JP2537868B2 - Resin-sealed semiconductor device - Google Patents

Description

The present invention relates to a resin-encapsulated semiconductor device having excellent reliability after solder immersion.

[Conventional technology]

Conventionally, as a resin-encapsulated semiconductor device in which semiconductor elements such as transistors, ICs, and LSIs are protected by a plastic package, a dual-in-line package (DIP) type in which a pin is inserted into a printed circuit board for mounting is a prize. Has been done.

However, in recent years, with the flow of development of small high-performance products such as wristwatches, calculators, VTR cameras, etc., high density mounting and thinning of semiconductor devices are required, and so-called flat package type surface mounting type semiconductor devices have been developed. It is becoming popular.

The surface-mount type semiconductor device is not one in which only the lead pins are partially solder-immersed as in the conventional DIP type, but usually the whole semiconductor device is immersed in a solder bath at 200 ° C. or higher, or an infrared heating method. After heating the entire semiconductor device by the vapor phase method or the like, the semiconductor device is mounted by being connected and fixed to a printed circuit board.

[Problems to be solved by the invention]

However, when the entire semiconductor device is immersed in the solder bath as described above, the semiconductor device undergoes a rapid temperature change from room temperature to 200 ° C. or higher, so that a thermal shock causes a package crack or a lead crack. A gap is created between the frame and the sealing resin, and the moisture resistance of the package is impaired.

Therefore, it has been strongly desired to improve the moisture resistance of the package so as to meet the demands for thinning and high-density mounting of the semiconductor device.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a resin-encapsulated semiconductor device having excellent moisture resistance after solder immersion.

[Means for solving problems]

In order to achieve the above object, the resin-sealed semiconductor device of the present invention is a resin-sealed semiconductor device in which a semiconductor element is attached to a lead frame and sealed with a resin composition. The lead frame is surface-treated with a water-repellent wax. The "surface in the surface treatment of the semiconductor element and the lead frame" is intended to include not only the literal surface but also the entire outer surface such as the back surface and the side surface. The lead frame includes a die bond plate (die pad) that supports the semiconductor element. The material of the lead frame may be any material such as copper or alloy (42 alloy), and any kind of plating may be applied.

That is, the inventors of the present invention first conducted research to elucidate the factors that reduce the moisture resistance of the package in order to improve the moisture resistance of the resin-sealed semiconductor device after immersion in solder. As a result, the water absorbed in the semiconductor device during the manufacturing process of the semiconductor device or the storage process after commercialization is mainly retained at the interface between the semiconductor element, the lead frame and the sealing resin. High temperature during immersion (200 ℃ or more)
Rapidly evaporates to high-pressure vapor, which creates a gap at the interface between the semiconductor element and the lead frame and the encapsulating resin, or creates a crack in the package, which makes it difficult to mount on the board. In addition, it was found that the moisture resistance of the package after dipping the solder deteriorates.

Therefore, as a result of further series of studies on the method of removing the water staying in the semiconductor device or the method of preventing the moisture absorption in advance, the present inventors have determined that the semiconductor element and the lead frame have a specific water-repellent wax. It has been found that when the surface treatment is made to be water-repellent, moisture does not enter the interface between the semiconductor element and the encapsulating resin, and the moisture resistance after solder immersion is greatly improved, and the present invention was reached.

The resin-sealed semiconductor device of the present invention comprises a semiconductor element and a lead frame whose surface is surface-treated with a specific water-repellent wax, and a resin composition for sealing the semiconductor element and the lead frame.

The water-repellent wax is not particularly limited as long as it has good wettability with respect to the semiconductor element and the lead frame and exhibits water-repellent property against water. However, a preferable one is that the contact angle with respect to the semiconductor element and the lead frame is 50 ° or less at a high temperature of about 175 ° C., and the contact angle with water at room temperature is 90 ° or more. By using the water repellent wax having such characteristics, the package crack and the moisture resistance after the solder immersion can be significantly improved.

Typical examples of the water-repellent waxes include higher fatty acid type, higher fatty acid ester type, higher fatty acid metal salt type, hydrocarbon type, acid amide type and the like. These water-repellent waxes may be used alone or in combination. In particular, among the water-repellent waxes exemplified above, higher fatty acid-based ones having 10 to 25 carbon atoms, higher fatty acid ester-based ones having 20 to 45 carbon atoms, and higher fatty acid metal chlorine having 10 to 45 carbon atoms It is preferable to use those having 35 to 350 carbon atoms, and those having 10 to 110 carbon atoms and amides.

Further, the resin composition used in the present invention is obtained by using a thermosetting resin, a curing agent, a filler, a pigment, etc., and is usually in the form of powder or a tablet formed by tableting. .

An epoxy resin is preferably used as the thermosetting resin, but a phenol resin, a urea resin, a melamine resin, a polyester resin, a diacrylic phthalate resin, a polyphenylene sulfide, or the like may be used as the whole or a part of the epoxy resin. It can be used instead.

As the epoxy resin, any known one such as glycidyl ether type epoxy resin such as bisphenol A type, phenol novolak type, cresol novolak type, alicyclic epoxy resin, halogenated epoxy resin may be used. It is particularly preferable to use a phenol novolac or cresol novolak type epoxy resin.
Furthermore, among these epoxy resins, the chlorine ion content is 10 ppm or less, and the content of hydrolyzable chlorine is 0.1 ppm.
A material having a weight% (hereinafter abbreviated as “%”) or less is suitable.

Examples of the curing agent for the epoxy resin include novolak type phenol resin (phenol novolac, cresol novolac, etc.), acid anhydride type curing agent (tetrahydrophthalic anhydride, trimellitic anhydride, benzophenone tetracarboxylic acid anhydride, etc.) , Amines (diaminodiphenylmethane, metaphenylenediamine, diaminodiphenyl ether, etc.) and the like are used. In particular, it is obtained by reacting a phenol resin, one or more of phenol, cresol, xylenol, resorcinol, phenylphenol, bisphenol A and the like with formaldehyde, paraformaldehyde and the like in the presence of an acid catalyst. Those are preferable. These curing agents are preferably blended in the range of 0.5 to 1.0 equivalent with respect to 1 equivalent of the thermosetting resin.

Further, together with the above curing agent, 2-ethyl-4-methylimidazole, 2-heptadecylimidazole, and a heterocyclic imidazole compound such as 2-methylimidazole,
A curing accelerator such as 1,8-diazabicyclo (5,4,0) undecene-7 and a salt thereof, or an organic tertiary phosphine compound such as triphenylphosphine may be added.

In addition, the above composition may contain conventionally used inorganic fillers, flame retardants, release agents, pigments and the like, if necessary.

The resin composition used in the present invention can be produced using the above-mentioned raw materials, for example, as follows.
That is, the above-exemplified resin and curing agent, pigments and other additives are appropriately blended, and the blended mixture is kneaded in a kneading machine such as a mixing roll machine in a heated state to give a semi-cured resin composition. Is cooled to room temperature, pulverized by a known means, and then tableted as it is or if necessary, to produce a tablet.

The resin-encapsulated semiconductor device of the present invention can be manufactured, for example, as follows using the resin composition as described above and the water-repellent wax. That is, first, the semiconductor element to be sealed is sprayed with the water-repellent wax, sprayed, or the semiconductor element and the lead frame are immersed in the water-repellent wax for surface treatment, and the surface of the semiconductor element and the lead frame is thickened. A wax layer having a thickness of several μm to several tens μm is formed. This wax layer is preferably formed on the entire surfaces of the semiconductor element and the lead frame, but this is not essential. It may be partially formed. Next, the semiconductor element thus surface-treated can be obtained by sealing with the above resin composition. The sealing of the semiconductor element is not particularly limited, and can be performed by an ordinary method, for example, a known molding method such as transfer molding.

The resin-encapsulated semiconductor device thus obtained has the semiconductor element and the lead frame surface modified to be water-repellent by the wax surface treatment before resin encapsulation. Water does not enter the interface between the lead frame and the sealing resin. Therefore, when the semiconductor device is dipped in solder, high-pressure steam is not generated at the interface between the semiconductor element and the lead frame and the sealing resin, and no gap is created at the interface.

〔The invention's effect〕

As described above, the resin-encapsulated semiconductor device of the present invention uses the special semiconductor element and the lead frame whose surface is treated with the water-repellent wax and modified to be water-repellent. Water does not enter from the interface with the sealing resin. Therefore, the package crack does not occur even after the solder dipping, and the moisture resistance does not decrease, so that the reliability is extremely high. In particular, by treating both the semiconductor element and the lead frame with a water-repellent wax in this way, not only a small package such as an 8-pin SOP (two-way flat package)
Pin 9FP (4-way flat package) or 68-pin PLCC
For a large package such as (chip carrier with plastic lead), it is possible to obtain the effect that it is possible to completely prevent the package crack from occurring in the sealing resin part on the back side of the die bond plate. .

According to the present invention, moisture does not enter the interface between the semiconductor element and the lead frame and the encapsulating resin, so that even if applied to any type of semiconductor device, a certain effect of improving moisture resistance can be obtained. However, the package crack after solder immersion, which has been a problem in the past when applied to a surface mount type semiconductor device,
It can be said that it is suitable because it eliminates the decrease in moisture resistance.

 Next, examples will be described together with comparative examples.

[Examples 1 to 4] A linear IC was prepared as a semiconductor element, and the surface of the semiconductor element and the lead frame were sprayed with a water-repellent wax shown in Table 1 below to form a wax layer having a thickness shown in the same table. Formed.

As shown in Table 1, the surface-treated semiconductor element and the lead frame have good wettability with the semiconductor element and the lead frame at high temperature and exhibit water repellency at room temperature.

Next, the semiconductor element and the lead frame surface-treated with the water-repellent wax were resin-sealed with an epoxy resin composition produced by a usual method using the raw materials shown in Table 2 below, and then 80 pink wax It was a dflat (80-pin QFP) type resin-sealed semiconductor device.

[Comparative Examples 1 and 2] An 80-pin QFP type resin-sealed semiconductor device was obtained in the same manner as in the example, but in comparative example 1, the semiconductor element and the lead frame were not subjected to surface treatment with a water-repellent wax. In Comparative Example 2, only the semiconductor element was wax treated.

The example product and comparative example product thus obtained were
Put it in the atmosphere of ℃, 85% RH for 72 hours to absorb the moisture, then 2
It was immersed in a solder bath at 60 ° C for 10 seconds. Then, the presence or absence of cracks after solder immersion was checked, and a reliability test (PCT test at 121 ° C, 100% RH) was performed using a pressurizing pot. The results are shown in Table 3 below.

From the above results, it can be seen that the product of Example did not cause cracking at all after immersion in solder and the PCT test performance was significantly superior to that of the product of Comparative Example.

That is, it can be seen that, unlike the comparative example product, the example product is extremely excellent in moisture resistance even after the solder immersion, because the surface treatment is performed with the water-repellent wax.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideto Suzuki 1-2 1-2 Shimohozumi, Ibaraki Nitto Electric Industry Co., Ltd. (56) Reference JP-A-56-27941 (JP, A) JP-A-SHO 59-107547 (JP, A) JP 59-219948 (JP, A)

Claims (3)

(57) [Claims] 1. A resin-sealed semiconductor device in which a semiconductor element is attached to a lead frame and sealed with a resin composition, wherein the semiconductor element and the lead frame are surface-treated with a water-repellent wax. A resin-encapsulated semiconductor device characterized in that 2. A water repellent wax at a high contact temperature of about 175 ° C. with respect to a semiconductor element and a lead frame.
The resin-encapsulated semiconductor device according to claim 1, wherein the contact angle with water at room temperature is 0 ° or less and 90 ° or more. 3. The water-repellent wax is at least one water-repellent wax selected from the group consisting of higher fatty acid type, higher fatty acid ester type, higher fatty acid metal salt type, hydrocarbon type and acid amide type. A resin-sealed semiconductor device according to claim 1.