JPH0129060B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for arranging pads of IC chips (integrated circuits such as SSI, MSI, and LSI) used as drive circuits for electronic devices such as thermal heads, displays, and sensor arrays.

Some thermal heads have IC chips serving as drive circuits arranged along heat generating resistors arranged along the longitudinal direction. As an example of the circuit configuration of one such IC chip, as shown in FIG.
A shift register 1 inputs and advances data from a load terminal, a latch circuit 2 that inputs and holds a signal from the shift register 1 in response to a load signal from a load terminal, and a heat generating resistor based on the signal held in the latch circuit 2. Some devices include an output transistor 3 that drives and heats a body (not shown) and a gate 4 that controls the timing at which the output transistor 3 operates based on a strobe signal from a strobe terminal. This IC drives 32 heating resistors per chip,
Both the shift register 1 and the latch circuit 2 have a capacity of 32 bits, each of 32 output transistors 3 and 32 gates 4 are provided, and a drive output pad 32 is connected to the collector of the output transistor 3 and connected to the heating resistor. There are ₁ to ₃₂ pieces. Note that the terminal is a clear terminal for the shift register 1, and the terminals _VDD and _VSS are power supply terminals and ground terminals for driving the shift register 1 and the latch circuit 2 themselves. A necessary number of such IC chips are provided depending on the number of heating resistors.

By the way, on the circuit diagram in Figure 1, the ground terminal
It is expressed as if the emitters of the output transistors 3 connected to GND are all connected to a common ground line, but in terms of implementation, one ground pad for every two output transistors is connected to the drive output pad. It is taken out in the same direction as O ₁ to O ₃₂ . Therefore, the pad arrangement of the IC chip is
As shown in FIG. 2, ground terminals GND ₁ to GND ₁₆ are arranged along one side of the chip 5 for every two drive output pads O ₁ to O ₃₂ . _I1 to _I8 are pads for DATA IN, CLOCK, and other input/output signal terminals.

However, in a thermal head, the heating resistors are arranged continuously in one direction, whereas the above IC chip has drive output pads O ₁ to O ₃₂ and ground pad GND ₁ as shown in Fig. 2 above. ~
Since the IC chips 5 and GND ₁₆ are arranged alternately at a ratio of 2:1, when mounting such an IC chip 5 on a thermal head using a tape carrier method, for example, the drive output pad and the ground pad are It is necessary to connect leads that go in opposite directions on the tape carrier, so the drive output pads O ₁ to O ₃₂ and the ground pad
It is not possible to bond the pad array consisting of GND ₁ to GND ₁₆ to leads formed within the same plane of the tape carrier (inner lead bonding). Therefore, it is necessary to use a tape carrier in which lead patterns are formed on both sides of the tape base material, or to use two ordinary tape carriers. Such a mounting method is disadvantageous in terms of the thermal head assembly process, yield, and cost.

These problems are not limited to thermal heads, but are also encountered in devices such as displays and sensor arrays in which a large number of display elements and detection elements are arranged, and IC chips as driving circuits are arranged and mounted along the arrangement. exists as a common problem.

In view of the above problems, the present invention aims to provide a pad arrangement method that makes it easy to mount an IC chip in an electronic device such as a thermal head. The purpose is to achieve the above object by arranging them continuously along the same line. Therefore, the ground pads are arranged at a different location from the drive output pads.

An example will be described below.

FIG. 3 is a pad layout diagram of an example in which the present invention is implemented in an IC chip having the circuit configuration shown in FIG. The drive output pads O ₁ to _{O 32} are arranged in a continuous line along the upper side of the surface of the IC chip 6, and three ground pads are arranged along the left side.
GND ₁ ~ GND ₃ , 3 along the right side GND ₄ ~
GND ₆ is arranged. I/O signal pad I ₁
~I ₈ is the same as in Figure 2.

In the present invention, the emitters of the 32 output transistors 3 are all connected to a common ground pad within the IC chip, instead of connecting two emitters of the output transistors 3 in common to the ground pad as in the conventional example shown in FIG. Connect to the ground line, and connect 3 pieces along the left side of IC chip 6 from the common ground line.
GND ₁ ~ GND ₃ , 3 pieces along the right side GND ₄ ~
This is the padded part of GND ₆ . In this way, by making the ground common, the yield of bonding to the ground pad is greatly improved.

As described above, according to the present invention, the drive output pads are arranged continuously along one side of the surface of the IC chip, so when mounting such an IC chip in a thermal head or other electronic device, For example, when using the tape carrier method, bonding can be carried out using a single ordinary tape carrier in which a lead pattern is formed on only one side of the tape base material, thus achieving the effect of making an IC chip easy to mount. be able to.

[Brief explanation of drawings]

Figure 1 is used in a thermal head drive circuit.
Circuit diagram showing an example of the circuit configuration of one IC chip, Part 2
The figure is a schematic plan view showing the pad arrangement of a conventional IC chip incorporating the circuit shown in Fig. 1, and Fig. 3 shows the pad arrangement of an IC chip incorporating the circuit shown in Fig. FIG. 6...IC chip, _O1 to _O32 ...Driving output pad, GND ₁ to _{GND 6} ...Ground pad.

Claims (1)

[Claims] 1. An IC chip pad arrangement method characterized by arranging drive output pads continuously along one side of the IC chip.