JP3434959B2 - Head drive IC - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head driving IC mounted on a thermal head, an LED array head or the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a head driving IC mounted on a thermal head or the like has a large number of output transistor sections 2 on one main surface of a rectangular IC substrate.
1 and the logic circuit section 22 are formed respectively.

Each of the output transistor portions 21 is composed of an output pad formed by depositing solder on the surface of a bump electrode made of chromium or the like, and a switching transistor connected to the output pad. The output transistor section 21 is divided into a plurality of columns (for example, three columns) and arranged in order to reduce the size of the IC.

The rows of such output transistor sections 21 are close to each other, and all the output transistor sections 2 are
1 is concentrated in a predetermined area (near one long side 20a of the IC substrate). The output pad has a diameter of 50.
The long side of the IC substrate is 20
a is arranged substantially in parallel with a at a pitch P1 of 150 to 250 μm, and is 100 to substantially parallel to the short sides 20c and 20d of the IC substrate.
They are arranged at a pitch P2 of 200 μm.

On the other hand, the logic circuit section 22 is composed of a shift register, a latch and a gate circuit. Like the output transistor section 21, this logic circuit section 22 is also near the other long side 20b of the IC substrate. It is centrally located in.

When such a head driving IC is used as a driver IC for a thermal head, the output pad of the output transistor portion 21 formed on one main surface of the IC substrate is brought into contact with the individual lead electrodes of the thermal head substrate. Then, a predetermined heat is applied to the contact portion between the output pad and the individual lead electrode, and the two are solder-bonded to be mounted at a predetermined position on the thermal head substrate. , Each output transistor section 2 based on an image signal or the like supplied from the outside (printer or the like)
By controlling the on / off of the power applied to the individual lead electrodes and the like by 1, the function as a head driving IC is achieved.

[0007]

However, in this conventional head driving IC, the output transistor section 21 and the logic circuit section 22 are concentrated in different regions, and the output transistor section 21 is arranged in an adjacent column. Close to each other. Therefore, the head drive I
When C is downsized, the interval between the adjacent output transistor sections 21 becomes extremely narrow, and the pitch of the individual lead electrodes solder-bonded to the output pads of the output transistor section 21 also depends on the pitch P2 of the output pads. Will have to be set extremely short. As a result, when forming the individual lead electrodes on the thermal head substrate by the photolithography technique or the like, it is difficult to accurately pattern these.

If the output transistor section 21 is close to that of the adjacent column, the size of the solder of the output pad becomes small, and therefore the head drive I
When C is mounted on a substrate such as a thermal head, the thermal expansion difference between the substrate and the head driving IC cannot be sufficiently absorbed by the elastic deformation of the solder, and the head driving IC
A defect that the thermal stress is disengaged from the substrate is induced.

Further, when the output transistor sections 21 are close to each other in the adjacent columns, the risk of short circuit due to contact between adjacent solders when the head driving IC is mounted on the substrate. There was also a nature.

[0010]

SUMMARY OF THE INVENTION Head drive I of the present invention
C is a large number of output transistor sections each including an output pad solder-bonded to an electrode on the head substrate and a switching transistor arranged in the immediate vicinity of the output substrate on one main surface of a rectangular IC substrate. Are arranged in a plurality of rows substantially parallel to one long side of the IC substrate, and a logic circuit portion connected to the switching transistor is arranged near the other long side of the IC substrate, and a part of the logic circuit portion is arranged. Are arranged in a region between the respective columns of the output transistor section. Further, the present invention is characterized in that the output transistor portions are arranged in a plurality of rows with a space of 50 μm to 200 μm.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of a head driving IC of the present invention, FIG. 2 is a block diagram showing an electrical configuration when the head driving IC of FIG. 1 is applied to a thermal head, and FIG. 1 is a schematic diagram showing a configuration of an output transistor section of the head driving IC of FIG. 1, 1 is an IC substrate, 2 is an output transistor section, 2a is an output pad, 2b is a switching transistor, 3 is a logic circuit section, 4 is a GND pads, 5a to 5d are control signal input pads, and 6a to 6
Reference numeral d is a control signal output pad.

The head drive IC shown in FIG. 1 is a flip chip type which has a predetermined quadrilateral shape (0.7 mm length × 6.0 mm width) in a plan view.
A large number of output transistor sections 2 are arranged in a plurality of rows (for example, three rows) substantially parallel to one long side 1a of the IC substrate 1.

The plurality of output transistor units 2 are n (for example, 32) in one line, and a space Q of 50 to 200 μm is provided between each line.

The output transistor section 2 is an output pad 2
a and a switching transistor 2b. For example, when this head driving IC is used as a driver IC of a thermal head, the output pad 2a is electrically connected to a heating element via an individual lead electrode on the thermal head substrate. It is connected and has a function of controlling on / off of a current flowing through a heating element or the like based on an image signal stored in a logic circuit section 3 described later.

The output pad 2a is formed in a circular shape (diameter 50 to 200 μm) by applying solder to the surface of a bump electrode made of, for example, chromium, copper or the like. When it is mounted on the thermal head substrate, it is soldered to each individual lead electrode on the thermal head substrate one by one.

The output pads 2a are arranged substantially parallel to the long side 1a of the IC substrate 1 at a pitch P3 of 150 to 250 μm, and the row of the output pads 2a is substantially parallel to the short side 1c of the IC substrate 1. They are arranged at a pitch P4 of 150 to 400 μm.

Further, the switching transistor 2b
Is a combination of a comb-teeth-shaped drain electrode D connected to the output pad 2a and a comb-teeth-shaped source electrode S connected to the GND pad 4, and will be described later between the two electrodes D and S. Has a structure in which a gate electrode connected to the gate circuit G of the logic circuit section 3 is provided, and when the switching transistor 2b is in a conductive state, it is provided to a heating element or the like of the thermal head via the output pad 2a. It is designed to pass an electric current.

Incidentally, such a switching transistor 2b is formed by a conventionally well-known integrated circuit forming technique.

On the other hand, the logic circuit section 3 is arranged on one main surface of the head driving IC including the area between the columns of the output transistor section 2 so as not to overlap with the output transistor section 2. And the logic circuit unit 3
Is, for example, a portion occupying an area of about ½ of the whole is arranged at a position close to the other long side 1b, and a portion occupying the other half is the first column of the output transistor section 2 and Half of each is arranged between the second rows and between the second and third rows.

The logic circuit section 3 has a shift register for serially transferring an image signal from the outside (printer or the like) bit by bit in synchronization with a clock signal, and for holding these image signals at the timing of the latch signal. And a gate circuit G that outputs a predetermined output to the switching transistor 2b based on the image signal and the strobe signal held by the latch circuit, and the logic circuit section 3 configured by them. Serves to control the above-mentioned switching operation of the switching transistor 2b of the output transistor section 2 according to the image signal and the strobe signal.

By arranging a part of the logic circuit section 3 between the columns of the output transistor section 2 as described above,
The output transistor portions adjacent to each other in the short side direction of the IC substrate 1 can be arranged with a distance Q therebetween. As a result, the individual lead electrodes and the like to be soldered to the output pad 2a can be provided with a margin, and the individual lead electrodes and the like can be easily and accurately formed on the substrate such as the thermal head by the photolithography technique or the like. It becomes possible.

As described above, since the output transistor section 2 is separated from the adjacent row by the distance Q, the solder size of the output pad 2a can be increased,
As a result, when the head driving IC is mounted on a substrate such as a thermal head, the thermal expansion difference between the substrate and the head driving IC is favorably absorbed by the elastic deformation of the solder, and the head driving IC can be securely mounted on the substrate. It is possible to firmly attach.

Further, in this case, since the output transistor section 2 is separated from the adjacent row by a distance Q, short circuit between adjacent solders is effectively prevented when the head driving IC is mounted on the substrate. It is also possible to manufacture a thermal head or the like with good yield.

Moreover, in this case, the head driving IC does not increase in size and can be manufactured in the same size as that of the conventional example.

Incidentally, such a head driving IC is an IC
Input pads 5a to 5d for image signals, clock signals, latch signals, and strobe signals are provided in the vicinity of one short side 1c orthogonal to the long side 1a of the base 1, and the other short side 1d opposite to the short side 1c. The image signal, clock signal, latch signal and strobe signal output pads 6a to
6d are arranged respectively.

Thus, when the above head driving IC is used as a driver IC for a thermal head, the output pad 2a of the output transistor section 2 formed on one main surface of the IC substrate 1 contacts the individual lead electrode of the thermal head substrate. As described above, the thermal head substrate is mounted on the thermal head substrate by applying predetermined heat to the contact portion between the output pad 2a and the individual lead electrode and soldering them together. It is mounted at a predetermined location and functions as a head driving IC by controlling ON / OFF of electric power applied to individual lead electrodes or the like in each output transistor section 2 based on an image signal supplied from the outside.

The present invention is not limited to the above embodiment, and various modifications and improvements can be made without departing from the gist of the present invention.

[0029]

According to the present invention, without increasing the size of the head driving IC, the space between the columns of the output transistor section is increased, and the individual lead electrodes and the like connected to the output transistor section are provided with a margin. Can be held. This makes it possible to easily and accurately form individual lead electrodes and the like on a substrate such as a thermal head by a photolithography technique or the like.

Further, according to the present invention, since the output transistor section is separated from the adjacent row by a predetermined distance, the size of the solder of the output pad can be increased. As a result, when the head driving IC is mounted on a substrate such as a thermal head, the thermal expansion difference between the substrate and the IC is well absorbed by the elastic deformation of the solder, and the IC is securely and firmly attached to the substrate. It becomes possible to keep it.

Further, according to the present invention, since the output transistor section is separated from the adjacent row by a predetermined distance, when the head driving IC is mounted on the substrate, a short circuit between adjacent solders is also effective. It is also possible to manufacture the thermal head and the like with high yield.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a head driving IC of the present invention.

FIG. 2 is a block diagram showing an electrical configuration when the head driving IC of FIG. 1 is applied to a thermal head.

FIG. 3 is a schematic diagram showing a configuration of an output transistor section of the head drive IC of FIG.

FIG. 4 is a plan view showing a conventional head driving IC.

[Explanation of symbols]

1 ... IC substrate 1a, 1b ... long side 1c, 1d ... Short side 2 Output transistor section 2a ... Output pad 2b ... Switching transistor 3 ... Logic circuit 4 ... Pad for GND 5a to 5d ... Control signal input pad 6a to 6d ... Control signal output pad

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/335 B41J 2/345 B41J 2/45 H01L 21/60 H01L 27/04

Claims (2)

(57) [Claims] 1. An output pad , which is solder-bonded to an electrode on a head substrate, on one main surface of a rectangular IC substrate ,
A switching transistor placed in the immediate vicinity of the output pad
And a plurality of output transistor sections each including a plurality of output transistors are arranged substantially parallel to one long side of the IC substrate, and
A head drive characterized in that a logic circuit section connected to the switching transistor is arranged in the vicinity of the other long side of the substrate , and a part of the logic circuit section is arranged in a region between each column of the output transistor section. IC. 2. The output transistor section is 50 μm to 20 μm.
Special feature is that they are arranged in multiple rows with an interval of 0 μm.
Head drive IC to be considered.