JPH0787271B2 - Method for manufacturing multilayer printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a multilayer printed wiring board, and in particular,
The present invention relates to a manufacturing method capable of improving plate thickness accuracy and suppressing generation of voids as much as possible.

<< Prior Art >> What is shown in FIG. 3 is a multilayer printed wiring board which is used as a wiring board of an industrial electronic device such as a computer and an automatic control circuit and in which four conductor layers are laminated.

In order to manufacture the above-mentioned multilayer printed wiring board, a double-sided copper clad laminate for inner layer (hereinafter referred to as an inner layer circuit board) 1 having circuit pattern portions 4 formed on the upper and lower surfaces is provided, and the inner layer circuit board 1
A copper foil or a glass cloth base material single-sided copper clad laminate for forming the conductor layer 3 for the outer layer is placed via the adhesive prepreg 2 such as a glass base prepreg, and the copper foil is placed outside so as to be laminated. Then, a multilayer printed wiring board is manufactured by heating and pressing with a laminating press.

That is, in manufacturing a multilayer printed wiring board, a resin impregnated in the prepreg 2 is used as an adhesive. In this case, the resin (epoxy resin or the like) is used as a base material such as glass cloth or paper. It is impregnated as the resin of the stage, and therefore becomes a viscous liquid by heating and is transferred to the resin of the C stage which is hardened by heat and solidified with time.

Therefore, in the laminating press, if the time from the start of heating to the start of pressurization is early, pressure will be applied when the viscosity of the resin is low, and therefore a large amount of resin will flow out in the lateral direction. In addition, there is a problem that the multilayer printed wiring board becomes thinner than a predetermined board thickness, and the board thickness accuracy is lowered.

Also, when the time from the start of heating to the start of pressurization is slow, the resin has a high viscosity, so the amount of resin that flows out due to pressurization is small, but the fluidity of the resin is low, so air bubbles are trapped inside. There is a problem that voids are generated and reliability is reduced.

Conventionally, in order to solve such a problem, as shown in FIG. 5, in an inner layer circuit board 1 on which a necessary circuit pattern portion 4 is formed, a copper foil is cut around the circuit pattern portion 4 in a constant width. To form a frame groove 5, and the frame groove 5 divides the circuit pattern portion 4 and the residual copper portion 6 provided on the outer periphery of the inner layer circuit board 1. The copper foil of the copper portion 6 is cut vertically and horizontally in a width of 10 to 15 mm to communicate with the air vent groove 7, and the inner layer circuit board 1 thus formed is connected to the outer layer conductor layer via the prepreg 2. A method for manufacturing a multilayer printed wiring board in which 3 is laminated and heated and pressed by a laminating press has been carried out.

<< Problems to be Solved by the Invention >> That is, in the method for manufacturing a multilayer printed wiring board as described above, bubbles generated in the resin at the time of heating and pressurizing may be discharged to the outside of the air vent groove through the frame groove. Therefore, the void point, which has been pointed out as a conventional problem, is improved.

However, if the width of the air vent groove is too wide,
A large amount of resin is embedded in the air vent groove, which reduces the thickness of the air vent groove, resulting in a drawback that the accuracy of the thickness is reduced.

Further, when the groove width of the air vent groove is too narrow, the amount of resin embedded in the air vent groove is small, the plate thickness of the air vent groove portion is not thin and the plate thickness accuracy does not decrease, but
Voids are likely to occur and the meaning of providing the air vent groove is lost.

That is, at the time of stacking press, air bubbles in the resin are satisfactorily removed from the air vent groove through the frame groove around the circuit pattern portion,
In order to prevent the generation of voids, the width of the air vent groove must be set wide. On the other hand, in order to keep the resin filling amount in both grooves small and prevent the plate thickness accuracy from being lowered, the groove width must be set narrow. Thus, there was a trade-off between trying to solve the relationship between the void and the plate thickness at the same time.

An object of the present invention is to provide a highly reliable method for producing a multilayer printed wiring board by forming a copper clad laminate for a multilayer printed wiring board, which is excellent in both the void surface and the board thickness accuracy surface.

<< Means for Solving the Problem >> The present invention provides a method for manufacturing a multilayer printed wiring board in which multiple layers are integrally bonded by heating and pressurization, around the circuit pattern portion 11 of the conductor layer forming the inner layer circuit, A frame groove 12 for partitioning the circuit pattern portion 11 and a residual copper portion 13 formed on the outer periphery of the inner layer circuit board is formed, and air vent grooves 14 are communicated with the corner portions of the frame groove 12 in the vertical and horizontal directions. In addition, an inner layer circuit board in which the groove width of the frame groove 12 is set to be wider by 1 to 2 mm outside the cut line 15 and the groove width of the air vent groove 14 is set to be 2 to 3 mm is provided through an insulating prepreg. It is characterized in that it is heated and pressed to integrally bond multiple layers.

<< Description of Embodiments >> Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a plan view of an inner layer circuit board used in the present invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and this inner layer circuit board 10 is as shown in FIG. Copper foils 10B and 10B are provided on the upper and lower surfaces of a prepreg 10A obtained by impregnating a reinforcing material such as a glass base material or a paper base material with a resin such as an epoxy resin or a polyimide. It is configured as a double-sided copper-clad laminate in which a necessary circuit pattern portion 11 is formed by etching on a portion.

Further, a frame groove 12 is formed around the circuit pattern portion 11 of the inner layer circuit board 10, and the circuit pattern portion is formed by the frame groove 12.
11 and other copper foil forming the outer periphery of the inner layer circuit board 10, that is, while partitioning the residual copper portion 13, in the corner portion of the frame groove 12, the copper foil of the residual copper portion 13 vertically with a constant width. An air vent groove 14 formed by cutting in the lateral direction is communicated.

Therefore, in the present invention, the width of the air vent groove 14 is set to 2 to 3 mm, and the width of the frame groove 12 is set to the planned cut line 15 of the multilayer printed wiring board.
Is formed to have a width 1 of 1 to 2 mm on the outside.

The prepreg is the same as the conventional one, and is a bonding prepreg in which a glass base material is impregnated with an epoxy resin. As shown in FIG. 3, the upper and lower surfaces of the prepreg 2 further have a copper foil on one side of the glass cloth base material 3A. A single-sided copper clad laminate made by laminating 3B,
It is provided as the conductor layer 3 for the outer layer.

Further, reference holes 9 as shown in FIG. 4 are respectively provided at the corners of the inner layer circuit board 10, the prepreg 2, and the conductor layer 3 for the outer layer, and as shown in FIG. A guide pin is inserted into the positioning pin 9 to position and stack it at a predetermined position, and is laminated and bonded as is well known by heating and pressurizing by a laminating press.
A multilayer printed wiring board is formed by cutting along the line 15.

That is, at the time of heating and pressing by the above-mentioned laminating press, the impregnating resin of the prepreg 2 is filled with the frame groove 12 of the inner layer circuit board 10,
The conductor layer 3 for the outer layer is laminated and integrated on the upper surface of the flow through the air vent groove 14.

<< Effects >> As described above, in the present invention, the resin flow path formed on the inner layer circuit board 10 has the frame groove 12 around the circuit pattern portion 11.
But 1 to 2 mm more than the cut line 15 of the multilayer printed wiring board
Since it is formed to have a large width of 1, the residual copper rate of the residual copper portion 13 on the outer periphery of the inner layer circuit board 10 can be set high, and the amount of resin embedded in the frame groove 12 can be suppressed to be small. .

Further, since the air vent groove 14 which is vertically and laterally communicated with the corner portion of the frame groove 12 is set to have a groove width of 2 to 3 mm, it is a minimum groove capable of favorably discharging bubbles in the resin. The width of the resin impregnated in the prepreg 2 can be less embedded in the air vent groove 14, so that the generation of voids can be suppressed and the thickness of the air vent groove 14 can be reduced. Can be prevented from becoming thin, and a multilayer printed wiring board excellent in both the void surface and the board thickness accuracy surface can be manufactured.

By the way, the inventor of the present application forms the width of the frame groove 12 outside the cut line 15 with a width 1 of 1 to 2 mm by the manufacturing method as described above, and sets the width of the air vent groove 14 as follows. The test was done. The results are shown in the table.

As is clear from the above experimental results, the air vent groove 14
When the width is less than 1 mm, the resin is less outflowed, so that a predetermined plate thickness can be maintained, but a void is generated. Further, when the groove width is 4 mm or more, the outflow amount of the resin increases, so that the generation of voids can be suppressed, but a wiring board having a predetermined board thickness cannot be obtained.

As a result of the experiment, when the groove width was set to 2 to 3 mm, a void was not generated and a multilayer printed wiring board excellent in plate thickness accuracy could be obtained.

[Brief description of drawings]

FIG. 1 is a plan view showing an inner layer circuit board according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is an explanatory sectional view showing a laminated state of a multilayer printed wiring board at a laminating press. FIGS. 4 and 5 are perspective views showing a state of the multilayer printed wiring board before being cut, and FIG.
The figure is a plan view showing a conventional inner layer circuit board. 10 ... Inner layer circuit board 11 ... Circuit pattern part 12 ... Frame groove 13 ... Remaining copper part 14 ... Air vent groove 15 ... Cut line

Claims (1)

[Claims] 1. A frame groove is formed around a circuit pattern portion of a conductor layer forming an inner layer circuit to partition the circuit pattern portion and a residual copper portion formed on the outer periphery of the inner layer circuit board, and
An air vent groove is connected to the corner portion of the frame groove in the vertical and horizontal directions, and the groove width of the frame groove is set to 1 outside the cut line.
The multilayer printed wiring is characterized in that the inner layer circuit board whose air vent groove width is set to 2 mm to 2 mm is integrally widened by heating and pressing through an insulating adhesive prepreg. Method of manufacturing a plate.