JP2000150763A - Lead frame and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid soldering mounting defect caused by package cracks and swell of a package rear in a solder reflow process when a semiconductor device is mounted on a board, by obtaining high bonding force by bonding sealing resin directly to a rear of a semiconductor element during resin sealing, relaxing stress to sealing resin, and decreasing water amount absorbed by adhesive by decreasing an amount of adhesive used for joining a semiconductor chip and a die pad when a semiconductor chip is mounted on a die pad. SOLUTION: A die pad joining a semiconductor element 10 of a lead frame has an opening in a central part and avoids troubles caused by stress relaxation and heating of soldering, etc. Additionally, heat dissipation property can be also improved by making a die pad of a semiconductor element junction part thicker than a lead part and exposing it outside a package during resin sealing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame suitable for a semiconductor device requiring particularly high heat dissipation in addition to a reduction in thickness and weight, and a semiconductor device using the same.

[0002]

2. Description of the Related Art Conventionally, as one of lead frames for providing external connection terminals to a resin-sealed semiconductor chip, an inner lead portion connected to an aluminum electrode pad formed on the semiconductor chip, an external terminal, Outer lead portion, a die pad portion for mounting a semiconductor chip,
There is a lead frame constituted by a suspension lead portion supporting the die pad portion. The die pad portion has an opening at or near the center, and has a plurality of joints around the opening for bonding with a semiconductor chip to be mounted. It is connected with the same material as the joint. A semiconductor device in which a semiconductor chip is mounted at a substantially central portion on a die pad of such a lead frame and further covered entirely with a molded epoxy resin is one of today's common semiconductor devices.

The bonding portion of the die pad has an outer shape smaller than that of the semiconductor chip. That is, when the semiconductor chip is mounted on the die pad, the bonding portion is located inside the semiconductor chip. Is as small as possible. By using such a lead frame,
When resin sealing, most of the back surface of the semiconductor chip is exposed due to the opening provided in the die pad, the area of the sealing resin directly adhered to the back surface of the semiconductor chip increases,
High adhesion is obtained. This is because the adhesion between the silicon on the back surface of the semiconductor chip and the sealing resin is larger than the adhesion between the die pad and the sealing resin. In addition to this, the stress with the sealing resin can be reduced, and when the semiconductor chip is mounted on the joint, the amount of the conductive adhesive used for joining the semiconductor chip and the joint is reduced. The amount of water absorbed by the adhesive can be reduced. Therefore, it is possible to avoid a thermal stress generated by heat in a solder reflow process when mounting a resin-encapsulated semiconductor device on a substrate, a package crack, a floating of a lead due to a swelling of the back surface of the package due to a vaporization expansion of moisture absorbed, and a defective soldering mounting. can do. The lead frame has the above-mentioned excellent characteristics.

[0004]

However, in a semiconductor device completed using a lead frame having the above-mentioned junction, the area of the junction in contact with the semiconductor chip is reduced, and a large number of semiconductors such as transistors are formed. In the case of a high-performance semiconductor chip in which elements are integrated at a high density, heat generated during operation is large, and it becomes difficult to release the heat. For this reason, there has been a problem that it becomes difficult to use a semiconductor device having the above-mentioned junction portion for a semiconductor chip which consumes large power and requires heat radiation. The present invention is to solve the problems of such a conventional lead frame or a semiconductor device using the same.

[0005]

In order to solve the above-mentioned problems, a lead frame according to the present invention comprises an inner lead portion,
A lead frame including an outer lead portion, a die pad portion for bonding a semiconductor chip, and a suspension lead portion for supporting the die pad portion, wherein the die pad portion has an opening and is bonded to the semiconductor chip. At least a part of the portion has a structure that is thicker than the thicknesses of the inner lead portion, the outer lead portion, and the suspension lead portion.

Further, in the semiconductor device of the present invention, a semiconductor chip is mounted on the die pad portion of the lead frame, and the semiconductor chip is thicker than the inner lead portion, the outer lead portion and the suspension lead portion. The semiconductor device is a semiconductor device in which the semiconductor chip is resin-sealed such that a bonding portion of the die pad portion with the semiconductor chip is exposed to the outside.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an example of a lead frame to which the present invention is applied, and is a plan view showing a main part thereof. FIG. 2 is a sectional view taken along line AA ′ of FIG. As shown in FIG. 1, the lead frame 1 of the present embodiment includes an inner lead portion 2, an outer lead portion 3,
Tie bar 4 and die pad portion 5 for mounting semiconductor chip
And a suspension lead portion 6 for supporting the die pad portion 5. The die pad portion 5 has bonding portions 8a, 8b, 8c, 8d for bonding to the semiconductor chip. And a bonding portion 8a, which is four small die pad portions,
The die pad portion 5 is formed by connecting 8b, 8c, and 8d. From a different point of view,
After the semiconductor chip is mounted on the die pad portion 5 of the lead frame 1, the die pad portion 5 is formed in order to alleviate the stress on the die pad portion 5 generated when the periphery is sealed with resin.
It can be said that it has the opening 7 itself.

[0008] The die pad portion 5 configured as described above is
It is formed thicker than other parts such as the inner lead part 2, the outer lead part 3, and the suspension lead part 6.
This is the greatest feature of the lead frame of the present invention. This lead frame may be formed by integral molding, or may be formed by punching a metal plate having a predetermined thickness and further bonding a metal plate to the joints 8a, 8b, 8c, and 8d. Things.

FIG. 3 is a plan view of a semiconductor product completed by mounting a semiconductor chip on the lead frame and sealing with resin, as viewed from the back surface, and FIG. 4 is a cross-sectional view taken along the line BB 'of FIG. . As can be seen from these drawings, when the semiconductor chip 10 is sealed with a resin to form a package, the back surfaces of the joining portions 8a, 8b, 8c, 8d of the die pad portion 5 are not covered with the resin but are exposed to the outside. Mold. This allows
Since the metal joints 8a, 8b, 8c, 8d having good thermal conductivity are exposed to the outside air, the heat radiation during the operation of the semiconductor chip is greatly improved. Thus, the reduced heat dissipation due to alleviating the inconvenience associated with the above can be recovered and compensated.

In the case of a thin semiconductor product having a package thickness of 1 mm or less, after the resin is sealed with the thickness of the semiconductor chip, the suspension lead portion 6 is depressed so that the surface thereof is not exposed. The portion 9 is formed, and the die pad portion 5 is lower than the inner lead portion 2. In this way, external lead terminals can be exposed from the center of the resin-sealed package (see FIG. 4). It is desirable that the amount of depression of the depressed portion 9 be approximately half the thickness of the semiconductor chip.

[0011]

As described above, the present invention uses a lead frame having a die pad having an outer shape smaller than a semiconductor chip and having an opening. Adhesive used to bond the semiconductor chip to the die pad when mounting the semiconductor chip on the die pad, in addition to obtaining a high adhesion force by being in close contact with the die pad. By reducing the amount of moisture absorbed by the adhesive, the amount of moisture absorbed by the adhesive can be reduced, and a package crack in a solder reflow process when the semiconductor device is mounted on a substrate and a defective solder mounting due to bulging of the back surface of the package can be avoided.

At the same time, by exposing a part of the rear surface of the die pad from the semiconductor product after the encapsulation molding, heat generated from the semiconductor chip can be easily released. The present invention is particularly effective when used in a semiconductor device having a small-sized package mounted on a high-density and highly integrated chip with a large power consumption.

[Brief description of the drawings]

FIG. 1 is a plan view showing a lead frame according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a lead frame according to the embodiment of the present invention;

FIG. 3 is a plan view showing a semiconductor device using the lead frame of the present invention.

FIG. 4 is a sectional view showing a semiconductor device using the lead frame of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead frame 2 Inner lead part 3 Outer lead part 4 Tie bar 5 Die pad part 6 Suspended lead part 7 Opening part 8a, 8b, 8c, 8d Joint part 9 Depress part 10 Semiconductor chip

Claims (2)

[Claims] 1. A lead frame comprising an inner lead portion, an outer lead portion, a die pad portion for joining a semiconductor chip, and a suspension lead portion for supporting the die pad portion, wherein the die pad portion has an opening. And a thickness of at least a part of a joint portion with the semiconductor chip is larger than thicknesses of the inner lead portion, the outer lead portion, and the suspension lead portion. 2. The die pad portion of claim 1, wherein a semiconductor chip is mounted on the die pad portion of the lead frame according to claim 1, and the thickness of the inner lead portion, the outer lead portion, and the suspension lead portion is larger than the thickness of the die lead portion. A semiconductor device using a lead frame, wherein the semiconductor chip is resin-sealed so that a joint portion with the semiconductor chip is exposed to the outside.