JPS5847713Y2 - Thin film hybrid circuit for thermal recording head - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a thin film hybrid circuit for a thermal recording head in which a thin film resistor as a heating element and other active or passive elements are wired on the same substrate using thin film wiring conductors.

Generally, in a thin film hybrid circuit having a thin film resistor such as a thermal recording head, a ceramic substrate covered with a glass layer is used as the substrate from the viewpoint of uniformity and reproducibility of the resistance value of the thin film resistor part. It will be done.

FIG. 1 is a cross-sectional view of a conventional thin film hybrid circuit, in which a glass layer 2 is formed on a ceramic substrate 1, and a thin film resistance layer and a thin film metal layer are deposited thereon by vacuum evaporation, plating, etc. A thin film resistor 3 and a thin film wiring conductor 4 are formed by chemical etching or the like.

In the peripheral area of the thin film resistor 3, semiconductor active elements such as diodes and transistors, chip capacitors, etc.
A passive element 5 such as a chip resistor is connected onto the thin film wiring conductor 4 by a method such as soldering, thermocompression bonding, or ultrasonic bonding.

However, in the thin film hybrid circuit formed in this way, the glass layer 2 may break due to heat and mechanical pressure during the mounting of the elements 5, and as a result, the thin film wiring conductor 4 at the connection part of these elements 5 may break. There is a risk of peeling off the wire, disconnection, and even destruction of the semiconductor active element.

This idea was devised in view of the above problems, and its purpose is to prevent the glass layer on the ceramic substrate from breaking when mounting element parts other than thin film resistors such as semiconductor active elements, thereby preventing peeling of the thin film wiring conductor. It is an object of the present invention to provide a thin film hybrid circuit for a thermal recording head, which prevents wire breakage and element destruction, and has a structure useful as a thermal recording head.

In this idea, a glass layer is interposed between the thin film resistor as a heating element, the thin film wiring conductor at the connection part thereof, and the semiconductor substrate, but active or passive elements other than the thin film resistor are connected to the thin film wiring conductor. By forming the conductors directly on the ceramic substrate without using a glass layer, these elements can be mounted without applying heat or pressure to the glass layer.

By doing this, destruction of the glass layer can be prevented.

In addition, since this glass layer is originally intended to obtain uniformity and reproducibility of the resistance value of the thin film resistor as mentioned above,
As mentioned above, there is no problem in removing the glass layer below the thin film wiring conductor at the connection portion other than the thin film resistor.

Further, in this invention, a thin film resistor is formed in a region covered with a glass layer of a ceramic substrate as a convex portion.

Therefore, when configuring a thermal recording head that uses a thin film resistor as a heating resistor, the thermal recording paper that runs in sliding contact with the head does not have to be bent that much, but only the heating resistor part can be easily bent. can be opposed with a certain contact pressure.

An embodiment of this invention will be described below with reference to FIG.

FIG. 2 shows a cross-sectional view of the thin film hybrid circuit according to this invention.

That is, the ceramic substrate 1 is covered with a glass layer 2 to form a convex portion, and the thin film resistor 3 and the thin film wiring conductor 4 at the connection portion thereof are formed on this glass layer 2. Among the wiring conductors, the conductor 4' at the connection part of the semiconductor active element such as a diode or transistor or the passive element (hereinafter simply referred to as an element) 5 such as a chip capacitor or chip resistor is formed directly on the ceramic substrate 1. .

To form such a thin film hybrid circuit, first, the glass layer 2 is formed only on the ceramic substrate 1 except for the wiring area of the element 5, or the glass layer 2 is formed on the entire surface of the substrate 1. After the formation, the glass layer is removed only in the wiring area by chemical etching or the like to expose the substrate 1.

Next, a thin film resistance layer and a thin film metal layer are formed by a vacuum deposition method, a plating method, etc., and each thin film layer is formed into a thin film resistor 3 and a thin film wiring conductor 4 by a chemical etching method or the like.

Then, the element 5 is connected to the thin film wiring conductor 4' in the wiring area where the ceramic substrate 1 is exposed by a method such as soldering, thermocompression bonding, or ultrasonic punching.

In the thin film hybrid circuit formed in this way, the element 5
Since the glass layer 2 is connected to the thin film wiring conductor 4' formed on the exposed portion of the ceramic substrate 1, the glass layer 2 will not be destroyed by heat or pressure when the element 5 is attached.

Therefore, a thin film hybrid circuit can be easily obtained with good reproducibility without peeling of the thin film wiring conductor 4' at the connecting portion of the element 5, disconnection, or destruction of the semiconductor element due to the destruction of the glass layer 2.

Also, in terms of tensile strength, glass has a tensile strength of 150kg/cm2.
On the other hand, ceramic has a weight of 1500 kg/cm2, which is about 10
Since there is a double difference, mounting active elements and passive elements other than the thin film resistor directly on the ceramic substrate as in the present invention also has the advantage of being more mechanically stable.

Further, when a thermal recording head is configured using the thin film resistor 3 as a heating resistor, it is possible to prevent unnecessary friction between the recording paper and the head and perform highly reliable thermal recording.

Note that this idea is not limited to single-layer wiring as shown in the diagram.
It can also be applied to thin film hybrid circuits with multilayer wiring structures.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional thin film hybrid circuit, and FIG. 2 is a sectional view of a thin film hybrid circuit showing an embodiment of this invention. 1... Ceramic substrate, 2... Glass layer, 3... Thin film resistor, 4, 4'...
Thin film wiring conductor, 5... Active or passive element other than thin film resistor.

Claims (1)

[Scope of utility model registration request] In a thin film hybrid circuit for a thermal recording head in which a thin film wiring conductor, a thin film resistor as a heat generating element, and other active or passive elements are integrated on a ceramic substrate, a convex portion covered with a glass layer and a glass layer are provided on the ceramic substrate. the thin film resistor and the thin film wiring conductor are formed on the convex portion covered with the glass layer, and a part of the thin film wiring conductor is extended to the region without the glass layer. A thin film hybrid circuit for a thermal recording head, characterized in that the extended portion is a connection portion to a terminal of an active or passive element other than the thin film resistor.