Method of fabricating print head for thermal printer

DETAILED DESCRIPTION OF THE INVENTION First, a substrate of alumina is prepared.
Then, the substrate is glazed.
Thereafter, a thin metal film, preferably less than about 1 .
mu.
m thick, is formed over the whole glazed surface of the substrate.
The metal of this thin film should be so selected that it is adapted as a metal backing a metal plating (described later).
If this thin metal film is too thick, a pattern will be formed with poor accuracy during later photoetching process (described later).
Further, it will take a long time to dissolve away metal layers during the last lift-off process.
Therefore, it is desired that the thin metal film have the least thickness required as the backing metal film for the plating layer.
Subsequently, the portion of the thin metal film that makes contact with the heater portion of the head is removed by photoetching process.
Then, a metal film is formed on the remaining metal film by plating process.
Any metal can be used as the material of the plating as long as it allows selective etching of the glaze layer and of an insulator layer (described later).
Preferably, this plating film is about two times or more as thick as the later formed insulator layer; otherwise, the insulator layer would cover large step walls, making it difficult to lift off the plating film in the final step.
The reasons why the plating film is used in this way in the invention are that thick films can be readily obtained and that they can be shaped according to the shape of the backing film.
In particular, since the backing film is thin, it can be patterned with good accuracy.
The plating film grows on this pattern and so a metal film accurately patterned can be derived.
In this way, large step coverage that is indispensable to the lift-off method can be easily realized by the method according to the invention.
Subsequently, a layer of a chemically stable and heat-resistant insulator is formed over the whole plated surface of the substrate.
At this time, it is not necessary to take a countermeasure to prevent the temperature of the substrate from rising when the insulator layer is formed as in the ordinary lift-off method using photoresist