JPH05206598A - Ceramic circuit board - Google Patents

Abstract

PURPOSE:To provide a ceramic circuit board which is excellent in wettability to solder and hardly lessened in adhesive strength to a conductor layer and where a fine pattern can be easily formed. CONSTITUTION:A conductive resin layer 3 is provided onto a ceramic multilayer board 1, and a metal foil layer 4 is provided thereon. The conductive resin layer 3 brings the metal foil layer 4 into close and firm contact with the ceramic multilayer board 1 and absorbs thermal stress generated between the board 1 and the layer 4. The metal foil layer 4 is finely worked with ease and excellent in wettability to solder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic circuit board which can be used for circuit construction of electronic equipment and the like and which enables highly accurate wiring.

[0002]

2. Description of the Related Art In recent years, a ceramic circuit board is superior in heat conductivity, heat resistance, and chemical durability to an organic material substrate, and thus its use is expanding as an alternative to the organic material substrate. In addition, with the miniaturization and diversification of electronic devices, they have come to be widely used as substrates capable of high-density wiring and high-density mounting. Furthermore, it is expected that demand for semiconductor bare chip mounting substrates will increase in the future, and it is considered that finer wiring is required.

An example of a conventional ceramic circuit board will be described below with reference to the drawings.

FIG. 3 shows the structure of a conventional ceramic circuit board. FIG. 4 shows a structure of a ceramic circuit board on which electronic parts are mounted by a conventional manufacturing method.

As shown in FIG. 3, the conventional ceramic substrate is formed by depositing Ag on a ceramic substrate 21 made of alumina or the like.
The conductive layer 22 is formed by printing a conductive paste composed mainly of powder or Cu powder and adding borosilicate glass or borosilicate glass and a thermoplastic resin thereto. The conductor layer 22 is also formed on the through holes and the via holes 23 filled with the conductive paste. The ceramic substrate thus configured is fired, circuit components are mounted on the ceramic circuit substrate as shown in FIG. 4, and used in an electronic device.

As shown in FIG. 4, the ceramic multilayer substrate 2
4 is provided with a via hole 25, which is connected to the surface layer 26 as required. Further, the semiconductor 27 and the chip component 30 are connected to the surface conductor layer 26 by the solder 29 via the leads 28 and the like.

[0007]

However, in such a conventional configuration, the pattern shape of the conductor layer 22 formed by screen-printing a conductive paste has a pattern of ink bleeding,
It has been difficult to realize the design accuracy because problems such as a decrease in the linearity of the contour portion occur due to the influence of a screen (shade) through which a beard or ink penetrates. In particular, fine patterns, for example, line printing with a line width of 60 μm or less caused problems such as line breaks, and the 60 μm pattern was not practical.

Further, the surface is poor in smoothness and requires a variation of surface roughness of ± 10 μm, so that it is difficult to adopt it for semiconductor flip mounting.

Further, at the time of forming the conductive pattern, 8
Since the entire substrate is baked at a temperature of 50 ° C to 900 ° C,
The glass increases the adhesion between the ceramic substrate 24 and the conductor layer 26, but the surface of the conductor layer 26 is changed by the glass.
There is a problem that the solder 29 gets worse than the metal foil. Further, as a change with time, the Sn component contained in the solder 29 diffuses inside the conductor layer 26 to form an alloy,
There was a very serious problem that the adhesion with the ceramic substrate was released by thermal shock.

Further, there is a problem that the firing at 850 to 900 ° C. causes contraction due to oversintering of the conductor forming the via hole 25, resulting in poor contact with the conductor layer 26.

The present invention solves the above problems and provides a highly reliable ceramic circuit board which can form a fine pattern with high accuracy, has good solder wettability, and does not deteriorate the adhesion strength due to thermal shock. It is intended to be provided.

[0012]

In order to solve this problem, a ceramic circuit board of the present invention provides a conductive resin layer composed of a metal filler and a resin on a ceramic substrate or a ceramic multilayer substrate having via holes, The metal foil layer is provided on the functional resin layer.

[0013]

According to the present invention, since the metal foil patterns, which have been preliminarily patterned with high precision, are laminated by the above-mentioned constitution, fine patterns can be formed with high precision as designed. Further, the metal foil layer can be formed to have a smooth surface and has good solder wettability. Since the metal foil has a high density, the Sn component contained in the solder does not easily diffuse, and the conductive resin layer absorbs the strain caused by thermal shock, so that the adhesive strength between the conductor layer and the ceramic substrate is not deteriorated over time. .

Further, as in the conventional case, 850 ° C. to 900 ° C.
Since the firing step is not performed, contact failure between the via hole and the metal foil layer due to shrinkage due to over-sintering of the metal powder conductor in the via hole does not occur, and high reliability can be maintained for a long period of time.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ceramic circuit board according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a ceramic circuit board according to an embodiment of the present invention. As shown in FIG. 1, a ceramic multi-layer substrate 1 made of alumina or glass is provided with a via hole 2 containing Cu conductor powder as a main material, and a photo-curing or thermosetting epoxy resin containing Ag powder as a conductive material is provided thereon. The conductor pattern 3 and the Cu foil 4 having a smoother surface are stacked, and the semiconductor bare chip 5 is passed through the Au bumps 6 by the solder 7 to form the Cu foil 4
Electrically connected to. Similarly, the chip capacitor 8 is electrically connected to the Cu foil 4 by the solder 7.

The operation of the ceramic circuit board configured as described above will be described below with reference to FIGS. 1 and 2. As shown in FIG. 2, the conductive resin layer 11 formed on the via hole 10 formed in the ceramic substrate 9
However, it also operates as an electrode that electrically connects the Cu foil 12 and the via hole 10, and also as an adhesive layer that firmly bonds the Cu foil 12 and the ceramic substrate 9.

Further, as shown in FIG. 1, the Cu foil 4 becomes a component pad for improving the wettability of the solder 7 for connecting the bare chip 5 and the chip capacitor 8 mounted thereon.
The conductive resin layer 3 operates as a buffer layer that absorbs strain due to the difference in thermal expansion generated between the ceramic substrate 1 and the component to be mounted.

As described above, according to this embodiment, the Cu foil 4 for mounting the component can be precisely patterned by a method such as etching, and then the Cu foil 4 can be adhered to the ceramic substrate through the conductive resin layer 3. . Further, since the Cu foil 4 does not contain glass, the solder wettability is good.

Further, the Cu foil 4 having a high density is slow in the diffusion of Sn, and the conductive resin layer 3 absorbs the strain caused by the difference in thermal expansion between the component and the ceramic substrate. The adhesion between the surface layer formed by the resin layer 3 and the ceramic multilayer substrate 1 is not reduced.

Further, as in the conventional example, 850 to 900 ° C.
Since the heat treatment at a high temperature is not performed, there is no shrinkage due to oversintering of the metal conductor of the via hole 2.
It is possible to eliminate poor contact between the conductive resin layer 3 and the conductive resin layer 3.

In this embodiment, the material of the ceramic multilayer substrate 1 is mainly composed of alumina and glass, but other ceramic materials can be used. Further, the epoxy resin conductive resin layer containing Ag as a filler may be a combination of another metal and another resin. Although Cu foil is used as the metal foil 4, any metal foil that can be soldered may be used.

[0023]

As is apparent from the above description of the embodiments, according to the present invention, a conductive resin layer made of a metal filler and a resin, in which a ceramic circuit board is formed on a ceramic substrate, and a conductive resin layer Since the metal foil layer is formed on the metal foil layer, the metal foil can be patterned in advance with high precision and a fine pattern can be formed. Further, since it is a metal foil, the solder wettability is good and there is no reduction in adhesion strength due to diffusion of Sn contained in the solder.

Further, since the high temperature treatment is not required, the conductive resin layer ensures the connection with the via hole, absorbs the strain between the component and the substrate due to the difference in thermal expansion, and does not reduce the adhesion strength between the conductor layer and the substrate.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state in which electronic components are mounted on a ceramic circuit board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of the ceramic circuit board.

FIG. 3 is a sectional view showing the structure of a conventional ceramic circuit board.

FIG. 4 is a sectional view showing a state where electronic components are mounted on the ceramic circuit board.

[Explanation of symbols]

 1 Ceramic Multilayer Substrate 2 Via Hole 3 Conductive Resin Layer 4 Metal Foil Layer

Claims (2)

[Claims] 1. A ceramic circuit comprising a ceramic substrate, a conductive resin layer mainly composed of a metal filler and a resin formed on the ceramic substrate, and a metal foil layer formed on the conductive resin layer. substrate. 2. The ceramic circuit board according to claim 1, wherein the ceramic board is a ceramic multilayer board having via holes.