JPH06340443A - Glass composition and glass-coated aluminum nitride sintered compact - Google Patents

Abstract

PURPOSE:To produce a glass capable of directly and densely adhering to an aluminum nitride sintered compact under high strength. CONSTITUTION:This glass composition for coating aluminum nitride consists of, by weight, 35-45% SiO2, 15-20% Al2O3, 3-15%, in total, of 0-15% PbO and 0-15% ZnO, 12-18%, in total, of MgO, CaO, SrO and BaO, 12-20%, in total, of ZrO2 and TiO2, 0-10% B2O3 and 0-2% Sb2O3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly heat-conductive circuit board having a glass layer which can be firmly bonded to aluminum nitride without cracking or foaming, and more particularly to a glass composition thereof and glass-coated aluminum nitride. The present invention relates to a sintered body and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a circuit board for a semiconductor, a circuit is generally formed by forming a circuit on an inexpensive alumina (Al ₂ O ₃ ) substrate and mounting various elements such as a semiconductor device on the circuit. Met.

[0003] However, in recent years, along with the large output of the semiconductor device, the heating value of the element is increasing, the above Al ₂ O
The problem with ₃ substrates is that they are not always satisfactory in terms of heat dissipation. To solve this problem, Al ₂
Instead of O ₃ , aluminum nitride (Al
The circuit board may be composed of N). However, AlN is A
It is much more expensive than l ₂ O ₃ , and it is hard to say that it is practical because peripheral technologies such as metallization are delayed.

Therefore, the surface of the aluminum nitride sintered body is previously oxidized by using a thermal oxidation method or a plasma oxidation method,
The method of coating with glass or metallizing on it is generally used (JP-A-3-177375, JP-A-3-14986).
No. 0, JP-A-2-306653, JP-A-61-119.
094, JP-A-62-46986).

In this case, the reason for forming the oxide film is that the oxide such as glass and aluminum nitride have poor wettability, and that the adhesion and airtightness cannot be obtained due to foaming by the reaction gas. . At this time, an oxide film of at least several μm is required. At this time, the main component of the obtained oxide film is usually α-Al ₂ O ₃ , and its coefficient of thermal expansion is 75 × 1.
Since it is 0 ^-7 / ° C (45 x 10 ^-7 / ° C for AlN), which is significantly different from aluminum nitride, it causes a decrease in adhesion after various reliability tests (especially heat cycle tests).

[0006]

DISCLOSURE OF THE INVENTION The present invention is intended to eliminate the above-mentioned drawbacks of the prior art, and is dense and high in strength directly with an aluminum nitride sintered body which has not been known so far. The present invention newly provides a circuit board having a high thermal conductivity on which a glass layer for coating aluminum nitride, which can be adhered by the method described above, is formed.

[0007]

The present invention has been made to solve the above-mentioned problems, and is a glass composition provided on an aluminum nitride sintered body, wherein SiO ₂ : 35
_{~45wt%, Al 2 O 3:} 15~20wt%, Pb
O: 0 to 15 wt%, ZnO: 0 to 15 wt%,
PbO + ZnO = 3-15 wt%, MgO + CaO + S
rO + BaO: 12-18 wt%, ZrO ₂ + TiO
_{2: 12~20wt%, B 2 O} 3: 0~10wt%, S
It is intended to provide a glass composition consisting essentially of b ₂ O ₃ : 0 to ₂ wt%, and a glass-coated aluminum nitride sintered body using the same. By doing so, it is possible to obtain a high thermal conductivity circuit board in which a glass layer is directly formed on the aluminum nitride sintered body without an oxide film layer interposed.

In view of the problems of the prior art as described above, the present inventors have made research efforts to directly adhere glass to an aluminum nitride (hereinafter abbreviated as AlN) sintered body, and as a result, the above composition was obtained. According to the glass composition of,
It has been found that a highly heat-conductive circuit board having a glass layer is obtained. According to this, since the coefficient of thermal expansion of glass is closer to that of AlN than that of the conventional AlN surface oxide layer, it is possible to increase the adhesive force and reliability of the joint.
Furthermore, since it is not necessary to oxidize the AlN surface, the number of steps can be reduced.

The glass layer has a coefficient of linear thermal expansion of α
(Room temperature to 350 ° C) 15 × 10 ^-7 / ° C ≦ α ≦ 5
It is preferably 5 × 10 ⁻⁷ / ° C. Considering the compressive stress and tensile stress applied to the glass due to the difference in thermal expansion between AlN and glass, the compressive stress is generally about 1000 kg.
The reason for this is that if the tensile stress is about 200 kg or less, defects such as cracks and peeling do not occur in the glass, and more preferably, 30 × 10 ⁻⁷ / ° C. ≦ α ≦ 45 × 10 ⁻⁷ / ° C. and a slight compressive stress. When glass is coated with glass to give it strength, it shows high adhesion even after various reliability tests.

The glass composition of the present invention is as follows. That in weight _{percentages, SiO 2: 35~45wt%, Al} 2 O 3: 15~20wt%, PbO: 0~15wt%, ZnO: 0~15wt%, however, PbO + ZnO = 3~15wt%, MgO + CaO + SrO + BaO: 12 _{~18wt%, ZrO 2 + TiO 2} : 12~20wt%, B 2 O 3: 0~10wt%, Sb 2 O 3: in which consists essentially of 0-2 wt%.

[0011] More preferably, in weight _{percentages, SiO 2: 37~43wt%, Al} 2 O 3: 16~19wt%, PbO: 0~12wt%, ZnO: 0~12wt%, however, PbO + ZnO = 5 to 10 wt%, MgO + CaO + SrO + BaO: 13 to 17 wt%, ZrO ₂ + TiO ₂ : 13 to 18 wt%, B ₂ O ₃ : 0 to 10 wt%, and Sb ₂ O ₃ : 0 to 1 wt%.

In such a composition, SiO ₂ is a glass network former and is essential as a main component of precipitated crystals. If it is less than 35 wt%, the crystallization becomes insufficient, and 45w
If it exceeds t%, the softening point becomes too high, which is not preferable.
It is preferably 37 to 43 wt%.

Al ₂ O ₃ is also a main component of precipitated crystals and is essential. If it is less than 15 wt%, the crystallization will be insufficient, and if it exceeds 20 wt%, the softening point will be too high, the wettability with the ceramic plate will be deteriorated, the bonding strength will be lowered, and devitrification may occur during glass melting, which is not preferable. Preferably 1
It is 6 to 19 wt%.

Next, ZnO + PbO is indispensable as a flux component to the glass, and if it is less than 3 wt%, the glass softening point becomes too high, and it may be difficult to melt and devitrify. on the other hand,
If it exceeds 15 wt%, the melting point of the glass tends to be too low, and a foaming reaction occurs with the aluminum nitride sintered body. Preferably 5
It is 10 wt%.

B ₂ O ₃ is used as a flux component similarly to ZnO + PbO, but it is a selective component and may not be added. When added, there is an upper limit from the viewpoint of chemical resistance and 10
If it is added in excess of wt%, the chemical resistance will be significantly reduced. Further, the softening point of the glass is lowered, which is not preferable. It is preferably 0 to 10 wt%.

MgO + CaO + SrO + BaO is essential for adjusting the coefficient of thermal expansion and the main component of precipitated crystals, and is 12 wt%.
If it is less than 18% by weight, crystallization becomes insufficient, and if it exceeds 18% by weight, devitrification occurs during melting of the glass, which makes vitrification difficult. Preferably 13
Is about 17 wt%.

TiO ₂ + ZrO ₂ is indispensable as a crystal nucleating agent, and if it is less than 12% by weight, crystallization is insufficient and 20
If it exceeds wt%, it will devitrify. It is preferably 13 to 18 wt%.

Finally, Sb ₂ O ₃ is a selective component to be added as a fining agent and may not be added. Further, even if added in excess of 2 wt%, the fining effect will be saturated, so 2 wt% or less is sufficient. It is preferably 0 to 1 wt%.

The composition according to the present invention may be prepared by adding an organic binder thereto and adding a solvent such as acetone or α-terpineol.

By crystallizing the glass powder of this composition at 800 ° C. or higher, it is possible to have heat resistance in the firing temperature range of 800 to 900 ° C. of the thick film material for general alumina.

When a thick film Ag / Pd conductor for alumina (TR4846 manufactured by Tanaka International) was actually baked on the surface of the AlN sintered body coated with this glass, the solder wettability was 100% and the adhesion strength was 2.0 kg / 2 mm □ or more. No swelling or peeling occurred, and even after the reliability test, the same results as those obtained by attaching this conductor to the alumina sintered body were obtained.

The AlN sintered body used in the present invention is an atmospheric pressure sintered by adding additives such as a rare earth element and an alkaline earth element to the AlN raw material (about 0.01 to 15 wt% in terms of metal element) and hot sintering. Method of pressing, A without adding additives
It is manufactured by an atmospheric pressure sintering method, a hot pressing method, or the like using the 1N raw material alone. The present invention can be applied to any AlN sintered body manufactured by any method regardless of the presence of additives.

Further, the glass film thickness of the present invention is preferably 0.1 to 50 μm or less so as to have 50 W / mK or more so as not to deteriorate the high thermal conductivity of the AlN material. If the thickness is less than 0.1 μm, it is difficult to uniformly coat the AlN sintered body, and reaction foaming may occur with the metallized portion on this and high adhesion may not be obtained.
This is because if it exceeds m, 50 W / mK cannot be obtained because the thermal conductivity of the glass itself is low.

The glass-coated AlN sintered body of the present invention is
After forming a circuit on the single-layer substrate, glass powder such as borosilicate glass is mixed with an organic binder to form a paste, which is printed on the surface of the substrate to form a borosilicate layer. It may be used as a multi-layer substrate formed by heating at a temperature equal to or higher than the softening point of glass, firing, and mutually bonding.

[0025]

EXAMPLE An organic vehicle was added to glass powder having the composition shown in Tables 1 and 2 and kneaded in an automatic mortar, and further 3
This roll was passed several times to produce a glass paste. This glass paste was screen-printed on an AlN substrate (AGN-2) manufactured by Asahi Glass to obtain a 2 inch square glass coating surface. Next, it was dried in air at 150 ° C. for 10 minutes to give a dry film thickness of about 10 μm.

On the other hand, in Table 1 and Table 2, No. For Nos. 13 to 16, the above glass paste was diluted with α-terpineol to prepare a glass powder dispersion solution, which was added to the above Al.
2 cc was dropped on the N substrate, and 3 by spin coating.
The glass solution is coated by keeping the rotation speed of 000 rpm for 30 seconds. After that, it was dried at 150 ° C. for 10 minutes to give a dry film thickness of 2 to 3 μm.

These glass-coated AlN substrates were kept in air at a predetermined temperature of 1000 to 1200 ° C. for 30 minutes at the maximum temperature, and the obtained glass-coated AlN substrates were fractured by a diamond cutter to obtain fracture surfaces and glass surfaces. Observation of foaming, cracks, peeling, etc. with a scanning electron microscope,
The thermal conductivity of the glass-coated AlN substrate was measured by the optical alternating current method. In addition, Ag / Pd conductor paste (TR4846 made by Tanaka International) as a thick film material for alumina was printed on the glass on these glass-coated AlN substrates by a screen printing method, and held and baked in air at 850 ° C. for 10 minutes, Metallized on AlN.

The resulting metallized AlN substrate was observed by an optical microscope for swelling, peeling, discoloration, etc. of the Ag / Pd conductor, and after applying flux (XA100 manufactured by Tamura Kaken Co., Ltd.) on a hot plate, 120 ° C. Preheat for several tens of seconds, then solder in dip bath,
The adhesive force between the glass and the AlN substrate was measured for the conductor portion of the 2 mm □ pad by using a solder-coated copper wire of 8 mmφ by the peel tension test method (n = 10 indicates the strength average value).

[0029]

[Table 1]

[0030]

[Table 2]

Further, No. 1 in Table 1 and Table 2 2 and No. 16
The test was also performed after various reliability tests under the following conditions (see Table 2). High temperature holding test: 150 ° C x 50 to 1000 hours High temperature and high humidity test: 80 ° C, 90% RH x 50 to 1000 hours
Time Heat cycle test: -65 ° C x 30 minutes ← → room temperature x 1
5 minutes ← → 150 ° C × 30 minutes 50 to 1000 cycles

At this time, as a comparative example, after keeping the AlN surface at a high temperature of 1200 ° C. for 0.5 to 10 hours in air, it was confirmed by an X-ray diffractometer that α-alumina was present in the surface layer, and a scanning electron microscope was used. The thickness of the alumina was measured with a film thickness of 2 μm, 5 μm, and 10 μm.
The above Ag / Pd conductor was metallized on the N substrate and the alumina substrate, and the adhesion was evaluated in the same manner. The appearance in the table is ○
Is good, and x is foamed or cracked.

[0033]

[Table 3]

[0034]

EFFECTS OF THE INVENTION The present invention provides a high thermal conductivity circuit board having a glass layer which can be directly and closely adhered to an aluminum nitride sintered body with high strength. That is, the process becomes easy by directly bonding the glass having the same coefficient of thermal expansion to the aluminum nitride sintered body,
In addition, high reliability can be realized, and metalization of a general thick film material for alumina or the like can be performed thereon.

Front page continued (72) Inventor Kazuki Orihara 1160 Matsubara, Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Pref., A-G Technology Co., Ltd. (72) Koichi Shibuya 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Asahi Glass Co., Ltd.

Claims (4)

[Claims] 1. A glass composition provided on an aluminum nitride sintered body, comprising: SiO ₂ : 35 to 45 wt%, A
_{l 2 O 3: 15~20wt%,} PbO: 0~15wt
%, ZnO: 0 to 15 wt%, provided that PbO + ZnO =
3-15 wt%, MgO + CaO + SrO + BaO: 1
2-18 wt%, ZrO ₂ + TiO ₂ : 12-20 wt
_{%, B 2 O 3: 0~10wt} %, Sb 2 O 3: 0~2w
A glass composition consisting essentially of t%. 2. A glass-coated aluminum nitride sintered body, comprising a layer of the glass composition according to claim 1 provided on the aluminum nitride sintered body and crystallized. 3. A glass-covered aluminum nitride sintered body, comprising a glass layer having a linear thermal expansion coefficient of 15 to 55 × 10 ⁻⁷ / ° C. provided on the aluminum nitride sintered body. 4. A method for producing a glass-coated aluminum nitride sintered body, which comprises providing a layer made of the glass composition according to claim 1 on an aluminum nitride sintered body and crystallizing at a temperature of 800 ° C. or higher.