WO2012058676A2

WO2012058676A2 - Substrate shipper

Info

Publication number: WO2012058676A2
Application number: PCT/US2011/058615
Authority: WO
Inventors: John Burns; Mark V. Smith; Eric S. Olson; Russ V. Raschke
Original assignee: Entegris, Inc.
Priority date: 2010-10-29
Filing date: 2011-10-31
Publication date: 2012-05-03
Also published as: WO2012058676A3; TW201219279A

Abstract

A substrate shipping container suitable for shipping solar cells, substrate wafers, or other suitable media. In some embodiments, the readily constructed container is made up of two identical container portions, each container portion having a horizontally-disposed base member and two adjacent vertically-disposed side members constructed of impact- absorbing double walls. The two container portions are shaped to be coupled using integrally formed tabs and slots located about the perimeter of the container portions. The horizontally-disposed base member of each container portion is equipped with a plurality of integrally formed pads. These pads serve as cushions to provide shock absorption in the vertical direction to substrates that are stacked between these members. Embodiments may further be comprised of molded polymers or pulp.

Description

SUBSTRATE SHIPPER

PRIORITY CLAIM

This application claims priority to U.S. Provisional Application No. 61 ,408,448 filed October 29, 2010, and incorporates same herein by reference.

FIELD OF THE INVENTION

The present invention relates to a substrate shipping device. More particularly, the present invention relates to a multiple piece container for packaging substrates such as solar cell wafers.

BACKGROUND OF THE INVENTION

Solar cells are manufactured from substrates and accordingly are fragile, requiring significant protection and care when being transferred from one location to another. Containers and packaging for such devices need to be well suited for the task. Clean and largely contamination free environments during their transport and in between manufacturing process steps are important. Additional required or desirable characteristics of containers to transport and/or store substrates like solar cells include light weight, rigidity, cleanliness, and cost effective manufacturability. Such containers need to keep the wafers clean, uncontaminated, and undamaged. Improvements to these shipping containers are desired.

Wafers and cells require protection before, during, and after shipping. To enhance the protection of these items it is desirable to reduce the number of transfers these wafers and cells make. It is further advisable to reduce the number of carriers that are required to be managed and to reduce any cell damage that might occur during the transfer or handling process. Also, a container or packaging providing cost reduction is desired.

A further desire is for waste and scrap costs to be reduced and to minimize the environmental impact of the shipping materials. The industry further is realizing a need for low cost, super green, high volume, just-in-time, high density with solid cushioning performance to protect cells during shipment. Solar cell shipping volumes call for environmentally responsible, sustainable packaging solutions. Limiting the use of restricted materials ozone-depleting substances is desired. Accordingly, it is desirable to minimize using materials such as plastics or foam which can be harmful to the environment. Further it is desirable to maximize the use of post-consumer recycled content when possible.

SUMMARY OF THE INVENTION

An embodiment of the invention generally comprises a two piece substrate shipping container suitable for shipping solar cells, substrate wafers, or other media. Two container portions are shaped to be readily coupled with one another using integrally formed tabs and slots or tongues and grooves located about, adjacent to, the lateral out perimeter of the container portions.

A feature and advantage of embodiments of the invention is that the impact absorbing double walls of the side members have an outer wall to absorb impacts and an inner wall for constraining the substrates in the interior of the container. The two walls joined at a flexing juncture portion such that after assembly the flexing juncture corner portion is not positioned at an exposed corner of the assembled shipping container. In embodiments of the invention, the two components when assembled, have a substantially square footprint and with four side walls each being rectangular and the entire upper and lower perimeters constituting a "free" edge portion that is part of the wall structure. The wall structure then extends substantially vertically from the edge portion, defining an upright exteriorly exposed wall, and then extends substantially horizontally, defining a wall juncture portion, before reaching the substrate confining wall. In embodiments, the entire upper corner, extending around the upper perimeter of the container and the entire lower corner extending around the lower perimeter of the container are free edge portions supported only by the upright wall and structurally isolated from the substrate receiving region by a substantially vertical portion and a substantially horizontal portion.

A feature and advantage of embodiments of the invention is the readily constructed container is made up of two identical container portions, each container portion having a horizontally-disposed base member and two vertically extending side walls. The two container portions are shaped to be readily coupled with one another when one is placed in a reversed and inverted orientation from the other. The container portions are adapted to couple with one another when the container portions are placed in reversed and inverted orientations with respect to one another.

A feature and advantage of embodiments of the invention is that each container portion may have a base with two adjacent walls and two open sides whereby the walls of one container portion form two of the four side walls and the walls of the other container portion form the other two of the four walls. A feature and advantage of embodiments of the invention is a slot extending along each of said adjacent walls and being continuous therethough. The slot defined by opposing interior surfaces of the inner side wall portion and the outer side wall portion. A feature and advantage of embodiments of the invention is the slot may be tapered and be a receiving slot for receiving another pair of adjacent walls therein for compact stacking of the container portions.

A feature and advantage of embodiments of the invention is that the top component portion is identical to the bottom container portion and each have a base portion and two walls on opposite sides of the base portion providing a U shaped configuration. The two identical U shapes interface to form the box enclosure. In other embodiments, one of the top and bottom portions may have three walls and the other one wall.

In embodiments of the invention, inwardly extending pads, defining substrate support surfaces, are separated from the exposed outer top surface of the container and the exposed bottom surface of the container by substantially vertically extending wall portions.

In embodiments of the invention, the outwardly exposed top surface and the outwardly exposed bottom surface, that are in vertical alignment with the substrate receiving region are recessed vertically inward from the upper and lower perimeters defined by the outer wall edge portions, that is the flared skirt portion.

A feature and advantage of embodiments of the invention, the inner side walls that constrain the stack of substrates are offset outwardly at the vertical corners of the stack so that the more fragile corners have enhanced shock protection. A feature and advantage of embodiments of the invention is that the structure defining the substrate stack region has recesses at the corners for providing better protection to the substrates.

Prior to assembly, the components may be nested together for maximum quantities in a reduced volume in an elongate stack for ease of shipping and storing, particularly nesting side walls into the recesses formed by the double wall side walls. After use, that is shipment of product and unloading of product, the components may be restacked for reuse, recycling, storage, shipment, or disposal.

In an embodiment of the invention, first and second container portions may each have edge and groove features located about their perimeters that cooperate and engage with each other for correct positioning and/or for a removable connection of the components.

In an embodiment of the invention the container is formed by an injection molding process from polymers. In an embodiment the container is formed from polymer sheets by vacuum molding. In other embodiments, the container is molded from pulp.

In an embodiment of the invention, the base of the container is equipped with plurality of spaced-apart shock absorbing cushions to absorb shocks in the vertical direction. These cushions may be equipped with access holes for allowing easy cell removal assistance of the packaging.

DESCRIPTION OF THE DRAWINGS

Figure 1 is an exploded view of a substrate shipping container according to an embodiment of the invention.

Figure 2 is a view of a closed or assembled substrate shipping container according to an embodiment of the invention.

Figure 3 is a cross-sectional view of the closed or assembled substrate shipping container of Figure 2.

Figure 4 is a top perspective view of one container portion of a substrate shipping container with a stack of substrates and cushioning materials therein according to an embodiment of the invention herein.

Figure 5 is an exploded view of a substrate shipping container according to an embodiment of the invention.

Figure 6 is a top perspective view of loaded substrate shipping containers being packed in a box according to an embodiment of the invention herein.

Figure 7 is a perspective view of a plurality of the boxes of Figure 6 on a pallet. Figure 8 is the boxes of Figure 7 further wrapped with cardboard and a cap for shipping.

Figure 9 is perspective view of a container portion according to an embodiment of the invention.

Figure 10 is a exploded perspective view of a stack of container portions according to an embodiment of the invention. Figure 1 1 is a perspective view of a stack of container portions according to an embodimemt of the invention.

Figure 12 is a front perspective view of container portion according to an embodiment of the invention.

Figure 13 is a back perspective view of container portion of Figure 12.

DETAILED DESCRIPTION

Referring to Figure 1-5, embodiments of a substrate shipping container 20 are illustrated. The shipping container 20 comprises generally two portions 22, namely, a first container portion 22A and a second container portion 22B. Each container portion, may be identical and each has a base wall 24 and a pair of side walls 26 and 28 that define a substrate stack receiving region 29. The container portions 22 are preferably made of a polypropylene material or other polymer. The base wall 24 is generally horizontally- disposed and serves as the bottom or top of the container shipping container. A stack 30 of square or pseudo square wafers or other substrates, such as solar cells, is received on the base 24.

The surface of the base 24 is generally a horizontal plane; however, it may be molded to include horizontally disposed grooves 32 (see Figure 2) or a matrix of pads 34 for cushion control in the vertical (i.e. "z") direction. Surrounding the base 24 is an integrally formed shallow locking groove 35. This groove 35 extends along the two sides of the container portion 22 which does not have side walls. The container portions have a flared skirt 70 which has an outer peripheral edge portion 64.

The side walls 26 and 28 are generally vertically-disposed with respect to the horizontal plane of the base. The walls 26 and 28 are impact-absorbing double walls. This means that the walls each have a flexible outer wall 36 to absorb and dampen impacts. Just inside each flexible outer wall 36 is an inner wall 38 disposed in a generally parallel direction thereto. The inner walls 38 are generally rigid to prevent flexing against the wafers or solar cell substrates 30. Accordingly, the side walls 26 and 28 provide cushioning from the side (i.e. the x-y direction). Moreover, the inwardly disposed surfaces of the inner walls 38 are smooth and vertical for minimal friction near the edges of the wafer or solar cells 30. The base portion 24 is generally horizontally-disposed and serves as the bottom or top of the container shipping container. Various substrates 30, including square or pseudo square wafers or solar cells, may be horizontally stacked in a "coin stack" disposition on the base 24. The surface of the base 24 is generally a horizontal plane; however, it is molded to include a plurality of pads 32 for cushion constraint and control in the vertical direction. The pads 32 provide uniform projections inwardly into the interior of the container and have flat projected surfaces 31 for contacting substrates or other packaged material above or below the substrates 30. Accordingly, opposite each of the interior pad projections in the base 24 are recesses 33. These recesses 33 form a pattern of outwardly extending recesses or depressions along top and bottom surfaces of a closed container. Surrounding the base 24 is an integrally formed shallow locking groove 34. This groove

34 extends along the two sides of the container portion 22 which do not contain side walls. At the base of the locking groove 34 are a plurality of spaced apart slots 35. These slots

35 are sized for coupled engagement with tab features in the corresponding oppositely- disposed container portion.

In an embodiment, the side walls 26 and 28 of each container portion may be adjacent one another, upright and vertically-disposed with respect to the horizontal plane of the base. The side walls 26 and 28 are impact-absorbing double walls. This means that the walls each have an outer side wall portion 36 to absorb and dampen impacts. Just inside each outer side wall portion 36 is an inner side wall portion 38 disposed in a generally parallel direction thereto. The inner side wall portions 38 define the substrate stack receiving region and constrain the wafers or solar cell substrates 30. Accordingly, the side walls 26 and 28 provide cushioning from the side (i.e. the x-y direction). Moreover, the inwardly disposed surfaces of the inner side wall portions 38 are typically relatively smooth for minimal friction near the edges of the wafer or solar cells 30. In some embodiments, wall portions 36 and 38 have differing properties from one another in terms of flexibility and rigidity such as by altering their respective thicknesses or providing rigidizing structure. For example, Fig. 3 illustrates a thicker inner wall portion compared to the outer wall portion. The inner wall portions and outer wall portions define a recess 38.2 that in embodiments may have a taper away from the opening of the recess for receiving and nesting a double wall of another container portion.

The outer side wall portions 36 and inner side wall portions 38 join one another juncture portion 39 defining an elongate top edge portion 40. This top edge portion 40 extends the length of the two walls 26 and 28 and bends at their adjoining corner 42 to forming a right angle and an "L" shaped protrusion from the base in particular embodiments. The top juncture portion is U-shaped and provides a shock absorption feature.

Figures 2 and 3 illustrate the assembled container 20. When the container is ready for assembly a first container portion 22A may be releasably engaged with a second container portion 22B to complete the shipping container. First, a second container portion 22B that is similarly oriented to container portion 22A would need to be inverted and rotated 180 degrees with respect to the first container portion 22A. The top edge 40 configured as a tongue of the first (lower) container portion 22A is fit into the groove portion 35 of the second container portion 22B. Further the top edge 40 of the second container portion 22B is fit into the groove portion 35 of the first container portion 22 A. These top edges 40 and groove portions 35 may be fit together in an interference fit with one another in a tongue and groove fashion to secure the container portions together.

In embodiments of the invention, the assembled container 20 generally has a generally square top side 46, a generally square bottom side 48, and four rectangular sides 50, 51 , 52, 53. Notably, in embodiments of the invention, the edge portion 60 extends entirely around the upper peripheral corner 62, on all four sides, and entirely around the lower peripheral corner 64, on all four sides, of the container, are flared outwardly at a flared portion configured as a flared skirt 70 and are "free", meaning the edge of the outer wall portions are supported only by said outer wall portion. Thus, the shock from any impact on any of the upper peripheral corner, lower peripheral corner edge must travel at least from the outer edge portion 60 through a section of upright or substantially vertical wall portion to a wall portion extending substantially horizontally before reaching any structure defining the substrate receiving region 29. Thus, said shock may be substantially absorbed by the bending of the intermediate structure before reaching the fragile substrates. As can be seen each peripheral edge portion has at least one U-shaped wall portion 80 intermediate said edge portion and the structure engaging or supporting the substrates. Said U-shaped wall portion may effectively absorb shocks at the corner portions by allow the outer wall to flex at said corner portion. The axis a of the U-shaped portions are in alignment with and parallel to the sides and sidewalls and side wall portions. In the various embodiments, further packing material such as, cardboard 84, and/or foam layers 86 may be stacked between the container and wafers or solar cells 30 for additional protection. A sleeve 88 formed of paper, cardboard, foam, or other sheet material may wrap around and support the stack. Further, similar materials may be placed around the outside of the container 20 and tape or shrink wrap may be placed around the outer periphery of the container and/or packaging material for a further seal. For example, in Figure 6, corrugated pads 56 are placed around the periphery of the container 20 and the exterior of the container and packaging is surrounded by shrink wrap 58.

Figures 6-8 illustrate the packaging process for assembling a pallet of substrate shipping containers according to an embodiment of the invention. The shipper containers 20 are generally first loaded with a predetermined number of wafers or cells 30 in each container 20. The containers are then vertically positioned with separation and cushioning 68 in master cartons 70, with five shipping containers 20 per carton for example. Next, master cartons 70 are loaded on pallets 72 and a pallet sleeve 74 is placed over the pallet contents and straps 76 are added.

In other embodiments, the component may be U-shaped from an end or side view with the two side walls 94, 95 opposing each other with respect to the base 96 as illustrated in Figure 9.

Referring to Figures 10 and 1 1 , in embodiments of the invention, the container portions 20 may be assembled into a stack of container portions providing a compact, high density shipping configuration.

Referring to Figures 12 and 13, the pads 1 10 may be arranged matrixically and may have finger holes 1 12 that may aid in removal of the stack.

Note that the substrate shipping containers can be vertically stacked as necessary during the shipping and storage process. First, due to the configuration of the containers, these containers can replace existing sort bins without equipment modifications. The containers work in both flat-mounted and angle-mounted sorting operations and the mold design generally allows for custom interface features in some embodiments. The containers also have built in locating features to align the shipping containers with the center of the wafer cells. Finally, stacking features for incoming wafer/cell storage are included. A removable insert in the mold can permit manufacturers' logos. Also, the containers are capable of handling many types of RFID tags, barcodes, and stickers for customer requirements. Further, a grid may be molded into the base for tracking, cleaning, reuse or other cycles. The outer surface of the container can provide external stacking features and a tapeable perimeter.

The components may generally be injected molded, vacuum formed or otherwise manufactured from polymers or pulp, suitable for semiconductor wafers. In some embodiments, a container of the type described may have a capacity of 150, 130, 125, or 100 stacked wafers or solar cells, for example. For example, shipping media having total dimensions of 6.19" x 6.19" x 1.75" and weighing 63 oz could be readily accomplished with such a container. The shipper may further serve as a shipper, sorting bin, finished cell shipper, or finished cell sorting bin, in various embodiments.

Claims

1. A container for shipping substrates comprises a pair of container portions engageable together, each container portion having a top, a bottom, and four sides and being a unitarily formed component, each container portion comprising a base portion with a substantially square footprint, and a pair of double wall side walls extending upwardly from the base portion at two of the four sides, each double side wall having a proximal portion adjacent to the base and a distal portion, the other two of the four sides being open, and the top of the container portion being open, the container portion further comprising a first connection structure at the distal portion of one of the two side walls and a second connection structure at the base portion at one of the open sides, the first and second connection structures cooperating to positionally engage the two container portions together whereby an enclosed substrate receiving region is defined by the two engaged container portions.

2. The container of claim 1 wherein the two engagement structures comprise a tongue portion and groove structure defining a groove for receiving the tongue.

3. The container of claim 1 wherein the tongue and groove structure cooperate to secure the pair of container portions together.

4. The container of claim 1 , wherein each of the double sidewalls have a first connection structure and the base has two second connection structures.

5. The container of claim 1 , wherein the two double sidewalls are adjacent to each other.

6. The container of claim 1, wherein the pair of container portions comprise a first container portion and a second container portion and the first container portion is structurally the same as the second container portion.

7. The container of claim 1, wherein the base portion has a plurality of pad portions defined by planar base wall portions surrounded by recessed regions.

8. The container of claim 1 , wherein the recessed regions are defined by a plurality of downwardly extending ribs traversing the base portion.

9. The container of claim 1, wherein each of the container portions has a lower peripheral edge portion that extends entirely around the base portion and defines the outer footprint of the container portion.

10. The container of claim 1, wherein the lower peripheral edge portion flares outwardly.

1 1. The container of claim 1, wherein each of the container portions are nestable within another container portion wherein the double wall portions each define a recess that configured for receiving the double wall portion of another container portion that is structurally the same.

12. The container of claim 1 , wherein each of the base portions has a peripheral recess extending entirely along and being continuous at the lower periphery of the base portion.

13. The container of claim 1 , wherein each of the base portions has an outer peripheral edge portion extending around the peripheral edge of the base portion at each side, and wherein intermediate the peripheral edge portion at each side and the substrate stack receiving region there is U shaped wall portion.

14. The container of claim 1 , the claim of 13 where in there is an additional U shaped wall portion intermediate at each peripheral edge of each side and the substrate stack receiving region for absorbing shock received at the peripheral edge of any of the respective sides.

15. A container for shipping substrates comprises a first container portion and a second container portion structurally the same as the first container portion, each container portion having a top, a bottom, and four sides, each container portion being a unitarily formed component and comprising a base portion with a substantially square footprint and a pair of double wall side walls extending upwardly from the base portion at two adjacent sides of the four sides, each double side wall having a proximal portion adjacent to the base and a distal portion, the other two of the four sides not having double side walls extending upwardly from the base portion, the two double side walls and the two sides not having double side walls defining a substrate stack receiving region, the container portion being open above the substrate stack receiving region, the first and second container portions cooperating to engage one another whereby an enclosure having a box shape with a top side, parallel bottom side, and four sides and an enclosed substrate receiving region is defined.

16. The container of claim 15, wherein the container is molded from one of polymer and organic pulp material.

17. The container of claim 15, wherein the first container portion is structurally the same as the second container portion.

18. A container for shipping rectangular substrates, the container comprising a first container portion and a cooperating second container portion that when assembled form an enclosure with a top, a bottom, and four sides, a substrate stack receiving region defined therein, the substrate stack receiving region defined by a planar bottom surface, a planar top surface, four side wall portions arranged in a rectangular configuration, the container having an upwardly extending top peripheral edge and a downwardly extending bottom peripheral edge, the container having at least one U-shaped shock absorbing structure intermediate each of the peripheral edges and the substrate stack receiving region, the U- shaped structures each having an axis, each of the axis positioned parallel to one of the sides.

19. A container for shipping rectangular substrates, the container comprising a first container portion unitarily formed and a cooperating second container portion unitarily formed that when assembled form an enclosure with a substrate stack receiving region defined therein, the substrate stack receiving region defined by a planar bottom surface, a planar top surface, four side wall portions arranged in a rectangular configuration, each of the side wall surfaces jutting outwardly at the corners to provide four corner recesses whereby when the stack of substrates are in the substrate stack receiving region there is additional separation between the side walls and corners of the stack of substrates.

20. A method of shipping a stack of solar cell substrates, the method comprising:

providing a stack of nested container portions, the container portions each having a base portion and plurality of side walls and cooperating connection structure such that two of the container portions may be assembled together with one inverted from the other to define an enclosed solar cell wafer stack receiving region, each of the side walls having recess where by the side wall of an adjacent container portion can be received in said recess;

selecting a first one of the stack of nested container portions;

seating the stack of solar cell substrates into the first one container portion;

selecting a second one of the stack of container portions; and inverting said container portion with respect to the first one and engaging the second one on the first one to provide an enclosure with the wafer stack enclosed therein.

21. The method of claim 20 further comprising putting cushioning material into the first container portion before seating the stack of solar cell substrates into the first one and adding cushioning material on top of the stack of solar cell substrates before engaging the second one on the first one.

22. The method of claim 20 further comprising repeating the previous steps to provide a multiplicity of enclosures with solar cell substrates and then boxing a plurality of the multiplicity of enclosures, stacking the boxes on a pallet, sleeving and then strapping the boxes to the pallet.

23. A stack of nested container portions, each container portion having a top, a bottom, and four sides and being a unitarily formed component, each container portion comprising a base portion with a substantially square footprint, and a pair of double wall side walls extending upwardly from the base portion at two of the four sides, each double side wall having a proximal portion adjacent to the base and a distal portion, the other two of the four sides being open, and the top of the container portion being open, the container portion further comprising a first connection structure at the distal portion of one of the two side walls and a second connection structure at the base portion at one of the open sides, the first and second connection structures cooperating to positionally engage the two container portions together whereby a closed substrate receiving region is defined by the two engaged container portions.

24. The container of claim 23, wherein the first connection structure and the second connection structure comprises a tongue and groove mechanism.

25. The container of claim 24, wherein the tongue and groove structure provides an interference fit to secure the two container portions together.

26. A stack of structurally the same nested container portions, each container portion having a top, a bottom, and four sides and being a unitarily formed component, each container portion comprising a base portion with a substantially square footprint, and a double wall side wall extending upwardly from the base portion, the double wall side wall having a recess therein receiving a double wall of an adjacent container portion, each container portion having a flared lower skirt with a recess extending continuously and uninterrupted inwardly of the flared lower skirt.

27. The container of claim 26, wherein the container has a maximum laterally extending dimension at each side and the said maximum lateral dimension at each side is at the outer periphery of the flared lower skirt.

28. Any of the above claims wherein each double wall side wall has an interior wall portion partially defining the substrate stack receiving region and an exterior wall outwardly exposed and wherein the interior wall portion is thicker than the exterior wall portion.

29. A container for shipping rectangular substrates, the container comprising a first container portion and a cooperating second container portion that when assembled form an enclosure with a top, a bottom, and four sides, a substrate stack receiving region defined therein, the substrate stack receiving region defined by a planar bottom surface, a planar top surface, four double wall side walls arranged in a rectangular configuration, the container having an upwardly extending top peripheral edge and a downwardly extending bottom peripheral edge, each of the double wall side walls has an interior wall portion partially defining the substrate stack receiving region and an exterior wall outwardly exposed and wherein the interior wall portion is thicker than the exterior wall portion.

30. The container of claim 29 where in each of the double walls has at least one U- shaped shock absorbing structure intermediate each of the peripheral edges and the substrate stack receiving region, the U-shaped structures each having an axis, each of the axis positioned parallel to one of the sides.

31. Any of the containers of the above claims in combination with a stack of substrates.

32. Any of the containers of above claims in combination with a stack of solar cell substrates.

33. A method of manufacturing enclosures for shipping a stack of substrates, the method comprising:

injection molding from a polymer a multiplicity of structurally identical container portions that have a base portion and a plurality of wall portions and that one of said container portions can be inverted to be assembled onto a second of said container portion to form an enclosure with an interior substrate stack receiving region.

34. The method of claim 33 further comprising the step of molding the structurally identical container portions to be nestable within each other.

35. The method of claim 33 further comprising the step of molding the structurally identical container portions to have four double side walls, one on each of four sides.

36. The method of claim 33 further comprising the step of molding the structurally identical container portions to have a plurality of double side walls, each double side wall having an inner portion at the interior substrate stack receiving region and an outer wall portion exteriorly exposed, the inner side wall thicker than the outer side wall.

37. A single container portion combinable with another like single container portion for forming a container for shipping substrates, the container portion having a top, a bottom, and four sides, the container portion being a unitarily formed component and comprising a base portion with a substantially square footprint and a pair of double wall side walls extending upwardly from the base portion at two adjacent sides of the four sides, each double side wall having a proximal portion adjacent to the base and a distal portion, the other two of the four sides not having double side walls extending upwardly from the base portion, the two double side walls and the two sides not having double side walls defining a substrate stack receiving region.