KR20110024092A - Rapid thermal processing apparatus for solar cell - Google Patents

Abstract

PURPOSE: A thermal processing apparatus for a solar cell is provided to improve process efficiency by performing a process while transferring a solar cell panel with an in-line shape. CONSTITUTION: A chamber unit(10) is arranged in one direction and is divided into a plurality of sections with different temperature ranges. A plurality of rollers(21) are separated along the longitudinal direction of the chamber unit. The roller is rotatably combined with the inner side of the chamber and transfers the solar cell panel. The driver drives the plurality of rollers. A plurality of contact rings which is supported and contacted with the solar cell panel are fitted to and combined with each roller.

Description

Rapid thermal processing apparatus for solar cell

The present invention relates to a silicon solar cell manufacturing apparatus, and more particularly, in the process of forming an electrode using a metal paste on a silicon wafer, a solar cell heat treatment apparatus for performing a binder removal process, a firing process and a cooling process It is about.

In order to cope with the depletion of fossil resources and environmental pollution, recently, as interest in clean energy such as solar power is increasing, research and development on solar cells that convert solar energy into electric energy is gaining vitality.

A solar cell refers to a device that generates an electromotive force by generating a voltage difference as a minority carrier excited by sunlight diffuses across a PN junction inside a semiconductor in which a PN junction is formed. To manufacture such a solar cell, a P-type or N-type semiconductor layer, a process of depositing an antireflection film on a substrate (collectively referred to as a silicon wafer or a glass substrate), a process of forming an electrode to move electrons, and an energy conversion efficiency In order to form a pattern necessary to improve the process, a process such as etching the deposited thin film must be performed.

In the process of forming the electrode of the above-described process, the upper and lower wirings are made of metal paste using screen printing for reasons of high productivity and economy. In more detail, after the metal paste is patterned on the wafer by screen printing, a binder removal process for removing organic matter and glass binder contained in the paste, a baking process for firing the metal components in the paste, and cooling the wafer It will go through a cooling process. The debinder process takes place at relatively low temperatures, but the firing process has to be processed rapidly at high temperatures.

The reasons for the rapid heat treatment during the firing process are as follows. That is, in manufacturing a bulk solar cell, a thin emitter junction is made by doping an N-type dopant on a P-type wafer, and the junction of the emitter and the base (P / N junction) ) Shows the characteristics of the solar cell. It is preferable that the emitter be formed thinly, since the efficiency of the solar cell can be increased when the depletion region formed during bonding is formed close to the front surface which receives a lot of light. Specifically, the generation of carriers that allow electricity to flow in the solar cell due to the high intensity of light near the surface increases, and thus the generated carriers are not extinguished by recombination in the depletion region, resulting in high battery efficiency.

However, the P / N junction that is already formed may appear to deepen as the emitter dopant is further diffused into the base in the heat treatment process for forming the metal electrode, so to prevent this, rapid heat treatment may be performed to minimize dopant diffusion. It is necessary.

Conventionally, the debinder process, the sintering process and the cooling process were performed while changing the temperature in a single chamber. As the debinder process proceeds to an excessively high temperature, the adhesion between the metal and the silicon interface is deteriorated, In addition to the technical problems such as difficulty in measuring the temperature due to the fume, there was also a problem that the productivity is reduced as all processes are performed in a single chamber.

In particular, in order to solve the problem of reduced productivity, the process was performed while continuously moving the belt while the solar cell wafer was placed on a mesh belt made of a metal material. By heating, the aluminum layer on the back side of the wafer that is in contact with the belt leaves mesh shape marks, which causes the back surface field to be formed on the back side of the wafer not to be uniformly formed.

In addition, although other equipments have been developed to ensure productivity and efficiency, these equipments also expose problems such as problems in temperature control or equipment complexity.

An object of the present invention is to provide a solar cell heat treatment apparatus having an improved structure such that a solar cell wafer can be heat-treated quickly and minimize contact with the transfer means during the wafer transfer process. There is this.

The solar cell heat treatment apparatus according to the present invention for achieving the above object is, for forming an electrode on a solar cell substrate, the chamber portion is disposed long in one direction, divided into a plurality of sections maintained in different temperature ranges, It is disposed spaced apart from each other along the longitudinal direction of the chamber portion rotatably coupled to the inside of the chamber portion, comprising a plurality of rollers for transporting the solar cell substrate and a driving means for driving the plurality of rollers. There is this.

According to the present invention, it is preferable that a plurality of contact rings are inserted into and coupled to each of the roller substrates in contact with each other.

In addition, according to the present invention, in order to minimize the contact area between the contact ring and the solar cell substrate, it is preferable that the thickness decreases toward the outside along the radial direction from the center of the contact ring.

In addition, according to the present invention, each of the rollers is fitted into the chamber so that one end thereof protrudes out of the chamber, the driving means is a plurality of gears are respectively fitted and coupled to a plurality of rollers protruding outward of the chamber portion, It is preferable to have a motor coupled to any one of the plurality of gears to rotate the gear, and a chain that is coupled to surround the plurality of gears so as to transmit the rotational force of the motor to the entire gears.

In addition, according to the present invention, the chamber part comprises a plurality of chambers and a connecting pipe connecting the plurality of chambers, wherein the plurality of chambers is preferably independently temperature controlled by a lamp installed in each chamber.

The solar cell heat treatment apparatus according to the present invention has an advantage that the process efficiency is improved by performing the process while transferring the solar cell substrate in an in-line form.

In addition, the solar cell heat treatment apparatus according to the present invention minimizes the area of the solar cell substrate in contact with the in-line transfer means during the series of heat treatment processes for forming the electrode on the back of the substrate by contact with the transfer means in the prior art This has the advantage that the problem of leaving marks is solved.

Hereinafter, with reference to the accompanying drawings, a solar cell heat treatment apparatus according to a preferred embodiment of the present invention will be described in more detail.

1 is a schematic perspective view of a solar cell heat treatment apparatus according to a preferred embodiment of the present invention, Figure 2 is a schematic partial cutaway perspective view of the main part of the solar cell heat treatment apparatus shown in Figure 1, Figure 3 is a III of FIG. Fig. 3 is a schematic cross-sectional view.

1 to 3, the solar cell thermal treatment apparatus 100 according to an exemplary embodiment of the present invention includes a chamber unit 10, a plurality of rollers 22, a lamp heater 30, and a plurality of rollers 22. It consists of a driving means for driving.

The chamber unit 10 has a space in which a process is performed to be heat-treated with respect to the solar cell substrate s. The chamber part 10 is formed to be elongated in one direction so that the heat treatment is performed while the solar cell substrate s progresses from one side to the other side.

The solar cell substrate s is introduced into the chamber part 10 while the metal paste is screen printed, and sequentially passes through a binder removal process, a firing process, and a cooling process, and these processes are performed at different temperature ranges. In the solar cell heat treatment apparatus 100 according to the present invention, the chamber part 10 is divided into a plurality of sections, and the partitioned spaces are maintained at different temperature ranges.

The method of partitioning the chamber portion 10 into a plurality of spaces may vary, but in the present embodiment, the plurality of chambers 11, 12, 13, and 14 and the connection pipe 15 connecting the chambers may be provided. The installation method is adopted. That is, the plurality of chambers 11 to 14 are arranged in a line, and the connecting pipe 15 is provided between them.

In each chamber 11 to 14, an inlet i through which the solar cell substrate s is introduced and an outlet o through which the processed substrate s is discharged are formed through. The connecting pipe 15 is interposed between the outlet o of the chamber located at the front end and the inlet i of the chamber located at the rear end on the traveling path of the solar cell substrate s. They are partitioned and connected together.

The temperature inside the chambers 11 to 14 should be kept different from each other, and the lamp heater 30 is installed at the upper portion of the chambers 11 to 13. The lamp heater 30 may be a non-contact halogen lamp for heating the solar cell substrate (s), the number of the lamp heater 30 is provided for each chamber may be different. The number of lamp heaters 30 is adjusted according to the temperature range set in each chamber.

The first chamber 11 and the second chamber 12 on the transfer path of the solar cell substrate are chambers for performing a binder removal process for removing organic matter in the metal paste printed on the solar cell substrate s. The chamber 13 is a chamber for performing a firing process of firing a metal paste, and the last chamber 14 is a process for cooling the solar cell substrate s that has been heated.

Although the process performance will be described later, the debinder process is performed at a relatively low temperature compared with the firing process, and thus, the first and second chambers 11 and 12 should be kept at a lower temperature than the third chamber 13, and the last chamber 14 needs to cool the heated substrate s so that the lamp heater 30 does not need to be installed.

On the other hand, in the debinder process, the organic material and glass generated by the heating evaporate and rise, and the vaporized organic material is easily discharged by installing a hood (not shown) in the first chamber 11 and the second chamber 12. It is desirable to be able to.

Meanwhile, in the present invention, a roller 21 for transferring the solar cell substrate s is provided in the chamber part 10 including the plurality of chambers 11 to 14 and the connection pipe 15. In addition, a plurality of rollers 21 are disposed to be continuously spaced apart from each other along the longitudinal direction of the chamber portion 10.

Bearings 23 are respectively provided on both sides of the inner walls of the chambers 11 to 14, and both ends of the rollers 21 are fitted to the bearings 23 to be rotatably supported with respect to the chambers 11 to 14. In addition, one end of the roller 21 extends to the outside of the chamber (11 ~ 14) is arranged to protrude.

The drive means for driving these rollers 21 includes a plurality of gears 24, a chain 25 and a motor 26. That is, one end of each roller 21 protruding to the outside of the chamber portion 10 is fitted with the outer gear 24, the gear is formed on the outer peripheral surface is coupled. One of the outer gears 24 is coupled to the motor 26 to apply a rotational force. The motor 26 is installed one for each chamber (11-14).

In addition, the chain 25 is provided to transmit the rotational force of the motor 26 to the other outer gear 24 of each chamber (11-14). Chain 25 is coupled to surround the outer gear 24 for each chamber (11-14). The inner side of the chain 25 is formed with a concave-convex portion to be engaged with the gears of the outer gear 24 so that when the chain 25 is circularly rotated, the outer gear 24 is also rotated together.

On the other hand, the contact ring 22 is fitted to the roller 21 is coupled. The contact ring 22 is in contact with the bottom surface of the solar cell substrate s to support the substrate s. As described in the problem of the prior art, in the conventional heat treatment apparatus that the substrate is transported by the belt in the form of mesh, the mesh marks remain on the lower surface of the substrate in a high temperature environment to reduce the efficiency of the solar cell. The contact ring 22 is used so that the bottom surface of the battery substrate s does not come into contact with the roller 21 as a whole and only the minimum area is in contact with the substrate s.

As shown in FIG. 3, by inserting the contact ring 22 into the roller 21, the substrate s contacts only the contact ring 22 in a small area, thereby solving a conventional problem. In particular, the use of the contact ring 29 as shown in Figure 4 can maximize the above effects by minimizing the area that the substrate (s) is in contact during transfer. That is, the thickness of the contact ring 29 shown in FIG. 4 decreases from the center toward the outside along the radial direction, so that line contact with the solar cell substrate s can be almost made.

As such, the bottom surface of the solar cell substrate s is minimized or disappeared by contact with other members during a high temperature heat treatment process, thereby forming a uniform diffusion film on the bottom surface of the substrate.

On the other hand, the roller 21 and the contact ring 22 is used in a high temperature environment, and is made of a stainless material having high heat resistance.

Hereinafter, a heat treatment process using the solar cell heat treatment apparatus 100 having the above-described configuration will be described in detail.

The motors 26 of the solar cell heat treatment apparatus 100 are driven to rotate all the rollers 21 installed in the chamber part 10 in one direction. In this state, the binder removal process is started by introducing the solar cell substrate s screen-printed with the metal paste into the chamber part 10 through the inlet i of the first chamber 11.

The debinder process is completed by heating the solar cell substrate s in the first chamber 11 at approximately 200 to 500 ° C. for several seconds and in the second chamber 12 at approximately 600 ° C. for several seconds. . That is, while the solar cell substrate s is transferred to the first and second chambers 11 and 12 for several seconds along the plurality of rollers 21, the solar cell substrate s is heated to the above-described heating temperature. If the heating temperature is too low or the treatment time is too short at this time, the organic components are not completely removed, which is not preferable. On the other hand, if the heating temperature is too high or the treatment time is too long, it is not preferable because the glass binder moves to the metal surface, resulting in poor adhesion between the metal and silicon interface and increased contact resistance.

When the debinder process is completed, the solar cell substrate s is introduced into the third chamber 13 through the connection pipe 15 and enters the firing process. In the firing process, it is necessary to perform a high-speed heat treatment under stringent conditions due to the characteristics of the electrode manufacturing process of the silicon solar cell. The reason for the high-speed heat treatment is as described in the prior art. The firing process is carried out in a state in which the solar cell substrate is heated to approximately 600 ° C. in the second chamber, and the temperature is raised to almost 900 ° C. in the third chamber 13. The temperature increase process is carried out at a very rapid rate, approximately 50 to 150 ℃ / sec.

If the temperature increase rate is too slow, the duration at high temperature is long, and the P / N junction deepens into the base, so the efficiency of the solar cell is lowered.

It is preferable to perform the baking process in which baking of a metal component is performed for several tens of seconds at the said temperature. If the firing temperature is too low or the firing time is too short, the resistance of the electrode may be high due to incomplete firing; conversely, if the firing temperature is too high or the firing time is too long, the P / N junction deepens into the base to It is not preferable because the efficiency is lowered.

After the firing process, the substrate s is discharged from the third chamber 13 and flows back into the fourth chamber 14 through the connecting pipe 15, and in the fourth chamber 14, the solar cell substrate s Complete by cooling. Natural cooling of the solar cell substrate s immediately in the last chamber 14 after the firing step may minimize thermal stress and further increase the efficiency of the solar cell.

The entire process can be performed rapidly within approximately 1 minute, thereby improving process efficiency and heat treatment quality.

Although the halogen lamp was used to heat the solar cell substrate s so far, it may further include a lamp (ultraviolet lamp) using an ultraviolet wavelength band in addition to the halogen lamp as a heat source.

Although the contents of the present invention have been described above, those skilled in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

1 is a schematic perspective view of a solar cell heat treatment apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a schematic partial cutaway perspective view of a main part of the solar cell heat treatment apparatus shown in FIG. 1.

3 is a schematic cross-sectional view taken along line III-III of FIG. 1.

FIG. 4 is a schematic cross-sectional view of a solar cell heat treatment apparatus in which a contact ring illustrated in FIG. 3 and a contact ring having a different shape are combined.

<Explanation of symbols for the main parts of the drawings>

100 ... solar cell heat treatment device 10 ... chamber part

11,12,13,14 ... chamber 15 ... connector

21 ... roller 22 ... contact ring

24 ... gear 25 ... belt

26 ... motor 30 ... lamp heater

Claims (5)

As for forming an electrode on a solar cell substrate, A chamber unit disposed to extend in one direction and divided into a plurality of sections maintained at different temperature ranges; A plurality of rollers disposed to be spaced apart from each other along the longitudinal direction of the chamber and rotatably coupled to the inside of the chamber to transfer the solar cell substrate; And Solar cell heat treatment apparatus comprising a; driving means for driving the plurality of rollers. The method of claim 1, Each of the rollers is a solar cell heat treatment apparatus, characterized in that the plurality of contact rings are coupled to each other and supported by the solar cell substrate. The method of claim 2, The solar cell heat treatment apparatus, characterized in that the thickness decreases toward the outside in the radial direction from the center of the contact ring to minimize the contact area between the contact ring and the solar cell substrate. The method of claim 1, Each roller is fitted into the chamber so that one end thereof protrudes out of the chamber, The driving means may include a plurality of gears that are respectively fitted into and coupled to a plurality of rollers protruding outward from the chamber, a motor coupled to any one of the plurality of gears to rotate the gears, and the rotational force of the motor to the gears. Solar cell heat treatment apparatus comprising a chain coupled to surround the plurality of gears to be transmitted to the entire field. The method of claim 1, The chamber part includes a plurality of chambers and a connection pipe connecting the plurality of chambers, And the plurality of chambers are independently temperature controlled by lamps installed in each chamber.

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