Microelectronics Overview

Formed in 1986 as a specialist thick-film hybrid design and microelectronics fabrication facility, the Portsmouth operation offers a wide range of proven production techniques and processes in the microelectronics and allied fields, supported by an innovative design team.

• Hybrid design
• Thick film hybrids
• Power electronics
• Sensor electronics
• Microwave electronics
• Chip on board
• Mixed technology hybrids
• Opto-electronics
• Sub-assembly
• Electronic design
• Software design
• Product miniaturisation

With clients spread over aerospace, defence, oil and gas, medical, communications and scientific instrumentation industry sectors, for both design and fabrication contracts, the accumulated expertise and range of capabilities place the Portsmouth facility amongst the leaders in the field of microelectronics engineering.

Product miniaturisation and improved performance using Hybrids

Where the size of a product or system is largely determined by the size of its electronics, the potential for miniaturising that product by using Hybrid technology instead of PCB technology is significant. Circuits that are largely digital in nature present the greatest potential for miniaturisation; possibly to 10% of the size of the equivalent PCB without any reduction in function. Largely analogue circuits are less easily reduced in size with reductions of between 30% to 50% of the equivalent PCB. However, analogue circuits perform more efficiently as Hybrids providing additional benefits.

Hybrids are statistically more reliable than PCB assemblies as they typically contain no solder joints. Components are interconnected by welded joints (wire bonding) or silver loaded conductive epoxy adhesive, an extremely reliable and long established joint technology.

Hybrids can sustain higher operating temperatures than PCBs, with componentry available now that can function in 200°C indefinitely. The alumina or aluminium nitride substrates have a very high coefficient of thermal conductivity and junction-damaging “hot spots” beneath individual semiconductors are avoided by the swift transfer of heat away from that device.

Hybrids are hermetically sealed, either by way of sealed metal enclosure or conformal coating, making them the most suitable technology for electronics that operates in hostile environments.

Hybrid technical information

Substrate
Standard	96% Alumina
Power applications	Alumina nitride
Maximum substrate size	150 x 100mm

Conductors
Wire bondable	Gold	4 - 7 mohms / square
Solderable	Palladium - silver	20 - 30 mohms / square
Solderable over gold	Platinum - gold	50 - 60 mohms / square
Standard track/gap	0.025mm width, 0.025mm gap
Conductor layers	6 each side
Through-printed holes	Gold	<20 mohms thru-hole
Double-sided printing	Palladium, silver	<50 mohms thru-hole

Resistors
Range	<1 ohm to >50 mohms
	<10 ohms	+/ - 0.5 ohms
	10 to 100 ohms	+/ - 0.5%
	100 ohms to 300 kohms	+/ - 0.3%
	>300 kohms	+/ - 0.5%
Stability	100 ohms to 1 mohm	+/ - 0.5%
Absolute TCR standard	+/ - 100ppm/°C
Absolute TCR special	+/ - 50ppm/° C
Matching	Mid-range values	+/ - 0.1%
Power dissipation	77.5 kwatts/metre2 nominal
Adjust on test facility	Active trim of circuit function (R or C)
Close tolerance resistors	Thin film chip resistors

Wire bonding
Gold	Thermosonic, 0.0177mm to 0.05mm Ø.
Aluminium	Ultrasonic, 0.0177mm to 0.05mm Ø.
Aluminium power	Ultrasonic, 0.127mm to 0.635mm Ø.

Add-on components
Chip and wire transistors, FETS, Diodes.	Digital and analogues IC's.
	Microprocessors and memory
	Thin film resistors
	Inductors, transformers, crystals.
	Capacitors, ceramic, tantalum or MOS.
Solder Surface Mount	All the above mounted as small outline plastic packs, LCC or PLCC, D-Packs (Power Devices)
	Chip resistors.

Packages
Mil spec chip and wire	Seam-sealed metal packs
MIL spec chip and wire	Epoxy-sealed ceramic packs
Industrial spec chip and wire	Silicone bond protected, epoxy coated
Industrial and commercial	Epoxy coated
Surface mounted	Epoxy coated
Format	Dual-in-line
	Single-in-line
	Double-sided, mixed build customised format to suit the application.

Group A screening tests
Fine/gross leak	< 5 x 10-8 att cc/s
Acceleration (steady state)	5000g
Rapid change of temperature	-65°C to +150°C, 5 cycles
Burn-in	160 hours at +125°C, powered
Functional tests at 25°C	To customers specification
Temperature tests (sample)	T max and min as required

Special features
Pin grid array hybrids	Customised packaging
Double-sided hybrids	Print through or clip round
Resistors on dielectric	Allows tracking under resistors
Fine line and space	0.1mm line and space (conventional printing)
	0.05mm line, 0.025mm space (new method, patent applied for)
Glass windows in metal or ceramic	Mounting on photo-devices or eprom.
Militarised ceramic hybrids	Using solder metal frame lids
High temperature hybrids	Up to 200°C.
Power hybrids	High dissipating devices