JP2013039773A - Mold regenerating sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold regenerating sheet having high cleanability, and capable of distinguishing a mixing state of a mold cleaning material composition.SOLUTION: A mold cleaning material comprising an unvulcanized rubber-based composition or a thermosetting resin-based composition is formed in a strip-like pattern on at least one surface of a base sheet 1 comprising a paper sheet or a cloth sheet. Respective protrusions 2A as the components of the strip-like pattern are formed parallely spaced apart from each other, the space serves as an air escape space. Also a thin film 3 comprising the composition is formed on the surface part of the base sheet 1 positioning at the air escape space part. This thin film 3 serves for distinguishing the mixing state of the composition based on hue and surface state of itself.

Description

  The present invention relates to a mold regeneration sheet used for cleaning a mold surface of a molding mold.

  In the step of resin-sealing a semiconductor element by transfer molding, resin molding using a mold is usually repeated. As the number of repetitions (the number of shots) increases, dirt such as components, flashes, and dust that have exuded from the resin accumulate on the mold surface, particularly the cavity surface. Such dirt deteriorates the releasability when the molded product is taken out from the mold, and causes rough skin on the surface of the molded product. Therefore, the mold surface (cavity surface) of the mold is cleaned every fixed number of molding repetitions (number of shots).

  As this cleaning method, a method using a mold cleaning material formed in a sheet shape has been proposed (see, for example, Patent Document 1). In this method, the mold cleaning material is clamped with the mold cleaning material sandwiched between the upper mold and the lower mold, the mold cleaning material is filled in the cavity, and the mold is heated and molded in that state. In this method, the dirt is attached to the mold cleaning material, and then the mold cleaning material is removed, and the dirt is removed from the mold surface (cavity surface) together with the mold cleaning material.

  Further, the present applicant has proposed a mold regeneration sheet with improved cleaning properties (see, for example, Patent Documents 2 and 3). In this mold regeneration sheet, a mold cleaning material is projected in a predetermined pattern having an air vent gap on at least one surface of a paper sheet or a fabric sheet. When this mold regeneration sheet is used, the air in the cavity can easily escape from the air bleed gap, so that no air can accumulate in the cavity, and the mold cleaning material is filled to every corner of the cavity. Become so. As a result, it becomes possible to clean every corner in the cavity, and the cleaning performance is improved.

Japanese Patent Laid-Open No. 2004-130819 JP 2007-196586 A JP 2008-132759 A

  However, even when the mold regeneration sheet with improved cleaning properties is used, the stains may not be sufficiently removed in some cases. Therefore, as a result of the pursuit of the cause by the present inventor, the cause is that the mixed state of the composition of the mold cleaning material is not uniform, and in such a case, in the cavity of the mold cleaning material It turned out that the filling property to the is reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a mold regeneration sheet that has high cleaning properties and can identify the mixed state of the composition of the mold cleaning material. .

  In order to achieve the above object, the mold recycling sheet of the present invention is a mold cleaning material comprising an unvulcanized rubber composition or a thermosetting resin composition on at least one surface of a paper sheet or a fabric sheet. However, a thin film made of the above composition is formed on the surface portion of the paper sheet or fabric sheet located in the air bleed air gap, and is projected in a predetermined pattern having air bleed air gaps. In this thin film formation state, the mixed state of the composition forming the pattern can be identified.

  The inventor of the present invention proposed by the above-mentioned applicant, making use of the high cleaning property of the mold recycling sheet in which the mold cleaning material is projected in a predetermined pattern having air-release air gaps. In order to be able to identify the mixing state of the composition of the cleaning material, research was repeated. As a result, when a thin film made of the mold cleaning material is formed on the surface portion of the paper sheet or fabric sheet located in the air bleed gap, the mold cleaning material is mixed from the thin film formation state. The inventors have found that the state can be identified and have reached the present invention.

  That is, the mold cleaning material is composed of an unvulcanized rubber-based composition or a thermosetting resin-based composition, and an inorganic filler such as silica powder or titanium oxide is dispersed in the composition in an undissolved state. doing. If the dispersion of the inorganic filler is not uniform, as described above, the filling property of the mold cleaning material into the cavity is lowered, and the cleaning property is lowered. The non-uniform dispersion of the inorganic filler cannot be identified in the protruding pattern portion because the mold cleaning material is thick. However, when a thin film is formed with the composition, when the inorganic filler is uniformly dispersed, the color of the thin film becomes uniform and the surface of the thin film becomes smooth. When the dispersion of the inorganic filler is non-uniform, the color of the thin film also becomes non-uniform, and when the inorganic filler is not dispersed and is in an aggregated state, the aggregated portion is a convex portion on the surface of the thin film Appears as The formation state of such a thin film can be identified visually.

  When discriminating by the color of the thin film as described above, it is preferable to make the color of the inorganic filler conspicuous with respect to the color of the main component (fabric) of the composition of the thin film (mold cleaning material). For example, when the main component of the composition is colorless and transparent, use a colored material such as white as the inorganic filler, and when the main component of the composition is a light color system such as white, the inorganic filler When the main component of the composition is a dark color such as brown or gray, use a light color such as white as the inorganic filler. Etc. are preferred. That is, it is preferable that the color of the main component of the composition and the color of the inorganic filler have a relationship of opposite colors or light and dark colors from the viewpoint of easy identification.

  In the mold regenerating sheet of the present invention, a mold cleaning material comprising an unvulcanized rubber composition or a thermosetting resin composition has an air vent gap on at least one side of a paper sheet or a fabric sheet. It protrudes in a predetermined pattern. For this reason, when the mold is cleaned using the mold regeneration sheet of the present invention, the mold cleaning material can be filled into the cavity while the air in the cavity is extracted from the air vent gap. . As a result, air cannot be accumulated in the cavity, and as a result, the filling property of the mold cleaning material into the cavity is improved, and it is possible to clean all the corners of the cavity. In the mold regeneration sheet of the present invention, a thin film made of the above composition is formed on the surface portion of the paper sheet or fabric sheet located in the air bleed gap. The color of the thin film and the state of the surface represent the mixed state of the composition. Therefore, it is possible to identify the mixed state of the composition forming the pattern in the formed state of the thin film. As a result, it is possible to avoid using a non-uniform mixed state as being unsuitable for mold cleaning. That is, the thin film can be used for quality inspection of the mold recycling sheet of the present invention.

  In particular, when the thickness of the thin film is 500 μm or less, the mixed state of the composition tends to appear in the thin film, and the mixed state of the composition can be more easily identified.

  Further, when the top of the pattern is formed in a non-flat shape, even if the opening of the cavity is small, the opening is partially blocked by the top of the mold cleaning material. The air in the cavity can be more easily extracted. As a result, the filling property of the mold cleaning material is further improved, and the cleaning property in the cavity is further improved.

  Furthermore, when the non-flat part at the top of the pattern is a convex part having a radius of curvature of 0.2 to 3.0 mm, the filling property of the mold cleaning material is further improved, and the inside of the cavity is improved. The cleaning property is further improved.

  When the pattern is formed of a plurality of bands or a plurality of spots, it is easy to set the shape and dimensions of the pattern and the air vent gap, and the mold cleaning material is filled into the cavity. It is possible to easily set an appropriate pattern.

  In particular, when the width or thickness of the band or spot is set within a range of 1 to 5 mm, and the gap between adjacent bands or spots is set within a range of 1 to 5 mm, a semiconductor element Therefore, the size of the transfer molding die used for sealing the resin is appropriate, and the transfer molding die can be properly cleaned.

  In addition, when the gap between adjacent bands or spots is set to 0.5 to 2.0 times the width of the band or spots, the volume of the air vent and the amount of the mold cleaning material This makes it possible to balance the air in the cavity, and to more appropriately carry out the air bleeding and the filling of the mold cleaning material.

  On the other hand, the width of the band or spot is excellent in the shape stability of the pattern set in the range of 0.8 to 1.2 times the thickness, and the filling property of the mold cleaning material is further improved.

  Further, when the fabric sheet is a non-woven fabric, the surface of the fabric sheet becomes rough, so that the anchor effect of the mold cleaning material is improved, and the adhesion between the fabric sheet and the mold cleaning material is improved. Can be powerful.

  In particular, when the nonwoven fabric is a spunbonded nonwoven fabric, the tensile strength is relatively non-directional, and the stress applied during heat molding is easily absorbed and relaxed, so that sheet breakage is unlikely to occur during heat molding. In addition, since the sheet is not broken during the peeling (demolding) from the mold, the peeling (demolding) operation is simplified.

  Further, even when the fabric sheet is embossed, the surface of the fabric sheet becomes rough, so that the anchor effect of the mold cleaning material is improved, and the fabric sheet and the mold cleaning material are in close contact with each other. Power can be strengthened.

It is a perspective view which shows 1st Embodiment of the sheet | seat for metal mold | die reproduction | regeneration of this invention. It is a perspective view which shows 2nd Embodiment of the sheet | seat for metal mold | die reproduction | regeneration of this invention. It is a perspective view which shows 3rd Embodiment of the sheet | seat for metal mold | die reproduction | regeneration of this invention. (A)-(g) is sectional drawing which shows the modification of the protrusion of the said sheet | seat for metal mold | die reproduction | regeneration. It is a perspective view which shows 4th Embodiment of the sheet | seat for metal mold | die reproduction | regeneration of this invention.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a first embodiment of a mold regeneration sheet of the present invention. The mold regeneration sheet of this embodiment has a mold cleaning material made of an unvulcanized rubber composition or a thermosetting resin composition on both surfaces of a base sheet 1 made of a paper sheet or a fabric sheet. It is formed in a belt-like pattern. That is, each protrusion (band) 2A, which is a component of the belt-like pattern, is formed in parallel with a gap between each other, and the gap serves as an air venting gap when the mold is cleaned. . In addition, a thin film 3 made of the composition is integrally formed with the protrusion 2A on the surface portion of the base sheet 1 located in the air vent gap. The thin film 3 can identify the mixed state of the composition by its own color and surface condition. As described above, it is a major feature of the present invention that the thin film 3 that can identify the mixed state of the composition of the mold cleaning material is formed.

  That is, the mold cleaning material and the composition of the thin film 3 (unvulcanized rubber-based composition or thermosetting resin-based composition) are prepared by adding silica powder to unvulcanized rubber or thermosetting resin (main component). Or an inorganic filler such as titanium oxide. The inorganic filler is dispersed in an undissolved state. However, if the dispersion is uniform, the color of the thin film 3 becomes uniform, and the surface of the thin film 3 becomes smooth. However, if the dispersion of the inorganic filler is non-uniform, the color of the thin film 3 is also non-uniform, and if the inorganic filler is not dispersed and is in an aggregated state, the aggregated portion of the thin film 3 is not dispersed. Appears as convex on the surface. For example, in the case of the thermosetting resin-based composition, the thermosetting resin (main component) is generally colorless and transparent to translucent, and when mixed with the inorganic filler, it becomes white and opaque. When the dispersion (mixed state) of the inorganic filler is not uniform, a transparent or translucent portion of the main component can be confirmed on the thin film 3. The formation state of such a thin film 3 can be identified visually.

  In the case where the mixed state of the composition is identified as being uniform from the formation state of the thin film 3, the mold cleaning material of the protrusion 2A is filled to every corner in the cavity, Every corner can be cleaned. On the other hand, those identified as non-uniform in the mixed state of the composition are not suitable for mold cleaning and are not used for mold cleaning.

  More specifically, the thickness of the thin film 3 is preferably 500 μm or less, more preferably in the range of 20 to 150 μm, from the viewpoint that the mixed state of the composition tends to appear in the thin film 3. If the thickness is less than 20 μm, it is too thin to identify the mixed state of the composition.

  As described above, the composition is obtained by mixing an unvulcanized rubber or a thermosetting resin with an inorganic filler such as silica powder or titanium oxide. Or it is about 40-50 weight part of silica powder and about 5 weight part of titanium oxide with respect to 100 weight part of thermosetting resins. If necessary, other components are also mixed as appropriate.

  Examples of the unvulcanized rubber include natural rubber (NR), chloroprene rubber (CR), butadiene rubber (BR), nitrile rubber (NBR), ethylene propylene diene rubber (EPDM), ethylene propylene rubber (EPM), and styrene. Examples include butadiene rubber (SBR), polyisoprene rubber (IR), butyl rubber (IIR), silicone rubber (Q), and fluorine rubber (FKM).

  As said thermosetting resin, a melamine resin etc. are mention | raise | lifted, for example.

  In the method for producing the mold regeneration sheet, for example, the composition is first kneaded with a continuous or batch kneader and then placed on both surfaces of the base sheet 1. Next, it is sandwiched between two molds in which concave portions corresponding to the belt-like pattern of the mold cleaning material and the thin film 3 are formed and pressed. Thereby, the said strip | belt-shaped pattern and the thin film 3 are integrally formed on both surfaces of the said base material sheet 1. FIG. And it winds up or cut | disconnects to an appropriate dimension. In this way, the mold regeneration sheet can be produced.

  In the above-described embodiment, the thin film 3 is formed on the entire surface portion of the base sheet 1 positioned between the strip-shaped protrusions 2A. Since it is for identifying the mixed state of the composition of the mold cleaning material, it may be formed on a part of the surface portion of the base sheet 1 between the protrusions 2A.

  Moreover, in the said embodiment, although the strip | belt-shaped pattern and the thin film 3 were simultaneously formed by mold forming, after forming only a strip | belt-shaped pattern, the thin film 3 may be formed by application | coating etc.

  And in the said embodiment, although the longitudinal direction of 2 A of strip-shaped protrusions was made into the same direction with the surface and the back surface of the base material sheet 1, you may make it differ as shown in FIG. 2 is 90 ° different). Moreover, as shown in FIG. 3, you may form the strip | belt-shaped pattern and the thin film 3 only in the single side | surface of the base material sheet 1. FIG.

  Furthermore, in the above-described embodiment, the strip-shaped protrusion 2A has a rectangular cross-sectional shape perpendicular to the longitudinal direction, but the cross-sectional shape may be other, for example, FIG. ), A trapezoid may be used, a triangle may be used as shown in FIG. 4B, or a semicircle may be used as shown in FIG. 4C. Further, the cross-sectional shape may be such that the top is formed in a dome shape and the lower part is formed in a rectangle as shown in FIG. 4 (d), or the top is formed in a shape as shown in FIG. 4 (e). It may be formed in a dome shape, and its lower part may be formed in a trapezoidal shape, or as shown in FIG. 4 (f), it may be formed in a pentagonal cross section in which the top part is formed in a curved surface. As shown in g), the dome shape of FIG. 4D may be formed with a small width.

  4 (b) to 4 (g), the top of the strip-shaped protrusion 2A is formed in a non-flat shape, so even if the opening of the cavity is small, the opening is partially Accordingly, the top of the mold cleaning material is blocked, and the air in the cavity can be more easily removed. As a result, the filling property of the mold cleaning material is further improved, and the cleaning property in the cavity is further improved. In particular, those shown in FIGS. 4D to 4G have a radius of curvature of the top portion of the non-flat shape of 0.2 from the viewpoint of further improving the filling property of the mold cleaning material and the cleaning property in the cavity. It is preferable to set within a range of ˜3.0 mm.

  Moreover, in the said embodiment, although the metal mold | die cleaning material was formed in the strip | belt-shaped pattern and the thin film 3, you may form in a spot-like pattern and the thin film 3, as shown in FIG. Examples of the shape of the spot 2B of the spot pattern include a cone, a truncated cone, a cylinder, a prism, a pyramid, a truncated pyramid, and a square tube in addition to the cylinder shown in FIG. In FIG. 5, the spotted pattern and the thin film 3 are formed only on one side of the base sheet 1, but may be formed on both sides of the base sheet 1.

  Further, in the embodiment of FIGS. 1 and 2, the cleaning material is formed in the same pattern on both surfaces of the base sheet 1, but the pattern may be different on both surfaces of the base sheet 1. For example, the surface of the base sheet 1 may be a strip pattern and the back surface may be a spot pattern.

  The dimensions of the strip-like pattern protrusions 2A and the spot-like pattern spots 2B are appropriately set depending on the size and arrangement of the mold cavity, but the transfer molding metal used for resin-sealing the semiconductor element. What is used for cleaning the mold is that the width and thickness of the ridges 2A and the spots 2B are set within a range of 1 to 5 mm, and the gaps between the adjacent ridges 2A and the spots 2B are 1 to It is preferably set within a range of 5 mm.

  Further, from the viewpoint of optimizing the balance between the volume of the air bleed gap and the amount of the mold cleaning material, and further optimizing the air bleed in the cavity and filling the mold cleaning material, they are adjacent to each other (facing each other). ) It is preferable to set the gap between the ridge 2A and the spot 2B to 0.5 to 2.0 times the width of the ridge 2A and the spot 2B. If the gap between the protrusion 2A and the spot 2B is narrower than 0.5 times the width of the protrusion 2A, the cavity opening tends to be blocked by the protrusion 2A or the spot 2B when the mold is cleaned. As a result, air bleeding in the cavity is deteriorated, and there is a possibility that unfilling of the mold cleaning material may occur. If the gap between the protrusions 2A is made larger than 2.0 times the width of the protrusions 2A, This is because the distribution density of the mold cleaning material in the mold regeneration sheet becomes small, and the mold cleaning material may not be filled. In particular, it is more preferable to set the cross-sectional area of the gap between the adjacent protrusions 2A and the spots 2B adjacent to each other to 0.5 to 5 times the cross-sectional area of the protrusions 2A and the spots 2B.

  Furthermore, from the viewpoint of stabilizing the shape of the protrusions 2A and the spots 2B and further improving the filling property of the mold cleaning material, the width of the protrusions 2A and the spots 2B is 0.8 to 1.2 times the thickness. It is preferable to set within the range. If the width of the ridges 2A and the spots 2B is narrower than 0.8 times the thickness, the ridges 2A and the spots 2B are easily deformed, and it is difficult to keep the air vent gap when cleaning the mold. As a result, air bleeding in the cavity deteriorates, and there is a possibility that unfilling of the mold cleaning material may occur. If the width of the protrusion 2A and the spot 2B is wider than 1.2 times the thickness, the mold There is a possibility that the opening of the cavity may be blocked before the cleaning material is completely filled in the cavity. As a result, the air in the cavity may not be sufficiently vented, and the mold cleaning material may not be filled. It is.

  And as a fabric sheet of the said base material sheet 1, since a woven fabric, a nonwoven fabric, a knitted fabric etc. are mention | raise | lifted, since the surface of the woven fabric and nonwoven fabric using a long fiber has an appropriate rough surface. Further, the anchor effect of the protrusions 2A and the spots 2B and the thin film 3 is improved, and the adhesion with the protrusions 2A and the like can be strengthened (having grip properties). From this viewpoint, a woven fabric and a nonwoven fabric using the above-mentioned long fibers are preferable, and a nonwoven fabric is more preferable from the viewpoint of uniform grip properties. In particular, as the nonwoven fabric, a spunbonded nonwoven fabric is preferable from the viewpoint of mechanical strength, uniformity, and processability. Further, the embossed fabric sheet is also preferable because the surface is formed to be rough and the anchor effect of the protrusion 2A and the like is improved. The thickness of the base sheet 1 is usually set within a range of 0.1 to 0.8 mm.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to the examples.

[Fabric sheet]
A spunbonded nonwoven fabric (Asahi Kasei Co., Ltd., ELTAS E01070) made of polyester long fibers was prepared as a base sheet. This nonwoven fabric had a tear strength of 8.5 N, a thickness of 0.35 mm, and a basis weight of 70 g / m ² .

[Mold cleaning material]
100 parts by weight of ethylene propylene rubber, 50 parts by weight of silica powder, 5 parts by weight of titanium oxide, 2 parts by weight of organic peroxide [n-butyl-4,4-bis (t-butylperoxy) valerate], imidazole {2, 4-Diamino-6- [2′-methylimidazolyl- (1 ′)] ethyl-s-triazine} 10 parts by weight and montan wax 5 parts by weight were prepared.

  Next, the above components were mixed and kneaded with a kneader. And the mold cleaning material prepared by fully carrying out this kneading and the mold cleaning material prepared by carrying out the above kneading insufficiently were obtained.

[Production of sheet for mold regeneration]
Prepare two sheets of the above-mentioned base material sheet, mold cleaning material prepared by sufficiently performing the above kneading on both surfaces of one base material sheet, and insufficiently kneading the above base material on both surfaces of the other base material sheet The mold cleaning materials prepared in the above are formed into a strip pattern (interval of protrusion 5 mm) and a thin film (thickness 100 μm) each having a rectangular cross section (width 5 mm × height 3 mm), and two mold regeneration sheets Got.

[Identification of sheet for mold regeneration]
The thin film formation state of the two mold regeneration sheets was visually inspected. As a result, in the case of using the mold cleaning material prepared by sufficiently performing the kneading, the color of the thin film was uniform. On the other hand, in the case of using the mold cleaning material prepared by insufficiently kneading, the color of the thin film was not uniform.

  Therefore, the mold cleaning material prepared by sufficiently performing the kneading has a uniform mixed state of the composition, and the mold cleaning material prepared by insufficiently performing the kneading is the composition of the composition. It can be seen that the mixed state is uneven.

[Cleanability]
The transfer mold used for sealing the semiconductor element with the resin was cleaned using the two mold regeneration sheets. As a result, in the case of using the mold cleaning material prepared by sufficiently carrying out the kneading, it was possible to clean every corner of the cavity. On the other hand, in the case of using the mold cleaning material prepared by insufficiently kneading, there was an uncleaned portion at the corner of the cavity.

  Therefore, the mold cleaning material prepared by sufficiently kneading is excellent in filling property (cleaning property) into the cavity, and the mold cleaning material prepared by insufficiently kneading is filled. It turns out that it is inferior to (cleaning property).

[Comparative Example]
In the same manner as in the above example, two mold regeneration sheets were obtained using mold cleaning materials having different kneading states. However, in this comparative example, the above thin film was not formed, and only a strip pattern was used. The base sheet was exposed between the strips of the strip pattern.

  The strips of the strip pattern of the comparative example were visually inspected, but the kneading state could not be identified.

  From the results of the above examples and comparative examples, it can be seen that the thin films of the above examples are effective in identifying the mixed state of the composition of the mold cleaning material.

  In the above examples, the thickness of the thin film was set to 100 μm. However, even when the thickness of the thin film was set to 20 μm, 150 μm, and 500 μm, a result showing the same tendency as described above was obtained.

  In the above examples, an unvulcanized rubber composition was used as a mold cleaning material. However, even when a thermosetting resin composition containing melamine resin as a main component is used, the same tendency as described above is exhibited. The result was obtained.

  The mold regeneration sheet of the present invention can visually identify the mixed state of the mold cleaning material, and can use only non-defective products for cleaning the mold surface of the mold.

1 base sheet 2A ridge 3 thin film

Claims (11)

  A mold cleaning material made of an unvulcanized rubber-based composition or a thermosetting resin-based composition protrudes from at least one surface of a paper sheet or a fabric sheet in a predetermined pattern having an air venting gap. A thin film made of the composition is formed on the surface portion of the paper sheet or fabric sheet positioned in the air vent gap, and the mixed state of the composition forms the pattern in the formed state of the thin film. A mold regeneration sheet characterized by being made identifiable.   The mold regeneration sheet according to claim 1, wherein the thin film has a thickness of 500 μm or less.   3. The mold regeneration sheet according to claim 1, wherein a top portion of the pattern is formed in a non-flat shape.   The mold regeneration sheet according to claim 3, wherein the non-flat portion at the top of the pattern is a convex portion having a curvature radius of 0.2 to 3.0 mm.   The mold regeneration sheet according to any one of claims 1 to 4, wherein the pattern is formed of a plurality of bands or a plurality of spots.   The width | variety and thickness of the said band or a spot are set in the range of 1-5 mm, The clearance gap between the said adjacent band or the spot is set in the range of 1-5 mm. Sheet.   The mold regeneration sheet according to claim 5, wherein a gap between adjacent bands or spots is set to 0.5 to 2.0 times a width of the band or spots.   6. The mold regeneration sheet according to claim 5, wherein a width of the band or spot is set within a range of 0.8 to 1.2 times the thickness.   The said sheet | seat for mold reproduction | regeneration as described in any one of Claims 1-8 which is a nonwoven fabric.   The mold regeneration sheet according to claim 9, wherein the nonwoven fabric is a spunbond nonwoven fabric.   The mold regeneration sheet according to any one of claims 1 to 10, wherein the fabric sheet is embossed.

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