JP2001028291A - Hot plate and conductor paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent peeling off from a conductor pattern by forming the conductor pattern on a ceramic substrate with substantially scale noble metal particles. SOLUTION: A wiring resistor 10 is formed into a concentric circle or a spiral shape as a conductor pattern on the bottom side of a ceramic substrate 9 made of aluminum nitride, for example. Pads 10a are formed at the ends of the wiring resistor 10. The wiring resistor 10 and the pads 10a are formed by printing conductive noble metal paste P1 on the surface of the ceramic substrate 9, and baking it by heating. The wiring resistor 10 and the pads 10a, derived from the noble metal paste P1, contain only one kinds of noble metal particles as the main component and furthermore contain sub-components such as glass frits. Flake metal particles preferably have an average particle size of 6 μm or smaller, more preferably about 3-5 μm. By selecting the average particle size in a suitable range, a void ratio is decreased, and tensile strength is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot plate and a conductive paste using a ceramic substrate.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, for example, when a silicon wafer having undergone a photosensitive resin coating step is heated and dried, a hot plate using a ceramic substrate has been frequently used in recent years.

A conductor layer is formed in a predetermined pattern on one side of a ceramic substrate, and terminal connection pads are formed on a part of the conductor pattern. Such a conductive pattern is formed by printing and applying a conductive noble metal paste on a substrate as described in JP-A-4-300249, and then heating and baking the paste. The conductor paste usually contains one kind of noble metal particles (for example, silver particles having an average particle diameter of about 5 μm and a substantially spherical shape). Terminal pins are soldered to the pads, and a power supply is connected to the terminal pins via wiring.

Then, a silicon wafer to be heated is placed on the upper surface side of the hot plate, and current is supplied in this state.
To be heated.

[0005]

However, when the above-mentioned conventional noble metal paste is printed on a substrate and baked, voids are easily formed in the conductor pattern and peeling is likely to occur. Therefore, there has been a strong demand for a conductor pattern that is difficult to peel.

Further, in order to increase the heat generation of the conductor pattern, it is necessary to increase the specific resistance. The present invention has been made in view of the above problems, and a first object of the present invention is to provide a hot plate having a conductor pattern that is difficult to peel. A second object of the present invention is to provide a hot plate having a conductor pattern which has a large specific resistance and is difficult to peel off. A third object of the present invention is to provide a conductor paste suitable for producing the above-mentioned excellent hot plate.

[0007]

According to a first aspect of the present invention, there is provided a hot plate comprising a ceramic substrate and a conductive pattern, wherein the conductive pattern is substantially scaly noble metal. The gist is a hot plate characterized by being composed of particles.

According to a second aspect of the present invention, in the first aspect, the average particle diameter of the substantially scaly noble metal particles is 6 μm or less. The invention according to claim 3 is the method according to claim 1 or 2, wherein the substantially scaly noble metal particles are gold particles,
At least one selected from silver particles, platinum particles and palladium particles.

The invention described in claim 4 is the first to third aspects of the present invention.
In any one of the above, the aspect ratio of the major axis to the minor axis of the substantially scaly noble metal particles is 1.5 or more.

According to a fifth aspect of the present invention, in the hot plate comprising a ceramic substrate provided with a conductor pattern, the conductor pattern is formed of substantially granular noble metal particles and substantially scaly noble metal particles. Make the plate an abstract.

According to a sixth aspect of the present invention, in the fifth aspect, the average particle diameter of the substantially granular noble metal particles is 3 μm or less, and the average particle diameter of the substantially scaly noble metal particles is 6 μm or less. did.

The invention according to claim 7 is based on claim 5 or 6, wherein the substantially scaly noble metal particles are composed of two or more kinds of particles having different average particle diameters. According to an eighth aspect of the present invention, in the conductive pattern according to any one of the fifth to seventh aspects, the substantially scaly noble metal particles are contained 5 to 25 times as large as the substantially granular noble metal particles. And

The gist of the invention according to the ninth aspect is a conductive paste composed of substantially scaly noble metal particles, an oxide and an organic vehicle. The gist of the invention according to claim 10 is a conductive paste composed of substantially granular noble metal particles, substantially scaly noble metal particles, an oxide, and an organic vehicle.

According to an eleventh aspect of the present invention, in the ninth or tenth aspect, the substantially scaly noble metal particles are at least one selected from gold particles, silver particles, platinum particles, and palladium particles. did.

According to a twelfth aspect of the present invention, in any one of the ninth to eleventh aspects, the substantially scaly noble metal particles comprise two or more kinds of particles having different average particle diameters. The invention according to claim 13 is the method according to any one of claims 10 to 12, wherein the substantially scaly noble metal particles are:
It is assumed that it is contained 5 to 25 times the substantially granular noble metal particles.

According to a fourteenth aspect of the present invention, in any one of the tenth to thirteenth aspects, the substantially granular noble metal particles have an average particle size of 3 μm or less, and the substantially scaly noble metal particles have an average particle size of 3 μm or less. The diameter was assumed to be 6 μm or less.

Hereinafter, the "action" of the present invention will be described. According to the first and ninth aspects of the present invention, the particles are more likely to come into surface contact with each other, and the noble metal particles are more likely to be densely packed after baking, as compared with a conventional conductor pattern including only substantially spherical noble metal particles. On the other hand, in the case of spherical noble metal particles, point contact occurs, so that voids are easily generated in the conductor pattern. As described above, in the present invention, the void ratio in the conductor pattern is reliably reduced, and the bonding area between the particles is increased. As a result, a sufficient tensile strength is secured for the conductor pattern, and a conductor pattern that is difficult to peel off can be obtained.

According to the second aspect of the present invention, by setting the average particle size of the substantially scaly noble metal particles to a preferable range of 6 μm or less, reduction of the void ratio and improvement of the tensile strength can be more reliably achieved. be able to. Especially 6 μm
When the value exceeds the above, the thickness variation of the conductor layer (resistor) becomes large (the surface roughness Ra becomes large), and the resistance value tends to vary.

According to the third and eleventh aspects of the present invention, these metal particles are relatively unlikely to be oxidized even when exposed to a high temperature, and exhibit a sufficiently large resistance value, so that they are suitable as a resistor for generating heat. A conductor pattern can be easily obtained.

According to the fourth aspect of the present invention, when the aspect ratio (length / thickness) between the major axis and the thickness is 1.5 or more, the particles are likely to come into surface contact with each other. Is less than 1.5, the particles come into point contact with each other, and it may not be possible to sufficiently reduce the void ratio and improve the tensile strength.

According to the fifth and tenth aspects of the present invention, the noble metal particles tend to be densely packed after baking, as compared with the conventional conductor pattern including only substantially spherical noble metal particles. Therefore, the void ratio in the conductor pattern decreases. On the other hand, since almost noble metal particles are used,
The particles do not completely come into surface contact, and a constant resistance value is obtained. For this reason, it is difficult to peel off, and a resistor having a high resistance value can be obtained. In addition, since it is easy to be dense, there is no variation in resistance value, and the temperature uniformity of the heated surface is high.

Examples of the shape of the granular particles include spherical, microcrystalline, and crushed particles. Among these, a spherical shape is particularly optimal. This is because the particle diameter is easily controlled and the reproducibility of the resistance value is excellent.

According to the present invention, the average particle diameter of the substantially granular noble metal particles and the average particle diameter of the substantially scaly noble metal particles are set in a suitable range, thereby reducing the void ratio. In addition, it is possible to more reliably achieve improvement in tensile strength and resistance value.

According to the seventh and twelfth aspects of the invention, if the substantially scaly noble metal particles are made of two or more kinds having different average particle diameters, the void ratio in the conductor pattern can be further reduced. Therefore, it is possible to reliably obtain a conductor pattern that is difficult to peel.

According to the eighth and thirteenth aspects of the present invention, the void ratio in the conductor pattern can be further reduced by setting the content ratio of the substantially scaly noble metal particles within the above-mentioned preferred range. Therefore, it is possible to more reliably obtain a conductor pattern that is difficult to peel. When the content ratio of the substantially scaly noble metal particles to the substantially granular noble metal particles is less than 5 times, the number of the substantially granular noble metal particles relatively increases, so that it is difficult to sufficiently reduce the void ratio. Also,
If the content ratio exceeds 25 times, on the contrary, the number of substantially flaky noble metal particles relatively increases, so that the resistance value may be too small.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hot plate unit 1 according to one embodiment of the present invention will be described below in detail with reference to FIGS.

Hot plate unit 1 shown in FIG.
Has a casing 2 and a hot plate 3 as main components. The casing 2 is a metal member having a bottom and has an opening 4 having a circular cross section on an upper side thereof. The casing 2 is not limited to a bottomed one, and may be a bottomless one. The hot plate 3 is attached to the opening 4 via an annular seal ring 14. On the outer periphery of the bottom portion 2a of the casing 2, there are formed lead wire drawing holes 7 for inserting lead wires 6 for supplying current, and each lead wire 6 is connected to the casing 2 from there.
Has been pulled out to the outside.

The hot plate 3 of the present embodiment comprising the ceramic substrate 9 is a low-temperature hot plate 3 for drying the silicon wafer W1 coated with the photosensitive resin at 50 to 300 ° C. The hot plate unit 1 has a working temperature range of 300 ° C to 800 ° C.

As the ceramic substrate 9, a nitride ceramic substrate having excellent heat resistance and high thermal conductivity is preferably selected. Specifically, an aluminum nitride substrate, a silicon nitride substrate, a boron nitride substrate It is preferable to select a titanium nitride substrate or the like. Among these, it is particularly desirable to select an aluminum nitride substrate, and then it is desirable to select a silicon nitride substrate. The reason is that these belong to the class of high thermal conductivity. Further, in addition to the nitride ceramic, an oxide ceramic or a carbide ceramic can be used as a substrate material. In particular, carbide ceramics are advantageous because of their high thermal conductivity. Silicon carbide, boron carbide, titanium carbide, or the like can be used as the carbide ceramic.

The ceramic substrate 9 of this embodiment is a disk-shaped plate having a thickness of about 1 mm to about 25 mm.
It is designed to have a slightly smaller diameter than the outer dimensions of the casing 2.

As shown in FIGS. 1 and 2, a wiring resistor 10 as a conductor pattern is formed concentrically or spirally on the lower surface of a ceramic substrate 9 made of aluminum nitride or the like. Pad 1 is located at the end of wiring resistance 10.
0a is formed. The wiring resistor 10 and the pad 10a are formed on the surface of the ceramic substrate 9 with a conductive noble metal paste (same as a conductor paste, which is a resistor paste for forming a resistor; hereinafter, referred to as a noble metal paste) P1. Is printed and then heated and baked. In the hot plate 3 of the present embodiment, the opposite side of the conductor pattern forming layer, that is, the upper surface side is the heating surface of the silicon wafer W1. The advantage of such a configuration is that temperature unevenness is less likely to occur in the hot plate 3,
This means that the silicon wafer W1 can be uniformly heated.

The wiring resistance 10 and the pad 10a of the present embodiment derived from the noble metal paste P1 contain only one kind of noble metal particles G2 (specifically, only flaky noble metal particles G2) as a main component, and further have a glass frit. Etc. are included. FIG. 3 conceptually shows a state of the scale-like noble metal particles G2. The amount of the glass frit is extremely smaller than the amount of the noble metal particles G2. Therefore, for convenience of illustration and description, the glass frit is intentionally omitted in FIG.

In this case, the flaky noble metal particles G2 preferably have an average particle diameter of 6 μm or less, and particularly preferably 3 μm to 5 μm.
It is preferable that it is about μm. By setting the average particle size in the above-described preferred range, it is possible to more reliably achieve the reduction of the void ratio and the improvement of the tensile strength.

The scaly noble metal particles G2 are made of gold particles (Au).
Particles), silver particles (Ag particles), platinum particles (Pt particles), and palladium particles (Pd particles). This is because these noble metals are relatively unlikely to be oxidized even when exposed to a high temperature, and exhibit a sufficiently large resistance value when generating heat by energization. Of course, these precious metals may be used alone,
Two, three or four types may be used in combination as described below. That is, Ag-Au, Ag-Pt, Ag-P
d, Au-Pt, Au-Pd, Pt-Pd, Ag-Au
-Pt, Ag-Au-Pd, Au-Pt-Pd, Ag-
Au-Pt-Pd.

In the present embodiment, the scaly noble metal particles G2 are plate-like or rod-like particles which do not exhibit a spherical shape, such as at least the noble metal particles G1, and have a ratio of the major axis to the minor axis, in other words, the major axis. It is desirable that the aspect ratio between the thickness and the thickness be 1.5 or more. Incidentally, in the present embodiment, the spherical noble metal particles G1 have an aspect ratio of 1.
It is preferably about 0 to 1.5 (but not including 1.5). Examples of the granular particles include a spherical shape, a microcrystalline shape, and a dendritic shape. The aspect ratio is not limited to a value within the above range. As long as the effects of the present invention are not impaired, it is acceptable to select scaly particles or granular particles.

When the aspect ratio of the scaly noble metal particles G2 is 1.5 or more, the shape tends to be different from the spherical one having an aspect ratio close to 1.0. As a result, the effect of the particle shape can be expected, and the reduction of the void ratio and the improvement of the tensile strength can be sufficiently achieved.

The wiring resistance 10 and the pad 10a of the present embodiment are formed of a plurality of types of noble metal particles G1, G2 having different shapes.
2 as a main component, and may further include a sub-component such as a glass frit. More specifically, the wiring resistance 10 and the like include not only the flaky noble metal particles G2 but also the granular noble metal particles G1 (that is, two kinds of noble metal particles G1 and G2). FIG. 4 conceptually shows the appearance of these noble metal particles G1 and G2. The amount of the glass frit is extremely smaller than the amounts of the noble metal particles G1 and G2. Therefore, for convenience of illustration and description, the glass frit is intentionally omitted in FIG.

In this case, the granular noble metal particles G1 preferably have an average particle size of 3 μm or less, and more preferably 0.5 μm to
The thickness is preferably about 2 μm. Scale-like noble metal particles G2
Preferably has an average particle size of 6 μm or less, particularly 3 μm.
m to 5 μm. The flaky noble metal particles G2 may be one composed of two or more kinds having different average particle diameters.

In the wiring resistance 10 and the pad 10a, the scale-like noble metal particles G2 are contained more than the granular noble metal particles G1. More specifically, the scale-shaped noble metal particles G2 are 5 to 25 times larger than the granular noble metal particles G1.
It is often contained twice, particularly preferably 6 to 20 times.

If the content ratio of the scale-like noble metal particles G2 to the substantially granular noble metal particles G1 is too small, the number of the granular noble metal particles G1 becomes relatively large, so that the void ratio cannot be sufficiently reduced depending on the condition setting. This is because there is a possibility. On the other hand, if the content ratio is too large, on the contrary, the scale-like noble metal particles G2 become relatively large, so that the paste printability may be reduced. Therefore, the printing thickness tends to vary, and the wiring resistance 10 and the pad 10a
It is difficult to accurately form a uniform thickness. Further, depending on the condition setting, the void ratio may not be sufficiently reduced.

Here, the granular noble metal particles G1 are also gold particles, silver particles, and gold particles for the same reason as the flaky noble metal particles G2.
Desirably, at least one selected from platinum particles and palladium particles. Of course, these noble metals may be used alone, or two, three, or four of them.
Seeds may be used in combination as described below. That is, A
g-Au, Ag-Pt, Ag-Pd, Au-Pt, Au
-Pd, Pt-Pd, Ag-Au-Pt, Ag-Au-
Pd, Au-Pt-Pd, and Ag-Au-Pt-Pd may be used in combination.

The metal species of the granular noble metal particles G1 and the flaky noble metal particles G2 may be a combination of the same type or a combination of different types.

As shown in FIGS. 1 and 2, a base end of a terminal pin 12 made of a conductive material is soldered to each of the pads 10a. As a result, each terminal pin 12
And the wiring resistance 10 is electrically connected. A socket 6 a at the tip of the lead wire 6 is fitted to the tip of each terminal pin 12. Therefore, when a current is supplied to the wiring resistor 10 via the lead wire 6 and the terminal pin 12, the temperature of the wiring resistor 10 increases, and the entire hot plate 3 is heated.

Next, an example of a procedure for manufacturing the hot plate 3 will be briefly described. A mixture is prepared by adding a sintering aid such as yttria, a binder, and the like to a ceramic powder typified by aluminum nitride or the like, if necessary, and the mixture is uniformly kneaded with a three-roll or the like. Using this kneaded material as a material, a plate-shaped formed body having a thickness of about several mm is produced by press molding.

Drilling is performed on the produced formed body by punching or drilling to form a pin insertion hole (not shown). Next, the substrate 9 made of a ceramic sintered body is manufactured by completely drying and sintering the formed body having undergone the drilling step by drying, preliminary firing, and main firing. The firing step is preferably performed by a hot press device, and the temperature is preferably set to about 1500 ° C. to 2000 ° C. Thereafter, the fired ceramic substrate 9 is cut into a circular shape having a predetermined diameter (230 mmφ in the present embodiment), and is subjected to surface grinding using a buffing apparatus or the like.

After the above steps, the noble metal paste P1 prepared in advance is uniformly applied to the lower surface of the ceramic substrate 9 by screen printing or the like. The noble metal paste P1 used here is the one kind of noble metal particles G described above.
2 (or the two kinds of noble metal particles G1 and G2), a glass frit, a resin binder as an organic vehicle, and a solvent.

The amount of the glass frit depends on the amount of the noble metal particles G2.
(Or G1 and G2) is preferably 1/5 or less, more preferably about 1/10 to 1/100. The reason is that noble metal paste P1
This is because the larger the conductive component in the above, the more advantageous it is in achieving a reduction in the specific resistance.

More specifically, in the noble metal paste P1, the total amount of the noble metal particles G2 (or G1 and G2) is about 60% to 80% by weight, and the glass frit is about 1% to 10% by weight. ing.

As the glass frit, zinc borosilicate
(SiO_Two: B_TwoO_Three: ZnO_Two) Based on
What added a small amount of metal oxide is used.
As a specific example of the metal oxide, aluminum oxide (Al
_TwoO_Three), Yttrium oxide (Y _TwoO_Three), Lead oxide (Pb
O), cadmium oxide (CdO), chromium oxide (Cr_Two
O_Three), Copper oxide (CuO), bismuth oxide (Bi_TwoO_Three)
One or more selected from the group consisting of

In addition, a resin binder as an organic vehicle is contained in the noble metal paste P1 in an amount of 3 to 15% by weight.
And the solvent is contained in an amount of about 10% by weight to 30% by weight. Examples of the resin binder include, for example, celluloses such as ethyl cellulose. The solvent is a component added for the purpose of improving printability and dispersibility, and specific examples thereof include acetates, cellosolves such as butyl cellosolve, and carbitols such as butyl carbitol.

When the noble metal paste P1 applied on the ceramic substrate 9 is heated at a temperature of about 750 ° C. for a predetermined time,
The solvent in the noble metal paste P1 evaporates, and the wiring resistance 10 and the pad 10a are burned. The molten glass frit tends to move in a direction approaching the ceramic substrate 9, and conversely, the noble metal particles G2 (or G1 and G2) tend to move in a direction away from the ceramic substrate 9.

Thereafter, the terminal pins 12 are joined to the pads 10a via the solder S1 to complete the hot plate 3, which is further attached to the opening 4 of the casing 2 to obtain a desired hot plate unit shown in FIG. 1 is completed.

Hereinafter, some examples and comparative examples will be introduced.

[0054]

EXAMPLES AND COMPARATIVE EXAMPLES [Preparation of sample (when the metal type of noble metal particles is the same)] In Examples 1 to 6 and Comparative Examples 1 to 3, aluminum nitride powder (average particle diameter 1.1 μm) 10
0 parts by weight, 4 parts by weight of Y ₂ O ₃ (average particle size 0.4 μm),
8 parts by weight of an acrylic resin binder (manufactured by Mitsui Chemicals, Inc., trade name: SA-545, acid value 1.0) as an organic vehicle was added and mixed. A kneaded product obtained by uniformly kneading the mixture thus obtained was put into a press mold and pressed to produce a plate-shaped formed body.

Next, after drilling and drying,
The molded body was degreased at 350 ° C. for 4 hours in a nitrogen atmosphere to thermally decompose the binder. Further, the degreased molded body is subjected to hot press firing at 1600 ° C. for 3 hours,
An aluminum nitride substrate was obtained as the ceramic substrate 9.
The pressure of the hot press was set at 150 kg / cm ² .

Thereafter, after the substrate was cut out and the surface was ground, a paste application step was performed. In this step, nine kinds of samples were prepared in accordance with the above procedure, using a noble metal paste P1 having the following composition and setting the thickness at the time of application to about 25 μm.

Noble metal particles: 70% by weight of silver particles in total, 5% by weight of glass frit (but containing 80% by weight of zinc borosilicate as a base), 5% by weight of ethyl cellulose as a resin binder, -Butyl carbitol as solvent: 15% by weight.

As the silver particles G1 and G2, 4 shown in Table 1 were used.
Species were appropriately combined and used. Then, Samples 1 to 6 were positioned as Examples 1 to 6, and Samples 7, 8, and 9 were positioned as Comparative Example 1 and Test Examples 1 and 2. Hereinafter, "Ag-126" manufactured by Shoei Chemical Industry Co., Ltd. was used as spherical silver particles, and "Ag-520, Ag-
530, Ag-540 "(B, C, D particles, respectively). “A particles” are spherical silver particles G1 having an average particle size of 1.00 μm (see FIG. 5 (a)).

The three types other than the A particles are all scale-like silver particles G
2 (see FIGS. 5B to 5D). The average particle size of “B particles”, “C particles”, and “D particles” is 3.94 μm and 4.
78 μm and 7.73 μm. The aspect ratio (major axis / thickness) of these particles was about 7.8, 9.5, and 15, respectively.

Specifically, in Examples 1, 2, 4, and 5, two types of spherical silver particles G1 and flaky silver particles G2 are used, and the flaky silver particles G2 Two different ones (ie, B particles and C particles) are used in combination.

In Example 3, two types of spherical silver particles G1 and flaky silver particles G2 were used, and only one flaky silver particle G2 (that is, only C particles) was used. In Example 6, only the flaky silver particles G2 are used, and two flaky silver particles G2 having different particle sizes (that is, B particles and C particles) are used in combination. That is, no spherical silver particles G1 are used for this.

In Comparative Example 1, the wiring resistance 10 and the like are formed using a noble metal paste P1 containing only one kind of spherical silver particles G1 as in the conventional case. In Test Examples 1 and 2,
Although the wiring resistance 10 and the like are formed using the noble metal paste P1 including two kinds of silver particles G1 and G2, D particles having a large average particle size are used as the flaky silver particles G2. Table 1 shows the volume ratio (wt%) of the four particles in the wiring resistance 10. [Comparative Test and Results] For each of the nine samples obtained, the wiring resistance 10 after the baking step was cut at an arbitrary position along the substrate thickness direction, and the cut surface was observed using an optical microscope. Photographed at 1000x. The value of the area of the void portion / the cross-sectional area of the paste was measured based on the enlarged photograph taken in this manner, and this value was defined as the void ratio (%) after firing. Table 1 shows the results. In addition,
The high void fraction (%) after firing means that the silver particles G
1 and G2 are densely packed, which means that the bonding area between the silver particles G1 and G2 is large.

The surface roughness (Ra) of the wiring resistance 10 surface
Was measured using a surface profiler (trade name: P-11, manufactured by KLA Tencor) in accordance with an ordinary method. The results are also shown in Table 1. The fact that the surface roughness is small and the surface is smooth means that the wiring resistance 10 has a uniform thickness, the resistance value is uniform and the variation is small.

Further, a tensile strength test was performed by a conventionally known method, and the tensile strength (kgf / kgf) of the wiring resistance 10 was determined.
2 mm □) was measured. Needless to say, if this value is large, the adhesion of the conductor pattern 10 is increased, and peeling is less likely to occur.

[0065]

[Table 1] As is clear from Table 1, the void ratio after firing in Comparative Example 1 showed a high value of 12% or more. On the other hand, in Example 3, it was confirmed that the void ratio after sintering was small but as low as 9.8%. Examples 1, 2, 4,
With respect to Nos. 5 and 6, it was confirmed that the void ratio after firing was significantly lower than that of Comparative Example 1 and Test Examples 1 and 2. Among them, particularly good results were obtained in Example 6, and then good results were obtained in Examples 1 and 4.

In Comparative Example 1, Test Examples 1 and 2, the value of the surface roughness Ra was 1.0 μm or more, whereas in each of Examples 1 to 6, the value was lower than 1.0 μm. Was confirmed. Above all, good results were obtained in Example 6, and then good results were obtained in Examples 1, 2, and 3.

When the wiring resistance 10 of each of Examples 1 to 6 was separately observed, no swelling or the like was observed, and no particular decrease in the adhesion was observed. In Comparative Example 1, the value of the tensile strength was 3.5 kgf / 2.
It was an extremely low value of about mm □. In contrast,
In each of Examples 1 to 6, it was confirmed that a value almost twice or more that of the comparative example was obtained. Above all, good results were obtained in Example 2, and then good results were obtained in Examples 1 and 6. From the above results, it is considered that the flaky particles have an effect of improving the tensile strength.

[Preparation of Sample (When Noble Metal Particles Have Different Metal Kinds)] In Example 7, 45 parts by weight of silicon nitride powder (average particle diameter 1.1 μm) was mixed with Y ₂ O ₃ (average particle diameter 0.4 μm).
m) 20 parts by weight, 15 parts by weight of Al ₂ O ₃ (average particle diameter 0.5 μm), 20 parts by weight of SiO ₂ (average particle diameter 0.5 μm), an acrylic resin binder as an organic vehicle (manufactured by Mitsui Chemicals, Inc. Trade name: SA-545, acid value 1.0) 8 parts by weight were mixed. A kneaded product obtained by uniformly kneading the mixture thus obtained was put into a press mold and pressed to produce a plate-shaped formed body.

Next, after drilling and drying,
The molded body was degreased at 350 ° C. for 4 hours in a nitrogen atmosphere to thermally decompose the binder. Further, the degreased compact was fired by hot press at 1600 ° C. for 3 hours to obtain a silicon nitride substrate as the ceramic substrate 9. The pressure of the hot press was set at 150 kg / cm ² .

Then, after the substrate was cut out and the surface was ground, a paste coating step was performed. Here, a noble metal paste P1 having the following composition was used,
Sample 1 was prepared by setting the thickness at the time of application to about 25 μm.
0 was produced.

Noble metal particles: 56.6 parts by weight of silver particles G2, 10.3 parts by weight of palladium particles G1, oxide glass component: 1.0 parts by weight of SiO ₂ , B ₂ O
₃ 2.5 parts by weight, ZnO is 5.6 parts by weight, PbO 0.6 parts by weight, the RuO ₂ 2.1 parts by weight, Resin binder: 3.4% by weight, butyl carbitol as Solvent : 17.9% by weight.

Here, the “silver particles G2” are scaly silver particles having an average particle size of 3.94 μm (ie, the B particles).
Was used. As the “palladium particles G1”, spherical palladium particles (Pd-215 manufactured by Shoei Chemical Industry Co., Ltd.) having an average particle size of 5.12 μm were used.

Then, by heating the applied noble metal paste P1 at a temperature of about 750 ° C. for a predetermined time, the wiring resistance 10 and the pad 10a were baked, and the hot plate 3 of Example 7 was completed. The weight ratio of the two particles in the conductor pattern 10, that is, the ratio of the silver particles G2 to the palladium particles G1 was 55:15. [Comparative Test and Results] The same comparative test as that performed for Examples 1 to 6 and the like was performed on the obtained sample of Example 7. As a result, the void ratio after firing was 7.
8%, surface roughness Ra of 0.7 μm, tensile strength of 10.
It was 8 kgf / 2 mm □.

Therefore, according to the embodiment of the present embodiment, the following effects can be obtained. (1) The wiring resistances 10 and the pads 10a of the above-mentioned Examples 1 to 5, 7 are composed of spherical noble metal particles G1 and scale-like noble metal particles G2. Further, the wiring resistance 10 and the pad 10a according to the sixth embodiment are composed of only the flaky noble metal particles G2.

Therefore, it is considered that the noble metal particles G2 (or G1 and G2) are more likely to be densely packed after baking, as compared with the one including only the spherical noble metal particles G1 (for example, Comparative Example 1). . Therefore, the void ratio in the wiring resistance 10 and the like decreases, and the adhesion to the ceramic substrate 9 increases. On the other hand, the noble metal particles G2 (or G
1 and G2) are point contacts. Therefore, the wiring resistance 1
A remarkable decrease in resistance value at 0 or the like is prevented, and the function as a resistor is not impaired.

(2) Further, if the scale-like silver particles G2 are made of two kinds having different average particle sizes as in Examples 1, 2, 4, and 5, wirings having a tensile strength of 10 kgf / 2 mm □ or more can be obtained. The resistor 10 can be obtained.

(3) As in Example 6, if the scale-like silver particles G2 are made of two kinds having different average particle sizes and the spherical noble metal particles G1 are not included at all, the void ratio is extremely low. Value, and the adhesion can be remarkably improved.

(4) In each of Examples 1 to 7 of this embodiment,
Since an aluminum nitride substrate or a silicon nitride substrate is used as the ceramic substrate 9, the hot plate 3 having excellent heat resistance and thermal conductivity can be realized.

Note that the embodiment of the present invention may be modified as follows. In place of a nitride ceramic substrate such as an aluminum nitride substrate or a silicon nitride substrate used in the embodiment, for example, an oxide ceramic substrate such as an alumina substrate or a carbide ceramic substrate such as a silicon carbide substrate is used. You can also.

The ceramic substrate 9 is not limited to one manufactured by the press molding method, but may be one manufactured by a sheet molding method using a doctor blade device, for example. When the sheet molding method is adopted,
For example, since the wiring resistors 10 can be arranged between the stacked sheets, the hot plate 3 for high temperature can be realized relatively easily.

The conductor pattern is not limited to the wiring resistor 10 and the pad 10a exemplified in the embodiment, but may be other conductor patterns, that is, a conductor pattern which is not a heating resistor.

The method of applying the noble metal paste P1 to the ceramic substrate 9 includes not only the screen printing method but also other methods such as a stamping method.

[0083]

As described above, according to the present invention, the void ratio can be reduced by the substantially scaly noble metal particles, so that the adhesion of the conductor pattern can be improved. Further, the surface roughness Ra can be set to 1 μm or less, and the variation in the resistance value of the conductor pattern can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a hot plate unit according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the hot plate unit of the embodiment.

FIG. 3 is a conceptual diagram showing a state of noble metal particles in a conductor pattern (when the noble metal particles are only one kind of scale-like one).

FIG. 4 is a conceptual diagram showing the appearance of precious metal particles in a conductor pattern (in the case of two types of precious metal particles, scaly ones and spherical ones).

FIG. 5 (a) is a spherical noble metal particle (ie, A particle),
(B) is a scale-like noble metal particle (namely, B particle), (c) is a scale-like noble metal particle (namely, C particle), and (d) is an enlarged photograph of a scale-like noble metal particle (namely, D particle) by SEM.

[Explanation of symbols]

Reference numeral 3 denotes a hot plate, 9 denotes a ceramic substrate, P1 denotes a conductor paste (noble metal paste), 10 denotes a wiring resistance as a conductor pattern, 10a denotes a pad that is a part of the conductor pattern, G1 denotes a substantially spherical noble metal particle, and G2 denotes a substantial portion. Scale-like noble metal particles.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05B 3/20 328 H01L 21/30 567

Claims (14)

[Claims] 1. A hot plate comprising a ceramic substrate provided with a conductive pattern, wherein the conductive pattern is made of substantially scaly noble metal particles. 2. An average particle size of said substantially scaly noble metal particles is 6.
2. The hot plate according to claim 1, wherein the diameter is not more than μm. 3. The hot plate according to claim 1, wherein the substantially scaly noble metal particles are at least one selected from gold particles, silver particles, platinum particles and palladium particles. . 4. The hot plate according to claim 1, wherein an aspect ratio between a major axis and a minor axis of the substantially scaly noble metal particles is 1.5 or more. 5. A hot plate comprising a ceramic substrate provided with a conductor pattern, wherein the conductor pattern comprises substantially granular noble metal particles and substantially scaly noble metal particles. 6. An average particle diameter of said substantially granular noble metal particles is 3 μm.
6. The hot plate according to claim 5, wherein the average particle diameter of the substantially scaly noble metal particles is 6 μm or less. 7. The hot plate according to claim 5, wherein said substantially scaly noble metal particles are composed of two or more kinds having different average particle diameters. 8. In the conductor pattern, the substantially scaly noble metal particles are five to two times as large as the substantially granular noble metal particles.
The hot plate according to any one of claims 5 to 7, wherein the hot plate is included five times. 9. A conductive paste comprising substantially scaly noble metal particles, an oxide and an organic vehicle. 10. A conductive paste comprising substantially granular noble metal particles, substantially scaly noble metal particles, an oxide, and an organic vehicle. 11. The substantially scaly noble metal particles are at least one selected from gold particles, silver particles, platinum particles and palladium particles.
Or the conductive paste according to 10. 12. The conductive paste according to claim 9, wherein the substantially scaly noble metal particles are made of two or more kinds having different average particle diameters. 13. The conductive paste according to claim 10, wherein the substantially scaly noble metal particles are contained 5 to 25 times the substantially granular noble metal particles. 14. An average particle diameter of said substantially granular noble metal particles is 3
2 .mu.m or less, and the average particle diameter of the substantially scaly noble metal particles is 6 .mu.m or less.
4. The conductive paste according to any one of 3.