JPH01138738A - Resin-sealed semiconductor device - Google Patents

Abstract

PURPOSE:To prevent any water content from permeating into the interface between a lead frame and a sealing resin by a method wherein the water repellency and the bond properties of the applicable lead frame are improved by processing the lead frame with specific butadien base rubber material. CONSTITUTION:The surface of a lead frame is covered with a specific butadien base rubber material represented by a general formula to be cover-processed. [R represents carboxyl group or amino group, x represents integers of 20-100, y represents integers of 0-100 and z represents integers of 1-200]. If z is specified to exceed 1, the bond properties of the lead frame to a sealing resin can be improved by the reaction of a functional group in the butadien base rubber material to an epoxy group in the sealing material so that any water content may be prevented from permeating into the interface between the lead frame and the sealing material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin-sealed semiconductor device that has excellent reliability after being dipped in solder.

[Conventional technology]

Traditionally, awards have been given to dual in-line package (DIP) type resin-sealed semiconductor devices in which semiconductor elements such as transistors, ICs, and LSIs are protected in plastic packages, and are mounted by inserting pins into printed circuit boards. has been done.

However, in recent years, with the trend of developing small and highly functional products such as wristwatches, calculators, and VTR cameras, there has been a demand for higher density packaging and thinner semiconductor devices. It is becoming widely used.

The above-mentioned surface mount type semiconductor device is not one in which only the lead pins are partially immersed in solder as in the conventional DIP type device, but the entire semiconductor device is usually immersed in a solder bath at 260"C and then connected to a printed circuit board. , which is implemented by fixing it.

[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 sudden temperature change from room temperature to 260°C, and the lead frame is damaged due to thermal shock. A gap is created between the sealing resin and the sealing resin, and the moisture resistance of the package is impaired.

Therefore, in order to meet the demands for thinner semiconductor devices and higher density packaging, it has been strongly desired to improve the moisture resistance of the package.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a resin-sealed semiconductor device that has excellent moisture resistance after being immersed in solder.

[Means for solving problems]

In order to achieve the above object, a 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, wherein the surface of the lead frame is The structure is such that it is coated with a butadiene-based rubber material represented by the following formula (1).

(Margin) [Function] That is, in order to improve the moisture resistance of resin-sealed semiconductor devices after being immersed in solder, the present inventors first conducted research to clarify the factors that reduce the moisture resistance of the package. Ta. As a result, moisture absorbed into semiconductor devices during the semiconductor device manufacturing process or post-commercial storage process remains mainly at the interface between the lead frame and the encapsulating resin, and this moisture is absorbed by the high temperature during solder dipping. (at temperatures above 240°C), it evaporates rapidly and becomes high-pressure steam, creating gaps at the interface between the lead frame and the sealing resin and cracks in the package. It was found that it lowers sex.

Therefore, the inventors of the present invention conducted a series of further studies on methods for removing moisture remaining in the semiconductor device or methods for preventing moisture absorption in advance. When treated, the lead frame significantly improves adhesion to the sealing resin due to the reaction between the functional groups in the butadiene rubber material and the epoxy groups in the sealing resin, thereby improving the bond between the lead frame and the sealing resin. The inventors have discovered that moisture infiltration into the interface can be prevented and the moisture resistance after solder immersion can be improved, and this invention has been achieved. In addition,
The lead frame in this invention includes a die pad (die bond plate) for mounting and supporting a semiconductor element.

The above-mentioned butadiene-based rubber material has the following general formula (1
) is used.

The butadiene rubber material represented by the above general formula (1) must have a carboxyl group or an amino group that exhibits reactivity with epoxy groups in its molecular structure,
Therefore, in equation (1), 2 is always set to 1 or more. X is an integer of 20 to 100, preferably 30 to 70
It is preferable from the viewpoint of effectiveness that y is an integer of 0 to 100, preferably an integer of 5 to 20, and 2 is an integer of 1 to 200, preferably an integer of 1 to 50. In the butadiene rubber material in the above general formula (1), the repeating units corresponding to the repeating number X and the repeating units corresponding to the repeating number y may be random or alternate, or There is no problem even if it is locked.

Butadiene rubber materials such as those mentioned above must be heated to 250°C when touched.
The viscosity is 200 to 2000 voids, and typical examples include the following.

The above-exemplified butadiene-based rubber materials may be used alone or in combination without any problem.

By using the above-mentioned butadiene-based rubber material, lead frames can be easily formed due to the water repellency of the butadiene-based rubber material itself and the reactivity of the functional groups in its molecular structure to the epoxy groups in the sealing resin. At the same time, the lead frame becomes water repellent and its adhesion to the sealing resin is significantly improved, making it possible to prevent moisture from entering the interface between the lead frame and the sealing resin.

The resin composition used for sealing the semiconductor element attached to the surface-treated lead frame as described above includes a thermosetting resin, a curing agent, a filler, and more! It is obtained using i-preparation, etc., and is usually in the form of a powder or a tablet formed by compressing it.

As the thermosetting resin, epoxy resins are preferably used, including phenol resins and urea resins.

Melamine resin, polyester resin, diallyl phthalate resin, polyphenylene sulfide, etc. can be used in place of all or part of the above epoxy resin.

Bisphenol A type epoxy resin.

Any known epoxy resins such as glycidyl ether type epoxy resins such as phenol novolac type and cresol novolac type, alicyclic epoxy resins, and halogenated epoxy resins may be used. Preferred for use. Further, among these epoxy resins, those having a chlorine ion content of 10 pp11 or less and a hydrolyzable chlorine content of 0.1% by weight (hereinafter abbreviated as "%") or less are suitable.

Examples of hardening agents for the above epoxy resins include novolac type phenolic resins (phenol novolac, talesol novolac, etc.), acid anhydride hardening agents (tetrahydrophthalic anhydride, trimellitic anhydride, benzophenone tetracarboxylic anhydride, etc.), and amines. (diaminodiphenylmethane,
metaphenylene diamine, diaminodiphenyl ether, etc.) are used. In particular, phenolic resins such as phenol, cresol, xynol, resorcinol,
Preferred are those obtained by reacting one or more of phenylphenol, bisphenol A, etc. with formaldehyde, paraformaldehyde, etc. in the presence of an acid catalyst. These curing agents are preferably blended in an amount of 0.5 to 1.0 equivalents per equivalent of the thermosetting resin.

Furthermore, in addition to the above-mentioned curing agent, heterozygous imidazole compounds such as 2-ethyl-4=methylimidazole, 92-heptadecyl imidazole, and 2-methylimidazole, and 1,8-diaza-bicyclo(5,4,O) undecene A curing accelerator such as -7 and its salt, an organic tertiary phosphine compound such as triphenylphosphine, etc. can also be blended.

In addition, the above-mentioned composition may contain conventionally used flame retardants, mold release agents, etc., if necessary.

The resin composition used in the present invention can be produced using the above-mentioned raw materials, for example, in the following manner. That is, the resin exemplified above, a curing agent, pigment, and other additives are appropriately blended, and this mixture is kneaded in a heated state using a kneading machine such as a mixing roll machine to form a semi-cured resin composition, which is then heated at room temperature. It can be produced by cooling it to a temperature, pulverizing it by known means, and then tableting it as it is or if necessary.

The resin-sealed semiconductor device of the present invention can be manufactured using the resin composition as described above and the butadiene-based rubber material, for example, in the following manner. That is, first, the butadiene-based rubber material is sprayed onto the lead frame to be sealed.

It can be obtained by treating the lead frame by spraying or immersing it in a butadiene-based rubber material, attaching a semiconductor element to the lead frame, and sealing it with the resin composition. Good results can be obtained when the lead frame is treated with the butadiene rubber material, especially when the die pad of the lead frame is treated. The above-mentioned sealing is not particularly limited, and can be performed by a conventional method, for example, a known molding method such as transfer molding.

In the resin-sealed semiconductor device obtained in this way, the bottom surface of the die pad that comes into direct contact with the lead frame, especially the sealing resin, is reduced by treating the butadiene-based rubber material before resin sealing.
Since it has been modified to have high hydrophobicity and adhesion, moisture will not infiltrate from the lead frame, especially the interface between the bottom surface of the die pad and the sealing resin. Therefore, at the interface between the lead frame and the encapsulating resin when immersing the semiconductor device in solder,
No high-pressure steam is generated, no gaps are formed at the interface, and no cracks occur in the package. It should be noted that the treatment of the butadiene-based rubber material on the lead frame is preferably carried out mainly on the lower surface of the die pad, since this area has a large contact area with the sealing resin, as mentioned above. It is preferable to apply the above-mentioned butadiene-based rubber material treatment to the parts of the lead frame that come into direct contact with the sealing resin, such as the roots of the leads. In this case, if the butadiene-based rubber material is treated by spraying, etc., the butadiene-based rubber material may be applied to parts of the lead frame other than the parts that come into direct contact with the sealing resin, such as the tips of the leads. Although the phenomenon of the rubber material adhering occurs, there is no problem at all even if this happens.

〔Effect of the invention〕

As described above, the resin-sealed semiconductor device of the present invention uses a special lead frame that has been treated with a butadiene-based rubber material to improve water clarity and adhesion. Moisture does not enter through the interface with the solder, and moisture resistance does not decrease even after soldering, making it extremely reliable.

Note that the resin-sealed semiconductor device of the present invention does not allow moisture to enter the interface between the lead frame and the sealing resin.
Although it can have a certain effect of improving moisture resistance when applied to any type of semiconductor device, it is particularly difficult to apply it to surface-mounted semiconductor devices, which has traditionally been a problem. This can be said to be suitable because it eliminates the decrease in moisture resistance after immersion.

Next, examples will be described together with comparative examples.

[Examples 1 to B] A 16-pin copper frame (4270I) for linear IC was prepared as a lead frame, and a butadiene-based rubber represented by the following general 2N) and in accordance with Table 1 below was coated on the surface of the frame. Surface treatment was performed by spraying a diluted solution prepared by diluting the material 10 times with toluene.

(Left below) Next, the lead frame surface-treated as described above was heated at 175°C for 2 hours using the raw materials shown in Table 2 below.
Transfer molding was performed under the conditions of 10 minutes to obtain an 8-pin small outline (SOP-8) type resin-sealed semiconductor device.

[Comparative Example 1] In place of the above butadiene rubber material, the following general formula C
A butadiene-based rubber material having no functional group represented by I (margin) was used. Other than that, a resin-sealed semiconductor device was obtained in the same manner as in the above example.

(Comparative Example 2) A resin-sealed semiconductor device was obtained in the same manner as in the above example except that the lead frame was not subjected to surface treatment with a butadiene-based rubber material.

The comparison height measurement with the actual product obtained in this way was carried out at 80°C.
After being placed in a 95% RH atmosphere for 20 hours to absorb moisture, it was immersed in a 260°C solder bath for 10 seconds. and,
In addition to checking for the presence of cracks after solder immersion, reliability tests were conducted using a pressure cooker (121°C, ioo%R1).
1 PCT test) was conducted. The results are shown in the third section below.
As shown in the table.

(Hereinafter in the margin) Table 11 L-1 From the above results, it can be seen that the sample according to the implementation is significantly superior in moisture resistance after being immersed in solder, compared to the comparative height measurement sample.

In other words, unlike the comparative height measurement products, the surface treatment of the special measurement products is made with a butadiene-based rubber material that has a functional group that can react with epoxy resins and phenolic resins, making them extremely moisture resistant even after being immersed in solder. It can be seen that it is excellent; Patent applicant: Nitto Electric Industry Co., Ltd. Agent, Patent attorney: Yukihiko Nishifuji

Claims (1)

[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 surface of the lead frame is made of a butadiene-based rubber material represented by the following formula [I]. A resin-sealed semiconductor device characterized by being coated with. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・[I] In formula [I], R is a carboxyl group or an amino group, x is an integer from 20 to 100, y is an integer from 0 to 100, z is an integer from 1 to 200.