JPH0213478B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a ceramic multilayer wiring board used for hybrid integrated circuits, etc., and in particular, a method for forming an oxidation-resistant conductor protective layer and a thick film conductor layer in one oxidation firing process. This invention relates to a method of manufacturing a ceramic multilayer wiring board. (Prior Art) As a conventional method for manufacturing a multilayer wiring board used in a hybrid integrated circuit, for example, as shown in FIG.
A plurality of layers of a high melting point metal conductor paste layer mainly composed of a high melting point metal such as W and Mo and an insulating paste layer having an opening through which a part of the conductor paste layer is exposed are superimposed on a ceramic green sheet 11,
A conductor paste layer that forms an oxidation-resistant conductor protective layer made of a noble metal such as W-Pt is printed on the exposed conductor paste in the opening of the uppermost layer of insulating paste, and is fired in a reducing atmosphere to form the high-melting point metal conductor layer 12.
Then, an oxidation-resistant conductor protective layer 13 and an insulating layer 14 are formed, and a thick film conductor paste layer of silver or the like is printed on the oxidation-resistant conductor protective layer 13, for example, at 620° C. in air.
JP-A-59-75695 discloses that a multilayer wiring board is obtained by baking at 10° C. for 10 minutes to form a thick film conductor layer 15. Furthermore, a manufacturing method for obtaining a multilayer wiring board by providing a conductive glass layer in which glass is uniformly interposed in the gaps between precious metal sintered bodies as the oxidation-resistant conductor protective layer described above is also disclosed in Japanese Patent Application No. 58-184420. It is known in (Problems to be Solved by the Invention) In the method described above, the oxidation-resistant conductor protective layer effectively prevents oxygen from entering the high melting point metal conductor layer during firing in an oxidizing atmosphere during the formation of the thick film conductor layer. However, in order to form these oxidation-resistant conductor protective layers, a unique heat treatment in a reducing atmosphere was required. In other words, when forming an oxidation-resistant conductor protective layer made of noble metal, it is necessary to sinter the conductive paste made of noble metal in a reducing atmosphere, and even when forming an oxidation-resistant conductor protective layer made of conductive glass, noble metal Since it is necessary to sinter the mixed paste of oxide and glass in a reducing atmosphere, two sinterings are required in a reducing atmosphere and an oxidizing atmosphere to form the oxidation-resistant conductor protective layer and the thick film conductor layer, respectively. However, it had the disadvantage of requiring more work steps. An object of the present invention is to solve the above-mentioned problems, to form an oxidation-resistant conductor protective layer and a thick film conductor layer in one firing, to reduce the number of work steps and to increase work efficiency. The present invention aims to provide a method for manufacturing a ceramic multilayer wiring board. (Means for Solving the Problems) The method for manufacturing a ceramic multilayer wiring board of the present invention is as follows:
In the method for manufacturing a ceramic multilayer wiring board, which comprises placing and connecting a conductor paste for forming a thick film element on the exposed conductor layer of a multilayer wiring board in which a plurality of insulating layers and high-melting point metal conductor layers are alternately laminated, and firing the same, The ratio of the low melting point glass containing at least 20 mol % or less of at least one of Pb and Bi oxides and the noble metals consisting of Ag and Pd on the exposed conductor layer is 33/67 to 67/33 by volume. The method is characterized in that a conductive paste made of a mixture is disposed, a thick film element forming paste is further disposed and connected thereon, and then fired in an oxidizing atmosphere. (Function) According to the present invention, if a conductive paste containing a noble metal and a low-melting point glass in the above-mentioned volume ratio is used as an oxidation-resistant conductor protective layer, one oxidation process can be performed without oxidizing the high-melting point metal conductor layer. This is due to the discovery that an oxidation-resistant conductor protective layer and a thick film conductor layer can be formed by firing in an atmosphere. Also, at this time, glass with a low melting point is required because
If low melting point glass is not used, when the thick film conductor layer forming paste is fired at 800 to 830°C in an oxidizing atmosphere, the glass will not melt sufficiently and the high melting point metal conductor layer will oxidize, increasing conduction resistance. It is. (Example) The details of the present invention will be sequentially explained for each step with reference to FIG. A ceramic green sheet containing alumina, beryllia, etc. as a main component is prepared by a known doctor blade method, and a ceramic green sheet 1 is prepared by cutting it into a size required for a hybrid integrated circuit board. Next, on the green sheet 1, a conductive paste whose main component is a high melting point metal such as tungsten or molybdenum, that is, a metal with a melting point higher than the firing temperature of the ceramic green sheet 1 and a low electrical resistance, and the conductive paste are coated. A green sheet 1 having a partially exposed opening and an insulating paste made of the same ingredients are alternately printed by screen printing, and as shown in the figure, a high melting point metal conductor layer 2 made of conductive paste and an insulating paste are printed. An insulating layer 3 is formed. Note that the number of layers of the high melting point metal conductor layer 2 and the insulating layer 3 is not limited, and may be determined according to the purpose. Then, the ceramic green sheet 1 on which the paste forming the high melting point metal conductor layer 2 and the insulating layer 3 is printed is fired in a reducing atmosphere. The firing conditions are determined by the components of the ceramic green sheet 1, and are 1400 to 1800°C and 5 to 180 minutes. Next, a paste layer 4 mainly composed of noble metal and glass is formed by printing on the high melting point metal conductor layer 2 exposed in the exposed opening portion 2a, and a thick film conductor paste layer for forming a thick film element is further applied thereon. 5 is formed by printing and then fired in an oxidizing atmosphere to obtain a ceramic multilayer wiring board of the present invention. In addition, as a component of the conductive paste whose main components are noble metals and glass, glass melts and coats the high melting point metal to completely block it from the outside air before the high melting point metal oxidizes and impairs conductivity. It is necessary that the oxygen constituting the oxide in the glass component is a component that does not severely oxidize the high melting point metal, and the precious metal has a small amount of solid solution of oxygen and has oxygen blocking properties. , it is necessary to contain a sufficient amount for conductivity. Further, as for the components of the glass paste, it is preferable that the glass _paste be melted before the exposed conductor is significantly oxidized, although it depends on the firing temperature and the material of the _exposed conductor. W, Mo
If there are many metal oxides with weaker oxygen bonding strength than other metal oxides, these components will supply oxygen to W, Mo, etc. and oxidize the conductor, so PbO, Bi ₂ O ₃ , etc. should be less than 20 mol%. is preferred. Furthermore, the firing conditions in an oxidizing atmosphere depend on the type of conductive paste constituting the oxidation-resistant conductor protective layer and the element forming paste connected thereto.
A temperature of 750 to 850°C for 5 to 20 minutes is appropriate. in this case,
The melting point of the glass in the conductive paste is preferably 700°C or lower. Furthermore, passive elements such as resistors are formed on the thick film conductor layer, and other circuit components are soldered or wire bonded to form an integrated circuit. Because the above-mentioned structure is adopted, even if the thick film conductor paste layer 5 is fired at, for example, 850°C in an oxidizing atmosphere, the glass will melt and oxygen will infiltrate into the substrate before the exposed part of the conductor is significantly oxidized. Since the metal component also has sufficient oxygen barrier properties, it is possible to protect the exposed conductor layer while maintaining conductivity. Example: As a ceramic component, 90% by weight of alumina, additives such as silica and magnesia, and an organic binder such as polyvinyl butyral are mixed,
A ceramic green sheet 1 with a thickness of 0.8 mm was prepared by the doctor blade method. Next, a conductive paste consisting of a metallization component consisting of tungsten powder with ethyl cellulose added as a printing aid, and an insulating paste made of powder of the same composition as the green sheet with ethyl cellulose added as a printing aid, are applied onto the green sheet. A laminate in which a high melting point metal conductor layer 2 and an insulating layer 3 were formed was obtained by printing alternately with a portion of the layer exposed. Next, the laminate was heated at a heating rate of 300°C/hour in a mixed atmosphere of hydrogen and nitrogen with a dew point of 35°C, and then held at 1550°C for 2 hours to sinter, and then the cooling rate was increased.
It was cooled at 600°C/hour to obtain a multilayer wiring board. Next, a conductive paste prepared by adding ethyl cellulose as a printing aid to a mixture of low-melting point glass and noble metal in the proportions shown in Tables 1 and 2 was printed over the high-melting point metal conductor layer 2 in the exposed opening portion 2a. ,
Further, a thick film conductor paste was printed on the paste and then baked at 800°C for 10 minutes in an oxidizing atmosphere to obtain a ceramic multilayer wiring board of the present invention. In addition, a comparative example with a volume ratio of noble metal and glass outside the range of the present invention was prepared, and the appearance of stains, initial resistance, and refiring change rate were measured in the same manner as the inventive example. I made a judgment. These results are shown in Table 1, in which ○ represents a good product and × represents a defective product. In addition, Table 2 shows the components of noble metal and glass of each sample and the melting point of glass.

【table】

[Table] As is clear from Tables 1 and 2, samples in which the ratio of low melting point glass to precious metal is within the range of the present invention do not suffer from visible stains or deterioration in resistance value due to oxidation of the high melting point metal conductor layer. Moreover, since the re-firing change rate was also small, a ceramic multilayer wiring board with sufficient performance could be obtained. On the other hand, in comparative examples outside the scope of the present invention, stains on the appearance and deterioration of the resistance value occurred, and it was not possible to obtain a ceramic multilayer wiring board with sufficient performance. The present invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, in the above-mentioned embodiment, an oxidation-resistant conductor protective layer made of noble metal and low melting point glass was provided directly on the exposed conductor layer 2 of the exposed opening portion 2a. An iron metal plating layer may be provided, and then the oxidation-resistant conductor protective layer of the present invention may be provided on the plating. (Effects of the Invention) As is clear from the detailed explanation above, according to the method for manufacturing a ceramic multilayer wiring board of the present invention, the process for forming an oxidation-resistant conductor protective layer, which has been conventionally performed, can be performed in a reducing atmosphere. No need to bake
Since the oxidation-resistant conductor protective layer and the thick film conductor layer can be formed by one oxidation firing, the number of work steps can be reduced and work efficiency can be increased. In addition, the glass melts and blocks oxygen before the exposed conductor layer is oxidized and loses its conductivity, and the precious metal components also block oxygen.
For example, the thick film conductor forming paste can be fired at a high temperature of 750°C to 850°C, making it possible to apply a wide variety of thick film pastes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of an embodiment of a ceramic multilayer wiring board produced by the manufacturing method of the present invention, and FIG. 2 is a sectional view of a main part of a conventional ceramic multilayer wiring board. DESCRIPTION OF SYMBOLS 1... Ceramic green sheet, 2... High melting point metal conductor layer, 3... Insulating layer, 4... Conductive paste layer, 5... Thick film conductor paste layer.

Claims (1)

[Claims] 1. A ceramic multilayer wiring in which a conductor paste for forming a thick film element is placed and connected on the exposed conductor layer of a multilayer wiring board in which a plurality of insulating layers and high melting point metal conductor layers are alternately stacked and then fired. In the manufacturing method of the substrate, the ratio of the low melting point glass containing at least 20 mol% or less of at least one of Pb and Bi oxides in total to the noble metal consisting of Ag and Pd on the exposed conductor layer is determined by volume. A ceramic multilayer wiring characterized in that a conductive paste made of a mixture of 33/67 to 67/33 is disposed, a paste for forming a thick film element is further disposed and connected thereon, and then fired in an oxidizing atmosphere. Substrate manufacturing method. 2. The method of manufacturing a ceramic multilayer wiring board according to claim 1, wherein iron plating is applied to the exposed conductor layer prior to disposing the conductive paste. 3. The method of manufacturing a ceramic multilayer wiring board according to claim 1, wherein iron metal plating is applied on the exposed conductor layer prior to placing the conductive paste. 4. The method for manufacturing a ceramic multilayer wiring board according to claim 1, wherein the low melting point glass contains 20 mol% or less of PbO.