JPS6219506B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field This invention relates to a method of etching a thin metal plate,
More specifically, the present invention relates to a method of etching a thin metal plate suitable for manufacturing support leads for a tuning fork crystal resonator.

Prior Art Hermetic terminals for crystal resonators have various structures depending on the shape of the crystal piece and the method of holding it.

Figure 1 is published in Tokuko Publication No. 50363, No. 57-5036, and Special Publication No. 58-58-
24968, Japanese Patent Application Laid-open No. 57-50177, etc., are shown cross-sectional views of airtight terminals for holding tuning fork-shaped crystal pieces, and FIG. 2 is an enlarged front view of the main parts, and FIG. A side view taken along the line - in the figure is shown. In the figure, reference numeral 1 denotes a metal outer ring made of Kovar (iron-nickel-cobalt alloy) or the like, to which support leads 3 and 4 are hermetically and insulatively sealed via glass 2 such as borosilicate glass. These support leads 3 and 4 include straight lead parts 5 and 6 that are sealed to the glass 2 and support parts 7 and 8 that are bent into a substantially U-shape. Part 7
A minute gap 9 is formed between a and 8a, and a tuning fork type crystal piece 10 is held in this minute gap 9.

The above-mentioned airtight terminal has conventionally been manufactured through the steps shown in FIGS. 4 to 7. First, a Kovar plate 11 of a predetermined size and thickness t is prepared (fourth
figure). Next, a photoresist film 12 is applied to the entire surface of this Kovar plate 11, a mask with a predetermined pattern is superimposed on it, and exposed and developed.
A photoresist film 12 is formed in a predetermined pattern (FIG. 5). After that, the whole is immersed in an etching solution to etch away the portions not covered with the photoresist film 12, and the photoresist film 12 is further dissolved and removed with an organic solvent, and the plurality of sets of support leads 3, 4 are removed. A lead frame 14 is manufactured in which the parts are integrated at the connecting part 13 (FIG. 6). Next, the lead frame 14 is assembled in a predetermined position with the metal outer ring 1 and the glass tablet 2' using a graphite sealing jig (not shown), and the whole is made of neutral or The glass tablet 2' was melted by heating to about 1000° C. in a weakly reducing atmosphere, and the support leads 3 and 4 were hermetically and insulated sealed inside the metal outer ring 1 via the glass 2. A connected envelope 15 is manufactured (FIG. 7). Finally, the lead frame 14 is cut and separated along the dashed lines 16 and 17 in FIG. 7 to obtain an airtight terminal as shown in FIGS. 1 to 3.

Disadvantages of the Prior Art Here, the width dimension W of the minute gap 9 between the tips 7a and 8a of the support parts 7 and 8 shown in FIG. 2 is required to be extremely small as the crystal piece 10 becomes thinner. This is becoming more and more common. However, the lead parts 5, 6 and the support parts 7, 8 need a predetermined thickness t for mechanical strength, but in order to remove the Kovar plate 11 with the thickness t by etching, it is necessary to have a predetermined thickness t. Etching time is required, and etching progresses in the lateral direction within this etching time.
Due to the influence of the thickness dimension t, it was not possible to obtain a minute gap 9 satisfying the relationship W<1.3t.

Purpose of the Invention Therefore, the present invention aims to form a minute gap that satisfies the relationship w<1.3t, where t is the thickness of a thin metal plate, and w is the width of a minute gap between metal members. The purpose of the present invention is to provide a method for etching a thin metal plate.

Composition of the Invention The present invention includes a step of forming a resist film of a predetermined pattern in which a portion where a micro gap is to be formed is opened on a thin metal plate, and etching away the thin metal plate exposed from the opening in the portion where the micro gap is to be formed. and a step of removing the resist film, in the step of forming the resist film, a portion wider than the opening is formed midway along the length of the opening in the portion where the minute gap is to be formed. This method is characterized by forming a resist film having a large opening.

In other words, the reason why it was not possible to make the width W of the microgap W = 1.3t for the thickness method t of the thin metal plate is because the width W of the opening in the portion of the resist film where the microgap is planned to be formed is small. In this case, the amount of etchant supplied to the thin metal sheet through this opening is small, and the etching speed in the thickness direction of the thin metal sheet is low, requiring a long etching time, which is likely to cause lateral etching. Was.

However, by forming a large opening wider than this opening midway along the length of the opening as described above, the amount of etchant supplied to the center of the opening increases, and the amount of etchant supplied from this central portion increases. As the etching progresses toward the openings on both sides, it becomes possible to etch the thin metal plate in a shorter time than before, and the lateral etching at the openings is suppressed, making it easier to etch the thickness t than before. This makes it possible to form a minute gap with a small width w.

Embodiment An embodiment of the present invention will be described with reference to the drawings. It should be noted that, except for the process of forming a resist film, the process is the same as the conventional process shown in FIGS. 4 to 7, so the process of forming a resist film, which is a characteristic feature of the present invention, will be described.

FIG. 8 shows an enlarged plan view of a main part of a state in which a photoresist film 12 of a predetermined pattern is formed on a Kovar plate 11. This photoresist film 12 covers the tips 7 of the support parts 7 and 8 of the support leads 3 and 4.
It has an opening 18 with a width w and a length L for the minute gap between a and 8a, and a circular hole with a diameter D larger than the width w is provided in the center of the opening 18 in the length direction. It has a large opening 19.
Other points are the same as in FIG. 5.

When the Kovar plate 11 on which such a photoresist film 12 has been formed is immersed in an etching solution and etched, the Kovar plate 11 exposed from the opening 18 is etched, but the part halfway along the length of the opening 18 is etched. Since a large opening 19 having a diameter D larger than the width w of the opening 18 is formed in the opening 18, the etching liquid passes through the large opening 19.
The etching rate in the thickness direction of the Kovar plate 11 exposed from the opening 18 increases as the etching becomes easier to be supplied to the opening 18. As a result, the time required for etching is significantly shortened, and the etching in the lateral direction of the opening 18 is accordingly suppressed.As a result, as shown in FIG. It became possible to form Furthermore, according to the present invention, lateral etching of the tips 7a, 8a of the support parts 7, 8 is suppressed and both ends are not curved, so the width w of the minute gap 20 can be set more accurately than before. This has the advantage that the crystal piece 10 can be held vertically more easily than before.
Further, the arc-shaped recess 21 formed at the location corresponding to the large opening 19 serves as a reservoir for adhesive such as solder that connects and fixes the crystal piece 10 held in the minute gap 20, and the adhesive flows. It also helps prevent the spread.

Although this invention is highly effective when applied to the manufacture of support leads for airtight terminals for tuning-fork crystal resonators shown in the above embodiments, it is also possible to form minute gaps by etching thin metal plates. Applicable in all cases.

Furthermore, the shape of the large opening can be any shape other than circular.

Furthermore, not only liquid but also gaseous etchants can be used.

Furthermore, the patterning of the resist film may be performed using electron beam exposure or the like instead of using mask exposure, and the resist film may be of any type as long as it exhibits corrosion resistance not only to the photoresist film but also to etchants.

Effects of the Invention As described above, the present invention has a large opening wider than the width of the opening in the middle of the opening in the portion where the micro gap is to be formed in the resist film forming process. Since a resist film is formed, the etchant is smoothly supplied to the opening through the large opening, and the thin metal plate can be etched while suppressing lateral etching. It is possible to form a minute gap with a width smaller than that of the conventional method in a thin metal sheet, and in other words, when forming a predetermined gap size, it is possible to etch a thin metal sheet that is thicker than that of the conventional method.

[Brief explanation of the drawing]

FIG. 1 shows a sectional view of an airtight terminal for a tuning fork type crystal resonator, which is the background of the present invention. FIG. 2 is an enlarged front view of essential parts of the airtight terminal shown in FIG. 1. Figure 3 is the second
FIG. 3 is a side view taken along line - in the figure. 4 to 7 show each step to explain the method for manufacturing the support lead, FIG. 4 is a plan view of the thin metal plate, FIG. 5 is a plan view of the thin metal plate after developing the resist film, and FIG. 6 is a plan view of the thin metal plate. The figure is a plan view of the lead frame, and FIG. 7 is a sectional view of the connected sealing body. FIG. 8 is an enlarged plan view of a main part of a thin metal plate after developing a resist film according to the present invention. FIG. 9 is an enlarged plan view of the main part of the lead frame after etching the thin metal plate. 1... Metal outer ring, 2... Glass, 3, 4... Support lead, 5, 6... Lead part, 7, 8...
Support part, 7a, 8a...Tip part, 11...Metal thin plate (Kovar plate), 12...Resist film (photoresist film), 14...Lead frame, 1
5... Connected sealed body, 18... Opening, 19...
Large opening, 20... minute gap, 21... recess.

Claims (1)

[Scope of Claims] 1. A step of forming a resist film with a predetermined pattern in which a portion where a minute gap is to be formed is opened on a thin metal plate, and a step of etching away the thin metal plate exposed from the portion where a minute gap is to be formed; In the method for etching a thin metal plate, which includes a step of removing a resist film, in the step of forming the resist film, a hole having a width wider than the width of the opening is formed midway along the length of the opening in the portion where the microgap is to be formed. A method for etching a thin metal plate, the method comprising forming a resist film having large openings.