JP2754806B2 - Conductor paste for aluminum nitride substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] With regard to a conductor paste for an aluminum nitride substrate, the purpose is to put a conductor paste having a low conductor resistance value into practical use, and perform screen printing on an aluminum nitride / green sheet and then sintering. The conductive paste used to form the conductive pattern is characterized in that 0.2 to 0.7% by weight of aluminum nitride powder is added to tungsten powder, and a binder and a solvent are added to the powder and kneaded. A conductor paste for a substrate is formed.

[Industrial applications]

The present invention relates to a conductor paste for an aluminum nitride substrate having a small conductor resistance.

Due to the necessity of processing a large amount of information at high speed, information-requiring devices have been reduced in size and capacity, and LSIs and VLSIs have been put into practical use as semiconductor integrated circuits, which are the main components of the devices, have been improved in integration degree.

Then, these integrated circuits are mounted on a chip mounting substrate (interposer) made of ceramics in the form of a chip, and then an LSI module is manufactured, and this is mounted on a printed wiring board or the like as a replacement unit. There is.

As described above, the degree of integration of a semiconductor integrated circuit increases, and the amount of heat generated by the device increases at an accelerated pace as high-density mounting is performed.

In other words, the calorific value per IC-chip is about 3.5W at first
Although the amount of heat was small, the amount of heat generated per LSI chip has now increased to about 10W.If a large number of these chips are mounted in a matrix, the amount of heat generated is enormous, and this is likely to increase further. is there.

Conventionally, a chip mounting substrate on which an LSI chip or the like is mounted has been made of alumina (Al ₂ O ₃ ) having high thermal conductivity and excellent heat resistance.

However, the thermal conductivity of alumina is excellent ゝ 20 W / mK
This is inadequate as a material for the above-mentioned chip mounting substrate.

Therefore, attention has been paid to AlN, which has a thermal conductivity as large as 320 W / mK (theoretical value) and a thermal expansion coefficient close to that of silicon (Si).
Practical use of this substrate is in progress.

In addition, AlN has a thermal expansion coefficient of 4.4 × 10 ⁻⁶ / ° C. in addition to its excellent thermal conductivity, and the thermal expansion coefficient of Si constituting LSI (3.6 ×
10 ^-6 / ° C).

[Conventional technology]

As a method of manufacturing a ceramic multilayer circuit board, a ceramic powder is kneaded with a sintering aid, a binder, a plasticizer and a dispersant to form a slurry, and the slurry is formed into a green sheet using a doctor blade method. Then, a via-hole is formed, and a conductive paste is screen-printed thereon to fill the via-hole and form a conductive line.

Then, the green sheets are laminated while being accurately positioned, integrated by pressing, and then fired at a high temperature to produce a multilayer ceramic circuit board.

Here, since AlN has a high melting point of 2200 ° C., a firing temperature of 1600 ° C. or higher is required. Therefore, as a constituent material of the conductor line, a high melting point metal such as tungsten (W) or molybdenum (Mo) Refractory-metal) is used.

A W conductor paste containing W powder as a main component is already commercially available.

However, this W conductor paste is intended for use on an alumina substrate, and even if it is applied to an AlN substrate as it is, the problem is that the adhesion is poor and a highly reliable conductor pattern cannot be formed. is there.

Now, as W conductor paste for AlN, 1
It has been reported that the conductor resistance is minimized by the addition of AlN powder by weight. (Hamaguchi et al., Proceedings of the Annual Meeting of the Ceramic Society of 1986, p305, 1986) However, according to experiments performed by the inventors, the addition of 1% by weight of AlN increases the conductor resistance.

This is because AlN has a high resistivity of> 10 ¹³ Ω · cm and is an insulator.AlN has a specific gravity of 3.26, whereas W has a specific gravity of 19.3, which is about 6 times as large. It is.

[Problems to be solved by the invention]

The resistivity of W is 4.9μΩ ・ cm (0 ℃) and that of Cu is 1.55μΩ ・ c
m (0 ° C.), the conductor line obtained by screen-printing the W conductor paste has a problem that the resistance is large and the power loss cannot be ignored.

Therefore, lowering the resistance of the conductor line is a problem in putting the AlN multilayer circuit board into practical use.

[Means for solving the problem]

The above problem is that a conductor paste used for forming a conductor pattern by performing screen printing on an AlN green sheet and then firing is prepared by adding 0.2 to 0.7% by weight of AlN to W powder, and adding a binder to this powder. It can be solved by forming a conductor paste for an AlN substrate, characterized by being kneaded by adding a solvent and a solvent.

[Action]

The inventors have studied the effect of adding AlN to the W conductor paste, and found that adding AlN powder to the W paste, firing and sintering would increase the densification of the W conductor compared to the case without the addition. Was found.

However, there is a relationship that the addition of AlN powder increases the resistivity because it is an insulator.

Therefore, the inventors investigated the relationship between the relative density of the W conductor and the volume resistance with respect to the amount of AlN added, and as a result, the addition of 0.2% by weight or more densified, and up to 0.8% by weight compared to the case of no addition. It was found that the resistivity decreased.

〔Example〕

AlN powder is added to the W powder in the range of 0 to 5% by weight.
3% by weight of ethyl cellulose as an organic binder and 15% by weight of butyl carbitol as a solvent based on 00 parts by weight
And 100% by weight of methyl ethyl ketone,
The mixture was kneaded using a grinder and a three-roll mill to prepare 17 types of W paste.

This paste was printed on an AlN green sheet having a thickness of about 500 μm, heated to 600 ° C. in a N ₂ stream to degrease, and each sample was fired in an N ₂ stream at 1700 ° C. for 9 hours to form an AlN wiring board. Was formed, and the sheet resistance of each of the wiring boards was measured.

Table 1 shows the relationship between the amount of AlN added to W and the sheet resistance. The sheet resistance gradually decreases with increasing AlN, shows a minimum value by adding 0.5% by weight, and then turns to an increase. FIG. 1 illustrates this relationship.

Here, the area resistance is 13 mΩ / □ or less and the range showing a much lower value than the case where no AlN powder is added is in the range of 0.2 to 0.7% by weight, and the addition of AlN powder in this range is effective. I understand.

〔The invention's effect〕

By implementing the present invention using a conductor paste obtained by adding 0.2 to 0.7% by weight of AlN powder to W powder, it is possible to manufacture an AlN multilayer ceramic circuit board provided with a conductor line having a lower resistance than before.

[Brief description of the drawings]

FIG. 1 shows the effect of adding AlN to the W conductor paste.

Continuation of the front page (56) References JP-A-2-83262 (JP, A) JP-A-63-303881 (JP, A) JP-A-63-195183 (JP, A) JP-A-62-197372 (JP) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09D 5/24 H01B 1/22 H01L 21/283 H05K 1/09 C04B 41/88

Claims (1)

(57) [Claims] 1. A conductor paste used for forming a conductor pattern by performing screen printing on an aluminum nitride green sheet and then baking the aluminum nitride green sheet is prepared by adding 0.2 to 0.7% by weight of aluminum nitride powder to tungsten powder. A conductive paste for an aluminum nitride substrate, comprising a binder and a solvent added to the powder and kneaded.