JP2006122826A - Sieve for microsphere screening and microsphere screening method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sieve for microsphere screening which enables an irregular sphere screening and a particle size screening simultaneously and efficiently, and a microsphere screening method using the same. <P>SOLUTION: The sieve is used for leaving a microsphere of an aimed diameter (a) which is 2 mm or less, that is, is a sieve for screening it, and a sieve for a microsphere screening, wherein a plurality of sieve meshes in a sieve face have an anisotropic shape of a narrow side (b) of a length of 0.95a or less, and a long side (c) of a length going beyond (a). The microsphere screening method by using the sieve for the microsphere screening is most suitable for leaving with the sieve aimed microspheres having a diameter of 2 mm or less, and is a microsphere screening method in which an aggregate containing the aimed microspheres before screening is flowed in a long side direction of the sieve meshes to screen. Preferably, the aggregate after screening, which contains the aimed microspheres left with the sieve, is flowed and fallen outside the sieve, by which the screening aiming only the aimed microspheres can be carried out utilizing the flying distance difference. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention targets microspheres having a diameter of 2 mm or less, such as applications of solder balls, bearing balls, dummy balls, and spacer balls, and mixes the microspheres with high roundness and uniform particle size distribution. The present invention relates to a sieve that sorts out irregularly shaped spheres or spheres with significantly different particle sizes with high efficiency, and a sorting method using this sieve.

  Conventionally, an apparatus has been proposed for sorting out deformed spheres from a target group of microspheres by rolling them into V-grooves. For example, a plurality of V-grooves are formed on the plate, the plate is tilted, and the plurality of V-grooves are parallel to the tilt direction. When microspheres are supplied from the higher side of the V-groove, the deformed sphere stops in the middle of the V-groove or flows down directly below the bottom of the plate. On the other hand, a good product draws a certain parabola and falls outside the plate, and this is a technique of selecting a deformed sphere by utilizing the difference of the drop points (Patent Document 1).

  Further, as an apparatus for performing particle size selection, an apparatus using a sonic sieve (Patent Document 2) or an apparatus (Patent Document 3) for selecting by forming a gap with two shafts has been proposed. In addition to the method of obtaining particles with a narrow particle size distribution by using a circular hole in the sieving sieve, strong vibrations can be applied to the stains and powders by sonic waves, thus eliminating clogging. High capacity and efficient classification are possible.

In the method described later, the gap between the two shafts is gradually widened from the end to the other end, and the ball is rolled into the gap so that the target sphere according to the position where the sphere falls is changed. Sorting is performed. Since the sphere rolls in contact with the two shafts at a two-point contact, it falls at the shaft position with the shortest diameter corresponding to each sphere diameter accurately, so that high-precision sorting can be performed.
JP 2001-300909 A JP 2003-225586 A Japanese Patent Application Laid-Open No. 06-023633

  The conventional sorting apparatus has the advantages described above, but has the following problems. First, an apparatus that only rolls the V-groove as in Patent Document 1 has a function only for selecting a deformed sphere, and it is difficult to add a highly accurate particle size selecting function.

  Next, in the case of using a sonic sieve, this has an excellent effect in terms of particle size selection. However, when screening for deformed spheres, it is a mechanism that applies extremely strong vibrations to remove clogging, so deformed spheres with slight deformation are easily clogged and removed without being distinguished from non-defective products. It is difficult. In addition, in a method in which a sieve object is retained and vibrated strongly, such as a sonic sieve, a deformed object deformed into a plate shape exhibits a behavior that rides on a microsphere. Therefore, in order to reach such a deformed object to the hole and pass through the sieve, it is necessary to reduce the amount of the object to be input, and the sorting speed becomes very slow. Further, when the deformed spheres (hereinafter referred to as double balls) in which two non-defective balls are adhered to each other, they are distinguished from non-defective products depending on the contact angle when they reach the hole, which may be difficult to select.

  And, a method such as Patent Document 3 that rolls and sorts a sphere in a gap formed by two shafts is effective for sorting foreign substances such as a deformed deformed sphere, in addition to particle size sorting, In order to supply the shaft so as to be in contact with two points without fail, it is necessary to supply the assembly before sorting in a single row to the shaft, so it is difficult to increase the sorting speed. Furthermore, there is a problem that a snowball-shaped double ball in which a ball having a diameter smaller than that of a non-defective product is attached to a non-defective product may not be distinguished from a non-defective product.

  The present invention provides a microsphere sorting sieve capable of simultaneously and efficiently performing irregular sphere sorting and particle size sorting, and a microsphere sorting method using the sieve.

  The present inventor simultaneously selects the deformed sphere and the particle size in the selection of microspheres that require high-precision dimension and shape management, such as bearing balls, dummy balls, spacer balls, particularly solder balls. We studied a method that can be performed at high speed. As a result, the use of the above-mentioned two-point contact is advantageous in solving the problem because the screen of the target sphere is left behind. It was found that these problems can be greatly improved by using, and the present invention has been achieved.

  That is, the present invention is a sieve for sorting out a microsphere having a diameter of 2 mm or less and having a target diameter a, and a plurality of sieves on the sieve surface have a length of 0.95 a or less. This is a sieve for sorting microspheres characterized by an anisotropic shape having a short side b and a long side c having a length exceeding a.

And preferably, the sieve for microsphere selection of the present invention,
(1) The plurality of sieve eyes on the sieve surface are formed such that their short sides are adjacent to each other in parallel,
(2) A plurality of sieves formed by adjacent short sides of each other have different short side lengths,
(3) The plurality of sieve eyes on the sieve surface are formed such that their long sides are adjacent to each other in parallel,
(4) The plurality of sieve eyes on the sieve surface are formed such that their long sides are adjacent to each other in parallel forming a slit,
Satisfy one or more of these requirements.

  Then, by using these microsphere screening sieves of the present invention, it is an optimal microsphere selection method for leaving a target microsphere having a diameter of 2 mm or less, and is a set before the selection including the target microsphere. A method for sorting microspheres, wherein the body is sorted by flowing in the long side direction of the sieve. Preferably, the screened aggregate containing the target microspheres remaining on the screen is washed away from the screen, and is used to select only the target microsphere using the difference in flight distance. This is a method for sorting microspheres.

  According to the present invention, it is possible to simultaneously perform irregular sphere sorting and particle size sorting, and it is possible to dramatically improve productivity. In particular, since it is effective for sorting microspheres having a diameter of 1000 to 10 μm, microspheres that require particularly high-precision dimension and shape management, such as applications of solder balls, bearing balls, dummy balls, and spacer balls. Even in this field, it becomes an indispensable technology in order to achieve the practical quality and price.

  As described above, an important feature of the present invention is that the size of the sieve mesh with which the non-defective sphere contacts two points is optimally adjusted, so that smaller spheres and deformed deformed spheres can be obtained. It has been found that the selection of screening or clogging and leaving the target ball to be sieved is ultimately effective in selecting only the target ball. Specifically, a sieve for selecting a microsphere having a target diameter a having a diameter of 2 mm or less is left by screening, and a plurality of sieves on the screen have a length of 0.95 a or less. This is a sieve for sorting microspheres, which has an anisotropic shape with a short side b and a long side c with a length exceeding a. Realized to get sex.

  Microspheres with a diameter of 2 mm or less are conscious of high-precision microspheres that are mainly used for solder balls, bearing balls, dummy balls, and spacer balls. A microsphere that requires high sphericity. Typical high-precision microspheres that can be selected by the present invention have an average diameter of 2 mm or less, an average diameter / longest diameter ≧ 0.9, and a particle size distribution within a target diameter a ± 10%. It is.

  In order to efficiently screen the microspheres having the target diameter a from the aggregate in which various deformed spheres are also mixed, it is better to leave the target spheres instead of sieving them. For this purpose, the plurality of sieve meshes have an anisotropic hole size having a short side b of 0.95a or less and a long side c exceeding a. In other words, if the long side is a dimension that does not allow the target sphere to pass, while the long side has a long anisotropic shape that exceeds a, the number of spheres before selection is long. Continuous sorting is possible by pouring in the side direction.

  In the present invention, the short side dimension of the sieve is important, and this is particularly effective for the selection of deformed spheres for the present invention characterized by the simultaneous achievement of deformed sphere selection and particle size selection. It is. The problem with deformed spheres is that there is the “double ball” mentioned above, apart from the “anisotropic shape (so-called spindle shape)” where the sphere is crushed. It is very important to select and remove “snowman-shaped double balls” with spheres with diameters less than good balls.

  That is, the above-mentioned anisotropic shape can be eliminated if its short axis is sufficiently crushed than the short side of the sieve of the present invention. And even if the minor axis dimension is an anisotropic shape near the short side of the sieve that cannot easily pass through the sieve, selection is achieved if it is caught and caught strongly by the sieve. And even if it is not even caught by the sieve of the present invention, as a result, the anisotropically shaped object left behind in the sieve and the double ball having a large size, it is washed away from the sieve as it is, compared with the target ball. Depending on the shape and mass difference that are sufficiently different, it is possible to sort by the difference in flight distance (difference in rolling behavior), and it is sufficient to sort and collect at each landing position. However, in the case of a snowball-shaped double ball here, in the case where a very small sphere (foreign matter) is attached as compared with the target sphere, the above-mentioned flight distance difference is not sufficient, and it becomes difficult to select.

  Therefore, such a snowball-shaped double ball is not a matter of sifting itself, but a short diameter smaller than the target diameter a so that the small-diameter sphere adhering to the non-defective sphere can be pinched and captured. If the sieve of the side b is used, it becomes possible to sufficiently sort all kinds of deformed spheres by combining with the sorting mechanism based on the above-mentioned flight distance difference. In other words, the snowball-shaped double ball has a small sphere attached to it that is strongly sandwiched by a sieve having a narrow width b as compared with the target diameter a, so that it can be easily collected and collected from the non-defective sphere. Because the diameter of the small sphere is relatively large, even if it is a double ball that has escaped this capture (or once it has been captured but removed), the speed of flowing over the sieve is reduced, Sorting is achieved. And by narrowing the short side b of this sieve, the probability that the double balls of other anisotropic shapes and non-defective shapes will be screened out or captured decreases, but the shape difference and mass difference Large deformed spheres can be sorted by the flight distance difference.

  As for the particle size selection that needs to achieve another effect, the target sphere itself is left behind by setting the short side of the sieve as the dimension b that does not pass the target sphere diameter a as described above. Thus, a sphere having a diameter smaller than the dimension b is eliminated even if its shape is a true sphere. However, according to the effect of the particle size selection, the short side b of the sieve is preferably close to the diameter a of the target sphere, although it is preferable to select the deformed sphere, particularly a snowball-shaped double ball. If the short side b of the sieve is too wide, there is no effect. Therefore, it is necessary to optimally adjust the short side dimension of the sieve, rather than simply narrowing, for the sieve characterized by the simultaneous achievement of the deformed sphere sorting and the particle size sorting of the present invention.

  As described above, in selecting the particle diameter of the microsphere having the target diameter a, the target sphere has some allowable dimension (for example, ± 10%). Therefore, if the size of the sieve mesh is just under a, even acceptable products with acceptable dimensions will be screened out. As a result, many of the sieve eyes may be clogged. When this happens, the efficiency of sieving falls extremely.

  Then, when the short side dimension of the sieve which solves said subject was examined, it can be eliminated by making it 0.95a at most. If the screen has a short side dimension b with a short side of 0.95a with respect to the target diameter a and a size c with a long side exceeding a, the non-defective product of the target diameter contacts the anisotropically shaped hole. However, the sieve can be left without being caught in the sieve. And even though the non-defective product within the allowable dimensions is small, even if it is caught in the sieve, it can be easily removed from the sieve simply by applying a very weak force (that is, a group of microspheres that flow one after another). The particle size can be selected without reducing the yield and efficiency.

  Then, if considering the action effect of the selection of the deformed sphere, if it is possible to select the above-mentioned snowman-shaped double ball, other deformed spheres can also be selected by, for example, the difference in flight distance in the next stage. The short side b may be determined within the range of 0.95a or less, taking into account the balance with the effect of particle size selection. In this case, for the present invention where it is important to first select and remove the snowball-shaped double ball first, it is necessary to identify the double ball that is difficult to remove due to the difference in flight distance. As a result of investigating the situation, if the short side dimension of the sieve is narrowed to 0.95a, a double ball with a very small size of the small sphere attached to it is captured by the sieve. Although it becomes difficult, it has been found that since it catches on the edge of the sieve screen, the flow velocity is reduced and the flight distance does not eventually increase, and it has a certain effect on selection from non-defective products.

  The long side of the sieve is made longer than the target sphere diameter a, and if many spheres before selection are poured in the long side direction, the remaining non-defective spheres and deformed spheres will flow in one direction. Since it can be dropped, it is easy to sort by the difference in flight distance, and continuous sorting is possible. From the above, the microsphere selection sieve of the present invention has an anisotropic shape in which the short side b of the sieve with respect to the microsphere of the target diameter a is 0.95a or less and the long side c is more than a. Preferably, the short side for reliably selecting snowball-shaped double balls is set to 0.7a or less, or further, the short side for maintaining the effect of particle size selection is set to 0.5a or more. If either of these effects is insufficient due to the balance between these two effects, a combination of a plurality of sieves whose dimensions are readjusted within the scope of the present invention may be supplemented.

  Here, the definition of the short side b and the long side c of the sieve of the present invention will be described. First, when a true sphere (non-defective sphere) having a diameter equal to or larger than the dimension b is placed on one sieve, there is a state where the hole edge and the true sphere are in contact at two points. In a state in which the edge and the true sphere are in contact with each other at two points, the straight line distance where the distance between the two points is the longest is the short side b of the hole. The long side c is a distance perpendicular to the short side b, and is the longest distance among the distances connecting arbitrary two points on the outer periphery of the hole edge with a straight line (FIG. 1). (A)).

  The anisotropic shape essential for the sieve of the present invention is not particularly limited as long as the relationship between the dimensions a, b, and c according to the above definition satisfies the present invention. For example, this shape includes a rectangle, a triangle, an ellipse, a parallelogram, a rhombus, and a tear shape, and rounded or chamfered shapes. It may have a spindle shape (for example, FIG. 1B). Although it is possible to use a shape with many irregularities such as a heart shape or a gourd shape, there is a problem that it is difficult to adjust the short side and the long side. Preferably, the sieve is such that the short side is adjusted to be substantially perpendicular to the long side, which is the flow direction of the assembly, and the shape is based on a rectangle. Further, a sieve having a slit shape as a result of increasing the long side c is also a preferable shape for the present invention.

  In addition, in the sieves of various shapes described above, when the microspheres are made to flow in the long side direction, the microspheres rotate and are continuously connected to both edges on the long side for each sieve eye. Or it moves while contacting two points intermittently. Both edges on the long side are elements that determine the distance of the short side b of the sieve. At this time, the snowball-shaped double ball, which is an important effect of the present invention, is efficiently removed. If so, it is only necessary to change the distance between the two points where the microspheres are in continuous or intermittent contact. In other words, the screen should be a sieve with various changes in the short side (but not exceeding 0.95a) that can be used to hold the double balls of various sizes. As an example, there is a triangular sieving. This is because the distance at which two microspheres contact each other changes continuously (in a range not exceeding 0.95a), so that various sizes of deformed spheres are sandwiched and selected. It is possible.

  However, the effect of adjusting the change of the short side is not limited to one sieve, but the short side of each of the sieves can be varied differently. But granting is possible. Although this will be described later, since the flow efficiency of microspheres is reduced when the short side adjustment is limited to one sieve, a method using a plurality of sieves is preferable.

  Next, a preferred embodiment of the present invention for the above sieve will be described. The plurality of sieve meshes on the sieve surface of the present invention can easily control the direction in which the microspheres roll by forming the arrangement of the short sides and / or the long sides adjacent to each other in parallel. (Fig. 2). With this sieve, the microspheres do not concentrate at a specific location on the sieve surface and can be easily dispersed, and the sorting efficiency can be improved. Note that “parallel” means that the sides of the substantially rectangular sieves are parallel to each other, but this is based on the long side direction (the direction in which the microsphere rolls) and the short side direction. Judgment and adjustment may be made based on the substantial operational effects.

  Here, when the short sides of the sieves are adjacent to each other in parallel, if the short side length of each sieve is made different, it is a single sieving operation to flow the aggregate in the long side direction of the sieves. While selecting and removing snowball-shaped double balls of various sizes and deformed spheres with different shapes of crushed spheres, particle size can also be selected. Therefore, it is suitable when a predetermined good product sphere is selected from an aggregate including many shaped spheres. Preferably, a double ball with a relatively small-diameter sphere that is difficult to be sorted can be efficiently removed by arranging a small short side length in the upstream sieve through which the aggregate flows (FIG. 3). .

  Then, when slit-like (c >> a) sieves are used and arranged so that their long sides are adjacent to each other in parallel, the aggregate flows in the long side direction (slit direction) on the sieve surface. In this case, there is no “separator” in contact with the short side direction of the sieve, so in addition to the above-mentioned deformed sphere sorting effect, plate-shaped (crushed into a disc shape) is sorted. The ability is particularly improved (Fig. 4). In the case of a slit-shaped sieve, the flow direction of the aggregates flowing in the slit direction is uniform and the speed is improved, so this is also a form suitable for efficient sorting.

  However, when a slit-shaped sieve is used, for example, when a wedge wire screen is applied to such a sieve, the wire to be used must have a certain width (diameter) due to manufacturing restrictions. Therefore, if this leads to a decrease in the aperture ratio of the sieve, the sorting speed will be slow. Also, if the slit-shaped sieve is formed by electroforming (plating) method, it will be necessary to reduce the thickness of the sieve due to manufacturing restrictions, so if the strength of the sieve body decreases, It becomes difficult to handle. Therefore, when adopting a slit-shaped sieve, examination in view of these problems is preferable.

  Next, regarding the method for sorting microspheres of the present invention, the effect after sorting using the sieve will be described. The aggregate after the sieving that contains microspheres of the target diameter left on the sieve due to the sieving remains is washed away to the outside of the sieve, using the difference in the flight distance, and the particle size outside the prescribed sphere. Spheres can be removed, and more accurate sorting becomes possible. In other words, for example, if the aggregate before sorting is flowed and supplied on the sieve surface of the present invention installed so as to form a slope, in addition to the sorting action by the sieve screen described above, the fall flight distance difference from the succeeding sieve screen Further sorting using can be performed. When a microsphere having the same degree of sphericity is rolled onto a slope and dropped after giving a speed, a heavier microsphere has a longer flight distance from the sieve if the microsphere has the same mass (density). In addition, even if the mass is similar, the flying distance of a microsphere having a higher sphericity is longer. In addition, in the sieve of the present invention, the specially adjusted sieve screen sandwiches deformed spheres and deformed objects with low sphericity, so that the moving speed can be further significantly reduced. Can be shortened.

  In the case of the conventional method using the difference in flight distance by rolling the V-groove, which can only secure one trajectory that is difficult to change, the deformed sphere flows through the V-groove at a slower speed than a good product. If a non-defective product flows backward, the non-defective product collides with a front deformed sphere. As a result, the flow speed (flying distance) between the non-defective product and the deformed sphere becomes approximately the same, and the function and effect of sorting using this flying distance are diminished. However, if the method of the present invention has a high degree of freedom in changing the trajectory with a plurality of sieves formed on a wide sieve surface, it is assumed that a non-defective product collides with the deformed sphere flowing forward and the deformed sphere sandwiched between the sieves However, since the non-defective product continues to flow to the extent that the moving direction is deflected, the above-described problem of yield reduction due to deceleration can be remarkably improved.

  As a means of flowing the aggregate on the sieve surface, and giving it a speed to let it flow outward, in addition to providing an inclination on the sieve surface, applying vibration to the sieve surface and applying wind to the aggregate It is also possible to give an initial speed. As for the means for inclining the sieve surface, the inclination angle (climbing to horizontal to descending) may be optimally adjusted according to the flow velocity of the aggregate. Further, in order to improve the rolling of the microspheres, the screen may be vibrated or an air flow may be generated. However, these means are preferable for the selection of particularly small microspheres having a diameter of less than φ200 μm. This is because the smaller the microsphere, the more easily affected by static electricity and the like, and the microspheres are attracted to each other, and the microspheres and the sieving surface are attracted. A plurality of the above means can be combined.

  The direction in which the aggregate is washed away is not limited to one direction but can be made to flow in multiple directions simultaneously by adjusting the direction of the plurality of sieves provided on the sieve surface of the present invention. For example, for a single sieve, if the direction of the plurality of sieves is arranged radially toward the outer periphery of the sieve, many aggregates can be washed out toward the outer periphery. For example, the size of the apparatus can be reduced as compared with a case where the sieve is designed only in one direction. On the other hand, a one-screen sieve shape designed in only one direction of the sieve is simple, and the apparatus cost can be reduced. These directions may be determined by looking at the difference in flow behavior between the deformed sphere and the non-defective product, such as adopting a flow path while bending.

  In the above-described present invention, a plurality of independent sieves may be combined, that is, the sorted aggregate that has flowed out from the sieve is received again by another sieve, and the same sorting operation is performed. May be repeated, and may be received by a simple flat plate without a sieve or a conventional V-groove. By repeating the selection method of the present invention, the remaining probability of different diameter / deformed spheres mixed in the target sphere can be further reduced. In addition, if the microspheres targeted for sorting according to the present invention are too small, adhesion between them due to static electricity or the like, or adhesion with a sieve can be considered, and the effect is reduced considerably. A preferable lower limit of the target diameter is 10 μm.

  FIG. 2 is a configuration diagram of an embodiment of an apparatus using the microsphere sorting sieve 7 of the present invention, and is an example using a rectangular sieve screen. This is for selecting solder balls with a target diameter of 300 μm from a collection of solder balls of various shapes and sizes. Each sieve has a short side of 260 μm, and the flow direction of the aggregate. The long side is adjusted to 360 μm, and these sides are formed in parallel. The sieving surface is inclined downward toward the downstream side of the aggregate. When this sieve is used, the deformed deformed sphere 1 and the double ball 2 can be captured by the sieve, and the remarkably small sphere 4 is eliminated, so that the non-defective solder balls 3 are left to be screened and can be selected.

  FIG. 3 is a block diagram of an embodiment of an apparatus using the microsphere sorting sieve 7 of the present invention for sorting solder balls having a target diameter of 70 μm, using an elliptical sieve screen, and In this example, two types of sieves having different sizes are designed so that the larger one is on the downstream side. The small screen on the upstream side has its minor axis adjusted to 30 μm and the major axis, which is the flow direction of the aggregate, has been adjusted to 75 μm. Has been. And the mutual axes are formed in parallel. The sieve surface has a downward slope toward the downstream side of the aggregate. By using this different short axis sieve, in addition to being able to catch the double ball 2 having a relatively large deposit with the short axis, the double ball 5 having a short axis and a small deposit. Can be captured. Since extremely small spheres 4 are also screened out, good solder balls 3 are left behind and screening becomes possible.

  FIG. 4 is a configuration diagram of an embodiment of an apparatus using the microsphere sorting sieve 7 of the present invention for sorting solder balls having a target diameter of 800 μm. In the example of sorting using the difference in flight distance, the slit-shaped shape is used for the sieve mesh, and the screened aggregates (microsphere group) that are left behind in particular are washed away from the sieve. is there. Each slit has a width (short side) of 750 μm and a slit length (long side) that is sufficiently longer than the target diameter, and they are parallel to the slit direction (flow direction of the assembly). is there. The sieve surface has a downward slope toward the downstream side of the aggregate.

  By using this slit-shaped sieve, it is effective for capturing and sieving the deformed sphere by the slit, and particularly for selecting the deformed object 6 in the form of a plate (crushed into a disk shape). Further, even if the deformed sphere 1 or the double ball 5 crushed in an elliptical shape, which is not captured by the sieve, is difficult to roll due to being caught by the slit, the speed is reduced, and the flying distance falls when it flows out of the sieve. short. On the other hand, the non-defective solder balls 3 are easy to roll, so the flight distance is long. By using this sorting function based on the flying distance difference, the sorting accuracy of the non-defective solder balls 3 is further improved.

  Using these solder ball sorting apparatuses A to C shown in FIGS. 2 to 4, a total of 10 defective balls of various sizes and shapes were intentionally mixed into 1 million good products. A screening experiment was conducted. Table 1 shows the results of 10 experiments conducted for each device. As can be seen from Table 1, the number of defective products selected is an average of 8.6 for the device A in FIG. 2, 9.0 on the device B in FIG. 3, and an average of 9. on the device C in FIG. It is 3 and it turns out that a high sorting ability is obtained.

  In order to further increase the sorting capability, the same sorting may be repeated a plurality of times. Therefore, in the same manner as in the above experiment, an assembly in which 10 defective products are intentionally mixed into 1 million non-defective products is prepared, and a sorting experiment using the devices A to C is performed. Sorting experiments repeated twice were performed 10 times. The results are shown in Table 2. By repeating the selection twice, the deformed spheres were selected with a probability close to 100%.

  Since the present invention is a method for selecting balls having high sphericity, it can also be applied to selecting ceramic balls and the like.

It is a schematic diagram explaining an example of a sieve. It is a block diagram which shows an example of this invention. It is a block diagram which shows another example of this invention. It is a block diagram which shows another example of this invention.

Explanation of symbols

1 deformed deformed sphere, 2 deformed sphere with small microspheres attached to non-defective microspheres,
3 Fine spheres, 4 Remarkably small spheres 5 Deformed spheres with extremely small spheres attached to good spheres,
6 Plate-shaped deformed sphere, 7 Sieve for microsphere selection

Claims (7)

A screen for sorting out microspheres having a target diameter a having a diameter of 2 mm or less, and a plurality of sieve screens on the screen have a short side b having a length of 0.95 a or less. A sieve for sorting microspheres, characterized by having an anisotropic shape with a long side c having a length exceeding a. The sieve for microsphere selection according to claim 1, wherein the plurality of sieves on the sieve surface are formed such that their short sides are adjacent to each other in parallel. The sieve for microsphere selection according to claim 2, wherein a plurality of sieves formed such that their short sides are adjacent to each other in parallel have different short sides. The sieve for microspheres according to any one of claims 1 to 3, wherein the plurality of sieves on the sieve surface are formed such that their long sides are adjacent to each other in parallel. The sieve for microsphere selection according to claim 1, wherein the plurality of sieves on the sieve surface are formed such that their long sides are adjacent to each other in parallel by forming a slit. A method for sorting microspheres that leave a target microsphere having a diameter of 2 mm or less by using the sieve according to any one of claims 1 to 5, wherein the aggregate before the selection containing the target microsphere is sieved. A method for sorting microspheres, wherein the particles are sorted by flowing in the long side direction. 7. The minute microsphere according to claim 6, wherein the target microsphere is sorted by using the difference in flight distance by allowing the sorted aggregate including the target microsphere remaining to be sieved to flow out of the sieve. Sphere sorting method.

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