JPH04340263A - Lead frame - Google Patents

Abstract

PURPOSE:To eliminate a need of performing a bending operation and to prevent a defect such as a short circuit or the like between outer leads due to a stress by a method wherein the connection of the outer leads to interconnections on a mounting board is made short. CONSTITUTION:A lead frame is a lead frame for direct bonding use; it is provided with the following: inner leads 1 which are extended to four directions from the mounting part of a semiconductor-element chip; and outer leads 3. The length (l) of the outer leads 3 is formed to be short at about 1mm. The outer leads 3 are not bent from a resin package 4; they are formed so as to be extended straight to the outside by 1mm on the same plane. Since the bending process of the outer leads is not required, their positional accuracy can be maintained to be good. It is possible to obtain a semiconductor device whose dimensional accuracy is high, which does not cause a short-circuit defect between the outer leads and whose reliability is high.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame, and more particularly to a lead frame having a structure in which leads extend straight from a package without being bent.

0002

[Prior Art] Lead frames for semiconductor devices such as ICs and LSIs are shaped into a predetermined shape by removing unnecessary portions of metal strips by either photo-etching or press processing. It is formed through a plating process in which parts are plated, a taping process in which tape is attached and the inner leads are fixed together, etc. Here, the part of the lead inside the package line will be referred to as the inner lead, and the part outside the package line will be referred to as the outer lead.

Incidentally, in recent years, surface mount technology in which the tips of the outer leads are connected to the wiring pattern formed on the surface of the mounting board has become popular. One method is to bend the outer lead to form the front side (semiconductor element mounting side) on the wiring pattern, and the other is to bend the outer lead into an L shape and form the back side of the outer lead (the back side of the semiconductor element mounting side) on the wiring pattern. Methods to do so have been put into practical use, and all of these methods require bending the outer lead.

For example, a semiconductor device in which the outer lead 13 is bent into an L-shape is shown in FIGS. 5(a) and 5(b). When bending the outer leads in this way, the stress applied during the bending process may cause the solder plating or palladium plating on the surface of the outer leads to easily peel off, cause distortion, and furthermore, this stress may also extend to the inner leads. This could also cause a short circuit between the leads. Further, positional displacement due to distortion of the outer lead causes poor connection with the wiring pattern of the mounting board.

[0005]Furthermore, the stress applied to the outer leads at this time may cause them to come off from the resin package.

[0006] As described above, the strain caused by the bending of the outer lead has been a major cause of deterioration in the reliability of semiconductor devices.

[0007]Furthermore, problems not only in surface mounting but also in bending the outer leads often cause a decrease in reliability.

[0008]

[Problems to be Solved by the Invention] As described above, in conventional semiconductor devices, stress applied during bending of the outer leads causes various causes of deterioration in reliability, such as deformation of the outer leads or coming off from the resin package. There was a problem.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a lead frame for forming a highly reliable semiconductor device with good dimensional accuracy.

0010

[Means for Solving the Problems] Therefore, the lead frame of the present invention is characterized in that the outer leads are short enough to be connected to wiring on a mounting board.

[0011]

[Function] According to the above structure, the outer leads are short enough to be connected to the mounting board, and even during mounting, the leads extend straight outward on the same plane from the resin package without being bent. Therefore, there is no need to bend the outer leads, which prevents distortion from occurring, and prevents defects such as short circuits between the leads due to this stress.

[0012] Also, by shortening the outer lead,
It can be formed using narrow strips, reducing material costs, and
The mold can also be made smaller and the cost of the mold can be reduced.

Furthermore, since distortion can be prevented from occurring in the outer leads, it is also possible to prevent poor connection with the wiring pattern of the mounting board due to positional displacement.

Furthermore, since there is no molding process after solder plating or Pd plating of the outer lead, the product can be stabilized.

Furthermore, it is possible to prevent the outer lead from coming off from the resin package due to the stress applied to the outer lead during bending.

Furthermore, since the outer leads can be significantly shortened, the area occupied by the semiconductor device on the mounting board can be reduced.

Note that a dam bar may be formed between the inner lead and the outer lead, or the dam bar may be omitted and the inner lead and outer lead may be used together.

[0018] If the dam bar is omitted, the mold becomes more compact and costs are reduced.

[0019] The length of this outer lead is 0.5 mm.
It is desirable that the length be approximately 3 mm.

[0020]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

A lead frame according to an embodiment of the present invention is shown in FIG.
), it is a lead frame for direct bonding, and is equipped with an inner lead 1 and an outer lead 3 extending in four directions from a semiconductor chip mounting part, and the length l of the outer lead 3 is about 1 mm. It is characterized by its short shape.

A semiconductor device formed using this lead frame is shown in a perspective view in FIG. 1(b) and in a sectional view in FIG. 1(c).
1 straight outward on the same plane without being bent
It is formed to extend by mm.

FIGS. 2(a) to 2(d) are diagrams showing a lead frame according to an embodiment of the present invention and a manufacturing process of a semiconductor device using the lead frame.

First, as shown in FIG. 2(a), the alloy 4
Inner leads 1 and outer leads 3 are formed from a strip-shaped material designated as 2 using a progressive die. 2 is a dumb bar, and 7 is a side bar. Since the outer leads 3 of this lead frame are formed short, the strip material may be narrow in width, and a small mold may be used.

After the lead frame is shaped in this way, a noble metal plating process, a taping process, an annealing process, etc. are performed to complete the formation of the lead frame.

Next, as shown in FIG. 2(b), the thin end of the inner lead of this lead frame is positioned so as to come into contact with the bonding pad of the semiconductor chip, and then a bonding head (not shown) is inserted from the thin end side. )
By applying pressure and heating, the thin end portion of the lead frame and each bonding pad of the semiconductor chip 5 are directly bonded to each other by bumps.

After that, as shown in FIG. 2(c), it is placed in a mold, filled with sealing resin, and molded.

Finally, as shown in FIG. 2(d), the tie bars 2 and side bars 7 are cut out while keeping the outer leads 2 straight, thereby completing the semiconductor device shown in FIG.

As shown in FIG. 3, in this semiconductor device, the hole h formed in the printed circuit board 8 for mounting on which the wiring pattern P is formed is filled about half of the package 4, and the desired outer lead 2 and wiring pattern are formed. P is connected and fixed with a conductive adhesive S such as silver paste.

[0030] According to this lead frame, the outer lead can be formed with a narrow strip material corresponding to the length of the shortened outer lead, which reduces material cost and also allows the mold to be made smaller, thereby reducing mold cost. be able to.

Furthermore, the semiconductor device obtained in this manner is significantly smaller than a conventional surface-mounted semiconductor device, and the packaging density on the mounting board can be increased.

Furthermore, since the bending process of the outer leads is not required, it is possible to maintain good positional accuracy, and to obtain a highly reliable semiconductor device with high dimensional accuracy and no short-circuit defects between the outer leads. be able to.

Furthermore, since there is no need to bend the outer lead after precious metal plating, the product quality can be stabilized without peeling of the plating layer.

In the above embodiment, a lead frame having a dam bar was described, but since the outer lead is extremely short, the dam bar is omitted and the outer lead and inner lead are integrated as shown in FIG. 4(a). You can also do this. Reference numeral 13 indicates a lead in which the outer lead and the inner lead are integrated. When this lead frame is used, the side bar 7 plays the role of a dam bar during the resin sealing process, and the resin is stopped at the position of this side bar. Therefore, the resin burr has reached the position of this side bar, but it is preferable to remove the burr at the same time as cutting out the side bar 7 after the resin sealing process is completed.

Furthermore, as a modification of the lead frame in which the dam bar is omitted, as shown in FIG. 4(b), only the inside of the package line (inner lead) is molded, and the part that will become the outer lead is left as a side bar 17. There are some things. In this case as well, the side bar 17 plays the role of a dam bar during the resin sealing process, and the resin is stopped at the position of this side bar. Then, after the resin sealing process is completed, it is preferable to leave a part of the side bar 17 as the outer lead 23 and remove the burr at the same time as punching out the remaining area (including the hatched area K). In this example, the shape of the outer lead is processed after resin sealing. In order to improve the shape processing of the outer lead, a slit is previously formed in the region that will become the tip of the outer lead.

[0036] In the above embodiment, a lead frame for direct bonding was explained, but it goes without saying that the present invention can also be applied to a lead frame for wire bonding, and also to a film carrier. .

[0037]

[Effects of the Invention] As explained above, according to the present invention, the outer leads are formed short enough to be connected to wiring, and during mounting, the outer leads extend straight from the package, and bending is not required. Therefore, it is possible to obtain an extremely reliable semiconductor device without distortion or positional deviation.

[0038]

[Brief explanation of drawings]

[0039]

FIG. 1 is a diagram showing a lead frame according to an embodiment of the present invention and a semiconductor device formed using the same.

[0040]

[Fig. 2] Manufacturing process diagram of a lead frame and a semiconductor device according to an embodiment of the present invention

[0041]

FIG. 3 is a diagram showing a mounting state of a semiconductor device according to an embodiment of the present invention.

[0042]

FIG. 4 is a diagram showing a lead frame used in a semiconductor device according to another embodiment of the present invention.

[0043]

[Fig. 5] Diagram showing a conventional semiconductor device

[0044]

[Explanation of symbols]

1 Inner lead 2 Dam bar 3 Outer lead 4 Package 5 Semiconductor chip 7 Sidebar 8 Printed circuit board S Conductive adhesive P Wiring pattern h hole 13. Lead 17 Sidebar K Area to be excised 23 Outer lead

Claims (1)

[Claims] 1. A lead frame comprising a plurality of leads extending outward from around a semiconductor element mounting portion, wherein an outer lead portion of the lead is short enough to be connected to wiring on a mounting board. A lead frame characterized by: