JP2927066B2 - Method for manufacturing resin-encapsulated semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device (hereinafter, referred to as a semiconductor device), and more particularly to a method of manufacturing a semiconductor device in which cracks in a mold resin due to thermal stress applied to the semiconductor device are prevented.

[0002]

2. Description of the Related Art With the recent miniaturization of electronic equipment,
In semiconductor devices used in these electronic devices, the size of packages has been reduced and thinned while the integration of semiconductor chips has been increasing, and the package size has been reduced.
Semiconductor devices such as SOPs and SOPs have been proposed. A QFP is shown as an example of this type of conventional semiconductor device. FIG.
6 is a partially cutaway plan view, and FIG. 6 is a sectional view taken along line BB of FIG. In this semiconductor device, a semiconductor chip 1 is mounted on a surface of a die pad 3 of a lead frame 2, and an electrode pad 4 of the semiconductor chip 1 and an inner lead 5 of the lead frame 2 are bonded by bonding wires 6. The second outer lead 8 is left and molded with the molding resin 7.

In this semiconductor device, an alloy of 42 alloy (Fe-Ni42) is generally used for a lead frame, and a semiconductor chip is fixed to a die pad with an Ag paste adhesive. Also, as a bonding wire,
An Au wire of about 30 μm is used, and an epoxy resin is used as a mold resin. The outer leads are bent downward.

[0004]

In the above-mentioned conventional semiconductor device, the nickel-based alloy used for the lead frame 2 and the thermo-liquefiable epoxy resin used for the molding resin 7 have different coefficients of thermal expansion, so that the adhesion is poor. Not good. For this reason, when subjected to thermal stress, peeling tends to occur between the lead frame 2 and the mold resin 7, and this peeling becomes remarkable especially on the back surface of the die pad 3 requiring a particularly large flat area inside the semiconductor device. When such peeling occurs,
Moisture is absorbed by the peeled portion, and in this state, when the heat of about 240 ° of reflow soldering when the semiconductor device is mounted on the printed circuit board is suddenly applied to the semiconductor device, the absorbed moisture is vaporized. When expanded, the pressure on the resin is rapidly increased, and a large stress is generated around the die pad 3. This stress causes cracks in the mold resin 7 on the back surface side of the die pad 3.

As a result, the moisture resistance of the semiconductor device is further degraded, and the semiconductor chip 1 generates heat during operation.
And the mold resin 7.
There is a problem that the cracks are further advanced and the semiconductor device is deteriorated. The cracks in the mold resin 7 are more likely to occur as the area of the die pad 3 increases and the thickness of the mold resin 7 on the back surface of the die pad 3 decreases. Therefore, even if the moisture in the mold resin 7 is reduced by pre-baking, there is a problem in forming a semiconductor chip having a large chip size into a thin package having a resin thickness of about 1.0 mm. An object of the present invention is to provide a method of manufacturing a semiconductor device having improved reliability by preventing separation of a lead frame and a mold resin due to thermal stress.
Is to provide a law .

[0006]

According to the present invention, there is provided a semiconductor device comprising:
Extending an end of a die pad of a lead frame for mounting a semiconductor chip in an outward direction; and partially etching the end.
And a step of bending the end toward the back side of the die pad.
In. For example, forming edges around the four sides of the die pad ,
The method includes a step of bending the end portion into an arc shape .

[0007]

According to the present invention, the mold resin on the back surface of the die pad of the semiconductor device is held by being pressed against the back surface of the die pad inside the portion formed by bending the end of the die pad, the thermal expansion is restrained, and Is prevented from peeling off.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 2 is a partially cutaway plan view of one embodiment of the semiconductor device of the present invention, and FIG. 1 is a sectional view taken along line AA of FIG. In this semiconductor device, the semiconductor chip 1 is mounted on the upper surface of the die pad 3 of the lead frame 2, and the electrode pads 4 of the semiconductor chip 1 and the inner leads 5 of the lead frame 2 are electrically connected by bonding wires 6, and this is resin-molded. It is placed in a mold and sealed with a mold resin 7. The outer leads 8 of the lead frame 2 are bent so as to be easily mounted on a printed circuit board (not shown).

The die pad 3 of the lead frame 2
As shown in the perspective view of FIG. 3 as viewed from the back side, it is formed in a substantially square shape, and the end 9 of each side around the four sides is extended so as to protrude outward. Are curved in an arc toward the back surface of the die pad 3. In this embodiment, the lead frame 2 is made of 42 alloy, and the die pad 3 has a thickness of 150 μm to maintain the strength for mounting and fixing the semiconductor chip.
Since there is no problem in strength, the die pad 3 is partially etched to a thickness of about 2/3 to facilitate processing. The lead frame 2 is manufactured by etching or pressing a pattern and then processing the end 9 of the die pad 3 by the above-described processing.

In the semiconductor device formed in this manner, the mold resin 7 that is in close contact with the back surface of the die pad 3 is held inside the arc-shaped curved end portion 9 of the die pad 3, It is in a state where it can be held down. Therefore, when this semiconductor device is soldered and mounted on a printed circuit board by infrared reflow or the like, about 23
Even when subjected to a thermal stress of 0 ° C., since the thermal expansion of the resin on the back surface side of the die pad 3 is restrained inside the end portion 9, the mold resin 7 is prevented from peeling over the entire back surface of the die pad 3. You. Therefore, moisture is not absorbed at the interface between the back surface of the die pad and the mold resin, and the mold resin 7 due to vaporization and expansion due to thermal stress is prevented.
Therefore, the occurrence of resin cracks during reflow soldering can be prevented, and deterioration of the semiconductor device can be prevented.

Further, in this semiconductor device, even if the chip size of the semiconductor chip 1 is increased and the area of the die pad 3 is increased, or if the thickness of the mold resin 7 on the back surface side of the die pad 3 is reduced, the die pad back surface is not damaged. A semiconductor device in which a semiconductor chip having a larger chip size than a conventional semiconductor chip is formed in a thin resin package (1 mm thick in TSOP) without the absorption of moisture and the like is prevented because separation of the resin from the resin is prevented. Become.

Next, a second embodiment of the present invention is shown in FIG. FIG. 4 is a perspective view of the die pad as viewed from the back side, similarly to FIG. In this embodiment, a plurality of end portions 9A provided around the four sides of the die pad 3 are formed in the side direction, here, divided into two, and each end portion 9A is curved in an arc shape toward the back surface side of the die pad 3. It is formed. With this configuration, each end 9A holds the mold resin on the back surface of the die pad 3 so as to press it against the back surface of the die pad. The mold resin can easily flow into the back surface of the die pad 3 from the gap between the divided end portions 9A, and no void (air pool) is generated on the back surface of the die pad. Here, in each of the above embodiments, the present invention is applied to a QFP type semiconductor device. However, the present invention is not limited to this and can be applied to an SOP or PLCC semiconductor device.

[0013]

As described above, according to the present invention, there are provided a step of extending an end of a die pad on which a semiconductor chip is mounted ;
Partially etch the end to reduce the thickness of this end only
And forming the end portion on the back side of the die pad, so that the manufactured semiconductor device improves the adhesion between the back surface of the die pad and the mold resin, and peels off the resin due to thermal stress. Can be prevented. Thus, cracks in the mold resin can be prevented from occurring due to rapid thermal stress when the semiconductor device is soldered and mounted on a printed circuit board, and the reliability of the semiconductor device can be improved. In the present invention, the partial etching
Since the end is thinner and bent, the end is curved
Can be easily performed.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of a semiconductor device of the present invention, and FIG.
3 is a sectional view taken along line AA of FIG.

FIG. 2 is a partially broken plan view of a first embodiment of the semiconductor device of the present invention.

FIG. 3 is a perspective view of the die pad of the lead frame of the present invention as viewed from the back surface side.

FIG. 4 is a perspective view of a die pad according to a second embodiment of the present invention as viewed from the back surface side.

FIG. 5 is a partially broken plan view of an example of a conventional semiconductor device.

FIG. 6 is a sectional view taken along line BB of FIG. 5;

[Explanation of symbols]

 Reference Signs List 1 semiconductor chip 2 lead frame 3 die pad 4 electrode pad 5 inner lead 6 bonding wire 7 molding resin 8 outer lead 9, 9A end

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-57651 (JP, A) JP-A-2-133951 (JP, A) JP-A-2-174149 (JP, A) JP-A-1- 181450 (JP, A) Japanese Utility Model Application Sho 62-5644 (JP, U) Japanese Utility Model Application No. 64-341 (JP, U) Japanese Utility Application No. 63-11433 (Japanese Utility Model Application No. 1-1116461) Microfilms of documents and drawings (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/56 H01L 23/28-23/30 H01L 23/50

Claims (2)

(57) [Claims] 1. A resin-sealed semiconductor device having a semiconductor chip mounted on a surface of a die pad of a lead frame and resin-sealing at least the die pad and the semiconductor chip, wherein an end of the die pad is directed outward. Work to extend
And partially etching the end to reduce the thickness of the end.
A method of manufacturing a resin-encapsulated semiconductor device , comprising: a step of thinning ; and a step of bending and forming the end portion toward a back surface of a die pad. 2. The end is formed around four sides of a die pad.
The method for manufacturing a resin-encapsulated semiconductor device according to claim 1 , further comprising a step of forming the end portion into an arc shape.