JPH0564859B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a lead frame used for fixing semiconductor chips such as ICs and LSIs.

[Background Art] Metal lead frames have conventionally been used to assemble semiconductor devices in which semiconductor chips are integrated with resin molding and have a plurality of protruding pins. This lead frame is formed by punching out a thin metal plate with a press or etching it.
Its shape is as shown in FIG.
A tab lead 3 that supports a rectangular tab 2 to which it is attached at its four corners, a plurality of fingers 4 whose inner ends face the periphery of the tab 2, and a frame 5 that supports these fingers 4 and the outer ends of the tab lead 3. It consists of sprocket holes 6 provided at regular intervals along both side edges of the frame portion 5.

To assemble a semiconductor device using such a lead frame 7, first attach the semiconductor chip 1 onto the tab 2, and then connect each electrode of the semiconductor chip 1 and the corresponding inner end of the finger 4 with a wire or a wire. Connect directly without using, and then connect the rectangular frame 5
The inner region of the semiconductor chip 1 is molded with synthetic resin to cover the semiconductor chip 1, and then the frame portion 5 is cut out to obtain a flat lead or in-line type semiconductor device.

By the way, extremely thin tab leads and fingers are formed on lead frames, but as semiconductor devices with multiple pins are desired these days, the diameters of tab leads, fingers, etc. have to become thinner and thinner, and they are no longer just thin plates. It is becoming difficult to form highly accurate lead frames using punching press processing.

Therefore, etching has been used to form lead frames having minute fingers, etc., but etching has the disadvantage that the manufacturing process is complicated and costs are high.

Further, the tab lead portion of the lead frame is separated from the frame portion after the semiconductor chip is covered with a mold. Conventionally, in order to facilitate this cutting operation, the tab lead portion of the lead frame is separated from the frame portion as shown in FIG. A half notch 3a is formed in the tab lead 3 by post-pressing or the like. However, the thickness of the tab lead 3 is generally extremely thin, about 35 .mu.m, and it is very difficult to accurately form the half notch 3a of about 17 .mu.m therein by press working. If the accuracy of the half notch 3a is not good, problems such as the tab lead 3 breaking before the semiconductor chip 1 is molded, and the efficiency of cutting the tab lead 3 after molding being reduced occur.

[Purpose of the invention]

The present invention has been made in view of the above points, and provides a method for manufacturing a lead frame for a semiconductor device that is easy to manufacture, can sufficiently form fine fingers, etc., and can form half notches for cutting with high accuracy in tab leads. It is an object.

[Summary of the invention]

In order to achieve the above object, the present invention forms a lead frame by electroforming, forms tab leads by electroforming to cover a resist layer that divides the non-resist part, and has a half notch for cutting the tab leads. It is characterized by being formed simultaneously during electroforming.

〔Example〕

FIG. 1 shows the manufacturing process of a lead frame according to an embodiment of the present invention, and shows an enlarged cross section of the tab lead 3 taken along line A--A in FIG.

First, as shown in Fig. a, an electrically insulating synthetic resin is coated on a substrate 8 whose surface is made of a conductive material such as aluminum or stainless steel, or a polyester film, polyimide tape, etc., and which has been made conductive by vapor deposition or electroless plating. A resist layer 9 is formed into a desired pattern by printing. In this case, the non-resist part 10 corresponds to the shape of the lead frame 7, and in Figure a, the non-resist part 10 is the tab lead 3.
It is the forming part of. It is also possible to use a dry film for this resist layer.

In the non-resist portion 10 of the tab lead 3 forming portion, a narrow resist portion 11 is formed near the base end at the same time as the resist layer 9 is printed, and the elongated non-resist portion 10 corresponding to the tab lead 3 forming portion is formed. It's divided.

Next, after peeling the substrate 8 using caustic soda or the like, copper, nickel, etc. are formed by electroforming.
Layering conductive metals such as gold and tin. As a result, a conductive metal layer 12 of a constant thickness is formed on the non-resist portion 10.
is formed, and as the electroforming progresses, a conductive metal layer also grows on the small width resist part 11, connects with the surrounding conductive metal, and covers the resist part 11 and becomes integrated as shown in Figure b. conductive metal layer 12
becomes.

When the resist layer 9 and the resist portion 11 are removed from the laminate thus obtained, a metal plate consisting only of the substrate 8 and the conductive metal layer 12 as shown in FIG. By peeling off the layer 12, a single lead frame 7 having tab leads 3 as shown in Figure d is obtained. At the base of the tab lead 3 of this lead frame 7, there is a half notch 3a having a constant width across the tab lead 3.
is formed.

In this embodiment, as shown in FIG. 2, the resist portion 11 that divides the tab lead 3 is formed into a continuous band shape with a constant width, but the shape may be changed as required. It can be deformed, and the resist portion 11 does not necessarily have to be a continuous body, as long as it forms a half notch 3a that facilitates cutting, at least in the metal layer 12 that is laminated by electroforming above the resist portion 11. good.

[Effects of the Invention] The present invention is as described above, and since electroforming is used, lead frames for multi-pin semiconductor devices having minute dimensions and shapes can be manufactured easily and at low cost. A half notch for cutting the tab lead can also be formed simultaneously and with high precision, and the efficiency of semiconductor device assembly work can be improved.

[Brief explanation of the drawing]

1A to 1D are diagrams illustrating the manufacturing process of a lead frame in an embodiment of the present invention, FIG. 2 is a plan view showing a part of a resist pattern in the embodiment,
Figure 3 is a plan view of a typical lead frame, Figure 4
The figure is a partial perspective view showing a half notch in a tab lead of a lead frame. DESCRIPTION OF SYMBOLS 1... Semiconductor chip, 2... Tab, 3... Tab lead, 4... Finger, 5... Frame, 7... Lead frame, 8... Conductive metal substrate, 9... Resist layer, 10... Non-resist part, 11... Resist part, 12... Conductive metal layer.

Claims (1)

[Claims] 1. A tab on which a resist layer is formed on a conductive substrate, a conductive metal layer of a desired shape is formed on the non-resist portion by electroforming, and this conductive metal layer is peeled off from the conductive substrate to place a semiconductor chip; A method for manufacturing a lead frame in which a lead frame is provided with a tab lead that supports a tab and a finger that connects to an electrode, wherein, when forming the resist layer, a non-resist portion for forming the tab lead is formed. A method for manufacturing a lead frame for a semiconductor device, characterized in that a half notch is formed in a tab lead by providing a resist portion that divides the non-resist portion and electroforming a conductive metal layer so as to cover the resist portion.