JPS6182493A - Manufacture of ceramic circuit board - 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 (Technical Field of the Invention) The present invention relates to a method of manufacturing a ceramic wiring board, and more particularly to a method of manufacturing a ceramic board that includes a step of surface treating the board using a predetermined solution after firing.

[Technical background of the invention and its problems]

A multilayer wiring board using an alumina ceramic substrate is generally manufactured through the following steps. That is, a desired conductor pattern is formed on an unfired ceramic substrate called an alumina green sheet using a conductor paste mainly made of a high melting point metal such as tungsten (W) or molybdenum (MO). . Next, screen printing is performed using an insulating paste mainly composed of alumina powder, which is the same material as the substrate, to form an interlayer insulating layer.

After the conductive patterns and interlayer insulating layers are formed alternately to form a multilayer structure, baking is performed at 1500 to 1600° C. in a slightly reducing atmosphere to firmly bond the substrate, conductive patterns, and interlayer insulating layers. Then, in order to mount IC chips and other components and enable wire bonding, nickel (N i ) is placed on the conductor pattern.
The multilayer wiring board is completed by plating with gold (Au) or the like.

However, in such a conventional manufacturing process of a ceramic wiring board, conductors scattered during firing often adhere to areas other than the conductor pattern on the board, especially after firing. If electroless plating is performed on a substrate with conductors still attached to unnecessary areas on the substrate surface, the plating film will not only be deposited on the conductor pattern but also on the conductors attached in other areas. It will be formed. For this reason, expensive materials such as Nt and Au, which are plated metals, are wasted and not only is there a problem in terms of cost, but in the worst case, the plating formed on unnecessary areas may lead to conductive patterns. There is a problem of short circuit between the two.

In addition, as mentioned above, the adhesion of the conductor that adheres to areas other than the conductor pattern on the substrate after firing is quite strong and is dispersed in a large number of places, so it should be checked using a microscope, etc. If an attempt is made to remove the material mechanically, it is very time consuming and there is a risk of accidentally damaging the substrate surface, conductor pattern, etc., which may actually reduce the yield.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a ceramic wiring board that can prevent a plating film from adhering to areas other than the conductor pattern on the board during the plating process after firing.

[Summary of the invention]

The method for manufacturing a ceramic substrate according to the present invention includes forming a desired conductive pattern on a ceramic substrate using a conductive paste and firing it, and then immersing the ceramic substrate in a solution that corrodes the conductive paste. The method is characterized in that it includes a step of peeling off the conductor attached to the area other than the conductor pattern on the substrate, and then plating the conductor pattern.

Here, when the conductive paste is mainly composed of tungsten or molybdenum, the solution is suitably an aqueous solution containing potassium ferricyanide and sodium hydroxide. Further, when the ceramic substrate is immersed in the solution and the conductor attached to the area other than the conductor pattern on the ceramic substrate is peeled off, the solution is subjected to ultrasonic imaging,
It is more effective to perform so-called ultrasonic cleaning.

(Effects of the Invention) According to the present invention, after forming a conductor pattern using a conductor paste and baking it, the substrate is immersed in a solution before the plating process to peel off the conductor attached to areas other than the conductor pattern. This prevents a plating film from being formed on areas other than the conductor pattern during the plating process.

Therefore, expensive materials such as Ni and Au, which are plating metals, are not wasted, and costs can be reduced. Further, defects such as short circuit between conductive patterns due to plating do not occur.

Further, the step of checking the substrate surface after firing is unnecessary or extremely simple, and agricultural productivity is improved.

Furthermore, unlike the method of mechanically removing the taming film adhering to areas other than the conductor pattern, this method does not damage the substrate surface or the conductor pattern, and the yield is improved accordingly. Moreover, as a secondary effect, the surface of the conductive pattern is appropriately roughened by the treatment with the solution, which increases the adhesion of the plating film and improves the reliability of the wiring board.

[Embodiments of the invention]

The present invention will be explained in detail below.

An alumina green sheet (unfired sheet) as a ceramic substrate was obtained by a doctor blade method using an inorganic powder containing 93% of alumina (Aj2203).

Printing was performed on this alumina green sheet using a conductor paste mainly composed of tungsten, and the paste was dried to form a desired conductor pattern. Next, an insulating paste containing the same inorganic powder as the alumina green sheet as its main component was similarly screen printed and dried to form an interlayer insulating layer. The printing and drying of these conductor patterns and interlayer insulating layers were alternately repeated several times to obtain a multilayer wiring structure with three layers of conductor patterns.

Next, the board with this multilayer wiring structure was heated to 1550°C to 1600°C.
It was fired in a slightly reducing atmosphere at 9°C. At least 30% of the fired substrates obtained at this time were found to have tungsten attached to areas other than the conductor patterns.

Therefore, the substrate with this unnecessary tungsten attached was immersed in an aqueous solution of 100 g of potassium ferricyanide (K3 Fe (ON)s), 100 G of sodium hydroxide (NaOH), and 1000 cc of water, and ultrasonic cleaning was performed for 150 seconds.

Next, the substrate was washed with water for 1 minute, and then the surface of the substrate was dried with air blow. Furthermore, put the substrate in acetone and
Ultrasonic cleaned for ~15 minutes. When the substrate subjected to such treatment was checked under a microscope, no tungsten was found to be attached to any part other than the desired conductor pattern. Next, on the conductor pattern of the substrate from which the tungsten that had adhered to areas other than the conductor pattern was peeled off and removed by surface treatment with a solution, an underlayer of Ni2 and Au as a surface layer was applied by electroless plating. was attached.

After this plating step, when it was checked again using a microscope, no plating film was observed in areas other than the desired conductor pattern, and a yield of 100% was obtained.

In place of tungsten in Example 1, molybdenum (M
When a multilayer wiring board was manufactured using a conductor paste mainly composed of O) and the other steps were exactly the same as in Example 1, no unnecessary plating film was observed after the plating process was completed. The yield was 100%.

Note that the present invention is not limited to the above embodiments,
For example, when the conductor paste is W or MO, the solution for peeling off the conductor attached to areas other than the conductor pattern on the board may be a combination of potassium permanganate, potassium hydroxide, etc., and sodium hydroxide, in addition to the solutions mentioned above. It was confirmed that the same effect could be obtained by using .

In addition, in the example, a conductor pattern and an interlayer insulating layer were formed on a green sheet, that is, an unfired ceramic substrate, and then the substrate, the conductor pattern, and an interlayer insulating layer were fired together. A pattern or the like may be formed and then fired. Furthermore, although the method for manufacturing a multilayer wiring board has been described in the embodiment, the present invention may include a process of forming a conductive paste on a ceramic substrate by printing or the like, and plating the conductive pattern after firing. , is also effective for manufacturing single-layer wiring boards.

Claims (3)

[Claims] (1) After forming a desired conductor pattern on a ceramic substrate using a conductor paste and firing it, the ceramic substrate is immersed in a solution that corrodes the conductor paste, thereby forming a conductor pattern other than the conductor pattern on the ceramic substrate. A method for manufacturing a ceramic wiring board, comprising the steps of peeling off a conductor adhering to a region, and then plating the conductor pattern. (2) Manufacturing the ceramic wiring board according to claim 11, wherein the conductive paste is mainly made of tungsten or molybdenum, and the solution is an aqueous solution containing potassium ferricyanide and sodium hydroxide. Method. (3) By immersing the ceramic substrate in a solution that corrodes the conductor paste, ultrasonic vibration is applied to the solution when peeling off the conductor attached to areas other than the conductor pattern on the ceramic substrate. A method of manufacturing a ceramic wiring board according to claim 1, characterized in that: