JPH0799270A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device, wherein each characteristic evaluated in a TCT test is improved and crack resistance property at the time of dipping into fused solder liquid is excellent. CONSTITUTION:In a semiconductor device, which is formed by sealing a semiconductor element with a plastic package, the surfaces of the plastic package 1, i.e., the top face 1A and the rear face 1B are coated with metallic foils 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which a semiconductor element is sealed with resin.

[0002]

2. Description of the Related Art Conventionally, semiconductor devices such as transistors, ICs and LSIs have been encapsulated into semiconductor devices by ceramic packages or the like, but from the viewpoint of cost and mass productivity, resin encapsulation using plastic packages is preferred. It is becoming mainstream. Epoxy resin has been used for this type of resin encapsulation and has achieved good results. On the other hand, technological innovation in the semiconductor field has led to an increase in the degree of integration and an increase in the size of elements. On the other hand, there is a strong demand for smaller and thinner packages, and therefore the volume occupied by the resin material for sealing is large. The rate is decreasing, and further improvement is required for the sealing material. In particular, in recent years, the size of semiconductor elements tends to become larger and larger, and further improvement in performance is required in comparison with a thermal cycle test (TCT test) which is an accelerated test for performance evaluation of semiconductor encapsulating resin. In addition, surface mounting is becoming the main method of mounting semiconductor packages, and therefore, it is required that the package does not crack or swell even if the semiconductor package is immersed in a solder melt while absorbing moisture. There is.

To meet these demands, the TCT has been conventionally used.
In order to improve each property evaluated in the test, it has been considered to modify the epoxy resin with a silicone compound to reduce the thermal stress. Further, improvement of adhesion with a lead frame has been studied in order to improve crack resistance during solder immersion, but the effect is not yet sufficient.

[0004]

As described above, the epoxy resin compositions for encapsulation up to now have not been satisfactory in the results of the TCT test and the crack resistance characteristics when immersed in solder.
For this reason, it is strongly desired to improve both of the above characteristics so as to cope with the increase in size of semiconductor elements and surface mounting due to the above technical innovation.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor device having improved characteristics evaluated by a TCT test and excellent crack resistance when immersed in a solder melt.

[0006]

A semiconductor device according to the present invention will be described with reference to FIG. 1 showing an embodiment. In the semiconductor device in which a semiconductor element is sealed by a plastic package, the plastic package 1 Is characterized in that its surface is covered with the metal foil 2.

Here, the "surface" of the plastic package 1 means the surface of the maximum surface (front surface 1A and back surface 1B) of the plastic package which is usually flat, and also as a mode of "covering with metal foil". As shown in 2,
As shown in FIG. 3 or 4, the entire surface of the plastic package is a flat surface, and the surface of the plastic package is buried in the surface layer of the plastic package and the surface of the metal foil is the same as the surface of the surrounding plastic package or is depressed. There are some that do.

A thermosetting resin is used as a plastic package for sealing the semiconductor element, and examples thereof include epoxy resin, phenol resin, urea resin, melamine resin, polyester resin, diallyl phthalate resin, and polyphenylene sulfide. To be Of these, it is preferable to use an epoxy resin. The epoxy resin is used as an epoxy resin composition in which conventionally known additives such as a curing agent, a curing accelerator and a filler are blended.

The sealing of the semiconductor element using the above materials is not particularly limited and can be performed by a known molding method such as ordinary injection molding or transfer molding. The metal foil covering the plastic package is not particularly limited as long as it is a metal having a melting point of 400 ° C. or higher. Examples of such a material include aluminum, stainless steel, copper, and an alloy of iron and nickel. The thickness is 0.1 to 100 μm.
m, preferably in the range of 5 μm to 50 μm. Those having a thickness of 0.1 μm or less are easily deformed by themselves and are difficult to handle, and those having a thickness of more than 100 μm are excessive in strength and hinder the thinning of the entire package, which is not preferable.

A thin metal layer 2 is formed on the surface of the plastic package.
As a method of coating the metal package, a method of bonding a thin metal to the surface of the plastic package after molding, and a method of temporarily fixing a metal foil to the inner surface of the mold before molding and then sealing the semiconductor element and the lead frame as usual. There is a way to do it.

According to the above method, as shown schematically in FIG. 2, the adhesive layer 5 is formed on the surface 1A of the package 1.
A semiconductor device having the metal foil 2 attached thereto can be obtained.
According to the method described later, as schematically shown in FIG. 3, the surface 1A of the package 1 and a tack for temporarily fixing the inner surface of the mold,
A semiconductor device in which the surface of the adhesive layer 6 is in the same plane and the metal foil 2 is embedded in the surface layer of the package is obtained.

Further, in the method described later, when physical means such as vacuum adsorption, magnetic force and gravity are used as means for temporarily fixing the metal foil 2 to the inner surface of the mold, the tacky adhesive layer 6 for temporary fixing is used. It is not necessary, and as shown schematically in FIG. 4, a semiconductor device in which the surface 1A of the package 1 and the surface of the metal foil 2 are the same can be obtained.

When the metal foil is adhered to the surface of the package after molding the plastic package, a metal foil material having a viscous and adhesive layer provided on one side of the metal foil is used.
The adhesive used in this case is not particularly limited, and an adhesive that has been conventionally used for metal foils can be used, and an epoxy type, a silicone type, an imide type or a composite type of these is used. It is preferable. On the other hand, the pressure-sensitive adhesives are not particularly limited, and pressure-sensitive adhesives conventionally used for metal foils can be used, and acrylic type, rubber type, and silicone type are preferably used. The thickness of the adhesive layer or the pressure-sensitive adhesive layer is 5 to 50 μm, preferably 10 to 20 μm.
It is set in the range of μm. Further, in order to effectively remove the heat generated from the semiconductor device, metal particles may be dispersed in the adhesive layer or the adhesive layer. Examples of such metal particles include silver, copper, aluminum and the like. The particle size is 0.1 to 5 μm, preferably 0.2 to 3 μm
It is set to the range of. Further, the content rate is set in the range of 10 to 70% by weight, preferably 40 to 60% by weight.

The covering of the plastic package with the above-mentioned metal foil covers 5 surface areas of the plastic package.
It is preferable to cover 0% or more, particularly preferably 8
It is 0% or more. That is, when the coating is 50% or more, the reliability of the obtained semiconductor device in the TCT test and the crack resistance at the time of dipping in the solder melt become significantly improved.

Further, the individual identification information such as the product name of the semiconductor device and the manufacturing lot number is usually recorded on the surface of the plastic package, but in the present invention, it is preferable to be recorded on the surface of the metal foil. This individual identification information may be recorded by a general method such as laser marking or stamping, but a method using a photosensitive resin is preferable from the viewpoint of recording a large amount of information, recognizing its own weight and the like.
In this method, a photosensitive resin layer is formed on a metal foil using a photosensitive resin, and ultraviolet rays (U
V) A method of irradiating light by a method such as an exposure method and recording the individual identification information. Examples of the photosensitive resin include acrylic-based, epoxy-based, and polyimide-based photosensitive resins. Among them, it is preferable to use the polyimide-based photosensitive resin from the viewpoint of heat resistance. The thickness of the recording layer is set in the range of 0.1 to 20 μm, preferably 1 to 5 μm. When recording individual identification information with this photosensitive resin, it is preferable to use a metal foil having the following characteristics (A) or characteristics (B) as the metal foil. (A) The glossiness of the metal foil surface is in the range of 70 to 250% according to JIS Z8741. (B) The average surface roughness is 0.1 to 10 μm. By using such a metal foil, the influence of excess reflected light is removed, and individual identification information can be accurately recognized from a wide angle.

[0016]

According to the present invention, since the surface of the plastic package is covered with the metal foil, the characteristics evaluated in the TCT test are improved and the life is extended. Also,
After the moisture absorption, even if it is dipped in the solder melt, the generation of the package crack can be prevented. Therefore, high reliability can be obtained in the semiconductor device. Further, by forming a recording layer of a photosensitive resin on the surface of the metal foil, it becomes possible to record a large amount of information and automatically recognize it. Further, by using a metal foil having a specific glossiness or surface roughness in the metal foil, it becomes possible to remove the influence of extra reflected light, etc., and it becomes possible to accurately recognize individual identification information. Become.

Further, as shown in FIG. 3 or 4, when the metal foil is set in the mold together with the semiconductor element and the lead frame and integrally molded, the metal foil does not protrude from the surface of the package and therefore is peeled off. There is no fear, the metal foil is directly bonded to the resin material, and there is no adhesive or adhesive, so the adhesive and adhesive layers do not penetrate moisture from the surroundings and the package material does not absorb moisture. Moisture resistance is significantly improved.

[0018]

【Example】

Example 1 A semiconductor element was transfer-molded using an epoxy resin composition (conditions: 175 ° C. × 2 minutes, 175 ° C.).
X 5 hours-post-curing) to seal. This package is an 80-pin 4-way flat package (80-pin
QFP, size 20 × 14 × 2 mm) and die pad size 8 × 8 mm. Compared to the above plastic package, the size is 18 mm x 12 mm and the thickness is 7 μm.
Of aluminum foil of silicon adhesive layer (thickness 15μ
The semiconductor device was manufactured by sticking to both sides of the package via m). (Example 2) An epoxy adhesive was used instead of the silicone adhesive. A semiconductor device was manufactured in the same manner as in Example 1 except for the above. The thickness of the epoxy adhesive layer is 5
It was set to 0 μm. (Comparative Example) The plastic package was not covered with the aluminum foil. Other than that, the same operation as in Example 1 was performed to manufacture a semiconductor device.

With respect to the semiconductor devices of the example products 1 and 2 and the comparative example product thus obtained, −50 ° C./5 min.
A TCT test was performed at 150 ° C / 5 minutes. Also, 85 ℃
A test was conducted in which the semiconductor device was left in a constant temperature bath of / 85% relative humidity to absorb moisture, and then immersed in a solder melt at 260 ° C. for 10 seconds. The results are shown in Table 1 below.

[0020]

[Table 1]

From Table 1 above, it can be seen that the semiconductor devices of Examples 1 and 2 had almost no cracks in the TCT test, and few cracks even when the solder melt was dipped. On the other hand, the semiconductor device of the comparative example was inferior in reliability because many cracks were generated during the TCT test and the immersion of the solder melt.

Further, recording layers were formed on the semiconductor devices of Examples 1 and 2 by using a polyimide photosensitive resin, and light was irradiated by a UV exposure method using a mask film to record individual identification information. At this time, the surface of the aluminum foil had a glossiness (JIS Z8741) of 100% and a surface roughness of 0.25 μm. This example product 1
The semiconductor devices of 2 and 2 were able to accurately recognize the individual identification information.

[Brief description of drawings]

FIG. 1 is a perspective view showing the appearance of an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing an embodiment of the present invention.

FIG. 3 is a schematic sectional view showing another embodiment of the present invention.

FIG. 4 is a schematic sectional view showing still another embodiment of the present invention.

[Explanation of symbols]

 1 ... Plastic package 2 ... Metal foil 3 ... Semiconductor element 4 ... Lead frame 5 ... Adhesive layer for adhering metal foil to package 6 ... Adhesive layer for temporarily fixing metal foil to inner surface of mold

Claims (4)

[Claims] 1. A semiconductor device in which a semiconductor element is sealed with a plastic package, wherein the surface of the plastic package is covered with a metal foil. 2. The semiconductor device according to claim 1, wherein the metal foil is a metal foil on which individual identification information is recorded. 3. The metal foil material according to claim 2, wherein the individual identification information is stored in a photosensitive resin. 4. The semiconductor device according to claim 1, wherein the metal foil has the following characteristic (A) or characteristic (B). (A) The glossiness of the metal foil surface is in the range of 70 to 250% according to JIS Z8741. (B) The average surface roughness is 0.1 to 10 μm.