Droplet ejection apparatus alignment

1. An assembly for mounting a printhead module in an apparatus for depositing droplets on a substrate, the printhead module having a surface including orifices from which the droplets are ejected, the assembly comprising:

a frame having an opening defined in a surface of the frame, the opening permitting the surface of the printhead module that is to be mounted on the frame to be exposed for depositing the droplets on the substrate, the surface of the frame extending in a plane parallel to the to-be-exposed surface of the printhead module;

a spring element adapted to spring load the printhead module against an edge of the opening in the frame when the printhead module is mounted in the assembly, the spring element being located in the opening; and

an alignment datum formed on an edge of the opening on a side opposite of the spring element for positioning the printhead module at a specific position with respect to the frame along an axis, the alignment datum and spring element being fixed relative to the frame, not operable to move the module, and in contact with the printhead module when the printhead module is mounted in the assembly.

2. The assembly of claim 1 , wherein the surface of the printhead module comprises an array of nozzles through which droplets are ejected and the spring element is adapted to spring load the printhead module against the frame by applying a mechanical force to the printhead module in a direction orthogonal to a droplet ejection direction.

3. The assembly of claim 1 , wherein the spring element comprises a flexure.

4. The assembly of claim 3 , wherein the frame comprises a plate formed to include the opening and the flexure.

5. The assembly of claim 4 , wherein the plate comprises metal.

6. The assembly of claim 5 , wherein the plate comprises stainless steel.

7. The assembly of claim 5 , wherein the plate comprises invar.

8. The assembly of claim 5 , wherein the plate comprises alumina.

9. The assembly of claim 4 , wherein the flexure is attached to the plate by a fastener.

10. The assembly of claim 1 , wherein the spring element comprises a coiled spring.

11. The assembly of claim 10 , wherein the frame comprises a plate and the coiled spring is attached to the plate.

12. The assembly of claim 1 , wherein the alignment datum comprises a precision surface that contacts the printhead module when the printhead module is mounted in the assembly.

13. The assembly of claim 12 , wherein the precision surface is offset from other portions of the edge of the opening.

14. The assembly of claim 1 , wherein the frame further comprises one or more additional openings extending through the frame, each opening being configured to receive a corresponding printhead module.

15. The assembly of claim 14 , further comprising one or more additional spring elements each corresponding to the one or more additional openings and each being adapted to spring load the corresponding printhead module against an edge of the respective opening when the corresponding printhead module is mounted in the assembly.

16. The assembly of claim 1 , further comprising the printhead module.

17. A droplet deposition system, comprising: the assembly of claim 16 ; and a substrate carrier configured to position the substrate relative to the assembly so that the printhead module can deposit droplets onto the substrate.

18. The assembly of claim 16 , wherein the printhead module comprises an alignment datum that corresponds with the alignment datum on the frame.

19. The assembly of claim 16 , wherein the assembly also comprises an additional printhead module and the printhead module comprises an alignment datum for precisely positioning the printhead module with respect to the additional printhead module.

20. The assembly of claim 1 , wherein the edge of the opening in the frame comprises a plurality of alignment datums that correspond with a plurality of alignment datums on a printhead module.

21. The assembly of claim 1 , wherein the alignment datum registers the printhead module along the axis.

22. The assembly of claim 1 , wherein the alignment datum comprises at least one of a planar surface, a bored hole, a post, a protrusion, and a recess.

23. An assembly comprising:

a frame having an opening defined in a surface of the frame, the opening permitting a surface, of a printhead module that is to be mounted on the frame, to be exposed for depositing droplets from orifices at the surface of the printhead module onto a substrate, the surface of the frame extending in a plane parallel to the to-be-exposed surface of the printhead module;

a spring element, located in the opening, to spring load the printhead module against an edge of the opening in the surface of the frame; and

an alignment datum, on an edge of the opening on a side of the opening opposite the spring element, for positioning the printhead module at a specific position with respect to the frame along an axis, the alignment datum and spring element being fixed relative to the frame, not operable to move the module, and in contact with the printhead module when the printhead module is mounted.

24. The assembly of claim 23 , wherein the spring element comprises a flexure.

25. The assembly of claim 24 , wherein the flexure is formed in the frame.

26. The assembly of claim 23 , wherein the spring element is attached to the frame by a fastener.

27. The assembly of claim 23 , wherein the alignment datum comprises a precision surface that contacts the printhead module when the printhead module is mounted in the assembly.

28. The assembly of claim 27 , wherein the precision surface is offset from other portions of the edge of the opening.