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Through-Hole Circuitization by an Anodic Etching Technique

IP.com Disclosure Number: IPCOM000102331D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Matthew, LC: AUTHOR [+3]

Abstract

Disclosed is a method for making through-holes in metal-core circuit boards in a parallel process. Current methods for putting vias in boards include punching, drilling and laser ablation, all of which are serial operations, and therefore slow for large hole matrices. Other drawbacks are that the problem of hole-to-hole registration must be addressed, and tool components which are subject to mechanical wear require routine replacement.

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Through-Hole Circuitization by an Anodic Etching Technique

       Disclosed is a method for making through-holes in
metal-core circuit boards in a parallel process.  Current methods for
putting vias in boards include punching, drilling and laser ablation,
all of which are serial operations, and therefore slow for large hole
matrices.  Other drawbacks are that the problem of hole-to-hole
registration must be addressed, and tool components which are subject
to mechanical wear require routine replacement.

      In the present invention, holes are created by
photolithographically patterning both sides of the metal substrate,
and then etching is under anodic bias in an appropriate electrolyte
solution.  The anodically-enhanced etching process is used to
increase the etch rate and improve the uniformity of the hole
profile.  Faster etching is also promoted by the double-side
patterning.  The figure shows the etching cell used.  The metal board
functions as the anode, and the cathodes are situated along the
walls, with baffles to aid solution stirring.  The solution is
circulated through the cell; it may contain a copper- complexing
agent, e.g., mercaptobenzothiazol or methylbutynol.  The use of an
alkaline etch solution would allow complexing agents, such as EDTA or
tartrate, to be used.  After etching, the photoresist can be
stripped, or left in place as a dielectric.

      The advantages of this method are substantial from the
standpoint of productivity...