JPH0451077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of manufacturing a ceramic multilayer wiring board.

[Technical background of the invention and its problems]

Conventional ceramic multilayer wiring boards were generally manufactured in the following manner.

That is, a certain amount of inorganic raw materials are weighed, mixed and pulverized to obtain the required average particle size, dried, and then a solvent, binder, plasticizer, dispersant, etc. are added, and if necessary, Further, an inorganic black agent and the like are added and thoroughly mixed. After that, it is placed in a defoaming machine, further stirred and defoamed, and the slurry is adjusted to the required viscosity.

When the required viscosity is reached, the slurry is supplied to the doctor knife section of the doctor blade device having a constant gap, and the slurry flowing out from the doctor knife section is placed on the carrier film with a constant thickness. The carrier film passes through a drying section as it travels, and at that time a certain amount of the slurry's solvent is scattered, creating a green color similar to chewing gum.
A sheet (referred to as an unsintered sheet or green sheet) can be obtained.

A conductive circuit layer is formed on the green sheet by printing a conductive paste containing molybdenum (Mo) or tungsten (W) as a main component using a screen printer or the like.

Next, an insulating paste layer is printed on the conductor layer except for through holes connecting the upper and lower conductors and other necessary locations. Further, on the insulating layer, multiple layers such as a conductor layer are sequentially printed again to form a printed multilayer wiring board.

This printing material, green sheet, is heated to 1400-1600℃
Then, if necessary, after plating, attaching a lead frame, etc., ICs, RCs, etc. are mounted at specific locations on the top layer printed pattern, and wires are attached to the ceramic. It becomes a multilayer wiring board.

A particular problem with this manufacturing method is that when a green sheet with multilayer printing is fired, the fired substrate warps so much that it is impossible to attach a lead frame afterwards, and even more so, it is impossible to attach an IC.
It was impossible to do CR chip mounting or wire bonding.

One effective method to solve this problem is to use the same inorganic raw material for the insulating paste as the substrate, as disclosed in Japanese Patent Publication No. 57-27060, for example. When an inorganic raw material having a particle size was used, there was still a problem that the fired substrate had a large degree of warpage.

[Purpose of the invention]

As described above, the present invention provides a method for improving the problem of the conventional method in which large warpage occurs even when a multilayer wiring board is formed using an insulating paste of the same quality as the board.

[Summary of the invention]

In the method of the present invention, after weighing the inorganic raw materials, they are mixed and pulverized until the average particle size required for the substrate is obtained, and then a part of the inorganic raw materials is mixed as is, or if necessary, a black agent is added, and then further mixed and pulverized. An inorganic raw material for an insulating paste is obtained by making the average particle size smaller than that of the inorganic raw material for a substrate. Using this, thoroughly mix and stir with ethyl cellulose, terpineol, etc. to make an insulating paste.

By using the insulating paste thus prepared, a ceramic multilayer wiring board with a small warpage of about 70 μm/1 inch can be obtained after firing.

〔Effect of the invention〕

By using the method of the present invention, the following effects can be obtained.

B) The warpage of the fired substrate is reduced, making a major contribution to industry.

This eliminates the need for re-firing for re-warping and prevents an increase in conductor resistance.

C. Similarly, re-firing for warping is no longer necessary, making subsequent plating or lead frame attachment easier.

[Embodiments of the invention]

92% by weight of aluminum oxide (Al ₂ O ₃ ) (the same applies hereinafter), 5% of silicic anhydride (SiO ₂ ), 1.5% each of magnesium oxide (MgO) and calcium oxide (CaO).
% and when these are taken as 100 parts, the second oxide
4 parts of chromium (Cr ₂ O ₃ ), 1 part of titanium oxide (TiO ₂ )
Each part by weight was weighed, and the mixture was mixed and pulverized using a vibrating mill until the average particle size was 1.8 μm.

A portion of it was further pulverized to an average particle size of 1.5 μm.

After drying these inorganic powders separately, 1.8μ
A solvent binder, a plasticizer, etc. were added to the large particle size powder of m for use as a substrate as follows.

Alumina powder 100 parts Trichlorethylene 20〃 n-butanol 10 parts Tetrachlorethylene 8〃 Polyvinyl butyral 5〃 TBP 2〃 After thoroughly mixing these, defoaming and viscosity
The slip at 30,000 centipoise (CP) was fed to a doctor blade device to obtain a green sheet. 50x this green sheet
The green sheet was cut into 60 mm pieces, and a conductive circuit layer was formed on the green sheet using molybdenum (Mo) paste using a screen printing machine. After drying, an insulating paste made of the pulverized insulating paste powder, ethyl cellulose, and terpineol was printed to an average particle size of 1.5 μm except for through holes or other specific areas.

Similarly, after this insulating layer was dried, a conductive layer was placed on top of the insulating layer, followed by an insulating layer, and so on to form a multilayer wiring. This layered structure is shown in cross section in FIG.

Next, this substrate was fired at 1500° C. in a weakly reducing atmosphere of a mixed gas of hydrogen gas (H ₂ ), nitrogen gas (N ₂ ), and wet H ₂ .

At the same time, a substrate made of the same inorganic raw material as the substrate with the same average particle size, i.e., 1.8 μm, was separately prepared and made into a multilayered structure using an insulating paste as described above, and was fired under the same conditions. .

This 1.8 μm insulating paste had a lot of warpage, so it was fixed and re-fired at a low temperature of just under 1400°C.

As a result, as shown in Figure 2, when using insulation paste with the same average particle size of 1.8 μm as the substrate, the warpage of the fired substrate was 0.24 on average for 10 sheets.
mm/50mm was also hot. On the other hand, when an insulating paste with a particle size of 1.5 μm, which is smaller than the substrate, was used, the average of the 10 sheets was 0.17 mm/50 mm. The warpage was measured using a 3E-3C universal surface profile measuring device manufactured by Kosaka Giken Co., Ltd.

Here, the warpage of the board after firing is generally 0.2
~0.14mm/50mm is required, so considering this point, a smaller average particle size may satisfy this standard, but particles with the same size will warp larger than the standard and have to be rewarped. Is required.

Therefore, as mentioned above, we refired at 1400°C to correct the warpage. Figure 3 shows the measurement results of the conductor resistance on the top layer conductor pattern before and after.
are the values after unwarping, and before unwarping, that is, the values for only one firing, and these are the average values measured for each of five samples.

As can be seen from this result, by passing through the firing furnace one more time, the Mo conductor on the surface is oxidized by the weakly reducing atmosphere, increasing the conductor resistance.

Therefore, if a multilayer wiring board is manufactured using an insulating paste made from a homogeneous inorganic raw material with a particle size smaller than that of the substrate, it can be fired with sufficiently small warpage without the need for warping, and an increase in conductor resistance can be prevented.

Here, the general conductor resistance standard is 20mΩ/□
It is.

Furthermore, since there is no need for re-firing to correct warpage, oxidation and scattering of the conductor pattern is prevented, which makes plating easier in the subsequent plating process. The brazing process is also much easier.

As the conductor pattern becomes thinner, the plating material will inevitably become thinner, resulting in poor plating or molybdenum.
This leads to a decrease in the adhesion of the lead frame. In this sense, the method of the present invention, which requires only one firing, can be said to make a great contribution.

Further, other embodiments of the present invention are shown below.

First, prepare AlN powder (F-B grade manufactured by Tokuyama Soda Co., Ltd.) with a specific surface area of 3 mm ² /g, and add 3.0% by weight of Y ₂ O ₃ , 1.0% by weight of Al ₂ O ₃ , and CaCO ₃ to this AlN powder.
was added in an amount of 1.0% by weight, mixed and pulverized in a pot mill until the average particle size was 1.8 μm. A portion of it was further ground to an average particle size of 1.5 μm.

After drying these inorganic powders separately, 1.8μ
A solvent binder, a plasticizer, etc. were added to the large particle size powder of m for a substrate in the following mixing ratio.

* AlN powder 100.0 parts * 1-1-1 trichloroethane 26.0 parts * n-butanol 19.0 parts * Tetrachlorethylene 15.0 parts * Polyvinyl butyral 15.0 parts * Tributyl phosphate (TBP)
5.0 parts After thoroughly mixing these, defoaming and viscosity
A slip of 30,000 centipoise (CP) is supplied to the doctor blade device, and the thickness
A 0.5 mm green sheet was obtained. Four pieces of this were laminated by thermocompression bonding at 20 to 100°C, 180 kg/cm ² , and held for 30 minutes to create a laminate with a thickness of 2.0 mm.

Cut this green sheet to 70 x 80 mm, use a screen printing machine to print on the green sheet,
A conductor circuit layer was formed using molybdenum (Mo) paste. After drying, an insulating paste made of the insulating paste powder pulverized to an average particle size of 1.5 μm, ethyl cellulose, and terpineol was printed except for through-holes or other specific locations.

Similarly, after this insulating layer was dried, a conductive layer and then an insulating layer were placed on the insulating layer again to form a multilayer wiring in the same manner as when Al ₂ O ₃ was used as the inorganic raw material. Next, this board was heated to 700℃ using a degreasing furnace.
Keep and degrease in _N2 . This was fired at a maximum temperature of 1750°C in a reducing atmosphere using a vacuum pressure sintering furnace.

At the same time, a substrate made of the same inorganic raw material as the substrate and with the same average particle size, that is, 1.8 μm, was separately prepared and made into a multilayered structure using an insulating paste as described above and fired under the same conditions. . This 1.8μm
The insulating paste had a lot of warpage, so it was refired at 1700℃ in a reducing atmosphere to correct the warpage. As a result, the warpage of the fired board was found to be
The average temperature of the 10 sheets was 0.25mm/50mm. On the other hand, when an insulating paste with a particle size of 1.5 μm, which is smaller than the substrate, was used, the average of the 10 sheets was 0.15 mm/50 mm. Warpage was measured using a 3E-3C universal surface profile measuring device manufactured by Koita Giken Co., Ltd.

As mentioned above, when a multilayer wiring board is manufactured using an insulating paste made from a homogeneous inorganic material with a particle size smaller than that of the board, the amount of warpage after firing is 0.16 mm/50 mm, which is a sufficiently small value. There was no need to repair it. On the other hand, when a multilayer wiring board is manufactured using an insulating paste made from a homogeneous inorganic raw material with the same particle size as the substrate, the amount of warpage after firing is large, requiring re-firing to correct the warpage. For this reason, the warpage was corrected by re-firing under the conditions described above, but after the warpage was corrected, the conductor resistance of the top layer conductor pattern had increased beyond the standard value.

In the above embodiment, an alumina multilayer substrate and
Although we have described an AlN multilayer substrate, analogies can be easily made to substrates using other general ceramic materials.

Furthermore, the same effect can be obtained by using a conductive paste other than the conductive paste mainly composed of Mo, for example, a conductive paste mainly composed of W.

Furthermore, the black agent may be added from the beginning and pulverized as in this example, or it may be pulverized into small particles in advance and then mixed with ethyl cellulose, terpineol, etc. when preparing the insulation paste. It's okay. In short, it is sufficient that the insulating paste has an average particle size as an inorganic raw material smaller than that of the substrate and is a homogeneous inorganic raw material.

Printing of conductor patterns or insulation paste is
For example, it can be formed by an inkjet method using ultrasonic waves without using a screen printing machine.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing an example of the layer structure of a ceramic multilayer wiring board, Figure 2 is a characteristic diagram showing warpage after firing the ceramic multilayer structure board, and Figure 3 is the conductor resistance when using the conventional method. Characteristic diagram showing changes in .

Claims (1)

[Claims] 1. A step of weighing inorganic raw materials, a step of mixing, pulverizing, and drying the inorganic raw materials, and a step of adding a solvent, a binder, a plasticizer, and a dispersant,
The process of mixing, stirring, and defoaming, as well as the doctor blade molding device, produce green products.
A process of creating a sheet, a process of forming a conductor circuit on the green sheet using molybdenum (Mo) or tungsten (W) based conductive paste using a screen printing machine, and a process of forming a connection between the upper and lower conductors through through holes. To do this,
The process consists of a process of printing insulating paste on a specific location excluding that part, a process of repeating the printing of the conductor and insulating paste alternately to form a multilayer structure, and a process of firing this in a weakly reducing atmosphere. A method for manufacturing a ceramic multilayer wiring board, characterized in that an inorganic raw material of the same quality as the board is used as the insulating paste, and the average particle size of the inorganic material is smaller than the average grain size of the inorganic raw material of the board. manufacturing method.