JPS6347346B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor lead frame made of a composite metal strip on which aluminum is vapor-deposited or clad.

BACKGROUND ART Conventionally, lead frames used in the manufacture of semiconductor devices such as transistor integrated circuits (ICs) use composite metal strips in which a portion of a base metal strip is clad or vapor-deposited with a different metal. Metals such as gold, silver, copper, and aluminum are mainly used as dissimilar metals, but due to the rise in the price of precious metals, gold,
There is a tendency to change from silver to cheaper materials such as copper and aluminum, and the areas covered by these materials tend to be limited to functional parts of semiconductors.

As a result, this kind of composite metal strip is
Base metal strips are often coated with dissimilar metals in the form of stripes or spots, and in this case, extremely strict values are required for the dimensional accuracy of the coated dissimilar metals, including the thickness. .

However, it is difficult to coat a base metal strip with a dissimilar metal in spots with high precision, not only in the case of plating but also in the case of cladding or vapor deposition. After the entire surface is coated with dissimilar metals and this is punched out into a predetermined pattern shape using a press, unnecessary portions of the dissimilar metals are removed by printing and etching methods.

The printing and etching method requires the printing and etching steps as well as the coating, baking, and peeling steps of the printing paint, which makes the process complicated and, depending on the paint used for printing, the mask may be incomplete. Moreover, since the printing boundaries are unclear,
It is generally difficult to strictly control the dimensional accuracy of coatings of dissimilar metals.

For this reason, the applicant first applied for
As seen in Publication No. 4, composite metal strips made of vapor-deposited or clad aluminum are used.
We proposed a method for manufacturing lead frames by removing unnecessary aluminum parts using an etching method using a mechanical mask as shown in the figure. The etching method using such a mechanical mask is an advantageous method that can omit the printing process, but in this case, in the etching after punching with a press, depending on the mask that is in contact with the required aluminum part, ,
The problem is that during etching, the etching liquid erodes the side surface (cut surface) formed by punching the tip of the aluminum part that requires it, as well as the side surface formed by etching, impairing the shape and dimensional accuracy of the necessary aluminum part after etching. There is. Furthermore, since the composite metal strip is easily deformed after punching, there is also concern about positioning it with the mask.

An object of the present invention is to solve the above-mentioned problems, and to obtain a lead frame with excellent shape and dimensional accuracy without eroding the necessary side surfaces of the aluminum part during etching after punching the composite metal strip. An object of the present invention is to provide a method for manufacturing a semiconductor lead frame by an etching method using a mechanical mask.

In other words, the gist of the present invention is to prepare a composite metal strip in which Fe-Ni alloy is used as a base metal strip, and aluminum is deposited or clad on a part or the entire surface of the composite metal strip, and unnecessary aluminum parts are removed from the composite metal strip using an etching solution. In a manufacturing method for a semiconductor lead frame in which the etching is removed by etching by erosion, when performing the etching before punching out the composite metal strip into a predetermined pattern shape using a press, chemical-resistant aluminum is added to the required aluminum portion of the composite metal strip. A mechanical mask made of a soft elastic material is brought into contact with a predetermined pressing force, and as etching progresses, the tip of the mask is eroded by the etching solution on the necessary aluminum part under the contact. A method of manufacturing a lead frame for a semiconductor is characterized in that the formed side surface is made to bite.

In the present invention, as the chemical-resistant soft elastic body, for example, silicone rubber, Teflon, polyethylene, soft vinyl chloride, etc. are used. These can be used alone or in combination.

The present invention will be further described below with reference to embodiments shown in the drawings.

Fig. 1 shows a base metal strip 1 made of Fe-42%Ni alloy with a thickness of 0.25 ₁₇ and a width of 30 ₁₇ , and a coating metal layer 2 of 0.01 ₁₇ in thickness provided by cladding aluminum on one side of the entire base metal strip 1. A part of the composite metal strip 3 is shown. Note that 4 is a pin hole provided for positioning the composite metal strip 3 in subsequent steps.

Next, FIG. 3 shows a mechanical mask etching device 5 that operates continuously, in which seven composite metal strips 3 are arranged in parallel and passed through by intermittent movement, and the coating metal layer 2 of each composite metal strip 3 is removed. Etching is performed on unnecessary aluminum parts. In this case, the movement interval and etching position of the composite metal strip 3 are set based on the pin hole 4. The seven composite metal strips 3 placed on the stage 6 are positioned by installing pins 7 in the pin holes 4 and further using end guides 8. Note that 9 is a mechanical mask, 10 is a hollow pressure chamber filled with etching liquid, 11 is an injection port, 12 is an etching liquid inlet, and 13 is an air cylinder.

Reference numeral 22 denotes a pressure adjusting plate, which is arranged so that the etching liquid is evenly ejected from each injection port 11.

The outline of the etching situation by this mechanical masking device will be explained with reference to FIG. 4. The etching liquid 14 sent from the etching liquid inlet 12 fills the hollow pressure chamber 10, passes through the injection port 11, and eliminates the need for a coating metal layer. collided with the aluminum part 15,
The unnecessary aluminum portion 15 is removed by etching. Here, the mask 9 is made of a chemical-resistant soft elastic material that is a combination of silicone rubber 9' and Teflon 9''. Such a mask 9 is applied to the required aluminum layer of the covering metal layer with a predetermined pressing force. As a result, as etching progresses, the tip of the mask comes to bite into the side surface 17 of the necessary aluminum part under its abutment, as shown in FIG.

By doing this, erosion of the side surface 17 by the etching liquid 14 is prevented, and as a result, as shown in FIG. It was possible to obtain a lead frame 20 made of a high quality partially coated composite metal strip.

Incidentally, in the conventional mechanical mask etching method, since the mask body is made of a rigid body, the seventh
As shown in the figure, the side surface of the aluminum part where the coating metal layer is required is eroded by the etching solution, making it impossible to secure the desired shape and dimensional accuracy.

After etching, as shown in FIG. 8, the composite metal strip 18 is punched out into a predetermined pattern shape 19 using a press to complete the lead frame 20. Note that the area within the dotted line frame 21 corresponds to the functional portion 16 of the lead frame 20, and is a portion having an aluminum coating on the surface.

As explained above, according to the present invention, in a method for manufacturing a semiconductor lead frame by an etching method using a mechanical mask, a chemical-resistant soft elastic material is used as the mask, and the mask is skillfully pressed. By performing etching, it is possible to prevent the necessary aluminum part of the coated metal layer from being eroded by the etching liquid during etching, and as a result, the shape and dimensional accuracy of the aluminum part can be significantly improved. This has the effect that a very excellent semiconductor lead frame can be obtained as a product.

Furthermore, bringing the punching process using a press to the end of the manufacturing process ensures the positioning of the composite metal strip during etching, which greatly contributes to the effect of improving the shape and dimensional accuracy of the aluminum part mentioned above. be.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view of a composite metal strip according to an embodiment of the present invention, FIG. 2 is a partial perspective view of the composite metal strip after etching, and FIG. 3 is an etching apparatus using the same mechanical mask. 4 is a schematic diagram showing the etching process using the etching apparatus using the same mechanical mask, FIG. 5 is an enlarged cross-sectional view of the main part of FIG. FIG. 7 is a sectional view of a composite metal strip after etching according to a conventional example, and FIG. 8 is a partial front view of a lead frame punched into a predetermined pattern. DESCRIPTION OF SYMBOLS 1: Base metal strip, 2: Coating metal layer, 3: Composite metal strip, 5: Mechanical mask etching device, 9:
Mechanical mask, 11: injection port, 14: etching liquid. 16: Functional part, 19: Pattern shape.

Claims (1)

[Claims] 1. A composite metal strip is prepared in which Fe-Ni alloy is used as a base metal strip and aluminum is vapor-deposited or clad on a part or the entire surface of the composite metal strip, and unnecessary aluminum parts are removed from the composite metal strip by etching using the corrosive action of an etching solution. In the method for manufacturing a semiconductor lead frame, when performing the etching before punching out the composite metal strip into a predetermined pattern shape using a press, necessary aluminum portions of the composite metal strip are made of a chemical-resistant soft elastic material. A mechanical mask is brought into contact with a predetermined pressing force so that, as etching progresses, the leading end of the mask bites into the side surface of the necessary aluminum part under the contact formed by the erosive action of the etching solution. A method for manufacturing a semiconductor lead frame, characterized by: