JPS6315992B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION For example, when manufacturing a semiconductor lead frame whose surface is partially coated with aluminum, the present invention eliminates the need for composite metal strips coated with aluminum in stripes or cladding on the entire surface or in the longitudinal direction. This invention relates to a partial etching method that can be applied to cases where aluminum is partially removed, and a mechanical mask used therein.

Traditionally, in the manufacture of lead frames used in the assembly of transistors and integrated circuits (ICs), or lead frames for electrical terminals, composite metal strips, in which parts of base metal strips are coated with dissimilar metals by cladding or vapor deposition, have been used. Used as a material. As dissimilar metals, metals such as gold, silver, copper, and aluminum are mainly used, but due to the rise in the price of precious metals, there is a tendency to change from gold and silver to cheaper ones such as copper and aluminum. There is also a tendency to change from covering the entire surface or stripes to spot-like coatings, limiting them to functional or necessary areas.

Currently, such composite metal strips are often made by coating a base metal strip with dissimilar metals in the form of stripes or spots, and in this case, the dimensional accuracy of the coated dissimilar metals, including the thickness, is extremely severe. things are required.

However, it is extremely difficult to coat and adhere dissimilar metals to a base metal strip with high precision in the form of spots, and apart from plating, methods such as cladding or vapor deposition are used to bond dissimilar metals to a base metal strip. After the entire surface is coated, unnecessary portions of dissimilar metals are generally removed partially by a printing-etching method.

By the way, in the printing-etching method, after applying etching resist ink to the necessary parts of the composite metal strip, the whole is immersed in an etching solution. It requires four steps: etching and ink stripping, which is complicated and requires strict quality control in each step.

Additionally, there are economic and environmental concerns due to the consumption of ink and release agent. Furthermore, as shown in FIG. 6, even if the ink 2' is applied to the required portion 3' of the composite metal strip 1', the metal pattern in the required portion 3' is damaged due to side etching, that is, erosion of the etching liquid from the cross-sectional direction. It has the disadvantage that it is thinner than the ink pattern and that the cross-sectional shape of the boundary is not at right angles, making the boundary shape of the metal pattern in the necessary part unclear.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a simple method by using a mechanical mask having a cylindrical tip at least in contact with the surface of a metal material, and further utilizing a pressure difference caused by gas. The object of the present invention is to provide a partial etching method that enables highly accurate etching processing that can prevent side etching, and a mechanical mask used therein.

That is, the gist of the present invention is to provide a method for partially etching a part of the surface of a metal material with an etching solution by contacting a part of the surface of the metal material with a mechanical mask having a predetermined thickness. The mask has a pointed end having a contoured shape that can come into contact with a part of the surface of the metal material and separate the part of the surface of the metal material into an etched part and a non-etched part, and at least the pointed part has a cylindrical structure. using a mask, and applying a pressure difference by gas or liquid between the etching portion and the non-etching portion separated by the contour shape of the pointed end of the mask in a direction to prevent the etching liquid from entering the non-etching portion. A partial etching method is characterized in that a part of the surface of the metal material is brought into contact with a mechanical mask of a required thickness, and a part of the surface of the metal material is partially etched with an etching solution. The mechanical mask used in the above-mentioned process has a tip having a contoured shape that can come into contact with a part of the surface of the metal material and separate the part of the surface of the metal material into an etched part and a non-etched part. and a mechanical mask for partial etching, characterized in that the width of the tip part is 1 mm or less and the structure of at least the tip part is a cylindrical structure.

In the partial etching method of the present invention, it is more preferable to use a rigid metal such as stainless steel as the structural material of the mechanical mask than to use a soft material such as rubber or plastic. In other words, if a rigid metal body is used as a mechanical mask, it will not easily deform even when subjected to the pressure difference, thereby improving etching accuracy.

Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings.

FIG. 1 shows the implementation of a partial etching method using a mechanical mask. As shown in FIG. 2, this mechanical mask body consists of a mask 1 made of stainless steel and having at least a cylindrical pointed end.The width of the pointed end 2 is ( The thickness is 1 mm or less. If the width of this point 2 is too large, the boundary shape of the etched part will become unclear, so the narrower the better, but in reality it should have a certain width in consideration of the mechanical strength for mask processing and mask pressing. . Further, as is clear from FIG. 2, the contour shape 3 forming the periphery of the pointed end is separated into a portion where the surface of the metal strip 5 is etched and a portion where it is not etched when it comes into contact with the surface of the metal strip 5. By the way.

According to FIG. 1, the above-mentioned mask body 1 made of a cylindrical body is pressed onto a metal strip 5 to be etched with a force of 10 kgf by an air cylinder 4, and in this state is immersed in an etching liquid 6. . Note that the metal strip 5 is an iron-nickel alloy base 7.
A mask body 1 having one side entirely coated with aluminum 7' is used, and the mask body 1 that abuts on the aluminum 7' is held at right angles by a guide cylinder 8 to prevent it from wobbling.

Here, when air is introduced into the inside of the mask body 1 and internal pressure is applied at a predetermined air pressure as shown by the arrow in FIG. Therefore, the pressure of the portion of the metal strip 5 that is left unetched is maintained at a higher pressure than the pressure of the exposed portion of the metal strip 5 that is immersed in the etching solution. By doing so, it is possible to prevent the etching liquid 6 from entering the mask body 1, and to perform etching by clearly separating the mask portion and the etching portion.As a result, the remaining coated metal after the etching process can be removed. (Aluminum 7') can be contoured with high precision and without side etching. Note that liquid may be used instead of air to apply internal pressure.

Incidentally, if such internal pressure was not applied, the etching solution would seep into the mask body, making it impossible to perform highly accurate etching.

On the other hand, according to the etching method shown in FIGS. 1 and 2 using a mechanical mask, the metal strip 5 to be etched is
By applying the above-mentioned internal pressure while pressing the mask body 1 with a constant pressure against the mask body, the mask body 1 also moves as etching progresses, so side etching does not occur and the inner shape of the mask body is changed as shown in Fig. 3. The same aluminum metal pattern 9 is formed.

Incidentally, FIGS. 3 and 4 show examples of partially etched products based on this embodiment.

FIG. 3 shows the aluminum pattern 11 after the mask body is pressed against the aluminum side of the iron-nickel alloy 10 and aluminum two-layer metal strip and unnecessary portions of the aluminum are removed by etching. This strip is then punched out using a press to form an IC lead frame having the shape shown in FIG.

Figure 4 shows a two-layer metal strip made of iron-nickel alloy 12 and aluminum, which is punched out using a press, and then etched by applying a mask to the aluminum side to form an aluminum pattern 1.
3 shows an IC lead frame formed by forming a lead frame.

Although this embodiment shows an example in which the portion covered by the mask body is left and the rest is etched, it is also conceivable to introduce an etching liquid inside the mask body and etch only that portion. In this case, it is necessary to increase the pressure on the outside of the mask body.

As is clear from the above description, according to the etching method of the present invention, at least By performing etching using a mechanical mask with a cylindrical tip, conventional printing
Compared to etching methods, the process can be significantly simplified, resulting in quality control and economic benefits, and the etching can be separated by the contour of the tip of the mechanical mask. By performing etching by applying a pressure difference between the etching part and the non-etched part using gas or liquid in a direction that prevents the etching liquid from entering the non-etched part, side etching can be prevented and it is extremely effective even for minute parts. This has the extremely remarkable effect of being able to perform partial etching with high precision. Further, according to the mechanical mask of the present invention, even if the surface of the metal material is somewhat uneven, by applying a pressure difference after the mask is brought into contact with the mask, it is possible to reliably prevent the etching solution from entering the mask side. As a result, it is possible to easily perform partial etching with extremely high precision.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a partial etching method according to an embodiment of the present invention, FIG. 2 is a partial sectional view and bottom view of a mechanical mask according to an embodiment of the present invention, and FIGS. Figure 4 is a partial front view of an IC lead frame that has been partially etched using the above method, Figure 5 is a partially enlarged sectional view showing the state of etching using a mechanical mask, and Figure 6 is a partial front view of an IC lead frame partially etched using the above-mentioned method. It is a partial sectional view showing a state. 1: mask body, 2: tip, 3: contour shape,
4: Air cylinder, 5: Metal strip, 6: Etching liquid.

Claims (1)

[Scope of Claims] 1. A method of partially etching a part of the surface of a metal material with an etching solution by contacting a part of the surface of the metal material with a mechanical mask having a predetermined thickness. The structure of at least the pointed end has a cylindrical structure, the pointed end having a contoured shape that can come into contact with a part of the surface of the metal material and separate the part of the surface of the metal material into an etched part and a non-etched part. Using a mask, a pressure difference is applied by gas or liquid between the etching portion and the non-etching portion separated by the contour shape of the tip of the mask in a direction to prevent the etching liquid from entering the non-etching portion. A partial etching method characterized by etching. 2. The mechanical mask used when partially etching a part of the surface of a metal material with an etching solution by contacting a mechanical mask with a required thickness to a part of the surface of the metal material, It has a tip with a contoured shape that can come into contact with a part of the surface of the metal material and separate the part of the surface of the metal material into an etched part and a non-etched part, and the width of the tip is 1 mm or less, and at least the tip part A mechanical mask for partial etching, characterized in that the structure is a cylindrical structure.