Method and circuit module package for automated switch actuator insertion

[0002] The present invention relates generally to circuit module packaging, and more specifically, to a method and circuit module package for automated switch actuator insertion.

[0003] Removable circuit modules or cards are increasing in use to provide storage and other electronic functions for devices such as digital cameras, personal computing devices and personal digital assistants (PDAs). Other memory cards uses include multi media cards and recently, secure digital (SD) cards.

[0004] SD cards require a movable switch actuator to activate a switch within mating receptacles for the SD cards. The switch actuator requirement typically dictates that a special housing be created that incorporates the switch actuator on the edge of the module housing.

[0005] Various solutions to switch actuator incorporation exist as write-protect switch actuators for SD card designs, such as metal clips that are attached after assembly of the SD card housings, plastic switch actuators that are manually inserted into a void in an SD card housing and plastic switch actuators that are manually inserted into the SD card housing prior to gluing the housing.

[0006] The assemblies are glued rather than ultrasonically welded to avoid welding the switch actuator to the housing, but care must also be taken to avoid gluing the switch actuator to the housing.

[0007] External metal actuators are not permitted in Secure Digital Card applications and manual placement of switch actuators is a time-consuming and error-prone process. Also, handling of the switch actuator component and housing assembly is complicated by designs wherein the actuator must be inserted prior to or after joining of the housing portions.

[0008] Therefore, it would be desirable to provide a circuit module package and method for automated switch actuator insertion whereby a circuit module housing may be integrated with a switch actuator prior to final assembly. It would further be desirable to provide a housing and switch actuator that may be assembled by ultrasonic welding without welding the switch actuator to the housing.

[0009] A method and circuit module package for automated switch actuator insertion provides automated assembly of circuit modules having an integrated switch actuator, such as Secure Digital cards. The circuit module package housing includes a channel for retaining the switch actuator during shipment of subassemblies and during the assembly of the final circuit module package. The switch actuator has a mating surface adapted to the surface of the channel within the housing, so that the switch is securely retained in the housing prior to assembly of the circuit module package.

[0010] FIG. 1A is a pictorial diagram depicting a top view and FIG. 1B is a pictorial diagram depicting a cross section of a circuit module in accordance with an embodiment of the invention;

[0011] FIG. 2 is a pictorial diagram depicting a top view and a cross section of a switch actuator in accordance with an embodiment of the invention;

[0012] FIG. 3 is a pictorial diagram depicting details of circuit module 10 of FIGS. 1A and 1B;

[0013] FIG. 4 is a pictorial diagram depicting a cross section of a switch actuator in accordance with an alternative embodiment of the invention; and

[0014] FIG. 5 is a pictorial diagram depicting details of circuit module 10A of FIG. 4.

[0015] The invention, as well as a preferred mode of use and advantages thereof, will best be understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein like reference numerals indicate like parts throughout.

[0016] Referring now to the figures and in particular to FIG. 1A and FIG. 1B, a circuit module 10 in accordance with an embodiment of the invention is depicted. Circuit module 10 is depicted as a circuit module as used in various multimedia memory applications and secure digital (SD card) applications.

[0017] The present invention is also applicable to cards and modules having other outlines such as multimedia cards, compact flash memory cards and other flash memory cards. The present invention applies to peripheral device cards (I/O cards), as well.

[0018] A housing bottom portion 14 holds a circuit assembly 16 which is generally one or mode integrated circuit dies 13 that are attached to a substrate and then encapsulated. Circuit contacts 12 are included on the bottom side of circuit assembly 16 and openings are provided for electrical contact through housing bottom portion 14. Circuit assembly 16 is covered by a housing top portion 15 that is bonded to housing bottom portion 14. A switch actuator 19 is attached to housing top portion 15, so that switch actuator 19 may slide within a recess 17. Switch actuator 19 is guided by a channel 18, that aids in retaining switch actuator 19 within housing top portion 15 prior to attachment of top portion 15 to housing bottom portion 14. Housing top portion 15 is generally attached to housing bottom portion by ultrasonic welding, which heats the housing portions to at or near the melting point of the material, joining housing top portion permanently to housing bottom portion 14, but other techniques may be used such as gluing without deviating from the scope of the present invention.

[0019] In order to perform ultrasonic welding joining the housing portions while switch actuator 19 is attached to housing top portion, switch actuator 19 should be made from a material having a higher melting point than the housing portions. For example, housing top portion 15 and bottom portion 14 may be made from a polycarbonate/Acrilonitrile Butadiene Styrene (PC/ABS), while the switch actuator 16 may be made from a semi-crystalline acetal resin such as CELCON. The result is that switch actuator 19 will not be distorted by the local heating produced by the ultrasonic welding and consequent joining of housing bottom portion 14 and housing top portion 15. Without the differing material properties, switch actuator 19 would have to be inserted after welding, otherwise the switch actuator may be permanently joined to the housing and immovable.

[0020] Table 1 comprises a list of suitable materials for the fabrication of switch actuator 19 and housing portions 14 and 15.

[0021] The purpose of switch actuator 19 is to provide binary information such as write-protect enabled to an external switch mounted within a receptacle that receives the circuit module. In one position of the switch actuator, switch actuator 19 will contact an electrical switch lever within the receptacle and in the alternate position, switch actuator 19 will not contact the no electrical switch lever, providing two states of the information provided by switch actuator 19. Prior art implementations of switch actuators to perform this function must be: 1) inserted manually after ultrasonic welding of the housing portions, to avoid bonding of the switch actuator to the housing; 2) inserted manually prior to assembly of the housing, since there is no 3) mechanism to retain the switch actuator to a housing portion; clipped on to the exterior of the housing, which typically requires a metal component not permitted in Secure Digital (SD) applications; or 4) inserted manually after ultrasonic welding of the housing portions, since there is no mechanism to retain the switch actuator to the housing.

[0022] The present invention provides a mechanism for retaining switch actuator 19 within housing top portion 15 (alternatively the mechanism could be implemented within housing bottom portion 14 and switch actuator 19 retained by housing bottom portion 14). Switch actuator 19 is held securely after attachment to housing top portion 15 and may be handled in that configuration prior to final assembly of circuit module 10. The combination of housing top portion 15 and switch actuator 19 is designed so that the housing top portion/switch actuator assembly may be stacked for feeding to the final assembly stage by a stack loader. As depicted in the illustrative embodiment, this is accomplished by designing a switch actuator 19 that does not exceed the profile of housing top portion 15, but could be accomplished by contouring the bottom of housing top portion 15 in the region of recess 18 to accept the top of switch actuator 19.

[0023] Referring now to FIGS. 2A and 2B, a switch actuator in accordance with an embodiment of the invention is depicted. Switch actuator 19 has a handle 22 for moving the switch within recess 17 of FIG. 1 by a finger or a device such as a stylus to change the activation state of switch actuator 19. Attached to handle 22 are a lower slide 21 and an upper slide 23. Attached to upper slide is a protrusion 24 that mates with channel 18 of FIGS. 1A and 1B. Protrusion 24, retains switch actuator 19 to housing top portion 15 prior to final assembly of circuit module 10 of FIGS. 1A and 1B. By providing means for clipping switch actuator 19 to housing top portion 15, housing top portion/switch actuator assemblies may be easily transported.

[0024] Referring now to FIG. 3, details of the circuit module 10 depicted in FIGS. 1A and 1B are shown. Switch actuator 19 is fastened to housing top portion 15 by applying a slight force F in the direction shown, causing lower slide 21 and upper slide 23 to deform temporarily, permitting protrusion 24 to enter channel 18, which retains switch actuator 19 to housing top portion 15. A cut-out in housing top portion 15 receives lower slide 21, so that the bottom of lower slide 21 is conformal with the remainder of the edge of housing top portion 15.

[0025] Since handle 22 does not exceed the bottom profile of housing top portion 15, the assemblies may be shipped in a stacked configuration and may be fed to a stack loader for final assembly. Circuit assembly 16 is placed on housing bottom portion 14, and the switch actuator/housing top portion assembly is bonded to housing bottom portion over circuit assembly 16. If switch actuator 19 is made from a material having a higher melting point than the material forming housing top portion 15 and bottom portion 14, ultrasonic welding may be used to thermally bond the two housing portions without deforming or bonding switch actuator 19 to the housing.

[0026] Alternative retaining mechanisms may be used to attach switch actuator 19 to housing top portion 15 or housing bottom portion 14, such as a protrusion on housing top portion 15 replacing channel 18, with a mating channel in switch actuator 19 in place of protrusion 24. The shape of protrusion 24 and the do corresponding channel 18 shape may also be adapted to other outlines.

[0027] Referring now to FIG. 4, a switch actuator 19A in accordance with an alternative embodiment of the invention is depicted. The alternative embodiment depicted is adapted for attachment after the housing portions of a circuit module assembly have been welded or glued. Slider 21A extends only to the edges of switch actuator handle 22A and is inserted into the bottom of a circuit module housing.

[0028] Referring now to FIG. 5, details of a circuit module 10A, adapted for use with switch actuator 19A of FIG. 4 are depicted. Housing bottom portion 14A has a cut-out for slider 21A, rather than having a cut-out in the housing top portion of FIG. 3. Protrusion 24 and channel 18 are implemented as in the above-described embodiment and the switch is securely held to circuit module 10A by protrusion 24A. A protrusion could alternatively be used on slider 21A, with a corresponding mating channel in housing bottom portion 14A. The alternative embodiment of the invention permits secure attachment of switch actuator 19A subsequent to welding or gluing of the housing portions.

[0029] The above description of embodiments of the invention is intended to be illustrative and not limiting. Other embodiments of this invention will be obvious to those skilled in the art in view of the above disclosure and fall within the scope of the present invention.