JPH0357656A - Thermal head - Google Patents

Abstract

PURPOSE:To make it possible to miniaturize a thermal head device by connecting a thermal head substrate to a wiring substrate for driving a thermal element on which the former is placed together using wire bonding technique. CONSTITUTION:A thermal head substrate 3 is bonded to a wiring substrate 2 on which the former is placed together. Then an IC chip 5 mounted on the wiring substrate 2 must be of the same thickness as the thermal head substrate 3, for example, 0.3 to 0.4mm and both are connected using wire bonding tech nique. A connecting cable is a flexible substrate and supplies a signal and power from an outside system. A heat release plate 1 has an about 5 deg. to 7 deg. inclination, and this inclination angle represents a gradient with a recording surface. As the surface of an IC chip 5 is almost at the same height as the surface of a thermal head substrate 3, it is possible to reduce the height of a sealing resin from the conventional 1.0mm to 0.5 to 0.6mm or half as much. In addition, as the wiring substrate 2 can be placed over the thermal head substrate 3, the overall size is reduced half or about 10mm compared to the conventional 20mm.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a thermal head.

[Conventional technology]

Thermal heads are often used in small portable recording devices.

Conventionally, this type of thermal head has a structure as shown in FIG.

A heating element portion 4 is formed on a thermal head substrate 3 made of ceramic or the like, an IC chip 5 is mounted on a wiring substrate 2, and the IC chip 5 is connected by wire bonding or the like.

These are heat sink 1. glued on top.

[Problem to be solved by the invention]

Incidentally, recently, thermal heads have been used as thermal transfer or thermal recording devices in portable hand-held copiers, word processors, and the like. In that case,
A common method is to manually record by pressing the thermal head portion from above against a document or recording paper placed on a desk or the like.

There are two types of thermal heads: one type has a heating element on the edge of the board and prints with the thermal head tilted at an angle of 5 degrees or more, and the other type has a heating element on the edge of the board and prints with the thermal head vertical. There is.

The latter case has the advantage of being able to make the thermal head the most compact, but it has the disadvantage that forming a heating element on the end face increases the burden on the manufacturing process and increases costs, and the former case has the disadvantage that the IC chip The inclination angle must be increased to prevent the sealing part from hitting the recording surface, or the overall size of the thermal head must be increased, which has the disadvantage of sacrificing printing quality and device size. Was.

[Means to solve the problem]

The thermal head of the present invention is constructed by stacking a thermal head substrate on which a heating element is formed on a wiring board on which an IC chip for driving the heating element is mounted, and connecting the thermal head substrate with wire bonding.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a sectional view of the first embodiment of the present invention. The thermal head board 3 is bonded to overlap the wiring board 2 and placed on a heat sink. Here, the thickness of the IC chip 5 mounted on the wiring board 2 and the thermal head board 2 are set to be approximately the same by 0.3 to 0.
．． The height is about 4+nm, and both are connected by bonding wire.

The connection cable 8 is a flexible board and supplies signals, power, etc. from the outside.

Here, the heat sink 1 has an inclination of about 5° to 7°, and this angle is the inclination angle with respect to the recording surface.

In this embodiment, the height of the IC chip 5 surface is approximately the same as the height of the thermal head substrate 3 surface, so the height of the sealing resin 7 should be halved from the conventional 1.0 mi to between 0.5 and 0.6. I can do it.

Also, since the wiring board 2 is overlapped with the thermal head board 3, the overall size has been reduced from the conventional 20 mm to 10 mm.
It can be reduced to half of 1llI1. FIG. 2 is a sectional view of a second embodiment of the invention.

The wiring board has an insulating layer 22 on the surface of an aluminum wiring board 21 which also serves as a heat sink, and can be further miniaturized than the first embodiment.

Furthermore, as shown in the difference from FIG. 1, wire bonding does not have to be a method of connecting directly onto the chip.

〔Effect of the invention〕

As explained above, in the present invention, the thermal head substrate and the wiring board are partially overlapped, so that the present invention has the advantage that it is possible to downsize the thermal head device.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a first embodiment of the invention, FIG. 2 is a sectional view of a second embodiment of the invention, and FIG. 3 is a sectional view of an example of a conventional thermal head. DESCRIPTION OF SYMBOLS 1... Heat sink, 2... Wiring board, 3... Thermal head board, 4... Heating element part, 5... IC chip,
6... Bonding wire, 7... Sealing resin, 8...
...Connection cable, 21...Aluminum wiring board, 22.
...Insulating layer, 23... Wiring pattern layer.

Claims (1)

[Claims] A thermal head characterized in that a thermal head substrate on which a heating element is formed is stacked on a wiring board on which an IC chip for driving the heating element is mounted and connected by wire bonding.