JPH0395233A - Manufacture of prepreg - Google Patents

Abstract

PURPOSE:To improve the infiltration of resin into a fabric to thereby efficiently obtain a prepreg of a reinforcing fabric by a technique wherein impregnating rolls in an impregnating tank containing a resin varnish for prepreg are ultrasonically vibrated so as to impart an ultrasonic vibration to a reinforcing fabric in contact therewith. CONSTITUTION:A method for the manufacture of a prepreg by introducing a reinforcing fabric (e.g. glass fiber fabric) into an impregnating tank containing a resin varnish (e.g. epoxy resin varnish) for prepreg, passing it through impregnating rolls provided in the tank and removing it from the tank to thereby accomplish the impregnation of the reinforcing fabric with the resin varnish, wherein the impregnating rolls are ultrasonically vibrated so as to impart an ultrasonic vibration to the reinforcing fabric in contact therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a reinforcing fabric, Bripreg, used in composite materials such as laminates.

[Conventional technology]

Laminated boards used as substrates for printed wiring boards for computers and electronic devices are generally made by impregnating textiles with resin, drying it, and removing the solvent to create B-stage Bripreg. It is obtained by stacking a plurality of sheets of this prepreg and hot-pressing or shaping the prepreg using a pressurizing or shaping machine.

In producing this prepreg, the reinforcing fabric is passed through a resin varnish to impregnate the fabric with the resin varnish. Impregnation methods include immersing the fabric in resin varnish, squeezing it with a pair of rolls while immersed in the resin solution, and impregnating the fabric with resin varnish from one side using a kiss roll. After drying, the resin varnish that has adhered excessively is squeezed to a predetermined thickness using a pair of rolls, etc., and then introduced into a drying chamber to remove the solvent. However, in the prepreg manufactured by these methods, the air bubbles do not escape from the warp and weft yarns constituting the fabric, and the prepreg is converted to the B stage with air bubbles generated inside the prepreg. Air bubbles generated in the warp and weft cannot be completely filled with the 8-stage resin during molding, and tend to remain as air bubbles in the laminate, adversely affecting performance such as water resistance, heat resistance, electrical properties, etc. This tends to lead to a decrease in the reliability of the board.

In addition, despite such problems, in the recent field of laminates, especially in the printed circuit board industry, the density and multilayering of circuits has progressed, and the performance of conventional printed circuit boards is not sufficient to meet the demands for higher density. It's getting harder to do. For example, as circuits become thinner and more dense, substrates with better surface smoothness are required, and with the advancement of surface mounting devices, the diameter of through-holes has become smaller, improving hole position accuracy. Substrates with good hole inner wall roughness are now required. The same applies to heat resistance.

[Problems to be Solved by the Invention] In order to obtain a laminate with fewer air bubbles as described above and to meet the increasingly sophisticated requirements for laminates, it is necessary to improve the impregnation of the reinforcing fabric with respect to the matrix resin. becomes. In addition, there was a limit to increasing the production speed of Bripreg due to restrictions on inclusion properties.

[Means for Solving the Problems] In order to solve the above problems, the inventors of the present invention have conducted extensive studies, and have developed the following.
When the reinforcing fabric is immersed in the resin varnish to impregnate it with the resin varnish, by directly applying ultrasonic vibration to the reinforcing fabric, the impregnability of the resin varnish and, ultimately, the impregnability of the matrix resin can be greatly improved. This can be improved, and as a means of applying ultrasonic vibration directly to the glass cloth, if the impregnating roll itself placed in the impregnation bath to guide the reinforcing fabric is ultrasonically vibrated, the reinforcing fabric can be We have discovered that it is possible to apply ultrasonic vibration without causing misalignment, etc., and have arrived at the present invention.

That is, in the present invention, a reinforcing fabric is introduced into an impregnation tank containing a resin varnish mixture, and the reinforcing fabric is removed from the impregnation tank through an impregnation roll provided in the impregnation tank, thereby reinforcing the resin varnish mixture. The gist of the present invention is a method for manufacturing a prepreg for reinforcing fabric, characterized in that the impregnating roll is ultrasonically vibrated and the reinforcing fabric in contact with the impregnating roll is subjected to ultrasonic vibration.

The present invention will be explained in detail below. Examples of reinforcing fabrics to which the present invention is applied include inorganic fiber fabrics such as glass fiber fabrics and carbon fiber fabrics, and organic fiber fabrics such as aramid fiber fabrics, but glass fiber fabrics are generally used. Therefore, the case of glass fiber fabric will be explained as an example.

The glass fiber fabric impregnated with a resin varnish according to the present invention is woven using a glass thread made by bundling a large number of glass filaments, and after removing the binding agent, the glass fiber fabric is surface-treated. It is. In addition, in the case of a glass fiber fabric made of glass yarn using a sizing agent that contains a surface treatment agent in the sizing agent and does not require deoiling, it can be used even if it is just woven. The glass component of the glass thread constituting the glass fiber fabric is not particularly limited, and includes, for example, E glass, C glass, etc. S glass etc. is optional. The fiber diameter of the glass filament is also arbitrary as long as the glass cloth can be woven. The thickness of the glass fiber fabric may range from 50 .mu.m to 400 .mu.m, but preferably 100 .mu.m or more. As the weave structure, ordinary weave structures such as plain weave, twill weave, and satin weave can be used, but hand weaving is preferable.

The impregnation tank used in the present invention contains a resin varnish preparation, and is used to immerse the glass fiber fabric in the preparation to impregnate the glass fiber fabric with the preparation. The type of resin varnish used here is not particularly limited as long as it is suitable as a matrix resin for the laminate.

An impregnation hole is provided in the impregnation chamber to guide the fiberglass fabric through the resin varnish preparation.

Figure 1 shows an example of an impregnating tank used in the present invention.
An impregnating bath 1 contains a resin varnish mixture 2, and an impregnating roll 3 is provided so as to be located within the mixture, and the glass fiber fabric 4 is immersed in the mixture. Also,
A guide roll 5, a squeezing roll 6, etc. are arranged above the impregnating tank 1. The impregnation roll 3 is driven by a drive device (not shown) to rotate in the direction of the arrow. In this way, the glass fiber fabric 4 is introduced into the blending liquid 2 after passing through the guide roll 5, and is separated from the blending liquid after passing through the impregnating roll 3. The liquid impregnates the glass fiber fabric. Here, it goes without saying that the length of immersion of the glass fiber fabric 4 in the liquid mixture is set to a length necessary to impregnate the glass fiber fabric 4 with the liquid mixture. An impregnated roll 3 may also be used. The contact angle θ of the glass fiber fabric with respect to the impregnation roll 3 is not particularly limited, but as will be described later, it affects the vibration time when the impregnation roll 3 ultrasonically vibrates the glass fiber fabric. , larger is preferable.

In the present invention, the impregnating roll 3 provided in the impregnating '#al
An ultrasonic vibrator is attached to at least one of the impregnating rolls (when a plurality of impregnating rolls are used), and the impregnating roll 30 is configured to vibrate ultrasonically. Although FIGS. 2 and 3 show an example of a structure for ultrasonic vibration of the impregnation roll, the present invention is not limited thereto.

In FIGS. 2 and 3, the impregnation roll 3 has a plurality of vibrators 9 attached to a roll body 8 made of stainless steel, for example, so that the surface thereof is flush with the outer peripheral surface of the roll body 8. , a connection cord 10 to the vibrator 9 is passed through the roll body 8, and a slip ring 11 and a brush 12 are connected from the shaft end.
It is connected to an ultrasonic oscillator and a power source (not shown) via a power source. Thus, by causing the vibrator 9 to vibrate ultrasonically using the ultrasonic oscillator, the impregnation roll 3 is vibrated ultrasonically. Note that instead of exposing the ultrasonic vibrator 9 on the surface of the impregnating roll 3, the roll body of the impregnating roll is formed into a cylindrical shape with a diameter of 17.
, the ultrasonic transducer 9 may be attached to the inner surface thereof.

[Function] In FIG. 1, the glass fiber fabric 4 is introduced into the impregnating tank 1 containing the preparation liquid 2 after passing through the guide roll 5, and is brought into contact with the impregnating roll 3, and is kept at a constant level with respect to the impregnating roll 3. After contacting at a contact angle θ, the liquid is removed from the impregnating tank 1, and after being squeezed with a squeezing roll 6, it is dried in a dryer (not shown). Here, the impregnation roll 3 rotates in synchronization with the traveling speed of the glass fiber fabric 4, and conveys the glass fiber fabric 4 without rubbing it.

This prevents the glass fiber fabric 4 from being misaligned, fuzzing, and the like.

As this impregnating roll 3 rotates, the impregnating roll itself vibrates ultrasonically, and the glass fiber fabric 4 that comes into contact with it receives a stronger impregnating action than that of a normal impregnating roll. In addition, by contacting the impregnated roll 3 which is undergoing ultrasonic vibration in the blended liquid, the warp yarns constituting the glass fiber fabric 4 are The weft threads are subjected to opening action.

This interlacing action is not only caused by ultrasonic vibration, but also by contacting the impregnated roll for a certain period of time, the blended liquid that has entered the inside of the thread is forced out of the thread by ultrasonic waves, and a new blend is created instead. The liquid enters the inside of the thread and is squeezed out again. This action is repeated while the glass fiber fabric is in contact with the impregnation roll. As a result, the filament bundles constituting the yarn come apart and become spread. Due to the opening action of the thread and the strong impregnating action, the resin varnish mixture can penetrate uniformly and quickly into the thread.

In the present invention, the frequency of the ultrasonic vibrations generated by the impregnating roll is usually selected in the range of 10 kHz to 60 kHz, preferably in the range of 20 to 40 kHz.

At frequencies lower than 10 kllz, the opening effect is small, and 6
If the frequency is higher than 0 kHz, adverse effects such as misalignment will occur on the glass fiber fabric. Further, the output of the oscillator is preferably in the range of 150 to 3000 watts.

The glass fiber fabric that has been impregnated and opened by the impregnating roll leaves the impregnating roll, passes through the mixing stage, leaves the impregnating tank, and is introduced into the squeezing roll 6, where the squeezing ratio is maintained at a nearly constant level. The liquid is squeezed out so that it is. The glass fiber fabric with a constant drawing rate enters a drying process, is dried at a constant temperature, is B-staged, and is wound or cut into a constant size.

In the glass fiber fabric prepreg produced in this manner, the warp and weft threads are impregnated with matrix resin, and the filaments inside the threads are also sufficiently coated with matrix resin. Further, the warp and weft yarns constituting the fabric are in an open state.

It is generally said that the bubbles remaining in the laminate are caused by the matrix resin not being impregnated into the inside of the thread. In the case of glass fiber fabrics, the warp and weft that make up the fabric are made up of several hundred monofilaments bundled together as threads, as described above, and the warp and weft intersect vertically to form the fabric. Therefore, it is not easy to completely impregnate the inside of the thread with resin varnish.

In the case of the present invention, since the matrix resin is impregnated into the inside of the thread, there are no air bubbles that occur due to non-impregnation.
This results in a laminate with fewer bubbles.

In addition, the laminate using the prepreg of the present invention has the advantage that the matrix resin has well penetrated into the inside of the glass fiber fabric, so the pressing effect is easily exerted, and the threads constituting the glass fiber fabric can be easily exerted. By opening the fibers and making them flat, the surface smoothness of the laminate is improved. Furthermore, since the uniformity of the glass fiber and resin is increased, drilling performance is improved, and hole position accuracy and hole inner wall roughness of a small-diameter drill are improved. Furthermore, since the adhesion of the matrix resin to the glass fiber surface becomes uniform, the interfacial adhesion between the matrix resin and the glass fiber surface becomes stronger, and the number of air bubbles is reduced, which improves the mechanical strength and heat resistance of the laminate. Improved.

Furthermore, by greatly improving the inclusion property, the prepreg manufacturing speed can be increased as necessary.

Example C] Surface-treated glass fiber fabric [manufactured by Nitto Boseki, VEA
l8W-1322 (thickness: 180 μs, unit weight: 2
10g/rr? , plain weave, surface treatment agent Nippon Unicar Oki Co., Ltd., 8-187)] was passed through an impregnating tank containing an epoxy resin varnish preparation (FR-4) under constant tension. The impregnation roll is made of stainless steel (outer diameter 250 + 1111) and has an ultrasonic vibrator [made by Shinmeidai Kogyo ■, Ultrasonic Vibrator US] inside.
12DOX FTI] was installed at 3 locations along the length of the roll, and 8 vibrators were attached to each location on the inner circumference of the roll. The wiring drawn out from each vibrator is guided to the end of the roll through a tube installed inside the roll, and then connected to an ultrasonic oscillator [manufactured by Shinmeidai Kogyo ■, ultrasonic oscillator UO] installed outside the roll via a brush.
1200FX]. Ultrasonic frequency is 2
The oscillator output is 1200 watts at 6 kHz.

The glass fiber fabric impregnated with the liquid mixture in the impregnation tank is squeezed with a squeezing roll and dried at a drying temperature of 130°C. The resin content of Bripreg was 44%.

8 m layers of this prepreg were layered, and 18 μm copper foil was layered on top and bottom of the prepreg to a thickness of t. An 8+sm copper foil-clad laminate was created. Pressing conditions are all surface pressure 50 dazzle/ctl 70℃
Using the obtained laminate, surface smoothness, inclusion property, hole inner wall roughness, and soldering heat resistance were measured. Etched copper foil is used for surface smoothness and solder heat resistance. The results are shown in Table 1.

[Comparative Example] A prepreg was produced under the same conditions as in the example except that the same glass fiber fabric as in the example was used and the impregnation treatment conditions were that an ordinary roll without an ultrasonic vibrator was used as the impregnation roll. A laminate corresponding to the example was made using this prepreg, and the same items as in the example were measured. The results are shown in Table 1.

Table 1 (Note 1) Observe the state of bubble formation in the Bripreg using a microscope.

(Note 2) The copper foil of the sample laminate was removed and PCT treatment (P
CT conditions (133°C) were performed under various conditions. After that, the soldering heat resistance was tested (soldering heat resistance test, 260°C, immersion for 20 seconds). At this time, the longest PCT treatment time without deterioration of solder heat resistance was determined.

(Note 3) Using Mityo Surf Test (■ Made by Mityo) (Note 4) Drilling a 1.6+++m thick laminate to 8.00
[]h1t, and then observed the roughness of the inner wall of the hole drilled using a microscope.

As is clear from Table 1, the laminate using the prepreg obtained in this example has superior properties compared to the comparative example in terms of inclusion property, surface smoothness, hole inner wall roughness, and soldering heat resistance. had.

[Effects of the Invention] In the prepreg manufacturing method of the present invention, a reinforcing fabric is immersed in a resin varnish formulation using an impregnating roll provided in the resin varnish formulation, and when impregnating the reinforcing fabric with the resin varnish, the reinforcing fabric is impregnated with the resin varnish. Since the impregnating roll itself that comes into contact with the fabric is vibrated ultrasonically, the reinforcing fabric is vibrated ultrasonically, which opens the warp and weft yarns that make up the fabric, and at the same time spreads the resin varnish mixture onto the warp and weft yarns. It penetrates well into the weft and adheres to the outer surface of each filament that makes up the warp and weft. In the reinforcing fabric thus obtained, the warp and weft yarns constituting the fabric are satisfactorily impregnated with the resin varnish, and are opened.

The Bripreg obtained by the present invention has good impregnation of the matrix resin into the reinforcing fabric during the production of the laminate, and therefore, the generation of air bubbles in the laminate is small, and the matrix resin and the reinforcing fiber are The interfacial adhesion strength with the surface is high, and therefore the surface smoothness, drilling properties, and heat resistance of the obtained laminate can be improved. Furthermore, it is also possible to increase the production speed of Bripreg.

[Brief explanation of drawings]

Fig. 1 is a schematic side view showing one example of an impregnating tank used in the method of the present invention, and Fig. 2 is a schematic side view showing one example of an impregnating roll used in the method of the present invention.
A schematic sectional view of the example taken perpendicular to the axis, and FIG. 3 a sectional view taken parallel to the axis of the impregnating roll. 1... Impregnation tank, 2... Resin varnish mixture, 3...
Impregnation roll, 4... Glass fiber fabric, 5... Guide roll, 6... Squeezing roll, 8... Roll body, 9...
... Vibrator, 10... Connection cord, 11... Slip ring, 12... Brush, 13... Squeeze knife.

Claims (1)

[Claims] The reinforcing fabric is introduced into an impregnation tank containing resin varnish for prepreg, and the reinforcing fabric is impregnated with the resin varnish by passing through an impregnation roll provided in the impregnation tank and leaving the impregnation tank. A method for producing a reinforcing fabric prepreg, characterized in that the impregnated roll is subjected to ultrasonic vibration to impart ultrasonic vibrations to the reinforcing fabric that comes into contact with the impregnated roll.