JPS633479B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer wiring board in which thin film wiring is formed on a multilayer wiring board, and in particular, to a multilayer wiring board that can accurately align thin film wiring on a large, high-density multilayer wiring board. The present invention relates to a method for manufacturing a substrate.

Conventionally, in order to manufacture a large, high-density multilayer wiring board by applying thin film wiring to a thick film ceramic substrate having a multilayer wiring structure, first, as shown in the process diagram of FIG. Mark metal 2 is deposited (see Figure 1b), then alignment marks 3 are created by photolithography (Figure 1c to f), and wiring metal 4 is further deposited (see Figure 1g). A method is adopted in which the thin film wiring pattern is aligned with the alignment mark 3 and photolithographically etched (FIG. 1h to k) to form the wiring portion 5. The reason for using this method, which requires complicated operations, is that the surface of the ceramic substrate is polished in order to apply thin film fine wiring, so the via 1a, which is the connection between the thick film and the thin film, is used.
This is because the wiring pattern cannot be accurately aligned by an optical method because it cannot be seen from above the metal vapor-deposited film for wiring. Another method of forming alignment marks on a ceramic substrate using a thick film method is that as the size of the ceramic substrate increases, the shrinkage rate during firing of the wiring printing paste becomes unstable, making it difficult to achieve highly accurate alignment. Appropriate. Furthermore, in the "lift-off method" using a photoresist, which is a well-known method, since the resist has no heat resistance, the substrate cannot be heated during vapor deposition, and therefore, satisfactory strength cannot be obtained between the ceramic and the wiring metal. This method cannot be used because ceramics have many pores and the resist remains in the pores, making it difficult to remove and clean.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a multilayer wiring board, which eliminates the above-mentioned drawbacks and allows thin film wiring to be easily and precisely formed on a thick film ceramic substrate.

In order to achieve this purpose, in the present invention, a film made of heat-resistant transparent resin is formed on a ceramic substrate having connection holes filled with conductors, and this film is photo-etched for a wiring pattern. After forming a mask, heating the ceramic substrate and depositing a metal for wiring on the surface having the mask, and then removing the mask and the metal deposited on the mask. This method is characterized by forming metal wiring on a ceramic substrate.

The present invention will be explained in detail below with reference to the drawings. FIG. 2 shows cross-sectional views at each step of an embodiment according to the present invention. In the figure, polyimide is first applied and dried as a heat-resistant transparent paint 6 on a substrate 1 (see FIG. 2B), and then a photoresist 7 is further applied and dried thereon. (See Figure 2 C)
This photoresist is exposed and developed (see Figure 2D).
Next, polyimide 6 is etched. (Figure 2 E
(See FIG. 2F) Next, the remaining photoresist 7 is removed (see FIG. 2F) and a wiring metal 8 is deposited. (See Figure 2G) Finally, polyimide 6 is removed to complete the process.

In the above process, since both the polyimide film 6 and the photoresist film 7 are transparent during exposure of the photoresist, the via 1a can be easily confirmed. Therefore, alignment of thick film and thin film wiring patterns can be easily and accurately performed. Also, when depositing wiring metal, heating to approximately 300°C is required to ensure good adhesion between the board and wiring metal, but polyimide has excellent heat resistance and can withstand this heating without causing the metal wiring pattern to deform. There isn't. Furthermore, since the polyimide can be easily removed using a caustic potash solution, hydrazine, etc., it does not remain in the pores of the ceramic substrate.

Compared to the conventional method, the present invention described above enables accurate alignment when thin film wiring is formed on a thick film ceramic substrate, and simplifies the manufacturing process. Furthermore, since there is no need to etch the wiring metal, the wiring metal can be freely selected regardless of the difficulty of etching, and highly reliable wiring can be achieved. Further, since sufficient heating can be performed during metal wiring deposition, metal-to-metal and metal-to-ceramic adhesion can be obtained to ensure sufficient strength for element bonding and bonding for circuit modification.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram of a conventional method for manufacturing a multilayer wiring board, and FIG. 2 is a process explanatory diagram of a method for manufacturing a multilayer wiring board according to the present invention. 1...Substrate, 2, 4, 8... Vapor deposited metal, 6...
Polyimide, 7...photoresist.

Claims (1)

[Claims] 1. A film made of heat-resistant transparent resin is formed on a ceramic substrate having connection holes filled with a conductor, and a mask is formed by photo-etching a wiring pattern on this film, and then the ceramic substrate is By depositing a wiring metal on the surface having the mask while heating, and then removing the mask and the metal deposited on the mask,
A method for manufacturing a multilayer wiring board, characterized by forming metal wiring on a ceramic substrate.