JPH0455536B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to metallization technology for ceramic substrates, and more particularly, to a method of attaching a conductive material to a ceramic substrate such as a ceramic substrate and metallizing it, and a conductive material used therein. (Conventional technology) In recent years, electronic equipment has become significantly thinner and more compact, and as the degree of integration increases, reliability has further improved.
Its uses are also continuing to expand. monolithic
ICs are rapidly increasing in density and becoming smaller, and on the other hand, in the field of hybrid ICs, large-scale hybrid ICs with excellent heat resistance and shock resistance are becoming more popular, especially in industrial equipment such as automotive control circuits and power supply devices. There is a strong tendency to Recent hybrid IC
In addition to active components such as diodes, transistors, and semiconductor ICs, coils and
It is equipped with most electrical components such as transformers and capacitors. Hybrid integrated circuits have been developed that have further increased the degree of integration and have dramatically improved reliability. These hybrid ICs have individual components or IC elements mounted on a ceramic substrate, or
It is constructed using thick film technology. Cer-Dip ICs are usually made by bonding a silicon IC chip onto an alumina substrate of about 96% A ₂ O ₃ using bonding paste, but even more durable bonding strength is required. Usually, Au-based conductive paste, solder, glass, etc. are used in bonding methods for deep-dip ICs. Au-based conductive paste has excellent conductivity, is extremely chemically stable, has the best bondability with Au wire, is easily alloyed with Si, and has extremely good adhesion to substrates, but it is expensive. There are some difficulties. To overcome this difficulty, an Ag-Pd paste has been developed in which Au is replaced with Ag and Pd is added to prevent migration, which is a disadvantage of Ag. There are various methods for metallizing ceramic substrates using these conventional pastes (see, for example, Japanese Patent Application Laid-Open No. 1950-798-60). For example, Au-based or Ag-
Glassy metal oxide is mixed with Ag-based metal powder such as Pd, Ag-Pt, etc., diluted and kneaded using a vehicle to form a conductive paste, and this is applied to the ceramic substrate 1 as shown in Figure 3a and b. After dotting on the bottom of the cavity 2, spread it over the entire surface for about 1 hour.
After leveling for about an hour, it is dried for about 1 hour, then fired at about 870-900℃ for Au-based pastes and about 900-930℃ for Ag-based pastes to perform metallization treatment, and then Si There is a way to mount chip 3 etc. (Problems to be Solved by the Invention) However, in this metallization method using conductive paste, it is very difficult to control characteristics such as color tone, surface roughness, and porosity, and the process is complicated.
It is difficult to handle because sedimentation occurs during dilution. Furthermore, although the film thickness is controlled by the dilution rate, it is not possible to obtain a uniform film thickness, and there is considerable individual variation.Furthermore, parts that do not contain Si are also metalized, which increases costs. There was a drawback. The present invention eliminates the drawbacks of the above-mentioned conventional techniques, and provides a technology that allows processing only the necessary parts through a simple process with good workability, and allows stable formation of a metallized layer with uniform properties and film thickness at low cost. The purpose is to provide (Means for Solving the Problems) In order to achieve the above object, the present inventor has developed a new conductive material that is not paste-like, considering that the drawbacks of the conventional metallization method are due to the properties of the conductive paste. As a result of extensive research, we discovered a metallization technology that can form a metallized layer with excellent film properties without the need for dilution, dotting, leveling, etc. by forming a conductive paste composition into a sheet form, and we have published this book. It is an invention. That is, the conductive sheet for metallizing a ceramic substrate according to the present invention is characterized in that it is a conductive paste composition, which is formed into a sheet shape and then dried as a green sheet. Further, the method for metallizing a ceramic substrate according to the present invention involves forming a conductive paste composition into a sheet, punching this sheet into appropriate dimensions, and then forming the conductive paste composition into a sheet.
It is characterized by being pasted onto a predetermined location on a ceramic substrate and fired. The present invention will be explained in detail below based on examples. As mentioned above, conventional conductive pastes are used after being diluted with a solvent, whereas in the present invention, a green sheet formed into a sheet is used, so there is no need for dilution or any subsequent steps associated with dilution. First, it only requires a step of pasting it on a predetermined location. First, as a starting material, it is possible to use an Au-based or Ag-based composition similar to the conventional conductive paste, a composition in which a small amount of glass frit is mixed therein, or even a glass powder. Examples of Au-based powders include 100% Au powder and Au-Pt-based powder. In addition, Ag-based powders include 100% Ag powder, Ag-Pd-based powder, Ag-Pt-based powder, and Ag-Cu powder.
These include Ag-Cu- (yttrium oxide and/or vanadium pentoxide)-based powder, Ag-Cu- (copper organic substance)-based powder, etc. In addition, in the case of Ag-based, an example of the composition is Ag-(0.1-10%) Cu, Ag-(0.2-10%)
Pt,Ag-(0.2~30%)Pd,Ag-(0.1~10%)Cu
- (20ppm ~ 2%) yttrium oxide and/or (20 ~ 500ppm) vanadium pentoxide, Ag - (0.1 ~
10%) Cu- (20ppm~2%) Yttrium oxide-
(Amount that makes the total copper purity in the composition 0.1 to 10%)
Copper organic matter, etc. For these compositions,
If Ag fine powder or composite fine powder such as Ag and Cu, Ag and Pd, or Ag and Pt is used, and if 30% or more of the total Ag fine powder is flake-like Ag particles, it is a fritless type with good adhesive strength and heat resistance. , impact resistance can be improved. Conventional conductive pastes mainly consist of the metal fine powder dispersed in an organic solvent, but in the present invention, the solid components only need to be the same, and if tape molding technology can be used, an organic solvent is not necessarily required. The above-mentioned raw material powder is kneaded with water, a binder, a surfactant, etc. added as appropriate, and formed into a sheet by tape molding technology. For tape molding, a viscosity of about 30 to 40 kcos provides the best moldability.
For tape molding, a sheet made of resin such as acrylic resin, preferably one whose surface is coated with Si resin in order to facilitate separation from the green sheet, is used. The desired thickness is made uniform on the sheet using a scraping board such as a doctor blade. After molding, it is naturally dried at room temperature and separated from the resin sheet to obtain a green sheet. Note that forced drying is not preferable because it causes many pores to occur in the green sheet. The obtained green sheet is cut to a specified size by punching, the surface to which the sheet is attached is soaked with a solvent such as water, ethyl alcohol, terpineol, butyl carbitol, etc., and then attached to a specified location such as the cavity of a ceramic substrate. . Thereafter, the metallized surface is obtained by firing as in the conventional method.
Note that the unnecessary green sheet portion remaining during punching can be re-kneaded to form a sheet again. 1 and 2 show an example of metallizing the cavity portion of a ceramic substrate 1 using a punched green sheet. As shown in FIG. When using a circular or rectangular (square) green sheet 5 with a slightly wider area than the above, or when using a jumper wire 6 as shown in FIG. The green sheet 5 may be used for each. Of course, the entire surface of the cavity can be metallized using a green sheet, and in this case, it is preferable to degrease the green sheet at about 600° C. and then attach it. A thick film firing furnace is available for general firing, and firing is performed in an atmospheric atmosphere. A regular Matsufuru furnace may also be used. To obtain a good metallized surface, the temperature should be up to 600℃.
Heating should be done at a rate of 50℃/min or less, and rapid heating should be used for temperatures above 600℃. (Example) Next, an example of the present invention will be shown. Example 1 Powder components having the following composition (wt%) were prepared and thoroughly mixed in a V-type mixer. Pd (average particle size 1.2μ) 2% Cu-Ag composite powder 0.8% Y ₂ O ₃ (average particle size 1.3μ) 0.003% Silver (average particle size 1.6μ) Balance Furthermore, add water and acrylic binder to this mixed powder. , surfactant, etc. in the following proportions, and
The mixture was mixed in a mill (made by Urethane Coating) for 24 hours. Water 12 parts Ceramo P-17 (manufactured by Daiichi Kogyo Yakuhin Co., Ltd.) 3 parts Ceramo TB-13 (manufactured by Daiichi Kogyo Yakuhin Co., Ltd.)
24 parts Anti-Floss F _1-102 (Daiichi Kogyo Yakuhin Co., Ltd.)
(Manufactured by Wako Pure Chemical Industries) 0.1 part Stearic acid (manufactured by Wako Pure Chemical Industries) 0.6 parts The above mixed powder 60 parts After mixing, the mixture was taken out of the pot mill and molded using doctor blade tape molding technology on a polyester sheet whose surface was coated with Si resin. It was molded. Thickness by doctor blade is 50μ,
The thickness was 100μ and 150μ. After molding, it was dried at room temperature for a day and a night. After drying, the green sheet obtained by peeling naturally from the polyester sheet had a size of 10 cm x 20 cm. Next, punch this sheet to 6 mm square and place it on black alumina (dimensions 31.7 x 13 x 2 mm).
The adhesive side of the sheet was soaked in water and attached to the bottom of the cavity. Also manufactured by Watkins Johnson
The film was fired in an atmospheric atmosphere using a 4MC type thick film firing furnace. The firing conditions were a 60-minute profile from heating to cooling, and the peak temperature was held at 920°C for 10 minutes.
By firing, the green sheet pasted area shrank to 4 mm square, and a good metallized surface was obtained. Example 2 As powder components, 96% gold powder (average particle size 1.3μ) and 4% glass powder (average particle size 5.2μ) were prepared and thoroughly mixed in a V-type mixer. In addition,
The composition of the glass powder is SiO ₂ 15%, B ₂ O ₃ 10%,
The contents were 40% PbO, 20% BaO and 15% ZnO. Water, an acrylic binder, a surfactant, etc. were added to this mixed powder in the following proportions. The above mixed powder 70 parts Ceramo P-17 2.5 parts Ceramo TB-13 20.6 parts Antifloss F-102 0.1 part Stearic acid 0.5 parts Water 10.3 parts Next, this was prepared in the same manner as in Example 1, and 20μ,
A 50μ green sheet was molded, attached to the cavity, and fired at 870°C to obtain a metallized surface. Example 3 Among the powder components, only the metal powder contained 0.4% Pt,
Other than that, the same powder components as in Example 1 were prepared, and Pt and Pd were not included as separate powder components.
Powders containing only Ag were prepared, and green sheets of 50 μm each were formed under the same conditions as in Example 1, adhered to the cavity, and fired to obtain metallized surfaces. However, the firing temperature is Pt
The temperature was set at 910°C when Ag was included, and 920°C when only Ag was used. In each of the above examples, we investigated the film thickness, color tone, and surface roughness of the metallized surface after firing, and also examined the die attachability and after mounting Si chips on the metallized surface by die bonding using an Au-Si preform. After the thermal shock test, a die shock test was carried out and the vertical tensile strength was investigated.
The results are shown in Table 1. Here, die attachability was determined by peeling off the silicon chip after mounting the silicon chip and checking whether an Au-Si eutectic film was formed on the back side of the silicon chip. The ◎ mark indicates that 10 samples were tested, and in all of them, an Au-Si eutectic film was observed on the back surface of the silicon chip. The die-pushability was tested by applying a shear stress to the silicon chip and performing a peel test after mounting the silicon chip. The mark ◎ indicates that 10 chips were tested, and none of the silicon chips peeled off from the metallized surface, and the silicon chips themselves were destroyed. Further, the vertical tensile strength was measured by the following method (see Fig. 4). Ceramic substrate 1 was maintained at 450 DEG C., preform 8 and stud 9 were placed on the metallized surface, rubbed two to three times, and then cooled to prepare a sample as shown in FIG. 4, after which a vertical tensile test was conducted. Stud…Adhesive part diameter 3.3mmφ, Ag plating 10μmt
Copper preform…Au-2%Si, 50μmt×2mm×2
mm Tensile speed...15mm/min Number of measurement points is 10, minimum value 30Kg or more, average value
Must be over 35Kg. It is desirable to be in stud break mode.

[Table] As can be seen from Table 1, the film has no pores, is uniform, has good color tone and surface roughness, and has better die attach properties than the conventional technology. In addition, the results of the die push test were good and the strength was high. (Effects of the Invention) As detailed above, according to the present invention, a conductive paste composition is made into a sheet shape by tape molding technology, and the sheet is pasted onto a desired location on a substrate,
Since the metallization process is performed by firing, there is no need for the dilution, dotting, and leveling processes that are required in conventional metallization processes, simplifying the process, and the resulting metallized surface has improved porosity, color tone, and surface roughness. It has a good and uniform film thickness and has excellent die attach properties. Furthermore, since it is used in sheet form, it is easy to work with, and only the necessary parts can be metalized, and the parts left after punching can be re-kneaded to form a sheet again, reducing the amount of precious metal used and lowering costs. .

[Brief explanation of the drawing]

Fig. 1 shows a state in which a ground for a Si chip is metallized in the cavity part of a sur-deep substrate using a conductive green sheet according to the present invention. Perspective view c is a perspective view when a rectangular green sheet is used, and Figure 2 similarly shows an example in which conductive green sheets are used as the ground for the Si chip and the jumper wire in the cavity and are metallized. 3 is a cross-sectional view, and FIG. 3 is a view showing a state in which the entire bottom of the cavity portion has been metallized as a ground for the Si chip according to the prior art; a is a cross-sectional view, and b is a perspective view;
FIG. 4 is a diagram explaining the vertical tensile strength measuring method. 1... Ceramic substrate, 2... Cavity part,
3... Si chip, 4... Metallized layer, 5... Conductive green sheet, 6... Jumper wire, 7...
...Lead, 8...Prehome, 9...Stud.

Claims (1)

[Scope of Claims] 1. A conductive sheet comprising a conductive paste composition, which is a green sheet formed into a sheet shape and then dried. 2. Molding the conductive paste composition into a sheet shape,
A method for metallizing a ceramic substrate, which comprises punching this sheet into appropriate dimensions, pasting it on a predetermined location on a ceramic substrate, and firing it.