Printed circuit board (PCB), a vital component in any electronic equipment, is becoming an integral part of almost every requirement in the strategic electronics for defence sector. In the past, many systems were free of electronics but now and in the near future everything that a soldier uses—from clothing to weapon to equipment, may have very sophisticated electronic gadgets with multiple integrated sensors network. All these electrical and electronics components are designed and interconnected using varieties of PCBs ranging from rigid to flexi rigid boards. PCBs are now increasingly being used in outdoor systems such as antenna control systems for satellite earth station, control systems for mobile radars, solid state flight data recorders for fighter aircrafts, air data computers for fighter aircrafts, surveillance, armoury, communication, control systems and even in defence transport vehicles. PCBs are also key to indoor and backend hardware systems such as ground control communication equipment, computer-controlled systems, missile launchers, electronic counter measures fire control systems, customised CPUs for nuclear reactors, etc.
By Sandhya Malhotra
Monday, September 05, 2011: With India committing to upgrade technology on almost every front in the defence sector, defence research organisations as well as defence production agencies have become more active. PCB being a critical and basic requirement for any electronic system, the industry will require to cater to these demands and meet the international standards.
In India, PCB makers are leaving no stone unturned in terms of innovations. Hence, PCBs are undergoing technological changes and following strigent test processes to meet the new requirements of applications.
PCBs requirement for defence sector
According to Anilkumar Muniswamy, director, SLN Technologies and IPCA president, “Presently, PCB requirement for defence sector stands at Rs 150 crore and it is likely to grow to Rs 500 crore in the next five years. However, the local industry is meeting only about 30 per cent of this demand, while the rest is being fulfilled through imports—either as assembled boards or finished products.”
States Janardhan Prabhakar, business development manager, Kontron Technology, “The defence sector spends more than 10 to 15 per cent of its budget only on PCBs. Stable and proven versions of any technology are used in the sector, hence long term availability is one of the key factors influencing the purchasing decisions. Plain PCBs do not play a major role in the defence sector, thus populated PCB boards are the ones that need to adopt this long term support strategy.”
Types of PCBs used in defence equipment
There are many special requirements of PCBs in defence equipment and devices, which are used for several defence and aerospace applications, for example—metal core and condution cooled PCB. These are extensively used in cockpit electronics of aircrafts and also in ground systems where fitting external heat sinks is not possible due to space constraint. Other PCBs used in defence equipment are impedance controlled flex and rigid flex; PCBs with traces and space width of three to four mils; PCBs with exotic base materials like teflon, polymide, hydrocarbon ceramic, etc, for RF applications; and buried capacitor and hybrid PCBs with combination of different materials.
“A lot of development is happening in the RF communication area where PCBs with exotic substrate materials instead of normal FR4 are increasingly required,” says Neeraj Jain, assistant manager, Precision Electronics Ltd.
PCBs undergoing changes
Since defence equipment are undergoing tremendous upgradation, technological advancement in PCBs is imperative. Technology demand in PCBs is driven by the devices which are planned to be assembled on board. The technological improvement in devices has been very steep. “The lifecycle of devices has been continuously shrinking and obsolescence of available devices drives the designers to look at high end designs with latest devices with ball grid array (BGAs), close pitch surface-mount devices (SMDs), etc. There is a continuous effort to make systems more compact, feature packed as well as reliable. Hence, technological transition is a reality which is going to affect changes in PCB fabrication. These changes cover every aspect of the fabrication including material, lithographic process, chemical processes like etching, plating, etc, surface finishes and also reliability checks,” says Bengaluru based K Srinivasan, president, Micropack Ltd, which has the capability of manufacturing multilayer PCBs up to 24 layers.
With every passing day, PCB manufacturers are gearing up for high quality, high density, high layer count PCBs that provide long term performance in defence and aerospace applications. Technological innovations have taken place in the field of miniature packaging, low layer count high density interconnection boards, felxi-rigid boards, metal core self cooling boards and high temperature withstanding flexible circuits.
Commenting on the fast changes in PCB technology, Prabhakar, says, “There is always a change in PCB technology as per the needs of the defence sector. PCBs fulfilling stringent demand of our defence forces is quite a niche area but adaptability will take its time.”
Agrees Srinivasan, “We have been witnessing more demanding changes in PCB technology, especially for the last couple of years. Earlier, designs were restricted to four to six layers with normal FR4. But now, we have requirements of 22 to 24 layers.”
Manufacturers in India are producing a wide range of PCBs including single side, double side, flexible, rigid flexible and multi-layer and high density boards. While most can produce up to 12 layer PCBs, some manufacturers claim to produce 16 to 20 layer boards. The eight layer boards are more common in the industry. Says CS Bhaskar, chief-customer support (technical), Circuit Systems India (CSIL), “While some manufacturers are trying to produce 16 to 20 layer PCBs, we are going to concentrate on rigid-flexible PCBs.”
About 10 to 15 manufacturers in India are producing multi-layer PCBs required in defence sector, but only a few are producing conduction cooled thermal boards, RF-flexible and rigid-flexible PCBs. These are being exported for use in military equipment. “A PCB fabricator should understand the applications and the end user should understand a fabricator’s capabilities and limitations. Proper communication, right from the design stage, can definitely help to make the designs easier to manufacture,” says Srinivasan.
PCB features required
According to Kumar, PCBs used in defence are of special grade with a wide range of temperature handling capabilities. These are generally known as MIL grade boards and the organisations which manufacture such boards are certified by IPC, USA. IPCA in association with IPC provides training on testing and certifying MIL grade PCBs and PCB assemblies. These boards are normally designed with impedance control and self cooling features. Some of the defence boards can have up to 40 layers with metal cores for self cooling purpose. Recent technological advancements have reduced the number of PCB layers, but these can handle more components through high density interconnection technology. Rigid and flexible defence boards also come in one package known as flexi-rigid boards, which are increasingly used in missiles and satellites.
“Every MIL board is assessed by subjecting the coupons through thermal stress and carrying out the micro section analysis. Currently, there are only one to two suppliers in India who can cater high grade MIL boards to defence sector and the rest are foreign suppliers,” informs Kumar.
The other critical feature of PCBs for defence is their reliability. The right choice of materials and the right process are the keys to achieve a reliable PCB for defence equipment.
Getting reasonable order from the defence sector is not an easy task for any PCB supplier, therefore, manufacturers should get the required approvals. “One must be very familiar with defence quality standards, approval procedures, environmental testing procedures and acceptance test criteria,” says Bhaskar.
Sometimes supplying to defence can be a long process, and therefore, companies should have the required financial strength and cash flow to sustain during development stages. “As major defence deals are through tenders, only the lowest bidder gets the chance to supply. Therefore, one must be very familiar with costing process and budget estimation to arrive at the best offer price,” adds Kumar.
The outlook for PCBs in defence looks very promising for the next decade. There is a huge opportunity for local companies in India. Moreover, the defence offset policy will boost the PCBs in india, as any foriegn supplier supplying system to defence must outsource 30 per cent of the value of the order through local sources, fore the value exceeding Rs 300 crore and therefore PCB industry is projected to grow at more than 30-35 per cent during the next five to 10 years. “The demand for quick turn boards are increasing steadily and Indian companies have the opportunity to supply to European and US companies,” says Kumar.
PCB usage in defence applications PCBs are used in:
• Telecommunication equipment
• Battle tanks
• Fighter aircrafts
• Control systems
• Nuclear reactors
• Handheld devices
• Power controls
• Communication systems, including RF communication areas
Electronics Bazaar, South Asia’s No.1 Electronics B2B magazine