JP2651852B2 - Electrode circuit board for printer head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrode circuit board for a print head of an energization transfer type printer.

(Prior Art) Conventional non-impact printers include thermal printers, electrostatic printers, and the like. However, in order to achieve high speed, low cost, and low power consumption, energetic transfer printers have been studied (see Japanese Patent Application Laid-Open No. -112649, JP-A-54-1126
No. 52, JP-A-59-79772). In a conventional thermal printer head, a heating resistor (printing portion) such as nickel-chrome is provided on a substrate such as alumina, and a current is applied to this portion to cause the resistor portion to generate heat, and the heat contacts the head. The ink on the ribbon was melted and the ink was transferred to the recording paper. On the other hand, an energization transfer printer has no heat-generating part in the head part of the printer, provides a resistive layer on the ribbon itself, generates heat by locally flowing an electric current through the resistive layer in the ribbon, melts the ink, and records paper. Is transferred to
The electrodes of the head are used merely for energizing. For this reason, unlike the thermal printer, the heat-generating portion is located in the ink ribbon, and the heat-generating portion moves away from the head in a short time, so that there is no need to wait for the head itself to cool down unlike a conventional thermal printer, and the speed can be increased by that amount. At the same time, it has features such as simplification of the structure of the printer itself.

The head used in such an energization transfer printer can be a head formed by etching a tungsten foil with a special chemical to form a circuit by bonding a tungsten foil to a polyimide film using an adhesive, or a ceramic substrate. A head is formed by printing a circuit using a tungsten paste thereon and firing it, and a head is formed by forming a chromium thin film layer on a ceramic substrate and then etching to form a circuit.

(Problems to be Solved by the Invention) Among these methods, those using a ceramic substrate include:
In the case of using the cheapest tungsten paste, since the electrodes are formed by a printing method, not only the accuracy (line width, thickness, etc.) of the electrode pattern is inferior, but also it is difficult to form 5 or more fine patterns per 1 mm. The thin-film method does not have these disadvantages but increases the manufacturing cost.

The head that uses tungsten and a polyimide film bonded with an adhesive to the head that uses this ceramic substrate has high flexibility, and by providing an elastic body at the lower end of the head, the contact between the ribbon and the electrode can be easily maintained. Is possible. However, in an energization transfer printer, the temperature becomes higher as the temperature locally exceeds 200 ° C. at the contact portion with the ribbon. Tungsten and polyimide films are sufficient for heat resistance, but the heat resistance of the adhesive layer used is not sufficient,
This causes a problem in life. For this reason, it is necessary to give consideration to the mechanism so that the print head can be easily and quickly replaced, and since expensive tungsten is used, there is a problem that the maintenance cost is high in addition to the high unit cost of the head. .

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to provide an electrode circuit board for a current transfer printer head having excellent heat resistance, excellent flexibility, low printing pressure, and excellent durability. .

According to the present invention, there is provided a circuit for a flexible printed wiring board obtained by processing a circuit using a flexible substrate to which a copper foil is bonded without using an adhesive. This is achieved by a head on which a metal bump electrode having a Vickers hardness of 500 or more is formed by electroless plating.

The heat-resistant flexible substrate used in the present invention is preferably a substrate having a polyimide film as a base material.
As a method of obtaining a flexible substrate without using an adhesive, a method in which a varnish of polyamic acid is directly applied to a copper foil and then heated to polyimide the polyamic acid, or a polyimide film is bonded through a varnish of polyamic acid There is a method of curing by heating.

A copper foil having a thickness of 18 μm or less is suitable for the purpose of obtaining flexibility.

There is no particular limitation on a method of processing a circuit on the flexible substrate, but a photoetching method is suitable for obtaining a fine pattern.

The bump electrodes are formed by applying a metal plating such that the Vickers hardness becomes 500 or more in a state where the area other than the bump forming portion of the circuit board is covered with a plating resist.

Nickel, nickel alloy,
It is selected from metals having excellent wear resistance, such as tungsten, tungsten alloy, chromium, chromium alloy and rhodium.

FIG. 1 shows an electrode circuit board according to the present invention,
FIG. 2 is a cross-sectional view taken along the line, showing a state in which the bump electrode 1 is provided on the circuit 3 formed on the heat-resistant base film 4, and FIG. It shows a cross section. Reference numeral 2 denotes a cover coat applied to protect the circuit 3 and the bump electrode 1 after the formation of the bump electrode. As a method for forming the bump electrode, a method using electroless plating is preferable in order to form a uniform bump having no variation in height and hardness.

The electrode circuit board is attached to the printer head via an elastic body having excellent heat resistance such as silicone rubber.

 Hereinafter, the present invention will be described specifically with reference to Examples.

(Example) This material using MCF-5000I (copper-clad laminate, trade name of Hitachi Chemical Co., Ltd.) as a flexible substrate is a polyimide layer (25 μm thickness) on a copper foil (18 μm thickness) to be a circuit.
And a peel strength of 1.6 kg / cm is maintained even at 200 ° C. in terms of heat resistance. A circuit was formed on the flexible substrate by a photoetching method. The line density of the portion corresponding to the electrode (the portion where a bump is to be formed later) is 6 lines / mm. After this, plating resist (PMER N
-HC600, trade name of Tokyo Ohka Kogyo Co., Ltd.)
As shown in the figure, the substrate was entirely covered except that the portion where the bump was to be formed was cut out in a slit shape. Thereafter, nickel electroless plating was performed on the circuit exposed in the slit shape. The plating thickness is 25 μm, which is the same as the resist thickness.
The plating solution used was BEL-801 (trade name, manufactured by Uemura Kogyo Co., Ltd.), and plating was performed at a solution temperature of 63 ° C. and PH 6.3. The resulting plating film contains about 1% boron. After that, the photoresist is removed with a special chemical solution and the temperature is 250 ° C.
For 1 hour. By this heat treatment, the bumped nickel has a Vickers hardness of more than 1000 and sufficiently withstands abrasion due to contact with the ribbon. Next, except for a terminal portion for connection between the bump and the drive circuit, overcoating (15 μm thickness) was performed with solder resist ink (PIR-33T, Asahi Chemical Laboratory, trade name). Then at 180 ℃ 30
After heat treatment for a minute and curing, only the bump portion was polished to expose the bump.

When the obtained electrode circuit board was mounted on a printer head of an actual machine and printing was performed by pressing the bumps against the ribbon at a pressure of 10 g per 1 cm width, printing of 150,000 to 200,000 sheets of A4 size paper was possible.

(Effects of the Invention) As described above, the flexible wiring board used according to the present invention is obtained by directly bonding a circuit metal and a polyimide film and does not have an adhesive layer having poor heat resistance. As a head material, not only sufficient heat resistance can be obtained, but also a thin structure is obtained because no adhesive is used, and excellent flexibility is achieved, and uniform contact with the ribbon can be easily obtained. In addition, the electrode circuit board according to the present invention is obtained by forming a circuit using a conventional etching method and then providing a high-hardness metal only to the bumps by plating. Is possible.

[Brief description of the drawings]

The drawings show an embodiment of the present invention.
FIG. 3 is a cross-sectional view of the electrode circuit board, and FIG. 3 is a plan view of the electrode circuit board in a manufacturing process. DESCRIPTION OF SYMBOLS 1 ... Bump (electrode), 2 ... Cover coat 3 ... Circuit, 4 ... Base film

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Junichi Imaizumi 1150 Goshomiya, Oaza, Shimodate City, Ibaraki Pref.Hitachi Kasei Kogyo Co., Ltd. Inside the Goshomiya Plant of Kogyo Kogyo Co., Ltd. (72) Inventor Eikichi Sato, 1150 Goshomiya, Oji, Shimodate City, Ibaraki Prefecture Inside the Goshonomiya Plant, Hitachi Chemical Co., Ltd. (56) References JP-A-63-35357 (JP, A) JP-A-61-198035 (JP, U)

Claims (2)

(57) [Claims] 1. A metal bump electrode having a Vickers hardness of 500 or more is formed by electroless plating on a circuit of a flexible printed wiring board obtained by performing circuit processing on a heat-resistant flexible substrate on which copper foil is bonded without using an adhesive. The formed flexible electrode circuit board for a printer head. 2. The circuit board for a printer head according to claim 1, wherein the bump electrode is selected from nickel, nickel alloy, tungsten, tungsten alloy, chrome, chrome alloy and rhodium.