JP2003090685A - Heat treatment furnace for functional film material formed on substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat treatment furnace for a functional film material formed on a substrate, which is capable of reducing an energy cost required for heat treatment and permitting quick temperature rise and temperature fall while requiring no trouble for maintenance. SOLUTION: The heat treatment furnace employed for the heat treatment of the functional film material formed on the substrate employs a walking beam as the transfer means of the substrate 1 in the furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment furnace used for heat treating a functional film material formed on a substrate such as an electrode paste formed on a polycrystalline silicon solar cell substrate.

[0002]

2. Description of the Related Art In manufacturing a polycrystalline silicon solar cell substrate, it is necessary to print an electrode paste on the substrate in a predetermined pattern and then heat-treat the electrode paste. Conventionally, this heat treatment uses a heat treatment furnace having a mesh belt conveyer as a transporting means, and a substrate is placed on the mesh belt, and an electric heater is used to continuously or intermittently move the inside of the furnace at 800 to 900 ° C. It is carried out in a process of heating to about a temperature and then cooling to room temperature.

[0003]

However, in a heat treatment furnace using a mesh belt conveyor as a conveyance means, the mesh belt having a remarkably large heat capacity with respect to the substrate must be heated at the same time as the substrate. There was a problem that the energy cost was high.

In addition, in heat treatment of an electrode paste formed on a polycrystalline silicon solar cell substrate, it has been found that rapid heating and cooling is advantageous in terms of product characteristics. It is ideal to heat from room temperature to a temperature of about 800 to 900 ° C within 1 minute and complete the entire heat treatment process including cooling in about 3 minutes. However, the performance of the current electric heater and mesh belt Considering the heat capacity, it is very difficult to realize such a rapid heat treatment.

Further, in the mesh belt conveyor, since the mesh belt itself gradually expands with the lapse of use time, there is a problem that maintenance for periodically correcting the expansion of the belt is required.

The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to reduce energy cost required for heat treatment, and to rapidly raise and lower the temperature for maintenance. Another object of the present invention is to provide a heat treatment furnace for a functional film material formed on a substrate that does not require any trouble.

[0007]

According to the present invention, there is provided a heat treatment furnace used for heat treating a functional film material formed on a substrate, wherein a walking beam is used as a means for transporting the substrate in the furnace. A heat treatment furnace (first invention) for a functional film material formed on a substrate is provided.

Further, according to the present invention, a heat treatment furnace used for heat-treating a functional film material formed on a substrate, characterized in that a roller is used as a means for transporting the substrate in the furnace. A heat treatment furnace (second invention) for a functional film material formed on a substrate is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the heat treatment furnace according to the first invention is characterized mainly in that a walking beam is used as a substrate transfer means in the furnace. The walking beam is used to convey products in the furnace.
The moving beam places the product, advances it to a predetermined position, lowers the product, and then returns to the original position to repeat the movement to move the product.

In a conventional substrate electrode paste heat treatment furnace using a conventional mesh belt conveyor as a conveying means, the mesh belt itself moves around the furnace as the substrate moves, and thus has a heat capacity as large as 20 to 30 times that of the substrate. Although it was necessary to always raise and lower the temperature of the mesh belt at the same time as the substrate, in the heat treatment furnace according to the first aspect of the invention, the walking beam, which is the conveying means, reciprocates back and forth within a narrow range. Since it stays at almost the same position inside, once the walking beam reaches the predetermined temperature,
After that, only the amount of heat required to maintain the temperature of the walking beam and the amount of heat required to bring the substrate itself to a predetermined temperature are required.

Therefore, the heat treatment furnace according to the first invention can significantly reduce the energy cost required for heat treatment of the functional film material such as the electrode paste formed on the substrate, as compared with the conventional heat treatment furnace, and the substrate It is possible to rapidly raise and lower the temperature.

FIG. 1 is a schematic diagram showing an embodiment of a transfer means (walking beam) in a heat treatment furnace according to the first invention. In this example, the walking beam is
It consists of a fixed beam 3 fixed in the furnace and a moving beam 5 that moves up and down and back and forth within a predetermined range. When the substrate 1 is stationary, the moving beam 5 is fixed as shown in FIG. The substrate 1 is further lowered and the substrate 1 is supported only by the fixed beam 3.

Then, when the substrate 1 is transferred, as shown in FIG.
As shown in (b), the moving beam 5 rises above the fixed beam 3 to receive the substrate 1 from the fixed beam 3, and the substrate 1 is placed and moved forward to a predetermined position. The moving beam 5 that has advanced to a predetermined position transfers the substrate 1 to the fixed beam 3 that is the moving destination while descending again, and moves backward to the original position to prepare for the next conveyance.

In the first invention, as shown in FIG. 1, it is preferable to provide support pins 7 and 9 on the walking beam (the fixed beam 3 and the movable beam 5) that come into contact with only a specific position of the substrate 1. Here, the specific position of the substrate 1 is, for example, a position in the vicinity of the outer periphery of the substrate 1 on which the electrode paste to be heat-treated is not formed, and the walking beam is brought into contact with the substrate only at such a position. The influence of the walking beam on the heat treatment of the substrate can be eliminated as much as possible.

As a material for the walking beam, it is preferable to use high-strength silicon carbide ceramics. In particular, Si-impregnated SiC obtained by firing a molded body whose main raw material is SiC powder while impregnating it with metallic Si is used. It is preferable. Further, as the material of the support pin, it is preferable to use a heat-resistant metal such as an iron-chromium-aluminum alloy or a nickel-chromium alloy in consideration of the furnace temperature and workability.

The heat treatment furnace according to the second invention is characterized mainly in that a roller is used as a means for transporting the substrate in the furnace. The rollers as the in-furnace conveying means are arranged in parallel so that the axial direction thereof is orthogonal to the conveying direction of the product, and the rollers are placed on the rollers by being rotated by a driving device connected to the rollers. Products are sequentially moved.

As described above, in the conventional substrate electrode paste heat treatment furnace using the conventional mesh belt conveyor as the transport means, it is necessary to constantly raise and lower the temperature of the mesh belt having a large heat capacity simultaneously with the substrate. In the heat treatment furnace according to the second aspect of the present invention, the roller, which is the conveying means, always rotates at the same position, and the roller itself does not move in the furnace together with the substrate, so once the roller reaches a predetermined temperature, Requires only the amount of heat required to maintain the temperature of the roller and the amount of heat required to bring the substrate itself to a predetermined temperature.

Therefore, similarly to the heat treatment furnace according to the first aspect of the present invention, the heat treatment furnace according to the second aspect of the present invention can heat the functional film material such as the electrode paste formed on the substrate as compared with the conventional heat treatment oven. The required energy cost can be significantly reduced, and the temperature of the substrate can be raised and lowered quickly.

FIG. 2 is a schematic view showing an embodiment of a conveying means (rollers) in the heat treatment furnace according to the second invention. As described above, the rollers 11 are arranged in parallel in the lower part of the furnace so that the axial direction thereof is orthogonal to the transport direction of the substrate 1, and are rotated by a driving device (not shown) connected to the rollers 11. As a result, the substrate 1 placed on the roller 11 is sequentially moved.

In the second invention, as shown in FIG. 2, the roller 11 is provided with the support portions 15 having a diameter larger than the diameter of the roller body 13 at predetermined intervals, and the roller 11 uses the support portions 15 to form a substrate. It is preferable to contact only one specific position. Here, the specific position of the substrate 1 is, as in the case of the first invention, for example, the substrate 1 on which a functional film material such as an electrode paste to be heat-treated is not formed.
It is a position in the vicinity of the outer periphery of the roller, and by making the roller contact the substrate only at such a position, the influence of the roller on the heat treatment of the substrate can be eliminated as much as possible.

Further, as shown in FIG. 2, a partition portion 17 having a diameter larger than the diameter of the support portion 15 is provided on the support portion 15, and adjacent substrates 1 supported by the support portion 15 are in contact with each other. This may be prevented. As the material of the roller, similar to the walking beam in the first invention, silicon carbide ceramics, particularly Si-impregnated S
It is preferable to use iC.

The heat treatment furnace of the present invention can be particularly preferably used as a heat treatment furnace for heat treating an electrode paste formed on a polycrystalline silicon solar cell substrate, but the use of the heat treatment furnace is not limited to this. Instead, it can be widely used for heat treatment of various functional film materials which are formed on a substrate by various means such as coating and printing and need to be heat-treated in order to exert a predetermined function.

[0023]

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Using a heat treatment furnace having a walking beam as a conveyance means (Example) and a heat treatment furnace having a conventional mesh belt conveyor as a conveyance means (Comparative Example) as shown in FIG. 1, a polycrystalline silicon solar cell substrate is used. From room temperature to about 85
The time required for raising the temperature to 0 ° C. and the time required for all the heat treatment steps required to cool the substrate after the temperature rise to room temperature again were examined. In addition, the heating means and cooling means in the furnace,
The same electric heater and water cooling jacket were used.

The results are shown in the graph of FIG. 3. In the heat treatment furnace of the comparative example, it took about 1 minute and a half to heat the substrate to about 850 ° C., and the whole heat treatment process including cooling was performed. It took more than 7 minutes. On the other hand, in the heat treatment furnace of the example, the substrate temperature reached 850 ° C. within 1 minute, and the entire heat treatment process including cooling was completed in an extremely short time of about 3 minutes.

[0026]

As described above, the heat treatment furnace for the functional film material formed on the substrate according to the present invention requires less energy for heat treatment than a conventional heat treatment furnace using a mesh belt conveyor as a transport means. The cost can be reduced significantly. Further, since it is possible to raise and lower the temperature quickly, it is possible to manufacture a substrate having more excellent product characteristics. Further, troublesome maintenance such as correction of expansion of the mesh belt becomes unnecessary.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a transfer means (walking beam) in a heat treatment furnace according to the first invention,
(A) shows the state when the substrate is stationary, and (b) shows the state when the substrate is transported.

FIG. 2 is a schematic view showing an embodiment of a conveying means (rollers) in the heat treatment furnace according to the second invention.

FIG. 3 is a graph showing the relationship between the temperature change of the substrate and the heat treatment time in the example.

[Explanation of symbols]

1 ... Substrate, 3 ... Fixed beam, 5 ... Moving beam, 7 ... Support pin, 9 ... Support pin, 11 ... Roller, 13 ... Roller body, 15 ... Support part, 17 ... Partition part.

Claims (6)

[Claims] 1. A heat treatment furnace used for heat-treating a functional film material formed on a substrate, characterized in that a walking beam is used as a means for conveying the substrate in the furnace. Heat treatment furnace for functional film materials. 2. The heat treatment furnace according to claim 1, wherein the heat treatment furnace is used for heat treating an electrode paste formed on a polycrystalline silicon solar cell substrate. 3. The heat treatment furnace according to claim 1, wherein support pins are provided on the walking beam so as to contact only a specific position of the substrate. 4. A heat treatment furnace used for heat-treating a functional film material formed on a substrate, characterized in that a roller is used as a means for conveying the substrate in the furnace. Heat treatment furnace for functional film materials. 5. The heat treatment furnace according to claim 4, wherein the heat treatment furnace is used for heat treating an electrode paste formed on a polycrystalline silicon solar cell substrate. 6. The support according to claim 4, wherein the rollers are provided with support portions having a diameter larger than the diameter of the roller body at predetermined intervals, and the rollers are brought into contact with a specific position of the substrate by the support portions. The heat treatment furnace described.