JPH05326815A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To provide the lead frame for a semiconductor device generating no package cracks by sudden heating in a reflow process when the semiconductor is packaged. CONSTITUTION:Notches 4 are formed on the circumference of a die pad 1 formed almost in rectangular shape. As a result, even when stress is concentrated on the circumference of the die pad 1 by the evaporative expansion of the moisture accumulated on the backside of the die pad 1, the stress can be alleviated by the abovementioned notches 4, and the generation of cracks on the package can also be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device lead frame.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional lead frame for a semiconductor device. In FIG. 2, a die pad 1 on which a semiconductor chip (not shown) is placed is formed in a rectangular shape, and its four corners are supported by the lead frame body by die pad support portions 2. A large number of inner leads 3 are arranged around the die pad 1.

When assembling a semiconductor device, a semiconductor chip is adhered to the surface of the die pad 1, the electrodes on the semiconductor chip and the inner leads 3 are connected with a thin metal wire, and then the semiconductor chip, the die pad 1, and the die pad support 2 ,
The inner lead 3 and the thin metal wire are sealed with a resin so that the lead frame portion outside the sealing resin is cut off.

[0004]

In recent years, in this type of semiconductor device, in particular, in a surface mounting type semiconductor device called QFP, a lower surface of the die pad 1 is subjected to a reflow process when the semiconductor device is mounted on the surface of a printed circuit board. There is a problem that cracks are generated in the resin. This is because the water accumulated on the back surface of the die pad 1 vaporizes and expands due to rapid heat application in the reflow process, so stress concentrates near the side surface of the die pad 1, and this stress is added to the resin, especially the die pad with a thin resin thickness. It is considered that a crack is generated on the lower surface of No. 1. Due to the occurrence of cracks, the moisture resistance of the semiconductor device is significantly reduced and the reliability is deteriorated.

The present invention provides a lead frame for a semiconductor device, which solves the above conventional problems.

[0006]

A lead frame for a semiconductor device according to the present invention has a notch formed in the peripheral edge of a die pad.

[0007]

By doing so, even if the water accumulated on the back surface of the die pad is vaporized and expanded by the rapid application of heat in the reflow process, stress concentration can be prevented by the notch provided in the peripheral edge of the die pad. It is possible to prevent the resin under the die pad from cracking.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows an embodiment in which the present invention is applied to a surface mount (QFP) type semiconductor device lead frame.

In FIG. 1, a semiconductor chip (not shown)
The die pad 1 on which is mounted is formed in a rectangular shape as a whole,
The four corners are supported by the lead frame body by the die pad support portion 2. A large number of inner leads 3 are arranged around the die pad 1.

Further, in this embodiment, the notch 4 is provided on the peripheral edge of the die pad 1 to form the irregularities on the peripheral edge of the die pad 1.

When assembling the semiconductor device, the semiconductor chip is adhered to the surface of the die pad 1, the electrodes on the semiconductor chip and the inner leads 3 are connected with a thin metal wire, and then the semiconductor chip, the die pad 1, and the die pad support 2 ,
The inner lead 3 and the thin metal wire are sealed with a resin so that the lead frame portion outside the sealing resin is cut off.

With this configuration, the notch 4 provided on the peripheral edge of the die pad 1 even if the water accumulated on the back surface of the die pad 1 is vaporized and expanded by the rapid heat application in the reflow process.
This can prevent stress concentration. Therefore, it is possible to prevent cracks from being generated in the resin below the die pad 1.

Experiments have shown that the package size is 14 m.
Taking an example of an m-square, a package thickness of 1.5 mm, and a die pad size of 9 mm square, the humidity is 85% and the temperature is 85%.
When moisture was absorbed for 168 hours in an environment of ° C, cracks occurred in the resin below the die pad 1 in the conventional configuration,
No cracks were generated in the configurations of the examples of the present invention.

The number of notches 4 is 4 to 4 per side.
Within the range of 15 pieces, the depth of the notch 4 is 0.1 to 0.8 mm
Within this range, the one having the greatest effect may be selected according to the package size, the package thickness, the die pad size, and the like.

[0015]

Since the lead frame for a semiconductor device of the present invention is provided with a notch at the periphery of the die pad, the water accumulated on the back surface of the die pad is vaporized and expanded by the rapid application of heat in the reflow process. However, stress concentration can be prevented by the notch provided in the peripheral edge of the die pad. Therefore, it is possible to prevent the resin under the die pad from being cracked, and it is possible to dramatically improve the reliability of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of a lead frame for a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part of a conventional lead frame for a semiconductor device.

[Explanation of symbols]

 1 Die pad 2 Die pad support part 3 Inner lead 4 Notch

Claims (1)

[Claims] 1. A lead frame for a semiconductor device, wherein a notch is provided in a peripheral edge of a die pad on which a semiconductor chip is mounted.