TWI447939B - Conductive die attach adhesive for LED - Google Patents

Description

Conductive die attach adhesive for LED

The present invention relates to an LED die bonding agent for bonding a light emitting diode (LED) wafer to a substrate or the like, and an LED obtained by using the conductive die attaching agent for the LED.

LED has long life, low power consumption, low heat generation, high-speed response, impact resistance, environmental and small features, and is used in various fields such as backlights, signal lamps, illumination lamps, and display devices for liquid crystal displays. . In the method of manufacturing an LED, a method of using a die bonding agent to fix an LED wafer to an interposer, a lead frame, a substrate, or the like is generally employed.

From the standpoint of exhibiting high modulus of elasticity and high adhesion, the die attach adhesive is generally an epoxy resin. However, when a general-purpose bisphenol A type epoxy resin or a phenol novolac type epoxy resin is used, since the epoxy resin absorbs 400 to 500 nm light emitted from the LED and discolors, it is damaged. Light stability, and high level of deterioration when LEDs are lit for a long time.

In order to cope with such problems, there is a proposal to use a hydrogenation type epoxy resin. However, when a general-purpose acid-based hardener such as methyl hexahydrophthalic anhydride is used as a curing agent in a hydrogenated epoxy resin (refer to the patent literature) 1), the pot life will be shorter, not only in terms of workability, but also the improvement effect of light stability. In addition, although attempts have been made to use polyoxyxylene resins (see Patent Document 2), the bonding strength is weak, and it is difficult to ensure the electrical properties. Reliability of sex. Thus, from the viewpoint of connection reliability and light stability, it is now desired to further improve the conductive die attaching agent for LEDs.

[Patent Document 1] JP-A-2003-26763 [Patent Document 2] Japanese Patent Laid-Open No. Hei 7-25987

An object of the present invention is to provide a conductive die attaching agent for an LED which can provide an LED excellent in connection reliability and light stability by using a conductive die attaching agent.

The inventors of the present invention have intensively studied in order to achieve the above object, and as a result, have found that the object can be achieved by a conductive die attaching agent for LEDs having a specific composition, and thus the present invention has been completed.

That is, the present invention relates to a conductive die attaching agent for LEDs comprising: (A) an alicyclic epoxy resin having an average of 0.5 or more hydroxyl groups per molecule, and (B) a non-aromatic polyisocyanate. A blocked polyisocyanate, and (C) a conductive filler, and an LED obtained by using the die attach adhesive.

By using the conductive die attach adhesive for LEDs of the present invention and fixing the LED wafer to an interposer, a lead frame, a substrate, or the like, it is possible to provide an LED excellent in connection reliability and light stability.

The conductive die attach adhesive for LEDs of the present invention contains: (A) an alicyclic epoxy resin having an average of 0.5 or more hydroxyl groups per molecule, (B) a blocked product of a non-aromatic polyisocyanate, and (C) a conductive filler.

The component (A) is an alicyclic epoxy resin which is an average of 0.5 or more hydroxyl groups per molecule. If the number of hydroxyl groups is within this range, a better crosslinking density can be obtained. The hydroxy group is preferably from 0.5 to 6 per molecule. Further, the component (A) may be used singly or in combination of two or more. When a plurality of alicyclic epoxy resins are used, although they may also contain no hydroxyl groups, on the whole, each molecule contains an average of 0.5 or more hydroxyl groups, preferably 0.5 to 6 per molecule. Hydroxyl group.

Examples of the alicyclic epoxy resin include hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, hydrogenated biphenyl type epoxy resin, and hydrogenated phenol novolac type epoxy. Hydrogenated epoxy resin such as resin or hydrogenated cresol novolac type epoxy resin; 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, 1, 2-epoxy-vinylcyclohexene, bis(3,4-epoxycyclohexylmethyl)adipate, 1-epoxyethyl-3,4-epoxycyclohexane, etc. An epoxy resin obtained by epoxidizing an olefin or the like. When an epoxy resin containing no hydroxyl group is used, it is used in combination with a hydroxyl group. As described above, on the whole, each molecule contains an average of 0.5 or more hydroxyl groups, preferably 0.5 to 6 per molecule. Hydroxyl group.

In the case of the component (A), a hydrogenated epoxy resin represented by the following formula is preferred: (wherein X is -CH ₂ -, -C(CH ₃ ) ₂ - or a direct bond; m is an average of 0.5 or more, preferably 0.5 to 6). Among these, from the viewpoint of storage stability, an epoxy resin of a hydrogenated bisphenol A type or a hydrogenated bisphenol F type is preferable.

In the present invention, by using the blocked compound of the non-aromatic polyisocyanate of the component (B) as a curing agent, the decrease in the reflectance of the hardened crystal grain adhesive can be suppressed, contributing to the light stability. In addition, since an urethane bond is generated by hardening, strong bonding strength can be maintained at a high temperature, resulting in an increase in connection reliability.

The component (B) may, for example, be an aliphatic polyisocyanate such as hexamethylene diisocyanate, diisocyanate diisocyanate or trimethylhexamethylene diisocyanate, isophorone. An alicyclic polyisocyanate such as a diisocyanate, a phenolic compound (for example, phenol, cresol, ethyl phenol, butanol, etc.) or an indoleamine compound (for example, ε-caprolactam, σ-valeramine, γ - indoleamine, beta-propionamide, etc., oxime compounds (eg, aldoxime (formaldehyde oxime, acetaldoxime, etc.), ketoxime (acetone oxime, methyl ethyl ketone) A ketone oxime, cyclohexanone oxime, etc.), a blocking agent such as diethyl malonate, ethyl acetate or ethyl acetonate is blocked. From the standpoint of light stability, the blocking agent is preferably a non-aromatic compound. Among them, from the viewpoint of light stability, the aliphatic diisocyanate (hexamethylene diisocyanate, etc.) is used as a lanthanide compound or an indoleamine. It is preferred that the compound is blocked by blocking. Further, the component (B) may be used alone or in combination of two or more.

(C) The conductive filler is not particularly limited, and examples thereof include metal fine powders such as silver, gold, copper, nickel, palladium, tin, and the like, or inorganic or organic fillers coated with gold, silver, and palladium. The shape is not particularly limited, and examples thereof include a spherical shape and a scaly shape, and a scaly shape is preferable, and the average particle diameter thereof is, for example, 5 to 15 μm. Further, the component (C) may be used singly or in combination of two or more.

In the present invention, the component (A) is preferably 2 to 15 parts by weight, more preferably 3 to 13 parts by weight, based on 100 parts by total of the total of the components (A), (B) and (C). The component (B) is preferably from 1 to 11 parts by weight, more preferably from 2 to 8 parts by weight. The component (C) is preferably from 74 to 97 parts by weight, more preferably from 79 to 95 parts by weight.

From the viewpoint of reactivity, the die attach adhesive of the present invention preferably contains a hardening catalyst. The hardening catalyst may, for example, be (D) an aluminum chelate compound. The (D) aluminum chelate compound is not particularly limited, and examples thereof include a compound in which three β-ketoenolate anions are coordinated to aluminum. It can be used as aluminum ethyl acefoacetate diisopropylate, aluminum triacetate, ethyl acetoacetate diisoxyl aluminum, bis(acetic acid ethyl acetate) single B It is obtained by using acetonyl aluminum or tris(acetonitrile)aluminum or acetonitrile acetate diisopropoxide aluminum. Among them, from the viewpoint of the pot life, an alkyl group (corresponding to R of the following formula) is preferably an _18- octadec-enyl group of an alkyl acetoacetate diisopropoxide aluminum of C ₁₈ H ₃₇ . -acetamidine acetate-O1', O3) dipropen-2-oxyaluminum: Further, the component (D) may be used singly or in combination of two or more.

The component (D) is preferably 0.05 to 1.1 parts by weight, more preferably 0.1 to 0.7 parts by weight, based on 100 parts by weight of the total of the components (A), (B) and (C).

Further, from the viewpoint of adhesion, the die attaching agent of the present invention preferably contains a coupling agent. The coupling agent may, for example, be an (E) decane coupling agent. The (E) decane coupling agent is not particularly limited, and examples thereof include a vinyl group-containing decane such as vinyl trichloromethane, vinyl trimethoxy decane or vinyl triethoxy decane; and 2-(3,4-ring); Oxycyclohexyl)ethyltrimethoxydecane, 3-glycidoxypropyltrimethoxydecane, 3-glycidoxypropylmethyldiethoxydecane, 3-epoxypropoxy a decyl group-containing decane such as propyltriethoxydecane; a styryl-containing decane such as p-styryltrimethoxydecane; or a 3-methylpropenyloxypropylmethyl dimethyl methoxide; Oxydecane, 3-methylpropenyloxypropyltrimethoxydecane, 3-methylpropenyloxypropylmethyldiethoxydecane, 3-methylpropenyloxypropyltriethoxylate a (meth)acrylonitrile-based decane, such as a decane or alkoxy-containing decane; 3-(meth) propylene oxypropyltrimethoxy decane; N-2-(aminoethyl)-3 -Aminopropylmethyldimethoxydecane, N-3-(aminoethyl)-3-aminopropyltrimethoxydecane, N-2-(aminoethyl)-3-amino Propyltriethoxyhydrazine , 3-aminopropyltrimethoxydecane, 3-aminopropyltriethoxydecane, 3-triethoxydecyl-N-(1,3-dimethyl-butylene)propylamine N-phenyl-3- An amino group-containing decane or the like such as aminopropyltrimethoxydecane. Among them, from the viewpoint of light resistance, it is preferred to use no aromatic ring, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane, 3-epoxypropoxypropane is used. A propylene group containing a propylene group such as a trimethoxy decane, 3-glycidoxypropylmethyldiethoxy decane or 3-glycidoxypropyltriethoxy decane may be suitably used. Further, the component (E) may be used singly or in combination of two or more.

The component (E) is preferably from 0.1 to 11 parts by weight, more preferably from 0.5 to 9.5 parts by weight, based on 100 parts by total of the total of the components (A), (B) and (C).

The present invention may contain, as an optional component, a viscosity modifier, an antifoaming agent, a flame retardant, an ultraviolet absorber, an antioxidant, a solvent, or the like, in addition to the above components, insofar as the effects of the present invention are not impaired.

The conductive die attach adhesive for LEDs of the present invention can be prepared by mixing (A) to (C) components and optionally adding any components including (D) and (E) as needed.

By applying the conductive die attach adhesive for LED of the present invention to an interposer, a lead frame, a substrate, or the like, the LED wafer is placed on the coated portion, and then at 140 to 170 ° C for 1 to 3 hours (for example, 150). The LED adhesive is heat-hardened to 170 ° C for 1 to 2 hours to form an LED. The LED chip can use either a blue LED chip or a white LED chip.

According to the present invention, a conductive die attach adhesive for LEDs excellent in light stability can be obtained. The light stability can be evaluated by measuring the reflectance of the grain adhesive after hardening, and the change in reflectance is small and the stabilizer can be regarded as excellent in light stability. Specifically, the die attach adhesive of the present invention is applied onto a glass substrate at a thickness of 150 μm, and is heat-hardened at 150 ° C for 2 hours. The film was further cooled to room temperature to obtain a coating film having a reflectance Xa of 450 nm at the initial stage of the coating film and a distance of 50 mm from a blue high-intensity discharge (HID) lamp (400 W, 8000 Lm, 20000 Lx) to the coating film. The reflectance Xb of 450 nm of the coating film after 1000 hours of irradiation at 150 ° C can satisfy Xb / Xa ≧ 0.75. Further, in the present specification, the reflectance is a value measured from an incident angle of 45 degrees from the back side of the glass substrate.

(Example)

The invention is illustrated by the examples, but the invention is not limited by the examples. In addition, in the following examples, "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified.

Each of the components was mixed in the composition shown in Table 1, and the conductive die attach adhesive for each of the LEDs of the examples and the comparative examples was prepared.

The following tests were carried out for each of the examples and the comparative examples.

(1) Reflectance Each of the agents was applied onto a glass substrate at a thickness of 150 μm, and heat-cured at 150 ° C for 2 hours to prepare a sample for reflectance measurement. For this sample, the reflectance was measured from the back surface of the glass substrate at an incident angle of 45 degrees by a color difference meter NF999 machine manufactured by Nippon Denshoku Industries Co., Ltd. Then, using a blue HID lamp (400 W, 8000 Lm, 20000 Lx, Fig. 1), the sample is irradiated with light at a distance of 50 mm from about 50 ° C for 50, 100, 400, 1000 hours, and the reflectance after the irradiation is the same as above. The method is carried out. The results are shown in Fig. 2.

(2) Contact resistance On the FR4 substrate with the Cu/Ni/Au electrode (Fig. 3-A), Each agent was applied to a square having a side length of 0.5 mm (Fig. 3-B) at a thickness of 70 μm, and a plate plated with silver by an iron-nickel alloy (iron: nickel = 58: 42). The pressure applied to the coated portion was such that the thickness of each agent was 50 μm (Fig. 3-C). Next, it was heat-hardened at 150 ° C for 2 hours, and a sealant (a mixture of a bisphenol F type epoxy resin, an alicyclic epoxy resin, a methyl nadic anhydride, and a hardening accelerator) was applied. The weight ratio was 17.5:32.0:50.0:0.5), and the mixture was heated at 180 ° C for 2 hours, and cooled to room temperature to prepare a sample for measuring a resistance value (Fig. 3-D). The probe was connected to the electrode of this sample, and a current of 10 mA was passed, and the resistance value was measured. Then, the sample was refluxed, and the sample was placed on a hot plate at 300 ° C for 15 seconds, and then cooled to room temperature, and the resistance value was measured in the same manner as above. This operation was repeated 3 times for 4 samples. The results are shown in Fig. 4.

In addition to this test, according to the JEDEC grade 3 test, the moisture absorption reflow is scheduled, and the sample for measuring the resistance value is placed at 30 ° C and a relative humidity of 70% for 168 hours, then passed to a reflux of 260 ° C, and then cooled to The resistance value was measured at room temperature in the same manner as above. This operation was repeated 3 times for 4 samples. The results are shown in Figure 5.

(3) Shear strength On the silver-plated copper-coated FR4 substrate, each agent was coated into a square having a side length of 2 mm at a thickness of 125 μm, and a square-shaped wafer having a side length of 2 mm was placed on the coated portion, and secondly, at 150 ° C. The mixture was heat-hardened for 2 hours, cooled to room temperature, and a sample for shear strength measurement was prepared. For this sample, apply force to the tantalum wafer from the horizontal direction at room temperature and 300 ° C. The force of departure (Figure 6). The results are shown in Figure 7.

On a glass substrate, each agent was applied to a square having a side length of 1 mm at a thickness of 50 μm, and a square wafer having a side length of 1 mm was placed on the coated portion, and secondly, heat-hardened at 150 ° C for 2 hours, and cooled. A sample for shear strength measurement was prepared at room temperature. For this sample, the shear strength was measured at room temperature in the same manner as described above. Then, the sample was irradiated with light at a distance of 50 mm from 150 mm for 50, 100, 400, and 1000 hours using a blue HID lamp (400 W, 8000 Lm, 20000 Lx, Fig. 1), and then the shear strength after the irradiation was measured. The results are shown in Fig. 8.

(4) Pot life Each of the agents was placed at 25 ° C and a relative humidity of 50%, and the viscosity at 25 ° C and 2.5 rpm was measured using an E-type viscometer (machine name TVE-22) manufactured by TOKIMEC. The results are shown in Figure 9.

* 1: Epoxy equivalent = 290 g/eq (average of 0.8 hydroxyl groups per molecule) * 2: Epoxy equivalent = 200 g/eq (average of 0.2 hydroxyl groups per molecule) * 3: Epoxy equivalent = 95 g/eq *4: Epoxy equivalent = 158 g/eq * 5: Coronate 2507, manufactured by Japan Polyurethane Industry Co., Ltd. * 6: (octadec-9-alkenyl-acetamidine acetate-O1', O3) dipropen-2-oxyl Aluminum*7: scaly silver powder with a BET specific surface area of 0.27 m ² /g, a tap density of 3.3 g/cm ³ , and a D50 particle size of 7.5 μm * A: epoxy equivalent = 1000 g/eq (average of 2.2 hydroxyl groups per molecule) )* B: Coronate B1301 manufactured by Japan Polyurethane Industry Co., Ltd.

As shown in Fig. 2, in Comparative Examples 2 to 4 and Comparative Example 2 using a polyoxyxylene resin, the reflectance did not change even after long-time light irradiation, and it was found that the light stability was excellent. Incidentally, in Example 1, the reflectance Xa at the initial 450 nm (wavelength) was 42.2%, and the reflectance Xb after light irradiation for 1000 hours was 33.8%, and Xb/Xa was 0.8. In Example 2, the reflectance Xa at the initial 450 nm was 29.4%, and the reflectance Xb after the light irradiation for 1000 hours was 3.1%, and Xb/Xa was 1.05. In Example 3, the reflectance Xa at the initial 450 nm was 30.2%, and after 10 hours of light irradiation, the reflectance Xb was 23.6%, and Xb/Xa was 0.78. In Example 4, the reflectance Xa at the initial 450 nm was 28.2%, and the reflectance Xb after the light irradiation for 1000 hours was 24.4%, and Xb/Xa was 0.87. On the other hand, in Comparative Example 1 in which the hydroxyl group number of the epoxy resin was outside the range of the present invention and the acid anhydride-based curing agent was used, the reflectance deterioration was gradually caused. In Comparative Examples 3 and 4 in which an aromatic epoxy resin was used, the reflectance deteriorated at a very fast time due to the influence of the aromatic ring, and occurred in a short time with the glass substrate. In Comparative Example 5 in which peeling (confirmation of choking phenomenon) and blocking of isocyanate was not used, some reflectance deterioration occurred.

As shown in Fig. 4, in the temperature cycle of 300 ° C and room temperature at a predetermined reflux, Examples 1 to 4 and Comparative Examples 3 and 4 were stabilized to exhibit a low resistance value. In Comparative Example 1, it was found that the resistance values were somewhat dispersed. On the other hand, in Comparative Example 2 using a polyoxyxylene resin, not only the resistance value was largely dispersed, but also the increase in the resistance value was observed. It is presumed that this is because the rhodium-oxygen skeleton is present in the polyoxynene resin, so that the thermal fluctuation is increased and the strength is lowered. Further, in Comparative Example 5 in which the blocked isocyanate was not used, not only the resistance value was largely dispersed, but also the increase in the resistance value was observed. Further, as shown in Fig. 5, even in the predetermined moisture absorption reflow and more severe temperature cycle, Examples 1 to 4 were still stable and showed a low resistance value.

As shown in Fig. 7, any of Comparative Example 2 using a polyoxyxylene resin exhibited a preferred shear strength at room temperature. The shear strength at high temperature in Example 1 and Comparative Example 3 was also high. Further, as shown in Fig. 8, the values of Examples 1 to 4 did not change even under the illumination of the blue HID lamp, and no deterioration was observed.

As shown in Fig. 9, in Comparative Examples 1 and 2, the viscosity became nearly doubled in 24 hours, and it was found that when an acid anhydride-based curing agent was used, the pot life was difficult to stabilize. Examples 1 to 4, Comparative Examples 3 and 4 are viscosity-stabilized and show a sufficient pot life. In particular, the viscosity of Example 1 was small, and it was found that workability was excellent.

As a result of the above, it is understood that the conductive die attaching agent for LED of the present invention is excellent not only in light stability but also in terms of shear strength and resistance value. Excellent, it provides LEDs with excellent connection reliability and light stability. In particular, it is excellent in that it can obtain a good shear strength even at a high temperature and can suppress a change in resistance value. Furthermore, since it is also excellent in the pot life, it is also convenient in terms of work.

(industrial availability)

The conductive die attach adhesive for LEDs of the present invention can provide an LED excellent in connection reliability and light stability, and contributes to the development of LEDs.

Figure 1 is the wavelength of the blue HID lamp.

Figure 2 is a graph showing the change in reflectance caused by illumination of a blue HID lamp.

Fig. 3 is a method of producing a sample for measuring a resistance value. Fig. 3-A shows the preparation of the substrate, Fig. 3-B shows the application of the agent, Fig. 3-C shows the arrangement of the plates, and Fig. 3-D shows the sealing.

Figure 4 is a graph showing changes in resistance values under conditions of predetermined reflow.

Figure 5 is a graph showing changes in resistance values under conditions of predetermined moisture absorption reflow.

Figure 6 is a schematic diagram of shear strength measurement.

Figure 7 is a graph showing the values of shear strength at room temperature and elevated temperature.

Figure 8 is a graph showing changes in shear strength caused by illumination of light from a blue HID lamp.

Figure 9 is a graph showing the change in viscosity.

No component symbol

Claims (7)

A conductive die attaching agent for LEDs comprising: (A) a hydrogenated epoxy resin represented by the following formula: (wherein, X is -CH ₂ -, -C(CH ₃ ) ₂ - or directly bonded; m is an average of 0.5 or more), (B) a blocked product of a non-aromatic polyisocyanate, and (C) conductivity a filler; wherein the component (A) is 2 to 15 parts by weight, and the component (B) is 1 to 11 parts by weight, based on 100 parts by weight of the total of the components (A), (B) and (C), and the component (C) It is 74 to 97 parts by weight. The die attaching agent of the first aspect of the invention, wherein the component (B) is a blocked product obtained by blocking an aliphatic diisocyanate with an oxime compound or an indoleamine compound. The grain-adhesive agent of claim 1 or 2, wherein the component (C) is a silver powder. The die attaching agent of (D) aluminum is compounded with the die attaching agent of claim 1 or 2. For example, the die attaching agent of claim 1 or 2 contains (E) a decane coupling agent. The die attaching agent of claim 1 or 2, wherein the die attaching agent is coated on the glass substrate with a thickness of 150 μm, The film was heat-hardened at 150 ° C for 2 hours, and then cooled to room temperature to obtain a coating film having an initial reflectance Xa of 450 nm (wavelength) and a blue HID lamp (400 W, 8000 lm, for the coating film). 20000Lx) The reflectance Xb of 450 nm after irradiating light at 150 ° C for 1000 hours from a distance of 50 mm satisfies Xb/Xa ≧ 0.75. An LED manufactured by using the die attaching agent of any one of claims 1 to 6.