JP2637175B2 - Method of manufacturing multi-pin lead frame for semiconductor - Google Patents

Description

The present invention relates to a method for manufacturing a multi-pin lead frame for semiconductors. In particular, the present invention relates to a method for manufacturing a multi-pin lead frame for a semiconductor by etching processing capable of increasing the number of pins.

<Prior Art> In recent years, semiconductor integrated circuits have been increased in density and integration. Accordingly, the number of pins of lead frames used in such semiconductor integrated circuits has been increasing especially for logic devices.

Lead frame manufacturing methods usually include a pressing method and an etching method.Especially, for manufacturing a multi-pin lead frame of 100 pin class or more, an etching method suitable for fine processing, particularly a photo etching method is used. I have.

Generally, in a method of manufacturing a lead frame by a photoetching method, first, a photoresist liquid is applied to a thin metal plate as a material and dried. Thereafter, exposure and development are performed using a photomask having a predetermined pattern to form a photoresist layer having a predetermined pattern shape. Next, an etching solution is sprayed using the photoresist layer as a mask to dissolve and remove unnecessary material metals, form a lead frame of a predetermined pattern, and finally remove and remove the unnecessary resist film. You.

In such a lead frame, the inner lead connected to the semiconductor element is usually formed in a rectangular cantilever shape facing the element arrangement portion.

<Problems to be Solved by the Invention> However, in such a method of manufacturing a lead frame by a photoetching method, there is no resist pattern for preventing the inflow of an etching solution into a photoresist layer at a tip portion.

Therefore, particularly at the tip of the inner lead, the etching liquid easily flows through the gap between the metal thin plate and the photoresist layer, and as shown in FIG. The amount of side etching (the amount of etching into the photoresist layer 8 in the in-plane direction) increases, and the tip 15 of the inner lead 4 becomes needle-shaped, so that the dimensions and shape required for wire bonding with the semiconductor element are obtained. There is a problem that it is difficult to obtain the accuracy of the above.

In order to make the tip 15 of the inner lead accurate in size and shape, the photoresist layer 8 is made wider as the tip 15 of the inner lead 4 in consideration of the amount of side etching as shown in FIG. 4b. There is also a method of making a correction such as providing projections 16 of various shapes for suppressing side etching on the photoresist layer 8 at a portion corresponding to the corner of the tip of the inner lead 4.

However, such a correction method generally requires complicated operations for designing the shape of a photomask, creating an original plate, and the like. In addition, since it is necessary to change the shape of the photoresist layer (the shape of the photomask) according to the desired pattern of the lead frame, in order to obtain the optimum inner lead shape, it is necessary to carry out trial and error confirmation experiments by etching and photolithography. The work of correcting the mask shape must be repeated, which is very troublesome.

In addition, as the amount of metal dissolved by the etching operation increases, the deterioration of the etching solution becomes severe, the etching rate decreases, and the side etch characteristics change. It is difficult to obtain a shaped lead frame.

Further, the pitch width between the leads becomes narrower as the number of pins of the lead frame increases, and in fact, the tip of the inner lead is corrected by correcting the photoresist layer shape (photomask shape) as shown in FIG. 4b. It is becoming impossible to correct the shape itself.

Therefore, it is desired to develop a lead frame manufacturing method capable of easily manufacturing a lead frame in which the tip of the inner lead has an accurate size and shape.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and does not require complicated and difficult correction by the shape of a photoresist layer (shape of a photomask). Another object of the present invention is to provide a method for manufacturing a multi-pin lead frame for a semiconductor, which can easily manufacture a lead frame having an inner lead portion having a correct size and shape.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a semiconductor lead frame having inner leads connected to a semiconductor element by etching a thin metal plate into a predetermined pattern. In manufacturing, the size of the inner lead obtained by the etching process is formed to be longer than the final predetermined size, and at the same time, the notch half-etched is formed at the final predetermined dimension position of the inner lead by the etching process, and the etching is performed. A method of manufacturing a multi-pin lead frame for a semiconductor, characterized in that a tip portion of the inner lead is cut and processed to a predetermined length after the processing.

Hereinafter, the method for manufacturing a semiconductor lead frame of the present invention will be described in detail.

The constituent material of the metal sheet to which the manufacturing method of the present invention is applied is not particularly limited, and any of those used for ordinary lead frames such as iron, iron-based alloy, copper, and copper-based alloy can be applied. Among them, 42 alloy (Fe-42% Ni alloy), Kovar (Fe-29% Ni-17% CO alloy), phosphor bronze, tin-containing copper and the like are particularly preferably used.

The thickness of the metal sheet used in the present invention may be the same as that of a normal lead frame, and is about 0.1 to 0.25 mm.

The method for manufacturing a multi-pin lead frame for a semiconductor according to the present invention involves etching such a thin metal plate. At this time, the size of the inner lead connected to the semiconductor element is formed longer than the final predetermined size. At the same time, a half-etched notch is formed at the position of the predetermined dimension, and then the tip is cut by press cutting or the like to be processed to a predetermined dimension.

FIG. 1 shows an example of a semiconductor lead frame obtained by the manufacturing method of the present invention.

The lead frame 1 shown in FIG. 1 has an outer lead 3 extending from a support frame 2 having a guide hole 6 toward the inside.
And an inner lead 4 connected to the semiconductor element by wire bonding or the like, formed continuously, and having an element disposing portion 5 at the center of the lead frame 1 in a direction in which the tip of the inner lead 4 is extended. It is.

In the method of manufacturing a multi-pin lead frame for a semiconductor according to the present invention, such a lead frame 1 is manufactured by etching.

The etching method used in the present invention is not particularly limited, but it is preferable to use photoetching in terms of easy formation of a fine pattern and high processing accuracy.

In the manufacturing method of the present invention, the above-mentioned thin metal plate is first washed, and a photoresist is applied to the surface thereof.

There is no particular limitation on the applicable photoresist, and a commercially available photoresist may be used.

 Either a negative type or a positive type may be used.

Specifically, FPER, FR-15 (Fuji Pharmaceutical Co., Ltd., KP
R, KTFR, KMER (manufactured by Kodak), AZ1350 (manufactured by Shipley), G-90, PMER (manufactured by Tokyo Ohka Kogyo Co., Ltd.) and the like are exemplified.

The method of applying the photoresist may be adjusted to an appropriate viscosity with various solvents as necessary, and may be applied by a known method such as spin coating, spray coating, roll coating, dip coating, among which spin coating and dip coating are preferred. Applied to

Next, in order to form a resist layer having a predetermined pattern, the applied photoresist is exposed and developed using a photomask to obtain a resist layer having a predetermined pattern.

In the manufacturing method of the present invention, since the inner leads formed by the etching process are formed to be longer than the final predetermined dimensions, as shown in FIG. (Extended toward the element disposition side) so as to be longer than the line A-A ', which is the final predetermined dimension. In forming the resist layer, as shown in FIG.
A resist opening 11 having a very small width is provided at the position of the line -A '.

Here, in the manufacturing method of the present invention, the inner lead 4 formed first by etching is formed to be longer than the final predetermined dimension, and the tip thereof is later formed to a predetermined length (A-A 'in FIG. 2a). Length).

Therefore, since it is not necessary to consider the influence of side etching at the tip, special correction of the tip shape by the resist pattern of the resist layer 8 as shown in FIG. Since only the side etch amount d in the width direction of the lead 4 needs to be considered, the resist layer 8 can be formed very easily.

In addition, removal of unnecessary portions of the photoresist during development
Depending on the type of photoresist used, it may be dissolved and removed using various organic solvents and the like.

Next, the exposed portion of the metal where the resist layer 8 is not formed is dissolved and removed with an etching solution to obtain a lead frame having a predetermined pattern, for example, the pattern shown in FIG.
In this etching process, the notch 12 is formed by half-etching the minute-width resist opening 11 provided at a position of a predetermined dimension of the inner lead 4.

In the manufacturing method of the present invention, the resist layer 8 is adjusted as described above, and the inner lead 4 obtained by the etching process is, as shown in FIG. The part 7 is formed longer than its final predetermined dimension.

Therefore, the formed inner lead 4 has a needle-like shape at the tip end portion 7 under the influence of the side etch.
The position of the line A-A ', which is the final predetermined dimension, is affected only by the side etch amount d in the width direction.

In addition, it is preferable that the length of such a tip 7 is 500 μm or more in the direction of the element disposing portion 5, and at this time, the tip of the inner lead 4 can be accurately formed by cutting the tip 7 later. A lead frame having various shapes and dimensions can be obtained. Further, it is preferable that the above-mentioned resist layer 8 is also formed according to this.

The etchant used in the etching treatment in the present invention may be appropriately determined according to the composition of the metal sheet to be used. For example, when 42 alloy is used as the metal sheet, a corrosive solution containing ferric chloride as a main component is used. In the case of copper or a copper alloy, a corrosive solution containing ferric chloride or 1, or cupric chloride as a main component is used.

In such an etching process, various etching conditions such as a temperature, a pressure, an etching rate, and an efficiency of removing an etchant may be appropriately determined so as to increase the etching accuracy.

After completion of the etching process, the resist layer 8 is peeled off and the tip 7 of the inner lead 4 formed longer than a predetermined length is half-etched and cut at the position of the line AA 'provided with the notch 12. The inner lead 4 is set to a predetermined length.

Here, as described above, the distal end portion 7 of the inner lead 4 has a needle-like shape under the influence of the side etch, but a portion having a final predetermined size indicated by the line AA ′ is: Only the side etch amount d in the width direction is affected.

Therefore, the inner lead 4 is formed to be longer than the final predetermined dimension in advance by etching, and the tip 7 is cut at a predetermined length (line AA '), so that the inner lead 4 is As shown in FIG. 2b, the tip has a favorable shape having an accurate size and shape, and when the semiconductor element is mounted, it is possible to make good and accurate electrical connection such as wire bonding.

There is no particular limitation on the method for cutting the tip 7, and various methods such as press cutting, cutting with a cutter, electric discharge machining, and laser machining can be applied. However, it is preferable to use press cutting in terms of productivity and the like.

In the manufacturing method of the present invention, when the resist layer 8 is formed, as shown in FIG.
A resist opening 11 having a very small width is provided at the position of the line AA 'on one of the surfaces, and a notch 12 is provided by half-etching the opening at the time of the etching process. Can be reduced in breaking load. Therefore, deformation of the lead frame 1 due to stress at the time of cutting can be prevented, and a better lead frame 1 can be manufactured.

<Example> Hereinafter, the present invention will be described in more detail with reference to specific examples of a method for manufacturing a multi-pin lead frame for a semiconductor according to the present invention.

(Example) A lead frame 1 (pins are omitted) as shown in FIG. 1 was manufactured by the following method.

A 0.15mm thick 42 alloy thin plate was coated with a photoresist (G
-90, manufactured by Tokyo Ohka Kogyo Co., Ltd.) by spin coating and drying.

Next, the photoresist was exposed through a photomask, and excess photoresist was dissolved and removed (developed) using warm water to form a resist pattern 8 having a predetermined pattern. Here, the resist layer 8 at the tip of the inner lead is used.
Was about 800 μm longer than the final predetermined dimension of the inner lead indicated by the line AA ′ in FIG.

Thereafter, an etching treatment is performed using a ferric chloride solution as an etchant to dissolve and remove unnecessary 42 alloy, thereby obtaining a 160-pin lead frame 1 having outer leads 3 and inner leads 4 connected to the support frame 2. Was.
Here, the tip shape of the inner lead 4 was as shown in FIG. 2a.

After completion of the etching process, the resist layer 8 is peeled off and removed.
Then, the tip 7 was cut and removed by pressing along the line AA 'provided with a notch by half etching in advance in FIG. 2a.

In the lead frame 1 thus obtained, the tip shape of the inner lead 4 is an accurate rectangular shape as shown in FIG. 2b, and both the width and the length of the inner lead 4 have predetermined dimensions. It was good.

<Effects of the Invention> According to the method for manufacturing a multi-pin code frame for a semiconductor of the present invention, it is not necessary to perform complicated and difficult correction by the shape of a photoresist layer to be formed (shape of a photomask), and it is necessary to perform 100 pin class or more. Even with this multi-pin type, a lead frame having an inner lead portion having accurate dimensions and shape can be easily manufactured.

In addition, the lead frame obtained by the manufacturing method of the present invention has an accurate size and shape of the inner lead and a shape suitable for bonding is obtained, so that the connection between the lead frame and the semiconductor element is ensured. And a highly reliable semiconductor element can be obtained.

Furthermore, even if the etching solution is deteriorated due to metal dissolution, it can be dealt with without adversely affecting the tip shape of the inner lead simply by changing the etching time according to the decrease in the etching rate. The frame can be manufactured stably.

[Brief description of the drawings]

FIG. 1 is a plan view of an example of a lead frame manufactured by the method for manufacturing a multi-pin lead frame for semiconductor according to the present invention. FIG. 2a is a partially enlarged plan view showing one embodiment of the method for manufacturing a multi-pin lead frame for semiconductor of the present invention. FIG. 2b is a partially enlarged plan view showing a tip portion of an inner lead of a lead frame manufactured by the method of manufacturing a multi-pin lead frame for semiconductor of the present invention. FIG. 3 is a partially enlarged cross-sectional view showing a state before the lead frame tip portion of the lead frame manufactured by the method of manufacturing a multi-pin lead frame for semiconductor according to the present invention is cut to a predetermined size. 4a and 4b are partially enlarged plan views showing a conventional method for manufacturing a lead frame for a semiconductor. DESCRIPTION OF SYMBOLS 1 ... lead frame, 2 ... support frame, 3 ... outer lead, 4 ... inner lead, 5 ... element disposition part, 6 ... guide hole, 7,15 ... tip part, 8 , 10 ... resist layer, 9 ... metal sheet, 11 ... resist opening, 12 ... notch 16 ... projection

Claims (1)

(57) [Claims] When manufacturing a lead frame for a semiconductor having inner leads connected to a semiconductor element by etching a thin metal plate into a predetermined pattern, the dimensions of the inner leads obtained by the etching process are finally adjusted. At the same time as being formed longer than a predetermined dimension, a half-etched notch is formed at the final predetermined dimension position of the inner lead by the etching process, and the tip of the inner lead is cut from the notch portion after the etching process. A method for manufacturing a multi-pin lead frame for a semiconductor, comprising processing to a predetermined length.