JPH02260602A - Jig for firing electronic component - Google Patents

Abstract

PURPOSE:To improve productivity by a method wherein a ceramic coating layer, having the crystal grain diameter of 1 to 90mum or above and the content of grain diameter within the range of average grain diameter + or -20% of 90% or more, is provided. CONSTITUTION:The first layer is a flame spray coating layer having the crystal grain diameter of 1 to 90mum. The flame spray coating layer is subjected to generation of cracks when it has crystal grain diameter less than 1mum, and on the other hand, film strength becomes weak if the crystal grain diameter is 90mum or above, and it becomes easier to exfoliate. The ceramic grains which form the second layer have the average grain diameter of 20mum or above, and they contain the grain diameter content of 90% within the range of average grain diameter + or -20% when the average grain diameter is 20mum or less, the first layer and the material to be fired are easily brought into contact with each other, and there is little effect even when the second layer is formed. Also, when the grain diameter of the average grain diameter of + or -20% or less than 90%, the recesses and projections on the surface of a coarse grain layer become larger, the above-mentioned contact is lessened, and the contraction of the material to be fired is hardly made uniform. As a result, the contact between the second layer and the material to be fired is lessened, and the infiltration diffusion into the first layer can be prevented by the thickness of the layer.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a jig for firing electronic components such as varistors, thermistors, piezoelectric elements, and capacitors, and particularly relates to jigs for firing electronic components such as varistors, thermistors, piezoelectric elements, and capacitors. The present invention relates to an electronic component firing jig suitable for firing electronic components containing electronic components.

(Prior art) Molded bodies mainly made of heat-resistant inorganic fibers and fire-resistant powder are lightweight (porous) and have excellent heat resistance, and have been widely used as jigs for firing electronic components. .

By the way, among these electronic component firing jigs, the electronic component firing jigs for firing capacitors, ferrite, etc. whose main ingredients are barium titanate, strontium titanate, etc. Because the heat-resistant inorganic fibers react with capacitors and ferrite during firing, the surface of the jig is brushed or sprayed with a slurry of ceramic powder such as zirconia, alumina, or magnesia to prevent the reaction. A coating layer was applied by coating or dipping and then baking.

(Problems to be Solved by the Invention) However, although electronic component firing jigs coated with coating layers as described above are effective to some extent, it is difficult to completely prevent reactions during firing. , and usually become virtually unusable after a few uses.

Furthermore, recently, attempts have been made to lower the firing temperature by incorporating low melting point oxides such as lead and bismuth in order to reduce the manufacturing cost of the electronic components. There has been no known electronic component firing jig capable of firing electronic components containing such low melting point oxides.

In addition, as a result of various studies on the reaction between the object to be fired and the firing jig as described above, the applicants of the present invention have previously published Japanese Patent Application No. 6121.
In No. 9579, the coating layer conventionally applied to the baking jig had a relatively low density and had continuous holes,
It was discovered that the above reaction occurs due to the permeation and diffusion of oxides in the object to be fired through these pores, and by increasing the density of the coating layer, The inventors have come up with the idea that it is possible to prevent the oxide from permeating and diffusing the coating layer, thereby preventing a reaction between the firing jig and the electronic component to be fired.

However, when firing electronic parts that contain reactive substances with high vapor pressure, such as lead, it is necessary to completely eliminate pores even in the above-mentioned high-density injection coating, so that the firing jig and the object to be fired must be completely free of pores. It was discovered that completely preventing reactions with certain electronic components is insufficient.

That is, an object of the present invention is to further improve the invention proposed by the present inventors, and to provide a jig for firing electronic parts that can completely prevent reactions with electronic parts.

(Means for Solving the Problems) As a result of further various studies on the reaction between the object to be fired and the firing jig as described above, the inventors of the present invention found that it is possible to We have come up with the idea that by providing a coarse particle layer on the surface by spray coating, it is possible to prevent the permeation and diffusion of the reactive substance to almost no state.

That is, while ensuring close adhesion between the molded body, the thermal spray coating layer, and the coarse particle layer, the densified thermal spray coating layer prevents diffusion into the molded body,
In addition, by reducing the contact with the object to be fired in the coarse particle layer, the amount of penetration into the thermal spray coating layer of the lower molded body is reduced, resulting in a firing jig that can withstand long-term use.

In a jig for firing electronic parts, the ceramic coating layer has a ceramic coating layer on the surface of a molded body having many voids mainly composed of heat-resistant inorganic fibers and refractory powder, and the ceramic coating layer has a crystal grain size of 1 to 1. No. 1111M of 90 μm and further formed on the surface with an average particle size of 2
2. The electronic component firing jig according to claim 1, further comprising a second layer having a particle size content of 90% or more within a range of 0 μm or more and ±20% of the average particle size.

The present invention will be explained in detail below.

First, in the electronic component firing jig of the present invention, it is necessary to form a first ceramic coating layer on the surface of the molded body having a large number of voids mainly composed of heat-resistant inorganic fibers and refractory powder. .

The first layer is preferably a thermal spray coating layer having a crystal grain size of 1 to 90 μm.

The reason why the crystal grain size of the thermal spray coating layer is preferably 1 to 90 μm is that if the crystal grain size is smaller than 1 μm, cracks will easily occur in the thermal spray coating layer, whereas if it is coarser than 90 μm, the film strength will decrease. This is because the adhesive tends to become weak and the adhesion to the molded body is weak, making it easy to peel off.

The first layer has a porosity of 20% or less and a thickness of 10 to 20%.
It is desirable that it is 0/7m. The reason why the porosity of the first layer needs to be 20% or less is that the porosity of the first layer is 20% or less.
If it is larger than , it will not be possible to prevent the oxide in the object to be fired from penetrating and diffusing into the first layer, and it will be impossible to prevent the reaction between the firing jig and the electronic component. Advantageously, it is below 15%. The reason why the thickness of the first layer is required to be 10 to 20,011 m is that if the thickness is thinner than 10 μm, the oxide in the object to be fired is substantially prevented from permeating and diffusing. On the other hand, if it is thicker than 200 μm, it is likely to peel off from the molded body due to thermal expansion and contraction during use, or cracks will easily occur in the first layer.

The first layer is preferably formed by a thermal spray coating, and particularly preferably a plasma sprayed coating layer. The reason for this is that in plasma-sprayed coating layers, ceramic powder is melted and sprayed in a hot plasma, and after the molten particles fuse together, they are cooled and solidified, forming a high-density film with few voids between particles. This is because it can be done.

As the ceramic powder for forming the first layer, magnesia, zirconia, alumina, or magnesia-iron spinel can be used, but zirconia is particularly preferred from the viewpoint of reactivity.

In addition, it is preferable that the first layer has a surface roughness of 70 to 500 μm in order to form a second layer to be described later.

If the surface roughness is less than 70 μm, the second layer cannot be firmly adhered to the second layer, resulting in peeling.

From this, the ceramic powder for forming the first layer preferably has a particle size of 10 to 90 μm, and a particle size of 20 to 50 II m provides the highest density and a good coating layer with excellent adhesion. can get.

Next, the firing jig of the present invention forms a second layer on the surface of the first ceramic coating layer.

This is especially true when firing electronic components containing reactive substances with high vapor pressure such as lead, since the ceramic coating layer alone is not sufficient to prevent the reaction. It is effective to spray coat ceramic as a second layer on the surface of the layer to provide a coarse particle layer.

That is, the second layer reduces contact with the object to be fired and prevents penetration and diffusion into the first layer due to its thickness.

The second layer is made of a chemically stable material that does not cause a chemical reaction with the reactive substance. Specifically, ceramics such as zirconia, alumina, and magnesia spinel can be used.

Further, in order to obtain a uniform shrinkage rate of the object to be fired, it is preferable to adopt a structure in which the object to be fired is supported by a plurality of point contacts with a group of particles having a shape close to a perfect sphere and a uniform distribution of particle diameters. good.

It is preferable that the ceramic particles forming the second layer have an average particle size of 20 μm or more, and contain 90% or more of the particle size within a range of ±20% of the average particle size. For example, commercially available spherical alumina fine powder, alumina balls used for pulverization, mullite balls, zirconia balls, etc. can be used. If the average particle diameter is less than 20 am, contact between the first layer and the object to be fired is likely to occur, and even if a second layer is formed, the effect is small and undesirable. % particle diameter is less than 90%, the roughness on the surface of the coarse particle layer becomes large and the number of contact points decreases, making it difficult to make the shrinkage rate of the object to be fired uniform, which is not suitable.

Furthermore, the thickness of the second layer is preferably in the range of 10 to 200 μm. If it is thinner than 10 μm, reactive substances from the object to be fired will easily penetrate into the base material of the baking jig, resulting in a shortened lifespan, and if it is thicker than 200 μm, due to the difference in thermal expansion and contraction rate with the first layer, The coarse particle layer will easily peel off.

Next, the molded body which is the base material of the electronic component firing jig of the present invention will be described.

The molded body constituting the electronic component firing jig of the present invention needs to be mainly composed of heat-resistant inorganic fibers and refractory powder. The reason for this is that molded products made mainly of heat-resistant inorganic fibers and fire-resistant powder have a large number of voids inside, so they have a small heat capacity, are resistant to thermal quenching, are lightweight, and have extremely high strength. This is because it is extremely suitable as a jig for firing electronic components.

Various types of heat-resistant inorganic fibers can be used, but at least one of amorphous silica-alumina fibers and alumina crystalline fibers is particularly effective. The silica-alumina fibers are usually A 1 ! 03 is 40 to 60 W[%] and SiOz is 40 to 60 wt%. Mullite crystals precipitate at around 900°C and cristobalite crystals precipitate at around 1200°C, resulting in grain growth. It is particularly preferred in the present invention because it promotes sintering with the organic powder and/or the inorganic binder. Further, the alumina crystalline fiber is Al□
0, is 7θ~99wt%, S i Oz is 1~30wL
%, and is composed of η-, r-, δ-1θ type transitional alumina, α-type stable alumina, or mullite. The transitional alumina is 140
When fired at around 0°C, it transforms into the α-type and causes grain growth, and α-type alumina and mullite also cause grain growth, so they can be expected to act as a firing accelerator in the same way as the silica/alumina fibers mentioned above. This is preferable.

However, it is advantageous to use these heat-resistant inorganic fibers containing 20% by weight or less of non-fibrous materials in order to eliminate the smoothness of the surface of the molded product.

The refractory powder is present between the heat-resistant inorganic fibers, exhibits a sintering effect during firing, and is blended to form a molded body that is a strong structure.

As the refractory powder, one or more selected from, for example, alumina, alumina/silica, zirconia, magnesia, and titania are preferable because of their high refractory temperature. Specifically, alumina, mullite, kaolinite, kibushi clay, frog's eye clay, sillimanite, steatite, forsterite, zirconia, magnesia, spinel, titania, etc. are advantageous.

In addition to the heat-resistant inorganic fibers and refractory powder, the molded article may contain an inorganic binder for the purpose of obtaining a molded article with higher strength. As the inorganic binder, silica/soda type, calcium borate type,
Any one type or two or more types selected from silica-based frits can be used. As a specific substance,
For example, feldspar, mica powder, boric acid, limestone, petalite, glass powder, silica stone, etc. are listed.

It is advantageous to use these refractory powders and inorganic binders by blending them in advance into a composition that allows sintering at a predetermined temperature, and then pulverizing them with a pulverizer such as a ball mill to a particle size of about 50 μm or less. Note that the inorganic binder is preferably in the form of a fine powder, and optimally one with a particle size of 1 μm or less.

Next, an example of a method for manufacturing an electronic component firing jig according to the present invention will be briefly described.

The jig for firing electronic parts of the present invention is produced by mixing a predetermined amount of heat-resistant inorganic fibers, fire-resistant powder, and an inorganic binder added if necessary, kneading or dispersing in water, shaping, and then firing. Manufactured by plasma spraying ceramic powder onto the surface.

Next, when forming a coarse particle layer as a second layer, place ceramic powder together with an organic binder such as methylcellulose or vinyl acetate in water or an organic solvent, sufficiently disperse it to form a mixed solution, and spray the mixed solution. Formed in close contact with the surface of the coating layer by a method such as dipping, and after drying 1.
It is fired at a temperature of 000 to 1600°C.

Examples of the present invention will be described below along with comparative examples.

As a heat-resistant inorganic fiber, by classifying it in water,
Average length 1 with non-fibrous content controlled at 6% by weight.
600 g of alumina/silica fiber with an average aspect ratio of 1000 μmm and an average particle size of 3 μm as a refractory powder
1100g of alumina powder and average secondary particle size of 6μm
300 g of wooden tablet clay and 150 g of montmorillonite with an average secondary particle size of 3 μm as an inorganic binder were mixed together, placed in a universal mixer, and mixed with 1400 g of water, organic molding aids and fiber treatment agents (wax, polyacrylamine acetate). )
After adding 300 g, kneading was continued for 5 minutes. After the kneaded product was degassed in vacuum, it was placed in a porous mold made of epoxy resin and press-molded to produce a molded product of 150 x 150 x 5' mm.

After drying, it was baked at 1500°C for 3 hours in an air atmosphere. The obtained molded body had a density of 1.1 g/cffl and an open porosity of 66%.

Next, Y! is applied to the surface of this molded body. 0. A stabilized zirconia powder containing 20% L and having an average particle size of 45 μm was plasma sprayed to form a ceramic coating layer (first layer) of about 100 μm. Plasma spraying is Ar/H,
45g/mi stabilized zirconia powder into gas plasma
The plasma gun was supplied at a speed of n, and the distance between the surface of the molded body and the plasma gun was about 70 mm. The surface temperature of the molded body during thermal spraying was always kept below 200°C, and no cracks occurred.

Note that plasma spraying was performed twice to form a film of about 50 μm each time.

The adhesion efficiency of the zirconia powder was about 55%.

The thickness of the coating layer was measured by observing the cross section of the molded body with an optical microscope and taking a photograph, and in this case, it was 100 μm. Also,
The density of the coating layer was approximately 4.2 g/c-.

Furthermore, ittria stabilized Zr0t (average particle size 30 μm)
was mixed and dispersed in water with methylululose and vinyl acetate to form a slurry, and then applied to the first plasma spray coating layer with a spray gun to a film thickness of 150 μm, and then baked at 1450°C for 6 hours. A second layer was formed. When the obtained molded body was used in a firing jig for a PTC thermistor, no peeling, cracking, or reaction of the coating layer was observed even after 30 cycles.

In the above cycle, after the PTC thermistor was placed on the sample, it was fired at 1100°C for 3 hours, and then cooled to room temperature to check whether there was any reaction or not.

After that, they replaced it with a new chip and repeated the operation.

A PTC thermistor was prepared under the same conditions as in Example 1 using the same method as in Example 1, except that only the first plasma spray coating layer was formed without forming the second layer. When used in a baking jig, the plasma spray coating layer peeled off from the base material after 15 cycles.

The thickness of the spray coating was set to 250 μm using the same method as in Example 1, and P was coated under the same conditions as in Example 1.
When used in a TC thermistor firing jig, the spray coat layer (second layer) rose up from the thermal spray coating (first layer) after 10 cycles, and completely disappeared after another 5 cycles. has peeled off.

(Effects of the Invention) As described above, the electronic component firing jig of the present invention can be used not only for electronic components such as varistors, thermistors, piezoelectric elements, and ceramic capacitors, but also for electronic components containing low melting point oxides. It can also be fired extremely efficiently, and has the great effect of increasing productivity by increasing firing speed and reducing product costs by saving energy.

that's all

Claims (3)

[Claims] (1) In a jig for firing electronic components, the jig has a ceramic coating layer on the surface of a molded body having many voids mainly composed of heat-resistant inorganic fibers and refractory powder,
The ceramic coating layer has a crystal grain size of 1 to 90μ.
m first layer and further formed on the surface with an average particle size of 2
2. The electronic component firing jig according to claim 1, further comprising a second layer having a particle size content of 90% or more within a range of 0 μm or more and ±20% of the average particle size. (2) The first layer has a porosity of 20% or less and a thickness of 10%.
The jig for firing electronic components according to claim 1, wherein the jig is a thermal spray coating layer of ~200 μm. (3) The electronic component firing jig according to claim 1, wherein the second layer has a thickness of 10 to 200 μm.