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Thin Film Bifilar Transformer Using Tab Cross-Points

IP.com Disclosure Number: IPCOM000103016D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 50K

Publishing Venue

IBM

Related People

Katyl, RH: AUTHOR

Abstract

A structure is described which interconnects upper and lower wiring of a two layer TAB (Tape Automated Bonding) structure to form a bifilar air cored transformer.

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Thin Film Bifilar Transformer Using Tab Cross-Points

      A structure is described which interconnects upper and lower
wiring of a two layer TAB (Tape Automated Bonding) structure to form
a bifilar air cored transformer.

      Advanced TAB structures have wiring available on two levels
over polyimide or over windows in the polyimide e.g., Kapton
(trademark of E.I. du Pont de Nemours & Co).  Wires on both levels
which cross one-another in a polyimide window area can be
thermocompression (TC) bonded together.  Such cross-over capability
gives rise to the possibility of making coil structures.

      In the figure, the light wires are on one level, and the dark
another.  By following the circuit, assuming the two levels are
bonded in the window area, one can see that two intertwined coils are
formed, with the polyimide film being in the core.  One coil goes
from node P1 to node P2, the other goes from S1 to S2.  Of course,
many other variations of wiring exist; the figure gives only one
example.

      Transformers wound with two adjacent wires are known as bifilar
wound, and have better coupling than those wound with adjacent
primary and secondary coils.  However, the coupling is not as good as
that of coils wound on a ferrite toroid.  But because of the
advantages of mass fabrication, cost of the TAB coils should be
substantially lower, and the electrical properties more consistent
and repeatable than that of hand wound coils.  The electrical
proper...