JPH0255957B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] A copper foil layer is left over the entire surface of the signal layer of a multilayer printed board in the power supply area that does not require a circuit pattern, so that the thickness of the printed board is equalized. This prevents the printed board from warping and improves the reliability of insertion of connectors having press-fit pin type terminals, mounted components, etc.

[Industrial application field]

The present invention relates to multilayer printed boards, and in particular to improvements in layer structure.

With advances in semiconductor technology, power supplies for small electronic devices have been developed that can be mounted on printed circuit boards.

On the other hand, high-density mounting of components on multilayer printed circuit boards has led to faster signal transmission, smaller electronic devices, and lower costs. As a result, in addition to supplying a large current to the printed board, in order to suppress the voltage drop during transmission, one or more layers of the multilayer printed board are used as a layer dedicated to power supply, and one or more layers are used as a layer dedicated to grounding for the return path. There is.

The signal circuit section and the power supply section within the printed board are mounted in divided areas in order to prevent the circuit section from being affected by switching noise caused by the high frequency of the power supply.

In addition, when an electronic unit is constructed from a large number of electronic circuit printed boards, a dedicated power supply mounting printed board is installed in order to supply power to these electronic circuit printed boards, and the power is supplied via a backboard printed board. do.

A common mounting method at this time is to separate the mounting area into a mounting area for a plurality of electronic circuit printed boards and a mounting area for a plurality of power supply mounting printed boards.

In addition, recent connectors or mounted components do not require soldering and insertion of terminals into through holes.
By using a press fit pin type that can be connected and fixed simply by pushing it into a through hole, we are promoting cost reductions in electronic devices.

FIG. 2 is a cross-sectional view of the electronic unit as described above, in which the box-shaped housing 1 with one side open has an area D on the side wall where the power supply mounting printed boards 4 are arranged in parallel;
It is divided into an area S in which electronic circuit printed boards 3 are arranged in parallel in the center.

Furthermore, multilayer backboard printed boards 2A and 2B of the same shape are attached to the bottom of the housing 1, and an electronic circuit printed board 3 is attached to each of the board-side connectors arranged on the inner surfaces of the backboard printed boards 2A and 2B. , and a power supply mounting printed board 4 are respectively inserted therein.

That is, to the electronic circuit printed board 3 parallel to area S, through-hole printed board 2A,
Alternatively, the configuration is such that power is supplied through the 2B power supply layer.

At this time, the backboard printed boards, electronic circuit printed boards, power supply mounting printed boards, etc. should not be warped so that mounted components do not come into contact with adjacent printed boards and can be inserted and installed smoothly into the housing. is required.

[Conventional technology]

Figure 3 is a cross-sectional view of an example of a multilayer printed board;
The figure is a configuration diagram of a conventional example of a backboard printed board.

Backboard printed boards 2A, 2 shown in FIG.
As shown in Fig. 4, B has signal layers L1, L2, L4, L5, L7, and L8 with a rectangular power supply area 11 on one side edge and a circuit area 10 on the other side, and a copper foil F over the entire surface. The ground layer L3 includes a ground layer L3, and a power layer L6. Note that the ground layer L3 is provided between the signal layer L2 and the signal layer L4, and the power layer L6 is provided between the signal layer L5 and the signal layer L7.

The signal layer L1 is formed by applying copper foil to the surface of the base material and etching the copper foil F as desired.The signal layer L1 has a signal pattern whose running direction is parallel to the Y axis and a through hole as desired in the circuit area 10. 8 is formed. Further, in the power supply area 11, only the through holes 8 are arranged in parallel, and no pattern is formed therein. That is, the copper foil is etched away and does not remain.

In the signal layer L2, which is the next layer, a signal pattern whose running direction is parallel to the X-axis is formed in the circuit area 10, and through holes 8 are formed as desired. The shape of the power supply area 11 is the same as that of the power supply area 11 of the signal layer L1.

A signal layer L4 is formed on the back surface of the base material of the ground layer L3, and a power layer L6 is formed on the back surface of the base material of the signal layer L5.
is formed. In addition, the signal layer L5, the signal layer L
8 has the same shape as the signal layer L2, and the signal layer L4 and the signal layer L7 have the same shape as the signal layer L1.

In this way, the signal patterns in the Y-axis direction and the X-axis direction are alternately formed in each of the signal layers L1 to L8, thereby increasing the density of the signal patterns.
Further, it is configured to be connected to a connector equipped with a press-fit pin type terminal via a through hole 8.

The above-mentioned layers are adhered to each other via prepregs 7, and are integrated and layered as shown in FIG. 3.

In addition, the board thickness T of such a multilayer printed board is
It is known that the following formula is followed.

T=T ₁ +T ₂ ...Tn+0.1×Pn-α・C+2×Tp Here, T ₁ , T ₂ ...Tn Thickness of each layer including copper foil Pn Number of prepregs 7 C Total thickness of inner layer copper foil α (removal rate) Area percentage of the etched portion of the inner layer copper foil Tp Plating thickness of the outer layer From the above formula, the board thickness T of the multilayer printed board shown in Figure 3
When α is 100%...T=2.258mm When α is 0%...T=2.678mm, resulting in a maximum difference of 0.42mm.

[Problem that the invention seeks to solve]

However, the conventional multilayer printed board mentioned above has
Since the copper foil is removed from the power supply area 11 of each signal layer, the thickness of the power supply area 11 is thinner than the thickness of the other circuit area 10.

Therefore, if a connector having a press-fit pin type terminal or a mounting component is mounted in the power supply area 11, the contact area will not be secured due to the small elastic contact area, resulting in poor contact. There is a problem.

Furthermore, since the plate thicknesses are unequal, there is a problem in that warping is likely to occur due to heating during multi-layer manufacturing or heating during mounting of components.

[Means for solving problems]

In order to solve the above conventional problems, the present invention utilizes a multilayer backboard printed board in which each signal layer is divided into a circuit area 10 and a power supply area 11, as shown in FIG. In a multilayer printed board, leave the copper foil on the entire surface of the power supply area and connect it to the ground pattern 15 or power supply pattern 1.
6.

[Effect]

According to the means of the present invention, the copper foil remains on the entire surface of each power supply area 11 of the multilayered signal layer, so that the removal rate of the copper foil approaches the removal rate of the circuit area 10. ing. Therefore, the board thickness of the power supply area 11 and the board thickness of the circuit area 10 are almost equal.

Therefore, even if a connector or the like having a press-fit pin type terminal is mounted in the power supply area 11, the elastic contact area is large enough to ensure a sufficient contact area and there is no risk of contact failure. .

Furthermore, since the plate thickness is equal and the structure is symmetrical, warping is less likely to occur during multi-layer manufacturing or when mounting components. Furthermore, by strengthening the power supply and grounding patterns, it is possible to supply large currents with low voltage drops.

〔Example〕

The present invention will be specifically explained below with reference to illustrated examples. Note that the same reference numerals indicate the same objects throughout the figures.

FIG. 1 is a block diagram of one embodiment of the present invention, in which backboard printed boards 2A and 2B shown in FIG.
The pattern configuration of each layer is shown.

That is, the backboard printed board has signal layers L1,
L2, L4, L5, L7, and L8 are layered in this order, and a ground layer L3 is provided between the signal layer L2 and the signal layer L4, and a power layer L6 is provided between the signal layer L5 and the signal layer L7.

The ground layer L3 and the power layer L6 are formed into a desired solid pattern with copper foil left on the entire surface.

On the other hand, the signal layers L1, L2, L4, L7, L8,
is divided into a rectangular power supply area 11 and the remaining circuit area 10 on one side edge. In the power supply area 11, leave the copper foil over the entire surface,
A ground pattern 15 is formed.

In addition, the signal layer L on the opposite side of the base material of the power supply layer L6
In the power supply area 11 of No. 5, a power supply pattern 16 is formed by leaving the copper foil over the entire surface.

Also, on the periphery of the circuit area 10 of each signal layer, there is a ground pattern 1 of the power supply area 11.
5, or a frame-like pattern connected to the power supply pattern 16 is formed.

As described above, since the copper foil was left on the entire surface of the power supply area 11 to form a solid pattern, the removal rate of the copper foil in the power supply area 11 and the circuit area 10 is almost equal.

Therefore, it is possible to easily obtain a multilayer backboard printed board in which the thickness of the power supply area 11 and the circuit thickness of the circuit area 10 are almost equal.

Therefore, the backboard printed board is less likely to warp, and the insertion area for the connector having press-fit pin type terminals is secured, so that there is less risk of contact failure.

The present invention is not limited to a backboard printed board as shown in the illustrated example, but can be applied to a multilayer printed board in which power supply components are mounted in some sections and circuit components are mounted in the other section, and similar effects can be achieved. be.

〔Effect of the invention〕

As explained above, in the present invention, the removal rate of copper foil in each layer of a multilayer printed board is equal and evenly distributed, the thickness of each part of the multilayer printed board is equal, and the press fit pin When mounting connectors with type terminals or other components, the contact area is secured, there is no risk of contact failure, and warping is unlikely to occur during manufacturing or component mounting, and the current As the capacity increases, it has excellent practical effects, such as being able to supply large currents with low fluctuations.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a sectional view of an electronic unit, Fig. 3 is a sectional view of an example of a multilayer printed board, and Fig. 4 is a configuration of a conventional multilayer printed board. It is a diagram. In the figure, 1 is a housing, 2A and 2B are backboard printed boards, 3 is an electronic circuit printed board, 4 is a power supply mounting printed board, 7 is a prepreg, 8 is a through hole, 10 is a circuit area, and 11 is a power supply area , 15 is an earth pattern, 16 is a power supply pattern, L1, L2, L4, L5, L7, and L8 are signal layers, L3 is an earth layer, L6 is a power supply layer, and F is a copper foil.

Claims (1)

[Claims] 1. In a multilayer printed board in which each signal layer is divided into a circuit area 10 and a power supply area 11, copper foil is left on the entire surface of the power supply area 11, and a ground pattern 15 or A multilayer printed board structure characterized by providing a power supply pattern 16.