JPH05198716A - Manufacture of lead frame - Google Patents

Abstract

PURPOSE:To reinforce an inner lead by insulating a semiconductor chip from leads through applying an insulating material to the position, which overlaps the semicondutor chip when bonded, of the surface at least on the semiconductor chip side on the inner lead. CONSTITUTION:In a state where the part to form a bump of an intermediate metal layer 2 is masked by a resist film 7, the intermediate metal layer 2 is etched while the resist film 7, inner lead 4 and outer lead 1 are used as masks so that unnecessary parts of the intermediate metal layer 2 are removed. An insulating material (e.g. polyimide paste) 5 is formed by a screen printing method from the side of a lead frame opposite to the side of a semiconductor device. In this case, the insulating material 5 is formed in the manner of overlapping the semiconductor device 8 when the semiconductor device is connected with the lead frame. The insulating material 5 prevents the short circuit of the semiconductor device 8 and lead frame. The insulating material 5 is preferably printed so as to go onto the part between respective adjacent inner leads 4. Thus, it is possible to also obtain a short circuit prevention effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a lead frame, and more particularly, to forming an inner lead made of a thin metal layer on one surface of an intermediate metal layer and an outer lead made of a thick metal layer on the other surface, The present invention relates to a method for manufacturing a lead frame, which removes unnecessary portions of the intermediate metal layer by etching the intermediate metal layer using the outer leads and the inner leads as masks.

[0002]

2. Description of the Related Art As a method of manufacturing a lead frame, metal layers having different thicknesses are formed on both sides of an intermediate metal layer which will be an etching stop layer, and the metal layers on both sides are selectively etched to increase the thickness. JP-A-3-148856 discloses a method of forming outer leads and thin inner leads, and then etching the intermediate metal layer using the outer leads and the inner leads as masks to remove unnecessary portions of the intermediate metal layers. Has been introduced by.

Further, the above publication introduces the formation of a reinforcing material made of, for example, resin in the inner lead portion. The reinforcing material is generally formed by pressing a polyimide film having a thickness of 50 μm with an adhesive (thickness of 10 μm) on the back surface thereof into a rectangular frame shape by press cutting, and then forming the reinforcing material on the lead frame. It was performed by a method of bonding to the inner lead portion by a hot press bonding method.

[0004]

By the way, there is a demand for thinner resin-encapsulated semiconductor devices, and in order to meet the demand, the gap between the semiconductor chip and the inner leads of the lead frame or the inner leads and outer leads is required. Needs to be small. However, in order to respond to this, there is a possibility that an electrical short circuit occurs between the semiconductor chip and the inner lead of the lead frame or the inner lead and the outer lead.

The present invention has been made to solve the above problems, and one object thereof is to provide a novel method for manufacturing a lead frame in which an electrical short circuit with a semiconductor chip does not occur. Another purpose is to reduce the incidence of short-circuit accidents between inner leads.

[0006]

According to a first aspect of the present invention, there is provided a method for manufacturing a lead frame, wherein an insulating material is applied to at least a surface of the inner lead on the side of the semiconductor chip and at a position overlapping with the semiconductor chip when bonded. It is characterized by having a process. A lead frame manufacturing method according to a second aspect of the present invention is characterized in that, in the lead frame manufacturing method of the first aspect, an insulating material is formed so as to enter between adjacent inner leads.

[0007]

According to the lead frame manufacturing method of the present invention, since the insulating material is formed in the portion of the semiconductor chip that overlaps the semiconductor chip, the insulating material insulates the semiconductor chip from the lead. be able to.
The insulating material can also be used to reinforce the inner leads. According to the manufacturing method of the lead frame of claim 2, since the insulating material is formed so as to enter between the adjacent inner leads, it is possible to prevent a short circuit between the inner leads.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a lead frame of the present invention will be described in detail below with reference to the illustrated embodiments. 1A to 1H are cross-sectional views showing an embodiment of a method for manufacturing a lead frame of the present invention in the order of steps. (A) As shown in FIG. 1A, a lead frame material is prepared in which a metal layer 1 made of copper and an intermediate metal layer 2 made of aluminum are laminated.

(B) As shown in FIG. 1B, a resist film 3 is selectively formed on the surface of the intermediate metal layer 2 and entirely on the surface of the metal layer 1. The resist film 3 on the surface of the intermediate metal layer 2 is formed into an inner lead pattern and a negative pattern to be formed. (C) Next, copper is plated on the surface of the intermediate metal layer 2 by electrolytic plating in a Cu sulfate plating bath to form inner leads 4 made of copper as shown in FIG. 1 (C).

(D) Next, as shown in FIG. 1D, an insulating material (eg, polyimide paste) is formed on the inner leads 4.
5 is formed by a screen printing method as shown in FIG. Needless to say, the insulating material 5 may be formed by a photographic technique using a photosensitive insulating material. As described above, when the insulating material 5 is formed by the screen printing method or the photographic technique, its pattern and formation position can be accurately controlled. (E) Next, a resist film 6 is selectively formed on the inner lead side surface of the lead frame and on the outer lead side surface, and the resist film 6 is formed as shown in FIG.
The outer lead 1 is formed by etching the metal layer 1 using the as a mask.

(F) Next, as shown in FIG. 1 (F), the resist film 7, the inner leads 4, and the outer leads are masked with the resist film 7 at the portions where the bumps of the intermediate metal layer 2 are to be formed. The unnecessary portion of the intermediate metal layer 2 is removed by etching the intermediate metal layer 2 using 1 as a mask. (G) Thereafter, as shown in FIG. 1 (G), an insulating material (for example, polyimide paste) 5 is applied from the side opposite to the semiconductor element of the lead frame by a screen printing method as shown in FIG. Of course, an insulating material made of a photosensitive material may be selectively formed by a photographic technique.

In this case, the insulating material 5 needs to be formed so as to overlap the semiconductor element when the semiconductor element is connected to the lead frame. This is because the insulating material 5 has a role of preventing a short circuit between the semiconductor element and the lead frame. Further, it is better to print the insulating material 5 so as to enter between the adjacent inner leads. This is because the insulating material 5 has an effect of preventing a short circuit between the semiconductor element and the lead frame, an effect of reinforcing the inner lead, and an effect of preventing a short circuit between the adjacent inner leads. Needless to say, if the insulating material 5 is formed by a screen printing method or a photographic technique, its pattern and formation position can be accurately controlled. 2a
Is a bump.

(H) After that, the bumps 2a of each inner lead 4 of the lead frame and the corresponding electrodes of the semiconductor element 8 are connected, and thereafter, the bumps 2a are sealed with a resin 9. Figure 3
FIG. 3 is a perspective view showing a part of the semiconductor device with a resin portion cut away.

According to the method of manufacturing the lead frame of the present invention, since the insulating material 5 is interposed between the semiconductor element 9 and the lead frame, a short circuit between the semiconductor element 9 and the lead frame can be prevented. Further, the lead frame can be arranged closer to the semiconductor element 9. Therefore, it is possible to reduce the thickness of the semiconductor device.

The insulating material 5 also has the effect of reinforcing the inner lead, which is required to be thin due to the increase in the number of pins and the mechanical strength tends to be weakened. Further, the insulating material is inserted between the leads. By forming such a structure, it is possible to prevent a short circuit between adjacent inner leads and a positional deviation.

4A to 4C show a modification of the method for manufacturing the lead frame shown in FIG. In this modification, as shown in FIG. 4 (A), a lead frame material having a three-layer structure in which metal layers 1 and 4 made of copper having different thicknesses are laminated on both surfaces of an intermediate metal layer 2 made of aluminum is prepared. Then, as shown in FIG. 4 (B), the surface of the thick metal layer 1 serving as the outer lead is entirely masked, and the surface of the thin metal layer 4 serving as the inner lead is selectively masked with the resist film 6, respectively. The embodiment is different from the embodiment shown in FIG. 1 in that the inner lead 1 is formed by etching in that state, and then the insulating material 5 on the inner lead 4 is formed.

After that, the lead frame manufacturing method and resin sealing are performed by the steps shown in FIGS. As described above, the embodiment shown in FIG. 1 has variations as shown in FIG. There is no particular difference in the method of forming the insulating material 5 and the effect obtained by forming the insulating material 5.

FIGS. 5A to 5D are cross-sectional views showing another embodiment of the method for manufacturing a lead frame of the present invention in the order of steps. (A) As shown in FIG. 5 (A), a lead frame material having a three-layer structure in which metal layers 1 and 4 made of copper having different thicknesses are laminated on both surfaces of an intermediate metal layer 2 made of aluminum is prepared, and a resist is prepared. Outer leads are formed by etching using the film 6 as a mask.

(B) Next, the insulating layer 5 is formed on the surface of the intermediate metal layer 1 on the semiconductor element side. The insulating layer 5 needs to be formed at a position overlapping the semiconductor element when the semiconductor element and the lead frame are connected. This is because, as described above, the insulating material 5 plays a role of preventing an electrical short circuit between the semiconductor element and the lead frame.

(C) Next, as shown in FIG. 5C, the inner layer is formed by etching the metal layer 4 using the resist film 6 as a mask. (D) After that, as shown in FIG. 5D, the intermediate metal layer 2 is etched by using the inner leads 4 and the outer leads as a mask to remove unnecessary portions of the intermediate metal layer 2. In this case, when the bump 2a is formed by the intermediate metal layer, it is necessary to mask that portion with a resist film.

In the present embodiment, since the insulating material 5 is not inserted between the adjacent inner leads, it is not possible to prevent the effect of preventing a short circuit due to foreign matter or the like that has entered between the inner leads. The effect of preventing a short circuit between the element and the inner lead can be exerted. The present invention can be implemented in such an aspect.

The method of manufacturing the lead frame of the present invention is L
It can also be applied to a lead frame for an OC (Lead On Chip) type semiconductor device. FIG. 6 shows an example of its application. To apply to the LOC type semiconductor device, FIG.
As shown in FIG. 3, the insulating layer 5 needs to be formed widely from the inner lead portion to the outer lead portion of the lead frame 10. However, the insulating layer 5 can electrically insulate the lead frame and the semiconductor element. Since it is possible, it is possible to bring them close to each other, and therefore LO
It is possible to reduce the thickness of the C-type semiconductor device.

[0023]

According to the method of manufacturing a lead frame of claim 1, the inner lead made of a thin metal layer is formed on one surface of the intermediate metal layer, and the outer lead made of a thick metal layer is formed on the other surface of the intermediate metal layer. In a method of manufacturing a lead frame for removing an unnecessary portion of a metal layer, a step of applying an insulating material to at least a surface of the inner lead which is a surface of the semiconductor chip and overlaps with the semiconductor chip when bonded, It is characterized by having at least. Therefore, according to the lead frame manufacturing method of the first aspect, the insulating material is formed in the portion of the lead frame that overlaps the semiconductor chip on the semiconductor chip side, so that the insulating material insulates between the semiconductor chip and the lead. can do. The insulating material can also be used to reinforce the inner leads.

A method for manufacturing a lead frame according to claim 2 is
The method of manufacturing a lead frame according to claim 1, wherein the insulating material is formed so as to enter between the adjacent inner leads. Therefore, according to the lead frame manufacturing method of the second aspect, since the insulating material is formed so as to enter between the adjacent inner leads, it is possible to prevent a short circuit between the adjacent inner leads.

[Brief description of drawings]

1A to 1H are cross-sectional views showing, in the order of steps, one embodiment of a method for manufacturing a lead frame according to the present invention.

FIG. 2 is a perspective view showing an example of a method of forming an insulating material.

FIG. 3 is a perspective view showing a semiconductor device with a resin cut out.

4A to 4C are cross-sectional views showing a modification of the method for manufacturing the lead frame shown in FIG. 1 in the order of steps.

5A to 5D are sectional views showing another embodiment of the method for manufacturing a lead frame of the present invention in the order of steps.

FIG. 6 is a diagram showing a state before resin-sealing of the LOC semiconductor device according to the application of the present invention.

[Explanation of symbols]

 1 thick metal layer (outer lead) 2 intermediate metal layer 4 thin metal layer (inner lead) 5 insulating material 8 semiconductor chip

Claims (2)

[Claims] 1. A lead frame in which an inner lead made of a thin metal layer is formed on one surface of an intermediate metal layer and an outer lead made of a thick metal layer is formed on the other surface, and thereafter unnecessary portions of the intermediate metal layer are removed. The method for manufacturing a lead frame, which comprises at least a step of applying an insulating material to at least a surface of the inner lead on the side of the semiconductor chip, which overlaps the semiconductor chip when bonded. Method 2. The method of manufacturing a lead frame according to claim 1, wherein an insulating material is formed so as to be inserted between adjacent inner leads.