PATENT DOCUMENT

Publication Number: US-8372502-B2
Application Number: US-75300510-A
Country: US
Kind Code: B2

Title: Structures for containing liquid materials and maintaining part alignment during assembly operations

Abstract:
Components may be interconnected using liquid materials such as liquid adhesive and solder. To prevent undesired movement between the components during the assembly process and to prevent the liquid material from flowing into undesired areas, an attachment and dam structure may be provided. The structure may be formed from a substrate such as a flexible polymer film coated with adhesive. When interposed between first and second components, the structure attaches the first and second components and prevents movement between the first and second components. The structure may have one or more edges adjacent to the liquid material to block the liquid material from flowing while the liquid material is in its liquid state. Once the components have been connected, the liquid material can be solidified.

Claims:
1. Apparatus, comprising:
 a first component; 
 a second component; 
 liquid material that has associated liquid and solid states; and 
 a structure with a substrate and adhesive that attaches the first component to the second component, wherein the structure has at least one edge adjacent to the liquid material that is configured to block flow of the liquid material in its liquid state, wherein the structure has a ring shape with an overflow structure. 
 
     
     
       2. The apparatus defined in  claim 1  wherein the structure comprises a double-sided tape structure. 
     
     
       3. The apparatus defined in  claim 1  wherein the substrate comprises a polymer. 
     
     
       4. The apparatus defined in  claim 1  wherein the substrate comprises a flexible sheet. 
     
     
       5. The apparatus defined in  claim 1  wherein the substrate comprises a flexible polymer sheet having a top surface that is coated with the adhesive and having a bottom surface that is coated with the adhesive. 
     
     
       6. The apparatus defined in  claim 5  wherein the edge comprises an outer peripheral edge for the structure and wherein the liquid material surrounds the structure. 
     
     
       7. The apparatus defined in  claim 5  wherein the edge comprises an inner peripheral edge for the structure and wherein the liquid material is surrounded by the structure. 
     
     
       8. The apparatus defined in  claim 5  wherein the structure has a rectangular ring shape. 
     
     
       9. The apparatus defined in  claim 5  wherein the structure has a circular ring shape. 
     
     
       10. The apparatus defined in  claim 1  wherein the first component comprises a camera module and wherein the second component comprises a trim member. 
     
     
       11. The apparatus defined in  claim 1  wherein the liquid material comprises liquid adhesive. 
     
     
       12. The apparatus defined in  claim 1  wherein the liquid material comprises solder. 
     
     
       13. Apparatus, comprising:
 a first component; 
 a second component; 
 a double-sided tape between the first and second components that attaches the first component to the second component; and 
 liquid adhesive between the first and second components adjacent to the double-sided tape, wherein the double-sided tape has an edge and wherein the edge blocks movement of the liquid adhesive, wherein the first component comprises a camera module and the second component comprises a trim. 
 
     
     
       14. The apparatus defined in  claim 13  wherein the liquid adhesive comprises cured and solidified liquid adhesive that attaches the first component to the second component. 
     
     
       15. The apparatus defined in  claim 13  wherein the double-sided tape has a ring shape with an overflow structure. 
     
     
       16. The apparatus defined in  claim 13  wherein the double-sided tape comprises an inner ring of double-sided tape and an outer ring of double-sided tape and wherein the liquid adhesive is interposed between the inner and outer rings of double-sided tape. 
     
     
       17. An electronic device, comprising:
 a first component; 
 a second component; 
 a structure with a substrate and adhesive that attaches the first component to the second component, wherein the structure comprises an inner ring, an outer ring, and an overflow structure; and 
 liquid material interposed between the inner ring and the outer ring, wherein the liquid material has associated liquid and solid states and wherein the structure is configured to block flow of the liquid material in its liquid state. 
 
     
     
       18. The electronic device defined in  claim 17  wherein the inner ring comprises an inner ring of double-sided tape and wherein the outer ring comprises an outer ring of double-sided tape. 
     
     
       19. The electronic device defined in  claim 17  wherein the liquid material comprises molten solder. 
     
     
       20. The electronic device defined in  claim 17  wherein the liquid material comprises ultraviolet-light-cured adhesive.

Description:
BACKGROUND 
     Liquid adhesive and solder are used in forming mechanical and electrical connections in a variety of contexts. For example, liquid adhesive may be used to attach parts together within an electronic device. Solder connections may be formed when it is desired to mount a component to a printed circuit board. 
     It can be challenging to properly control liquid materials during manufacturing. Liquid materials such liquid adhesives and solder that are not well controlled may intrude into undesired portions of a workpiece. For example, a liquid material that is not properly controlled may wick into undesired areas between closely spaced parts. This excess material can then interfere with the desired operation of a product. Attempts to reduce undesired movement of intrusions of liquid materials by reducing the volume of liquid material that is used are sometimes counterproductive. Solder joints that are formed without using sufficient solder may be unreliable or may not exhibit satisfactory low-resistance electrical connections. Adhesive joints that are formed without using sufficient liquid adhesive may be weak. 
     To address these concerns, solder dam and glue dam structures have been developed. These structures use features such as ridges to block the flow of liquid materials during assembly operations and thereby contain adhesive and solder in desired areas. 
     During assembly operations that involve that involve the use of liquid materials, undesired movements of workpiece parts relative to one another should be avoided. If parts are allowed to move with respect to each other before an adhesive or solder joint has been properly formed, the parts may become permanently misaligned. Unintended movement during assembly is sometimes addressed by providing parts with alignment features such as alignment posts and holes. 
     Strips of double-sided adhesive tape have been used in conjunction with epoxy when mounting display cover glass panels to housing structures in cellular telephones. In this type of arrangement, rectangular pieces of double-sided tape are used at the upper and lower ends of the display. A peripheral bead of epoxy that is sandwiched between the panels and that is separated from the double-sided tape by a raised housing ridge is used in mounting the panel. In this type of scenario, the double-sided tape does not constrain the flow of the epoxy. Conventional dam structures may help prevent undesired adhesive movements, but do not prevent relative movement between parts before a finished adhesive bond has been formed. This can lead to parts that are tilted or otherwise misaligned with respect to each other. 
     It would therefore be desirable to provide improved ways in which to use liquid materials in the assembly of parts during manufacturing. 
     SUMMARY 
     Components may be interconnected using liquid materials such as liquid adhesive and solder. For example, a trim member may be attached to the surface of a camera module using liquid adhesive or an electronic component may be mounted to traces on a printed circuit board using solder. 
     To prevent undesired movements between the components during the assembly process and to prevent the liquid material from flowing into undesired areas, an attachment and dam structure may be provided. The structure may be formed from a substrate such as a flexible polymer film coated with adhesive. The structure may have a shape such as a ring shape or other suitable shape. When interposed between first and second components, the structure attaches the first and second components and prevents movement between the first and second components. The structure may have one or more edges adjacent to the liquid material that constrain the locations into which the liquid material can flow while the liquid material is in its liquid state. Once the components have been connected, the liquid material can be solidified. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional side view of a conventional camera module to which a trim is being attached using adhesive. 
         FIG. 2  is a cross-sectional side view of the conventional camera module of  FIG. 1  following attachment of the trim. 
         FIG. 3  is a perspective view of a component such as a camera module with a structure for constraining movement of liquid material and for ensuring proper alignment between the component and another component such as a trim piece during assembly in accordance with an embodiment of the present invention. 
         FIG. 4  is a cross-sectional side view of components of the type shown in  FIG. 3  during assembly in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of another illustrative arrangement for containing liquid material and maintaining part alignment during assembly operations in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of an arrangement for preventing liquid material from intruding inwards into a given area between two parts while maintaining alignment between the parts during assembly operations in accordance with an embodiment of the present invention. 
         FIG. 7  is a top view showing illustrative arrangements that may be used for constraining the flow of liquid material and maintaining part alignment during assembly operations in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as cellular telephones may contain cameras and other components. A camera may have a trim piece that is attached to a camera module base. In connecting components such as camera components and other parts in an electronic device, liquid materials such as liquid adhesive and solder may be used. 
     A conventional camera module to which a camera trim piece is being attached is shown in  FIG. 1 . As shown in  FIG. 1 , camera module base  10  contains camera components  30 . Base  10  is typically formed from a housing member such as a cube-shaped structure. Camera components  30  include image sensor components, lenses, and other components. Camera components  30  are aligned with opening  28  in base  10 . A trim piece such as trim  14  may be attached to base  10  (e.g., to provide the camera with a finished appearance). Opening  26  in trim  14  is aligned with opening  28  to allow light to enter camera components  30 . In a typical configuration, openings  26  and  28  are circular in shape. 
     Trim  14  and camera base  10  have mating alignment features. As shown in  FIG. 1 , trim  14  has alignment posts  16  and camera base  10  has corresponding alignment holes. Before inserting posts  16  into holes  18 , drops of epoxy  20  are placed between upper surface  24  of camera base  10  and opposing lower surface  22  of trim  14 . Following insertion of posts  16  into holes  18 , epoxy drops  20  are compressed between surfaces  22  and  24 . This flattens epoxy  20  and forces epoxy  20  inwards against the ridge edges  32 , which serve as a glue dam, as shown in  FIG. 2 . Epoxy  20  is then cured to bond trim  12  to housing  10 . 
     Conventional camera assembly operations of the type shown in  FIGS. 1 and 2  rely on alignment features such as alignment posts and holes, which can add undesired complexity. Alignment features such as alignment posts and mating alignment holes are also generally not able to completely prevent movement between the parts of a workpiece during assembly. As a result, parts such as trim  14  of  FIG. 2  may become tilted with respect to base  10  before the epoxy curing process is complete. 
     An arrangement for assembling components using liquid materials in accordance with an embodiment of the present invention is illustrated in  FIG. 3 . As shown in  FIG. 3 , a first component (e.g., camera trim  36 ) may be attached to a second component (e.g., camera module base  48 ) to form an assembled structure (e.g. camera  34 , shown disassembled in the exploded view of  FIG. 3 ). In general, any types of parts may be assembled using liquid materials. For example, structural parts such as housing parts, frame structures, mounting brackets, component housings, and other mechanical parts may be assembled using liquid materials such as liquid adhesive and solder. Electrical components may also be assembled using liquid materials. For example, an electrical component that has conductive terminals may be mounted to mating conductive traces on a printed circuit board using liquid materials such as liquid adhesive, liquid conductive adhesive, and solder. Liquid adhesive materials that may be used for assembling components include epoxy and cyanoacrylate (as examples). Solder joints may be formed by melting solder or by depositing solder paste and reflowing the deposited paste in a reflow oven. 
     As shown in the example of  FIG. 3 , the components that are being attached to each other may include a trim structure (trim  36 ) and a camera base structure (structure  48 ). In general, any suitable electrical and/or mechanical components may be assembled using liquid materials. The attachment of a trim to a camera housing is merely described as an illustrative example. 
     As shown in  FIG. 3 , trim  36  may have an opening such as circular hole  38 . Light may pass through hole  38  to lens  40  and other camera components in camera base  48 . Electrical components that may be used in camera base  48  include circuitry such as an integrated circuit image sensor that converts received image light into digital image data. 
     Components such as components  36  and  48  may be formed from glass, plastic, metal, ceramics, or other suitable materials. Liquid material  46  may be used in connecting components  36  and  48 . Material  46  may be a liquid adhesive, solder, or other suitable material. 
     Liquid material  46  solidifies as part of the assembly process. For example, liquid adhesives such as epoxy are initially liquid, which allows the adhesive to coat the surfaces of the parts being joined. Following application of the liquid adhesive to the parts of a workpiece, the liquid is cured to form a completed bond. The curing process may involve application of heat (e.g., heat to maintain the workpiece at room temperature or sufficient heat to raise the workpiece to an elevated temperature). Applying heat for a sufficient amount of time will cause the liquid epoxy to solidify and form a stable bond. Some liquid adhesives are cured (and thereby solidified) by application of ultraviolet light (e.g., UV-cured liquid polymer adhesives such as UV epoxy). Combinations of heat and light can also be used to cure liquid adhesives. 
     Materials such as solder can initially be solid (e.g., solder wire), can initially be applied as a paste, etc. During solder reflow operations, heat is applied (e.g., to raise the solder to a temperature above 200° C. or more). This causes the solder to melt and form a liquid. The liquid solder flows over exposed metal parts such as the terminals on electronic components and the associated exposed traces (solder pads) on printed circuit boards during reflow operations. When reflow operations are complete, the workpiece is cooled to room temperature and the solder solidifies into a finished solder joint. 
     To ensure that trim  36  is held in a desired orientation with respect to housing  48  while liquid material  46  is being hardened (e.g., by curing an adhesive or by cooling molten solder), structure  34  may be provided with attachment and liquid dam structure  42 . Structure  42  may be formed from a layer of double-sided tape or other material that serves to connect components together. The shape of structure  42  may also allow structure  42  to serve as a barrier to the flow of the liquid material while in its liquid state. Structure  42  may therefore serve both as a dam (i.e., a solder dam or glue dam) and as a attachment structure that holds the workpiece together or at least prevents undesired movement of workpiece components during assembly (i.e., before the liquid material enters its solid state). As part of the assembly process, additional attachment mechanisms may be used to improve the strength of the bond between components in the workpiece. For example, the bond between the components may be strengthened by use of the liquid material (e.g., liquid adhesive). 
     Structure  42  may include a substrate. Layers of adhesive may be used in attaching structure  42  to the components of the workpiece (i.e., components  36  and  48  in the example of  FIG. 3 ). For example, if structure  42  is provided in the form of a thin disk-shaped member as shown in  FIG. 3 , adhesive may be provided on the upper surface of structure  42  to facilitate attachment of structure  42  and component  36  and may be provided on the lower surface of structure  42  to facilitate attachment of structure  42  to component  48 . The adhesive may be provided using any suitable adhesive-dispensing technique (e.g., spraying, dipping, painting, pad printing, screen printing, etc.). These techniques may be used to apply adhesive to the substrate of structure  42 , the surfaces of the workpiece, or both the substrate of structure  42  and one or more surfaces of the workpiece. The substrate in structure  42  may be formed from metal, plastic, ceramic, glass, composites, or other suitable materials. The substrate may be rigid or flexible. Flexible substrates may be used to conform to complex workpiece surfaces during assembly. 
     With one suitable arrangement, structure  42  may be formed from a sheet of double-sided tape. The tape may have a substrate such as a thin flexible polymer sheet (e.g., polyimide, polyethylene terephthalate, etc.). The polymer sheet may have upper and lower surfaces that are coated with adhesive. During assembly, movement of liquid material  46  may be impeded by the presence of structure  40 . For example, in the arrangement of  FIG. 3 , outer peripheral edge  44  of ring-shaped structure  42  may prevent liquid material  46  from intruding onto lens  40  and other structures within the inner portion of structure  42 . The substrate material that is used in forming structure  42  may be chosen to resist expected process temperatures. For example, if liquid material  46  is solder that is being heated to 240° C. (as an example), the substrate material of structure  42  may be chosen to be capable of withstanding damage when exposed to materials at temperatures of 250° C. or less. When liquid material  46  is in its liquid state, it flows up against edge  44  and structure  42  and remains in this position, adjacent to edge  44  and structure  42  when liquid material  46  enters its solid state (e.g., when liquid adhesive cures or when solder solidifies). 
     Structure  42  may be attached to one or both of the components in a workpiece by hand or using an automated positioning tool. As an example, structure  42  may be attached to the lower portion of apparatus  34  (i.e., component  48 ) by hand (or using an automated tool) before an automated tool (or hand assembly) is used in attaching upper component  36  to component  48 . 
     Consider, as an example, the use of the automated assembly system (system  50 ) of  FIG. 4 . As shown in  FIG. 4 , assembly tool  50  may include a computer-controlled actuator such as actuator  52 . Actuator  52  may hold component  36  and/or component  48 , so that the position of component  36  relative to component  48  may be adjusted. Tool  54  may have a control unit such as control unit  54 . Control unit  54  may include a computer or other suitable computing equipment that issues control commands for actuator  52 . One or more cameras such as camera  56  may be used to gather images for control unit  54 . Control unit  54  may use gathered image data or other feedback to determine how to adjust the relative position of components  36  and  48  relative to each other. Once component  36  has been aligned properly with component  48  (i.e., when camera  56  detects that hole  38  is aligned with lens  40  or when camera  56  detects that alignment marks or other alignment features on the workpiece components are aligned as desired), actuator  52  may be directed to press component  36  downwards (in the  FIG. 4  example), thereby compressing structure  42  between the opposing surfaces of components  36  and  48  and forming an adhesive bond. 
     As shown in  FIG. 4 , structure  42  may include substrate  42 B (e.g., a flexible polymer sheet that serves as a tape substrate) and adhesive coating layers  42 A and  42 C. When components  36  and  48  are forced together by actuator  52  (or by manual manipulation of the workpiece components), components  36  and  48  become attached to each other. The shape of structure  42  also forms a dam that contains the movement of liquid material  46 . In the  FIG. 4  example, liquid material  46  (e.g., liquid adhesive) has been placed on the outside of structure  42 . Structure  42  may have a ring shape as shown in  FIG. 3 ). When components  36  and  48  are pressed towards each other, liquid material  46  will flow along the exposed surface of components  36  and  48 , coating these surfaces in preparation for formation of a bond. The outer edge  44  of structure  42  prevents undesired movement of liquid material  46 . 
     The adhesive nature of structure  42  serves to prevent undesired movement of components  36  and  48  relative to each other while liquid material  46  is still in its liquid state. This ensures that components  36  and  48  will not be misaligned laterally (horizontally in the view of  FIG. 4 ) and will not be misaligned rotationally (tilted off of the horizontal axis in the view of  FIG. 4 ). Rotational and lateral alignment in other planes (i.e., a plane perpendicular to the page of  FIG. 4 ) may also be ensured. 
     While the positions of components  36  and  48  are fixed with respect to each other by structure  42 , tool  50  may form a solid out of liquid material  46 . Tool  50  may, for example, using bonding tool  58  to apply ultraviolet light, heat, etc. Bonding tool  58  may use these techniques to cure liquid adhesives and/or to reflow solder paste. Following cooling to room temperature (if elevated temperatures were involved), the liquid material  46  will solidify (e.g., to form a properly aligned adhesive joint or to form a properly aligned solder joint). 
     As shown in the example of  FIG. 5 , structure  42  may have multiple parts such as outer ring part  42 - 1  and inner ring part  42 - 2 . This allows liquid material  46  (e.g., liquid adhesive or solder) to be confined in multiple dimensions. For example, by use of an outer ring and an inner ring for structure  42 , liquid material  46  may be confined to a ring shape having its outer edge bounded by inner edge  44 - 1  of outer ring  42 - 1  and having its inner edge bounded by outer edge  44 - 2  of inner ring  44 - 2 . 
       FIG. 6  is a cross-sectional side view of a workpiece showing how components  36  and  48  may be attached by a solid structure. Structure  42  in the  FIG. 6  arrangement has a solid shape (e.g., a circle or rectangle when viewed from direction  110 ) with a single outer edge  44  around its periphery. This type of structure may be used to prevent inward movement of liquid material  46 . 
       FIG. 7  is a top view of an illustrative electronic device (device  80 ) showing different types of patterns that may be used for structure  42  (which is shown as structures  42 A,  42 B,  42 C,  42 D,  42 E,  42 F, and  42 G in  FIG. 7 ). Device  80  may include a first component (e.g., a housing structure or other suitable structure) and a second component (e.g., a cover glass or other suitable structure) that are joined using structures such as structures  42 A,  42 B,  42 C,  42 D,  42 E,  42 F, and  42 G and liquid material  46  (e.g., solder or liquid adhesive). 
     Structure  42 A forms a rectangular ring that contains liquid material  46  within an inner rectangular region. 
     Structure  42 B forms a circular ring that prevents liquid material  46  from entering interior area  88 . 
     Structure  42 C is an example of a rectangular ring that prevents liquid material  46  from entering interior rectangular region  92 . 
     Structure  42 D is a rectangular ring that contains liquid material  46  within its interior, so that the contained liquid material does not flow outwards into exterior  96 . 
     Structures  42 E and  42 F work together to form a ring-shaped containment area for liquid material  46 . As illustrated by overflow structure  104 , any of structures  42  may, if desired, be provided with shapes that help accommodate the flow of excessive liquid material  46 . Overflow structures may take the form of additional liquid reservoirs, wavy edges, etc. 
     Structure  42 G is a solid central structure (as with the example of  FIG. 6 ) that prevents liquid material  46  from intruding inwardly. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20100401
Publication Date: 20130212
Grant Date: 20130212
Priority Date: 20100401
Inventors: HILL MATTHEW
WEBER TRENT
Assignee: APPLE INC
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Family ID: 44709992