JPH09134987A - Cutting of distal end of inner lead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain generation of an angular burr by providing a vertical angle of a predetermined length on the side of an inner die pad which is to be punched off, then providing a crush portion in the direction of thickness in a crush die having a predetermined angle with respect to the horizontal, and punching off the crush portion in the die from the opposite side to an inner lead. SOLUTION: A crush portion having a depth of approximately 0.03mm by lead depth is formed by a lower die 102 which has a vertical angle of about 0.05mm provided on the side of a die pad from a distal end cut position 110 of an inner lead 1, and which makes an approximately light acute angle of 1-10 degrees with respect to the horizontal, with the side on the die pad being made vertical and the side on the inner lead being tapered. An upper die 101 is formed flatly. By thus providing a crush portion on the side of the die to make a tapered shape from a slightly outer removal position where the lead is to be cut, in a process prior to a lead cutting process, the distal end of the lead is elastically deformed in cutting and flatly abutted against the die so as to be cut. After the cutting, the distal end of the lead returns to the initial position by elastic deformation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting the tips of inner leads of a lead frame using a progressive die by a press.

[0002]

2. Description of the Related Art In recent years, semiconductor packages have become lighter, thinner, shorter and smaller, and development of higher densities has been intensely developed, and lead frames are required to have a large number of pins and a narrow pitch. When the lead frame is punched out, the lead frame material is stamped out in order according to the lead pattern. Since the lead frame has an extremely fine pattern, when the lead frame material is actually punched out, twisting, deformation, or
Design and manufacturing are performed in consideration of burrs and the like to finally obtain a lead frame having a predetermined lead pattern.

In the conventional lead frame, the lead frame is formed through various processes and, depending on the product, through various patterns. In the case of an IC having a large number of pins, especially in the case of QFP, usually, the inner lead ends are pulled out while being connected and subjected to coining. Then, after undergoing a predetermined process such as an annealing process, a plating process, and a process of attaching a tape at a predetermined position substantially in the center of the inner lead tip, cutting is performed by a press to finally form the inner lead tip. In the case of a product that cannot be processed in such a process, it is necessary to perform coining after cutting the lead tips.

FIG. 6 shows a state in which the inner lead tips are pulled out by a conventional method in the case of a product which requires coining after cutting the lead tips. FIG. 6 is an enlarged view of the lead frame when the tip of the inner lead is cut from the same side as the punch surface when the inner lead is cut in the press cutting process. Similar to FIG. 6, FIG. 7 shows the surface opposite to the punch surface when the lead tip is cut and the coining process is performed by the conventional method, and the inner lead is cut in the press cutting process. FIG. 4 is an enlarged view of the lead frame when the tips of the inner leads are cut off.

[0005]

As described above, the lead frame pattern is formed by punching the lead frame with the punch and die by press punching. Therefore, as shown in FIGS. 6 and 7, when the cross section after cutting is viewed, a slight sagging 14 occurs at the entrance where the punch enters the lead frame, and then about 1/3 to 1/1 of the plate thickness.
The cut surface 10 is up to 2, and the remaining surface is the fracture surface 12. Furthermore, a square burr 1 with the lead frame pulled to the die side.
8 and 19 are generated on the die side. The size of this sag 14,
Length of cutting surface 12, length of fracture surface 10, square burr 18, 1
The size of 9 changes depending on the characteristics of the material, the clearance between the punch and the die, the wear condition, etc., but it does not occur in the case of the 42ALLOY type and copper type leadframes used in this leadframe, and never disappears. It does not happen. 6 and 7, (a) is a three-dimensional view,
(B) is a view seen from the end face of the inner lead, and (c).
Is a view seen from the side of the inner lead.

The inner lead of the lead frame has a tip pressure of about 0.1 mm for a plate pressure of 0.15 mm, for example.
Has been formed. Therefore, instead of pulling out both sides of the inner lead at the same time, the inner leads are pulled out in order from one side. Therefore, once pulling out one side of the inner lead causes the inner lead to twist, and pulling out the other side causes the phenomenon that the inner lead twists to the opposite side. It becomes a shape (also called a ridge) 20. In the case of FIG. 6, this boat bottom shape 2
When cutting the tip further so as to cross the inner lead 1 of 0, the bottom of the boat bottom is pressed against the die and slightly crushed, but the upper part of the slope of the boat bottom is not pressed against the die. Since it is cut while being pulled by, the corner burr 19 is generated by being torn off. This phenomenon is not limited to the case where the boat bottom shape 20 is on the die side, and even when the sagging side is on the die side as shown in FIG. 7, the angular burr 18 phenomenon similarly occurs on the sagging portion. .

The above-mentioned angular burr cannot be completely eliminated in the case of cutting with an ordinary punch and die, but if it is small, it does not cause much problem. However, in recent years, the inner lead pitch of about 0.2 mm may exceed the specified value of the space. When a lead frame that exceeds the specified value is plated, it may cause a trouble such as an electrical short circuit between the inner leads. Even if angular burrs appear in the plate thickness direction, if coining is performed to secure the wire bond area in the subsequent process, the angular burrs will fall as they are in the lateral direction, so the specified value There are cases where it will exceed.

The present invention provides a method for manufacturing a lead frame capable of suppressing the occurrence of the above-described angular burr as much as possible, preventing an electrical short circuit between the inner leads, and forming a good inner lead pitch. is there.

[0009]

[MEANS FOR SOLVING THE PROBLEMS] After forming a lead by press punching of a lead frame, the lead is formed so as to cut across the inner lead tip. In the preceding process of cutting the lead tip of a cutting die, the inner die pad side is withdrawn. The vertical angle is about 0.05mm and the horizontal angle is 1-10
The crushing die having an angle of degrees is used to insert the crushing member 30 in the plate thickness direction, and the crushing member 30 is punched out from the surface opposite to the inner lead having the crushing member 30.

Further, as another embodiment, after the lead frame is formed by press punching, the lead is formed by cutting and the inner lead is cut off so as to cross the inner tip of the inner die. The inside of the die pad side is about 0.05 mm as the apex angle, and a crushing punch having an angle of 1 to 10 degrees with respect to the horizontal is used to crush in the plate thickness direction. A method of cutting the tip of the inner lead, which is characterized by pulling it off.

[0011]

[Operation] When the lead frame material is pressed to a predetermined width of the inner lead and then the inner lead tip is cut, the lead is floated above the die, so that many burrs are generated. Make sure there is no gap between and. In the cutting method according to the present invention, before the inner lead cutting step, the lead tip is elastically deformed at the time of cutting by crushing on the die side so as to form a taper shape from the slightly outside removal position where the lead is cut, and the die is flattened. Will be cut. It utilizes that the tip of the lead returns to its original position by elastic deformation after cutting.

[0012]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 3 shows a side view of the crushing process after cutting the lead frame material on both sides of the inner lead 1 with a predetermined width and before cutting the inner lead 1 into a predetermined length. In this process, the apex angle is about 0.05 mm on the die pad side (left side in this figure) from the tip cutting position 110 of the inner lead 1, the die pad side is vertical, and the inner lead side is tapered surface. Lower die 1 with an acute angle of approximately 10 to 10 degrees
02, a crushed portion 30 having a lead depth of about 0.03 mm is formed. At this time, the upper mold 101 is formed flat.

Since the crushing 30 is weakly plastically deformed, its shape remains in the next process. FIG. 5A is a diagram on the verge of cutting the inner lead tip in the next step, and is a diagram at the moment when the punch 201 hits the inner lead 1. At this time, the crushing 30 comes to the die side. The surface of the crushing 30 has the apex angle portion inserted inside the punch 201, and the taper of the crushing 30 is on the inner lead side from the punch end, and there is crushing on the die side sandwiching the lead of the punch 201.
A slight triangular gap is formed between the upper surface of the die 202 and the inner lead.

FIG. 5B is a diagram in which the punch 201 is further lowered. Since the triangular gap containing the crushed inner lead 30 is pushed downward, the inner lead 1 is brought into contact with the crush side die 202. In this figure, the left side is the die pad side. At the boundary with the punch on the die pad side, sagging starts on the upper surface of the lead. FIG. 5C is a diagram when the punch is further lowered and the inner lead 1 is cut. The unnecessary portion is cut by the punch 201, and the tip of the inner lead is returned by the amount of the elastically deformed taper, so that a gap is formed between the inner lead and the die 202.

A perspective view after processing is shown in FIGS.
FIG. 1 shows a state in which the tip of the inner lead is cut from the same surface as the surface of the lead frame into which the punch is inserted, that is, the sag surface 14. 2 is the opposite of FIG. 1,
It shows a state in which the tip of the inner lead is cut from the surface opposite to the surface on which the punch having the processed width of the lead frame is inserted. In the case of FIG. 2, when processing the width of the inner lead, as shown in FIG. 4, it is preferable to crush the inner lead with a punch 103 having a protrusion on the punch side. In this case, the die surface 104 may be flat. After performing a predetermined process thereafter, the inner lead is cut from the side opposite to the punch surface.

[0016]

As described above, according to the method of manufacturing a lead frame using the progressive die of the present invention, the lead frame having a very narrow lead width is cut across the inner lead tips by press punching. In the case of cutting into small pieces, it is possible to easily set a suitable lead frame within the prescribed value without forming a lot of angular burrs. Therefore, there are few troubles such as electrical short-circuiting, and in processing, it is possible to produce suitable results with only simple processing such as tapering the die surface side or punch surface side inside the inner lead at the cutting position. It is possible, and it has a remarkable effect that it does not adversely affect the subsequent process.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an enlarged view of a first embodiment in which an inner lead of a lead frame is cut.

FIG. 2 is an explanatory view showing an enlarged view of a second embodiment in which an inner lead of a lead frame is cut.

FIG. 3 is an explanatory diagram showing a configuration of a first embodiment in which inner leads of a lead frame are crushed.

FIG. 4 is an explanatory diagram showing a configuration of a second embodiment in which inner leads of a lead frame are crushed.

FIG. 5 is an explanatory diagram showing a process of cutting the crushed inner lead tips according to the present embodiment.

FIG. 6 is an explanatory view showing an enlarged view of an inner lead tip cut by a conventional technique.

FIG. 7 is an explanatory view showing an enlarged view of the tips of the inner leads cut by another conventional technique.

[Explanation of symbols]

 1 Inner lead part of lead frame 10 Cut surface of lead frame 12 Fracture surface of lead frame 14 Sagging 18, 19-corner burr 20 Boat bottom shape 30 Crushing 101 Flat punch 102 Crushing die 103 Crushing punch 104 Flat die 110 Lead Tip position 201 Lead cutting punch 202 Lead cutting die

Claims (1)

[Claims] 1. A die pad that is pulled out in the preceding step of cutting the inner lead tip of a cutting die that cuts the lead frame after forming both sides of the inner lead by press punching. The side is about 0.05mm apex angle and the crushing die having an angle of 1 to 10 degrees to the horizontal, or crushing punch is used to crush in the plate thickness direction, and from the opposite surface of the inner lead where the crushing is put. A method of cutting the tip of the inner lead, which is characterized by pulling out with a punch or a die.