KR101139759B1 - Resin composition for no-flow underfill - Google Patents

Abstract

The present invention relates to a non-flow underfill resin composition (no-flow underfill) for protecting and strengthening wiring of a semiconductor chip. The present invention provides a non-flow underfill resin composition (no-flow underfill) comprising an epoxy resin and an acid hardener having an imide bond structure. The non-flowable underfill resin composition of the present invention can be cured quickly at a soldering process temperature, and has excellent crack resistance and thermal stability after curing.

Semiconductor, non-flowable underfill, imide bond structure, acid hardener, epoxy resin

Description

Non-flowable underfill resin composition {RESIN COMPOSITION FOR NO-FLOW UNDERFILL}

The present invention relates to a non-flowable underfill resin composition used for bonding a semiconductor chip and a substrate, and a flip chip package assembly using the same, and more particularly, to a long service life at room temperature including an acid hardener having an imide bond structure. And a resin composition for non-flowable underfill and a flip chip package assembly using the same, which can exhibit good reliability during a heat cycle process.

The semiconductor assembly typically includes an integrated circuit component electrically connected to a printed circuit board, such as a lead frame or package substrate, mounted on the lead frame or package substrate. In the trend of electronic products requiring small size, light weight, and high functionality, there is a demand for a method of increasing the number of signal input / output terminals while reducing the mounting area of such integrated circuit components. For this reason, the bare chip is mounted as it is instead of the semiconductor device electrically connected to the lead frame by wire bonding and molded with epoxy resin, ceramics, or the like. Flip chip packages are becoming mainstream.

The flip chip package method is a method of electrically connecting a bonding pad on a semiconductor chip and a pad on a substrate using conductive bumps. The substrate can be attached at the same time. However, it has been a problem that mismatches occur due to differences in coefficient of thermal expansion (CTE) of semiconductor chips, wiring materials, and package substrates. Accordingly, in order to solve the mismatch problem described above and to physically support the electrical connection through the metallization or the conductive polymer, the gap between the semiconductor chip and the package substrate is sealed around the electrical connection. Charge the material. Such materials are known as underfills, and the use of such underfills can extend the fatigue life of the solder joints. In general, the underfill method is a capillary flow underfill method in which a liquid underfill material such as an epoxy resin is injected between a semiconductor chip and a package substrate, and then cured to adhere between the semiconductor chip and the package substrate. Mainly used.

In the case of applying a conventional capillary flow underfill, the curing reaction of the underfill injected and supplied underfill is performed after the metal solder or conductive polymer is reflowed to form the wiring. When a predetermined amount of underfill material is supplied along one or more edges of the electronic component assembly, the underfill material is drawn in by capillary action in the gap between the semiconductor chip and the package substrate. In general, flip chip packages are mostly subjected to the capillary flow underfill described above.

As a more effective method, a so-called filling method using no-flow fluxing underfill has been proposed. 1 is a schematic diagram of a non-flowable fluxing underfill method. In FIG. 1, the first step of applying the non-flowable underfill is applying the underfill resin composition 11 onto the package substrate 14. As a second step, the flip chip 15 and the metal pad part 12 of the package substrate to which the underfill resin composition is applied are aligned. Flip chip alignment is used to position the solder bumps 16 of the flip chip and the metal pads 12 of the package substrate to correspond, respectively, and adjust the flip chip and the package substrate to be horizontal. The final step of the non-flowable underfill process is to bond the aligned flip chip and package substrate and then through the solder reflow oven to complete the electrical connection through soldering and at the same time, underfill resin composition It is the step of curing.

In the non-flowable fluxing underfill method of FIG. 1, a metal junction connection method of electrically connecting a semiconductor terminal portion and a terminal portion of a package substrate by reflowing and forming a metal junction using a high temperature in the final step of bonding the semiconductor chip ( metal-joint connection) has been proposed. As a metal joint connection method, a solder joint has been proposed, in which a solder bump of a semiconductor chip and a package substrate metal pad are reflowed while passing through a reflow oven, and then joined. . Conventional capillary flow underfill process that injects underfill depending on capillary phenomenon has no limitation on the size of semiconductor chip to be mounted. However, in the above non-flowable underfill process, there is no limitation on the area of the semiconductor component to be mounted. There is an advantage that can significantly reduce the curing time. In addition, the metal-joint connection method of the non-flowable underfill process is a method proven in connection reliability between terminals and insulation reliability between terminal connection portions by adopting a connection through a solder joint used in a conventional capillary flow underfill process.

In a non-flowable underfill process using a metal bonded connection, it is key to maintain the appropriate viscosity and the appropriate curing rate of the underfill material when performing the soldering and curing of the underfill described above. In order to melt the solder between the semiconductor component and the package substrate so that the connection can be easily formed, the underfill must maintain a low viscosity of about 2,000 to 6,000 cps. In addition, the curing reaction of the underfill should not occur after too long time that the solder is cured, it is preferable that the underfill is quickly cured in one reflow fluidization step after the solder is melted. In addition, the underfill should provide excellent adhesion to the solder mask, the passivation layer of the solder and semiconductor components.

Thus, the inventors of the present invention improved the heat resistance stability and mechanical strength of the flip chip package assembly with excellent adhesion while maintaining a constant viscosity when using an epoxy resin containing an acid hardener for underfill. It came.

An object of the present invention is to provide a non-flowable underfill resin composition having improved thermal stability and mechanical strength of a flip chip package assembly.

Another object of the present invention is to provide a flip chip package assembly manufactured using the non-flowable underfill resin composition.

Non-flowable underfill resin composition of the present invention for achieving the above object (A) epoxy resin; (B) a curing agent and curing accelerator comprising an acid curing agent having an imide bond structure; (C) thermoplastic resin for modification; And (D) a melting agent. In the above, an imide-acid having a carboxylic acid structure at its terminal may be used as the acid hardener having an imide bond structure.

The epoxy resin is selected from the group consisting of mono- or polyfunctional glycidyl ethers of bisphenol-A or bisphenol-F, aliphatic and aromatic epoxys, saturated epoxy resins, unsaturated epoxy resins, alicyclic epoxy resins and aglycidyl ether epoxides Being more than one.

The acid hardener which has the said imide bond structure is an imide-acid which has a carboxylic acid structure at the terminal. Preferably, the imide-acid is at least one selected from the group consisting of structures (a) to (d) of the formula:

(a)

(b)

(c)

(d)

The content of the curing agent and the curing accelerator including the acid hardener is preferably 1 to 110 parts by weight based on 100 parts by weight of the epoxy resin.

The modifying thermoplastic resins include acrylic rubber, epoxy rubber dispersed in epoxy resins, carboxy terminated butadiene nitrile (CTBN), acrylonitrile butadiene styrene rubber (acrylonitrile-butadiene- at least one selected from the group consisting of styrene rubber and polymethyl siloxane.

The content of the modifying thermoplastic resin is preferably 3 to 80 parts by weight based on 100 parts by weight of the epoxy resin.

The melting agent may be ethylene glycol, glycerol, 3- [bis (glycidyloxymethyl) methoxy] -1,2-propanediol (3- [bis (glycidyloxymethyl) methoxy] -1 , 2-propanediol), glutaric acid, and trifluoroacetate.

The content of the melting agent is preferably 1 to 10 parts by weight based on 100 parts by weight of the total weight of the curing agent and curing accelerator including the epoxy resin, an acid curing agent having an imide bond structure, and a thermoplastic resin for modification.

The non-flowable underfill resin composition of the present invention may further include at least one selected from the group consisting of a monofunctional epoxy reactive diluent, a surfactant, an adhesion imparting agent, an inorganic filler, a flame retardant, and an ion trapping agent. have.

On the other hand, the present invention provides a flip chip package assembly manufactured using the non-flowable underfill resin composition.

In the present invention, by mixing the acid curing agent having the imide-bonded structure with the underfill resin composition, it is possible to cure quickly at the soldering process temperature, non-flowable underfill resin to achieve excellent crack resistance and thermal stability after curing It is possible to provide a composition.

The non-flowable underfill resin composition of the present invention is based on 100 parts by weight of an epoxy resin; 1 to 110 parts by weight of a curing agent and a curing accelerator including an acid curing agent having an imide bond structure; 3 to 80 parts by weight of the thermoplastic resin for modification; And 1 to 10 parts by weight of a melting agent based on 100 parts by weight of the total weight of the curing agent and curing accelerator including the epoxy resin and an acid curing agent having an imide bond structure, and a thermoplastic resin for modification.

At this time, exemplifying epoxy resins include mono- and polyfunctional glycidyl ethers of bisphenol-A and bisphenol-F, aliphatic and aromatic epoxy, saturated and unsaturated epoxy, alicyclic epoxy resins or combinations thereof. The epoxy resin is preferably 470 or less, more preferably 300 or less, in order to secure the glass transition temperature and mechanical strength after curing. Moreover, as an epoxy resin, an aromatic epoxy resin is preferable from a viewpoint of the preferable physical property etc. of hardened | cured material. In the present invention, the aromatic epoxy resin means an epoxy resin having an aromatic ring skeleton in an epoxy resin molecule. Therefore, as a component, aromatic epoxy resin which has two or more epoxy groups in 1 molecule, and whose equivalent is 470 or less is preferable. These epoxy resins can be used individually, respectively and can also be used in combination of 2 or more type. It is also possible to use modified liquid epoxy treated with a relatively high viscosity elastomer in order to increase the film formability of the overall underfill composition.

Non-glycidyl ether epoxides that can be used as epoxy resins include, for example, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclo containing ester bonds with two epoxide groups that are part of the ring structure. Hexane carboxylate (ERL 4221), vinylcyclohexene dioxide, which contains two epoxide groups, one of which is part of the ring structure, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxycyclohexane Carboxylates and dicyclopentadiene dioxides. The aglycidyl ether epoxide can be used in combination with the glycidyl ether epoxy. Specific examples of such epoxy resins include HP4032 series (Japanese ink chemical industry), Epicoat 807 (Yuka Shell Epoxy Co., Ltd), Epicoat 828EL (Yuka Shell Epoxy Co., Ltd), and Epicoat 152 (Yuka). Shell Epoxy Co., Ltd). Examples of the elastomer-modified liquid epoxy include TSR960 (Japanese Ink Chemical Industry, Epoxy Equivalent 240, Viscosity 60000 to 90000cp at 25 ° C) and the like.

On the other hand, the acid hardening | curing agent which has an imide bond structure is for promoting hardening reaction of the said epoxy resin component. At this time, the curing agent may further include a curing accelerator. The acid hardener having an imide bond structure suitable for the present invention is preferably a phthalimide having a terminal carboxylic acid structure or a trimellitimide having a terminal carboxylic acid structure. More specifically, an imide-diacid having a structure such as the following formulas (a) to (d) is preferable:

(a)

(b)

(c)

(d)

The imide-diacid of Formula (1) may be produced by the reaction of trimellitic anhydride and an amine. When the imide-dieside and epoxy having the structure described above are cured, an imide group may be introduced into the crosslinked network to improve heat resistance and mechanical properties of the cured product. The imide-dieside crosslinking network after the curing reaction of bisphenol F epoxy with formula (d) is illustrated in Scheme (1) below:

Scheme (1)

As the curing agent component used in the present invention, it is possible to further use an epoxy curing agent and a curing accelerator in addition to the acid curing agent having the imide bond structure. By using an epoxy curing agent and a curing accelerator which are used in addition to the acid curing agent, it is possible to control the rate of curing reaction of the epoxy resin component and to improve reliability after curing. As a curing agent other than the acid curing agent having an imide bond structure, conventional epoxy curing agents such as anhydride, amine, and phenol may be used, and the curing start temperature is 140 ° C. As mentioned above, the hardening | curing agent which hardening reaction produces at high speed in the range of 240 degreeC-250 degreeC which is the highest temperature range is preferable. That is, it is preferable that the curing reaction is completed in the temperature profile of a conventional soldering process. In addition, such a curing agent is preferably a long pot life (pot life). Specific examples of the epoxy curing agent include phenol novolak resin, cresol novolak resin, and the like, as examples of anhydrides such as dicyandiamide, amines, and methylhexahydrophthalic anhydride, or phenolic curing agents. can do. In addition to the curing agent, organic phosphine compounds such as triphenylphosphine, imidazole compounds such as 2-ethyl-4-methylimidazole, tertiary amine And the like can be added as a curing accelerator. The content of the curing agent and the curing accelerator including an acid curing agent having an imide bond structure is preferably 1 to 110 parts by weight based on 100 parts by weight of the epoxy resin. When using an amine curing agent, it is preferable that the usage-amount makes the epoxy equivalent ratio per reactive hydrogen of an amine group 0.05-5. When using an anhydride type hardening | curing agent, it is preferable to make the epoxy equivalent ratio per anhydride ring into 0.05-5. When the compounding quantity of a hardening | curing agent is not adjusted in the said range, there exists a high possibility that reaction other than the intended hardening reaction to a resin composition may arise because of the unreacted material of an epoxy or a hardening | curing agent. On the other hand, when using a hardening accelerator, the usage-amount is preferable to use in 0.1-10 weight part with respect to 100 weight part of compounding quantities of a hardening | curing agent. When the curing accelerator is used in an amount less than 0.1 parts by weight, it is difficult to expect a promoting effect of the curing reaction, and when it exceeds 10 parts by weight, the curing reaction may occur at a rapid rate and may adversely affect storage.

The role of the modifying thermoplastic resin is to improve the brittle properties of the epoxy curing system to increase fracture toughness and to mitigate internal stress. Such modified thermoplastic resins include acrylic rubber, acrylic rubber dispersed in epoxy resins, core shell rubber, carboxy terminated butadiene nitrile (CTBN), acryl Any one used for general purposes such as nitrile butadiene-styrene rubber (acrylonitrile-butadiene-styrene rubber), polymethyl siloxane, or the like can be used in accordance with the properties of the curable resin composition. The core shell rubber particles are rubber particles in which the particles have a core layer and a shell layer. For example, the shell layer of the outer layer is a glassy polymer and the core layer of the inner layer is rubbery. The two-layer structure which consists of a polymer, or the shell layer of an outer layer is a glassy polymer, the intermediate | middle layer has a rubber | gum polymer, and the core layer consists of a three-layer structure etc. are mentioned. The glass layer is composed of, for example, a polymer of methyl methacrylate and the like, and the rubbery polymer layer is composed of, for example, a butyl acrylate polymer and the like.

When mix | blending this thermoplastic resin, it is preferable that the content rate with respect to the total solid of the whole underfill resin composition is 3-80 weight part with respect to 100 weight part of said epoxy resins, although it changes with the required characteristic. When it is 3 parts by weight or less, it is difficult to achieve the purpose of increasing fracture toughness and relieving internal stress. When it is 80 parts by weight or more, the content of the curable component in the resin composition is excessively reduced, so that mechanical and electrical reliability may be degraded after curing.

The melting agent serves to maintain high fluidity of the composition resin so that the electrical connection through the solder joint is simultaneously made with the curing reaction of the underfill resin composition in the non-flowable underfill process. In addition, the melting agent should remove the metal oxides generated from the copper pad of the package substrate during the soldering process while minimizing the adverse effect on the curing reaction of the underfill composition, and prevent the solder recording phenomenon due to the reoxidation reaction during the high temperature process. Generally, in order to prevent boiling at high temperatures, organic materials having terminal hydroxyl groups such as organic acids and alcohols having low vapor pressure at the soldering process temperature may be used as a melting agent. However, organic acids are most likely to participate as an additional reaction in the curing reaction of the epoxy curing agent system, so organic acids with low reactivity should be selected. As a specific example, ethylene glycol, glycerol, 3- [bis (glycidyloxymethyl) methoxy] -1,2-propanediol (3- [bis (glycidyloxymethyl) methoxy] -1, 2-propanediol), glutaric acid, trifluoroacettic acid, and the like. A suitable blending amount of the melting agent is preferably 1 to 10 parts by weight, more preferably 2 to 8 parts by weight, based on 100 parts by weight of the total weight of the curing agent including the epoxy resin and the acid curing agent having an imide bond structure, the curing accelerator and the thermoplastic resin for modification. More preferred. A melter of less than 1 part by weight is difficult to impart fluidity suitable for solder joints to the underfill resin composition, and a melter of more than 10 parts by weight may interfere with curing of the underfill resin composition, and the heat resistance and moisture resistance of the underfill cured product It may decrease.

In addition to the resin composition for underfill as described above it is possible to use additional additives for the desired physical properties. For example, the use of monofunctional reactive diluents can gradually delay viscosity increase without adversely affecting the properties of the cured underfill. As the diluent, substances such as aliphatic glycidyl ether, allyl glycidyl ether, glycerol diglycidyl ether, and mixtures thereof may be used. Meanwhile, various kinds of surfactants may be added to suppress voids during flip chip bonding and soldering, and to increase flowability of the underfill composition. Preferred examples of the surfactant include organic acrylic polymers, high molecular siloxanes such as polyols, or fluorine compounds such as 3M's FC-430. The surfactant is preferably added in the range of 0.01 to 2 parts by weight based on 100 parts by weight of the total weight of the epoxy resin, the thermally polymerizable resin including the acid catalyst, the curing agent and the curing accelerator, and the modifying thermoplastic resin. In addition, by adding an adhesion imparting agent to the underfill composition may improve the interface adhesion between the chip and the package substrate to be mounted. Imidazole type, thiazole type, triazole type, silane coupling agent, etc. can be used, and it can be used in the range of 0.01-2 weight part with respect to 100 weight part of compounding quantities of the said epoxy resin. It is preferable to add. In addition, the underfill composition resin may include silica, alumina, barium sulfate, talc, clay, aluminum hydroxide, magnesium hydroxide, silicon nitride, and boron nitride. It is possible to add an inorganic filler such as to control the viscosity and flow characteristics of the underfill composition resin, and it is possible to further add a flame retardant, an ion trapping agent and the like according to the purpose.

Hereinafter, the present invention will be described in more detail with reference to Examples. This is for explaining the present invention more specifically, but the scope of the present invention is not limited to these Examples.

<Examples>

1. Formulation of non-flowable underfill resin composition

(1) Epoxy resin: 100.0 g of a weight ratio 4: 1 blend of bisphenol F epoxy resin (liquid, epoxy equivalent 190) and bisphenol A epoxy resin (liquid, epoxy equivalent 250)

(2) a curing agent and curing accelerator comprising an acid curing agent having an imide bond structure: Formula (1)-(c) and methylhexahydrophthalanhydride and 2PHZ-PW (2-phenyl-4methyl-5- Hydroxymethylimidazole) in a weight ratio of 2000: 1000: 3

(3) Modified thermoplastic: 5.0 g of carboxy-terminated butadiene nitrile rubber (CTBN)

(4) Melting agent: 8.0 g of glycerol

(5) Additives: FC430 (3M, Surfactant) 0.3g

2. Performance Analysis

The resin composition of Example 1 was stirred and thermally cured by differential scanning calorimetry, wherein the curing start temperature, curing peak temperature and curing calorific value were measured using a DSC instrument (NETZSCH Motel DSC 200 F3 Maia). . The glass transition temperature (Tg) and coefficient of thermal expansion (CTE1 before Tg, CTE2 after Tg) of the composition were measured using a Thermal Mechanical Analyzer (Model TMA 2920 from TA Instruments) on a sample cured at 175 ° C. for 2 hours. . The heat-curing properties (% at weight reduction at 300 ° C. and 5% at weight loss) were measured through a thermogravimetric analyzer (Model TG 209 F3 Tarsus, NETZSCH) on the samples cured under the same conditions. To determine whether it has the ability of fluxing solder, 0.2 g of the composition is dispensed onto a copper test piece, solder balls (Sn / Ag / Cu, melting point 217-219 ° C.) are added dropwise to the composition, and a glass cover slide over the composition. Was covered and placed on a hot plate preheated to 145 ° C. and after 2 minutes, immediately transferred to another hot plate preheated to 230-235 ° C. and held for 2 minutes. The fluxing result evaluated the joining of a copper test piece and a lead-free solder by microscopic observation of a cross section. The performance results are summarized in Table 1 below.

Comparative Example

1. Formulation

(1) Epoxy resin: 100.0 g of a weight ratio 4: 1 blend of bisphenol F epoxy resin (liquid, epoxy equivalent 190) and bisphenol A epoxy resin (liquid, epoxy equivalent 250)

(2) Curing agent and curing accelerator: 100.0 g of a weight ratio 1000: 1 blend of methylhexahydrophthalic anhydride and 2PHZ-PW (2-phenyl-4methyl-5-hydroxymethylimidazole)

(3) Modified thermoplastic: 5.0 g of carboxy-terminated butadiene nitrile rubber (CTBN)

(4) Melting agent: 8.0 g of glycerol

(5) Additives: FC430 (3M, Surfactant) 0.3g

2. Performance Analysis

After stirring the resin composition of the comparative example was subjected to DSC analysis, bonding analysis, thermomechanical analysis and thermogravimetric analysis in the same manner as in Example and summarized together in Table 1 below.

(Table 1)

Performance analysis Example Comparative example Differential Scanning Calorimetry DSC start temperature (℃) 202 209 DSC peak temperature (℃) 245 260 Solder Bond Analysis Solder flux Junction Junction Thermal mechanical analysis Tg of hardened | cured material (degreeC) 92 75 CTE1 of the cured product (ppm) 75 80 CTE2 of the cured product (ppm) 170 170 Thermogravimetric analysis % Weight reduction at 300 ° C 2.01 1.48 Temperature at 5% weight loss (℃) 344 360

It can be seen from Table 1 that the composition is maintained at a low temperature below the solder joint temperature range, the curing is suppressed, the curing reaction occurs in the soldering process temperature range, and the composition is maintained to maintain a low viscosity to enable solder bonding during the curing reaction. As a result of thermomechanical analysis, it was confirmed that the composition of Example 1 containing an acid hardener having an imide bond structure had a higher Tg and a lower difference in coefficient of thermal expansion than the composition of Comparative Example 1. In addition, the thermogravimetric analysis showed that the heat resistance was improved through the formulation of an acid hardener having an imide-bonded structure.

While the invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

1 is a schematic diagram of a non-flowable underfill package method.

Claims (11)

Per 100 parts by weight of epoxy resin; 1 to 110 parts by weight of a curing agent and a curing accelerator including an acid curing agent having an imide bond structure; Acrylic rubber, acrylic rubber dispersed in epoxy resins, carboxy terminated butadiene nitrile (CTBN), acrylonitrile-butadiene-styrene rubber and polymethyl siloxane 3 to 80 parts by weight of at least one modified thermoplastic resin selected from the group consisting of (polymethyl siloxane); And Ethylene glycol, glycerol, 3- [bis (glycidyloxymethyl) methoxy] -1,2-propanediol (3- [bis (glycidyloxymethyl) methoxy] -1,2-propanediol ), Glutaric acid, and one or two or more mixtures selected from the group consisting of trifluoroacetic acid, wherein the curing agent and curing accelerator comprising the epoxy resin, an acid curing agent having an imide bond structure. And 1 to 10 parts by weight of a melting agent based on 100 parts by weight of the total weight of the thermoplastic resin for modification. The method of claim 1, wherein the epoxy resin is a mono- or polyfunctional glycidyl ether of bisphenol-A or bisphenol-F, aliphatic and aromatic epoxy, saturated epoxy resin, unsaturated epoxy resin, alicyclic epoxy resin and aglycidyl ether. Resin composition for the non-flowable underfill, characterized in that at least one selected from the group consisting of an epoxide. The resin composition for non-flowable underfill according to claim 1, wherein the acid hardener having an imide bond structure is an imide-acid having a carboxylic acid structure at its terminal. The non-flowable underfill resin composition according to claim 3, wherein the imide-acid is at least one selected from the group consisting of structures (a) to (d) of the formula: (a)

(b)

(c)

(d)

delete delete delete delete delete The method of claim 1, further comprising at least one selected from the group consisting of monofunctional epoxy reactive diluents, surfactants, adhesion imparting agents, inorganic fillers, flame retardants and ion trapping agents. The non-flowable underfill resin composition. A flip chip package assembly prepared using the non-flowable underfill resin composition according to any one of claims 1 to 4 and 10.

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