JP2549187B2 - Ceramic substrate firing method - Google Patents

Description

The present invention relates to a method for firing a ceramic substrate.

[Conventional technology]

2. Description of the Related Art Conventionally, when firing a ceramic substrate, for example, as shown in FIG. 2, a laminated unfired ceramic substrate 1 with a back surface 1a thereof facing down is made of a sintered body mainly composed of alumina, for example. Placed on the tool 2, covered with a cover 3 made of, for example, a sintered body containing alumina as a main component, and then inserted into a firing furnace 4 filled with an inert gas such as nitrogen. The procedure is to heat the heater 5 arranged in the above. The heating is, for example, the third
As shown in the figure, after heating the ceramic substrate 1 for about 5 hours at a relatively low temperature of about 400 ° C. for the purpose of scattering the organic binder from the ceramic substrate 1, for example, about 1000 ° C. for the purpose of sintering the ceramic. The ceramic substrate 1 is heated at a relatively high temperature of about 3 hours for about 3 hours.

Further, as disclosed in, for example, Japanese Patent Application Laid-Open No. 3-275571, the firing process of the green sheets (ceramic substrates) stacked in multiple stages is divided into two steps, and after the first firing process is completed, the green sheets are stacked in the above multiple stages. There is also proposed a multi-stage firing method of a green sheet in which the obtained green sheet is turned upside down and then the turned green sheet is fired a second time.

The first firing step of this conventional method is performed to remove the binder contained in the unfired ceramic substrate.
The firing process is mainly performed for sintering the green sheet. Then, by turning the green sheet upside down between the first firing step and the second firing step,
A uniform firing heat is applied to each green sheet as a whole of the firing and the second firing, and the warpage caused by the first firing step is
It is eliminated by the warpage caused by the firing process.

In this method, the first firing furnace for performing the first firing step and the second firing furnace for performing the second firing step are firing furnaces having the same configuration, and the temperature distribution inside the furnace is almost the same, so the first firing The process and the second baking process are almost the same baking process, and a similar flat heat treatment is repeated by sandwiching the green sheets stacked in multiple stages upside down to obtain a flat substrate without warpage. That is, the green sheet placed in the first firing furnace is heated to the in-furnace temperature with a constant temperature gradient similarly to the green sheet placed in the second firing furnace, and subsequently, is heated to the in-furnace temperature for a predetermined time. By being held and taken out from the first baking furnace, it is cooled with the same temperature gradient as that taken out from the second baking furnace.

[Problems to be Solved by the Invention]

By the way, in the conventional method for firing a ceramic substrate, the fired ceramic substrate is relatively warped. For example, 360mm square size and 15mm (before firing)
When firing the ceramic substrate 1 having a thickness of about 0.
A warp of about 9 mm occurs.

The reason why the ceramic substrate 1 is warped is that heat is transferred to the back surface 1a of the ceramic substrate 1 from the jig 2 heated by the atmosphere, while heat is transferred from the atmosphere to the front surface 1b of the ceramic substrate 1. It is considered that the conduction of heat causes a difference in the temperature history between the front surface side and the back surface 1a side of the ceramic substrate 1, resulting in a difference in the degree of sintering between the front and back surfaces.

The multi-stage firing method for green sheets disclosed in the above-mentioned Japanese Patent Laid-Open No. 3-275571 is effective in reducing the warpage of the ceramic substrate. However, in this method, since it is determined by the specific heat of the green sheet having a temperature gradient that reaches the temperature in the furnace after the green sheet is put in the furnace and the temperature in the furnace, the green sheet is heated in a relatively short time in the first firing step. Vitrification starts, and a part of the binder is confined in the vitrified green sheet to cause blow holes.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a method for firing a ceramic substrate, which can reduce the warpage of the ceramic substrate due to firing without generating blowholes.

[Means for solving the problem]

For example, as shown in FIG. 1, the present invention includes a step of heating an unfired ceramic substrate for a predetermined time to scatter the binder, and a step of sintering the ceramic substrate after the step of scattering the organic component. It is characterized by comprising a sintering process and a second process in which the ceramic substrate after the first sintering process is turned upside down and then fired.

[Action]

In the present invention, since the ceramic substrate 1 is turned upside down in the process of sintering the ceramic substrate 1 after scattering the organic components of the ceramic substrate 1, the ceramic substrate 1
Both sides of the ceramic substrate 1 will experience a period of heating while being in contact with the jig and a period of being heated while being in contact with the atmosphere, the difference in temperature history will be small, and both front and back surfaces of the ceramic substrate 1 will be sintered. The difference in degree becomes small.

〔Example〕

Hereinafter, a method of firing a ceramic substrate according to an embodiment of the present invention will be described with reference to the drawings.

The method of firing the ceramic substrate is the same as the conventional one except for the heating temperature profile.

That is, as shown in FIG. 2, an unfired ceramic substrate 1 is placed with a back surface 1a facing down on a jig 2 made of a sintered body containing alumina as a main component, and alumina is a main component. After being covered with a cover 3 made of a sintered body, it is inserted into a firing furnace 4 filled with nitrogen, and heaters 5 arranged at the top, bottom, left and right of the firing furnace 4 are operated to heat.

The heating is, as shown in FIG. 1 (a), the first firing in which the organic component scattering step and the first half step of the sintering step are continuously performed,
As shown in FIG. 2 (b), it is performed separately from the second firing, which is the latter half of the sintering step.

In the first firing, first, an organic component scattering step is performed. That is, the temperature in the furnace is raised from room temperature with a temperature gradient of 30 ° C./hour, and after reaching a temperature of about 400 ° C., this temperature is maintained for about 5 hours. As a result, the organic components in the ceramic substrate 1 scatter in the furnace.

Next, the first half step of the sintering step is performed continuously with the organic component scattering step. That is, the temperature in the furnace is raised in nitrogen from 400 ° C. with a temperature gradient of about 40 ° / hour, and when it rises to 700 ° C. or more, vitrification of the ceramic particles occurs, so that the sintering process is started. In the sintering step, the ceramic substrate 1 is heated at a relatively high temperature of about 800 to 900 ° C. (here, about 900 ° C.) for about 4 hours. In the first half of this sintering step, the ceramic substrate 1 begins to vitrify from the point where the temperature rises to the glass point and the range thereof gradually expands, but the vitrification progresses to a relatively high temperature.
On the back surface 1a side, the sintering is fast, and on the front surface 1b side, the sintering proceeds slowly. Since the degree of sintering is high on the back surface 1a side of the ceramic substrate 1 in which vitrification proceeds rapidly, and the shrinkage rate accompanying sintering also increases,
The ceramic substrate 1 will warp back to the middle height.

After lowering the furnace temperature to room temperature, the ceramic substrate 1
Was taken out of the firing furnace 4, turned upside down, placed on the jig 2, and covered with a cover 3 made of a sintered body containing alumina as a main component and inserted into the sintering furnace 4 filled with nitrogen. A second firing step, which is the latter half of the sintering step, is performed.

That is, the heaters 5 arranged on the upper, lower, left and right sides of the sintering furnace 4 are operated to heat them, and the temperature inside the furnace is increased with a temperature gradient of 80 ° C / H from room temperature to a relatively high temperature of about 1000 ° C for about 3 hours. After holding, it is lowered by natural cooling.

In this second firing step, the back surface 1a, which was heated while being in contact with the jig 2 in the first firing step, was heated while being in contact with the atmosphere, and the front surface 1b, which was heated while being in contact with the atmosphere in the first firing step. Will be heated while contacting the jig 2.

Also in this second firing step, vitrification starts from the point where the temperature rises to the glass point of the ceramic substrate 1 and its range gradually expands. The progress of vitrification is relatively high on the surface 1b side of the ceramic substrate 1 which is relatively high. Vitrification proceeds slowly on the back surface 1a side. Then, the particles are sintered and contracted. However, since the back surface 1a side of the ceramic substrate 1 has already been sintered in the first firing step, the difference in shrinkage amount between the front surface 1b side and the back surface 1a side of the ceramic substrate 1 becomes small, and the warpage of the ceramic substrate 1 Becomes smaller. For example, 36
In the case of the ceramic substrate 1 having a size of 0 mm square and a thickness of 15 mm (before firing), a warp of about 0.9 mm occurred according to the conventional method, but in this embodiment, the warp size should be reduced to about 0.4 mm. I was able to.

〔The invention's effect〕

As described above, according to the present invention, since the binder is scattered in the furnace in the organic component scattering step and then the first sintering step is started, the binder does not remain in the ceramic substrate, and There is no risk of blowholes.

After the first sintering step, the ceramic substrate is turned upside down and the second sintering step is performed, and both sides of the ceramic substrate are heated while being in contact with the jig and being heated while being in contact with the atmosphere. Since the difference between the temperature histories on the front and back surfaces is reduced and the difference in the degree of sintering is reduced, the warp of the ceramic substrate can be reduced.

Further, since the warp of the ceramic substrate can be reduced, it is possible to shorten the polishing time in the polishing step to be performed later and to obtain a ripple effect such as preventing the inner layer pattern from being exposed or broken due to polishing. it can.

[Brief description of drawings]

FIG. 1 is a temperature profile diagram of a ceramic substrate firing method according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a firing furnace, and FIG. 3 is a temperature profile diagram of a conventional method. , 1 ... Ceramic substrate.

Claims (1)

(57) [Claims] 1. An organic component scattering step of heating an unsintered ceramic substrate for a predetermined time to scatter a binder, and a ceramic substrate is sintered following this organic component scattering step.
A method of firing a ceramic substrate, comprising: a sintering process; and a second firing process in which the ceramic substrate after the completion of the first sintering process is turned upside down and then fired.