JPS5933983B2 - Method for manufacturing lead frames for semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a lead frame for a semiconductor device, and in particular, an object of the present invention is to economically manufacture lead frames having a plurality of connected lead frames with high pitch accuracy.

For example, a lead frame used in a semiconductor device is formed into a plurality of interconnected shapes as shown in FIG. Processing is added.

In this case, a tolerance is determined for the pitch P between each lead frame 1, and the dimensional tolerance is strictly determined.
This is because if the overall dimensional tolerance is not within a certain range, assembly work of the semiconductor device will be hindered. For example, in a structure formed by connecting 25 lead frames, if the pitch between each lead frame is 5.4±0.035, then the dimensions of part A in the figure should be 118.8±O, o577Ia. For example, depending on whether the pitch of individual pellets is large or small by O,005u, these will accumulate and result in an error of O,llu, which will cause a deviation in the standard dimension of the part A, which will not satisfy the standard, resulting in a problem. The lead frame described above is formed by continuous punching using a die as shown in FIG.

For example, a ribbon-shaped long thin copper plate is sequentially punched out while being conveyed in the direction of the arrow in the figure by this mold, and a semiconductor pellet pedestal 6 and an inner lead surrounding it bridge each lead with each other. It is formed in a shape connected by connecting part elements, 8. Therefore, in order to keep the dimensional tolerance of the part A as mentioned above within a predetermined value, the pitch machining accuracy corresponding to each lead frame of the mold should be set to 0.00.
It is necessary to keep the thickness to about 1 to 0.002 u, and manufacturing such a mold is labor-intensive and expensive. Furthermore, even when forming lead frames of the same shape, if the ribbon-shaped metal plates are made of different materials, thicknesses, and hardnesses, the balance between the side pressure during punching with the die and each bridging part of the material will be different. Separate molds must be used, which is extremely uneconomical. The present invention has been made to eliminate the above-mentioned drawbacks and provides an improved method for manufacturing lead frames for semiconductor devices in which a plurality of lead frames are connected.

In other words, using a mold with a bit smaller dimension between the lead frames than the predetermined size, continuous punching is performed on a ribbon-like metal plate in order, and after the predetermined shape is obtained, the inner leads of the lead frame are formed. Each bridge section of the lead frame is notched to provide a predetermined pitch between each lead frame in a very economical manner. The present invention will be described below with reference to the drawings.

For example, using the mold shown in Figure 2, a ribbon-shaped copper plate (thickness 0.
Considering the case of performing continuous punching on 35v1), the pitch P1 between each lead frame of the mold is made smaller than the standard dimension of 5.4 mm, that is, 5.395 mm, and a 25-cavity lead frame is manufactured. do. At this time, after the lead frame is punched into a predetermined shape, each bridge portion of the lead frame is notched. The work part corresponds to point C in the figure. The notched state is shown in FIG. 3, and the formed lead frame is shown in FIG. 4. That is, the protrusion 13 at the tip of the notch punch 12 falling onto the plate 11 made of copper is H=0, 12711J1, W=0.2.
7V1, and a recess is formed in the copper plate by notching. At this time, when the lead frame was punched, the copper plate elongated due to the pressure on that side (←≠ mark), and the pitch dimension was 3μ.
Becomes large. In the end, 25 pieces were connected and cut into a lead frame (part of which is shown in Figure 4). Each bridging portion 16 of the inner lead 15 is notched to form a recess 17, increasing the dimensions of the copper plate, and the pitch between each lead frame is 5.4u, with a tolerance of 0.001vt. It will come to an extent. In this way, in the case of 25 pieces, the pitch P shown in FIG.
The value of is within a predetermined value, and the dimensional accuracy of the portion corresponding to A in FIG. 1 is also within a predetermined value. Therefore, during the die bonder and wire bonder processes for each lead frame, when semiconductor pellets are sequentially bonded to the pedestal of the lead frame, work can be carried out efficiently without causing positional deviations, and production during the assembly process can be carried out efficiently. can improve sex. It is also economical because the dimensional accuracy of the mold does not have to be as high as conventional methods.
The dimensions of the metal plate are slightly elongated by performing the above-mentioned notch process, but if the amount of elongation required is minute, the necessary elongation can be obtained by adjusting the notch punch up and down, and when this range is exceeded, the size of the metal plate is slightly elongated. The elongation can be adjusted by appropriately changing the shape (W or H in the figure) of the wedge-shaped protrusion 13 of the notch punch shown in FIG.

Conventionally, when looking at one lead frame, even if the pitch between adjacent lead frames falls within the error range, when connecting multiple lead frames to form one, the overall length may not fit within the specified value. It was occurring, but
The method of the present invention eliminates the occurrence of such problems and allows the manufacture of lead frames with high dimensional accuracy.

Furthermore, when forming lead frames of the same shape, separate molds were used when the material and thickness of the metal plate were different, but with this invention, the shape of the notch punch when punching the notches can be changed. There is an advantage that the same mold can be used to adjust the dimensional accuracy to a predetermined value. In addition, since the notch is formed and a recess is formed in the bridging part of the inner lead,
Dividing the individual semiconductor pellets into bonded lead frames can be done very easily.

Although the method of the present invention has been described with respect to a lead frame having the shape shown in the drawing, it is not limited thereto, and the gist of the present invention can be applied to lead frames of various shapes and metal plates made of various materials. It goes without saying that the same effect can be obtained by appropriately notching each lead frame as a means of obtaining dimensional accuracy. This is an excellent method for manufacturing.

[Brief explanation of drawings]

Fig. 1 is a plan view of a plurality of connected lead frames, Fig. 2 is a plan view illustrating a part of a mold that forms the lead frame by continuous punching, and Fig. 3 is a notch cut on a metal plate. FIG. 4 is a plan view of the lead frame in which the inner lead bridging portion is notched, and FIG. 4 is a side view of the lead frame. 1... Lead frame, 11... Metal plate, 12... Notch punch, 15...
Inner lead, 16... Bridging portion of the inner lead, 17... Concave portion subjected to notch processing.

Claims (1)

[Claims] 1. Perform continuous punching on a ribbon-shaped metal plate using a mold to produce a plurality of connected lead frames, surrounding the pedestal of the semiconductor pellet in the lead frame to form an inner lead,
A method for manufacturing a lead frame for a semiconductor device, characterized in that notching is performed on each bridge portion between the adjacent inner leads to adjust the pitch between each lead frame to a predetermined value.