BACKGROUND OF THE INVENTION

One or more embodiments of the invention are related to the fields of electronics and 3D printing. More particularly, but not by way of limitation, one or more embodiments of the invention enable a system and method of adding interconnection features to a plate using electrochemical additive manufacturing.

Additive manufacturing, also known as 3D Printing, is often used for the production of complex structural and functional parts via a layer-by-layer process, directly from CAD (computer aided drafting) models. Additive manufacturing processes are considered additive because materials are selectively deposited on a substrate to construct the product. Additive manufacturing processes are also typically layered meaning that layers of the product to be produced are fabricated sequentially.

Currently, widespread use of metal additive manufacturing techniques is limited due to the high cost associated with selective laser melting (SLM) and electron beam melting (EBM) systems. Further, most metal additive manufacturing devices currently in the industry use powdered metals which are thermally fused together to produce a part, but due to most metals' high thermal conductivity this approach leaves a rough surface finish because unmelted metal powder is often sintered to the outer edges of the finished product.

An emerging alternative for additive metal manufacturing is to use electrochemical reactions. In an electrochemical manufacturing process, a metal part is constructed by plating charged metal ions onto a surface in an electrolyte solution. This technique relies on placing a deposition anode physically close to a substrate in the presence of a deposition solution (the electrolyte), and energizing the anode causing charge to flow through the anode. This creates an electrochemical reduction reaction to occur at the substrate near the anode and deposition of material on the substrate. An illustrative apparatus that enables additive manufacturing via electroplating is described for example in U.S. Pat. No. 10,465,307, “Apparatus for Electrochemical Additive Manufacturing,” by the inventors of the instant application. This apparatus demonstrated a novel approach to electrochemical additive manufacturing that uses a printhead with an array of anodes to build portions of each layer of a part in parallel, instead of moving a single anode across a part to sequentially construct portions of the layer.

BRIEF SUMMARY OF THE INVENTION

Additive manufacturing processes known in the art typically add material in pre-programmed patterns. For example, material may be emitted from a printhead for a preprogrammed period of time at a preprogrammed rate to construct a layer of a part. In electrochemical manufacturing, the rate and pattern of material deposition depends on many dynamic factors, such as the distance between the printhead and each location of the part, the local density of metal ions in the electrolyte, and electrolyte flow patterns. As a result, it is difficult or impossible to achieve high quality parts using strictly preprogrammed (“open loop”) control. However, feedback control methods for electrochemical additive manufacturing processes are not well-developed.

One or more embodiments described in the specification are related to an electrochemical additive manufacturing method using deposition feedback control. An object to be manufactured may be constructed by placing a cathode and an anode array into an electrolyte solution. Deposition anodes of the anode array may provide current that flows from the anode to the cathode through the electrolyte solution, resulting in deposition of the material onto the cathode. The manufacturing process may use a build plan with a layer description for multiple layers of the object; each layer description may include a target map, which describes the presence or absence of material at locations within the layer, and one or more process parameters that affect the layer build. Manufacturing of a layer may begin by setting or confirming the position of the cathode relative to the anode array. Then control signals may be sent to the anode array based on the layer description. One or more feedback signals may be measured across the anode array, and these signals may be analyzed to generate a deposition analysis that indicates the extent to which deposition has progressed at locations within the layer. The deposition analysis may be used to determine whether the layer is complete, and to modify the process parameters associated with the layer. When a layer is complete, manufacturing may continue for a subsequent layer.

In one or more embodiments, the layer description of one or more layers may be modified before manufacturing the layers. For example, layer densities may be changed.

Analysis of feedback signals may apply one or more transformations to these signals, such as morphological filters or Boolean operators.

Feedback signals may for example include a map of current across the anode array. The deposition analysis may be generated by applying a thresholding operation to this current map.

Determining whether a layer is complete may for example include comparing the number of actual deposited pixels to the number of desired deposited pixels within the layer. In one or more embodiments, a layer may be complete when the ratio of actual to desired deposited pixels reaches or exceeds a threshold value. In one or more embodiments, a layer may be complete when a desired fraction of the desired deposited pixels are within a threshold distance from an actual deposited pixel. In one or more embodiments, the layer may be divided into components, and completion tests may be applied to each component; a layer may be considered complete when all components are complete. For example, a component may be complete when the ratio of actual to desired deposited pixels within the component reaches or exceeds a threshold value, or when a desired fraction of the desired deposited pixels within the component are within a threshold distance from an actual deposited pixel.

In one or more embodiments, a layer description may include identification of whether a layer has an overhang. Manufacturing of a layer with an overhang may include successively depositing portions of the overhang so that they extend laterally from one or more previously deposited portions.

In one or more embodiments, a layer target map may be divided into regions, and construction of the layer may include alternately activating deposition anodes associated with each region.

In one or more embodiments, manufacturing of a layer may include calculating a map of desired current output from each deposition anode, so that this current output will generate deposition corresponding to the layer's target map. This current map calculation may involve applying one or more transformations to the layer target map.

In one or more embodiments, modification of process parameters associated with a layer may include calculation of voltage, current, or time of activation for one or more deposition anodes.

In one or more embodiments, setting or confirming the position of the cathode relative to the anode may include obtaining sensor signals that vary based on this relative position, such as a current value or a voltage value.

In one or more embodiments, manufacturing of a layer may include one or more maintenance actions that maintain the condition of the anode array or the electrolyte solution. For example, these maintenance actions may replace material onto one or more deposition anodes that have eroded. Maintenance actions may activate one or more deposition anodes to remove a film that has formed. Maintenance actions may include removal of bubbles from the electrolyte solution.

In one or more embodiments, electrochemical additive manufacturing may be used to manufacture one or more interconnection features, such as wafer bumps or pillars, for example. A plate, such as for example a silicon wafer or other substrate, may have one or more tiles, each of which has one or more connection points. The plate may have a conductive seed layer. To construct interconnection features that are electrically coupled to these connection points, the conductive seed layer may be coupled to a power supply, placed into contact with an electrolyte, and aligned with an anode array; the current flowing from each deposition anode of the anode array may be controlled to deposit material onto the plate in the desired locations, forming the desired interconnection features.

Aligning the plate and the anode array may use one or more sensors to determine the three-dimensional position and three-dimensional orientation of the plate relative to the anode array, and using one or more actuators to modify this three-dimensional position and three-dimensional orientation of the plate relative to the anode array.

In one or more embodiments, after depositing material, portions of the conductive seed layer not covered by interconnection features may be removed. In one or more embodiments, the initial conductive seed layer may be thickened using electrodeposition.

In one or more embodiments, some or all of the interconnection features may have portions that are not substantially perpendicular to the plate; for example, they may extend horizontally. These portions may be constructed by successively activating horizontally offset anodes to grow the deposit horizontally. In one or more embodiments, a vertical portion of one or more features may be deposited, followed by deposition of an inert material onto the plate to provide support for subsequent horizontal portions. In one or more embodiments, non-perpendicular features may be constructed by rotating the plate so that the previously constructed vertical segments become horizontal, and depositing the subsequent portions vertically.

In one or more embodiments, the anode array may be successively placed in position near different sets of tiles to construct interconnection features for each tile.

One or more embodiments of the invention may include an electrochemical additive manufacturing system, which may be used for example to create interconnection features. The system may have a reaction chamber that contains an ionic solution that can be decomposed by electrolysis. It may have an anode array disposed in the reaction chamber and configured to be immersed in the ionic solution. It may have a substrate disposed in the reaction chamber, where a conductive seed layer on a surface of the substrate is configured to be in contact with the ionic solution. It may have a mechanical positioning system that is configured to modify one or more of the position and orientation of one or both of the anode array and the substrate. It may have a microcontroller that is programmed to transmit control signals to the mechanical positioning system to modify the relative position and orientation of the anode array and the substrate so that the anode array and the substrate are substantially coplanar, and the anode array is aligned with one or more features of the substrate. The microcontroller may also accept a three-dimensional model of interconnection features to be added to the substrate. Based on this model, the microcontroller may control the current through each anode of the anode array to construct the interconnection features on the substrate.

One or more embodiments of the electrochemical additive manufacturing system may include one or more attachments that are configured to provide an electrical connection to the conductive seed layer.

In one or more embodiments of the electrochemical additive manufacturing system, the substrate may have two or more tiles. The microcontroller may successively position the anode array relative to the substrate to step through the tiles. For example, it may transmit a first set of control signals to the mechanical positioning system to align the anode array with a first tile of the two or more tiles, and then control the current through each anode of the anode array to construct the interconnection features on the first tile. Afterwards it may transmit a second set of control signals to the mechanical positioning system to align the anode array with a second tile of the two or more tiles, and then control the current through each anode of the anode array to construct the interconnection features on the second tile.

