TWI843873B - Resin molded article for optical semiconductor sealing and method for producing the same - Google Patents

Abstract

The subject of the present invention is to provide a resin molded article for encapsulating optical semiconductors and a method for manufacturing the same, wherein the deviation of the spiral flow length or gelation time of the resin molded article is small and the transfer molding can be performed stably. A resin molded article for encapsulating optical semiconductors, wherein the standard deviation σ(SF) of the spiral flow length SF measured according to EMMI (Epoxy Molding Materials Institute) Standard 1-66 is less than 20 cm under the conditions of mold temperature 150°C, molding pressure 970 kgf/ ^cm2 , curing time 120 s, and injection speed 2.0 cm/s.

Description

Resin molded article for encapsulating optical semiconductor and method for producing the same

The present invention relates to a resin molded article for encapsulating an optical semiconductor and a method for producing the same.

Optical semiconductor components are packaged and sealed in ceramic or plastic packages. Since the materials used to make ceramic packages are expensive and have poor mass production, plastic packages are the mainstream. Among them, in terms of workability, mass production, and reliability, the transfer molding technology of pre-molding the epoxy resin composition into a tablet shape has become the mainstream.

In addition, in the epoxy resin composition for encapsulating optical semiconductors used in plastic packaging, the components of epoxy resin, hardener, and hardening accelerator are relatively difficult to disperse and not easy to mix and disperse uniformly as a whole. Therefore, there is a problem that the hardening reaction becomes uneven and easily generates uneven forming or forming gaps. Due to such unevenness or gaps, there is a problem that optical unevenness is generated and the reliability of the optical semiconductor device is damaged.

In order to solve these problems, Patent Document 1 discloses a technology that uses an epoxy resin composition obtained by very finely pulverizing it and tableting it, thereby ensuring the uniform dispersion of the composition, reducing uneven forming or forming gaps, and eliminating optical unevenness. Furthermore, Patent Document 2 discloses a technology that granulates the epoxy resin composition into granules and tablets it. [Prior Technical Document] [Patent Document]

[Patent document 1] Japanese Patent Publication No. 3-3258 [Patent document 2] Japanese Patent Publication No. 2011-9394

[The problem the invention is trying to solve]

The purpose of the present invention is to provide a resin molded product for optical semiconductor sealing and a method for manufacturing the same, wherein the spiral flow length or gelation time of the resin molded product is less uneven and transfer molding can be performed stably. [Technical means for solving the problem]

The present invention relates to a resin molded product for encapsulating optical semiconductors, wherein the standard deviation σ(SF) of the spiral flow length SF measured under the conditions of a mold temperature of 150°C, a molding pressure of 970 kgf/cm ² , a curing time of 120s, and an injection speed of 2.0 cm/s is less than 20 cm.

The difference between the maximum and minimum values of the spiral flow length SF is preferably less than 80 cm.

The present invention also relates to a resin molded product for encapsulating optical semiconductors, wherein the standard deviation σ(GT) of the gelation time GT measured under the conditions of a mold temperature of 150°C, a molding pressure of 970 kgf/ ^cm2 , a curing time of 120 s, and an injection speed of 2.0 cm/s according to EMMI (Epoxy Molding Materials Institute) Standard 1-66 is 1.8 seconds or less.

The difference between the maximum and minimum values of the gelation time GT is preferably less than 6 seconds.

The optical semiconductor sealing resin molded product preferably contains a thermosetting resin, a curing agent, and a curing accelerator.

Furthermore, the present invention relates to a method for producing the above-mentioned resin molded article for encapsulating optical semiconductors, which is characterized by comprising: a step of kneading a thermosetting resin, a curing agent and a curing accelerator to obtain a curable resin composition; a step of heat-treating the curable resin composition; a step of granulating the curable resin composition to obtain a granular curable resin composition; and a step of molding the granular curable resin composition. [Effect of the invention]

The variation of the spiral flow length or gelation time of the optical semiconductor sealing resin molded product of the present invention is small not only in the same batch but also between batches, so the transfer molding can be carried out stably.

The optical semiconductor encapsulation resin molded product of the present invention is characterized in that: according to EMMI (Epoxy Molding Materials Institute) Standard 1-66, the standard deviation σ(SF) of the spiral flow length SF measured under the conditions of mold temperature 150°C, molding pressure 970 kgf/ ^cm2 , curing time 120 s, and injection speed 2.0 cm/s is less than 20 cm, or the standard deviation σ(GT) of the gelation time GT is less than 1.8 seconds. In the optical semiconductor encapsulation resin molded product of the present invention, since the microscopic unevenness of the curing reaction speed is small, the standard deviation of the spiral flow length or the gelation time becomes small. Here, the optical semiconductor sealing resin molded article refers to a member formed so as to cover an optical semiconductor element constituting an optical semiconductor device and seal the element, and examples thereof include tablets and sheets.

The volume of the optical semiconductor sealing resin molded product is not particularly limited, but is preferably 1 to 100 cm ³ , and more preferably 10 to 100 cm ³ . If the volume is too small, the difference in reaction state non-uniformity tends to be difficult to see.

The measuring device for measuring the spiral flow length SF and the gelation time GT includes: a barrel for filling the sample, a mold with a spiral cavity, and a mold for pressing the sample. The whole device is heated to the measuring temperature, and the resin composition is put into the barrel. After a certain period of time, the plunger is pressed to pressurize. The spiral flow length SF and the gelation time GT can be measured by the device. The measuring device complies with the EMMI (Epoxy Molding Materials Institute) standard 1-66.

The spiral flow length SF is calculated by measuring the displacement of the plunger and its time. The gelation time GT is the time from the start of the measurement until the plunger speed reaches a certain fixed value.

In the present invention, the spiral flow length SF and the like are measured according to EMMI standard 1-66 at a mold temperature of 150°C, a molding pressure of 970 kgf/cm ² , a curing time of 120 s, and an injection speed of 2.0 cm/s.

The spiral flow length SF is not particularly limited, but is preferably 50 to 350 cm, more preferably 150 to 250 cm. If the spiral flow length is too short, the filling property of the mold is reduced, and if the spiral flow length is too long, the resin leaks out of the mold and causes resin burrs.

The gelling time GT is not particularly limited, but is preferably 10 to 40 seconds, more preferably 20 to 30 seconds. If the gelling time is too short, the mold tends to be difficult to fill due to too fast hardening, and if the gelling time is too long, the productivity tends to decrease due to too slow hardening.

The minimum number of samples for obtaining the standard deviation is 5, preferably 8 or more, more preferably 10 or more, and even more preferably 12 or more. Since the more the better, there is no particular upper limit.

The standard deviation of the spiral flow length SF is 20 cm or less, preferably 10 cm or less. If it exceeds 20 cm, the unevenness is large and the transfer and forming cannot be performed stably. In addition, the difference between the maximum value and the minimum value of the spiral flow length SF is preferably 80 cm or less, more preferably 50 cm or less. Furthermore, the ratio of the maximum value to the minimum value of the spiral flow length SF is preferably 0.60 or more, more preferably 0.70 or more.

The standard deviation of the gelation time GT is 1.8 seconds or less, preferably 1.0 seconds or less. If it exceeds 1.8 seconds, the unevenness is large and the transfer molding cannot be performed stably. In addition, the difference between the maximum value and the minimum value of the gelation time GT is preferably 6 seconds or less, more preferably 3 seconds or less. Furthermore, the ratio of the maximum value to the minimum value of the gelation time GT is preferably 0.78 or more, more preferably 0.83 or more.

The standard deviation σ(SF) of the spiral flow length SF or the standard deviation σ(GT) of the gelation time GT can be adjusted by controlling the reaction state. Specifically, the control of the reaction state can be performed by appropriately adjusting the type of thermosetting resin, the type of hardener, the type and amount of hardening accelerator, the reaction temperature, the reaction time, the resin shape, etc.

The standard deviation of the time required for the optical semiconductor encapsulation resin molded article to reach 50% torque is preferably 1.5 seconds or less, more preferably 1.0 seconds or less, and further preferably 0.7 seconds or less. Here, the torque can be measured by monitoring the torque required when stirring at 150°C using a stirring blade made of Teflon (trademark registration) that performs a rotational revolution motion.

With respect to the optical semiconductor sealing resin molded product of the present invention, the pressing time until the plunger is pressed to the bottom is preferably less than 10 minutes, and more preferably less than 5 minutes. If the pressing time is too long, there is a tendency that the fast-hardening components and the slow-hardening components will be mixed in the molded product, and the transfer molding cannot be stably performed. This index shows that the gelation time is shortened when the spiral flow length is the same. Here, with respect to the measurement conditions of the pressing time, the time when the plunger starts to be pressed is set as the starting time, the time when the plunger can no longer be pressed due to the molding pressure is set as the ending time, and the difference between the two is set as the pressing time.

Furthermore, the optical semiconductor encapsulation resin molded product of the present invention has a minimum melt viscosity of 300 dPa·s or less measured under the conditions of a mold temperature of 150°C, a molding pressure of 970 kgf/cm ² , a curing time of 120s, and an injection speed of 2.0 cm/s according to EMMI (Epoxy Molding Materials Institute) Standard 1-66, and preferably a ratio b/a of a value obtained by subtracting the minimum melt viscosity from the index viscosity of 800 dPa·s to the time a for the minimum melt viscosity to reach 800 dPa·s again during the curing process of 20 or more.

The minimum melt viscosity is preferably 300 dPa·s or less, more preferably 200 dPa·s or less. If it exceeds 300 dPa·s, there is a tendency for poor filling of the product during molding. The lower limit is not particularly limited, but is preferably 30 dPa·s or more, and may be 50 dPa·s or more, or 80 dPa·s or more.

The value b obtained by subtracting the minimum melt viscosity from the index viscosity of 800 dPa·s is not particularly limited, and is preferably 500 to 770, and may be 500 to 750 or 500 to 720. In addition, the value b obtained by subtracting the minimum melt viscosity from the index viscosity of 800 dPa·s and the time a for the minimum melt viscosity to reach 800 dPa·s again during the curing process are not particularly limited, and are preferably 5 to 32, and more preferably 10 to 30.

The ratio b/a of the time a for the minimum melt viscosity to reach 800 dPa・s again during the curing process is 20 or more, preferably 22 or more, and more preferably 25 or more. If it is less than 20, it takes time until curing, and the molding cycle becomes longer, and a high cycle cannot be achieved.

Here, the measuring device for measuring the melt viscosity can be directly used as the measuring device for measuring the spiral flow length SF and the gelation time GT mentioned above.

The optical semiconductor sealing resin molded product of the present invention preferably contains a reaction product of the thermosetting resin and the curing agent in addition to the thermosetting resin, the curing agent and the curing accelerator. In addition, fillers such as silicon dioxide powder can be mixed as long as they do not impair light transmission.

Examples of thermosetting resins include epoxy resins, silicone resins, and hybrid resins of epoxy resins and silicone resins. Among them, epoxy resins are preferred.

As the epoxy resin, preferably one with less coloration, for example, there can be cited: bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, alicyclic epoxy resin, triglycidyl isocyanate, hydantoin epoxy resin and other epoxy-containing epoxy resins, hydrogenated bisphenol A type epoxy resin, aliphatic epoxy resin, glycidyl ether type epoxy resin, etc. These can be used alone or in combination of two or more.

As the curing agent, it is preferred to use an acid anhydride that has less coloring on the cured body of the resin composition during or after curing. For example, phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyl naphthalic anhydride, naphthalic anhydride, glutaric anhydride, etc. can be listed. In addition, as other curing agents, m-phenylenediamine, dimethyldiphenylmethane, diaminodiphenylsulfone, m-phenylenediamine, tetraethylenepentamine, diethylamine, propylamine, etc., which are amine-based curing agents, or phenolic resin-based curing agents can be listed. These can be used alone or in combination of two or more.

The amount of hardener to be added is not particularly limited, but is preferably 20 to 80 parts by weight, more preferably 40 to 60 parts by weight, relative to 100 parts by weight of epoxy resin. If the amount is less than 20 parts by weight, the curing speed will be slow, and if it exceeds 80 parts by weight, there is a risk that the amount is excessive for the curing reaction, resulting in a decrease in various physical properties.

Examples of the hardening accelerator include tertiary amines such as triethanolamine, or imidazoles such as 2-methylimidazole; organophosphorus compounds such as tetraphenylphosphonium-tetraphenylborate or triphenylphosphine; and diazabicycloolefin hydrocarbon compounds such as 1,8-diazabicyclo[5,4,0]undecene-7 or 1,5-diazabicyclo[4,3,0]nonene-5. These may be used alone or in combination of two or more.

The amount of the curing accelerator to be added is not particularly limited, and can be appropriately selected from the range of 0.1 to 5 parts by mass, preferably 0.5 to 3 parts by mass, and more preferably 1 to 2 parts by mass, relative to 100 parts by mass of the epoxy resin. If the amount of the curing accelerator to be added is too small, the curing speed may be slowed down, and productivity may be reduced. On the other hand, if the amount of the curing accelerator to be added is too large, the curing reaction speed may be faster, and it may become difficult to control the reaction state, and there may be a risk of uneven reaction.

In the photo-semiconductor encapsulation resin composition of the present invention, in addition to the above-mentioned components, additives such as anti-coloring agents, lubricants, modifiers, anti-degradation agents, and mold release agents may be used as needed.

Examples of anti-coloring agents include phenolic compounds, amine compounds, organic sulfur compounds, and phosphine compounds.

As lubricants, there can be listed: waxes such as stearic acid, magnesium stearate, calcium stearate, or talc. Furthermore, when the above lubricants are prepared, the preparation amount is appropriately set according to the tableting conditions, for example, preferably set to 0.1-0.4 mass % of the entire resin composition.

The method for producing a resin molded article for encapsulating an optical semiconductor of the present invention is characterized in that it includes: a step of kneading a thermosetting resin, a curing agent and a curing accelerator to obtain a curable resin composition; a step of heat-treating the curable resin composition; a step of granulating the curable resin composition to obtain a granular curable resin composition; and a step of molding the granular curable resin composition.

The kneading method is not particularly limited, and for example, a method using an extruder can be cited. The kneading temperature is also not particularly limited, and can be appropriately changed according to the characteristics of the thermosetting resin, and the temperature can also be set higher in order to allow the reaction to proceed during kneading. Specifically, it is preferably 80 to 150°C, and more preferably 110 to 130°C.

The shape of the curable resin composition obtained by kneading is not particularly limited, and may be a film, a sheet, a granule, a block, or the like.

The thickness of the hardening resin composition obtained by kneading is not particularly limited, but is preferably 1 to 30 mm, more preferably 2 to 20 mm. If it is less than 1 mm, the thickness is thin and tends to be easily affected by moisture absorption. If it exceeds 30 mm, it takes time to cool down and tends to react unevenly due to internal heat accumulation.

The hardening resin composition obtained by kneading is heat-treated to obtain a B-stage (semi-hardened) optical semiconductor encapsulation resin composition. The heat treatment temperature is not particularly limited, but is preferably 25 to 100°C, and more preferably 60 to 80°C. If it is less than 25°C, the hardening reaction tends to be slow and productivity tends to decrease. If it exceeds 100°C, the hardening reaction tends to be fast and it tends to be difficult to terminate in a specific reaction state. The heat treatment time is not particularly limited and can be appropriately changed according to the characteristics of the thermosetting resin.

The heat-treated resin composition is granulated to obtain a granular resin composition. Before granulation, the composition may be crushed using a ball mill, a turbo pulverizer, or the like. The granulation method is not particularly limited, and a method using a dry compression granulator may be cited. The average particle size of the granules obtained by granulation is not particularly limited, but is preferably 1 to 5000 μm, and more preferably 100 to 2000 μm. If the particle size exceeds 5000 μm, the compression rate tends to decrease.

The obtained granular resin composition is molded to obtain a molded product. The molded product may be a tablet or a sheet, and the molding method may be tableting for the obtained tablet or extrusion for the obtained sheet. The obtained molded product has fewer defects, cracks, and weight variations, and as mentioned above, the unevenness of the hardening reaction is also small, so the unevenness of the spiral flow length or the gelation time is also small, resulting in a high-quality molded product.

When the molded product is a tablet, the conditions for tablet pressing can be appropriately adjusted according to the composition of the granular curable resin composition, the average particle size, the particle size distribution, etc. Generally speaking, the compression ratio during tablet pressing is preferably set to 90-96%. That is, if the compression ratio is less than 90%, the density of the tablet may be reduced and it may be easy to break. On the contrary, if the compression ratio is greater than 96%, there is a risk of cracking during tablet pressing and defects or fractures during demolding.

The above-mentioned molded article is an optical semiconductor device manufactured by sealing the optical semiconductor element by transfer molding. Since the unevenness of the spiral flow length or the gelation time is also small, it becomes an optical semiconductor element with high reliability and high quality without optical unevenness. Therefore, when the optical semiconductor device is operated to obtain an image, it has the following advantages, that is, no stripe pattern caused by optical unevenness is generated, and a clear image can be obtained.

Furthermore, the optical semiconductor sealing resin molded product of the present invention can be used for resin sealing of optical semiconductor elements such as light-receiving elements, and therefore is preferably transparent from an optical point of view. In this case, "transparent" means that the transmittance of the cured product of the curable resin composition constituting the above-mentioned molded product at 400 nm is 98% or more. [Example]

Next, the embodiments are described in conjunction with comparative examples. However, the present invention is not limited to the following embodiments.

The materials used are shown below. Epoxy resin 1: Bisphenol type epoxy resin A (epoxy equivalent 650) Epoxy resin 2: Triglycidyl isocyanurate (epoxy equivalent 100) Curing agent: Tetrahydrophthalic anhydride (anhydride equivalent 152) Curing accelerator: 2-ethyl-4-methylimidazole

Examples 1 to 7 and Comparative Examples 1 to 2 The raw materials were mixed in the amounts shown in Tables 1 to 2 and heated, melted and mixed in an extruder set to the temperature shown in Tables 1 to 2. The resin from the extruder was formed into a 2 to 10 mm thick film and heat-treated at 60°C for 60 minutes. The retention time in the extruder was about 2 minutes. The epoxy resin composition was granulated and sized using a roller granulator (manufactured by NIPPON GRANULATOR, testing machine: 1531 model) to obtain an epoxy resin composition for encapsulating optical semiconductors. The obtained optical semiconductor encapsulating resin composition was pelletized using a No. 20 rotary tablet press to produce the optical semiconductor encapsulating resin tablets shown in Table 1. The compression ratio was 90 to 93%.

Using the tablets prepared in each embodiment, 15 samples were evaluated for spiral flow length SF and gelation time GT by the method shown below, 9 samples were evaluated for time to reach 50% torque by the method shown below, and 3 samples were evaluated for bottom pressing time. The evaluation results are shown in Tables 1 and 2.

<Spiral flow length SF, gelation time GT> According to EMMI (Epoxy Molding Materials Institute) standard 1-66, the conditions of mold temperature 150℃, molding pressure 970 kgf/ ^cm2 , curing time 120s, and injection speed 2.0 cm/s are measured. Specifically, the obtained tablets are coarsely crushed and passed through a sieve with an opening diameter of 5 mm. The powder is put into a barrel maintained at 150℃ using a flowability measuring device, and the plunger is pressed at a fixed speed to apply pressure. The spiral flow length SF is calculated by measuring the displacement of the plunger and its time. The gelation time GT is measured as the time from the start of the measurement until the plunger speed becomes a fixed value.

<Time for torque to reach 50%> Using an automatic hardening time measuring device (manufactured by Cyber Co., Ltd., automatic hardening time measuring device MADOKA, model MDK10G-06SP), the obtained tablets were coarsely crushed and passed through a sieve with an opening diameter of 5 mm. 0.2 g of the powder obtained was placed on a hot plate maintained at 150°C, and the time change of the torque was measured to find the time for the torque to reach 50%.

<Viscosity characteristics> The viscosity characteristics were measured under the same conditions using a flowability measuring device for measuring spiral flow length. Specifically, the obtained tablets were coarsely crushed using a flowability measuring device and passed through a sieve with an opening diameter of 5 mm. The powder was put into a cylinder maintained at 150°C and the plunger was pushed in at a fixed speed to apply pressure. The melt viscosity calculated from the measured torque was plotted against time to obtain the value b obtained by subtracting the minimum melt viscosity from the index viscosity of 800 dPa・s, and the time a for the minimum melt viscosity to reach 800 dPa・s again during the curing process was obtained.

[Table 1] Example No. Embodiment Comparison Example 1 2 3 4 1 Preparation (mass) Epoxy resin 1 80 80 80 80 80 Epoxy 2 20 20 20 20 20 Hardener 50 50 50 50 50 Hardening accelerator 1.8 1.6 1.4 1.2 1.0 Processing conditions Extruder set temperature (℃) 130 130 130 130 130 Evaluation results SF(cm) max 171.5 180.9 190.0 202.0 213.1 min 137.0 131.4 127.0 124.0 120.4 σ 9.1 10.0 12.0 15.0 25.1 max-min 34.5 49.5 63.0 78.0 92.7 min/max 0.80 0.73 0.67 0.61 0.56 GT(s) max 18.9 20.4 23.3 25.8 27.6 min 16.8 17.6 19.4 20.2 20.9 σ 0.6 0.8 1.0 1.5 2.0 max-min 2.1 2.8 3.9 5.6 6.7 min/max 0.89 0.86 0.83 0.78 0.76 Time for torque to reach 50% (s) σ 0.3 0.7 1.0 1.3 1.6

[Table 2] Example No. Embodiment Comparison Example 5 6 7 2 Preparation (mass) Epoxy resin 1 80 80 80 80 Epoxy 2 20 20 20 20 Hardener 50 50 50 50 Hardening accelerator 1.4 1.2 0.8 0.6 Processing conditions Extruder set temperature (℃) 150 110 100 70 Evaluation results SF(cm) max 182.4 190.7 205.3 220.4 min 132.8 128.4 131.2 133.0 σ 11.0 12.1 18.4 21.0 max-min 49.6 62.3 74.1 87.4 mm/max 0.73 0.67 0.64 0.60 GT(s) max 19.0 21,7 24.9 26.8 min 16.3 17.6 19.0 20.4 σ 0.9 1.0 1.4 1.8 max-min 2.7 4.1 5.9 6.4 min/max 0.86 0.81 0.76 0.76 Time for torque to reach 50% (s) σ 1.0 1.2 1.4 1.5 Viscosity characteristics a 14.6 23.1 28.0 38.0 b 722 720 740 715 b/a 49.5 31.2 26.4 18.8

According to the experimental results shown in Tables 1 to 2, in Examples 1 to 7, tablets with smaller standard deviations of the spiral flow length SF and the gelation time GT were obtained. Therefore, transfer molding can be performed stably. On the other hand, in Comparative Examples 1 to 2, only tablets with larger standard deviations of the spiral flow length SF and the gelation time GT were obtained. Therefore, it is difficult to perform transfer molding stably. [Industrial Applicability]

The present invention can be applied to a method for producing a photo-semiconductor sealing resin molded product, the photo-semiconductor sealing resin molded product obtained thereby, and a photo-semiconductor device using the same. The photo-semiconductor sealing resin molded product can be used to seal photo-semiconductor elements.

Claims (6)

A resin molded article for encapsulating optical semiconductors, wherein the standard deviation σ(SF) of the spiral flow length SF measured under the conditions of mold temperature 150°C, molding pressure 970 kgf/ ^cm2 , curing time 120 s, and injection speed 2.0 cm/s is less than 20 cm. A resin molded article for encapsulating optical semiconductors as claimed in claim 1, wherein the difference between the maximum and minimum values of the spiral flow length SF is less than 80 cm. A resin molded article for encapsulating optical semiconductors, wherein the standard deviation σ(GT) of the gelation time GT measured under the conditions of a mold temperature of 150°C, a molding pressure of 970 kgf/ ^cm2 , a curing time of 120 s, and an injection speed of 2.0 cm/s according to EMMI (Epoxy Molding Materials Institute) Standard 1-66 is 1.8 seconds or less. A resin molded article for encapsulating optical semiconductors as claimed in claim 3, wherein the difference between the maximum value and the minimum value of the gelation time GT is less than 6 seconds. A resin molded article for encapsulating an optical semiconductor as claimed in any one of claims 1 to 4, comprising a thermosetting resin, a curing agent and a curing accelerator. A method for producing a resin molded article for encapsulating an optical semiconductor as claimed in any one of claims 1 to 5, characterized in that it comprises: a step of kneading a thermosetting resin, a hardener and a hardening accelerator to obtain a hardening resin composition; a step of heat-treating the hardening resin composition; a step of granulating the hardening resin composition to obtain a granular hardening resin composition; and a step of molding the granular hardening resin composition.