JP2017160348A - Thermally conductive adhesive, adhesive for dispensing, adhesive for screen printing, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally conductive adhesive which prevents occurrence of coarse grains, and is particularly suitable for dispensing and screen printing.SOLUTION: There is provided a thermally conductive adhesive which contains (A) thermosetting resin powder, (B) a thermally conductive filler, (C) at least one coupling agent selected from the group consisting of (c1) silane coupling agent powder and (c2) a liquid sulfide silane coupling agent, and (D) a paraffin-based solvent, where average particle sizes of the (A) component, the (B) component and the (c1) component are 50 μm or less.SELECTED DRAWING: None

Description

  The present invention relates to a thermally conductive adhesive, an adhesive for dispensing, an adhesive for screen printing, and a semiconductor device.

  In recent years, with the increase in heat generation of semiconductor packages due to miniaturization of wiring, and lead-free soldering of power ICs and power modules such as MOSFETs and IBGTs, as a material for joining semiconductor elements to substrates, thermal conductivity instead of solder There is a need for adhesives.

  Conventional heat conductive adhesives have a problem that warpage occurs in a substrate or the like due to the stress of curing shrinkage due to heating. In order to solve this problem, a technique in which a highly flexible resin is blended with a heat conductive adhesive has been studied.

  On the other hand, the heat conductive adhesive is required to have moisture resistance, and one of the test items is PCT (Pressure Cooker Test) pressure resistance. The present inventors consider that the addition of a silane coupling agent is effective for improving the PCT resistance.

  In order to solve the above problems, the following has been proposed.

  First, it comprises (A) an organic polymer resin, (B) an inorganic filler, and (C) an easily removable liquid in a predetermined ratio, and (A) and (B) are particles of a specific particle size. Although an adhesive paste (Patent Document 1) having a solubility in 20) or less in the composition is proposed, since this adhesive paste uses a thermoplastic polymer as a main component of the component (A), Applications are limited and no consideration is given to silane coupling agents.

  In addition, an epoxy resin, a phenol resin, a predetermined silane coupling agent (liquid), an epoxy resin composition including a predetermined amount of an inorganic filler (Patent Document 2), and a polymer including a predetermined compound having two vinyl bonds , A filler, a resin composition containing a silane coupling agent containing a predetermined sulfur (Patent Document 3), an epoxy resin, a phenol-based curing agent, a predetermined amount of silver-coated copper powder, an imidazole-based curing accelerator, and a silane coupling A die attach paste (Patent Document 4) containing an agent and a diluent as essential components has also been proposed.

Japanese National Patent Publication No. 9-501197 JP2013-232527A JP 2011-052043 A JP 2000-103940 A

  However, even if these are used alone or in combination to produce an adhesive with high adhesive strength, coarse particles are generated in the thermally conductive adhesive, and in particular, workability and quality in dispensing, screen printing, etc. There is a problem that will be reduced. Specifically, when coarse particles are generated in the heat conductive adhesive, the needle (inner diameter: about 400 to 500 μm) is clogged in the dispense, and the heat conductive adhesive does not spread out after dispensing. Clogging, normal coating thickness (about 50-100 μm) cannot be achieved, and the coating amount is not stable.

  Accordingly, an object of the present invention is to provide a heat conductive adhesive that does not generate coarse particles and is particularly suitable for dispensing and screen printing.

The present invention relates to a thermally conductive adhesive, an adhesive for dispensing, an adhesive for screen printing, and a semiconductor device that have solved the above problems by having the following configuration.
[1] (A) thermosetting resin powder,
(B) a thermally conductive filler,
(C) containing (c1) silane coupling agent powder and (c2) at least one coupling agent selected from the group consisting of liquid sulfide silane coupling agents, and (D) paraffinic solvents, ) Component, (B) component, and (c1) component have an average particle size of 50 μm or less, a heat conductive adhesive.
[2] The heat conductive adhesive according to [1], wherein the component (c1) contains imidazole silane.
[3] The heat conductive adhesive according to [1] or [2], further comprising (E) a thermoplastic resin powder.
[4] The heat conductive adhesive according to any one of [1] to [3], wherein the component (B) is silver powder.
[5] An adhesive for dispensing or an adhesive for screen printing using the heat conductive adhesive according to any one of the above [1] to [4].
[6] A semiconductor device having a cured product of the thermally conductive adhesive according to any one of [1] to [4] or a cured product of the adhesive for dispensing or the adhesive for screen printing according to [5]. .

  According to the present invention [1], it is possible to provide a heat conductive adhesive which does not generate coarse particles and is particularly suitable for dispensing and screen printing.

  According to the present invention [5], it is possible to provide an adhesive for dispensing or an adhesive for screen printing that does not generate coarse particles.

  According to the present invention [6], it is possible to obtain a highly reliable semiconductor device manufactured with a heat conductive adhesive, a dispensing adhesive or a screen printing adhesive that does not generate coarse particles.

The heat conductive adhesive of the present invention (hereinafter referred to as a heat conductive adhesive)
(A) thermosetting resin powder,
(B) a thermally conductive filler,
(C) containing (c1) silane coupling agent powder and (c2) at least one coupling agent selected from the group consisting of liquid sulfide silane coupling agents, and (D) paraffinic solvents, ) Component, (B) component, and (c1) component have an average particle size of 50 μm or less.

  The thermosetting resin powder of component (A) is solid at 25 ° C. which is a general working temperature, has a melting point or softening point of 35 to 150 ° C. before curing, and cures to 50 to 200 ° C. Has an onset reaction temperature and provides dimensional stability and heat resistance of the adhesive after curing. (D) It does not melt | dissolve in a component substantially, Specifically, the solubility to (D) component is 10 mass% or less. The thermosetting resin powder of the component (A) contains at least a thermosetting resin and a curing agent and / or a curing accelerator.

  The thermosetting resin used for the thermosetting resin powder of component (A) is a polyester resin, epoxy resin, acrylic resin, bismaleimide resin, phenol resin having a reactive group having a melting point or softening point of 90 to 130 ° C., A melamine resin, a xylene resin, a urea resin, etc. are mentioned, You may use independently and may use 2 or more types together. Further, these thermosetting resins are preferably polyester resins and epoxy resins from the viewpoints of flexibility and heat resistance.

  Curing agents and curing accelerators used in combination with these thermosetting resins include block isocyanate, uretdione resin, triglycidyl isocyanurate (TGIC), β-hydroxyalkylamides, dicyandiamides, aromatic amines. , Polyamines, acid anhydrides, dibasic acids, imidazoles, organotin compounds, tertiary amines, Lewis acid complexes, and the like.

  In addition, an additive such as a leveling agent, an antifoaming agent, a blocking inhibitor, and an antioxidant is added to the thermosetting resin powder as necessary within the range not impairing the object of the present invention.

  The thermosetting resin powder is prepared by dry premixing these raw materials with a mixer, mixing by hot melt kneading with a kneader or hot roll, etc., then cooling, and crushing the mixture with a mechanical pulverizer or jet mill. It is produced by classification with a classifier such as a sieving machine.

  Examples of such thermosetting resin powders include thermosetting resin powders used in powder coatings and toners, such as P01CW06P and P01CW035 manufactured by Yodogawa Paper Company; Clear polymer 156C102 manufactured by Akzo-nobel, Clear polyester 156C105-A and the like.

(B) The heat conductive filler of a component means a thing with a heat conductivity of 5 W / m * K or more. The component (B) does not need to be particularly limited as long as it does not substantially dissolve in the component (D), specifically, the solubility in the component (D) is 10% by mass or less. ) Components include silver, copper, gold, palladium, platinum, bismuth, tin, bismuth-tin alloy, indium tin oxide, silver-coated copper, silver-coated aluminum, metal-coated glass sphere, MgO, Al ₂ O ₃ , AlN , BN, diamond, ZnO, SiC, and a mixture thereof, and silver having a thermal conductivity of 427 W / m · K is preferable.

Furthermore, as (B) component, when the thing of tap density: 5-7g / cm < ³ > and BET specific surface area: 0.07-1.0m < ² > / g is included, (B) component is contained in a heat conductive adhesive. Even if the filling is high, a low-viscosity paste-like adhesive can be obtained, and the heat-conducting adhesive can be further increased in thermal conductivity by increasing the amount of the component (B). Further, the shape of the component (B) is more preferably a flake shape from the viewpoint of reducing resistance. (B) A component may be individual or may use 2 or more types together.

  The coupling agent as component (C) is preferably substantially insoluble in component (D), specifically, has a solubility in component (D) of 10% by mass or less. In conventional heat conductive adhesives, liquid silane coupling agents were used. However, liquid silane coupling agents dissolved or swelled thermosetting resin powder. There was a problem that the thermosetting resin powder reacted to gel, or the thermosetting resin powder or the heat conductive filler aggregated to generate coarse particles.

  (C1) Component silane coupling agent powder is a solid silane coupling agent that is difficult to dissolve in component (D), or a mixture of a resin having a melting point of 50 ° C. or higher and a liquid silane coupling agent in powder form. This is crushed. As a commercial product of the silane coupling agent of component (c1), a mixture of N- (2-hydroxypropyl-trimethoxysilyl ether) -imidazole and novolak resin manufactured by JX Nippon Mining & Metals Co., Ltd. (trade name: Imidazolesilane SP -10) and a mixture of [3- (2,3-epoxypropoxy) propyl] trioxysilane and resin (trade name: Deoline Epoxy TE) manufactured by King Industries.

  The liquid sulfide-based silane coupling agent as component (c2) is a liquid, but since S atoms act on the surface of (B) the thermally conductive filler, it is difficult to dissolve the thermosetting resin powder, It is thought that it is hard to generate. This sulfide-based silane coupling agent is more preferably 3-octanoylthio-1-propyltriethoxysilane represented by the formula (2). (C) A component may be individual or may use 2 or more types together.

  The paraffinic solvent as the component (D) can impart an appropriate viscosity to the thermally conductive adhesive without substantially dissolving the components (A), (B), and (c1). The paraffinic solvent is preferably normal paraffin, more preferably a mixture of normal paraffins having 14 to 16 carbon atoms. (D) A component may be individual or may use 2 or more types together.

  Moreover, as for the heat conductive adhesive, the average particle diameter of the component (A), the component (B), and the component (c1) is 50 μm or less, and if it is 50 μm or less, the adhesive for dispensing or the adhesive for screen printing is used. It is suitable as an agent. Here, the average particle diameter is a volume-based median diameter measured by a laser diffraction method.

  (A) As for a component, 1-10 mass parts is preferable with respect to 100 mass parts of heat conductive adhesives. If it is less than 1 part by mass, the adhesiveness of the heat conductive adhesive tends to deteriorate, and if it exceeds 10 parts by mass, the viscosity increases and the workability tends to deteriorate.

  (B) As for a component, 75-90 mass parts is preferable with respect to 100 mass parts of heat conductive adhesives. If it is less than 75 parts by mass, the thermal conductivity of the heat conductive adhesive tends to be low, and if it exceeds 90 parts by mass, the viscosity of the heat conductive adhesive tends to be high and workability tends to be poor.

  (C) As for a component, 0.05-2 mass parts is preferable with respect to 100 mass parts of heat conductive adhesives from a PCT characteristic of a heat conductive adhesive, and an adhesive viewpoint. If it is less than 0.05 parts by mass, the adhesiveness of the heat conductive adhesive, the PCT resistance of the heat conductive adhesive after curing tends to be poor, and if it exceeds 2 parts by mass, the thermal conductivity tends to be low, Also, the volume resistivity tends to be high.

  (D) As for a component, 5-15 mass parts is preferable with respect to 100 mass parts of heat conductive adhesives from a viscous viewpoint of a heat conductive adhesive.

  It is preferable that the heat conductive adhesive further includes (E) a thermoplastic resin powder from the viewpoint of reducing the warpage of the chip by reducing the elasticity of the heat conductive adhesive. Examples of the component (E) include polyester powder, polyamide powder, polyurethane powder, and silicone powder. Examples of the commercially available polyester powder include Schaetti (Shanghai) Hotmelt Adhesive polyester powder (product name: Schaetti Fix 376 / 0-80).

  (E) As for a component, 1-10 mass parts is preferable with respect to 100 mass parts of heat conductive adhesives from a viewpoint of making the heat conductive adhesive after hardening low elasticity.

  In the heat conductive adhesive, a silver resinate, an antioxidant, a leveling agent, an ion trapping agent, other additives, and the like can be further blended as necessary without departing from the object of the present invention.

  The heat conductive adhesive can be obtained, for example, by stirring, melting, mixing, and dispersing the components (A) to (D) and other additives simultaneously or separately. The mixing, stirring, and dispersing devices are not particularly limited, and a stirring, three roll mill, planetary mixer, planetary mixer, and the like can be used. Moreover, you may use combining these apparatuses suitably.

  The heat conductive adhesive preferably has a viscosity at a temperature of 25 ° C. of 7 to 30 Pa · s from the viewpoint of dispensing workability and screen printability. Here, the viscosity is measured at 5 rpm and 25 ° C. using an E-type viscometer (3 ° cone). Moreover, the viscosity after storing a heat conductive adhesive at room temperature for 24 hours is preferable from a viewpoint of dispensing workability | operativity and screen printing property as 7-30 Pa.s.

  The thermally conductive adhesive is formed and applied to a desired position of an electronic component such as a conductive portion of a substrate, a die attach portion (die attachment portion), or an electrode portion of a semiconductor element by a dispenser, screen printing, or the like. As for hardening of a heat conductive adhesive, 150-200 degreeC is preferable.

  The above-mentioned thermally conductive adhesive is used for the dispensing adhesive or the screen printing adhesive of the present invention.

  In addition, the semiconductor device of the present invention has a cured product of the above-described thermally conductive adhesive, or a cured product of the above-described dispensing adhesive or screen printing adhesive.

  In the semiconductor device of the present invention, surface mount components, metal plates, semiconductor chips, etc. are bonded by a heat conductive adhesive, a dispensing adhesive, or a screen printing adhesive that does not generate coarse particles. Reliability.

  The present invention will be described with reference to examples, but the present invention is not limited thereto. In the following examples, parts and% indicate parts by mass and mass% unless otherwise specified.

[Examples 1 to 5, Comparative Examples 1 to 4]
[Preparation of sample for evaluation]
The thermosetting resin powder used was pulverized by a jet mill and then passed through a # 325 mesh screen. The silane coupling agent powder was used after being crushed with a mortar and pestle and then passing through a # 500 size mesh sieve. Similarly, the thermoplastic resin powder and the liquid epoxy resin curing accelerator imidazole 2P4MZ used those that passed through a # 325 mesh screen.

  In Examples / Comparative Examples, the components shown in Table 1 were mixed with each component other than silver powder for 1 minute with a rotating / revolving stirrer (Shinky Awatori Nertaro), and silver powder was added to this solution. It was added and dispersed for 30 seconds with a self-revolving stirrer, and then degassed under reduced pressure to prepare a paste-like thermally conductive adhesive. The properties were measured for each agent. The results are shown in Table 1.

〔Evaluation method〕
"viscosity"
The initial viscosity of the thermally conductive adhesive produced within 1 hour was measured at 5 rpm at 25 ° C. using an E-type viscometer (3 ° cone) manufactured by Tokimec. Further, the viscosity after storage at room temperature for 24 hours (viscosity after storage for 24 hours at room temperature) was measured in the same manner. The rate of increase in viscosity was determined from [(viscosity after storage for 24 hours at room temperature) / (initial viscosity) × 100]. Table 1 shows these results. The viscosity is preferably 5 to 30 Pa · s. The rate of increase in viscosity is preferably 25% or less. The results are shown in Table 1.

《Maximum grain size》
Place the prepared paste in the groove of a grind gauge (grind gauge manufactured by Yasuda Seiki Seisakusyo Co., Ltd.) consisting of a 0 to 100 μm gauge and a scraper as defined in JIS K5600-2-5, and cut the groove with a scraper. While pressing, the gauge was moved from a depth of 100 μm to 0 μm, and the depth value of the gauge at the start position of the line appearing on the paste surface of the groove was measured. The maximum particle size is preferably 50 μm or less. The results are shown in Table 1.

"Thermal conductivity"
The thermally conductive adhesive is heated from room temperature to 200 ° C. in 30 minutes, held in an oven at 200 ° C. for 15 minutes and cured to produce a film-like cured product, and LFA447 Nanoflash device manufactured by NETZSCH The thermal conductivity (W / m · K) was measured by a laser flash method. Table 1 shows the results. The thermal conductivity is preferably 25 W / m · K or more. The results are shown in Table 1.

《Volume resistivity》
The prepared thermally conductive adhesive was applied on a slide glass at a length of 75 mm, a width of 5 mm, and a thickness of 100 μm, and the temperature was raised from room temperature to 200 ° C. in 30 minutes. After being kept for a minute and cured, the volume resistivity of the cured product was measured by the 4-terminal method. Table 1 shows the results. The volume resistivity is preferably 40 μΩ · cm or less. The results are shown in Table 1.

《Die shear strength》
A silicon chip of 5 mm x 5 mm was mounted on a silver-plated copper lead frame using the produced heat conductive adhesive, heated from room temperature (25 ° C) to 200 ° C in 30 minutes, and in a 200 ° C oven And was cured for 15 minutes to prepare a test piece (n = 12). Thereafter, the test pieces were divided into two groups (n = 6). The initial die shear strength group, the first group, measured the die shear strength immediately after curing. The die shear strength group after PCT, which is the second group, was measured for die shear strength after being cured and exposed to a PCT oven at 121 ° C. and 2 atm for 20 hours. In both groups, the die shear strength is a value measured at room temperature (25 ° C.) using a Dage shear tester. Further, the die shear strength retention rate was calculated as follows.
Die shear strength retention (%) = {[(die shear strength after PCT) / (initial die shear strength)] × 100}
The results are shown in Table 1.

  As can be seen from Table 1, in all of Examples 1 to 5, the viscosity was in an appropriate range, the viscosity increase rate was low, the maximum particle size was small, the thermal conductivity after curing was high, and the volume resistivity was low. Further, the die shear strength retention rate (die shear strength after PCT test of cured product (121 ° C., 2 atm, 20 hours) / initial die shear strength of cured product) was also good. Further, when the component (C) was in the form of a silane coupling agent powder of the component (c1), the die shear strength was higher than that of the (c2) liquid sulfide silane coupling agent. On the other hand, in Comparative Example 1 using a liquid thermosetting resin instead of the component (A), the maximum particle size was too large. In Comparative Example 2 using a liquid silane coupling agent which is not a sulfide type instead of the component (C), the maximum particle size was too large. In Comparative Example 3 using a non-paraffinic solvent instead of the component (D), gelation occurred and the viscosity was too high, so that the viscosity could not be measured and was not cured. It was not possible to measure. Comparative Example 4 not containing the component (C) had a low die shear strength retention.

  As described above, the heat conductive adhesive of the present invention does not generate coarse particles, and can provide a heat conductive adhesive particularly suitable for dispensing and screen printing.

Claims (6)

(A) thermosetting resin powder,
(B) a thermally conductive filler,
(C) containing (c1) silane coupling agent powder and (c2) at least one coupling agent selected from the group consisting of liquid sulfide silane coupling agents, and (D) paraffinic solvents, ) Component, (B) component, and (c1) component have an average particle size of 50 μm or less, a heat conductive adhesive.   The heat conductive adhesive according to claim 1, wherein the component (c1) contains imidazole silane.   The heat conductive adhesive according to claim 1 or 2, further comprising (E) a thermoplastic resin powder.   (B) The heat conductive adhesive of any one of Claims 1-3 whose component is silver powder.   An adhesive for dispensing or an adhesive for screen printing using the thermally conductive adhesive according to any one of claims 1 to 4.   The semiconductor device which has the hardened | cured material of the heat conductive adhesive of any one of Claims 1-4, or the hardened | cured material of the adhesive for dispensing or the adhesive for screen printing of Claim 5.