Housing construction for snap-in retention

1. An electronic device comprising:

a base unit including:

a top surface forming a cavity with a peripheral edge, and

a fitting tab integral with the peripheral edge and located above the top surface; and

an attachable unit configured to fit inside the cavity and connect to the base unit, wherein the attachable unit includes:

a bottom housing structure,

a top housing structure ultrasonically welded to the bottom housing structure, wherein the top housing structure includes an integral toe portion configured to contact and interlock with the fitting tab for connecting the attachable unit to the base unit when the attachable unit is inside the cavity, and

one or more weld spots that attach the bottom housing structure and the top housing structure based on an ultrasonic welding process;

wherein:

the integral toe portion of the top housing structure configured, through shape and a relative location with respect to the one or more weld spot, to direct forces to compress the weld spots, wherein the forces are associated with contact between the attachable unit and the base unit.

2. The electronic device of claim 1 , wherein:

the fitting tab includes an arm portion and a locking portion, wherein the arm portion is integral with the top surface, extends away from the top surface, and is integral with the locking portion opposite to the top surface; and

the integral toe portion is located below and directly contacting the locking portion interlock with the fitting tab when the attachable unit is inside the cavity.

3. The electronic device of claim 1 , wherein the top housing structure includes a support director integral with a bottom surface thereof and located near the toe portion and between the toe portion and a center portion, wherein the support director is an energy director for an ultrasonic welding process that attaches the top housing structure and the bottom housing structure.

4. The electronic device of claim 3 , wherein the top housing structure includes a primary director configured to melt before the support director during the ultrasonic welding process.

5. The electronic device of claim 4 , wherein the support director is located between the primary director and the integral toe portion, located below the primary director, or a combination thereof.

6. The electronic device of claim 4 , wherein the support directors are configured to provide a mechanical fit and/or alignment between the bottom housing structure and the top housing structure during an ultrasonic welding stage.

7. The electronic device of claim 1 , wherein the integral toe portion is configured to receive a downward force from the fitting tab and direct the downward force to compress the weld spots that are located within a threshold distance from the integral toe portion.

8. The electronic device of claim 1 , wherein:

the top surface includes:

a second peripheral edge forming the cavity and located horizontally opposite the peripheral edge,

a second tab integral with the second peripheral edge and above the top surface; and

the attachable unit includes a protrusion located horizontally opposite the integral toe portion, wherein the protrusion is configured to contact and interlock with the second tab when the attachable unit is inside the cavity.

9. The electronic device of claim 8 , wherein:

the second tab extends downward and below the fitting tab; and

the protrusion is integral with the bottom housing structure, located below the integral toe portion, and extends horizontally away from a peripheral surface thereof.

10. An electronic device comprising:

a bottom housing structure;

a top housing structure ultrasonically welded to the bottom housing structure, wherein the top housing structure includes an integral toe portion for providing a snap-fit with a base unit when the ultrasonically welded combination of the bottom housing structure and the top housing structure is placed within a cavity of the base unit; and

one or more weld spots that attach the bottom housing structure and the top housing structure based on an ultrasonic welding process;

wherein:

the integral toe portion of the top housing structure configured, through shape and a relative location with respect to the one or more weld spot, to direct forces to compress the weld spots, wherein the forces are associated with contact between the attachable unit and the base unit when the device is placed within the cavity.

11. The electronic device of claim 10 , wherein the integral toe portion is configured, through shape and a relative location with respect to a corresponding portion in the base unit, to directly contact and interlock with the corresponding portion when the device is placed within the cavity.

12. The electronic device of claim 10 , wherein the top housing structure includes a support director integral with a bottom surface thereof and located near the toe portion and between the toe portion and a center portion, wherein the support director is an energy director for an ultrasonic welding process that attaches the top housing structure and the bottom housing structure.

13. The electronic device of claim 12 , wherein the top housing structure includes a primary director configured to melt before the support director during the ultrasonic welding process.

14. The electronic device of claim 13 , wherein the support director is located between the primary director and the integral toe portion, located below the primary director, or a combination thereof.

15. The electronic device of claim 10 , wherein the integral toe portion is configured to receive a downward force from the base unit direct the downward force to compress the weld spots that are located within a threshold distance from the integral toe portion.

16. The electronic device of claim 10 , wherein the bottom housing structure includes a protrusion located horizontally opposite the integral toe portion and configured to contact and interlock with the base unit when the device is within the cavity.

17. The electronic device of claim 10 , wherein the protrusion is integral with the bottom housing structure, located below the integral toe portion, and extends horizontally away from a peripheral surface thereof.

18. A method of manufacturing an electronic device, the method comprising:

providing a bottom housing structure;

providing a top housing structure including an integral toe;

aligning the top housing structure and the bottom housing structure along a plane, wherein the top housing structure overlaps the bottom housing or a portion therein and directly contacts the bottom housing at one or more locations; and

forming one or more weld spots that attach the bottom housing structure and the top housing structure based on ultrasonically welding the bottom housing structure and the top housing structure through applying ultrasonic energy to the top housing structure, the bottom housing structure, a portion therein, or a combination thereof;

wherein:

the integral toe is configured to provide a snap-fit for the ultrasonically welded combination of the bottom housing structure and the top housing structure when it is placed within a cavity of a base unit, and

the integral toe portion is configured, through shape and a relative location with respect to the one or more weld spot, to direct forces to compress the weld spots, wherein the forces are associated with contact between the attachable unit and the base unit when the device is placed within the cavity.