JP7464198B2 - Conductive paste, hardened product and semiconductor device - Google Patents

Description

The present invention relates to a conductive paste, a cured product, and a semiconductor device.

A technique is known for manufacturing semiconductor devices using a thermosetting resin composition containing metal particles with the intention of increasing the heat dissipation of the semiconductor device. By including metal particles, which have a higher thermal conductivity than the resin, in the thermosetting resin composition, the thermal conductivity of the cured product can be increased.

As a specific example of application to semiconductor devices, a technique is known in which a composition containing metal particles is used to bond/join a semiconductor element to a substrate (support member), as described in the following Patent Documents 1 and 2.

Patent Document 1 discloses an adhesive composition containing silver particles, a thermosetting resin such as an acrylic resin, and a dispersion medium. The document states that the adhesive composition has sufficiently high adhesive strength and high thermal conductivity.

Patent Document 2 discloses a resin composition containing silver particles, a thermosetting resin, and a binder resin such as an acrylic resin. The document states that by using a thermally conductive adhesive sheet made of the resin composition, it is possible to obtain a semiconductor device that has high thermal conductivity and excellent reliability even under low-temperature sintering conditions.

JP 2017-031227 A JP 2021-036022 A

However, when the compositions described in Patent Documents 1 and 2 are used to bond a semiconductor element to a substrate, the adhesive strength is insufficient, and when a semiconductor device is manufactured by die bonding a semiconductor element to a lead frame or the like and the semiconductor device is mounted on a substrate and the substrate is heated to bond the semiconductor device to the substrate (during reflow soldering), the adhesive layer made of the composition may peel off. Furthermore, the adhesive layer made of the composition described in these documents has a high modulus of elasticity at room temperature (25°C), leaving room for improvement in the reliability of connection with the semiconductor element.

The present inventors have discovered that a conductive paste containing a specified (meth)acrylate compound as a binder has excellent adhesion to semiconductor elements, substrates, and lead frames, and further that a semiconductor device manufactured using the conductive paste has excellent connection reliability, and have completed the present invention.
That is, the present invention can be shown as follows.

According to the present invention,
A conductive filler (a);
A binder (b);
Including,
A conductive paste is provided in which the binder (b) contains a terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1).

According to the present invention,
A cured product is provided by curing the conductive paste.

According to the present invention,
A substrate;
A semiconductor element mounted on the base material via an adhesive layer,
The adhesive layer is formed by curing the conductive paste, thereby providing a semiconductor device.

The present invention provides a conductive paste having excellent adhesion to semiconductor elements, substrates and lead frames, and a semiconductor device having excellent connection reliability manufactured using the conductive paste.

1 is a cross-sectional view illustrating an example of an electronic device according to an embodiment. 1 is a cross-sectional view illustrating an example of an electronic device according to an embodiment. FIG. 2 is a schematic diagram showing a method for measuring chip peel strength in the examples.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In all drawings, similar components are given similar reference numerals and their description will be omitted as appropriate. In addition, "a to b" indicates "a or more" to "b or less" unless otherwise specified.
In this specification, the term "(meth)acrylic" refers to a concept that includes both acrylic and methacrylic. The same applies to similar terms such as "(meth)acrylate."

The conductive paste of this embodiment contains a conductive filler (a) and a binder (b).

[Conductive filler (a)]
The conductive paste of the present embodiment may contain a conductive filler (a).
The conductive filler (a) aggregates to form a metal particle connection structure by subjecting the conductive paste to heat treatment. That is, in the die attachment paste layer obtained by heating the conductive paste, the metal powders are present in an aggregated state. This allows electrical conductivity, thermal conductivity, and adhesion to the substrate to be exhibited.

The conductive filler (a) used in the conductive paste of this embodiment may be silver powder, gold powder, platinum powder, palladium powder, copper powder, nickel powder, or an alloy thereof. From the viewpoints of conductivity and ease of handling, it is preferable to use silver powder.

The shape of the conductive filler (a) is not particularly limited, but examples thereof include spherical, flake, and scale-like shapes. In this embodiment, it is more preferable that the conductive filler (a) contains spherical particles. This can improve the uniformity of the aggregation of the conductive filler (a). In addition, from the viewpoint of reducing costs, a mode in which the conductive filler (a) contains flake-like particles can also be adopted. Furthermore, from the viewpoint of improving the balance between cost reduction and aggregation uniformity, the conductive filler (a) may contain both spherical particles and flake-like particles.

The average particle size (D ₅₀ ) of the conductive filler (a) is, for example, 0.1 μm or more and 10 μm or less, preferably 0.3 μm or more and 8 μm or less, more preferably 0.6 μm or more and 5 μm or less. When the average particle size of the conductive filler (a) is equal to or more than the lower limit, the adhesion is improved, and an excessive increase in the specific surface area is suppressed, and it is possible to suppress a decrease in thermal conductivity due to contact thermal resistance. In addition, when the average particle size of the conductive filler (a) is equal to or less than the upper limit, the adhesion is improved and it is possible to improve the formability of the metal particle connection structure between the conductive fillers. In addition, from the viewpoint of improving the dispensability of the conductive paste, the average particle size (D ₅₀ ) of the conductive filler (a) is preferably 0.3 μm or more and 8 μm or less, more preferably 0.6 μm or more and 5 μm or less, more preferably 0.6 μm or more and 2.7 μm or less, and particularly preferably 0.6 μm or more and 2.0 μm or less. The average particle size (D ₅₀ ) of the conductive filler (a) can be measured, for example, by using a commercially available laser type particle size distribution analyzer (eg, SALD-7000, manufactured by Shimadzu Corporation).

The maximum particle size of the conductive filler (a) is not particularly limited, but can be, for example, 1 μm or more and 50 μm or less, more preferably 3 μm or more and 30 μm or less, and particularly preferably 4 μm or more and 18 μm or less. This makes it possible to more effectively improve adhesion.

The content of the conductive filler (a) in the conductive paste affects the viscosity of the conductive paste, and from the viewpoint of the effects of the present invention, the content is preferably, for example, 30% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 80% by mass or less, relative to the entire conductive paste.

[Binder (b)]
In this embodiment, the binder (b) contains a terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1) (hereinafter also simply referred to as (meth)acrylate (b1)).

(Terminal Hydroxyl Group-Containing Polyalkylene Glycol (Meth)acrylate (b1))
As the terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1), any known (meth)acrylate compound can be used as long as it has the above structure and the effects of the present invention can be achieved.

In this embodiment, from the viewpoint of the effects of the present invention, it is preferable that the (meth)acrylate (b1) contains at least one compound (b1-1) represented by the following general formula (1).

In formula (1), R represents a hydrogen atom or a methyl group.
m represents an integer of 1 to 40, preferably 1 to 37, more preferably 1 to 35, and particularly preferably 15 to 35.
n represents an integer of 0 to 10, preferably 0 to 8, more preferably 0 to 6, and particularly preferably 0.

From the viewpoint of the effects of the present invention, the number average molecular weight of the compound (b1-1) calculated as the hydroxyl value can be 400 or more, preferably 600 or more, and more preferably 800 or more.
The upper limit of the number average molecular weight is not particularly limited, but is 5,000 or less, and preferably 3,000 or less.

In this embodiment, from the viewpoint of the effects of the present invention, it is more preferable that compound (b1-1) has n of 0 in the general formula (1) and a number average molecular weight calculated in terms of hydroxyl value of 800 or more.

In this embodiment, the content of (meth)acrylate (b1) in binder (b) is preferably 5% by mass or more and 60% by mass or less, and more preferably 15% by mass or more and 50% by mass or less, relative to the entire binder (b).

In this embodiment, from the viewpoint of the effects of the present invention and the adhesion of the resulting conductive paste to a substrate, etc., the content of compound (b1) in the conductive paste is preferably 1 mass% or more and 20 mass% or less, and more preferably 2 mass% or more and 10 mass% or less, relative to the entire conductive paste.

The binder (b) of this embodiment may further contain at least one selected from a (meth)acrylate compound (b2) and an acrylic resin (b3).

((Meth)acrylate compound (b2))
The (meth)acrylate compound (b2) (excluding the above (b1)) is used as a reactive diluent having a reactive group that participates in the crosslinking reaction of the binder resin contained in the conductive paste.

As the (meth)acrylate compound (b2), a monofunctional acrylic monomer having only one (meth)acrylic group, or a polyfunctional acrylic monomer having two or more (meth)acrylic groups can be used.

Examples of monofunctional acrylic monomers include 2-phenoxyethyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxyethyl (meth)acrylate, diethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethylhexyl diethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, Nonylphenol ethylene oxide modified (meth)acrylate, phenylphenol ethylene oxide modified (meth)acrylate, isobornyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate quaternized product, glycidyl (meth)acrylate, neopentyl glycol (meth)acrylic acid benzoate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl acid phosphate, and 2-(meth)acryloyloxyethyl acid phosphate. As the monofunctional acrylic monomer, one or a combination of two or more of the above specific examples can be used.

As the monofunctional acrylic monomer, it is preferable to use 2-phenoxyethyl methacrylate among the above specific examples, from the viewpoint of the effects of the present invention and the adhesion of the resulting conductive paste to the substrate, etc.

Specific examples of polyfunctional acrylic monomers include ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, 1,6-hexanediol dimethacrylate, 4,4'-isopropylidenediphenol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,6-bis((meth)acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane Examples of the acrylic acid ester include acrylic acid ester, 1,4-bis((meth)acryloyloxy)butane, 1,6-bis((meth)acryloyloxy)hexane, triethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-di(meth)acryloylethylenediamine, N,N'-(1,2-dihydroxyethylene)bis(meth)acrylamide, and 1,4-bis((meth)acryloyl)piperazine.

Of the above specific examples, it is preferable to use 1,6-hexanediol dimethacrylate as the polyfunctional acrylic monomer, from the viewpoint of the effects of the present invention and the adhesion of the resulting conductive paste to a base material or the like.
From the viewpoint of the effects of the present invention, the (meth)acrylate compound (b2) more preferably contains both a monofunctional acrylic monomer and a polyfunctional acrylic monomer.

In this embodiment, the content of (meth)acrylate compound (b2) in binder (b) is preferably 20% by mass or more and 70% by mass or less, and more preferably 30% by mass or more and 60% by mass or less, relative to the entire binder (b).

In this embodiment, from the viewpoint of the effects of the present invention and the adhesion of the resulting conductive paste to a substrate, etc., the content of the (meth)acrylate compound (b2) in the conductive paste is preferably 2% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, relative to the entire conductive paste.

(Acrylic resin (b3))
As the acrylic resin (b3), a liquid resin having two or more acrylic groups in one molecule can be used.

Specifically, the acrylic resin (b3) may be a resin obtained by polymerizing the above-mentioned acrylic monomer or copolymerizing it with another monomer.
Examples of other monomers include ethylene; linear α-olefins having 3 to 20 carbon atoms, such as propylene, butene, pentene, hexene, heptene, and octene; aromatic vinyl compounds having 8 to 20 carbon atoms, such as styrene, methylstyrene, dimethylstyrene, ethylstyrene, vinylnaphthalene, vinylanthracene, diphenylethylene, isopropenylbenzene, isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, isopropenylnaphthalene, and isopropenylanthracene; and the like.
Here, the polymerization or copolymerization method is not limited, and a known method using a general polymerization initiator and a chain transfer agent, such as solution polymerization, can be used. As the acrylic resin, one type may be used alone, or two or more types having different structures may be used.

The acrylic resin (b3) may, for example, have an epoxy group, an amino group, a carboxyl group, or a hydroxyl group in its structure. If the acrylic resin has an epoxy group in its structure, it can react with a curing agent described later and cure and shrink. If the acrylic resin has an amino group, a carboxyl group, or a hydroxyl group in its structure and contains an epoxy resin as a base, the acrylic resin and the epoxy resin can react and cure and shrink. The acrylic resin may, for example, have a carbon-carbon double bond C=C in its structure. If the acrylic resin has a carbon-carbon double bond in its structure, it can be involved in a polymerization reaction caused by a radical polymerization initiator and cure and shrink.

Specific examples of commercially available products of the above-mentioned acrylic resin (b3) include ARUFON UG-4035, ARUFON UG-4010, ARUFON UG-4070, ARUFON UH-2000, ARUFON UH-2041, ARUFON UH-2170, and ARUFON UP-1000, all manufactured by Toagosei Co., Ltd.

In this embodiment, the content of acrylic resin (b3) in binder (b) is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less, relative to the entire binder (b).

In this embodiment, from the viewpoint of the effects of the present invention and the adhesion of the resulting conductive paste to a substrate, etc., the content of acrylic resin (b3) in the conductive paste is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less, relative to the entire conductive paste.

From the viewpoint of the effects of the present invention, the binder (b) preferably contains a (meth)acrylate (b1), a (meth)acrylate compound (b2) and an acrylic resin (b3).
That is, the binder (b) (100% by mass) is
(Meth)acrylate (b1) is preferably 5% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 50% by mass or less,
The (meth)acrylate compound (b2) is preferably from 20% by mass to 70% by mass, more preferably from 30% by mass to 60% by mass,
The acrylic resin (b3) is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 30% by mass or less,
may be included in an amount of

[Other ingredients]
In addition to the above-mentioned components, the conductive paste of the present embodiment may contain various additional components commonly used in the field, as necessary. The additional components include, but are not limited to, organic solvents, silane coupling agents, curing accelerators, radical polymerization initiators, stress reducing agents, inorganic fillers, etc., and can be selected according to the desired performance.

Examples of the organic solvent include alcohols such as ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, methyl methoxybutanol, α-terpineol, β-terpineol, hexylene glycol, benzyl alcohol, 2-phenylethyl alcohol, isopalmityl alcohol, isostearyl alcohol, lauryl alcohol, ethylene glycol, propylene glycol, and glycerin;
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) or diisobutyl ketone (2,6-dimethyl-4-heptanone), and γ-butyrolactone;
Esters such as ethyl acetate, butyl acetate, diethyl phthalate, dibutyl phthalate, acetoxyethane, methyl butyrate, methyl hexanoate, methyl octanoate, methyl decanoate, methyl cellosolve acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, 1,2-diacetoxyethane, tributyl phosphate, tricresyl phosphate, and tripentyl phosphate;
Ethers such as tetrahydrofuran, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol monobutyl ether, propylene glycol dimethyl ether, ethoxyethyl ether, tripropylene glycol monobutyl ether, 1,2-bis(2-diethoxy)ethane, and 1,2-bis(2-methoxyethoxy)ethane;
Ester ethers such as 2-(2-butoxyethoxy)ethane acetate;
Ether alcohols such as 2-(2-methoxyethoxy)ethanol;
Hydrocarbons such as toluene, xylene, n-paraffin, isoparaffin, dodecylbenzene, turpentine oil, kerosene, or light oil;
Nitriles such as acetonitrile or propionitrile;
Amides such as acetamide or N,N-dimethylformamide;
Examples of the oil include low molecular weight volatile silicone oil and volatile organic modified silicone oil.

Curing accelerators are used to accelerate the reaction between the epoxy monomer used as a reactive diluent or the epoxy resin used as a binder resin and the curing agent. Examples of curing accelerators include phosphorus atom-containing compounds such as organic phosphines, tetra-substituted phosphonium compounds, phosphobetaine compounds, adducts of phosphine compounds and quinone compounds, and adducts of phosphonium compounds and silane compounds; amidines and tertiary amines such as dicyandiamide, 1,8-diazabicyclo[5.4.0]undecene-7, and benzyldimethylamine; and nitrogen atom-containing compounds such as quaternary ammonium salts of the above amidines or tertiary amines.

Specific examples of radical polymerization initiators that can be used include azo compounds and peroxides.

Examples of inorganic fillers include fused silica such as fused crushed silica and fused spherical silica, silica such as crystalline silica and amorphous silica, nanosilica, silicon dioxide, alumina, aluminum hydroxide, silicon nitride, and aluminum nitride. From the viewpoint of thixotropy control of the conductive paste, it is preferable to use nanosilica.
The nanosilica may be fumed silica or colloidal silica, and the particle size of the nanosilica is, for example, 1 nm to 100 nm, and preferably 2 nm to 50 nm.

The conductive paste of the present embodiment contains a conductive filler (a) and a binder (b), and the binder (b) preferably contains a (meth)acrylate (b1), a (meth)acrylate compound (b2), and an acrylic resin (b3).
That is, the conductive paste (100 mass%) of this embodiment is
The conductive filler (a) is preferably 30% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less,
(Meth)acrylate (b1) is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 10% by mass or less,
The (meth)acrylate compound (b2) is preferably from 2% by mass to 20% by mass, more preferably from 5% by mass to 15% by mass,
The acrylic resin (b3) is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less,
may be included in an amount of

(Preparation of Conductive Paste)
The method for preparing the conductive paste is not particularly limited, but for example, the above-mentioned components are premixed, then kneaded using a triple roll, and further vacuum degassed to obtain a paste-like composition. In this case, by appropriately adjusting the preparation conditions, for example by performing the premixing under reduced pressure, the long-term workability of the conductive paste can be improved.

The viscosity of the conductive paste of this embodiment can be adjusted according to the application. The viscosity of the conductive paste can be controlled by adjusting the type of binder resin used, the type of diluent, and the amount of each of them. The lower limit of the viscosity of the conductive paste of this embodiment is, for example, 10 Pa·s or more, preferably 20 Pa·s or more, and more preferably 30 Pa·s or more. This can improve the workability of the conductive paste. On the other hand, the upper limit of the viscosity of the conductive paste is, for example, 1×10 ³ Pa·s or less, preferably 5×10 ² Pa·s or less, and more preferably 2×10 ² Pa·s or less. This can improve the coatability.

(Application)
The applications of the conductive paste of this embodiment will be described.
The conductive paste according to the present embodiment can be cured to obtain a cured product. The cured product can be preferably used as a highly thermally conductive material, for example, to bond a substrate and a semiconductor element and provide high thermal conductivity and high electrical conductivity. Examples of the semiconductor element include a semiconductor package and an LED.

The cured product (highly thermally conductive material) obtained from the conductive paste according to this embodiment has an elastic modulus (storage elastic modulus) measured at room temperature (25°C) of 200 MPa or more and 6,000 MPa or less, preferably 300 MPa or more and 3,000 MPa or less, more preferably 400 MPa or more and 2,000 MPa or less, and particularly preferably 500 MPa or more and 1,500 MPa or less.
As described above, the cured product obtained from the conductive paste of this embodiment has a low elastic modulus at room temperature (25° C.) and has excellent adhesion to semiconductor elements, substrates, and lead frames, making it possible to provide a semiconductor device with excellent connection reliability.

The conductive paste according to this embodiment has improved connection reliability and product reliability compared to conventional conductive pastes. This makes it suitable for use when semiconductor elements that generate a large amount of heat are mounted on a substrate or when the size of the semiconductor package is small. In this embodiment, LED stands for light emitting diode.

Specific examples of semiconductor devices using LEDs include bullet-type LEDs, surface mount device (SMD) LEDs, COB (Chip On Board), and power LEDs.

Specific types of semiconductor packages include CMOS image sensors, hollow packages, MAP (Mold Array Package), QFP (Quad Flat Package), SOP (Small Outline Package), CSP (Chip Size Package), QFN (Quad Flat Non-leaded Package), SON (Small Outline Non-leaded Package), BGA (Ball Grid Array), LF-BGA (Lead Frame BGA), FC-BGA (Flip Chip BGA), MAP-BGA (Molded Examples of such BGAs include Array Process BGA (eWLB), Embedded Wafer-Level BGA (eWLB), Fan-In type eWLB, and Fan-Out type eWLB.

An example of a semiconductor device using the conductive paste according to this embodiment will be described below.
FIG. 1 is a cross-sectional view showing an example of a semiconductor device according to the present embodiment.
The semiconductor device 100 according to this embodiment includes a base material 30 and a semiconductor element 20 mounted on the base material 30 via an adhesive layer 10 which is a cured product of a conductive paste. The semiconductor element 20 and the base material 30 are electrically connected via, for example, a bonding wire 40. The semiconductor element 20 is sealed with, for example, a sealing resin 50.

Here, the lower limit of the thickness of the adhesive layer 10 is, for example, preferably 5 μm or more, and more preferably 10 μm or more. This improves the heat capacity of the cured product of the conductive paste, and improves heat dissipation. The upper limit of the thickness of the adhesive layer 10 is, for example, preferably 50 μm or less, and more preferably 30 μm or less. This allows the conductive paste to exhibit suitable adhesion while improving heat dissipation.

1, the substrate 30 is, for example, a lead frame. In this case, the semiconductor element 20 is mounted on the die pad 32 or the substrate 30 via an adhesive layer 10. The semiconductor element 20 is also electrically connected to the outer lead 34 (substrate 30) via, for example, a bonding wire 40. The substrate 30, which is a lead frame, is composed of, for example, a 42 alloy or a Cu frame.

The substrate 30 may be an organic substrate or a ceramic substrate. The organic substrate is preferably made of, for example, epoxy resin, cyanate resin, maleimide resin, or the like. The surface of the substrate 30 may be coated with a metal such as silver or gold. This can improve the adhesion between the adhesive layer 10 and the substrate 30.

Figure 2 is a modified example of Figure 1 and is a cross-sectional view showing an example of a semiconductor device 100 according to this embodiment. In the semiconductor device 100 according to this modified example, the substrate 30 is, for example, an interposer. A plurality of solder balls 52, for example, are formed on the other surface of the substrate 30, which is an interposer, opposite to the surface on which the semiconductor element 20 is mounted. In this case, the semiconductor device 100 is connected to another wiring board via the solder balls 52.

(Method of manufacturing a semiconductor device)
An example of a method for manufacturing a semiconductor device according to this embodiment will be described.
First, a conductive paste is applied onto the substrate 30, and then the semiconductor element 20 is disposed thereon. That is, the substrate 30, the conductive paste, and the semiconductor element 20 are laminated in this order. There are no limitations on the method for applying the conductive paste, and specifically, dispensing, printing, inkjet, or the like can be used.

The conductive paste of this embodiment has excellent wetting and spreading properties between the substrate 30 and the semiconductor element 20, excellent thermal conductivity and connectivity, and suppresses protrusion (formation of a fillet) from the region directly below the semiconductor element 20, resulting in an excellent balance of these properties. In other words, the semiconductor device obtained using the conductive paste of the present invention has improved thermal conductivity, connection reliability, and contamination resistance, resulting in excellent product reliability.

Next, the conductive paste is pre-cured and then post-cured to harden the conductive paste. The heat treatments of pre-curing and post-curing cause the silver particles in the conductive paste to aggregate, and the interfaces between the multiple silver particles disappear, forming a thermally conductive layer in the adhesive layer 10. This bonds the substrate 30 and the semiconductor element 20 via the adhesive layer 10. Next, the semiconductor element 20 and the substrate 30 are electrically connected using a bonding wire 40. Next, the semiconductor element 20 is sealed with a sealing resin 50. This allows the semiconductor device to be manufactured.

The above describes embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can be adopted as long as they do not impair the effects of the present invention.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
The components used in the examples and comparative examples are shown below.

[Terminal Hydroxyl Group-Containing Polyalkylene Glycol (Meth)acrylate (b1)]
PAG methacrylate 1: polyoxypropylene monomethacrylate represented by general formula (1) in which R is a methyl group, m is 9, and n is 0 (number average molecular weight calculated as hydroxyl value: 582, product name: PP-500D, manufactured by NOF Chemical Industries, Ltd.)
PAG methacrylate 2: Polyoxypropylene monomethacrylate represented by general formula (1) in which R is a methyl group, m is 17, and n is 0 (number average molecular weight calculated as hydroxyl value: 1079, product name: PP-1000D, manufactured by NOF Chemical Industries, Ltd.)
PAG methacrylate 3: Polyoxypropylene monomethacrylate represented by general formula (1) in which R is a methyl group, m is 34, and n is 0 (number average molecular weight calculated as hydroxyl value: 2018, product name: PP-2000D, manufactured by NOF Chemical Industries, Ltd.)
PAG methacrylate 4: Polyoxypropylene monomethacrylate represented by general formula (1) in which R is a hydrogen atom, m is 17, and n is 0 (number average molecular weight calculated as hydroxyl value: 1069, product name: AP-1000D, manufactured by NOF Chemical Industries, Ltd.)
PAG methacrylate 5: Propylene glycol polybutylene glycol monomethacrylate represented by general formula (1) in which R is a methyl group, m is 1, and n is 6 (number average molecular weight calculated as hydroxyl value: 563, product name: 10PPB-500BD, manufactured by NOF Chemical Industries, Ltd.)

[(Meth)acrylate (b2)]
Monofunctional acrylic monomer: 2-phenoxyethyl methacrylate (product name: Light Ester PO, manufactured by Kyoeisha Chemical Co., Ltd.)
Bifunctional acrylic monomer: 1,6-hexanediol dimethacrylate (product name: Light Ester 1.6HX, manufactured by Kyoeisha Chemical Co., Ltd.)

[Acrylic resin (b3)]
Acrylic resin 1: glycidyl group-containing acrylic/styrene copolymer (weight average molecular weight 11,000, epoxy equivalent 556 g/mol, product name: ARUFON UG-4035, manufactured by Toagosei Co., Ltd.)

[Radical initiator]
Radical initiator 1: dicumyl peroxide (Perkadox BC, peroxide, manufactured by Kayaku Akzo Co., Ltd.)

[Conductive filler]
Silver filler: flake silver particles (manufactured by DOWA Electronics, TKR-88, _D50 : 3 μm)

(Comparative Example 1, Examples 1 to 5)
<Preparation of Paste Adhesive Composition>
First, a varnish-like mixture was prepared by kneading the components in the amounts shown in the "Varnish composition" in Table 1 at room temperature using a three-roll mill. Next, the obtained varnish-like mixture was mixed with silver powder in the amounts shown in the "Paste composition" in Table 1, and kneaded at room temperature using a three-roll mill to obtain a paste-like composition (conductive paste).
The conductive pastes of the respective Examples and Comparative Examples were evaluated for the following items.

<Die shear strength after moisture absorption (silicon chip with length 5 mm x width 5 mm x thickness 350 μm)>
Curing conditions: The conductive paste obtained above was applied onto a copper frame, and a 5 mm x 5 mm silicon chip was mounted thereon to a thickness of 20 μm. The temperature was then raised to 175° C. in a nitrogen atmosphere for 30 minutes, and the chip was left for 5 hours (1 hour curing and post-mold curing) to obtain a test specimen.
Moisture absorption conditions: The obtained test pieces were treated in an environment at a temperature of 120° C. and a relative humidity of 100% for 24 hours.
Measurement conditions for die shear strength: The test piece after moisture absorption treatment was placed on a plate at 260° C. for 20 seconds, and in that state, the chip peel strength was measured using a bond tester (DAGE 4000P type). FIG. 3 is a schematic diagram showing a method for measuring chip peel strength. The silicon chip 220 is bonded via a conductive paste 210 onto a copper frame 200 whose surface has been treated with a bleed-out inhibitor. The die shear strength was measured as the maximum stress when a force was applied in the direction of the arrow shown in FIG. 3 under conditions of a measurement speed of 50 μm/sec and a measurement height of 50 μm, and this was taken as the adhesive strength. The die shear strength and its standard deviation are shown in Table 1. The unit of die shear strength is "N". The larger the value of the die shear strength, the stronger the adhesion between the silicon chip and the copper frame.

<Elastic modulus (storage modulus) of cured product measured at room temperature (25° C.)>
The heat-treated paste-like polymerizable composition was cut into a rectangular sample of about 0.1 mm × about 10 mm × about 4 mm for evaluation. The storage modulus (E') at 25°C was measured by DMA (dynamic viscoelasticity measurement, tensile mode) at a heating rate of 5°C/min and a frequency of 10 Hz.

<Hot elastic modulus of cured product measured at 250° C.>
The heat-treated paste-like polymerizable composition was cut into a rectangular sample of about 0.1 mm × about 10 mm × about 4 mm for evaluation. The storage modulus (E') at 250°C was measured by DMA (dynamic viscoelasticity measurement, tensile mode) at a heating rate of 5°C/min and a frequency of 10 Hz.

<Reliability (package peel test)>
The conductive paste obtained above was applied onto a copper frame, and a 200 μm thick silicon chip with a length of 8 mm and a width of 8 mm was mounted thereon to a thickness of 20 μm. The temperature was then raised to 175° C. in a nitrogen atmosphere for 30 minutes, and the chip was left for 1 hour to obtain a test piece. The chip was then sealed with an epoxy molding compound to obtain a package. Post-mold curing was then performed at 175° C. for 4 hours to obtain a package structure. This package structure was 14 mm long, 14 mm wide, and 0.8 mm thick. The obtained package structure was then left at a temperature of 85° C. and a relative humidity of 85% for 168 hours.
The package structure exposed for a predetermined time was taken out and then passed through a reflow process at 260° C. three times. Thereafter, the package structure was checked for peeling between the paste layer and the copper frame, and between the sealing material and the copper frame. Package structures in which peeling was not observed were evaluated as ◯, and package structures in which peeling was observed were evaluated as ×. The results are shown in Table 1.

The results in Table 1 make it clear that by using the conductive paste of the present invention, a semiconductor device can be obtained that has excellent adhesion to semiconductor elements, substrates, and lead frames, as well as excellent connection reliability.

This application claims priority based on Japanese Patent Application No. 2021-094962, filed on June 7, 2021, the disclosure of which is incorporated herein in its entirety.

Reference Signs List 100 Semiconductor device 10 Adhesive layer 20 Semiconductor element 30 Support member 32 Die pad 34 Outer lead 40 Bonding wire 50 Sealing resin 52 Solder ball 200 Copper frame 210 Conductive paste 220 Silicon chip 230 Jig

Claims (12)

A conductive filler (a);
A binder (b);
Including,
A conductive paste, wherein the binder (b) comprises a terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1) represented by the following general formula (1), and further comprises at least one selected from a (meth)acrylate compound (b2) (excluding the above (b1)) and an acrylic resin (b3):

(In general formula (1), R represents a hydrogen atom or a methyl group, m represents an integer of 1 to 40, and n represents an integer of 0 to 10.) The conductive paste according to claim 1, wherein the number average molecular weight calculated based on the hydroxyl value of the terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1) represented by the general formula (1) is 400 or more. The conductive paste according to claim 1, wherein the terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1) represented by the general formula (1) is polyoxypropylene monomethacrylate represented by R: methyl group, m: 9, n: 0, polyoxypropylene monomethacrylate represented by R: methyl group, m: 17, n: 0, polyoxypropylene monomethacrylate represented by R: methyl group, m: 34, n: 0, polyoxypropylene monomethacrylate represented by R: hydrogen atom, m: 17, n: 0, or propylene glycol polybutylene glycol monomethacrylate represented by R: methyl group, m: 1, n: 6. The conductive paste according to claim 1, wherein the terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1) represented by the general formula (1) has n of 0 and a number average molecular weight calculated as a hydroxyl value of 800 or more. The (meth)acrylate compound (b2) contains at least one selected from a monofunctional acrylic monomer and a polyfunctional acrylic monomer,
The monofunctional acrylic monomers include 2-phenoxyethyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 2-ethylhexyl diethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonyl phenoxy Nol ethylene oxide modified (meth)acrylate, phenylphenol ethylene oxide modified (meth)acrylate, isobornyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate quaternized, glycidyl (meth)acrylate, neopentyl glycol (meth)acrylic acid benzoate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-methyl ... 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-(meth)acryloyloxyethyl acid phosphate, and 2-(meth)acryloyloxyethyl acid phosphate;
The polyfunctional acrylic monomers include ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, propoxylated bisphenol A di(meth)acrylate, 1,6-hexanediol dimethacrylate, 4,4'-isopropylidenediphenol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,6-bis((meth)acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, 1,4-bis((meth)acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane, and the like. 2. The conductive paste according to claim 1, wherein the acryloyloxy group is at least one selected from the group consisting of 1,6-bis((meth)acryloyloxy)butane, 1,6-bis((meth)acryloyloxy)hexane, triethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, N,N'-di(meth)acryloylethylenediamine, N,N'-(1,2-dihydroxyethylene)bis(meth)acrylamide, and 1,4-bis((meth)acryloyl)piperazine. The acrylic resin (b3) is a polymer of the acrylic monomer or a copolymer of the acrylic monomer with another monomer,
The conductive paste according to claim 5, wherein the other monomer is at least one selected from ethylene, a linear α-olefin having 3 to 20 carbon atoms, and an aromatic vinyl compound having 8 to 20 carbon atoms. The conductive paste according to claim 1, wherein the binder (b) comprises a terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1), a (meth)acrylate compound (b2) and an acrylic resin (b3). The conductive paste according to claim 1, wherein the binder (b) (100% by mass) contains a terminal hydroxyl group-containing polyalkylene glycol (meth)acrylate (b1) in an amount of 5% by mass or more and 60% by mass or less. The conductive paste according to claim 1, wherein the binder (b) (100 mass%) contains the (meth)acrylate compound (b2) in an amount of 20 mass% or more and 70 mass% or less. The conductive paste according to claim 1, wherein the binder (b) (100% by mass) contains acrylic resin (b3) in an amount of 5% by mass or more and 50% by mass or less. A cured product obtained by curing the conductive paste according to any one of claims 1 to 10. A substrate;
A semiconductor element mounted on the base material via an adhesive layer,
The semiconductor device, wherein the adhesive layer is formed by hardening the conductive paste according to any one of claims 1 to 10.

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