JPH0964492A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise safety and obtain a printed wiring board which is suitable for high density mounting by counterposing electrode patterns for detecting a resistance of a resin layer with a resin layer in between. SOLUTION: On a printed wiring board 1 wherein a wiring pattern is formed on a resin board 1, electrode patterns for detecting the resistance of a resin layer 5 are arranged in opposition with the resin layer 5 in between. Thereby, when a single layer or multilayer glass epoxy board 2 is used as the printed wiring board 1, an electric power supplied to the board 2 by a signal generation circuit is cut off and an alarm is given to inform that something is wrong on measuring a resistance value when a temperature of the resin layer 5 between electrode patterns arranged in an area near an electric component 6 which generates heat attains a glass transition point by a resistance measurement circuit put integrally with the substrate 2. Thereby, safety of the wiring board 1 itself and an electric component 6 to be mounted can be raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board having a wiring pattern formed on a resin substrate, on which a semiconductor device such as an IC or LSI can be mounted.

[0002]

2. Description of the Related Art Conventionally, a resin substrate is generally used as a printed wiring board on which a semiconductor device such as an IC or LSI can be mounted. This resin substrate is one in which a wiring pattern made of copper foil is formed on a resin substrate using a polymer material as a binder. In addition, with the recent high-density mounting of semiconductor devices (for mounting IC cards, PGAs, BGAs, etc.),
A large number of multilayer resin substrates are used, and among these, a glass epoxy substrate is widely used. This glass epoxy substrate is obtained by impregnating a glass fiber of a base material into a cloth shape, impregnating it with an epoxy resin, and after drying, laminating it to a required thickness, laminating a copper foil on the surface, and thermocompression bonding.

The printed wiring board usually does not have a temperature sensor circuit. Therefore, in order to improve the safety of the circuit, if a temperature sensor circuit that detects the heat generated by the mounted components and the short circuit of the circuit is provided,
As a separate component, a thermistor or a thermal fuse was used, and it was necessary to separately configure a safety circuit that shuts off the power when the temperature of the mounted component becomes abnormally high.

[0004]

As described above, since the conventional printed wiring board is not equipped with a temperature sensor circuit or the like, due to abnormal heat generation of mounted components on the wiring board or heat generation due to short circuit of the circuit, Even if the epoxy resin, which is the base material of the printed wiring board, might be carbonized or ignited, it was left as it was. In addition, if a safety circuit is configured as a countermeasure against this, a separate component such as a thermistor is required, which increases the manufacturing cost due to an increase in the number of components, and electronic components are mounted on the wiring pattern. This reduces the design area on the board and hinders high-density mounting of components.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a printed wiring board which is significantly higher in safety than conventional printed wiring boards and which is suitable for high-density mounting. .

[0006]

In order to solve the above problems, the present invention has the following constitution. That is, in a printed wiring board in which a wiring pattern is formed on a resin substrate, electrode patterns for detecting the resistance of the resin layer are opposed to each other with the resin layer sandwiched therebetween.

According to the above structure, when a single-layer or multi-layer glass epoxy substrate is used as the printed wiring board, the temperature of the resin layer between the electrode patterns arranged in the vicinity of the heat-generating electronic component reaches the glass transition point. When the resistance value at that time is measured by a resistance measuring circuit integrally provided with the substrate, the power supply to the substrate is shut off by the signal generating circuit, or an alarm is issued to notify the abnormality.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, one embodiment of a printed wiring board according to the present invention will be described with reference to the drawings. This embodiment will be described by using a glass epoxy multilayer substrate capable of mounting electronic components on both sides as an example of a printed wiring board. FIG.
2 is a cross-sectional view showing the main structure of the printed wiring board, FIG. 2 is a block diagram showing the circuit structure of the printed wiring board, and FIG. 3 is a graph showing the temperature-resistance characteristics of the glass epoxy resin.

First, the overall structure of a glass epoxy multilayer substrate will be described with reference to FIGS. In FIG. 1, reference numeral 1 is a glass epoxy multilayer substrate used as a printed wiring board. This glass epoxy multilayer substrate 1 is
A hole is formed by drilling a glass epoxy substrate 2 on which copper foil is attached on both sides to form a through hole 3 and electroless copper plating 4 is used to establish continuity between upper and lower surfaces, and then formed on a surface layer by electrolytic copper plating. The wiring pattern P is electrically connected to the wiring pattern P.

In this embodiment, a surface layer L _{1 having} a wiring pattern P formed thereon, a ground layer L ₂ for taking a ground (GND) of the wiring pattern P, and a power supply V _CC for supplying a power supply V _CC to a wiring board.
A four-layer substrate in which _three layers and a surface layer L ₄ on which the wiring pattern P is formed are sequentially laminated via a resin layer 5 is used.
On the surface layer L ₁ of the glass epoxy multilayer substrate 1, IC
Highly heat-generating electronic components such as semiconductor devices such as transformers 6
Are surface-mounted by wire bonding. Corresponding to the mounting surface of the electronic component 6 having high heat generation, electrode patterns 7 and 7 made of metal foil are formed to face the surface layer L ₁ and the ground layer L ₂ with the resin layer 5 interposed therebetween. The electrode patterns 7 and 7 are formed, for example, so as to correspond to a die pad on which a semiconductor chip is mounted, a die pad heat spreader, or the like, or to also serve as these.

The electrode patterns 7 and 7 can be provided so as to correspond to the entire mounting surface of the electronic component 6, or can be provided partially corresponding to the individual electronic components.
Further, the glass epoxy multilayer substrate 1 can be applied not only to four conductor layers but also to one having three layers or a multilayer substrate, and further to a single-layer glass epoxy substrate. is there.

The structure of the temperature sensor circuit built in the glass epoxy multilayer substrate 1 will be described. As shown in FIG. 2, the electrode patterns 7 and 7 are connected to a resistance measuring circuit 8 as resistance measuring means. The resistance measuring circuit 8 is connected to the heat radiation ground circuit 9. The resistance measuring circuit 8 has a predetermined voltage (for example, about 5V) between the electrode patterns 7 and 7 arranged to face each other with the glass epoxy resin layer 5 interposed therebetween.
Is applied to detect a change in resistance value of the resin layer 5 between the electrode patterns 7 and 7. The measurement result of the resistance measuring circuit 8 is input to a signal generating circuit 10 as a control means, and the signal measuring circuit 10 uses the resistance value measured by the resistance measuring circuit 8 as a threshold value (for example, a glass transition point described later). In the following cases, the power supply V _CC supplied to the glass epoxy multilayer substrate 1 is cut off, or an alarm is issued by an alarm circuit to notify the abnormality.

Here, the temperature detecting structure of the glass epoxy multilayer substrate 1 will be described in detail. The glass epoxy substrate 2 described above is obtained by impregnating a glass fiber of a base material into a cloth shape by impregnating it with an epoxy resin and drying it. It is then formed into a copper-clad laminate by laminating it to a required thickness, stacking a copper foil on the surface, and thermocompression bonding. The glass epoxy resin has good adhesiveness to the copper foil and excellent insulating properties, and thus is preferably used as a base material.

The glass epoxy resin has temperature-resistance characteristics as shown in the graph of FIG. That is, there is a property that the electric resistance changes drastically with respect to the temperature change of the resin, specifically, the resistance value drastically decreases when the temperature rises. Therefore, if the temperature of the resin rises abnormally, dielectric breakdown may occur. Further, the glass epoxy resin has a glass transition point (generally 130 ° C to 140 ° C) which is a structure slightly looser than the solid before the resin is changed from solid to liquid when the resin is dissolved.
° C). As shown in FIG. 3, when the temperature rises near the glass transition point, the resistance value drastically decreases. Therefore, the resistance measuring circuit 8 sets the resistance value near the glass transition point (for example, about 10 ⁵ Ω) as a threshold value. It becomes possible to detect the temperature by capturing the change in the value. Further, the resistance measuring circuit 8 does not need to be detected with high accuracy because the change in measured value is large, and can be integrally designed on the substrate 1 at low cost.

According to the above construction, by incorporating the temperature sensor circuit in the wiring board itself, not as a separate component, in the necessary portion of the printed wiring board, the wiring is formed when the temperature of the resin layer reaches the glass transition point. By shutting off the power supplied to the board or sending an alarm to notify, the safety of the wiring board itself and the electronic components to be mounted is significantly increased compared to the conventional printed wiring board, and PL (Product Liab)
It is possible to provide a high-value-added printed wiring board that conforms to the (i. In addition, the electrode pattern formed on the printed wiring board can be arranged corresponding to the electronic components with high heat generation that are surface-mounted, and can be integrated with the printed wiring board. It is possible to provide a printed wiring board that can contribute to realization.

Next, another structure of the above-mentioned printed wiring board will be described with reference to FIG. In FIG. 4, the glass epoxy multilayer substrate 1 of the present embodiment has a surface layer L ₁ on which a wiring pattern P is formed and L ₂ which supplies power V _CC to the wiring board.
A four-layer substrate is used in which a layer, a ground layer L ₃ for taking the ground (GND) of the wiring pattern P, and a surface layer L ₄ on which the wiring pattern P is formed are sequentially laminated via a resin layer 5.

Electrode patterns A, B, C and D connected to the resistance measuring circuit 8 are formed on the substrate 1. Specifically, the electrode patterns A and B are L ₂ which supplies the power source V _CC.
The layers and the electrode patterns C and D are respectively provided on the surface layer L ₄ , and a predetermined voltage (for example, about 5 V) is applied between the layer and the electrode patterns C and D and the ground layer L ₃ provided on the entire surface of the substrate 1 to change the resistance value. Is configured to measure.

According to the above structure, the electrode patterns A, B,
By disposing C and D between the wiring patterns P and also using the ground layer L ₃ as an electrode, the resistance value is measured at a plurality of points on the surface of the wiring board with a simplified structure and the temperature of the resin layer is the glass transition point. When the temperature reaches, the control means cuts off the power supply to the wiring board, etc., whereby it is possible to provide a printed wiring board of high added value with significantly improved safety.

Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, but can be applied to, for example, a single-sided mounting glass epoxy substrate or the like. Also, the present invention can be applied to a package in which various semiconductor chips such as PGA and BGA can be mounted. Further, the material of the printed wiring board is not limited to the epoxy resin, for example, a polyimide resin or a modified polyimide resin can be used, and even if other resin is used, the temperature reaches the glass transition point. Then, it can be applied to a resin having a property of causing a rapid change in resistance value. In this way, it goes without saying that many modifications can be made without departing from the spirit of the invention.

[0020]

As described above, according to the present invention, the electrode pattern for detecting the resistance of the resin layer (for example, the glass epoxy resin layer) is integrally provided not at another component but at the necessary portion of the printed wiring board, as described above. As a result, when the temperature of the resin layer rises and reaches a threshold value (for example, glass transition point), the power supply to the wiring board is shut off or an alarm is sent to notify It is possible to significantly enhance the safety of the wiring board itself and the electronic components to be mounted as compared with the wiring board, and provide a printed wiring board having a high added value that is compatible with the PL method. In addition, the electrode pattern can be arranged corresponding to the electronic components with high heat generation mounted on the printed wiring board, and can be integrated with the printed wiring board, which contributes to high-density mounting of electronic components. A wiring board can be provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main configuration of a printed wiring board.

FIG. 2 is a block diagram illustrating a circuit configuration of a printed wiring board.

FIG. 3 is a graph showing resistance temperature characteristics of glass epoxy resin.

FIG. 4 is a cross-sectional view showing a configuration of main parts of a printed wiring board according to another example and a block explanatory diagram showing a circuit configuration.

[Explanation of symbols]

 1 Glass Epoxy Multilayer Substrate 2 Glass Epoxy Substrate 3 Through Hole 4 Electroless Copper Plating 5 Resin Layer 6 Electronic Components 7, A, B, C, D Electrode Pattern 8 Resistance Measurement Circuit 9 Heat Dissipation Ground Circuit 10 Signal Generation Circuit P Wiring Pattern

Claims (4)

[Claims] 1. A printed wiring board in which a wiring pattern is formed on a resin substrate, and electrode patterns for detecting the resistance of the resin layer are opposed to each other with a resin layer sandwiched therebetween. 2. The printed wiring board according to claim 1, wherein one of the electrode patterns is also used as a heat dissipation member of an electronic component mounted on the resin substrate. 3. The resin substrate is a multilayer resin substrate formed by laminating a plurality of resin layers on a thin plate-shaped base material, and the electrode pattern detects resistance between any one of the resin layers. The printed wiring board according to claim 1 or 2. 4. The printed wiring board according to claim 1, wherein the electrode pattern is formed on a package on which a semiconductor chip is mounted.