JP3293655B2 - Manufacturing method of prepreg - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a prepreg used as a bonding sheet in manufacturing a printed circuit board.

[0002]

2. Description of the Related Art A prepreg used as a bonding sheet in the manufacture of a printed circuit board is formed by coating a glass cloth as a base material with a thermosetting epoxy resin or the like. As the density of the printed circuit board increases, the printed circuit board is required to have improved reliability.

In recent years, there has been a tendency to reduce the pressure at the time of molding in order to reduce variations in the thickness of printed circuit boards. For example, a press apparatus for molding at a pressure of 10 kgf / cm ² or less such as an autoclave system has been used. I have. Further, as the circuit pattern becomes finer, a copper foil as a conductor has been used from a conventional thickness of 18 to 70 μm to a thinner foil of 5 to 12 μm.

[0004]

In implementing the above-described conductor configuration using low-pressure molding and thin foil, wrinkles and dents occur during molding. These problems can be solved to some extent by using a cushion at the time of molding or by making the mold plate for pressing the product at the time of molding a mirror finish, but the dent at the time of molding based on the convex portion of the prepreg surface in contact with the copper foil. Can not be solved.

[0005] The convex portion of the prepreg is caused by fuzzing of the glass cloth base material, fraying of the glass fiber, or jumping out of the glass thread at the time of coating on the prepreg; In some cases, this is caused by the resin adhering to the surface, which can be reduced by improving the coating technique, but cannot be eliminated at all.

The present invention has been made based on the above circumstances, and provides a method of manufacturing a prepreg capable of smoothing the surface of the prepreg.

[0007]

Means for Solving the Problems The method for the prepreg production present invention, impregnating the <br/> thermosetting resin made of epoxy resin or polyimide resin to a glass cloth substrate, dried, made by semi-cured prepreg The method for producing
The reduction after the step ends, by heating a first step of crushing the convex portion of the surface of the prepreg continuously by applying a pressure by the front surface of the smooth roll to the whole prepreg, followed this with no pressure And a second step of smoothing the crushed portion.

[0008]

In the method for producing a prepreg of the present invention having the above-mentioned structure, the convex portion on the surface is crushed by the first step.
By the second step, the crushed portion, the crack portion and the whitened portion in the vicinity thereof are smoothed, and a prepreg having a smooth surface is obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a glass cloth substrate impregnated and cured with a thermosetting resin such as an epoxy resin or a polyimide resin. Based on the finding that by heating to a temperature equal to or higher than the melting point, the convex portions of the prepreg can be eliminated.

That is, in the method for producing a prepreg according to the present invention, a metal roll having a smooth surface or a material whose surface is coated with Teflon to prevent powder adhesion is used. The method for producing a prepreg according to the present invention is characterized in that a glass base material impregnated with a thermosetting resin is solidified by the above-mentioned rolls at 2 kgf / cm ^{2 to} 50 kgf / cm ² , preferably 3 kgf / cm ² .
/ Cm ^{2 to 5} kgf / cm ² , and a first step of crushing the projections on the surface of the prepreg,
The protrusions crushed by the step and the surrounding cracks and whitened portions are at or above the melting point of the prepreg, that is, 80 ° C. to 10 ° C.
A second step of heating and melting to about 0 ° C. to return the surface to a smooth state.

The prepreg obtained by the above-mentioned manufacturing method has a smooth surface without any convex portions on its surface. Therefore, when a printed board is manufactured using this as a bonding sheet, the thin foil is used as a conductor. In the manufacture of a printed circuit board by low-pressure molding, generation of wrinkles and dents on the product surface is prevented.

As the resin to be impregnated and cured, any resin can be used as long as it is generally used for a printed circuit board, and the resin is not limited to the above examples. Further, the substrate is not limited to the glass cloth described above, and any substrate suitable for a printed circuit board configuration can be used.

Hereinafter, the present invention will be described in detail with reference to examples.

(Example 1) (1) FR-4 was applied to a continuous glass cloth having a thickness of 180 μm.
Impregnated with epoxy thermosetting resin for drying and dried
A prepreg of 0% and 25% in a JIS resin flow test was obtained.

(2) A pressure of 3 kgf / cm ² was uniformly applied to the continuous prepreg sheet obtained as described above using a pair of stainless steel rolls having a diameter of 100 mm.

(3) The prepreg sheet subjected to the above pressure treatment was heated to the melting point or higher by radiant heat, and immediately passed through a cooling roll to be cooled.

(4) Eight prepregs obtained as described above are laminated, mirror plates are abutted on both sides of the laminate via 18 μm copper foil, and 170 ° C. is applied by an autoclave-type press. Vacuum forming was performed under the conditions of (forming temperature) × 90 minutes and 9 kgf / cm ² (forming pressure) × 120 minutes.

(Embodiment 2) In the above embodiment 1, (4)
The copper foil in the step (2) was 12 μm thick. The other conditions are the same as in the above embodiment.

Example 3 The molding pressure in the step (4) of Example 1 was 6 kgf / cm ² . The other conditions are the same as in the above embodiment.

For comparison with the above embodiment, the following comparative example 1
To 3 to produce a printed circuit board.

(Comparative Example 1) In Example 1, (2)
The printed circuit board was manufactured under the same conditions except that the step (3) was omitted.

Comparative Example 2 In the above Example 2, (2)
The printed circuit board was manufactured under the same conditions except that the step (3) was omitted.

(Comparative Example 3) In Example 3, (2)
The printed circuit board was manufactured under the same conditions except that the step (3) was omitted.

The following table shows the evaluation of the printed circuit board obtained by each of the above examples and the evaluation of the printed circuit board obtained by each of the comparative examples.

[0025]

[Table 1] As is clear from the above, if a printed board is manufactured using the prepreg obtained by the manufacturing method of the present invention as a bonding sheet, a thin foil is used as a conductor, and even when low-pressure molding is performed, there is no dent on the surface and A product without wrinkles can be obtained.

FIG. 1 is a schematic view of a manufacturing apparatus for carrying out the present invention. In this figure, a glass cloth 2 pulled out from a glass cloth roll 1 passes through a guide roll 4 in an epoxy resin tank 3, and after being coated with an epoxy resin, proceeds into a drying tower 5 and moves to an upper guide roll. 6
And passes through the drying tower 5, during which the epoxy resin is dried to form a prepreg 2a.
Next, the prepreg 2 a is turned in the horizontal direction by a guide roll 7 provided below the drying tower 5.

The horizontal portion of the prepreg 2a is provided with a pressure roll 8 and a cooling roll 9 at a certain interval.
Is provided between the rolls, a far-infrared furnace 10
Is provided. The prepreg 2 a that has passed through the far-infrared furnace 10 is wound around a prepreg roll 11.

In the manufacturing apparatus having the above structure, the step (2) is carried out by the pressure roll 8, and the far-infrared
Then, the above-mentioned step (3) is performed by the cooling roll 9. The manufacturing apparatus shown in FIG. 1 performs coating, drying, and stress removal as a series of continuous operations.
As shown in FIG. 2 in which the same portions as those in FIG. 1 are denoted by the same reference numerals, the prepreg 2 a is cut into required dimensions when it leaves the drying tower 5, and the cut prepreg 2 a is cut by a pressure roll 8 and a cooling roll 9. The heating by the far-infrared ray furnace 10 and the cooling by the cooling roll 9 may be performed while sending while nipping. In addition,
In FIG. 2, reference numeral 12 denotes the cutter for cutting, and reference numeral 13 denotes a product loading table.

[0029]

As is apparent from the above, according to the prepreg manufacturing method of the present invention, it is possible to obtain a prepreg having an extremely smooth surface. Even when low-pressure molding is performed, there is no possibility that dents or wrinkles will occur on the product surface, so that a printed circuit board with a fine circuit pattern can be manufactured with high productivity.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of an apparatus for implementing the present invention.

FIG. 2 is a schematic view of another example of an apparatus for implementing the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass cloth roll, 2 ... Glass cloth, 2a ... Prepreg, 3 ... Epoxy resin tank, 4, 6, 7 ... Guide roll, 5 ... Drying tower, 8 ... Pressure roll, 9 ... Cooling roll,
10: Far infrared furnace, 12: Loading table, 13: Cutter.

Claims (1)

(57) [Claims] From 1. A epoxy resin or a polyimide resin
Impregnating the composed thermosetting resin into a glass cloth substrate, dried, in the manufacturing method of a prepreg made by semi-curing, the following curing step ends, continuously applying pressure by the surface of the smooth roll to the whole prepreg A first step of crushing the convex portion of the prepreg surface, and a second step of heating the prepreg under no pressure to smooth the crushed portion.