JPH0376296A - Multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To prevent glass fiber from coming into contact with a circuit so as to protect a wiring board of this design against dielectric breakdown by a method wherein the wiring boards are jointed together as laminated through the intermediary of a base material provided with prepreg materials of prescribed thickness provided, at least, on its joining side. CONSTITUTION:Printed wiring boards 3 provided with a circuit on its upside and underside are jointed together as laminated through the intermediary of base material provided with prepreg materials 4 and 4' of 0.05-0.07mm in thickness on its joining side. For instance, three of two-layered printed wiring boards 3 and 8 provided with a core 1, 0.2mm in thickness on the upside and the underside and a core 5, 0.3mm in thickness at the middle point, where a circuit 2 is provided to the upsides and the undersides of the cores 1 and 5 respectively, are joined together as laminated through the intermediately of a base material 6 of epoxy resin provided with prepreg materials 4, 0.06mm in thickness (glass fiber diameter: 5mum, fiber count of a glass fiber bundle: 100) on an upper and a lower joining side and two prepreg materials 4', 0.1mm in thickness at the middle point to constitute a six-layered wiring board 7. Therefore, an epoxy resin is interposed between the circuit 2 and glass fiber, a CAF phenomenon is restrained from occurring, so that it takes a longer time until dielectric breakdown occurs in a multilayer printed wiring board.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to improvements in multilayer printed wiring boards.

(Prior Art) A conventional multilayer printed wiring board is made up of printed wiring boards having circuits on both the upper and lower surfaces, which are stacked and bonded via a base material of prepreg material (epoxy resin) with a thickness of 0.1 mm. .

(Problems to be Solved by the Invention) By the way, in the above-mentioned multilayer printed wiring board, one of the electrochemical migration phenomena in which ions move in the presence of moisture by applying a voltage between the circuits. Conductive Anodic
Because the filament growth phenomenon occurs along the glass fibers in the base material, dielectric breakdown occurs that causes a short circuit with an adjacent circuit.

Therefore, the present inventor focused on the fact that the above-mentioned dielectric breakdown occurs along the glass fibers, and moreover, the dielectric breakdown does not occur without increasing the thickness of the multilayer printed wiring board and without bringing the glass fibers and the circuit into contact. We have discovered a multilayer printed wiring board, and would like to provide it.

(Means for Solving the Problems) A multilayer printed wiring board of the present invention for solving the above problems has a printed wiring board having circuits on both upper and lower surfaces.
It is made by stacking and joining prepreg materials having a thickness of 5 to 0.07 mm through a base material arranged at least on the joining surface side.

(Function) The multilayer printed wiring board of the present invention configured as described above has the following features:
Between printed wiring boards with circuits on both sides, 0.05 to 0
．． Since there is a base material in which prepreg material with a thickness of 0.7 mm is arranged at least on the bonding surface side, the circuits in the inner layer of each printed wiring board are not in contact with the glass fibers. That is, 0.05~
The diameter of the glass fibers in the 0.07 mm thick prepreg material is 2μ smaller than that of the conventional 0.1 mm thick prepreg material, and the glass fiber cloth has fewer fibers than the conventional glass fiber cloth. Since it is woven into glass fiber bundles, the epoxy resin is sufficiently filled into the glass fibers, so that the circuits of each printed wiring board do not come into direct contact with the glass fibers. Therefore, the CAF phenomenon that occurs along the glass fibers is less likely to occur, and dielectric breakdown that causes a short circuit with an adjacent circuit is less likely to occur.

In addition, since prepreg materials with a thickness of 0.05 to 0.07 mm have a large amount of epoxy resin as a whole, the epoxy resin exists between the circuit and the glass fibers, suppressing the occurrence of the CAF phenomenon and leading to dielectric breakdown. It takes longer.

(Embodiment) An embodiment of the multilayer printed wiring board of the present invention will be described with reference to FIG. The two-layer printed wiring boards 3 and 8 are made of 0.06 mm thick prepreg material (glass fiber diameter: 5μ, glass fiber bundle Number of fibers: 100) 4 are placed on the upper and lower joining surfaces, and 3 sheets are stacked and joined via an epoxy resin base material 6 with 2 sheets of 0.1 mm thick prepreg material 4' placed in the middle, resulting in 6 layers. Printed wiring board 7
is configured.

Another embodiment will be explained with reference to FIG. 2. The thickness is 0.2 m.
A two-layer printed wiring board 3 and a 2-layer printed wiring board 3 in which a 0.3 mm core material 1 is placed on the top surface and a 0.3 mm core material 5 on the bottom surface, and a circuit 2 is provided on both the top and bottom surfaces of each core material I and 5. 8 is 0.
06mm thick prepreg material (glass fiber diameter: 5μ, number of fibers in glass fiber bundle: 100) 3 sheets are stacked and bonded via an epoxy resin base material 6' on which 5 sheets of 4 are arranged to form a 6-layer printed wiring board. 7' is constructed.

On the other hand, to explain the conventional example with reference to Fig. 3, the thickness is 0.2
A two-layer printed wiring board 3 with a 0.3 mm core material 1 on the top surface and a 0.3 mm core material 5 on the bottom surface, and a circuit 2 on both upper and lower surfaces of each core material 1 and 5. 8 is 0
．． 1mm thick prepreg material (glass fiber diameter near μ, number of fibers in glass fiber bundle: 200) 3 sheets of 4' are stacked and bonded via an epoxy resin base material 6'' to form 6-layer printed wiring. A plate 7' is constructed.

However, 100V was applied between the circuits 2 and the six-layer printed wiring boards 7, 7', 7' of Example 1.2 and the conventional example were left in an atmosphere of 85° C. and 85% humidity.

The insulation value was measured at regular intervals, and values of 10'Ω or less were considered out. As a result, the conventional 6-layer printed wiring board 7'' broke down in 3×10'' hours, but the 6-layer printed wiring board of Example 1.2
It can be seen that the layered printed wiring board 7.7' undergoes dielectric breakdown in 5×10 2 hours, and the time required for dielectric breakdown to occur is significantly extended.

(Effects of the Invention) As can be seen from the above explanation, in the multilayer printed wiring board of the present invention, since the circuits in the inner layer of each printed wiring board are not in direct contact with the glass fibers of the prepreg material, CAF occurs along the glass fibers. This phenomenon is less likely to occur, and dielectric breakdown that causes short circuits with adjacent circuits is less likely to occur. In addition, without increasing the thickness of the multilayer printed wiring board, the epoxy resin exists between the circuit and the glass fiber of the prepreg material, suppressing the occurrence of the CAF phenomenon, which increases the time required for dielectric breakdown to occur. It is.

[Brief explanation of drawings]

1 and 2 are diagrams showing an embodiment of the multilayer printed wiring board of the present invention, respectively, and FIG. 3 is a diagram showing a conventional multilayer printed wiring board. 2...Circuit, 3...Printed wiring board, 4,4'...
・Prepreg material, 6,6'...epoxy resin base material,
7.7'...6-layer printed wiring board.

Claims (1)

[Claims] 1. A multilayer printed wiring board is a multilayer printed wiring board in which printed wiring boards having circuits on both the upper and lower sides are stacked and bonded via a base material having a prepreg material with a thickness of 0.05 to 0.07 mm arranged at least on the bonding surface side. printed wiring board.