Resin composition for injection molding and injection molding method of the composition

Abstract

To provide a resin composition for injection molding which suppresses backflow, has high metering accuracy and high moldability, and an injection molding method using the composition.SOLUTION: A resin composition for injection molding contains at least one wax having a melting point of less than 80°C.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin composition for injection molding and a method for injection molding the composition. [Background technology]

[0002] Development of injection molding of semiconductor encapsulation materials is underway. Injection molding can improve productivity because the encapsulation material is supplied as is.

[0003] Patent Document 1 discloses an epoxy resin composition containing, as essential components, an epoxy resin, a phenol compound curing agent, a curing accelerator, and an inorganic filler. The document also describes that the epoxy resin composition may contain a wax.

[0004] Patent Document 2 discloses an epoxy resin injection molding material that contains only a multifunctional epoxy resin, a bifunctional epoxy resin, an epoxy resin curing agent, a curing accelerator, an inorganic filler, a silane coupling agent, and a mold release agent, is solid at room temperature, and satisfies predetermined physical properties. Carnauba wax is described as the mold release agent. The document also describes that the epoxy resin injection molding material has excellent moldability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-67741 [Patent Document 2] JP 2013-127042 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the resin compositions for injection molding described in Patent Documents 1 and 2 have room for improvement in moldability, such as the resin in the cylinder flowing back into the hopper during injection (hereinafter also referred to as backflow) or adhering to the screw or the like, making it impossible to measure accurately. [Means for solving the problem]

[0007] The present inventors have found that the above problems can be solved by including a specific wax, and have completed the present invention. That is, the present invention can be described as follows.

[0008] [1] A resin composition for injection molding, comprising at least one wax (a) having a melting point of less than 80°C. [2] The resin composition for injection molding according to [1], wherein the wax (a) contains a wax having a melting point of 65° C. or lower. [3] The resin composition for injection molding according to [1] or [2], further comprising at least one wax (b) having a melting point equal to or higher than the melting point of the wax (a). [4] An injection unit comprising a cylinder and a screw inserted into the cylinder; a mold having a cavity into which the molten composition is filled from the injection unit; A resin composition for injection molding used in an injection molding apparatus comprising: The temperature T at the tip of the screw in the cylinder is 60 to 100° C. The resin composition for injection molding according to any one of [1] to [3], wherein the wax includes a wax (b) having a melting point higher than a temperature T of the tip of the screw, and a wax (a) having a melting point lower than a temperature T of the tip of the screw. [5] The resin composition for injection molding according to [4], wherein the temperature inside the cavity is 150 to 160°C. [6] The resin composition for injection molding according to any one of [1] to [5], comprising an epoxy resin having a softening point of less than 80°C or a curing agent having a softening point of less than 80°C. [7] An injection unit comprising a cylinder and a screw inserted into the cylinder; A mold having a cavity; An injection molding method using an injection molding apparatus comprising: a step of melting the resin composition for injection molding according to any one of [1] to [6] in the cylinder; a step of injecting a molten resin composition using the screw to fill the cavity; The injection molding method comprising: [8] The injection molding method according to [7], wherein the temperature T of the tip of the screw in the cylinder is 60 to 100°C. [9] The injection molding method according to [7] or [8], wherein the temperature inside the cavity is 150 to 160°C. Effect of the Invention

[0009] According to the present invention, it is possible to provide a resin composition for injection molding which is suppressed in backflow, has excellent metering accuracy, and has excellent moldability, and an injection molding method using the composition. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic cross-sectional view showing an example of an injection molding apparatus according to the present embodiment. [Diagram 2] 1 is a schematic cross-sectional view illustrating an example of an in-vehicle electronic control unit according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. In all drawings, the same components are denoted by the same reference numerals, and the description will be omitted as appropriate. For example, "1 to 10" means "1 or more" to "10 or less" unless otherwise specified.

[0012] The resin composition for injection molding of the present embodiment contains a wax.

[0013] [wax] The wax contained in the resin composition for injection molding of this embodiment includes at least one wax (a) having a melting point of less than 80°C.

[0014] From the viewpoint of the effects of the present invention, the wax (a) having a melting point of less than 80° C. preferably contains a wax having a melting point of 65° C. or less. An example of the wax a is stearic acid (melting point: 59 to 61° C.).

[0015] In this embodiment, from the viewpoint of the effects of the present invention, the wax (a) can be contained in an amount of preferably 0.01 part by mass or more and 10 parts by mass or less, more preferably 0.02 part by mass or more and 5 parts by mass or less, even more preferably 0.05 part by mass or more and 1 part by mass or less, and particularly preferably 0.1 part by mass or more and 0.5 part by mass or less, per 100 parts by mass of the resin composition for injection molding.

[0016] In this embodiment, the wax preferably further comprises at least one wax (b) having a melting point equal to or higher than that of the wax (a). The melting point of the wax (b) is 80°C or higher than that of the wax (a), preferably 80°C or higher and 140°C or lower, more preferably 80°C or higher and 100°C or lower, and even more preferably 80°C or higher and 90°C or lower. By including wax (b) in addition to wax (a), backflow is suppressed, measurement accuracy is excellent, and furthermore, the releasability of the cured product from the mold after injection molding is excellent.

[0017] Examples of the wax (b) include carnauba wax (melting point 80 to 86° C.), oxidized polyethylene wax (melting point 120 to 125° C.), zinc stearate (melting point 120 to 130° C.), etc., and one or more of these can be used.

[0018] When the wax (b) is contained, the weight ratio a:b of the wax (a) to the wax (b) can be preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and further preferably 30:70 to 70:30.

[0019] The resin composition for injection molding of this embodiment can be injection molded using an injection molding apparatus 1 shown in Fig. 1. The injection molding apparatus 1 includes an injection unit 20 consisting of a cylinder 21 and a screw 22 inserted into the cylinder 21, and a mold 10 having a cavity 12. Details of the injection molding apparatus 1 will be described later.

[0020] The temperature T at the tip of the screw 22 in the cylinder 21 is 60 to 100°C. In this embodiment, the wax includes wax (b) having a melting point that is greater than the temperature T of the tip of the screw and is equal to or greater than 80° C., and wax (a) having a melting point that is less than the temperature T of the tip of the screw and is less than 80° C. This suppresses backflow and provides excellent metering accuracy, and further provides excellent releasability of the cured product of the injection molding resin composition from a mold, enabling continuous injection molding and providing excellent productivity.

[0021] [Thermosetting resin] The resin composition for injection molding of the present embodiment may contain a thermosetting resin. The thermosetting resin may include, for example, one or more selected from the group consisting of epoxy resin, phenolic resin, oxetane resin, (meth)acrylate resin, unsaturated polyester resin, diallyl phthalate resin, and maleimide resin. Among these, it is particularly preferable to include an epoxy resin from the viewpoint of improving curability, storage stability, heat resistance, moisture resistance, and chemical resistance.

[0022] As the epoxy resin contained in the thermosetting resin, a monomer, oligomer, or polymer having two or more epoxy groups in one molecule may be used in general, and the molecular weight or molecular structure is not particularly limited. In the present embodiment, the epoxy resin may be, for example, a biphenyl type epoxy resin; a bisphenol type epoxy resin such as a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a tetramethyl bisphenol F type epoxy resin; a stilbene type epoxy resin; a novolac type epoxy resin such as a phenol novolac type epoxy resin or an orthocresol novolac type epoxy resin; a multifunctional epoxy resin such as a trisphenol type epoxy resin exemplified by a triphenol methane type epoxy resin or an alkyl-modified triphenol methane type epoxy resin; a phenol aralkyl type epoxy resin having a phenylene skeleton, a naphthol aralkyl type epoxy resin having a phenylene skeleton, or the like. the epoxy resins include one or more selected from the group consisting of phenol aralkyl type epoxy resins, phenol aralkyl type epoxy resins having a biphenylene skeleton, naphthol aralkyl type epoxy resins having a biphenylene skeleton, and other naphthol type epoxy resins; dihydroxynaphthalene type epoxy resins, naphthol type epoxy resins such as epoxy resins obtained by glycidyl etherifying a dimer of dihydroxynaphthalene; triazine nucleus-containing epoxy resins such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; and bridged cyclic hydrocarbon compound-modified phenol type epoxy resins, such as dicyclopentadiene-modified phenol type epoxy resins.

[0023] Among these, from the viewpoint of the effects of the present invention, it is preferable to contain one or more types selected from orthocresol novolac type epoxy resins, phenol novolac type epoxy resins, and bisphenol A type epoxy resins.

[0024] The epoxy resin preferably contains a polyfunctional epoxy resin having three or more epoxy groups in the repeating structure of the epoxy resin skeleton. By using the polyfunctional epoxy resin, the glass transition temperature of the cured product can be improved.

[0025] The polyfunctional epoxy resin is not particularly limited, but examples thereof include tetraphenylethane type epoxy resin, 2-[4-(2,3-epoxypropoxy)phenyl]-2-[4-[1,1-bis[4-(2,3-epoxypropoxy)phenyl]ethyl]phenyl]propane, tetrakis(glycidyloxyphenyl)ethane, α-2,3-epoxypropoxyphenyl-ω-hydropoly(n=1-7){2-(2,3-epoxypropoxy)benzylidene-2,3-epoxypropoxyphenylene}, etc. These may be used alone or in combination.

[0026] It is more preferable that the thermosetting resin contains an epoxy resin having a softening point of less than 80° C. By using an epoxy resin having a softening point of less than 80° C., a resin composition for injection molding having a low viscosity can be obtained, and continuous injection molding becomes possible, resulting in superior productivity.

[0027] The content of the thermosetting resin in the resin composition for injection molding is preferably 2% by mass or more, more preferably 3% by mass or more, and particularly preferably 4% by mass or more, based on the entire resin composition for injection molding. By making the content of the thermosetting resin equal to or more than the above lower limit, the flowability during molding can be improved. Therefore, the resin composition has better room temperature storage properties, and can also improve filling properties and molding stability. On the other hand, the content of the thermosetting resin in the resin composition for injection molding is preferably 50% by mass or less, more preferably 30% by mass or less, and particularly preferably 15% by mass or less, based on the entire resin composition for injection molding. By making the content of the thermosetting resin equal to or less than the above upper limit, the resin composition is stable against heat treatment in an extruder for injection molding, and the molding cycle can be shortened.

[0028] [Hardening agent] The resin composition for injection molding of this embodiment may contain a curing agent. Curing agents can be roughly divided into three types: polyaddition type curing agents, catalyst type curing agents, and condensation type curing agents.

[0029] The polyaddition type curing agents used as curing agents include, for example, aliphatic polyamines such as diethylenetriamine (DETA), triethylenetetramine (TETA), and metaxylylenediamine (MXDA), aromatic polyamines such as diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diaminodiphenylsulfone (DDS), as well as polyamine compounds including dicyandiamide (DICY) and organic acid dihydralazide; alicyclic acid anhydrides such as hexahydrophthalic anhydride (HHPA), methyltetrahydrophthalic anhydride (MTHPA), The curing agent includes one or more organic acids selected from the group consisting of acid anhydrides including aromatic acid anhydrides such as trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), benzophenonetetracarboxylic acid (BTDA), etc.; phenolic resin-based curing agents such as novolac-type phenolic resins, polyvinylphenols, aralkyl-type phenolic resins, etc.; polymercaptan compounds such as polysulfides, thioesters, thioethers, etc.; isocyanate compounds such as isocyanate prepolymers, blocked isocyanates, etc.; and carboxylic acid-containing polyester resins.

[0030] The catalyst type curing agent used as the curing agent includes one or more selected from the group consisting of tertiary amine compounds such as benzyldimethylamine (BDMA) and 2,4,6-trisdimethylaminomethylphenol (DMP-30); and Lewis acids such as BF3 complexes.

[0031] The condensation type curing agent used as the curing agent includes, for example, one or more selected from the group consisting of resol type phenolic resins; urea resins such as methylol group-containing urea resins; and melamine resins such as methylol group-containing melamine resins.

[0032] Among these, it is more preferable to include a phenolic resin-based curing agent from the viewpoint of improving the balance of flame resistance, moisture resistance, electrical properties, curability, storage stability, etc. As the phenolic resin-based curing agent, a monomer, oligomer, or polymer having two or more phenolic hydroxyl groups in one molecule can be used, and the molecular weight and molecular structure are not particularly limited. The phenolic resin-based curing agent used as a curing agent includes one or more types selected from the group consisting of novolac-type phenolic resins such as phenol novolac resins, cresol novolac resins, and bisphenol novolac; polyvinylphenol; multifunctional phenolic resins such as triphenol methane-type phenolic resins; modified phenolic resins such as terpene-modified phenolic resins and dicyclopentadiene-modified phenolic resins; phenol aralkyl-type phenolic resins such as phenol aralkyl resins having a phenylene skeleton and / or biphenylene skeleton, and naphthol aralkyl resins having a phenylene and / or biphenylene skeleton; and bisphenol compounds such as bisphenol A and bisphenol F. Among these, from the viewpoint of improving the curability of the resin composition for injection molding, it is more preferable to contain at least one of a novolac type phenolic resin and a phenol aralkyl type phenolic resin.

[0033] The content of the curing agent in the resin composition for injection molding is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, based on the entire resin composition for injection molding. By setting the content of the curing agent to the above lower limit or more, the resin composition can have excellent room temperature storage properties, and can achieve excellent fluidity during molding, thereby improving filling properties and moldability. On the other hand, the content of the curing agent in the resin composition for injection molding is preferably 40% by mass or less, more preferably 25% by mass or less, and particularly preferably 10% by mass or less, based on the entire resin composition for injection molding. By setting the content of the curing agent to the above upper limit or less, the resin composition can be stable against heat treatment in an extruder for injection molding and can shorten the molding cycle.

[0034] The resin composition for injection molding of this embodiment more preferably contains, as the thermosetting resin, an epoxy resin having a softening point of less than 80° C., or as the curing agent, a curing agent having a softening point of less than 80° C., and it is more preferable that both the epoxy resin and the curing agent have softening points of less than 80° C. By using an epoxy resin having a softening point of less than 80° C. and / or a curing agent having a softening point of less than 80° C., a resin composition for injection molding with low viscosity can be obtained, and continuous injection molding becomes possible, resulting in superior productivity.

[0035] [Inorganic filler] The resin composition for injection molding of the present embodiment may contain an inorganic filler. The inorganic filler may include, for example, one or more selected from the group consisting of glass fiber, fused crushed silica, spherical silica, crystalline silica, and other silica, alumina, aluminum hydroxide, magnesium hydroxide, calcium carbonate, silicon nitride, and aluminum nitride. Among these, from the viewpoint of excellent versatility, it is preferable to include glass fiber, spherical silica, fused crushed silica, and calcium carbonate, and it is more preferable to include spherical silica and fused crushed silica.

[0036] When the inorganic filler contains silica, for example, the average particle size D 50 It is preferable that the silica has an average particle diameter D of 1 μm or more and 50 μm or less. This makes it possible to more effectively improve the balance of filling properties, adhesion, moisture resistance, heat resistance, etc. 50 can be measured, for example, by using a commercially available laser type particle size distribution analyzer (eg, SALD-7000 manufactured by Shimadzu Corporation).

[0037] The content of the inorganic filler in the resin composition for injection molding is preferably 50% by weight or more, more preferably 60% by weight or more, based on the entire resin composition. By making the content of the inorganic filler equal to or more than the above lower limit, it is possible to improve low moisture absorption and low thermal expansion, and more effectively improve the moisture resistance reliability of the encapsulant. On the other hand, the content of the inorganic filler in the resin composition for injection molding is preferably 90% by weight or less, more preferably 85% by weight or less, based on the entire resin composition for injection molding. By making the content of the inorganic filler equal to or less than the above upper limit, it is possible to more effectively improve the fluidity and filling property of the resin composition for injection molding during molding.

[0038] [Cure accelerator] The resin composition for injection molding of the present embodiment may contain a curing accelerator (curing catalyst). The curing accelerator may be any accelerator that accelerates the crosslinking reaction between the thermosetting resin and the curing agent, and any known accelerator may be used.

[0039] Examples of the curing accelerator include imidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole (EMI24), 2-phenylimidazole, 2-phenyl-4-methylimidazole (2P4MZ), 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl (1' )]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4-methylimidazolyl(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4-methylimidazolyl(1')]-ethyl-s-triazine, isocyanuric acid adduct of 2,4-diamino-6-[2'-methylimidazolyl(1')]-ethyl-s-triazine, isocyanuric acid adduct of 2-phenylimidazole, isocyanuric acid adduct of 2-methylimidazole, 2-phenyl-4,5-dihydroxydimethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)ethyl]-1,3,5-triazine and other imidazole catalysts; Examples of the urea catalyst include 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea), N,N'-dimethylurea, etc. These may be used alone or in combination of two or more kinds.

[0040] Among these, from the viewpoint of improving low-temperature curing properties and filling properties, it is preferable to contain one or more selected from the group consisting of 2-phenyl-4,5-dihydroxymethylimidazole, 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea), and N,N'-dimethylurea. From the viewpoint of the balance between low-temperature curing properties and filling properties, the curing accelerator preferably has 3 or less functional groups, and more preferably 2 or less functional groups.

[0041] In this embodiment, the lower limit of the content of the curing accelerator is, for example, preferably 0.02% by mass or more, more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more, based on the total solid content of the resin composition for injection molding. By making the content of the curing accelerator equal to or more than the above lower limit, it is possible to effectively improve the curability during molding. On the other hand, the upper limit of the content of the curing accelerator is, for example, preferably 3.0% by mass or less, more preferably 2.0% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less, based on the total solid content of the resin composition for injection molding. By making the content of the curing accelerator equal to or less than the above upper limit, it is possible to improve the flowability during molding.

[0042] The lower limit of the content of the curing accelerator is, for example, preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 0.8% by mass or more, based on the total solid content of the epoxy resin. By making the content of the curing accelerator equal to or more than the lower limit, it is possible to effectively improve low-temperature curing properties during molding. On the other hand, the upper limit of the content of the curing accelerator is, for example, preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and particularly preferably 2.0% by mass or less, based on the total solid content of the epoxy resin. By making the content of the curing accelerator equal to or less than the upper limit, it is possible to improve the flowability during molding.

[0043] (Other Ingredients) The resin composition for injection molding of this embodiment may contain, as necessary, one or more of various additives such as a silane coupling agent, a colorant, an ion scavenger, an oil, a stress reducing agent, and a flame retardant.

[0044] <Resin composition for injection molding> The resin composition for injection molding of the present embodiment can be obtained by mixing the above-mentioned components by a conventionally known method. The resin composition for injection molding of the present embodiment has excellent moldability because backflow into the hopper is suppressed and the measurement accuracy is excellent. The resin composition for injection molding of this embodiment can be molded at a low pressure of 40 MPa or less, and can be continuously molded at an injection speed of 10 mm / sec.

[0045] <Injection molding method> The injection molding method of this embodiment can be performed using an injection molding apparatus 1 shown in Fig. 1. The injection molding apparatus 1 includes an injection unit 20 including a cylinder 21 and a screw 22 inserted into the cylinder 21, and a mold 10 having a cavity 12.

[0046] The injection molding method of the present embodiment includes: A step of melting the injection molding resin composition of the present embodiment in a cylinder 21; and a step of injecting the molten resin composition using the screw 22 to fill the cavity 12.

[0047] The injection molding apparatus 1 includes a mold 10 having a molding space (cavity 12) including a gate, a runner, and a gate, and an injection molding machine 20 for performing injection molding. The injection molding machine 20 includes, for example, a cylinder 21, a screw 22 rotatable within the cylinder 21, a hopper 23 capable of feeding a resin composition for injection molding into the cylinder 21, a heater 24 for heating the phenolic resin composition via the cylinder 21, and a nozzle 25 for sending the molding material kneaded within the cylinder 21 to the mold 10. The screw 22 includes a check valve 26 at its tip.

[0048] In the injection molding method of the present embodiment, first, a resin composition for injection molding is charged into a heated injection molding machine 20. As a result, the resin composition for injection molding is kneaded by a screw 22 while being heated and melted by a heater 24 in a cylinder 21. The temperature T of the tip of the screw 22 in the cylinder 21 is 60 to 100°C. In this embodiment, the wax includes wax (b) having a melting point that is greater than the temperature T of the tip of the screw and is equal to or greater than 80° C., and wax (a) having a melting point that is less than the temperature T of the tip of the screw and is less than 80° C. This suppresses backflow and provides excellent metering accuracy, and further provides excellent releasability of the cured product of the injection molding resin composition from a mold, enabling continuous injection molding and providing excellent productivity.

[0049] The resin composition for injection molding molten by the screw 22 is compressed and kneaded while being sent in the direction of the nozzle 25, while the screw 22 moves backward (the opposite direction to the nozzle 25). At this time, back pressure is applied to the screw 22 from the rear, so that pressure can be applied to the resin composition for injection molding that has gathered at the nozzle 25. Then, the resin composition for injection molding that has gathered at the nozzle 25 at the tip of the screw 21 is metered up to a set position. The resin composition for injection molding of this embodiment is prevented from sticking to the screw, etc., and can be metered accurately.

[0050] Then, by advancing the screw 21 lowered to the rear, the measured resin composition for injection molding is injected into the cavity 12 of the mold 10 through the nozzle 25 by the pressure of the screw 22. The resin composition for injection molding of this embodiment has excellent moldability, and backflow of the resin composition for injection molding in the cylinder into the hopper during injection is suppressed. The resin composition for injection molding of this embodiment has excellent low-temperature moldability, and the temperature inside the cavity 12 can be set to 150 to 160°C.

[0051] The injection molding resin composition is cured in the cavity 12, and then the mold 10 is opened and the molded body is removed from the cavity 12. The injection molding resin composition containing the wax (a) and the wax (b) of this embodiment has excellent releasability.

[0052] In this embodiment, it is possible to provide an in-vehicle electronic control unit or the like that is sealed with the resin composition for injection molding. The following description will be given taking an in-vehicle electronic control unit as an example.

[0053] [Automotive electronic control unit] The in-vehicle electronic control unit 30 is used to control an engine, various in-vehicle devices, and the like. As shown in FIG. 1, the in-vehicle electronic control unit 30 includes, for example, a wiring board 32, a plurality of electronic components 36 mounted on at least one surface of the wiring board 32, and a sealing resin 34 made of the injection molding resin composition of the present embodiment for sealing the electronic components 36. The wiring board 32 has a connection terminal 38 for connecting to the outside on at least one side. The in-vehicle electronic control unit 30 according to one example of the present embodiment is electrically connected to the counterpart connector via the connection terminal 38 by fitting the connection terminal 38 to the counterpart connector.

[0054] The wiring board 32 is a wiring board in which circuit wiring is provided on one or both of one surface and the other surface opposite to the one surface. As shown in FIG. 1, the wiring board 32 has, for example, a flat plate shape. In this embodiment, an organic substrate formed of an organic material such as polyimide can be used as the wiring board 32. The wiring board 32 may have, for example, through holes 40 that penetrate the wiring board 32 and connect the one surface to the other surface. In this case, the wiring provided on one surface of the wiring board 32 and the wiring provided on the other surface are electrically connected via a conductor pattern provided in the through holes 40.

[0055] The wiring board 32 has a solder resist layer on one side on which the electronic components 36 are mounted, for example. The solder resist layer can be formed using a resin composition for forming a solder resist that is commonly used in the field of semiconductor devices. In this embodiment, for example, the solder resist layer can be provided on one side and the other side of the wiring board 32.

[0056] The solder resist layer provided on one surface or on both surfaces of the wiring board 32 is formed from a resin composition containing a silicone compound, for example, which makes it possible to realize a solder resist layer with excellent surface smoothness. 2, the plurality of electronic components 36 are mounted, for example, on one surface and the other surface of the wiring board 32. On the other hand, the electronic components 36 may be provided only on one surface of the wiring board 32, and may not be provided on the other surface of the wiring board 32. There is no particular limitation on the electronic components 36 as long as they can be mounted in an in-vehicle electronic control unit, and examples of the electronic components 36 include microcomputers.

[0057] The sealing resin 34 is formed by molding the injection molding resin composition of this embodiment so as to seal the electronic components 36 and curing it. In this embodiment, the sealing resin 34 is formed so as to seal, for example, the wiring board 32 together with the electronic components 36. In the example shown in FIG. 2, the sealing resin 34 is provided so as to seal one side and the other side of the wiring board 32 and the electronic components 36 mounted on the wiring board 32. The sealing resin 34 is also formed so as to seal, for example, a part or the whole of the wiring board 32. FIG. 2 illustrates a case in which the sealing resin 34 is provided so as to seal the entire other part of the wiring board 32 without sealing the connection terminals 38 so that the connection terminals 38 are exposed.

[0058] In the in-vehicle electronic control unit 30 of this embodiment, the wiring board 32 may be mounted on, for example, a metal base. The metal base can function as a heat sink for dissipating heat generated from, for example, the electronic components 36. In this embodiment, for example, the metal base and the wiring board 32 mounted on the metal base are integrally sealed and molded with a resin composition for injection molding to form the in-vehicle electronic control unit 30. The metal material constituting the metal base is not particularly limited, but may include, for example, iron, copper, aluminum, and alloys containing one or more of these metals. Note that the in-vehicle electronic control unit 30 does not need to have a metal base.

[0059] The in-vehicle electronic control unit 30 shown in FIG. 1 is formed by injection molding a plurality of electronic components 36 encapsulated with the resin composition for injection molding of this embodiment.

[0060] Specifically, first, a wiring board 32 on which a plurality of electronic components 36 are mounted is placed in a cavity 12 of a mold 10. The shape of the cavity 12 is appropriately changed so as to conform to the shape of an in-vehicle electronic control unit 30. Then, the resin composition for injection molding of this embodiment is charged into a cylinder 21 having a screw 22 therein via a hopper 23, and the resin composition for injection molding is melted at an extruder temperature of 80°C or higher and 100°C or lower. The molten resin is moved through the extruder by the screw, and injected into the cavity 12 of the mold through a gate, sealing the plurality of electronic components 36.

[0061] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted as long as they do not impair the effects of the present invention. EXAMPLES

[0062] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0063] [Comparative Examples 1 to 4, Examples 1 to 4] For each of Examples 1 to 4 and Comparative Examples 1 to 4, a resin composition for injection molding was prepared as follows. First, according to the formulation shown in Table 1, each component was premixed for 20 minutes in a Henschel mixer (volume 200 liters, rotation speed 900 rpm) set at room temperature. Next, the obtained mixture was finely pulverized using a continuous rotary ball mill (Dynamic Mill MYD25 manufactured by Nippon Coke & Engineering Co., Ltd., screw rotation speed 500 rpm, alumina ball diameter 10 mm, ball volume filling rate with respect to the device volume 50%) at a material supply rate of 200 kg / hr while keeping the material temperature at 30°C or less. Next, the finely pulverized mixture was kneaded using a 10-inch two-roll mill. The roll temperatures were set to 105°C and 15°C for kneading. The kneading time was 5 minutes. Next, the kneaded mixture was cooled and pulverized to obtain a resin composition for injection molding. Note that each process from premixing with the Henschel mixer to obtaining the resin composition for injection molding was performed continuously. Note that the details of each component in Table 1 are as follows. Also, the units in Table 1 are weight %. In the examples, the following components were used.

[0064] Inorganic Fillers Silica 1: Fused spherical silica (FB-105, Denka, average particle size 10.6 μm, specific surface area 5.1 m 2 / g, upper cut limit 71μm) Silica 2: Fused spherical silica (SC-2500-SQ, manufactured by Admatechs, average particle size 0.6 μm) Silica 3: Crushed silica (RD-8, Tatsumori Co., Ltd., average particle size 15 μm)

[0065] Coupling Agent Coupling agent 1: N-phenyl-3-aminopropyltrimethoxysilane (KBM-573, Shin-Etsu Chemical Co., Ltd.) Coupling agent 2: 3-mercaptopropyltrimethoxysilane (S810, manufactured by Chisso Corporation) Coupling agent 3: 3-glycidoxypropyltrimethoxysilane (S510, manufactured by Chisso Corporation)

[0066] thermosetting resin Epoxy resin 1: Cresol novolac type epoxy resin (EOCN-1020-55, Nippon Kayaku Co., Ltd., softening point 55°C, equivalent weight 196g / eq, number average molecular weight 490) Epoxy resin 2: Cresol novolac type epoxy resin (EOCN-1020-65, Nippon Kayaku Co., Ltd., softening point 65°C, equivalent weight 199g / eq, number average molecular weight 614) Epoxy resin 3: Cresol novolac type epoxy resin (EPICRON N680, manufactured by DIC, softening point 85°C, equivalent weight 211g / eq) Epoxy resin 4: Bisphenol A type epoxy resin (JER1001, manufactured by Mitsubishi Chemical Corporation, softening point 64°C, equivalent weight 450-500g / eq, number average molecular weight 900)

[0067] Hardener Hardener 1: Novolac phenolic resin (PR-HF-3, manufactured by Sumitomo Bakelite Co., Ltd., softening point 80°C, equivalent weight 105g / eq, number average molecular weight 392, weight average molecular weight 667) Hardener 2: Novolac phenolic resin (PR-51470, manufactured by Sumitomo Bakelite Co., Ltd., softening point 110°C, equivalent weight 103g / eq, number average molecular weight 617, weight average molecular weight 2201)

[0068] curing catalyst Curing catalyst 1: 2-phenylimidazole (2PZ-PW, manufactured by Shikoku Kasei Co., Ltd.)

[0069] wax Wax 1: Oxidized polyethylene wax (Licowax PED191, Clariant Japan, melting point 120-125°C) Wax 2: Carnauba wax (Nikko Carnauba, manufactured by Nikko Fine Co., Ltd., melting point 80-86°C) Wax 3: Stearic acid (SR-Sakura, Nippon Oil & Fats Co., Ltd., melting point 59-61°C)

[0070] Coloring agent Colorant 1: Carbon black (#5, manufactured by Mitsubishi Chemical Corporation)

[0071] (Backflow / Metering Torque Stability) Using a 100t electric horizontal injection molding machine, weighing and injection were repeated 20 times under the following conditions, and the cases where no backflow occurred were evaluated as ◯, and the cases where backflow occurred were evaluated as ×. ·conditions Screw temperature control (80℃ / 20℃ / 20℃ from the tip) Back pressure: 1MPa Screw rotation speed: 10 rpm Injection speed: 10mm / sec Metering 62mm, VP switching position 5mm, holding pressure 10MPa In addition, the stability of the metering torque was evaluated by assigning a ◯ to a curve of the clock torque that showed the same behavior and values ​​for 20 shots, and an × to a curve in which the behavior varied from shot to shot and the values ​​also varied.

[0072] (Mold releasability (resin residue inside the mold)) Using the above conditions, 20 shots were molded using an ISO test piece in the mold. Those that were able to be molded for 20 shots were marked with an ◯, and those that stuck to the fixed side of the mold or were not filled were marked with an ×. The mold temperature was set at 160°C and the curing time was 80 seconds.

[0073] (Spiral Flow) Using a low-pressure transfer molding machine (KTS-15, manufactured by Kotaki Seiki Co., Ltd.), the resin composition for injection molding was injected into a spiral flow measurement mold conforming to ANSI / ASTM D 3123-72 under conditions of a mold temperature of 175°C, an injection pressure of 6.9 MPa, and a pressure retention time of 120 seconds, and the flow length was measured. Spiral flow is a parameter of fluidity, and the larger the value, the better the fluidity.

[0074] (NGFP) The rectangular channel pressure (rectangular pressure) of the resin composition for injection molding obtained in each example was measured as follows. First, the resin composition for injection molding (ground material) was preheated and softened in a plunger (plunger size: φ18 mm) at 175° C. for 3 seconds. Using a low pressure transfer molding machine (NEC, 40t manual press), the softened resin composition for injection molding obtained above was injected into a rectangular flow path 13 mm wide, 0.5 mm thick, and 175 mm long under conditions of a mold temperature of 175°C and an injection speed of 24.7 mm / sec. At this time, the change in pressure over time was measured with a pressure sensor embedded 25 mm from the upstream end of the flow path, and the minimum pressure (kgf / cm) at which the resin composition for injection molding flowed was recorded. 2 ) was measured and used as the square root pressure. Square root pressure is a parameter of melt viscosity, and a smaller value indicates a lower melt viscosity.

[0075] (Glass transition temperature (Tg)) A JIS6911 bending test piece was molded at 175°C for 3 minutes, and TMA measurement was performed in the flow direction, with the bending point being the Tg. The measurement was performed at a temperature increase rate of 5°C / min. It is believed that the higher the Tg after molding (without curing), the shorter the molding cycle can be.

[0076] [Table 1]

[0077] As shown in Table 1, the resin compositions for injection molding in the examples containing a wax having a melting point of less than 80°C had excellent moldability because backflow was suppressed and the measurement accuracy was excellent. Furthermore, as in Examples 1, 3, and 4, the combination of a wax having a melting point of less than 80°C and a wax having a melting point higher than that of the wax provided excellent releasability. In addition, as in Examples 2 to 4, by including an epoxy resin or a curing agent having a softening point of less than 80°C, the rectangular wave pressure was small and the melt viscosity was low, so that a low-viscosity injection molding resin composition was obtained, and continuous injection molding became possible, which resulted in excellent productivity.

[0078] 1 Injection molding equipment 10. Mold 12 Cavity 20 injection molding machine 21 Cylinder 22 Screw 23 Hopper 24 Heater 25 Nozzles 26 Backflow valve 30. Automotive Electronic Control Unit 32 Wiring board 34 Sealing resin 36 Electronic Components 38 Connection terminal 40 through hole

Claims

1. A resin composition for injection molding, comprising at least one wax (a) having a melting point of less than 80°C.

2. The resin composition for injection molding according to claim 1 , wherein the wax (a) contains a wax having a melting point of 65° C. or lower.

3. 3. The resin composition for injection molding according to claim 1, further comprising at least one wax (b) having a melting point equal to or higher than the melting point of the wax (a).

4. an injection unit comprising a cylinder and a screw inserted into the cylinder; a mold having a cavity into which the molten composition is filled from the injection unit; A resin composition for injection molding used in an injection molding apparatus comprising: The temperature T at the tip of the screw in the cylinder is 60 to 100° C. The resin composition for injection molding according to any one of claims 1 to 3, wherein the wax comprises a wax (b) having a melting point higher than a temperature T of the tip of the screw, and a wax (a) having a melting point lower than a temperature T of the tip of the screw.

5. The resin composition for injection molding according to claim 4, wherein the temperature inside the cavity is 150 to 160°C.

6. 6. The resin composition for injection molding according to claim 1, comprising an epoxy resin having a softening point of less than 80°C, or a curing agent having a softening point of less than 80°C.

7. an injection unit comprising a cylinder and a screw inserted into the cylinder; A mold having a cavity; An injection molding method using an injection molding apparatus comprising: A step of melting the resin composition for injection molding according to any one of claims 1 to 6 in the cylinder; a step of injecting a molten resin composition using the screw to fill the cavity; The injection molding method comprising:

8. 8. The injection molding method according to claim 7, wherein the temperature T of the tip of the screw in the cylinder is 60 to 100° C.

9. The injection molding method according to claim 7 or 8, wherein the temperature in the cavity is 150 to 160°C.

Images