JPH03217792A - How to clean inside the furnace - Google Patents

Abstract

PURPOSE:To clean the inside of a furnace so as to cope easily with a case, in which the kind of a calcining furnace or the kind of calcined products is changed, by a method wherein a sheet, obtained by kneading the fine powder of glass with resin binder, is adhered to the surface of a substrate and is burnt in the furnace to remove foreign materials by adhering them to the surface of the softened sheet. CONSTITUTION:A sheet, obtained by kneading the fine powder of glass with resin binder, is cut in accordance with the size of a substrate to be calcined in a calcining furnace and is adhered to the surface of the substrate. When the resin binder in the sheet is water soluble, an adhesive agent for this purpose, which is easily soluble into a organic solvent, is employed as the adhesive agent but when the resin binder is easily soluble into organic solvent, water soluble adhesive agent is employed for the adhesive agent of this purpose. When the sheet is adhered to the substrate in the shape of dots or reticulated shape and the substrate is thrown into a furnace to burn it in such a manner, the fine powder of glass in the sheet is molten and a molten glass layer is formed on the surface of the substrate whereby foreign materials in the atmosphere in the furnace are adhered to the substrate and are removed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is used to clean the atmosphere inside the furnace before firing a circuit board, etc. in a firing furnace such as a single furnace or a tunnel furnace. This relates to a method of cleaning the inside of a furnace.

(Prior Art) When firing a circuit-forming board or the like, even if a small amount of foreign matter such as fine metal powder present in the atmosphere in the furnace adheres to the surface of the product, it may become a defective product. To this end, efforts have been made to make the firing furnace a Masoflu furnace, which does not generate foreign matter, and to make the belt made of ceramics, which does not generate foreign matter, but these efforts have not produced sufficient results. Therefore, the inventors of the present invention have previously developed a method for cleaning the inside of a furnace in which a cleaning plate made of glass coated on a ceramic substrate is flowed into the furnace in advance to adsorb foreign matter inside the furnace, and this method has been published in Japanese Patent Application No. 63-233343. proposed as. However, for this type of purification plate, it is preferable to use a ceramic substrate of the same size as the product to be actually fired in the furnace in order not to affect the firing conditions. It was necessary to prepare a cleansing plate, which was extremely troublesome.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and easily adapts to changes in the type of firing furnace and the type of fired products. This was completed to provide a method for cleaning the inside of a furnace. (Means for solving the problem) The above problem is solved by adhering a sheet made by kneading fine glass powder and a resin binder to the surface of a substrate, and baking it in a furnace so that foreign particles in the furnace can be detected on the surface of the softened sheet. This can be achieved by a method of cleaning the inside of the furnace, which is characterized by depositing and removing.

As described above, in the present invention, instead of the conventional purifying plate coated with glass, a sheet made by kneading fine glass powder and a resin binder is used, which is adhered to the surface of the substrate in dots or grids. . The type of glass is not particularly limited, but it needs to be softened at a temperature that is, for example, 100 to 200° C. lower than the firing temperature, so that foreign matter in the atmosphere in the furnace can adhere to it. The resin binder is used to form the entire sheet into a sheet, and can be made of water-soluble resins such as polyvinyl alcohol, carboxymethylcellulose, and methylcellulose, and organic resins such as polyvinyl butyral, styrene resin emulsion, acrylic resin emulsion, and butadiene resin emulsion. A readily solvent soluble resin is used. In addition, a small amount of plasticizer such as diethylene glycol may be added.

The mixing ratio of fine glass powder in the sheet is 20 to 90
The weight percentage is appropriate. This is because if the mixing ratio of glass is less than 20%, a sufficient foreign matter adhesion effect cannot be obtained, whereas if it exceeds 90%, there is a relative shortage of resin binder, making it difficult to form a sheet. Also, the thickness of the entire sheet is 50 to 40
Approximately 0 μm is preferable.

In the present invention, the above-mentioned sheet is cut in the firing furnace to match the dimensions of the substrate to be actually fired, and then adhered to the surface of the sheet.The adhesive used for this purpose is the resin binder in the sheet. If the resin binder in the sheet is water-soluble, use an adhesive that is easily soluble in organic solvents, and if the resin binder in the sheet is easily soluble in organic solvents, use a water-soluble adhesive. This is to prevent the sheet from being melted by the adhesive.

Furthermore, in the present invention, it is preferable that the entire surface of the sheet is not bonded to the substrate, but rather that several points are bonded in dots or a mesh pattern. This is because by providing a gap between the sheet and the substrate, the gas generated by thermal decomposition of the adhesive during firing can escape from the bottom surface of the sheet, and when the entire surface is bonded, the gas bubbles inside the sheet and becomes uniform. There is a risk that a suitable molten glass layer may not be formed. Also, if there is no adhesion at all, the sheet will be extremely thin and will move off the substrate. If the sheet is adhered to the surface of the substrate in dots or grids in this way and is placed in a furnace prior to firing,
The fine glass powder in the sheet is melted to form a molten glass layer on the surface of the substrate, and foreign matter in the atmosphere in the furnace adheres to this layer and is removed.

In the present invention, it is only necessary to cut the sheet according to the substrate to be fired, so there is an advantage that the present invention can be easily applied to the case of firing a substrate of any size as long as the sheet is prepared.

Next, examples of the present invention will be shown.

(Example) Sin2 50%, Altos 6%, Ca0 9%
, BaO 20%, κ, 03%, B! OS 5%, M
It has a composition of g0 5%, Zn0 1%, SrO 1%, and has a thermal expansion coefficient of 6.7X at 40 to 400°C.
A glass of IO-'/''C was produced and made into a fine powder of 300 mesh under.The fine powder of this glass 6
5 parts and 34 parts of polyvinyl alcohol, which is a water-soluble resin binder, are kneaded together with 1 part of diethylene glycol, which is a plasticizer, and the resulting mixture has a thickness of 120 μm and a basis weight of 190 g/m.
” as a sheet.

Cut this sheet into a size of 75m x 270M,
It was adhered at 4 points to the surface of 10 alumina circuit forming boards measuring 5 cm x 250 cm x 0.8 m'. The adhesive used was an acrylic adhesive that had no risk of melting polyvinyl alcohol, and this fixed the sheet to the surface.
Two circuit-formed substrates were obtained.

When these circuit-forming substrates were poured into a tunnel furnace with a firing temperature set at 900°C for 30 minutes, the sheet melted onto the circuit-forming substrate to form a molten glass layer with a thickness of about 70 μm, and the sheet was released from the furnace. When I observed the surface after
Foreign matter was found on all of the 0 substrates. The size of foreign particles is 20 to 100 μm, with an average of 2 particles per substrate.
At most, six foreign objects were attached.

Furthermore, when ordinary circuit-forming boards were fired following these circuit-forming boards, the defective rate due to foreign matter adhesion was about 6%, which was 175, compared to about 30% in the past. was able to reduce the rate. In this way, according to the present invention, the product fired in the firing furnace can be used as it is to remove foreign matter, so regardless of the type of firing furnace or the type of fired product, the inside of the furnace can be easily cleaned. It can be performed.

In addition, in the example, the substrate with the sheet adhered was placed on top of other substrates and flowed into the furnace, but the method is not necessarily limited to this method, and various methods may be used depending on the type of firing furnace and the product. Application is possible.

(Effects of the Invention) As explained above, the present invention makes it possible to easily remove foreign substances from the atmosphere in the furnace by simply using the product to be fired and attaching a sheet to the surface of the product. It is possible to perform reliable cleaning, and the sheets can be glued on the spot depending on the type of firing furnace and the type of fired product, and there is no need to create multiple types of cleaning plates as in the past. There are advantages.

Therefore, the present invention greatly contributes to the development of industry as a furnace cleaning method that eliminates the problems of the conventional method.

Claims (1)

[Claims] A furnace characterized in that a sheet made by kneading fine glass powder and a resin binder is adhered to the surface of a substrate, and foreign matter in the furnace is attached to the surface of the softened sheet by firing in a furnace and removed. Cleaning method.