JPS61147597A - 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 such as a mounting motherboard, a high frequency board or a high power board, and a method for manufacturing the same.

(Conventional technology) Conventionally, this kind of ceramic circuit board.

Ag/Pd, Ag/
There is a substrate (hereinafter referred to as a thick-film substrate) that is printed and fired with a conductor such as Pf or Au and glass. Also, W.

There is also a ceramic circuit board (hereinafter referred to as a co-fired board) manufactured by forming a pattern of Mo or the like on a ceramic green sheet by a printing method and then performing co-firing.

Furthermore, a ceramic circuit board (hereinafter referred to as "ceramic circuit board") was manufactured by printing and firing a thick film with low conduction resistance on the fired board formed by simultaneous firing.

A hybrid substrate (called a hybrid substrate) has also been proposed.

(Problem to be solved by the invention) Among the circuit boards mentioned above, thick film boards.

When a conductor and glass are laminated, the reliability of the laminated portion is low, making it difficult to form a complicated circuit or realize a circuit element such as a capacitor element at low cost.

On the other hand, co-fired substrates have a dimensional tolerance of ±1%, which means that unevenness or waviness may occur on the surface.

High-precision mounting 1 For example, I
This is difficult to apply when implementing C.

Also, W, Mo, etc. have high conductor resistance.

Particularly, problems arise with substrates used in high frequency bands of 100 MHz or higher.

Furthermore, in the case of hybrid substrates, the effects of warping and ridges on the fired substrate must be taken into consideration.

High precision patterns cannot be obtained.

(Object of the Invention) An object of the present invention is to provide a ceramic circuit board on which a highly accurate circuit is formed together with circuit elements such as capacitive elements.

Another object of the present invention is to provide a ceramic circuit board that can be used even at high frequencies.

Still another object of the present invention is to provide a ceramic circuit board on which even high-power semiconductor devices can be mounted.

Another object of the present invention is to provide a method for manufacturing a ceramic circuit board that allows circuits to be formed with high precision and also allows for mounting high frequency and high power devices.

(Means for Solving the Problems) According to the present invention, in a ceramic circuit board having internal wiring and surface wiring electrically connected to the internal wiring, one surface wiring is formed with higher precision than the internal wiring. A ceramic circuit board is obtained.

In the present invention, the internal wiring is formed by simultaneous firing, and the other 9
A method for manufacturing a ceramic circuit board formed by a method that allows pattern formation with higher precision than surface wiring during baking is obtained.

(Example 1) First, in this example, the present invention is applied to the production of a motherboard for flip-chip mounting and a motherboard for high-precision mounting. A predetermined number of alumina green sheeters are prepared, and through holes are formed in each sheet according to the intended wiring.

In this state, a conductor such as W or Mo is printed on each sheet. Printed conductors are filled into the through holes and drawn onto the surface of each sheet. The conductors on each side are patterned in areas that are to become internal wiring inside the board. On the other hand, the above-mentioned conductor is printed on the entire surface of the sheet, which is to become the surface of the board. Full-page printing may be applied to one side of two sheets that provide both surfaces of the board, or may be applied to one side of one sheet.

After printing, the sheets are stacked with other sheets to form a laminate. In this case, the conductor pattern on each sheet is electrically connected to the conductor pattern on the other sheet through the conductor filled in the through hole.

The laminate is fired and integrated in a reducing atmosphere at about 1600° C. to form a fired substrate. This fired substrate has W inside it.
, Mo, etc., and a surface conductor such as W, Mo, etc. that is deposited over the entire surface of one surface.

As described above, the fired substrate formed by co-firing the conductor and the sheet shrinks during firing. Since this firing shrinkage fluctuates irregularly, a dimensional tolerance of about 1φ occurs. therefore.

When automatically mounting components on a large motherboard.

Alternatively, when a flip-chip type IC chip is directly mounted on a motherboard, problems often occur in the connecting portions due to the above-mentioned dimensional tolerances.

In this embodiment, a surface conductor provided on the surface of a fired substrate is etched using a photoresist to form two-surface wiring. Surface wiring formed by etching has better dimensional tolerance and higher precision than internal wiring.

FIG. 1 shows a ceramic circuit board according to this embodiment, which is formed by laminating and firing two sheets.

As shown in the figure, there is an internal wiring 10 between the two fired notebooks.
Each internal wiring is electrically connected to a surface wiring 12 provided on the surface of the substrate through a conductor 11f filled in a through hole. The surface wiring is formed by etching after firing. In this configuration, since the diameter of one surface wiring is not affected by firing shrinkage, it can be formed with higher precision than internal wiring.

After etching, Ni, Au,
Cu.

It is also possible to form Sn or the like by plating or the like and perform surface treatment. Further, a capacitive element, a resistive element, or the like may be included in the internal wiring 10. On the other hand, a capacitive element and a resistive element may be included in the first surface wiring 12.

(Example 2) In a second example (Example 2) of the present invention, only a conductor pattern corresponding to internal wiring is provided on a green sheet, and no surface conductor is formed. In this state, simultaneous firing is performed to create a fired substrate.

On the surface of the fired substrate, the conductor is exposed only in the portion filled with the through hole, and there are irregularities and undulations depending on the firing conditions.

In this example, the surface of the fired substrate was polished.

Flatten. Cu, Au on the flattened surface.

A conductive paste such as Ag/PD is printed and fired.

Form surface wiring. Since the surface wiring formed in this manner is not affected by surface warping or waviness, it has smaller dimensional tolerances than internal wiring. If surface wiring with higher precision is required, etching may be performed on the nine surface wirings.

(Example 6) The substrate obtained in Example 1 was provided with a surface pattern with higher precision than the internal wiring. On this surface pattern, N
i, after plating with Cu, etc.

As in Example 2, Cu, Au, kg/
Print and fire a conductor paste such as Pd. In this way, by using a pattern consisting of a multilayer structure of different metals as surface wiring, it is possible to not only form high-precision surface wiring, but also to print and attach high-precision resistors as passive components. Surface wiring that is less affected by warpage, cracks, etc. can be created.

(Example 4) With reference to FIGS. 2(a), (b), and (c),
A method for manufacturing a ceramic circuit board according to Example 4 will be described.

As shown in FIG. 2(a), through holes and conductors such as W and Mo are printed and fired on two green sheets to create fired substrates. As shown in FIG. 2(a), this fired substrate includes a capacitive element in the internal wiring 10, and no surface wiring is provided on the surface 9. Therefore, a through hole filled with a conductor is exposed on the surface.

As described above, undulations or undulations occur on the surface of the fired substrate. In this example.

As shown in FIG. 2(b), both sides of the fired substrate are polished,
Make a uniform surface. In this state, N is applied to the surface of the through hole.
After plating with Cu, etc., a tough pitch Cu foil or a high-purity oxygen-free copper (OFHC) foil with an oxidized surface was placed, and N2. In an inert atmosphere such as Ar, from 1065℃
Heat at a temperature of 1083°C.

Through this heat treatment, the Cu foil adheres to the alumina and the conductor in the through hole, forming surface wiring 12 as shown in FIG. 2(c). A small amount of oxygen is required during bonding, but in the case of tough pitch Cu that already contains oxygen, there is no need to supply oxygen again. Further, in the case of 0FHC which does not contain oxygen, two surfaces may be oxidized in advance, or oxygen may be contained in an inert atmosphere.

In this example, since the surface of the fired substrate is polished, the Cu foil can be bonded without any non-bonded portions (voids).

In addition, the surface wiring formed of Cu foil can be electrically connected to the internal wiring and the surface wiring on the other side via through holes.

A multilayer ceramic circuit board using Cu foil bonding technique (direct copper bonding technique) is obtained.

With this bonding technique, surface wiring can be formed with higher precision than internal wiring, and it is also possible to create surface wiring that is thicker than conductors deposited by thick film methods or the like. In other words,
Surface wiring deposited in this manner has a lower conduction resistance than internal wiring. Therefore, the ceramic circuit board according to this embodiment can be used as a high frequency or high power board.

By the way, surface wiring with a thickness of 18 to 55 microns has a current of 5 m
It is effective when used at frequencies below A and from IGHz to 4GHz, and surface wiring with a thickness of Oy3m can constitute a circuit in which a current of 25A or less flows. Similarly, surface wiring having a thickness of 0.5 or more can be applied to a circuit in which a current of 600 A or more flows.

Since the above-mentioned surface wiring is made of copper, it has better electrical characteristics than aluminum or the like and is cheaper than gold, silver, or the like.

Furthermore, there is an advantage that mounting such as soldering and bonding is possible without performing surface treatment. As in this example, direct copper bonding techniques can be combined with co-firing techniques to form multilayer circuits.

FIG. 6 shows another embodiment of the ceramic circuit board according to the present invention. In this embodiment, first, ceramic green sheets 21 and 22 are prepared, through holes n are made in each of the green sheets 21 and 22, through hole printing is performed, and conductors are embedded in the through holes. next.

A conductor layer 5 serving as part of the internal wiring is formed on one surface (upper surface in the figure) of the green sheet 21 by printing, and then an insulating layer 26 is applied by printing. A connection opening 27 is formed in this insulating layer 26 . On the insulating layer 26, an intermediate conductor layer track is formed by printing, which is connected to the conductor layer 5 via a connecting hole 27.

Thereafter, the insulating layer 31 and the upper conductor layer 32 are formed by printing in the same manner. It can be seen that the illustrated intermediate conductor layer and part of the upper conductor layer 32 constitute a capacitive element. Next, the green sheet 22 is mounted on the insulating layer 31 and the upper conductor layer 32.

A laminate is formed and subsequently co-fired.

Thereafter, surface wiring 33 is applied to the upper and lower surfaces of the ceramic laminate using the above-described method to form a ceramic circuit board.

Nine embodiments of the present invention have been described above.

The present invention is not limited to the above embodiments, and can be modified in various ways. For example, the internal and surface wiring may include a capacitive element or the like, and one surface wiring may have a multilayer structure. Furthermore.

In the sixth embodiment, if the surface wiring is made thicker, the seventh surface wiring can be used for heat radiation.

As a modification of the present invention, Ni is added to the conductor surface of the co-fired substrate.
After complete plating with Cu, etc., Cu, Au.

It is also possible to print and bake a thick film paste of Ag/Pd or the like to form a multilayer structure. As a result, the dielectric strength voltage that was generated by multilayering only thick film paste has been reduced.

Problems related to warpage, cranks, etc. can be solved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a ceramic circuit board according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view for sequentially explaining the manufacturing process of a ceramic circuit board according to another embodiment of the present invention. and FIG. 6 is a sectional view showing a ceramic circuit board according to still another embodiment of the present invention. Explanation of symbols 10: Internal wiring 11: Conductor 12: Surface wiring Figure 1 Figure 2 (a) <b)

Claims (1)

[Claims] 1. A ceramic plate having two surfaces facing each other, and a surface wiring formed on at least one of the surfaces;
In a ceramic circuit board having an internal wiring electrically connected to the surface wiring and arranged inside the ceramic, the internal wiring is formed by co-firing a ceramic green sheet and a conductor pattern, A ceramic circuit board characterized in that the surface wiring is formed with higher precision than the internal wiring. 2. Prepare a predetermined number of ceramic green sheets, provide through holes in each green sheet, form patterns using a printing method, and establish electrical continuity between each pattern via the through holes. A method for manufacturing a ceramic circuit board, characterized in that a fired ceramic board is formed by simultaneous firing, and then surface wiring is formed on the surface of the fired ceramic board with higher precision than the internal wiring. 3. A method of manufacturing a ceramic circuit board according to claim 2, wherein the surface wiring is formed by etching a metal layer deposited over the entire surface. 4. The method of manufacturing a ceramic circuit board according to claim 2, wherein the surface wiring is provided by polishing the entire surface and then forming a pattern. 5. The method of manufacturing a ceramic circuit board according to claim 4, wherein the pattern formation is performed using a direct copper bonding technique.