Product category:
Boards and Backplanes
News Release from: UltraSource | Subject: UltraBridge technology
Edited by the Electronicstalk Editorial
Team on 03 February 2006
Thin film substrates take more
components onboard
A novel multilayering approach provides repeatable wire-bond-less cross-under bridges and allows integration of circuit functions onto a single thin film substrate.
Modifying techniques traditionally reserved for costly MIMIC fabrication, UltraSource has perfected a novel thin film multilayering approach that has proven to provide repeatable, wire-bond-less, cross-under bridges, and has allowed for further integration of not only resistors, but also inductors, capacitors, and other circuit functions onto a single thin film substrate The key innovation from UltraSource is its UltraBridge technology
This article was originally published on Electronicstalk on 8 Nov 2004 at 8.00am (UK)
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By eliminating the need for a wire bond, or an air bridge, this consistent, reliable, cost effective solution should aid circuit designers at high frequencies.
In this process, the interconnect conductor layer right is applied and patterned right on the substrate surface as an "under" bridge.
This is where this technique varies from an air bridge process, which applies the interconnect layer after the thin film conductor layer is complete.
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Next, silicon nitride (Si3N4) is applied over the interconnect layer to encapsulate it and insulate it from the next metal layer.
Then the silicon nitride features are patterned and etched.
Contact windows to the interconnect conductor are also made during the pattern and etch of the silicon nitride.
Finally, the conventional thin film conductor and resistor layers are applied using standard techniques and processes.
The result is a simple, cost effective method for fabricating high frequency interconnects for Lange Couplers, integrated capacitors, and integrated spiral inductors.
The UltraBridge technique also reduces the number of mask steps by 30% over air bridge techniques, resulting in reduced design complexity and increased reliability.
The hardness of the silicon nitride creates a very robust interconnect design unaffected by accidental compression during inspection or assembly.
Until now, the only element available for integration into complex RF and microwave thin film interconnects has been the thin film resistor.
This is facilitated by a layer of resistive metallisation of either Ni-chrome or tantalum nitride in a predetermined sheet resistivity and etched or laser trimmed to the value and tolerance required by design.
As the next step to complete integration of all passive elements into a single thin film circuit, UltraSource offers the UltraInductor and UltraCapacitor.
UltraInductor technology uses the silicon nitride in the same configuration used for the UltraBridge to facilitate interconnects with the centre tap colocated on the circuit with other critical components, minimising the parasitic components and variability.
UltraCapacitor uses the same process steps as UltraBridge and UltraInductor and offers the designer the ability to integrate capacitors with values of 2 to 250pF right onto the substrate.
Silicon nitride is the ideal dielectric for this application with the thickness of the silicon nitride controlling capacitance density of the dielectric, lending to flexibility in the capacitor layout.
The UltraBridge, UltraInductor and UltraCapacitor technologies are being used as the intelligent alternative to outdated interconnect technologies in common wireless components, multichip modules and subsystems throughout the world combining proven high technology expertise with benefits of increased reliability and lowered overall cost of ownership.
Thin film interconnects are a standard circuit technology used in high frequency design components and subsystems where transmission line widths of 0.005in and under are critical to performance, as well as high power applications, where thermal conductivity is of concern and materials such as beryllium oxide and aluminium nitride must be considered.
This unique technology is employed in a variety of military and homeland security platforms from radar to EW and counter-measure applications, to missile and armament receivers and sensors.
UltraSource's approach has been successfully employed in the design and fabrication of Lange couplers, offering layout of line spaces as precise as 10um and controlled to tolerances of 1.5um.
A Lange coupler is a common circuit used in microwave applications.
It provides equal power division and 90 degrees of phase shift between the coupled ports.
They are widely used as power combiner and splitters in microwave amplifiers and in mixers/modulators.
They are based on interdigitated lines with narrow lines and tight spaces.
The connections between fingers of the coupler are made by the metal traces which are isolated from the fingers.
This creates a highly reliable connection.
Another benefit is that the connection is very repeatable.
This is important for obtaining repeatable performance from circuits such as balanced amplifiers and modulators.
Lange couplers provide a simple example of the varied potential for employing multilayer thin film techniques in next generation high frequency designs.
UltraTechnology should be looked at for advanced interconnect designs which would benefit from combining microstrip transmission lines, filled vias, resistors, capacitors, spiral inductors, underbridges, and selectively deposited gold-tin all on a single substrate device.
To begin the design process using UltraTechnology, a designer should talk to the factory to decide on the level of integration desired and to procure design assistance on high frequency models.
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