JP7490376B2 - Semiconductor element and resin sheet for forming semiconductor element - Google Patents

Description

The present invention relates to a semiconductor element and a resin sheet for forming a semiconductor element.

Several semiconductor elements such as inductors have been proposed in the past. For example, Patent Document 1 proposes a metal-polymer composite film for inductors, which is made of a film-like mixture containing metal powder and amorphous epoxy resin, with the weight ratio of the metal powder being 75 to 98 wt %, and a method for manufacturing an inductor using the same.

JP 2014-11467 A

When an inductor such as that disclosed in Patent Document 1 is mounted on a substrate or the like, it is soldered using flux-containing solder or after flux has been applied.
If any flux remains as residue after that, it may cause bonding defects, solder balls, and reduced insulation reliability in later processes, so the flux is usually cleaned using a flux cleaner.

However, the resin parts of conventional semiconductor elements have low resistance to flux cleaners. If the resin parts are damaged by flux cleaners, they may swell, reducing the magnetic permeability of the semiconductor element.

The present invention aims to solve the above problems. In other words, the present invention aims to provide a semiconductor element having a resin portion that is highly resistant to flux cleaning agents, and a resin sheet that can be used to form the semiconductor element.

The present inventors have conducted extensive research to solve the above problems and have completed the present invention.
The present invention relates to the following (1) to (8).
(1) A resin sheet for forming semiconductor elements, which is made of a mixture containing an epoxy resin, a diene rubber, and metal powder.
(2) The resin sheet according to (1) above, wherein the diene rubber is a random copolymer.
(3) The resin sheet according to the above (1) or (2), wherein the diene rubber is NBR and/or SBR.
(4) The mass ratio of the epoxy resin to the total amount of the epoxy resin and the diene-based rubber (mass of epoxy resin/(mass of epoxy resin+mass of diene-based rubber)×100) is 30 to 80 mass%. A resin sheet according to any one of (1) to (3).
(5) A semiconductor element including a cured resin body having a metal powder dispersed therein and including a circuit therein,
A semiconductor device, wherein the cured resin is a reaction product of an epoxy resin and a diene rubber.
(6) The semiconductor element according to (5) above, wherein the diene rubber is NBR and/or SBR.
(7) The semiconductor element according to (5) or (6) above, wherein the mass ratio of the epoxy resin to the total amount of the epoxy resin and the diene-based rubber (mass of epoxy resin/(mass of epoxy resin+mass of diene-based rubber)×100) is 30 to 80 mass%.
(8) The semiconductor element according to any one of (5) to (7) above, which is an inductor.

The present invention provides a semiconductor element having a resin portion that is highly resistant to flux cleaning agents, and a resin sheet that can be used to form the semiconductor element.

1 is a schematic perspective view for explaining a process for forming a semiconductor element according to the present invention; 4 is another schematic perspective view illustrating the process of forming a semiconductor element according to the present invention. FIG. 1 is a schematic perspective view showing an example of a semiconductor element of the present invention.

The present invention will now be described.
The present invention is a resin sheet for forming semiconductor elements, which is made of a mixture containing an epoxy resin, a diene rubber, and metal powder.
Such a resin sheet will hereinafter be referred to as the "sheet of the present invention."

The present invention also relates to a semiconductor element including a cured resin having metal powder dispersed therein and containing a circuit therein, the cured resin being a reaction product of an epoxy resin and a diene rubber.
Such a semiconductor element will hereinafter be referred to as the "semiconductor element of the present invention."

Hereinafter, when simply referring to "the present invention," this means both "the sheet of the present invention" and "the semiconductor element of the present invention."

<Sheet of the present invention>
The sheet of the present invention will now be described.
The sheet of the present invention is made of a mixture containing an epoxy resin, a diene rubber, and a metal powder.

In the present invention, the epoxy resin is not particularly limited, and any conventionally known epoxy resin can be used.
The epoxy resin has two or more epoxy groups in one molecule. The epoxy resin is preferably a phenol novolac type, a bisphenol A type, a bisphenol F type, a bisphenol S type, a naphthalene type, a biphenyl type, or a dicyclopentadiene type. The epoxy equivalent is preferably 90 to 100,000 g/eq, more preferably 200 to 20,000 g/eq, and particularly preferably 500 to 5,000 g/eq.
Regarding the molecular weight of the epoxy resin, the number average molecular weight (Mn) is preferably from 100 to 100,000, more preferably from 200 to 50,000, and particularly preferably from 500 to 10,000.

In the present invention, the diene rubber is not particularly limited, and any conventionally known diene rubber can be used.
Examples of diene rubbers include acrylonitrile butadiene rubber (NBR), styrene-butadiene copolymer rubber (SBR), hydrogenated styrene-based thermoplastic elastomer (SEBS: a polymer in which the double bond portion of a block copolymer consisting of styrene and butadiene is hydrogenated), natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), ethylene-propylene-diene copolymer rubber (EPDM), styrene-isoprene rubber, isoprene-butadiene rubber, nitrile rubber, and hydrogenated nitrile rubber.
The diene rubber may be modified at its terminals with a functional group, such as a carboxyl group, an epoxy group, an amino group, or a hydroxyl group.

In the present invention, the diene rubber is preferably NBR and/or SBR, since this provides greater resistance to flux cleaners.

In the present invention, the diene rubber is preferably a random copolymer, since this provides greater resistance to flux cleaners.

In the present invention, the mass ratio of the epoxy resin to the total amount of the epoxy resin and the diene rubber (mass of epoxy resin/(mass of epoxy resin+mass of diene rubber)×100) is preferably 30 to 80 mass%, and more preferably 30 to 70 mass%. This is because resistance to the flux cleaning agent is further increased.

In the present invention, the metal powder is preferably a magnetic powder. As the magnetic powder, known magnetic powders can be used. For example, hard magnetic materials such as ferrite magnets and samarium-cobalt magnets, and soft magnetic materials such as iron powder, silicon steel, sendust, and soft ferrite can be used.

The particle size of the metal powder is not particularly limited, and for example, the average particle size measured using a conventionally known laser diffraction type particle size distribution measuring device can be about 0.5 to 150 μm.
The shape of the metal powder is not particularly limited, and examples thereof include spherical, elliptical, flat, needle-like, fibrous, dendritic, amorphous, etc. From the viewpoint of increasing the ratio of metal powder contained in the resin cured body in the semiconductor element of the present invention or the sheet of the present invention, the shape is preferably spherical or flat.
The metal powder may have one or more of the above shapes.
The surface of the metal powder may be coated with an insulating material, for example, by forming an oxide of the metal that forms the metal powder on the surface, coating the surface of the metal powder with an insulating resin film, or attaching insulating fine particles to the periphery of the metal powder.

The metal powder content in the sheet of the present invention is preferably 70 to 93 mass %, and more preferably 80 to 90 mass %.

The sheet of the present invention is made of a mixture containing an epoxy resin, a diene rubber, and metal powder, and the total content of the epoxy resin, diene rubber, and metal powder in this mixture is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more.

The mixture constituting the sheet of the present invention may contain components other than the epoxy resin, diene rubber and metal powder, such as a curing agent and a dispersing agent.
The curing agent here is a cross-linking agent that has the function of cross-linking the epoxy resin and the diene rubber by the application of heat, and examples thereof include imidazole and amine curing agents.
The dispersant also has the function of suppressing aggregation of the metal powder in the mixture, and specific examples thereof include ester salts of polymer copolymers having functional groups that have good affinity with the metal powder.

The sheet of the present invention is obtained by thoroughly kneading the above-mentioned epoxy resin, diene rubber, and metal powder, and processing the mixture into a sheet.
Methods for processing the mixture into a sheet include a method in which the kneaded mixture is heated and compressed to form a sheet, and a method in which the kneaded mixture is diluted in an organic solvent, coated, and the solvent is dried to form a sheet.

The thickness of the sheet of the present invention is not particularly limited, but is preferably 0.03 to 5 mm, and more preferably 0.05 to 3 mm.

<Semiconductor element of the present invention>
The semiconductor element of the present invention will now be described.
The semiconductor element of the present invention includes a cured resin body having a circuit therein, and the metal powder is dispersed in the cured resin body.

The circuit is not particularly limited as long as it can be electrically conductive by connecting to an external electrode. There is also no particular limit to the shape, and it may be, for example, a coil. If the circuit is a coil, the semiconductor element can be an inductor.

The cured resin is a reaction product obtained by reacting the epoxy resin with the diene rubber.
The epoxy resin and the diene rubber may be a reaction product formed by crosslinking with a curing agent (crosslinking agent).
The ratio of the amounts of epoxy resin, diene rubber, and metal powder that constitute the resin cured body, other components, and the preferred ratio of epoxy resin and diene rubber are the same as those in the sheet of the present invention described above.

The metal powder content in the portions of the cured resin body other than the circuits may be the same as the metal powder content contained in the sheet of the present invention described above.

<Production Method>
A method for producing a semiconductor element of the present invention from the sheet of the present invention will be described with reference to the drawings.
FIG. 1 shows a state in which two sheets 1 and 3 of the present invention are prepared, and one of the sheets, the sheet 1 of the present invention, has a circuit 5 formed on its main surface.
Thereafter, as shown in FIG. 2, the main surfaces of the sheet 1 of the present invention and the sheet 3 of the present invention are attached to each other so that the circuit 5 is sandwiched between the two sheets 1 and 3 of the present invention.
Then, the two sheets 1 and 3 of the present invention are pressed against each other by heat pressing. The heating temperature may be any temperature at which the epoxy resin and diene rubber contained in the sheets 1 and 3 of the present invention are thermally cured (crosslinked by the action of heat). For example, when NBR is used as the diene rubber and imidazole is used as the crosslinking agent, the temperature is preferably 165°C or higher, and it is preferable to perform press processing at 0.1 to 10 MPakgf/ ^m2 and a vacuum degree of 0.1 Torr or less while maintaining the temperature at about 165 to 200°C. In this way, the two sheets of the present invention react with each other and can be integrated.
Thereafter, as shown in FIG. 3, it is preferable to attach an external electrode 7 that is electrically connected to the internal circuit.
In this manner, the semiconductor device 10 of the present invention is preferably obtained.

The following raw materials were prepared and mixed in specific ratios to obtain compositions. The ratios in each of the examples and comparative examples are shown in Table 1.
Epoxy resin: jER1009F, manufactured by Mitsubishi Chemical Corporation. SEBS (hydrogenated styrene-based thermoplastic elastomer): Tuftec M1913, manufactured by Asahi Kasei Chemicals. Acrylic rubber: NIPOL AR 51, manufactured by Zeon Corporation. Dispersant: DISPERBYK142, manufactured by BYK. Hardener (imidazole): 2PHZ-PW, manufactured by Shikoku Chemical Industry Co., Ltd. Magnetic powder: Spherical iron powder containing 3.5 wt% silicon and 4.5 wt% chromium was flattened to produce magnetic powder with an average particle size of 30 μm.
The NBR was synthesized by the following method.
<Method of synthesizing NBR>
In a reaction vessel, 180 parts of ion-exchanged water, 25 parts of a 10% by weight aqueous solution of sodium dodecylbenzenesulfonate, 28.0 parts of acrylonitrile, 3 parts of mono n-butyl maleate, and 0.5 parts of t-dodecyl mercaptan (molecular weight modifier) were added in this order, and the inside was replaced with nitrogen, and then 43 parts of 1,3-butadiene was charged. The reactor was kept at 5°C, and 0.1 parts of cumene hydroperoxide (polymerization initiator) was added and stirred. After 18 hours of polymerization reaction, 0.1 parts of a 10% aqueous solution of hydroquinone (polymerization terminator) was added to terminate the polymerization reaction, and the residual monomer was removed using a rotary evaporator with a water temperature of 60°C to obtain NBR. Next, 2 volumes of methanol were added to the obtained NBR to coagulate it, and then the solid was filtered to take out, and this was vacuum dried at 60°C for 12 hours to obtain an NBR solid. The obtained NBR had an acrylonitrile monomer unit content of 27% by mass and a mass average molecular weight of 300,000.

Next, the compositions of each of the Examples and Comparative Examples were cured by hot pressing at 195° C., 8 MPa kgf/m ² and a vacuum degree of 0.1 Torr to obtain cured resin bodies.
The obtained cured resin was subjected to the following tests.

<Solvent resistance test>
A solvent was prepared by mixing normal propyl alcohol, isopropanol, and ethanol in a mass ratio of 1:1:1. The composition of this solvent is similar to that of commonly used flux cleaners.
Each cured resin was immersed in such a solvent at 65° C. for 20 minutes to evaluate the solvent resistance. The evaluation criteria are as follows. The results are shown in Table 1.
A: After immersion, the thickness change was less than 5%.
◯: After immersion, the thickness change was 5% or more and less than 10%.
Δ: After immersion, the change in thickness was 10% or more and less than 20%.
×: After immersion, the thickness change increased by 20% or more.

<Powder fall test>
The degree to which the magnetic powder was retained inside the hardened resin was evaluated. The evaluation criteria were as follows. The results are shown in Table 1.
⊚: When the hardened molded product is touched with a fingertip, almost no powder is transferred to the finger.
◯: When the hardened molded product was touched with a fingertip, almost no powder was transferred to the finger, but when rubbed, magnetic powder adhered to the finger.
Δ: When the hardened molded product was touched with a fingertip, little powder was transferred to the finger.
×: When the hardened molded product was touched with a fingertip, powder was transferred to the entire finger.

<Processability verification test>
The cured resins were cut with a dicer and the processability was evaluated according to the following criteria. The results are shown in Table 1.
◎: No burrs, whiskers, or fallen particles on the end surface after processing.
○: Burrs, whiskers, particles falling off, etc. occurred in a very small area on the end surface after processing.
×: Defects such as burrs, whiskers, and particle loss occurred during processing, or the cured product was significantly deformed.

It was confirmed that the resin cured bodies of Examples 1 to 10, which were made of a mixture containing an epoxy resin, a diene-based rubber (NBR or a hydrogenated styrene-based thermoplastic elastomer), and a metal powder (magnetic powder), all had excellent solvent resistance.
In addition, the resin sheets of Examples 3 to 5, in which the value of epoxy resin mass/(epoxy resin mass+diene rubber mass)×100 is 30 to 80 mass%, were confirmed to have excellent solvent resistance, powder fall-off properties, and processability.

In contrast, the cured resin material of Comparative Example 1, which did not contain a diene rubber, was poor in solvent resistance and powder falling off properties.
Moreover, the cured resin material of Comparative Example 2, which did not contain a diene rubber (containing an acrylic rubber instead), had significantly poor solvent resistance.

1 Sheet of the present invention 3 Sheet of the present invention 5 Circuit 7 External electrode 10 Semiconductor element of the present invention

Claims (8)

The adhesive is made of a mixture containing an epoxy resin, a diene rubber, and a magnetic powder,
a total content of the epoxy resin, the diene rubber, and the magnetic powder in the mixture is 90 mass% or more;
The content of the magnetic powder in the mixture is 70 to 93 mass %,
A resin sheet for forming a semiconductor element, in which a mass ratio of the epoxy resin to a total amount of the epoxy resin and the diene-based rubber (mass of epoxy resin/(mass of epoxy resin+mass of diene-based rubber)×100) is 30 to 80 mass % (excluding 48.2 mass % or more) . The resin sheet according to claim 1, wherein the diene rubber is a random copolymer. The resin sheet according to claim 1 or 2, wherein the diene rubber is NBR and/or SBR. The resin sheet according to any one of claims 1 to 3, wherein the magnetic powder is at least one selected from the group consisting of ferrite magnets, samarium-cobalt magnets, iron powder, silicon steel, sendust, and soft ferrite. A semiconductor element including a resin cured body having a magnetic powder dispersed therein and including a circuit therein,
the cured resin is a reaction product of an epoxy resin and a diene rubber,
a total content of the epoxy resin, the diene rubber, and the magnetic powder in the cured resin body is 90 mass% or more;
the content of the magnetic powder in the cured resin body is 70 to 93 mass %,
a mass ratio of the epoxy resin to a total amount of the epoxy resin and the diene-based rubber (mass of epoxy resin/(mass of epoxy resin+mass of diene-based rubber)×100) is 30 to 80 mass % (excluding 48.2 mass % or more) . The semiconductor element according to claim 5, wherein the diene rubber is NBR and/or SBR. The semiconductor element according to claim 5 or 6, wherein the magnetic powder is at least one selected from the group consisting of ferrite magnet, samarium-cobalt magnet, iron powder, silicon steel, sendust, and soft ferrite. An inductor including a resin cured body having magnetic powder dispersed therein and including a circuit therein,
the cured resin is a reaction product of an epoxy resin and a diene rubber,
a total content of the epoxy resin, the diene rubber, and the magnetic powder in the cured resin body is 90 mass% or more;
the content of the magnetic powder in the cured resin body is 70 to 93 mass %,
An inductor, wherein a mass ratio of the epoxy resin to a total amount of the epoxy resin and the diene-based rubber (mass of epoxy resin/(mass of epoxy resin+mass of diene-based rubber)×100) is 30 to 80 mass % (excluding 48.2 mass % or more) .

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