JPH03218981A - Sheet for roasting ceramics base plate - Google Patents

Abstract

PURPOSE:To obtain a sheet from which a smooth ceramics base plate is produced without adverse effect on ceramics based on an unevenness at is time roasting of the ceramics base plate by combining an alumina-based binder with alumina-based ceramics fiber and manufacturing the sheet. CONSTITUTION:This sheet is manufactured by combining an alumina-based binder with alumina-based ceramics fiber. The utilized alumina-based ceramics fiber is obtained by using Al2O3-SiO2-based ceramics as a starting raw material and fabricating it into fiber. Al2O3 content incorporated in this fiber is regulated to high blending of 80-95%. As the alumina-based binder, colloid liquid of alumina hydrate wherein water is used as a dispersion medium, namely alumina sol is applied. Ammonia is used for fixing of alumina sol and pH is regulated to 7-10. When pH is deviated form this range, fixing of alumina sol is not made good and necessary strength of the sheet is not obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a sheet for firing ceramic substrates as a separate sheet used in firing ceramic substrates used in the production of circuit boards for electronic devices.

[Prior Art] [Problem to be Solved by the Invention] Conventionally, circuit boards have been manufactured by placing unfired ceramic substrates made of alumina or the like on a ceramic base plate in multiple stages as necessary. A high-melting point metal oxide powder such as alumina powder is sprinkled in between by a machine or manually, and then the unfired substrate is fired to produce a substrate.

This method has poor workability, and the high melting point metal oxide is not uniformly dispersed, causing warpage and waviness in the manufactured substrate, as well as adhesion of the substrates to each other, resulting in high costs and other problems. was there.

Another method is glass fiber. Ceramic sheets made using rock wool, alumina silicate, etc. as basic materials have been used as sheets for firing ceramics, but in recent years, the firing temperature of ceramics has increased due to the development of new ceramic materials. There is a tendency for sheets using such fibers to reach temperatures of 1000°C.
When the substrate is fired in the above-mentioned high-temperature range, there are problems such as the sheet reacting with the substrate or the substrates being fused together, which adversely affects the firing of the substrate.

[Means to solve the problem]

The present invention was developed as a result of intensive studies in view of the above-mentioned circumstances, and is made by combining alumina-based ceramic ≦7 fibers and an alumina-based binder. The seat was adopted as follows.

The alumina ceramic fiber constituting the present invention is Al
Tos-Sift material is made into fibers as a starting material, for example, the product name is Denka Arsene (manufactured by Denki Kagaku Kogyo Co., Ltd.).
Those commercially available as . are applicable to the present invention. And its feature is that the A1 and 0 contained in the fibers are
, is in a high blend of 80 to 95%. In other words, normal alumina silicate fibers (ceramic fibers) are AlzO. The upper limit of the content is 55%, whereas the alumina ceramic fiber applied in the present invention uses a special fiberization technology called the precursor method, for example.
By turning the stock solution containing a spinning aid into fibers, AI
,0. The content is about 80 to 95%.

By using alumina-based ceramic fibers composed of A1 and 0, which have a high content, it is possible to significantly improve the heat resistance temperature compared to the glass fibers, rock wool, and alumina silicate fibers mentioned above.
The fibers do not deteriorate or shrink even at operating temperatures of °C.

On the other hand, the alumina-based binder constituting the present invention is a colloidal liquid of alumina hydrate using water as a dispersion medium, that is, an alumina sol. The alumina sol has a diameter of 5 mμ to 200
It is a milky white liquid in which polymerized particles of boehmite-based alumina hydrate with a colloid size of mμ are dispersed using anions in water as a stabilizer. What is available is used.

A wet papermaking method is used in carrying out the present invention. That is, alumina ceramic fibers are dispersed in water to form a slurry, and a binder, such as alumina sol, is added thereto in an amount of 5 to 60% by weight based on the alumina ceramic fibers to form paper. In this case, if the alumina sol is less than 5% by weight, the sheet produced will not have the desired strength, while if it exceeds 60% by weight, the yield of alumina sol will be poor.
It does not contribute to increasing the strength of the sheet.

Ammonia is used to fix the alumina sol, and the pH is 7.
Adjust so that it is ~10. If the pH is outside this range, the fixation of the alumina sol will not be successful and the required strength of the sheet will not be obtained.

The appropriate thickness of the sheet obtained is 0.05 to 2 m,
If it is less than 0.05 ws, the required strength of the sheet cannot be obtained after firing, and there is a possibility that the substrates will fuse together during firing, which is not preferable. Moreover, if the thickness of the sheet exceeds 2,000 yen, the sheet will simply become thicker than necessary, which will only increase the cost and will not produce any other advantageous effects.

Further, in cases where the strength of the sheet is insufficient with an inorganic binder alone, it is preferable to use an organic binder such as PVA, SWP, natural pulp, or synthetic pulp. However, the amount of organic binder added is 2 to the total amount of binder.
It is desirable that the amount is 0% by weight or less. If it exceeds 20% by weight, there is a possibility that it will have an adverse effect on the ceramic substrate during firing of the ceramic. However, if the effect is within an acceptable range, it is not disadvantageous to add it within that range, even if it exceeds 20% by weight.

The sheet for firing ceramic substrates of the present invention produced by the above method has a smooth surface, and when the sheet is fired, unevenness of the sheet does not have an adverse effect on the ceramics, and a smooth ceramic substrate can be obtained.

〔Example〕

The present invention will be specifically explained below using examples.

Example 1 40 g of alumina-based ceramic fiber (trade name: Denka Alkasen, manufactured by Denki Kagaku Kogyo Co., Ltd.) with an AhOi content of about 80% in 101 water, and the dry weight of an alumina-based binder (trade name: Alumina Sol, manufactured by Nissan Chemical Co., Ltd.) After adding an amount equivalent to 10 g and stirring well, adjust the pH with ammonia and sulfuric acid band, fix the binder, and then add a polyacrylamide-based flocculant (trade name: Sanfurosoku AH-200P, manufactured by Nissan Chemical Co., Ltd.). 2 liters of the raw material was placed in a TAPPI type hand paper machine and subjected to hand paper making to produce a sheet for firing ceramic substrates of the present invention.

Comparative Example 1 Alumina ceramic fiber in Example 1? Same as Example 1 except that the alumina silicate fiber (50% Al 03 content, trade name Ibiwool, manufactured by Ibiden) was replaced, and the alumina binder was replaced with a silica binder (trade name Snowtex, manufactured by Nissan Chemical Co., Ltd.). A ceramic substrate firing sheet was prepared for comparison.

Comparative Example 2 A comparative ceramic substrate for firing was prepared in the same manner as in Example 1, except that the alumina-based ceramic fiber in Example 1 was replaced with alumina silicate fiber (trade name: Ibiwool, manufactured by Ibiden Co., Ltd. with an Al 03 content of 50%). I created a sheet.

Comparative Example 3 A ceramic substrate firing sheet for comparison was prepared in the same manner as in Example 1 except that the alumina binder in Example 1 was replaced with a silica binder (trade name Snowtesox, manufactured by Nissan Chemical Co., Ltd.).

The sheet 1 for firing ceramic substrates obtained in Example 1 and Comparative Examples 1 to 3 above was heated to a thickness of 1 mm as shown in FIG.
．． 900-1 sandwiched between alumina unfired ceramic substrates 2 having a length of 5 m and an area of 50 tm x lOOtm.
As a result of firing at a temperature of 500T, the results shown in Table 1 were obtained. Note that 3 in FIG. 1 is a ceramic base plate.

Table 1 Note) As is clear from Table 1 above, sheets using alumina silicate fibers (Comparative Examples 1 to 3) have a relatively small shrinkage rate up to 1000°C, and even when used as separate sheets, they cannot be used as ceramic substrates. There was no effect on 12
It was found that when the temperature exceeds 00°C, the sheet begins to shrink, and at 1500°C, it shrinks by about 50% (area retention rate), which causes shrinkage and unevenness on the surface of the ceramic substrate.

However, the sheet made of the combination of Denka alkacene and alumina sol according to the present invention (Example 1) had no effect even when fired at 1500°C.

The binder is also silica-based (Comparative Examples 1 to 3)
It was found that when the temperature exceeds 1000°C, reaction and fusion with the substrate occur, making it impossible to use it as a separator.

Example 2 Alumina ceramic fiber with 80% alumina content (
(trade name: Denka Arsene, manufactured by Denki Kagaku Kogyo Co., Ltd.) and an alumina binder (alumina sol) are adjusted in water so that the dry weight ratio of the former is 80 parts and the latter is 20 parts, and the mixture is stirred and mixed using an agitator. . Ammonia water is added to this papermaking raw material so that the pH becomes 9.0, and the alumina sol is fixed thereon. Furthermore, a polyacrylamide-based flocculant (trade name Sunfloc AH-200P,
(manufactured by Nissan Chemical Co., Ltd.). This papermaking raw material is used to make paper width 200.
Paper is made using M's Ford Linear paper machine, and the basis weight is 15.
A sheet for firing a ceramic substrate of the present invention having a weight of 0 g/rrl and a thickness of 200 μm was obtained.

As shown in FIG. 2, this sheet 4 is sent out from the reel in the direction of the arrow and passed through a continuous firing furnace 6 in an oxidizing atmosphere containing a heater 5, to remove the unfired ceramic sheet for substrates inside. After firing, the test was carried out by winding it up on a reel.

At that time, the ceramic substrate firing sheet 4 of the present invention was utilized to serve as a support for the unfired ceramic substrate 7 in an attempt to implement the present invention.

Specifically, the continuous firing furnace 6 has a length of 1 m and a width of 15 cm.
No. 11 apparatus was used, and the firing conditions were such that the temperature was 1200° C. in an oxidizing atmosphere, the temperature was moved at a rate of 5 dl per minute, and the firing took 20 minutes.

During firing, unfired ceramic substrates 7 of alumina measuring 50×50 mm were placed on the ceramic substrate firing sheet 1 of the present invention running on a large number of rolls 8 at equal intervals. As a result, there is no fusion to the substrate, good peelability, and no cracks or scratches on the substrate, and there are no practical problems when using such a continuous firing furnace. There was no. [Effects of the Invention] According to the present invention, when substrates such as alumina are stacked in multiple stages and fired, firing up to 1500°C is possible, and furthermore, when the sheet for firing ceramic substrates of the present invention is in contact with the smooth surface, Because it is fired, there are no cracks or scratches on the substrate, unlike when using bed powder.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing a state in which a substrate is fired using the ceramic substrate firing sheet of the present invention. 1: Ceramics substrate firing sheet 2: Unfired ceramics substrate 3: Ceramics base plate 4: Ceramics substrate firing sheet 5: Heater 6: Continuous firing furnace 7: Unfired ceramics substrate 8: Roll

Claims (1)

[Scope of Claims] 1) A sheet for firing a ceramic substrate, characterized in that it is formed by combining alumina ceramic fibers and an alumina binder. 2) The ceramic according to claim 1, which also contains an organic binder. Board firing sheet