JPH0531816A - Laminated sheet - Google Patents

Abstract

PURPOSE:To obtain the above laminated sheet where a resin flow within prepreg becomes uniform, residual stress is made uniform and a warp is little, by a method wherein a metallic foil is superposed upon the outside of one circular prepreg or a plurality of the circular prepregs superposed upon each other and they are heated and pressurized. CONSTITUTION:Although a prepreg is heated and pressurized by making the same a circule, in case of a metallic foil plated laminated sheet, a metallic foil 1 is superposed upon one side or both the sides of the outside of a circular prepreg 2 and a laminated body is formed by heating and pressurizing them. Although even a form other than the circle may be good as the form of the metallic foil, it is preperable that the same is made into a size which can cover the whole of the prepreg and possesses a little margin further. Since the circular prepreg is used, the whole of distances from the center up to the circumference become identical to each other. Therefore, since resin of the prepreg in a semicured state flows uniformly radially toward the outside from the center at the time of heating and molding and residual stress does not become uneven, generation of a warp can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated board having less warpage.

[0002]

2. Description of the Related Art A metal foil-clad laminate is manufactured by stacking a predetermined number of prepregs, metal foils, in many cases copper foils, on one or both outer sides of the prepregs and heating and pressing. The prepreg is obtained by impregnating a long base material with a liquid resin and heating it to a semi-cured (called B stage) state. The shape is square because the semi-cured material is cut and provided to the user.
Copper foil is also cut into long materials according to the shape of the prepreg,
It is supplied to the pressing process.

If the metal foil-clad laminate used for manufacturing a printed wiring board has a warp, it becomes a great obstacle when mounting electronic functional parts after it is processed into a printed wiring board. Therefore, many proposals have been made regarding a technique for reducing the warpage of the laminated plate.

However, all of these proposals
It was concerned with the process of forming laminates. As an example, when the constituent materials are heated and pressed and then cooled to room temperature, the press is not opened but kept at a low pressure to reduce the warpage of the copper-clad laminate (JP-A-54-1252).
No. 67).

In addition, when a plurality of sets of prepreg constituents are inserted and arranged between a single-stage press heating platen for molding, a prepreg having a small resin flow is used for a set arranged near the press heating platen (Japanese Patent Laid-Open No. 59-59). -197194).

[0006]

The warp can be reduced by devising the molding process as described above.
Recently, the wiring density of printed wiring boards has been further increased, and the accuracy required for mounting electronic functional components has become stricter, and a laminated board with less warpage has been required.

The warpage of the laminated plate occurs because the residual stress of the molded body is not uniform. This will be described with reference to FIG.
When the prepreg is heated and pressed, the resin is first melted and flows radially from the center to the periphery. At this time, if the prepreg is rectangular, the distance between the center and the corner is longer than the distance between the center and the center of the side, so the resin flow from the center to the corner becomes slower than the flow from the center to the center of the side. A diffuse flow is generated from the direction from the center to the corners. The pressure distribution also differs between the center of the side and the corner. Due to such a cause, the residual stress in the corners becomes non-uniform.

[0008]

Such non-uniformity of stress can be eliminated by making the distance from the center to the periphery of the prepreg equal. That is, the present invention is characterized in that the prepreg is circular. Figure 1 for metal foil-clad laminates
As shown in (a), the metal foil 1 is superposed on one side or both sides of the circular prepreg 2 and heated and pressed. The shape of the metal foil may be circular or another shape, but at least the entire surface of the prepreg is covered and a size with some margin is provided. The laminated plate of the present invention is used after being cut into a predetermined shape after manufacturing. The present invention can be applied not only to laminated plates but also to manufacturing of multilayer plates.

[0009]

By using a circular prepreg, all distances from the center to the periphery become visible to humans. Therefore,
As shown in FIG. 1B, the resin of the prepreg in the semi-cured state flows radially outward from the center as shown in FIG. 1B, and the residual stress does not become uneven. Because of this, there is almost no warpage.

[0010]

EXAMPLE A liquid thermosetting epoxy resin having a thickness of 200 μm
m glass cloth impregnated and dried to semi-cured diameter 1
Eight pieces of 130 mm circular prepregs 1 were stacked, and circular copper foils 2 each having a thickness of 35 μm and a diameter of 1160 mm were stacked on both sides thereof. 200 sets of such structural bodies were prepared, and each structural body was sandwiched between end plates and pressed and heat-molded by a press to manufacture 200 circular copper-clad laminates. The average warpage of this laminate is 1
It was 2 mm.

Comparative Example Eight prepregs of the same quality as those of the above-described example were stacked except that the square was 1000 mm on a side, and 103 was on each side.
A copper foil having a thickness of 35 μm, which is the same quality as that of the above-described example, was stacked, except that it was a 0 mm square. Such a structure is
Two sets of square copper-clad laminates were manufactured by preparing a set, sandwiching each component with a mirror plate, and pressurizing and heating with a press. The warpage amount of this laminated plate was 23 mm on average.

[0012]

According to the present invention, the resin flow without prepreg is made uniform and the residual stress is made uniform, so that a laminated board with less warpage can be obtained.

[Brief description of drawings]

FIG. 1A is a perspective view of an embodiment of the present invention,
(B) is a plan view for explaining the resin flow.

FIG. 2 is a plan view for explaining a resin flow in a rectangular prepreg.

[Explanation of symbols]

1 prepreg 2 copper foil

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 1/03 K 7011-4E // B29K 105: 06 B29L 9:00 4F

Claims (2)

[Claims] 1. A laminated plate formed by stacking circular prepregs and heating and pressing the prepregs. 2. A laminated plate obtained by stacking one or a plurality of circular prepregs, stacking a metal foil on the outer side thereof, and heating and pressing.