KR100983303B1 - Lead Frame and Manufacturing Method Thereof - Google Patents

Abstract

According to the present invention, an inner portion extending radially outward from the center and half-etched such that at least a portion thereof has a thickness thinner than that of other portions, and wherein the surface area of the half-etched portion is larger than the surface area of the non-half-etched portion Lead; Provided is a lead frame having an outer lead extending from an end of the inner lead.

Description

Lead Frame and Manufacturing Method Thereof

1 is a schematic plan view showing the structure of a conventional lead frame.

2 is an enlarged plan view of a portion of the lead frame illustrated in FIG. 1.

3 schematically illustrates a method of manufacturing a lead frame as shown in FIGS. 1 and 2 by a chemical etching method.

4 shows a cross section of a lead frame made in the manner shown in FIG. 3.

Shown in FIG. 5 is a schematic plan view of a portion of a lead frame according to the invention.

6 to 8 are cross-sectional views taken along the Z-Z line of a portion indicated by circle A in FIG.

9 to 11 show cross sections of the inner lead shown in FIGS. 6 to 8, respectively.

Shown in FIG. 12 is a schematic flow chart illustrating a method of manufacturing a lead frame as described above.                 

Description of the Related Art

11.Lead frame unit 12.Pad

13. Tie bar 15. Inner lead

16.Outer lead 18.Rail

FIELD OF THE INVENTION The present invention relates to a lead frame and a method of manufacturing the same, and more particularly, to reduce the thickness of a portion of the inner lead tip to optimize pitch, width, and space in the manufacture of the lead frame inner lead. A lead frame and a method of manufacturing the same.

The semiconductor lead frame is one of the core components of the semiconductor package together with the semiconductor chip, and serves as a lead connecting the inside and the outside of the semiconductor package and a support for the semiconductor chip. Plays a role. Such a semiconductor lead frame is typically manufactured by a stamping method or an etching method. Among the semiconductor lead frame manufacturing methods, an etching method is a chemical etching method of forming a product by corroding a local part of a material using chemicals, which is mainly applied when a small amount of lead frames having a fine pitch is produced. to be.

1 is a plan view of a typical lead frame.                         

Referring to the drawings, the lead frame unit 11 includes a pad 12, an inner lead 15, and an outer lead 16. In the pad 12, a semiconductor chip (not shown) is supported thereon at the time of assembling the semiconductor package. The plurality of inner leads 15 are formed with ends adjacent to the pads 12 interconnected. Reference numeral 15a denotes a portion where the ends of the inner lead 15 are interconnected. The tie bar 13 has a function of supporting the die pad 12 against the rail 18. When the assembly of the semiconductor package is completed, the rail 18 together with the connection part 15a is removed. In addition, a dam bar 17 is formed between the inner lead 15 and the outer lead 16 so as to maintain the rigidity of the lead frame 10. The dam bar 17 is also removed when the semiconductor package is assembled.

2 is an enlarged plan view of a portion of the lead frame illustrated in FIG. 1. FIG. 2 is an enlarged view of a portion indicated by reference numeral 20 of FIG. 1 and is an enlarged plan view of a portion of an inner lead.

Referring to the figure, the distance between the centers of the widths of the respective inner leads is indicated by ILP, which represents an inner lead pitch. This inner lead pitch is related to the intensity of the lead, and as the pitch decreases, the inner lead pitch may be used to manufacture a semiconductor package having a high intensity. In addition, the width of each inner lead is denoted by ILW, which represents the inner lead width. The width ILW of the inner lead is related to the area to which the bonding wire is bonded in the wire bonding operation, and the larger the inner lead width may be adapted to the wire bonding operation. The inner lead space, on the other hand, is denoted by ILS, which is related to the width of the space where the package can be molded while minimizing the noise that can be generated between the leads in the finished semiconductor package. Such ILP, ILW, and ILS become management items at the time of manufacture of a semiconductor lead frame.

3 schematically illustrates a method of manufacturing a lead frame as shown in FIGS. 1 and 2 by a chemical etching method.

Referring to the drawings, photoresist 31 is formed in a predetermined pattern on both surfaces of the material 32. The pattern of the photoresist 31 is formed through the application, exposure and development of the photoresist as is known. When etching liquid is sprayed through the nozzles 33 from both surfaces of the material 32 on which the pattern of the photoresist 31 is formed, a part of the material 32 to which the surface is exposed is removed from the surface as indicated by reference numeral 32 '. Etched, and consequently, the thickness of the material 32 becomes thin, and ultimately the thickness of the material 32 may be completely removed.

4 shows a cross section of a lead frame made in the manner shown in FIG. 3.

Referring to the drawings, an empty space 42 from which material is removed by etching is formed between the inner leads 41. A bevel 43 is formed on the side of the inner lead 41. This bevel 43 is a phenomenon that occurs because the etching solution is injected to the upper and lower surfaces of the material in the bidirectional etching method as shown in FIG. As shown in FIG. 4, the bevel 43 forms a vertex by gently protruding the side surface of the inner lead 41 without being etched into a plane.                         

In FIG. 4 the spacing between the leads at the upper and lower surfaces of the inner lead 41 is indicated by S ′. However, the narrowest gap of the inner lead 41 is indicated by S, which is the gap between the bevels 43. The height of the bevel 43 is S'-S = B, which is the difference between the gaps.

The bevel 43 as described above serves as a major factor that makes it difficult to achieve the goal of the management item in manufacturing the lead frame described above. That is, as the lead frame approaches the inner lead from the outside, the pitch (ILP) between the leads tends to decrease, and the bevel 43 formed at the time of etching makes it difficult to design the ILP small. Similarly, there is a problem that it is difficult to achieve the management goal because of the formation of the bevel 43 for the other management items ILW and ILS.

The present invention has been made to solve the above problems, an object of the present invention is to provide an improved lead frame and a method of manufacturing the same.

Another object of the present invention is to provide a lead frame in which no bevel is formed in the inner lead, and a manufacturing method thereof.

Another object of the present invention is to provide a lead frame in which a part of the surface of the inner lead is formed by half etching, and a manufacturing method thereof.

In order to achieve the above object, according to the present invention, it is radially extended from the center to the outside, and is half etched so that the thickness of at least a portion thereof is thinner than the thickness of the other portion and the surface area of the half etched portion is not half etched. An inner lead formed larger than the surface area of the unshaped portion;

Provided is a lead frame having an outer lead extending from an end of the inner lead.

According to one feature of the invention, the portion of the inner lead formed by the half etching is an end of the inner lead close to the center.

According to another feature of the invention, the half etching is performed at the upper surface of the inner lead.

According to another feature of the invention, the half etching is performed at the lower surface of the inner lead.

According to another feature of the invention, the half etching is performed simultaneously on the upper and lower surfaces of the inner lead.

In addition, according to the present invention, the step of applying the photoresist on the lead frame material; Forming a photoresist pattern having a predetermined shape by exposing and developing the photoresist, and forming a photoresist pattern having a fine hole for half etching in a portion corresponding to an inner lead; Etching the lead frame material having the photoresist pattern formed thereon; And peeling the photoresist pattern. A method of manufacturing a lead frame is provided.

Hereinafter, the present invention will be described in more detail with reference to an embodiment shown in the accompanying drawings.                     

5 is a schematic plan view of a part of the lead frame according to the present invention, which can be understood as showing a part of the conventional lead frame shown in FIG.

Referring to the drawings, the lead frame unit 51 includes a die pad 52 on which a semiconductor chip is mounted, a tie bar 53 supporting the die pad 52, and the die pad 52. And a plurality of inner leads 55 extending radially. The lead frame unit 51 may be manufactured by a conventional chemical etching method, for example, by applying a photoresist on a material of the lead frame, exposing and developing the photoresist under a mask of a predetermined pattern and developing the photoresist. By forming a pattern and spraying etching liquid again, it etches so that it may have a shape of a lead frame. Finally, the pattern of the photoresist is removed.

According to a feature of the invention, at least a part of the material corresponding to the portion where the inner lead 55 of the lead frame is to be formed is formed by half etching. That is, when forming the inner lead, the thickness between at least a portion of the inner lead is formed thin by half etching, and at the same time, the etching material is sprayed from the upper and lower surfaces of the material as shown in FIG. Is removed by etching. As such, when the lead is formed after the thickness reduction by the half etching, the bevel may be eliminated from the side of the inner lead portion having the reduced thickness.

As is known, half etching can be accomplished by controlling the shape of the photoresist pattern. For example, when the photoresist pattern is formed on the lead frame material, the portion not exposed by the photoresist pattern is not removed at the time of etching, while the portion exposed to the etchant because the photoresist pattern is not formed is removed. Meanwhile, the surface of the material is coated with a photoresist pattern on a part requiring half etching, and a portion of the material is exposed to the etchant by forming a fine hole in the photoresist pattern of the corresponding portion. The etching liquid introduced into the fine holes formed in the photoresist pattern may not remove the entire thickness of the material, but may remove some thickness of the material, and thus half etching may be performed.

Half etching may be performed on the upper surface of the corresponding portion of the inner lead, or may be performed on the lower surface, and in other examples, may be performed simultaneously on the upper and lower surfaces of the portion.

In the figure, since the inner leads 55 are closer to the die pad 52, the spacing to each other becomes smaller, so that the achievement of management items such as ILW, ILP, and ILS as mentioned above is achieved in the die pad 52. This is particularly difficult in close proximity to the device. In addition, since the portion to which the bonding wire is bonded is a portion close to the die pad 52 in the inner lead 55, it is preferable that the half etching according to the feature of the present invention is performed at the portion close to the die pad 52.

On the other hand, in another example lead frame not shown in the figure, a shape without the die pad 52 may be provided. Such a lead frame is known in the art as a lead on chip (LOC) type lead frame, and the semiconductor chip is supported by a portion of the inner lead. It should be understood that half etching may be performed on a portion of the inner lead for the lead frame without the die pad 52, thereby facilitating the achievement of the management items as mentioned above.

In practice, in the prior art, the protrusion height of the bevel on the side of the inner lead reached 10% of the thickness of the lead frame material. However, when the inner lead is formed through half etching according to the present invention, the bevel protrusion height is only 0 to 5% of the material thickness. This lower bevel height can also increase ILW, one of the control items, which can increase the thickness of the lead frame material by up to 20%.

6 to 8 are cross-sectional views taken along the Z-Z line of a portion indicated by circle A in FIG. 9 to 11 show cross sections of the inner lead shown in FIGS. 6 to 8, respectively.

Referring to FIG. 6, the end of the inner lead 61 proximate to the die pad 52 shown in FIG. 5 is formed thin by half etching to the lower surface. As a result of the half etching, the lower portion indicated by reference numeral 63 has been removed, and the end portion of the inner lead 61 has a thickness thinner than other portions as indicated by reference numeral 62.

Referring to FIG. 9, this shows a cross-sectional view of the end of the inner lead shown in FIG. 6. As can be seen in FIG. 9, when the inner lead is completed by removing part of the thickness 63 from the lower surface of the inner lead by half etching and performing upper and lower etching, no bevel occurs on the side of the inner lead 62. Do not. Therefore, the width of the inner lead 62 becomes W '= W + 2B by adding B which is the width | variety corresponding to the height of a bevel to W which is the width when half etching is not performed.

The reason why the width of the inner lead is increased in comparison with the past is because the bevel that can occur on the side of the inner lead can be suppressed in the manufacturing process through half etching. Increasing the width of the inner lead means increasing the surface area at which the wire bonding takes place in the inner lead. That is, when the inner lead is formed through half etching, the surface area for wire bonding is increased as compared with the inner lead without half etching.

Referring to FIG. 7, the end of the inner lead 71 proximate to the die pad 52 shown in FIG. 5 is formed by half etching to the top surface. As a result of the half etching, the portion indicated by reference numeral 73 has been removed, and the end portion of the inner lead 71 has a thickness thinner than other portions as indicated by reference numeral 72.

Referring to FIG. 10, this shows a cross section of the end of the inner lead shown in FIG. 7. As can be seen in FIG. 10, when the inner lead is completed by removing the thickness 73 from the upper surface of the inner lead by half etching and performing upper and lower etching, no bevel occurs on the side of the inner lead 72. Do not. Therefore, the width of the inner lead 72 becomes W '= W + 2B by adding B on both sides corresponding to the height of the bevel to W which is the width when half etching is not performed.

Referring to FIG. 8, the end of the inner lead 71 proximate to the die pad 52 shown in FIG. 5 is formed by half etching on the upper and lower surfaces. As a result of the half etching, the portion indicated by reference numeral 83 has been removed from the upper and lower surfaces of the raw material, and the end of the inner lead 81 has a thickness thinner than other portions as indicated by reference numeral 82.

Referring to FIG. 11, this shows a cross-sectional view of the end of the inner lead shown in FIG. 8. As can be seen in FIG. 11, when the upper and lower surfaces of the inner lead are partially removed from the upper and lower surfaces by half etching, and the upper and lower double-sided etching is performed to complete the inner lead, the side surface of the inner lead 82 is formed. Bevel does not occur in Therefore, the width of the inner lead 82 becomes W '= W + 2B by adding B which is the width | variety corresponding to the height of a bevel to W which is the width | variety when half etching is not performed.

Shown in FIG. 12 is a schematic flow chart illustrating a method of manufacturing a lead frame as described above.

Referring to the drawings, first, a photoresist is applied to the surface of the lead frame material (step 121). Next, the photoresist pattern is formed on the surface of the material by performing exposure under a mask and developing the photoresist (step 122). The photoresist pattern formed in the exposure and development of the photoresist pattern forming step (step 122) substantially corresponds to the planar shape of the lead frame. Here, as described above, at least a portion of the inner lead forms a fine hole in the photoresist pattern of the portion so that half etching can be performed.

Next, half etching and double sided etching are performed simultaneously (step 124). When the etching solution is sprayed onto the surface of the material on which the photoresist pattern is formed, the etching solution penetrates through the minute hole formed in the photoresist pattern in the corresponding portion of the inner lead requiring half etching to remove only a part of the thickness of the material. On the other hand, in the part where the surface of the material is exposed because no photoresist pattern is formed, the entire thickness of the material is removed, and thus a lead frame having a predetermined shape can be manufactured. After the etching is completed, a peeling step (step 124) is performed to remove the photoresist pattern.

In the lead frame according to the present invention and a method of manufacturing the same, an inner lead is formed after the thickness of at least a portion of the inner lead is reduced by half etching, so that no bevel is formed on the side of the inner lead. Therefore, there is an advantage that the management item of the inner lead can be easily achieved, and the quality of the lead frame can be improved.                     

Although the present invention has been described with reference to the accompanying embodiments, these are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true scope of the invention should be defined only by the appended claims.

Claims (7)

An inner lead extending radially outward from the center and half etched such that at least a portion thereof has a thickness thinner than that of the other portion, wherein the surface area of the half etched portion is greater than the surface area of the non-half etched portion; And an outer lead extending from an end of the inner lead. The method of claim 1, A portion of the inner lead formed by the half etching is an end of the inner lead close to the center. The method of claim 1, Wherein said half etching is performed at the upper surface of the inner lead. The method of claim 1, Wherein said half etching is performed at the lower surface of the inner lead. The method of claim 1, And the half etching is performed simultaneously on the upper and lower surfaces of the inner lead. Front coating the photoresist on the lead frame material; Forming a photoresist pattern having a predetermined shape by exposing and developing the photoresist, and forming a photoresist pattern having a fine hole for half etching in a portion corresponding to an inner lead; Etching the lead frame material having the photoresist pattern formed thereon; And, Peeling the photoresist pattern. The method of claim 6, The said half etching is a manufacturing method of the lead frame characterized by the inner lead extended radially from a center in the edge part which is close to the said center.

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