JPS62200749A - Lead frame - Google Patents

Abstract

PURPOSE:To prevent the generation of mustachelike flashes on the outer leads at the time of cutting of tie bars by a method wherein the tie bars for coupling mutually a plurality of the outer leads are each constituted by a plurality of fine bars and the holding of each outer lead and the prevention of outflow of a resin are contrived. CONSTITUTION:Outer leads 2 are coupled to one another by tie bars 3 extending in the rectangular direction to these outer leads. These tie bars 3 are each constituted of a common piece 3b provided at the central part between the mutually adjoining outer leads and 2 parallel fine bars 3a and 3a which are each extended toward the outer leads 2 from both sides of this common piece 3b and are each coupled to the adjoining outer leads 2. According to this lead frame 1, an element chip is resin-sealed in such a way as to include each point part of the outer leads 2 and a resin package 10 is constituted. When the tie bars 3 are cut after the resin sealing, a punch 4 of a comparatively smaller width compared to the mutually interval between the outer leads 2 is utilized. Therefore, even though a position deviation is generated in the outer leads 2 by the shrinkage or the deformation of the lead frame 1 after the resin sealing, the punch 4 does never interfere with the outer leads 2 and no mustachelike flash is generated on the outer leads 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead frame used in a semiconductor device, and particularly to a lead frame with improved quality.

[Conventional technology]

Lead frames are often used to encapsulate semiconductor element chips with resin.The element chips are mounted on the lead frame, which is then encapsulated with resin, and then the external leads are cut from the frame of the lead frame. It constitutes a semiconductor device. Conventionally, in this type of lead frame, in order to improve the shape retention of the large number of external leads provided, and to prevent resin from flowing outward from the external leads during resin sealing, A connecting portion called a tie bar is formed to connect these external leads.

For example, as shown in Figure 3, lead frame 11
A tie bar 13 is integrally formed between each external lead 12 so as to interconnect a plurality of external leads 12 arranged in parallel, and this tie bar 13 connects each external lead 12.
It maintains the position in the juxtaposed direction, and prevents the packaging resin 10 for sealing semiconductor elements (not shown) from flowing downward in the drawing.

Note that this tie bar 13 is attached to the punch 1 after the resin sealing is completed.
4 to configure each external lead 12 as an independent lead.

[Problem that the invention seeks to solve]

In the conventional lead frame described above, the tie bar 13 is formed to have approximately the same width dimension as the external lead 12. For this reason,
When cutting the tie bars 13, a punch having a cutting length approximately equal to the length of the tie bars 13, that is, the interval between adjacent external leads 12, is prepared, and the tie bars 13 are cut using a shearing force with high cutting strength using the punch 14. There is a need.

Therefore, if the external lead 12 is misaligned due to deformation such as shrinkage of the lead frame after resin sealing, the tie bar 13 and the external lead 12 relative to the punch 14
As a result, the punch 14 may interfere with the external lead 12 when cutting the tie bar 13. When such interference occurs, the external lead 12
The edge of the metal is scraped by the punch 14, and a whisker-like cutting edge of the metal is generated. These whiskers not only impair the appearance of the semiconductor device, but also short-circuit the external leads 12 to each other, resulting in a deterioration in the quality of the semiconductor device.

[Means for solving problems]

The lead frame of the present invention aims to improve the quality of semiconductor devices by preventing the occurrence of whiskers on external leads when cutting tie bars.

The lead frame of the present invention has a structure in which a tie bar that connects a plurality of external leads to each other is composed of a plurality of thin bars to hold each external lead and prevent resin from flowing out.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and particularly shows a part of the lead frame in a resin-sealed state.

The lead frame 1 can mount a semiconductor element chip on an element mounting part (not shown), and a plurality of external leads 2 are arranged in parallel at a predetermined pitch around the element mounting part, and are connected to electrode pads of the element chip. It is configured to electrically connect each external lead 2 with a metal wire. These external leads 2 are connected by tie bars 3 extending perpendicularly thereto. This tie bar 3 includes a common piece 3b provided at the center, and two parts extending from both sides of this common piece 3b toward the external leads 2 and connected to the adjacent external leads 2, respectively.
It consists of parallel thin bars 3a, 3a of books.

According to this lead frame 1, the package 10 is constructed by sealing the element chip with resin so as to include each tip of the external portion 2. When cutting the tie bar 3 after resin sealing, a punch 4 having a width smaller than the mutual spacing between the external leads 2 is used as shown by the chain line in the figure. Then, if a force is applied in the plane direction to the common piece 3b of the tie bar 3 using this punch 4, since each bar 3a is formed thin, it can be easily torn off from the outer part 2. Then, the tie bar 3 is cut.

Therefore, even if the punch 4 is sufficiently smaller than the external lead interval, it is possible to effectively cut the tie bar 3, and as a result, the external lead 2 will not be misaligned due to contraction and deformation of the lead frame l after resin sealing. Even if this occurs, the punch 4 will not interfere with the external lead 2. This prevents whisker-like cracks from occurring on the external lead 2.
Deterioration in the quality of semiconductor devices can be prevented.

Note that the tie bar 3 has a planar shape as a thin bar 3a.

3a, the thickness remains the same as before, and it goes without saying that the resin can be prevented from flowing out. Furthermore, since the two thin bars 3a, 3a are connected, there will be no problem in terms of strength.

FIG. 2 shows another embodiment of the present invention, and the same parts as those in FIG.

In this embodiment, a thin bar 3 extends in all directions from a central common piece 3b of a tie bar 3A that connects external leads 2 to each other.
a and 3a are connected to the external leads 2, respectively, so that the overall planar shape is approximately X-shaped.

Also in this embodiment, each bar 3a, 3 of the tie bar 3A
Since a is configured to be thin, it is possible to easily cut into the tie bar 3 using a punch 4 whose width is narrower than the mutual spacing between the external leads 2, thereby preventing the occurrence of whiskers on the external leads 2. What can be prevented is the same as in the previous embodiment.

In this embodiment, by configuring the bars 3a, 3a in an X-shape, the longitudinal position of the external lead 2 can also be maintained effectively.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and in particular, the shape and structure of the tie bars can be modified in various ways. For example, the number of bars may be three or more, and can be changed as appropriate depending on the holding strength.

〔Effect of the invention〕

As explained above, in the present invention, the tie bar is composed of a plurality of thin bars to hold each external lead and prevent resin from flowing out, so a punch with a width smaller than the mutual spacing between the external leads can be used. It is possible to cut the tie bar, thereby avoiding interference between the punch and the external lead, preventing the occurrence of whiskers on the external lead, and improving the quality of the semiconductor device by preventing short circuits of the external lead.

[Brief explanation of drawings]

FIG. 1 is a plan view of a main part of an embodiment of the present invention, FIG. 2 is a plan view of a main part of another embodiment of the invention, and FIG. 3 is a plan view of a part of a conventional lead frame. be. 1.11...Lead frame, 2,12...External lead, 3.13...Tie bar, 3a...Thin bar,
3b... Common piece, 4, 14... Punch, 10...
Resin (package).

Claims (2)

[Claims] (1) In a lead frame configured such that a plurality of external leads are connected to each other using tie bars, and the tie bars are used to hold each external lead and prevent packaging resin from flowing out, the tie bars are connected to a plurality of thin A lead frame characterized by comprising: and connected to each external lead. (2) A lead frame as set forth in claim 1, wherein the tie bar is comprised of a common piece at the center and two thin bars on both sides of the common piece that are connected to adjacent external leads, respectively.