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Constant Pressure Gradient Chemical Process Tank

IP.com Disclosure Number: IPCOM000041122D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Wiley, JP: AUTHOR [+2]

Abstract

In the manufacture of printed circuit boards, it is often necessary to pass chemical solutions through the board's drilled holes. As the boards become thicker and larger with smaller, higher aspect ratio drilled holes, cleaning becomes more difficult. Hole cleaning is typically accomplished by agitation in a wet process tank. The flow of fluid around the edges of the board reduces pressure, and the full pressure gradient is reached only near the center of the board which is inadequate for the high aspect ratio holes. A process which passes chemical solutions through the holes, in a uniform manner, is described in the following.

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Constant Pressure Gradient Chemical Process Tank

In the manufacture of printed circuit boards, it is often necessary to pass chemical solutions through the board's drilled holes. As the boards become thicker and larger with smaller, higher aspect ratio drilled holes, cleaning becomes more difficult. Hole cleaning is typically accomplished by agitation in a wet process tank. The flow of fluid around the edges of the board reduces pressure, and the full pressure gradient is reached only near the center of the board which is inadequate for the high aspect ratio holes. A process which passes chemical solutions through the holes, in a uniform manner, is described in the following.

As seen in the drawing, a stationary wet process basket 1 acts as a primary tank and holds boards 2 in a vertical position by means of holding racks (not seen). The boards 2 are spaced such that solutions are permitted access to the board's surface. The fluid level in the wet basket 1 is maintained by weir A.

A secondary tank 3 maintains a constant solution level by weir B. The fluid flowing over weir B enters sump 4. A pump 5 supplies solution to the primary tank 1 which is filled to overflowing at weir A. The constant difference in solution height between the tanks 1 and 3 creates a differential solution pressure. The pressure differential is maintained across the entire surface of the board causing constant and uniform solution flow through the drilled holes.

The boards 2 are removed afte...