JPH01147896A - Manufacture of multilayer printed circuit board - Google Patents

Abstract

PURPOSE:To separate the void liable to remain on the laminated surface in order to secure the plate thickness accuracy of a molding by laminating an inner layer plate, to which a copper foil is stuck, a copper foil or a copper- pasted laminated layer plate on the peripheral part and between circuit units through prepreg. CONSTITUTION:Four pieces of the same circuit units 1 are arranged on an inner layer plate 5, while circular copper foils having a diameter of 5mm are stuck between the units 1 and 2 as well as on the peripheral part 3. Epoxy resin prepreg 6 and a copper foil 7 of 18mum are piled up and down the inner layer plate 5 for being molded with heat and pressure. Even when a copper- plated laminated plate, wherein the copper foil is laminated on a glass epoxy resin substrate, is used in place of the copper foil 7, a multilayer plate being excellent in the plate thickness accuracy and having no remaining void can be obtained. Thereby, the void liable to remain on the lamination surface is removed so that the plate thickness accuracy of the molding can be secured.

Description

[Detailed description of the invention] Technical fields> The present invention relates to a method for manufacturing multilayer printed circuit boards.

<Prior Art> Conventionally, a multilayer printed circuit board was manufactured by laminating an inner layer board on which a circuit was formed and a copper-clad laminate or copper foil via Gripreg, forming a circuit on the outer layer, and providing through-hole holes.

The inner layer board has one circuit or multiple circuit units, but in the latter case, voids cannot be removed from the prepreg and laminated surfaces, dents occur between circuit units, and board thickness accuracy cannot be ensured. Furthermore, in cases where copper foil of 15 to 30 μm is laminated, wrinkles may appear on the copper foil, and the adhesion of protective films such as dry films may be incomplete, causing poor circuit formation, resulting in product defects. Ta.

<Purpose of the Invention> The present invention has been made to solve such problems, and has excellent board thickness accuracy without leaving voids between laminated layers, and also improves adhesion of dry film that causes wrinkles in copper foil when copper foil is used. It is an object of the present invention to provide a method for manufacturing a multilayer printed circuit board in which defects are avoided during the formation of outer layer circuits due to the completeness of the process.

<Disclosure of the Invention> The gist of the present invention is as described above, and will be explained in detail below. FIG. 1 shows an inner layer board according to an embodiment of the present invention, in which four identical circuit units (1) are arranged, and between the circuit units (2) and on the outer periphery (3) are circular Copper foil piece (
4) is attached.

Epoxy resin prepreg (6) and 18μ copper foil (7) were layered on top and bottom of the inner layer plate (5) as described in Example 1 and hot-press molded, resulting in high quality products as shown in Table 1. A multilayer board was obtained.

Furthermore, even when a copper-clad laminate in which copper foil is laminated on a glass epoxy substrate is used instead of copper foil, a multilayer board with excellent board thickness accuracy and no residual voids can be obtained.

The size of the copper foil pieces placed between and around the circuit units of the inner layer board is preferably 30 scale or less, and the gap between them is 0.
．． 5 to 6 m is desirable. If the copper foil piece is too large, material loss will be large, and if the gap is too large, it will cause dents and voids to remain. The shape of the copper foil piece can be circular or other shapes.

Next, an explanation will be given according to an example.

Example 1 Four circuit units (1) are formed on a glass epoxy base material, and an inner layer in which circular copper foil pieces (4) with a K diameter of 5 mm are arranged between the circuit units (2) and in the surrounding area (3). Copper foil (7) was layered on top and bottom of the plate (5) with epoxy resin prepreg (6) interposed therebetween, and hot pressure molded to form the multilayer plate of Example 1.

Comparative Examples 1 and 2 A multilayer board (2) of Comparative Example 1 was molded in the same manner as in Example 1, using an inner layer board used in Example 1 in which circular copper foils were not arranged between circuit units. A multilayer board C of Comparative Example 2 was molded in the same manner as in Example 1 using an inner layer board in which no circular steel foil was placed between and around the six circuit units.

The quality of the multilayer boards of Example 1 and Comparative Examples 1 and 2 is shown in Table-1.
In general, the multilayer board of Example 1 has extremely high quality.

Table 1: Copper foil appearance measured with a 2-micrometer plate thickness/sheath index:
Check for the presence or absence of wrinkles ○No wrinkles Since the inner layer plate is arranged with the inner layer plate provided, the voids remaining on the laminated surface can be easily removed and the remaining voids can be avoided. Furthermore, since no dents occur between the circuit units, the thickness accuracy of the molded product is ensured.

In particular, even in the case where a thin, wrinkled copper foil of 15 to 35 μm is layered on top of the prepreg, wrinkles in the copper foil around the edges and between circuit units can be avoided, and when forming the outer layer circuit, it is possible to prevent the copper foil from being laminated. It has good adhesion with protective films such as dry films, and circuits can be formed accurately, resulting in remarkable effects such as avoiding product defects.

[Brief explanation of the drawing]

Figure 1 is a plan view of the inner layer plate (5) according to the present invention, and Figure 2 is a prepreg (6) and copper foil (7) above and below the inner layer plate (5).
It is a state diagram in which are arranged. 1...Circuit unit 2...Between circuit units 3.
...Outer periphery 4...Copper foil piece 5...Inner layer plate
6... Prepreg 7... Copper foil patent applicant Aikanigyo Co., Ltd.

Claims (1)

[Claims] (1) A plurality of circuit units are separated by circuit units, and an inner layer plate with copper foil pieces attached to the outer periphery and between the circuit units and a copper foil or copper-clad laminate are laminated via prepreg. A method for producing a multilayer printed circuit board characterized by: