JPH07273456A - Manufacturing method of laminated layer ceramic substrate - Google Patents

Abstract

PURPOSE:To manufacture the title laminated layer ceramic substrate having conductive patterns such as bumps, etc., having excellent surface flatness by a method wherein a green sheet laminated bodies having conductor patterns in the surface and inner layer are baked and then the baked bodies whose surfaces and rear surfaces held by the same or homogeneous quality high melting point metallic sheet are re-baked. CONSTITUTION:Green sheets 1a, 3a, 4a printed with conductor patterns are laminated, heated and pressurized to produce a laminated body 7 furthermore, baked in a baking furnace in a reducing atmosphere to produce a baked body 8. Next, so as to avoid the warping of the baked body 8 due to the thermal deformation in the baking step, the surface and rear surface of the baked board 8 are held by high melting point metallic sheets 9, 10 to be mounted on a jig 11 for re-baking in the baking furnace in reducing atmosphere. At this time, the high melting point metallic sheets 9, 10 in the same or homogeneous quality are used to keep the warping not more than 5m/25.4mm. Furthermore, the surface roughness Ra of the minimum conductor pattern 2 side of the high melting point metallic sheet 9 is specified to be 1.0mum-50.0mum by honing process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a laminated ceramic substrate, and more particularly to mounting a semiconductor chip on the surface layer and providing a conductor pattern such as a bump for electrically connecting to the semiconductor chip. The present invention relates to a method for manufacturing a monolithic ceramic substrate, which is provided and suppresses warpage due to thermal deformation during firing.

[0002]

2. Description of the Related Art Generally, a laminated ceramic substrate is prepared by forming a green sheet from a raw material containing a ceramic powder, a resin and a binder, and printing a conductor pattern forming paste such as tungsten on the surface of the green sheet. After stacking a plurality of sheets, they are heated and pressed under a predetermined pressure for a certain period of time by using a mold, and the laminated body is heated to 150.
It is produced by firing in a reducing atmosphere of 0 to 1600 ° C.

However, since this monolithic ceramic substrate is manufactured by firing at a high temperature, it is susceptible to thermal deformation, and "warpage" occurs due to the thermal deformation, which lowers the yield of products. . Such problems are usually
The surface where "warpage" has occurred is polished to eliminate the "warpage" and to provide surface flatness.

By the way, in recent years, there is a multilayer ceramic substrate called a control-collapse chip connection in which a semiconductor chip is mounted on the surface layer in advance and bumps for electrically connecting to the semiconductor chip are provided.
In this laminated ceramic substrate, a circuit is usually formed afterward by a thin film and polyimide on the substrate. However, in the case of this configuration, there are problems that many steps are required for its fabrication and that the manufacturing cost is high because of the thin film technology.

Therefore, the present inventor has proposed to manufacture a multilayer ceramic substrate having bumps on its surface layer by printing the bumps on a green sheet and co-firing with other conductor patterns. However, even in the case of the laminated ceramic substrate having bumps on its surface layer, since the semiconductor chip is mounted on the bumps, the surface flatness of the bumps is required, so that there is the above-mentioned "warpage" problem.

Therefore, in recent years, in view of such a problem of "warpage", the following method has been proposed. That is, after forming the conductor pattern on the green sheet,
A laminated ceramic in which an insulating coating having a thickness equal to or larger than the film thickness of the conductor pattern is formed on the green sheet excluding the conductor pattern and fired, and then a refractory metal plate is placed on the surface of the conductor pattern and refired. Substrate manufacturing method (JP-A-61-2
No. 93002). Although it is different from the laminated ceramic substrate, it is a general method of correcting the warp of the ceramic substrate, in which the warped ceramic substrate is placed on a flat jig and a uniform load is applied on the ceramic substrate. A method of correcting the warp by re-baking (see Japanese Patent Laid-Open No. 4-31368). Is proposed. Then, according to this method, it is possible to suppress the occurrence of "warpage" due to thermal deformation during firing, or to correct the "warpage".

[0007]

However, the conventional method for manufacturing a laminated ceramic substrate and the method for correcting warpage as described above have the following problems. That is, in the former case, it is necessary to form an insulating coating having a thickness equal to or larger than the thickness of the conductor pattern on the green sheet, and it is difficult to form the insulating coating. Also, after firing the green sheet, put a weight with a refractory metal plate on the upper surface,
The warp is corrected by the load at the time of re-firing, but it is difficult to obtain the uniform load. In the latter case, when applied to a monolithic ceramic substrate, there is a limit to the correction of warpage because the conductor pattern exists in the inner layer even if a uniform load is applied. And other issues remain.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a laminated ceramic substrate having a surface conductor pattern such as bumps having excellent surface flatness. To provide.

[0009]

A method for manufacturing a laminated ceramic substrate according to the present invention as a means for achieving the above object is to laminate a plurality of green sheets each having a conductor pattern printed on the surface thereof, and to form a surface layer and an inner layer. After producing a green sheet laminate having a conductor pattern on the substrate and firing the green sheet laminate, the front and back surfaces thereof have a flat or uniform warp of 5 μm or less / 25.4 mm and a surface roughness Ra = 1 μm. It is structured such that it is sandwiched between high melting point metal plates of ˜50 μm and refired.

[0010]

According to the method for producing a laminated ceramic substrate of the present invention, a green sheet laminate having conductor patterns on the surface layer and the inner layer is produced and the green sheet laminate is fired to produce a fired body having conductor patterns on the surface layer. After that, the front and back surfaces of the fired body are sandwiched between flat or identical high-melting-point metal plates, and the fired body is placed on a jig and fired again to soften the ceramic components in the fired body. And, since the front and back surfaces of the fired body are sandwiched by flat plate-shaped same or similar high melting point metal plates, a uniform pressurization state is maintained from the front and back surfaces, and "warpage" generated during the first firing. Is corrected and deformation due to heat shrinkage during cooling is suppressed, so that a laminated ceramic substrate having excellent surface flatness can be manufactured.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram showing one embodiment of the present invention and explaining a manufacturing process of a laminated ceramic substrate.

This embodiment is a method of manufacturing a laminated ceramic substrate having three layers, and, as shown in FIG. 1, as shown in FIG. 1, green sheet preparation, through hole formation, conductor filling step, conductor pattern printing step, There are five steps of a green sheet laminated body manufacturing step, a laminated body firing step, and a re-firing step. Each step of to is the same as the conventional laminated ceramic substrate manufacturing step. It is characterized by the "refiring process".

Green sheet production / through hole drilling /
The conductor filling step, the conductor pattern printing step, the green sheet laminate manufacturing step, and the laminate firing step are shown in FIG.
As shown in (d) to (d), the manufacturing process of the conventional laminated ceramic substrate is the same as the manufacturing process of the conventional laminated ceramic substrate, and thus detailed description thereof will be omitted. Hole drilling
On the surface of the green sheet 1a forming the surface layer 1 produced in the conductor packing step, a plurality of fine conductor patterns 2 each having a semiconductor chip mounted thereon and bumps for electrically connecting the semiconductor chips are printed. There is. Internal conductor patterns 5 and 6 are printed on the green sheets 3 a and 4 a forming the inner layer 3 and the back surface layer 4. In addition,
Reference numerals 13, 14, and 15 are through holes filled with conductors.

Then, in the next step of producing a green sheet laminate, the green sheets 1a, 2a and 3a are stacked and the temperature is 100 to 130 ° C. and the pressure is 50 to 8 by using a mold.
A green sheet laminate 7 is produced by heating and pressurizing at 0 kg / cm ² , and the internal temperature is 150 in the laminate firing process.
The fired body 8 is manufactured by firing in a firing furnace in a reducing atmosphere of 0 to 1600 ° C. By the way, some of the fired bodies 8 undergo "warping" due to thermal deformation during firing.
Therefore, in this embodiment, there is a "rebaking step" which is a fifth step of rebaking the fired body 8.

This re-firing step is a step of correcting the "warpage" generated in the step of firing the laminated body to produce a monolithic ceramic substrate having excellent surface flatness. That is, in this step, as shown in FIG. 1E, flat refractory metal plates 9 and 10 are arranged on the front and back surfaces 8a and 8b of the fired body 8 so that the front and back surfaces of the fired plate 8 are raised. Sandwiched between melting point metal plates 9 and 10,
This is a step of correcting the "warpage" by placing it on a jig 11 and re-baking it in a baking furnace in a reducing atmosphere having an internal temperature of 1500 to 1600 ° C., as in the above-mentioned laminated body baking step.

Here, the refractory metal plates 9 and 10 are the same or similar metal plates, and are flat molybdenum plates or tungsten plates. This high melting point metal plate 9,
It is necessary to use a flat metal plate having a small warpage as No. 10, and the warpage is 5 μm or less / 25.
It is held down to 4 mm. Then, the surface 8 of the fired body 8
The refractory metal plate 9 arranged on the a side has a surface roughness of the surface 9a on the side of the fine conductor pattern 2 on the surface 8a of the fired body 8 which is Ra = 1.0 μm to 50.0 by honing.
μm. Ra = 1.0 μm or more is to prevent the high melting point metal plate 9 and the fine conductor pattern 2 from adhering to each other at the time of re-firing, and Ra = 50.0 μm or less is the work of honing. It is due to consideration of sex.

Then, the front and back surfaces 8a and 8b of the fired body 8 are sandwiched between the high melting point metal plates 9 and 10, and this is placed on the jig 11 and refired. Here, as the jig 11, a jig (mounting table) made of molybdenum or tungsten, like the refractory metal plates 9 and 10, is used. The jig 11 is not required to have an allowable warpage range of the high melting point metal plates 9 and 10. In this fired body 8, the ceramic components in the fired body 8 are softened by re-firing, but
a and 8b are flat plate-like high-melting metal plates 9 of the same or same quality,
Since it is sandwiched by 10, the uniform pressure state is maintained from the front and back surfaces, and "warpage" generated during the firing process of the laminated body.
Is corrected, and deformation due to heat shrinkage during cooling is further suppressed. Therefore, a laminated ceramic substrate having excellent surface flatness can be manufactured.

Next, in order to confirm the action and effect of the manufacturing method of this embodiment, the manufacturing method according to this embodiment, a manufacturing method without re-baking, and a molybdenum plate (having a warp of 20 μm are used. , And a re-firing method is used to fabricate a three-layer laminated ceramic substrate (size: length: 35 mm × width: 35 mm).
× thickness: 1.5 mm), and the state of “warpage” was examined. In all of the above, the same conditions were applied to the green sheet production / through hole drilling / conductor filling step, the conductor pattern printing step, the green sheet laminate producing step, and the laminate firing step. In the manufacturing method of this example, a molybdenum plate (size: length: 40 mm × width: 40 mm × thickness: 2 mm, warpage: 2 μm) was used as the high melting point metal plate.

As a result, the warp of the fired body before re-fired had an average value of 126.3 μm and a maximum value of 142.4.
According to the manufacturing method of this embodiment, the average value: 2.6 μm, the maximum value: 3.7 μm, and the minimum value: 1.5 μm. However, when the weight of molybdenum plate was placed on the fired body and re-fired, the average value: 26.2 μm, maximum value: 37.7, minimum value: 20.4 μm "warpage" Was recognized.

As can be seen from the above, according to the manufacturing method of this embodiment, the warp of the fired body generated in the firing step of the laminate can be almost corrected, and the laminated ceramic substrate having excellent surface flatness can be manufactured. It could be confirmed. This is because the front and back surfaces of the fired body that has warped are sandwiched by flat plate-shaped high melting point metal plates, and when re-fired, the softened ceramic component is surely held, and thermal deformation due to thermal contraction during cooling is caused. Because it can suppress the occurrence.

It should be noted that the present invention is not limited to the above-mentioned embodiment, but includes a configuration that can be modified and implemented within the scope of the present invention. Incidentally, in the above-described embodiment, the case where the conductor pattern on the surface layer is a bump has been described, but the same applies to the case where other conductor patterns are used.

[0022]

As is apparent from the above description, according to the method for producing a laminated ceramic substrate of the present invention, a green sheet laminate having conductor patterns on the surface layer and the inner layer is produced and the green sheet laminate is fired. Then, after producing a fired body having a conductor pattern on the surface layer, the front and back surfaces of the fired body are sandwiched between flat or identical high-melting-point metal plates, and this is placed on a jig and refired. By doing
Since the ceramic component in the fired body is softened, and the front and back surfaces of the fired body are sandwiched between flat or the same high-melting-point metal plates, a uniform pressure state is maintained from the front and back surfaces. The "warpage" that occurred during the first firing was corrected,
Further, since deformation due to heat shrinkage during cooling is suppressed, there is an effect that a laminated ceramic substrate having excellent surface flatness can be manufactured.

Therefore, according to the present invention, it is possible to provide a method for manufacturing a laminated ceramic substrate having a surface conductor pattern such as bumps having excellent surface flatness.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating a manufacturing process of a laminated ceramic substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Surface layer, 1a ... Green sheet, 2 ... Micro conductor pattern consisting of bumps, 3 ... Inner layer, 3a.
..Green sheets, 4 ... Back surface layer, 4a ... Green sheets, 5, 6 ... Internal conductor patterns, 7 ...
Green sheet laminate, 8 ... Green sheet fired body, 8a ... Front of fired body, 8b ... Back side of fired body, 9 ... Refractory metal plate, 9a ... Micro conductor pattern Side surface, 10 ... high melting point metal plate, 11 ... jig,
13, 14, 15 ... Through holes filled with conductors

Claims (1)

[Claims] 1. A plurality of green sheets each having a conductor pattern printed on the surface thereof are laminated to form a green sheet laminate having conductor patterns on the surface and inner layers, and the green sheet laminate is fired, and then the front and back surfaces thereof are A method for producing a laminated ceramic substrate, which is characterized in that it is sandwiched between high melting point metal plates having a flat plate-like warp of the same or the same quality of 5 μm or less / 25.4 mm and a surface roughness Ra = 1 μm to 50 μm, and is fired again.