JP3207015B2 - Manufacturing method of ceramic wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for manufacturing a ceramic wiring board used for a hybrid integrated circuit device, a package for housing a semiconductor element, and the like.

[0002]

2. Description of the Related Art Conventionally, a ceramic wiring board used for a hybrid integrated circuit device or a package for housing a semiconductor element is made of an electrically insulating material such as alumina ceramics, and a high melting point metal such as tungsten or molybdenum is drawn out from the inside to the surface. It is known that a surface wiring conductor connected to the internal wiring conductor is formed by a thin film technique on a surface of a ceramic sintered body having an internal wiring conductor made of powder.

In order to form surface wiring conductors on the surface of the ceramic sintered body with good dimensional accuracy by a thin film technique, the surface of the ceramic sintered body having internal wiring conductors is usually wrapped by a lapping machine or a surface grinder. The surface is polished flat by employing a mechanical polishing method such as that described above.

However, in this conventional ceramic wiring board, since the relative dielectric constant of alumina ceramics constituting the ceramic sintered body is as high as 9 to 10, the propagation delay time of a signal transmitted through the internal wiring conductor and the surface wiring conductor is large. As a result, it has a drawback that it cannot be used as a ceramic wiring board used for a high-speed operation hybrid integrated circuit device or a semiconductor element housing package for housing a high-speed operation semiconductor element.

Further, since the ceramic wiring board has a high firing temperature of about 1600 ° C. for the alumina ceramic constituting the ceramic sintered body, the metal constituting the internal wiring conductor is made of tungsten or molybdenum which is a high melting point metal. Since the electrical resistance of the tungsten, molybdenum, etc. is high, the attenuation of the signal propagating through the internal wiring conductor is large especially in high-speed signals, and accommodates a high-speed operation hybrid circuit device and a high-speed operation semiconductor element. It cannot be used as a ceramic wiring board used for a package for accommodating a semiconductor element.

Therefore, the ceramic sintered body is formed of glass-ceramic having a low relative dielectric constant of about 5.0 or less and a firing temperature of about 1000 ° C., and the internal wiring conductor is made of copper or copper which is a low-resistance material. A ceramic wiring substrate formed of silver, gold, or the like has been proposed.

[0007]

However, when the internal wiring conductor of the ceramic sintered body is formed of copper, silver, gold, or the like, the hardness of the internal wiring conductor made of copper, silver, gold, or the like is lower than that of the ceramic sintered body. When the surface of the ceramic sintered body having the internal wiring conductor is flatly polished by a mechanical polishing method, the internal wiring conductor is preferentially polished and removed, so that the internal wiring conductor is exposed. The surface has a shape depressed from the surface of the ceramic sintered body.

[0008] When the exposed surface of the internal wiring conductor is depressed from the surface of the ceramic sintered body in this way, a gap is easily generated between the internal wiring conductor and the surface wiring conductor connected to the internal wiring conductor. The disadvantage is that the electrical connection between the wiring conductor and the surface wiring conductor cannot be made reliably.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to manufacture a ceramic wiring board capable of ensuring an electrical connection between an internal wiring conductor and a surface wiring conductor. It is to provide a method.

[0010]

The present invention SUMMARY OF THE INVENTION The preparation of copper, silver, gold and a ceramic sintered body having over from the inside to the surface of the internal wiring conductors consisting of at least one of metal mainly composed of these And a step of polishing the surface of the ceramic sintered body flat by a mechanical polishing method,
A step of applying a plating metal layer to the exposed surface of the internal wiring conductor polished and removed to a shape depressed from the surface of the polished ceramic sintered body so that the plating metal layer protrudes from the surface of the ceramic sintered body. And polishing and removing the plated metal layer protruding from the surface of the ceramic sintered body to the same height as the surface of the ceramic sintered body by a mechanical polishing method. A step of chemically polishing and removing a part of the metal layer, and a step of forming a surface wiring conductor connected to the ceramic metal layer on the surface of the ceramic sintered body by a thin film technique. .

[0011]

According to the present invention, the recesses on the exposed surface of the internal wiring conductor formed by mechanical polishing are filled with a plated metal layer and the plated metal layer is polished to the same height as the surface of the ceramic sintered body. Therefore, no gap is formed between the internal wiring conductor and the surface wiring conductor, and as a result, the internal wiring conductor and the surface wiring conductor can be reliably electrically connected.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

1 (a) to 1 (e) are cross-sectional views of each step showing one embodiment of the manufacturing method of the present invention, wherein 1 is a ceramic sintered body, 2 is an internal wiring conductor, and 3 is a surface wiring. Conductor.

First, as shown in FIG. 1A, a ceramic sintered body 1 having an internal conductor wiring 2 is prepared.

The ceramic sintered body 1 is made of glass-ceramics, for example, silica (SiO 2) 72 to 76.
%, Boron oxide (B2 O3) 15-17% by weight, alumina (Al2 O3) 2-4% by weight, magnesia (Mg
O) 1.5% by weight or less, zirconia (ZrO2) 1.1
Borosilicate glass powder 41 comprising sodium oxide (Na2 O), potassium oxide (K2 O) and lithium oxide (Li2 O) in a total of 2.0 to 3.0% by weight.
Alumina (Al2 O3) powder 19-2
1% by weight, 11 to 12% by weight of quartz (SiO2) powder, cordierite (2MgO.2Al2O3.5SiO2)
A powder of 18 to 23% by weight is prepared, a suitable binder and a solvent are added and mixed to form a slurry, and a ceramic green sheet is formed by employing a doctor blade method. It is manufactured by performing appropriate punching, forming a predetermined shape, laminating a plurality of pieces, and firing at a temperature of about 1000 ° C.

The ceramic sintered body 1 is warped up and down by about 10 to 100 μm due to uneven shrinkage during firing.

On the lower surface of the ceramic sintered body 1, there are formed a plurality of concave portions A and a through hole B penetrating from the bottom surface of the concave portion A to the upper surface of the ceramic sintered body 1. The inside is filled with an internal wiring conductor 2.

When a plurality of recesses A and through holes B are punched into a ceramic green sheet to be a ceramic sintered body 1, through holes to be recesses A and through holes B in the ceramic green sheet are appropriately sized. The internal wiring conductor 2 formed at a predetermined position of the ceramic sintered body 1 and filled in the recess A and the through hole B is made of copper, silver, gold, or a metal containing these as main components. In the case of copper, for example, copper, a metal paste obtained by adding and mixing an appropriate binder and a solvent to copper powder is used as a ceramic sintered body 1.
The ceramic green body 1 is formed from the upper surface to the lower surface of the ceramic sintered body 1 by previously filling the recesses A and the through holes B formed in the ceramic green sheet.

Further, the internal wiring conductor 2 filling the recess A of the ceramic sintered body 1 is a wide area lead attachment pad to which an external lead terminal 5 described later is attached. The external lead terminal 5 is brazed to the terminal.

If the recess A of the ceramic sintered body 1 is formed so as to increase in size from the lower surface side of the ceramic sintered body 1 to the back, the concave portion A is formed in the ceramic sintered body 1 of the lead attachment pad. Has a high adhesion strength. Therefore, the concave portion A of the ceramic sintered body 1 has a size that increases from the lower surface side of the ceramic sintered body 1 to the back in order to increase the adhesion strength of the lead mounting pad to the ceramic sintered body 1. It is preferable that it is formed so as to spread.

Next, the upper and lower surfaces of the ceramic sintered body are mechanically polished so that the upper and lower surfaces of the ceramic sintered body 1 are flat as shown in FIG.

The mechanical polishing is performed by, for example, a lapping machine or a surface grinder. The surface of the ceramic sintered body 1 is warped by about 10 to 100 μm to a flat one having a warpage of 5 μm or less. I do.

When the upper and lower surfaces of the ceramic sintered body 1 are mechanically polished, the copper constituting the internal wiring conductor 2 is significantly softer than the glass ceramic constituting the ceramic sintered body 1. The wiring conductor 2 is polished and removed more preferentially than the ceramic sintered body 1. As a result, the upper and lower exposed surfaces of the internal wiring conductor 2 are depressed from the upper and lower surfaces of the ceramic sintered body 1.

Next, as shown in FIG. 1 (c), the upper and lower exposed surfaces of the internal wiring conductor 2 of the ceramic sintered body 1 are plated with copper by using a conventionally known electrolytic plating method or electroless plating method. The metal layer 4 is applied to a thickness such that its surface protrudes from the upper and lower surfaces of the ceramic sintered body 1.

The plating metal layer 4 is applied to both upper and lower exposed surfaces of the internal wiring conductor 2 by, for example, sintering the ceramic sintered body 1 having the internal wiring conductor 2 with copper sulfate: 7 g / liter and Rossier salt: 75 g. / Liter, triethanolamine: 10 ml / liter, formalin: 25 ml / liter, sodium hydroxide: 20 g / liter, sodium carbonate: 10 g / liter, in an electroless copper plating bath at a liquid temperature of 50 to 55 ° C. And depositing copper on the exposed surface of the internal wiring conductor 2.

Next, as shown in FIG. 1 (d), the plated metal layer 4 protruding from the upper and lower surfaces of the ceramic sintered body 1 is formed.
Is polished and removed by mechanical polishing such as a lapping machine, and the surface thereof is made the same height as the upper and lower surfaces of the ceramic sintered body 1. In this case, a portion of the polished and removed plating metal layer 4 may be rubbed and adhered to the upper and lower surfaces of the ceramic sintered body 1 due to polishing friction. After removing the layer by mechanical polishing, it is preferable to chemically remove the plated metal layer adhered to the upper and lower surfaces of the ceramic sintered body 1 with an etching solution such as hydrochloric acid.

Next, the ceramic sintered body 1 is shown in FIG.
As shown in FIG. 5, a surface wiring conductor 3 connected to the internal wiring conductor 2 is formed on the upper surface thereof by applying a thin film forming technique such as sputtering, and an external lead terminal 5 is provided on its lower surface with gold-tin. It is joined via a low melting point brazing material such as an alloy, a gold-silicon alloy, or a gold-germanium alloy, thereby forming a ceramic wiring board as a final product. In this case, on both upper and lower surfaces of the internal wiring conductor 2,
A plating metal layer 4 whose surface is the same height as the upper and lower surfaces of the ceramic sintered body 1 is applied, and the depressions formed on both upper and lower surfaces of the internal wiring conductor 2 are filled. No gap is formed between the wiring conductor 3 and the wiring conductor 3, and as a result, electrical connection between the internal wiring conductor 2 and the surface wiring conductor 3 is ensured.

The surface wiring layer 3 formed on the upper surface of the ceramic sintered body 1 has a two-layer structure of, for example, an adhesion layer 6 made of chromium and a main conductor layer 7 made of copper. Chromium as the adhesion layer 6 and copper as the main conductor layer 7 are deposited to a predetermined thickness on the upper surface of the substrate 1 by a thin film forming technique such as a vapor deposition method or a sputtering method, and each layer of the adhesion layer 6 and the main conductor layer 7 is photo-coated. A predetermined pattern is etched using lithography technology, and is adhered to the predetermined pattern so as to be connected to the internal wiring conductor 2 on the upper surface of the ceramic sintered body 1.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. Although copper was used as the plating metal layer 4 to be adhered to the exposed surface of the above, another metal such as nickel or gold may be used for the plating metal layer 4.

In the above-described embodiment, the lead attachment pad for attaching the external lead terminal 5 is formed by the internal wiring conductor 2 filled in the recess A provided on the lower surface of the ceramic sintered body 1. As shown, the internal wiring conductor 2 is led out to the lower surface of the ceramic sintered body 1 through the through hole B, and a wide area lead attachment pad is formed on the lower surface of the ceramic sintered body 1 by the thin film technique at the site where the internal wiring conductor 2 is led out. C may be formed.

[0031]

According to the method for manufacturing a ceramic wiring board of the present invention, after the surface of a ceramic sintered body having an internal wiring conductor is mechanically polished, a plated metal layer is formed on the exposed surface of the internal wiring conductor by ceramic firing. Since the plating metal layer is applied to a thickness protruding from the surface of the sintered body and the plated metal layer is polished to the same height as the surface of the ceramic sintered body, the depression formed on the exposed surface of the internal wiring conductor is formed by the plated metal layer. As a result, the internal wiring conductor and the surface wiring conductor can be reliably electrically connected without forming any gap between the internal wiring conductor and the surface wiring conductor.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (e) are cross-sectional views for respective steps for explaining a method for manufacturing a ceramic wiring board of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the ceramic wiring board manufactured by the method for manufacturing a ceramic wiring board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic sintered body 2 ... Internal wiring conductor 3 ... Surface wiring conductor 4 ... Plating metal layer

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3/24 H05K 3/22 H05K 3/40 H05K 3/46 H05K 1/11

Claims (1)

(57) [Claims] 1. A copper, silver, a step of preparing a ceramic sintered body having subjected to the surface gold and internal wiring conductor made of at least one of metal mainly composed of them from the inside, the ceramic sintered Polishing the surface of the body flat by a mechanical polishing method, and plating a plated metal layer on an exposed surface of the internal wiring conductor that has been polished and removed to a shape depressed from the surface of the polished ceramic sintered body. A step of applying a metal layer to a thickness protruding from the surface of the ceramic sintered body, and polishing and removing the plated metal layer protruding from the surface of the ceramic sintered body to the same height as the surface of the ceramic sintered body by a mechanical polishing method. A step of chemically polishing and removing a part of the plated metal layer adhered to the surface of the ceramic sintered body which has been polished and removed; and Forming a surface wiring conductor connected to the layer by thin film technology.