JPH01112794A - Manufacture of ceramic two-sided wiring substrate - Google Patents

Abstract

PURPOSE:To manufacture a ceramic two-sided wiring substrate having highly reliable through-holes by applying a resist which shows a higher resistance to etching on an etching resist of a through-hole land as well as on the etching resist at inside walls of a hole for use in the through-hole prior to etching. CONSTITUTION:Laser processing makes it possible to make holes for use in through-holes by using an alumina substrate and phosphorus makes the surface of an alumina sintering substrate as well as the inside well faces of the holes for use in the the through-holes rough uniformly and after cleaning and drying the surface of the foregoing substrate and holes, copper layers 6 are formed by plating them chemically and then, after polishing the move copper layers 6, a positive photoresist material 7 is coated on the copper layer by using a roll coating utensil. Then, the photoresist material becomes film like when it is exposed and developed to/with ultraviolet rays by using a positive mask pattern and after that, an etching resist 8 is screen-printed on an etching pattern of a through-hole land and toward the inside of the holes for use in the through- holes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a ceramic double-sided wiring board with high through-hole reliability.

[Background technology]

Through hole (part lead wire insertion hole for parts installation)
One of the manufacturing methods for a ceramic double-sided wiring board with A method is known in which a resistor paste is applied by screen printing, dried, and then fired. As a method for filling the inside of the through-hole hole with the conductive paste, there is a method of filling the inside of the through-hole hole with the conductive paste using a nozzle, or a method of filling the inside of the through-hole with the conductive paste by reducing the pressure inside the through-hole and using a pressure difference. methods etc. are used. However, all of these filling methods have the disadvantage that the steps are complicated and conduction defects are likely to occur. Since a noble metal paste such as Au, Ag, or Pd is used as the conductor paste, the price of the paste is high, resulting in high costs. Furthermore, since glass frit was included in the paste, there was also the drawback that solder adhesion was poor. Therefore, this method is not suitable for manufacturing a ceramic double-sided wiring board having holes for through holes.

On the other hand, a method of forming a conductor layer of a ceramic substrate by a plating method is also known. According to this method, the formation of conductor layers and the formation of through holes on both sides of the ceramic substrate can be performed simultaneously, which is advantageous because the number of steps is small. Moreover, since the formed conductor layer contains almost no impurities, solder adhesion can be improved and fine wiring becomes possible. However, with this method, it is necessary to form the circuit by etching, and in this case, the thickness of the etching resist tends to be weakened at the edges of the through-hole holes. The conductive part formed on the wall surface and the wiring pattern parts on both the upper and lower surfaces of the board do not necessarily have a good connection.This will be explained in detail based on Figure 3.The figure shows a through-hole for a double-sided ceramic wiring board. The hole is shown enlarged.A land 2, which is part of the wiring pattern, is formed around the through-hole hole of the board 1.
and a conductive portion 4 formed on the wall surface of the through-hole hole 3 are connected at edges 5a to 5d. However, the thickness of the conductive part at all edges is not sufficient, and as shown in the figure, for example, the thickness of the conductive part at edges 5c and 5d becomes very thin, sometimes causing disconnection, etc. This may cause trouble.

[Purpose of the invention]

In view of the above circumstances, it is an object of the present invention to provide a method for manufacturing a ceramic double-sided wiring board with high through-hole reliability.

[Disclosure of the Invention] - In order to achieve the above object, the present invention provides a method for forming conductor layers by plating on both surfaces of a ceramic substrate in which through-hole holes are formed at desired positions and on the inner wall surface of the through-hole holes. After that, an etching resist is formed on the conductor layer, and a desired circuit is formed by etching. The gist of this invention is a method for manufacturing a ceramic double-sided wiring board characterized by further coating an etching-resistant resist on the etching resist on the inner wall surface of the hole.

The present invention will be explained in detail below.

FIG. 1 shows each step of the invention according to the flow.

The manufacturing method of the double-sided ceramic wiring board according to the present invention will be explained below in detail according to the above process order. Ceramic substrates used as starting materials include oxide ceramic substrates such as alumina, forsterite, steatite, zirconia, titania, etc. , carbide-based ceramic substrates such as silicon carbide and aluminum nitride, and nitride-based ceramic substrates, but are not limited to these.

This board has holes for through holes. The through-holes can be formed by punching a ceramic green sheet before firing and then firing it, or by firing it to obtain a substrate and then forming it by laser processing or drilling. Examples include, but are not particularly limited to. The diameter of the through-hole hole is usually 1.0 W or less, but is not particularly limited.

The ceramic substrate surface and the inner wall surface of the through-hole hole are roughened. This roughening is not necessarily necessary for the manufacturing method of the present invention, but if the surface is roughened in this way, it will be possible to form a conductor layer (metal layer) on the surface of the ceramic substrate and in the hole for the through hole. This is preferable because the anchor effect improves the adhesion between the ceramic substrate and the conductor layer. As a method for performing such roughening, there is a method of immersion in a solution such as hot phosphoric acid, molten alkali, HF, etc., but there is no particular limitation.

First, a conductor layer is formed on the surface of the ceramic substrate and the inner wall surface of the through hole by plating. To do this, if necessary, after roughening the surface of the ceramic substrate and the inner wall surface of the through-hole hole, known sensitizing/activation is performed to roughen the exposed inner wall surface of the through-hole hole and the exposed surface of the ceramic substrate surface. Activate the surface by precipitating metal palladium etc. Next, the ceramic substrate is immersed in a chemical copper or chemical nickel bath to form a metal conductor layer of copper, nickel, or the like.

The conductor layer obtained by the above chemical plating is thin, with a thickness of 1 to several μm, so if a thicker conductor layer is required, the conductor layer can be formed by the chemical plating as necessary. Afterwards, further electrolytic plating is performed to increase the thickness of the conductor layer.

The surface of the conductor layer formed by chemical plating or electrolytic plating is polished as necessary. By polishing, the surface is smoothed to a maximum surface roughness of 3 μm or less, and the oxidized layer, fat bones, dirt, etc. on the surface layer can be removed. The polishing method is generally physically polished using a polishing machine or the like, but is not particularly limited. The degree of polishing is preferably within the range of 0.1 to 10 μm, more preferably within the range of 0.2 to 2 μm.

Next, on the conductor layer formed on the ceramic substrate,
Form an etching resist for circuit formation. As is well known, this method involves applying a photoresist material to the entire surface of the substrate, drying it, exposing it to ultraviolet light using an appropriate mask pattern, and developing it to form an etching pattern. This is done using a photoresist method, etc.

In the photoresist method, it is preferable to use a positive type resist material, but the resist material is not particularly limited. The coating method is by spinner, roll coater 1 printing, etc. By using the photoresist method, it is possible to form fine patterns with a line width of 30 μm between lines, which has never been seen before.

In the conventional method, the circuit was formed by etching immediately after the above process, but as mentioned above, the resist film thickness at the edge of the through-hole land was thin, and the etching process did not allow the resist film to form at the edge. The thickness of the conductive part may become very thin, and depending on handling, troubles such as disconnection may occur, causing a reduction in the yield of conductivity in the through-hole part. Therefore, in the present invention, after forming an etching pattern on the surface of the conductor layer, an etching-resistant resist for edge protection is further applied on the etching resist film on the through-hole land and the inner wall surface of the through-hole hole. Apply and let dry. The application method includes filling the etching resist into the through-hole land portion and the inside of the through-hole hole using a nozzle, or applying the etching resist by screen printing, etc., but there are no particular limitations. do not have.

The drying temperature is also not particularly limited, but may be 50 to 200 ℃.
It is preferably within the range of °C. The pattern for applying etching resist is the same shape as the through-hole land.
Alternatively, a smaller pattern may be formed on the etching pattern.

Next, a circuit is formed by etching. In some cases, a necessary circuit can be formed immediately by chemical plating or electrolytic plating, but in the case of full-surface plating, etching is generally used to form the circuit. FIG. 2 shows the through-hole openings in the ceramic substrate before etching. A conductor layer 6 is formed on the substrate 1 by a plating method, and an etching pattern is formed on the conductor layer 6 using an etching resist 7 in order to form a desired circuit. A protective etching resist 8 is formed. By forming the edge protection etching resist 8 in this way, the resist film thickness at the through-hole edges 5a to 5d increases, and after etching, the conductor layer becomes thinner at the through-hole edges 5a to 5d, resulting in disconnection, etc. No problems will occur.

Then, the etching resist for circuit formation and edge protection is removed. NaOH, Nag as a stripper
Examples include alkaline solutions such as COs, but organic solvents and the like may also be used and are not particularly limited. Methods for stripping the resist include immersion in a stripping solution, spraying a stripping solution, and the like.

The surface layer of the substrate on which the circuit is formed by etching is polished, degreased, and cleaned as necessary. The degree of polishing is 0.1
It is preferable that it is -10 micrometers, and it is more preferable that it is 0.2-2 micrometers. The method of polishing is not particularly limited, but it is common to physically polish using a polisher or the like. Degreasing and cleaning may be carried out by conventional methods.

Next, the method for manufacturing a double-sided ceramic wiring board according to the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

(Example 1) A 96% alumina substrate was used as a sintered ceramic substrate, and through holes with a diameter of 0.4 μm were formed by laser processing. Next, the surface of the alumina sintered substrate and the inner wall surface of the through hole were uniformly roughened using phosphoric acid. After thoroughly cleaning and drying the roughened substrate, a 5 μm thick copper layer was formed on the surface of the alumina substrate and the inner wall surface of the through hole by chemical plating. After physically polishing the surface of this copper layer using a polishing machine, a positive type photoresist material was applied onto this copper layer using a roll coater. After applying the photoresist material, it was dried at 90° C., exposed to ultraviolet light using a positive mask pattern, and further developed to form a film of the photoresist material to form an etching pattern. After that, an etching resist was screen printed on the etching pattern of the through-hole land and inside the through-hole hole. After printing, it was dried at 120° C. to form an etching circuit. After etching, all resist films are 3%
Peeling was performed using a NaOH solution to obtain a ceramic double-sided wiring board.

When the through-hole conductivity of this wiring board was examined, no defects such as disconnections were found, and the through-hole reliability showed a much higher value than that of the conventional subtractive method.

(Example 2) A 96% alumina substrate was used as a sintered ceramic substrate, and through holes with a diameter of 0.3 μm were formed by laser processing. After roughening the surface of this sintered substrate with phosphoric acid, a 5 μm thick copper layer was formed by chemical plating.
A 25 μm thick copper layer was further formed by electrolytic plating to produce a ceramic double-sided wiring board. After physically polishing the surface of this copper layer using a polishing machine, a positive type photoresist material was applied onto this copper layer using a roll coater. After applying the photoresist material, it was dried at 90° C., exposed to ultraviolet light using a positive mask pattern, and further developed to form a film of the photoresist material to form an etching pattern.

After that, an etching resist was screen printed on the etching pattern of the through-hole land and inside the through-hole hole. After printing, it was dried at 120° C. to form an etching circuit. After etching, all the resist films were peeled off with a 3% NaOH solution, and degreased and cleaned with an acidic organic aqueous solution to obtain a ceramic double-sided wiring board.

When the through-hole conductivity of this wiring board was examined, no defects such as disconnections were found, and the through-hole reliability showed a much higher value than that of the conventional subtractive method.

(Example 3) A1!0! 96 parts by weight of powder and S t OZ % Ca
The mixture was mixed with 4 parts by weight of a sintering aid such as OlMgO, and 12 parts by weight of an organic substance (binder, plasticizer, etc.) was added and further mixed. This mixture was formed into a sheet by a doctor blade method. I made it. This green sheet was heated to a semi-hardened state, and then pressed with a mold to form a through hole with a hole diameter of 0.4. This green sheet was dried at 150°C, and after drying,
An alumina sintered substrate with through holes was created by firing at 0°C.

After the surface of this sintered substrate was roughened with phosphoric acid, a copper layer with a thickness of 8,111 mm was formed on the surface of the substrate and the inner wall surface of the through hole by chemical copper plating. Thereafter, a ceramic double-sided wiring board was created in the same manner as in Example 1.

(Example 4) The same procedure as Example 2 was carried out except that a 92% alumina substrate was used as the sintered ceramic substrate and the etching resist material was filled onto the through-hole lands and inside the through-hole holes using a dispenser. A ceramic double-sided wiring board was obtained. When the through-hole conductivity of this wiring board was examined, no defects such as disconnections were found, and the through-hole reliability showed a much higher value than that of the conventional subtractive method.

(Example 5) A ceramic double-sided 4IA substrate was obtained in the same manner as in Example 1 except that a 99% alumina substrate was used as the sintered ceramic substrate and the photoresist material was applied using a spinner. When the through-hole conductivity of this wiring board was examined, no defects such as disconnections were found, and the through-hole reliability showed a much higher value than that of the conventional subtractive method.

〔Effect of the invention〕

Since the method for manufacturing a double-sided ceramic wiring board of the present invention is configured as described above, it is possible to manufacture a double-sided ceramic wiring board with high through-hole reliability.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram of an embodiment of the method for manufacturing a double-sided ceramic wiring board according to the present invention, and FIG. 2 is a process diagram showing an example of applying an etching resist on the through-hole land and inside the through-hole hole according to the present invention. FIG. 3 is a sectional view of the through-hole portion of the ceramic double-sided wiring board manufactured by the conventional method. 1...Sintered ceramic substrate 2...Through hole land 3...Through hole hole 4...Through hole inner wall surface 5a-5d...Through hole edge 6.
...Conductor layer 7...Photoresist 8...Etching resist for edge protection Agent Patent attorney Takehiko Matsumoto Figure 1

Claims (4)

[Claims] (1) After forming a conductor layer by plating on both sides of a ceramic substrate in which through-hole holes are formed at desired positions and on the inner wall surface of the through-hole holes, an etching resist is formed on the conductor layer, A method for manufacturing a double-sided ceramic wiring board in which a desired circuit is formed by etching, wherein, prior to the etching, an etching-resistant resist is further applied on the etching resist of the through-hole land and the etching resist on the inner wall surface of the through-hole hole. A method for manufacturing a ceramic double-sided wiring board characterized by: (2) The method for producing a ceramic double-sided wiring board according to claim 1, wherein the plating method is chemical plating. (3) The method for manufacturing a double-sided ceramic wiring board according to claim 1, wherein the plating method is to perform chemical plating and then electrolytic plating. (4) The double-sided ceramic according to any one of claims 1 to 3, wherein the surface of the ceramic substrate and the inner wall surface of the through hole are roughened before forming the conductor layer by plating. Manufacturing method for wiring boards.