JPS61149368A - Forming method of lead wire for thermal head - Google Patents

Abstract

PURPOSE:To form low cost lead wire maintaining a normal level of performance with reduced gold consumption by providing a thick gold film only on a smaller part of lead wire width and a thin gold film on a larger part of lead wire width. CONSTITUTION:A gold film is formed on a substrate 1 such as ceramic by printing and baking using gold paste. When a pattern of lead wire 2 is formed by a photoetching method, a thick gold film is provided on a lead wire part 2a of an area where a heating resistor is formed, i.e. a lead wire part of smaller film width and a thin gold film on a lead wire part 2b of the other area, i.e. a part of lager film width. A conductor part 2a has a smaller lead wire width such as 15-25mum. When this small pattern is formed by a photoetching method, the film is thickened by repeating a printing and baking cycle 2-3 times. The film thickness of the conductor part 2b is smaller than that of the lead wire part 2a. However, it is sufficiently possible to form a lead wire despite such a design.

Description

[Detailed description of the invention] Industrial applications This invention is a method for forming a conductor for a thermal head.

It is related to

2. Description of the Related Art Conventionally, as shown in FIG. 8, conductive wires of a thermal head are formed by printing and firing a pressure gold paste on the surface of a substrate 111 two to three times on a substrate 1j made of ceramic or the like, and then using a photo-etching method. By patterning the conductor (2
) was fully formed.

The commonly used gold paste is made by mixing gold with a frit such as glass and a vehicle made of a certain type of resin, and the size of the gold particles is 1 to 1 Bpm. It is necessary to use this gold paste to form a film as thin and uniform as possible, but the gold particles must be 1-1111ml2l and agglomeration of gold particles will inevitably occur during the firing process after printing. Therefore, in order to obtain a dense gold film, it was necessary to repeat the printing and firing process S~8 times, resulting in a film thickness of about 8 to 5 μm.

[Problem that the invention seeks to solve]

In the conventional method, a gold thickness of about 8 to 5 μm is required, which means that a large amount of gold is used, which is expensive, and there is also a large loss of gold due to etching during patterning.
This had the disadvantage of increasing manufacturing costs, such as increasing losses due to process defects.

The present invention aims to solve the above-mentioned drawbacks, and focuses on the relationship between the density of the gold film and the required width of the conductor wire, and reduces the amount of gold used without degrading the performance of the conductor wire. The purpose is to form a conductor wire with low cost.

[Means for solving problems]

In this invention, the density of the gold film is increased (@increase the thickness) only in the part where the conductor width is small, and the gold film is increased in the part where the conductor width is large compared to the part where the conductor width is small. Decrease density (
It has a thinner till thickness.

[Workbook] The method of forming a conductor in this invention uses a total film thickness, with a thin film in the wide part and a thick film in the narrow part, corresponding to the conductor width, so the amount of gold used is small. This reduces manufacturing costs.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 11) is a substrate made of ceramic or the like, 21 is a patterned conductive wire, and a part on which a heating resistor (not shown) is formed. The conductor portion C5b) is the conductor portion of the other portion.

The conductive wire portion (2a) in FIG. 1 is a portion where a heating resistor is formed, and for example, the dot density of the resistor is 8 dots//.
In the case of Hl, the pitch h between patterns in (2a) of the conductor part
6B for tgsμm s 16 dots/H, 5μm
becomes. The dot resistance is ((inter-pattern pitch) -C
Therefore, the conductor width dimension of the (jla) part is important.If the dot density is 8 to 16 dots h/ass, the conductor width of the (ga) part is approximately 15 to 2.
A very thin pattern of 5 μm is required.

By the way, we formed a film by printing and firing gold paste,
When forming a conductor pattern by photoetching, the density of the gold film after forming the Vc#f film is very important to form a very thin pattern of 15 to 25 μm in the conductor as described above.

The inventor obtained experimental data regarding the density of the gold film, and the results are shown in FIG. The second l- is the density of the gold film expressed as the backlight density (100x magnification).
The 8th placement [A] has a pinhole of about 5μmg1 or less.The 8th placement [mouth] has a pinhole of 10μm5i1 degree, Figure 2 W [)) #-! , 15 to 15 flopm-, respectively. Figure 8 (1III-1, 8th position) shows the relationship between the density of the gold film and the total weight. Figure 8 (q is the relationship between the total weight and total film thickness) This is what is shown.

Now, the conductor part in Figure 1 (20 is the conductor width of 15 to 2
When a thin pattern of 5 μm is formed by photoetching, the density of the gold film is as shown in Figure 8 (2).
The degree shown in [B] is required. In other words, the conductor width dimension (in contrast, a film density that only has a pinhole diameter of about A or less is required. Therefore, conventionally, printing and firing were repeated 2 to 8 times. As a result, the IBI in Figure 2,
(As you can see from Q, the overall film thickness became thicker and the amount of gold used also increased.

However, the four-wire width of the conductor portion (2b) in FIG. 1 is usually sufficiently wider than that of the conductor portion (2a). For example, in a pattern where the conductor portion (2b) has a conductor width of about 50 pm, even if the film density is as shown in No. B [c],
It can be formed satisfactorily, and there is almost no difference in conductor resistance from person to person. Therefore, even if the film thickness of the conductor portion (2b) is made thinner than that of the conductor portion (gb), sufficient conducting wire formation is possible.

By the way, the conductor part (2a) and the conductor part (8b) in FIG.
) area ratio is usually 5 (all mi"10~4G
The body part (2b) is overwhelmingly wider.

Therefore, only the conductor portion (2a) in FIG. 1 has a gold film density of 2.
The film was formed to the extent shown in [A], and the conductor part (2) in Figure 1 was formed.
b) is achieved by forming a gold film with a density of about 2l-[c], that is, compared to the conductor part (2a), the conductor part (2b)
) By forming a thin film of gold, the amount of gold used can be reduced without impairing the performance of the conductor.

In the above embodiment, the 4-wire wire in FIG. It can also be applied to small h portions and large h portions.

Furthermore, the present invention is not limited to forming conductive wires for thermal heads, but can be similarly applied to the formation of conductive wires in the case where gold is used as a conductor in a circuit board with a general film thickness.

〔Effect of the invention〕

As described above, according to the present invention, since the gold film is formed thinner in the large part of the conducting wire part than in the small part of the conducting wire part,
It is possible to reduce the amount of trays used without impairing the conductor performance, and it is possible to form conductors at low manufacturing costs with less loss of gold due to etching or process defects, and is of extremely practical value. It's expensive.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the structure of one embodiment of the present invention.
Rotation shows a plan view, and FIG. 1 IBI shows a cross-sectional view. Figure 2 is a diagram showing experimental data related to the present invention, where the second position is the backlight density of the gold film density, Figure 2 IBI is the relationship between the gold film density and the amount of gold, and Figure 2 ( q shows the relationship between the total weight and the gold film thickness.8 Figure is a diagram explaining the conventional structure, the 8th position is a plan view, and Figure 8 iB+ is a cross-sectional view. Board, (2)″-conductor,
(2a)--m--conducting wire portion of a heating resistor forming portion (not shown); (gb)--conducting wire portion of another portion; Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A method for forming a conductive wire for a thermal head, characterized in that the film thickness at a portion where the conductor width is small is made thicker than at a portion where the conductor width is large. (2) A method for forming a conductor for a thermal head according to claim 1, wherein the metal constituting the conductor film is gold.