JPH03115153A - Step coverage sheet - Google Patents

Abstract

PURPOSE:To obtain a sintered body of laminated ceramic green sheets having superior adhesive strength and no gap between the layers by mixing ceramic powder with a heat-sensitive flowable binder and a polymer binder and molding the mixture into a sheet shape. CONSTITUTION:20-95wt.% ceramic powder of 0.1-10mum average particle size sintered at the time of sintering a ceramic green sheet, e.g. alumina powder is mixed with 5-70wt.%, in total, of a heat-sensitive flowable binder, e.g. lauric acid and a polymer binder having <=100 deg.C glass transition temp., e.g. polyalkyl methacrylate. A filler and a solvent are added to the mixture as required and the mixture is molded into a sheet shape to obtain a step coverage sheet of 5-200mum thickness. A ceramic green sheet is laminated on a body to be adhered with the step coverage sheet in-between and the sheets are press-bonded under 5-150kg/cm<2> pressure and sintered at 800-2,000 deg.C to obtain a sintered body of laminated ceramic green sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a step compensating sheet suitable for forming multilayer ceramic circuit boards, layered ceramic capacitors, and the like.

Background and Problems of the Invention When firing a laminate of ceramic green sheets to form a monolithic laminate sintered body, a pattern consisting of a conductive powder layer is applied, as in the case of obtaining a ceramic circuit board, a ceramic capacitor, etc. Ceramic green sheets may be used.

Conventionally, methods for manufacturing a laminated fired body in such cases include coating a polymer adhesive to adhere and laminate ceramic green sheets, and then firing it, or hot pressing a simple laminate of ceramic green sheets. There is a known method in which the binder in the sheet is molten and pressed and then fired.

However, in the obtained laminated fired product, there is a problem in that a gap is formed in the vicinity of the pattern at the interface between the conductor powder layer in the ceramic green sheet provided with the pattern made of the conductor powder layer. Such patterns form electrical circuits, and gaps in the vicinity become water ingress routes, which poses a fatal problem. In addition, in the case of the adhesive application method, it is difficult to apply the adhesive evenly, and voids and swells occur during firing, which impairs the adhesion between the sheets and reduces the yield and quality of the resulting product. There was a problem. In addition, it was difficult to automate the entire process because it required a high degree of control over things such as the state of adhesive application (there was also the problem of poor manufacturing efficiency).

On the other hand, in the case of the hot press method, there is a problem in that the conductive powder layer applied to the ceramic green sheet is divided, leading to poor conduction. In addition, there were also problems such as insufficient adhesive strength, complicated and difficult control of temperature and pressure for laminating sheets while preventing sheet deformation, and problems such as warping and shrinkage of laminated fired products, which tend to occur, and poor dimensional accuracy. .

An object of the present invention is to develop a technique that can prevent the formation of gaps due to the steps when ceramic green sheets are laminated on an adherend with the involvement of steps and then baked and fixed.

2. Description of the Related Art Conventionally, the above-mentioned ceramic green sheet using a polymer as a binder has been known as a product in which ceramic powder is held in the form of a sheet with a binder.

However, as described above, the use of such ceramic green sheets causes the above-mentioned problems.

Means for Solving the Problems The present invention has succeeded in developing a ceramic sheet that can overcome the above problems.

That is, the present invention is a sheet for adhering a ceramic green sheet to an adherend during firing, and the ceramic powder fired during firing of the ceramic green sheet is shaped into a sheet using a heat-sensitive fluid binder and a polymer binder. The present invention provides a level difference compensating sheet characterized by shape-retaining.

Effect: In the above-mentioned level difference compensating sheet, the ceramic powder in the level difference compensating sheet is well filled into the level difference portions etc. based on the easy-flowing property of the heat-sensitive flowable binder. As a result, the ceramic green sheets can be laminated to the adherend with good adhesion without forming gaps even at interfaces involving steps, and when punching the formed laminate as necessary,
Even during other handling, peeling or misalignment between the laminated layers is unlikely to occur. In addition, a high-quality laminated fired body that can be fired without producing voids or swelling and has excellent interlayer adhesion can be produced with a high yield.

Therefore, when used for laminating ceramic green sheets having a pattern made of conductor powder layers, for example, in addition to the ease of adjusting and uniformity of the adhesive layer thickness due to the sheet method, it is possible to laminate ceramic green sheets without deforming the ceramic green sheets. In addition, patterns made of conductor powder layers can be laminated easily and in a homogeneous adhesive state without disconnection, and disconnections in the conductor patterns and gaps in the vicinity thereof are less likely to occur. Further, the process from forming the laminate to forming the fired body can be easily automated.

Examples of Constituent Elements of the Invention The level difference compensating sheet of the present invention is made by holding the ceramic powder fired during firing of the ceramic green sheet into a sheet form using a heat-sensitive fluid binder and a polymer binder.

Any suitable ceramic powder may be used depending on the firing conditions and the like. It is preferable to use a ceramic green sheet having the same composition as the ceramic green sheet to be fired, from the viewpoint of bondability. When joining different types of ceramic products, it is also possible to use a combination system of them or a laminated sheet of layers containing each product separately. Examples of commonly used ceramic powders include:
Examples include alumina powder, aluminum nitride powder, zirconia powder, titania powder, beryllia powder, barium titanate powder, magnesium titanate powder, mullite powder, steatite powder, and other ceramic powders for low-temperature firing. The average particle size of the ceramic powder to be used is suitably 0.1 to 1OμI, and the amount used is suitably an amount that provides a content composition of 20 to 95% by weight. If the content is less than 20% by weight, sufficient bonding strength will not be developed, and shrinkage during firing will be large and gaps will easily form near the steps formed by the conductor powder layer, etc.
If it exceeds % by weight, it becomes difficult to handle it as a sheet.

The heat-sensitive fluid binder may be appropriately determined depending on the heating temperature during lamination of the ceramic green sheets. Generally, waxes that are solid at room temperature such as carboxylic acid waxes such as stearic acid and lauric acid, paraffin waxes such as octadecane and tetracosane, higher alcohol waxes, polyethylene waxes, ester waxes, and amine waxes are used. Preferably used.

The amount of thermosensitive fluid binder used is 5 to 70% of the total binder.
% by weight, especially from 20 to 50% by weight, is suitable. If the amount used is less than 5% by weight, it may not be possible to compensate for differences in level during lamination, and if it exceeds 70% by weight, sheet formation becomes difficult.

As a polymer binder, the glass transition temperature is 100℃
Hereinafter, among others, polymers having a temperature of -5 to 20°C, such as hydrocarbon polymers, vinyl-based or styrene-based polymers, acetal-based polymers, (meth)acrylic polymers, ester-based polymers, urethane-based polymers, etc., are used.

If the glass transition temperature exceeds 100° C., it may not be possible to compensate for the difference in level during lamination.

The step compensation sheet is formed by mixing one or more of ceramic powder, thermosensitive fluid binder, and polymer binder as necessary, for example, using an appropriate solvent such as xylene, toluene, or butanol. This can be carried out by spreading it on a separator or other sheet body using an appropriate coating machine such as a roll coater.

When forming the level difference compensation sheet, talc,
Fillers such as kaolin, calcium oxide, silica, and magnesia, or sintering aids may be added.

The thickness of the level difference compensating sheet to be formed is appropriately determined depending on the level difference to be compensated for. By the way, the height difference is 5 to 100μ.
In the case of a conductor powder layer having a thickness of m, the typical thickness of the level difference compensating sheet used is 5 to 200 pm.

In particular, it is 30 to 120 μm. If the level difference compensating sheet is too thin, peeling or misalignment will easily occur between the laminates during punching, etc., and if it is too thick, voids or omissions will occur at the bonding interface, resulting in poor glabella adhesion.

The level difference compensating sheet of the present invention is for adhering a ceramic green sheet to an adherend during firing. In particular, it is advantageously used when bonding a ceramic green sheet to an adherend by firing in a state where a step is involved, such as in the case of a ceramic green sheet having a pattern consisting of a conductive powder layer. In this case, it is preferable to interpose a level difference compensating sheet at least between layers where a level difference will occur.

The bonding process between the ceramic green sheet and the adherend can be carried out, for example, by first press-bonding the ceramic green sheet and the adherend through a step compensation sheet to form a laminate, and then subjecting the laminate to a firing process. .

The pressing force for forming the laminate is 5 to 150 kg.
/crl, especially 20 to 100 kg/c+J is suitable. If the pressure is too low, the level difference compensating sheet will not be enough to compensate for the level difference, and gaps will easily occur. If the pressure is too strong, there will be problems with deformation of the ceramic green sheet, and if the level difference is a layer of conductive powder, there will be problems with disconnection. induce.

The compression temperature may be appropriately determined depending on the glass transition temperature of the polymer binder, the melting point of the heat-sensitive fluid binder, the mixing ratio thereof, and the like. Generally, the temperature ranges from room temperature to 100°C. When forming the laminate, the level difference compensating sheet may be attached to the ceramic green sheet or the adherend in advance. Note that it is also possible to adopt a method in which a level difference compensating sheet is interposed on a part of the surface of the ceramic green sheet and laminated.

As the ceramic green sheet to be bonded, any suitable material may be used, such as one formed by forming a mixture of ceramic powder and a binder using an organic solvent or the like into a sheet form by a screen printing method, a doctor blade method, or the like. An appropriate adherend may also be used.

The formed laminate may be subjected to intermediate processing such as punching, if necessary, before the firing process. Firing conditions such as firing temperature and firing atmosphere may be determined as appropriate depending on the type of ceramic green sheet. Generally, 800-2
It is fired at a temperature of 000°C. Through the firing process, organic components such as binders in the ceramic green sheet and the step compensation sheet are thermally decomposed and disappear, leaving the ceramic powder that forms the ceramic green sheet, and the conductor powder if there is a conductor powder layer. At the same time, the ceramic powder in the step compensation sheet causes interlayer bonding between the fired ceramic green sheet and the adherend, forming a target object such as a laminated fired ceramic green sheet. be done.

The level difference compensating sheet of the present invention is produced by laminating a ceramic green sheet having a level difference with another ceramic green sheet and bonding it by firing, such as a ceramic green sheet having a conductive powder layer when producing a ceramic circuit board, a ceramic capacitor, etc. It can be advantageously used when It can also be advantageously used when a flat ceramic green sheet is laminated and bonded by firing on an adherend having unevenness or other steps on its surface, such as a printing plate made of glass, metal, or the like.

Effects of the Invention According to the level difference compensating sheet of the present invention, since it contains a heat-sensitive flowable binder, the ceramic powder in the level difference compensating sheet can be supplemented to the level difference based on the conductor powder layer, etc., and the ceramic green sheet is laminated with excellent adhesion. A fired body can be obtained without interlayer gaps.

Further, based on the sheet method, ceramic green sheets can be laminated via a thin (and homogeneous) adhesive layer, and a high-quality laminated fired body can be manufactured with a high yield.

Example 95 parts of alumina powder (parts by weight, the same applies hereinafter) with an average particle size of 1.5, 2.5 parts of talc, 2.5 parts of kaolin, 20 parts of polymethacrylic acid alkyl ester, 5 parts of lauric acid with a melting point of 45°C and 100 parts of toluene were uniformly mixed in a ball mill to prepare a slurry, spread on a separator made of a polyester film that had been released with a silicone resin, and dried to form a step compensation sheet with a thickness of 40 mm. I got it.

The level difference compensating sheet obtained in the evaluation test example was adhered to one side of a ceramic green sheet having a thickness of 1 inch under the conditions of 50° C. and 10 kg/cr&. The above ceramic green sheet contains 95 parts of alumina powder with an average particle size of 1.5 μm and 2.5 parts of talc.
2.5 parts of kaolin and 10 parts of polyvinyl butyral.

Next, on one side of the same type of ceramic green sheet as above, a conductive powder paste made by mixing 100 parts of platinum powder with an average particle size of 5 μs, 2 parts of nitrocellulose, and 1210 parts of oxygen was applied in a pattern using a screen printing method. , thickness 30
A 17 m long conductor powder layer is laminated on the level difference compensating sheet with the conductor powder layer side interposed therebetween.
A laminate was obtained by pressure bonding at 0° C., 20 kg/cd, and 10 seconds. This laminate had excellent adhesion or adhesion between the ceramic green sheets, and no deformation of the ceramic green sheets or separation of the conductor powder layer was observed, and no gaps were observed in the vicinity of the conductor powder layer.

The above laminate was fired in air at 1600° C. for 30 minutes to obtain a laminate fired product with a total thickness of 1.7 mm+. The laminated fired product has very good interlayer adhesion and bonding strength, shows no swelling or voids, and no shape changes such as warping (and exhibits good electrical conductivity with no disconnections in the conductor parts). No gaps were observed near the conductor.

Comparative example Same as the example except that lauric acid is not used (step compensation)
Got a sheet.

When a laminate was formed using the above-mentioned sheets according to the above evaluation test and fired to obtain a laminate, a gap was observed in the laminate near the conductor powder layer between the ceramic green sheets. Gaps were also observed in the vicinity of the conductor parts in the laminated fired body.

Claims (1)

[Claims] 1. This is a sheet for adhering a ceramic green sheet to an adherend during firing, and is made by holding the ceramic powder fired during firing of the ceramic green sheet into a sheet form with a heat-sensitive fluid binder and a polymer binder. A level difference compensation sheet characterized by: