The black art that still beguiles
14 September 2009
Thick film technology has been a constant in the industry ever since I joined the merry throng 25 years ago. My impression has always been that it is a rather quaint, specialised and slightly mysterious branch of the electronics family and one that no one wishes any ill of, but at the same time would not notice if it just disappeared.
Just shows how little I know.
I was at DSEi (the defence show in London) last week and chatted to all sorts of people about all sorts of things. One company I spent a bit of time with was C-MAC, a UK-based contractor (with operations in Canada and France) with a large reliance on the mil/aero sector. The reason for this is the core specialisation in thick film technology – a technology with the characteristics to satisfy the demands for use in harsh environments.
It would make sense to believe that advances in both the PCB and semiconductor sides are putting a squeeze on hybrid technology. After all, the PCB is far more versatile and manufacturable in volume than a hybrid, and advances in surface mount technology have made it a hugely reliable process – no ‘black art’ involved in printing or reflow anymore! Equally, the convergence of analogue and digital on single chips and the myriad of processing capabilities semiconductors now offer, mean that the old hybrid advantages of stacking dies, reducing space by reducing component packaging and so on, are now largely obsolete. Or are they?
The truth seems to be less that thick film hybrids are being squeezed from both sides, rather that they are taking the advances from both PCB and semi industries to enhance its own offering. As they are normally based on ceramic substrates, thick film circuits can operate in temperatures that far exceed those of FR4 and the printed inks provide a far more stable foundation mechanically than copper tracks do. So harsh environments have become the playground of the hybrid circuit.
Similarly, the increasing functionality on silicon has not taken a chip (excuse the pun) out of the hybrid market. Semiconductors cost a fortune to develop and it is not therefore practical to develop a new chip for the relatively low volume applications fulfilled by thick film hybrids. Semiconductors also lack the flexibility for customisation that hybrid circuits have.
So rather than being a black art on the wane, thick film circuits seems to be an improving technology on the up. Bob Hunt at C-MAC for example, talked about how his military designs were finding applications further afield, a particular case at the moment being oil and gas exploration. Maybe if you are working on projects that involve excessive heat and mechanical stresses (eg vibration) then it is time to turn back the clock and re-investigate what thick film technology has to offer.
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