Damping element for the transport of semiconductor material, transport pallet and packaging unit

Abstract

The invention relates to a damping element (10) for the transport of semiconductor material, the element comprising a guide sleeve (6) and an elastic shaped body (8) having a base and a height h, wherein the shaped body is surrounded by the guide sleeve for at least up to 20% and at most up to 60% of its height h and the shaped body has: - a density from 0.1 to 0.6 g / cm3; - a tensile strength from 1.5 to 6.5 N / mm2; - an E-modulus from 0.3 to 0.7 MPa; and - an elongation at break of ≥ 250%. The invention also relates to a transport pallet (100) having such a damping element (10).

Description

[0001] Damping element for the transport of semiconductor material, transport pallet and packaging unit

[0002] The invention relates to a damping element for transporting semiconductor material, comprising a guide sleeve and an elastic molded body with a base area and a height h, wherein the molded body is surrounded by the guide sleeve for at least up to 20% and a maximum of up to 60% of its height h. Furthermore, a transport pallet with such a damping element is encompassed by the invention.

[0003] Polycrystalline silicon (polysilicon) and silicon carbide (SiC) can be produced in the form of long rods using a chemical vapor deposition process. Polysilicon is the starting material in the production of single-crystal silicon, which is manufactured, for example, using the Czochralski process. Polycrystalline silicon carbide also serves as a starting material for the production of single crystals, for example, using the PVT (physical vapor transport) process. Both processes usually require the respective semiconductor material to be crushed into fragments. These fragments, packaged in a variety of sizes, usually represent the transport form.

[0004] Since contamination can lead to misalignment (one-dimensional) and stacking (two-dimensional) defects in the crystal structure, contamination must be prevented. The fragments are typically packaged in sealed plastic foil bags or double-foil bags. The sample weight is typically 5 or 10 kg. Double-foil bags can reduce the risk of punctures caused by sharp-edged fragments. WO 2022 / 199813 A1 describes an efficient transport of such bags in outer packaging.

[0005] Punctures can occur during transport, particularly due to vibrations, shocks, and shifting of the bags. These events usually also lead to unwanted re-shredding. The resulting fine particles (abrasion) must generally be removed in an additional step before further use, as they negatively impact further processing.

[0006] Transport on trucks equipped with steel springs on poor road conditions (gravel / sand tracks) is often problematic. Here, the vibrations triggered by the road can be transferred to the packaging units of the semiconductor material. If these vibrations correspond to the natural frequency (4 to 10 Hz) of the packaging units, a resonance cascade can be triggered and the packaging units, including the pallets, begin to jump, producing a significant amount of fines. This can be up to 10 g / kg. For longer journeys even up to 15 g / kg. Since polysilicon and SiC refract visible light differently above a certain grain size (approx. 0.1 pm), the fines formed also appear brownish and reduce the visual impression of the product.

[0007] From WO 2015 / 007490 Al a transport container is known which contains at least two plastic bags with polysilicon fragments and has a packing density of 650 kg / m 3 up to a maximum of 950 kg / m 3 The plastic bags are arranged partially overlapping and provided with damping materials between the layers. A disadvantage is that the arrangement of the bags creates empty spaces, which can transfer the kinetic energy generated when the pallets bounce to the fragments of the semiconductor material.

[0008] EP 1 321 254 A1 describes molded bodies designed as pallet feet made from a material mixture consisting of a thermoplastic, a fine-particle fiber such as wood flour, and shredded rubber from scrap tires. The fine-particle fiber combined with the thermoplastic results in relatively high rigidity, which results in poor damping properties in the lower frequency range (< 30 Hz).

[0009] The objective of the invention was to reduce the fines generated during the transport of crushed semiconductor material under difficult road conditions, particularly in areas where air-sprung trucks are unavailable.

[0010] This object is achieved by a damping element for the transport of semiconductor material, comprising a guide sleeve and an elastic molded body with a base area and a height h, wherein the molded body is surrounded by the guide sleeve for at least up to 20% and a maximum of up to 60% of its height h, and the molded body

[0011] - a density of 0.1 to 0.6 g / cm 3 , preferably from 0.1 to 0.5 g / cm 3 , particularly preferably from 0.2 to 0.3 g / cm 3 ,

[0012] - a tensile strength of 1.5 to 6.5 N / mm 2 , preferably from 2 to 4 N / mm 2 ,

[0013] - a modulus of elasticity of 0.3 to 0.7 MPa,

[0014] - has an elongation at break of > 250%, preferably from 250 to 600%. The density can be determined according to DIN 53420. The tensile strength can be determined according to DIN 53571 (Specimen A). The modulus of elasticity can be determined according to DIN EN ISO 3386. The elongation at break can also be determined according to DIN 53571 (Specimen A).

[0015] The semiconductor material is preferably silicon and / or SiC, particularly in a polycrystalline form. The semiconductor material is preferably in comminuted form, with the grain size of the fragments being between 0.1 and 150 mm. The grain size is defined as the longest distance between two points on the surface of a fragment.

[0016] It has been shown that the elastic molded body, when guided in a sleeve, is ideal for transporting semiconductor material. The fines content could be significantly reduced by using the damping elements, especially during transport using older, steel-sprung trucks.

[0017] The molded body preferably has a pore volume of 40 to 75%, particularly preferably 50 to 65%. The pore volume is determined according to DIN ISO 4590.

[0018] The molded body preferably contains an elastomer selected from the group consisting of polyurethanes, polyolefins (e.g., EPP - expanded polypropylene and EPE - expanded polyethylene), silicones (especially silicone rubbers), and mixtures thereof. In particular, the molded body consists of such an elastomer.

[0019] The molded body particularly preferably contains or consists of polyurethane. The base area of ​​the molded body is preferably rectangular, circular, or ring-shaped. The base area can also be referred to as the standing area and corresponds to the area on which the load is applied.

[0020] The guide sleeve preferably has a correspondingly similar or (e.g. in the case of a force-locking connection) a congruent base area.

[0021] The length, width or diameter of the base area is preferably 10 to 250 mm, more preferably 15 to 200 mm, particularly preferably 20 to 150 mm.

[0022] The guide sleeve is preferably made of a material selected from the group consisting of steel, aluminum, wood, thermosets, and thermoplastics. The guide sleeve is particularly preferably made of plastic or aluminum.

[0023] In particular, the guide sleeve is an injection-molded part.

[0024] The elastic molded body is preferably glued to the guide sleeve. It is preferred that the bonding be made only on the base of the sleeve, so that the molded body can slide along the sleeve wall during compression or relaxation.

[0025] The elastic molded body can also be connected to the guide sleeve in a force-locking manner.

[0026] The shaped body is preferably surrounded by the guide sleeve to at least 30% and a maximum of 60% of its height h. According to a preferred embodiment, the shaped body can have a cap. This preferably encloses the part of the shaped body not covered by the sleeve. During compression, the cap can slide along the sleeve either on the outside or on the inside.

[0027] A further aspect of the invention relates to a transport pallet with a storage area and at least one damping element.

[0028] Preferably, the damping element is a component of a pallet base or is designed as a pallet base. The damping element can be attached, if necessary, over the entire surface, to the underside of the support surface.

[0029] It is preferred that the guide sleeve of the damping element is connected to the support surface, for example screwed or glued.

[0030] The base can be a wooden or plastic panel. The thickness of the panel can be 10 to 30% of the total height H of the damping element.

[0031] The total height H of the damping element is preferably at least 5% of the length of a longest side of a rectangular base. The total height H can also be at least 5% of the length of the diameter of a round base.

[0032] According to a preferred embodiment, the footprint corresponds to the base area of ​​a CP3 pallet (1140 x 1140 mm) or a CP5 pallet (760 x 1140 mm). The footprint can also correspond to the base area of ​​a CP1 (1000 x 1200 mm), CP2 (800 x 1200 mm), or CP4 (1100 x 1300 mm) pallet.

[0033] The transport pallet preferably comprises three, six, or nine damping elements. The damping elements are arranged equidistantly. Particularly preferably, the transport pallet corresponds in size to a CP3 or CP5 pallet and has nine damping elements.

[0034] Furthermore, packaging units for semiconductor material, in particular for polycrystalline SiC and / or silicon, are described. These preferably comprise a weight of 5 to 10 kg and preferably consist of foil bags, in particular double foil bags, which are sealed after the weight has been added.

[0035] The semiconductor material is preferably packaged in fragments of fraction sizes (BG) 1 to 4.

[0036] BG 1 (>90% of the fragments between 4 to 15 mm grain size)

[0037] BG 2 (>90% of the fragments between 5 and 50 mm grain size)

[0038] BG 3 (>90% of the fragments between 20 and 70 mm grain size)

[0039] BG 4 (>90% of the fragments between 35 and 150 mm grain size)

[0040] The grain size is defined as the longest distance between two points on the surface of a fragment.

[0041] The packaging process typically results in a fines fraction of 4 to 7 g per 10 kg bag. During transport, this fines fraction can increase by a factor of 10 to 30 per 100 km of transport distance, with the factor heavily dependent on road conditions.

[0042] When damping elements according to the invention are used for transporting the semiconductor material, a significant reduction in fines formation occurs. In some of the bags, no further fines formation was detected after transport. Overall, even under difficult road conditions, an average increase in fines formation of only a factor of 1.5 to 8 was observed.

[0043] The invention therefore also relates to a packaging unit for semiconductor material with a weight of 5 to 10 kg, wherein the semiconductor material is present in fragments of size 1 to 4 and has a fine fraction of fragments < 2 mm of 0.045 to 1%.

[0044] The fine fraction is preferably 0.046 to 0.6%, in particular 0.048 to 0.5%.

[0045] Fig. 1 shows a damping element

[0046] Fig. 2 shows a damping element with cap

[0047] Fig. 3 shows a transport pallet

[0048] Fig. 4 shows three variants of a transport pallet

[0049] Figure 1 shows the cross-section of a damping element 10 having a total height H. It consists of an elastic molded body 8 with a height h and a guide sleeve 6. The guide sleeve 6 surrounds the molded body 8 to approximately 50% of its height h. The base area 9 of the elastic molded body 8 can be round or rectangular in this cross-sectional view.

[0050] Figure 2 shows the cross-section of another embodiment of a damping element 11 according to the invention. In contrast to Figure 1, this has a cap 7. When the damping element 11 is loaded, the cap 7 slides along the outside of the guide sleeve 6. Figure 3 shows the cross-section of a transport pallet 100 according to the invention. This consists of a rectangular base 4, to the underside of which three, six, or nine damping elements 10 are attached (the variants are shown in Figure 4). The base 4 can be made of wood, and the guide sleeves 6 can be screwed to the base 4.

[0051] Figure 4 shows three variants A, B, and C of a transport pallet 100 according to the invention from below. Variant A has nine damping elements 10 attached to the support surface 4. Variant B has six damping elements 10 attached to the support surface 4. Variant C has three damping elements 10 attached to the support surface 4. The dashed line indicates the cross-sectional plane shown in Figure 3.

[0052] Examples

[0053] EPAL CP5 comparison pallets (LxWxH: 1140 x 760 x 138 mm) and transport pallets according to the invention with different damping elements, each loaded with two stacked packaging units of 480 kg each, each consisting of six cartons, each containing eight 10 kg (polysilicon fragment weight) double-foil bags. The pallets were subjected to a standardized transport simulation test ASTM D4169-14 DC3 (vertical vibration test) for a duration of 4 hours with both polysilicon fragments of fragment size 2 (> 90% of the fragments between 5 and 50 mm grain size) and fragment size 4 (> 90% of the fragments between 35 and 150 mm grain size). The test was conducted at ITT level with an effective acceleration of 0.37 m / s. 2This corresponds to approximately 1,000 km of truck transport with a steel spring at full load on secondary (non-main roads; e.g., country roads in reasonably good condition) and tertiary (smaller connecting roads between towns / villages; e.g., single-lane country roads, possibly only gravel and with road damage) roads.

[0054] The fine fraction was then determined by sieving with a 2.0 mm mesh sieve per bag.

[0055] EPAL CP5 comparison pallets (damping: 9 solid wood blocks):

[0056] For a solid wood block (e.g. pine) the following information can be given.

[0057] Bulk density according to DIN EN 350: about 0.52 g / cm 3

[0058] Young's modulus: 11,000 N / mm 2

[0059] Tensile strength: 100 N / mm 2 (according to DIN 68364)

[0060] The two packaging units, each containing 480 kg of polysilicon of fraction sizes 2 and 4, were stacked on the pallet and subjected to the transport simulation. During the simulation, a total of three of these pallets were stacked on top of each other, with only the bags in the topmost carton of the topmost pallet being tested, as this is where the greatest vibrations are expected.

[0061] Eight bags containing silicon of fraction size 2 had fines of 45 to 60 g.

[0062] Eight bags containing silicon of fraction size 4 had fines of 60 to 100 g.

[0063] The transport pallets according to the invention with different damping (versions 1-6, see Table 1):

[0064] The loading was carried out analogously to the above-described

[0065] Comparison pallets. The transport pallets corresponded in their dimensions to CP5 pallets. The base was made of wood and equipped with nine damping elements (corresponding to versions 1-6), as

[0066] Table 1

[0067] It should be noted that a value for the fines fraction of on average 4.8 g per bag (fraction size 2) and a value of on average 7 g per bag (fraction size 4) corresponds to the baseline fines fraction which results from the usual packaging in the bags.

[0068] First version:

[0069] Eight bags containing silicon of fraction size 2 had fines ranging from 5 to 40 g.

[0070] Six bags containing silicon of fraction size 4 had fines ranging from 7 to 20 g.

[0071] Second version:

[0072] Eight bags containing silicon of fraction size 2 had fines ranging from 4.8 to 42 g.

[0073] Six bags containing silicon of fraction size 4 had fines ranging from 7 to 22 g.

[0074] Third version:

[0075] Eight bags containing silicon of size 2 had fines ranging from 5.2 to 41 g. Six bags containing silicon of size 4 had fines ranging from 7.5 to 21 g.

[0076] Fourth version:

[0077] Eight bags containing silicon of fraction size 2 had fines ranging from 4.8 to 41 g.

[0078] Six bags containing silicon of fraction size 4 had fines ranging from 7 to 25 g.

[0079] Fifth version:

[0080] Eight bags containing silicon of fraction size 2 had fines ranging from 4.9 to 47 g.

[0081] Six bags containing silicon of fraction size 4 had fines ranging from 8.1 to 29 g

[0082] Sixth version:

[0083] Eight bags containing silicon of fraction size 2 had fines ranging from 4.8 to 45 g.

[0084] Six bags containing silicon of fraction size 4 had fines ranging from 7.3 to 27 g.

Claims

Patent claims 1. Damping element for the transport of semiconductor material, comprising a guide sleeve and an elastic shaped body with a base area and a height h, wherein the shaped body is surrounded by the guide sleeve for at least up to 20% and a maximum of up to 60% of its height h, and the shaped body - a density of 0.1 to 0.6 g / cm 3 , - a tensile strength of 1.5 to 6.5 N / mm 2 , - a modulus of elasticity of 0.3 to 0.7 MPa; - has an elongation at break > 250%.

2. Damping element according to claim 1, characterized in that the shaped body has a pore volume of 40 to 75%, preferably 50 to 65%.

3. Damping element according to claim 1 or 2, characterized in that the molded body comprises, preferably consists of, an elastomer selected from the group consisting of polyurethanes, polyolefins, silicones and mixtures thereof.

4. Damping element according to one of the preceding claims, characterized in that the base area is rectangular, circular or annular.

5. Damping element according to one of the preceding claims, characterized in that the guide sleeve consists of a material selected from the group consisting of steel, aluminum, wood, thermosets and thermoplastics.

6. Damping element according to one of the preceding claims, characterized in that the guide sleeve is an injection-molded part.

7. Damping element according to one of the preceding claims, characterized in that the elastic molded body is glued to the guide sleeve.

8. Damping element according to one of claims 1 to 6, characterized in that the elastic shaped body is force-fittingly connected to the guide sleeve.

9. Transport pallet comprising a support surface and at least one damping element according to at least one of the preceding claims.

10. Transport pallet according to claim 9, characterized in that the damping element is part of a pallet foot or is designed as a pallet foot.

11. Transport pallet according to claim 9 or 10, characterized in that the guide sleeve of the damping element is connected to the support surface.

12. Transport pallet according to one of claims 9 to 11, characterized in that the support surface is a wooden or plastic plate.

13. Transport pallet according to one of claims 9 to 12, characterized in that a total height H of the damping element is at least 5% of the longest side of a rectangular base or at least 5% of the diameter of a round base.

14. Transport pallet according to one of claims 9 to 13, characterized in that the footprint corresponds to the base area of a CP3 or CP5 pallet.

15. Transport pallet according to one of claims 9 to 14, comprising three, six, or nine damping elements.

16. Packaging unit comprising semiconductor material with a net weight of 5 to 10 kg, wherein the semiconductor material is present in fragments of size 1 to 4 and has a Fine fraction of fragments < 2 mm grain size of 0.045 to 1%.

Images