JPH0336790A - Baking of multilayer aluminum nitride circuit board - Google Patents

Abstract

PURPOSE:To obtain an aluminum nitride multilayer circuit board having small conductor resistance by adding specific amount of Ca or Ca and Y baking assistants to aluminum nitride, setting a green sheet board in which W paste is interconnected in multilayers as a conductor material in a NB sealed vessel, and baking it. CONSTITUTION:0.5-10.0 pts.wt. of Ca or Ca and Y baking assistants are added to 100 pts.wt. of aluminum nitride, a green sheet board 4 in which W paste is laid out in multilayers as a conductor material is set in a BN sealed vessel 1, and baked at 1550-1750 deg.C. Thus, an aluminum nitride multilayer circuit board having high density, high thermal conductivity and low conductor resistance can be obtained.

Description

[Detailed description of the invention]

[Summary] Regarding a method for firing an aluminum nitride substrate, the purpose is to provide a method for firing an aluminum nitride multilayer wiring board with low conductor resistance. A green sheet substrate with 0.5 to 10.0 parts by weight added to it and wired in multiple layers using W paste as a conductive material is set in a sealed BN container and fired at a temperature of 1550°C or higher and 1750°C or lower. Configure it as follows. [Industrial Application Field] The present invention relates to a method for firing an aluminum nitride substrate, which is promising as a material for LSI packages, multilayer circuit boards, etc. because it has high thermal conductivity and thermal expansion close to that of silicon. [Conventional technology J Aluminum nitride has attracted attention as a ceramic with excellent thermal conductivity, and for this reason, it has been
Various methods have been devised for firing aluminum nitride substrates, but these mainly involve increasing the thermal conductivity by firing in a high-temperature, long-time graphite furnace in a neutral or reducing atmosphere. This is an experimental firing method. In order to use aluminum nitride in a multilayer wiring board, it is necessary to prepare a conductive paste and sinter the aluminum nitride at the same time. Conventional experimental firing conditions do not meet these requirements. [Problems to be Solved by the Invention] Conventional firing conditions do not deteriorate the properties of aluminum nitride, such as sintered density and thermal conductivity, but other properties required for a multilayer wiring board, namely conductor It is not possible to obtain an aluminum nitride multilayer wiring board with low resistance. Therefore, an object of the present invention is to provide a method for firing an aluminum nitride multilayer wiring board with low conductor resistance. [Means for Solving the Problems] The method of the present invention includes adding 0.5 to 10.0 parts by weight of Ca-based or Ca-based and Y-based sintering aids to 100 parts by weight of aluminum nitride, and The method is characterized in that a green sheet substrate with multilayer wiring using W paste as a conductive material is set in a sealed BN container and fired at a temperature of 1550° C. or more and 1750° C. or less. The present invention will be explained in detail below. As a result of studying various firing methods, the present inventors have found that the jigs used for firing, such as a container, have a large effect on the sintered state of the substrate. For materials such as aluminum nitride, which are fired at high temperatures, the jigs used for firing are limited to BN (boron nitride) and graphite, but substrates fired using graphite containers show a significant weight reduction and are highly densified. What not to do - 10,000 BN
It was found that densification can be achieved by sealing and firing in a container. Next, the firing temperature of 7512 has been changed from 1800℃ to 19
Although it is said that 00°C is preferable, as a result of studying the influence on the conductor resistance, it was found that the conductor resistance becomes smaller when the firing temperature is in the range of 1500°C to 1750°C. However, considering the sinterability of aluminum nitride, 155
A temperature of 0°C or higher is required, and if the temperature is not higher than this temperature, the aluminum nitride green sheet will not be sufficiently densified even if it is fired for a long time.
A temperature range of 1750°C is useful. Ordinary W paste is used as the conductor material. Sintering aids for aluminum nitride substrates can be broadly classified into Y (yttrium) compounds and Ca (calcium) compounds. Among these, the Y type has a high liquid phase generation temperature, so it is not preferable to use it alone when firing at a lower temperature than conventionally as in the present invention. Therefore, it is preferable to use Ca-based material or a mixture of Ca-based material and Y-based material. The amount of the sintering aid added may range from 0.5 to 10.0 parts by weight per 100 parts by weight of aluminum nitride; if the amount added is less than 0.5 parts, sintering will be insufficient. , 10
．． If it exceeds 0 parts by weight, the thermal conductivity tends to decrease.

[Effect]

According to the above method, it is possible to obtain an aluminum nitride multilayer wiring board that is dense, has high thermal conductivity, and has low conductor resistance. Hereinafter, the present invention will be explained in more detail with reference to Examples.

【Example】

Calcium carbonate and yttrium oxide as sintering aids were added to 100 parts by weight of aluminum nitride powder as shown in Table 1, an organic binder and a plasticizer were added, and the mixture was kneaded in a ball mill. This was formed into a sheet using a doctor blade, dried, and then punched into a 100 mm opening. W paste was screen printed on these green sheets, and after lamination, 900
After degreasing for 4 hours in a nitrogen atmosphere at 0.degree. C., these substrates were set in a BN sealed container as shown in FIG. In the figure, l is a BN box (container), 2 is a BN lid, and 3 is a BN box.
The substrate support 4 is a laminate of aluminum nitride green sheets screen-printed with W paste. All of these (1 to 4) were set in a heating furnace, the atmosphere of the furnace was nitrogen, and fired under various conditions shown in Table 1, and the density, thermal conductivity, and conductor resistance of the substrate were measured. The results are also shown in Table 1. (Left below) Characteristics were evaluated based on the following criteria. ○: Sintered density 99.0% or more, thermal conductivity 180 W/m
k, or more, conductor resistance 20 mΩ/mouth or less△: sintered density 97.0-99.0%, thermal conductivity 150-
180w/mk, conductor resistance 20-30 raΩ/mouth x:
Sintered density: 97.0%, thermal conductivity: 150 W/mk or less Conductor resistance: 30 IllΩ/mouth or more Comparative example 1.2 is an example in which the firing temperature is too high, and the conductor resistance increases regardless of whether the firing time is long or short. Not excellent, comparative example 3
．． Sample No. 4 is an example in which the sintering was performed at a low temperature for a long time, and the sintered density and thermal conductivity were not excellent. [Effects of the Invention] As explained above, according to the present invention, a multilayer wiring board with low conductor resistance can be obtained without deteriorating various properties such as density and thermal conductivity of aluminum nitride.

[Brief explanation of drawings]

FIG. 1 shows a BN container used in the method of the present invention. I-BN box, 2-BN lid, 3-BN support stand, 4-Aluminum nitride green sheet laminate

Claims (1)

[Claims] 1. In a method for firing an aluminum nitride multilayer wiring board, 0.5 to 10.0 parts by weight of Ca-based or Ca-based and Y-based sintering aids are added to 100 parts by weight of aluminum nitride, and W paste is used as a conductive material. 1. A method for firing an aluminum nitride multilayer wiring board, which comprises setting a green sheet board with multilayer wiring in a sealed BN container and firing it at a temperature of 1550°C or higher and 1750°C or lower.