JPH08283966A - Etching method - Google Patents

Abstract

PURPOSE: To improve the etching rate and precision at the time of forming an anti-etching fine film pattern on a metallic sheet and then etching the sheet by spraying a liq. etchant consisting of ferric chloride soln. by specifying the spraying pressure and the temp. and concn. of the etchant. CONSTITUTION: A liq. etchant consisting of ferric chloride soln. is sprayed on the film pattern side of the sheet-shaped or continuous metallic sheet or iron alloy, copper alloy, etc., provided with the film pattern with the width of the exposed opening at the metallic part controlled to <=30μm to etch the sheet. In this case, the spraying pressure is controlled to >=4.0kgf/cm<2> , the etchant is kept at >=70 deg.C when the sheet is made of iron alloy, and the sp.gr. is controlled to >=47 Baum. Besides, when a resist pattern is formed on both sides of the metallic sheet, the sheet is preferably etched by horizontal etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method suitable for microfabrication of a shadow mask, a lead frame and the like.

[0002]

2. Description of the Related Art Heretofore, an etching method has been used as a method for processing metal products such as a shadow mask for a color television and a lead frame used as an assembly member of a semiconductor device. Further, since high mass productivity and processing accuracy are required for the etching process of the shadow mask and the lead frame, a sheet-shaped metal plate or a continuous metal plate whose predetermined part is covered with an etching liquid resistant resist is almost horizontal. A horizontal etching method has been adopted in which an etching solution ejected from a nozzle is applied to the upper and lower sides (front and back) of a metal plate while continuously moving in such a state that the metal plate is corroded from both the front and back sides and processed. This method is generally adopted because it has better processing accuracy than the vertical etching method, in which the metal plate surface is almost vertical and corrosion is performed.

A conventional horizontal etching type etching method will be described below with reference to FIG. First, degreasing and washing treatments are applied to both front and back surfaces of the metal plate 210 (FIG. 2A), and a resist 220 such as casein containing potassium dichromate is applied to both front and back surfaces of the metal plate 210, followed by a drying treatment. And so on. (FIG. 2B) Next, using the predetermined pattern plates 230A and 230B on the front and back surfaces of the metal plate 110, the resist 22 on both front and back surfaces is formed.
0 is selectively exposed (FIG. 2C), and subjected to development processing, drying processing, etc., to form resist patterns 220A and 220B each having a predetermined pattern on both surfaces of the metal plate. (FIG. 2D) After that, the metal plate 210 is brought into a substantially horizontal state through a drying process or the like, and the metal exposed portions 210A on both front and back (upper and lower) surfaces are exposed to an etching solution 240 sprayed from a spray nozzle to perform etching. Then, the through hole 250 is formed, and the etching is finished at a predetermined position. (FIG. 2 (e)) Next, after removing the resist patterns on the front and back of the etched metal plate with an alkaline solution or the like, a product is obtained through cleaning treatment, drying treatment, and the like. (Fig. 2
(F))

In particular, the resist patterns 120A, 120
Since the processing accuracy, quality, and processing speed of the product are determined in the etching step after forming B, it has been an important point to properly set the etching conditions.

The conventional horizontal etching type etching method is carried out by the etching apparatus shown in FIG. 3A is a plan view of the etching apparatus 300, and FIG. 3B is a cross-sectional view taken along line A1-A2 of FIG. 3A. In FIG.
320D is a spray nozzle, 330U and 330D are spray tubes, 340 is a transfer roll, 350 is an etching liquid,
Reference numeral 380 is a metal plate. When etching, the metal plate 380
While being transported in a substantially horizontal state by the transport roll 340, the spray nozzle 320
The etching liquid 350 jetted from U and 320D is received and etched. Spray tube 330
U and 330D supply the etching liquid 350 to the spray nozzles 320U and 320D, and are arranged at a predetermined interval parallel to the traveling direction of the metal plate. The spray nozzles 320U and 320D respectively have a spray tube 330.
The spray pipes 330U and 330D are attached to U and 330D at a predetermined interval, and the spray pipes 330U and 330D are swung as shown by arrows in FIG. It is performed while swinging the injection direction. As a result, the entire metal plate is etched as uniformly as possible. In this way, the etching apparatus 300 adjusts the nozzle arrangement, the nozzle spraying position, the nozzle spraying direction, etc. so that the entire metal plate 380 is etched as uniformly as possible.
Various ideas have been made. The etching conditions are as follows: the temperature of the etching solution is about 50 ° C., the specific gravity is about 47 Baume, and the pressure of the spray nozzle is 3.0 Kgf / cm ^2.
It was done below.

As described above, various devices have been devised so that the entire metal plate can be etched as uniformly as possible. However, iron alloy or copper alloy is used as a ferric chloride solution as a corrosive solution (etching solution). It is known that when etching is performed, the temperature and the specific gravity of the etching solution have a great influence on the etching characteristics, as well as the devising of the above-mentioned apparatus-like etching conditions. For example, as shown in FIG.
It is known that for (aluminum killed) material and Invar material (36% nickel-iron alloy), the higher the etching solution temperature, the faster the etching rate, and the higher the specific gravity of the etching solution, the slower the etching rate. ing. In addition, an etching factor EF defined by the following equation (1) is generally used as a criterion for judging the progress of etching. This indicates the progress of etching. Generally, the smaller the widthwise spread with respect to the depthwise spread, the less the spread direction variation and the more uniform etching. Therefore, the etching factor EF is usually The larger the size, the better. As shown in FIG. 5B, the etching factor EF is larger as the liquid temperature is higher and the specific gravity of the etching liquid is larger.
In FIG. 5A, the etching factor EF is defined by the equation (1). EF =
2d / (W2-W1) (1) where d, W1 and W2 are respectively the large diameter side diameter W2, the large diameter side resist diameter W1 and the large diameter side etching depth in the openings shown in FIG. The height d is shown.

[0007] However, such a tendency of the etching solution temperature and specific gravity to affect the etching characteristics is that the opening width of the resist pattern provided on the surface of the metal plate to be etched is wide to some extent. In the case where N is about 30 μm or less, the non-corrosive reaction product (mainly ferrous chloride) generated in the etching hole is not removed by the spray pressure, and the progress of etching is hindered. Spray pressure 3Kg
f / cm ² or less), a desired shape could not be obtained.

On the other hand, in the lead frame, fine processing has been required more and more in response to the increase in the number of terminals of the semiconductor element and the miniaturization of the package. Figure 6
As shown in (a), a lead frame (referred to as a single-layer lead frame) is electrically connected to a die pad portion 610 for mounting a semiconductor element, a terminal portion (electrode pad) of the semiconductor element, and a gold wire (wire). An inner lead 620 for wire connection, an outer lead 630 for integrally connecting to the inner lead 620 to connect to an external circuit, and for preventing resin leakage when mounting a semiconductor element and sealing with a resin. The dam bar 640 and the frame 6
The inner lead tip is required to have a narrow pitch, and is especially used for wire bonding to electrically connect a terminal (electrode pad) of a semiconductor element with a gold wire (wire). A suitable shape is required. The cross-sectional shape of the tip of the inner lead portion of the lead frame formed by etching has a shape as shown in FIG. 6B, but the wire bonding surface side has a flat portion 620F as wide as possible and It is required to make the pitch 620P between the leads as small as possible. At present, it is necessary to secure a flat portion 620F of the wire bonding surface side of about 90 μm, and an interval 620D between the inner leads of about 50 to 60 μm. Is needed. Therefore, even in the lead frame etching process, the width should be as narrow as possible.
There has been a need for a method of forming deeper etching holes. Further, there has been a demand for a processing method that can sufficiently cope with the productivity and quality of etching processing.

[0009]

As described above, a film pattern having etching resistance is formed on the surface, and the surface of the sheet pattern or continuous metal plate made of an iron alloy or a copper alloy on the film pattern side is treated with chloride chloride. In the etching method for etching metal products by spray-injecting a corrosive liquid consisting of ferric iron, there is no problem in terms of quality, and it is also suitable in terms of productivity. Was required. In particular, in terms of quality and productivity, it is possible to cope with etching processing of minute openings in which the width of the opening of the exposed film pattern is 30 μm or less, which cannot be substantially processed under the conventional etching processing conditions. An etching processing method has been demanded. The present invention addresses this, and while ensuring processing accuracy, quality, and productivity,
It is intended to provide a method for etching a metal plate made of an iron alloy or a copper alloy having a fine resist pattern opening.

[0010]

According to the etching method of the present invention, an etching resistant film pattern is formed on the surface,
It is an etching method for etching a metal product by spray-injecting a corrosive liquid made of ferric chloride liquid onto the film pattern side surface of a sheet-shaped or continuous metal plate made of an iron alloy, a copper alloy or the like. The spray pressure applied to the metal plate is 4.0 Kgf / cm ² or more. The etching-resistant film pattern is characterized by having a portion in which the width of the opening of the film pattern in which the metal portion is exposed is 30 μm or less. And again, in the above, the metal plate is an iron alloy, the corrosive liquid consisting of ferric chloride liquid,
The liquid temperature is 70 ° C. or higher, and the specific gravity is 47 baume or higher. Also, in the above,
The etching-resistant film pattern is a resist pattern, and resist patterns are formed on both the front and back surfaces of a sheet-shaped or continuous metal plate, and the metal plate is corroded from above and below while being transported while being placed in a substantially horizontal state. The present invention is characterized in that a metal product is etched by spraying a liquid, and the metal product is a lead frame.

[0011]

With the above construction, the etching method of the present invention can perform etching processing of a metal plate made of an iron alloy or a copper alloy having a fine resist pattern opening with respect to processing accuracy, quality, and productivity. It is possible to carry out etching processing of a metal plate made of an iron alloy or a copper alloy having a fine resist pattern opening of 30 μm or less at the same time, in terms of processing accuracy, quality,
In terms of productivity, it can be performed without any problems. Specifically, a sheet-shaped or continuous metal plate made of an iron alloy or a copper alloy having an etching resistant film pattern formed on its surface is sprayed with a corrosive liquid made of a ferric chloride solution on the surface of the film pattern side. Is a method for etching metal products, and the spray pressure applied to the metal plate is 4.0 Kgf / cm ² or more, so that there is no problem in terms of processing accuracy, quality, and productivity. Is possible. Further, even though the opening width of the etching-resistant film pattern is as narrow as 30 μm or less, non-corrosive reaction products (mainly ferrous chloride) generated in the etching holes of the metal plate do not stay, It enables the progress of etching and, as a result, enables the etching process itself. Further, the etching speed can be secured by the corrosive liquid composed of ferric chloride liquid using a metal plate as an iron alloy at a liquid temperature of 70 ° C or higher and a specific gravity of 47 Baume or higher, and also in terms of productivity. The problem is that there is no problem, and at the same time, the average surface roughness value (Ra) is small, and a smooth etched surface can be formed. Specifically, under the spray etching conditions of ⁴ Kgf / cm ² , the conventional etching liquid conditions (liquid temperature 50 ° C., specific gravity 4
7 baume), the resist pattern opening width is 40 to 50
In the case of .mu.m, it took about 8 to 9 minutes for the etching opening diameter to reach 100 .mu.m, but when the opening width of the resist pattern is 30 .mu.m, it takes about twice as long to reach the opening diameter of 100 .mu.m. is necessary. Therefore, if it is left as it is, the productivity will be approximately halved. Further, a resist pattern having an opening width of about 30 μm and an opening width of 40 to 50
In the case where the particles having a size of μm are mixed, the variation due to etching is large, which causes a problem in quality. By doing so, it is possible to solve these productivity problems and quality problems. With respect to copper alloys, productivity problems and quality problems can be solved by increasing the etching speed and the etching solution temperature. Further, the etching-resistant film pattern is a resist pattern,
A resist pattern is formed on both front and back surfaces of a sheet-shaped or continuous metal plate, and while the metal plate is conveyed in a substantially horizontal state, a corrosive liquid is sprayed and sprayed onto the metal plate from above and below to etch a metal product. As a result, it is possible to perform processing by using the conventional etching processing apparatus and by the usual etching method of the process shown in FIG. In particular, the metal product is 42 alloy (42% nickel-iron alloy)
In the case of a lead frame made of copper or a copper alloy, it is possible to cope with the narrower pitch of the inner leads and the wire bonding shown in FIG. 5 (b).

[0012]

EXAMPLES The etching processing method of the present invention will be described with reference to FIGS. First, as shown in FIG. 1A, as a metal plate 110 to be etched, a 42 alloy (42% nickel-iron alloy) having a thickness of 0.15 mm is used.
After both surfaces were subjected to cleaning treatment, a photoresist made of PVA (polyvinyl alcohol) containing chromium was used as the resist 120 on both surfaces of the metal plate 110, and uniformly applied to a thickness of 5 μm and dried. After that, as shown in FIG. 1B, the resist 120 was selectively exposed and developed using predetermined pattern plates 130A and 130B.
Then, as shown in FIG. 1C, the width of the metal exposed portion 110A on the surface of the metal plate 110 is 20 μm, 30 μm, 40 μm, and 50 μ, respectively, through a burning process and the like.
Resist patterns 120A and 120B having an opening having a width of m and exposing the metal portion were formed. The exposure is performed by vacuum-bonding the pattern plates 130A and 130B to the resist 120 on the surface of the metal plate 110, and then using a high pressure mercury lamp at 1900 mJ.
I went in. Develop with pure water and burn with 200
It was performed at ° C. Next, as shown in FIG. 1D, with respect to the metal plate 110 on which the resist pattern is formed,
Spray pressure of etching solution at 70 ° C and 47 Baume 2.
^{0Kg / cm 2, 3.0Kg / cm} 2, 4.0Kg / c
Etching was carried out under the conditions of m ² and 5.0 kg / cm ² to process the metal plate. After that, as shown in FIG. 1E, the resist patterns 120A and 120B are removed.
The predetermined processing was completed after washing processing and the like, and the opening hole 150 was obtained. However, in the actual work, the diameter of the opening hole 150 for etching is set to 100 in advance by changing the etching time.
The time required to reach μm was obtained, and a plurality of etchings were performed at that time to obtain the following data as an average value. FIG.
In (e), D is the depth (μm) when the opening hole 150 reaches 100 μm. Table 1 shows the etching depth (unit: μm) and the required etching time (unit: minutes) obtained by processing the metal plate, when the etching opening diameter reaches 100 μm. From Table 1, when the spray pressure is 4.0 Kg / cm ² or more, the case where the opening width W of the resist pattern is narrower is
It can be seen that when the etching opening diameter of 100 μm is obtained, the depth D (μm) of the opening portion of the etching is large as compared with the case where the opening is wide. This means that the spray pressure is 4.0 kg.
The higher the pressure is / cm ² or more, the lower the spray nozzle pressure is. 3.
It can be seen that it is more suitable for forming fine holes than the case of 0 Kg / cm ² or less. From the required etching time T,
Even when the resist pattern openings having various resist pattern opening widths W (μm) are mixedly present, by appropriately correcting the resist pattern opening widths W (μm), all the opening widths can be obtained. Thus, it can be seen that it was possible to obtain the one excellent in processing accuracy with the same etching time.

Next, a comparative example will be described. After plate making under the same conditions using the same metal plate (42 alloy) as in the above example,
The temperature of the etching solution is 50 ° C, the specific gravity is 47 baume, and the spray nozzle pressure is 2.0 Kg / cm ² , 3.0 Kg.
/ Cm ² , 4.0 Kg / cm ² and 5.0 Kg / cm ² were etched under the respective conditions to process the metal plate. Table 2
Is obtained by the etching process of this metal plate,
It shows the etching depth (unit: μm) when the etching aperture diameter becomes 100 μm. In Table 2, * 1 is 10 minutes after etching for 20 minutes.
A 0 μm opening was not obtained, and * 2 was also etched for 20 minutes, but a 100 μm opening was not obtained. From Table 2, the spray nozzle pressure is approximately 4 kg.
When it is smaller than / cm ² , the etching is practically impossible when the opening width W of the resist pattern is 30 μm or less. The spray nozzle pressure is about 4 kg / cm.
^It can be seen that in the case of ² or more, even if the opening width of the resist pattern is 30 μm or less, an opening can be formed in the metal plate by taking some time.

The average surface roughness (Ra) of the etched surface was 0.14 μm when the ferric chloride solution at 70 ° C. and 47 Baume was used and the etching was performed at a spray pressure of 4.0 Kg / cm ^2. , 50 ° C, 47 Baume ferric chloride solution, the average surface roughness (Ra) of the etched surface was 0.32 μm when etching was performed at a spraying pressure of 4.0 Kg / cm ^2. Comparing to the solution conditions in the above, a ferric chloride solution with an etching solution temperature of 50 ° C. and a specific gravity of 47 Baume is used, and compared with the case where etching processing is performed at a spray pressure of 4.0 Kg / cm ² , the chloride content of 47 Baume is 70 ° C. It can be seen that the etching surface becomes smoother and the quality is better when etching is performed with a ferric solution at a spray pressure of 4.0 Kg / cm ² . In addition, since the etching is performed with the liquid temperature of the ferric chloride solution at 70 ° C., it is necessary to form the etching tank with a metal such as titanium.

In the above embodiment, 42 alloy (42%
Nickel-iron alloy) was used, but for other iron alloys and copper alloys, the spray pressure was about 4.0 Kg / cm.
^By setting the temperature to ² or more and raising the temperature of the etching solution to 70 ° C, almost the same effect was obtained. In addition, using the etching apparatus shown in FIG. 3, in the step shown in FIG.
Lead frames were made from various iron alloys and copper alloys, but in both cases, the cross-sectional shape of the tip of the inner lead is more suitable for microfabrication and bonding properties than those of the same conventional materials. I was able to get it.

[0016]

As described above, the etching method of the present invention has a sheet shape or an iron alloy or a copper alloy in which the opening of the etching-resistant liquid-resistant film pattern in which the metal portion is exposed has a fine width. The surface of the continuous metal plate on the side of the film pattern is sprayed with a corrosive liquid consisting of ferric chloride liquid,
It is possible to provide a spray etching method that does not have a problem in quality in an etching method for etching a metal product and can also cope with productivity. It is possible to provide a spray etching method capable of coping with quality and productivity in a practical range even when the width of the opening of the etching resistant liquid film pattern is 30 μm or less. Is. In particular, in recent years, it is possible to cope with the production of lead frames, which are increasingly required to be processed with precision, and the production of sheer dough masks for finer and larger sizes. INDUSTRIAL APPLICABILITY The etching processing method of the present invention enables the processing of a metal plate having a fine resist pattern opening by a relatively simple adjustment of adjusting the temperature and specific gravity of the etching solution and the adjustment of the spray nozzle pressure, and makes it possible to manufacture at a practical use level. In particular, it does not require any special device improvement or improvement.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an etching method in an example.

FIG. 2 is a diagram for explaining an etching processing method.

FIG. 3 is a diagram for explaining an etching processing apparatus.

FIG. 4 is a diagram for explaining an etching speed.

FIG. 5 is a diagram for explaining an etching factor.

FIG. 6 is a diagram of a (single layer) lead frame.

[Explanation of symbols]

110 metal plate 120 resist 120A, 120B resist pattern 130A, 130B pattern plate 110A metal exposed part (resist opening part) 140 etching liquid 150 opening hole 210 metal plate 220 resist 220A, 220B resist pattern 230A, 230B pattern plate 210A metal exposed part ( Resist opening) 240 Etching liquid 250 Through hole 300 Etching device 310 Etching tank 320U, 320D Spray nozzle 330U, 330D Spray pipe 340 Conveying roll 350 Etching liquid 380 Metal plate 600 (single layer) Lead frame 610 Die pad 620 Inner lead 620F Flat part 620P Pitch 620D Distance between inner leads 630 Outer leads 640 Dam bar 650 Frame (frame Part

Claims (5)

[Claims] 1. A corrosive liquid comprising ferric chloride liquid is formed on a surface of a sheet-like or continuous metal plate made of an iron alloy, a copper alloy or the like, on which the film pattern is formed, on the surface of which an etching resistant film pattern is formed. Is a spraying method for etching a metal product, wherein the spray pressure applied to the metal plate is 4.0 Kgf / cm ² or more. 2. The etching processing method according to claim 1, wherein the etching-resistant film pattern has a portion in which the width of the opening of the film pattern in which the metal portion is exposed is 30 μm or less. 3. The method according to claim 1, wherein the metal plate is an iron alloy, and the corrosive liquid containing ferric chloride liquid has a liquid temperature of 70.
An etching method characterized by having a specific gravity of 47 degrees or more at a temperature of ° C or higher. 4. The resist pattern as the etching-resistant film pattern according to claim 1, wherein the resist pattern is formed on both front and back surfaces of a sheet-shaped or continuous metal plate to make the metal plate substantially horizontal. An etching method for etching a metal product by spraying a corrosive liquid onto the metal plate from above and below while transporting the metal product. 5. A method for etching according to claim 1, wherein the metal product is a lead frame.