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Locating Internal Printed Circuit Planes

IP.com Disclosure Number: IPCOM000096203D
Original Publication Date: 1963-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Kirk, JP: AUTHOR

Abstract

The machine automatically locates an internal central layer of a multilayered printed circuit board. Then, circuitry can be applied to the outer layers in register with the internal layer.

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Locating Internal Printed Circuit Planes

The machine automatically locates an internal central layer of a multilayered printed circuit board. Then, circuitry can be applied to the outer layers in register with the internal layer.

Multilayer board 1 has copper clad surfaces and etched internal layer 2 having defined edges. X-rays from source 3 pass through a pair of entrance windows 4 to detectors 5 which are rigidly connected together by bar 6. The count rate for an X-ray detector over three layers of thin copper is about one-half that over two layers.

The count rates from detectors 5 are applied to difference amplifier 7. This produces a difference signal to actuate servo motor 8 to adjust board 1 until there is a null signal. A null signal is received when the edges of internal layer 2 are over windows 4 and the count rates are equal. Three servos, each operating from its own signal, are sufficient to fully position the board. At this time, locating holes are punched in board 1. The double detectors, besides compensating for variations in the X-ray source, allow the drive to position the board even if there is several thousandths variation in the undercutting in the etching of the internal layer.

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