JPS61247658A - Method of burning ceramic wire distribution substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing an alumina-based co-fired ceramic wiring board.

(Prior art) A co-fired ceramic wiring board is a clean sheet in which wiring is made of high melting point conductive metal powder paint on a ceramic green sheet in a reducing atmosphere to prevent oxidation of the ceramic green sheet. It is manufactured by sintering the ceramics and metal powder at the same time and bonding the metal powder to the ceramics.

In this case, the organic binder contained in the ceramic screen sheet is not sufficiently incinerated in a reducing atmosphere, and a small amount of t-element remains in the ceramic, which tends to result in insufficient sintering of the ceramic. In the industry, hydrogen containing water vapor is used to reduce the binder's incineration tendency.
It is customary to fire in a steam atmosphere or a weakly reducing nitrogen-hydrogen-steam atmosphere mixed with nitrogen.

In this case, the /H,2O partial pressure ratio has a great influence not only on the incineration property of the binder, but also on the sinterability of the safe powder and the bonding strength between ceramics and metal. The sintering properties of the metal powder and the bonding strength between the ceramic and the metal are contradictory to each other.In other words, in terms of the incineration property of the binder, the smaller the /HrO partial pressure ratio and the stronger the oxidizing property, the better; In terms of powder sinterability and bonding strength between ceramics and safes,
/H,2O partial pressure ratio, the stronger the reducing property, the more preferable. Under these circumstances, it has conventionally been customary to operate the firing atmosphere in an atmosphere with a partial pressure ratio of about 5 to 8, which is a compromise between the two.

However, with the recent demand for more precise wiring patterns,
Ceramic substrates themselves are now required to have finer grains, and raw material powders are also becoming increasingly finer. The binder incineration properties of these ceramic green sheets deteriorate, and a conventional firing method results in insufficient sintering.

As a countermeasure against this problem, the following methods are commonly used.

■ A method of increasing the firing time to compensate for the poor burnability of the binder.

(2) A method of improving the method of dipping the material to be fired in the firing furnace, and increasing the supply layer of atmospheric gas to direct the ventilation of the atmospheric gas inside the kiln, thereby promoting the complete reaction of binder incineration.

These countermeasures have been effective to a certain extent, and it has become possible to use powders that are quite fine in terms of specific axis, and at present, powder average diameters of 2 to 3 μm are the mainstream.

However, when trying to achieve further refinement, there are limitations such as the reduction in firing efficiency becomes noticeable with the above-mentioned extension measures, and there is a technical limit to the incineration property of the binder. New countermeasures were needed.

(Problems to be Solved by the Invention) The present invention is based on the above-mentioned requirements, and has good results in all of the above-mentioned points, including the incineration property of the binder, the sinterability of the metal powder, and the bonding strength between ceramics and metal. The overall purpose of the present invention is to provide a new method for manufacturing a co-fired ceramic wiring board that yields a co-fired ceramic wiring board.

(Means for Solving the Problems) The present invention has been developed in the past in accordance with the present invention.
This was done after reviewing the method using the partial pressure ratio of H and 2O and gaining new knowledge about the interrelationship between binder incineration properties and metallization properties (continuity resistance, metallization strength).

That is, the important temperature range for binder incineration is from room temperature to 1200° C. and 1300'C4. In this temperature range, shrinkage of ceramics is slow and it is a convenient temperature range for binder removal by incineration. This will be referred to as the binder removal temperature range. On the other hand 13
When the temperature reaches t = 00°C, the shrinkage of ceramics is accelerated, and if carbon remains at this point, the '-1! - This temperature range that is confined within the ceramic and causes sintering failure will be referred to as the sintering temperature range.

Therefore, it is necessary to complete the incineration removal of the binder within the same temperature range for binder removal.For this reason, the basic idea is to perform baking in a highly oxidizing atmosphere and remove the binder by incineration, even at the cost of sacrificing metallization properties. It should be completed. However, in this case, the metallization property once sacrificed must be recovered in the subsequent firing process, but the degree of oxidation of the ambient gas in the debinding temperature range and the reducing property of the atmospheric gas in the sintering temperature range Based on the discovery that by appropriately selecting the degree of oxidation and reducing the temperature at which the atmosphere gas is switched between oxidation and reduction, the metallization property can be restored and both binder removal by incineration and metallization property can be achieved. It is something.

The gist of the present invention is the following method.

Ceramic Nugreen whose main component is At2OJ, contains one or two of SiC2゜MgO, CaO as a sintering aid, and also contains a metal oxide or hydroxide as a coloring agent if necessary. Wiring was applied to the sheet using high-melting point metal powder paste, and pre-firing was performed in a slightly reducing atmosphere with a partial pressure ratio of ``/HrO'' of 05 to 40 in a temperature range below the melting temperature of the above-mentioned sintering aid in the ceramic. Then, as main firing, H is heated from a temperature range below the melting temperature of the sintering aid.
A method for firing a co-fired ceramic wiring board in which firing is performed in a strongly reducing atmosphere with a 2/H, 2O partial pressure ratio of 5 or more.

Also, a method for firing a co-fired ceramic wiring board, in which oxidation firing at a temperature of 150 to 350 ℃ is performed as pre-firing, and then the above-mentioned preliminary firing and the above-mentioned main firing are performed.

and a method for firing a co-fired ceramic wiring board, which performs steam oxidation firing at 300 to 700°C as pre-firing, and then performs the preliminary firing and the main firing.

Furthermore, oxidation firing at 150 to 350°C as pre-calcination,
Subsequently, steam oxidation firing was performed at 300 to 700 °C.
A method for firing a co-fired ceramic wiring board, which then performs the preliminary firing and the main firing.

The ceramic material used in the present invention is At2O3
as a main component, and S3-02. as a sintering aid. MgO.

Although it contains one or more kinds of CaO and the like, the composition and the particle size of the raw material powder are not particularly limited.

It may also contain a suitable oxide or hydroxide as a coloring agent. Also, high melting point metal powder is W.

It is composed of one or more of MO and Mn, and its composition and powder particle size are not particularly limited.

Next, regarding the method of adjusting the H'/HrO partial pressure ratio in the firing atmosphere, in the industry, H2 is generally added to the H2-containing gas.
Although 2O is mixed in, this method is limited to this method.An adjustment method such as mixing Oa and achieving a predetermined Hr/H2O partial pressure ratio as a result of H,2-0,2 equilibrium in the firing process may also be used. .

Here, the gas containing H2 means hydrogen gas 1 or a mixed gas of hydrogen gas and inert gas, and nitrogen gas is often used as the inert gas.

Further, in carrying out the present invention, the firing may be carried out by separating the molten metals in the calcining furnace and the kido, or the firing may be performed by combining the molten metal into a single furnace and dividing the atmosphere inside the furnace, and the effect will be the same.

(Function) Next, in the present invention, the H-shield during preliminary firing and main firing]
, 2O partial pressure ratio and temperature range are limited as above 3]
Let me explain 11 reasons.

[Removal of binder in ceramics] In order to efficiently remove the binder, Hx7 peaks are required during pre-firing. It is effective to set the partial pressure ratio to 4 or less and to calcinate under relatively oxidizing conditions. However, as long as the ``''/H,2O partial pressure ratio was kept below 4,
If the final firing is carried out, a problem will arise in terms of metallization properties.

As a result of conducting various experiments on the possibility of meta-wise recovery, the following 41 results were discovered.

■ In order to recover metallizability, H
-VH2O partial pressure ratio of 5 or more is required.

■ Even if the Hs/H,2O partial pressure ratio is set to 5 or more in the main firing, the Hs/H,2O partial pressure ratio is 0 or more in the preliminary firing.
When it is less than 5, recovery of metallizability is impossible.

■ H-2//H2O partial pressure ratio during pre-firing is set to 05 to 4.
Even in the case where the ceramic is fired to a temperature exceeding the melting temperature of the sintering aid in the ceramic, in the subsequent main firing, even if the 2O partial pressure ratio is 5 or more,
It is no longer possible to recover the metallizability.

Based on these results, it has been determined that two important basic elements of metallizability are the contact condition between the ceramic and the metal powder and the surface condition of the metal powder when the sintering aid in the ceramic is melted.

In order to maintain good contact between the ceramic and the metal powder, it is important not to oxidize it too much during calcination. Excessive oxidation causes the metal powder to swell, which is why "/H2O"
It is considered that a partial pressure ratio of 05 or more is required.

Next, when melting the sintering aid in ceramics, the metal powder must be in a reduced state, so the highly oxidizing pre-firing must be performed at a temperature below the melting temperature of the sintering aid. Furthermore, it is necessary to reduce the surface of the metal powder between the time when the main firing, which has a strong reducing property, reaches the melting temperature of the sintering aid. Therefore, from the l crystallinity range below the melting temperature of the sintering aid,
○It is necessary to perform firing in an atmosphere with a partial pressure ratio of 5 or more.

At this time, some time is required for the reduction of the metal powder between the start of the main firing and the melting of the sintering aid, and this time is preferably several tens of minutes or more, but there are no particular limitations. do not.

Next, the reason for determining the temperature and atmosphere for pre-firing will be described.

As already mentioned, it is preferable to use an atmosphere with as strong an oxidizing property as possible in the preliminary firing in order to increase the incineration property of the organic binder, and in that sense, oxidizing firing in air can be considered. This discovery is disclosed, for example, in Japanese Patent Application Laid-open No. 59-98594, which discloses that firing at a temperature of 350 DEG C. or lower is effective in removing the binder by incineration without adversely affecting the metallization 1 raw material.

The present inventor has discovered that by combining the low-temperature oxidation firing of 150 to 850 C in air with the present invention described in item 1, the binder can be removed by incineration even more effectively, and there is no problem with metallization. It was confirmed that there were no That is, even in the pre-calcination after the low-temperature 150 to 850°C oxidative firing in air, the stronger the oxidizing nature of the firing atmosphere, the more advantageous it is for removing the binder by incineration. In this regard, in the past, due to concerns about metallization properties, the actual situation was to compromise with an atmosphere with an H'lHrO partial pressure ratio of about 5 to 8.
The above combination, i.e. low temperature 150-350°C in air
By making it possible to perform calcination in a highly oxidizing atmosphere as a preliminary calcination after oxidation calcination, the binder can be removed by incineration more effectively. It is clear that the oxidation firing in the preliminary firing in this method is effective not only in air but also in a mixed gas of oxygen and an inert gas and oxygen gas.

Next, regarding the limitation of steam oxidation firing at 300 to 700°C as a preliminary firing, this is atmospheric firing in steam that does not contain hydrogen or in a steam-inert gas atmosphere, but it is effective for removing the binder by incineration. 30 to do
Firing is required at a temperature of 0° C. or higher, and from the viewpoint of metallizability, it is necessary to keep the firing temperature to 700° C. or lower.

(Effects of Examples and Invention) The main component is A1.2O394% and Si0.
A resin, a plasticizer, and a solvent were further added to the inorganic substance to which 6% of 2°MgO, Ca0f:)-tal had been added and mixed, and a green sheet with a thickness of 0.9 mm was prepared by a general tape casting method. The particle size of the raw material powder in this example is an average diameter of 12μ, which is considerably finer than that commonly used in the industry.

This Green Sea 11-140 x 25 piece was cut into a sample for evaluation of binder incineration properties. In addition, a sample was prepared by cutting this green sheet into a size of 100 squares and having a printed pattern formed thereon using tungsten beanute made from W powder, and used as a sample for metallization evaluation. The average particle size of the W powder is 08μ.

Using these two types of samples, the binder incineration properties and metallization properties were comparatively evaluated using the firing method according to the present invention, the firing method according to the conventional technology, and various firing methods in the process of completing the present invention. The results are shown in Table 1. .

Note 1: Temporary firing of Examples in Table 1 is 12 unless otherwise specified.
The conditions were 50°C for 2 hours, and main firing for 152°C for 2 hours.The melting temperature of the sintering aid in the ceramic was approximately 1850°C.

Note 2: The unit of sintered density in Table 1 is gX. The conduction resistance is evaluated by the volume resistivity, and the unit is 10-5Ω, and the metallization strength is evaluated by the peeling strength of tungsten metallize and ceramics, and the unit is kQ.

As shown in Table 1, by using the firing method of the present invention, it is possible to increase the sintered density without deteriorating the metallization properties. However, its effect is clearly demonstrated.

Claims (4)

[Claims] (1) The main component is Al_2O_3, and S as a sintering aid.
A ceramic green sheet containing one or more of iO_2, MgO, and CaO and, if necessary, a metal oxide or hydroxide as a coloring agent, is wired with a high melting point metal powder paste and pre-fired. , H_2/ in the temperature range below the melting temperature of the above sintering aid in ceramics.
Calcination was performed in a weakly reducing atmosphere with a H_2O partial pressure ratio of 0.5 to 4.0, and then as main firing, the H_2/H_2O partial pressure ratio was set to 5 or more from a temperature range below the melting temperature of the sintering aid. A method for firing a co-fired ceramic wiring board, characterized by firing in a strongly reducing atmosphere. (2) Main component is Al_2O_3 and S as a sintering aid.
A ceramic green sheet containing one or more of iO_2, MgO, and CaO and, if necessary, a metal oxide or hydroxide as a coloring agent, is wired with a high melting point metal powder paste and pre-fired. 150-35
Oxidation firing is performed at 0°C, followed by pre-calcination at H_2 in a temperature range below the melting temperature of the above-mentioned sintering aid in the ceramics.
/H_2O partial pressure ratio is 0.5 to 4.0 in a weakly oxidizing atmosphere, and as main firing, the H_2/H_2O partial pressure ratio is set to 5 or more from a temperature range below the melting temperature of the sintering aid. A method for firing a co-fired ceramic wiring board, characterized by firing in a strongly reducing atmosphere. (3) The main component is Al_2O_3, and S as a sintering aid.
A ceramic green sheet containing one or more of iO_2, MgO, and CaO and, if necessary, a metal oxide or hydroxide as a coloring agent, is wired with a high melting point metal powder paste and pre-fired. 300-70
Steam oxidation firing was performed at 0°C, followed by pre-firing in a weakly oxidizing atmosphere with a H_2/H_2O partial pressure ratio of 0.5 to 4.0 in a temperature range below the melting temperature of the above-mentioned sintering aid in the ceramics. A co-fired ceramic wiring board characterized in that the main firing is performed in a strong reducing atmosphere with a H_2/H_2O partial pressure ratio of 5 or more from a temperature range below the melting temperature of the sintering aid. firing method. (4) Main component is Al_2O_3 and S as a sintering aid.
A ceramic screen sheet containing one or more of iO_2, MgO, and CaO and, if necessary, a metal oxide or hydroxide as a coloring agent, is wired with a high melting point metal powder paste and pre-fired. , 150-3
Oxidation firing was performed at 50°C, followed by steam oxidation firing at 300 to 700°C, and then temporary firing was performed at H_2/H_ in a temperature range below the melting temperature of the above-mentioned sintering aid in the ceramics.
Firing was performed in a weakly reducing atmosphere with a 2O partial pressure ratio of 0.5 to 4.0, and as main firing, the H_2/H_2O partial pressure ratio was set to 5 or more from a temperature range below the melting temperature of the sintering aid. A method for firing a co-fired ceramic wiring board, characterized by firing in a strongly reducing atmosphere.