JPS62172788A - Manufacture of ceramics wiring substrate - 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] The present invention belongs to the field of manufacturing technology for ceramic wiring boards used as electronic substrates.

[Background Art] Various methods have been used for metallizing ceramics, such as the Telefunken method, the active metal method, the thick film method, the thin film method, and the plating method. Among these, the plating method: (1) Since a metal element can be directly metallized on a ceramic substrate, the resulting metal layer exhibits high conductivity.

(2) The thickness of the metal layer can be easily controlled over a wide range.

(3) Through-hole metallization is easy and highly reliable.

(4) Fine pattern formation is possible.

There are other benefits.

Conventionally, ceramic wiring boards are manufactured using the plating method using the following process.

The conventional manufacturing process will be explained below with reference to the block diagram shown in FIG.

■ Prepare a sintered ceramic substrate.

Sintered substrate materials include alumina, forsterite, steatite, zircon, mullite, cordierite,
Oxide ceramics such as titania are mainly used, but carbide and nitride ceramics can also be used.

■ Perform roughening treatment on both sides of the ceramic substrate.

This is done to make the anchor effect work effectively. As a processing agent used for roughening treatment, H3PO
4. Examples include solutions or melts of borax, V2O5, HF, alkali metal compounds, etc., but there is no particular specification as to which one to use.

Surface roughening treatment is carried out by holding these treatment agents at high temperatures and immersing the ceramic substrate in it, or by immersing the ceramic substrate in treatment agents at room temperature and heat-treating the substrate. .

■ After cleaning the ceramic substrate surface with hot water, water, acid, etc.
Wash thoroughly and dry.

(2) After applying a catalyst to the substrate surface in advance, a metal layer is formed by chemical plating on the ceramic substrate surface and, if there are through holes, also on the inner wall surfaces of the through holes.

Catalyst application usually involves depositing metallic palladium on the surface of the ceramic/cus substrate by a sensitizing-activation method using a stannous chloride solution and a palladium chloride solution. After that, chemical copper or chemical nickel plating is performed.

■ When used as a wiring board for low power such as high frequency circuits or digital signal circuits, chemical plating described in (■) above is sufficient, but when used as a wiring board for high power, further metal plating is required. It is necessary to increase the thickness of the layer, and the thickness is increased by applying electrolytic plating. In electrolytic plating, after sufficiently activating the chemically plated surface, copper plating,
Alternatively, perform nickel plating.

■ Form the circuit pattern. The formation method is a commonly used subtractive method.

In addition to the subtractive method, additive methods and semi-additive methods can also be used for circuit formation. When forming a circuit using these methods, it is sufficient to add a process of applying a plating resist in a desired pattern to the above processes (1) and (2).

In this way, a ceramic wiring board is obtained through the processes ① to ②.

Wiring boards are exposed to high temperatures in subsequent processes such as soldering of components, bonding and wire bonding of ICs, and brazing of metal parts, so its heat resistance, especially the stability of the adhesion between the ceramic substrate and the metal layer, is important. gender is one of the important evaluation items.

Among the wiring boards created using the above-mentioned process, on the wiring boards where a relatively thin metal layer of 15 μm or less was formed only by chemical plating, the adhesion was extremely strong even after heat treatment at 250 to 700°C for about 10 minutes. However, in wiring boards with thick metal layers using electrolytic plating,
During the heat treatment at 250°C for 10 minutes, "blurring" occurred at the interface between the ceramic substrate and the chemically plated layer, and this development became more pronounced as the plating became thicker, posing a serious problem.

[Purpose of the Invention] This invention was made in view of the current situation, and it is possible to solve the problem that "blister" does not occur during heat treatment even if the thickness of the metal layer formed on the surface of the ceramic substrate by the plating method is increased. First, the purpose is to manufacture a ceramic wiring board in which the adhesion between the ceramic substrate and the plated metal layer is stable.

[Disclosure of the Invention] As mentioned above, various analyzes have revealed that the main cause of "blister" caused by heat treatment is water trapped at the interface between the ceramic substrate and the plating layer during the plating process. I found out something.

That is, it is thought that this is because water remaining at the interface between the ceramic substrate and the plating layer is vaporized by the heat treatment. If the plating layer is relatively thin, such as when only chemical plating is applied, gas will pass through the plating layer and be extracted, but if the plating layer is thickened using electrolytic plating, the gas will pass through the plating layer. The layer cannot be pulled out, and ``blister'' occurs. For example, when electrolytic plating is used, "blistering" may occur in plating layers of 20 μm or more, although this varies depending on the surface roughening state of the substrate, the type of deposited plating layer, and physical properties.

The occurrence of "blister" has nothing to do with the above-mentioned wiring board manufacturing process ■ to ■, and to suppress this,
It is necessary to add some innovation to the process. As long as a plating solution is used, it is inevitable that water will remain at the interface between the ceramic substrate and the deposited plating layer, so the key is how to extract the water and increase the thickness of the plating layer.

In order to solve these problems and achieve the above-mentioned object, this invention, when metallizing a ceramic substrate by a plating method, first performs chemical plating and then further thickens the metallizing layer by electrolytic plating. In this method, before electrolytic plating or after electrolytic plating is applied thinly, heat treatment is performed in a non-oxidizing atmosphere or vacuum to remove water remaining at the interface between the ceramic substrate and the chemically plated layer, and then the electrolytic plating is applied again. The gist is a method for manufacturing a ceramic wiring board, which is characterized by performing electrolytic plating at least once.

Hereinafter, the present invention will be described by way of examples along with diagrams illustrating the manufacturing process of a ceramic wiring board according to the present invention.

[Example 1] On the surface of a 96% sintered Ax203 substrate that had been roughened by immersing it in phosphoric acid heated to 250 to 360'C for 3 to 10 minutes,
Metallic palladium was applied by a sensitizing-activation method, and then ordinary chemical copper plating was applied to a thickness of about 3 μm. Let this sample be A.

Sample A is heat treated in a nitrogen atmosphere at 250 to 1083°C, preferably 100 to 1083°C for 5 to 60 minutes, and further, after sufficiently activating the surface to be chemically plated, electroplating is performed in a copper sulfate bath, Three types of samples with a total plating thickness of 18, 35, and 70 μm were prepared.

These samples are designated as B.

Sample C was prepared under the same conditions as sample B, except that heat treatment in a nitrogen atmosphere was not performed, and at the same time heat treatment was performed at 700 ° C. for 10 minutes in a nitrogen atmosphere.
In sample B, the adhesion between the Al1203 substrate and the plating layer is stable and there is no change in appearance, but in sample C
In this case, "blister" occurred at the interface between the A1203 substrate and the chemical plating.

[Example 2] Metallic palladium was applied by a sensitizing-activation method to the surface of a 96% sintered AA203 substrate that had been roughened by immersing it in phosphoric acid heated to 250 to 360°C for 3 to 10 minutes, and then, Approximately 1μ of normal chemical plating
m was given.

After sufficiently activating the chemically plated surface, electrolytic plating was further performed to a thickness of 5 μm in a copper sulfate bath. Let this sample be D.

Sample D is heat-treated in a nitrogen atmosphere at 250 to 1083°C, preferably 700 to 1083°C, for 5 to 60 minutes, and the plated surface is sufficiently activated.
Copper sulfate electrolytic plating is applied again, total thickness is 18.3
Three types of samples of 5.70 μm were prepared. Let these samples be E.

Sample F was prepared under the same conditions as sample E except that heat treatment in a nitrogen atmosphere was not performed, and at the same time heat treatment was performed at 700°C for 10 minutes in a nitrogen atmosphere. Although the adhesion with the plating layer was stable and no change in appearance was observed, in sample F, "blurring" occurred at the interface between the Al2O3 substrate and the chemical plating.

[Example 3] Sample B shown in Example 1 and Sample E shown in Example 2 were heated at 700°C-1083°C for 5 minutes in a nitrogen atmosphere.
After heat treatment for ~60 minutes, the plating surface layer was sufficiently activated and electrolytic copper plating was performed in a copper sulfate bath to give a total plating thickness of 150 μm.

When these samples were heat-treated at 700° C. for 10 minutes in a nitrogen atmosphere, no “blister” occurred and the adhesion was stable. In this way, the thickness of the plating layer could be increased by repeating the process of electrolytic plating and heat treatment multiple times.

[Example 4] Sample A shown in Example 1 and sample D shown in Example 2 were heated to 250 to 1 in vacuum (10 to 10 Pa).
After heat treatment at 083℃ for 5 to 60 minutes, the plating surface layer was sufficiently activated and electrolytic copper plating was applied in a copper sulfate bath, resulting in a total plating thickness of 31F of 18.35.50 μm.
The fi sample was prepared. Let these samples be G and H, respectively.

For those heat-treated in vacuum, the
Even after heat treatment at 00°C for 10 minutes, no "blurring" occurred and the adhesion was stable.

[Example 5] Samples G and H shown in Example 4 were heated for 70 minutes in a nitrogen atmosphere.
After heat treatment at 0° C. for 10 minutes, the plating surface layer was sufficiently activated and electrolytic copper plating was performed in a copper sulfate bath to give a total plating thickness of 150 μm.

Even when these samples were heat-treated at 700° C. for 10 minutes in a nitrogen atmosphere, “blister” did not occur and the adhesion was stable.

[Effects of the Invention] As described above, when forming a thick metallizing layer by electrolytic plating after chemically plating a ceramic substrate, it is possible to form a thick metallizing layer by electrolytic plating before electrolytic plating or after thinly electrolytic plating. Heat treatment is performed in an oxidizing atmosphere or vacuum to remove water remaining at the interface between the ceramic substrate and the chemical plating layer, and electrolytic plating is performed again at least once. It is possible to manufacture a ceramic wiring board that has stable layer adhesion and does not cause "bulges."

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a manufacturing process for a ceramic wiring board according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a manufacturing process for a ceramic wiring board using a conventional plating method. Patent applicant Matsushita Electric Works Co., Ltd. Patent attorney Toshimaru Takemoto (and 2 others) Figure 1 Figure 2

Claims (1)

[Claims] (1) When metallizing a ceramic substrate by plating, first chemical plating is applied and then electrolytic plating is used to thicken the metallizing layer. A method for manufacturing a ceramic wiring board, characterized by performing heat treatment in a non-oxidizing atmosphere or vacuum, and then performing electrolytic plating again at least once.