JP2825262B2 - Method for forming thick film on AIN substrate - Google Patents

Description

Description: Object of the Invention (Industrial application field) The present invention relates to a thick film paste that can be used as a conductor, a resistor or a dielectric, and particularly a thick film suitable for use in an AlN substrate. Regarding paste.

(Prior Art) With the recent miniaturization of electronic devices, with the demand for high-density mounting of elements, heat dissipation of a substrate on which the elements are mounted has become a problem. To solve this problem, Al ₂ O ₃
An AlN substrate, which has a thermal conductivity 5 to 10 times larger than that of a substrate and also has excellent electrical insulation properties, has attracted attention. To put this AlN substrate into practical use, a thick film paste suitable for forming conductors, resistors, dielectrics, and the like on the AlN substrate is indispensable.

A thick film paste that can be suitably used on such an AlN substrate requires sufficient bonding strength with the AlN substrate in addition to the required electrical characteristics when fired to form a thick film. . The bonding strength between the AlN substrate and the thick film is determined by the adhesiveness derived from the reactivity between AlN and the material used for the thick film paste,
The presence or absence of a foaming phenomenon accompanying such a reaction
It is known that it depends on the difference in thermal expansion coefficient between the substrate and the thick film paste. In other words, when the reactivity between AlN and the thick film paste is large, a kind of bonding layer made of a reaction product is generated at the interface between the AlN substrate and the thick film, and the adhesion between the AlN substrate and the thick film increases, and the bonding strength increases. Is strengthened. However, when the foaming phenomenon of generating gas such as N ₂ and NO ₂ becomes severe due to such a reaction, a large number of blisters and Al
Due to a gap at the interface between the N substrate and the thick film, etc.
The joining strength is rapidly reduced. Furthermore, if the difference between the thermal expansion coefficients of the AlN substrate and the thick film paste is large, excessive stress is generated in the AlN substrate or the thick film when cooled to room temperature after heating during firing, and the thickness is larger than that of the AlN substrate. The film is easily peeled, and the bonding strength is reduced.

Considering the bonding strength between the AlN substrate and the thick film paste, the thick film paste that has been used for the Al ₂ O ₃ substrate does not satisfy the above requirements and cannot be applied to the AlN substrate. . Therefore, the development of a new thick-film paste that can be applied to AlN substrates has been promoted.
HYBRIDS vol.4, No.4 discloses a thick film resistor paste containing a ternary crystallized glass component of ZnO, B ₂ O ₃ and SiO ₂ . However, even in a thick film paste newly developed for such an AlN substrate, Al
The bonding strength with the N substrate was not enough to be practical.

(Problems to be Solved by the Invention) Although the AlN substrate has excellent characteristics as described above, it has a sufficient bonding strength with the AlN substrate and can be directly formed on the AlN substrate. Has not yet been put to practical use.

In view of such a problem, an object of the present invention is to provide a thick film paste that can be directly formed on an AlN substrate.

[Configuration of the invention]

(Means and Actions for Solving the Problems) In the present invention, ZnO of 20% or more and 70% or less and B of 10% or more and 70% or less in terms of% by weight when converted into oxides.
_It contains a glass component having a composition in which ₂ O ₃ , 30% or less of SiO ₂ , and 40% or less of an additive component are mixed, and the additive component is 20% or less of Al _{2 by} weight% in the glass component. O
₃ , 10% or less of PbO, 10% or less of CuO, 10% or less of Bi ₂ O ₃ ,
At least one selected from the group consisting of MgO of 20% or less, ZrO _{2 of} 40% or less, P ₂ O ₅ of 10% or less, and ZnF _{2 of} 5% or less.
Forming a thick film paste made of a seed on the surface of an AlN substrate, and sintering the thick film paste.
This is a method for forming a thick film on a substrate.

The thick film paste usually contains a glass component, a functional component (a conductive material, a dielectric material, and the like) and an organic vehicle in a desired ratio. In the present invention, the glass component is prepared from components having the above-described composition ranges. Configured. That is, the thick film paste of the present invention is obtained by dissolving the glass component in an organic vehicle together with an appropriate amount of the functional component. The functional component is a metal material such as Ag, Pd, or Cu in a conductor thick film paste, a resistor material such as RuO _{2 in} a resistor thick film paste, or a dielectric material such as BaTiO ₃ in a dielectric thick film paste. Material. However, in the dielectric thick film paste, since the glass component has a property as a dielectric, a thick film paste containing no functional component separately from the glass component may be used.

The present inventors formed a thick film paste containing a glass component consisting of a ternary system of ZnO, B ₂ O ₃ and SiO _{2 on} an AlN substrate in order to examine the bonding strength between the AlN substrate and the thick film paste,
When the change in the interface during firing was observed, the following knowledge was obtained.

ZnO and SiO ₂ react with AlN to form a reaction product such as ZnAl ₂ O ₄ at the interface, thereby increasing the adhesion between the AlN substrate and the thick film.
The reaction involves the foaming of N ₂ and NO ₂ gas at the interface, but as the reaction proceeds, a bonding layer consisting of the reaction product is formed at the interface, so that the subsequent foaming does not occur with the reaction . Also, the amount of N ₂ and NO ₂ gas generated before the formation of the bonding layer is small, and no blistering which causes deterioration of the bonding strength is generated. In addition, B ₂ O ₃ forms a liquid phase film at the interface during firing, and Al
It has the function of suppressing the foaming phenomenon due to the reaction of N. Also, the above three-component glass component may partially crystallize depending on the composition range and firing conditions, but the smaller the amount of such crystallization, the stronger the bonding strength between the AlN substrate and the thick film. Is done. The reason for this is not particularly clear, but it is presumed that when the glass component crystallizes, the effective contact area with the substrate decreases, and the adhesive effect of the glass weakens.

Next, based on such knowledge, the present inventors conducted experiments by changing the composition range of the above-mentioned ternary system in the glass component. As a result, the weight ratio of ZnO was 20% or more and 70% or less, and B ₂ O
_{When 3} was 10% or more and 70% or less and SiO ₂ was 30% or less, it was found that the adhesive strength between the AlN substrate and the thick film was strong. Further, it is preferable that SiO ₂ be contained in an amount of 1% by weight or more. In such a composition range, the thermal expansion coefficient of the glass component is 3.0 to 4.6 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the AlN substrate is 4.4.
It is close to × 10 ^-6 / ° C, and the crystallization component in the glass component is also small.

Further, the present inventors have searched for an additive to a ternary system having the above composition range in order to further increase the adhesive strength between the AlN substrate and the thick film, and have found the following.

PbO, CuO, and Bi ₂ O ₃ are highly reactive with AlN at a high temperature of 500 ° C. or higher, and the adhesion between the AlN substrate and the thick film is increased by adding it to the glass component. However, PbO, CuO or Bi ₂ O ₃
As the reaction between AlN and AlN progresses, blistering occurs due to the generation of N ₂ gas.
Not more than 10% by weight. Especially PbO Because the accompanied vigorous foaming phenomenon causes a reaction of AlN and _{2AlN + 3PbO → Al 2 O 3} + 3Pb + N 2, 5 wt%
The addition content of less than is preferred. Further, the total content of the three components of PbO, CuO and Bi ₂ O ₃ is preferably 10% by weight or less. Also, by adding Al ₂ O ₃ , MgO, and ZrO ₂ to the glass component, the same effects as those of PbO, CuO, and Bi ₂ O ₃ can be obtained.
The reactivity with 1N is smaller than that of PbO, CuO, Bi ₂ O _3
The maximum content of ₂ O ₃ and MgO is 20% by weight, and the maximum content of ZrO ₂ is 40% by weight.

Further, since P ₂ O ₅ and ZnF ₂ have a function of suppressing crystallization of the glass component, the addition thereof enhances the bonding strength between the AlN substrate and the thick film. P ₂ O ₅ up to 10% by weight, ZnF ₂
Adding content of up to a maximum amount 5 wt% is acceptable, especially P ₂ O ₅
Has a great effect on suppressing crystallization of the glass component.

Therefore, in the ternary system of ZnO, B ₂ O ₃ and SiO _{2 in} the composition range described above, Al ₂ O ₃ , PbO, CuO, Bi ₂ O ₃ , MgO,
A thick film paste containing an amorphous component mainly containing a glass component containing at least one of ZrO ₂ , P ₂ O ₅ , and ZnF ₂ ,
It has excellent bonding strength with AlN substrates and can be formed directly on AlN substrates. However, the effect of each additive is 0.1
It becomes remarkable at more than weight%. Further, among the added components, P ₂ O ₅ is particularly preferred because of its crystallization preventing effect.

(Example) Hereinafter, an example of the present invention will be described in detail.

Example 1 Ag having an average particle size of 0.5 μm and an average particle size of 0.8 μm were used as the conductor material.
90/10 (wt%) mixed powder of m Pd (Mitsui Metal Mining)
Was used, and a glass component having a composition shown in Table 1 as a glass component was added in an amount of 5% by weight based on the conductive material. These were thoroughly mixed with a vehicle obtained by dissolving the binder component ethyl cellulose (manufactured by Tokyo Chemical Industry) in terpineol (manufactured by Wako Pure Chemical Industries) to prepare a uniform thick film conductor paste.

The obtained thick film conductor paste is directly applied to an AlN substrate (Toshiba T
AN-170) 2 × 2m using a 325 mesh screen
After printing in a square shape of 120 m and drying in air at 120 ° C for 10 minutes, 85
Calcination was performed in air at 0 ° C. for 10 minutes. After firing, the surface of the thick film was visually observed and observed with an optical microscope, and no blister was observed.

Next, a soft copper wire (about 0.5 mm
φ) was soldered, pulled up at a speed of 0.2 cm / sec by an Instron tensile tester, and the load when peeling occurred was measured to evaluate the adhesion to the AlN substrate. The results are shown in Table 1. Each of the thick films had a tensile strength of 1.0 kg / mm ² or more, indicating that they had sufficient adhesion.

Furthermore, a heat cycle test (-
55 ° C, 30 minutes + 125 ° C, 30 minutes; 1000 cycles).
The intensity ratio S ₁₀₀₀ / S ₀ of the heat cycle tester to the initial tensile strength shown in Table 1. For any thick film
S ₁₀₀₀ / S ₀ was 0.80 or more, and almost no deterioration in strength was observed even after the heat cycle test.

Thus, the thick film conductor paste according to the present embodiment is
It has good adhesion to the substrate, no blistering, shows sufficient resistance to the heat cycle test, and has excellent bonding strength with the AlN substrate. Further, it can be seen that particularly excellent bonding strength was obtained with the thick film conductor paste containing P ₂ O ₅ .

Example 2 RuO ₂ having an average particle size of 0.4 μm (manufactured by Soegawa Rikagaku Co., Ltd.) was used as a material for a resistor, mixed with the same glass components as in Example 1 at a weight ratio of 60:40, and mixed with Example 1. The mixture was mixed with the same vehicle as in Example 1 to prepare a thick film resistor paste.

The obtained thick film resistor paste was used in the same manner as in Example-1.
3 × 3mm using 325 mesh screen on AlN substrate
After printing in a pattern of
Calcination was performed in air at ℃ for 10 minutes. After firing, the surface of the thick film was visually observed and observed with an optical microscope, and no blister was observed.

Next, the adhesion to the thick AlN substrate was examined. Since the resistor contained a large amount of glass components and soldering of the lead wire was not possible, the AlN substrate and the thick film were cut in a direction perpendicular to the interface, and the fracture surface was observed by SEM (scanning electron microscope). . As a result, it was found that at the interface between the AlN substrate and the thick film, the glass component firmly adhered the two,
It was confirmed that sufficient adhesion was obtained.

Example 3 BaTiO ₃ having an average particle diameter of 10 μm (manufactured by Kojundo Chemical Laboratory) was used as a dielectric material and mixed with the same glass components as in Example 1 at a weight ratio of 80:20. -1 was mixed with the same vehicle to prepare a thick film dielectric paste.

The obtained thick film dielectric paste was fired in the same manner as in Example 2, and the same observation as in Example 2 was performed. AlN
No blistering is observed at the interface between the substrate and the thick film,
It was also confirmed that sufficient adhesion was obtained.

Comparative Example A thick film conductor paste was prepared in the same manner as in Example 1 using a glass component having the composition shown in Table 2. The obtained thick film conductor paste was fired in the same manner as in Example 1 to form a thick film on the AlN substrate. After the firing, the surface of the thick film was visually observed and observed with an optical microscope. As a result, many blisters were observed on the surface of each of the thick films.

Was further repeated except tensile strength test and heat cycle test as in Example 1, the deviation also tensile strength as shown in Table 2 0.6 kg / mm ² or less, S ₁₀₀₀ / S ₀ is 0.5
0 or less, and the bonding strength between the AlN substrate and the thick film was much lower than in Example-1.

Also, using the glass components having the compositions shown in Table 1, thick film resistor pastes and thick film dielectric pastes were prepared in the same manner as in Examples 2 and 3 to form resistors and dielectrics on the AlN substrate. did. When the surface of each thick film was visually observed and observed with an optical microscope, many blisters were observed, and it was found that the bonding strength between the AlN substrate and the thick film was insufficient.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a thick film paste which has excellent bonding strength with an AlN substrate and can be directly formed on an AlN substrate.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C04B 41/80-41/91

Claims (1)

(57) [Claims] (1) 20% or more and 70% or less of ZnO and 10% or more and 70% or less of B in terms of weight% when the constituent components are converted into oxides.
_It contains a glass component having a composition in which ₂ O ₃ , 30% or less of SiO ₂ , and 40% or less of an additive component are mixed, and the additive component is 20% or less of Al _{2 by} weight% in the glass component. O
₃ , 10% or less of PbO, 10% or less of CuO, 10% or less of Bi ₂ O ₃ ,
At least one selected from the group consisting of MgO of 20% or less, ZrO _{2 of} 40% or less, P ₂ O ₅ of 10% or less, and ZnF _{2 of} 5% or less.
A method for forming a thick film on an AlN substrate, comprising: a step of forming a thick film paste made of a seed on the surface of an AlN substrate; and a step of sintering the thick film paste.