JP3103170B2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used by being pressed against a platen.

[0002]

2. Description of the Related Art A thermal head used while being pressed against a platen is often used for printing. In general, a thermal head includes a thermal print head substrate formed with a heating resistor arranged in the print scanning direction, an IC chip for driving the heating resistor, and a conductor connecting the two, and the head substrate is pressed against a platen. Is what is done. It is to be noted that the head substrate is usually fixed on a support plate that also serves as heat radiation.

In such a thermal head, a face-down method may be used for attaching an IC chip to a head substrate. In the face-down method, a large number of bumps (protruding electrodes) made of solder or the like are provided on the chip surface, and the chip surface is bonded to a conductor on a substrate with the chip surface facing down, which is suitable for high-density mounting. In the bonding by the face-down method, it is general that the bumps of the IC chip are made of solder, and the solder bumps are soldered to the conductor pads of the substrate. However, when heat or mechanical stress acts on the IC chip or the substrate, the solder is easily peeled off, which may result in poor conduction between the IC chip and the conductor. Also, for soldering,
It is difficult to make the contact pad smaller than this, which hinders higher-density mounting.

To solve the above problem, as shown in FIG. 3, bumps 3 on an output side and an input side of an IC chip 32 are provided.
The gold bumps 2a, 32b, and 32c are made of gold, and the gold bumps are pressed and connected to the conductors 31 of the head substrate 30 by applying pressure. Further, an insulating resin (typically, an ultraviolet-curable insulating resin) is provided around the IC chip 32. There is also a case where the IC chip 32 is fixed and held on the head substrate 30 by applying and curing the IC chip 33 and contracting force of the insulating resin 33 at the time of curing.

[0005]

The bumps formed on the surface of the IC chip 32 are arranged as shown in FIG. The output side is composed of two rows of an outer bump 32a and an inner bump 32b, and the input side is a bump 32c.
In one column. In each bump row, bump 32
a, 32b and 32c are arranged at regular intervals.

In the method of mounting the IC chip 32 as shown in FIG. 3, in order to make electrical connection between the bump and the conductor, the IC
The chip 32 must be pressed against the head substrate 30 with a certain force F. However, as shown in FIG.
Since the bumps of the C chip 32 are large on the output side and small on the input side, the force F is difficult to be evenly transmitted to the bumps. For this reason, there are bumps that are insufficiently bonded and bumps that cannot be bonded, and there is a high possibility that an electrical failure will occur.

For example, in the state shown in FIG. 3, since the force transmitted to the bump 32c on the input side becomes large, the bump 32c
The conductor 31 is sufficiently bonded, but the output side bump 3
Since the force transmitted to the bumps 2a and 32b is small, the bump 32
b and the conductor 31 are not sufficiently bonded or the bump 32
a is not bonded to the conductor 31. Accordingly, an object of the present invention is to provide a thermal head in which the force applied when bonding an IC chip to a conductor on a substrate by pressing is transmitted evenly to the bumps of the IC chip, and the electrical connection between the bump and the conductor is good. Is to do.

[0008]

In order to achieve the above object, a thermal head according to the present invention comprises a heating resistor, an IC chip for driving the heating resistor, and a conductor for connecting the heating resistor to the IC chip. IC chip comprising a substrate having
On the surface of each row so as to form multiple rows in the longitudinal direction
To a plurality of bumps, it pressed against the O Rishirube body bumps of the IC chip to the Fe <br/> Isudaun method, I an insulating resin
In a thermal head having a C chip fixed to a substrate, the bumps of the IC chip have the same shape and substantially the same size.
Where the bumps in each row are arranged at equal intervals, and the
Are equal .

In the thermal head of the present invention, all the bumps on the output side and the input side have the same shape and substantially the same size.
In addition, the bumps of each row are arranged at equal intervals, and
Since the gaps are also equal , the force applied to the IC chip is evenly transmitted to the bumps, and the occurrence of electrical failure due to insufficient bonding or non-bonding between the bumps and the conductor is minimized. The bump I
The distribution form on the surface of the C chip is not limited as long as the force applied when the bump is pressed against the conductor of the substrate is uniformly transmitted to the bump. However, the pressurizing force is effectively evenly distributed the bumps, in addition to the first aspect, the spacing of the bumps of adjacent in the transverse and longitudinal directions of the IC chip are substantially equal, respectively (claim 2) is desirable.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal head according to the present invention will be described below with reference to embodiments. FIG. 1 is a plan view of the surface of an IC chip mounted on a thermal print head substrate in the thermal head according to the embodiment. The rectangular parallelepiped bumps of the same size provided on the front surface 1a of the IC chip 1 are composed of three rows of bumps 2, 3, and 4 on the output side and one row of bumps 5 on the input side. The number of bumps 2 to 5 arranged in each row in the longitudinal direction of the IC chip 1 is all the same (8 in this embodiment).
In the transverse direction, the bumps 2 to 5 in each row are equally spaced (C ₁ , C ₂ ,
C ₃ , C ₄ ) are arranged in the longitudinal direction, and the intervals in each row are also equal (C ₁ = C ₂ = C ₃ = C ₄ ).

[0011] In this embodiment, the interval of the bumps of adjacent in the transverse direction of the IC chip 1, i.e. distance A ₁ between the bump 2 and the bump 3, distance A ₂ between the bump 3 and the bumps 4,
The distance A ₃ between the bumps 4 and 5 is substantially equal (A ₁
≒ A ₂ ≒ A ₃ ). Also, the interval between adjacent bumps in a row, that is, the interval B between the bumps 2 and 4 and the bumps 3 and 5 is all the same.

FIG. 2 shows a state in which such an IC chip 1 in which the distribution of all the bumps 2 to 5 is uniform is attached to the conductor 11 of the thermal printhead substrate 10. As described above, the method of mounting the IC chip 1 on the head substrate 10 by the face-down method is as follows.
Is pressed and connected to the conductor 11 of the head substrate 10 by applying pressure, an insulating resin (for example, an ultraviolet-curing insulating resin) 12 is applied around the IC chip 1 and cured, and the contraction force of the insulating resin 12 at the time of curing is applied. The IC chip 1 is fixed and held on the head substrate 10. In this embodiment, conductor pads are provided at relative positions of the head substrate 10 corresponding to the bumps 2 to 5.

When the force F is applied to the back surface of the IC chip 1 when the IC chip 1 is pressed, the bumps 2 to
5 is uniform, the magnitude of the force applied to the output side and the input side does not vary, and the force F is transmitted evenly to each of the bumps 2 to 5, so that the joint between each of the bumps 2 to 5 and the conductor 11 is formed. Be full and complete. For this reason, there is no electrical defect such as a weak connection between the bump and the conductor or an incomplete connection between the bump and the conductor.

[0014]

According to the thermal head of the present invention, as described above, the bumps provided on the surface of the IC chip have the same shape.
And almost the same size, and the bumps in each row are equally spaced
Since they are arranged at intervals and the intervals between rows are equal , the following effects are obtained. (1) Since the pressing force is evenly transmitted to the bumps, the connection between the bumps and the conductor on the substrate is assured, and no electrical failure occurs due to disconnection or poor connection between the bumps and the conductor. (2) Since the fixing of the IC chip to the substrate is performed without using solder and using the contraction force generated when the insulating resin is cured,
Both the conductor pads on the substrate and the bumps on the IC chip need to be small in size, and are suitable for higher density mounting. (3) According to the configuration of claim 2, an IC chip table of bumps
The above effects (1),
(2) becomes more remarkable.

[Brief description of the drawings]

FIG. 1 is a plan view showing the surface of an IC chip mounted on a thermal print head substrate in a thermal head of the present invention.

FIG. 2 is a sectional view showing a state where the IC chip shown in FIG. 1 is mounted on a head substrate.

FIG. 3 is a cross-sectional view showing a conventional thermal head in which a normal IC chip is mounted on a head substrate.

FIG. 4 is a plan view showing the surface of the IC chip shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 IC chip 1a Surface of IC chip 2, 3, 4, 5 Bump 10 Thermal print head board 11 Conductor 12 Ultraviolet curing type insulating resin

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/345 H01R 11/01

Claims (2)

(57) [Claims] And 1. A heating resistor, an IC chip for driving the heating resistor comprising a substrate having a conductor to contact the heating resistor and the IC chip, the surface of the IC chip, the longitudinal
Set multiple bumps for each row so that multiple rows are
The bumps of this IC chip are
Pressed against the Rishirube body, the thermal head comprising an IC chip is fixed to the substrate by an insulating resin, the bumps of the IC chip Oh substantially the same size in the same shape
The bumps in each row are arranged at equal intervals, and the
A thermal head, characterized in that Shii. 2. The thermal head according to claim 1, wherein the intervals between adjacent bumps in the transverse direction and the longitudinal direction of the IC chip are substantially equal to each other.