Precision laser adjustable thin film capacitors
Disclosed are apparatus and methodology for providing a precision laser adjustable (e.g., trimmable) thin film capacitor array. A plurality of individual capacitors are formed on a common substrate and connected together in parallel by way of fusible links. The individual capacitors are provided as laddered capacitance value capacitors such that a plurality of lower valued capacitors corresponding to the lower steps of the ladder, and lesser numbers of capacitors, including a single capacitor, for successive steps of the ladder, are provided. Precision capacitance values can be achieved by either of fusing or ablating selected of the fusible links so as to remove the selected subcomponents from the parallel connection. In-situ live-trimming of selected fusible links may be performed after placement of the capacitor array on a hosting printed circuit board.
1. An adjustable thin film capacitor, adapted for adjusting the resulting capacitance value thereof while said capacitor is in operation in a circuit, comprising:
respective first and second terminals; and
a capacitor array, situated electrically between said respective first and second terminals, said capacitor array comprising a plurality of respectively valued sub-component capacitors, arranged so that respective of said sub-component capacitors may be removed from the resulting capacitance value of said adjustable thin film capacitor;
wherein said sub-component capacitors comprise a base value capacitor and plural parallel coupled capacitors coupled by way of fusible links, and configured in a capacitive laddering effect, so that selected removal of respective said parallel coupled capacitors correspondingly adjusts the resulting capacitance value of said thin film capacitor.
2. An adjustable thin film capacitor as in claim 1 , wherein:
said fusible links coupling the plurality of capacitors in parallel may be respectively ablated by laser irradiation; and
said thin film capacitor further includes a laser radiation transparent passivation layer covering at least said fusible links, whereby said resulting capacitance value of said thin film capacitor may be adjusted while said thin film capacitor is in an intended use environment.
3. An adjustable thin film capacitor as in claim 1 , wherein said fusible links are situated such that no electrode of a respective sub-component capacitor lies either above or below a respective fusible link, so that subsequent ablation of any fusible link does not create potential shorts or leakages.
4. An adjustable thin film capacitor as in claim 1 , wherein said capacitive laddering configuration includes at least two respective single capacitors of relatively larger capacitive values and a plurality of substantially duplicative capacitors of at least two relatively lower capacitive values.
5. An adjustable thin film capacitor as in claim 1 , wherein:
said fusible links may be respectively disrupted by ablation with laser irradiation; and
said thin film capacitor further includes a laser radiation transparent passivation layer covering at least said fusible links, whereby said resulting capacitance value of said thin film capacitor may be adjusted while said thin film capacitor is in an intended use environment.
6. An in-situ adjustable thin film capacitor, adapted for post production adjustment of the resulting capacitance value thereof, comprising:
respective first and second terminals; and
a capacitor array, situated electrically between said respective first and second terminals, said capacitor array comprising a base value capacitor and plural parallel coupled capacitors coupled with at least one of said terminals by way of fusible links, and configured in a capacitive laddering effect, so that selected removal of respective said fusible links correspondingly removes parallel coupled capacitors so as to adjust the resulting capacitance value of said thin film capacitor;
wherein said fusible links are situated such that no electrode of a respective capacitor of said capacitor array lies either above or below a respective fusible link, so that subsequent disruption of electrical connection of any fusible link does not create potential shorts or leakages; and
said capacitive laddering configuration includes at least one respective single capacitor of relatively larger capacitive value and a plurality of substantially duplicative capacitors of at least two relatively lower capacitive values.
7. An in-situ adjustable thin film capacitor as in claim 6 , wherein:
said fusible links coupling said plurality of capacitors in parallel may be respectively ablated by laser irradiation; and
said thin film capacitor further includes a laser radiation transparent passivation layer covering at least said fusible links, whereby said resulting capacitance value of said thin film capacitor may be adjusted while said thin film capacitor is operative in a circuit.
8. An in-situ adjustable thin film capacitor as in claim 6 , wherein:
said capacitive laddering configuration includes at least two respective single capacitors having capacitive values respectively of at least 1.0 pF; and
said plurality of substantially duplicative capacitors includes at least ten of said capacitors having capacitive values of respectively no more than 0.5 pF.