JPS60172554A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain an inexpensive thermal head high in reliability wherein the required wiring conductor comprises substantially one layer, by providing a recording current earth conductor between connection terminals of adjacent ICs. CONSTITUTION:A recording current supplied to a heat generating resistor flows to the driver circuit in IC32 from connection terminals T1-Tn of IC32 through indivisual conductors L1-Lm and again flows the recording current terminals TG on a circuit board from the earth electrode of IC32 to be flowed to the recording current earth conductor PG connected in common so as to include said earth terminals TG of IC32. This conductor PG is formed so as to be extended to the earth terminal G of the circuit board. An electric signal for driving IC32 is supplied to wiring conductors S1'-SK' from signal terminals S1-SK of the circuit board. The electric signal supplied to the wiring conductors S1'-SK' is supplied to the electrodes in IC32 through bonding wires W1-WK.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a thermal head using a plurality of driver ICs that directly drive all of the heating resistors, and more particularly to a thermal head having substantially one layer of wiring conductors.

(Prior art) Conventionally, a thermal head board has substantially a single layer of wiring conductor, a circuit section requiring multilayer wiring is formed on an inexpensive printed circuit board, etc., and an inner board is formed of IC connection terminals. There are two types of thermal heads: one with a thermal head structure, and the other with a structure in which a thermal head is constructed using a multilayer wiring method on a single substrate. The former thermal head had, for example, the structure shown in FIG. That is, a heating resistor array R is formed on the substrate 11J: and conductors C□ to Cm branched into strips from the common electrode C are connected to one end of this resistor.

A large number of individual conductors L1 to L, TI are connected to one end of the resistor, and each m individual conductors form one group,
It is formed to extend to the connection terminals T□ to Tm to the IC.

The first lead wire group 13 connected to the driver IC 12 is bonded to this connection terminal by thermocompression bonding.

Connections can be made by soldering, etc. The second lead wire group 14 connected to the other end of the IC is a printed circuit board.

It is connected to an IC driving substrate 15 such as a ceramic substrate by a method such as soldering. The board 15 is an inexpensive multilayer wiring board for driving ICs. however,
The thermal head with this structure is structurally unstable because the TC or lead wire group is held in the hollow part, and it is necessary to fix the substrates while strictly adjusting the relative positions between them. There was a major drawback.

Therefore, a second example in which a driver IC is fixed on a substrate has also been put into practical use, but this structure has been realized, for example, by the multilayer wiring technology shown in FIG.

A thermal head with this structure essentially has two layers of wiring conductors, and an interlayer insulating layer is provided between the conductor layers. That is, as shown in the first example, the individual conductors L1 to Lm connected to the resistor are formed by extending every m to the connection terminal to the IC, and the connection terminal is connected to a lead wire such as a gold wire. It is connected to the driver circuit of the IC 22 mounted on the substrate 21h by wire bonding, thermocompression bonding, or the like.

Further, the electric power 1d for dividing and driving the plurality of ICs into several blocks is, for example, the signal terminals 81 to SK.
It is simultaneously supplied to the ICs in each block. These Electrical No. 100 are, for example, through holes formed in the interlayer insulating layer from the first conductor layers SL to SK. [Through the through-holes, the second conductor 1p1Sx' to SK' is commonly supplied to the ICs in each block, and the second conductor is further supplied from the second conductor layer to the first conductor layer S1'' to SK'' through the through holes. They are supplied individually. S1'' to SK// are formed by extending the connection terminals 11 to the IC.

The thermal head of this structure has a complicated manufacturing process due to the fact that the wiring tank/electrical layer consists of the first and second electrically conductive layers. It was inevitable that the wiring would be low and expensive, and that the number of connection points between multilayer wiring would be large, resulting in low reliability.

(Object of the Invention) Therefore, the object of the present invention is to provide a thermal head in which all the writing points are removed, the driver IC is mounted on a single substrate, and the wiring conductor is substantially formed in one layer.

(Structure of the Invention) With the advancement of technology, semiconductor ICs have become highly integrated, and the external dimensions of ICs that achieve all the same functions as conventional ICs are
By using C technology, the size can be significantly reduced. For example, a conventional IC with 32 heating resistors driven by a single IC had a width of around 2.5 mwt and a vertical length of around 4.5 to 6 mm. On the other hand, if the vertical length of a highly integrated IC is the same as the conventional one, the horizontal width will be 1
It can be approximately 1.5 to 1.5 degrees. Therefore, if we take as an example an 84th edition thermal head with a resolution of 8 resistors and a total number of resistors of 2048, the total number of ICs is 64 at a pitch of 4.0.
Highly integrated ICs will be arranged in parallel on individual boards.
When using the IC, the gap between the ICs can be formed approximately one degree wider than in the conventional case. Furthermore, a highly integrated IC whose external dimensions are comparable to those of conventional ICs can simultaneously drive about 48 heating resistors with a single IC. In this case, a total of 43 ICs are arranged on the substrate at a pitch of 6.0, so that the gap between the ICs can be made about two times wider than in the past. In any of the above examples, high integration degree rceq = mounted thermal head is I
The gap between C and IC becomes wider. The present invention provides a recording current grounding conductor core or jumper wire in the gap, thereby eliminating the need for a second conductor layer. In the thermal head equipped with the conventional IC shown in Fig. 2,
Because the gap was small, the IC connection terminals T1~ were placed inside the gap.
When Tn was formed, the recording current grounding conductor was substantially not provided.

An embodiment of the present invention will be described below.

FIG. 3 schematically shows the vicinity of the driver IC mounting portion of the thermal head. The individual conductors L1 to Lr, which are connected to the heating resistor, are formed to extend to the connection terminals at both ends of the IC. Therefore, the recording current that energizes the heating resistor flows from the connection terminal to the driver circuit within the TC 32. The connection terminals and the electrodes in the IC are connected by full-line wire bonding or the like. The recording current flowing through the driver is transferred from the ground electrode of the IC to the recording current ground terminal T on the board. and optionally adjacent I
The recording current flows to the commonly connected grounding conductor PG including the grounding terminal TG of the recording current. This conductor PG is connected to the ground terminal G of the board from an arbitrary position every IIC or every few ICs.
It is formed by extending to.

Further, electric signals for driving the IC are supplied from signal terminals S□ to SK of the board to wiring conductors Sl' to SK'. In this case, the wiring conductor passes through the lower surface of the bonding wires W1 to WK as described. The electrical signals supplied to the wiring conductors S□' to SK' pass through the bonding wires W1 to WK and are supplied to the electrodes within the IC. The electrodes within the IC that are supplied with the required electrical signals are
A pair of each is formed as required, and they are commonly connected within the IC. By using such ICs, electrical signals can be transmitted between adjacent ICs sequentially or simultaneously.

(Effects of the Invention) The dual head of the present invention in which the recording current grounding conductor is provided between the connecting terminals of adjacent TCs has a substantially single layer of conductive rods for wiring, which is relatively inexpensive and high cost. 1d
It serves as a support.

As long as the present invention exhibits the above-described effects, it goes without saying that the IC may be of any circuit type such as bipolar type, MOS type, PI-CMO8 type, etc. -Also, the desired electrodes for receiving electrical signals do not necessarily have to be provided in pairs within the IC; for example, an image signal input electrode and an image signal output electrode to be printed and recorded on the heating resistor may be provided in a single pair. be. Further, a pair of corresponding electrodes for the signal Sx which are not commonly connected in the IC can be crossed over by wire bonding at a position where a recording current grounding conductor is provided. This can be realized, for example, by the bonding wire Wl shown in FIG. It goes without saying that the electrodes in an IC that can be used in this manner do not necessarily need to be in a pair, but can be made in a single pair. Further, since a large current flows through the common electrode or the recording current grounding conductor, the purpose of the present invention can be achieved even if the electrode or conductor is formed to be partially thick or partially thickened by plating. is not damaged in any way. As long as the present invention exhibits the above effects, the thermal head of the present invention is not particularly limited in its uses.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are plan views showing a conventional thermal head. FIG. 3 is a plan view showing an embodiment of the thermal head of the present invention. L1~Lrn...Individual conductor, T1~Tn...
... Connection terminal s TG ... Recording current grounding terminal, Po ... Recording current grounding conductor, W1 to WK
...Bonding wire, S□. S2. SK, Sx...1g terminal, 807,8
2', SKl, Sx'... Wiring conductor, O...
...Board ground terminal. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A thermal head characterized in that a plurality of ICs are mounted on a wiring board having substantially a single conductor layer. 2. In the thermal head according to claim 1, the individual conductor connected to the heating resistor and extending from the resistor = the mounted IC as a connection terminal to the iIC.
1. A thermal head, characterized in that a conductor is provided on both sides of the head to ground a recording current near the center of the connection terminal of an adjacent mounted IC. 3. In the thermal head according to claim 1, the mounted IC is provided with at least one pair of electrodes for receiving desired electrical signals, and the electrodes are commonly connected within a single IC. Thermal head with all features.