WO2016149209A1

WO2016149209A1 - Modified spring cushion for film frame shipper

Info

Publication number: WO2016149209A1
Application number: PCT/US2016/022355
Authority: WO
Inventors: Jason Todd Steffens; Russ V. Raschke
Original assignee: Entegris, Inc.
Priority date: 2015-03-13
Filing date: 2016-03-14
Publication date: 2016-09-22
Also published as: TWM510539U; CN107534006B; TWI693658B; JP2018509767A; JP6523479B2; CN107534006A; TW201703175A

Abstract

A film frame shipper that provides enhanced prevention of the jumping of film frames within the film frame shipper. In addition, the structures that prevent jumping also augment alignment of the film frames during loading into the shipper. Furthermore, in certain embodiments, these structures enable a closer tolerance fit between the thickness of the film frames and the registration slots, thereby reducing play between the film frame and the registration slot and attendant particle generation.

Description

MODIFIED SPRING CUSHION FOR FDLM FRAME SHD7PER

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/133,131, filed on March 13, 2015, the disclosure of which is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

The disclosure is directed generally to wafer shippers and more specifically to film frame or tape frame shippers.

BACKGROUND OF THE DISCLOSURE Film frames or tape frames are generally comprised of a stainless-steel frame with a film extending across the frame. The film has an adhesive on one side thereof. After being processed, a round semiconductor wafer is typically placed on the film. After being positioned on the film, the semiconductor wafer may be sectioned into individual pieces (e.g., chips), transported for further processing, or stored. The semiconductor processing industry is using larger and thinner wafers that present processing, transportation, and storage handling challenges due to their greater fragility. To this end, conventional film frame wafer carriers can be improved upon for handling film frames with these larger and thinner wafers.

Film frame shippers are widely used in the semiconductor manufacturing industry for shipping film frames. A variety of film frame shippers provide a safe and effective way to ship and store up to 25 wafers, or singulated die, mounted to film frames. A replaceable top cover cushion allows for reuse of the shipper. Film frame shippers are available for film frames used to ship wafers of 300mm, 200mm and 150mm diameter.

Film frames that are loaded within conventional film frame shippers have been known to "jump" during an impact event. For example, when the film frame shipper is dropped on a corner, the significant weight of the film frames therein can cause momentary deformation of the shape of the polymer and the inertial forces of the film frames contained therein can cause the film frames to become dislodged from their designated registration slots and contact adjacent film frames and wafers thereon or the shipper, causing damage to the respective wafers.

Referring to FIG. 5, a known film frame 40 is depicted. The film frame 40 includes a frame 42 that defines an outer edge 44. An adhesive membrane 46 spans the frame 42, to which a wafer 48 is adhered. When the film frames are dislodged during an impact event, the wafers on the dislodged film frames can contact other wafers, frames 42, or portions of the shipper, causing damage to the wafers.

A film frame shipper that more reliably retains film frames in a designated registration position during impact events would be welcomed. SUMMARY OF THE DISCLOSURE

Various embodiments of the disclosure provide enhanced prevention against the jumping of film frames within a film frame shipper. In addition, the structures that prevent jumping also augment alignment of the film frames during loading into the shipper. Furthermore, in certain embodiments, these structures enable a closer tolerance fit between the thickness of the film frames and the registration slots, thereby reducing play between the film frame and the registration slot and attendant particle generation.

Each wafer is supported on a metal or polymer wafer support ring or frame. The wafer support rings are received in and retained by a spring cushion positioned at the top and/or bottom of the film frame shipper. The spring cushion exerts a radial force on the film frames to secure each film frame within a respective registration slot, thereby reducing movement of the film frame within the registration slot and reducing particle transfer or generation during shipping. In some embodiments, the spring cushions are removable and/or replaceable and may include snap features facilitating coupling of the spring cushions to the shipper. Additional features of the film frame shipper include: a positive snap latch for securing closure of the shipper; a non-obtrusive latch and stackable design for reducing storage space and shipping costs; and rounded corners and sloped sides for reducing water entrapment during cleaning. The film frame shipper is available in ESD safe materials. Radio frequency identification (RFID) and laser marking options are also available. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembly view of a film frame shipper and resident film frame in an embodiment of the disclosure.

FIG. 2A is a schematic of a film frame being loaded into a receptacle of the film frame shipper of FIG. 1.

FIG. 2B is a perspective view of a film frame receptacle loaded with film frames.

FIG. 3 is a perspective view of the film frame shipper of FIG. 1.

FIG. 4A is a sectional view of the film frame shipper of FIG. 1.

FIG. 4B is a perspective sectional view of the film frame shipper with film frames of FIG. 1.

FIG. 5 is a plan view of a prior art film frame.

FIG. 6 is a perspective view of a spring frame cushion in an embodiment of the disclosure.

FIG. 6A is an enlarged perspective view of the spring frame cushion of FIG. 6 in an embodiment of the disclosure.

FIG. 7 is a perspective view of a spring frame cushion in an embodiment of the disclosure.

FIG. 8 is a sectional view of either of the spring frames of FIGS. 6 or 7.

FIG. 8A is a perspective view of the inside of the top cover of the film frame shipper of FIG. 1 illustrating attachment posts for receiving the spring frame.

FIG. 8B is the view of FIG. 8A with the spring frame received therein.

FIG. 9 is a perspective sectional view of a film frame shipper in an embodiment of the disclosure. FIG. 10 is an enlarged perspective sectional view of a side comb structure of FIG. 9 in an embodiment of the disclosure.

FIG. 11 is an enlarged perspective sectional view of bottom comb structures of FIG. 9 in an embodiment of the disclosure. FIG. 12 is a sectional schematic of a film frame shipper having an upper spring frame cushion and a lower spring frame cushion in an embodiment of the disclosure.

FIG. 13 is a sectional schematic of a film frame shipper having an upper spring frame cushion and a pair of lower spring frame cushions in an embodiment of the disclosure. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-4 depict a film frame shipper 20 in an embodiment of the disclosure. The film frame shipper 20 includes a receptacle 22 and a cover 24 that forms a closure over the receptacle portion to define an interior chamber 26 for storing a plurality of film frames 28. The receptacle 22 includes side portions 32 which can include guides 34 for guiding the film frames 28 into the receptacle 22 (FIG. 2). A spring frame cushion 36 is coupled to at least one of the receptacle 22 and the cover 24. In one embodiment, the frame cushion 36 is detachably mounted to slotted rails 38 on the receptacle 22 or cover 24. As shown, the film frames 28 are directed into the interior chamber 26 of the receptacle 22 in a direction A and the cover 24 is then moved in the same direction A to couple with the receptacle 22.

Referring to FIGS. 6 through 8, versions of the spring frame 36 are depicted in embodiments of the disclosure. The spring frames 36 are referred to specifically as spring frame 36a (FIG. 6) and spring frame 36b (FIG. 7), and generically or collectively as spring frame(s) 36. The spring frame 36 includes opposing rails or side walls 52, 54 that extend in a fore/aft direction 56 and that connect to end walls 55, 57 forming a rectangular framework 59. The rails support a main cushion portion 58 spanning therebetween with a plurality spring cushion elements 60. Each spring cushion element 60 defining a registration slot 62. Each of the plurality of registration slots 62 extend in a lateral direction 64 orthogonal to the fore/aft direction 56, the registration slots 64 being adapted to capture the outer edge 44 of the film frame 40 to restrict movement of the film frame 40 in the fore/aft direction 56.

In various embodiments, a first comb structure 72 includes a plurality of first comb protrusions 74 that extend in a vertical direction 76 from the first opposing side wall 52 of the spring frame cushion 36. (The vertical direction 76 is orthogonal to the fore/aft direction 56 and orthogonal to the lateral direction 64.) The plurality of first comb protrusions 74 are spaced apart from one another to define a plurality of first comb gaps 78. Each protrusion has a straight portion 79 and a tapered portion 80. Adjacent first comb protrusions of the plurality of first comb protrusions 74 are adapted to engage and receive the outer edge of the film frame 40, and each of the plurality of first comb gaps 78 is defined between adjacent ones of the first comb protrusions 74 of the first comb structure 72, the plurality of comb gaps 78 being adapted to capture the outer edge 44 of the film frame 40 to restrict movement of the outer edge 44 in the fore/aft direction 56. Also, each of the plurality of registration slots 62 is in alignment with a respective one of the plurality of first comb gaps 78 in the lateral direction 64.

In some embodiments, a second comb structure 82 includes a plurality of second comb protrusions 84 that extend in the vertical direction 76 from the second opposing side wall 54 of the spring frame cushion 36. The plurality of second comb protrusions 84 are spaced apart from one another to define a plurality of second comb gaps 88. Adjacent ones of the plurality of second comb protrusions 84 are adapted to engage and receive the outer edge 44 of the film frame 40, and each of the plurality of second comb gaps 88 is defined between adjacent ones of the plurality of second comb protrusions 84 of the second comb structure 82, each of the plurality of second comb gaps 88 being adapted to capture the outer edge 44 of the film frame 40 to restrict movement of the outer edge 44 in the fore/aft direction 56. Also, each of the plurality of registration slots 62 is in alignment with a respective one of the plurality of second comb gaps 88 in the lateral direction 64.

In various embodiments, as best viewed in FIG. 6A, at least a portion of the plurality of first comb protrusions 74 and/or the plurality of second comb protrusions 84 each include a proximal end 92 and a distal end 94 and defines a tapered profile 96 projected in the lateral direction 64. The tapered profile 96 can be symmetrical about a protrusion axis 98 (FIG. 6A) that extends in the vertical direction 76, the tapered profile 96 sloping toward the protrusion axis 98 from the proximal end 92 to the distal end 94. In one embodiment, at least a portion of the tapered profile 96 is arcuate (not depicted).

In one embodiment, the main cushion portion 58 defines a plurality of through- slots 102, each of the plurality of through slots 102 (FIG. 7) being disposed between adjacent spring cushion elements 60 each with respective registration slots 62.

Referring to FIGS. 8 through 9, the spring frame cushion 36 is attached to the cover 24 by way of an interference fit with tapered posts 104 unitary with and extending from the inside surface 106 of the cover 24. The posts form slots 105 that such that the rails are tight enough therein to frictionally secure the spring frame cushion to the top cover. The top cover 24 and receptacle 22 have ribs 107 defining slots 108 for receiving and constraining the film frames.

Referring to FIGS. 9 through . 11, other comb structures are disclosed in embodiments of the disclosure. In one embodiment, at least one base comb structure 1 10 is disposed on a base portion 112 of the receptacle 22, the base comb structure 1 10 including a plurality of base comb protrusions 114 extending in the vertical direction 76 into the interior chamber 26 from the base portion of the receptacle 22. The plurality of base comb protrusions 114 are being spaced apart from one another to define a plurality of base comb gaps 118. Adjacent ones of the plurality of base comb protrusions 1 14 are adapted to engage and receive the outer edge 44 of the film frame 40, and each of the plurality of base comb gaps 1 18 is defined between adjacent ones of the plurality of base comb protrusions 114 of the base comb structure 110.

The plurality of base comb gaps 118 are adapted to capture the outer edge 44 of the film frame 40 to restrict movement of the outer edge 44 in the fore/aft direction 56. Also, each of the plurality of registration slots 62 of the spring frame cushion 36 is in planar alignment with a respective one of the plurality of base comb gaps 1 18. That is, each of the base comb gaps 118 is centered on a plane that is also centered on one of the registration slots 62, the plane being orthogonal to the fore/aft direction 56. In one embodiment, at least a portion of the plurality of base comb protrusions 114 include the tapered profile depicted in FIG. 6 A.

In one embodiment, a registration rail 1 16 projects from the base portion and extends in the fore/aft direction 56, the registration rail defining a rail height 122 in the vertical direction 76 above the base portion 112 of the receptacle 22, wherein a proximal extremity 124 (i.e., the "bottom" of the gap 118) of each of the plurality of base comb gaps 118 defines a gap offset 126 from the base portion 112 that is less than the rail height 122 (FIG. 11), and wherein a distal extremity 128 of each of the plurality of base comb protrusions 114 relative to the base portion 112 defines a protrusion height 132 that is greater than the rail height 122.

Functionally, because the rail height 122 is greater than the gap offset 126 from the base portion 112, a film frame 40 that is inserted into the base comb 112 will rest on the registration rail 116. This can relive the base comb 1 10 from certain stresses, and provide a more accurate registration of the film frame 40 within the film frame shipper 20.

In some embodiments, at least one side comb structure 140 disposed on the side portion 32 of the receptacle 22, the side comb structure 140 including a plurality of side comb protrusions 142 extending in the vertical direction 76 into the interior chamber 26. The plurality of side comb protrusions 142 spaced apart from one another to define a plurality of side comb gaps 148. Adjacent ones of the plurality of side comb protrusions 142 are adapted to engage and receive the outer edge 44 of the film frame 40, each of the side plurality of side comb gaps being defined between the adjacent side comb protrusions of the side comb structure.

The plurality of side comb gaps are adapted to capture the outer edge 44 of the film frame 40 to restrict movement of the outer edge 44 in the fore/aft direction 56. Also, each of the plurality of registration slots 62 of the spring frame cushion 36 is in planar alignment with a respective one of the plurality of side comb gaps 148. In one embodiment, at least a portion of the plurality of side comb protrusions 142 include the tapered profile depicted in FIG. 6A. In various embodiments, and in reference to FIG. 8, each of the plurality of first comb gaps 78 and second comb gaps 88 defines gap depth 152 having a proximal extremity 154. Each of the plurality of first and second comb protrusions 74, 84 defines a protrusion height 156 in the vertical direction 76 from the proximal extremity 154 of an adjacent one of the plurality of first and second comb gaps 78, 88 to a distal extremity 158 of an adjacent one of the plurality of first/second comb protrusions 74, 84. Each of the plurality of registration slots 62 defines a slot depth 162 in the vertical direction 76 relative to an upward face 164 of the main cushion 58.

In various embodiments, a ratio of the protrusion height 152 to the slot depth 162 is in a range of 1.5 to 5 inclusive. In some embodiments, the ratio is in a range of 2 to 4 inclusive. In some embodiments, the ratio is in a range of 2.5 to 3.5 inclusive. (Herein, a range that is said to be "inclusive" includes the endpoints of the stated range.) In all of these embodiments, the first and second comb protrusions 74, 84 are greater than the slot depth 162.

Functionally, the first and second comb protrusions 74, 84 being greater than the slot depth 162 helps to prevent or counter "jump" of the film frame 40 during an impact event. The depictions presented herein depict the spring frame cushion 36 in an undeflected state; upon being loaded with a film frame 40, the main cushion 58 will deflect so that a bottom of the slot 166 is at the same level as the proximal extremities 154. Accordingly, if the film frame 40 "jumps" the registration slot 62, the greater height of the protrusions 78, 88 will arrest the outer edge 44 of the film frame 40 and redirect the film frame 40 back into the registration slot 62.

Referring again to FIG. 6A, in one embodiment, at least a portion of the plurality of first and second comb gaps 78, 88 each define a minimum gap dimension 172 in the fore/aft direction 56. The minimum gap dimension 172 can be dimensioned for a close sliding fit with the film frame 40. In some embodiments, the minimum gap dimension 172 is in the range of 0.05 inches and 0.085 inches inclusive. In some embodiments, the minimum gap dimension 172 is in the range of 0.055 inches and 0.075 inches inclusive. In some embodiments, the minimum gap dimension 172 is in the range of 0.055 inches and 0.065 inches inclusive. Functionally, the tighter tolerance of the minimum gap dimension 172 relative to the outer edge 44 of the film frame 40 holds the film frame 40 more tightly, thereby reducing movement of the film frame 40 in the fore/aft direction 56, which acts to reduce particle generation. Meanwhile, the slots 62 can remain oversized in order to accommodate easy alignment during loading and re-alignment during an impact event. In various embodiments, the spring frame cushion 36 is detachable from the film frame shipper 20 by being mounted by a press fit into the slotted rails 38. Referring to FIG. 12, a first spring frame cushion 36 disposed on the cover and a second spring frame cushion 36 disposed on the receptacle.

Referring to FIG. 13, a third spring frame cushion 36 is disposed on the receptacle.

In various embodiments, and again in reference to FIGS. 6 and 7, the spring frame cushion 32 includes a continuous frame 182. The continuous frame 182 includes four walls to define four corners 184. For the spring frame cushion 36b, first and second comb structures 72 and 82 includes protrusions 186 that extends around the four corners 184.

Claims

CLAIMS claimed is: A film frame shipper comprising: a receptacle; a cover that forms a closure over said receptacle portion to define an interior chamber; a spring frame cushion coupled to at least one of said receptacle and said cover, said spring frame including opposing side walls that extend in a fore/aft direction and that support a main cushion portion, said main cushion portion defining a plurality of registration slots, each of said plurality of registration slots extending in a lateral direction orthogonal to said fore/aft direction and being adapted to capture an outer edge of a film frame to restrict movement of said film frame in said fore/aft direction; and a first comb structure including a plurality of first comb protrusions that extend in a vertical direction from a first of said opposing side walls of said spring frame cushion, said plurality of first comb protrusions being spaced apart from one another to define a plurality of first comb gaps, said vertical direction being orthogonal to said fore/aft direction and orthogonal to said lateral direction, wherein adjacent ones of said plurality of first comb protrusions are adapted to engage and receive said outer edge of said film frame, and each of said plurality of first comb gaps is defined between adjacent ones of said first comb protrusions of said first comb structure, each of said plurality of said first comb gaps being adapted to capture said outer edge of said film frame to restrict movement of said outer edge in said fore/aft direction, and wherein each of said plurality of registration slots is in alignment with a respective one of said plurality of first comb gaps in said lateral direction.

2. The film frame shipper of claim 1, comprising: a second comb structure including a plurality of second comb protrusions that extend in said vertical direction from a second of said opposing side walls of said spring frame cushion, said plurality of second comb protrusions being spaced apart from one another to define a plurality of second comb gaps, wherein adjacent second comb protrusions of said plurality of second comb protrusions are adapted to engage and receive said outer edge of said film frame, and a second comb gap of said plurality of second comb gaps is defined between said adjacent second comb protrusions of said second comb structure, said second comb gap being adapted to capture said outer edge of said film frame to restrict movement of said outer edge in said fore/aft direction, and wherein each of said plurality of registration slots is in alignment with a respective one of said plurality of second comb gaps in said lateral direction.

3. The film frame shipper of claim 1, wherein said main cushion portion defines a plurality of through-slots, each of said plurality of through slots being disposed between adjacent registration slots of said plurality of registration slots.

4. The film frame shipper of any one of claims 1-3, comprising at least one base comb structure disposed on a base portion of said receptacle, said base comb structure including a plurality of base comb protrusions extending in said vertical direction into said interior chamber from said base portion of said receptacle, said base comb structure including a plurality of base comb protrusions spaced apart from one another to define a plurality of base comb gaps, wherein adjacent ones of said plurality of base comb protrusions are adapted to engage and receive said outer edge of said film frame, each of said plurality of base comb gaps being defined between adjacent ones of said plurality of base comb protrusions, said plurality of base comb gaps being adapted to capture said outer edge of said film frame to restrict movement of said outer edge in said fore/aft direction, and wherein each of said plurality of registration slots of said spring frame cushion is in planar alignment with a respective one of said plurality of base comb gaps.

5. The film frame shipper of claim 4, comprising a registration rail that projects from said base portion and extends in the fore/aft direction, said registration rail defining a rail height in said vertical direction above said base portion of said receptacle, wherein a proximal extremity of each of said plurality of base comb gaps defines a gap offset from said base portion that is less than said rail height, and wherein a distal extremity of each of said plurality of base comb protrusions relative to said base portion defines a protrusion height that is greater than said rail height.

6. The film frame shipper of claim 4, comprising: at least one side comb structure disposed on a side portion of said receptacle, said side comb structure including a plurality of side comb protrusions extending in said vertical direction into said interior chamber, said side comb structure including a plurality of side comb protrusions spaced apart from one another to define a plurality of side comb gaps, wherein adjacent ones of said plurality of side comb protrusions are adapted to engage and receive said outer edge of said film frame, each of said plurality of side comb gaps being defined between adjacent ones of said plurality of side comb protrusions, each of said plurality of side comb gaps being adapted to capture said outer edge of said film frame to restrict movement of said outer edge in said fore/aft direction, and wherein each of said plurality of registration slots of said spring frame cushion is in planar alignment with a respective one of said plurality of side comb gaps.

7. The film frame shipper of claim 6, wherein at least a portion of said plurality of first comb protrusions, said plurality of second comb protrusions, said plurality of base comb protrusions, and/or said plurality of side comb protrusions each include a proximal end and a distal end and defines a tapered profile projected in said lateral direction, said tapered profile being symmetrical about a protrusion axis that extends in said vertical direction, said tapered profile sloping toward said protrusion axis from said proximal end to said distal end.

8. The film frame shipper of claim 7, wherein at least a portion of said tapered profile is arcuate.

9. The film frame shipper of claim 7, wherein: each of said plurality of first comb gaps defines a gap depth having a proximal extremity; each of said plurality of first comb protrusions defines a protrusion height in said vertical direction from said proximal extremity of an adjacent one of said plurality of first comb gaps to a distal extremity of an adjacent one of said plurality of first comb protrusions; each of said plurality of registration slots defines a slot depth in said vertical direction relative to an upward face of said main cushion; and a ratio of said protrusion height to said slot depth is in a range of 1.5 to 5 inclusive.

10. The film frame shipper of claim 9, wherein said ratio is one of a group of ranges consisting of a range of 2 to 4 inclusive and a range of 2.5 to 3.5 inclusive.

11. The film frame shipper of claim 6, wherein at least a portion of said plurality of first comb gaps, said plurality of second comb gaps, said plurality of base comb gaps, and/or said plurality of side comb gaps each define a minimum gap dimension in said fore/aft direction, said minimum gap dimension being dimensioned for a close sliding fit with said film frame.

12. The film frame shipper of claim 11, wherein said minimum gap dimension is one of a group of minimum gap dimensions consisting of a range of 0.05 inches and 0.085 inches inclusive, a range of 0.055 inches and 0.075 inches inclusive, and a range of 0.055 inches and 0.065 inches inclusive.

13. The film frame shipper of claim 1, wherein said at least one spring frame cushion is detachable from said film frame shipper.

14. The film frame shipper of claim 1 or claim 13, wherein said at least one spring frame cushion includes a first spring frame cushion disposed on said cover and a second spring frame cushion disposed on said receptacle.

15. The film frame shipper of claim 14, wherein said at least one spring frame cushion includes a third spring frame cushion disposed on said receptacle.

16. The film frame shipper of claim 1, comprising at least one film frame disposed therein.

17. A spring frame cushion for coupling to a film frame shipper, the spring frame cushion comprising: opposing sides extending in a fore/aft direction and that support a main cushion portion, said main cushion portion defining a plurality of registration slots, each of said plurality of registration slots extending in a lateral direction orthogonal to said fore/aft direction and being adapted to capture an outer edge of a film frame to restrict movement of said outer edge in said fore/aft direction; and a first comb structure including a plurality of first comb protrusions that extend in a vertical direction from a first of said opposing sides of said spring frame cushion and spaced apart from one another to define a plurality of first comb gaps, said vertical direction being orthogonal to said fore/aft direction and orthogonal to said lateral direction, wherein adjacent ones of said plurality of first comb protrusions are adapted to engage and receive said outer edge of said film frame, and each of said plurality of first comb gaps is defined between adjacent ones of said first comb protrusions of said first comb structure, each of said plurality of said first comb gaps being adapted to capture said outer edge of said film frame to restrict movement of said outer edge in said fore/aft direction, and wherein each of said plurality of registration slots is in alignment with a respective one of said plurality of first comb gaps in said lateral direction.

18. The spring frame cushion of claim 17, comprising: a second comb structure including a plurality of second comb protrusions that extend in said vertical direction from a second of said opposing side walls of said spring frame cushion, said plurality of second comb protrusions being spaced apart from one another to define a plurality of second comb gaps, wherein adjacent ones of said plurality of second comb protrusions are adapted to engage and receive said outer edge of said film frame, and each of said plurality of second comb gaps is defined between adjacent ones of said plurality of second comb protrusions of said second comb structure, each of said plurality of second comb gaps being adapted to capture said outer edge of said film frame to restrict movement of said outer edge in said fore/aft direction, and wherein each of said plurality of registration slots is in alignment with a respective one of said plurality of second comb gaps in said lateral direction.

19. The spring frame cushion of claim 17, wherein said main cushion portion defines a plurality of through-slots, each of said plurality of through slots being disposed between adjacent registration slots of said plurality of registration slots.

20. The spring frame cushion of claim 17, wherein at least a portion of said plurality of first comb protrusions each include a proximal end and a distal end and defines a tapered profile projected in said lateral direction, said tapered profile being symmetrical about a protrusion axis that extends in said vertical direction, said tapered profile sloping toward said protrusion axis from said proximal end to said distal end.

21. The spring frame cushion of claim 20, wherein at least a portion of said tapered profile is arcuate.

22. The spring frame cushion of claim 20, wherein: each of said plurality of first comb gaps defines a gap depth having a proximal extremity; each of said plurality of first comb protrusions defines a protrusion height in said vertical direction from said proximal extremity of an adjacent one of said plurality of first comb gaps to a distal extremity of an adjacent one of said plurality of first comb protrusions; each of said plurality of registration slots defines a slot depth in said vertical direction relative to an upward face of said main cushion; and a ratio of said protrusion height to said slot depth is in a range of 1.5 to 5 inclusive.

23. The spring frame cushion of claim 25, wherein said ratio is one of a group of ranges consisting of a range of 2 to 4 inclusive and a range of 2.5 to 3.5 inclusive.

24. The spring frame cushion of claim 17, wherein at least a portion of said plurality of first comb gaps each define a minimum gap dimension in said fore/aft direction, said minimum gap dimension being dimensioned for a close sliding fit with said film frame.

25. The spring frame cushion of claim 24, wherein said minimum gap dimension is one of a group of minimum gap dimensions consisting of a range of 0.05 inches and 0.085 inches inclusive, a range of 0.055 inches and 0.075 inches inclusive, and a range of 0.055 inches and 0.065 inches inclusive.

26. The spring frame cushion of claim 17, wherein said opposing side walls are part of a continuous frame.

27. The spring frame cushion of claim 26, wherein said continuous frame includes four side walls to define four corners.

28. The spring frame cushion of claim 27, wherein said first comb structure includes protrusions that extends around two of said four corners.