JPH0428549B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a thermal head that provides contact conduction using an external connection board such as a flexible board.

(b) Prior Art An example of a conventional thermal head will be explained using FIG. 6. 21 is a thermal head board;
A heating resistor 23, a common electrode 24, individual electrode (not shown) connection terminals 25,..., 25 are formed on an insulating substrate 22 made of alumina ceramic, etc. for driving.
It is made by mounting IC26,...,26.
The heating resistor 23 and the common electrode 24 are connected to the insulating substrate 2
The common electrode 24 extends in the longitudinal direction of the heat generating resistors 23, and the common electrode 24 commonly energizes the heating resistors 23. Both ends of the common electrode 24 serve as connection terminals 24a, 24a.

The individual electrodes individually energize the heating resistor 23 and are wire-bonded to the driving IC 26, respectively. Further, the driving IC 26 is also wire-bonded to the connection terminal 25. Connection terminal 25
are assigned to each drive IC 26 in a predetermined number, and each drive IC 26 independently
For example, DI (data in), DO (data out),
It will have connection terminals such as V _DD and GND.

An edge 31a of a flexible substrate 31, which is an external connection substrate, is placed on the connection terminals 24a and 25. A conductor pattern (not shown) is formed on the flexible substrate 31 and is electrically connected to each of the connection terminals 24a and 25. Further, the flexible substrate 31 is reinforced by a reinforcing plate 32, and a connector (not shown) for connecting the flexible substrate 31 to the outside is attached to the reinforcing plate 32.

The flexible substrate edge 31a is secured to the thermal head substrate 2 by the silicone rubber 36 of the cover 35.
1. This cover 35 has screws 37,
..., 37 (only two at both ends are shown)
The tightening force of these screws 37, . . . , 37 generates a pressing force between the flexible substrate edge 31a and the thermal head substrate 21.
Further, this cover 35 has a function of protecting the driving IC 26. Note that 35a and 33 are insertion holes for the screws 37, and 30a is a female screw hole into which the screws 37 are screwed.

(C) Problems to be Solved by the Invention In the conventional thermal head described above, the flexible substrate edge 31a extends over substantially the entire length of the thermal head.
must be pressed onto the insulating substrate 22. For example, a thermal head for JIS-A4 size is approximately 21
cm, approximately 26 cm for JIS-B4 size thermal head
It is necessary to perform pressure welding over an interval of cm. Moreover,
This pressure-welding must be performed with a uniform force over the entire length of the section, and the cover 35 is attached to the heat sink 30 using a large number of screws 37,..., 37 (eight screws in the case of FIG. 6).
The tightening torque of these screws 37, . . . , 37 is controlled so that a uniform contact force can be obtained.

When the cover 35 is attached to the heat sink 30 using a large number of screws 37, . Due to the difference in thermal expansion coefficients between the plate 30 and the cover 35, a problem arises in that the thermal head becomes warped (so-called bimetal phenomenon).

In addition, a large number of screws 37 are required, and the insertion hole 35a and female screw hole 30a corresponding to the number of screws 37 are
must be processed into the cover 35 and the heat sink 30, respectively, which increases costs. Furthermore, since it is necessary to control the tightening torque of the screws 37, the time required for assembly becomes longer, which also raises the problem of increased costs.

The present invention has been made in view of the above, and an object thereof is to provide a thermal head which can prevent the bimetal phenomenon and reduce costs.

(d) Means for Solving the Problems The structure of the thermal head according to the first aspect of the present invention will be explained with reference to FIGS. 1 and 4, which correspond to one embodiment. The heating resistor 3, electrodes 4 and 7 for energizing the heating resistor 3, and connection terminals 5 for external circuit connection are formed on the surface of the heat sink 10, and the heating resistor 3 is placed on the heat sink 10. A plurality of drive circuit elements 6 that drive 3.
an insulating substrate 2 provided with a A conductor pattern 5a is provided on the insulating substrate 2 to commonly connect the same terminals of each of the drive circuit elements 6,
This conductor pattern 5a is integrally connected to the connection terminal 5, and the connection terminal 5 is connected to the insulating substrate 2.
, and the pressure-welded section is a part of the long side edge of the insulating substrate 2.

Further, the structure of the thermal head according to the second claim is as follows:
In the thermal head according to the first claim, the cover 1
5 is attached to the heat sink 10 with two screws 17a, and these two screws 17a press the external connection substrate 11 to the insulating substrate 12 in the shortened section.

(E) Effect In the present invention, the connection terminal 5 is placed at a proper position 2 on the insulating substrate 2.
Since the cover 15 and the heat dissipation plate 10 are tightly connected to each other, the section where the cover 15 and the heat sink 10 are firmly connected can be shortened because the pressure welding section is shortened. Therefore, even if the temperature rises, the cover 15 and the heat sink 10 can freely expand with each other, thereby preventing the bimetal phenomenon. Note that since the connection between the drive elements 6 and 6 was conventionally made on an external connection board,
There is no problem even if this is done using the conductor pattern 5a on the insulating substrate 2.

Also, by shortening the pressure welding section, the number of screws 17a can be reduced (two in the case of the second claim),
The number of parts and processing can be reduced, and the number of screws required for controlling the tightening torque can be reduced (two screws in the case of the second claim), and the assembly time can be shortened.

(F) Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

Fig. 1 is an exploded perspective view of the thermal head of the embodiment, Fig. 2 is a vertical sectional view of the thermal head, Fig. 3 is a rear view of the main parts of the thermal head, and Fig. 4 is a diagram of the thermal head. FIG. 2 is an enlarged plan view of the main parts of the thermal head substrate 1. FIG.

The thermal head substrate 1 has a conductor pattern formed on an insulating substrate 2 made of alumina ceramic or the like, and has a common electrode 4, connection terminals 5, individual electrodes 7, and a ground electrode 8. In addition, the insulating substrate 2
On the top, drive ICs 6, . . . , 6 are arranged in a row.

Looking more closely, the connection terminals 5 are arranged in a row at the center portion 2a of the rear edge of the insulating substrate. The number of connection terminals 5 is very small compared to the conventional one, but this is because the wiring, which was conventionally done on the flexible substrate side, is now done on the conductor pattern 5a on the insulating substrate 2. A part of these conductor patterns 5a is shown in FIG.
It is bonded to the pad 6a of the IC 6 and the wire W. Note that since the present invention does not involve the connection circuit itself of the driving IC 6 as a main part, a detailed explanation thereof will be omitted.

The conductor pattern 5a is connected to the connection terminal 5, and DI, DO, LA (latch), CLK (clock), _VDD , and STR (strobe) 1 to 4 are assigned. In addition, the drive IC6 located in the center,
Since it is difficult to directly wire bond the terminals 6 to the ground electrode 8 due to their arrangement, a dedicated ground terminal 5 (GND) is provided for each terminal.

The common electrode 4 is formed along the periphery of the insulating substrate 2, and its ends reach the rear central portion 2a of the insulating substrate to serve as connection terminals 4a, 4a. Connection terminal 4a
are three conductor patterns 4 having the same shape as the connecting terminal 5.
b is assigned, and silver paste 4c is applied overlappingly to lower the resistance value.

Reference numeral 7 denotes an individual electrode, and its tip portion 7a is arranged so as to mesh with the comb tooth portion 4d of the common electrode 4. The base ends 7b of the individual electrodes 7 are drawn out to the vicinity of the driving IC 6 and bonded to the corresponding pads 6b with wires W. Note that the reason why the individual electrodes 7 are drawn out obliquely is to provide a space between the driving ICs 6, 6.

A thick-film heating resistor 3 is formed on the common electrode comb tooth portion 4d and the individual electrode tip portion 7a. A portion of the heating resistor 3 sandwiched between the comb teeth portions 4d corresponds to one dot. Of course, the heating resistor 3 can also be made into a thin film, and the design can be changed as appropriate.

The ground electrodes 8, 8 extend in the longitudinal direction of the insulating substrate 2 along the inside of the common electrode 4 from the rear central portion 2a of the insulating substrate toward both ends 2b, 2b, respectively. The connection terminal 8a of the ground electrode 8 has conductor patterns 8b, . . . , 8b having a similar shape to the connection terminal 5.
is assigned, and silver paste 8c is applied to lower the resistance value. Both ground electrodes 8, 8 are bonded by wires W to the GND pads of the driving ICs 6, . . . , 6 except for the two central driving ICs 6, 6. In addition, for driving
IC6,...,6 are coated with resin 9, and wires W,
..., are protected by insulation together with W.

This is because the thermal expansion coefficients of the thermal head substrate 1 and the heat sink 10 are different, and this is to prevent the thermal head substrate 1 and the heat sink 10 from being warped by freely expanding each other as the temperature rises. .

The flexible substrate edge 11a overlaps the rear edge central portion 2a of the insulating substrate, and is formed with a conductor pattern (not shown) that is electrically connected to the connection terminals 4a, 5, and 8a. As described above, since the connection terminals 5 are concentrated at the center portion 2a of the rear edge of the insulating substrate, the width of the flexible substrate 11 (also the reinforcing plate 12) can be reduced.

The flexible substrate 11 has a reinforcing plate 1 as in the conventional case.
It is reinforced by 2. A connector 14 is attached to the reinforcing plate 12.
The pin 14a is connected to a conductive pattern (not shown) on the flexible substrate 11.

The reinforcing plate 12 is attached to the cover 15 with two screws 1.
It is fixed to the heat sink 10 by screws 7a (see also FIG. 2, only one screw 17a is shown). Screw 17a is
It is inserted through the insertion hole 15a of the cover 15 and the insertion hole 13 of the reinforcing plate 12, and is screwed into the female screw hole 10a of the heat sink 10. At this time, the silicone rubber 16 on the bottom surface of the cover 15 presses the flexible substrate edge 11a against the rear edge central portion 2a of the insulating substrate. Conductor pattern on flexible board edge 11a and connection terminals 4a, 5, 8
The tightening torque of the screws 17a, 17a is controlled so that uniform contact and conduction with the screws 17a and 17a can be achieved. In this embodiment, the pressure welding is performed only by the tightening force of the two screws 17a, 17a, but this is because the width of the flexible substrate 11 may be narrow as described above, and the screws can be attached more easily than before. The tightening torque can be controlled.

Large-diameter insertion holes 15b are bored at both ends of the cover 15. A spacer 18 is inserted into the insertion hole 15b, and a screw 17b is screwed into the female screw hole 10b of the heat sink 10 through the spacer 18. (See also FIG. 3; only one screw 17b and only one spacer 18 are shown).
The head of the screw 17b is in contact with the cover 15, but the tightening force of the screw 17b is solely due to the spacer 18, and the screw 17b is simply attached to the cover 15.
The structure is such that the head of No. 5 is prevented from lifting up. Therefore, the cover 15 is firmly connected to the heat sink 10 only at the portion sandwiched by the screws 17a, and no bimetal phenomenon occurs when the temperature rises.

Note that the heat sink 10 and the cover 15 have two female screw holes 10a, 10a and two insertion holes 15a, 1
As long as the pitch p of 5a is present, the conventional 8-hole heat sink (not shown) and cover 15', and the 6-hole heat sink (not shown) and cover 15'' can be used, as shown in FIGS. 5a and 5b. can be used as is.

Not only that, in the past, the number of screws was large and the pitch varied depending on the model, and each part had to be made differently for each model, making it difficult to mass produce and resulting in high costs. Since there are fewer parts and their positions can be easily standardized, the heat sink and cover can be made common to all models, increasing mass production and reducing costs.

Further, in the above embodiment, the connection terminals are gathered at the center of the rear edge of the insulating substrate, but the position where the connection terminals are gathered is not limited to this, and the design can be changed as appropriate.

Further, the external connection board is not limited to a flexible board, and the design can be changed as appropriate.

(G) Effects of the Invention According to this invention, a conductor pattern is provided on the insulating substrate to commonly connect the same terminals of each drive circuit element, and this conductor pattern is integrally connected to the connection terminal, and If the connection terminals are collectively formed at appropriate locations on the insulating board, and the pressure welding section is a part of the long edge of the insulating board, for example, if the cover, support plate, and insulating board are fixed near the connection terminals, then , the so-called bimetal phenomenon can be prevented, the number of fixing screws, etc. can be reduced, and the external circuit board can also be made smaller, so that costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a thermal head according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the thermal head, and FIG. 3 is a partially cutaway view of the thermal head. Figure 4 is a plan view of the main part of the thermal head board of the same thermal head;
5a and 5b are plan views showing the thermal head with a conventional cover applied thereto, and FIG. 6 is an exploded perspective view of the conventional thermal head. 2... Insulating substrate, 2a... Center portion of rear edge of insulating substrate, 3... Heat generating resistor, 4... Common electrode, 5...
Connection terminal, 5a...Conductor pattern, 6...For driving
IC, 7... Individual electrode, 10... Heat sink, 11...
...Flexible board, 15...Cover, 17a...
…Screw.

Claims (1)

[Scope of Claims] 1. A support plate, a heat generating resistor placed on the support plate, on the surface of which a heat generating resistor, an electrode for energizing the heat generating resistor, and a connection terminal for connecting an external circuit are formed, and An insulating substrate provided with a plurality of drive circuit elements for driving a resistor, an external connection substrate that makes contact with the connection terminal, and a cover that presses the external connection substrate against the insulating substrate. In the thermal head, a conductor pattern is provided on the insulating substrate to commonly connect the same terminals of each of the drive circuit elements, the conductor pattern is integrally connected to the connection terminal, and the connection terminal is connected to the connection terminal. 1. A thermal head, characterized in that the thermal head is formed all together at a proper location on an insulating substrate, and the pressure-welded section is a part of a long edge of the insulating substrate. 2. The cover is attached to the heat sink with two screws, and the tightening force of these two screws presses the external connection board to the insulating board in the shortened section. The thermal head according to item 1.