JPH0795627B2 - Structure of multi-layer printed circuit board with metal plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding the structure of a multilayer printed circuit board containing a metal plate, at least one circuit wiring layer is provided for the purpose of preventing cracks from occurring in clearance holes of the metal plate during lamination. In a multi-layer printed circuit board containing a metal plate having a large number of clearance holes, for stacking pressure distribution formed around the clearance holes before stacking, at a place where the distribution density of the clearance holes is low. The dummy hole is provided.

[Industrial application field]

The present invention relates to a structure of a multilayer printed circuit board containing a metal plate.

[Conventional technology]

In recent years, with the progress of semiconductor technology, the integration density of circuit elements on a printed circuit board has been rapidly increased. Moreover, it is necessary to increase the capacity of the power supply at the same time that the circuit elements are highly integrated. Under such a background, for example, as shown in FIG. 4, at least one layer (here, two layers) of circuit wiring layers for power supply or ground is, for example, 0.1 mm to 0.4 mm.
A multilayer printed circuit board 11 containing a metal plate, which is composed of a metal plate 12 rolled to a certain degree, for example, a copper plate, has been put to practical use. On the metal plate 12, a clearance hole 14 having a diameter larger than that of the through hole 13 is formed at a position to be insulated from the through hole 13, and then the circuit board is laminated with another circuit wiring layer to be pressure-bonded by heating and pressing. . Then, after that, the through holes 13 are drilled and the through holes are plated at predetermined positions in order.

[Problems to be Solved by the Invention]

By the way, the clearance holes 14 are not evenly distributed over the entire surface of the metal plate 12.
As shown in the figure, a portion of the metal plate 12 (in this case, the central portion) is densely distributed, and another portion (in this case, the peripheral portion).
Then it is opened so as to be roughly distributed. Therefore, the pressing force acting on the prepreg composition resin 15 when laminated and pressure-bonded is dispersed in a large number of clearance holes 14 at locations where the clearance holes 14 are densely distributed, whereas the distribution of the clearance holes 14 is In the roughened area, it concentrates in a small number of clearance holes 14 and gives a relatively large internal strain to the prepreg composition resin that expands by heating, and when cooled, the prepreg composition resin 15 in the clearance hole 14
As a result of the contraction, cracks 16 reaching the inner peripheral surface of the clearance hole 14 may be generated as shown in FIG. When this crack 16 occurs, the plating solution penetrates into the crack 16 when performing through-hole plating later,
There is a disadvantage that the through-hole plating layer 17 and the metal plate 12 are short-circuited.

The present invention has been made in consideration of the above circumstances,
It is an object of the present invention to provide a structure of a multi-layer printed circuit board containing a metal plate, which is capable of preventing the occurrence of cracks generated in clearance holes of the metal plate during lamination.

[Means for Solving the Problems]

The structure of a multilayer printed circuit board containing a metal plate according to the present invention is premised on a multilayer printed circuit board containing a metal plate in which at least one circuit wiring layer is composed of a metal plate having a large number of clearance holes. In order to achieve the above purpose, the following measures are taken.

That is, as shown in FIG. 1, the metal plate 2 is provided with a dummy hole 4 for pressure distribution formed around the clearance hole 3 before stacking at a location where the distribution density of the clearance hole 3 is low.

[Action]

In this way, when the dummy holes 4 are formed around the clearance holes 3, the pressure force that acts on the prepreg composition resin during lamination pressure bonding is dispersed into the clearance holes 3 and the dummy holes 4, and inside the clearance holes 3 and the dummy holes 4. It is possible to suppress the internal strain of the prepreg composition resin that has been press-fitted to a certain level or less, and cracks occur in the prepreg composition resin in the clearance hole 3 and the dummy hole 4 when the prepreg composition resin is cooled after completion of pressurization. Can be prevented.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a metal plate used for a multilayer printed circuit board containing a metal plate according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view schematically showing a cross section of a main part of the multilayer printed circuit board. is there.

As shown in FIG. 2, in this multilayer printed circuit board 1 containing a metal plate, two layers of metal plates 2 are stacked, and a large number of clearance holes 3 are opened in the metal plate 2 before stacking. As shown in FIG. 1, the clearance holes 3 are formed so as to be densely distributed in the central portion of the metal plate 2 and roughly distributed in the peripheral portion, and many clearance holes 3 are formed around the clearance hole 3 in the peripheral portion. Dummy holes 4 are formed. The number and size of the dummy holes 4 are not particularly limited, but it is preferable that the aperture ratio of the dummy hole 4 and the portion surrounded by the clearance hole 3 is the same as the aperture ratio of the central portion. Therefore, the dummy holes 4 can be formed to have the same diameter as the clearance holes 3, but here, the dummy holes 4 have a diameter smaller than that of the clearance holes 3 so that the dummy holes 4 are distributed as evenly as possible around the clearance holes 3. Many dummy holes 4 are opened.

When laminating and pressing the metal plate 2 with another circuit wiring layer,
At the same time, heating is performed, and the softened prepreg composition resin 5 is pressed into the clearance holes 3 and the dummy holes 4. In the peripheral portion, the stacking pressure acting on the prepreg composition resin 5 is dispersed between the resin in the clearance hole 3 and the resin in the dummy hole 4, so that it acts on the prepreg composition resin 5 in the clearance hole 3 and the dummy hole 4. The pressure can be suppressed below a certain level, and the internal strain of the prepreg composition resin 5 in the clearance hole 3 and the dummy hole 4 can be reduced below a certain level. After the prepreg composition resin 5 is thermoset, the pressing and heating are stopped, and the prepreg composition resin 5 in the clearance hole 3 and the dummy hole 4 begins to shrink. Here, since the internal strain of the prepreg composition resin 5 in the clearance hole 3 and the dummy hole 4 is reduced below a certain level,
The prepreg composition resin 5 shrinks without cracks in the prepreg composition resin 5 in the clearance holes 3 and the dummy holes 4.

When an insulation test was performed on the multilayer printed circuit board 1 containing a metal plate, the metal plate 2 was completely insulated,
Further, when the cross section was observed, no crack was confirmed.

〔The invention's effect〕

As described above, according to the present invention, since the metal plate is provided with the dummy hole for stacking pressure distribution formed before stacking around the clearance hole at the place where the distribution density of the clearance holes is low, the prepreg during stacking and pressure bonding. The pressure acting on the resin composition is dispersed and applied to the clearance holes and dummy holes to reduce the internal strain generated in the prepreg composition resin in the clearance holes and dummy holes to below a certain level. It is possible to prevent cracks from being generated when the prepreg composition resin in the hole contracts. as a result,
The occurrence of a short circuit between the through-hole plating layer and the metal plate can be prevented, the incidence of defective products can be reduced, and the reliability of the product can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a metal plate used in a multilayer printed circuit board containing a metal plate according to an embodiment of the present invention, FIG. 2 is a sectional view of the multilayer printed circuit board containing a metal plate, and FIG. FIG. 4 is a plan view of a metal plate used in a conventional multilayer printed circuit board containing a metal plate, and FIG. 4 is a sectional view of a conventional multilayer printed circuit board containing a metal plate. In the figure, 1 ... multilayer printed circuit board with metal plate, 2 ... metal plate, 3 ... clearance hole, 4 ... dummy hole.

Claims (1)

[Claims] 1. A multilayer printed circuit board (1) containing a metal plate, wherein at least one circuit wiring layer is composed of a metal plate (2) having a large number of clearance holes (3) formed therein, wherein the metal plate (2) is A dummy hole (4) for stacking pressure distribution formed around the clearance hole (3) before stacking at a location where the distribution density of the clearance hole (3) is low.
A structure of a multi-layer printed circuit board containing a metal plate, comprising: