JPS61148897A - Ceramic circuit board and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic circuit board and a method of manufacturing the same.

(Prior Art and its Problems) A multilayer ceramic circuit board such as a ceramic package for a semiconductor device is formed by laminating a required number of green sheets each having a conductive paste pattern formed thereon and firing the stacked sheets. In order to improve the reliability of the semiconductor elements mounted on such a multilayer ceramic circuit board, airtightness is particularly required between the laminated layers.

By the way, conventionally, in order to form the above-mentioned conductive paste pattern on a green sheet, a conductive paste is formed on the surface of the green sheet by screen printing or the like.

When such a method is used, the conductive paste after printing rises in a semi-cylindrical shape on the surface of the Green Sea 10 as shown in FIG. 6, and a flat upper surface cannot be obtained. There is a problem in that it is difficult to reliably bond wires on the upper surface of the conductive paste to establish conduction with the semiconductor element.

Further, since the conductive paste bulges on the upper surface of the green sheet 10, as shown in FIG. 7, there is a problem that voids are generated when the sheets are laminated, which deteriorates airtightness.

In order to solve this problem, sometimes a method is adopted in which the conductor paste is pressed and press-fitted onto the upper surface of the green sheet 10 after the conductor paste has dried.

In this case, the voids during lamination can be made smaller and the airtightness improved to some extent, but in addition to the need for a pressing process, the upper surface of the conductive paste is After all, it almost remains like a kamaboko shape,
Less reliable than wire bonding. Further, since the conductive paste is press-fitted into the green sheet 10, the density of the green sheet 10 becomes non-uniform, and there is a problem that the multilayer ceramic or circuit board warps after firing.

Another method for forming a conductive paste pattern on the green sheet 10 is the method disclosed in Japanese Patent Laid-Open No. 132698/1983.

In the above method, the upper surface of the green sheet corresponding to the position where the conductive paste will be printed is pressed in advance with a press mold to form a concave groove, and the conductive paste is heaped up in this concave groove by screen printing etc. By doing so, the cross-sectional area of the conductor paste is increased and the resistance of the conductor paste is lowered.

According to the above method, the cross-sectional area of the conductive paste can be increased (and its resistance can be lowered) without having to pile up the conductive paste on the green sheet.

Therefore, it is also possible to improve the airtightness when laminated as described above.

However, in the above method, since the viscous conductor paste is filled in the groove, the upper surface of the conductor paste still takes on a semicylindrical shape to some extent, resulting in a lack of reliability in wire bonding. Since the green sheet is formed by pressing with a press mold, the problem of warping of the substrate due to non-uniform density after firing the green sheet remains unresolved.

(Summary of the Invention) The present invention has been made to solve the various problems mentioned above, and its objectives are to have excellent airtightness, □buoy + - bonding properties, and to prevent warping (which occurs) after firing. The purpose of the present invention is to provide a ceramic circuit board and an effective method for manufacturing the same.'□・And its characteristics are that in a ceramic circuit board made by firing a green sheet, a conductive pattern is formed on the ceramic surface, and the surface of the conductive pattern is is formed on a flat surface, and the position of the flat surface is aligned with the position of the ceramic surface. A necessary conductor paste pattern is formed on the surface, and a ceramic slurry containing a mixture of ceramic powder, solvent, binder, etc. is shift-molded onto the support from above the conductor paste pattern, and after drying, the support is The step is to peel off the green sheet and form a conductive paste pattern on the green sheet.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail based on the accompanying drawings.

First, as shown in FIG. 1, a conductor paste 22 is screened onto a support 2o made of polyethylene terephthalate film or the like in a pattern that is a mirror reflection of the conductor paste pattern to be obtained on the green sheet. Print.

Next, this is dried and a conductive paste 22 is placed on the support 2o.
solidify. Note that the conductor paste 22 used is one obtained by kneading tungsten powder, a solvent, a binder, and the like.
``The dried and solidified conductor paste 22 rises in a semicircular shape on the support 20, as in the conventional case.

Next, as shown in FIG. 2, a ceramic slurry 24 containing a mixture of ceramic powder, a solvent, a binder, etc. is formed into a sheet by a doctor blade method on the surface of the support 20 on which the conductor paste 22 has been dried and solidified. .

After drying this green sheet 26, the support 2
0 from the surface of the green sheet 26. As a result, the conductive paste 22 remains on the green sheet 26 side, and a desired conductive paste pattern is formed on the surface of the green sheet 26. When the aforementioned polyethylene terephthalate film was used as the support 20, the conductive paste 22 was suitably transferred to the green sheet 26 without adhering to the support.

As shown in FIG. 3, the pier holes 28 are formed in the support 20 before the support 20 is peeled off after the green sheet 26 is dried.
It is preferable to fill the inside of the pier hole 28 with a conductive paste by simultaneously providing the conductive paste through the pier hole 28 and placing an appropriate mask in contact with the support 20 side, or by using the support 20 itself as a mask. In this case, since the support 20 is in close contact with the surface of the green sheet 26, the conductor paste does not bleed onto the surface of the green sheet 26, and the problem of short circuit between the conductor paste and the conductor paste pattern due to bleed is solved. .

Further, in order to prevent the conductor paste pattern from seeping into the ceramic slurry, it is preferable to use a combination of solvent and binder such that the solvent in the ceramic slurry does not dissolve the binder in the conductor paste.

FIG. 4 shows the green sheet 26 after the support 20 has been peeled off. As is clear from the figure, the conductive paste pattern formed on the surface of the green sheet 26
The inside of the green sheet 26 has a semi-cylindrical cross section, and its upper surface is a completely flat surface that coincides with the surface of the green sheet 26. Therefore, wire bonding can be performed reliably, and even when stacked as shown in FIG. 5, no voids are created, resulting in perfect airtightness. Also green sheet 26
Since the density is also uniform, warping does not occur after firing.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide an extremely reliable ceramic circuit board that is particularly excellent in wire bonding properties and airtightness.

Furthermore, according to the method of the present invention, the above-mentioned ceramic circuit boards can be manufactured continuously and efficiently, and since the green sheet maintains the uniform density as it was when the sheet was formed, the ceramic circuit board does not warp after firing. Circuit boards can be manufactured.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a state in which conductive paste is printed on the surface of a support, Fig. 2 is an explanatory diagram showing a sheet forming method using a doctor blade method, Fig. 3 is a cross-sectional view with a pier hole provided, and Fig. 4 is an explanatory diagram showing a state in which conductive paste is printed on the surface of a support. FIG. 5 is an explanatory view showing the green sheet after peeling off the support, and FIG. 5 is an explanatory view showing the stacked state of the green sheets. Figure 6 is an explanatory diagram showing the formation state of conventional conductive paste, Figure 7 is an explanatory diagram showing the laminated state of green sheets, and Figure 8 is an explanatory diagram showing the state of conventional conductor paste formation. Figure 8 is an explanatory diagram showing the state of formation of the conventional conductive paste. It is an explanatory diagram showing a state. 10...Green sheet, 20...Support,
22...Conductor paste, 24...Ceramic slurry 226...Green sheet. 28... Pier Hall.

Claims (1)

[Claims] 1. In a ceramic circuit board obtained by firing a green sheet, a conductor pattern is formed on the ceramic surface, and the surface of the conductor pattern is formed as a flat surface, and the position of the flat surface is the same as the position of the ceramic surface. Ceramic circuit board formed to match. 2. The ceramic circuit board according to claim 1, wherein the ceramic circuit board is a multilayer ceramic circuit board obtained by laminating and firing green sheets having the conductor pattern formed on at least the surface thereof. 3. In the method of manufacturing a ceramic circuit board using a green sheet, a necessary conductor paste pattern is formed in advance on the surface of a support such as a polyester film, and ceramic powder and solvent are applied onto the support from above the conductor paste pattern. , a binder, etc. are mixed into a sheet, and after drying, the support is peeled off from the green sheet to form a conductive paste pattern on the green sheet. 4. The method of manufacturing a ceramic circuit board according to claim 3, wherein the ceramic circuit board is a multilayer ceramic circuit board obtained by laminating and firing green sheets having the conductor paste pattern formed on at least the surface thereof.