JPH09266272A - Resin-sealed semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability against repetitive thermal shocks and prevent the cracking or bulging by covering either the periphery of the die pad of a lead frame or periphery of hang pins with a material having a low elastic modulus and high moisture permeability before resin sealing. SOLUTION: At least either the periphery of the die pad 1 of a lead frame or periphery of hang pins 2 is covered with a material 4 having a low elastic modulus and high moisture permeability (e.g. Si compds. typically polydimethylsiloxane) and resin sealing is made whereby the thermal stress generated between the sealed resin and the coat 4 of the Si compd. is absorbed by this coat to relax, and hence it is durable against repetitive thermal shocks. If the contained water is pressured and evaporated in the solder reflow step at mounting, it will pass through the coat 4 round the pins 2 and vent out therethrough as an escape. Thus it is possible to obtain a high solder dip resistance without cracking or bulging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-sealed semiconductor device.

[0002]

2. Description of the Related Art Semiconductor devices such as transistors, ICs, and LSIs are initially packaged with ceramic packages that hermetically seal semiconductor elements, but recently, from the viewpoint of cost and mass productivity, plastic packages that seal semiconductor elements with resin have been used. It is becoming mainstream. Epoxy resin has been mainly used as the encapsulating resin, and good results have been obtained.
However, as is well known, the sealing resin has a larger coefficient of thermal expansion than the semiconductor element and the lead frame, causing internal stress in the semiconductor device, but the semiconductor element becomes larger and the wiring becomes finer. Since the package tends to be smaller and thinner, it is required to reduce internal stress and further improve heat resistance of the semiconductor device. In particular, in recent years, semiconductor elements have tended to become larger and larger, so that the package does not crack even when repeatedly subjected to thermal shock, and the semiconductor device is designed to withstand heating during mounting of the semiconductor device, for example, reflow. It is required that the package does not crack or swell even when dipped in a solder melt after absorbing moisture.

In response to these requirements, Japanese Patent Laid-Open No. 61-39
The "semiconductor device" disclosed in Japanese Patent No. 553 discloses a semiconductor device in which a corner of a semiconductor element chip is obliquely cut and resin-sealed to relieve stress concentrated on the corner. The "Hybrid integrated circuit device" according to Japanese Patent No. 64049 discloses a hybrid integrated circuit device in which a power chip having a large heat generation amount is not resin-sealed but enclosed in a hollow portion, and parts such as resistors and capacitors are resin-sealed. There is. That is, in these, structural measures are taken for the semiconductor device.

On the other hand, in the "semiconductor device" disclosed in Japanese Patent Laid-Open No. 63-245948, measures are taken from the viewpoint of the encapsulating resin. There is disclosed a semiconductor device using an epoxy resin in which a polyorganosiloxane which is a silicon compound is added and mixed with an epoxy resin and modified to reduce the generated thermal stress and improve the adhesiveness to a semiconductor element. In addition, in order to improve the crack resistance at the time of dipping the solder, improvement of the adhesion with the lead frame has been studied. However, these measures are not always sufficient for the recent large-sized semiconductor devices.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention provides a semiconductor device which can withstand repeated thermal shocks and which does not crack or swell even when immersed in molten solder after being absorbed by a semiconductor package. This is an issue.

[0006]

According to the present invention, when a semiconductor element is sealed with resin, at least one of the peripheral portion of the die pad 1 of the lead frame and the periphery of the hanging pin 2 has a small elastic modulus and a high moisture permeability. After forming the coating 4 of the material, resin sealing is performed. By this coating 4, even if a large thermal stress occurs in the obtained semiconductor device, the coating around the hanging pin 2 is alleviated even when the built-in water is heated and pressurized steam is generated in the reflow process at the time of mounting the semiconductor device. Since it is released via 4, cracks and blisters that occur in the package are prevented.

[0007]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows that before the resin is sealed in forming the semiconductor device of the present invention, the elastic modulus is small and the moisture permeability is large between the periphery of the die pad 1 to which the semiconductor element 3 is die-bonded and the periphery of the hanging pin 2. It is a top view of the principal part of the lead frame in which material coating 4 was formed. This coating 4
After forming the resin, the semiconductor device of the present invention sufficiently resistant to repeated thermal shock and immersion in molten solder after absorbing moisture by performing resin sealing with an epoxy resin by means of transfer molding, for example. Is obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Semiconductor devices according to embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a semiconductor element 3 before resin sealing.
FIG. 2 is a plan view of a main part of a lead frame for a flat package in which a silicon compound coating 4 as a material having a small elastic modulus and a high moisture permeability is formed around the periphery of the die pad 1 to which the die bonding is performed and the periphery of the hanging pin 2; There are 8 leads on each side, 32 leads 5 in total, and a molding line of the sealing resin 7 to be molded later is indicated by a chain line.

A silicon compound typified by polydimer siloxane is a compound having a main chain of-(Si-O) _-n , and since the Si-O bond is in the intermediate state between covalent bond and ionic bond ( The CH ₃ ) ₂ Si unit thermally moves with a relatively large amplitude and has a large influence range. Therefore, the adjacent molecules are not brought close to each other, the intermolecular distance becomes large, and the intermolecular force is small. As a result, the silicon compound has many voids, and therefore has a small elastic modulus, is flexible, exhibits low stress, and has high moisture permeability. As the silicon compound, there are silicon rubber and silicon resin, and any of them may be used, but a silicon compound that can be applied to form a coating, that is, a silicon compound that is liquid at room temperature, is used because of the ease of forming the coating. Preferably. Heat after coating, if necessary
What can be cured by ultraviolet rays or the like may be adopted.

In consideration of adaptability to process changes as a coating method, a silicon compound is applied by a dispensing system for supplying a predetermined amount of liquid silicon compound to each application portion, for example, by using a syringe or a metering pump. It is desirable to do.

After the coating, wire bonding for electrically connecting the connecting electrode of the semiconductor element 3 and the lead 5 on the package side with a gold wire 6 is performed according to a normal semiconductor device manufacturing process, and then transfer molding or transfer molding is performed. A known molding means such as injection molding is used to perform resin sealing with, for example, an epoxy resin. FIG. 2 shows a semiconductor device in which a lead frame having a silicon compound coating 4 formed around the periphery of a die pad 1 to which the semiconductor element 3 of FIG. 2 is a cross-sectional view taken along line [2]-[2] in FIG.
Similarly, FIG. 3 is a sectional view taken along line [3]-[3].

In the semiconductor device obtained as described above, the silicon compound coating 4 absorbs and relaxes the thermal stress generated between the semiconductor device and the encapsulating resin. Therefore, a thermal cycle test in which thermal shock is repeated, for example, (-) 65 ° C. ~ Room temperature ~ 150 ° C cycle does not crack at all in the encapsulating resin of the package even in the test repeated 500 times, and it is contained in the test in which the semiconductor device absorbs moisture and then is immersed in the molten solder at the temperature of 260 ° C. Even if the moisture contained in the package is pressurized and vaporized, the package penetrates the silicon compound coating 4 around the suspension pin 2 and is released, so that cracks and blisters do not occur in the package.

In FIGS. 1, 2 and 3, a silicon compound coating 4 is formed on the periphery of the die pad 1 of the lead frame and around the four suspension pins 2, but one of the suspension pins 2 is used. When used as a gate or an air vent during resin encapsulation, it may be applied to the periphery of the three hanging pins 2 and the peripheral portion of the die pad 1, and if necessary, the coating 4 may be partially applied. May be omitted.

The silicon compound coating 4 is preferably applied to both the peripheral portion of the die pad 1 and the periphery of the hanging pin 2, but the coating may be formed on either one. For example, in order to improve only the thermal shock resistance, it is possible to obtain a sufficient effect by forming the coating 4 only on the peripheral portion of the die pad 1, and in order to improve cracks or blisters due to the vaporization of the water content, the coating is suspended. The coating 4 may be formed only around the pin 2.

Although FIGS. 1, 2 and 3 show the case of a 4-pin flat package, the case of 2 pins or
It goes without saying that the semiconductor device of the present invention includes various semiconductor devices including the case of the dual in-line package.

Although a thermosetting epoxy resin is used as the sealing resin, other thermosetting resins or thermoplastic heat resistant resins such as polyphenylene sulfide may be used.

[0019]

The present invention is carried out in the form as described above, and has the following effects.

It is obtained by forming a coating 4 of a material having a small elastic modulus and a high moisture permeability on at least one of the periphery of the pad 1 of the lead frame and the periphery of the hanging pin 2 and then sealing with a resin. The semiconductor device of the present invention is
The coating 4 relaxes internal stress mainly concentrated around the periphery of the die pad 1 and around the hanging pins 2 due to the temperature difference, and thus exhibits high thermal shock resistance, and the moisture contained therein is, for example, pressurized steam in a solder reflow process during mounting. Even if it is formed, it penetrates through the coating 4 around the hanging pin 2 and is released as an escape route, so that cracks and blisters do not occur and high solder dipping resistance is exhibited.

[Brief description of drawings]

FIG. 1 is a plan view of a main part of a lead frame in which a coating of a silicon compound having a low elastic modulus is formed around the periphery of a die pad to which a semiconductor element is bonded and around a hanging pin.

2 is a cross-sectional view taken along line [2]-[2] in FIG. 1 when the lead frame of FIG. 1 is resin-sealed to form a semiconductor device.

3 is a sectional view taken along line [3]-[3] in FIG. 1 when the lead frame of FIG. 1 is resin-sealed to form a semiconductor device.

[Explanation of symbols]

1 ... Die pad, 2 ... Hanging pin, 3 ... Semiconductor element, 4 ... Cover, 5 ... Lead, 6 ... Gold wire, 7 ...
Sealing resin.

Claims (3)

[Claims] 1. After forming a coating (4) of a material having a small elastic modulus and a high moisture permeability on at least one of the periphery of the die pad (1) of the lead frame and the periphery of the hanging pin (2). A resin-encapsulated semiconductor device, which is resin-encapsulated. 2. The resin-sealed mold according to claim 1, wherein the material having a low elastic modulus and a low moisture permeability is a liquid at room temperature, or is curable by heat, ultraviolet rays or the like and is a liquid at room temperature. Semiconductor device. 3. The resin-encapsulated semiconductor device according to claim 1, wherein the material having a low elastic modulus and a high moisture permeability is a silicon compound.