JPH027596A - Wiring board with interlayered film element - Google Patents

Abstract

PURPOSE:To prevent a film resistor element from being damaged by connecting a conductor pattern and a surface layer wiring pattern through an insulating resin layer to a wiring board in which an inorganic thick film conductor pattern and a thick film circuit element are printed and baked on an enamel layer formed on a metal base material. CONSTITUTION:Enamel paste 2, 2' comprising a glass base material is printed and welded on a metal base material 1 at a desired position, and thereafter thick film conductor paste is applied on the base material 1 and a thick film circuit pattern on an electrode 3 is printed and baked. Then, thick film resistor paste is printed and baked at a desired portion on the base material 1 which is connected to a thick film circuit pattern 3 to form a thick film resistor element 4, and then a via hole 5 is printed and baked. The thick film resistor element 4 is trimmed by a laser, etc., to be adjusted to a desired resistance. Further, after an insulating resin material 6 is printed and superimposed over the surface of a wiring board, and polymer conductive paste is printed and superimposed to form a circuit pattern 7, on which soldering resist paste 8 is printed and superimposed at a desired portion. Thus, a high reliability inorganic film resistor element can be constructed without damaging the inner layer of the wiring board.

Description

[Detailed Description of the Invention] [Summary] Regarding wiring boards that have film elements such as resistors and capacitors inside, printing and baking are particularly important when forming wiring boards with thick film circuits as the main process. In order to prevent the film resistance element from being damaged by oxidation, reduction, etc. during the firing process, an enamel layer is formed on the metal base material, and an inorganic thick film conductor pattern and the pattern are formed on the enamel layer. An insulating resin layer is formed on a wiring board formed by printing and firing a desired thick film circuit element to be connected to the conductive pattern and the insulating resin layer, as desired, via a via hole or the like via the insulating resin layer. A wiring board having a film element as an inner layer is constructed, which is characterized in that the film element is connected to a surface layer wiring pattern formed in the above.

[Industrial application field]

The present invention relates to a wiring board for electronic circuits, and more particularly to a wiring board having film elements such as resistors and capacitors in the inner layer.

When film elements such as resistors and capacitors are formed inside a wiring board to make the wiring board multilayered, the film elements are not damaged during processes such as printing and baking, and can be realized at low cost.
A flexible wiring board is required depending on the application.

[Conventional technology]

Conventionally, when configuring film elements (resistors, capacitors, etc.), which are individual parts, in a wiring board, highly reliable, industrial,
As shown in FIG. 5, as a method widely adopted for consumer use, copper (Cu), silver palladium (Ag
- Printing and firing a conductor paste made of Pd), silver platinum (Ag-PL) powder, glassy powder, etc., and forming a thick film conductor pattern 12 by sintering or melting the inorganic component,
A resistive paste (made of ruthenium oxide (Rust) powder, glassy powder, etc.) 13 is fired at a desired position of the thick film conductor pattern 12 to form an inorganic film resistive element, and this resistive paste is trimmed by laser irradiation or the like. (Membrane resistance element) This is used to adjust the resistance value of 13.

In addition, in making this wiring board multilayer, as shown in FIG. 6, conductor paste 12 and insulator paste 14 are alternately printed and fired, and connection vias 15 are provided to form conductor pattern 12 and surface layer wiring pattern. 16 is connected to perform multilayer wiring. However, the film resistance element 13
Forming the membrane resistor element 13 on the inner layer of the wiring board by providing the circuit pattern 16 thereon involves firing the insulator paste 1-14, the connection vias 15, and the inorganic paste constituting the surface layer wiring pattern with the membrane resistor element 13. Since the firing temperatures are about the same, consideration must be given to the firing process so that the film resistance element 13 is not altered by oxidation or reduction, and it is also difficult to trim the resistance.

In addition, polymer thick film resistance paste, which is formed by heating and curing carbon powder as a resin component, is considered to have insufficient reliability for industrial use as a film resistance element. Since it is formed by heating and polymerizing a polymer, it is necessary to adjust the heating conditions in the subsequent process and the resistance value of the film resistor element by trimming with sand plus, laser, etc., and the inner layer of the wiring board of the resistive film element It is difficult to

In addition, as a method that does not require harsh firing conditions in the post-process, a photosensitive polymer is coated on an inorganic wiring board to serve as an insulating layer for the inorganic wiring board, and holes for via connections are formed in this photosensitive polymer using a photoetching method. A method of forming a desired wiring pattern thereon by electroless plating or photoetching has been proposed for the purpose of lowering the dielectric constant of an insulating layer, particularly in digital high-speed signal circuits. However, this method uses photosensitive polymers, photoresists,
It is a process of repeating conductor etching, coating, or plating, and it is known that photosensitive polymer The method using this method involves complicated steps and high costs.

In addition, since inorganic wiring boards mainly made of ceramics such as alumina are hard and brittle materials, they are susceptible to bending and impact, making it difficult to obtain large boards. Furthermore, in order to increase the added value of wiring boards, there is an increasing demand for multifunctional wiring boards and lower costs, such as bending the board to have a structural purpose as a housing, especially for portable electronic devices. There is.

[Problem to be solved by the invention]

Therefore, the first problem of the present invention is to form a wiring board with a W-film circuit as an inner layer using printing and baking as the main steps.
In particular, it is an object of the present invention to provide a wiring board in which a film resistance element is not damaged by oxidation, reduction, etc. during printing, baking, and other processes.

In addition to the above, a second object of the present invention is to provide a flexible wiring board that can be used as a part of a structure such as a casing.

[Means to solve the problem]

As a means for solving the first problem, according to the present invention, an enamel layer is formed on a metal base material, and an inorganic thick film conductor pattern and a desired thick film circuit element connected to the pattern are printed on the enamel layer.・An insulating resin layer was formed on the baked wiring board, and the conductor pattern and the surface layer wiring pattern formed on the insulating resin layer were connected as desired through the insulating resin layer through via holes, etc. A wiring board having a film element as an inner layer is provided.

In addition, as a means to solve the second problem, enamel layers are divided into metal substrates, printed and fired at intervals, and a non-aluminum thick film circuit is formed on the enamel layers, and each divided enamel layer is printed and fired at intervals. An insulating resin layer is formed to cover the thick film circuit on the layer, and the thick film circuits on each divided enamel layer are interconnected by a wiring pattern formed on the insulating resin layer. A wiring board having a film element as an inner layer is provided.

[Action]

According to the first means of the present invention, a thick film circuit structure in which an inorganic sintered bond is formed by melting, and a polymer thick film circuit structure in which a resin is polymerized and hardened are formed by sintering or heating during polymerization. There is a large difference in temperature or heat resistance of thick film circuits, and even if a polymer thick film circuit is formed on top of an inorganic thick film circuit, the polymerization temperature may cause a non-Aljt thick film circuit, especially (film resistance elements may be oxidized). Therefore, it is possible to provide a multilayer wiring board in which circuit elements are embedded in the inner layer of the wiring board, which is not damaged by reduction and can be manufactured at low cost using printing and baking as the main processes.

Further, according to the second means of the present invention, by bending the wiring board at a portion avoiding the enamel layer, that is, at an interval between a plurality of enamel layers, a structural element can be provided and the wiring board can be used as a part of a casing. It becomes possible to use it.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the wiring board of the present invention, in which a vitreous enamel N is placed on a metal base material 1 such as iron or aluminum.
This is an embodiment of a wiring board in which a large integrated circuit (LSI) 9 and a chip component 10 are mounted and mounted on a hollow layer board printed and fired as desired.

FIG. 2 shows a second embodiment of the wiring board of the present invention, in which vitreous enamel layers 2 and 2' are formed on a metal substrate 1 by dividing them at intervals. This is an embodiment of a wiring board in which the enamel layers 2 and 2' are connected by a wiring pattern 7 made of a polymer resin layer, and the enamel layers 2 and 2' are bent.

FIG. 3 shows an embodiment in which wiring circuits are formed on both sides of the metal base material 1 and are interconnected through through holes 31.

FIG. 4 shows the manufacturing process of the wiring board according to the embodiment shown in FIG. 1. In FIG.
．． Enamel paste 2 made of glass base material is printed on the desired position on this base material 1 with 2 to 2 liters of low carbon steel (
2') is printed and welded (a). Thereafter, a thick film conductor paste, for example a paste of a mixture of silver palladium (Ag-Pd) and glass flint, is applied, and a desired thick film circuit pattern or electrode 3 is printed and fired (b). In the next step, a thick film resistor paste (for example, Ru5t) is printed and fired at a desired position to be connected to the thick film circuit pattern 3, thereby forming a piezoelectric film resistor element 4 (c). In the next step, via holes 5 for multilayer connection of the thick film circuit pattern 3 are printed and fired on the rJ-film circuit pattern 3 (d).

In the next step, the thick film resistive element 4 is trimmed using a laser or the like to adjust the resistance to a desired value. In the next step, insulating resin material 6 is printed and polymerized on the entire surface of the wiring board (e), and in the next step, polymer conductor paste is printed and polymerized to form the desired circuit pattern 7, and then solder is placed at the desired position on top of the polymer conductor paste. Print and polymerize resist paste 8 (f). When forming the circuit pattern 7, this circuit pattern 7 is connected to the thick film circuit pattern 3 in the inner layer via the via hole 5.

In addition, enamel paste 2, thick film conductor (circuit pattern)
3. The firing temperature of the thick film resistor paste (resistance element) 4 varies greatly depending on the material, but is in the range of about 500 to 1000°C. On the other hand, the polymerization temperature of the polymer material (insulating resin material 6, circuit pattern 7) is in the range of about 150 to 250°C, and even if the thick film resistor element 4 is internally layered on the wiring board, the multilayer process, i.e., the polymer material This temperature range is low enough to be used in the polymerization process.

In addition, in FIG. 1, a large integrated circuit (LSI) is connected to the surface circuit pattern 7 of the multilayered wiring board.
9 and chip components 10 are placed on solder paste and reflow soldered to fix and mount them. Also,
On the other enamel layer 2, a thick film conductor (circuit pattern) 3 and a thick film resistor paste (resistance element) are placed in the same manner as above.
4 is printed and fired, and the polymer material (insulating resin material 6, circuit pattern 7) is polymerized. Enamel layer 2.2
An insulating resin material 6, a circuit pattern 7, and, if desired, a solder resist paste 8 extend in the area between the holes, and the film element 4 on one enamel N2 and the film element 4 on the other enamel N2 are on the surface. They are connected to each other via the circuit pattern 7 of the layer.

As mentioned above, the embodiment shown in FIG. 2 is obtained by bending the region 21 between the enamel N2.2" of the wiring board shown in FIG. Although it is difficult to bend the substrate after circuit firing, it is possible with polymer substrates, making the embodiment shown in Figure 2 possible.
As long as excessive stress is not applied to the O, etc., these parts can be bent before or after they are mounted. Further, if the size of the enamel layer 2.2'' is limited to a desired value, the thermal stress caused by the difference in expansion coefficient between the metal of the base material 1 and the glassy enamel layer 2 can be suppressed within an allowable range.

This makes it possible to use a light metal such as aluminum as the base metal l.

FIG. 3 shows an embodiment in which wiring circuits are formed on both sides of the metal base material 1 and interconnected by through holes 31, as described above. That is, on the upper surface of the metal base material 1, a multilayered circuit is constructed in the same manner as in the embodiment shown in FIG. A circuit pattern 7° is formed on an insulating resin material 6 without forming a large scale integrated circuit (LSI) 9, a chip component 10, etc. thereon. A through hole 31 passing through the upper and lower surfaces is formed in a region between the enamel layers 2 and 2 on the upper surface.
The upper and lower circuit patterns 7.7'' are connected to each other via the conductor portion 7'' in this through hole.

〔Effect of the invention〕

As described above, according to the present invention, a highly reliable inorganic film resistance element can be formed in the inner layer of a wiring board, and high-density component mounting and wiring patterns are possible.

Furthermore, when a hollow substrate is used, by configuring the bending portion of the substrate with a polymer material, a bent hollow substrate to which wiring is connected becomes possible. It is possible to use lightweight aluminum or the like as the base material of the hollow substrate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a first embodiment of a wiring board having a film element of the present invention as an inner layer, FIG. 2 is a cross-sectional view of a second embodiment of a wiring board of the present invention in which the board is bent, and FIG. 3 is a board 4 is a cross-sectional view of a third embodiment of the wiring board of the present invention in which the upper and lower surfaces of the wiring board are connected by through holes, FIG. 4 is a diagram showing the manufacturing process of the wiring board of the embodiment of FIG. 1, and FIGS. 5 and 6 1 is a cross-sectional view for explaining a conventional wiring board. DESCRIPTION OF SYMBOLS 1... Metal base material, 2... Hollow layer, 3... Circuit pattern, (thick film conductor paste) 4... Thick film resistance element, 5... Via hole, 6... Insulating material, 7...Circuit pattern, (polymer-only paste)...Solder resist pattern,...Large integrated circuit (LSI), O...chip component, l...bending part, l...through hole .

Claims (2)

[Claims] 1. An enamel layer (2) is formed on a metal base material (1), and an inorganic thick film conductor pattern (3) and a desired thick film circuit element (4) connected to the pattern are printed and fired on the enamel layer. An insulating resin layer (6) is formed on the wiring board, and a surface layer wiring is formed on the conductor pattern (3) and the insulating resin layer as desired via a via hole (5) or the like via the insulating resin layer. A wiring board having a film element as an inner layer, characterized in that a pattern (7) is connected to the wiring board. 2. Enamel layers (2, 2') are divided into metal base material (1), printed and fired at intervals, and an inorganic thick film circuit (3, 4) is formed on the enamel layer. An insulating resin layer (6) is formed to cover the thick film circuit on the layers (2, 2'), and the thickness on each divided enamel layer is A wiring board having a membrane element as an inner layer, characterized in that membrane circuits (3, 4) are interconnected.