JPS6346597B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer circuit board for mounting semiconductor integrated circuit devices and the like.

Multilayer circuit boards for mounting semiconductor integrated circuit devices used in high-speed electronic devices are composed of an insulating material with a low dielectric constant and high thermal conductivity and a conductive material with a low electric resistance, and a wiring pattern is formed on the conductor layer. It is required to have good dimensional accuracy and to be able to form at high density. Conventional multilayer circuit boards are made by screen-printing conductive paste and insulating paste alternately over the entire surface of a ceramic board fired at high temperatures.
It is manufactured by a lamination method in which each layer is fired and the steps of forming via holes, wiring patterns, etc. are repeated.

Conductive materials for such multilayer circuit boards include:
Gold, which has a low conductor resistance and can be fired in an oxygen atmosphere, is mainly used, and as the insulating material, glass, crystallized glass, glass ceramic, etc., which have a low dielectric constant and high thermal conductivity, are used.

However, when conventionally printing a gold conductor layer and an insulating layer such as glass or ceramic, which has a low dielectric constant and high thermal conductivity, and then laminating and firing them, there has been a problem that blistering occurs on the surface of the gold conductor layer. Ta. That is,
These blisters usually occur around 10 per ^1cm2 , and can cause peeling between the conductor layer and insulating layer and breakage of the conductor circuit.They also tend to occur more easily as the number of firings increases and the number of layers increases. , therefore 5
Conventional multilayer ceramic circuit boards having six or more layers have extremely low reliability.

The present invention provides a highly reliable ceramic multilayer circuit board that prevents the occurrence of the above-mentioned blistering. It is characterized by the interposition of a thin metal film with good properties.

The present invention discloses that the cause of blistering is the high temperature firing of an insulating layer, which is mainly composed of oxides such as glass, crystallized glass, glass/ceramic, etc., and has a low dielectric constant and high thermal conductivity, and a gold conductive layer. We believe that this is because the wettability is poor, the contact angle between the gold conductor layer and the insulating layer is large, and the contact area is small. Therefore, we used a metal thin film with better wettability with the insulating layer than the gold conductor layer with the gold conductor layer. This is based on the discovery that the occurrence of blisters is reduced when it is interposed between an insulating layer and an insulating layer.

In the present invention, the wettability between the gold conductor layer and the insulating layer during high-temperature firing corresponds to the quality of the adhesion between the gold conductor layer and the insulating layer after firing.

The gold heated to near the melting point by high-temperature firing is applied to the surface of the insulating layer.The bond between the insulating layer and the gold depends on the cohesive force of the nearly molten gold and the adhesion between the insulating layer and the gold. If the adhesion force is greater than the cohesive force of gold, it will spread and the contact area will be large, resulting in good adhesion after firing. If the adhesion force between the insulating layer and gold is smaller than the cohesive force of gold, it will spread. The contact area becomes small, resulting in poor adhesion after firing. In the present invention, rather than the gold conductor layer,
By interposing a thin metal film with excellent wettability with the insulating layer between the gold conductor layer and the insulating layer, the insulating layer has good wettability with the thin metal layer during high-temperature firing. The contact angle is small, resulting in good adhesion. Further, the wettability between the thin metal layer and the gold conductor layer is good.

Therefore, the adhesion between the gold conductor layer and the insulating layer with the metal thin layer interposed therebetween is good. The metal to be interposed between the gold conductor layer and the insulating layer should have excellent wettability with the insulating layer and be suitable for the electrical properties of the conductor layer of the ceramic multilayer circuit board and the electrical, thermal, and mechanical properties of the insulating layer. It must have no negative impact. Desirable examples of such metals include copper, nickel, and chloro.

The present invention will be explained in detail based on the following examples.

Example 1 FIG. 1 shows a partial process diagram for manufacturing a multilayer circuit board according to the present invention.

(a) First, for the fired ceramic substrate 1 that will serve as the base, it is desirable to use a material with a low dielectric constant and high thermal conductivity, and also to be stable and resistant to thermal deformation and mechanical strength during firing of conductors and insulators. It is necessary to use a material that does not cause a decrease in the temperature. Alumina, mullite, magnesia, etc. are used as such ceramic materials.

A hole (via hole) 2 is formed in a ceramic substrate 1 serving as a base by a drill or a laser, and a gold conductor layer 3 is filled into the hole by a printing method. (See Figure 1a) (b) Next, print gold conductor paste on the entire surface of the base ceramic substrate with the holes filled, and heat it at 900 to 950℃.
After firing in an oxygen atmosphere to form a gold conductor layer 3, a thin copper coating 4 is formed on the surface of the gold conductor layer 3 by electrolytic plating. (See Figure 1b) (c) A resist pattern 5 is formed on the surface of the copper film 4, and using this resist 5 as a mask, the copper film 4 is etched with a pyrophosphoric acid-based etching solution, and then an iodine-based etching solution is used. The gold conductor layer 3 is etched to form a conductor circuit. (See FIG. 1c) (d) A glass ceramic paste containing borosilicate glass and alumina as main components is printed and coated on the surface of the conductive circuit pattern and fired to form an insulating layer 6. (See FIG. 1d) FIG. 2 shows the relationship between the thickness of the copper plating layer of the ceramic circuit board thus formed, the number of blisters, and the electrical resistance.

As is clear from Figure 2, the number of blisters tends to decrease significantly when the thickness of the copper coating is 0.05 μm or more, but on the other hand, as the thickness of the copper coating increases, the electrical resistance increases. Therefore, the thickness of the copper plating film is preferably 0.05 to 2 μm.

In addition, when forming a multilayer circuit board by laminating a conductor layer and an insulating layer, apply photolithography to the insulating layer 6 below to form a hole (via hole), and then layer the gold conductor layer 3. The step of filling the hole by a printing method (referred to as step (a)') is followed by repeating the steps (b) to (d).

Example 2 In the same manner as in Example 1, holes (via holes) 2 were formed in the base ceramic substrate 1, and then a conductor layer 3 was printed. After baking, a nickel plating film was applied over the entire conductor layer instead of the copper plating film in Example 1), a conductor circuit was formed using photolithography, and an insulating paste was printed. Firing forms an insulating layer and a ceramic circuit board.

FIG. 3 shows the relationship between the thickness of the nickel plating film of the ceramic circuit board thus formed, the number of blisters, and the electrical resistance.

As is clear from FIGS. 2 and 3, according to the present invention, the performance of the ceramic circuit board, such as the dielectric constant of the insulating layer and the electrical resistance of the conductive layer, can be maintained without degrading the performance of the ceramic circuit board. A high-quality multilayer circuit board can be obtained.

The present invention is not limited to the above-mentioned embodiments, but may be a multilayer circuit board made of other insulating materials and conductive materials, in which a metal thin film having excellent wettability with each insulating material is interposed.

[Brief explanation of drawings]

FIG. 1 is a partial process diagram of a circuit board according to the present invention;
FIGS. 2 and 3 show the number of blisters and changes in electrical resistance of the ceramic substrate according to the present invention. In FIGS. 2 and 3, the solid line represents the change in the number of blisters occurring with respect to the thickness of the metal film, and the covered line represents the change in electrical resistance with respect to the thickness of the metal thin film. DESCRIPTION OF SYMBOLS 1... Base ceramic substrate, 2... Hole (via hole), 3... Conductor layer, 4... Metal thin film, 5...
Insulating layer.

Claims (1)

[Claims] 1 Gold conductor layers, glass, crystallized glass, glass, etc. are sequentially laminated and fired on the surface of a ceramic insulating substrate.
A multilayer circuit board characterized in that a metal thin film selected from copper, nickel, and chromium is interposed between an insulating layer selected from ceramic and a metal thin film selected from copper, nickel, and chromium to reduce the occurrence of blistering.