packing (19) is attached at the upper end and an exhaust pipe (16) for evacuating the inside is connected.
7) and a bottom plate (18) and a box body (14) and a lid plate (15), and the height from the lower end to the upper end of the side plate is smaller than the thickness of the work (11), A vacuum box characterized in that a height from a lower end of the side plate to an upper end of the vacuum packing is larger than a thickness of the work.