WO2007073087A1

WO2007073087A1 - Sheet for using in extreme environments and tray for electronic parts produced therefrom

Info

Publication number: WO2007073087A1
Application number: PCT/KR2006/005580
Authority: WO
Inventors: Kwang Suck Suh; Jong Eun Kim; Tae Young Kim
Original assignee: Kwang Suck Suh; Jong Eun Kim; Tae Young Kim
Priority date: 2005-12-19
Filing date: 2006-12-19
Publication date: 2007-06-28
Also published as: KR100649887B1

Abstract

Disclosed is an antistatic tray for electronic parts, which is usable in environments of extreme temperature and humidity. A polymer sheet, which is used to produce a tray for electronic parts, having dimensional stability related to the distortion, contraction and etc. of the tray under extreme conditions between -50 °C and 85 °C and without the generation of impurities from the surface thereof during a vibration test in a state in which the parts are mounted, and a tray for electronic parts, which is imparted with permanent antistatic performance by forming a permanent antistatic layer on the surface of the sheet, are provided. The tray for electronic parts is imparted with permanent antistatic performance to thus inhibit electrostatic damage, and the dimensional stability of the tray is assured even under conditions of rapid changes in temperature and humidity during transport and storage, thus preventing damage to the parts in the tray.

Description

SHEET FOR USING IN EXTREME ENVIRONMENTS AND TRAY FOR ELECTRONIC PARTS PRODUCED THEREFROM

Technical Field

[1] The present invention relates to an antistatic tray for electronic parts, which can be used in environments of extreme temperature and humidity, and in particular, to a sheet, which is used to produce a tray for electronic parts without dimensional changes, including distortion or contraction, in an environment of extreme temperatures ranging from -5O⁰C to 85⁰C and relative humidity of 10-90%, and also without the generation of impurities from the surface of the tray upon a vibration test in a state in which the parts are mounted, and to a tray produced using the same. Background Art

[2] Various electronic part modules must be transported using a tray that has been subjected to permanent antistatic treatment in order to decrease damage due to the generation of static electricity during transport and handling. The trays in which the electronic parts are contained may pass through the hottest regions near the equator, where the temperature can be as high as 85⁰C or relative humidity can reach a maximum of 90%, or through the coldest regions, where the temperature in the winter season is decreased to about -5O⁰C or the relative humidity is decreased to about 10%, or otherwise, may be stored in such extreme environments. In such cases, attributable to the dimensional change of the material for trays, the packaged parts may be damaged.

[3] Conventional trays have been produced using a polymer sheet extruded from a styrene polymer or high impact polystyrene mixture essentially including 20-30 parts by weight of carbon black. However, since this tray material has a large amount of carbon black in order to prevent static electricity from being generated, there are problems in which black impurities are generated due to friction between the electronic part and the surface of the packaging material during transport. Recently, in order to impart the tray with antistatic performance, an antistatic coating layer including a conductive polymer as an effective component is applied, instead of using carbon black.

[4] A styrene polymer is a typical polymer that can be easily produced into a tray through a thermoforming process using a thermoforming machine. A general styrene polymer, including general-purpose polystyrene or high impact polystyrene, has low heat resistance in its form, and thus cannot be used in the hottest and coldest regions. It is also difficult for a binary styrene polymer, modified using a component of butadiene, acryl or acrylonitrile, to satisfy the above requirements. For example, in the case of a styrene copolymer including butadiene, it has problems in which heat resistance is drastically decreased depending on the amount of the butadiene component, and thus it cannot be used. In addition, a styrene copolymer, modified using a component of acryl or acrylonitrile, has too little elongation and is thus highly brittle, and consequently cannot be used unchanged.

[5] Accordingly, there is a need to invent a sheet to which dimensional changes or distortion are not caused even under extreme conditions, including the coldest temperature (-5O⁰C), the hottest temperature (85⁰C), and very low relative humidity (10 RH%), while almost no black impurities are generated due to friction between the packaged part and the tray during transport, and also to invent a tray produced using the same.

Disclosure of Invention Technical Problem

[6] Therefore, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a sheet for use in a tray for electronic parts to which dimensional changes or distortion are not caused even under extreme conditions, including the hottest temperature, the coldest temperature and very low relative humidity, while almost no black impurities are generated due to friction between an electronic part and a tray during transport, and also to provide a tray produced using the same.

Technical Solution

[7] In order to achieve the above object, in the present invention, among styrene copolymers, used is a styrene polymer, which is modified using an acrylonitrile or acryl component to increase heat resistance, and is furthermore modified using a butadiene or acryl rubber component to eliminate a problem of high brittleness due to too little elongation. Among the styrene copolymers, in the case of the styrene polymer modified using the acrylonitrile component or acryl component, the heat resistance is increased depending on the amount of the above component. Thereby, it is possible to prepare a sheet for forming a tray, which satisfies the requirements for heat resistant and cold resistance. However, in the case of the styrene polymer modified using the acrylonitrile or acryl component, the extent of heat resistance varies depending on the range of the amount of the above component. In the case of the styrene polymer modified using only this component, heat resistance may be increased, however, polystyrene itself is a highly brittle polymer, and furthermore, even if the above component is added to thus increase heat resistance, the resultant mixture or copolymer is also very brittle. Hence, in order to eliminate such problems, the acryl or butadiene rubber component should be further added or copolymerized, so that the resultant mixture or copolymer can withstand a thermal shock test comprising tens of cycles of temperature shifts in the temperature range from -5O⁰C to 85⁰C, without undergoing distortion or dimensional changes.

[8] With the goal of satisfying heat resistance and cold resistance, the present invention uses a styrene polymer, which is designed in the form of a ternary styrene polymer using the acrylonitrile or acryl component to enhance heat resistance, and furthermore, using the acryl or butadiene rubber component to exhibit cold resistance. Additionally, a polymer sheet may be designed using a process in which a component for helping heat dissipate, that is, an inorganic filler, is added.

[9] The styrene polymer modified using the acrylonitrile component includes a styrene- acrylonitrile copolymer or a styrene-acrylonitrile copolymer and an acrylonitrile - butadiene-styrene terpolymer. Among these polymers, the styrene-acrylonitrile copolymer has excellent heat resistance but has too little elongation, and therefore cannot be used unchanged. Thus, the acryl or butadiene rubber component is further used, or a polymer containing both acrylonitrile and rubber, for example, an acry- lonitrile-butadiene- styrene terpolymer, is used. In the case of the copolymer or mixture modified using the acryl component, the same principle is applied. As such, in the final styrene mixture of copolymer, the molar ratio of the amount of acrylonitrile or acryl component, the amount of butadiene or acryl rubber component, and the amount of styrene component should be adjusted to be within the range of (5~30):(5~30):(40~90). When the acrylonitrile or acryl component is used at a molar ratio less than 5, the effect of enhancement of tensile strength or heat resistance is insignificant. On the other hand, when the amount thereof exceeds 30 parts by weight, brittleness is undesirably increased. Further, when the butadiene or acryl rubber component, which is used for heat resistance enhancement and impact reinforcement, is used at a molar ratio less than 5, the effect of impact reinforcement is insignificant. On the other hand, if the amount thereof exceeds 30 parts by weight, elongation is excessively increased, that is, ductility becomes too high.

Advantageous Effects

[10] According to the technique of the present invention, provided is a styrene-based antistatic tray, which withstands the thermal shock of repeated heating and cooling between -5O⁰C and 85⁰C, generates no impurities during transport, and is easily subjected to thermoforming. Mode for the Invention

[11] When excessive heat or cold is locally applied to a polymer having very low heat transfer rate, such heat is not dissipated to the surroundings, and thus, a polymer sheet itself or a tray formed therefrom may be distorted due to the difference in the temperature upon the temperature shift between a high temperature and a low te mperature. To prevent this problem, the locally applied heat or cooling temperature must be rapidly dissipated to the surroundings. As such, when an inorganic filler is uniformly dispersed in the polymer, heat transfer is achieved through the inorganic filler particles, thus making it possible to prevent local overheating or overcooling. To this end, an inorganic filler, including a silica filler such as fused silica or precipitated silica, a titanate filler such as titanium dioxide, talc (Mg Si O (OH) ), mica (XY Z O

(OH,F) ), feldspar, calcium carbonate, calcium oxide, or magnesium oxide, is added in an amount of 0.5-30 parts by weight. When the amount of the inorganic filler is less than 0.5 parts by weight, the effect of heat transfer due to the inorganic filler is insignificant. On the other hand, when the amount of the filler exceeds 30 parts by weight, it is difficult to perform an extrusion process and a process of thermoforming the extruded polymer sheet. As the amount of the inorganic filler is increased, it is difficult to perform thermoforming, and therefore the sharp corner portion cannot be expected to be precisely shaped upon thermoforming. Consequently, it is preferable that the amount of the inorganic filler be in the range of 1-5 parts by weight.

[12] Upon the addition of the inorganic filler, if 0.001-5 parts by weight of a colorant is added, the tray can exhibit a desired color, which is more effective.

[13] On the surface of the styrene polymer sheet thus prepared, the process of forming an antistatic coating layer including a conductive polymer as an effective component is conducted as follows. First, 0.02-10 parts by weight of a conductive polymer, 5-40 parts by weight of a binder, and 50-94.98 parts by weight of a solvent are mixed. Preferably, 0.1-5 parts by weight of a dispersant, 0.1-5 parts by weight of a thickener, 0.01-0.1 parts by weight of a lubricant, and 0.01-5 parts by weight of an antioxidant, based on 100 parts by weight of the coating solution, are further included, thus preparing a conductive polymer coating solution having a total solid content of 0.1-10%. The coating solution thus prepared is applied on the surface of the polymer sheet and is then dried at 30~150°C for 0.5-5 min, thereby forming an antistatic layer 0.05-5 D thick.

[14] The conductive polymer used in the preparation of the antistatic coating solution of the present invention includes polyaniline, polypyrrole, polythiophene, polyphenylene vinylene, or modified conductive polymers derived therefrom. In consideration of environmental contamination and toxicity problems, particularly preferable is the use of polyethylenedioxythiophene, which is a conductive polymer available from H.C.Starck, Germany.

[15] The binder usable in the present invention may be one or more selected from among an acrylic binder, a urethane binder, an epoxy binder, an amide binder, an imide binder, a hydroxyl binder, a carboxylic acid binder, an ester binder, and mixtures thereof. In some cases, when various silicate and titanate binders are used together with an organic binder, the coating film becomes harder, which is more effective.

[16] The dispersant includes silicon compounds or fluorine compounds, and the thickener includes cellulose compounds, acryl compounds, or urethane compounds. Also, the solvent may be any one or a mixture of two or more selected from among various solvents, including water, alcohol solvents having 4 or fewer carbons, ketone solvents having 5 or fewer carbons, toluene, xylene, cresol, chloroform, N- methylpyrrolidinone, acetate solvents, and cellosolve solvents.

[17] The process of applying the conductive polymer on the surface of the polymer sheet includes, for example, gravure coating, reverse gravure coating, roll coating, bar coating, comma coating, etc. In addition, a combination process including dip coating or spray coating and then leveling using a bar coater may be used.

[18] Below, the present invention is described in detail through the following examples, which are set forth to illustrate, but are not to be construed to limit the scope of the present invention.

[19]

[20] <Comparative Example 1>

[21] In Comparative Example 1, a high impact polystyrene mixture including 25 parts by weight of carbon black, commercially available, was subjected to thermoforming to thus produce a tray, which was then subjected to a thermal hysteresis test and a vibration test.

[22] The surface resistivity of the tray was measured to be 10 ohm/sq, which is considered to be a good antistatic property. As results of a thermal shock test comprising 30 cycles of heating and cooling between -5O⁰C and 85⁰C, the dimensions of the tray were observed to decrease. Further, upon a vibration test through 60 back- and-forth movements of a distance of 1 cm, great amounts of impurities were detected. However, a phenomenon in which the tray was partially distorted did not occur. This is believed to be because heat applied to the tray is efficiently dissipated by carbon black included in the styrene resin.

[23]

[24] <Comparative Example 2>

[25] Comparative Example 2 was conducted in the same manner as Comparative

Example 1, with the exception that a commercially available sheet, three layer extruded at a thickness ratio of 10:80:10, in which the middle layer was composed of high impact polystyrene and the surface layer was composed of high impact polystyrene containing a surfactant as an antistatic agent, was subjected to thermoforming to thus produce a tray. [26] The tray thus produced was subjected to a thermal shock test as in Comparative Example 1. As the results, a phenomenon in which the tray was partially distorted occurred.

[27] In Comparative Examples 1 and 2, the conventional resin containing carbon black withstood the thermal shock test, but great amounts of black impurities were detected in the vibration test. Therefore, the above trays were unsuitable for use as a tray that must withstand the thermal shock test without generating black impurities in the vibration test, as is required in the present invention.

[28] [29] <Comparative Examples 3-4, Examples 1~3> [30] In Comparative Examples 3-4 and Examples 1-3, polymer sheets having various molar ratios of acrylonitrile, butadiene, and styrene components of the present invention were used. The test methods were the same as in Comparative Example 1.

[31] The antistatic coating solution used in Comparative Examples 3-4 and Examples 1-3 of Table 1 below was prepared by mixing 5 parts by weight of Baytron PH which is a conductive polymer available from H. C. Starck, Germany, 20 parts by weight of a urethane binder, and 0.4 parts by weight of a dispersant with 74.6 parts by weight of a solvent mixture comprising ethylalcohol and isopropylalcohol mixed at 1:1, was applied on the polymer sheet, and was then dried, thereby forming an antistatic layer 1 D thick.

[32] Table 1

[33] : molar ratio of respective components in a final compound, : test method: ASTM D3359, ³: ESD STM 11.11

[34] O: No, X: Yes [35] [36] <Comparative Examples 5-6, Examples 4~6> [37] In Comparative Examples 5-6 and Examples 4-6, polymer sheets having various molar ratios of acryl, butadiene, and styrene components of the present invention were used. The test methods were the same as in Comparative Example 1. [38] The antistatic coating solution used in Comparative Examples 5-6 and Examples 4-6 of Table 2 below was prepared by mixing 5 parts by weight of Baytron PH, which is a conductive polymer available from Starck, Germany, 20 parts by weight of a urethane binder, and 0.4 parts by weight of a dispersant with 74.6 parts by weight of a solvent mixture comprising ethylalcohol and isopropylalcohol mixed at 1:1, was applied on the polymer sheet, and was then dried, thereby forming an antistatic layer 1 D thick.

[39] Table 2

1 9

[40] : molar ratio of respective components in a final compound, : test method: ASTM D3359, ³: ESD STM 11.11

[41] O: No, X: Yes [42] [43] As is apparent from the results of Comparative Examples 3-6 and Examples 1-6, when the amount of the acrylonitrile or acryl component was 5% or more and the amount of the butadiene or acryl rubber component was about 30%, neither dimensional changes nor distortion were observed in the thermal shock test. Further, in the vibration test, there was no generation of black impurities. Furthermore, when the antistatic layer including the conductive polymer, that is, polyethylenedioxythiophene, as an effective component, was formed on the surface of the above material, the surface resistivity was measured to be 10 ohm/sq, which is considered to be very good antistatic performance.

[44] [45] <Example 7> [46] In Example 7, a polymer sheet having a predetermined amount of acrylic inorganic filler of the present invention was used. The test methods were the same as in Comparative Example 1.

[47] The antistatic coating solution used in Example 7 of Table 3 below was prepared by mixing 5 parts by weight of Baytron PH, which is a conductive polymer available from H. C. Starck, Germany, 20 parts by weight of a urethane binder, and 0.4 parts by weight of a dispersant with 74.6 parts by weight of a solvent mixture comprising ethylalcohol and isopropylalcohol mixed at 1:1, was applied on the polymer sheet, and was then dried, thereby forming an antistatic layer 1 D thick.

[48] Table 3

1 9

[49] : molar ratio of respective components in a final compound, : test method: ASTM D3359, ³: ESD STM 11.11

[50] O: No, X: Yes [51] [52] As is apparent from the results of Example 7, in the case of using 5% of the acry- lonitrile or acryl component, 15% of the butadiene or acryl rubber component, 80% of the styrene component, and 2 parts by weight of the inorganic filler (talc), neither dimensional changes nor distortion were observed in the thermal shock test. In addition, in the vibration test, there was no generation of black impurities. When the antistatic layer including the conductive polymer, that is, polyethylenedioxythiophene, as an effective component, was formed on the surface of the above material, the surface resistivity was measured to be 10 ohm/sq, which is considered to be very good antistatic performance. Industrial Applicability

[53] According to the present invention, a sheet for use in extreme environments and a tray for electronic parts produced using the same can assure the dimensional stability of the tray even under conditions of rapid changes in temperature and humidity during the transport and storage of electronic parts, thus preventing damage to the parts in the tray.

Claims

[1] A polymer sheet for thermoforming, comprising a styrene mixture or copolymer, in which an acrylonitrile or acryl component, a butadiene or acryl rubber component, and a styrene component are ultimately included at a molar ratio of (5~30):(5~30):(40~90).

[2] The polymer sheet according to claim 1, wherein 0.5-30 parts by weight of an inorganic filler is included in order to transfer heat to the mixture or copolymer.

[3] The polymer sheet according to claim 1 or 2, wherein 0.001-5 parts by weight of a colorant is added so that a predetermined color is exhibited.

[4] The polymer sheet according to claim 2 or 3, wherein the inorganic filler is one or more selected from among a silica filler, including fused silica or precipitated silica, a titanate filler, including titanium dioxide, talc, mica, feldspar, calcium carbonate, calcium oxide, and magnesium oxide.

[5] The polymer sheet according to claims 1 to 4, wherein an antistatic coating layer including a conductive polymer as an effective component is formed on the sheet.

[6] The polymer sheet according to claim 5, wherein the antistatic coating layer is formed by applying a coating solution comprising 0.02-10 parts by weight of the conductive polymer, 5-40 parts by weight of a binder, and 50-94.98 parts by weight of a solvent.

[7] The polymer sheet according to claim 6, wherein the coating solution further comprises 0.1-5 parts by weight of a dispersant, 0.1-5 parts by weight of a thickener, 0.01-0.1 parts by weight of a lubricant, and 0.01-5 parts by weight of an antioxidant, based on 100 parts by weight thereof, to thus prepare a conductive polymer coating solution having a total solid content of 0.1-10%.

[8] The polymer sheet according to any one of claims 5 to 7, wherein the conductive polymer is polyaniline, polypyrrole, polythiophene, polyphenylene vinylene, or a modified conductive polymer, including polyethylenedioxythiophene, derived therefrom.

[9] The polymer sheet according to any one of claims 6 to 8, wherein the binder is one or more selected from among an acrylic binder, a urethane binder, an epoxy binder, an amide binder, an imide binder, a hydroxyl binder, a carboxylic acid binder, an ester binder, and a multifunctional binder thereof, or comprises a silicate binder and a titanate binder mixed with an organic binder.

[10] A tray, produced by thermoforming the sheet of any one of claims 1 to 9, to thus have heat resistance and cold resistance and less dimensional change and distortion at low relative humidity.