Abstract:
A stencil assembly includes a stencil foil, having a stencil pattern thereon and of a planar configuration, with a peripheral edge, which is a captured by rigid frame. The rigid frame includes a base and a cover attached thereto. The assembly adapts a standard stencil foil for use in a stretch frame that requires an elongated groove. The assembly thereby facilitates mounting the stencil to a stretching machine during printing. Also, the stencil assembly protects a user from injury by preventing contact with the sharp outer edges of the stencil foil. Further, the assembly protects the stencil foil portion from damage and greatly facilitates handling thereof.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is related to and claims priority to earlier filed U.S. provisional patent application 61/916,972, filed Dec. 17, 2013, and the entire contents thereof is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to the manufacture of circuit boards and pertains, more specifically, to the placement of pads of solder paste in a prescribed pattern on a printed circuit board being prepared for the surface mounting of components onto the circuit board by subsequent soldering. 
     Current manufacturing techniques for making printed circuit boards call for the mounting of components to the circuit board by “surface mounting”. That is, rather than passing the leads of a component through holes in a circuit board and then soldering the leads at the holes, the circuit board is provided with pads of solder paste and the components are placed on the pads for soldering directly to the surface of the board. 
     In order to place the pads of paste in appropriate locations on the circuit board, just before affixing the components to the board, a stencil-like screen or foil is juxtaposed with the circuit board and provides a pattern of openings registered with the locations where the pads are to be placed. The paste then is spread over the screen with a squeegee to lay down the pattern of pads. The stencil screen is in the form of a thin foil, which is supported by a stretcher frame in an appropriately tensioned state. The frame fits into a machine, which registers the tensioned screen with the circuit board and then applies the paste. Typically, the machine also stretches the stencil foil to achieve the desired tension of the stencil to ensure accuracy during printing. 
     However, the foregoing stencils pose serious safety and operational problems and are difficult to securely mount to a stretcher apparatus. For example, traditional foil stencils are potential safety hazards to those technicians that handle them due to the presence of sharp edges around the entire periphery of the foil stencil. Such sharp edges can easily cut a person handling the foil stencil and putting them at risk of exposure to infection. This is a particular concern due to the presence of solder paste, which can be toxic, in the work environment. In light of the aforementioned safety hazards, transportation and storage of foil stencils are problematic because technicians are constantly transporting foil stencils to and from a storage location during the normal course of circuit board manufacture. During this normal handling, the foil stencil undergoes bending, for example, that threatens its integrity. As a result, foil stencils are prone to damage. 
     There have been many attempts in the prior art to address the foregoing problems with foil stencils relating to safety to the handler and damage during handling and storage. For example, it is common in the prior art to mount foil stencils to an aluminum frame with a polyester border to ensure proper tensioning of the foil stencil. While the encapsulation of the periphery of the foil stencil with polyester keeps the foil tight and covers the sharp edges from the handler, it is time consuming and expensive to encapsulate the foil stencil and requires special molding machinery. As a result, such polyester encapsulated foil stencils require an additional preparation step, which typically requires outsourcing to a special subcontractor for such operation. Moreover, these encapsulated foil stencils are difficult to store and cannot be easily retrieved when stacked. 
       FIG. 1  shows a prior art stencil foil assembly  10  that has a frame  12  on which a stencil foil  14  can be supported. Mounting apertures  16  on the stencil foil  14  are spaced apart and arranged to engage an array of studs  18  that extend upwardly on the frame  12  when the stencil foil  14  is placed on the frame  12 . The frame  12  engages a stretching machine (not shown), so that stretching of the frame  12  pulls the stencil foil  14  into tension. A stencil pattern  20  is shown towards the center of the stencil foil of  FIG. 1 . 
     In view of the foregoing, there is a demand for a frame for a foil stencil assembly that protects that handler from the sharp edges to avoid injury. There is a further demand for a foil stencil assembly that can be easily stored and retrieved. There is a demand for a foil stencil assembly that can lay flat or hang from a vertical hook in a high density storage cabinet. There is a further demand for a foil stencil assembly that is inexpensive and easy to assemble without special tools or special equipment. There is also a demand for a foil stencil assembly that has stencil tension that does not decrease over time and is machine washable. In addition, there is a further demand for a foil stencil assembly with a large print area. 
     Also, in the prior art, there is need to facilitate adapting a stencil foil for mounting thereof to a stretcher frame. It is known in the art to bend the peripheral edges of the stencil foil so such periphery can be gripped and secured by a stretching apparatus. However, this requires that a custom stencil frame be created to provide such bent free edges. Moreover, these bent edges are difficult to form and can easily break. 
     Therefore, there is a need for a stencil foil assembly that can be easily affixed to existing and standard stencil foils to provide a rigid frame for securing the entire assembly into a stretching apparatus for printing. 
     SUMMARY OF THE INVENTION 
     The present invention preserves the advantages of prior art stencil foil assemblies for the surface mount solder paste stencil printing industry. In addition, it provides new advantages not found in currently available assemblies and overcomes many disadvantages of such currently available assemblies. 
     The present invention preserves the advantages of prior art stencil foil assemblies for the surface mount solder paste stencil printing industry. In addition, it provides new advantages not found in currently available assemblies and overcomes many disadvantages of such currently available assemblies. 
     The invention is generally directed to a stencil foil assembly includes a stencil foil, having a stencil pattern thereon, of a planar configuration. The assembly also includes a rigid frame with a base and a cover. 
     Generally, a stencil foil assembly kit for holding a stencil foil has a base, a cover, and an engagement member. The base has a top surface that provides an upper surface for supporting a peripheral portion of a stencil foil. A plurality of apertures are defined along the top surface of the base, and a plurality of apertures are defined along the peripheral edge of the stencil foil. The apertures on the base are spaced to each be in alignment with one of the stencil apertures when the stencil is supported on the base. 
     The cover has a main body that has a lower surface for engaging a stencil. A plurality of snap posts extend from the main body, and are each configured to be respectively routed through the stencil apertures and to be in secured engagement with the base apertures, thereby sandwiching a peripheral portion of the stencil foil between the top surface of the base and the lower surface of the cover. 
     An engagement member is secured to (or formed integrally on) the cover, the base, or both the cover and the base. The engagement member is configured to engage a stretch frame apparatus. 
     A manufacturer provides a user with components described herein for forming a stencil foil assembly for protecting and supporting a stencil foil. In the preferred embodiment, the assembly includes a set of base members and a set of cover members. In the preferred embodiment, there are four congruent base members for forming a base and four congruent cover members for forming a cover. The user assembles the base members to form a base, which is configured to extend around the peripheral edge of a stencil foil. In the preferred embodiment, the stencil foil has a substantially square peripheral edge when viewed from above, and the base members form a base that is substantially square when viewed from above. The user then places the stencil foil onto the assembled base, so the peripheral edge of the stencil foil is supported on an upper surface of the base. Finally, the user places the cover members over the stencil, so the peripheral edges of the stencil are sandwiched between the cover and the base. In particular, each of the four sides of the square stencil foil is secured between a respective mating pair of a base member and a cover member. 
     The assembly further includes an engagement member for engaging a stretch frame apparatus, which is typically provided to the user separately from the stencil frame of the present invention. The engagement member can be formed integrally with the cover member, or can be formed by formations on the cover member and the base member. Although not shown herein, the engagement member could also be formed integrally with the base member. 
     In the preferred embodiment, the engagement member is integrally formed with the cover. Each cover member has an inwardly sloped cover grip surface that is formed adjacent the lower surface of the cover. Together, these inwardly sloped cover grip surfaces form the engagement member. 
     The base members are congruent, and each base member has a male post located at the first end of the base member and a female socket defined in the female socket housing at the second end of the base member. When the base members are brought together to form a base, the male post of one base member is received in the female socket of an adjacent base member. 
     The lower surface of the male post and the upper surface of the male post are configured and arranged to be in facing engagement with a lower female socket surface and an upper female socket surface, respectively, when the male post is received in the female socket of an adjacent base member. This provides a snug, friction fit between the respective male post and the respective female socket of adjacent base members. 
     The side surfaces of the post are in facing relation with side surface of the female socket, but there is a gap between the sides of the post and the sides of the socket in the preferred embodiment. 
     The male post extends longitudinally along the axis of the base member and in a horizontal direction from a male post platform on the base member. The female socket is formed in a female socket housing. 
     In the preferred embodiment, each cover member is dimensioned and configured to extend between the male post platform and the female socket housing on its respective base member. 
     In the first embodiment, each cover member is secured to each respective base member by snap posts. Each snap post includes a substantially cylindrical post wall with a tapered latching formation at its lower end. The latching formation has an annular latching face. Each base member has apertures for respectively receiving the snap posts. Each base aperture has an annular post retention face extending between an annular base aperture wall and a recessed annular wall. The annular post retention face is configured to engage the annular latching face of a respective snap post for retaining the respective snap post within the aperture. 
     When the base members are assembled, and when the cover members are secured to their respective base members, an outer peripheral edge of the assembly is defined by the outer peripheral edge of the female socket housing and the outer peripheral edge of the cover members. The outer peripheral edge of the assembly allows a user to easily, safely, and comfortably grip the assembly. 
     In a second embodiment, the base has a generally L-shaped profile with an upstanding wall and a support flange emanating inwardly from the upstanding wall. The stencil foil resides on the support flange with the bottom surface of the periphery of the stencil foil being in communication with the top surface of said support flange. The outer edge of the stencil foil is positioned adjacent to the inner surface of said upstanding wall. The periphery of the stencil foil is secured to the rigid frame. The stencil foil assembly protects a user from injury by preventing contact with the sharp outer edges of the stencil foil and also provides a structure for interconnecting the assembly to a stretch frame for printing. The assembly protects the stencil foil portion from damage, maintains it in a tensioned condition and greatly facilitates handling thereof. 
     The stencil foil is secured to the support flange of the outer rigid frame by use of a snap-on cover. The cover includes downwardly depending studs that engage female apertures in the stencil and corresponding apertures in the base. When the base and cover are installed on the periphery of the stencil foil, the edge of the stencil foil is protected and a structure is provided so that the entire stencil foil assembly can be secured to a stretching frame. 
     It is therefore an object of the present to provide a stencil foil assembly that protects the user from injury from sharp edges during handling of the foil. 
     Another object of the present invention is to provide a stencil foil assembly that protects the stencil foil from damage during shipping and handling. 
     There is another object of the present invention to provide an outer frame to facilitate interconnection of a stencil foil to a stretch frame. 
     It is a further object of the present invention to provide a stencil foil assembly that is inexpensive and easy to manufacture and assemble. 
     Another object of the present invention is to provide a stencil foil assembly that reduces setup time and the need for tools for such setup. 
     Yet a further object of the invention is to enable a standard stencil to be easily and quickly modified for use in a stretch frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features which are characteristic of the present invention are set forth in the appended claims. However, the invention&#39;s preferred embodiments, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a stencil foil assembly of the prior art; 
         FIG. 2  is a perspective view of the preferred embodiment of the stencil foil assembly of the present invention; 
         FIG. 3  is a perspective view of a stencil foil that is supported in the stencil foil assembly of  FIG. 2 ; 
         FIG. 4  is a perspective view of the base of the stencil foil assembly of  FIG. 2 ; 
         FIG. 5  is a perspective view of the base of  FIG. 4  with a stencil foil placed thereon; 
         FIG. 6  is a side view of a base member for constructing the base of the preferred embodiment; 
         FIG. 7  is a perspective view of a first end of the base member of  FIG. 6 ; 
         FIG. 8  is a side view thereof; 
         FIG. 9  is a perspective view of a second end of the base member of  FIG. 6 ; 
         FIG. 10  is a cross sectional view through a male post and female socket of  FIG. 2 ; 
         FIG. 11  is a perspective view of a cover member of the assembly of  FIG. 2 ; 
         FIG. 12  is a bottom view thereof; 
         FIG. 13  is a side view thereof; 
         FIG. 14  is a cross-sectional view of the base member of  FIG. 6 , showing an aperture defined in the base; 
         FIG. 15  is a perspective cross-sectional view of the assembly of  FIG. 2 ; 
         FIG. 16  is perspective view of the stencil foil assembly of a second embodiment of the present invention with base and cover installed on the stencil foil in accordance with the present invention; 
         FIGS. 17A-17C  show the process of installing the base and cover to a stencil foil for the assembly of  FIG. 16 ; 
         FIGS. 18A and 18B  are cross-sectional views through the line  318 - 318  of  FIG. 16 ; 
         FIGS. 19A and 19B  are cross-sectional views through the line  319 - 319  of  FIG. 16 ; 
         FIGS. 20A and 20B  are cross-sectional views through the line  320 - 320  of  FIG. 16 ; 
         FIG. 21  is a top view of the base used in the assembly of the present invention; and 
         FIGS. 22A-22B  are different views of the cover used in the assembly of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The stencil foil of the present invention is shown generally in  FIGS. 2-22B . Referring to  FIG. 2 , the preferred embodiment of the stencil foil assembly  100  is shown in fully assembled form and ready for use. The stencil foil assembly has a stencil foil  114  with a stencil pattern  120  defined thereon, and the stencil foil  114  is supported by four base members  122 A-D and four cover members  124 A-D that extend along and grip the peripheral portions (or peripheral edges)  128 A-D of the stencil foil  114 . The base members  122 A-D and cover members  124 A-D are described in more detail herein, and substantially make up the frame of the stencil foil assembly  100 . The stencil foil  114  can be provided to a user separately from the base members  122 A-D and the cover members  124 A-D of the present invention, or it can be provided to a user with the base members and the cover members of the present invention. 
     As shown in  FIGS. 2 and 3 , in the preferred embodiment, the stencil foil assembly is useful for supporting a substantially square stencil foil  114 . The stencil foil  114  is dimensioned and configured to extend over a circuit board (not shown), and the lower surface  132  of the stencil foil  114  can be positioned in facing engagement with an upper surface of a circuit board (not shown). The pattern  120  is defined in a central region  130  of the stencil foil  114 , so that when a paste is spread over the upper surface  134  of the stencil foil  114 , a user can cause the paste to fill the space defined by the pattern  120 . The pattern is shown in  FIGS. 2 and 3  as a circular pattern by way of example, however other patterns are within the scope of the present invention. The thickness of the stencil foil  114  in the region of the pattern  120  is configured so that the desired thickness of the paste is disposed on the circuit board through this process. When viewed from above, the stencil foil  114  has four main sides along peripheral edge regions  128 A-D. The stencil foil  114  shown in the figures has chamfered corners  136 . The four main sides together form the peripheral edge of the stencil foil  114 . 
     As described herein, a user can pull the stencil foil  114  into a desired tension by using the base and cover of the assembly to pull the peripheral edge regions  128 A-D of the stencil foil away from the center region  130  of the stencil foil. To facilitate gripping of the peripheral edges  128 A-D of the stencil foil  114  by the assembly of the present invention, a plurality of apertures  126  are defined along the peripheral edges  128 A-D of the stencil foil  114 . Preferably the apertures  126  are substantially evenly spaced apart by a distance D near the peripheral edge. The stencil apertures  126  are preferably cylindrical openings defined within a cylindrical stencil aperture wall  138 . These stencil apertures  126  are engaged by the respective mating cover members and base members of the assembly of the present invention, as described in more detail below, particularly in relation to  FIG. 15 . It can be seen that the peripheral edge portions  128 A-D of the stencil foil  114 , shown in  FIG. 3 , are captured by a base and cover construction in  FIG. 2 . 
     To secure the stencil foil  114  to the frame, the user first assembles the base.  FIG. 4  shows a base of the frame assembled of base members  122 A-D, and  FIG. 5  shows a stencil foil  114  extending over the base members  122 A-D before the stencil has been secured over the base by the cover members  124 A-D. In the preferred embodiment of the present invention, there are four base members  122 A-D that substantially form a square base, and there are four cover member  124 A-D, shown in  FIG. 2 , that are received respectively on the four base members  122 A-D. The four cover members  124 A-D are collectively referred to herein as the cover, though the cover members  124 A-D are not connected directly to each other in the preferred embodiment. Thus, the stencil foil assembly  100  includes four mating pairs composed of a cover member and a base member, and the stencil foil  114  has a peripheral edge that is secured between each respective pair of a cover member and a base member. 
     The four base members  122 A-D are substantially congruent, so that a user can arrange the four base members  122 A-D in any order to form a square as shown in  FIG. 4 , with the upper surfaces of the base members  122 A-D facing in substantially the same direction. As shown in  FIG. 6 , each base member has a first end  140  and a second end  142 , with a male post  144  located at the first end  140 , and a female socket  146  located at the second end  142 . When the base members  122 A-D are fully assembled to form a base, the post  144  of a first base member  122 A is received in the female socket  146  of a second base member  122 B; the post  144  of the second base member  122 B is received in the female socket  146  of a third base member  122 C; the post  144  of the third base member  122 C is received in the female socket  146  of a fourth base member  122 D; and the post  144  of the fourth base member  122 D is received in the female socket  146  of the first base member  122 A. 
     Where there are more base members, such as may be the case in embodiments where the stencil  114  is in the form of a hexagon, a triangle, or another shape that is not substantially square, the base members are arranged and configured in a similar fashion, with male posts of each base member being received in a female socket of an adjacent base member. 
     As shown in  FIGS. 7-8 , each male post  144  has an upper surface  148 , a lower surface  150 , and side post surfaces  152 . As shown in  FIG. 8 , each female socket  146  has an upper socket surface  154 , a lower socket surface  156 , and side socket surfaces  158 . As shown in  FIG. 10 , when a male post  144  is received in a female socket  146 , the lower post surface  150  and the upper post surface  148  are in adjacent facing relation with the lower female socket surface  156  and the upper female socket surface  154 , respectively. This provides a snug, friction fit between the respective male post  144  and the respective female socket  146 . Thus, when a user assembles the four base members  122 A-D to form the base, the base members are biased to remain in assembled relation during the rest of the assembly process, which includes the subsequent steps of placing the stencil on the base and securing the stencil between the base members  122 A-D and the cover members  124 A-D. The base members  122 A-D can also be held together by an adhesive or another fastener. 
     When the base members  122 A-D are in assembled relation to form a base, the side post surfaces  152  of a male post  144  on a first base member are in facing relation with the respective side socket surfaces  158  of the respective female socket  146  of a second base member. As shown in  FIG. 10 , in the preferred embodiment, there is a gap between at least one of the side post surfaces  152  and the respective side socket surface  158 . In the cross-section shown, there are gaps between both side post surfaces  152  and the respective side socket surfaces  158 . This allows for some relative movement of the base members  122 A-D during assembly. 
     Each base member  122 A-D has a top surface  160  that provides a support surface for supporting a peripheral portion of a stencil foil  114 . In the preferred embodiment, the upper surface  160  of each base member  122 A-D is located in the middle portion of the base member and defines a substantially planar surface. The upper surface  160  of the base member  122 A-D defines a plurality of base apertures  164  in this middle portion. The base apertures  164  extend from the upper surface  160  of the base member to the bottom surface  162  of the base member. The base apertures  164  are spaced apart, and they are each configured and arranged to be in alignment with a respective one of the stencil foil apertures  126  when the stencil is supported on the base. 
     Once a user aligns the stencil apertures  126  with the base apertures  164 , the user secures the stencil foil  144  between a cover and the base, by individually securing each cover member  124 A-D to its respective base member  122 A-D. The cover member, shown in  FIGS. 11-12 , includes four cover members  124 A-D, each configured to be received by one of the base members  122 A-D. Each cover member has a main body  170  having a lower surface  172  for engaging the stencil  114 . A plurality of snap posts  174  depend downwardly from the lower surface  172  of the cover member, and are spaced apart by the same distance D as the apertures in the stencil  114 . The snap posts  174  are configured to be respectively routed through the stencil apertures  126 , and are configured to be in secured engagement with the base apertures  164 . When the cover member  124 A-D is secured to the respective base member  122 A-D, the stencil foil  114  is sandwiched between the cover member and the base member, so the stencil foil is held in frictional engagement between the upper surface  160  of the base member and the lower surface  172  of the cover member, for each pair of cover member  124 A-D and base member  122 A-D around the peripheral edge of the stencil foil. 
     As shown in  FIG. 13 , each snap post  174  has a post wall  176  that extends downwardly from the lower surface  172  of the cover member  124 A. In the preferred embodiment, the post wall  176  is substantially cylindrical. A tapered latching formation  178  is formed at the lower end of the post wall. This tapered latching formation has a tapered annular outer wall  179 . An annular latching face  180  extends between the post wall  176  and the tapered outer wall  179 . The latching face  180  extends along a plane that is substantially perpendicular to the longitudinal axis of the snap post  176 , so that a substantially right angle is formed between the post wall  176  and the annular latching face  180 . 
     The apertures  164  in the base member, shown in  FIG. 14 , are configured for receiving the snap posts  174 . Additionally, the apertures  164  on the base members and the snap posts  174  on the cover members are respectively configured and arranged to secure the cover members  124 A-D to the respective base members  122 A-D. Preferably, the snap posts  174  and apertures  164  allow for a substantially permanent or permanent connection between a respective pair of a cover member and a base member. This allows a user to assemble a base and a cover around a stencil foil  114 , and to have a stencil foil assembly  100  that substantially permanently or permanently secures a stencil foil  114  thereon. Thus, the stencil foil assembly does not easily come apart during use or storage. This allows a user to handle the stencil frame safely and to store the stencil frame safely for future use. 
     To provide this secure connection, each base aperture  164  includes an annular base aperture wall  182 , a recessed aperture wall  184 , and an annular post retention face  186  that extends between the annular base aperture wall  182  and the recessed annular wall  184 . The annular post retention face  186  is configured to engage the annular latching face  180  of a respective snap post  174  for retaining the respective snap post  174  within the aperture  164 . 
     The cross-sectional view of  FIG. 15  shows how the stencil is supported and gripped by the cover member  124 A and the base member  122 A along peripheral edge  128 A of the stencil foil. The lower surface  172  of the cover member  124 A engages the upper surface  134  of the stencil. The upper surface  160  of the base member  122 A engages the lower surface  132  of the stencil foil  114 . The posts of the cover member are received in the apertures of the base member. The latching face  180  of the post  172  is in facing relation with the retention face  186  of the base member aperture  164 . The outer wall  176  of the post  172  extends through the stencil aperture  126 , and the post&#39;s outer wall  176  extends past the inner wall  138  of the stencil aperture  126 . The frictional engagement of the stencil foil  114  with the base member  122 A and cover member  124 A helps to transfer the load from the cover member  124 A to the stencil foil  114 . Thus, when the cover member  124 A is pulled away from the center region  130  of the stencil foil  114 , the peripheral region  128 A of the stencil foil  114  is pulled away from the center region  130  of the stencil foil  114 . 
     The stencil foil assembly  100  also includes a stretching machine engagement member (or an engagement member)  123  that is configured to engage a stretch frame apparatus (not shown). In the preferred embodiment, an engagement member  123  is integrally formed on each cover member  124 A-D. Each engagement member  123  is an inwardly sloped cover grip surface (or engagement surface)  125  that is formed adjacent to the lower surface of the cover member  124 A-D. An engagement member  123  extension depends downwardly from the main body of the cover member  124 A-D. When the stencil foil assembly  100  is mounted on a stretching machine (not shown), the stretching machine engages the cover grip surface  125  to pull the assembly and the stencil foil in tension, away from the center of the stencil foil. When the stencil foil assembly  100  of the preferred embodiment is mounted on the stretching machine, the cover members are pulled in tension outwardly, away from the center region  130  of the stencil foil  114 , substantially along the arrow A in  FIG. 13 . As described above, the cover members are secured to the base members around a peripheral edge of the stencil foil  114 . Thus, the outwardly directed tension on the cover members results in a tension on the stencil foil and the base members, so that the stencil foil is pulled away from the stencil&#39;s center region  130  towards the peripheral outer edges  128 A-D. 
     Returning now to  FIGS. 6-11 , which show the male post and female socket formations, the male post  144  extends horizontally outwardly from a male post platform  190 . The male post platform extends upwardly and outwardly from the upper surface  160  of the middle portion of the base member. The male post platform  190  has a proximal platform surface  191 , a distal platform surface  192 , and an upper surface  193 . The proximal and distal platform surfaces are on opposite sides of the platform. The upper surface  160  of the middle portion of the base member extends from the proximal platform surface  191 , while the male post extends from the distal platform surface  193 . 
     At the other end of the base member  122 A-D, a female socket housing  164  provides a housing in which the female socket is defined. The female socket housing  164  has a proximal housing surface  194  and a distal housing surface  195 . The upper surface  160  of the middle portion of the base member  122 A-D extends from the proximal housing surface  194 . Thus, the middle portion of the base member extends between the proximal housing surface  194  and the proximal post platform surface  191  on the base member. The female socket housing extends upwardly and outwardly from the middle portion of the base member. 
     Each cover member  124 A-D has a first end surface  141  at its first end, and a second end surface  143  at its second end. The cover member  124 A-D is dimensioned and configured so the first end surface  141  of the cover is in facing relation with the proximal platform surface  191 , and the second end surface  143  of the cover is in facing relation with the proximal socket housing surface  194  when the cover member  122 A-D and the base member  124 A-D are secured in assembled relation. 
     When the stencil foil kit is fully assembled to form a stencil foil assembly, the outer peripheral edge of the stencil foil assembly (or stencil foil assembly peripheral edge) is formed by the outer geometry of the female socket housings  146 , the post platforms  190 , and the outer peripheral cover edge  197  that is defined on each cover member  122 A-D. Due to the dimensions and configuration of the cover members and the base members, the outer peripheral edge of the stencil foil assembly is substantially continuous. 
     In the embodiment shown herein, the female socket extends from one side of the female socket housing  146  to the other, so that there is an open end of the female socket on the outer peripheral face of the female socket housing  146 . However, in an embodiment not shown, the female socket housing is configured to have female socket that does not fully extend through the female socket housing, and thus only has one opening on the female socket housing. 
       FIGS. 16-22B  show a second embodiment of the present invention. In the second embodiment  200 , each base member  222 A-D has an upstanding wall  230 , and a flange  232  emanates inwardly from the upstanding wall  230 . The support flange  232  has a top flange surface  234  that forms at least a part of the top surface of the base member for supporting the stencil foil  214  thereon.  FIGS. 17A-B  show the stencil foil  214  can be placed on the top flange surface  234 . 
     A plurality of notches  240  are defined along a length of each base member  222 A-D. Each cover member  224 A-D further includes a plurality of fingers  242 . Each finger  242  extends from the main body  244  of the cover, and each finger  242  is configured to align with a respective notch  240  along the length of the base. 
     Each finger  242  has an inner surface  246 . Each base member  222 A-D has a reverse cut flange  248  that is adjacent to the notches. Together, the inner surface  246  of the fingers  242  and the inner surface of the reverse cut flange  248  of the base together form a grip surface (an engagement surface) for engaging a stretching machine (not shown). Thus, in the second embodiment, an engagement member is formed by surfaces on the base member and the cover member. In this embodiment, the tension of the stretching machine is transferred directly to the cover member and the base member. 
       FIGS. 18A and 18B  show a cross-sectional view that is not through a finger or a snap post to further illustrate the interconnection of the base and cover. In  FIGS. 19A and 19B , a cross-sectional view through one of the fingers  242  is shown to illustrate how the fingers  242  also provide a reverse flange for engaging with a stretch frame apparatus.  FIGS. 20A and 20B  show that the second embodiment has a snap post  260  construction, like the preferred embodiment, to secure the cover members  224 A-D to the respective base members  222 A-D. 
     With the base members  222 A-D and cover members  224 A-D secured to the periphery of the stencil foil  214 , the peripheral regions or edges of the stencil foil  214  are protected and a grip surface (or engagement surface) is now provided by the reverse cut flange provided by the bottom of the base and the free ends of the fingers in cooperation with each other. Most notably, as seen in  FIGS. 18B, 19B and 20B , a reverse cut flange is provided by the bottoms of the fingers and cover to provide a reverse cut groove running the length of, preferably, each of the four sides of the assembly of the present invention. As can be understood, such as reverse cut groove can be used to secure the assembly, with stencil foil captured therein, to a stretching frame. In this example, the stretching machine at hand (not shown), includes a complementary member that moves outwardly to carry out the stretching operation to prepare the stencil foil for printing. Thus, the present invention enables such a stretching frame to be used with a standard stencil foil that does not have such a gripping structure by adapting a standard stencil frame for use with such a machine. It should be understood that the underside or other portion of the assembly can be modified to accommodate other stretching machines and other structures so that a stencil foil equipped with the present invention can be stretched and used thereon for printing. 
     It should be understood that the stencil foil in the figures is not shown with a desired array of holes for screen/stencil printing therethrough. However, any stencil pattern may be employed on a stencil for use with the assembly with the present invention. Also, is preferred that the base is preferably aluminum while the covers are preferably plastic. However, any type of material may be used and still be within the scope of the present invention. 
     In view of the foregoing, the stencil foil assembly of the present invention enjoys significant advantages over prior art assemblies. The present invention obviates the need for custom stencil foils to enable use in many types of stretch frames. A standard stencil foil can be adapted over for use in such stretch frames. This greatly reduces the cost of the manufacture of stencil foils. 
     It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.