JPH0897553A - Structure for conductive pattern - Google Patents

Abstract

PURPOSE: To prevent the peeling of a conductive pattern constituted in a multilayered structure from a ceramic substrate even when the substrate is heated and cooled by making the content of a glass component in the uppermost layer of the multilayered structure lower than that of the glass component in the lowermost layer which is in contact with the insulating substrate body. CONSTITUTION: A copper-made conductive pattern has a two-layer structure composed of a conductive pattern 6 which is formed of copper-based metallic paste containing a large amount of glass component and formed on the surface of a ceramic substrate 5 and another conductive pattern 7 which is formed of copper-based metallic paste containing a small amount of glass component and formed on the surface of the pattern 6. It is also possible to constitute the conductive pattern formed on the ceramic substrate 5 in a three or more layers near the terminal section of electronic parts, etc. When the conductive pattern is formed in a three or more layers, the conductive pattern is improved in strength of adhesion and resistance to temperature change when the contents of the glass component in the layers constituting the multilayered structure are gradually reduced from the layer adhering to the surface of the ceramic substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board provided with an electronic component or the like on a conductive pattern on an insulator, and more particularly to a circuit board in which the conductive pattern is not separated from the insulator.

[0002]

2. Description of the Related Art In recent years, a hybrid IC has been proposed and put into practical use, in which electronic components and the like are fixed to a printed circuit board on which wiring is printed to have a certain function. As shown in FIG. 2, the hybrid IC has a ceramic substrate 1 composed of 90% or more of ceramic and a ceramic sintering aid or the like.
, A conductive paste sufficiently containing a conductive substance is applied by a screen printing method or the like, and then subjected to heat treatment to be cured to form a conductive pattern 2 having a thickness of 10 to 20 μm,
It is general that a desired electronic component or the like 3 is fixed to a predetermined position of the conductive pattern 2 with a conductive adhesive 4 such as solder.
The conductive patterns are typically silver-palladium-based and copper-based, but it is generally recognized that the copper-based conductive patterns have higher reliability.

In the manufacturing process of the hybrid IC, there may occur a problem such as a wrong mounting position of the electronic component or the like on the ceramic substrate, or a shift of the position when mounting. In such a case, heat the solder
If it melts, the mounting position of the electronic parts etc.
Alternatively, it is possible to easily correct a defect such as a position shift, but if this correction is performed several times, a disadvantage occurs that the copper-based conductive pattern near each terminal of the electronic component etc. being soldered is separated from the ceramic substrate, In some cases, the conductive pattern is cut off, which causes a defect that the electronic parts and the like cannot be conducted.

As described above, this is because heating and cooling are performed in order to melt the solder when the mounting positions of electronic parts and the like on the ceramic substrate are corrected, and the heating and cooling are repeated to repeat the heating and cooling. It is considered that the adhesive strength between the copper-based conductive pattern and the copper-based conductive pattern decreases and the copper-based conductive pattern peels off. Therefore, a copper-based conductive pattern was formed on the ceramic substrate, and a temperature cycle test of repeatedly heating and cooling the ceramic substrate was carried out to measure the change in the adhesive strength.

The temperature cycle is -55 ° C. as shown in FIG.
Leave in low temperature tank for 30 minutes A, + 25 ° C constant temperature for 5 minutes B, + 125 ° C high temperature tank for 30 minutes C, + 25 ° C constant temperature in 5 minutes D (Ref: MIL-STD-883B, test method 1010.2 conditions (B)) was set as one cycle. FIG. 4 shows the result of measurement of how the adhesive strength of the copper-based conductive pattern and the ceramic substrate changes depending on the number of temperature cycles. The adhesive strength between the ceramic substrate and the copper-based conductive pattern was about 1.6 kilograms / square millimeter before the temperature cycle test, but decreased to about 0.6 kilograms / square millimeter after 200 temperature cycles. I got the result.

Therefore, according to the result obtained by the temperature cycle test, in the repair work of the electronic parts and the like constituting the hybrid IC, the copper-based conductive pattern is heated and cooled by heating and cooling the solder, and as a result, It was confirmed that the conductive pattern was easily separated from the ceramic substrate.

Therefore, a conductive pattern which is difficult to be separated from the ceramic substrate was studied. Attention was paid to the glass component present in the conductive pattern, and the glass component was increased compared with the conventional one so as to obtain the adhesive strength with the ceramic substrate. However, if the glass component is increased, there is a drawback that the adhesive strength between the solder for fixing the electronic component and the like and the conductive pattern is deteriorated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to eliminate the drawbacks of the copper-based conductive pattern as described above, and provides a circuit board in which the conductive pattern does not peel off from the ceramic board even when heated and cooled. The purpose is to

[0009]

SUMMARY OF THE INVENTION To achieve the above object, the structure of a conductive pattern according to the present invention is applied to a circuit board for forming a conductive pattern on an insulating substrate and arranging electronic parts and the like on the conductive pattern. At least a conductive pattern in a region electrically connected to a terminal portion of the electronic component or the like has a multilayer structure, and the electronic component or the like is connected to a lowermost layer in contact with the insulating substrate of the conductive pattern having the multilayer structure. The uppermost layer is formed so that the content of the glass component is smaller.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments and the experimental results. FIG. 1 is a side view of a conductive pattern showing an embodiment of the present invention.

That is, the conductive pattern adhered on the ceramic substrate 5 is a conductive pattern 6 made of a copper-based metal paste containing a large amount of glass component in order from the surface of the ceramic substrate, and a conductive pattern made of a copper-based metal paste having a smaller glass component than the conductive pattern 6. 7 is a copper-based conductive pattern having a two-layer structure.

As described above, the present invention focuses on the glass component contained in the conductive pattern. Since the copper-based conductive pattern containing a large amount of glass component is attached to the ceramic substrate, the wettability is improved and the adhesive strength is high. Therefore, the copper-based conductive pattern having a small glass component has improved wettability with solder and improved adhesive strength with electronic components and the like. Since the conventional copper-based conductive pattern is a single layer, the composition was determined so as to obtain the minimum required adhesive strength for both the ceramic substrate and the solder, but according to the present invention, the ceramic substrate and the conductive pattern, and The strength to bond the conductive pattern and solder,
A conductive pattern that can be higher than each was obtained.

An experiment was conducted in which an oscillator was manufactured according to the present invention, the oscillator was subjected to a temperature cycle, and the peeling state between the ceramic substrate and the conductive pattern was confirmed. The temperature cycle is the same as the temperature cycle described in the related art, and the result of confirming the number of malfunctions of the oscillator when the number of parameters after completion of the temperature cycle cycle is 100 is shown in Table 1.

[0014]

[Table 1]

From the experimental results, even if the temperature cycle is carried out by utilizing the copper-based conductive pattern according to the present invention, that is, the solder is melted to correct the electronic parts, etc., the copper-based conductive pattern is more conductive than the ceramic substrate. It has become possible to realize a hybrid IC in which the pattern does not peel off.

Further, the entire conductive pattern formed on the ceramic substrate does not necessarily have to be a conductive pattern having a two-layer structure, and only the vicinity of the terminal portion of the electronic component or the like has a two-layer structure.
The other portion may be a single layer conductive pattern.

The vicinity of the terminal portion of the electronic part or the like of the conductive pattern formed on the ceramic substrate may have a structure of three layers or more. If the glass component is gradually reduced from the layer adhering to the surface of the ceramic substrate, the adhesive strength is further increased. A conductive pattern having a high resistance to temperature changes can be obtained.

Although the present invention has been described by way of example in which the present invention is applied to a hybrid IC having a conductive pattern made of a copper-based metal paste, the present invention is not limited to this and a silver-palladium-based conductive pattern is used. The conductive pattern may be made of another material such as.

[0019]

Since the present invention is configured as described above, in the process of manufacturing a hybrid IC, after fixing an electronic component or the like with solder on a conductive pattern formed on a ceramic substrate, the solder is attached to the conductive pattern. A significant effect is exhibited in correcting defects such as incorrect mounting positions of the electronic parts by heating and melting, and a highly reliable conductive pattern is obtained.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a conductive pattern according to the present invention.

FIG. 2 is a side view showing the configuration of a conventional hybrid IC.

FIG. 3 Detailed view of temperature cycle

FIG. 4 is a diagram of experimental data showing adhesion strength characteristics of conductive patterns by temperature cycling.

[Explanation of symbols]

 5 ... Ceramic substrate 6 ... Conductive pattern containing a large amount of glass component 7 ... Conductive pattern containing a small amount of glass component

Claims (2)

[Claims] 1. A circuit board for forming a conductive pattern on an insulating substrate and arranging an electronic component or the like on the conductive pattern, which is electrically connected to at least a terminal portion of the electronic component or the like. The conductive pattern of the region has a multi-layered structure, and the uppermost layer of the conductive pattern of the multi-layered structure has a lower glass component content than the lowermost layer in contact with the insulating substrate, The structure of the pattern. 2. The conductive pattern according to claim 1, wherein each layer of the conductive pattern is configured such that the content of the glass component gradually decreases from the lowermost layer on the surface side of the insulator toward the uppermost layer. Structure.