JPH085202B2 - Method of manufacturing thermal head - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal head used in a thermal recording device such as a facsimile or a printer.

(B) Conventional Technology In recent years, thermal heads have been widely used in various recording devices such as facsimiles and word processor printers. These devices are required to be small, lightweight, and low in price, and a small and inexpensive thermal head is desired.

A conventional thermal head is formed by using a heat storage layer of a grade glass layer which is printed and fired on an alumina ceramic substrate having a purity of 90% or more.

FIG. 3 is a sectional view of a main part of a conventional thermal head, and FIG. 4 is a flow chart showing a manufacturing process of the conventional thermal head. That is, in the conventional thermal head,
First, the grade glass heat storage layer 17 is formed on the ceramic substrate 11, and then the heating resistance film 14 is formed by vapor deposition or sputtering.
After forming, the electrode film is formed by the vapor deposition method or the sputtering method, and then patterned by the photolithography method to form the common electrode 13. Next, the electrode film is formed again by the vapor deposition method or the sputtering method, and is patterned by the photolithography method, the lead electrode 12 is formed to form the heating resistance portion, and then the protective film 15 is formed. The thermal head substrate thus formed is divided into a predetermined size, the driving IC chip is mounted by face-down bonding, and a molding process is performed with resin, and then the assembly is performed.

(C) Problems to be Solved by the Invention However, the conventional thermal head is complicated in the manufacturing process as described above, and the purification, polishing, and polishing of the raw material alumina powder are performed.
Since many processes including high-temperature processing such as printing and baking are required, there is a problem that the production cost becomes high.
Moreover, since the alumina ceramics is used as the substrate, there is a problem that the size of the substrate is limited due to the size of the high temperature firing furnace, and the increase in size is hindered.

In order to solve these problems, a thermal head using a polyimide flexible substrate or an enameled substrate instead of a glaze ceramic substrate has been studied recently, but a printed circuit portion for connecting a connector, a capacitor, a thermistor, etc. In addition to having to be installed separately, it also requires a large number of parts such as the circuit board, rubber retainer, retainer fittings, screws, etc. required for connection with the printed circuit board, and also requires a lot of man-hours for assembly. However, there is a problem that the problem cannot be solved by simply replacing the substrate forming the thermal head portion with another material.

The present invention has been made in consideration of such circumstances, and by using a heat-resistant double-sided copper-clad laminate as a circuit board instead of the glaze alumina board, the board can be increased in size, and the common electrode and the lead can be used. The electrode formation process can be simplified by patterning the electrodes simultaneously, and the assembly process can be simplified by integrating the heating resistor part and the circuit board on which the driver IC is mounted on the substrate. An inexpensive thermal head is provided.

(D) Means for Solving the Problems The present invention provides a method for manufacturing a thermal head, in which a heating resistance layer and lead electrodes and a common electrode for energizing the heating resistance layer are provided on a substrate. Using a substrate with copper and aluminum foil laminated in advance, first peel off the aluminum layer and pattern the copper foil to form the lead electrode and common electrode at the same time. Forming a layer, forming a heating resistance layer extending from the lead electrode to the common electrode on the heat storage layer, and further forming a protective layer covering the lead electrode, the common electrode, and the heating resistance layer, and manufacturing the thermal head. Is the way.

The thickness of the copper foil, which is the electrode, depends on the pattern accuracy, and the electrode pattern accuracy for the thermal head is ± 3 μm ~
In order to achieve ± 5 μm, the thickness of the copper foil is preferably 3 to 18 μm, but there is a demerit that the accuracy decreases as the thickness increases. However, there is an advantage that the resistance value of the common electrode is reduced. Therefore, the thickness of the copper foil is preferably 5 to 12 μm because the conductor resistance value of the common electrode can be 500 mΩ or less in terms of pattern accuracy.

(E) Action By using a heat-resistant resin substrate as the substrate, the lead electrode pattern and the common electrode pattern can be simultaneously formed in the same process, and the size of the substrate can be increased. It is possible to provide an inexpensive thermal head. That is, it is possible to increase the size of the binding substrate, simplify the electrode forming process, and reduce the amount of equipment required for the electrode forming process.

(F) Embodiments The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a cross-sectional view of the vicinity of a heat storage layer of a thermal head showing an embodiment of the present invention, and FIG. 2 is a flowchart showing a manufacturing process of this thermal head.

First, a glass cloth is impregnated with a high heat resistant resin, a curing agent, an accelerator and a solvent, and then dried and cut. Then, after the surface treatment of the substrate so that the two-layer foil obtained by laminating aluminum and copper is easily adhered to each other, heating and pressing are performed, and the two-layer foil is laminated on both sides with the glass cloth as the core material. -Preparing a copper clad laminate (hereinafter, this substrate is referred to as a UTC substrate: Ultra Thin Cuper).

Next, the aluminum foil of this UTC substrate is removed with an etching solution containing caustica and sodium gluconate to obtain a copper clad laminate having a copper foil thickness of 3 to 12 μm. This is cut into a predetermined size to form a flat heat-resistant resin substrate 1, which is washed and heat-treated, and then the surface-adjusting treatment of the copper foil is performed.

Next, the lead electrode portion and the common electrode portion are simultaneously patterned using a liquid positive photoresist.

Next, after forming the lead electrode 2a and the common electrode 3a by spray etching with a ferric chloride or cupric chloride solution, electroless NiP plating is performed to form a Ni electrode having a thickness of about 1.0 μm.
Layers 2b and 3b are formed, and then electroless Au plating is applied to form 0.1 to
The Au layers 2c and 3c having a thickness of 0.5 μm are formed. At this time, an electrode structure that enables face-down bonding to the common electrode of the thermal head, the lead electrode, and the driver IC part is made at one time.

Next, a polyimide precursor on the substrate is applied to a predetermined thickness using a roll coater, a spin-on coater or a screen printing machine, and after drying, after a predetermined pattern etching of the layer of the polyimide precursor, Curing is performed to form polyimide layers 6 and 7. That is, the heat storage layer 7 made of polyimide resin and the solder dam 6 for face-down bonding are patterned.

Furthermore, by sputtering method, Ta-Si-O, Ta ₂ N, Ni
After forming a thin film heating resistance layer made of any one of -Cr and the like, patterning by a photolithography method to form a heating resistance layer pattern 4, and then forming Ta ₂ O ₅ , SiO ₂ , sialon, SiC, SiON. The protective film 5 made of any of the above is formed by the sputtering method or the plasma CVD method, and the thermal head substrate for face-down bonding is completed.

Furthermore, the driver IC is mounted on the board by face down bonding, solder reflow, resin molding,
The thermal head is completed by assembling and testing the parts.

In this way, the thermal head using the UTC substrate has a copper foil of 12 μm or less, which is thinner than the conventional copper-clad laminate,
There is an advantage that the patterning accuracy of the common electrode and the lead electrode can be ± 10 μm or less even though it is the structure of the conventional printed circuit board. It is possible to form a thermal head electrode of 8 dots / mm with good yield. Also, the substrate size is 1200mm
Since it can be easily provided in a size of about 1200 mm,
Compared to a glazed alumina substrate, it is less subject to substrate size restrictions, thus increasing the number of heads per substrate, the substrate unit price per unit area is low, and expensive vapor deposition machines and sputtering equipment are used in the electrode formation process. It has the feature that it does not require a device, it can be made at low cost, and meets the needs of thermal heads that are being searched by the industry.

(G) Effect of the Invention According to the present invention, it is possible to provide a thermal head that can reduce the number of steps by simultaneously performing the pattern formation of the common electrode and the lead electrode, and can reduce the cost.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part configuration of a thermal head showing an embodiment of the present invention, FIG. 2 is a flow chart showing a manufacturing process of the thermal head of FIG. 1, and FIG. 3 is a conventional thermal head of FIG. FIG. 4 is a diagram corresponding to FIG. 2 of the conventional thermal head. 1 ... Heat-resistant insulating substrate, 2a ... Lead electrode, 2b, 3b ... Ni layer, 3a ... Common electrode, 2c, 3c ... Au layer, 4 ... Heating resistance layer pattern, 5 ... Protective film, 6,7 …… Polyimide layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 61-181658 (JP, A) JP-A 51-6035 (JP, A) JP-A 61-280951 (JP, A) JP-A 53- 58249 (JP, A) Actual development Sho 59-126644 (JP, U)

Claims (1)

[Claims] 1. A method of manufacturing a thermal head having a heating resistance layer, a lead electrode for energizing the heating resistance layer, and a common electrode on a substrate, wherein copper and aluminum foil are preliminarily laminated on the surface of a heat-resistant resin plate. Using the substrate, first peel off the aluminum layer,
A copper foil is patterned to form a lead electrode and a common electrode at the same time, a heat storage layer made of a resin is formed between the lead electrode and the common electrode, and a heating resistance layer extending from the lead electrode to the common electrode is formed on the heat storage layer. Furthermore, a method of manufacturing a thermal head, characterized in that a protective layer covering the lead electrode, the common electrode, and the heating resistance layer is formed.