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Automatic Inspection of Via Fill

IP.com Disclosure Number: IPCOM000083381D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 46K

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Johnson, AH: AUTHOR


Presently there is no automatic system to detect the via fill of multilayer ceramics (MLC).

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Automatic Inspection of Via Fill

Presently there is no automatic system to detect the via fill of multilayer ceramics (MLC).

The via fill (conductor paste) is typically 80% Mo or MoRu. The green sheet can be placed against a metal grounding plate. Full or half-full via holes can be detected by either testing the via capacitance or shortening the via conductive path for high voltage, which is in proportion to the amount of paste in the via hole. Fig. 1 shows a detection circuit 2 making contact 4 to an MLC 6 that is against a metal plate 8, which exposes only the via holes 10.

Fig. 2 shows a continuous roller sensor 12 which has separate circuits 14 for roller position. If the via pitch is finer than the roller pitch, multiple passes are required in order to test every via hole. Also shown is an empty via hole 15, half- full via hole 16, and full via hole 18. Fig. 3 shows via hole testing using the step and repeat method.

When the high-voltage method is used, damage to the MLC is prevented by immediately quenching the arc or limiting the current through a high impedance.


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