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Apparatus and method for improving solution flow in immersion processing vessels

IP.com Disclosure Number: IPCOM000204158D
Publication Date: 2011-Feb-16
Document File: 6 page(s) / 121K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method to modify an existing immersion processing tool to improve solution flow around the product being processed is described. The improved solution flow is achieved without increasing operating energy requirements.

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Apparatus and method for improving solution flow in immersion processing vessels

Many submerged wet chemical processes depend on solution flow or product agitation to provide adequate mass transport of process chemicals to, and reaction products away from, the areas of the product being acted upon by the process. As technology advances and product features change, processes that had adequate mass transport for previous generation features, may reach a point where the mass transport is no longer adequate.

An example is blind via technology in build-up layer organic packaging substrates. As the aspect ratio of the vias increases (diameters get smaller or dielectric layers get thicker), the mass transport into/out of the via becomes more difficult, and may reach the point of being diffusion controlled. If the mass transport across the surface containing the vias is inadequate, then the diffusion/depletion layer at the surface becomes thicker, and the diffusion of process reactants/products into/out of the via is reduced even further. At some point the concentration of active species at the base of the blind via may no longer be adequate for sufficient processing to occur. At this point process related defects can begin to appear. For example, dielectric residue at the base of a laser drilled blind via, which can cause unreliable via connections.

One straight forward way to improve the solution flow across the surface of the product, and reduce the thickness of the diffusion/depletion layer, is to mechanically displace the product in a direction that forces solution flow over the surface of the product, thus disrupting the diffusion/depletion layer. However, applying this method to existing process equipment may not be feasible due to space constraints within the tool, or excessive capital investment required for equipment modifications or ancillary handling fixture modifications.

The present invention provides a simple modification that can be retrofitted into an existing process which will improve the flow patterns to achieve higher flow rates across the surface of the product being processed. The method involves redirecting existing flow occurring in the process tank (for example flow from a solution recirculation system) away from regions not containing product being processed, to regions that do contain product, thus improving the flow around the product. The invention is to use baffles, optionally in combination with flo...