JPH0964502A - Thick film integrated circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] Improving the performance and reliability of thick-film ICs without changing the alumina-ceramic substrates that have been used in the past, without lowering manufacturing efficiency and increasing costs. . [Structure] An underlayer such as glass is partially interposed between a conductor layer forming a through-hole wiring portion or a joint portion of different-layer wiring and the surface of an alumina / ceramic substrate. [Effect] The underlayer can disperse the shrinkage stress of the conductor layer formed on the underlayer, or can improve the printability when printing the copper paste.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick film integrated circuit, and further to a thick film IC (integrated circuit) using an alumina / ceramic substrate and a copper thick film paste for firing in an atmosphere using an inert gas such as nitrogen. ) Is effective when applied to the above), and is effective when applied to a high frequency hybrid IC, for example.

[0002]

2. Description of the Related Art In a thick film IC, a wiring conductor layer is formed by firing a wiring pattern of a conductor paste printed on an insulating substrate at a high temperature. This thick film IC is often used for a high frequency circuit that is difficult to form with a monolithic IC (see, for example, "Integrated Circuit Engineering (1)" published by Corona Co., Yoshiyoshi Yanai, Minoru Nagata, pp. 12-14). FIG. 2 shows a schematic structure of a thick film IC examined by the present inventors. 1 is an alumina / ceramic substrate, 11 is a through hole portion, 21 and 22 are inert gases such as nitrogen. Conductor layers 3 using a copper thick film paste for firing in a different atmosphere are interlayer insulating layers.

For the conductor layers 21 and 22, a copper paste is used as a conductor paste, and this copper paste is printed on the substrate 1 to form a pattern of a copper thick film paste layer, which is then treated with an inert gas such as nitrogen. It is formed by firing at high temperature in the atmosphere used.

Conductor layers 21, 22 using the copper thick film paste for firing in an atmosphere using an inert gas such as nitrogen
According to the knowledge of the present inventors, compared with the one using a silver palladium paste, the resistance increase due to diffusion and chemical reaction during firing is small, and thus it is particularly suitable for a high-frequency thick film IC. There was found.

[0005]

However, it has been clarified by the present inventors that the above-described technology has the following problems.

That is, in the thick film IC described above, the substrate 1
When the copper thick film paste layer is printed on the through hole 1
Partial defects due to printing blur are likely to occur at the edge portion 12 of No. 1. Further, when the conductor layer 21 is formed by firing, there is a problem that cracks and peeling are likely to occur due to the shrinkage stress during firing being concentrated at the edge portion 12.

Further, in the multilayer wiring in which the two conductor layers 21 and 22 are formed with the interlayer insulating layer 3 sandwiched therebetween, a large step d is generated between the interlayer insulating layer 3 and the lower conductor layer 21, and this step d
Causes deterioration of printability when the upper conductor layer 22 is formed by printing a copper paste.

All of these problems greatly affect the performance and reliability of thick film ICs.

As a means for solving the above-mentioned problems, the present inventors have used silver-palladium paste instead of copper paste, chamfered the edge portion 12 of the through-hole portion 11, and overprinted on cracks and peeled portions. Then, the method of re-baking was examined.

However, as described above, the silver-palladium paste causes a large amount of resistance increase due to diffusion and chemical reaction during firing, which causes a problem in high-frequency characteristics.

The chamfering of the edge portion 12 is meaningless unless it is performed from both sides of the substrate 1.
It is not enough to process the shape of the through-hole molding pin to perform it only in the ceramic molding process, and the molding method itself must be fundamentally changed, and it is extremely difficult to actually implement this. is there. A liquid honing treatment is a possible method. However, if the liquid honing process is performed, the edge portion 11 may be chamfered, but since other surfaces are also shaved together, the flatness or surface roughness of the substrate surface may be changed. Is accompanied by. Further, in the high frequency hybrid IC, the alumina / ceramic substrate is an important factor that determines the characteristic impedance of the strip line, and therefore the shape such as the thickness cannot be unnecessarily changed.

In the method of overprinting and re-baking, a baking step for baking in an atmosphere using an inert gas such as nitrogen, which requires a large amount of inert gas such as nitrogen, must be carried out. There are problems in manufacturing efficiency and cost.

The object of the present invention is to modify the alumina-ceramic substrate, which has been used in the past, without any change.
Also, without lowering manufacturing efficiency and increasing costs,
It is to provide a technique for improving the performance and reliability of a thick film IC.

The above and other objects and features of the present invention will be apparent from the description of the present specification and the accompanying drawings.

[0015]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, a base layer such as glass is partially interposed between the conductor layer forming the through-hole wiring portion or the joining portion of the interlayer wiring and the surface of the substrate made of alumina / ceramics or the like.

[0017]

According to the above-mentioned means, the underlayer can disperse the shrinkage stress of the conductor layer formed on the underlayer, or can improve the printability when printing the copper paste.

Thus, the purpose of the present invention is to improve the performance and reliability of the thick film IC without changing the alumina / ceramic substrate which has been used in the past, without lowering the manufacturing efficiency and increasing the cost. Is achieved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

In the figures, the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows a thick film IC to which the technique of the present invention is applied.
An example will be described.

The thick film IC shown in the figure is constructed as a high frequency hybrid IC, where 1 is alumina.
Ceramic substrate, 11 is through hole portion 21, 22
Is a conductor layer using a copper thick film paste for firing in an atmosphere using an inert gas such as nitrogen, 3 is an interlayer insulating layer, and 4 is a base layer.

The alumina / ceramics substrate 1 is manufactured through a conventional molding process, and the through-hole portion 11 has an edge portion 12 which is not chamfered as pin-molded.

Each of the conductor layers 21 and 22 is formed by firing a pattern-printed copper thick film paste layer on the substrate 1 at a high temperature in a unitary atmosphere using an inert gas such as nitrogen. The first conductor layer 21 forms the lower wiring layer of the multilayer wiring, and the second conductor layer 22 forms the upper wiring layer thereof. Each of the conductor layers 21 and 22 is formed only by one printing process and one firing process.

The underlayer 4 is made of a glass material. Unlike the conductor layers 21 and 22, the glass underlayer 4 is formed by firing in air without using an inert gas such as nitrogen gas. Further, the glass base layer 4 is selectively formed partially on the surface of the substrate to be the through hole wiring portion A and the joining portion B of the interlayer wiring. Then, after the glass base layer 4 is formed, the first conductor layer 21, the interlayer insulating layer 3, and the second conductor layer 22 are sequentially formed.

Next, the operation will be described.

As shown in FIG. 1, in the through hole wiring portion A, the edge portion 12 of the through hole portion 11 is covered with the glass underlayer 4 and smoothed, so that the copper thick film at the edge portion 12 is formed. The printability of the paste is improved, and it is possible to eliminate a partial defect due to a print scrap.
At the same time, the stress concentration at the time of firing is dispersed, and the conductor layer 21 can be prevented from cracking or peeling.

At the joint portion B of the interlayer wiring, the step d generated between the lower conductor layer 21 and the interlayer insulating layer 4 is reduced and relaxed by the glass underlayer 4, so that the upper conductor layer 22 is formed. The printability of the copper thick film paste is improved, and the conductor layer 22 having predetermined electrical characteristics is stably formed.

As described above, the shrinkage stress of the conductor layer is dispersed, and the printability at the time of printing the copper thick film paste is improved, so that the shape of the alumina / ceramic substrate 1 which has been used in the past can be obtained. The conductor layer can be stably formed without making a change, and without lowering the manufacturing efficiency and increasing the cost.
The performance and reliability of can be improved.

The invention made by the present inventor has been specifically described above based on the embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the underlayer 4 may be a material other than glass as long as it is a material that can be fired in air and has a different shrinking point and shrinking amount during firing than the copper paste. . Specifically, a silver-palladium paste may be used.

In the above description, the case where the invention made by the present inventor is mainly applied to a high frequency hybrid IC which is the field of application which is the background of the invention has been described. It can also be applied to integrated circuits.

[0033]

The effects of typical inventions disclosed in the present application will be briefly described as follows.

That is, the conductor layer can be stably formed without changing the shape of the alumina-ceramic substrate 1 which has been used in the past, and without lowering the manufacturing efficiency and increasing the cost. , Thick film IC
The effect that the performance and reliability of can be improved can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a thick film integrated circuit to which the technique of the present invention is applied.

FIG. 2 is a sectional view showing an outline of a conventional thick film integrated circuit.

[Explanation of symbols]

 1 Alumina / Ceramics Substrate 11 Through Hole 12 Edge 21 Lower Conductor Layer 22 Upper Conductor Layer 3 Interlayer Insulating Film 4 Underlayer A Through Hole Wiring Part B Interlayer Joint Part

Claims (4)

[Claims] 1. A thick film integrated circuit in which a base layer is formed in advance on a through hole portion of a substrate having a through hole, and a wiring layer is formed on the base layer. 2. The thick film integrated circuit according to claim 1, wherein the wiring layer is formed of silver, platinum, gold, or silver palladium, and the underlayer is formed of glass. . 3. The thick film integrated circuit according to claim 1, wherein the substrate is an alumina / ceramic substrate. 4. A thick film integrated circuit characterized in that an underlayer is formed in advance on a joint portion of different layer wirings of an integrated circuit substrate having a multilayer wiring structure, and a wiring layer is formed on the underlayer. .