JPS6124995B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mounting structure of a thermal head in which a drive circuit section is composed of a plurality of integrated circuits.

Thermal heads for heat-sensitive recording used in the recording section of facsimile machines have traditionally been of the matrix type, but recently, due to the demand for faster recording speeds and a reduction in the number of external wires, heat-generating resistors have been used. A thermal head in which individual driving elements are provided in correspondence with each other on the body is attracting attention.

Figure 1 is a circuit diagram showing an example of such a thermal head, where R is a heating resistor arranged in a row, Q is a drive element, E is a drive power supply, and SR is input in series from an input terminal IN. This is a shift register for distributing recording signal data such as an image signal to each drive element Q, and the output of the shift register SR is once latched in a latch register LR as required, and then supplied to the drive element Q.

Here, the drive element Q, shift register SR, and latch register LR constitute a drive circuit section D, and this drive circuit section D consists of n integrated circuits (LSIs) each including a predetermined number () of Q, SR, and LR. ) IC ₁ ~
Composed by IC _o . Fig. 2 schematically shows an example of the mounting structure of this thermal head, where B is an insulating substrate such as a ceramic substrate, and the heating resistor R is used to immediately see the recording results on thermal paper. They are arranged in a line on the glaze layer G formed on one end side of the substrate B so that the glaze layer G is formed on one end side of the substrate B. Then, integrated circuits IC ₁ to _{IC o} are arranged in the drive circuit section D.

Now, in FIG. 1, the integrated circuits IC ₁ to _{IC o} each include a drive element Q such as a transistor through which a large current flows and generates heat, and a shift register SR ₁ to
Since it includes a high-density logic circuit consisting of SR _o and latch registers LR ₁ to LR _o , an LSI based on I ² L technology, for example, is suitable. Now, suppose the low resistance value of the heating resistor R is 400Ω, and the applied voltage (voltage of power supply E) is
If the voltage is 20V, the current per drive element Q is 50mA.
becomes. In this case, the number of shift registers and latch registers per integrated circuit IC ₁ to _{IC o} is 32.
If it is a bit, the chip size that can withstand the above current is about 4 mm square. On the other hand, if the arrangement density of the heating resistors R is 8 pieces/mm, the width dimension occupied by 32 pieces is 4 mm. Therefore, since the width of each of IC ₁ to _{IC o} and the width occupied by the heating resistor R connected thereto are approximately equal, it is extremely difficult to connect the two in terms of space.

This invention has been made in view of the above-mentioned circumstances, and it is possible to easily connect a heating resistor to an integrated circuit including at least a predetermined number of drive elements and shift registers without impairing the packaging density of the integrated circuit. The purpose is to provide thermal heads.

The present invention includes a plurality of heating resistors arranged in a line on a substrate, driving elements connected to each of these heating resistors, and a shift register that distributes recording signal data input in series to these driving elements. The drive circuit section includes at least a predetermined number of the drive elements and shift registers, and at least a side facing the heating resistor and two sides perpendicular to the arrangement direction of the heating resistors. It is composed of a plurality of integrated circuits having drive output terminals, and these integrated circuits are arranged on one side of the arrangement position of the heat generating resistors on the substrate so that adjacent ones are not located on the same line in the arrangement direction. In the thermal head disposed above, a part of the wiring from one of the two sides perpendicular to the arrangement direction of the heat generating resistors of the integrated circuit to the heat generating resistors and the heat generating circuit of the integrated circuit adjacent thereto. A part of the wiring from the other of the two sides perpendicular to the arrangement direction of the resistors to the heating resistor is overlapped with an insulating layer interposed therebetween.

According to this invention, a portion of the wiring from adjacent integrated circuits to the heat generating resistors is multilayered with an insulating layer interposed therebetween, so that the integrated circuits can be connected without leaving any gaps in the arrangement direction of the heat generating resistors. , can be arranged in high density.

In addition, since the drive output terminals for energizing and driving the heating resistor can be placed on at least three sides of the integrated circuit, it is possible to increase the distance between the drive output terminals on the integrated circuit, which increases the wiring between the integrated circuit and the board. This makes wiring easier. In other words, in a structure in which drive terminals are arranged only on one side of an integrated circuit, it is necessary to arrange the drive terminals at extremely small intervals, for example, about 100 μm or less, and in practice, the drive terminals on the integrated circuit are It becomes nearly impossible to connect the wires and the wiring on the substrate with a high yield. On this point, if the drive terminals are distributed and arranged on at least three sides of the integrated circuit as in the present invention, the distance between the drive output terminals will be tripled by simple calculation, and connection with the wiring on the board will be much easier. Become. The reason why the drive output terminals can be arranged on at least three sides of the integrated circuit is that part of the wiring from one of the two sides perpendicular to the arrangement direction of the heat generating resistors of the integrated circuit to the heat generating resistors is covered with an insulating layer. Through,
This is because it overlaps with a portion of the wiring that extends from the other of the two sides perpendicular to the arrangement direction of the heat generating resistors of the adjacent integrated circuits to the heat generating resistors.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a mounting structure of a thermal head according to an embodiment of the present invention. In FIG. 3, 1 is a board corresponding to B in FIG. 2,
Although not shown, the heat generating resistors R in FIGS. 1 and 2 are arranged in a row in the lateral direction of the figure at the upper part of the figure.

Reference numerals 11, 21, . . . are integrated circuits each having, for example, 32 shift registers R, latch registers LR, and drive elements Q shown in FIG. 1, and correspond to IC ₁ , IC ₂ , . . . in FIG. 1, respectively. Among these integrated circuits, the odd-numbered integrated circuits 11 are arranged at the bottom in the figure on the substrate 1, and the even-numbered integrated circuits 21 are arranged at the top in the figure. That is, the odd-numbered and even-numbered integrated circuits 11 and 21 are arranged on different lines in the arrangement direction of the heating resistors R, respectively. 12 and 22 are drive output terminals provided in the integrated circuits 11 and 21 (corresponding to the collector of the drive element Q in FIG. 1), and are connected to wires 13 and 23, respectively.
The pads 14 and 24 are connected to the bonding pads 14 and 24, respectively, and the pads 14 and 24 are further connected to wires 15 and 25 that reach the heating resistor R, respectively.
In this case, the wirings 15 and 25 are a portion of the wiring 15 that extends from one of the two sides perpendicular to the arrangement direction of the heating resistors R of the integrated circuit 11 to the heating resistor R, and a portion of the wiring 25 that connects the integrated circuit. The portions extending from the other of the two sides perpendicular to the arrangement direction of the eleven heat generating resistors R to the heat generating resistors R overlap with each other with the insulating layer 2 interposed therebetween. Note that the wirings 15 and 25 are formed of, for example, a thin film conductor. Also, the terminals 1 of the integrated circuits 11 and 21
6 and 26 are input terminals, clock terminals, control terminals, etc., and wiring to these terminals is omitted from illustration.

With the above configuration, the integrated circuits 11 and 21
It is possible to easily form the wirings 15 and 25 without substantially lowering the packaging density on the substrate 1.

Now, the drive output terminals 12 of the integrated circuits 11 and 21,
Considering the arrangement of 22, the pitch is about 160μ, so it is physically impossible to arrange 32 within 4 mm, and for example, they cannot be arranged on one side B at the top of the figure. Therefore, the terminals 12 and 22 must be arranged on three sides A, B, and C as shown in the figure. Furthermore, considering the pattern arrangement inside the integrated circuits 11 and 21, it is necessary to distribute the drive elements Q, so it is desirable that the terminals 12 and 22 be distributed almost equally on three sides. In this case, the wires 15, 25 from the terminals 12, 22 on sides A and C must be bent at right angles, so the wires 15, 25
The portion 5 requires space on the side of the space occupied by the integrated circuits 11 and 21. For this reason, the total dimension of the space occupied by the integrated circuits 11 and 21 clearly exceeds 4 mm, and therefore, wirings 15 and 25 cannot be formed by arranging the integrated circuits 11 and 21 in a horizontal row. However, as shown in FIG.
By shifting the position of 5 in a direction perpendicular to the arrangement direction of the heating resistors R, the wirings 15 and 25 can be expanded and formed there by utilizing the space on the side of the integrated circuits 11 and 21. In particular, as shown in the diagram, wiring 1
5 and the horizontally expanding portion of the wiring 25 are overlapped with the insulating layer 2 interposed therebetween, the integrated circuits 11 and 21 are connected to the heating resistor R.
It is possible to arrange the substrates 1 at a high density with almost no spacing in the arrangement direction, and the size of the substrate 1 can be reduced. Moreover, the integrated circuit 11,
21, the drive terminals 12, 22 are provided dispersedly on three sides, so the distance between the terminals can be increased, and the terminals 12, 22
Connection between the wires 15 and 25 by wire bonding or the like becomes easy.

Further, in the above embodiment, since the insulating layer 2 is formed in a band shape, the portion of the wiring 25 on the insulating layer 2,
There is an advantage that a portion formed not on the insulating layer 2 but directly on the substrate 1 can be smoothly connected without a via hole or via film.

Furthermore, this insulating layer 2 is connected to the integrated circuit 2 as shown in the figure.
Since the lower side of 1 is hollowed out and does not exist at the location where the integrated circuit is installed, the drive element Q through which a large current flows.
The heat generated by the integrated circuit due to the built-in integrated circuit can be quickly dissipated to the substrate 1 side.

In the above embodiment, the integrated circuits are arranged in two rows, but it goes without saying that they may be arranged in three or more rows.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a thermal head according to an embodiment of the present invention, Fig. 2 is a plan view schematically showing its overall mounting structure, and Fig. 3 is a plan view showing the main part of the mounting structure in detail. It is a diagram. R...Heating resistor, Q...Drive element, SR (SR ₁ ~
SR _o )...shift register, LR (LR ₁ to _{LR o} )... latch register, IC ₁ to _{IC o} ... integrated circuit, D... drive circuit section, 1... substrate, 2... insulating layer, 11, 21... integrated circuit, 12, 22... Drive output terminal, 13, 23...
Wire, 14, 24...Bonding pad, 1
5, 25...Wiring.

Claims (1)

[Claims] 1. A drive including a plurality of heat generating resistors arranged in a line on a substrate, drive elements connected to each of these heat generating resistors, and a shift register that distributes recording signal data input in series to these drive elements. the drive circuit section includes at least a predetermined number of the drive elements and shift registers, and has a drive output on at least the side facing the heating resistor and the two sides perpendicular to the arrangement direction of the heating resistors. It is composed of a plurality of integrated circuits having terminals, and these integrated circuits are arranged on one side of the arrangement position of the heating resistors on the substrate so that adjacent integrated circuits are not located on the same line in the arrangement direction. In the thermal head, a part of the wiring from one of the two sides perpendicular to the arrangement direction of the heating resistors of the integrated circuit to the heating resistor, and the heating resistor of the integrated circuit adjacent thereto. A thermal head characterized in that a part of the wiring from the other of the two sides perpendicular to the arrangement direction of the heating resistor to the heating resistor is overlapped with an insulating layer interposed therebetween.