JPH05343846A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To avoid the uneveness in the solder paste amount on a surface packaging pad for diminishing the package defects in components by a method wherein the dent in a surface via hole in the title printed wiring board wherein the surface via hole is arranged on the position of the packaging pad is to be eliminated. CONSTITUTION:A through hole 7a is bored in a copper coated laminated board 1 to be inner layer plated 2 for the formation of a surface via hole 3, furthermore, inner layer boards formed of inner layer circuits 4 holding a prepreg 5 are laminated to be heated for fusing a resin which is pressurized later to run out of the surface via hole 3 and after finishing the lamination, outer layer surface is polished to be flatteded.

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 printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board which is suitable for surface mounting of components.

[0002]

2. Description of the Related Art Conventionally, in a multilayer printed wiring board, electrical connection between wiring layers is made by through holes. Further, in order to increase the density of wiring, there is also an example in which surface via holes that electrically connect the outermost layer and the inner layer thereunder are used instead of through holes penetrating the front and back.

On the other hand, in recent years, the method of mounting components on a printed wiring board has been rapidly switched from the insertion method to the surface mounting direction. As a result, the function of the through hole is changed from the function of inserting the lead of the component to the function of electrical connection between the wiring layers. Therefore, in order to further improve the wiring density, a method of arranging the surface mounting pads on the surface via holes is drawing attention.

[0004]

In the method of manufacturing a printed wiring board in which a surface via hole is formed in a copper-clad laminate and a surface mounting pad is arranged on the surface via hole by the conventional technique, the process diagram of FIG. As shown in a) to (c), a through hole 3a is opened in the copper clad laminate 1, an inner layer plating 2 is applied to form a surface via hole 3, and an inner layer circuit 4 is formed by an exposure technique or the like to form an inner layer plate. To create. This inner layer board is attached to the prepreg 5 as shown in FIG.
And heat and pressurize at the same time. At this time, since the resin is pressed while the resin is not sufficiently melted, the surface via hole 3 may not be sufficiently filled with the resin as shown in FIGS. 5 (e) and 5 (f).
Even after the outer layer plating 6 is applied as shown in (g) and the outer layer circuit 8a is formed as shown in FIG. 6 (h), the mounting pad 8b is also formed.
There was a problem that a hollow 9 was formed.

The occurrence of the depression causes troubles such as non-uniformity of the amount of the solder paste when mounting the component, for example, when printing the solder paste on the pad. In particular, LS
The lead pitch of packages such as I tends to become narrower, and the pad width also becomes narrower, and making the pad surface uniform has become an important issue. Incidentally, when the surface via hole is not arranged under the surface mounting pad, there is no particular problem even if the depression is generated.

[0006]

According to the method of manufacturing a printed wiring board of the present invention, when the internal wiring layers are laminated, the resin is caused to flow out from the through hole of the inner layer serving as the surface via hole to the external wiring layer side to form the depression. Is buried, and after laminating, the outer surface of the package is polished to obtain a flattened mounting pad surface.

Therefore, unlike the conventional method, the resin filling into the surface via hole portion does not become insufficient,
In addition, since excess spilled resin can be removed by polishing, it is possible to form an extremely flat pad without forming recesses on the mounting pads formed on the surface via holes after plating the outer layer and forming the outer layer circuit. Become.

[0008]

The present invention will be described below with reference to the drawings. 1, FIG. 2, and FIG. 3 are views for explaining one embodiment of the present invention, and FIGS. 1 (a) to 1 (c), 2 (d) to (f), and FIG.
(G), (h) is sectional drawing which shows a manufacturing process. A hole 3a for a through hole is formed in a portion of the copper-clad laminate 1 where the mounting pad is located (FIG. 1 (a)).
Surface via-holes 3 are formed by applying inner layer plating 2 to the substrate (FIG. 1 (b)). The inner layer circuit 4 is formed only on the inner layer on the copper-clad laminate 1 in which the surface via holes 3 are formed (FIG. 1C). A copper clad laminate (inner layer plate) on which the inner layer circuit 4 is formed is laminated with the prepreg 5 interposed therebetween (FIG. 2 (d)). By laminating the inner layer plate and the prepreg 5, the resin is filled in the surface via holes 3 and the resin flows out to the surface of the laminated plate (FIG. 2 (e)).

Here, the prepreg 5 has the same amount of resin as the conventional one, and first, the prepreg 5 in the cured state (B stage) is sandwiched between the inner layer plates and is heated to 130.degree. After that, the resin of the prepreg 5 is in a molten state (A
Stage), 35-40 by vacuum press
Pressurize at atmospheric pressure. At this time, it is more effective to use a prepreg with a large amount of resin and set the laminating conditions such as heating and pressurization so that the resin flow increases, and perform laminating.

After the completion of the lamination, the resin which has flown out to the surface of the substrate is polished and removed together with the upper layer portion of the inner layer plating 2 by a belt sander device to be flattened, and subsequently, outer layer through holes for mounting components and for conducting the front and back are formed. Through hole 7
Open a (Fig. 2 (f)). An outer layer through hole 7 is formed by applying outer layer plating 6 to this (FIG. 3).
(G). Thereafter, the surface mounting pad 8b is formed on the surface via hole 3 formed according to FIGS. It should be noted that ordinary exposure technology, etching technology and the like are used in the circuit formation and the like of this embodiment.

[0011]

As described above, according to the present invention, even if the surface mounting pad is arranged on the surface via hole, the pad surface can be finished flat, so that the non-uniformity of the amount of solder paste can be eliminated. As a result, it is possible to reduce defects when mounting lead components with a narrow pitch.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention, in which FIG.
(C) is each sectional drawing which shows a manufacturing process.

2 (d) to (f) are cross-sectional views showing the manufacturing process subsequent to FIG.

3 (g) and 3 (h) are cross-sectional views showing the manufacturing process following FIG.

FIG. 4 is a diagram for explaining a conventional manufacturing method, which is shown in FIG.
(C) is each sectional drawing which shows a manufacturing process.

5 (d) to 5 (f) are cross-sectional views showing the manufacturing process following FIG.

6 (g) and 6 (h) are cross-sectional views showing the manufacturing process following FIG.

[Explanation of symbols]

 1 Copper-clad laminate 2 Inner layer plating 3 Surface via hole 3a Through hole 4 Inner layer circuit 5 Prepreg 6 Outer layer plating 7 Outer layer through hole 7a Through hole 8a Outer layer circuit 8b Mounting pad 9 Recess

[Procedure amendment]

[Submission date] March 23, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Here, the prepreg 5 has the same amount of resin as the conventional one, and first, the prepreg 5 in a semi-cured state is laminated by an inner layer plate vertically and heated to 130.degree. Then, after the resin of the prepreg 5 is in a re-melted state, it is pressurized with a vacuum press machine at 35 to 40 atmospheres. At this time, it is more effective to use a prepreg with a large amount of resin and set the laminating conditions such as heating and pressurization so that the resin flow increases, and perform laminating.

Claims (2)

[Claims] 1. A method of manufacturing a printed wiring board in which a surface mounting pad is formed on a surface via hole that electrically connects a surface layer and an inner layer, and a pair of inner layer boards in which circuits are previously formed only on the surface via hole and the inner layer surface. Is laminated with the inner layer circuit forming surface inside through a prepreg, and the resin of the prepreg is melted by heating, and then the molten resin is flown out to the outer layer surface side through a surface via hole, and after completion of lamination, the outer layer surface A method for manufacturing a printed wiring board, which comprises a step of polishing. 2. The method of manufacturing a printed wiring board according to claim 1, wherein when the outer layer surface is polished, the outflowing resin is removed by polishing while leaving a lower layer portion of the inner layer plating applied to the outer layer surface.