JPS616895A - Multilayer printed circuit board with inner layer resistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multilayer printed wiring board in which a resistor is provided in an inner layer.

(Background of the Invention) With the recent increase in density and integration of semiconductors and integrated circuits, printed wiring boards used in electronic devices are also required to have higher densities, and single-sided or double-sided printed wiring boards cannot meet this demand. be. For this reason, printed wiring boards are showing a trend toward multilayering.
Multilayer printed wiring boards with 10 to 20 layers are already in practical use.

In addition, due to this situation, there is a need for the wiring board itself to have component functions as well. An example thereof is a printed wiring board with a printed resistor.

In general, a surface resistance circuit board using an insulating substrate such as a phenol substrate or glass epoxy has poor resistance characteristics (heat resistance, moisture resistance, etc.). In order to eliminate this, it is conceivable to cover it with a resin layer, but the drawback is that it requires a large number of steps. In order to overcome this drawback, a good solution for multilayer printed wiring boards is to make the resistance layer an internal layer. However, placing the resistor in the inner layer causes heat generation due to power consumption of the resistor, resulting in an increase in substrate temperature. This increase in substrate temperature may cause an increase in the specific resistance value of the resistor, and may also lead to a decrease in the heat resistance reliability of the mounted components. Therefore, in order to provide a resistance layer in the inner layer of a printed wiring board, it is necessary to consider heat dissipation characteristics.

In the conventional method, it is necessary to insert a metal core unrelated to the multilayer board circuit into the multilayer board, making the manufacturing process complicated and expensive.

Additionally, the metal core makes the board thick and results in a multilayer board with mold needles.

(Object of the Invention) An object of the present invention is to provide a multilayer printed wiring board with an inner layer resistor having excellent heat dissipation characteristics.

(Structure of the Invention) The present invention is a multilayer printed wiring board with an inner layer resistor, characterized in that a resistor layer is disposed as an inner layer adjacent to a power supply layer and/or a ground layer provided as an inner layer.

That is, the present invention heats and presses an insulating substrate on which a resistor circuit is formed and a plurality of insulating substrates on which conductive circuits are formed so that the resistor circuit is internally formed therein, and provides a through hole in the integrated insulating substrate. In a multilayer printed wiring board configured to provide electrical continuity between other layers and the resistance layer through hole plating, the K, power supply, and ground layers are made into a resistance layer in order to improve the heat dissipation of heat generated by power consumption of the inner layer resistor. It is a multilayer printed wiring board with a closely spaced structure.

The power supply layer and ground layer of a multilayer printed wiring board are for connecting the II source that drives the circuit board elements, and the pattern shape of the power supply layer and ground layer used in this case is a clearance type full-surface solid copper. By adopting a similar structure, even higher heat dissipation effects can be obtained.

An example of the method for manufacturing the multilayer printed wiring board of the present invention will be specifically described. Polyimide material with copper foil, which is an insulating board with good heat resistance, such as MCL-1-67 (plate thickness 0.20 mm, copper foil thickness 1
First, an electrode pattern is formed on the 8 μm (trade name, manufactured by Hitachi Chemical Co., Ltd.) by the subtract method, which is a normal wiring board manufacturing process.

Next, a carbon/resin type resistor such as ink T
U-IM (@1 Asahi Kagaku Institute Art Trade Name) is printed on one side by a screen printing method. After that, 150℃～
After precuring at 160° C. for about 30 minutes, printing is performed on one side of the board and precuring is carried out in the same manner. Further 180℃
Main baking is performed at a temperature of ~190°C for 1 to 1.5 hours to completely cure the ink. 1. This substrate with resistor and the same material base material (plate thickness 0.20 mm, copper foil thickness 35 μm) are used by the subtract method. After treating several insulating boards with conductor circuits that were designed to be made with a black oxide film on the copper foil to improve adhesive strength, we coated them with polyimide prepreg, such as GIA-67-N.
(Part name manufactured by Hitachi Chemical) Laminated press is performed. In order to establish internal conduction in this laminated insulating plate, after drilling a hole with a diameter Q of 5 mm, for example, CU
Electroless copper plating is performed using the ST201 no-glare copper plating system (part name manufactured by Hitachi Chemical), and 79 lines of copper plating with a diameter of approximately 20 μm are immediately applied to complete the through hole. Thereafter, a surface layer circuit is formed by a tenting method or the like to produce a multilayer printed wiring board.

The drawing shows a cross-sectional view of a multilayer printed wiring board manufactured in this manner, in which 1 is a surface circuit, 2 is a power supply and ground circuit, 5 is a printed resistor, 4 is a signal line, 5 is a through hole,
6 is an insulating layer.

It has a structure in which two resistive layers are sandwiched between a power supply/gudo layer, and since the copper foil area with high thermal conductivity (385 kal/m・h・℃) is large in the clearance method, it is difficult to use the signal layer,
Compared to the case of sandwiching between the power supply and ground layers of the line method, it is very advantageous in terms of heat dissipation. Also, placing the signal tS close to the resistance layer may cause malfunctions due to electromagnetic induction, etc.
Sandwiching the resistor layer with a ground bar is 18
It is also important to have a shielding effect between the optical layer and the resistive layer. To explain the flow of heat specifically, most of the heat generated in the resistor 3 is transferred from the insulating layer 6 to the power supply/ground 2, and not only flows out into the air from the board surface and edges (through Since heat is also dissipated through the holes, the thermal resistance of the insulating layer is greatly reduced, and a sufficient heat dissipation effect can be obtained.

(Effects of the invention) By using the power supply/ground layer of a multilayer printed wiring board as a heat dissipation path for the heat generated by the inner layer resistor, the thermal resistance of the board can be lowered, suppressing the rise in board temperature, and The reliability of component mounting can be improved.

[Brief explanation of drawings]

The drawing is a sectional view showing an embodiment of the present invention. Explanation of symbols 1 Surface circuit 2 Power/ground circuit 6 Printed resistor 4 Signal line 5 Through hole 6 Insulating layer

Claims (1)

[Claims] 1. A multilayer printed wiring board with an inner layer resistor, characterized in that a resistor layer is arranged as an inner layer adjacent to a power supply layer and/or a ground layer provided as an inner layer.