KR20090077242A - Paste composition for die attachment containing epoxy-rubber adducts - Google Patents

Abstract

A paste composition for die attachment is provided to increase compatibility with epoxy resin and rubber resin and to ensure excellent reliability after curing while preventing the degradation of adhesive force after B-staging. A paste composition for die attachment comprises an epoxy 30-60 parts by weight, a rubber resin 15-35 parts by weight, an epoxy-rubber adduct 5-15 parts by weight, a hardener 5-20 parts by weight and an inorganic filler 7-20 parts by weight. The mixing ratio of liquid and solid is 3:7 - 7:3. The rubber resin is a mixture of one or at least two kinds selected from the group consisting of liquefied polybutadiene with molecular weight of 50,000, acrylonitrile butadiene, glycidyl acrylate, styrene-butadiene rubber, epoxy-terminated butadiene rubber and carboxyl-terminated butadiene rubber.

Description

Paste composition for die attachment containing epoxy-rubber adducts

The present invention relates to an epoxy resin based die bonding paste composition used in a semiconductor packaging process. More specifically, the present invention relates to a paste composition further comprising an addition product between the epoxy resin and the carboxyl terminated butadiene rubber.

In the packaging process of semiconductor devices, epoxy resin-based die bonding pastes are widely used as adhesives used when laminating chips or adhering to supporting members such as printed circuit boards (PCBs) or lead-frames. Epoxy-based polymers have excellent thermal stability and are widely used as paste resins because they have excellent processability because they can be cured by heat treatment after screen printing. Epoxy-based paste compositions are generally based on epoxy resins, thermosetting agents, rubber resins for reducing stress and increasing adhesion, and organic and inorganic additives for increasing heat resistance.

The epoxy resin-based paste is screen printed on the support member, and then the chips can be stacked through a so-called non-staging process. When the raw material of the adhesive material is a solid, the solid is dispersed or dissolved in a solvent to form a paste, and the paste is applied to a substrate. The adhesive is then heated or irradiated with ultraviolet light to evaporate the solvent, leaving the uncured adhesive on the substrate as a solid, which is B-staging. The adhesive is then cured by applying heat or heat and pressure to bond the chip and support member. In the case of a paste adhesive, the solvent evaporates and the adhesive remaining on the substrate solidifies with curing by heating.

Removing the solvent through non-staging has the advantage that it can be stopped at a desired step without the need to quickly carry out each process such as adhesive application, assembly and thermal curing of semiconductor packaging. If the non-staging treatment is not performed after the application of epoxy-based adhesives, serious bottlenecks occur in the production process because the process must proceed to the next step and proceed in a continuous process manner.

If the manufacturing process is suspended after the non-staging is completed and the subsequent processing is withheld, the adhesive must be in solidified form in order to remain intact. However, as described above, after the die paste adhesive paste is applied onto the PCB substrate or the lead frame, the non-staging or various heat treatment processes must be repeatedly performed, and in the actual treatment process, 60 to 90 at a high temperature of 145 to 165 ° C. It is either left for a long time or is processed. As such, the packaging process was performed in a high temperature environment for a long time, such that poor die adhesion or a decrease in screen printing performance such as bleeding of organic components such as resins or additives in the adhesive composition was often caused. In addition, it was difficult to maintain high reliability such as moisture resistance while maintaining high die adhesion.

Therefore, the related industry has continuously made efforts to solve the stability and reliability problems of semiconductor devices that may occur in the prior art epoxy resin-based die paste.

An object of the present invention is to improve the compatibility of the epoxy resin and rubber resin contained in the epoxy resin-based paste resin composition used in the semiconductor packaging process to develop a paste having excellent reliability after curing without deterioration in adhesive strength after non-staging.

For this purpose, the present invention provides a die comprising 30 to 60 parts by weight of epoxy, 15 to 35 parts by weight of rubber resin, 5 to 15 parts by weight of epoxy-rubber addition product, 5 to 20 parts by weight of hardener and 7 to 20 parts by weight of inorganic filler. The adhesive paste composition is provided.

The die bonding paste composition of the present invention preferably has a composition such that the weight of the epoxy-rubber addition product is 10 to 60% of the weight of the rubber resin.

As the epoxy-rubber addition product in the die-bonding paste composition of the present invention, a polymer obtained by polymerizing a bisphenol A epoxy and a carboxyl-butadiene rubber is suitable.

The die bonding paste composition of the present invention does not have a decrease in adhesive strength even after the non-staging step, and is excellent in reliability after curing.

The composition of the die-bonding paste composition provided by the present invention is 30 to 60 parts by weight of epoxy, 15 to 35 parts by weight of rubber resin, 5 to 15 parts by weight of epoxy-rubber addition product, 5 to 20 parts by weight of curing agent and 7 to 7 inorganic fillers. 20 parts by weight.

The epoxy is a polymer resin having excellent thermal stability and used for handling control and flexibility. If the content range of the epoxy is less than 30 parts by weight, the adhesive strength and thermal stability is lowered, and if more than 60 parts by weight, the curing degree is lowered, which is not preferred because the thermal stability is lowered. The general purpose epoxy resin of a solid state or a liquid can be used for the die adhesion paste composition of this invention. Preferably, the epoxy has a mixing ratio of solid and liquid in the range of 3: 7 to 7: 3. When the ratio of the solid phase and the liquid phase is out of the above range, the resin viscosity, rigidity, tackiness and adhesiveness and adhesion and reliability deteriorate and are not suitable.

Suitable epoxy resins for the paste composition of the present invention are any one or two or more epoxy resins selected from bisphenol A, bisphenol F, cresol novolac and phenoxy epoxy resins.

In the paste composition of the present invention, the rubber resin serves to increase the adhesive force and add elasticity to extinguish the stress applied to the adhesive. When the content range of the rubber resin in the paste composition of the present invention is less than 15 parts by weight, it is not preferable because the required degree of elasticity and reinforcement cannot be obtained. In addition, when the rubber resin content exceeds 35 parts by weight, the heat resistance is insufficient, so this value is appropriate as an upper limit.

As a rubber resin suitable for the present invention, a molecular weight of 50,000 or more and a liquid resin are suitable. For example, polybutadiene, acrylonitrile butadiene, glycidyl acrylate, styrene-butadiene rubber, epoxy-terminated butadiene rubber (ETNN) and carboxyl-terminated butadiene rubber , CTBN) any one substance selected from the group consisting of or mixtures of two or more thereof. The use of rubber resins having a molecular weight of less than 50,000 is not preferred because the adhesion of the paste composition to the die is insufficient.

The paste composition of the present invention is for producing a paste having excellent reliability even after curing without deterioration in adhesive strength after non-staging. Since the epoxy polymer and the rubber resin must be uniformly dispersed in the composition to obtain a highly reliable die attach paste composition, the present invention provides a paste composition further comprising an addition reaction product between the epoxy resin and the rubber. . The adduct increases the compatibility between the epoxy resin and the rubber resin and serves to maintain the adhesion and reliability of the paste composition.

Epoxy-rubber addition product in the present invention is included 5 to 15 parts by weight, preferably 10 to 60% by weight based on the weight of the rubber resin. Paste composition having an addition product content lower than the lower limit of the content range has a disadvantage in that the strengthening degree is lowered, a problem that the adhesive strength is lowered at a content higher than the upper limit.

As the epoxy-rubber addition product of the present invention, it is preferable to use a polymerization product of bisphenol A-based epoxy resin and carboxyl-terminated butadiene rubber (CTBN). At this time, the ratio of the epoxy resin and the CTBN is suitable from 20:80 to 80:20, because the problem that the phase is non-uniform occurs outside this range. The epoxy-rubber addition product of the present invention can be easily obtained by thermal polymerization reaction. For example, a die bonding paste composition may be prepared using a liquid resin of bisphenol A resin and an addition product obtained by thermally polymerizing CTBN having a molecular weight of 50,000 or more at a composition ratio of 50:50 by weight at 120 ° C. for 2 hours. .

The die attach paste composition of the present invention contains 5 to 20 parts by weight of a curing agent in addition to the polymer material. The curing agent is preferably phenol, acid anhydride and / or amine. When the content of the curing agent is excessively high, the storage property of the composition is reduced, the molecular weight of the final resin is reduced, and when the content of the curing agent is low, the curing rate is lowered.

The die attach paste composition of the present invention further contains 7 to 20 parts by weight of an inorganic filler. Inorganic fillers in the present invention impart moisture resistance and serve as a buffer. If the inorganic filler is insufficient, the reliability of the paste composition is low, and if excessive, the adhesive strength is lowered. Examples of suitable inorganic fillers include silica particles, aluminum oxide particles, antimony particles and / or titanium particles and the like.

Since the die bonding paste composition of the present invention maintains excellent adhesion and reliability even after the non-staging, the die bonding paste composition may be used in BOC semiconductor devices as well as overall packaging of semiconductor devices manufactured by using the screen printing method.

<Example>

In order to illustrate the present invention more specifically, the following examples are given. In addition to the aspects shown in the examples below, the present invention may be modified in various other equivalent forms. These examples are provided for the purpose of more fully describing the present invention to those skilled in the art, and thus the scope of the present invention should not be construed as being limited to the following embodiments.

In order to compare the performance of the paste composition for semiconductors according to the present invention with the prior art, the paste compositions of Comparative Examples and Examples were prepared according to the compositions of Table 1 below. The epoxy used in Examples and Comparative Examples below was a bisphenol A-based epoxy polymer having an epoxy end group ratio of 200 to 400, and a mixing ratio of the solid and liquid phases was 4: 6 by weight. The rubber resin was an acrylonitrile butadiene rubber having a molecular weight of 50,000 or more having a carboxyl group end. As the epoxy-rubber addition product, a bisphenol A-based resin and a CTBN having a molecular weight of 50,000 or more were thermally polymerized at 120 ° C. for 2 hours at a composition ratio of 50:50 by weight. The viscosities of epoxy and CTBN used at this time were 15,000-25,000 and 40,000-70,000, respectively.

Silica was used as a filler used in Comparative Examples and Examples, and a phenolic curing agent was used as a curing agent.

Component (unit weight part) Example 1 Example 2 Comparative Example 1 Comparative Example 2 Epoxy 45 45 45 45 Rubber resin 20 17 ― 25 Epoxy-Rubber Addition Products 5 8 25 ― Filler 15 15 15 15 Hardener 10 10 10 10

A brief manufacturing method is as follows. The components of Table 1 are mixed together with the Example and Comparative Example compositions to obtain a liquid paste resin first. The paste resin is screen printed onto a printed circuit board using a stencil. After a non-staging treatment by heating at a temperature of 110 ° C. for 30 minutes, it is attached to the silicon chip and completely cured.

[Performance evaluation]

The paste resin compositions of Examples and Comparative Examples were cured by the above production method, and then evaluated for printing performance, adhesive force, wire bonding properties, epoxy molding compound (EMC) properties, and reliability (moisture resistance). .

Evaluation of printing performance was made by observing the following three items with an optical microscope. That is, tailing and voids in which the wafer is contaminated due to bleeding out, which is a phenomenon in which organic components such as reactive diluents in the paste liquid are separated or moved, and the stencil printing is not easily detached from the stencil due to the large adhesive force of the resin. There are three phenomena of clogging that are closed because the void does not fall out.

Die adhesion was measured by 180 ^o peel test method.

Wire bonding properties were evaluated by confirming that voids occurred after the paste resin had cured.

Epoxy molding compound properties were measured by EMC compression method.

Reliability was judged to be good when passed the Level 2 (L2) prescribed by the Joint Electronic Device Engineering Council (JEDEC), moisture resistance test (MRT) under hygroscopic conditions. It was determined that the test failed. The test conditions were stored for 7 days (168 hours) at a relative humidity of 85% and a temperature of 85 ° C., followed by a solder reflow zone at 260 ° C., a Pb-free free reflow condition. To pass. As a result of the observation, failure was determined when there was a crack or delamination of the adhesive layer.

Characteristic evaluation item Example 1 Example 2 Comparative Example 1 Comparative Example 2 Printing performance (component spill / tailing effect / shield) Good Good Good Good Die Adhesion (g / cm2) 800 ± 100 600 ± 100 135 ± 100 1560 ± 100 Wire bonding characteristic (150 ℃) Good Good Good Good EMC characteristics Good Good Good crack Reliability (Water Resistance) Good Good Good crack

As can be seen in Table 2, the example compositions according to the paste composition of the present invention had excellent die adhesion after the non-staging step and excellent water resistance when compared to the comparative composition of the prior art.

The composition of the comparative example 1 is a structure which lacks a rubber resin in the structure of the composition of this invention, and the comparative example 2 lacks an epoxy-rubber addition product. In Comparative Example 1, wire bonding, epoxy molding compound properties, and reliability were good, but the die adhesion was remarkably inferior. In the case of Comparative Example 2, the die adhesion is excellent, but it does not satisfy the criteria in epoxy molding compound properties and reliability.

As seen through the examples, the die-bonding paste composition of the present invention boasts excellent bonding strength and moisture resistance of JEDEC standard level 2 or higher with respect to copper foil that greatly exceeds 300 g / cm 2.

Optimal embodiments of the present invention described above have been disclosed. Although specific terms have been used herein, they are used only for the purpose of describing the present invention in detail to those skilled in the art, and are not used to limit the scope of the present invention as defined in the meaning or claims.

Claims (7)

30 to 60 parts by weight of epoxy; 15 to 35 parts by weight of rubber resin; 5 to 15 parts by weight of an epoxy-rubber addition product; 5 to 20 parts by weight of curing agent; And 7 to 20 parts by weight of an inorganic filler; die bonding paste composition comprising a. The method of claim 1, The epoxy, Die-attach paste composition, characterized in that the mixing ratio of the solid and liquid phase is 3: 7 to 7: 3. The method of claim 1, The epoxy, A die bonding paste composition, characterized in that one or a mixture of two or more selected from bisphenol A, bisphenol F, cresol novolac and phenoxy epoxy resins. The method of claim 1, The rubber resin, Liquid polybutadiene, acrylonitrile butadiene, glycidyl acrylate, styrene-butadiene rubber, epoxy-terminated butadiene rubber (ETNN) and carboxyl-terminated butadiene rubber (CTBN) with a molecular weight of 50,000 or more A die bonding paste composition, characterized in that one material or a mixture of two or more selected from the group consisting of. The method of claim 1, The weight of the epoxy-rubber addition product is Die bonding paste composition, characterized in that 10 to 60% of the weight of the rubber resin. The method of claim 1 wherein the epoxy-rubber addition product, A die bonding paste composition, comprising: a polymer obtained by polymerizing a bisphenol A epoxy and a carboxyl-butadiene rubber. The method of claim 6, The epoxy-rubber addition product, The die attach paste composition, characterized in that the bisphenol A-based epoxy and the carboxyl-butadiene rubber is a material polymerized in a content ratio of 3: 7 to 7: 3 by weight.