JP2902013B2 - Porous electronic parts molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a molded article for electronic parts having excellent moisture resistance and solder heat resistance, and more specifically, polyarylene sulfide (hereinafter abbreviated as PAS) resin. An electronic component encapsulation molded product obtained by encapsulation molding with a composition, since the resin portion has independent pores, especially when the lead frame portion of the encapsulation molded product is immersed in a solder bath. The present invention relates to a molded article of a porous electronic component which is free from interfacial peeling and stress cracking (crack) between the resin and a resin portion and therefore has excellent moisture resistance.

<Conventional technology> Electronic components, such as capacitors, diodes, transistors, ICs, and LSIs, are synthesized for the purpose of maintaining electrical insulation, preventing changes in characteristics due to the external atmosphere, and improving productivity and cost. Sealing with resin is widely performed.

Conventionally, as a synthetic resin for sealing, a thermosetting resin such as an epoxy resin or a silicone resin has been used.However, it takes a long time for thermosetting and a long molding cycle, and is used to prevent the progress of curing. It has been pointed out that the method of preserving the resin is not easy and that the spool and the runner cannot be reused.

Therefore, in recent years, a resin composition mainly composed of PAS resin, which is a thermoplastic resin excellent in heat resistance, flame retardancy, electrical properties, etc., particularly, polyphenylene sulfide (hereinafter abbreviated as PPS) resin, which is a typical resin, It has been proposed to use the product as a resin composition for sealing electronic components (for example, Japanese Patent Publication No. 56-9014, Japanese Patent Application Laid-Open No. 57-21844, Japanese Patent Application Laid-Open No. 57-40557).
No., JP-A-59-20910, JP-A-59-20911, JP-B-60-4
0188, JP-A-62-65351, JP-A-62-197451).

However, when sealing with the PAS resin composition, P
AS resin has poor adhesion to the lead frame or bonding wire of electronic components, so when placed in a high humidity atmosphere, moisture easily penetrates from the interface between the sealing resin part and the lead frame, etc., resulting in electrical insulation. This has the drawback of causing deterioration in electrical properties, corrosion of lead frames and wires, and the like, and lowering the electrical characteristics of electronic components.

Electronic components formed by resin sealing are required to be particularly excellent in moisture resistance. However, the improvement effect in this regard is still insufficient with electronic component sealed moldings made of resin compositions so far. This was an important issue to be solved above.

<Problems to be Solved by the Invention> An object of the present invention is to obtain a molded article for electronic parts which has good heat resistance, electrical characteristics and moldability, and is particularly excellent in moisture resistance.

The present inventors have intensively studied to solve the problems of the prior art. The cause of the poor moisture resistance of the electronic component-sealed molded product sealed with the PAS resin composition is not only the poor adhesion between the PAS resin and the electronic component such as a lead frame, but also the resin portion and the lead frame. Interfacial delamination and cracks are caused by differences in linear expansion coefficients.Such interface delaminations and cracks are caused not only by thermal changes during immersion in a solder bath, but also by mechanical stress and shrinkage strain during sealing molding. For example, attention was paid to the generation of stress inside the molded product, particularly the concentration of stress at the interface between the resin portion and the lead frame.

Increasing the amount of the inorganic filler is an effective method for reducing the difference in linear expansion coefficient between the resin part and the lead frame, etc., in order to eliminate the relatively large shrinkage strain during solidification and crystallization of the PAS resin, which is a crystalline resin. Is effective, but the adhesion to the lead frame is reduced and there is nothing to be seen in improving the moisture resistance. Further, there is a disadvantage that the degree of the adverse effect of bending the bonding wire is increased.

The present inventors have further studied by focusing on shrinkage strain during solidification crystal when using PAS resin, and conventionally, it has been found that the adhesion between the sealing resin and the electronic component is improved, In order to prevent voids from being formed, the sealing resin composition was filled in a mold at a high pressure and subjected to sealing molding to obtain a sealing molded product without sink marks and voids. In addition, by positively providing pores in the resin portion of the electronic component sealing molded product, the sealing molded product absorbs shrinkage strain, thermal stress, and the like by generating the pores,
As a result, the stress at the interface between the resin portion and the lead frame is reduced, the separation of the interface between the resin portion and the lead frame and the occurrence of cracks, and the moisture and moisture from the separated portion and the crack at the interface are reduced. We found that invasion could be prevented.

In this case, the pores are independent and do not communicate with each other, and the pores are not substantially present in the surface layer of the molded product. It has been found that the pores need to be distributed. This is because PAS resin itself does not have the hygroscopic property of epoxy resin which is a thermosetting resin, and even if pores are formed, if they are independent pores and are not substantially present in the surface layer of the molded product, moisture will not be absorbed. And withstand moisture ingress.

Further, in order to generate the above-mentioned pores and to have excellent heat resistance and solder heat resistance, a PAS resin composition having a specific molding shrinkage rate is used, and the maximum pore diameter and the porosity of the pores (occupied by the pores) Volume%) to a specific range.

The present invention has been completed based on these findings.

<Means for Solving the Problems> That is, the gist of the present invention is to provide an electronic component having a molding shrinkage rate.
An electronic component encapsulation molded product obtained by encapsulation molding with a 0.2 to 0.8% PAS resin composition, wherein the resin portion of the molded product has a maximum pore size.
A molded article of a porous electronic component, characterized in that closed pores of 50 to 300 μm are present at a ratio of 1 to 5% by volume and a surface layer of the molded article is dense.

 Hereinafter, each component of the present invention will be described in detail.

(PAS resin composition) The PAS resin composition used in the present invention needs to have a molding shrinkage of 0.2 to 0.8% under the conditions described below. Here, the molding shrinkage refers to shrinkage that occurs while the size of a molded product is taken out of a mold and cooled to room temperature.

A composition having a molding shrinkage of less than 0.2% can be obtained by increasing the amount of the inorganic filler to be filled, but the melt viscosity increases and molding processability is poor. Conversely, if the content exceeds 0.8%, it becomes difficult to provide the target pores in the sealed molded product, and the molded product is liable to sink.

Such a PAS resin composition can be prepared by mixing a PAS resin, an inorganic filler, a heat-resistant oil, and the like.

PAS Resin The PAS resin used in the present invention is a p-phenylene sulfide repeating unit as a main structural unit of the polymer. Is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 90% by weight or more, and preferably has a substantially linear structure.

PAS having such a structure is a polymer obtained from a monomer mainly composed of a bifunctional monomer. However, PAS having a slight cross-linked or branched structure introduced by copolymerizing a polyhalobenzene such as trichlorobenzene as a small component can also be used within a range that does not impair the object of the present invention.

Corresponding to the proportion of the p-phenylene sulfide repeating unit being 50% by weight or more, the copolymer may contain another copolymer repeating unit of less than 50% by weight. Examples of such a structural unit include an m-phenylene sulfide unit, a diphenyl sulfone sulfide unit, a diphenyl sulfide unit,
There are a diphenyl ether sulfide unit and a 2,6-naphthalene sulfide unit. Further, a block copolymer composed of 70 to 95% by weight of a p-phenylene sulfide repeating unit and 5 to 30% by weight of a m-phenylene sulfide repeating unit is also preferably used.

As described in JP-A-61-7332, such a PAS resin is prepared by combining an alkali metal sulfide and a dihalo aromatic compound in an organic amide solvent such as N-methylpyrrolidone in the presence of water. It can be suitably obtained by a specific two-step temperature raising polymerization method.

Inorganic filler As the inorganic filler that can be used in the present invention, silica, alumina, talc, mica, kaolin, clay, silica alumina, titanium oxide, calcium carbonate, calcium silicate, calcium phosphate, calcium sulfate, magnesium carbonate, magnesium oxide, Granular, spherical, or powdery fillers such as magnesium phosphate, silicon nitride, glass, hydrotalcite, and zirconia; and fibrous fillers such as glass fibers, potassium titanate fibers, and mica ceramic fibers.

These inorganic fillers can be used alone or in combination of two or more.

Heat resistant oil Examples of the heat resistant oil that can be used in the present invention include monoisopropyl biphenyl, diisopropyl biphenyl, diisopropyl naphthalene, and silicone oil. Each of these heat-resistant oils can be used alone or in combination.
More than one species can be used in combination.

The viscosity of the heat-resistant oil is not particularly limited, but usually,
Those with 10 to 10,000 centistokes (25 ° C.) are preferred.

Composition ratio The preferred composition ratio for preparing the PAS resin composition of the present invention is such that the inorganic filler is 6 to 40 to 40% by weight of the PAS resin.
The amount of the heat-resistant oil is from 1.5 to 5 parts by weight based on 100 parts by weight of the total of the PAS resin and the inorganic filler.

If the compounding ratio of the inorganic filler is too small, the molding shrinkage of the resin composition becomes large, and the linear expansion coefficient becomes large, so that sink is likely to occur and the moisture resistance is poor. Conversely, if the mixing ratio of the inorganic filler is too large, the viscosity of the resin composition increases, resulting in poor moldability.

If the compounding ratio of the heat-resistant oil is too small, the moisture resistance is inferior due to poor adhesion between the resin portion and the lead frame, and if it is too large, the mechanical strength of the molded product decreases, and bleeding occurs. Not preferred.

The melt viscosity of the PAS resin composition used in the present invention is not particularly limited, but is preferably 50 to 400 poise (measured at 310 ° C. and a shear rate of 10,000 sec ⁻¹ ).

In addition, a small amount of an additive such as a pigment may be added to the resin composition.

(Porous Electronic Component Encapsulation Molded Product) In the porous electronic component encapsulation molded product of the present invention, the proportion of independent pores having a maximum pore diameter of 50 to 300 μm in the resin portion of the molded product is 1 to 5% by volume (porosity). Exists, and the surface layer of the molded product is dense. Due to the presence of the pores, concentration of stress estimated to be caused by thermal, mechanical or molding shrinkage strain,
Above all, the concentration of stress at the interface between the resin portion inside the sealing molded product and the sealed electronic component such as the lead frame is reduced, thereby preventing the separation of the interface between the resin portion and the lead frame and the occurrence of cracks, Moisture resistance can be improved. The molded article for sealing a porous electronic component of the present invention is particularly excellent in moisture resistance after being immersed in a solder bath.

The pores are mainly present in the resin portion around the element of the sealed electronic component such as the lead frame in the molded product, and are not substantially present in the surface layer of the molded product. Therefore, the porosity of the surface layer is different from that of the element periphery, and the porosity of the surface layer is 0 at most.
About 0.5% by volume. Therefore, the surface layer is dense, and the moisture resistance through the resin layer is sufficiently maintained.

The surface layer varies depending on the shape, size and the like of the sealing molded product, but is about 0.7 mm.

In addition, the pores need to be present independently of each other, and must not communicate with each other. If there are communicating pores, moisture and moisture enter and the moisture resistance deteriorates.

Further, each pore needs to have a maximum pore diameter in the range of 50 to 300 μm. If the maximum pore diameter is less than 50 μm, the effect of lowering the stress at the interface between the sealed electronic component and the element is not sufficient, and the peeling of the interface between the resin portion and the lead frame causes cracks, resulting in poor moisture resistance. The maximum hole diameter is
If it is 300 μm or more, sinks are generated in the molded product, which is not preferable.

The porosity needs to be 1 to 5% by volume, and preferably 1.5 to 4% by volume. The porosity around the element such as a sealed lead frame (excluding the molded article surface layer) is preferably in the range of 2 to 15% by volume. If the porosity is too small, the effect of alleviating stress concentration on the interface between the resin portion and the lead frame or the like is small. Conversely, if the porosity is too large, sinks occur, which is not preferable.

The formation state, shape, and pore size of the pores are determined by sealing the molded electronic parts obtained by sealing molding with a soft X-ray device (HITEX Co., Ltd.).
It can be measured and observed by taking an X-ray photograph from the top, side, bottom and other directions under the conditions of 80 kV and 2.5 mA using TYPE HP-100).

In addition, by slicing an electronic component encapsulant obtained by encapsulation and taking an electron micrograph, it is possible to confirm in detail the shape of the pores, the pore diameter, and the state of the surface layer of the encapsulant.

The volume% of the pores (porosity) is obtained by
Approximately halved from the sealed lead frame, etc., and the specific gravity of the part without the lead frame, etc., was measured with the density gradient piping method (methanol / acetone mixed system, 25 ° C) and calculated as (a). From the true specific gravity obtained from the values (the specific gravity calculated from the specific gravity and the composition ratio of each component of the resin composition with the porosity set to zero), the volume% of the pores (porosity) = [1−actual value (a) / True specific gravity] × 100.

In addition, the porosity (volume%) around the sealed element is 0.
The specific gravity of the portion shaved off with a file of about 7 mm was calculated from the actually measured value (b) actually measured by the above-described method using the above-described formula.

On the other hand, the porosity (volume%) of the surface layer is a volume (A) which is the volume of a sample whose specific gravity is actually measured in order to calculate the porosity (volume) of the above pores and the porosity (volume%) around the element.
And the volume (B) were measured, and the porosity of the surface layer was determined from this value and the measured value (a) and the measured value (b), which were the measured specific gravities, by the following equation.

Porosity (volume%) of surface layer = (1—specific gravity of surface layer / true specific gravity) × 100 (Sealing Molding Method) A preferred sealing molding method in the present invention is a method of sealing and molding an electronic component by injection molding using the resin composition.

The injection molding holding pressure during sealing molding is reduced to a low pressure, and the holding pressure of the injection molding machine is set to 100 to 1300 kg / cm ² , preferably 150 to 70
Set to 0kg / cm ^2. If the holding pressure is less than 100 kg / cm ² , a stable molded product cannot be obtained, and if the pressure exceeds 1300 kg / cm ² , the porosity becomes less than 2% around the element,
As a result, internal stress increases, interface separation between the resin portion and the lead frame and cracks occur, and the moisture resistance decreases.

Usually, the cylinder temperature of the injection molding machine is 280 to 3
Set the mold temperature to 40 ° C and 180-220 ° C.

In order to obtain an electronic part encapsulation molded article having a maximum pore diameter of 50 to 300 μm at a rate of 1 to 5% by volume in the resin portion of the molded article and a dense molded article surface layer, the injection molding holding is particularly necessary. It is important to reduce the pressure to a low pressure, but the conditions for these injection moldings include the composition of the resin composition, the model of the injection molding machine,
Since it changes depending on the size of the mold and the like, it is preferable to set the optimum conditions by trial in advance.

<Examples> Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

[Example 1] Polyphenylene sulfide (PPS manufactured by Kureha Chemical Industry Co., Ltd .; manufactured by the method described in JP-A-61-7332 using only paradichlorobenzene and sodium sulfide as monomers, at 310 ° C and a shear rate of 10,000 sec. Melt viscosity at ^-1
35 parts by weight of 35% by weight and 100 parts by weight of a composition obtained by mixing 65% by weight of silica (fused silica; P-447K manufactured by Nippon Electric Glass Co., Ltd.) and a diisopropyl biphenyl mixture (viscosity of 500 centistokes) as a heat-resistant oil After uniformly mixing using a Henschel mixer at a mixing ratio of 2.5 parts by weight,
Using a twin screw extruder with a screw diameter of 45 mm, the mixture was extruded at a cylinder temperature of 300 ° C. and pelletized.

Using these pellets, Toshiba Machine's injection molding machine IS-25E
Using P-1YV, cylinder temperature 300 ℃, mold temperature 200 ℃,
Encapsulation molding is performed under the conditions of an injection speed of 20 cc / sec and a holding pressure of 200 kg / cm ² , and a T0-92 type transistor molded product (JEDEC standard, T0-9
2; 5.0 mm × 4.5 mm × 4.0 mm).

The surface of the obtained sealed molded product was dense and no pores were observed in the surface layer. No sink marks were observed.

The following methods were used to measure and evaluate the molding shrinkage of the resin composition and the porosity, pore diameter, moisture resistance, and the like of the obtained sealing molded product.

 The results are collectively shown in Table 1.

<Measurement method> Mold shrinkage: Using an injection molding machine IS-75E-2AV manufactured by Toshiba Machine Co., Ltd., a bending test piece (12.7 mm × 12.7 mm × 1) with a cylinder temperature of 300 ° C., a mold temperature of 150 ° C. and a holding pressure of 300 kg / cm ² (3 mm x 127 mm), and the molding shrinkage in the length direction was measured.

Moisture resistance test: Moisture resistance test A method: After the molded article for electronic parts was penetrated into the red ink at 120 ° C. and 2 atm for 24 hours, the permeation degree of the red ink at the interface with the metal was observed.

Moisture resistance test B method: The sealed molded product was placed at 85 ° C and a humidity of 85% for 24 hours, and then immersed in a solder bath at 260 ° C for 10 seconds only for the lead frame portion. After penetration, the degree of penetration was observed and judged.

 Then, the degree of moisture resistance was evaluated on the following three levels.

；: Penetration degree small △: Penetration degree Medium ×: Penetration degree large Mold sink: Light is applied to the flat part of the molded article surface, and the flatness of the molded article surface is visually judged by the reflection. Those with no surface sink were evaluated with ○, and those with many sinks were evaluated with x.

Melt viscosity: Measured at 310 ° C and a shear rate of 10,000 sec ^-1 .

Porosity: The porosity of the sealed molded product is determined by dividing the sealed molded product into two parts having substantially the same size with the lead frame as a boundary, measuring the specific gravity of the part without the lead frame with a density gradient tube, It calculated from the above-mentioned formula using the true specific gravity obtained from the calculation.

Further, the specific gravity around the element was obtained by shaving off the surface layer with about 0.7 mm or a file, and the porosity around the element was obtained from the true specific gravity calculated.

In addition, the porosity of the surface layer was calculated by the above-described method using the measured volume of the specific gravity and the measured value of the specific gravity.

Pores and pore diameters: The sealed molded product was photographed with a soft X-ray device (HITEX TYPE HP-100) at 80 kV and 2.5 mA from the top, side and bottom surfaces, and the photographs were observed to observe pores. The occurrence location, shape and pore diameter were determined.

Example 2 The same resin composition as in Example 1 was used except that the silicone oil (viscosity: 700 centistokes) was used as the heat-resistant oil, and the sealing pressure was similarly set at a holding pressure of 400 kg / cm ² during injection molding. Was obtained and evaluated in the same manner.

Example 3 Using the same resin composition as in Example 2, the holding pressure during injection molding was set to 600 kg / cm ² , and a sealed molded product was obtained in the same manner and evaluated in the same manner.

[Comparative Example 1] Using the same resin composition as in Example 2, the holding pressure during injection molding was set to 2,200 kg / cm ² , and a sealed molded product was obtained in the same manner and evaluated in the same manner.

Comparative Example 2 Using the same resin composition as in Example 2, without applying a holding pressure at the time of injection molding, a sealed molded product was obtained in the same manner and evaluated in the same manner.

[Comparative Example 3] The same resin composition as in Example 2 was used, except that no heat-resistant oil was added, to obtain a sealed molded product in the same manner, and evaluated in the same manner.

[Comparative Example 4] The same resin composition as in Example 2 was used, except that the composition ratio of the PPS resin and silica in the resin composition of Example 2 was changed to 45% by weight and 55% by weight. And evaluated similarly.

 The results are collectively shown in Table 1.

As is clear from Table 1, the molded product of the present invention is:
The molded article has excellent moisture resistance, especially after soldering heat test, and has no sink mark. On the other hand, the sealing molded product of Comparative Example 1 in which the resin composition was densely filled did not generate sink marks in the molded product, but did not sufficiently generate pores and was inferior in moisture resistance after the solder heat test. I have. When the lead frame portion is immersed in the solder bath, peeling or cracks occur at the interface between the resin portion and the lead frame, which causes a decrease in moisture resistance. In addition, the sealed molded product of Comparative Example 2 having a large maximum pore diameter and a large porosity had poor moisture resistance after the soldering heat test, caused sink marks on the molded product surface, and had no commercial value.

On the other hand, Comparative Example 3 using the resin composition to which the heat-resistant oil was not added and Comparative Example 4 in which the molding shrinkage of the resin composition was large were both inferior in moisture resistance, and moreover, the molded product had many sink marks. Obviously, this is not the purpose of the invention.

<Effect of the Invention> According to the present invention, a molded article of an electronic component using a PAS resin composition as a sealing resin and having excellent moisture resistance and solder heat resistance, and particularly excellent in moisture resistance after being immersed in a solder bath. Can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshitaka Kayama 4-2-1-12 Nakaokacho, Iwaki-shi, Fukushima (72) Inventor Yasuo Sakaguchi 1-5 Nukazuka, Nishikicho, Iwaki-shi, Fukushima (72) Inventor Hiromitsu Sakai Shizuoka 885-11 Miyajima, Fuji-shi (72) Inventor Masaki Adachi 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside Toshiba Production Technology Laboratory Co., Ltd. (56) References JP-A-63-258953 (JP, A) JP-A-63 −268740 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 23/28-23/30 H01C 1/02 H01G 1/02

Claims (1)

(57) [Claims] An electronic component encapsulation molded product obtained by encapsulating and molding an electronic component with a polyarylene sulfide resin composition having a molding shrinkage of 0.2 to 0.8%, wherein the resin portion of the molded product has a maximum pore diameter of 50%. A molded article for sealing a porous electronic component, characterized in that closed pores of up to 300 μm are present in a proportion of 1 to 5% by volume, and the surface layer of the molded article is dense.