JP2001329048A - Liquid epoxy resin composition for sealing/filling agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid epoxy resin composition for a sealing/filling agent having a flux function of removing oxide film from bump electrodes or the like and resin characteristics as an underfill (sealing/filling agent). SOLUTION: The liquid epoxy resin composition for use at the sealing/filling stage in the packaging of flip chips indispensably contains (A) a liquid thermosetting epoxy resin and (B) an acid anhydride to function as a hardener for the liquid thermosetting epoxy resin, wherein an equivalent of the liquid thermosetting epoxy resin of (A) should contain 1.0-2.0 equivalents of the acid anhydride of (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid epoxy resin composition for a sealing filler used for sealing and filling in flip chip mounting, and a sealing and filling method using the same. More specifically, when performing heat curing of the sealing filler by heating, the solder bumps used for flip chip mounting are also melted, and the electrodes and the bumps are soldered and fixed and joined. The present invention relates to a liquid epoxy resin composition suitable for a sealing filler which also covers solder bumps in the step of performing.

[0002]

2. Description of the Related Art In order to reduce the weight, size, and thickness of electronic devices, a flip-chip mounting method has been adopted as a method of mounting a semiconductor chip component on a printed wiring board. In this flip-chip mounting method, an electrode for a chip component is formed on a mounting surface (back surface) of the chip component, and this is opposed to a predetermined region (mounting region) of the electrode for a substrate formed on a printed wiring board. A bump electrode is used to place and achieve the desired continuity between the electrodes. For example, a bump electrode made of spherical solder is provided in advance on a chip component electrode formed on the mounting surface (back surface) of the chip component, and this bump electrode is placed in a predetermined region (mounting region) of the substrate electrode. Make contact. In this arrangement, when the solder is melted, the solder is fixed and joined at a desired position in contact with the substrate electrode. Thereby, a desired electrical connection is achieved between the chip component and the electrodes of the printed wiring board via the bump electrodes. Alternatively, a method of providing a bump electrode on an electrode of a printed wiring board may be used.

In the flip-chip mounting method, the chip component is fixed only by the bump electrode connecting between the chip component and both electrodes of the printed wiring board.
Since the mounting method is aimed at miniaturization and thinning, the bump electrodes are made as small as possible. Chip components and printed wiring boards have different coefficients of thermal expansion,
When the thermal expansion or thermal contraction of the printed wiring board relatively occurs due to the temperature change during operation, the bump electrode has no play or bending to absorb or reduce the thermal displacement. When the temperature change (thermal cycle) is repeated, the stress-strain resulting from the above-mentioned thermal displacement is repeated, and as a result, peeling may occur at the joint (soldering part) between the bump electrode and the electrode.

In order to suppress the thermal cycle deterioration, filling and sealing with a resin having a role of reducing relative thermal displacement is performed by bonding and fixing the chip component and the printed wiring board to each other in a gap. . This sealing filler is called an underfill. However, from the purpose of use, the sealing filler fills the gap between the chip component and the printed wiring board densely and does not cause unfilled residue (void) called a void. Is filled. Furthermore, filling and sealing are performed so as to cover the periphery of the bump electrode densely.

Conventionally, a method has been used in which bonding (soldering) between a bump electrode and an electrode is performed first, and thereafter, a liquid epoxy resin composition is injected into a gap between the chip component and the printed wiring board and soaked. Was. In this method, the chip component itself becomes larger with the increase in integration, the number of electrodes (number of terminals) to be connected to the substrate electrode of the printed wiring board increases, the interval between the bump electrodes, the chip component and the printed wiring board increase. If the gap between them is further narrowed, there is a concern that the frequency of occurrence of voids will increase. In addition, the step of injecting the liquid epoxy resin composition is an obstacle to further increasing work efficiency.

As a technique for avoiding these problems, a layer of a liquid epoxy resin composition is formed in advance by a means such as screen printing in accordance with a predetermined area on a printed wiring board, and a chip is formed on the printed wiring board. Place the parts,
A method has been proposed in which a layer of a liquid epoxy resin composition is stretched on the mounting surface (back surface) of a chip component when making contact between the bump electrode and the electrode (Japanese Patent Application Laid-Open No. H11-354555). In the step of press-contacting the chip components, the liquid epoxy resin composition is filled with no gap between the chip components and the printed wiring board, together with the contact between the bump electrodes and the electrodes. Next, in order to perform bonding (soldering) between the bump electrodes and the electrodes, heating is performed in a reflow furnace to melt the solder bumps. During this heat treatment,
The filled liquid epoxy resin composition is also thermally cured, so that the formation of a bond (soldering) between the bump electrode and the electrode and the cured adhesion of the underfill (sealing filler) are simultaneously achieved. An underfill (sealing filler) can be prepared in advance by means such as screen printing with high reproducibility and workability.
Since the heating process can be integrated, the working efficiency is greatly improved.

[0007] The method of performing the bonding (soldering) between the bump electrode and the electrode and the curing and bonding of the underfill (encapsulating filler) in the same process is an excellent method in terms of workability. In addition, there is a great advantage that the chip component itself accompanying the high integration can easily cope with an increase in the number of electrodes (the number of terminals). On the other hand, when forming (soldering) the bond between the bump electrode and the electrode, the bump (spherical solder)
If the oxide film remains on the surface of the surface or on the electrode surface of the circuit, the melting of the bump (spherical solder) itself will not be uniform, or the solder between the electrode surface of the circuit and the solder will be defective. Occurs. This problem of poor soldering can be eliminated by applying a flux treatment.

However, in the method in which the heat treatment is performed in one step, the underfill is filled so as to cover the bump (spherical solder) itself, so that it is necessary to perform a flux treatment in advance. Nevertheless, the effect of the oxide film formed after the flux treatment remained, and the effect increased with the passage of time after the treatment. Therefore, even if a flux treatment is performed in advance, occurrence of soldering failure and conduction failure due to poor wetting with solder has been found not a little.

[0009]

In the method of performing the underfill filling in one step together with the placement and press-contact of the chip components on the printed wiring board, if the flux treatment is performed immediately before this step, Although the influence of the oxide film described above can be generally eliminated, the effect of the oxide film can be eliminated to the same degree or more instead of such means for limiting the degree of freedom in the process, and the degree of freedom in the process is limited. A new means that does not have to be developed is desired.

[0010] The present invention solves the above problems,
An object of the present invention is to eliminate the influence of an oxide film in advance, so that the same heat treatment can be applied to bond formation (soldering) between a bump electrode and an electrode and curing and bonding of an underfill (sealing filler) without performing a flux treatment. It is to provide a means that can effectively prevent the occurrence of poor soldering and poor conduction due to poor wetting with solder when performed in the process, and more specifically, a liquid epoxy resin composition for sealing filler When the material itself contains a component that has the same function as flux treatment that eliminates the effect of an oxide film on the formation of solder (bonding) between the bump electrode and the electrode, and is filled as an underfill (sealing filler), Bump electrodes and components related to the electrodes can be supplied,
It is an object of the present invention to provide a liquid epoxy resin composition for a sealing filler having a flux treatment effect, which can remove a surface oxide film such as a bump electrode and an electrode at the time of subsequent heating.

Further, the present invention has as a final object:
By using the liquid epoxy resin composition for a sealing filler also having the above-mentioned flux treatment effect, it is possible to prevent the occurrence of poor soldering and poor conduction due to poor wetting with solder, and a method of sealing and filling in flip chip mounting. Is to provide.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have to prepare any liquid epoxy resin composition for a sealing filler having a desired flux treatment effect. Whether the composition should contain
Research progressed. In the process, as described above, the liquid epoxy resin composition for sealing filler usually needs to be applied to a region limited by a considerable thickness by means such as screen printing on a printed wiring board. In consideration of its use form, it was determined that it was desirable to have a certain degree of viscosity, although it had fluidity that allowed application. Under these restrictions, when contained in a liquid epoxy resin composition, its thermosetting properties, adhesiveness, and resin strength after curing can be maintained within a desired range, and furthermore, it can be applied to surface oxide films such as bump electrodes and electrodes. On the other hand, a component that can be added at a concentration that can exhibit the same effect as the flux treatment was searched for. As a result, the solder material used for the bump electrode and the metal material such as copper used for the electrode on the printed wiring board have a function of removing and acting on the metal oxide forming the surface oxide film, It has been found that an acid anhydride that functions as a curing agent can be used for a liquid epoxy resin. In particular, the action of the acid anhydride on the metal oxide becomes higher when heated, while, when the acid anhydride consumed in the surface oxide film treatment is excessively contained in the liquid epoxy resin composition, However, since the surplus part is preferentially consumed in the reaction to the metal oxide, even if the content of the acid anhydride (curing agent) is initially high to some extent, the properties of the finally obtained thermoset product may not be sufficient. Found that it had only a slight effect.

That is, usually, the ratio recommended for the use of the underfill (encapsulating filler), that is, at most acid anhydride (curing agent) per 1 equivalent of the liquid epoxy resin
Less than 1 equivalent, preferably less than 1 equivalent, preferably 0.1 equivalent.
Although about 8 equivalents are used, an acid anhydride (curing agent) is used in excess for the purpose of the present invention. At this time, the liquid epoxy resin contained in the liquid epoxy resin composition, the ratio of the acid anhydride that functions as a curing agent for the liquid epoxy resin, a range (upper limit) in which the effect on the properties of the finally obtained thermosetting product is acceptable,
Further studies and studies were conducted to identify a range (preferable lower limit) in which the same effect as the intended flux treatment can be effectively achieved. As a result, with respect to the ratio of the liquid epoxy resin contained in the liquid epoxy resin composition and the acid anhydride functioning as a curing agent thereof, the acid anhydride (curing agent) was set to 1.0 with respect to 1 equivalent of the liquid epoxy resin. It is good to make it into the range of -2.0 equivalent, preferably, 1.1-1.6 equivalent, more preferably, when it is selected in the range of 1.1-1.4 equivalent, the same effect as the intended flux treatment. Have been found to be more reliably achieved, and the present invention has been completed.

That is, the liquid epoxy resin composition for a sealing filler of the present invention is a liquid epoxy resin composition used in a sealing and filling step of flip chip mounting, wherein the liquid epoxy resin composition is an essential component. (A) a liquid thermosetting epoxy resin, (B) an acid anhydride having a function of a curing agent for the thermosetting epoxy resin,
For one equivalent of the thermosetting epoxy resin (A),
A liquid epoxy resin composition comprising 1.0 to 2.0 equivalents of the acid anhydride (B). Preferably,
A liquid epoxy resin composition comprising 1.05 to 1.6 equivalents of the acid anhydride (B).

In the liquid epoxy resin composition for a sealing filler of the present invention, in addition to the above-mentioned essential components, a secondary liquid epoxy resin composition for a conventional sealing filler is added. Components may also be added. So, for example,
Liquid epoxy for a sealing filler, characterized by containing, as a secondary additive, at least one additive selected from a curing accelerator, a stress relieving agent, a leveling agent, a coupling agent, and an antioxidant. It can also be a resin composition.

Preferably, the thermosetting epoxy resin (A) is a diglycidyl ether having a bisphenol type skeleton, a polyglycidyl ether of a phenol resin, a diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid, or a fatty acid. A liquid epoxy resin composition for a sealing filler, which is at least one thermosetting epoxy resin selected from the group of epoxy resins composed of cyclic epoxy resins.

In addition, in the liquid epoxy resin composition for a sealing filler of the present invention, the acid anhydride of (B) is tetrahydrophthalic acid, hexahydrophthalic acid or endomethylenetetrahydrophthalic acid (methanotetrahydrophthalic acid). ) Acid anhydrides or derivatives having a substitution on the hydrocarbon ring thereof, phthalic anhydride or derivatives having a substitution on the benzene ring of phthalic anhydride, succinic anhydride or having a substitution on the hydrocarbon chain of succinic anhydride It is more preferable to prepare a liquid epoxy resin composition for a sealing filler, which is one or more acid anhydrides selected from the group of acid anhydrides composed of derivatives.

When a curing accelerator is also added to the liquid epoxy resin composition for a sealing filler of the present invention, it is preferable that (A)
A curing accelerator having a function of accelerating the curing reaction of the thermosetting epoxy resin with the acid anhydride of (B),
0.1 parts by weight per 100 parts by weight of the thermosetting epoxy resin (A).
More preferably, the liquid epoxy resin composition contains 1 to 20 parts by weight. Preferably, the content of the curing accelerator is selected in the range of 0.5 to 5 parts by weight per 100 parts by weight of the thermosetting epoxy resin (A).

Further, the liquid epoxy resin composition for a sealing filler of the present invention is used for sealing and filling in flip-chip mounting and exerts its effects. A method of sealing and filling in flip chip mounting, wherein (1) mutual conduction between a printed wiring board having substrate electrodes and a chip component having chip component electrodes using bump electrodes made of solder. (2) contact between the solder bump electrodes and the electrodes after disposing the chip components in a predetermined area on the printed wiring board to achieve After or in conjunction with
The sealing filling according to the present invention as described above, so as to cover the gap between the printed wiring board and the chip component disposed on a predetermined region thereon with the solder-made bump electrode and the electrode in which the contact is made. A filling step of filling the liquid epoxy resin composition for an agent; (3) heating the epoxy resin in the liquid epoxy resin composition filled in the gaps of the predetermined region, and then thermally curing the epoxy resin; A step of melting the solder bumps covered with the resin composition, heating for a predetermined time, cooling, and re-solidifying the once melted solder, soldering and bonding and bonding the bump electrode and the electrode, and simultaneously A liquid for a sealing filler of the present invention described above as a sealing filler, comprising a step of completing sealing filling with a thermosetting epoxy resin, and a series of steps (1) to (3) described above. Or equal to the method of sealing the filling, which comprises using the epoxy resin composition.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid epoxy resin composition for a sealing filler of the present invention has the same bonding (soldering) between the bump electrode and the electrode and the cured adhesion of the underfill (sealing filler). In the method performed in the step, the original effect is exhibited.

In the thermosetting epoxy resin, there are various means for inducing the thermosetting, not only a curing agent but also a curing catalyst. In addition to the acid anhydride, the curing agent may be a polyamine-based resin. There are also organic acid-containing polyesters, polyphenols, polymercaptans, isocyanates and the like. The present invention selects a curing agent, in particular, an acid anhydride from these various means for inducing thermal curing, and when the acid anhydride is used as the curing agent, it is mixed in a sufficiently high concentration in the liquid epoxy resin. In addition, it also takes advantage of the fact that the curing temperature can be selected to be about the melting temperature of solder.

Hereinafter, the liquid epoxy resin composition for a sealing filler of the present invention, its preparation method, and the procedure of sealing and filling using the liquid epoxy resin composition for a sealing filler will be described in more detail. I do.

The liquid epoxy resin composition for a sealing filler of the present invention has, as essential components, (A) a liquid thermosetting epoxy resin, and (B) a function of a curing agent for the thermosetting epoxy resin. This is a liquid epoxy resin composition containing an acid anhydride and uniformly mixing the two. In this case, the liquid epoxy resin composition used for underfill (sealing filler) is usually used in an amount equivalent to 1 equivalent of the liquid epoxy resin, and the acid anhydride of the curing agent is slightly less than 1 equivalent. However, in the present invention, an acid anhydride is added in excess of this recommended ratio. That is, it is characterized in that the acid anhydride of (B) is contained in an amount of 1.0 to 2.0 equivalents to 1 equivalent of the thermosetting epoxy resin of (A). Preferably, with respect to the acid anhydride of (B), a range of 1.05 to 1.6 equivalents, more preferably a range of 1.1 to 1.6 equivalents, still more preferably 1.1 to 1.4 equivalents. The content ratio is selected in the range.

By adding an excessive amount of the acid anhydride, the solder material used for the bump electrode and the metal material such as copper used for the electrode on the printed wiring board are inevitably present on the surface due to natural oxidation. An oxide film is provided with a function of removing an acid anhydride contained therein by acting on the metal oxide to convert the metal oxide into a carboxylate. This reaction proceeds faster as the concentration of the acid anhydride is higher.However, if the content of the acid anhydride is too high, the cured product obtained by thermosetting has a desired resin strength and less than the desired adhesiveness. Therefore, there is naturally an upper limit.

According to what the inventors have studied,
For one equivalent of the thermosetting epoxy resin (A),
If the acid anhydride of (B) does not exceed 2.0 equivalents, it falls within an acceptable range. Preferably, the amount of the acid anhydride is not more than 1.6 equivalents with respect to 1 equivalent of the thermosetting epoxy resin. More preferably, the acid anhydride is added to 1.
Make it 4 equivalents or less. That is, the acid anhydride is allowed to act to remove the metal oxide. If the oxide film inevitably existing on the surface of the solder material used for the bump electrode is thick, the reaction of converting the metal oxide into a carboxylate is more likely. In order to quickly supply the acid anhydride consumed in this reaction from the liquid epoxy resin composition near the bump electrode,
It is desirable to increase the concentration of the acid anhydride. Under such poor conditions, the acid anhydride may be higher than 1.4 equivalents,
The range may be 1.6 equivalents or more and not more than 2.0 equivalents. However, in the process where normal attention is paid, the oxide film unavoidably present on the surface is not so thick, and even if the amount of the acid anhydride is 1.4 equivalents or less, it is still an excessive amount.

On the other hand, the lower limit of the content ratio of the acid anhydride in the present invention is determined by the mechanism described above, even when the acid anhydride is consumed in the treatment of the oxide film, even when the liquid epoxy resin composition near the bump electrode is used. In 1 of liquid epoxy resin
The acid anhydride of the curing agent is selected so as to remain at a recommended ratio to the equivalent, that is, about 0.8 equivalent. Therefore, in the process where normal attention is paid, even if the content ratio of the acid anhydride is 1.0 equivalent, even if the acid anhydride is consumed, the amount that does not fall significantly below 0.8 equivalent in the vicinity of the bump electrode is Remains. Considering that the interval between the bump electrodes is narrow, the content ratio of the acid anhydride slightly exceeds 1.0 equivalent, for example, 1.05 equivalent,
When the acid anhydride is contained in an amount of 1.1 equivalents or more, even in the vicinity of the bump electrode where the concentration decrease due to its consumption is largest, the amount of the remaining acid anhydride can be reliably contained in the range of 0.7 equivalent to 1.0 equivalent. be able to.

In addition, as the temperature at which the thermosetting is performed is lowered, the temperature at which the flux treatment is performed is also lowered. In that case, it is desirable to slightly increase the content of the acid anhydride to compensate for the decrease in the reaction rate caused by the temperature decrease. Therefore, it is more preferable that the content of the acid anhydride is, for example, 1.05 equivalents, and that the acid anhydride be contained in an amount of 1.1 equivalents or more in view of safety.

Note that, under poor conditions in which an oxide film is frequently formed, more acid anhydride is consumed. Therefore, even if the acid anhydride is initially contained in an amount of 1.6 equivalents, near the bump electrode,
The amount of residual acid anhydride is 以下 or less of the initial amount, for example,
It may be 0.7 equivalent. In practice, as long as one of ordinary skill in the art takes the usual precautions to avoid excessive natural oxidation,
Even if the content ratio of the acid anhydride is selected in the range of 1.1 equivalents, at most 1.4 equivalents, even in the vicinity of the bump electrode, the amount of the remaining acid anhydride is 0.7 equivalents to 1.0 equivalents. Generally fits within range.

The sealing filler mainly has a function mainly to reinforce the area near the bump electrode, that is, the bonding and fixing area between the chip component and the printed wiring board. It is most preferable that the final content of the acid anhydride of the curing agent is in a preferable range, specifically, the acid anhydride of the curing agent is about 0.8 equivalent. As the distance from the metal surface such as a bump electrode increases, the content of the acid anhydride of the curing agent increases, but in this region, the equivalent ratio between the thermosetting epoxy resin and the acid anhydride of the curing agent is not so important. . At least, as long as there is no unfilled portion in the gap between the chip component and the printed wiring board and no voids are generated, unlike the sealing filler near the bump electrode, which is usually arranged on the outer peripheral portion of the chip component, after curing. Even if there is a slight variation in the resin properties of the above and a shift from the optimum sealing filler composition, this does not cause a serious problem. Accordingly, in the liquid epoxy resin composition of the present invention, the acid anhydride of the curing agent is, for example, 1.6 per equivalent of the liquid epoxy resin.
As in the case of the equivalent, even if it is twice the amount of 0.8 equivalent, which is generally preferred, the sealing and filling effect is sufficiently achieved so as not to cause any practical problem.

The acid anhydride used as the curing agent (B) is
Acid anhydrides of dicarboxylic acids which cause the curing of thermosetting epoxy resins are generally utilized. In the present invention, since the acid anhydride also has an action of removing an oxide film formed on the surface of the bump electrode, it is preferable that the acid anhydride also has a high reactivity with the metal oxide. Specifically, it acts on metal oxides,
Among the dicarboxylic acid ion-type ligands, those capable of forming a 6-membered ring structure, including the central metal cation species, are more preferable. In other words, in the acid anhydride used, it is more preferable that the ring structure containing -CO-O-CO- forms a 5-membered ring. Among the acid anhydrides used as curing agents for thermosetting epoxy resins, those having the above structure include, for example, tetrahydrophthalic acid,
Acid anhydrides of hexahydrophthalic acid or endomethylenetetrahydrophthalic acid (methanotetrahydrophthalic acid) or derivatives thereof having a substitution on the hydrocarbon ring, derivatives of phthalic anhydride or phthalic anhydride having a substitution on the benzene ring, anhydrides Acid anhydrides comprising a derivative of succinic acid or succinic anhydride having a substitution on the hydrocarbon chain, and the like. The derivatives of tetrahydrophthalic anhydride and hexahydrophthalic anhydride suitably used in the present invention include methylhexahydrophthalic anhydride (trade name B-650; manufactured by Dainippon Ink and Chemicals, Inc.). Derivatives of succinic anhydride include dodecenyl succinic anhydride and the like.

The type of the epoxy resin (A) is not limited as long as it is an epoxy resin that can be used as a sealing filler. From the resin strength at the time of curing, adhesiveness, etc., for example, diglycidyl ether having a bisphenol-type skeleton, polyglycidyl ether of a phenol resin, diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid, an alicyclic epoxy resin, etc. It is widely used in sealing fillers. In the present invention, diglycidyl ether having a bisphenol-type skeleton, polyglycidyl ether of a phenol resin, diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid, and an epoxy resin including an alicyclic epoxy resin are selected. It is more preferable. At that time, a single resin compound can be used, or a mixture of two or more resin compounds can be used. More specifically, as a diglycidyl ether having a bisphenol type skeleton, Epicoat 828
(Product name: Yuka Shell Epoxy Co., Ltd .: Epoxy equivalent 19)
0) or the like, as a polyglycidyl ether of a phenolic resin, Epicoat 154 (trade name; manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent: 178), or as a diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid; Cellulide 2021 (trade name; trade name; epoxy equivalent: 430), EPOMIC R540 (trade name; Mitsui Chemicals: epoxy equivalent: 195), etc.
Epoxy equivalent 135) manufactured by Daicel Chemical Industries, Ltd. is used.

For example, any one of the above-mentioned diglycidyl ether having a bisphenol type skeleton, polyglycidyl ether of a phenol resin, diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid, and an alicyclic epoxy resin is selected as the epoxy resin. In this case, examples of the acid anhydride that functions as a curing agent include, for example, an acid anhydride of tetrahydrophthalic acid, hexahydrophthalic acid, or endmethylenetetrahydrophthalic acid (methanotetrahydrophthalic acid) or a substitution on a hydrocarbon ring thereof. A more preferred combination is selected from the group consisting of a derivative having phthalic anhydride, a derivative having substitution on the benzene ring of phthalic anhydride, and a derivative having substitution on the hydrocarbon chain of succinic anhydride or succinic anhydride.

The liquid epoxy resin composition for a sealing filler of the present invention may contain, in addition to the essential components described above, secondary components commonly used in this type of epoxy resin composition. Specifically, as a secondary component, a curing accelerator,
Stress relaxation agents, leveling agents, coupling agents, antioxidants, etc., as well as plasticizers, thixotropic agents, etc. can be added. Which one to add, and the amount of addition, depending on the thermosetting epoxy resin and acid anhydride used for the essential components,
It is good to select appropriately.

For example, as the curing accelerator, amines, polyamides, imidazoles, Lewis acids, etc. which accelerate the polymerization addition reaction of the epoxy ring and the acid anhydride can be used. In addition to promoting the polymerization of the epoxy resin. Therefore, the amount to be added is appropriately selected according to the type and content of the acid anhydride of the curing agent and the target curing temperature and time. Specifically, for example,
Per 100 g of epoxy resin having an epoxy equivalent of 190,
0.5 to 10 mmol (mmol) for imidazoles
It is good to select in the range. Although it depends on the molecular weight of each curing accelerator, for example, it is in the range of 0.1 to 20 parts by weight, preferably 0.5 to 20 parts by weight per 100 parts by weight of the liquid epoxy resin.
It can be added in the range of 5 parts by weight. Further, the antioxidant can be previously mixed into the epoxy resin for the purpose of improving the heat resistance of the epoxy resin during the thermosetting treatment after sealing and filling. As the antioxidant, hydroquinone having an oxygen removing / reducing action, phosphites and the like can be used, and the amount of addition depends on the heat treatment environment, for example, the residual oxygen concentration and temperature in a reflow heating furnace. It is selected appropriately taking into consideration.

The amount of the leveling agent to be added is appropriately selected according to the viscosity of the liquid epoxy resin composition itself for the sealing filler, and accordingly to the type and content ratio of the thermosetting epoxy resin and the acid anhydride used as the essential components. Good to do. For example, as a leveling agent, ST80PA (trade name; manufactured by Dow Corning Silicone Co., Ltd.) or the like can be used, and it is added in a range of 0 to 5% by weight based on the whole liquid epoxy resin composition. Can be. Adeka resin EPR-1309 (trade name; manufactured by Asahi Denka Kogyo Co., Ltd.)
Epoxy equivalent 280) and the like, and can be added in the range of 0 to 10% by weight based on the whole liquid epoxy resin composition.

The coupling agent is preferably a suitable one as required according to the type of epoxy resin to be used in consideration of the material of the printed wiring board and the type of material exposed on the back surface of the chip component. Select and add. Examples of widely used coupling agents include, for example, silane-based coupling agents such as γ-glycidylotrimethoxysilane. From these, a suitable amount of a suitable coupling agent may be added according to the above selection criteria. Generally, the coupling agent is used in an amount of from 0 to the entire liquid epoxy resin composition.
It can be added in the range of 10% by weight.

The plasticizer and the thixotropic agent are added as necessary in consideration of the coating processability of the liquid epoxy resin composition. As the plasticizer, for example, dibutyl phthalate and the like may be used, and a suitable amount of a preferable plasticizer may be added according to the type of the epoxy resin. Examples of the thixotropic agent include triglyceride of hydroxystearic acid, fumed silica, and the like, and a suitable amount of the preferable thixotropic agent may be added according to the type of the epoxy resin.

The liquid epoxy resin composition for a sealing filler of the present invention comprises a thermosetting epoxy resin and an acid anhydride, which are essential components, and the above-mentioned commonly used secondary components which are optionally added. Are sufficiently mixed, and bubbles generated or taken in by stirring in the preparation step or the like are degassed under reduced pressure to produce the compound. In addition, the acid anhydride contained in the liquid epoxy resin composition for a sealing filler of the present invention is a compound that originally dislikes moisture, and also for maintaining the action of removing an oxide film on the surface of a metal material. Preparation and storage are performed while suppressing the mixing of water into the manufactured liquid epoxy resin composition.

The liquid epoxy resin composition for a sealing filler of the present invention is used for sealing and filling in flip chip mounting and exhibits its effect. Specifically, in flip-chip mounting, the effect is exhibited in a method in which the solder bump electrodes are melted together with the thermosetting after filling the underfill with the underfill.

The in-situ removing action of the oxide film remaining on the metal surface such as a bump made of solder can be obtained irrespective of the filling method of the liquid epoxy resin composition. When taken, the effect is higher. Specifically, as a method of sealing and filling in flip chip mounting, (1) a printed wiring board having substrate electrodes and a chip component having chip component electrodes are connected between the two electrodes by using solder bump electrodes. A step of arranging the chip component in a predetermined area on the printed wiring board so as to achieve mutual conduction, and then making contact between the solder bump electrode and the electrode; (2) a step of connecting the solder bump electrode and the electrode After or together with the step of making contact, in the gap between the printed wiring board and the chip component disposed on a predetermined region thereon, the solder bump electrode and the electrode, which have made the contact, Filling the liquid epoxy resin composition for a sealing filler according to the present invention so as to cover the liquid epoxy resin; (3) heating the liquid epoxy resin to fill the gap in the predetermined region; A step of melting the solder bumps covered with the liquid epoxy resin composition while heating the epoxy resin in the resin composition, and after heating for a predetermined time, cooling and re-heating the once melted solder. The step of solidifying, soldering and bonding the bump electrode and the electrode, and simultaneously completing the sealing and filling with the thermosetting epoxy resin, and performing the sealing and filling by the series of steps (1) to (3) described above. This is preferable.

That is, a liquid epoxy resin composition having a predetermined viscosity is applied thickly on a printed wiring board in advance, and a chip component is pressed on the liquid epoxy resin composition. And the liquid epoxy resin composition that has been crushed and spread at the same time covers the metal wiring electrodes and the bump electrodes. At this time, since the top surface of the applied liquid epoxy resin composition is substantially flat, pressing the chip component from above does not generate an unfilled portion or a void portion. Further, the surface of the metal wiring electrode and the bump electrode that have made physical contact can be in a state in which the liquid epoxy resin composition is densely covered. In this state,
Since heating is performed to melt the solder bumps, the oxide film remaining on the metal surface is removed as described above.

[0042]

EXAMPLES Hereinafter, specific examples will be given to explain the liquid epoxy resin composition for a sealing filler of the present invention and the effect of removing an oxide film achieved by sealing and filling using the same. Will be described. The following examples are examples of the best embodiment of the present invention, but the present invention is not limited to these examples.

First, the effect of removing the oxide film formed on the surface of the solder material, which is a characteristic of the liquid epoxy resin composition for a sealing filler of the present invention, was examined.

(A) a liquid thermosetting epoxy resin contained as an essential component in the liquid epoxy resin composition, (B)
The content ratio of the acid anhydride having the function of a curing agent to the thermosetting epoxy resin was variously selected, and the flux action of the solder material on the oxide film was examined. Whether or not an effective flux action was achieved was determined based on the presence or absence of conduction failure in a conduction test between electrodes, which was presumed to be due to solder failure, for a sample filled and cured with a sealing filler.

(Comparative Example 1) Conventionally, a composition recommended as an epoxy resin for underfill, that is, one equivalent of a liquid epoxy resin is added with one part of an acid anhydride as a curing agent.
A liquid epoxy resin composition to be used in an amount less than the equivalent but slightly lacking the equivalent, specifically, about 0.8 equivalent was prepared.

To 100 parts by weight of Epicoat 828 (trade name; manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent: about 190) of bisphenol A type epoxy resin, methylhexa used as an acid anhydride curing agent for Epicoat 828 was used. Hydrophthalic anhydride B-650 (trade name; manufactured by Dainippon Ink and Chemicals, Inc .: acid anhydride equivalent: about 170) 75
2 parts by weight of 1-benzyl-2-methylimidazole BM112 (trade name; manufactured by Yuka Shell Epoxy Co., Ltd., molecular weight: 172) were further added and uniformly mixed as a curing accelerator. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. The desired curing of the liquid epoxy resin composition is performed at a curing temperature of 230 ° C. for 3 minutes as a thermosetting condition.

Example 1 This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride is used for 1 equivalent of a liquid epoxy resin, specifically, A liquid epoxy resin composition was prepared using about 1.3 equivalents.

With respect to 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, methylhexahydrophthalic anhydride B-
650 (described above) and 1-benzyl-2-methylimidazole BM as a curing accelerator.
112 (mentioned above) and 2 parts by weight were added and mixed uniformly. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition is also subjected to desired curing at a curing temperature of 230 ° C. for 3 minutes as a thermal curing condition.

Example 2 This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride is added to 1 equivalent of a liquid epoxy resin, specifically, A liquid epoxy resin composition was prepared using about 1.05 equivalents.

Based on 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, methylhexahydrophthalic anhydride B-
650 (supra), and BM1 of 1-benzyl-2-methylimidazole as a curing accelerator.
12 parts (described above) and 2 parts by weight were added and uniformly mixed. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition is also subjected to desired curing at a curing temperature of 230 ° C. for 3 minutes as a thermal curing condition.

Example 3 This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride is used for 1 equivalent of a liquid epoxy resin, specifically, , About 1.1 equivalents of a liquid epoxy resin composition was prepared.

With respect to 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, B-methylhexahydrophthalic anhydride used as a curing agent
650 (described above), and BM1 of 1-benzyl-2-methylimidazole as a curing accelerator.
12 parts (described above) and 2 parts by weight were added and uniformly mixed. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition is also subjected to desired curing at a curing temperature of 230 ° C. for 3 minutes as a thermal curing condition.

Example 4 This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride is added to 1 equivalent of a liquid epoxy resin, specifically, And about 1.0 equivalent of a liquid epoxy resin composition was prepared.

With respect to 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, methyl hexahydrophthalic anhydride used as a curing agent
650 (described above), and BM1 of 1-benzyl-2-methylimidazole as a curing accelerator.
12 parts (described above) and 2 parts by weight were added and uniformly mixed. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition is also subjected to desired curing at a curing temperature of 230 ° C. for 3 minutes as a thermal curing condition.

The liquid epoxy resin compositions of Examples 1, 2 and 3 and 4 and the liquid epoxy resin composition of Comparative Example 1 were flip-chip mounted under the same conditions, respectively. With respect to the mounted semiconductor device, the presence or absence of a conduction failure between the chip component and the electrode of the printed circuit board was evaluated. Table 1 also shows the results of the continuity test. The continuity test result is represented by the ratio of the number of accepted products having no continuity failure to the total number of 50 samples as an index.

As shown in Table 1, all of the liquid epoxy resin compositions of Examples 1, 2, and 3 containing the acid anhydride of the curing agent in an amount exceeding 1 equivalent passed all the tests. In the liquid epoxy resin composition of Comparative Example 1, conduction failure occurred in approximately half. However, when the acid anhydride of the curing agent is 1 equivalent as in Example 4, depending on the case, conduction failure may occur in several pieces. Therefore, in the liquid epoxy resin composition of the present invention, it was determined that the bonding with the good bump electrodes was performed as described above by the reflow treatment as a result of the flux property being imparted by the acid anhydride contained in an excessive amount. Is done.

[0057]

[Table 1]

Comparative Example 2 An acid anhydride of a curing agent was added to a composition conventionally recommended as an epoxy resin for underfill, that is, 1 equivalent of a liquid epoxy resin.
A liquid epoxy resin composition to be used in an amount less than the equivalent but slightly lacking the equivalent, specifically, about 0.8 equivalent was prepared.

Dodecenyl succinic anhydride (manufactured by Wako Pure Chemical Industries, Ltd .; acid anhydride) used as an acid anhydride-based curing agent for the epicoat 828 is used with respect to 100 parts by weight of epicoat 828 (described above) of a bisphenol A type epoxy resin. 260) 115 parts by weight and BM11 of 1-benzyl-2-methylimidazole as a curing accelerator
2 (described above) and 2 parts by weight were added and uniformly mixed. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. The desired curing of the liquid epoxy resin composition is performed at a curing temperature of 230 ° C. for 3 minutes as a thermosetting condition.

Example 5 This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride is used for 1 equivalent of a liquid epoxy resin, specifically, A liquid epoxy resin composition was prepared using about 1.3 equivalents.

To 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, 180 parts by weight of dodecenyl succinic anhydride (described above) used as a curing agent were added, and 1-benzyl was used as a curing accelerator. −
2 parts by weight of BM112 of 2-methylimidazole (described above) were added and mixed uniformly. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition also has a curing temperature of 230
At 3O 0 C, the desired cure is achieved in 3 minutes.

(Example 6) This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride to 1 equivalent of a liquid epoxy resin, specifically, A liquid epoxy resin composition was prepared using about 1.05 equivalents.

To 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, 145 parts by weight of dodecenyl succinic anhydride (described above) used as a curing agent were added, and 1-benzyl was further used as a curing accelerator. −
2 parts by weight of BM112 of 2-methylimidazole (described above) were added and mixed uniformly. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition also has a curing temperature of 230
At 3O 0 C, the desired cure is achieved in 3 minutes.

(Example 7) This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride is added to 1 equivalent of a liquid epoxy resin, specifically, , About 1.1 equivalents of a liquid epoxy resin composition was prepared.

To 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, 153 parts by weight of dodecenyl succinic anhydride (described above) used as a curing agent were added, and 1-benzyl was used as a curing accelerator. −
2 parts by weight of BM112 of 2-methylimidazole (described above) were added and mixed uniformly. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition also has a curing temperature of 230
At 3O 0 C, the desired cure is achieved in 3 minutes.

Example 8 This is an example of the liquid epoxy resin composition for a sealing filler of the present invention, that is, 1 equivalent or more of an acid anhydride is used for 1 equivalent of a liquid epoxy resin, specifically, And about 1.0 equivalent of a liquid epoxy resin composition was prepared.

To 100 parts by weight of Epicoat 828 (described above) of a bisphenol A type epoxy resin, 135 parts by weight of dodecenyl succinic anhydride (described above) used as a curing agent were added, and 1-benzyl was used as a curing accelerator. −
2 parts by weight of BM112 of 2-methylimidazole (described above) were added and mixed uniformly. Thereafter, a degassing treatment under reduced pressure was performed to prepare a liquid epoxy resin composition. This liquid epoxy resin composition also has a curing temperature of 230
At 3O 0 C, the desired cure is achieved in 3 minutes.

The liquid epoxy resin compositions of Examples 5, 6 and 7, and 8 and the liquid epoxy resin composition of Comparative Example 2 were flip-chip mounted under the same conditions, respectively. With respect to the mounted semiconductor device, the presence or absence of a conduction failure between the chip component and the electrode of the printed circuit board was evaluated. Table 2 also shows the results of the continuity test. The continuity test result is represented by the ratio of the number of accepted products having no continuity failure to the total number of 50 samples as an index.

As shown in Table 2, all of the liquid epoxy resin compositions of Examples 5, 6, and 7 containing more than 1 equivalent of the acid anhydride of the curing agent passed the test. In the liquid epoxy resin composition of Comparative Example 2, approximately 1 /
3 has a conduction failure. However, in the case of the liquid epoxy resin composition of Example 8 containing one equivalent of an acid anhydride as a curing agent, conduction failure may occur in several pieces in some cases. Therefore, in the liquid epoxy resin composition of the present invention, it was determined that the bonding with the good bump electrodes was performed as described above by the reflow treatment as a result of the flux property being imparted by the acid anhydride contained in an excessive amount. Is done.

[0070]

[Table 2]

As shown in the comparison results of Tables 1 and 2 described above, in the present invention, when the content ratio of the acid anhydride is 1.0 equivalent or more, it is judged that a sufficient flux action is exhibited. Considering also the resin properties of the obtained thermosetting resin cured product, the content ratio of the acid anhydride is preferably 2.0 equivalents or less, preferably 1.6 equivalents or less, more preferably 1.4 equivalents or less. It is also concluded that it should be.

Example 9 On the basis of the above results, a liquid epoxy resin composition for a sealing filler was prepared in which the content ratio of the acid anhydride was selected to the most preferable range of 1.3 equivalents. Using this liquid epoxy resin composition, underfill was filled according to the following procedure. As a result, when the bump was melted, there was no soldering failure due to the surface oxide film, and there was no filling failure or void generation.

The present invention was applied to flip chip mounting in which bump electrodes were provided on a printed wiring board. First, the epoxy resin composition for underfill is applied in a predetermined pattern by screen printing on a printed wiring board on which the bump electrodes are formed in advance. Again, the chip component with the bump electrode formed on the back side, the bump electrode on the wiring board printed with this underfill agent pattern,
Positioning is performed so that both electrode positions are aligned. In this position, the chip component is pressed so that the electrodes come into contact with each other. In the process, the applied underfill agent layer is spread and adheres to the back surface of the chip component. Also, the contacting bump electrode, the corresponding wiring surface on the substrate, and the back electrode surface of the chip component are firmly covered with the spread underfill agent.

While being pressed from the upper surface of the chip component, the chip component is placed in a reflow furnace to perform bump melting. Bump soldering is completed, and thermal curing of the epoxy resin as an underfill agent further proceeds.

As described above, according to this procedure, since the chip component is pressed, no air bubbles remain between the chip component and the back surface of the chip component, so that no void is generated. Further, as described above, the oxide film is also removed in situ, so that there is no soldering failure. In this way, there is no electrode bonding failure, and the filling and curing of the underfill can be achieved without excess or shortage.

[0076]

According to the liquid epoxy resin composition for a sealing filler of the present invention, (A) a liquid thermosetting epoxy resin which is contained as an essential component, and (B) a function of a curing agent for the thermosetting epoxy resin. The content ratio of the acid anhydride having
For one equivalent of the thermosetting epoxy resin (A),
The acid anhydride of (B) is usually used in a liquid epoxy resin composition of this kind in an amount of 0.8 equivalent, at most 1 equivalent.
A significantly higher ratio than an amount slightly less than the equivalent.
Specifically, 1.0 to 2.0 equivalents of the acid anhydride of (B)
Preferably it is selected in the range of 1.0 to 1.6 equivalents, more preferably in the range of 1.05 to 1.6 equivalents. In a state where the liquid epoxy resin composition is filled, when a solder bump electrode arranged to form physical contact between the chip component and the electrode of the printed wiring board is melted by heating, an excessive amount of acid is generated. The anhydride also acts as a flux to remove the oxide film on the surface. As a result, even when the acid anhydride is consumed, approximately 0.8 equivalents of the acid anhydride remain in the liquid epoxy resin composition near the bump electrode, which is considered to be preferable. The effect of becoming a cured product is obtained. Therefore, the solder used for the bump electrodes can be melted well, and the electrodes can be joined together by soldering, and at the same time, the sealing filler can be used without removing the oxide film on the surface of the bump electrodes etc. The advantage is that thermosetting can be performed. In addition, this method of sealing and filling has high work efficiency, and in particular, a desired liquid epoxy resin composition layer is applied and formed on a printed wiring board by means such as screen printing.
Irrespective of the shape and material of the printed wiring board, it is possible to shorten the overall process and eradicate defective factors such as generation of voids.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference)

Claims (7)

[Claims] 1. A liquid epoxy resin composition used in a sealing and filling step of flip chip mounting, wherein the liquid epoxy resin composition comprises, as an essential component,
(A) a liquid thermosetting epoxy resin, (B) an acid anhydride having a function of a curing agent for the thermosetting epoxy resin, and (A) one equivalent of the thermosetting epoxy resin;
A liquid epoxy resin composition for a sealing filler, comprising 1.0 to 2.0 equivalents of the acid anhydride of (B). 2. The content ratio of the acid anhydride of (B) is 1.05 to 1 equivalent of the thermosetting epoxy resin of (A).
2. The method according to claim 1, wherein the amount is selected in a range of 1.6 equivalents.
4. The liquid epoxy resin composition for sealing filler according to item 1. 3. A curing accelerator as a secondary additive component,
The liquid epoxy resin composition for a sealing filler according to claim 1 or 2, further comprising one or more additional components selected from a stress relieving agent, a leveling agent, a coupling agent, and an antioxidant. 4. The thermosetting epoxy resin (A) is a diglycidyl ether having a bisphenol type skeleton, a polyglycidyl ether of a phenol resin, a diglycidyl ester of an aliphatic carboxylic acid or an aromatic carboxylic acid,
The liquid epoxy resin for a sealing filler according to any one of claims 1 to 3, wherein the liquid epoxy resin is at least one thermosetting epoxy resin selected from the group of epoxy resins including an alicyclic epoxy resin. Composition. 5. The acid anhydride of (B) is an acid anhydride of tetrahydrophthalic acid, hexahydrophthalic acid or endmethylenetetrahydrophthalic acid (methanotetrahydrophthalic acid) or a derivative having a substitution on a hydrocarbon ring thereof; At least one acid selected from the group consisting of phthalic anhydride or a derivative having a substitution on the benzene ring of phthalic anhydride, and succinic anhydride or a derivative having a substitution on the hydrocarbon chain of succinic anhydride The liquid epoxy resin composition for a sealing filler according to any one of claims 1 to 4, wherein the composition is an anhydride. 6. A curing accelerator having a function of accelerating the curing reaction of (A) with the acid anhydride of (B) with respect to the thermosetting epoxy resin of (A), further comprising 100 parts by weight of (A) the thermosetting epoxy resin. The liquid epoxy resin composition for a sealing filler according to any one of claims 1 to 5, wherein the content is 0.1 to 20 parts by weight per unit. 7. A method of sealing and filling in flip-chip mounting, comprising: (1) using a bump electrode made of solder to connect a printed wiring board having substrate electrodes and a chip component having chip component electrodes to both electrodes; A step of arranging the chip component in a predetermined region on the printed wiring board so as to establish a mutual connection between the solder bump electrode and the solder bump electrode; and After the step of making contact between the electrodes, or in conjunction with the step, in the gap between the printed wiring board and the chip component disposed on a predetermined region thereon, a solder bump electrode that has made the contact, A filling step of filling the liquid epoxy resin composition for a sealing filler according to any one of claims 1 to 6 so as to cover the electrodes, (3) then heating to fill the gap in the predetermined region. I In the liquid epoxy resin composition, a step of advancing the thermosetting of the epoxy resin and melting the solder bumps covered by the liquid epoxy resin composition; heating for a predetermined time; cooling; and melting once. Re-solidifying the solder, soldering and bonding and bonding the bump electrode and the electrode, and simultaneously completing the sealing and filling with a thermosetting epoxy resin; and a series of steps (1) to (3) above. A method for sealing and filling, comprising using the liquid epoxy resin composition for sealing filler according to any one of claims 1 to 6 as a sealing filler.