JPH069315B2 - Multilayer printed circuit board and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed board and a manufacturing method thereof, and more particularly to a multilayer printed board having a high wiring density and a large number of laminated layers, and a manufacturing method suitable therefor.

[Conventional technology]

A conventional method for manufacturing a multilayer printed board is disclosed in JP-A-56-30.
As described in Japanese Patent Publication No. 797, a wiring pattern of copper foil is formed on the surface of a base material for a multilayer printed board, and at the same time, a copper foil is left in a frame shape on the outer periphery, and one or more strips are formed on the frame-shaped copper foil. A method for manufacturing a multilayer printed board is characterized in that blank portions are provided and the positions of the blank portions on the front and back surfaces of the base material are alternately arranged so as not to overlap each other.

Further, Japanese Patent Application Laid-Open No. 58-157192 discloses a method for producing a printed wiring board in which a copper foil having a pattern of a linear shape or a partly cutout is left in the peripheral portion.

Further, Japanese Patent Application Laid-Open No. 61-189688 discloses a printed circuit board in which a copper foil portion is provided in a frame shape in a portion other than the circuit wiring portion.

[Problems to be solved by the invention]

In the above-mentioned conventional technology, a portion of the multilayer printed board substrate provided with a copper foil wiring pattern on the surface and a portion provided with a plurality of peripheral frame-shaped copper foil lines on the surface of the entire substrate including the copper foil pattern. No consideration has been given to making the elastic coefficient and linear expansion coefficient close to each other.When a plurality of base materials are stacked with a prepreg sandwiched between them, heat shrinkage occurs when they are heated and pressed to bond, and deformation due to curing shrinkage of the prepreg resin is caused. There were different problems depending on the location.

It is an object of the present invention to provide a multilayer printed board and a method for manufacturing the same in which the above deformation can be made uniform at each place and can be applied in a wide wiring density region.

[Means for solving problems]

Briefly describing the present invention, the first invention of the present invention relates to a multilayer printed board, which is a multilayer in which a plurality of printed board substrates made of an insulating board to which a copper foil having a wiring pattern is adhered is laminated. In the printed board, a bent pattern made of one or more thin copper wires is provided on each side around the wiring pattern portion of the printed board base material.

A second invention of the present invention relates to a method for producing the multilayer printed board of the first invention, which is a printed board substrate having a wiring pattern formed on a copper foil bonded to at least one surface of an insulating board. In the method for producing a multilayer printed board by stacking a plurality of sheets with a prepreg sheet interposed therebetween, and then heating and pressurizing the same, in any process of producing the printed board substrate, a wiring pattern part of the printed board substrate It is characterized in that a bending pattern made of one or more thin copper wires is provided on each side of the periphery of.

The purpose of bringing the internal copper foil wiring pattern forming portion and the peripheral copper foil remaining portion of the peripheral portion of the base material for a multilayer printed board close to the elastic coefficient and the linear expansion coefficient is to bend the thin copper wire pattern provided in the peripheral portion. It is achieved by

The insulating plate for the multilayer printed board is a glass cloth impregnated with epoxy resin, polyimide resin, etc. and cured, and the longitudinal elastic modulus in the case where the copper foil is not adhered to the surface,
The linear expansion coefficient is 1000-2000 kgf / mm ² ,
It is 1.5 to 2.0 × 10 ^-5 ° C ^-1 . On the other hand, the longitudinal elastic modulus and linear expansion coefficient of copper foil are 9000 to 11000 kg, respectively.
It is f / mm ² , 1.7 × 10 ^-5 ° C ^-1 , and the longitudinal elastic modulus of the copper foil is more than 5 times higher than that of the insulating plate. Further, the thickness of the copper foil bonded to the insulating plate is 35 to 70 μm, and the thickness of the insulating plate is 1
It is around 00 μm. For this reason, the elastic modulus of the printed board base material changes greatly depending on the presence or absence of the copper foil. The longitudinal elastic modulus E _a when the copper foil and the insulating plate are integrated together can be expressed by the following equation (1).

Where E _{f is} the longitudinal elastic modulus of the insulating plate E _{c is} the longitudinal modulus of the copper foil t _{f is} the thickness of the insulating plate t _{c is} the thickness of the copper foil. 35
The average longitudinal elastic modulus E _a of the whole printed board substrate having a copper foil of μm adhered to it is E _f = 1000 kgf / mm ² , E _c = 10
Assuming that 000 kgf / mm ² , from Eq. (1), E _a = 4706 kgf / m
m ^2, and becomes four times or more the value of the copper foil is not insulating plate. Therefore, when laminating multiple layers with a prepreg sandwiched on the base material and performing pressure bonding, the flow rate of the resin at the time of pressurization and the deformation amount of the base material due to the curing shrinkage of the resin are different in the elastic coefficient depending on the presence or absence of the copper foil. Will change significantly. In particular, if this high elastic modulus portion is present in the peripheral portion of the printed board base material, the center portion of each side of the base material is deformed to bend inward due to the curing shrinkage of the resin, and the strain distribution at each location of the base material is It will be very different.

Therefore, the present invention, in order to solve this problem, by bending the wire of the copper foil formed in the peripheral portion of the base material into a shape such as a sine wave, a triangular wave, a trapezoidal wave, a rectangular wave or a combination thereof, The rigidity of the outer peripheral portion of the substrate in the side direction is reduced. This reduction in rigidity is manifested by the following mechanism. The tensile rigidity of the copper foil in the side direction when the linear pattern of the copper foil is linearly formed in the side direction is the product of the elastic modulus, the thickness and the width, but the line of the copper foil is bent. In this case, the curved beam becomes rigid and the width of the copper wire is 1mm.
When the bending cycle is about 10mm, the rigidity of the copper wire in the side direction is 1 /
It can be reduced to 50 or less. For this reason, the rigidity of the outer peripheral portion of the substrate and the rigidity of the internal wiring pattern forming portion can be made equal, and the strain generated at the time of laminating and bonding can be made uniform at each place.

The method of providing the peripheral pattern of the copper wire on the outer periphery in the present invention can be performed simultaneously with the formation of the internal wiring pattern, as in the conventional method. However, the peripheral pattern may be formed before or after the wiring pattern is formed, or the separately formed one may be fixed.

Further, the peripheral pattern may be formed by a plurality of copper wires arranged in parallel.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these examples.

Embodiment 1 One embodiment of the present invention will be described with reference to FIGS.

That is, FIG. 1 is a top view of a printed board base material according to one embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA 'of FIG. 1, and FIG. 3 is a prepreg of the printed board shown in FIG. It is a block diagram which shows arrangement | positioning of each material at the time of carrying out multilayer lamination using a sheet. In each drawing, reference numeral 1 is a peripheral copper wire, 2 is a copper foil wiring, 3 is an insulating plate, 4 is a guide hole, 5 is a printed board base material, 6 is a prepreg sheet, 7 is a jig plate, and 8 is a guide pin. means.

Two prepreg sheets impregnated with epoxy resin on glass cloth, 35 μm thick copper foil on the front and back, heated, pressed and bonded, M with a finished thickness of 170 μm
Make CL, then attach a resist film on the surface of each copper foil,
The peripheral pattern and the wiring pattern shown in FIG. 1 and FIG. 2 are exposed, the unnecessary portion of the copper foil is etched, and the peripheral copper wire 1 and the copper foil wiring 2 are formed on the insulating plate 3. The base material 5 was obtained. A guide hole 4 is formed in the printed board base material 5, and a guide pin is passed through when a plurality of printed board base materials are stacked and adhered to prevent misalignment between layers. The printed board base material 5 thus obtained and the prepreg sheet 6 in which glass cloth is impregnated with epoxy resin are alternately laminated by passing the guide pins 8 standing on the jig board 7 as shown in FIG. Finally, after applying the above jig plate, it was put between hot plates of a press, heated and pressed to cure the prepreg sheet 6, and each printed board substrate was adhered to obtain a multilayer printed board. The bending angle of the peripheral copper foil 1 adopted here with respect to the outer periphery of the multi-layered lint plate was ± 45 °. The width of the peripheral copper wire 1 is 10 mm and the repeating pitch is 80 mm. The deformation situation of the multilayer printed board obtained in this way was evaluated by the amount of deviation from the straight line at the three points B, C and D in FIG. It was confirmed that it was reduced by 40% compared with the case of using.

Example 2 Another embodiment of the present invention will be described with reference to FIG.

That is, FIG. 4 is a top view of a 1/4 part of the printed board base material of one embodiment of the present invention, and reference numerals 1 to 4 are synonymous with FIG.

In the embodiment shown in FIG. 4, the peripheral copper wire 1 has a sinusoidal bend. The width of the peripheral copper wire 1 is 10 mm,
The repeated pitch was 80 mm, and it was confirmed that the amount of deviation from the straight line on the long side was further reduced by 5% as compared with the embodiment of FIG.

Example 3 Another embodiment of the present invention will be described with reference to FIGS.

That is, FIG. 5 shows a printed circuit board substrate according to an embodiment of the present invention.
FIG. 6 is a top view of the 1/4 portion and FIG. 6 is a cross-sectional view taken along the line EE ′ of FIG. 5, and reference numerals 1 to 4 have the same meanings as in FIG.

In the embodiment shown in FIG. 5, the bending angle of the peripheral copper wire 1 with respect to the outer edge of the multilayer printed board is ± 45 ° as in the embodiment of FIG. It was done.
By halving the width of the copper wire, the rigidity of the copper wire portion in the side direction can be reduced to 1/4. In this embodiment, the deformation amount (deviation amount from the straight line) of each side is shown in FIG. 1 more than in the case of
It was confirmed that the number was relatively low.

〔The invention's effect〕

As described above, according to the present invention, the curing shrinkage of the prepreg sheet when laminating and bonding the printed board base material on which the printed circuit is formed using the prepreg sheet, the difference between the locations of the strain generation amount due to the temperature change. According to the present invention, 40% or more can be made uniform, so that the relative displacement between the laminated layers can be reduced. As a result, it is not necessary to increase the size of the pad provided with the through hole connecting between the layers by the amount of relative displacement, and accordingly, the wiring density of the printed circuit can be increased.

[Brief description of drawings]

FIG. 1 is a top view of a printed board substrate according to one embodiment of the present invention,
2 is a sectional view taken along the line AA 'in FIG. 1, and FIG. 3 is a configuration diagram showing the arrangement of each material when the printed board substrate shown in FIG. 1 is laminated in multiple layers using prepreg sheets, 4 and 5 are top views of the 1/4 part of the printed board base material of one embodiment of the present invention, and FIG. 6 is a sectional view taken along the line EE 'of FIG. 1: peripheral copper wire, 2: copper foil wiring, 3: insulating plate, 4: guide hole, 5: printed board base material, 6: prepreg sheet,
7: jig plate, 8: guide pin

Claims (4)

[Claims] 1. A multilayer printed board in which a plurality of printed board bases made of an insulating board to which a copper foil having a wiring pattern is adhered is laminated, and each side of the printed board base is surrounded by a wiring pattern part. A multilayer printed board, characterized in that a bent pattern made of one or more thin copper wires is provided. 2. The multilayer printed board according to claim 1, wherein the pattern made of the copper wire is a bent pattern made of a sine wave, a triangular wave, a trapezoidal wave, a rectangular wave, or a combination thereof. 3. The multilayer printed board according to claim 1 or 2, wherein the pattern of the copper wire is formed by a plurality of copper wires arranged in parallel. 4. A multilayer printed board is manufactured by stacking a plurality of printed board base materials each having a wiring pattern formed on a copper foil adhered to at least one surface of an insulating board, sandwiching a prepreg sheet therebetween, and then heating and pressurizing. In any one of the processes for producing the printed board base material, a method of providing a bent pattern made of one or more thin copper wires on each side around the wiring pattern portion of the printed board base material A method for manufacturing a multilayer printed board, characterized in that the method is performed.