Electrochemical additive manufacturing method using deposition feedback control
A system and method of using electrochemical additive manufacturing to add interconnection features, such as wafer bumps or pillars, or similar structures like heatsinks, to a plate such as a silicon wafer. The plate may be coupled to a cathode, and material for the features may be deposited onto the plate by transmitting current from an anode array through an electrolyte to the cathode. Position actuators and sensors may control the position and orientation of the plate and the anode array to place features in precise positions. Use of electrochemical additive manufacturing may enable construction of features that cannot be created using current photoresist-based methods. For example, pillars may be taller and more closely spaced, with heights of 200 μm or more, diameters of 10 μm or below, and inter-pillar spacing below 20 μm. Features may also extend horizontally instead of only vertically, enabling routing of interconnections to desired locations.
1. A method of electrochemically additive manufacturing an object using deposition-feedback control, the method comprising steps of:
placing a surface of a cathode into an electrolyte solution;
placing an anode array in contact with the electrolyte solution, wherein:
the anode array comprises a plurality of deposition anodes; and
each of the plurality of deposition anodes is configured to provide an electric current that flows to the cathode through the electrolyte solution, resulting in deposition of material onto the cathode;
transmitting control signals to the anode array based on one or more process parameter values of a build plan for a layer of the object;
producing a deposition analysis by analyzing one or more feedback signals, generated by one or more sensors responsive to the deposition of the material onto the cathode; and
performing one or more maintenance actions on the anode array, when, based on the deposition analysis.
2. The method according to claim 1 , wherein the one or more feedback signals constitute a map of current density across the anode array.
3. The method according to of claim 1 , further comprising steps of:
dividing a target map, associated with the layer, into regions, wherein subsets of the plurality of deposition anodes are associated with different ones of the regions; and
alternately activating the subsets of the plurality of deposition anodes.
4. The method according to of claim 1 , wherein the step of producing the deposition comprises, for at least one of the plurality of deposition anodes, determining one or more of:
an electric potential difference relative to the cathode;
an electric current through the electrolyte solution to the cathode; or
a period of activation.
5. The method according to of claim 1 , further comprising removing bubbles from the electrolyte solution by vibrating at least one of the electrolyte, the cathode, or the anode array.
6. The method according to of claim 1 , wherein the one or more sensors comprise at least one of an electric-current sensor, a position sensor, or an optical imager.
7. The method according to claim 1 , wherein the step of performing the one or more maintenance actions on the anode array comprises a step of depositing replacement material onto at least one of the plurality of deposition anodes to replace lost material that has eroded from at least the one of the plurality of deposition anodes.
8. The method according to claim 7 , wherein the step of depositing the replacement material onto at least the one of the plurality of deposition anodes to replace the lost material that has eroded from at least the one of the plurality of deposition anodes comprises reversing direction of the electric current so that at least the one of the plurality of deposition anodes acts as a cathode, and the electric current flows from a secondary anode to at least the one of the plurality of deposition anodes, acting as the cathode.
9. The method according to claim 8 , wherein the secondary anode is a bulk anode that is larger than at least the one of the plurality of deposition anodes.
10. The method according to claim 8 , wherein the secondary anode is made of an inert material.
11. The method according to claim 10 , wherein the inert material comprises platinum.
12. The method according to claim 8 , wherein the secondary anode is composed of a material that is identical in composition to the material, deposited onto the cathode.
13. The method according to claim 7 , further comprising transmitting control signals to the anode array based on one or more process parameter values of a build plan for a subsequent layer of the object, so that an electric potential difference, created between at least the one of the plurality of deposition anodes and the cathode, is such that only the replacement material, deposited onto at least the one of the plurality of deposition anodes to replace the lost material that has eroded from at least the one of the plurality of deposition anodes, is dissolved into the electrolytic solution when the electric current flows from at least the one of the plurality of deposition anodes to the cathode through the electrolyte solution, resulting in deposition of the material onto the cathode.
14. The method according to claim 7 , wherein the replacement material, deposited onto at least the one of the plurality of deposition anodes, is more soluble than the lost material, eroded from at least the one of the plurality of deposition anodes.
15. The method according to claim 1 , wherein the step of performing the one or more maintenance actions on the anode array comprises a step of activating two adjacent ones of the plurality of deposition anodes, onto which a film has formed that bridges a gap between at the two adjacent ones of the plurality of deposition anodes, so that the film is removed.
16. The method according to claim 15 , wherein the step of activating the two adjacent ones of the plurality of deposition anodes, onto which the film has formed that bridges the gap between the two adjacent ones of the plurality of deposition anodes, comprises moving the cathode away from the plurality of deposition anodes and activating only the two adjacent ones of the plurality of deposition anodes, onto which the film has formed.
17. The method according to claim 15 , wherein the step of activating the two adjacent ones of the plurality of deposition anodes, onto which the film has formed that bridges the gap between the two adjacent ones of the plurality of deposition anodes, is performed when an electric current, passing through each of the two or more adjacent ones of the plurality of deposition anodes, is higher than an electric current, passing through any other one of the plurality of deposition anodes.
18. The method according to claim 7 , wherein the step of performing the one or more maintenance actions on the anode array further comprises a step of activating two of the plurality of deposition anodes, onto which a film has formed that bridges a gap between the two of the plurality of deposition anodes, so that the film is removed.
19. The method according to claim 7 , further comprising removing bubbles from the electrolyte solution by vibrating at least one of the electrolyte, the cathode, or the anode array.
20. The method according to claim 7 , further comprising steps of:
dividing a target map, associated with the layer, into regions, wherein subsets of the plurality of deposition anodes are associated with different ones of the regions; and
alternately activating the subsets of the plurality of deposition anodes.