Thick film hybrid

Ultra Electronics CEMS offers a near unique service aimed at bringing miniaturisation to both new designs and existing products.

Main benefits:

  • Experienced designers
  • Re-setting expectations
  • Smaller and lighter
  • Higher reliability
  • Advanced substrates
  • Mechanical advantage
  • Thermal conductivity
  • Low profile/small outline
  • High temperatures
  • ROHS and hybrids
  • Traditional concerns

Smaller and lighter

The use of unpackaged (i.e. bare die) semiconductors and laser trimmed printed ink resistors are the main drivers in reducing the size and weight of a thick film hybrid. The next most significant saving being the substitution of conductive epoxy adhesive for the very much heavier solder joints associated with PCB assemblies.

Higher reliability

Switching from packaged semiconductors on a PCB to bare die on ceramic removes an entire layer of interconnects as the wire bonding traditionally between a die and its package becomes wire bonding between a die and the substrate, cutting out the process of soldering the package legs to the PCB. Solder joints are potential points of failure and their replacement with incredibly reliable gold wire bonding and conductive epoxy adhesive greatly extends MTBF ratings. All components in a hybrid are protected in an inert atmosphere within a protective metal enclosure, this, coupled with the more efficient cooling of devices on a ceramic substrate further extend the reliability.

Experienced design team

With some 30 years experience of designing and manufacturing microelectronics hybrids, small geometry PCB assemblies and small mechanical structures, our Portsmouth facility has a proven track record of miniaturising products to give customers competitive advantage in their traditional markets as well as opening up new markets.

With experience accumulated in high reliability sectors including Nuclear, Aerospace, Defence, Medical and Maritime and also including Automotive and Civil utilities the business has a resourceful engineering team focussed on delivering robust designs with a speciality in problem solving.

Re-setting expectations

It's common to find that most design teams start a development programme assuming, by default, the use of PCB based electronics. This then sets expectations in terms of realistic functionality in the available space, size and weight of the finished product as well as its thermal tolerance, power dissipation and the internal infrastructure required to support the PCBs, PSU and other contents.

The Ultra CEMS approach to new development programmes is to start without pre-conceived ideas about the interconnect technology or materials to be used. First establishing budget limits on weight, space, power dissipation, cost, IP rating, operating temperature, functionality, stretched functionality, MTBF and sales volumes, they then choose from a range of interconnection technologies and materials.

Advanced substrates

The culmination of 3 years of development, Ultra CEMS has brought to market a new approach to implementing complex digital circuits; in miniature. Far exceeding the capacity of traditional thick film hybrids and being substantially smaller and lighter than the equivalent PCB technology, "chip-HDI" combines the size reduction associated with the use of bare die and the increased layer count possible with PCB technology. Using high performance materials instead of fibreglass the "chip-HDI" hybrids are typically supplied in a hermetically sealed and EMC tight kovar metal case.

Choosing from chip-HDI hybrid, traditional ceramic thick film hybrid, mixed component technology hybrid, mixed substrate hybrid, chip-on-board or chip-in-board to traditional PCB technology; or combination of the above is at the core of the Ultra CEMS versatile approach to designing smaller products.

Mechanical advantages

Where electronics has been miniaturised the reduction in size and weight can allow savings in other aspects of a product such as internal support structures and mounting brackets. The use of lighter gauge metal brackets further reduces overall weight and where structural plastics can be used the assembly process can often be greatly simplified to reduce weight and overall costs.

Thermal conductivity

Thermal conductivity

Unlike PCB material, ceramic has an extremely high thermal conductivity and heat is quickly moved away from hot spots, preventing semiconductor junctions from over heating and failing.

FPGAs are commonplace now and yet few design engineers are aware that unpackaged (i.e. bare die) FPGAs are often a small fraction of the price of the same device when packaged for use on a PCBA, as well as being <10th the size.

Low profile/small outline

The use of small packaged components on PCBs does allow a moderate level of miniaturisation, however in this area microelectronics is a game changer, allowing substantial reductions in size. In applications where the Z axis is critical, Ultra has achieved the implementation of complex circuits in 0.75mm overall height, using flip-chip and lapped substrate. For applications demanding small size in X and Y axes but with no constraint in Z axis, to achieve a small outline Ultra have refined over many years a folding substrate technique.

High Temperatures

Industries including Oil and Gas, Aerospace and Defence are demanding electronics that can survive high temperatures with long endurance, e.g. for down hole electronics or integral jet engine sensors and controls. Unlike traditional PCB technology the ceramic substrate used for hybrid circuits isn't a limiting factor for high temperatures, only the temperature rating of individual components thereon dictates the maximum rating of the finished hybrid. By careful selection of the components designed into a hybrid extremely high thermal tolerance can be achieved. Long term tolerance in the range 175ºC to 200ºC is currently feasible using ceramic hybrid technology which greatly exceeds that of PCB technology.

Traditional concerns:

Hybrids are expensive

In early years hybrids were the preserve of high level and high budget space and defence programmes, however over the decades the costs of bare die and a maturing hybrid fabrication process have fallen significantly making the hybrid solution of today cost effective in most industry sectors; it was black art but is no longer!

Hybrid NRE costs are very high

Costs vary but in almost every case the engineering and other NRE costs fall within the range £5,000 to £15,000. This covers the design of the hybrid, identification and selection of the semiconductors, engineering support of first build, design and construction of a functional test box used to test each finished hybrid.

Hybrid design times are lengthy

The first stage is to identify the devices to be used and get them on order. Completion of the design is well within typical lead times for delivery of those devices.

Hybrid are designed by strangers

Ultra CEMS design team work closely with the customer engineering team to ensure maximum benefit from the use of hybrid technology.

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Product Miniaturisation in the UK

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