JPH07312466A - Wiring board - Google Patents

Abstract

PURPOSE:To realize the migration resistance and long-term insulation properties of a wiring board by a method wherein insulative bonding agent layers are formed of a formation material of a specified glass transition temperature or higher and insulative bonding agent layers, which correspond to wiring conductors, are formed of a formation material of the specified glass transition temperature or lower between the insulative bonding agent layers and a plurality of the wiring conductors. CONSTITUTION:A wiring board 1 is formed by a method wherein each insulative bonding agent layer 12 is formed on both surfaces of an insulating base film 11, a plurality of wiring conductors 14 are formed on each of the two insulative bonding agent layers 12 at prescribed intervals between them and moreover, insulative bonding agent layers 3, which correspond to the conductors 14, are respectively formed between the two layers 12 and the conductors 14. The layers 12 are formed of a formation material of a glass transition temperature of 100 deg.C or higher and the layers 13 are formed of a formation material of a glass transition temperature of 80 deg.C or lower. Thereby, the layers 13, in which a migration is easy to generate, do not exist between the conductors 14 and the migration resistance and long-term insulation reliability of the wiring board can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to thermal shock resistance electrical characteristics,
The present invention relates to a wiring board having migration resistance and vibration resistance.

[0002]

2. Description of the Related Art Conventionally, a wiring board mounted on a place where vibration is applied to a passenger car, etc.
It is required that the solder joints with lead wires, electronic components, terminals of devices, etc. should not be damaged even after long-term use. Therefore, as a wiring board, a three-layer base wiring board made of three kinds of constituent materials, that is, a base film, an adhesive layer and a wiring conductor is generally used. Since the vibration absorbing layer such as the adhesive layer is formed in this three-layer base wiring board, for example, like a two-layer base wiring board made of two kinds of materials only of the base film and the wiring conductor, Vibrations from the outside are difficult to be directly transmitted to the solder joints, and as a result, the solder joints are less likely to be damaged.

[0003]

[Problems to be Solved by the Invention] However, the above 3
When the glass transition temperature of the adhesive forming the adhesive layer is low in the layer base wiring board, the conductor elutes due to the potential difference between the wiring conductors of the wiring board and the conductor moves in the adhesive layer or on the surface of the adhesive layer to cause a short circuit. It has been recently known that the possibility of occurrence of migration that causes the above-mentioned problem increases. As a result, insulation reliability becomes a problem during long-term use.
Further, in a three-layer substrate wiring board, it is difficult to approximate the linear expansion coefficient of the adhesive layer and the linear expansion coefficient of the wiring conductor, so that the line between the wiring conductor and the adhesive layer is subjected to a thermal cycle. Thermal stress is generated in the wiring conductor due to the difference in expansion coefficient. If an adhesive having a high glass transition temperature is used to improve the migration resistance, the adhesive retains a high elastic modulus up to a high temperature, and as a result, a large tensile stress is applied to the wiring conductor. Therefore, the tensile stress and the compressive stress are repeatedly applied to the wiring conductor during the thermal cycle together with the compressive stress at a low temperature, which causes a new problem that the wiring conductor is easily broken.

The present invention has been made in view of such circumstances, and an object thereof is to provide a wiring board excellent in all of thermal shock resistance electrical characteristics, migration resistance and vibration resistance.

[0005]

In order to achieve the above object, the wiring board of the present invention has an insulating adhesive layer A formed on at least one surface of an insulating film, and the insulating adhesive layer A surface is formed on the insulating adhesive layer A surface. A wiring in which a plurality of wiring conductors are formed at a predetermined interval from each other, and an insulating adhesive layer B corresponding to the wiring conductor is interposed between the plurality of wiring conductors and the insulating adhesive layer A. A plate, wherein the insulating adhesive layer A is formed of a forming material having a glass transition temperature of 100 ° C. or higher, and the insulating adhesive layer B is formed of a forming material having a glass transition temperature of 80 ° C. or lower. Take

[0006]

That is, in the wiring board of the present invention, the insulating adhesive layer A is formed on at least one surface of the insulating film, and a plurality of wiring conductors are formed on the insulating adhesive layer A surface. . The insulating adhesive layer B corresponding to the wiring conductors is interposed between the plurality of wiring conductors and the insulating adhesive layer A. Moreover, each of the materials for forming the insulating adhesive layers A and B has a specific glass transition temperature. For this reason, the insulating adhesive layer B that easily causes migration does not exist between the wiring conductors, migration does not easily occur, and long-term insulation reliability is improved. In addition, since the insulating adhesive layer B that is in direct contact with the wiring conductor has a low glass transition temperature, the elastic modulus of the adhesive decreases from a relatively low temperature, the disconnection of the wiring conductor does not easily occur, and it has excellent thermal shock resistance electrical characteristics. ing. Moreover, as the vibration absorbing layer, the insulating adhesive layer A is formed on the surface of the insulating film, and the insulating adhesive layer B corresponding to the wiring conductor is provided between the insulating adhesive layer A and the wiring conductor.
Since it is formed, it has excellent resistance to external vibration.

Next, the present invention will be described in detail.

FIG. 1 is a sectional view showing an example of the wiring board of the present invention. The wiring board 1 has an insulating base film 11
Insulating adhesive layer A12 is formed on both surfaces of. Further, a plurality of wiring conductors 14 are formed on the both insulating adhesive layers A12 with a predetermined space therebetween. Moreover, an insulating adhesive layer B13 corresponding to the wiring conductor 14 is formed between the insulating adhesive layer A12 and the wiring conductor 14.

The glass transition temperature of the insulating adhesive layer A12 forming material must be 100 ° C. or higher, and the glass transition temperature of the insulating adhesive layer B13 forming material must be 80 ° C. or lower. In the present invention, each glass transition temperature is a value measured by a thermomechanical analysis (TMA) method. More specifically, the glass transition temperature is obtained from the bending point of the elongation-temperature curve by measuring the amount of elongation of the sample with respect to temperature. The measurement conditions at this time were such that the temperature rising rate was 5 ° C./min and the load was 1 g.

As described above, according to the wiring board 1, since the glass transition temperature is as low as 80 ° C. or less and the insulating adhesive layer B13 in which the migration easily occurs is not present between the wiring conductors 14, the migration is caused. Is less likely to occur, and long-term insulation reliability is improved. Furthermore, the wiring conductor 1
4 has a low glass transition temperature, the elastic modulus of the adhesive decreases from a relatively low temperature, and there is a difference in linear expansion coefficient between the wiring conductor 14 and the insulating adhesive layer B13. However, tensile stress is not applied to the wiring conductor 14 at high temperature. Therefore, even if a thermal cycle is applied, the wire conductor 14 is unlikely to be broken. Moreover, as the vibration absorbing layer, the insulating adhesive layer A is formed on both surfaces of the insulating base film 11.
12 is formed, and the insulating adhesive layer B13 corresponding to the wiring conductor 14 is formed between the insulating adhesive layer A12 and the wiring conductor 14, so that vibration resistance from the outside is also excellent. ing.

The material of the insulating base film 11 is not particularly limited, but examples thereof include polyimide film, polyethylene terephthalate film, polycarbonate film, polyetherimide film, polytetrafluoroethylene film and the like. Also, the thickness of the insulating base film 11 is not particularly limited, and is preferably set to, for example, about 1 to 1000 μm.

The material for forming the insulating adhesive layer A12 formed on the surface of the insulating base film 11 is, for example,
Examples include epoxy resin adhesives, acrylic resin adhesives, polyimide resin adhesives, and the like. The glass transition temperature of the forming material of the insulating adhesive layer A12 must be 100 ° C. or higher.
It is preferably 120 ° C. or higher. By setting this glass transition temperature to 100 ° C. or higher, migration resistance is improved. That is, when the glass transition temperature is lower than 100 ° C., the conductor is largely eluted and the mobility of the eluted conductor ions is high, so that the possibility of short circuit due to migration becomes high. In addition, the insulating adhesive layer A1
The thickness of 2 is not particularly limited, but is 0.1 to 50.
The thickness is preferably set in the range of 0 μm, particularly preferably 5 to 100 μm.

The insulating adhesive layer A12 and the wiring conductor 14
The material for forming the insulating adhesive layer B13 that is formed so as to correspond to the above-mentioned wiring conductor 14 is not particularly limited as long as it has a glass transition temperature of 80 ° C. or lower. That is, various adhesives having a glass transition temperature of 80 ° C. or lower, for example, epoxy resin adhesives, acrylic resin adhesives, polyimide resin adhesives and the like can be mentioned. As described above, if the glass transition temperature is not higher than 80 ° C., it becomes difficult to relax the thermal stress, and disconnection of the wiring conductor is likely to occur during the thermal cycle. The glass transition temperature is preferably 70 ° C. or lower.

The material for forming the plurality of wiring conductors 14 is not particularly limited, but copper, aluminum,
Examples include gold, stainless steel, tungsten, and copper compounds, which may be soldered, nickel, gold plated, or the like. Then, the wiring conductor 14 is manufactured using any of these forming materials by any one of patterning, etching, and plating methods. The thickness of the wiring conductor 14 is not particularly limited, but it is preferably set in the range of 1 to 100 μm, particularly preferably 12 to 50 μm. The mutual spacing between the plurality of wiring conductors 14 is 10
The thickness is preferably set to 0 μm or less, more preferably 50 to 100 μm, particularly preferably 75 to 10 μm.
It is 0 μm.

The wiring board of the present invention is manufactured, for example, as follows. That is, as shown in FIG. 2, the insulating adhesive layer A is formed on each side of the insulating base film 11.
An adhesive sheet 12a, which is a forming material, is provided, and then an adhesive sheet 13a, which is an insulating adhesive layer B forming material, is provided on the surface of each adhesive sheet 12a. Further, the metal foil 15 is disposed on the surface of the adhesive sheet 13a, and the materials are adhered by laminating and pressing. Then, as shown in FIG. 3, the metal foil 15 is patterned into a predetermined circuit shape by a known chemical etching method to form the wiring conductor 14. Next, this is immersed in an etching solution to remove unnecessary portions of the adhesive sheet 13a so as to correspond to the wiring conductors 14 to produce the wiring board 1 having a cross-sectional shape as shown in FIG.

The insulating adhesive layer A12 and the insulating adhesive layer B13a before the unnecessary portion is removed may be formed by coating or the like without using a sheet material.

Examples of the chemical etching method applied when patterning the above-mentioned predetermined circuit shape include wet etching treatment with cupric chloride and ferric chloride.

Further, as a method of forming the insulating adhesive layer B13 by removing the unnecessary portion, in addition to the method of removing the unnecessary portion by immersing the etching solution such as sulfuric acid or permanganate, a specific mixed gas is used. It may be formed by a dry etching method in plasma.

Further, another example of the wiring board of the present invention will be shown. That is, as shown in FIG. 4, this wiring board has an insulating adhesive layer A1 only on one surface of the insulating base film 11.
2, a single-sided wiring board on which an insulating adhesive layer B13 and a plurality of wiring conductors 14 are formed.

[0020]

As described above, in the wiring board of the present invention, the insulating adhesive layer A is formed on at least one surface of the insulating film, and a plurality of wiring conductors are formed on the insulating adhesive layer A surface. Are formed. The insulating adhesive layer B corresponding to the wiring conductors is interposed between the plurality of wiring conductors and the insulating adhesive layer A. Moreover, the materials for forming the insulating adhesive layers A and B are set to have specific glass transition temperatures. For this reason, the insulating adhesive layer B in which migration easily occurs
Does not exist between the wiring conductors and has excellent migration resistance and long-term insulation reliability is realized. In addition, since the insulating adhesive layer B that is in direct contact with the wiring conductor has a low glass transition temperature, the elastic modulus of the adhesive decreases from a relatively low temperature, the disconnection of the wiring conductor does not easily occur, and the thermal shock resistance electrical characteristics are also improved. Are better. Moreover, the insulating adhesive layer A is formed on the surface of the insulating film, and the insulating adhesive layer B corresponding to the wiring conductor is formed between the insulating adhesive layer A and the wiring conductor. Therefore, since both of the insulating adhesive layers A and B act as a vibration absorbing layer, the vibration resistance from the outside is also excellent.

Next, examples will be described together with comparative examples.

[0022]

Example 1 As shown in FIG. 2, an insulating adhesive layer A was formed on each side of a polyimide film 11 having a thickness of 75 μm.
A polyimide resin adhesive sheet 12a (glass transition temperature 120 ° C.) having a thickness of 50 μm, which is a forming material, is arranged, and then an epoxy resin adhesive having a thickness of 5 μm, which is an insulating adhesive layer B forming material, is provided on each adhesive sheet 12a surface. Adhesive sheet 13
a (glass transition temperature 50 ° C.) was provided. Further, a 35 μm thick copper foil 15 was provided on the surface of the adhesive sheet 13a, laminated and pressed to bond the above materials. Then, as shown in FIG. 3, the copper foil 1 is formed by a conventional chemical etching method (cupric chloride).
5 was patterned into a predetermined circuit shape to form a wiring conductor 14. At this time, the mutual spacing between the wiring conductors 14 is 1
It was set to 00 μm. Next, this was immersed in sulfuric acid to remove unnecessary portions of the adhesive sheet 13a so as to correspond to the wiring conductors 14. Thus, a wiring board 1 having a cross-sectional shape as shown in FIG. 1 was produced.

[0023]

Example 2 As shown in FIG. 5, an epoxy resin adhesive sheet 12b (glass transition temperature 100 ° C.) having a thickness of 35 μm, which is a material for forming an insulating adhesive layer A, is provided on one surface of a polyethylene terephthalate film 11 having a thickness of 50 μm. Then, an acrylic resin adhesive sheet 13b (glass transition temperature 50 ° C.) having a thickness of 5 μm, which is an insulating adhesive layer B forming material, was provided on the surface of the adhesive sheet 12b. Furthermore, a copper foil 1 having a thickness of 18 μm is formed on the surface of the adhesive sheet 13b.
The above materials were adhered by arranging and stacking No. 5 and pressing. Then, as shown in FIG. 6, the copper foil 15 is patterned into a predetermined circuit shape by a conventionally known chemical etching method (ferric chloride), and the wiring conductor 1
4 was formed. The mutual distance between the wiring conductors 14 at this time was set to 50 μm. Next, this is CF ₄ / O ₂
By performing dry etching in the plasma of the mixed gas (conditions: O ₂ 70% / CF ₄ 30%, pressure 26.6 Pa, power 3.5 kW, 20 minutes), the adhesive sheet 13 b is made to correspond to the wiring conductor 14. The unnecessary part of was removed. In this way, a wiring board having a cross-sectional shape as shown in FIG. 4 was produced.

[0024]

Comparative Example 1 An epoxy resin adhesive sheet (glass transition temperature 120 ° C.) having a thickness of 50 μm, which is an insulating adhesive layer forming material, is provided on one surface of a polyimide film having a thickness of 75 μm, and then the adhesive sheet surface is Copper foils having a thickness of 35 μm were arranged in this order, laminated, and pressed to bond the above materials. Then, the copper foil was patterned into a predetermined circuit shape by a conventionally known chemical etching method (cupric chloride) to form a plurality of wiring conductors. In this way, a wiring board having a cross-sectional shape as shown in FIG. 7 was produced. The mutual distance between the wiring conductors 34 at this time was set to 100 μm. In the figure, 31 is a polyimide film, and 32 is an epoxy resin-based insulating adhesive layer.

[0025]

Comparative Example 2 An acrylic resin adhesive sheet (glass transition temperature 50 ° C.) having a thickness of 35 μm, which is a material for forming an insulating adhesive layer, is provided on both sides of a polyethylene terephthalate film having a thickness of 50 μm, and then each of the above adhesive sheets is used. On the surface, a copper foil having a thickness of 18 μm was arranged in this order, laminated, and pressed to bond the above materials. And
Conventionally known chemical etching method (ferric chloride)
By patterning the copper foil into a predetermined circuit shape,
A plurality of wiring conductors are formed. In this way, a wiring board having a cross-sectional shape as shown in FIG. 8 was produced. The mutual distance between the wiring conductors 46 at this time was set to 50 μm. In the figure, 43 is a polyethylene terephthalate film, 44
Is an acrylic resin-based insulating adhesive layer.

Table 1 below shows the results of the measurement and evaluation of the thermal shock resistance electrical characteristics of the wiring boards of the respective Examples and Comparative Examples thus obtained. The thermal shock resistance electrical characteristics were measured as follows. That is, using a liquid tank thermal shock tester, (-65 ° C / 5 minutes) to (25 ° C / 0
Min) to (155 ° C / 5 min) to (25 ° C / 0 min) as one cycle of the cooling / heating cycle, and the number of cooling / heating cycles until the wiring conductor of each wiring board was broken was measured. The presence or absence of disconnection of the wiring conductor was determined by measuring the resistance values at both ends of the wiring conductor.

[0027]

[Table 1]

Next, Table 2 below shows the migration resistance of the wiring boards of the respective Examples and Comparative Examples.
The migration resistance was measured as follows. That is, a comb-shaped wiring was formed as the wiring of each wiring board. And, the wiring board is 85 ℃ × 85%
The temperature was kept in a thermo-hygrostat under the environmental conditions of RH, a DC voltage was applied between the comb-shaped wires so that the electric field strength was 500 kV / m, and the time until a short circuit was measured. The time until the short circuit was defined as the time when the insulation resistance between the comb-shaped wirings first fell below 10 ⁸ Ω.

[0029]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the product of Comparative Example 1 has a migration resistance of 10%.
Although no short circuit occurred even after 00 hours, the wiring conductor was broken in the thermal shock resistance electrical characteristics at 600 cooling / heating cycles. Further, the product of Comparative Example 2 has a thermal shock resistance electrical property of 10
Although the wire was not broken even after 00 cycles, a short circuit occurred after 300 hours in migration resistance. On the other hand, in both of the example products, the thermal shock resistance did not break after 1000 cycles, and the migration resistance did not cause a short circuit even after 1000 hours.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a wiring board of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the wiring board.

FIG. 3 is a cross-sectional view showing a manufacturing process of the wiring board.

FIG. 4 is a cross-sectional view showing another example of the wiring board of the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing process of the wiring board.

FIG. 6 is a cross-sectional view showing a manufacturing process of the wiring board.

FIG. 7 is a cross-sectional view showing an example of a conventional wiring board.

FIG. 8 is a cross-sectional view showing another example of a conventional wiring board.

[Explanation of symbols]

 1 Wiring Board 11 Insulating Base Film 12 Insulating Adhesive Layer A 13 Insulating Adhesive Layer B 14 Wiring Conductor

Claims (1)

[Claims] 1. An insulating adhesive layer A is formed on at least one surface of an insulating film, and the insulating adhesive layer A surface is provided with:
A wiring board in which a plurality of wiring conductors are formed at a predetermined interval from each other, and an insulating adhesive layer B corresponding to the wiring conductors is interposed between the plurality of wiring conductors and the insulating adhesive layer A. And the insulating adhesive layer A has a glass transition temperature of 1
A wiring board, which is formed of a forming material having a temperature of 00 ° C. or higher, and the insulating adhesive layer B is formed of a forming material having a glass transition temperature of 80 ° C. or lower.