JPS61101093A - Manufacture of thick film circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a double-sided through-hole type thick film circuit board used in a wide range of electronic equipment such as television receivers and video tape recorders.

Conventional configurations and their problems In recent years, as the demand for smaller, lighter, and more highly functional electronic devices has increased, how to increase the density and reliability of these electronic circuits has become an extremely important issue. ing.

Under these circumstances, recently, a mounting method of configuring electronic circuits using hybrid integrated circuit components called hybrid ICs has become widely used.

This hybrid integrated circuit component generally has a desired function on a so-called thick film circuit board in which a metal glaze conductor circuit mainly composed of silver and a metal glaze resistor circuit consisting of ruthenium oxide are formed on a ceramic insulating substrate such as alumina. It is constructed by soldering the circuit elements necessary to construct the circuit.

Such hybrid integrated circuit components are mounted on a mother printed wiring board together with many other circuit elements to form an electronic circuit.
This makes it possible to make the entire electronic circuit J-shaped and highly reliable, but on the other hand, the cost of this mounting method is high, so its field of use is limited.

The most important reason for this is the high cost of thick film circuit boards constituting hybrid integrated circuit components, especially double-sided thick film circuit boards designed for high circuit density.

Conventionally, double-sided through-hole type thick film circuit boards have been manufactured through the manufacturing process shown in A to D in FIG.

That is, this manufacturing method uses a ceramic insulating substrate 1 made of alumina, etc., as shown in FIG. A metal glaze type conductive paste made of silver or silver-palladium is applied to both the front and back sides of the board using a screen printing method to form the desired wiring circuit diagram shape.
The circuit conductor layers 3a and 3b are formed by firing at a high temperature of 00 to 860 degrees.

At this time, there is a method of establishing electrical continuity between the circuit conductor layers 3a and 3b formed on the front and back sides of the alumina insulating substrate 10, and in steps 1 to 1, printing the conductor paste in the form of a wiring circuit and simultaneously filling the through hole 2 with the conductor paste. Alternatively, it is coated to make through-hole connections.

Then, as shown in FIG. 1C, a metal glaze-based resistance paste made of ruthenium oxide is applied on at least one main surface of the ceramic insulating substrate by a screen printing method, and the same is fired at a high temperature of 80 to 850 degrees. A resistor layer 4 is formed.

Then, as shown in the first diagram, a glass-based insulating protective layer 5 is formed on the surface of this resistor layer 4, and then the surface of the resistor layer 4 is cut through the glass insulating protective layer 6 using laser trimming technology. The resistance value is adjusted to a predetermined value to produce a double-sided through-hole type thick film circuit board having a plurality of resistor elements.

However, double-sided through-hole thick-film circuit boards made using this method are not only uneconomical because the conductor circuits are all made of silver or extremely expensive precious metals such as silver-palladium, but also have problems specific to silver thread conductor circuits. As a point of view, silver migration between conductor circuits due to high temperature and high humidity loads, and the phenomenon of silver crinkling occurring during 3A, 3, fr3 bonding work, lead to short circuits and disconnections in the circuit conductor layer, resulting in reduced reliability and yield. This causes a problem in that it is difficult to obtain a double-sided thick film circuit board with high density and high reliability.

Purpose of the Invention The purpose of the present invention is to solve the above-mentioned drawbacks of the conventional example, and to make it possible to perform through-hole connections reliably, and to ensure reliability that migration and soldering do not cause disconnection or short-circuit defects during work. An object of the present invention is to provide a method for manufacturing a high-density double-sided through-hole thick film circuit board having a circuit conductor layer with excellent properties.

Structure of the Invention The thick film circuit board according to the present invention has a through hole formed in a predetermined position of a ceramic insulating substrate, and a metal glaze-based noble metal conductor paste is selectively applied to required locations on both the front and back surfaces of the ceramic insulating substrate, a step of forming a conductor layer for connection terminals by high-temperature firing; a step of forming a metal glaze-based resistor layer at necessary locations between the conductor layers for connection terminals formed on at least one main surface of the ceramic insulating substrate; a step of forming an insulating protective layer on the surface of the body layer, a step of printing an active paste for electroless plating in a desired wiring diagram shape continuous with the connection terminal conductor layer and baking it to form an active layer; It is made through a process of depositing a conductive metal layer on the surface of the layer by electroless plating, and as a result, a double-sided thick film circuit board with excellent reliability can be obtained, and a conductor circuit with no disconnection or short circuit defects can be obtained. A low cost double-sided thick film circuit board with layers can be realized.

do.

FIGS. 2A to 2E are cross-sectional views of essential parts in each manufacturing process for explaining a method for manufacturing a double-sided thick film circuit board according to an embodiment of the present invention.

In FIG. 2, 6 is a ceramic insulating substrate, 7 is a through hole,
8a and 8b are metal glaze-based connecting conductor layers, 9 is a resistor layer, 10 is a resistor insulation protection layer, 11 is an active layer, 12
is a conductive metal layer.

The details of the method for manufacturing the thick film circuit board according to this embodiment configured as described above will be explained below. 6, use a laser beam to make a through hole 7 for through-hole connection, or use a mold to make a through hole 7 in an alumina insulating sheet, i.e., a green sheet, before firing. An alumina substrate made by firing at a high temperature of 14°C to 1,600°C is used.

Next, as shown in FIG. 2B, a so-called ordinary metal glaze conductor made by dispersing and mixing fine silver powder into a glass frit and a resin binder is placed at predetermined positions on both the front and back surfaces of this alumina insulating substrate 6. Using a conductor paste, the conductor paste is selectively applied to a desired shape by a known method such as screen printing, and the conductor paste is coated with an 800 to 85
Metal glaze-based connection conductor layers sa and sb are formed by high-temperature firing in air at 0 degrees Celsius. In this case, the conductive paste must not only have excellent adhesion to the alumina insulating substrate, but also have excellent resistance to chemicals such as acids and alkalis, and the conductive paste that meets this purpose must be In this example, a conductive paste made by mixing borosilicate glass frit and fine silver powder with a resin binder was used.

In addition, the reason why silver thread material is used as a conductor material in this process is that it can obtain a good connection state as an electrode terminal for the resistor layer formed in the next process, and it can also be used as an alumina insulating substrate for soldering circuit elements. Although any metal glaze type conductor paste can be used to provide good adhesion, in this embodiment, a conductor paste consisting only of silver was used in consideration of economic efficiency.

Next, as shown in FIG. 2C, the conductor layer 8a for the connection terminal is
, ab is formed on at least one main surface of the alumina insulating substrate 6 by applying ruthenium oxide in a predetermined shape using a fine powder method, and baking it at a high temperature of 8oO to 850 degrees Celsius like the conductor paste. A resistor layer 9 is formed, and a resistor insulation protection layer 10 is formed on the surface of the resistor layer. Then, as shown in the second diagram, an active paste for electroless plating is printed on both the front and back sides of this ceramic insulating substrate 6 in the shape of a wiring diagram including a part of the conductor layer for connection terminals, and is fired to form an active layer 11. , After that, this ceramic substrate is immersed in an electroless plating solution such as copper or nickel to expose a portion of the connecting terminal conductor layers 8a and 8b as shown in FIG. 2E.
A conductive metal layer 12 such as copper or nickel is deposited on the activated 10B layer 8 attached to the surface of the ceramic insulating substrate and the inner wall of the through hole 7,
A circuit conductor layer was formed.

Furthermore, in order to obtain a predetermined resistance value, this resistor layer 9 is coated with a resistor insulating protective layer 1 using a laser beam or sandblasting method.
It was cut from above 0 and adjusted to a predetermined resistance value.

In this example, a metal glaze type active paste was printed as an active paste for electroless plating, and
Calcined at ℃. 1. Nickel plating was performed as electroless group plating, and the nickel plating bath used was an electroless nickel plating solution with a pH of 6 to 7 consisting of nickel sulfate, ethylenediamine, and sodium hypophosphite, and the bath temperature was 66 to 70. Metallic nickel is plated at 5 to 2 degrees Celsius.
It was deposited to a thickness of 0μ.

In addition, a glass-based insulating paste is used that also serves as a plating-resistant protective film on the surface of the resistor, which quickly improves chemical and environmental resistance, and has a low melting point that makes it suitable for ceramic substrates and metal glaze-based resistors. Borosilicate lead glass is used as a glass insulation paste that has a similar coefficient of thermal expansion to the resistor layer, has little effect on the resistor layer, and is highly absorbent to laser light.This glass paste is then printed using a screen printing method. Apply to both sides of ceramic insulating substrate and heat to 400-500℃
A plating-resistant resistor insulating protective layer 10 was formed by firing at a temperature of .

Effects of the Invention As is clear from the above explanation, the membrane circuit board according to the present invention uses a ceramic insulating substrate with through holes in predetermined locations, and injects silver thread metal glaze conductor paste into necessary locations on both the front and back surfaces of the substrate. A conductor layer for connection terminals is formed by selectively applying and firing at a high temperature, and then a metal glaze-based resistor layer is formed on at least one surface of this ceramic insulating substrate, and then this resistor layer is formed. An insulating protective layer with plating resistance is formed on the surface of the resistor layer so that the resistor layer is completely protected, and an active paste for electroless plating is printed and fired in the desired wiring shape continuous with the conductor layer for the connection terminal. After that, electroless plating is performed to deposit a conductive metal layer on the exposed surface of the ceramic substrate and the inner wall surface of the through hole.

Therefore, the circuit conductor layer to be soldered on the thick film circuit board according to the present invention is electroless plated on the metal glaze conductor layer, and the other circuit conductor layers that do not require soldering are electroless plated. Since the structure is made of a conductive metal layer, short circuit failure due to migration between circuit conductors, which is a problem with conventional silver thread metal glaze conductor layers, and circuit conductors during soldering of circuit elements can be avoided. There are no layer disconnections, and the through-hole connections of the circuit conductor layers formed on both sides of the ceramic substrate are compensated by electroless plating, making the through-hole connections more reliable and improving reliability and yield. Many effects not found in conventional examples can be obtained, such as improved performance.

[Brief explanation of the drawing]

FIGS. 1A to 1D are cross-sectional views of the manufacturing part for explaining the manufacturing process of a thick film circuit board according to a conventional example, and FIGS. − A cross-sectional view of the main parts to explain the construction process = Zakuho≠Gyebong. It is a blood groove. 6...Ceramic insulating substrate, 7...Through hole, 8a8b...Conductor layer for connection terminal, 9...
...Resistor layer, 1°...Resistor insulating protective layer, 11...Active layer, 12...Conductive metal layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] A step of drilling a through hole at a predetermined position in a ceramic insulating substrate, selectively applying a metal glaze-based noble metal conductor paste to required locations on both the front and back surfaces of the ceramic insulating substrate, and forming a conductor layer for a connecting terminal by high-temperature firing. , a step of forming a metal glaze-based resistor layer at necessary locations between the connection terminal conductor layers formed on at least one main surface of the ceramic insulating substrate, and a step of forming an insulating protective layer on the surface of the resistor layer. , a step of printing an active paste for electroless plating in a desired wiring diagram shape that is continuous with the conductor layer for the connection terminal, and baking it to form an active layer; selectively forming a conductive metal layer on the surface of the active layer by electroless plating; A method for manufacturing a thick film circuit board comprising the step of depositing