JPH05212807A - Manufacture of porous sintered sheet - Google Patents

Abstract

PURPOSE:To obtain a porous sintered sheet which is thin but free from cracking by applying plastic powder or a blend of plastic powder and a filler to the surface of a base material coated with a surfactant, then shaping the blend to a specified thickness and sintering it passing through a heating furnace. CONSTITUTION:A metal belt such as stainless steel or plastic film such as polyester is used as a base material 2. A specified amount of a surfactant solution is supplied to a sponge roll 3 using a rotary pump, and the solution is applied to the surface of the base material 2 by pressing the sponge roll 3 against the surface of the base material 2. The solution applied to the surface of the base material 2 comes in contact with supplied thermoplastic or thermocurable plastic powder, or a blend of plastic powder and a filler to moisten the powder or the blend, and thus restricts the slippage of the base material 2 over the powder 1. In addition, these materials are shaped to a specified thickness in a clearance, between a bovine nose-type roll 4 and the base material 2. Further, the plastic powders are fused along a stainless steel belt 7 using a heating furnace 5 to obtain a porous sintered sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous sintered sheet made of plastic powder or a mixture of plastic powder and a filler.

[0002]

2. Description of the Related Art A porous sintered sheet obtained by sintering plastic powder is used as a dielectric for a filter material and a printed wiring board material. Conventionally, a porous sintered sheet is made by spraying plastic powder on a base material such as a metal belt or a plastic film, and passing it through a beef-nose type coater, a roll bar, an L-shaped bar, etc., which has a certain gap with the base material. In this way, it was shaped into a certain thickness, sintered by heating, heat-sealed the plastic powders, and peeled off from the substrate. The apparent density of the porous sintered sheet thus obtained can be changed by changing the heating temperature and the heating time. The longer the heating temperature and the longer the heating time, the more apparent density the porous sintered sheet will have. Since it becomes high, it is possible to obtain a porous sintered sheet having a desired apparent density by adjusting these.

In the case of plastic powder, this can be molded into a porous sintered sheet and heated and pressed by a compression molding machine such as a press to crush the voids in the porous sintered sheet to form a sheet.
If the plastic powder is ultra high molecular weight polyethylene,
Because of its high melt viscosity, extrusion molding and injection molding are very difficult, similar to polytetrafluoroethylene, and cannot be molded by ordinary molding methods. To produce films and sheets. Although this molding method is complicated and requires skill, a sheet can be more easily manufactured by producing a porous sintered sheet and compression-molding it as described above. This ultra high molecular weight polyethylene is usually 2-20
Unlike PE, which has a molecular weight of 10,000, the soldering temperature is 2
Even at 60 ° C, the resin has low fluidity and retains its shape.
Further, it has a low dielectric constant and dielectric loss tangent similarly to polytetrafluoroethylene, and can be used as a dielectric for a high frequency printed wiring board.

However, non-polar polyethylene has poor adhesion to metal foil such as copper foil and epoxy resin, and for example, copper foil, epoxy resin and polyethylene sheet are laminated in this order,
The laminated plate obtained by heating and pressing this to cure the epoxy resin may be easily peeled off at the interface between the epoxy resin and the polyethylene sheet. However, the present inventors have found that instead of the polyethylene sheet, polyethylene porous material is used. Using a sintered sheet, when heated and pressed, the heated and melted epoxy resin flows into the voids of the polyethylene porous sheet,
It was proposed that the adhesiveness between the epoxy resin and the polyethylene sheet is improved due to the mutual anchoring effect of the epoxy resin and polyethylene because the voids of the remaining porous sintered sheet are crushed and become a sheet at the same time as the curing. (Japanese Patent Application No. 2-153388)

In general, when a filler is added to plastic, the coefficient of thermal expansion and dimensional change are small, and heat resistance and mechanical strength can be improved. Even in the case of a printed wiring board, a porous sintered sheet of plastic powder is used as the dielectric, and the heat and pressure are applied as described above to crush the voids in the porous sintered sheet to produce a laminated substrate, and through holes are formed by drilling. The through-hole reliability was not sufficient when through-hole plating was performed by electroless plating and electroplating, but by using a porous sintered sheet prepared by mixing plastic powder with a filler, And 26
The number of test cycles in the through-hole reliability test in which the operation of maintaining the temperature of 0 ° C. as one cycle was significantly increased, and the through-hole reliability was improved. By mixing the filler with the plastic in this way, it is possible to improve the function and characteristics and it is put into practical use.

In recent years, a multilayer board has been used for a printed wiring board due to the miniaturization, light weight and high density of electronic equipment, and a wiring board having a small dielectric constant and a low dielectric loss tangent has been obtained due to high speed propagation of signal speed and low attenuation of signal. There has been a demand for the dielectric material used for the multilayer board to be thin.

[0007]

A porous sintered sheet obtained from a plastic powder is often mixed with a filler in order to improve its characteristics, and the larger the amount added, the greater the effect in many cases. However, when the filler is mixed with the plastic powder to produce the porous sintered sheet, the base material and the plastic powder or the mixture of the plastic powder and the filler are slipped, or the plastic powders are mixed with each other or the plastic powder and the filler. However, there was a problem that it could not be shaped into a sheet because of poor sliding and poor fluidity.
Furthermore, even with only plastic powder, the shapeability changes depending on the narrow gap and the transport speed of the base material. However, the part where the particles are not filled becomes streaky, and the plastic powder is not conveyed at all and cannot be shaped into a sheet. In particular, when a filler is mixed with plastic powder, the shapeability becomes significantly worse than in the case of plastic powder alone, and a sheet cannot be obtained even under the condition that a plastic powder alone can be shaped and a porous sintered sheet can be obtained. There was a problem. Then, even if it could be shaped into a sheet, there was a problem that cracks were generated in the porous sintered sheet during sintering. The cracks here are cracks that are almost parallel to the width direction of the porous sintered sheet and have a relatively short length, and are thought to be caused by the shrinking of the apparent volume due to the plastic powder sintering and shrinking. Be done. Cracking is especially prevalent in sintered sheets obtained from plastic powder and filler mixtures.
When manufacturing a porous sintered sheet with such a thin thickness or a mixture of plastic powder with a filler, it is important to prevent its shapeability and crack generation during sintering. is there.

[0008]

As a result of various studies to solve the above-mentioned problems, the present inventors have spread plastic powder or a mixture of plastic powder and a filler on a substrate to form a constant gap. In the method for producing a porous sheet, which is manufactured by sintering the porous sheet after shaping by the provided gap, slippage between the powder and the substrate is caused by applying a surfactant solution to the surface of the substrate and shaping. By being suppressed,
The inventors have found that the shapeability is remarkably improved, and that a thin porous sheet or a crack-free porous sheet, which has been difficult to manufacture conventionally, can be obtained, and the present invention has been completed. Furthermore, when the surfactant solution is an aqueous solution of a fluorine-based surfactant, the surface tension of the aqueous solution is remarkably lowered by a small addition amount, and the aqueous solution is uniformly applied on the surface of the base material without being repelled. Also,
If it is an aqueous solution, there is no possibility of explosion even if the equipment is not explosion-proof equipment at the time of sintering, and non-explosion-proof equipment can be used. Further, since the amount of the surfactant adhering to the porous sheet is extremely small, the influence of the surfactant on the hygroscopicity and the dielectric properties is reduced. If the plastic powder particles are ultra high molecular weight PE,
Substrates with low dielectric constant and low dielectric loss tangent required for high-frequency substrates can be obtained, and with heat-curable resins such as epoxy resins, which have been difficult to heat resistance and adhesion in the past due to extremely high melt viscosity at high temperature. Can be composited, and the adhesiveness is further improved.

The present invention will be described below with reference to the drawings. Figure 1
An example of an apparatus for producing a porous sheet of plastic powder particles or a mixture of plastic powder particles and a filler is shown in FIG. 1
Is a plastic powder particle or a mixture of a plastic powder particle and a filler. The surfactant solution is applied to the base material of 2 with a sponge roll of 3, and the plastic powder or the plastic powder is mixed with the gap between the cattle and nose coater of 4 and the base material. The filler mixture is shaped into a sheet of constant thickness. Then, it is heated and sintered in a heating furnace of 5 to manufacture a porous sintered sheet of 6.

The plastic powder is a powder of a thermoplastic or thermosetting resin, and is, for example, a fluororesin such as polytetrafluoroethylene or poly-4-fluoroethylene-6-fluoropropylene copolymer, polyethylene, polypropylene or poly. Polyolefin resin such as -4-methyl-1-pentene, polystyrene resin, polyphenylene ether resin, polyetherimide resin, polyetheretherketone resin, polyphenylene sulfide resin, polysulfone resin, polyimide resin, polyester resin, epoxy resin, bis Particles of maleimide / triazine resin or the like are preferably used. Among them, ultra high molecular weight P
E is particularly preferable because it has a low dielectric constant or dielectric loss tangent value and is easily heat-molded into a porous sheet. Ultra-high molecular weight PE is produced by, for example, the Ziegler method polymerization technique, and its average molecular weight is 1 to 5,000,000 as measured by a viscosity method, which is an extremely large molecular weight as compared with general PE of 200,000. Petrochemical industry (Hi-Zex million, Miperon), Asahi Kasei (Suntech),
Those on the market such as West German Hoechst Co. (HOSTALEN.GUR) and US Hercules Co. (HIFAX.1000) are preferably used. The plastic powder preferably has an average particle size of 0.001 to 1 mm. In order to make the surface of the obtained porous sintered sheet smooth, it is particularly preferable that the average particle diameter is 0.001 to 0.1 mm.

The filler is in the form of powder and is added for the purpose of improving the physical properties and characteristics or reducing the cost, and is in the form of fiber, flake or balun.
For example, carbonates such as calcium carbonate and magnesium carbonate,
Hydroxides such as aluminum hydroxide and magnesium hydroxide, oxides such as zinc oxide, titanium dioxide, magnesium oxide and silicon dioxide, silicic acid such as aluminum silicate, magnesium silicate, calcium silicate and silicic acid, silicic acid Salt, mica, asbestos, mineral fiber, short glass fiber,
Typical examples include zonolite, potassium titanate, elestadite, glass balloon, fly ash balun, etc., and inorganic and organic substances such as flame retardants, antioxidants, colorants, etc., which are effective for flame retardancy when added to plastics. is there. The particle size of the filler is preferably smaller than the particle size of the plastic powder so as not to hinder the fusion between the plastic powders. The plastic powder and the filler are mixed by a commonly used method such as a Henschel mixer, a V blender, or a ribbon blender. Reference numeral 2 in FIG. 1 denotes a base material, and a metal belt such as stainless steel or a plastic film such as polyester, polypropylene, polyphenylene sulfide or polyimide film is used.

Since it is necessary to apply a surfactant solution to the base material and wet the surface of the base material with the liquid, it is more preferable that the surface is roughened because it is easier to wet with the liquid than it is smooth.
Reference numeral 3 in FIG. 1 denotes a sponge roll for applying a surfactant solution to the base material 2. Although not shown in the drawing, a rotary pump supplies a constant amount of the surfactant solution. .. By pressing this sponge roll against the surface of the base material, the surface active agent solution can be applied to the surface of the base material. The surfactant solution is prepared by dissolving a surfactant in a liquid and has such a composition and concentration that the surface tension of the surfactant solution becomes smaller than the surface tension of the substrate. Surfactants are classified into anionic surfactants, cationic surfactants, zwitterionic surfactants, and nonionic surfactants according to the properties of the portion exhibiting surface activity.As anionic surfactants, fatty acid salts, higher alcohol sulfate ester salts, fats Oil sulfate ester salts, sulfate salts of fatty amines and aliphatic amides, fatty alcohol phosphate ester salts, dibasic fatty acid ester sulfone salts, fatty acid amide sulfonates, alkylallyl sulfonates, formalin condensation naphthalene sulfonate Examples thereof include salts, and examples of cationic activators include aliphatic amine salts, quaternary ammonium salts, and alkylpyridinium salts. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, and polyoxyethylene sorbitan alkyl esters. Examples of the zwitterionic activator include carboxylic acid type, sulfuric acid ester salt type, sulfonic acid type and phosphoric acid ester type. Surfactants are composed of organic compounds in which hydrophobic groups and hydrophilic groups are combined, but fluorine-based surfactants in which some or all of the hydrogen atoms of the hydrophobic groups are replaced with fluorine atoms have a low surface tension in aqueous solution. It can be suitably used because it can be reduced by the amount added and has excellent heat resistance and chemical resistance. Examples of such a fluorinated surfactant include ammonium salts and potassium salts of perfluoroalkylsulfonic acid and potassium salts of perfluoroalkylcarboxylic acid as anionic surfactants. Examples of the cationic activator include perfluoroalkyl quaternary ammonium iodide. Examples of the nonionic activator include perfluoroalkyl polyoxyethylene ethanol and fluorinated alkyl esters.

The surfactant solution applied to the surface of the substrate is brought into contact with the supplied plastic powder or plastic powder and the filler mixture, and a part of the surfactant solution causes the surface of the plastic powder or the plastic powder and filler mixture to come to the surface. It is wetted and shaped to have a constant thickness by the gap between the beef-nose roll of 4 and the substrate 2, and the plastic powders are fused to each other in a drying furnace to obtain a porous sintered sheet.

[0014]

When the plastic powder or the mixture of the plastic powder and the filler is sprinkled on the base material and shaped by a shaping device having a certain gap with the base material to produce a porous sintered sheet, the base material There is a problem that the plastic powder or the mixture of the plastic powder and the filler slips on the above, a part where the powder is not filled is generated on the streaks, and the powder is not conveyed together with the base material to obtain a sheet. By coating the surface of the base material with the surfactant solution, the powder is wetted by the applied liquid and the slippage between the base material and the powder is suppressed. Become so. In addition, as a result, a thin porous sintered sheet could not be manufactured due to the slippage between the base material and the powder, but the slippage between the base material and the powder does not occur even if the gap between the shaping devices is narrow. It becomes possible to manufacture a porous sintered sheet without using the method. The slippage of the base material and the powder becomes difficult due to the presence of the liquid at the interface between them, but the surface tension of the liquid is smaller than the surface tension of the base material so that the liquid can be applied uniformly to the surface of the base material. If it is large, the liquid agglomerates into polka dots, and the surface of the substrate cannot be evenly wetted. If the surface active agent is a fluorine-based surface active agent, the surface tension of the liquid is remarkably lowered with a small addition amount, and therefore a small amount of the surface active agent is sufficient. On the surface of the obtained porous sheet, the surfactant applied to the base material adheres, which deteriorates the hygroscopicity and electrical characteristics, but the addition amount of the fluorine-based surfactant is small. The characteristics are not greatly affected.

[0015]

【Example】

Example 1 Using the apparatus shown in FIG. 1, a polyester film (SL type, Teijin Ltd.) substrate 2 having a thickness of 50 μm is placed on a stainless belt 7, and a sponge roll 3 has a rotary shaft (not shown). Fluorine surfactant F by pump
C-170 (perfluoroalkyl polyoxyethylene ethanol, Sumitomo 3M Co., Ltd.) was supplied with a 0.1% by weight aqueous solution, and the sponge roll 3 was pressed against the base material 2 to form a uniform fluorine-based interface on the base material surface. The activator was applied. And as a plastic powder, ultra-high molecular weight PE: Miperon XM-220 (average particle size 0.03
mm, melting point 136 ° C., true density 0.94 g / cm ³ , Mitsui Petrochemical Industry Co., Ltd.), the gap between the beef-nose coater 4 and the base material 2 coated with the surfactant solution was adjusted to give a plastic powder. 1 to a thickness of 0.8 mm, heating furnace 6 (160
Was heated at ° C.) perform sintering, apparent density 0.5 g / cm ^3, to obtain a porous sintered sheet of ultra high molecular weight PE having a thickness of 0.8 mm. Similarly, when the gap was narrowed to reduce the thickness of the porous sintered sheet, a 0.2 mm porous sintered sheet could be obtained.

Comparative Example 1 A porous sintered sheet was produced in the same manner as in Example 1 except that the surfactant solution was not applied, but it could be produced up to a thickness of 0.4 mm, and thinner sheets were filled with plastic powder. As a result, undesired streaks were generated, or the plastic powder stagnated in the cow-nose-type coater and was not conveyed together with the sliding base material, so that the porous sintered sheet could not be manufactured.

Example 2 As a mixture of a plastic powder and a filler, ultra-high molecular weight PE and Miperon XM-220 were used as the plastic powder, and 100 parts by weight of dechlorane plus-25 (1, 2, 3, 3) was used as the filler. 4,7,8,9,10,13,1
3,14,14-dodecachloro-1,4,4a, 5
80 parts by weight of 6,6a, 7,10,10a, 11,12,12a-dodecahydro-1,4: 7,10-dimethanodibenzo (a, e) cyclooctene, Occidental Chemical Co., Ltd., particle size 5 μm) Mix with a mixer. A thickness of 0.8 mm and an apparent density of 0.53 g / c were obtained in the same manner as in Example 1 except that this powder mixture was used.
A porous sintered sheet of m ³ was obtained. When the gap was narrowed to reduce the thickness of the porous sintered sheet, a 0.2 mm porous sintered sheet could be obtained.

Comparative Example 2 A porous sintered sheet was produced in the same manner as in Example 2 except that the surfactant solution was not applied. However, when the gap was 0.8 mm, the plastic powder and the filler were frequently mixed on the base material. The mixture slipped, and a continuous porous sintered sheet could not be obtained.

In Example 2, since the powder mixture was in intimate contact with the base film via the surfactant solution, the volume shrinkage due to sintering was probably suppressed to some extent, but cracks did not occur. There wasn't. The surface tension of the substrate film used was 40 to 45 dyne / cm, and the surface tension of 0.1% by weight of the fluorosurfactant FC-170C was about 20 dyne / cm (25 ° C). It was possible to wet evenly. Similarly, with a 0.01% by weight aqueous solution, 2
It was 0 dyne / cm, which seemed to sufficiently wet the surface of the base material, but was repelled due to the mechanical vibration of the base film and the fact that it was conveyed upward after coating.

The porous sintered sheets obtained in Example 1 and Comparative Example 1 were formed into a sheet by a compression molding machine (180 ° C., 10
Min., 100 kg / cm ² ) relative permittivity and dielectric loss tangent were measured by the cavity resonator method (12 GHz), and showed almost the same value with almost no influence of the surfactant.

Example 3 A polyester film (SL type) having a thickness of 50 μm, which was mat-processed on one side by a sandblasting treatment, was used as a base material, and 0.5% of Emar O (sodium lauryl sulfate, Kao Atlas) was used as a surfactant solution. A porous sintered sheet was produced in the same manner as in Example 2 except that a wt% aqueous solution was used.

The porous sintered sheets obtained in Examples 2 and 3 were formed into a sheet by a compression molding machine and the dielectric properties were measured. The sheet of Example 3 had an average relative dielectric constant of 0.01 and a dielectric loss tangent. Was only slightly higher on average at 0.0005.

[0023]

Industrial Applicability As in the present invention, a surface active agent solution is applied to a substrate, and a plastic powder or a mixed powder of a plastic powder and a filler is shaped into a sheet and then sintered to obtain a porous sintered sheet. With the method for producing, it becomes possible to produce a thin porous sintered sheet which was conventionally unable to slip-form the base material and the mixed powder. When a porous sintered sheet is prepared by mixing a plastic powder and a filler, since the filler is present between the plastic powders, the plastic powders are less likely to be fused to each other and cracks are likely to occur in the sheet. However, it is considered that the mixed powder is fixed to some extent by the surfactant solution applied on the base material and resists the shrinkage force due to fusion, but the occurrence of cracks can be suppressed. Further, by using an aqueous solution of a fluorine-based surfactant, the surface tension can be remarkably reduced with a small amount of the surfactant added, so the amount added can be small.
The influence of the surfactant adhering to the obtained porous sintered sheet is reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a porous sintered sheet manufacturing apparatus.

[Explanation of symbols]

1 plastic powder or a mixture of plastic powder and a filler 2 base material 3 sponge roll impregnated with an aqueous solution of a surfactant 4 beef nose type coater 5 heating furnace 6 porous sintered sheet 7 stainless steel belt

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display area C08L 23:00

Claims (3)

[Claims] 1. A method in which a plastic powder or a mixture of a plastic powder and a filler is sprinkled on a substrate coated with a surfactant, shaped into a certain thickness, and then sintered through a heating furnace. And a method for producing a porous sintered sheet. 2. The method for producing a porous sintered sheet according to claim 1, wherein the plastic powder is ultra high molecular weight polyethylene. 3. The method for producing a porous sintered sheet according to claim 1, wherein the surfactant solution is an aqueous solution of a fluorine-based surfactant.