Partnership adds impetus to thick film hybrids

Perllo Technologies has formed a new partnership with Hampshire-based Extec Integrated Systems.

Perllo Technologies has formed a new partnership with Hampshire-based Extec Integrated Systems.

Together, these two pioneering companies will provide industry leaders in Aerospace, Military Defence and Space technology and design, access to Extec's expertise in innovative solutions and hybrid microcircuits facilitated by Perllo Technologies' superior logistics options and unsurpassed customer service.

Extec has been an industry leader in the design and manufacturing of thick film hybrid microcircuits for over 18 years.

Using thick film hybrid technology, Extec has perfected innovative techniques in the manufacturing and development of thick film inks onto steel for use in pressure sensors, Peltier (thermoelectric) coolers, and 3D structure applications.

Standard thick film technology has a ceramic substrate sequentially screen printed with precious metal and dielectric inks, producing a multilayer interconnected pattern.

The layered pattern is then dried and fired at 850C to form a bond to the substrate.

Resistors are also printed onto the pattern where they are then laser trimmed to better than 0.5% accuracy.

Once the printed substrate is complete, components can be added either in the form of semiconductor die and chip capacitors (which are epoxy attached), or small-outline surface-mount devices and capacitors (which are soldered down).

After the components are attached, they are wire-bonded into circuit using 0.001in-diameter gold or aluminium wire, thus completing the circuit and making it ready for testing.

A typical pressure sensor will have a Wheatstone bridge printed onto an area of the steel, such that deflection of the steel either by applied pressure or mechanical force will cause a distortion of the resistors in the bridge and a consequent change in value.

This change will cause a detectable output from the bridge.

Extec's new advancements in steel pressure sensors allow for the particular advantage of e-beam welding to a variety of fixtures to suit any application.

This e-beam welding effectively minimises stress caused to the bridge's diaphragm and has resulted in exceptional linearity with minimal to zero hysteresis.

Frank Bellion, Extec's Technical Director explains: "When we first saw the linearity results from the steel sensors, we did not believe the graph; it looked as though someone had drawn a straight line and then added the measurement points to it".

Peltier coolers are another application where Extec has used thick film ink technology on steel.

Extec has designed and fabricated many Peltier coolers ranging in size from very small to several inches long to suit a variety of applications.

One advantage of these coolers is that the steel substrate becomes the heatsink, thus removing one layer of thermal resistance.

Combining thick film printing onto the top face of a Cooler can provide an electronic circuit with its own heat dissipater.

Chris Warne, Extec's Managing Director, states: "We have seen an enormous interest in providing tailor-made Peltier coolers for our customers' specific applications including coolers for infra-red diodes, high-dissipating electronic circuitry and even beer dispensing pumps".

"We have been able to provide custom Peltiers of better efficiency, both in terms of mechanical effectiveness and superior specification, than those available off the shelf".

Another Extec advancement has been to use thick film technology to form 3D structures on ceramic substrates by printing a release layer as a first process step.

This release layer can cover the entire substrate (if the whole circuit is required to be released) or be printed only under isolated areas (if only parts of the structure are to be released).

Printing of the substrate is then carried on as normal until the circuit has been built up, finally allowing the release layer to be removed.

The remaining layers may be attached to the surrounding structure forming movable elements, or can be completely released forming a multilayer circuit only microns thick.

John Holliman, Extec's Principal R and D Engineer, states: "When we discovered that we could release entire structures from the underlying ceramic we were very excited; the applications for this technique in the area of sensors are quite enormous".

"We have already successfully produced pressure sensors, accelerometers and carbon monoxide gas detectors and are finding new applications for our customer's needs all the time".

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