JPH03103337A - Glass for bonding ceramic - Google Patents

Abstract

PURPOSE:To obtain a bonding glass suitable for the bonding of glass ceramic and aluminum nitride by using a glass frit having a restricted composition and containing specific amounts of especially PbO, B2O3, SiO2 and Al2O3. CONSTITUTION:The objective glass is composed of 70-100wt.% of glass frit and 0-30wt.% of a filler and the glass frit is composed of 20-50wt.% of PbO, 1-15wt.% of B2O3, 35-55wt.% of SiO2, 3-15wt.% of Al2O3, 0-15wt.% of MgO+CaO + BaO+SrO, 0-5wt.% of ZnO, 0-5wt.% of TiO2, 0-5wt.% of ZrO2 and 0-5wt.% of Li2O+Na2O+K2O. Since the thermal expansion coefficient of the glass layer of the present bonding glass at the bonding part is close to that of glass ceramic substrate or AlN substrate compared with conventional soldering material such as a silver solder, the reliability of the bonding part can be improved. Furthermore, the number of steps can be decreased because it is not necessary to form a metallized layer on the bonding part of the glass ceramic substrate or the AlN substrate in contrast to soldering process.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a bonding glass for ceramics, and more particularly to a bonding glass suitable for bonding glass ceramics and aluminum nitride.

(Prior art) Conventionally, inexpensive alumina (Al
aOi) It was common to form circuits on a substrate, and to mount various elements such as semiconductor devices thereon.

However, in recent years, with the increase in the output of semiconductor devices, the amount of heat generated by the elements has increased, and a problem has arisen in that the above-mentioned Al20s substrate is not necessarily satisfactory in terms of heat dissipation. In order to solve this problem, the circuit board can be constructed of aluminum nitride (AIN), which has excellent heat dissipation properties, instead of A1i03, but ALN is much more expensive than Alias, and the peripheral parts such as metallization are required. It is difficult to say that it is practical because the technology is behind the times.

Therefore, recently, a circuit board is constructed by combining an Altos board and an AIN board, and by placing the AIN board only under the elements that generate a particularly large amount of heat, composite circuit devices, etc. are constructed, and heat dissipation is improved. Attempts are also being made to reduce costs.

However, since there is a large difference in the coefficient of thermal expansion between AIN and Aliam (AIN is approximately 45 × 10-”C
-', A1xOs has a coefficient of thermal expansion of approximately 75X 10-' °C) Due to this difference in coefficient of thermal expansion during use, stress is generated, which causes cracks in the joint,
In extreme cases, the AIN board fell off. Furthermore, if this circuit board is sealed and made into a package, there are disadvantages such as a decrease in airtightness.

It has also been reported that a special metal layer is formed at the joint between the AIN board and the Alias board in order to alleviate such a difference in thermal expansion and improve reliability. (Special application 1986-16
(No. 1783) However, since the AIN substrate and the Atzox board, which have different coefficients of thermal expansion, are essentially bonded, when an accelerated reliability test is performed, for example, 1000 cycles at +1256C to -50'C, the bonded portion may peel or peel. This has the disadvantage that defects such as cracks occur and the airtightness deteriorates.

Therefore, instead of the Ahos plate, the thermal expansion coefficient is A1aOs.
There are also reports of bonding a glass ceramic substrate and an AIN substrate using a glass ceramic substrate that is closer to an AIN substrate than a plate (Japanese Patent Application No. 286664/1983).
.

However, in this method, the glass-ceramic substrate and the AIN substrate are joined by brazing, and the coefficient of thermal expansion of the brazing filler metal is about five times larger than that of the glass-ceramic substrate or the AIN substrate, so the reliability of the joint is poor. There were some things that were unsatisfactory.

Furthermore, in order to perform brazing, a metallized layer must be formed in advance at each joint between the glass ceramic substrate and the AIN substrate.

? Here, we have reported that a glass ceramic substrate and an AIN substrate are bonded via a glass layer, and that the glass layer has a coefficient of thermal expansion close to that of the glass ceramic substrate and the AIN substrate. (Japanese Patent Application No. 63-28664) However, the composition of the glass was not specified.

(Problems to be Solved by the Present Invention) The present invention has been made to solve the above-mentioned problems, and provides a ceramic bonding glass for bonding a glass ceramic substrate and an AIN substrate. It is.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and the present invention consists essentially of a glass frit of 70 to 100 and a filler of 0 to 30 in weight percent. is expressed as weight %, Pb0 20~50BzOs
1~15SL0■ 35
~55? I. On 3 ~l
5MgO+CaO+BaO+SrO
B ~ l5ZnO
O ~ 5TiO■
0 ~ 5Zr02
0 ~ 5LiaO+Na*0+KiO
The present invention provides a glass for bonding ceramics, characterized in that it consists of O to 5.

In other words, the coefficient of thermal expansion (γ) of the glass layer at the joint is more suitable for glass ceramic substrates and AIN than for conventional brazing filler metals.
Since it is close to the substrate, the reliability of the joint can be increased. Furthermore, since it is not necessary to form a metallized layer at the joint portion of the glass ceramic substrate or the AIN substrate, which is necessary when brazing, the number of steps can be reduced.

Such a glass layer has a thermal expansion coefficient (γ) of 1β - γl < 30, where β is the thermal expansion coefficient of the AIN substrate.
X 10-'C lower. It is desirable that 1β-γ1
If it exceeds 30XIO-"C"', the difference in coefficient of thermal expansion between the glass layer and the glass-ceramic substrate or the aluminum nitride plate is large, and sufficient reliability of the bonded portion cannot be obtained. More preferably, 1β-γ1≦5X to””C-'.

The composition of the glass frit that satisfies the above thermal expansion conditions is within the following composition range.

In the following, % means weight % unless otherwise specified.

? bO20 ~50
%Bias 1 ~
15%Si0■ 35
~55%A1*Os
3 ~15%MgO+CaO+BaO+Sr0
0 to 15% Zn0
0~5%TiO■
0 ~ 5%Zr0■
0 to 5% LizO+NaiO+KzO
It consists essentially of 0 to 5%. In this composition, Sin2 is a glass network former, and if it is less than 35%, the softening point becomes too low, the heat resistance decreases, and deformation tends to occur during re-firing, which is not preferable. On the other hand, Sin. If it is more than 55%, the softening point becomes too high, the wettability with the ceramic substrate deteriorates, and the bonding strength decreases, which is not preferable. It is preferably 40 to 50%. A.I. 0. is essential from the viewpoint of improving the meltability of the glass or the water resistance of the glass properties. If it is less than 3%, there is a risk of devitrification during glass melting, and if it is more than 15%, the glass softening temperature will become too high.

Desirably 3 to 12%.

PbO is used as a flux component to the glass. 20
If the amount is less than %, the glass softening point becomes too high and it becomes difficult to melt the glass. On the other hand, if it is more than 50%, the difference in the thermal expansion coefficients of the glass becomes too large, and stress is generated due to the difference in thermal expansion between the glass ceramic substrate and the AIN substrate, which lowers the bonding strength, which is not preferable. Desirably it is 35 to 45%.

B203 is used as a flux component like PbO, but there is an upper limit in terms of chemical resistance, and the amount introduced is limited. That is, if it is less than 1%, there is no flux effect, and if it is more than 15%, the chemical resistance is significantly reduced. Desirably 1-1O
%.

MgO+CaO+SrO+BaO is added for the purpose of adjusting the thermal expansion coefficient and improving glass meltability. 10l
If the amount exceeds 0%, devitrification occurs during melting, making vitrification difficult.

Although ZnO is not essential, up to 5% of ZnO may be introduced for the purpose of improving solubility.

Although LizO + NazO + KzO is not essential, it is possible to improve the reactivity with the ceramic substrate and the glass meltability by adding it, but it is an unfavorable component in terms of electrical properties, especially insulation resistance properties, so add 5% as necessary. It is preferable to keep it below, preferably 3% or less. ZrO2. Although TiOa is not essential, adding it can improve the chemical resistance of the glass.

The amount is sufficient to be 5% or less, and preferably 3% or less.

In addition to glass frit, AlzOa. Magnesia (MgO). Subinel? Mg
*Si04) + Mullite (3A1i0a・2SiO2)
．． Forsterite (2MgO・SiO■). steatite (MgO・SiO*), cordierite (2MgO
・2A1t01・5SiO■), quartz, AIN, silica (StOz), zircon (ZrSiOs), and other ceramic powders added alone or in combination to the glass frit as fillers are effective in improving bonding strength.

The following ratio of the filler and the glass frit according to the present invention is appropriate.

Glass frit: 70-100% Filler: 0-30'% If the filler exceeds 30%, sinterability deteriorates and is not suitable.

Also, the desirable range is Glass frit 76-80% Filler 4-20% It is.

The composite circuit device according to the present invention will be explained below.

FIG. 1 shows a sectional view of a typical example of a composite circuit device according to the present invention. In Figure 1, 1 is the AIN board, 2.3
is a glass ceramic substrate, 4 is a gold (Au) layer, 5 is A
A joint between the IN substrate 1 and the glass-ceramic substrate 2, 6 an opening in the glass-ceramic substrate 2, 7 a side surface of the glass-ceramic substrate 2.3, 8 a lead frame, 9 a joint between the top cover and the glass-ceramic substrate 3, 10 is an opening of the glass-ceramic substrate 3, 1l is an IC bare chip, 12 is a wire 14 is a glass-ceramic top cover,
It is.

The AIN substrate 1 preferably has a thermal conductivity of IOOW/+nK or more for heat dissipation of the IC bare chip 11 mounted on the AIN substrate l. The AIN
As the substrate 1, for example, commercially available AGN-1, A manufactured by Asahi Glass Co., Ltd.
GN-2 (trademark) etc. can be used.

The composite circuit device according to the present invention includes, for example, the first. The use of glass ceramic substrates 2 and 3 having openings 6 and 10 as shown in the figure has the advantage that IC chips can be easily sealed and the amount of AIN substrate 1, which is unproductive, is reduced.

The opening 6, IO is not limited to one location, and may have a structure having a plurality of openings.

Furthermore, the dielectric constant of the glass ceramic substrates 2 and 3 is preferably less than 9.0 in order to prevent delay in signal transmission speed.

The lead frame 8 is made of Kovar (trademark) 42-alloy (
Trademark) etc. are usually used as materials.

The composite circuit device shown in FIG. 1 described above is manufactured as follows.

FIG. 2 is a sectional view of each component showing the manufacturing procedure of the composite circuit device shown in FIG. 1. In FIG. 2, 13 is a sealing glass, and 15 is a gold plated portion formed on the lead frame 8.

A glass ceramic substrate 2 having an opening 6 and an AIN substrate 1 are prepared, and an organic vehicle is added to the glass frit according to the present invention and kneaded, and a paste is applied so as to form a joint 5. Board 2 and A
It is sufficient to press the IN substrate 1 and bake it to solidify it. The paste may be applied to either the glass-ceramic substrate 2 or the AIN substrate 1, but it may be applied to both the glass-ceramic substrate 2 and the AIN substrate 1.

Next, a gold layer 4 for mounting the bare chip 11 is placed on the AIN board 1.
Form an Au paste by printing or the like.

Note that the ceramic bonding glass of the present invention is not limited to the above-mentioned glass-ceramic substrates, but can also be used for bonding ordinary ceramic substrates.

(Function) In the present invention, since the glass ceramic substrate and the aluminum nitride plate are bonded through a glass layer with a coefficient of thermal expansion close to that of the glass layer, the reliability of the bonded portion is improved compared to conventional bonding by brazing. can be increased. Furthermore, is the glass layer a glass ceramic substrate or an aluminum nitride plate? Since it can be formed directly on the surface, there is no need to form a metallized layer, which is required in conventional brazing bonding, and the number of steps can be reduced.

(Example 1) An organic vehicle was added to a glass frit having the composition shown in Table 1, and the mixture was kneaded in an automatic mortar, and then passed through three rolls to prepare a glass paste. This glass paste was screen printed on an A1On-SiOa-PbO glass ceramic substrate to obtain several dozen pads with a diameter of 2 mm. Next, dry in air at 150°C for 10 minutes, with a dry film thickness of 30
~35 μm. On the other hand, Ag-Pd paste was screen-printed on an AIN substrate made by Asahi Glass (AGN-1) in advance and dried in air at 80°C for 10 minutes to give a dry film thickness of 15 to 17 μm. Bake for a minute. After this firing, the AIN board was cut into 2mm blocks, placed on the glass printing of the glass ceramics board, and fired in air at 850°C for 15 minutes. Joined.

In order to determine the glass bonding strength of the obtained composite of AIN substrate and glass ceramic substrate, Ag-Pd on AIN was used.
A copper bottle of φ=0.8 was soldered to the bottle using the same method, and beer strength was measured. The results are shown in Table-1. The composition of the filler is shown in Table 2. As a pass/fail criterion, when the glass layer was observed under a microscope as a dense sintered body with good hermetic properties, it was given a score of 0, and when the glass layer had good hermetic properties but some bubbles were observed, it was given a score of ○. (The bonding strength is at least 2
It is desirable that the weight is 72mm0 or more. ) As is clear from Table 1l, in all Examples 1 to 23, the bonding strength was 2. By optimizing the composition of the glass, the type of filler, the amount added, etc., it is possible to obtain a high bonding strength that exceeds the bonding strength of 10kg/2mm.

On the other hand, as shown in the comparative examples, in comparative examples 1 to 5, the bonding strength was 2. Although there are some that exceed 0 kg/2 mm, in most cases the AIN substrate and the glass ceramic substrate are not bonded, and in terms of the sinterability of the glass layer, the result is a low-density sintered body with very many pores, resulting in poor sealing performance. I think there is a problem in this respect.

(Example 2) A green sheet having a thickness of 1.2 mm was prepared by adding a plasticizer and a solvent to a glass frit, cross-wiring the glass frit, and molding the glass frit.

The above glass frit composition is Sins 44%, Al2
on 5%, B. 0.5%, Ba0 5911;,
It contained 41% Pb0.

This green sheet has an outer size of 30 mm square with 201 square meters in the center.
Shape with III+ corner opening and 25m in the center
Punch out 100 sheets each into a shape with an m square opening, 1
A glass ceramic substrate having openings 6 and 1o as shown in FIG.
I got the seeds.

The thermal expansion coefficient α of this glass ceramic substrate is 45X
It was 10-"C-'.

Apart from this, commercially available AIN board (25x 25x 1.
0+nm) (AGN-2 manufactured by Asahi Glass, thermal conductivity 2
00W/mK, thermal expansion coefficient 45X 10""C"')
A gold layer 4 was formed by printing a gold paste on the substrate and firing it in air at 900° C. for 3 hours.

Then PbO 4 1%, B. O15%, SiO
An organic vehicle was added to a glass frit consisting of 44% Z, 5% AlzOa, and 5% Mg0, and the mixture was kneaded in an automatic mortar and passed through three rolls to prepare a glass paste.

The composition of the organic vehicle was ethyl cellulose: 5%,
Consisted of 95% alpha-terpineol. and,
This glass paste was applied to the above AI. Screen printing was performed on the bonding portion of the N substrate, and the glass ceramic substrate having the above-mentioned opening was bonded to the glass ceramic substrate, and the glass ceramic substrate was bonded to the AIN substrate by firing in air at 850° C. for 10 minutes. The thermal expansion coefficient of the glass layer at this joint is 43X.
It was 10-T°C-'.

Next, sealing glass paste was printed on the upper surface of the glass ceramic substrate bonded to the AIN substrate and the lower surface of the glass ceramic substrate that was to become the upper side, and a Kovar lead frame was sandwiched between them. By heating for 10 minutes, a glass ceramic substrate having an opening was bonded with this Kovar lead frame in between. Next, this Kovar lead frame was bent to obtain a composite circuit device as shown in FIG. Note that the tip of the Kovar lead frame used was gold-plated in advance.

Next, as shown in FIG. 1, the bare chip was bonded onto the AIN substrate at 430° C., and then bonded with gold wire.

Then, the above-mentioned upper lid is joined by heating it at 380° C. for 10 minutes using a sealing glass paste, and the first
A composite circuit device as shown in the figure was obtained.

In this composite circuit device, 1α-β+ = + 44X 10-'-45 X 1
0-7= IX 10-"C-' 1β-γI = l 45X 10-'-43 X 1
0-? =2×10-'°C-1.

For 1000 pieces of this composite circuit device, +250℃~
-50℃ heat cycle test for 30 minutes 1000 times
Although it was cycled, there was no occurrence of defects such as peeling/separation of joints or cracks, and both airtightness and reliability were sufficient.

(Comparative example) In the same manner as in Example 2, St (1245%, Aiao
A glass ceramic substrate having an opening as shown in FIG. 1 was obtained using a glass frit containing slO%, 5% BgOa3, and 10% BaQ. The coefficient of thermal expansion of this glass-ceramic substrate was 62 x 10-'°C-1.

Next, silver (
Ag) A metallized layer was formed.

Apart from this, on the Asahi Glass AIN board (AGN-2),
A gold metallized layer and a silver metallized layer were formed.

Next, the glass ceramic substrate having the silver metallized layer and the AIN substrate were soldered with silver solder (Ag72%, C
Bonding was carried out by heating at 900° C. for 10 minutes using U 28%). The thermal expansion coefficient of this silver solder is 190X1
It was 0-'°C-1.

Thereafter, in the same manner as in Example 2, a composite circuit device shown in FIG. 1 was obtained.

In this composite circuit device, the coefficient of thermal expansion of the glass ceramic is α, and the coefficient of thermal expansion of the aluminum nitride plate is β.
, if the coefficient of thermal expansion of the silver soldered joint is γ, then 1α - βl = l 62X 1.0-'-45 X
10-' 1= 17 xlO-'℃"1 1β-γI = l 45X 10-'-190X 1
0-71 = 145X 10"'°C"1.

A heat cycle test of -50° C. + 125° C. was conducted for 1,000 composite circuit devices for 1,000 cycles, but no defects such as peeling of joints or clutches occurred. However, the conditions are more severe -5
When a heat cycle test of 0°C - 250°C was performed for 1000 cycles, minute cracks were found in 1 out of 1000 cases, and when the cycle was continued to 2000 cycles, 1 out of 1000 cases showed peeling, and 13 out of 1000 cases showed peeling. Small cracks were observed.

(Effects of the Invention) The thermal expansion coefficient of the glass layer of the joint of the present invention is higher than that of conventional brazing materials such as silver solder.
Since it is close to the N substrate, the reliability of the joint can be increased. Furthermore, since it is not necessary to form a metallized layer at the joint portion of the glass ceramic substrate or the AIN substrate, which is necessary when brazing, the number of steps can be reduced.

[Brief explanation of drawings]

FIG. 1: A sectional view of a typical example of the composite circuit device of the present invention. FIG. 2: A cross-sectional view of each component showing the manufacturing procedure of the composite circuit device shown in FIG. 1. 1: AIN board 2.3: Glass ceramics board 5: Joint part

Claims (1)

[Claims] (1) Glass frit is substantially 70 to 10 in weight%
0, filler 0 to 30, and the glass frit is substantially composed of: PbO, 20 to 50 B_2O_3, 1 to 15 SiO_2, 35 to 55 Al_2O_2, 3 to 15 MgO+CaO+BaO+SrO, 0 to 15 ZnO, 0
-5 TiO_2, 0-5 ZrO_2, 0-5 Li_2O+Na_2O+K_2O, 0-5. Glass for bonding ceramics.