JPS5979776A - Thermal head - Google Patents

Abstract

PURPOSE:To enable to easily manufacture a thermal head, by a method wherein belt form insulating films are provided on small common electrodes and on individual electrodes between a row of heating resistors and integrated circuit chips in the direction of the row of the heating resistors, and large common electrodes are provided thereon. CONSTITUTION:The row of heating resistors 13 is provided at a substantially central part of an aluminum substrate 11 covered by a glaze layer 12, and 64- element IC chips 14 are provided alternately on opposite sides of the row. Both ends of each of the row of heating resistors 13 are connected to individual electrodes 16a, 16b consisting of the first lead layer 15, the electrodes 16a are connected in common to the IC chips 14, while the electrodes 16b are connected in common to the small common electrodes 17 on a group basis, and belt form insulating films 18a, 18b parallel with the row of heating resistors 13 are provided on the individual electrodes 16a and the small common electrodes 17. On this assembly, the large common electrodes 19a, 19b consisting of the second lead layer are provided, whereby the small common electrodes 17 are connected in common. Accordingly, the thermal head can be easily manufactured, and the size thereof is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a direct drive thermal head.

[Technical background of the invention and its problems]

As a means of achieving high-speed thermal recording, there is a direct drive method in which drive circuits are provided one-to-one for each heat-generating resistor and each heat-generating resistor is driven individually. The drive circuit and its control circuit are generally integrated into an LSI and mounted on an electrode on a substrate on which a heating resistor is provided.

However, when it comes to high-density thermal heads, it is difficult to provide the same number of drive circuits and control circuits as heating resistors in one-to-one correspondence due to space limitations.

For example, if 2,560 heating resistors are lined up to cover the length of 213 gates at a density of 12 resistors/mm, a logic LSI with built-in drive circuits and control circuits will have 64 elements on 1 chip and 2 chips. Assuming that it is accommodated, 40 chituzo will be required. Control circuits that require low power consumption and high speed can be made highly dense, but the chip size of logic LSIs cannot be made that small because they have drive circuits that require high voltage and high current. The built-in one is about 53 square degrees. The length of the heating resistor array of 12/rnTn is 64, which is approximately 5.3mm, so the logic LS
It would seem that arranging the chips in one row would be sufficient for I, but at present there is no high-density wiring technology such as 12 wires per row, so such a layout is not possible. Approximately 980 terminals per chip, including the logic terminal, 'f[i', source, and ground terminals, are placed at 411 of the chip, and the terminals connected in series with the heating resistor are on the top, left, and right. The control terminals are placed on the bottom side. Therefore, space is required to form leads connected to both the left and right sides on the board. In other words, the LS is approximately the same as the length of the heating resistor row.
If an I-mounting section is to be accommodated, multilayer wiring (at least two layers of wiring) is definitely required. However, the formation of this multilayer wiring is technically difficult due to the lack of space between the LS4 depths, and it has been difficult to achieve this at a high yield and at low cost.

As an improvement over the above difficulties! 1. Opened in 1977-1.
There is a thermal head described in Japanese Patent No. 06878.

As shown in Fig. 1, the heat generating resistor row 1 is arranged approximately in the center of the board, and it is divided into a plurality of groups each consisting of, for example, 8 resistors, and each group is alternately placed in the heat generating resistor row 1. A drive circuit 2 and a control circuit 3 are arranged on both sides. The drive circuit 2 and the control circuit 3 are grouped together to form a concentrator circuit chip (hereinafter referred to as an IC chip) 4. +5a.

Reference numeral 6b indicates a common electrode 15, which commonly connects the ends of the heating resistor array 1 opposite to the IC chip 4 side, and 7 indicates a drive power source.

In this way, the space on both sides of the heating resistor row 1 can be used effectively, which is advantageous in terms of mounting.

However, due to power, if we take this arrangement, the common jID
The problem is how to get the electrons J:'$, 6a, and 6b out of the board. One is the individual electrode 5
There are several methods of extending a, 5b to near the edge of the board and providing common electric bullets 6a, 6b in the same extended portion, but the individual electrodes 5a, 5b have a large box current. For this reason, in a thin film, it is necessary to have a wide line width of several mm and 8 degrees, and in this case, when the IC chips 4 are arranged in a row on both sides of the heating resistor row 10, individual electrodes 5a and 5b are formed between the IC chips 4. It is physically difficult to pass through.

Another method is to use a flying wire lead, but the lead may deform due to contact with other elements.
It is easily damaged and has reliability problems.

[Purpose of the invention]

An object of the present invention is to provide a direct drive type thermal head in which a heating resistor array, a drive circuit, and a control circuit are arranged on the same substrate, which is easy to manufacture, compact, and inexpensive. The goal is to provide a 1° Maruhek.

[Summary of the invention]

In this invention, a row of heating resistors is disposed approximately in the center of a substrate, and on both sides of the array, integrated circuit chips in which drive circuits for individually driving the heating resistors and their control circuits are arranged in predetermined groups are arranged alternately. In a thermal head that is arranged in a divided manner, a small common electrode that commonly connects the ends of the heat generating resistor row opposite to the side connected to the integrated circuit chip in groups is connected to the heat generating resistor row and the integrated circuit chip. A band-shaped insulation j [α A large common electrode is formed on the insulating film to connect small common electrodes on the same side with respect to the heating resistor array through via holes.

〔Effect of the invention〕

According to this invention, in order to make a common connection between the ends of the heat generating resistor array connected to the integrated circuit chip between the heat generating resistor array and the integrated circuit chip arrangement position, the individual electrodes are connected to the integrated circuit chip. There is no need to pass between chips. Therefore, the integrated circuit chips are arranged in a row on both sides of the heating resistor row.
It is now possible to arrange them without leaving large gaps,
It is possible to downsize the legal head.

- Maka 9, one end of the heating resistor for each gnoto is connected to the small common electrode, ), JIH connection <, 7+: at rTHj, so a wide space can be devoted to the small common electrode, and its area can be increased. The large common positive electrode connecting between these electrodes can have a simple structure in the form of ii), and the via pole connection with the small common electrode can also be made with a rough or slightly turned structure, making it easy to manufacture and reliable. Sexuality also improves.

Furthermore, individual products ranging from heating resistors to integrated circuit chips? 1.
, the insulating film that insulates the poles and the large common electrode is also simple'! j
This insulating film can be easily formed by screen printing, since it can be a wide '+'-shaped insulating film and can be formed in two nonparallel ways with the heating resistor array sandwiched therebetween. In this case, if polyimide resin is used as the insulating film, the thermal process can be performed at a lower temperature than when glass or the like is used, and the occurrence of warping of the substrate can be avoided. A pinhole-free insulating film can be obtained over a wider area than when a small Si02 film is deposited. Even when the polyimide resin insulating film is provided by screen printing, spin coating, and photoetching, it is possible to form a via hole with a good tapered shape, resulting in good step coverage and excellent reliability.

From the above, according to the present invention, a defect-free thermal head over a wide area can be realized with lead wiring density that is approximately 1/2 of the density of the heating resistor array, so it is smaller, cheaper, and more reliable than the conventional one. An excellent thermal head can be obtained.

[Embodiments of the invention]

FIG. 2(a) is a plan view of a thermal head according to an embodiment of the present invention, and FIG. 2(b) is a sectional view taken along the line A-A' in FIG. 2(a). In the figure, numeral 11 is an insulating substrate made of alumina or the like with a glaze layer 12 adhered to its surface, and #1 has a heating resistor row 13 formed in the center, and on both sides various electrodes and integrated circuit chips, which will be described later. (hereinafter referred to as IC chip)
14 are arranged. The IC chip 14 has a drive circuit for individually driving the heating resistor and its control circuit, for example, 6.
They are grouped into predetermined groups each consisting of four elements, and are arranged alternately on both sides of the heating resistor row 13 in J+-.

Both ends of each of the heating resistor rows 13 are connected to individual electrodes 16a and 16b made of the first lead layer 15. One individual electrode 16a is connected to the IC chip 014, and the other individual 'f [pole 16b is Each group is commonly connected by a small common electrode 17. A strip-shaped insulating film 18a is provided on the individual electrodes 16a and the small common electrodes 17 between the heating resistor row 13 and the IC chip 14 in parallel with the heating resistor row 13.

18b is formed. and an insulating film 18a.

a large common positive electrode 19a consisting of a second lead layer on 18b;
19b is formed, and the small common electrodes 17 are commonly connected by the large common electrodes 19m and 19b.

Next, an example of the manufacturing process of the rim head constructed in this manner will be described with reference to FIGS. 3(a) and 3(b). First, a flat substrate made of a thermally good conductor, for example, the glazed alumina substrate 11, on which a heat insulating layer having a thermally designed thickness is stuck is prepared. This may be a hollow metal plate. On this glazed alumina substrate 1, a resistive film, for example, a Ta
-8102 sputtering film is deposited, and then the first lead layer 15 is made of, for example, Cr/Au/Cr! [Details of lamination by means such as empty evaporation. This can also be made of an inexpensive metal first material such as Cr/At that does not use Au. FIG. 2(b) shows that the first lead layer 15 is the latter Cr layer J.
A case of a two-layer film of 5JL and At layer 15b is shown. Next, the first lead layer 15 is photo-etched in a pattern as shown in FIG. 3(a). This pattern has 64 trees as one group, and one end of the heating resistor row 13 is individually +11, pole 16.
A pattern in which 64 individual 'i', I, poles 16a running 2jh apart are connected to the small common electrode 1.7 through the small common electrode 1.7, and the other end is connected to the IC chip 14 containing the drive circuit and the control circuit.
As a single attachment, it consists of a pattern in which multiple groups are arranged at the same pitch by repeating each group while reversing each other. It is also possible that one group has 128 pieces.

Next, a row of heating resistors 13 is placed near the center of the board 11.J: 2-I+ for the length of the heating resistors, 1 lead-
Remove the layer 15 by pot etching for 4 times;
U+, IF,! The heating resistor array 13 is formed into a shape JJi,'. Next, the heating resistor array 13 is covered with a wear-resistant protective film (not shown). This is intended to prevent wear caused by pressure roller 1: ffl'l of thermal paper and significantly shorten the lifespan of the heating resistor.
SiN or the like is attached by suction or tsukling. next,
+iiJ Apply a thermosetting polymer film, for example, a polyimide face 6 After coating, apply 11% of thermoset 4 as an insulating film 18 a, 18
As b, it is attached only to a part of the first lead f@15. The insulating films IFIa and 18b are arranged in the same direction across the heating resistor array 13 as shown in FIG.
Cloth is possible. Other examples include chemical etching using photoresist as a mask after coating the entire surface using Subi-coat or Roller-coat 1 method:
j. Dry etching may be performed. In either case, insulation 1 to 1\18a.

Since 18b has a good Q/F shape, when the next second lead layer is attached, the via hole connection with the first lead layer 15 is easily achieved, causing a complete condensation reaction. In order to make polyimide (6 meshes 11), it is heated at 350° C. with LH in a nitrogen atmosphere. This temperature is sufficiently lower than the 850°C that is required for glass insulation, and the yield is 21. improves. A second lead layer is then deposited by means such as vacuum deposition.

The second lead layer is made of a thin film such as 'l''i/Au or At. When this second lead layer is photoetched as shown in Figure 1()3(1)), the odd-numbered small common electrodes of the divided groups are A large common electrode 19a that connects the two small common electrodes and a large common electrode 19b that connects the numbered small common electrodes are formed.These large common electrodes 19n and 19b are connected to the insulating film 18g.
, 18b, the individual (Hi, chair 16 a
+16b is kept insulated from the other side. Large common electrode 19
a, take out 19b to the outside of the board J1 6', 1 to pole 1
9a and 19b run parallel to the heating resistor row 13, and then they can be taken out from the ends of the bases 4M and 11 in the same direction, or they can be guided from there in the direction of the wire and connected to other logic terminals, etc. You can take it out from the same side as -. (The space is small because it can be stopped at just one).

Next, as shown in FIGS. 2(a) and 2(b), the first lead layer is exposed to the pumping pad t'N! J second Ic
Chichin 14 appetizers - Soo Ichishi, Igao 1 'rJ￥ 4d ward 16th and logic i7i! Connect to A terminal 2o% + H by wire debugging.

[Brief explanation of the drawing]

5> Figure 1 is a configuration diagram of a conventional thermal head, Figure 2 (
FL) (b) A plan view of a thermal head according to an embodiment of the present invention and a sectional view taken along the line A-A', FIG.
a) (h) is an explanation of the membrane edge process.
It is a diagram. DESCRIPTION OF SYMBOLS 11... Board, 13... Heating resistor row, 14...
IC chip, 1611. , 16 b...individual type rod,
17... Small common electrode, IFIt+, lRb-... Insulating film, 19a. 19b...Large common electrode. Applicant's agent Patent attorney Takehiko Suzue 1 Kuchima Figure 2 Shin Figure 2 (b) Figure 3 (a)

Claims (2)

[Claims] (1) An integrated circuit chip in which a row of heat generating resistors is arranged approximately in the center of the substrate, and drive Sh circuits and control circuits for driving the heat generating resistors individually are arranged in predetermined groups on both sides. Alternately distributed arrangement r1: In a thermal head made of A small common electrode is formed between the resistor array and the integrated circuit chip arrangement position (11)", and heat is generated on the individual electrodes that individually connect the heat generating resistor array and the integrated circuit chip. In the direction of resistor arrangement? 1) A band-shaped insulating film is formed, and a large common electrode is formed in this insulating film to connect the small common electrodes on the same side with respect to the heating resistor array through via holes. Thermal head. (2) The thermal hesode according to item 1 of the patent scope, characterized in that the coating is made by coating and curing polyimide varnish.